Construction machine, and electric actuator of construction machine

Abstract

To make a boom swing using an electric motor as a drive source.SOLUTION: A shovel car 500 comprises: a mother machine 520 having a first through hole 520H; an electric motor 20 attached to the mother machine 520; a speed reducer 70 located at the opposite side of the electric motor 20 with the first through hole 520H interposed therebetween and reducing a rotational speed of an output shaft 20B of the electric motor 20; a transmission shaft 25 arranged within the first through hole 520H and connected to the output shaft 20B of the electric motor 20 and an input shaft 76 of the speed reducer 70; an output member 30 receiving power from the speed reducer 70 and rotating around a central axis Q of the transmission shaft 25; and a boom 530 connected to the output member 30.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a construction machine and an electric actuator for the construction machine. [Background technology]

[0002] The excavator disclosed in Patent Document 1 comprises a traveling device, a vehicle body, a boom, an arm, and a bucket. The traveling device is self-propelled. The vehicle body is located above the traveling device. The vehicle body includes a seat for an operator, etc. The boom extends forward from the vehicle body. The arm is connected to the tip of the boom. The bucket is connected to the tip of the arm. The boom is connected to the vehicle body so that it can swing left and right. The left and right swing of the boom is driven hydraulically. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-174615 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 only discloses hydraulic pressure as a power source for swinging the boom, and does not consider at all swinging the boom using a power source other than hydraulic pressure. [Means for solving the problem]

[0005] A construction machine for solving the above problem comprises a vehicle body, a drive unit including an electric motor and outputting torque centered on a central axis of rotation extending above and below the vehicle body, a swing bracket connected to the vehicle body and receiving torque from the drive unit, which rotates about a central axis of rotation parallel to the central axis of rotation or about the central axis of rotation, and a boom fixed to the swing bracket.

[0006] In the construction machine, the swing bracket rotates due to torque output from a drive unit including an electric motor, which in turn causes the boom to swing. That is, with the above configuration, the boom can be swung using the electric motor as a drive source.

[0007] An electric actuator for a construction machine that solves the above problems includes a drive unit that includes an electric motor and outputs torque centered on a central axis of rotation, and a swing bracket that receives torque from the drive unit, rotates around a central axis of rotation that is parallel to the central axis of rotation, or around the central axis of rotation, and is fixed to the boom.

[0008] In the electric actuator, the swing bracket rotates due to torque output from a drive device including an electric motor, which in turn causes the boom to swing. That is, with the above configuration, the boom can be swung using the electric motor as a drive source.

[0009] In the electric actuator for a construction machine, the drive unit may include: a transmission shaft that is arranged in a first through hole provided in the body of the construction machine and is rotatable around the central axis of rotation; an electric motor that is attached to the body and has an output shaft connected to the transmission shaft; a reducer that is attached to the body at a position opposite the electric motor across the first through hole, has an input shaft connected to the transmission shaft, and amplifies and outputs the torque output by the output shaft of the electric motor; and an output member that receives torque from the reducer and rotates around the central axis of rotation and is connected to the swing bracket, and the swing bracket may receive torque from the output member and rotate around the central axis of rotation.

[0010] The electric actuator of the construction machine may be cylindrical with the transmission shaft disposed inside, and may include a pin disposed in the first through hole together with the transmission shaft, and the swing bracket may be in contact with the pin.

[0011] In an electric actuator for a construction machine, the swing bracket may have an opposing wall having a third through hole at a position opposite the second through hole provided in the output member, and may include a connecting member connecting the output member and the opposing wall, and the connecting member may have a base that is disposed within the second through hole and the third through hole, and a buffer portion that is cylindrical with the base disposed inside, is disposed within the second through hole and the third through hole together with the base, and has a smaller elastic modulus than the base.

[0012] In an electric actuator for a construction machine, the swing bracket has an opposing wall facing the output member, and is equipped with a connecting member connecting the opposing wall and the output member, and there may be a gap between the opposing wall and the output member.

[0013] In the electric actuator for construction machinery, the drive unit may be attached to a vehicle body of the construction machinery, and the swing bracket may be connected to the vehicle body so as to be rotatable about the central axis of rotation. The electric actuator may include a drive member that receives torque from the drive unit and rotates about the central axis of rotation, a driven member that is attached to the swing bracket and rotates about the central axis of rotation, and a transmission mechanism that rotates the drive member and the driven member in conjunction with each other.

[0014] In an electric actuator for a construction machine, the driving member may be a driving sprocket that is annular about the central axis of rotation and has a plurality of teeth on its outer peripheral surface, the transmitted member may be a driven sprocket that is annular about the central axis of rotation and has a plurality of teeth on its outer peripheral surface, and the transmission mechanism may be a chain wound around the driving sprocket and the driven sprocket.

[0015] In an electric actuator for a construction machine, the driving member may be a ring-shaped driving pulley centered on the central axis of rotation, the transmitted member may be a ring-shaped driven pulley centered on the central axis of rotation, and the transmission mechanism may be a belt wound around the driving pulley and the driven pulley.

[0016] In the electric actuator for a construction machine, the driving member may have an outer diameter smaller than the outer diameter of the driven member. In an electric actuator for a construction machine, the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is supported rotatably on the lower body by a swivel bearing, and when the direction in which the swivel center axis is located when viewed from the swivel center axis of the upper body is defined as a first direction and the point of the swivel bearing that is closest to the swivel center axis in the first direction is defined as a specific point, at least a part of the drive member may be located on an imaginary line connecting the specific point and the swivel center axis.

[0017] In an electric actuator for a construction machine, the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is rotatably supported on the lower body by a swivel bearing, and is provided with one or more intermediate members attached to the vehicle body and that rotate around a central axis parallel to the central axis of rotation, and the transmission mechanism is configured to rotate all of the intermediate members, the driving member, and the transmitted member in conjunction with each other, and when the direction in which the central axis of rotation is located as viewed from the central axis of rotation of the upper body is defined as a first direction and the direction opposite to the first direction is defined as a second direction, all of the intermediate members are located on the first direction side as viewed from the driving member, and the driving member and the driving device are located on the second direction side as viewed from the central axis of rotation of the upper body.

[0018] In an electric actuator for a construction machine, the drive unit may be attached to the body of the construction machine, and the swing bracket may be fixed to an output member of the drive unit and rotate around the central axis of rotation upon receiving torque from the drive unit.

[0019] In an electric actuator for a construction machine, the drive device may have a reducer that amplifies and outputs the torque output by the electric motor, and the reducer may output the torque centered on the central axis of rotation output by the electric motor to the swing bracket coaxially with the electric motor.

[0020] In the electric actuator for a construction machine, the drive unit may be located below the swing bracket, and the swing bracket may be fixed to the output member of the drive unit with a bolt.

[0021] In the electric actuator for a construction machine, the swing bracket may be aligned with the drive unit in a direction along the central axis of rotation. The electric actuator may include: a transmission member interposed between the drive unit and the swing bracket and transmitting torque of the drive unit to the swing bracket; an annular bearing attached to the body of the construction machine, through which the transmission member passes and which rotatably supports the transmission member; a retaining member located on the opposite side of the bearing from the swing bracket in the direction along the central axis of rotation and through which the drive unit passes; and a buffer member connecting the retaining member to the body and having a smaller elastic modulus than the retaining member, wherein the swing bracket receives torque from the drive unit via the transmission member and rotates about the central axis of rotation.

[0022] The electric actuator for the construction machine may include a plurality of the bearings, and the plurality of bearings may be arranged in a direction along the central axis of rotation. In the electric actuator for a construction machine, the drive unit may be cylindrical and centered on the central axis of rotation, and the swing bracket may be aligned with the drive unit in a direction along the central axis of rotation, fixed to an output member of the drive unit, and rotate around the central axis of rotation by receiving torque from the drive unit.The electric actuator may include: a flange wall located on the opposite side of the swing bracket with respect to the drive unit in the direction along the central axis of rotation, supporting the drive unit, and fixed to a body of the construction machine; a retaining member located between the swing bracket and the flange wall, and through which the drive unit passes; a buffer member connecting the retaining member to the body, the buffer member having a smaller elastic modulus than the retaining member; and a pin that passes through the drive unit and is fixed to the flange wall.

[0023] In the electric actuator for a construction machine, the swing bracket may be connected to a vehicle body of the construction machine so as to be rotatable about the central axis of rotation. The electric actuator may include a pinion gear that receives torque from the drive unit and rotates about the central axis of rotation, and a gear wall provided in a position facing the pinion gear, the gear wall having an arc-shaped surface that is arc-shaped about a central axis that is parallel to the central axis of rotation, and a plurality of teeth that protrude from the arc-shaped surface and mesh with the teeth of the pinion gear, the arc diameter of the arc-shaped surface being larger than the outer diameter of the pinion gear, and one of the gear wall and the drive unit being fixed to the swing bracket, and the other being fixed to the vehicle body.

[0024] In an electric actuator for a construction machine, the arc surface may extend over a range of 165 degrees or more and 195 degrees or less in a circumferential direction around a central axis parallel to the central axis of rotation, and both ends of the arc on the gear wall may be connected by a flat surface extending in a straight line.

[0025] The electric actuator for the construction machine may be attached to the body of the construction machine and include: an annular inner ring centered on the central axis of rotation; an outer ring that is coaxial with the inner ring, has a plurality of teeth on its outer peripheral surface, is fixed to the swing bracket, and rotates together with the swing bracket about the central axis of rotation; rolling elements that are interposed between the inner ring and the outer ring and guide the relative rotation between the inner ring and the outer ring; and a pinion gear that is arranged at a position facing the outer peripheral surface of the outer ring, rotates about the central axis of rotation when it receives torque output by the drive unit, and has teeth on its outer peripheral surface that mesh with the teeth of the outer ring.

[0026] A construction machine for solving the above problem comprises a vehicle body, a cylindrical first member, a second member inserted into the first member from one end along the central axis of the first member and capable of reciprocating in a direction along the central axis of the first member, an electric motor that drives the reciprocating movement of the second member relative to the first member, a swing bracket connected to the vehicle body so as to be rotatable about a central axis of rotation extending vertically from the vehicle body, and a boom fixed to the swing bracket, wherein the first member is connected to one of the vehicle body and the swing bracket in a state where it can rotate about a central axis parallel to the central axis of rotation, and the second member is connected to the other of the vehicle body and the swing bracket in a state where it can rotate about a central axis parallel to the central axis of rotation.

[0027] In the construction machine, the electric motor drives the reciprocating movement of the second member relative to the first member. This reciprocating movement causes the swing bracket and, ultimately, the boom to swing. That is, with the above configuration, the boom can be swung using the electric motor as a drive source.

[0028] An electric actuator for a construction machine that solves the above problem comprises a cylindrical first member, a second member that is inserted into the first member from one end in a direction along the central axis of the first member and is capable of reciprocating in a direction along the central axis of the first member, an electric motor that drives the reciprocating movement of the second member relative to the first member, and a swing bracket that is connected to the body of the construction machine so as to be rotatable about the central axis of rotation and is fixed to a boom, wherein the first member is connected to one of the body and the swing bracket in a state where it can rotate about a central axis that is parallel to the central axis of rotation, and the second member is connected to the other of the body and the swing bracket in a state where it can rotate about a central axis that is parallel to the central axis of rotation.

[0029] In the electric actuator, the electric motor drives the reciprocating movement of the second member relative to the first member. This reciprocating movement causes the swing bracket and, ultimately, the boom to swing. That is, with the above configuration, the boom can be swung using the electric motor as a drive source.

[0030] In the electric actuator for construction machinery, the second member may be cylindrical and extend along the central axis of the first member, and may have a female thread formed on its inner circumferential surface.The electric actuator may further include a screw shaft inserted into the second member from an end of the second member opposite to the one side, having a male thread formed on its outer circumferential surface, and rotating about the central axis of the second member in response to rotation of the electric motor, and balls interposed between the screw shaft and the second member.

[0031] In the electric actuator for a construction machine, the central axis of rotation of the electric motor may extend parallel to the central axis of the second member at a position different from the central axis of the second member, and the electric actuator may include a transmission mechanism that transmits rotation of the electric motor to the screw shaft.

[0032] In the electric actuator for construction machinery, the first member may define a fluid chamber to which a fluid is supplied or discharged, and the second member may have a piston that divides the fluid chamber into two in a direction along the central axis of the first member, and a rod extending from the piston to the one side.The electric actuator for construction machinery may also include a fluid circuit that supplies or discharges a fluid to or from each of the two divided fluid chambers in response to drive of a pump driven by the electric motor.

[0033] In the electric actuator for a construction machine, the second member may be columnar and extend in a direction along the central axis of the first member, and may have a plurality of rack teeth on its outer surface aligned in the direction along the central axis of the first member. The electric actuator may also include a pinion gear that is rotatable about an axis that intersects with the central axis of the second member, has teeth on its outer circumferential surface that mesh with the rack teeth, and is rotationally driven by the electric motor.

[0034] In an electric actuator for a construction machine, the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is rotatably supported on the lower body by a swivel bearing, and the central axis of rotation of the electric motor coincides with the central axis of the pinion gear, and when viewed in a plane facing in a direction along the central axis of rotation, when an imaginary line segment connecting the central axis of rotation of the upper body and the central axis of rotation is defined as a first line segment, and when an imaginary line segment connecting an end of the first member opposite to the side where the second member is inserted and an end of the second member on one side in the direction along the central axis of the first member is defined as a second line segment, the central axis of rotation of the electric motor may be located between the first line segment and the second line segment.

[0035] A construction machine for solving the above problem comprises a vehicle body, an electric motor attached to the vehicle body and outputting torque centered on a central axis of rotation, a swing bracket connected to the vehicle body so as to be rotatable about a central axis of rotation that intersects the central axis of rotation and extends above and below the vehicle body, a conversion mechanism that converts the torque of the electric motor centered on the central axis of rotation into torque centered on the central axis of rotation, a transmission member that transmits the torque converted by the conversion mechanism to the swing bracket, and a boom fixed to the swing bracket.

[0036] In the construction machine, the torque of the electric motor, whose direction has been converted by the conversion mechanism, is transmitted to the swing bracket via the transmission member. Then, as the electric motor operates, the boom swings together with the swing bracket. In other words, with the above configuration, the boom can be swung using the electric motor as a drive source.

[0037] An electric actuator for a construction machine that solves the above problem comprises an electric motor that outputs torque centered on a central axis of rotation, a swing bracket that is connected to the body of the construction machine so as to be rotatable about a central axis of rotation that extends in a direction intersecting the central axis of rotation and that is fixed to the boom, a conversion mechanism that converts the torque of the electric motor centered on the central axis of rotation into torque centered on the central axis of rotation, and a transmission member that transmits the torque converted by the conversion mechanism to the swing bracket.

[0038] In the electric actuator, the torque of the electric motor, whose direction has been converted by the conversion mechanism, is transmitted to the swing bracket via the transmission member. Then, as the electric motor operates, the boom swings together with the swing bracket. In other words, with the above configuration, the boom can be swung using the electric motor as a drive source. [Effects of the Invention]

[0039] According to the above technical concept, the boom can be swung using the electric motor as a drive source. [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 is a diagram schematically illustrating the overall configuration of a backhoe according to a first embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating a swing operation of the boom according to the first embodiment. [Figure 3] FIG. 3 is an end view of the boom swing mechanism of the first embodiment. [Figure 4] FIG. 4 is an enlarged end view of a portion of FIG. [Figure 5] FIG. 5 is a side view that schematically illustrates the backhoe of the second embodiment. [Figure 6] FIG. 6 is a top view schematically illustrating the backhoe of the second embodiment. [Figure 7] FIG. 7 is a top view schematically showing a modified example of the backhoe of the second embodiment. [Figure 8] FIG. 8 is a top view schematically showing a modified example of the backhoe of the second embodiment. [Figure 9] FIG. 9 is a side view that schematically illustrates the backhoe of the third embodiment. [Figure 10] FIG. 10 is a side view that schematically illustrates the backhoe of the fourth embodiment. [Figure 11] FIG. 11 is a top view schematically showing the backhoe of the fourth embodiment. [Figure 12] FIG. 12 is an end view that schematically shows the power unit of the fourth embodiment. [Figure 13] FIG. 13 is a top view illustrating a state in which the boom of the fourth embodiment is swung to the left. [Figure 14] FIG. 14 is a top view illustrating a state in which the boom of the fourth embodiment is swung to the right. [Figure 15] FIG. 15 is a cross-sectional view that schematically shows a modified example of the power unit of the fourth embodiment. [Figure 16] FIG. 16 is a cross-sectional view that schematically shows a modified example of the power unit of the fourth embodiment. [Figure 17] FIG. 17 is a diagram schematically showing an example of the arrangement of the power unit according to FIG. 16. [Figure 18] FIG. 17 is a perspective view schematically illustrating a first member and a second member of the power unit according to FIG. 16. [Figure 19] FIG. 19 is a side view that schematically illustrates the backhoe of the fifth embodiment. [Figure 20] FIG. 20 is a side view schematically showing a modified example of the buffer member of the fifth embodiment. [Figure 21] FIG. 21 is a side view that schematically shows a modified example of the backhoe of the fifth embodiment. [Figure 22] FIG. 22 is a side view that schematically illustrates the backhoe of the sixth embodiment. [Figure 23] FIG. 23 is a top view schematically illustrating the gear wall and the pinion gear of the sixth embodiment. [Figure 24] FIG. 24 is a side view that schematically shows a modified example of the backhoe of the sixth embodiment. [Figure 25] FIG. 25 is a side view that schematically illustrates the backhoe of the seventh embodiment. [Figure 26] FIG. 26 is a side view that schematically illustrates the backhoe of the eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0041] First Embodiment A first embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to Figures 1 to 4. Note that the drawings may show components enlarged to facilitate understanding, and the dimensional ratios of the components may differ from those in the actual drawings or from those in other drawings.

[0042] <Overall structure> As shown in FIG. 1 , a backhoe 500, which is a construction machine, includes a traveling device 510, a mother machine 520 serving as a vehicle body, a boom 530, an arm 540, and a bucket 550. The traveling device 510 includes crawlers for traveling, etc. The mother machine 520 is located on the opposite side of the traveling device 510 from the road surface. The mother machine 520 includes a seat for an operator, a battery storage section, etc. Note that FIG. 1 does not illustrate the exterior of the seat. In this embodiment, up, down, left, right, front, and rear are defined with respect to the backhoe 500. That is, the direction in which the mother machine 520 is located as viewed from the traveling device 510 is the upward direction. Furthermore, the front direction when an operator sits in the seat of the mother machine 520 is the forward direction. The mother machine 520 can rotate left and right relative to the traveling device 510 around an axis extending substantially upward. The boom 530 extends forward from the mother machine 520. The boom 530 will be described in detail below. The arm 540 is long. A base end of the arm 540 is connected to a tip end of the boom 530 on the opposite side from the mother machine 520. The arm 540 is rotatable relative to the boom 530 around the base end of the arm 540. The arm 540 extends forward from the boom 530. A base end of the bucket 550 is connected to a tip end of the arm 540 on the opposite side from the boom 530. The bucket 550 is rotatable relative to the arm 540 around the base end of the bucket 550. The bucket 550 is box-shaped with an opening.

[0043] <Boom swing mechanism> The backhoe 500 is provided with a boom swing mechanism 10 at the connection between the mother machine 520 and the boom 530. The boom swing mechanism 10 constitutes an electric actuator. As shown in FIG. 2, the boom swing mechanism 10 is a mechanism for swinging the boom 530 left and right relative to the mother machine 520. The boom swing mechanism 10 of this embodiment includes the mother machine 520 as a component of the boom swing mechanism 10. A front portion of the mother machine 520 is referred to as the mother machine front section 520A. As shown in FIG. 3, the mother machine front section 520A has an overall rectangular parallelepiped shape. The mother machine front section 520A is provided with a first through-hole 520H. The first through-hole 520H passes through the mother machine front section 520A in the vertical direction. The central axis Q of the first through-hole 520H extends substantially upward. Note that in each drawing, cross-sectional structures of some components of the boom swing mechanism 10 are omitted and shown as plan views.

[0044] <First holding member> As shown in FIG. 3, the boom swing mechanism 10 includes a first retaining member 41. The first retaining member 41 is located above the mother machine front section 520A. The first retaining member 41 includes a first mounting wall 41A, a first standing wall 41B, and a first retaining wall 41C. The first mounting wall 41A is disposed along the upper surface of the mother machine front section 520A. The first mounting wall 41A is fixed to the upper surface of the mother machine front section 520A by a bolt B. Note that in FIGS. 1, 3, and 4, the bolt B is indicated by a dot. The first standing wall 41B extends upward from the front end of the first mounting wall 41A. The first retaining wall 41C extends forward from the upper end of the first standing wall 41B. The first retaining wall 41C includes a through-hole 41H. The through-hole 41H passes vertically through the first retaining wall 41C. The central axis Q of the through hole 41H substantially coincides with the central axis Q of the first through hole 520H. In addition, in Fig. 1, Fig. 3, and Fig. 4, the axis whose central axis substantially coincides with that of the first through hole 520H is commonly designated by the symbol Q.

[0045] <Electric motor> The boom swing mechanism 10 includes an electric motor 20. The electric motor 20 is located above the first retaining wall 41C as a whole. The electric motor 20 includes a housing 20A and an output shaft 20B. The housing 20A is fixed to the upper surface of the first retaining wall 41C. That is, the housing 20A is attached to the mother machine front section 520A via the first retaining member 41. The housing 20A accommodates a stator, a rotor, and other components (not shown). The output shaft 20B extends inside the housing 20A and protrudes downward relative to the housing 20A. The output shaft 20B is cylindrical. The diameter of the output shaft 20B is smaller than the diameter of the through-hole 41H in the first retaining wall 41C. The central axis Q of the output shaft 20B substantially coincides with the central axis Q of the through-hole 41H in the first retaining wall 41C. The output shaft 20B is rotatable about a central axis Q of the output shaft 20B and is rotatable relative to the housing 20A. The output shaft 20B is rotatable in both forward and reverse directions by receiving power from a battery (not shown).

[0046] <Transmission shaft> The boom swing mechanism 10 includes a transmission shaft 25. The transmission shaft 25 is disposed within the first through-hole 520H of the mother machine front section 520A. The transmission shaft 25 passes through the first through-hole 520H. The transmission shaft 25 is cylindrical. The central axis Q of the transmission shaft 25 substantially coincides with the central axis Q of the first through-hole 520H. Hereinafter, the direction along the central axis Q of the transmission shaft 25 will be simply referred to as the axial direction. The radial direction centered on the central axis Q of the transmission shaft 25 will be simply referred to as the radial direction. The circumferential direction centered on the central axis Q of the transmission shaft 25 will be simply referred to as the circumferential direction. In the axial direction, the dimension of the transmission shaft 25 is larger than the dimension of the first through-hole 520H. The transmission shaft 25 protrudes both upward and downward from the first through-hole 520H. The upper end of the transmission shaft 25 is connected to the output shaft 20B of the electric motor 20. For example, the upper end of the transmission shaft 25 and the output shaft 20B of the electric motor 20 are fixed to each other by a spline connection. The central axis Q of the transmission shaft 25 substantially coincides with the central axis Q of the output shaft 20B. The transmission shaft 25 is coaxial with the output shaft 20B and rotates integrally with the output shaft 20B.

[0047] <Pin> The boom swing mechanism 10 includes a pin 28. The pin 28 is disposed within a first through-hole 520H in the mother machine front section 520A. The pin 28 passes through the first through-hole 520H. The pin 28 is cylindrical. The central axis Q of the pin 28 substantially coincides with the central axis Q of the first through-hole 520H. The inner diameter of the pin 28 is larger than the diameter of the transmission shaft 25. The transmission shaft 25 is disposed within the pin 28. The transmission shaft 25 passes through the pin 28. In this manner, the pin 28 is disposed within the first through-hole 520H together with the transmission shaft 25. In the axial direction, the dimension of the pin 28 is larger than the dimension of the first through-hole 520H and smaller than the dimension of the transmission shaft 25. The pin 28 protrudes both upward and downward from the first through-hole 520H. The upper end of the pin 28 is located below the upper end of the transmission shaft 25. The lower end of the pin 28 is located above the lower end of the transmission shaft 25. The lower end of the pin 28 is supported by the opposing wall 53, which will be described later. The outer diameter of the pin 28 is slightly smaller than the diameter of the first through hole 520H. Therefore, a small gap (not shown) exists between the outer circumferential surface of the pin 28 and the inner surface of the first through hole 520H in the radial direction. This gap is referred to as the first gap. A restricting member C is inserted into the pin 28, extending from the front surface of the mother machine front section 520A to the pin 28. The restricting member C prevents the pin 28 from moving in the circumferential direction while allowing the pin 28 to move radially through the first gap. The gap between the inner circumferential surface of the pin 28 and the transmission shaft 25 is referred to as the second gap. The dimension of the second gap is larger in the radial direction than the dimension of the first gap. Therefore, even if the pin 28 moves radially through the first gap, the inner circumferential surface of the pin 28 does not come into contact with the transmission shaft 25. At the upper end of the pin 28, a seal member S1 is disposed between the inner peripheral surface of the pin 28 and the transmission shaft 25 to prevent foreign matter from entering from the outside.

[0048] <Second holding member> The boom swing mechanism 10 includes a second holding member 42. The second holding member 42 is located below the mother machine front section 520A. As shown in FIG. 4, the second holding member 42 includes a second mounting wall 42A, a second standing wall 42B, and a second holding wall 42C. The second mounting wall 42A is disposed along the lower surface of the mother machine front section 520A. The second mounting wall 42A is fixed to the lower surface of the mother machine front section 520A by bolts B. The second standing wall 42B extends downward from the front end of the second mounting wall 42A. The second holding wall 42C extends forward from the lower end of the second standing wall 42B. A reducer 70 is located on the upper surface of the second holding wall 42C. Details of the reducer 70 will be described later.

[0049] <Output component> As shown in FIG. 4, the boom swing mechanism 10 includes an output member 30. The output member 30 is located between the reducer 70 and the mother machine front section 520A. The output member 30 includes an output wall 32 and a protruding wall 34. The output wall 32 is annular and plate-shaped. A central axis Q of the output wall 32 substantially coincides with the central axis Q of the transmission shaft 25. The output wall 32 includes a plurality of second through holes 32H. Each second through hole 32H is located at an end of the output wall 32 closer to the outer periphery. The plurality of second through holes 32H are aligned at equal intervals in the circumferential direction. Each second through hole 32H passes through the output wall 32 in the vertical direction. The central axis of each second through hole 32H is substantially parallel to the central axis Q of the output wall 32. Note that a circumferential portion of the end of the output wall 32 closer to the outer periphery is located forward of the mother machine front section 520A.

[0050] The protruding wall 34 protrudes from the upper surface of the output wall 32. The protruding wall 34 is located at the end of the output wall 32 closer to the inner periphery. The protruding wall 34 extends annularly along the central hole in the output wall 32. The inner surface of the protruding wall 34 is flush with the inner surface of the central hole in the output wall 32.

[0051] <Swing wall> 3, the boom swing mechanism 10 includes a swing wall 50. The swing wall 50 includes an opposing wall 53, a guide wall 59, an intermediate wall 57, and a contact wall 54. The swing wall 50 is an example of a swing bracket.

[0052] As shown in Fig. 4, the opposing wall 53 is located between the upper surface of the output wall 32 and the lower surface of the mother machine front part 520A. The opposing wall 53 is disk-shaped. The diameter of the circle of the opposing wall 53 approximately coincides with the outer diameter of the output wall 32. The central axis Q of the disk of the opposing wall 53 approximately coincides with the central axis Q of the output wall 32. The opposing wall 53 is supported at this position by the output wall 32 via a washer W, which will be described later.

[0053] The opposing wall 53 has a central hole 53A. The central hole 53A passes through the opposing wall 53 from top to bottom. The central axis Q of the central hole 53A substantially coincides with the central axis Q of the opposing wall 53. The diameter of the central hole 53A substantially coincides with the inner diameter of the pin 28. The lower end of the transmission shaft 25, which is disposed inside the pin 28, is located within the central hole 53A.

[0054] The opposing wall 53 has a central recess 53U. The central recess 53U is recessed upward from the lower surface of the opposing wall 53. The central recess 53U is a cylindrical recess. The central axis Q of the cylinder of the central recess 53U approximately coincides with the central axis Q of the central hole 53A. The diameter of the cylinder of the central recess 53U is slightly larger than the outer diameter of the protruding wall 34 of the output member 30. The protruding wall 34 extends into the central recess 53U. A seal member S2 that prevents foreign matter from entering is arranged between the side surface of the central recess 53U and the outer peripheral surface of the protruding wall 34.

[0055] The portion of the opposing wall 53 that is radially outward of the central recess 53U is referred to as the specific portion 53P. The lower surface of the specific portion 53P faces the upper surface of the output wall 32 in the axial direction.

[0056] The opposing wall 53 has a plurality of third through holes 53H. The third through holes 53H are provided for each second through hole 32H in the output wall 32. That is, each third through hole 53H is provided in a pair with a corresponding one of the plurality of second through holes 32H. The number of third through holes 53H matches the number of second through holes 32H. Each third through hole 53H is located at an end of the specific portion 53P closer to the outer periphery. Each third through hole 53H is arranged at the same position as its paired second through hole 32H in both the circumferential and radial directions. The central axis of each third through hole 53H substantially coincides with the central axis of its paired second through hole 32H. That is, each third through hole 53H faces its paired second through hole 32H. The diameter of each third through hole 53H substantially coincides with the diameter of each second through hole 32H.

[0057] A plurality of washers W are interposed between the specific portion 53P of the opposing wall 53 and the output wall 32. Each washer W is annular and plate-shaped. A washer W is provided for each third through hole 53H. That is, each washer W is paired with a plurality of third through holes 53H and, ultimately, with a second through hole 32H. Each washer W is disposed at the same position as its corresponding third through hole 53H in both the circumferential and radial directions. The presence of the washers W between the specific portion 53P and the output wall 32 creates a gap between the specific portion 53P and the output wall 32 in the axial direction that corresponds to the thickness of the washer W. This gap is referred to as a third gap. The dimension of the third gap in the axial direction is larger than the dimension of the first gap in the radial direction.

[0058] <Guide wall> As shown in FIG. 4 , the guide wall 59 protrudes from the upper surface of the opposing wall 53. The guide wall 59 is integrally molded with the opposing wall 53. The guide wall 59 is cylindrical. The central axis Q of the guide wall 59 substantially coincides with the central axis Q of the opposing wall 53. The inner diameter of the guide wall 59 is slightly larger than the outer diameter of the pin 28. The inner circumferential surface of the guide wall 59 and an inner circumferential portion of the opposing wall 53 that is located radially inward of the guide wall 59 define an accommodating recess that accommodates the lower end of the pin 28. The inner circumferential portion supports the lower end surface of the pin 28.

[0059] <Intermediate wall> As shown in FIG. 3 , the intermediate wall 57 protrudes from the upper surface of the opposing wall 53. The intermediate wall 57 is integrally molded with the opposing wall 53. The intermediate wall 57 is located in a forward portion of the opposing wall 53. The intermediate wall 57 surrounds the portion of the mother unit front section 520A that is forward of the pin 28 from the outside. In other words, the intermediate wall 57 faces the front surface of the mother unit front section 520A and the portions of the left and right side surfaces of the mother unit front section 520A that are forward of the pin 28. For example, when viewed from above, the intermediate wall 57 has an arc shape centered on the central axis Q of the first through hole 520H. In terms of the radial direction, the intermediate wall 57 is located slightly inward from the third through hole 53H of the opposing wall 53. The upper end of the intermediate wall 57 is located above the upper surface of the mother unit front section 520A and below the lower surface of the first holding wall 41C of the first holding member 41.

[0060] <Contact wall> As shown in FIG. 3, the contact wall 54 is positioned above the upper end of the intermediate wall 57 as a whole. The contact wall 54 includes a main portion 54A and an extension portion 54B. The main portion 54A covers the upper opening of the intermediate wall 57 and extends rearward from the upper opening. The rear end of the main portion 54A reaches between the upper surface of the mother machine front portion 520A and the lower surface of the first retaining wall 41C. A plurality of locations on a front portion of the main portion 54A are fixed to the upper end of the intermediate wall 57 by bolts B. The main portion 54A includes through holes. The through holes are located in a rearward portion of the main portion 54A. The through holes pass vertically through the main portion 54A. The extension portion 54B protrudes from the lower surface of the main portion 54A. The extension portion 54B is cylindrical. The central axis Q of the extension portion 54B substantially coincides with the central axis Q of the through hole in the main portion 54A. The inner diameter of the extension portion 54B substantially coincides with the diameter of the through hole in the main portion 54A. The inner peripheral surface of the extension portion 54B and the inner surface of the through hole in the main portion 54A form a continuous fourth through hole 54H. The central axis Q of the fourth through hole 54H substantially coincides with the central axis Q of the pin 28. The diameter of the fourth through hole 54H substantially coincides with the outer diameter of the pin 28. A portion of the pin 28 that protrudes upward relative to the first through hole 520H is inserted into the fourth through hole 54H. The inner surface of the fourth through hole 54H and the outer peripheral surface of the pin 28 are in contact. The lower end surface of the extension portion 54B is supported by the upper surface of the mother machine front portion 520A.

[0061] <boom> As shown in FIGS. 1 and 3, the boom swing mechanism 10 of this embodiment includes a boom 530 as a component of the boom swing mechanism 10.

[0062] The boom 530 includes a base wall 534, a connecting shaft 532, and a boom main body 531. The base wall 534 extends forward relative to the intermediate wall 57. The base wall 534 is fixed to the surface of the intermediate wall 57 opposite to the surface facing the mother machine front section 520A. As described above, the contact wall 54 and the opposing wall 53 are fixed to the intermediate wall 57. That is, the contact wall 54 and the opposing wall 53 are fixed to the base wall 534 via the intermediate wall 57.

[0063] The connecting shaft 532 connects the base wall 534 and the boom main body 531. The connecting shaft 532 is cylindrical. The central axis of the connecting shaft 532 extends to the left and right. The connecting shaft 532 is rotatable relative to the base wall 534 by receiving power from an electric motor (not shown).

[0064] As shown in Fig. 1, boom main body 531 has an elongated shape. One end of boom main body 531 is fixed to connecting shaft 532. As shown by arrow P1 in Fig. 1, boom main body 531 rotates integrally with connecting shaft 532. An arm 540 is connected to the other end of boom main body 531.

[0065] <Connection parts> As shown in FIG. 4, the boom swing mechanism 10 includes a plurality of connecting members 90. One connecting member 90 is provided for each second through hole 32H in the output wall 32. That is, each connecting member 90 is provided in a pair with one of the plurality of second through holes 32H. Each connecting member 90 includes a base 91 and a buffer portion 92. The base 91 has a stepped shape. That is, the base 91 includes a cylindrical first portion 91A and a cylindrical second portion 91B having a larger diameter than the first portion 91A. The diameter of the second portion 91B is larger than the diameter of the second through hole 32H. The central axis of the first portion 91A and the central axis of the second portion 91B are substantially aligned. The base 91 is made of an iron-based metal.

[0066] The buffer portion 92 is cylindrical. The inner diameter of the buffer portion 92 is approximately the same as the diameter of the first portion 91A of the base portion 91. The outer diameter of the buffer portion 92 is approximately the same as the diameter of the second through-hole 32H. The first portion 91A of the base portion 91 is disposed inside the buffer portion 92. The first portion 91A of the base portion 91 penetrates the buffer portion 92. The central axis of the buffer portion 92 is approximately the same as the central axis of the base portion 91. The buffer portion 92 is made of rubber. That is, the buffer portion 92 is made of a material that is softer than the base portion 91. In other words, the elastic modulus of the buffer portion 92 is smaller than the elastic modulus of the base portion 91.

[0067] The buffer portion 92, together with the first portion 91A of the base 91, is disposed inside the second through-hole 32H, the washer W, and the third through-hole 53H that form a pair. The buffer portion 92, together with the first portion 91A, passes through the second through-hole 32H, the washer W, and the third through-hole 53H. The central axis of the buffer portion 92 substantially coincides with the central axes of the second through-hole 32H and the third through-hole 53H. The outer peripheral surface of the buffer portion 92 contacts the inner surfaces of the second through-hole 32H and the third through-hole 53H. The second portion 91B of the base 91 is located below the lower ends of the buffer portion 92 and the second through-hole 32H. The upper end of the first portion 91A of the base 91 protrudes upward relative to the upper ends of the buffer portion 92 and the third through-hole 53H. The portions of the first portion 91A that protrude from the buffer portion 92 and the third through-hole 53H are prevented from coming off by a nut N. The second portion 91B and the nut N define the vertical position of the connecting member 90. At the same time, the connecting member 90 connects the output wall 32 and the opposing wall 53. As described above, the opposing wall 53 is fixed to the base wall 534 of the boom 530. That is, the output wall 32 is connected to the boom 530 via the connecting member 90 and the opposing wall 53.

[0068] <Reducer> 3, the boom swing mechanism 10 includes a reducer 70. The reducer 70 is located on the opposite side of the first through-hole 520H of the mother machine 520 from the electric motor 20. The reducer 70 is a transmission that changes the rotational speed of the output shaft 20B of the electric motor 20 and outputs the result.

[0069] The reducer 70 includes a carrier 80. The carrier 80 includes a first wall 81, a second wall 82, and a plurality of pillar walls 83. As shown in FIG. 4, the first wall 81 is located on the upper surface of the second retaining wall 42C. The first wall 81 is disk-shaped. The lower surface of the first wall 81 is in contact with the upper surface of the second retaining wall 42C. The first wall 81 is fixed to the upper surface of the second retaining wall 42C by bolts B. That is, the first wall 81 and therefore the reducer 70 are attached to the mother machine front part 520A via the second retaining member 42. The central axis Q of the disk of the first wall 81 substantially coincides with the central axis Q of the output wall 32.

[0070] The first wall 81 has an input shaft hole 81A. The input shaft hole 81A is located near the center of the first wall 81. The input shaft hole 81A passes through the first wall 81 from top to bottom. The central axis Q of the input shaft hole 81A substantially coincides with the central axis Q of the first wall 81. A seal member K is disposed at the lower end of the input shaft hole 81A.

[0071] The first wall 81 has a plurality of eccentric shaft holes 81B. The number of eccentric shaft holes 81B is, for example, three. In terms of the radial direction, each eccentric shaft hole 81B is located at a position deviated from the central axis Q of the first wall 81. Each eccentric shaft hole 81B penetrates the first wall 81 from top to bottom. The multiple eccentric shaft holes 81B are lined up at equal intervals in the circumferential direction. A seal member K is disposed at the lower end of each eccentric shaft hole 81B.

[0072] The plurality of pillar walls 83 protrude from the upper surface of the first wall 81. The number of pillar walls 83 is, for example, three. In the radial direction, each pillar wall 83 is located at a position deviated from the central axis Q of the first wall 81. Each pillar wall 83 is cylindrical. The plurality of pillar walls 83 are arranged at equal intervals in the circumferential direction. Each pillar wall 83 is integrally molded with the first wall 81.

[0073] The second wall 82 is located above each pillar wall 83. The second wall 82 basically has the same configuration as the first wall 81. That is, the second wall 82 is disk-shaped and has an input shaft hole 82A that pairs with the input shaft hole 81A of the first wall 81. The central axis Q of the input shaft hole 82A of the second wall 82 approximately coincides with the central axis Q of the input shaft hole 81A of the first wall 81. The second wall 82 has a plurality of eccentric shaft holes 82B that respectively pair with the plurality of eccentric shaft holes 81B of the first wall 81. That is, the number of eccentric shaft holes 82B of the second wall 82 matches the number of eccentric shaft holes 81B of the first wall 81. The central axes of the paired eccentric shaft holes 81B, 82B approximately coincide with each other. The second wall 82 is fixed to the upper end surface of each pillar wall 83 with bolts B. The upper surface of the second wall 82 faces the bottom of the recess of the central recess 53U in the opposing wall 53. The upper surface of the second wall 82 is located at a position away from the bottom of the recess of the central recess 53U. The diameter of the circle of the second wall 82 is slightly smaller than the diameter of the circle of the first wall 81.

[0074] <Case> As shown in FIG. 4, the reducer 70 includes a case 75. The case 75 is located above the first wall 81. The case 75 includes a case body 75A and a plurality of teeth 75B. The case body 75A is cylindrical. The outer diameter of the case body 75A approximately matches the diameter of the circle of the first wall 81. The inner diameter of the case body 75A is larger than the diameter of the circle of the second wall 82. The inner diameter of the case body 75A approximately matches the diameter of the central hole in the output wall 32. The central axis Q of the case body 75A approximately matches the central axis Q of the output wall 32. The lower end surface of the case body 75A faces a portion of the upper surface of the first wall 81 that is closer to the outer periphery. The upper end surface of the case body 75A faces the lower surface of the output wall 32. The case body 75A is fixed to the output wall 32 with bolts B.

[0075] A plurality of teeth 75B protrude from the inner peripheral surface of the case body 75A. The plurality of teeth 75B are arranged at equal intervals in the circumferential direction. In the axial direction, each tooth 75B is located near the center of the case body 75A. In the axial direction, bearings G are located on both the upper and lower sides of each tooth 75B. The upper bearing G is interposed between the inner peripheral surface of the case body 75A and the outer peripheral surface of the second wall 82. The lower bearing G is interposed between the inner peripheral surface of the case body 75A and the stepped surface of the first wall 81. Each bearing G rotatably supports the case body 75A. And, by being supported by each bearing G, the case body 75A is rotatable relative to the carrier 80.

[0076] <External gear> The reducer 70 includes a first external gear 71. The first external gear 71 is located between a first wall 81 and a second wall 82 of the carrier 80 and is located inside the case main body 75A. In each drawing, the external appearance of the rear side of the cross section of the first external gear 71 and a second external gear 72 (described later) is also shown to clearly show their structures. The first external gear 71 is generally disk-shaped. The diameter of the first external gear 71 is smaller than the inner diameter of the case main body 75A. The central axis of the disk of the first external gear 71 is approximately parallel to the central axis Q of the case main body 75A. A plurality of teeth are formed on the outer peripheral surface of the first external gear 71. The plurality of teeth are arranged at equal intervals in the circumferential direction. In each drawing, the teeth of the first external gear 71 are not shown. Among the plurality of teeth, teeth located in a partial range in the circumferential direction mesh with teeth 75B of the case 75. On the other hand, among the plurality of teeth, there is a gap between the teeth positioned outside the above range in the circumferential direction and the teeth 75B of the case 75.

[0077] The first external gear 71 has an input shaft hole X1. The input shaft hole X1 is located near the center of the first external gear 71. The input shaft hole X1 passes through the first external gear 71 from top to bottom. The input shaft hole X1 communicates with an input shaft hole 81A of the first wall 81.

[0078] The first external gear 71 has a plurality of eccentric shaft holes X2. The plurality of eccentric shaft holes X2 are provided in pairs with the plurality of eccentric shaft holes 81B provided in the first wall 81. In other words, the number of eccentric shaft holes X2 is the same as the number of eccentric shaft holes 81B provided in the first wall 81. In the radial direction, each eccentric shaft hole X2 is located at a position deviated from the central axis of the first external gear 71. Each eccentric shaft hole X2 passes through the first external gear 71 from top to bottom. Each eccentric shaft hole X2 is in communication with its corresponding eccentric shaft hole 81B in the first wall 81.

[0079] The first external gear 71 has a plurality of columnar holes X3. In the radial direction, each columnar hole X3 is located at a position deviated from the central axis of the first external gear 71. Each columnar hole X3 passes through the first external gear 71 from top to bottom. A columnar hole X3 is provided for each column wall 83. The column wall 83 passes through each columnar hole X3.

[0080] The reducer 70 includes a second external gear 72. The second external gear 72 is located between the first external gear 71 and a second wall 82 of the carrier 80, and is located inside the case main body 75A. The second external gear 72 has basically the same configuration as the first external gear 71. That is, the second external gear 72 includes a column hole Y3 for each column wall 83. The second external gear 72 also includes an input shaft hole Y1 near the center of the second external gear 72. The input shaft hole Y1 communicates with the input shaft hole X1 of the first external gear 71 and the input shaft hole 82A of the second wall 82. As a result, the input shaft hole 81A of the first wall 81, the input shaft hole X1 of the first external gear 71, the input shaft hole Y1 of the second external gear 72, and the input shaft hole 82A of the second wall 82 form a continuous first communicating hole. The second external gear 72 also has a plurality of eccentric shaft holes Y2 that pair with the plurality of eccentric shaft holes X2 formed in the first external gear 71 and the plurality of eccentric shaft holes 82B formed in the second wall 82. Each eccentric shaft hole Y2 is in communication with the corresponding eccentric shaft hole X2 in the first external gear 71 and the corresponding eccentric shaft hole 82B in the second wall 82. As a result, the eccentric shaft hole 81B in the first wall 81, the eccentric shaft hole X2 in the first external gear 71, the eccentric shaft hole Y2 in the second external gear 72, and the eccentric shaft hole 82B in the second wall 82 form a continuous second communicating hole. There are a plurality of second communicating holes corresponding to the number of eccentric shaft holes 81B in the first wall 81. The second communicating holes are also arranged at equal intervals in the circumferential direction.

[0081] <Crankshaft> The reducer 70 includes a plurality of crankshafts 77. A crankshaft 77 is provided for each of the series of second communication holes formed by the eccentric shaft holes 81B and the like of the first wall 81. Each crankshaft 77 includes a main shaft portion 77P, a first eccentric portion 77A, and a second eccentric portion 77B.

[0082] A majority of the main shaft portion 77P is located in the second communicating hole. The main shaft portion 77P is cylindrical. The main shaft portion 77P extends in the axial direction. The upper end of the main shaft portion 77P protrudes upward from the upper end of the second communicating hole, i.e., the upper end of the eccentric shaft hole 82B in the second wall 82. A bearing L is interposed between the outer peripheral surface of the main shaft portion 77P and the inner surface of the eccentric shaft hole 82B in the second wall 82. The main shaft portion 77P is rotatably supported by the bearing L. Although not shown, the main shaft portion 77P is also rotatably supported by a bearing within the eccentric shaft hole 81B in the first wall 81.

[0083] The first eccentric portion 77A is located in a midway portion of the main shaft portion 77P in the axial direction. The first eccentric portion 77A is located inside the eccentric shaft hole X2 of the first external gear 71. The first eccentric portion 77A protrudes from the outer peripheral surface of the main shaft portion 77P. In a plan view facing the axial direction, the outer shape of the first eccentric portion 77A is circular. In a plan view facing the axial direction, the center of the first eccentric portion 77A is offset from the center of the main shaft portion 77P. A bearing J is interposed between the outer peripheral surface of the first eccentric portion 77A and the inner surface of the eccentric shaft hole X2 of the first external gear 71. The first eccentric portion 77A is rotatably supported by the bearing J.

[0084] The second eccentric portion 77B is located in a midway portion of the main shaft portion 77P in the axial direction. The second eccentric portion 77B is located within the eccentric shaft hole Y2 of the second external gear 72. Like the first eccentric portion 77A, the second eccentric portion 77B protrudes from the outer peripheral surface of the main shaft portion 77P. In a plan view facing the axial direction, the outer shape of the second eccentric portion 77B is circular. In a plan view facing the axial direction, the center of the second eccentric portion 77B is shifted from the center of the first eccentric portion 77A and the center of the main shaft portion 77P. A bearing J is interposed between the outer peripheral surface of the second eccentric portion 77B and the inner surface of the eccentric shaft hole Y2 of the second external gear 72. The second eccentric portion 77B is rotatably supported by the bearing J.

[0085] The reducer 70 includes a plurality of driven gears 79. One driven gear 79 is provided for each crankshaft 77. Each driven gear 79 is attached to a portion of the main shaft portion 77P of the crankshaft 77 that protrudes upward relative to the eccentric shaft hole 82B of the second wall 82. Each driven gear 79 is in the shape of a roughly annular plate. The main shaft portion 77P is fixed to a central hole of each driven gear 79. Each driven gear 79 rotates integrally with the main shaft portion 77P. A plurality of teeth are formed on the outer peripheral surface of each driven gear 79. The plurality of teeth are arranged at equal intervals in the circumferential direction.

[0086] <Input shaft> The reducer 70 includes an input shaft 76. A portion of the input shaft 76 is located in a continuous first communication hole formed by the input shaft hole 81A of the first wall 81 and other components. The input shaft 76 is cylindrical. The input shaft 76 extends upward from the first communication hole to the lower end of the transmission shaft 25. The central axis Q of the input shaft 76 substantially coincides with the central axes Q of the case 75 and the transmission shaft 25. The upper end of the input shaft 76 is connected to the lower end of the transmission shaft 25. For example, the upper end of the input shaft 76 is fixed to the lower end of the transmission shaft 25 by a spline connection. The input shaft 76 is coaxial with the transmission shaft 25 and rotates integrally with the transmission shaft 25. The input shaft 76 is rotatably supported by a bearing F in the input shaft hole 82A in the second wall 82. Although not shown, the input shaft 76 is also rotatably supported by a bearing in the input shaft hole 81A in the first wall 81.

[0087] The reducer 70 includes a drive gear 78. The drive gear 78 is attached to an input shaft 76. More specifically, the drive gear 78 is attached to a portion of the input shaft 76 that protrudes upward relative to the first communicating hole. The drive gear 78 is in the shape of a roughly annular plate. The input shaft 76 is fixed to a central hole of the drive gear 78. The drive gear 78 rotates integrally with the input shaft 76. A plurality of teeth are formed on the outer circumferential surface of the drive gear 78. The plurality of teeth are arranged at equal intervals in the circumferential direction. Some of the plurality of teeth mesh with the teeth of a driven gear 79.

[0088] The boom swing mechanism 10 is configured as described above. All of the components of the boom swing mechanism 10 of this embodiment are made of metal, except for the buffer section 92 and the sealing members.

[0089] <Operation 1 of First Embodiment> The operation of the boom swing mechanism 10 shown in Figure 3 will be described. In the boom swing mechanism 10, when the output shaft 20B of the electric motor 20 rotates, the transmission shaft 25 and the input shaft 76 of the reducer 70 rotate together with the output shaft 20B. When the input shaft 76 of the reducer 70 rotates, the drive gear 78 and the driven gear 79 rotate. When the driven gear 79 rotates, the crankshaft 77 rotates. The crankshaft 77 transmits the rotation input thereto to the first external gear 71 and the second external gear 72 via the first eccentric portion 77A and the second eccentric portion 77B. The first external gear 71 and the second external gear 72 receive forces from the first eccentric portion 77A and the second eccentric portion 77B and swing and rotate. That is, the first external gear 71 revolves around the central axis Q of the input shaft 76 and therefore the transmission shaft 25 while oscillating so that the circumferential range in which it meshes with the teeth 75B of the case 75 alternates. The second external gear 72 also operates in the same manner as the first external gear 71. The above-described operations of the first external gear 71 and the second external gear 72 drive the rotation of the case 75. When the case 75 rotates, the output wall 32 fixed to the case 75 rotates integrally with the case 75. That is, the output wall 32 receives torque from the reducer 70 and rotates around the central axis Q of the transmission shaft 25. The rotational speed of the case 75 and therefore the output wall 32 is reduced by a predetermined ratio relative to the rotational speed of the output shaft 20B of the electric motor 20. That is, the reducer 70 amplifies and outputs the torque output by the output shaft 20B of the electric motor 20. When the output wall 32 rotates, the opposing wall 53 connected to the output wall 32 via the connecting member 90 rotates. The opposing wall 53 rotates around the central axis Q of the transmission shaft 25. When the opposing wall 53 rotates, the base wall 534 of the boom 530 rotates together with the intermediate wall 57. This causes the boom main body 531 to rotate. Through this series of force transmissions, the boom 530 swings left and right around the output shaft 20B of the electric motor 20, as shown by arrow P2 in FIG. 2.

[0090] In the boom swing mechanism 10, the transmission shaft 25, the electric motor 20, the reducer 70, and the output member 30 constitute a drive device. The central axis Q of the transmission shaft 25 constitutes the central rotation axis of the drive device. In the drive device, the electric motor 20 is the drive source of the drive device. As described above, in the drive device, the output member 30 outputs torque centered on the central rotation axis in response to the electric motor 20 being driven. The swing wall 50 connected to this output member 30 is linked to the mother machine front section 520A via a pin 28 and the drive device so as to be rotatable about the central rotation axis. As described above, the swing wall 50 receives torque from the drive device and rotates about the central rotation axis.

[0091] <Operation 2 of First Embodiment> The functions of the pin 28 and the contact wall 54 will now be described. During excavation work by the excavator 500 shown in FIG. 1 , the bucket 550 collides with the excavation target. When the bucket 550 collides with the excavation target, a reaction impact from the excavation target is transmitted to the boom 530 via the arm 540. The direction of the load acting on the boom 530 due to the impact varies. For example, as shown by arrow P1 in FIG. 1 , the direction of the load acting on the boom 530 may be a direction that rotates the boom 530 up and down. Furthermore, as shown by arrow P2 in FIG. 2 , the direction of the load acting on the boom 530 may be a direction that rotates the boom 530 left and right. When the boom 530 receives a load in a direction including up and down, left and right, or both, it attempts to move in the direction in which the load is received. In the configuration of this embodiment, such movement of the boom 530 is transmitted to the mother machine 520 via the first path. As shown in FIG. 3 , the first path is a path that passes through the intermediate wall 57 of the swing wall 50, the contact wall 54, the pin 28, and the mother machine 520. In other words, when the boom main body 531 and therefore the base wall 534 move in response to the load acting on the boom 530, the intermediate wall 57 of the swing wall 50 moves accordingly. Since the contact wall 54 of the swing wall 50 is in contact with the pin 28, the movement of the intermediate wall 57 is transmitted to the pin 28 via the contact wall 54. The outer peripheral surface of the pin 28 then strikes the inner surface of the first through-hole 520H in the mother machine front part 520A. In this way, the load acting on the boom 530 is transmitted to the mother machine 520. The mother machine 520 then receives this load.

[0092] The function of the buffer portion 92 of the connecting member 90 will now be described. The boom 530, and therefore the swing wall 50, may rotate left or right due to the load described above. In this case, the movement may be transmitted to the reducer 70 via the second path described below. The second path is the intermediate wall 57 of the swing wall 50, the opposing wall 53, the connecting member 90, the output wall 32, and the case 75 of the reducer 70. Here, the buffer portion 92 of the connecting member 90 is made of rubber. Therefore, when transmitting a force from the opposing wall 53 to the output wall 32, the buffer portion 92 attenuates the force input from the opposing wall 53 and transmits it to the output wall 32. In other words, the movement of the output wall 32 is smaller than the movement of the opposing wall 53. Therefore, even if the load acting on the reducer 70 is transmitted to the reducer 70 via the second path, the force is significantly smaller.

[0093] <Effects of the first embodiment> (1-1) As described in Operation 1 of the above embodiment, according to the configuration of this embodiment, the rotation of the output shaft 20B of the electric motor 20 can be transmitted to the boom 530 via the following transmission path. This transmission path runs through the electric motor 20, the transmission shaft 25, the reducer 70, the output member 30, and the swing wall 50 to the boom 530. The output shaft 20B of the electric motor 20 can be operated through the transmission of power along this path to swing the boom 530 left and right. That is, according to this embodiment, a swing mechanism for the boom 530 using the electric motor 20 as a drive source can be realized. Furthermore, in order to realize a swing mechanism for the boom 530 using the electric motor 20 as a drive source, a layout in which the electric motor 20 and the reducer 70 are arranged above and below the mother machine front section 520A, as in this embodiment, can be adopted, thereby reducing the bulkiness of the components and effectively utilizing the space around the mother machine front section 520A. Therefore, the boom swing mechanism 10 can be made smaller overall.

[0094] (1-2) As described in action 2 of the above embodiment, when an impact is applied to the boom 530 via the bucket 550, the impact is transmitted to the mother machine 520 via the contact wall 54 and eventually the pin 28. The mother machine 520 then absorbs the impact. At this time, the mother machine 520 absorbs the load acting on the boom 530. By having the mother machine 520 absorb the load, the load reaching the reducer 70 via the second path described above is reduced. If the load acting on the reducer 70 is large, various components of the reducer 70, such as the column wall 83 or each bearing, need to be enlarged to absorb the load. As a result, the reducer 70 may become larger. According to the configuration of this embodiment, as described above, the load reaching the reducer 70 can be reduced, and therefore it is not necessary to enlarge each component of the reducer 70 to withstand the load. Therefore, the reducer 70 can be prevented from becoming larger.

[0095] (1-3) As described in action 2 of the above embodiment, when the boom 530 and therefore the opposing wall 53 of the swing wall 50 rotate left or right due to the load acting on the boom 530, the connection member 90 reduces the movement of the opposing wall 53 and transmits it to the output wall 32. Therefore, in the configuration of this embodiment, it is possible to prevent the left or right rotation acting on the opposing wall 53 from being transmitted to the reducer 70. Due to this and the effect obtained in (1-2) above, the load transmitted to the reducer 70 is significantly reduced. Therefore, similar to (1-2) above, it is possible to prevent the reducer 70 from becoming large.

[0096] <Modification of the first embodiment> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0097] The washer W may be eliminated. The third gap may exist throughout the entire range where the specific portion 53P of the opposing wall 53 and the output wall 32 face each other. Even in this case, the lower end surface of the extension portion 54B of the contact wall 54 is supported by the upper surface of the mother machine front section 520A, so the swing wall 50 can be held in the following position. This position is where the specific portion 53P of the opposing wall 53 and the output wall 32 face each other while being spaced apart. Eliminating the washer W and providing the third gap throughout the entire range where the specific portion 53P of the opposing wall 53 and the output wall 32 face each other can achieve the following effect. That is, when an impact is applied to the boom 530 via the bucket 550, even if the specific portion 53P of the opposing wall 53 moves up and down together with the base wall 534 of the boom 530, the specific portion 53P is less likely to come into contact with the output wall 32 due to the presence of the third gap in the axial direction. Therefore, when the specific portion 53P of the opposing wall 53 moves up and down, the load is prevented from being directly transmitted from the opposing wall 53 to the output wall 32. Accordingly, the load acting on the opposing wall 53 is less likely to be transmitted to the output wall 32. As described in the above embodiment, the dimension of the third gap in the axial direction is larger than the dimension of the first gap in the radial direction between the outer peripheral surface of the pin 28 and the inner surface of the first through-hole 520H in the mother machine front section 520A. Therefore, when the opposing wall 53 moves together with the base wall 534 due to an impact acting on the boom 530, the pin 28 strikes the mother machine front section 520A before the opposing wall 53 strikes the output wall 32. Therefore, most of the load acting on the boom 530 is absorbed by the mother machine 520. As a result, the load acting on the output wall 32 and, ultimately, the load acting on the reducer 70 can be significantly reduced. This contributes to preventing the size of the reducer 70 from increasing, similar to the above (1-2) and (1-3).

[0098] The material of the buffer portion 92 in the connecting member 90 is not limited to the example in the above embodiment. For example, the buffer portion 92 may be made of resin. As with the buffer portion 92, the material of the base portion 91 in the connecting member 90 is not limited to the example in the above embodiment. The materials of the buffer portion 92 and the base portion 91 only need to satisfy the following relationship: the elastic modulus of the buffer portion 92 is smaller than the elastic modulus of the base portion 91.

[0099] The configuration of the connecting member 90 is not limited to the example of the above embodiment. For example, the buffer portion 92 may be a polygonal cylindrical shape. Furthermore, the buffer portion 92 may be eliminated. The connecting member 90 may be configured in any way as long as it can connect the output wall 32 and the opposing wall 53. In other words, the connecting member 90 may be configured in any way as long as it can transmit the movement of the output wall 32 corresponding to the output of the reducer 70 to the opposing wall 53.

[0100] The connecting member 90 may be omitted. In this case, for example, the output wall 32 and the opposing wall 53 may be integrally molded. If the output wall 32 and the opposing wall 53 are integrally molded, the rotation of the reducer 70 can be transmitted to the boom 530 through this integral molding. Essentially, regardless of the presence or absence of the connecting member 90, it is sufficient that the structure extending from the output member 30 to the boom 530 is configured so that the rotation of the reducer 70 can be transmitted to the boom 530. With such a structure, the boom 530 can be swung left and right by the driving force of the electric motor 20 and, in turn, the power of the reducer 70. In other words, regardless of the presence or absence of the connecting member 90, it is sufficient that the electric motor 20 and the reducer 70 are connected by the transmission shaft 25, and that the output member 30, which rotates upon receiving the power of the reducer 70, is connected to the boom 530. Even without the connecting member 90, the presence of the pin 28 and the contact wall 54 can reduce the load input from the boom 530 to the reducer 70 when an impact is applied to the boom 530. As will be described later, the pin 28 and the contact wall 54 are not essential. That is, the connecting member 90 may be eliminated, and then the pin 28 and the contact wall 54 may also be eliminated.

[0101] The configuration of the output member 30 is not limited to the example of the above embodiment. For example, when the shape of the buffer portion 92 in the connection member 90 is changed as in the above modified example, the shape of the second through hole 32H may be changed accordingly. The output member 30 may be configured to receive power from the reducer 70 and rotate about the central axis Q of the transmission shaft 25.

[0102] The configuration of the swing wall 50 is not limited to the example of the above embodiment. The swing wall 50 only needs to be configured to transmit the power of the reducer 70 transmitted from the output member 30 to the boom 530. For example, as in the modified example of the output member 30 described above, when the shape of the buffer portion 92 in the connecting member 90 is changed, the shape of the third through-hole 53H in the opposing wall 53 may be changed accordingly. The guide wall 59 may be eliminated from the swing wall 50. Furthermore, in cases where the output wall 32 and the opposing wall 53 are integrally molded as in the modified example described above, the opposing wall 53 may be eliminated, or the swing wall 50 may not even exist as a wall portion.

[0103] As an example of changing the configuration of the swing wall 50, the shape of the contact wall 54 may be changed. The contact wall 54 may be fixed to the boom 530 and configured to come into contact with the pin 28 as the boom 530 moves when an impact is applied to the boom 530. If the contact wall 54 is configured to satisfy these conditions, when an impact is applied to the boom 530, the contact wall 54 can transmit the impact to the mother machine 520 via the pin 28.

[0104] The contact wall 54 is not essential. Even if the contact wall 54 is not provided, it is sufficient that the electric motor 20 and the reducer 70 are connected by the transmission shaft 25, and that the output member 30, which rotates by receiving power from the reducer 70, is connected to the boom 530. With this configuration, the boom 530 can be swung left and right by the driving force of the electric motor 20, as described above. Furthermore, if the contact wall 54 is eliminated and a connecting member 90 having a buffer portion 92 is employed or a configuration having a third gap is adopted, the load input from the boom 530 to the reducer 70 when an impact is applied to the boom 530 can be reduced, as described above. After eliminating the contact wall 54, either or both of the connecting member 90 having the buffer portion 92 and the third gap may be eliminated.

[0105] The restricting member C that restricts the movement of the pin 28 in the circumferential direction is not essential. The configuration of the pin 28 is not limited to the example of the above embodiment. For example, the pin 28 may be a polygonal cylindrical shape. The pin 28 is simply required to be cylindrical with the transmission shaft 25 disposed therein and to be disposed in the first through-hole 520H of the mother machine 520 together with the transmission shaft 25. If the pin 28 is configured to satisfy these conditions, the pin 28 can transmit the load from the contact wall 54 to the mother machine 520.

[0106] The pin 28 may be eliminated. As with the modified example of the contact wall 54, regardless of whether the pin 28 is present or not, it is sufficient that a structure is adopted in which the boom 530 can be swung left and right by the driving force of the electric motor 20.

[0107] The configuration of the reducer 70 is not limited to the example of the above embodiment. The reducer 70 may be configured to reduce the rotational speed of the output shaft 20B of the electric motor 20 and output the reduced rotational speed. Furthermore, a mechanism other than the reducer 70 may be used as the transmission. The transmission may be configured to change the rotational speed of the electric motor 20 input via the transmission shaft 25 and output the reduced rotational speed.

[0108] The configuration of the first holding member 41 is not limited to the example in the above embodiment. The first holding member 41 may have any configuration as long as it can hold the electric motor 20 at an appropriate position and in an appropriate posture. The same applies to the second holding member 42. In other words, the second holding member 42 may have any configuration as long as it can hold the reducer 70 at an appropriate position and in an appropriate posture. The appropriate position and posture are those that allow the transmission shaft 25 to transmit the rotation of the output shaft 20B of the electric motor 20 to the input shaft 76 of the reducer 70.

[0109] The shape of the mother machine front part 520A is not limited to the example of the above embodiment. The mother machine front part 520A only needs to have a through hole in which the transmission shaft 25 is disposed, and to be able to mount the electric motor 20 and the reducer 70 on one side and the other side of the through hole, respectively.

[0110] The overall configuration of the boom swing mechanism 10 is not limited to the example of the above embodiment. For example, the extension direction of the center axis Q of the transmission shaft 25 may be slightly tilted upward. The center axis Q of the transmission shaft 25 may extend generally above and below the mother machine and may be tilted upward within a range of approximately 15 degrees, for example. The boom swing mechanism 10 may connect the output shaft of the electric motor to the input shaft of the reducer via a transmission shaft disposed in the first through-hole of the mother machine, and may rotate the swing wall 50 and, ultimately, the boom via an output member that rotates upon receiving power from the reducer. The materials of the components of the boom swing mechanism 10 may be changed from those of the above embodiment. Appropriate materials may be used for each component so that the boom 530 can be swung by the driving force of the electric motor 20.

[0111] In the above embodiment, the components of the boom swing mechanism 10 include the mother machine 520. However, in the excavator 500, the mother machine 520 may be treated as a component separate from the boom swing mechanism 10. That is, it is not essential that the components of the boom swing mechanism 10 include the mother machine 520. The same can be said for the boom 530. That is, in the excavator 500, the boom 530 may be treated as a component separate from the boom swing mechanism 10. It is not essential that the components of the boom swing mechanism 10 include the boom 530.

[0112] The construction machine to which the boom swing mechanism 10, which is an electric actuator, is applicable is not limited to the excavator 500. In the above embodiments, an object made up of multiple objects may be integrated, and conversely, an object made up of a single object may be divided into multiple objects. Regardless of whether the objects are integrated, it is sufficient that the object of the invention can be achieved. For example, with regard to the wall portions configured as an integrally molded object in the above embodiments, these wall portions may be molded separately in advance and then integrated with bolts or the like. Furthermore, the wall portions that were fixed together with bolts in the above embodiments may be molded integrally in advance.

[0113] The technical concepts that can be understood from the above embodiments and modifications are described below. [1] A boom swing mechanism for a construction machine comprising: a mother machine having a first through hole; an electric motor attached to the mother machine; a transmission located on the opposite side of the first through hole from the electric motor and configured to change the rotational speed of the output shaft of the electric motor; a transmission shaft located within the first through hole and connected to the output shaft of the electric motor and the input shaft of the transmission; an output member that receives power from the transmission and rotates around the central axis of the transmission shaft; and a boom connected to the output member.

[0114] [2] A boom swing mechanism for a construction machine as described in [1], which is cylindrical with the transmission shaft disposed inside, and comprises a pin disposed in the first through hole together with the transmission shaft, and a contact wall fixed to the boom and in contact with the pin.

[0115] [3] A boom swing mechanism for a construction machine described in [1] or [2], wherein the output member has a second through hole and is fixed to the boom, and comprises an opposing wall having a third through hole at a position opposite the second through hole, and a connecting member connecting the output member and the opposing wall, and the connecting member has a base that is arranged within the second through hole and the third through hole, and a buffer part that is cylindrical and has the base arranged inside, and is arranged within the second through hole and the third through hole together with the base, and has an elastic modulus smaller than that of the base.

[0116] [4] A boom swing mechanism for a construction machine described in any one of [1] to [3], comprising: an opposing wall fixed to the boom and facing the output member; and a connecting member connecting the opposing wall and the output member, wherein there is a gap between the opposing wall and the output member.

[0117] Second Embodiment A second embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to Figures 5 and 6. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from the actual ones or from those in other drawings. In Figures 5 and 6, parts that are the same as or function substantially the same as those in Figures 1 to 4 are given the same reference numerals as in Figures 1 to 4. In the following description, parts that overlap with the first embodiment may be omitted or simplified as appropriate.

[0118] <Overall structure> As shown in FIG. 5 , a backhoe 600, which is a construction machine, includes a lower body 602, an upper body 606, which is a vehicle body, and a pair of traveling devices 510. The upper body 606 is located on the opposite side of the ground from the lower body 602. In this embodiment, up, down, front, rear, left, and right are defined based on the backhoe 600. That is, the direction in which the upper body 606 is located as viewed from the lower body 602 is the upward direction, and the opposite direction is the downward direction. Furthermore, a specific direction among directions perpendicular to the upward direction is the forward direction, and the opposite direction is the backward direction. Furthermore, one direction perpendicular to both the upward direction and the forward direction is the left direction, and the other is the right direction. Hereinafter, the forward direction and the backward direction may be collectively referred to as the X direction, the left direction and the right direction may be collectively referred to as the Y direction, and the upward direction and downward direction may be collectively referred to as the Z direction. Note that for convenience of explanation, FIG. 5 shows some components of the backhoe 600 in cross section.

[0119] The outer shape of the lower body 602 is, for example, a rectangular parallelepiped. The lower body 602 houses various mechanisms, devices, parts, etc. required to operate the backhoe 600. A pair of traveling devices 510 are located on both the left and right sides of the lower body 602. The traveling devices 510 include crawlers for traveling, etc. The traveling devices 510 cause the backhoe 600 to travel.

[0120] As shown in FIG. 5 , the upper body 606 includes a storage section 607, a riding section 608, and a support wall section 609. The storage section 607 has a rectangular parallelepiped outer shape. The interior of the storage section 607 is hollow. Like the lower body 602, the storage section 607 houses various mechanisms, devices, and parts. For example, a counterweight 629 is disposed at the rear end of the storage section 607. The counterweight 629 is a weight used to balance the weight of the backhoe 600. The underside of the storage section 607 faces the lower body 602. The riding section 608 is located above the storage section 607. The riding section 608 includes a seat for the operator, etc. The support wall section 609 protrudes forward from the front surface of the storage section 607. The support wall section 609 is fixed to the storage section 607. The support wall portion 609 straddles the center of the storage portion 607 in the Z direction. As shown in FIG. 6, the support wall portion 609 straddles the center of the storage portion 607 in the Y direction. Note that the riding portion 608 is not shown in FIG. 6. As shown in FIG. 5, the support wall portion 609 has a through hole 609A. The through hole 609A passes through the support wall portion 609 from top to bottom. The central axis of the through hole 609A extends substantially in the Z direction. Hereinafter, the central axis of the through hole 609A may be referred to as a swivel central axis 610V. As shown in FIG. 6, the swivel central axis 610V is located substantially in the center of the storage portion 607 in the Y direction.

[0121] <Slewing bearing> As shown in FIG. 5, the excavator 600 includes a slewing bearing 603. The slewing bearing 603 is located between a lower body 602 and an upper body 606. Note that in FIG. 5, the vertical width of the slewing bearing 603 is exaggerated in relation to the Z direction. As shown in FIG. 6, the slewing bearing 603 includes an annular inner ring 604, an annular outer ring 605, and multiple rolling elements. Note that the rolling elements are not shown in FIG. 6. The outer diameter of the inner ring 604 is smaller than the inner diameter of the outer ring 605. The central axis of the inner ring 604 approximately coincides with the central axis of the outer ring 605. The inner ring 604 is located inside the outer ring 605 in the radial direction centered on its own central axis. The central axes of both the inner ring 604 and the outer ring 605 extend approximately in the Z direction. Hereinafter, the central axis of the inner ring 604 will be referred to as a bearing axis 603V. The bearing axis 603V is located approximately in the center of the accommodating portion 607 in both the X and Y directions. The multiple rolling elements are, for example, balls. The multiple rolling elements are located between the inner ring 604 and the outer ring 605. The multiple rolling elements support the inner ring 604 and the outer ring 605 so that they can rotate relative to each other. As a result, the outer ring 605 can rotate relative to the inner ring 604 around the bearing axis 603V. The inner ring 604 is fixed to the lower body 602. The outer ring 605 is fixed to the accommodating portion 607 of the upper body 606. That is, the upper body 606 can rotate relative to the lower body 602 around the bearing axis 603V. The rear end of the outer ring 605 is located forward of the counterweight 629.

[0122] Although not shown in the figure, a slewing drive unit is located near the slewing bearing 603. The slewing drive unit includes an electric motor and a reducer that reduces the rotational speed of the electric motor and outputs the reduced speed. The electric motor can rotate in both forward and reverse directions. As the electric motor can rotate in both forward and reverse directions, the slewing drive unit can output torque in both forward and reverse directions. The torque output by the slewing drive unit drives the rotation of the outer wheel 605 relative to the inner wheel 604. At the same time, the upper body 606 rotates left and right relative to the lower body 602. As described above, the upper body 606 is rotatably supported relative to the lower body 602 by the slewing bearing 603. The bearing axis 603V forms the central axis of rotation of the upper body 606 relative to the lower body 602.

[0123] <Excavation equipment> As shown in FIG. 5 , the excavator 600 includes a boom 530, an arm 540, and a bucket 550 as an excavation work machine. The configurations of the boom 530, the arm 540, and the bucket 550 are basically the same as those in the first embodiment. That is, the boom 530 includes a base wall 534, a connecting shaft 532, and a boom main body 531. The base wall 534 is located forward of the upper body 606. The base wall 534 is fixed to a swing bracket 610, which will be described later. The base wall 534 may have any shape as long as it can be fixed to the swing bracket 610. The connecting shaft 532 connects the base wall 534 and the boom main body 531. One end of the boom main body 531 is fixed to the connecting shaft 532. The boom main body 531 can rotate up and down around the connecting shaft 532. The arm 540 is connected to the other end of the boom main body 531. Arm 540 is rotatable relative to boom main body 531 around the point where arm 540 is connected to boom main body 531. Bucket 550 is connected to the tip of arm 540 on the side opposite boom main body 531. Bucket 550 is rotatable up and down relative to arm 540 around the point where arm 540 is connected to bucket 550.

[0124] <Boom swing mechanism> The backhoe 600 is equipped with a boom swing mechanism 600A. As indicated by an arrow 600V in Fig. 6, the boom swing mechanism 600A is a mechanism for swinging the boom 530 left and right relative to the upper body 606. The boom swing mechanism 600A constitutes an electric actuator.

[0125] 5, the boom swing mechanism 600A includes a swing bracket 610. The swing bracket 610 is located between the housing portion 607 of the upper body 606 and the boom 530. The swing bracket 610 includes an upper wall 611, a lower wall 612, and a connecting wall 613.

[0126] The upper wall 611 is located above the support wall portion 609. The upper wall 611 extends forward from a front portion of the support wall portion 609. The front end of the upper wall 611 extends forward of the front surface of the support wall portion 609. The upper wall 611 is plate-shaped with thicknesses in both the top and bottom directions. As shown in FIG. 6, when viewed from above, the upper wall 611 is pentagonal. That is, when viewed from above, the upper wall 611 has a configuration in which a rectangular first portion and a triangular second portion are joined together. The second portion is located rearward of the first portion. As shown in FIG. 5, a through-hole 611A penetrates vertically near the joint between the first portion and the second portion. The central axis of the through-hole 611A extends substantially in the Z direction. The central axis of through hole 611A substantially coincides with rotation central axis 610V. As described above, rotation central axis 610V is the central axis of through hole 609A in support wall portion 609. The diameter of through hole 611A is smaller than the diameter of through hole 609A in support wall portion 609.

[0127] As shown in FIG. 5, the connecting wall 613 protrudes downward from the lower surface of the upper wall 611. For example, the connecting wall 613 is integrally molded with the upper wall 611. As shown in FIG. 6, the connecting wall 613 is located in a front portion of the upper wall 611. The connecting wall 613 extends along the edge of the upper wall 611. As shown in FIG. 5, the base wall 534 of the boom 530 is fixed to the surface of the connecting wall 613 opposite to the surface facing the support wall portion 609. The dimension of the connecting wall 613 in the Z direction is approximately the same as the dimension of the support wall portion 609 of the upper body 606 in the Z direction.

[0128] The lower wall 612 is located below the connecting wall 613. The lower wall 612 is configured to have approximately the same shape and dimensions as the upper wall 611. When the lower wall 612 is viewed in plan from above, each side of the pentagon of the lower wall 612 overlaps with each side of the pentagon of the upper wall 611. The central axis of the through-hole 612A in the lower wall 612 approximately coincides with the central axis 610V of rotation. For example, the lower wall 612 is integrally molded with the connecting wall 613.

[0129] The boom swing mechanism 600A includes a pin 620. The pin 620 is disposed in a through-hole 609A of the support wall portion 609. The pin 620 is cylindrical. The central axis of the pin 620 extends substantially in the Z direction. The central axis of the pin 620 substantially coincides with the rotation central axis 610V. The diameter of the pin 620 is smaller than the diameter of the through-hole 609A of the support wall portion 609. A gap is provided between the outer surface of the pin 620 and the inner surface of the through-hole 609A of the support wall portion 609. In FIG. 5, the gap between the inner surface of the through-hole 609A and the outer surface of the pin 620 is exaggerated. The pin 620 is rotatably supported by the inner surface of the through-hole 609A. The pin 620 is rotatable about the rotation central axis 610V.

[0130] The pin 620 passes through a through-hole 611A in the upper wall 611 and a through-hole 612A in the lower wall 612 of the swing bracket 610. The upper end of the pin 620 is located above the upper surface of the upper wall 611. The lower end of the pin 620 is located below the lower surface of the lower wall 612. At the same time, in the Z direction, the lower end of the pin 620 is located below the lower surface of the accommodation section 607 in the upper body 606. The diameter of the pin 620 is approximately the same as the diameters of the through-hole 611A in the upper wall 611 and the through-hole 612A in the lower wall 612. The pin 620 is fixed to the upper wall 611 and the lower wall 612. Therefore, when the pin 620 rotates about the rotation central axis 610V, the upper wall 611 and the lower wall 612 rotate integrally with the pin 620. In this way, the swing bracket 610 is connected to the support wall portion 609 via the pin 620 so as to be rotatable about the central axis of rotation 610V.

[0131] <Drive unit> 5, the boom swing mechanism 600A includes a drive device 615. The drive device 615 is located entirely inside the housing section 607. The drive device 615 includes an electric motor 616, a reducer 617, and a transmission shaft 618.

[0132] The electric motor 616 is a drive source for the drive device 615. The electric motor 616 includes a housing 616A and an output shaft 616B. The electric motor 616 operates in response to power supplied from a battery (not shown). The housing 616A is located inside the accommodation portion 607. The housing 616A is attached to the inner wall of the accommodation portion 607. The housing 616A is located forward of the swivel bearing 603. In the Y direction, the housing 616A is located approximately in the center of the accommodation portion 607. The housing 616A has a cylindrical outer shape. The central axis of the housing 616A extends approximately in the Z direction. The central axis of the housing 616A is approximately parallel to the swivel central axis 610V of the swing bracket 610. The output shaft 616B protrudes downward from the housing 616A. The output shaft 616B is cylindrical. The central axis of the output shaft 616B substantially coincides with the central axis of the housing 616A. The output shaft 616B is rotatable relative to the housing 616A. The output shaft 616B rotates around its own central axis. The output shaft 616B can rotate in both forward and reverse directions depending on the power supply to the housing 616A.

[0133] The reducer 617 is located below the electric motor 616. The reducer 617 is located inside the accommodation portion 607. The reducer 617 is attached to the inner wall of the accommodation portion 607. The reducer 617 has a cylindrical outer shape. The outer diameter of the reducer 617 substantially coincides with the outer diameter of the housing 616A of the electric motor 616. The central axis of the reducer 617 substantially coincides with the central axis of the output shaft 616B of the electric motor 616. The reducer 617 is connected to the output shaft 616B of the electric motor 616. The torque of the output shaft 616B of the electric motor 616 is input to the reducer 617. The reducer 617 amplifies the torque of the output shaft 616B of the electric motor 616 by a predetermined ratio and outputs the amplified torque. The reducer 617 may be, for example, an eccentric oscillating gear type or a planetary gear type. The reducer 617 may be of any type as long as it is configured to amplify and output the torque from the electric motor 616 .

[0134] The transmission shaft 618 is located below the reducer 617. A portion of the transmission shaft 618 is located inside the accommodation portion 607. The remaining portion of the transmission shaft 618 protrudes downward from the bottom surface of the accommodation portion 607. The transmission shaft 618 is cylindrical. The diameter of the transmission shaft 618 is smaller than the diameter of the reducer 617. The central axis of the transmission shaft 618 substantially coincides with the central axis of the output shaft 616B of the electric motor 616. The transmission shaft 618 is connected to the reducer 617. The transmission shaft 618 receives torque from the reducer 617 and rotates about its own central axis. In other words, when the central axis of the transmission shaft 618 is defined as a rotational central axis 615V, the transmission shaft 618, and therefore the drive unit 615, outputs torque centered around the rotational central axis 615V.

[0135] The position of the driving device 615 in the X and Y directions will be described in detail. The position of the driving device 615 is determined relative to a swivel center axis 610V, which is the central axis of the through-hole 609A of the support wall portion 609, and a bearing axis 603V, which is the central axis of the swivel of the upper body 606. The direction in which the swivel center axis 610V is located as viewed from the bearing axis 603V is referred to as the first direction. In this embodiment, the first direction is the forward direction. Also, as shown in FIG. 6, a portion of the outer ring 605 of the swivel bearing 603 that is closest to the swivel center axis 610V in the first direction is referred to as a specific position 603P. The specific position 603P is the front end of the outer ring 605 of the swivel bearing 603. Furthermore, when the excavator 600 is viewed in a direction along the turning center axis 610V, the imaginary line segment connecting the specific location 603P and the turning center axis 610V is referred to as the specific line segment 603S. The driving device 615 is positioned so as to satisfy the following first condition. The first condition is that when the excavator 600 is viewed in a direction along the turning center axis 610V, the rotation center axis 615V of the driving device 615 is located on the specific line segment 603S.

[0136] <Drive sprocket> As shown in FIG. 5, the boom swing mechanism 600A includes a drive sprocket 621. The drive sprocket 621 is a driving member. The drive sprocket 621 is attached to a transmission shaft 618. That is, the drive sprocket 621 is attached to the housing 607 via a drive unit 615. As shown in FIG. 6, the drive sprocket 621 includes a main body 621A and a plurality of teeth 621B. In FIG. 6, only a portion of the plurality of teeth 621B is shown schematically. The main body 621A is annular. The central axis of the main body 621A substantially coincides with the central axis of rotation 615V. The transmission shaft 618 passes through a central hole in the main body 621A. The main body 621A is fixed to the transmission shaft 618. The main body 621A rotates integrally with the transmission shaft 618. In other words, main body 621A receives torque from drive device 615 and rotates about central rotation axis 615V. A plurality of teeth 621B protrude from the outer peripheral surface of main body 621A. The plurality of teeth 621B are arranged at equal intervals in the circumferential direction around central rotation axis 615V. Note that the fact that teeth 621B protrude from the outer peripheral surface of main body 621A in drive sprocket 621 corresponds to drive sprocket 621 having teeth 621B on the outer peripheral surface of main body 621A.

[0137] <Driven sprocket> As shown in FIG. 5, the boom swing mechanism 600A includes a driven sprocket 622. The driven sprocket 622 is a member to which force is transmitted. The driven sprocket 622 is attached to a pin 620. That is, the driven sprocket 622 is attached to the swing bracket 610 via the pin 620. As shown in FIG. 6, the driven sprocket 622 includes a main body 622A and a plurality of teeth 622B. Note that FIG. 6 schematically shows only a portion of the plurality of teeth 622B. The main body 622A is annular. The outer diameter of the main body 622A is larger than the outer diameter of the main body 621A of the drive sprocket 621. The central axis of the main body 622A substantially coincides with the swing central axis 610V. The pin 620 passes through a central hole in the main body 622A. The main body 622A is fixed to the pin 620. The main body 622A rotates integrally with the pin 620. That is, main body 622A rotates around central axis of rotation 610V. Teeth 622B protrude from the outer peripheral surface of main body 622A. Teeth 622B are arranged at equal intervals in the circumferential direction around central axis of rotation 610V. Note that teeth 622B protruding from the outer peripheral surface of main body 622A in driven sprocket 622 is equivalent to driven sprocket 622 having teeth 622B on the outer peripheral surface of main body 622A.

[0138] <Chain> The boom swing mechanism 600A includes a chain 623. The chain 623 is a transmission mechanism. The chain 623 is wound around a drive sprocket 621 and a driven sprocket 622. The chain 623 meshes with teeth 621B of the drive sprocket 621 and teeth 622B of the driven sprocket 622. The chain 623 transmits the rotation of the drive sprocket 621 to the driven sprocket 622. The chain 623 rotates the drive sprocket 621 and the driven sprocket 622 in conjunction with each other.

[0139] <Operation of the Second Embodiment> In the boom swing mechanism 600A, when the output shaft 616B of the electric motor 616 rotates, the transmission shaft 618 rotates together with the output shaft 616B. When the transmission shaft 618 rotates, the drive sprocket 621 rotates. The rotation of the drive sprocket 621 drives the rotation of the chain 623, which in turn drives the rotation of the driven sprocket 622. When the driven sprocket 622 rotates, the swing bracket 610 rotates together with the pin 620. When the swing bracket 610 rotates, the boom 530 swings left and right about the rotation central axis 610V, as shown by arrow 600V in FIG. 6.

[0140] <Effects of the second embodiment> (2-1) As described in the operation of the above embodiment, in the back shovel 600 of this embodiment, the electric motor 616 can be used as a drive source to swing the boom 530 left and right.

[0141] As described in the first embodiment, an external load may be input to the boom 530 when the bucket 550 collides with an excavation target. This load is referred to as a collision load. As shown in FIG. 5 , in the excavator 600 of this embodiment, the collision load may be transmitted to the driven sprocket 622 via the swing bracket 610 and the pin 620. When the collision load is input, the driven sprocket 622 moves slightly. This movement of the driven sprocket 622 is absorbed by the chain 623, for example, by slight bending of the chain 623. Therefore, the movement of the driven sprocket 622 is hardly transmitted to the drive sprocket 621 or the drive unit 615. In this way, the excavator 600 of this embodiment can prevent the collision load input to the boom 530 from reaching the drive unit 615. Therefore, the configuration of this embodiment does not require the reduction gear 617 and the electric motor 616 to have a configuration for withstanding the collision load, as described in the first embodiment. Therefore, for example, the size of the reducer 617 can be prevented from increasing.

[0142] (2-2) In this embodiment, a sprocket and a chain are used as a mechanism for transmitting the torque of the driving device 615 to the boom 530. By using a sprocket and a chain, the torque of the driving device 615 can be efficiently transmitted to the pin 620 and ultimately to the boom 530 through the meshing of the sprocket teeth and the chain without loss. Also, as described in (2-1), by using a chain, the load reaching the driven sprocket 622 can be absorbed by flexure.

[0143] (2-3) In the configuration of this embodiment, the outer diameter of the driven sprocket 622 is larger than the outer diameter of the drive sprocket 621. By adopting such a sprocket size relationship, the torque of the drive unit 615 can be converted into a large torque and transmitted to the pin 620 and ultimately to the boom 530. Therefore, in the configuration of this embodiment, the torque of the drive unit 615 required to swing the boom 530 can be reduced.

[0144] (2-4) In this embodiment, the drive unit 615 and therefore the drive sprocket 621 are disposed so as to satisfy the first condition. That is, the rotation center axis 615V of the drive unit 615 and therefore the drive sprocket 621 is located between the front end of the outer ring 605 of the swing bearing 603 and the swing center axis 610V, which is the center axis of the driven sprocket 622. When such an arrangement is adopted, the distance from the drive sprocket 621 to the driven sprocket 622 is shortened. Therefore, the chain 623 wound around the drive sprocket 621 and the driven sprocket 622 can be shortened, thereby suppressing loss of force transmitted from the drive sprocket 621 to the driven sprocket 622. That is, force can be transmitted efficiently from the drive sprocket 621 to the driven sprocket 622.

[0145] <Modification of the second embodiment> The second embodiment can be modified as follows: The first and second embodiments and the following modifications can be combined and implemented as long as no technical contradiction occurs.

[0146] The driving member is not limited to the example of the above embodiment. The driving member may be, for example, an annular driving pulley centered on the central axis of rotation 615V. That is, the driving member may not have teeth on its outer circumferential surface. When a driving pulley is used as the driving member, it is possible to use an annular driven pulley centered on the central axis of rotation 610V as the driven member. Like the driving pulley, the driven pulley has no teeth on its outer circumferential surface. When a driving pulley is used as the driving member and a driven pulley is used as the driven member, it is possible to use a belt wound around the driving pulley and the driven pulley as the transmission mechanism. When these driving pulley, driven pulley, and belt are used, noise and vibration can be suppressed when power is transmitted from the driving pulley to the driven pulley. Note that the driving member, the driven member, and the transmission mechanism are not limited to the pulleys and belts listed here, and may be configured to transmit power between them. For example, the driving member, the driven member, and the transmission mechanism may be configured as a series of gear mechanisms.

[0147] For example, as shown in FIG. 7, the driving member, the force-receiving member, and the transmission mechanism may be configured as a series of link mechanisms. Specifically, in the configuration shown in FIG. 7, the driving member is a driving link 630. The force-receiving member is a driven link 632. The transmission mechanism includes a transmission link 631, a first link shaft 633, and a second link shaft 634. The driving link 630, the driven link 632, and the transmission link 631 are each long and plate-shaped. The first link shaft 633 and the second link shaft 634 are each cylindrical. A first end of the driving link 630 is fixed to a transmission shaft 618 of the driving device 615. The driving link 630 rotates integrally with the transmission shaft 618. A second end of the driving link 630 is connected to the transmission link 631 via the first link shaft 633. Specifically, the first link shaft 633 is fixed to the second end of the driving link 630. The central axis of the first link shaft 633 extends substantially in the Z direction. The first link shaft 633 penetrates a first end of the transfer link 631. The transfer link 631 and the first link shaft 633 are rotatable relative to each other. The first link shaft 633 is retained relative to the drive link 630 and the transfer link 631. A second end of the transfer link 631 is connected to the driven link 632 via the second link shaft 634. Specifically, the second link shaft 634 penetrates the second end of the transfer link 631. The central axis of the second link shaft 634 extends substantially in the Z direction. The transfer link 631 and the second link shaft 634 are rotatable relative to each other. The second link shaft 634 is fixed to a first end of the driven link 632. The second link shaft 634 is retained relative to the transfer link 631 and the driven link 632. A second end of the driven link 632 is fixed to the pin 620. The driven link 632 rotates integrally with the pin 620. In the above configuration, when the transmission shaft 618 rotates, the drive link 630 rotates about the rotation central axis 615V. This rotation of the drive link 630 is transmitted to the driven link 632 via the transmission link 631. Then, the driven link 632 rotates together with the pin 620 about the swing central axis 610V. Then, together with the pin 620, the swing bracket 610, and therefore the boom 530, rotate.Here, for example, other members may be disposed between the transmission shaft 618 of the drive unit 615 and the pin 620. To connect the transmission shaft 618 and the pin 620 while avoiding interference with such members, it is effective to employ a link mechanism as shown in FIG. 7. When employing such a link mechanism, the number of link components constituting the link mechanism and the arrangement of each link component can be changed as appropriate. In FIG. 7, parts that are the same as or function substantially the same as those in FIGS. 5 and 6 are denoted by the same reference numerals as in FIGS. 5 and 6. Also, in FIG. 7, as in FIG. 6, the riding section 608 is not shown.

[0148] When the driving member and the force-receiving member are annular, cylindrical, or columnar, the relationship in size between the outer diameter of the driving member and the outer diameter of the force-receiving member is not limited to the example in the above embodiment. For example, the outer diameter of the driving member and the outer diameter of the force-receiving member may be approximately the same.

[0149] The manner of connection between the drive member and the drive device 615 is not limited to the example of the above embodiment. The drive member may be attached to a mating member so as to receive torque from the drive device 615 and be rotatable around the central axis of rotation 615V of the drive device 615. For example, another member may be interposed between the drive member and the drive device 615. The arrangement of the drive member may vary from the example of the above embodiment depending on the manner of connection between the drive member and the drive device 615, etc.

[0150] The manner in which the force-receiving member and the swing bracket 610 are connected is not limited to the example of the above embodiment. For example, instead of the pin 620 penetrating the lower wall 612, a columnar member may be attached to the lower surface of the lower wall 612 instead of the pin 620. The force-receiving member may then be attached to this columnar member. The force-receiving member may be directly fixed to the lower surface of the lower wall 612. The arrangement of the force-receiving member may vary from the example of the above embodiment depending on the manner in which the force-receiving member and the swing bracket 610 are connected. The force-receiving member may be positioned so as to rotate around the central axis 610V of rotation of the swing bracket 610.

[0151] The configuration and arrangement of the swing bracket 610 are not limited to those of the above embodiment. The swing bracket 610 only needs to be fixed to the boom 530 and connected to the vehicle body so as to be rotatable about the central axis of rotation 610V. For example, the shape of the upper wall 611 may be changed from that of the above embodiment.

[0152] The manner of connection between the swing bracket 610 and the vehicle body is not limited to the example of the above embodiment. As long as the swing bracket 610 can be connected to the vehicle body so as to rotate around the central axis of rotation 610V, any connection manner can be used.

[0153] The configuration of the vehicle body for supporting the swing bracket 610 is not limited to the example of the above embodiment. For example, the through-hole 609A of the support wall portion 609, and therefore the central axis of rotation 610V, may be shifted from the center of the accommodation portion 607 in the Y direction. The position of the swing bracket 610 relative to the vehicle body may vary depending on the configuration of the vehicle body for supporting the swing bracket 610, etc.

[0154] The location where the boom 530 is fixed to the swing bracket 610 is not limited to the example in the above embodiment. The boom 530 may be fixed to any location on the swing bracket 610.

[0155] The configuration and arrangement of the swivel bearing 603 are not limited to the example in the above embodiment. As long as the upper body 606 can be supported rotatably relative to the lower body 602, the configuration and arrangement of the swivel bearing 603 are not important.

[0156] The positional relationship between the bearing axis 603V and the swivel center axis 610V, and thus the specific location, first direction, and specific line segment related to the first condition, may vary from the example of the above embodiment depending on the position of the through hole 609A, the arrangement of the swivel bearing 603, etc.

[0157] The configuration and arrangement of the drive unit 615 are not limited to the examples of the above-described embodiment. The drive unit 615 is only required to be attached to the vehicle body, include the electric motor 616, and output torque centered on the central axis of rotation. For example, the outer shape of the electric motor 616 may be changed from a cylindrical shape. For example, the reducer 617 and the transmission shaft 618 may be eliminated from the drive unit 615. A drive member may be directly attached to the output shaft 616B of the electric motor 616. The drive unit 615 may also be configured so that the central axis of the output shaft 616B of the electric motor 616 and the central axis of rotation of the torque output by the drive unit 615 to the outside are positioned at different positions. Such a configuration is possible if the drive unit 615 is provided with a mechanism for converting the rotation direction of the electric motor 616. The central axis of rotation of the torque output by the drive unit 615 is only required to extend vertically along the vehicle body, and may be tilted, for example, within a range of approximately 15 degrees with respect to the Z direction.

[0158] The first condition regarding the arrangement of the drive unit 615 and thus the drive member is not limited to the example of the above embodiment. The first condition only needs to be that at least a part of the drive member is located on the specific line segment 603S when the backhoe 600 is viewed in a direction along the central axis of rotation 610V. If the drive member is arranged so as to satisfy this first condition, an effect equivalent to that of (2-4) above can be achieved.

[0159] The arrangement of the drive members does not necessarily have to satisfy the first condition. As an example of an arrangement of the drive members that is unrelated to the first condition, the boom swing mechanism 600B shown in FIG. 8 may be employed. As in the above embodiment, the boom swing mechanism 600B constitutes an electric actuator. Note that in FIG. 8, parts that are the same as or function substantially the same as those in FIGS. 5 and 6 are denoted by the same reference numerals as in FIGS. 5 and 6. Also, as in FIG. 6, the riding section 608 is not shown in FIG. 8.

[0160] In the following, as in the above embodiment, the direction in which the turning center axis 610V is located as viewed from the bearing axis 603V will be referred to as the "first direction." The direction opposite to the first direction will be referred to as the "second direction." In the example shown in FIG. 8, the first direction is the forward direction, and the second direction is the rearward direction.

[0161] In the boom swing mechanism 600B shown in Fig. 8, the drive unit 615 and the drive sprocket 621 are located rearward with respect to the bearing axis 603V. That is, the drive unit 615 and the drive sprocket 621 are located on the second direction side with respect to the bearing axis 603V. The drive unit 615 and the drive sprocket 621 are also located rightward with respect to the outer ring 605 of the slewing bearing 603. The connection between the drive unit 615 and the drive sprocket 621 is the same as that described in the above embodiment.

[0162] In the boom swing mechanism 600B shown in Fig. 8, the driven sprocket 622 is disposed in the same position as in the above embodiment. Note that in the boom swing mechanism 600B shown in Fig. 8, the outer diameter of the driven sprocket 622 is approximately the same as the outer diameter of the drive sprocket 621.

[0163] The boom swing mechanism 600B includes a first intermediate shaft 627 and a second intermediate shaft 628. The first intermediate shaft 627 is located forward of the drive sprocket 621. Specifically, the first intermediate shaft 627 is located forward of the outer ring 605 of the swing bearing 603. The first intermediate shaft 627 is located at approximately the same position as the drive sprocket 621 in the Y direction. The first intermediate shaft 627 is cylindrical. The central axis of the first intermediate shaft 627 extends approximately in the Z direction. In other words, the central axis of the first intermediate shaft 627 is approximately parallel to the rotation central axis 615V of the drive unit 615. The upper end surface of the first intermediate shaft 627 is fixed to the lower surface of the accommodating portion 607. In other words, the first intermediate shaft 627 is attached to the accommodating portion 607.

[0164] The second intermediate shaft 628 is located to the left of the first intermediate shaft 627. When the excavator 600 is viewed in a direction along the turning center axis 610V, the second intermediate shaft 628 is located on an imaginary line segment connecting the bearing axis 603V and the turning center axis 610V. That is, in the X and Y directions, the second intermediate shaft 628 is located at approximately the same position as the transmission shaft 618 in the above embodiment. Like the first intermediate shaft 627, the second intermediate shaft 628 is cylindrical. The diameter of the second intermediate shaft 628 is approximately the same as the diameter of the first intermediate shaft 627. The central axis of the second intermediate shaft 628 extends approximately in the Z direction. That is, the central axis of the second intermediate shaft 628 is approximately parallel to the rotation central axis 615V of the drive unit 615. The upper end surface of the second intermediate shaft 628 is fixed to the lower surface of the accommodation portion 607. That is, the second intermediate shaft 628 is attached to the receiving portion 607 .

[0165] The boom swing mechanism 600B includes a first intermediate sprocket 625 and a second intermediate sprocket 626. Both the first intermediate sprocket 625 and the second intermediate sprocket 626 are intermediate members. The first intermediate sprocket 625 is attached to a first intermediate shaft 627. Although not shown in detail, the first intermediate sprocket 625 includes an annular main body, a first set of teeth protruding from the outer circumferential surface of the main body, and a second set of teeth protruding from the outer circumferential surface of the main body. For example, the first set of teeth is located at one end of the main body in the direction along the central axis of the main body. The second set of teeth is located at the other end of the main body in the direction along the central axis of the main body. The inner diameter of the main body is slightly larger than the diameter of the first intermediate shaft 627. The first intermediate shaft 627 passes through a central hole in the main body. The central axis of the main body approximately coincides with the central axis of the first intermediate shaft 627. The main body is rotatable relative to the first intermediate shaft 627. The main body rotates around the first intermediate shaft 627 and its own central axis. Although not shown, a cylindrical member for preventing the first intermediate sprocket 625 from falling is attached to the first intermediate shaft 627 on the side opposite the lower surface of the accommodating section 607 with the first intermediate sprocket 625 in between. In other words, the first intermediate sprocket 625 is attached to the accommodating section 607 and, therefore, the vehicle body via the first intermediate shaft 627. When the first intermediate sprocket 625 is attached to the accommodating section 607, a first set of teeth on the first intermediate sprocket 625 is positioned at approximately the same position in the Z direction as the teeth of the drive sprocket 621. A second set of teeth on the first intermediate sprocket 625 is positioned at approximately the same position in the Z direction as a second set of teeth (described below) on the second intermediate sprocket 626.

[0166] The second intermediate sprocket 626 has the same configuration as the first intermediate sprocket 625. That is, the second intermediate sprocket 626 has an annular main body and first and second sets of teeth protruding from the outer circumferential surface of the main body. The first and second sets of teeth are spaced apart along the central axis of the main body. A second intermediate shaft 628 penetrates a central hole in the main body. The main body is rotatable relative to the second intermediate shaft 628. The main body rotates around the second intermediate shaft 628 and its own central axis. Note that a cylindrical member is attached to the second intermediate shaft 628 on the side opposite the lower surface of the accommodating section 607 across the second intermediate sprocket 626 to prevent the second intermediate sprocket 626 from falling off. That is, the second intermediate sprocket 626 is attached to the accommodating section 607 and thus to the vehicle body via the second intermediate shaft 628. When the second intermediate sprocket 626 is attached to the receiving portion 607, the first set of teeth of the second intermediate sprocket 626 is positioned at approximately the same position in the Z direction as the teeth of the driven sprocket 622.

[0167] The boom swing mechanism 600B includes a first chain 623A, a second chain 623B, and a third chain 623C. The first chain 623A, the second chain 623B, and the third chain 623C form a transmission mechanism.

[0168] The first chain 623A is wound around the drive sprocket 621 and the first set of teeth of the first intermediate sprocket 625. The first chain 623A meshes with the teeth of the drive sprocket 621 and the teeth of the first set of teeth of the first intermediate sprocket 625. The first chain 623A transmits the rotation of the drive sprocket 621 to the first intermediate sprocket 625. In other words, the first chain 623A causes the drive sprocket 621 and the first intermediate sprocket 625 to rotate in conjunction with each other.

[0169] The second chain 623B is wound around the second group of teeth of the first intermediate sprocket 625 and the second group of teeth of the second intermediate sprocket 626. The second chain 623B meshes with the teeth of the first intermediate sprocket 625 and the teeth of the second intermediate sprocket 626. The second chain 623B transmits the rotation of the first intermediate sprocket 625 to the second intermediate sprocket 626. In other words, the second chain 623B causes the first intermediate sprocket 625 and the second intermediate sprocket 626 to rotate in conjunction with each other.

[0170] The third chain 623C is wound around the first set of teeth of the second intermediate sprocket 626 and the driven sprocket 622. The third chain 623C meshes with the teeth of the first set of teeth of the second intermediate sprocket 626 and the teeth of the driven sprocket 622. The third chain 623C transmits the rotation of the second intermediate sprocket 626 to the driven sprocket 622. In other words, the third chain 623C rotates the first intermediate sprocket 626 and the driven sprocket 622 in conjunction with each other.

[0171] In boom swing mechanism 600B shown in Fig. 8, when drive device 615 outputs torque, drive sprocket 621, first intermediate sprocket 625, second intermediate sprocket 626, and driven sprocket 622 rotate in unison in accordance with the torque. When driven sprocket 622 rotates, swing bracket 610 rotates together with pin 620. As swing bracket 610 rotates, boom 530 swings left and right about rotation central axis 610V, as shown by arrow 600W in Fig. 8.

[0172] When the boom swing mechanism 600B shown in FIG. 8 is employed, the drive unit 615 and the drive sprocket 621 can be positioned as far rearward as possible in the backhoe 600. In this case, the weight of the backhoe 600 shifts rearward by the weight of the drive unit 615 and the drive sprocket 621. In this case, the weight balance of the backhoe 600 can be maintained even if the weight of the counterweight 629 disposed at the rear end of the storage section 607 is reduced. Therefore, it is permissible to reduce the weight of the counterweight 629. This contributes to reducing the weight of the backhoe 600 as a whole.

[0173] In the boom swing mechanism 600B shown in Fig. 8, the number and positions of intermediate sprockets interposed between the drive sprocket 621 and the driven sprocket 622 are not limited to the example shown in Fig. 8. The number and positions of the intermediate sprockets may be determined appropriately so as to enable smooth power transmission from the drive sprocket 621 to the driven sprocket 622.

[0174] The manner in which the intermediate sprocket is connected to the vehicle body is not limited to that described in Fig. 8. An appropriate connection manner may be designed so that the intermediate sprocket can rotate around a central axis that is parallel to the central rotation axis 615V of the drive unit 615.

[0175] Regarding the boom swing mechanism 600B shown in FIG. 8, the configurations of the driving member, the driven member, the intermediate member, and the transmission mechanism are not limited to the above example. The driving member, the driven member, the intermediate member, and the transmission mechanism may be any member capable of transmitting the torque of the driving device 615 to the swing bracket 610. For example, instead of sprockets, pulleys without teeth on the outer circumferential surface may be used as the driving member, the driven member, and the intermediate member. When pulleys are used as the driving member, the driven member, and the intermediate member, a belt may be used as the transmission mechanism. The driving member, the driven member, the intermediate member, and the transmission mechanism may be configured using a link mechanism or a gear mechanism.

[0176] The swivel bearing 603 is not essential for the backhoe 600. That is, depending on the configuration of the backhoe 600, the upper body 606 may not be able to swivel relative to the lower body 602, and the upper body 606 and the lower body 602 may be integrated. In this case, the upper body 606 and the lower body 602 constitute the vehicle body. That is, the vehicle body is not limited to the example of the above embodiment.

[0177] The construction machinery to which the boom swing mechanisms 600A and 600B, which are electric actuators, can be applied is not limited to the excavator 600. In the above embodiment, various means may be used to fasten the two members together, such as bolting, welding, integral molding, spline connection, etc.

[0178] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved.

[0179] <Third embodiment> A third embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to FIG. 9. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from the actual ones or from those in other drawings. In FIG. 9, parts that are the same as or function substantially the same as those in FIGS. 1 to 8 are given the same reference numerals as in FIGS. 1 to 8. In the following description, parts that overlap with the first and second embodiments may be omitted or simplified as appropriate.

[0180] <Overall structure> As shown in FIG. 9, a backhoe 650, which is a construction machine, includes a lower body 602, an upper body 653, which is a vehicle body, a pair of traveling devices 510, and a swivel bearing 603. The configurations of the lower body 602, the pair of traveling devices 510, and the swivel bearing 603 are the same as those in the second embodiment. Therefore, a description thereof will be omitted. The upper body 653 will be described later. The upper body 653 is located on the opposite side of the ground from the lower body 602. Note that in this embodiment, up, down, left, right, front, and rear are defined in the same way as in the second embodiment. For convenience of explanation, FIG. 9 shows some members of the backhoe 650 in cross section.

[0181] The upper body 653 includes a storage section 607, a riding section 608, and a support wall section 654. The configurations of the storage section 607 and the riding section 608 are the same as those in the second embodiment. The support wall section 654 protrudes forward from a front surface 607F of the storage section 607. The support wall section 654 is fixed to the front surface 607F of the storage section 607. The support wall section 654 straddles the center of the storage section 607 in the Y direction. The support wall section 654 includes a through hole 654A. The through hole 654A passes through the support wall section 654 in the vertical direction. The central axis of the through hole 654A extends approximately in the Z direction.

[0182] The backhoe 650 is equipped with an excavation work machine including a boom 530, an arm 540, and a bucket 550. The boom 530, the arm 540, and the bucket 550 are positioned forward of the upper body 653. The configurations of the boom 530, the arm 540, and the bucket 550 are the same as those in the second embodiment. Therefore, a description thereof will be omitted.

[0183] <Boom swing mechanism> The backhoe 650 is provided with a boom swing mechanism 650A. The boom swing mechanism 650A is a mechanism for swinging the boom 530 left and right relative to the upper body 653. The boom swing mechanism 650A constitutes an electric actuator.

[0184] The boom swing mechanism 650A includes a swing bracket 665. In terms of the X direction, the swing bracket 665 is located between the housing portion 607 of the upper body 653 and the boom 530. More specifically, in terms of the X direction, the swing bracket 665 is located at approximately the same position as the support wall portion 654. The swing bracket 665 is a plate-like member having thicknesses in the top and bottom. The base wall 534 of the boom 530 is fixed to the front end of the swing bracket 665.

[0185] The boom swing mechanism 650A includes a drive device 660. The drive device 660 is located below a swing bracket 665. The drive device 660 includes an electric motor 661, a reducer 662, and an output member 663.

[0186] The electric motor 661 includes a housing 661A and an output shaft 661B. The electric motor 661 operates in response to power supplied from a battery (not shown). The housing 661A is located below the support wall 654 of the upper body 653. The housing 661A has a cylindrical outer shape. The central axis of the housing 661A extends substantially in the Z direction. The output shaft 661B protrudes upward from the housing 661A. The output shaft 661B is cylindrical. The central axis of the output shaft 661B substantially coincides with the central axis of the housing 661A. The output shaft 661B is rotatable relative to the housing 661A. The output shaft 661B rotates around its own central axis. The output shaft 661B is rotatable in both forward and reverse directions in response to power supplied to the housing 661A.

[0187] The reducer 662 is located above the electric motor 661. The reducer 662 includes a reducer body 662A and a flange 662B. The reducer body 662A has a cylindrical outer shape. The central axis of the reducer body 662A extends substantially in the Z direction. The central axis of the reducer body 662A substantially coincides with the central axis of the housing 661A of the electric motor 661. The diameter of the reducer body 662A substantially coincides with the diameter of the through-hole 654A of the support wall portion 654. The reducer body 662A passes through the through-hole 654A of the support wall portion 654. A portion of the reducer body 662A is located within the through-hole 654A. The housing 661A of the electric motor 661 is fixed to the lower end surface of the reducer body 662A. The portion of the output shaft 661B of the electric motor 661 that protrudes from the housing 661A is inserted inside the reducer body 662A. The torque of the output shaft 661B of the electric motor 661 is input to the reducer body 662A. The reducer body 662A amplifies the torque output by the output shaft 661B of the electric motor 661 at a predetermined ratio and outputs the amplified torque. The reducer body 662A may be, for example, an eccentric oscillating gear type or a planetary gear type. Any type of reducer body 662A may be used as long as it is configured to amplify and output the torque from the electric motor 661.

[0188] The flange 662B protrudes from the outer peripheral surface of the reducer body 662A. The flange 662B extends over the entire area of the reducer body 662A in the circumferential direction centered on the central axis of the reducer body 662A. In other words, the flange 662B is annular. The flange 662B is located above the upper surface of the support wall portion 654. The lower surface of the flange 662B faces the upper surface of the support wall portion 654. The flange 662B and the support wall portion 654 are fixed to each other by a plurality of bolts 667. In this way, the reducer 662, and therefore the drive unit 660, are attached to the support wall portion 654, which is part of the vehicle body, via the flange 662B.

[0189] The output member 663 is located above the reducer body 662A. The output member 663 is disk-shaped. The central axis of the output member 663 substantially coincides with the central axis of the reducer body 662A. The output member 663 is connected to the reducer body 662A. The torque output by the reducer body 662A is input to the output member 663. The output member 663 receives the torque from the reducer body 662A and rotates about its own central axis. In other words, when the central axis of the output member 663 is set as the rotational central axis 660V, the output member 663, and therefore the drive device 660, outputs torque centered around the rotational central axis 660V.

[0190] The upper surface of the output member 663 faces the lower surface of the swing bracket 665. The output member 663 and the swing bracket 665 are fixed to each other with a plurality of bolts 666. Therefore, the swing bracket 665 receives torque from the output member 663 and, ultimately, the drive unit 660, and rotates about the rotational axis 660V. As described above, the drive unit 660 is attached to the support wall portion 654. That is, the swing bracket 665 is connected to the support wall portion 654 via the drive unit 660 so as to be rotatable about the rotational axis 660V. Here, as described above, the electric motor 661, the reducer 662, and the output member 663 are provided coaxially. From this, the following can be said. That is, the output shaft 661B of the electric motor 661 outputs torque centered on the rotational axis 660V. The reducer 662 outputs the torque output by the electric motor 661 to an output member 663 and, ultimately, to a swing bracket 665 coaxially with the electric motor 661 .

[0191] <Operation of the Third Embodiment> The following describes the procedure for assembling the drive unit 660 and the swing bracket 665 during the manufacturing process of the excavator 650. As a preliminary step to this assembly, the worker prepares an integrated assembly of the swing bracket 665 and the base wall 534 of the boom 530. The worker also prepares the drive unit 660, which is an integrated assembly of the electric motor 661, the reducer 662, and the output member 663. In this state, the worker first attaches the drive unit 660 to the support wall 654 of the upper body 653. Specifically, the worker inserts the drive unit 660 into the through-hole 654A of the support wall 654 from above. When the flange 662B of the reducer 662 contacts the upper surface of the support wall 654, the worker secures the flange 662B to the support wall 654 with the bolts 667. After this, the worker places the swing bracket 665 on the output member 663 of the drive unit 660 from above. Then, the worker fixes the swing bracket 665 and the output member 663 with the bolt 666. That is, the worker inserts the bolt 666 into the swing bracket 665 from above to unite the swing bracket 665 and the output member 663 together.

[0192] <Effects of the third embodiment> (3-1) In the backhoe 650 of this embodiment, when the output shaft 661B of the electric motor 661 rotates, the swing bracket 665 rotates. At the same time, the boom 530 swings left and right. In this way, in the backhoe 650 of this embodiment, the boom 530 can be swung left and right using the electric motor 661 as a drive source.

[0193] Here, in the excavator 650 of this embodiment, the drive unit 660 and the swing bracket 665 are directly connected. With the configuration of this embodiment, in order to realize a swing mechanism for the boom 530 using the electric motor 661 as a drive source, no other mechanism or member is required between the drive unit 660 and the swing bracket 665 for transmitting the torque of the electric motor 661 to the swing bracket 665. Therefore, with the configuration of this embodiment, it is possible to minimize the number of parts in realizing a swing mechanism for the boom 530 using the electric motor 661 as a drive source.

[0194] (3-2) In the driving device 660 of this embodiment, the electric motor 661, the reducer 662, and the output member 663 are arranged coaxially. In this configuration of this embodiment, the overall shape of the driving device 660 is columnar. If the driving device 660 is columnar, when attaching the driving device 660 to the support wall portion 654, the driving device 660 can be attached to the support wall portion 654 simply by inserting the driving device 660 straight into the through-hole 654A. In this configuration of this embodiment, the assembling work of the driving device 660 to the support wall portion 654 is facilitated.

[0195] (3-3) In the backhoe 650 of this embodiment, the swing bracket 665 is positioned above the drive unit 660. Consider the following comparative example for the configuration of this embodiment. That is, in this comparative example, the position of the drive unit 660 in the Z direction is maintained the same as in the above embodiment, and the swing bracket 665 is positioned below the drive unit 660. In this comparative example, the following problem occurs when a worker assembles the drive unit 660 and the swing bracket 665. That is, the worker must crawl into a narrow space below the drive unit 660 and the swing bracket 665 to perform the work in an environment with poor visibility. When working in such a situation, the workability of assembling the drive unit 660 and the swing bracket 665 deteriorates.

[0196] In this regard, when the swing bracket 665 is positioned above the drive unit 660 as in this embodiment, the worker is not restricted by the working space when assembling the drive unit 660 and the swing bracket 665, and the worker can easily ensure a wide field of vision for the work. In other words, the configuration of this embodiment improves the workability of assembling the drive unit 660 and the swing bracket 665.

[0197] Furthermore, when the swing bracket 665 is positioned above the drive unit 660, the swing bracket 665 and the output member 663 of the drive unit 660 can be positioned at a relatively high position away from the ground. In this case, sediment is less likely to accumulate around the swing bracket 665 and the output member 663. If sediment accumulates around the swing bracket 665 and the output member 663, this sediment may create frictional resistance against the rotation of the output member 663 and the swing bracket 665, placing a strain on the operation of the output member 663 and the swing bracket 665. To avoid this strain, if sediment accumulates around the output member 663 and the swing bracket 665, maintenance is required to remove the sediment. With the configuration of this embodiment, the frequency of maintenance to remove sediment from around the output member 663 and the swing bracket 665 can be reduced.

[0198] <Modification of the third embodiment> The third embodiment can be modified as follows: The first to third embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0199] The positional relationship between the swing bracket 665 and the drive unit 660 is not limited to the example in the above embodiment. For example, the drive unit 660 may be located above the swing bracket 665.

[0200] The means for fixing the swing bracket 665 and the driving device 660 is not limited to the bolt 666. Any means can be used as long as the swing bracket 665 and the driving device 660 can be fixed.

[0201] The configuration of the swing bracket 665 is not limited to the example of the above embodiment. The swing bracket 665 may be configured to be fixed to the boom 530 and to be able to receive torque from the drive unit 660 and rotate around the central axis of rotation of the drive unit 660. For example, the shape of the swing bracket 665 may be changed from that of the above embodiment.

[0202] The location where the boom 530 is fixed to the swing bracket 665 is not limited to the example in the above embodiment. The boom 530 may be fixed to any location on the swing bracket 665.

[0203] The structure of the vehicle body for mounting the drive unit 660 is not limited to the example of the above embodiment. The structure of the vehicle body may be designed as appropriate so that the drive unit 660 can be mounted appropriately.

[0204] The configuration of the drive unit 660 is not limited to the example of the above embodiment. The drive unit 660 is attached to the vehicle body, includes the electric motor 661, and outputs torque centered on the central axis of rotation. For example, the outer shape of the electric motor 661 may be changed from a cylindrical shape. For example, the reducer 662 and the output member 663 may be eliminated from the drive unit 660. In this case, the output shaft 661B of the electric motor 661 may be treated as the output member of the drive unit 660. Then, the swing bracket 665 may be directly attached to the output shaft 661B of the electric motor 661. The drive unit 660 may also be configured so that the central axis of the output shaft 661B of the electric motor 661 and the central axis of rotation of the torque output by the drive unit 660 to the outside are positioned differently. Such a configuration is possible if the drive unit 660 is provided with a mechanism for changing the rotation direction of the output shaft 661B of the electric motor 661. The central axis of rotation of the torque output by the drive unit 660 may extend generally in the vertical direction of the vehicle body, and may be tilted relative to the Z direction within a range of, for example, about 15 degrees.

[0205] The swivel bearing 603 is not essential for the backhoe 650. That is, depending on the configuration of the backhoe 650, the upper body 653 may not be swivelable relative to the lower body 602, and the upper body 653 and the lower body 602 may be integrated. In this case, the upper body 653 and the lower body 602 constitute the vehicle body. That is, the vehicle body is not limited to the example of the above embodiment.

[0206] The construction machinery to which the boom swing mechanism 650A, which is an electric actuator, can be applied is not limited to the excavator 650. In the above embodiment, various means may be used to fasten the two members together, such as bolting, welding, integral molding, spline connection, etc.

[0207] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved.

[0208] <Fourth embodiment> A fourth embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to Figures 10 to 14. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from those in the actual product or from those in other drawings. In Figures 10 to 14, parts that are the same as or function substantially the same as those in Figures 1 to 9 are given the same reference numerals as in Figures 1 to 9. For the sake of convenience, some components are shown in cross section in Figures 10, 11, 13, and 14. In the following description, explanations of parts that overlap with those of the first to third embodiments may be omitted or simplified as appropriate.

[0209] <Overall structure> As shown in FIG. 10, a backhoe 680, which is a construction machine, includes a lower body 602, an upper body 606 which is a vehicle body, a pair of traveling devices 510, and a swivel bearing 603. The configurations of the lower body 602, the pair of traveling devices 510, and the swivel bearing 603 are the same as those in the second embodiment. Therefore, a description thereof will be omitted. The upper body 606 will be described later. The upper body 606 is located on the opposite side of the ground from the lower body 602. Note that in this embodiment, up, down, left, right, front, and rear are defined in the same way as in the second embodiment.

[0210] The configuration of the upper body 606 is basically the same as that of the second embodiment. That is, the upper body 606 includes a rectangular parallelepiped storage section 607, a riding section 608 located above the storage section 607, and a support wall section 609 located forward of the storage section 607. The support wall section 609 includes a through-hole 609A extending substantially in the Z direction. The central axis of the through-hole 609A forms the central axis 610V of rotation of the boom 530. Unlike the second embodiment, the upper body 606 includes an opening 607H in a lower portion of the front wall of the storage section 607, which communicates between the inside and outside of the storage section 607. In consideration of the presence of this opening 607H, the support wall section 609 protruding from the front wall of the storage section 607 is provided only above the opening 607H. As a result, the dimension of the support wall portion 609 in the Z direction is smaller than the dimension in the Z direction of a connecting wall 613 of a swing bracket 610, which will be described later. For convenience, the support wall portion 609 is shown by a two-dot chain line in Figures 11, 13, and 14. Also, in Figures 11, 13, and 14, a portion of the storage portion 607 is shown cut away.

[0211] As shown in Fig. 10, the backhoe 680 includes, as an excavation work machine, a boom 530, an arm 540, and a bucket 550. The boom 530, the arm 540, and the bucket 550 are located forward of the upper body 606. The configurations of the boom 530, the arm 540, and the bucket 550 are the same as those in the second embodiment. Therefore, a description thereof will be omitted.

[0212] <Boom swing mechanism> 10, the backhoe 680 is provided with a boom swing mechanism 680A. The boom swing mechanism 680A is a mechanism for swinging the boom 530 left and right relative to the upper body 606. The boom swing mechanism 680A constitutes an electric actuator.

[0213] The boom swing mechanism 680A includes a swing bracket 610 and a pin 620. The configurations of the swing bracket 610 and the pin 620 are the same as those in the second embodiment. That is, as shown in FIG. 10, the swing bracket 610 includes an upper wall 611, a lower wall 612, and a connecting wall 613. As shown in FIG. 11, the upper wall 611 and the lower wall 612 are pentagonal in plan view. As in the second embodiment, the upper wall 611 has a configuration in which a rectangular first portion and a triangular second portion are joined together. The same is true for the lower wall 612. Note that in FIGS. 11, 13, and 14, a portion of the upper wall 611 is cut away. As shown in FIG. 10, the connecting wall 613 connects the front portions of the upper wall 611 and the lower wall 612. A base wall 534 of the boom 530 is fixed to the surface of the connecting wall 613 opposite the surface facing the support wall portion 609. Further description of the upper wall 611, the lower wall 612 and the connecting wall 613 will be omitted.

[0214] The swing bracket 610 is connected to the support wall portion 609 of the upper body 606 via a pin 620. That is, the pin 620 penetrates the upper wall 611 and the lower wall 612 as well as the through-hole 609A of the support wall portion 609. In FIG. 10, the gap between the through-hole 609A and the pin 620 is exaggerated. As in the second embodiment, the pin 620 is rotatable with respect to the through-hole 609A. The pin 620 is supported by the through-hole 609A so as to rotate about a rotation central axis 610V, which is the central axis of the pin 620. Meanwhile, the pin 620 is fixed to the upper wall 611 and the lower wall 612. Therefore, when the pin 620 rotates about the rotation central axis 610V, the upper wall 611 and the lower wall 612 rotate together with the pin 620. That is, the swing bracket 610 is rotatable about the central axis of rotation 610V.

[0215] As shown in Fig. 11, boom swing mechanism 680A includes an extension member 685. Extension member 685 is located at a rear portion of swing bracket 610. Extension member 685 includes an extension wall 685A and a swing connecting shaft 685B. Note that illustration of extension member 685 is omitted in Fig. 10.

[0216] As shown in FIG. 11, the extension wall 685A has, for example, a rectangular plate shape. The extension wall 685A is fixed to the lower wall 612 of the swing bracket 610. More specifically, the extension wall 685A is fixed to an edge of the lower wall 612 that corresponds to one side of a triangle. In this embodiment, the extension wall 685A is located to the right of the rotation central axis 610V. As shown in FIG. 12, the swing connecting shaft 685B protrudes upward from the upper surface of the extension wall 685A. The swing connecting shaft 685B has a cylindrical shape. The central axis of the swing connecting shaft 685B extends substantially in the Z direction. That is, the central axis of the swing connecting shaft 685B is substantially parallel to the rotation central axis 610V.

[0217] As shown in FIG. 11, the boom swing mechanism 680A includes a vehicle body connecting shaft 687. The vehicle body connecting shaft 687 is located in the housing 607 of the upper body 606. In the X direction, the vehicle body connecting shaft 687 is located forward of the bearing axis 603V. As described in the second embodiment, the bearing axis 603V is located approximately in the center of the housing 607 in both the X and Y directions. In the Y direction, the vehicle body connecting shaft 687 is located to the right of the right end of the outer ring 605 of the swivel bearing 603. In addition, in the Y direction, the vehicle body connecting shaft 687 is located to the right of the swing connecting shaft 685B. As shown in FIG. 12, the vehicle body connecting shaft 687 protrudes upward from the bottom wall of the housing 607. The vehicle body connecting shaft 687 is cylindrical. The central axis of the vehicle body connecting shaft 687 extends approximately in the Z direction. That is, the central axis of the body connecting shaft 687 is substantially parallel to the turning central axis 610V.

[0218] <Power unit> 10 and 11, the boom swing mechanism 680A includes a power unit 700. For convenience, the power unit 700 is shown by a two-dot chain line in FIG. 10. Most of the power unit 700 is located inside the housing portion 607. A portion of the power unit 700 protrudes forward from the housing portion 607.

[0219] As shown in FIG. 12, the power unit 700 includes a first member 701. The first member 701 is cylindrical. Hereinafter, the central axis of the first member 701 will be referred to as a reference axis 701C. The reference axis 701C extends in a direction substantially perpendicular to the Z direction. Hereinafter, when there is no need to distinguish between two directions along the reference axis 701C, these will be collectively referred to as a reference axial direction 701L. One specific direction of the reference axial directions 701L will be referred to as a positive direction, and the opposite direction will be referred to as a negative direction.

[0220] The power unit 700 includes a first connecting wall 705. The first connecting wall 705 is located downward relative to the first member 701. The first connecting wall 705 is located near the end of the first member 701 on the negative side. The first connecting wall 705 is fixed to the first member 701. The first connecting wall 705 is cylindrical. The central axis of the first connecting wall 705 extends substantially in the Z direction. The inner diameter of the first connecting wall 705 substantially matches the diameter of the vehicle body connecting shaft 687. The first connecting wall 705 accommodates the vehicle body connecting shaft 687. The first connecting wall 705 is rotatable relative to the vehicle body connecting shaft 687. In other words, the first connecting wall 705, and therefore the first member 701, are coupled to the accommodation portion 607 in a rotatable state about the central axis of the vehicle body connecting shaft 687.

[0221] The power unit 700 includes a second member 702. The second member 702 is inserted into the first member 701 from the positive-side end of the first member 701. A portion of the second member 702 near the positive-side end protrudes from the first member 701 toward the positive side. The second member 702 extends along a reference axis 701C. The second member 702 is cylindrical. The central axis of the second member 702 substantially coincides with the reference axis 701C. The dimension of the second member 702 in the reference axial direction 701L is larger than the dimension of the first member 701 in the reference axial direction 701L. The outer diameter of the second member 702 is slightly smaller than the inner diameter of the first member 701. The outer peripheral surface of the second member 702 is slidable relative to the inner peripheral surface of the first member 701. An internal thread is formed on the inner peripheral surface of the second member 702. The female thread is formed over substantially the entire area of the second member 702 in the reference axial direction 701L. The female thread is not shown in Fig. 12. The second member 702 is reciprocatable relative to the first member 701 in the reference axial direction 701L by a force from a drive mechanism 710, which will be described later.

[0222] The power unit 700 includes a second connecting wall 707. The second connecting wall 707 is located at the end of the second member 702 on the positive side. For example, the second connecting wall 707 has a rectangular parallelepiped shape. The second connecting wall 707 closes the opening at the end of the second member 702 on the positive side. The second connecting wall 707 is fixed to the end of the second member 702 on the positive side. The second connecting wall 707 includes an accommodating recess 707A. The accommodating recess 707A is open downward. The outer shape of the accommodating recess 707A is cylindrical. The diameter of the accommodating recess 707A is approximately the same as the diameter of the swing connecting shaft 685B. The accommodating recess 707A accommodates the swing connecting shaft 685B. The second connecting wall 707 is rotatable relative to the swing connecting shaft 685B. That is, the second connecting wall 707 and therefore the second member 702 are connected to the extension member 685 and therefore the swing bracket 610 in a state in which they can rotate about the central axis of the swing connecting shaft 685B.

[0223] 11, due to the positions of the body connecting shaft 687 and the swing connecting shaft 685B, the first member 701 and the second member 702 connected thereto are located to the right of the center of the accommodating section 607 in the Y direction. At the same time, the reference axis 701C is inclined with respect to the X direction so that it is positioned more to the right as it moves rearward.

[0224] <Drive mechanism> As shown in FIG. 12, the power unit 700 includes an electric drive mechanism 710. The drive mechanism 710 includes a case 711. The case 711 includes a first portion 711A and a second portion 711B. The first portion 711A is located upward relative to the first member 701. With respect to the reference axis direction 701L, the first portion 711A is located on the negative side of the center of the first member 701. The first portion 711A is cylindrical. The central axis of the first portion 711A is approximately parallel to the reference axis 701C. The end of the first portion 711A on the positive side is closed. The second portion 711B is located on the negative side of the first portion 711A. The second portion 711B is rectangular parallelepiped-shaped. The second portion 711B is hollow. In the Z direction, the second portion 711B exists in a range spanning the first portion 711A and the first member 701. A first side wall 711P, which is one of the side walls of the second portion 711B, is connected to the negative side end of the first portion 711A and the negative side end of the first member 701. The interior of the second portion 711B is in communication with the interior of the first portion 711A. The interior of the second portion 711B is also in communication with the interior of the first member 701.

[0225] The drive mechanism 710 includes an electric motor 712. The electric motor 712 is a drive source of the drive mechanism 710 and drives the reciprocating motion of the second member 702 relative to the first member 701. The electric motor 712 is located inside the first portion 711A of the case 711. The electric motor 712 operates in response to power supplied from a battery (not shown). The electric motor 712 includes a housing 712A and an output shaft 712B. The housing 712A is fixed to the inner wall of the first portion 711A. The output shaft 712B protrudes from the housing 712A. The output shaft 712B is cylindrical. The central axis of the output shaft 712B extends approximately parallel to the reference axis 701C. The output shaft 712B is rotatable relative to the housing 712A. The output shaft 712B rotates around its own central axis. That is, the central axis of the output shaft 712B is the central axis of rotation of the electric motor 712. The output shaft 712B is rotatable in both forward and reverse directions in response to the supply of power to the housing 712A.

[0226] The drive mechanism 710 includes a reducer 713. The reducer 713 is adjacent to the electric motor 712 in the reference axial direction 701L. The reducer 713 is located on the negative side of the electric motor 712. Like the electric motor 743, the reducer 713 is located inside the first portion 711A of the case 711. The reducer 713 is fixed to the inner wall of the first portion 711A. The reducer 713 is connected to the output shaft 712B of the electric motor 712. The torque of the output shaft 712B of the electric motor 712 is input to the reducer 713. The reducer 713 amplifies the torque of the output shaft 712B of the electric motor 712 by a predetermined ratio and outputs the amplified torque. The reducer 713 may be, for example, an eccentric oscillating gear type or a planetary gear type. The reducer 713 may be of any type as long as it is configured to amplify and output the torque from the electric motor 712 .

[0227] The drive mechanism 710 includes an output member 714. The output member 714 protrudes from the reducer 713 toward the negative direction. The output member 714 is located inside the second portion 711B of the case 711. The output member 714 is cylindrical. The central axis of the output member 714 substantially coincides with the central axis of the output shaft 712B of the electric motor 712. In other words, the central axis of the output member 714 is substantially parallel to the reference axis 701C. The output member 714 is coupled to the reducer 713. The output member 714 receives torque from the reducer 713 and rotates about its own central axis.

[0228] The drive mechanism 710 includes a screw shaft 718. The screw shaft 718 is inserted into the second member 702 from the end on the negative side of the second member 702. A portion of the screw shaft 718 closer to the negative side protrudes from the second member 702 toward the negative side. The portion of the screw shaft 718 protruding from the second member 702 is located inside the second portion 711B of the case 711. The screw shaft 718 is cylindrical. The diameter of the screw shaft 718 is smaller than the inner diameter of the second member 702. The central axis of the screw shaft 718 substantially coincides with the reference axis 701C. A male thread is formed on the outer circumferential surface of the screw shaft 718. A female thread is formed over substantially the entire area of the screw shaft 718 in the reference axis direction 701L. The negative end of the screw shaft 718 is located at approximately the same position as the negative end of the output member 714 in relation to the reference axial direction 701L.

[0229] The drive mechanism 710 includes a plurality of balls 719. FIG. 12 shows six of the plurality of balls 719 as a representative. The number of balls 719 is not limited to six. The plurality of balls 719 are interposed between the inner circumferential surface of the second member 702 and the outer circumferential surface of the screw shaft 718. The plurality of balls 719 are held between the inner circumferential surface of the second member 702 and the outer circumferential surface of the screw shaft 718. The plurality of balls 719 guide the relative rotation of the screw shaft 718 with respect to the second member 702. Guided by the balls 719, the screw shaft 718 rotates about its own central axis, and therefore about the reference axis 701C.

[0230] The drive mechanism 710 includes a transmission mechanism 715. The transmission mechanism 715 is located inside the second portion 711B of the case 711. The transmission mechanism 715 includes, for example, a cylindrical first pulley, a cylindrical second pulley, and a belt. An output member 714 is attached to the first pulley. The first pulley rotates integrally with the output member 714. A threaded shaft 718 is attached to the second pulley. The second pulley rotates integrally with the threaded shaft 718. The belt is wound around the first pulley and the second pulley. The belt transmits the rotation of the first pulley to the second pulley. The belt causes the first pulley and the second pulley to operate in conjunction with each other. With this configuration, the transmission mechanism 715 transmits the rotation of the output shaft 712B of the electric motor 712, and therefore the rotation of the output member 714, to the threaded shaft 718. The electric motor 712 then rotates the screw shaft 718. That is, the screw shaft 718 rotates about the reference axis 701C in response to the rotation of the output shaft 712B of the electric motor 712. Note that any type of transmission mechanism 715 may be used as long as it can cause the output member 714 and the screw shaft 718 to operate in conjunction with each other. For example, the transmission mechanism 715 may use a combination of a sprocket and a chain instead of a combination of a pulley and a belt. For example, the transmission mechanism 715 may be a gear mechanism that causes the output member 714 and the screw shaft 718 to operate in conjunction with each other through the meshing of gears.

[0231] <Operation of the Fourth Embodiment> In the power unit 700, when the output shaft 712B of the electric motor 712 rotates, the rotation of the output shaft 712B is transmitted to the screw shaft 718. The screw shaft 718 rotates in either the forward or reverse direction depending on the rotation direction of the output shaft 712B of the electric motor 712. The rotation of the screw shaft 718 is transmitted to the second member 702 via balls 719. When the screw shaft 718 rotates, the second member 702 moves relative to the screw shaft 718 and the first member 701 in the reference axial direction 701L. That is, the second member 702 moves due to the force received from the screw shaft 718 via the balls 719. As indicated by arrow 702V in FIG. 12 , the second member 702 moves in the positive or negative direction relative to the first member 701 depending on the rotation direction of the screw shaft 718. As the second member 702 moves in this manner, the amount of protrusion of the second member 702 relative to the first member 701 increases or decreases. That is, the power unit 700 expands and contracts in the reference axial direction 701L.

[0232] The extension and contraction of the power unit 700 as described above drives the left and right swing of the swing bracket 610 and therefore the boom 530. This point will be explained below. In the following, as shown in FIG. 11, the position of the extension member 685 when the swing bracket 610 and the boom 530 face forward relative to the upper body 606 is defined as the basic position. The total length of the power unit 700 at this time is defined as a first value. Specifically, the total length of the power unit 700 is the length of the power unit 700 in the direction along the reference axis 701C.

[0233] First, the swing of the boom 530 to the left will be described. It is assumed that the extension member 685 is currently in its home position. In this state, it is assumed that the second member 702 moves in the forward direction relative to the first member 701. At the same time, it is assumed that the overall length of the power unit 700 becomes longer than the first value. Then, as shown in FIG. 13 , the extension member 685 connected to the power unit 700 moves forward relative to the home position shown in FIG. 11 . That is, the extension member 685 moves away from the front wall of the accommodation section 607 of the upper body 606. Accordingly, the swing bracket 610 connected to the extension member 685 rotates leftward about the rotation central axis 610V. At the same time, the boom 530 rotates leftward about the rotation central axis 610V.

[0234] Next, the swing of the boom 530 to the right will be described. It is assumed that the extension member 685 is currently in its home position. In this state, it is assumed that the second member 702 moves in the negative direction relative to the first member 701. At the same time, it is assumed that the power unit 700 becomes shorter than the first value. Then, as shown in FIG. 14, the extension member 685 moves rearward relative to the home position shown in FIG. 11. That is, the extension member 685 approaches the front wall of the accommodation section 607 of the upper body 606. Accordingly, the swing bracket 610 connected to the extension member 685 rotates to the right about the rotation central axis 610V. At the same time, the boom 530 rotates to the right about the rotation central axis 610V.

[0235] As described above, the boom 530 swings in response to the extension and retraction of the power unit 700. Although detailed illustration is omitted, when the boom 530 swings, the reference axis 701C rotates left and right about the vehicle body connecting shaft 687. This rotation of the reference axis 701C allows the power unit 700 to freely extend and retract. In other words, in this embodiment, the power unit 700 is rotatably connected to the vehicle body connecting shaft 687 and the swing connecting shaft 685B, which allows the power unit 700 to extend and retract by a large amount. Furthermore, by ensuring a large extension and retraction amount of the power unit 700, the swing bracket 610 can rotate over a wide range.

[0236] <Effects of the Fourth Embodiment> (4-1) As described in the operation of the above embodiment, in the back shovel 680 of this embodiment, the electric motor 712 can be used as a drive source to swing the boom 530 left and right.

[0237] (4-2) In the back shovel 680 of this embodiment, the rotational motion of the electric motor 712, which serves as the drive source, is converted into linear motion of the second member 702, thereby causing the second member 702 to reciprocate relative to the first member 701. In this embodiment, a so-called ball screw mechanism is used as the mechanism responsible for converting such motion. A ball screw mechanism can smoothly convert rotational motion into linear motion.

[0238] (4-3) As described in the first embodiment, an external load may be input to the boom 530 in response to a collision between the bucket 550 and an excavation target. This load is referred to as a collision load. In the case of the excavator 680 of this embodiment, the collision load may be transmitted to the screw shaft 718 via the swing bracket 610, the extension member 685, and the second member 702. Here, the collision load acting on the screw shaft 718 mainly has a component in the reference axial direction 701L, which is the extension direction of the screw shaft 718. On the other hand, this collision load is unlikely to act as a force that moves each component in a direction intersecting the reference axial direction 701L. In other words, the collision load acting on the screw shaft 718 is unlikely to be transmitted as a force from the screw shaft 718 in the Z direction. Therefore, the collision load acting on the screw shaft 718 is unlikely to be transmitted to the transmission mechanism 715 or the output member 714. Therefore, the configuration of this embodiment can prevent the collision load acting on the screw shaft 718 from reaching the reducer 713 and the electric motor 712. As explained in the second embodiment, this eliminates the need to provide the reducer 717 and the electric motor 712 with a configuration for withstanding the collision load. Therefore, for example, it is possible to prevent the reducer 713 from becoming larger.

[0239] <Modification of the Fourth Embodiment> The fourth embodiment can be modified as follows: The first to fourth embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0240] The configuration of the power transmission path from the electric motor 712 to the screw shaft 718 is not limited to the example of the above embodiment. For example, in this power transmission path, the reducer 713 and the output member 714 may be eliminated from between the electric motor 712 and the screw shaft 718. The output shaft 712B of the electric motor 712 may be connected to the screw shaft 718 by the transmission mechanism 715. In addition, in this power transmission path, the transmission mechanism 715 may be eliminated. In addition, the screw shaft 718 and the electric motor 712 may be arranged coaxially. In other words, it is not necessary for the rotational center axis of the electric motor 712 and the reference axis 701C to be arranged parallel to each other at different positions. The power transmission path may be configured so as to be able to transmit the rotation of the electric motor 712 to the screw shaft 718.

[0241] The connection destination of the first member 701 and the connection destination of the second member 702 may be reversed from the example of the above embodiment. That is, the first member 701 may be connected to the swing connection shaft 685B, and the second member 702 may be connected to the vehicle body connection shaft 687.

[0242] The location of the vehicle body connecting shaft 687 is not limited to the example in the above embodiment. The vehicle body connecting shaft 687 may be provided anywhere on the vehicle body, taking into consideration the rotation range of the swing bracket 610 and therefore the boom 530.

[0243] The location of the swing connecting shaft 685B is not limited to the example in the above embodiment. For example, the swing connecting shaft 685B may be provided on the swing bracket 610 itself. The swing connecting shaft 685B only needs to be provided so as to operate integrally with the swing bracket 610, taking into consideration the rotation range of the swing bracket 610 and therefore the boom 530, which is determined by the positional relationship with the vehicle body connecting shaft 687.

[0244] If the positions of the swing connecting shaft 685B and the vehicle body connecting shaft 687 are changed from those in the above embodiment, the position of the power unit 700 may also be changed accordingly. Even in this case, the backhoe 680 may be configured so as not to hinder the extension and contraction of the power unit 700 and to transmit the extension and contraction to the swing bracket 610.

[0245] The configuration and arrangement of the first connecting wall 705 are not limited to the example of the above embodiment. For example, the first connecting wall 705 may be located near the center of the first member 701 in the reference axial direction 701L. The first connecting wall 705 only needs to be able to accommodate the body connecting shaft 687 and be rotatable relative to the body connecting shaft 687. As with the first connecting wall 705, the configuration and arrangement of the second connecting wall 707 are not limited to the example of the above embodiment. The second connecting wall 707 only needs to be able to accommodate the swing connecting shaft 685B and be rotatable relative to the swing connecting shaft 685B.

[0246] The manner in which the first member 701 and the second member 702 are rotatably coupled to the opposing object is not limited to the example of the above embodiment. For example, the first member 701 and the second member 702 may be coupled to the opposing object without using a group of walls such as the first coupling wall 705 and the second coupling wall 707. The first member 701 may be coupled to one of the vehicle body and the swing bracket 610 in a state in which it can rotate about a central axis parallel to the turning central axis 610V. The second member 702 may be coupled to the other of the vehicle body and the swing bracket 610 in a state in which it can rotate about a central axis parallel to the turning central axis 610V.

[0247] As with the modified example of the second embodiment, the configuration, arrangement, and connection mode of the swing bracket 610 to the vehicle body are not limited to those of the above embodiment. The swing bracket 610 only needs to be fixed to the boom 530 and connected to the vehicle body so as to be rotatable about the central axis of rotation 610V. Also, as with the modified example of the second embodiment, the configuration of the vehicle body supporting the swing bracket 610 is not limited to those of the above embodiment. The central axis of rotation 610V may be offset from the center of the storage section 607 in the Y direction. The central axis of rotation 610V may extend vertically along the vehicle body as a whole, and may be tilted relative to the Z direction within a range of approximately 15°, for example. The configuration, arrangement, and connection mode of the swing bracket 610 to the vehicle body may be the same as that of the sixth embodiment shown in FIG. 24, which will be described later.

[0248] The location where the boom 530 is fixed to the swing bracket 610 is not limited to the example in the above embodiment. The boom 530 may be fixed to any location on the swing bracket 610.

[0249] The swivel bearing 603 is not essential for the backhoe 680. That is, depending on the configuration of the backhoe 680, the upper body 606 may not be able to swivel relative to the lower body 602, and the upper body 606 and the lower body 602 may be integrated. In this case, the upper body 606 and the lower body 602 constitute the vehicle body. That is, the vehicle body is not limited to the example of the above embodiment.

[0250] The construction machinery to which the boom swing mechanism 680A, which is an electric actuator, can be applied is not limited to the excavator 680. In the above embodiment, various means may be used to fasten the two members together, such as bolting, welding, integral molding, spline connection, etc.

[0251] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved.

[0252] The configuration of the power unit 700 is not limited to the example of the above embodiment. The power unit 700 only needs to be configured so that its overall length can expand and contract in response to the relative movement of the second member 702 with respect to the first member 701. The excavator 680 only needs to be configured so that the expansion and contraction of the power unit 700 can be transmitted to the rotation of the swing bracket 610. For example, the first member 701 only needs to be cylindrical as a whole and is not limited to being a complete cylinder. The second member 702 only needs to be configured so that it can reciprocate within the first member 701. The configuration and arrangement of the first connecting wall 705 may be changed from the example of the above embodiment as long as the first member 701 can be rotatably connected to either the vehicle body or the swing bracket 610. The same applies to the configuration and arrangement of the second connecting wall 707. The drive mechanism 710 is not limited to one that uses a ball screw mechanism. The drive mechanism 710 only needs to be electrically driven and be able to output a force that causes the second member 702 to reciprocate in the reference axial direction 701L.

[0253] For example, instead of the power unit 700 of the above embodiment, a power unit 730 shown in Fig. 15 may be employed. In Fig. 15, parts that are the same as or have substantially the same functions as those in Figs. 10 to 14 are given the same reference numerals as those in Figs. 10 to 14.

[0254] The power unit 730 includes a first member 731. The first member 731 includes a peripheral wall 731A, a first end wall 731B, a second end wall 731C, a first porthole 731D, and a second porthole 731E. The peripheral wall 731A is cylindrical. Hereinafter, the central axis of the peripheral wall 731A will be referred to as a reference axis 731V. The reference axis 731V extends in a direction substantially perpendicular to the Z direction. Hereinafter, when there is no need to distinguish between two directions along the reference axis 731V, these will be collectively referred to as a reference axial direction 731L. One specific direction of the reference axial direction 731L will be referred to as a positive direction, and the opposite direction will be referred to as a negative direction.

[0255] The first end wall 731B closes the end of the circumferential wall 731A on the positive side. The second end wall 731C closes the end of the circumferential wall 731A on the negative side. The circumferential wall 731A, the first end wall 731B, and the second end wall 731C define a fluid chamber 731P to which hydraulic oil is supplied and discharged. The first porthole 731D is located near the end of the circumferential wall 731A on the positive side. The first porthole 731D penetrates the circumferential wall 731A in the radial direction about the reference axis 731V. The second porthole 731E is located near the end of the circumferential wall 731A on the negative side. The second porthole 731E penetrates the circumferential wall 731A in the radial direction.

[0256] The power unit 730 includes a first connecting wall 705. The first connecting wall 705 is located downward relative to a peripheral wall 731A of the first member 731. The first connecting wall 705 is located near the negative end of the peripheral wall 731A. The first connecting wall 705 is fixed to the peripheral wall 731A. The configuration of the first connecting wall 705 is the same as that described in FIG. 12. That is, the first connecting wall 705 is cylindrical. The first connecting wall 705 accommodates the vehicle body connecting shaft 687. The first connecting wall 705 is rotatable relative to the vehicle body connecting shaft 687. That is, the first connecting wall 705, and therefore the first member 731, is connected to the accommodation portion 607 in a rotatable state about the central axis of the vehicle body connecting shaft 687.

[0257] The power unit 730 includes a second member 732. The second member 732 includes a piston 732A and a rod 732B. The piston 732A is located in a fluid chamber 731P. The piston 732A is, for example, disk-shaped. The central axis of the piston 732A substantially coincides with the reference axis 731V. The diameter of the piston 732A substantially coincides with the inner diameter of the peripheral wall 731A of the first member 731. The piston 732A divides the fluid chamber 731P into two in the reference axis direction 731L. Hereinafter, of the two fluid chambers 731P, the portion located on the positive side will be referred to as a first fluid chamber 731P1, and the portion located on the negative side will be referred to as a second fluid chamber 731P2. The rod 732B is inserted into the first member 731 from the positive end of the first member 731. That is, rod 732B penetrates first end wall 731B and is inserted inside peripheral wall 731A. Rod 732B is cylindrical. The central axis of rod 732B substantially coincides with reference axis 731V. The tip of rod 732B on the negative side is fixed to piston 732A. That is, when viewed from piston 732A, rod 732B extends from piston 732A toward the positive side. A portion of rod 732B near the end on the positive side protrudes from first member 731. The entire rod 732B and piston 732A can reciprocate in reference axis direction 731L relative to first member 731 by force from drive mechanism 740, which will be described later.

[0258] The power unit 730 includes a second connecting wall 707. The second connecting wall 707 is located near the positive end of the rod 732B of the second member 732. The second connecting wall 707 is located downward relative to the rod 732B. The second connecting wall 707 is fixed to the rod 732B. The configuration of the second connecting wall 707 is the same as that described in FIG. 12. That is, the second connecting wall 707 includes an accommodating recess 707A that is open downward. The accommodating recess 707A accommodates the swing connecting shaft 685B. The second connecting wall 707 is rotatable relative to the swing connecting shaft 685B. That is, the second connecting wall 707, and therefore the second member 732, is connected to the extension member 685 in a rotatable state about the central axis of the swing connecting shaft 685B.

[0259] The power unit 730 includes an electric drive mechanism 740. The drive mechanism 740 includes a case 741, a tank 742, an electric motor 743, a pump 744, and a switching valve 745. The drive mechanism 740 also includes, as fluid passages, a first base flow path 746A, a second base flow path 746B, a first extension flow path 747A, and a second extension flow path 747B. The drive mechanism 740 forms a fluid circuit.

[0260] The case 741 is located above the first member 731. The case 741 is fixed to the first member 731. The case 741 houses each of the components of the drive mechanism 740.

[0261] The tank 742 stores hydraulic oil. The first base flow path 746A connects the tank 742 and the switching valve 745. The second base flow path 746B connects the tank 742 and the switching valve 745. The first extension flow path 747A connects the switching valve 745 and the first porthole 731D. The second extension flow path 747B connects the switching valve 745 and the second porthole 731E. The switching valve 745 switches the connection destination of the first base flow path 746A between the first extension flow path 747A and the second extension flow path 747B. The switching valve 745 switches the connection destination of the second base flow path 746B between the first extension flow path 747A and the second extension flow path 747B. Specifically, the switching valve 745 switches between a first mode and a second mode. In the first mode, the switching valve 745 connects the first base flow path 746A to the first extension flow path 747A, and also connects the second base flow path 746B to the second extension flow path 747B. In the second mode, the switching valve 745 connects the first base flow path 746A to the second extension flow path 747B, and also connects the second base flow path 746B to the first extension flow path 747A. The pump 744 is located midway along the first base flow path 746A. The pump 744 is driven by the electric motor 743, and is driven by the electric motor 743. The pump 744 pumps the hydraulic oil in the tank 742 to the switching valve 745 side. Note that the electric motor 743 is supplied with power from a battery (not shown). The power unit 730 is configured as described above.

[0262] The operation of the power unit 730 will now be described. In the power unit 730, the second member 732 can reciprocate in the reference axial direction 731L in response to the operation of the drive mechanism 740, as indicated by the arrow 730V in FIG. 15. Of this reciprocating motion, the movement of the second member 732 in the negative direction will first be described. Assume that the piston 732A is located near the center of the peripheral wall 731A of the first member 731 in the reference axial direction 731L. Assume that both the first fluid chamber 731P1 and the second fluid chamber 731P2 are filled with hydraulic oil. This state is referred to as the basic state. Assume that in the basic state, the switching valve 745 is set to the first mode and the pump 744 is driven. Then, hydraulic oil in the tank 742 is supplied to the first fluid chamber 731P1 via the first base flow path 746A and the first extension flow path 747A. That is, the first base flow path 746A and the first extension flow path 747A supply hydraulic oil to the first fluid chamber 731P1 in response to the operation of the pump 744. When hydraulic oil is supplied to the first fluid chamber 731P1, hydraulic pressure is applied to the piston 732A in the negative direction. This causes the piston 732A to move in the negative direction. At the same time, hydraulic oil in the second fluid chamber 731P2 is discharged to the tank 742 via the second extension flow path 747B and the second base flow path 746B. That is, the second extension flow path 747B and the second base flow path 746B discharge hydraulic oil from the second fluid chamber 731P2 in response to the operation of the pump 744. Now, when the piston 732A moves in the negative direction, the piston 732A and the rod 732B as a whole move in the negative direction relative to the first member 731. Accordingly, the overall length of the power unit 730 in the reference axial direction 731L becomes shorter than that in the basic state.

[0263] Next, the movement of the second member 732 in the forward direction will be described. In the above-described basic state, assume that the switching valve 745 is set to the second mode and the pump 744 is driven. Then, hydraulic oil in the tank 742 is supplied to the second fluid chamber 731P2 via the first base flow path 746A and the second extension flow path 747B. That is, the first base flow path 746A and the second extension flow path 747B supply hydraulic oil to the second fluid chamber 731P2 in response to the driving of the pump 744. When hydraulic oil is supplied to the second fluid chamber 731P2, hydraulic pressure is applied to the piston 732A in the forward direction. Then, the piston 732A moves in the forward direction. At the same time, hydraulic oil in the first fluid chamber 731P1 is discharged to the tank 742 via the first extension flow path 747A and the second base flow path 746B. That is, the first extension flow path 747A and the second base flow path 746B discharge the hydraulic oil from the first fluid chamber 731P1 in response to the driving of the pump 744. Now, when the piston 732A moves in the forward direction, the piston 732A and the rod 732B as a whole move in the forward direction relative to the first member 731. Accordingly, the overall length of the power unit 730 in the reference axial direction 731L becomes longer than that in the basic state.

[0264] As described above, second member 732 operates by receiving hydraulic oil pressure from drive mechanism 740. Accordingly, power unit 730 extends and retracts. The extension and retraction of power unit 730 drives the left and right swing of swing bracket 610 and therefore boom 530, in the same way as described with reference to Figures 11 to 14.

[0265] Adopting the power unit 730 in the excavator 680 has the following advantages. As described in (4-3) above, an external load may be input to the boom 530 when the bucket 550 collides with an excavation target. This load is referred to as a collision load. When the power unit 730 is adopted, the collision load may be transmitted to the second member 732 via the swing bracket 610 and the extension member 685. The collision load may then act on the second member 732 so as to move the second member 732 in the reference axis direction 731L. Here, the piston 732A of the second member 732 is located in the fluid chamber 731P. Therefore, when the second member 732 attempts to move due to the collision load, resistance from the hydraulic oil is applied to the piston 732A located in the fluid chamber 731P. The movement of the piston 732A is then suppressed by the hydraulic oil. Therefore, the movement of the piston 732A and therefore the second member 732 is limited to an extremely small amount. In other words, when the power unit 730 is employed, the collision load input to the second member 732 can be attenuated by the hydraulic pressure of the fluid chamber 731P. Therefore, when the power unit 730 is employed, for example, it is not necessary to provide the drive mechanism 740 with a configuration for withstanding the collision load. This makes it possible to prevent the drive mechanism 740 from becoming larger, for example.

[0266] The configuration of the power unit 730 is not limited to the example shown in FIG. 15 . The power unit 730 only needs to be configured to move the second member 732 relative to the first member 731 in response to fluid pressure. For example, the configuration of the flow path from the tank 742 to the fluid chamber 731P may be changed from the example shown in FIG. 15 . The flow path only needs to be configured to supply and discharge hydraulic oil to and from the first fluid chamber 731P1 and the second fluid chamber 731P2 in response to operation of the pump 744 driven by the electric motor 743. The fluid supplied and discharged to and from the first fluid chamber 731P1 and the second fluid chamber 731P2 is not limited to hydraulic oil. The fluid may be, for example, air. The peripheral wall 731A of the first member 731 is not limited to a cylindrical shape. The peripheral wall 731A may be a rectangular tubular shape. The peripheral wall 731A only needs to be cylindrical overall. The shape of the piston 732A may be appropriately changed to match the shape of the peripheral wall 731A. It is sufficient that the piston 732A is able to divide the fluid chamber 731P into two in the reference axis direction 731L. The shape of the rod 732B is not limited to a cylindrical shape, and may be any shape as long as it is columnar.

[0267] The power unit 750 shown in Figures 16 to 18 may be used in the backhoe 680. In Figures 16 to 18, parts that are the same as or have substantially the same functions as those in Figures 10 to 15 are denoted by the same reference numerals as those in Figures 10 to 15.

[0268] As a premise for explaining the power unit 750, when the backhoe 680 is viewed from above in a direction along the turning center axis 610V as shown in Fig. 17, an imaginary line segment connecting the turning center axis 610V and the bearing axis 603V is referred to as a first line segment 680X. As described in the second embodiment, both the turning center axis 610V and the bearing axis 603V are located at approximately the center of the storage section 607 in the Y direction. Therefore, the first line segment 680X extends in the X direction at approximately the center of the storage section 607 in the Y direction.

[0269] As shown in FIG. 16, the power unit 750 includes a first member 751. As shown in FIG. 17, the first member 751 is located on the right side of the first line segment 680X, i.e., the center of the accommodation portion 607 in the Y direction. As shown in FIGS. 16 and 17, the first member 751 has a rectangular cylindrical shape. Hereinafter, the central axis of the first member 751 will be referred to as a reference axis 751V. The reference axis 751V extends in a direction substantially perpendicular to the Z direction. Hereinafter, when there is no need to distinguish between two directions along the reference axis 751V, these will be collectively referred to as a reference axial direction 751L. One specific reference axial direction 751L will be referred to as a positive direction, and the opposite direction will be referred to as a negative direction.

[0270] As shown in FIG. 16, the first member 751 includes a first wall 751A, a second wall 751B, and a third wall 751C. Furthermore, as shown in FIG. 17, the first member 751 includes a fourth wall 751D. Each of these walls has a rectangular plate shape and is elongated in the reference axis direction 751L. As shown in FIG. 16, the main surface of the first wall 751A and the main surface of the second wall 751B face each other vertically. The main surface is the surface of a plate-shaped member with the largest area. The first wall 751A is located above the second wall 751B. As shown in FIGS. 16 and 17, the third wall 751C connects the long sides of the first wall 751A and the second wall 751B. The fourth wall 751D connects the long sides of the first wall 751A and the second wall 751B to each other on the opposite side of the third wall 751C with the first wall 751A and the second wall 751B in between. As shown in FIG. 17, the fourth wall 751D is located closer to the center of the accommodation section 607 than the first wall 751A, the second wall 751B, and the third wall 751C. As shown in FIG. 18, the fourth wall 751D has a communication opening 751P. The communication opening 751P is an opening that communicates between the inside and the outside of the first member 751. As shown in FIG. 17, the communication opening 751P is located near the center of the fourth wall 751D in the reference axial direction 751L.

[0271] As shown in FIG. 16 , the power unit 750 includes a first connecting wall 705. The first connecting wall 705 is located downward relative to the second wall 751B of the first member 751. The first connecting wall 705 is located near the negative end of the second wall 751B. The first connecting wall 705 is fixed to the second wall 751B. The configuration of the first connecting wall 705 is the same as that described in FIG. 12 . That is, the first connecting wall 705 is cylindrical. The first connecting wall 705 accommodates the vehicle body connecting shaft 687. The first connecting wall 705 is rotatable relative to the vehicle body connecting shaft 687. That is, the first connecting wall 705, and therefore the first member 751, is connected to the accommodation portion 607 in a rotatable state about the central axis of the vehicle body connecting shaft 687.

[0272] The power unit 750 includes a second member 752. The second member 752 extends from the inside to the outside of the first member 751. The second member 752 includes a main body 752A and a plurality of rack teeth 752B. The main body 752A is shaped like a rectangular column. The central axis of the main body 752A substantially coincides with the reference axis 751V. The main body 752A is inserted into the first member 751 from the end of the first member 751 on the positive side. A portion of the main body 752A near the end on the positive side is exposed from the first member 751. The plurality of rack teeth 752B protrude from the outer surface of the main body 752A that faces the fourth wall 751D of the first member 751. The plurality of rack teeth 752B are arranged at equal intervals in the reference axis direction 751L. The rack teeth 752B are provided over almost the entire area of the main body 752A in the reference axial direction 751L. The second member 752 is reciprocable relative to the first member 751 in the reference axial direction 751L by the force of a drive mechanism 755, which will be described later.

[0273] The power unit 750 includes a second connecting wall 707. The second connecting wall 707 is located near the end of the main body 752A of the second member 752 on the positive side. The second connecting wall 707 is located downward relative to the main body 752A. The second connecting wall 707 is fixed to the main body 752A. The configuration of the second connecting wall 707 is the same as that described in FIG. 12. That is, the second connecting wall 707 includes an accommodating recess 707A that is open downward. The accommodating recess 707A accommodates the swing connecting shaft 685B. The second connecting wall 707 is rotatable relative to the swing connecting shaft 685B. That is, the second connecting wall 707, and therefore the second member 752, is connected to the extension member 685 in a rotatable state about the central axis of the swing connecting shaft 685B.

[0274] The power unit 750 includes an electric drive mechanism 755. The drive mechanism 755 is located near the center of the first member 751 in the reference axis direction 751L. As shown in FIG. 17, the drive mechanism 755 is disposed at a position closer to the fourth wall 751D with respect to the reference axis 751V. As shown in FIG. 16, the drive mechanism 755 includes an electric motor 756, a reducer 757, and a pinion gear 758.

[0275] The electric motor 756 operates in response to power supply from a battery (not shown). The electric motor 756 includes a housing 756A and an output shaft 756B. The housing 756A is located outside the first member 751. The housing 756A is located above the first wall 751A of the first member 751. The output shaft 756B protrudes downward from the housing 756A. The output shaft 756B is cylindrical. The central axis of the output shaft 756B extends substantially in the Z direction. The output shaft 756B is rotatable relative to the housing 756A. The output shaft 756B rotates about its own central axis. In other words, the central axis of the output shaft 756B is the rotational central axis 756V of the electric motor 756. The output shaft 756B is rotatable in both forward and reverse directions in response to power supply to the housing 756A.

[0276] The reducer 757 is located below the electric motor 756. The reducer 757 includes a reducer body 757A and a transmission shaft 757B. Like the electric motor 756, the reducer body 757A is located outside the first member 751 and above the first wall 751A of the first member 751. The reducer body 757A is fixed to the first wall 751A. The reducer body 757A is connected to the output shaft 756B of the electric motor 756. The torque of the output shaft 756B of the electric motor 756 is input to the reducer body 757A. The reducer body 757A amplifies the torque of the output shaft 756B of the electric motor 756 by a predetermined ratio and outputs the amplified torque to the transmission shaft 757B. The transmission shaft 757B protrudes downward from the reducer body 757A. The transmission shaft 757B is cylindrical. The central axis of the transmission shaft 757B substantially coincides with the central rotation axis 756V of the electric motor 756. In the Z direction, a portion of the transmission shaft 757B that is lower than the center is located inside the first member 751. The transmission shaft 757B is rotatable relative to the reducer main body 757A. The transmission shaft 757B rotates around its own central axis. The reducer 757 may be, for example, an eccentric oscillating gear type or a planetary gear type. Any type of reducer 757 may be used as long as it is configured to amplify and output the torque from the electric motor 756.

[0277] The pinion gear 758 is located below the reducer body 757A. In the Z direction, the pinion gear 758 is located between the first wall 751A and the second wall 751B of the first member 751. As shown in FIG. 17, in the Y direction, the pinion gear 758 is disposed so as to straddle the fourth wall 751D of the first member 751. That is, a portion of the pinion gear 758 is located outside the first member 751. The remaining portion of the pinion gear 758 enters the inside of the first member 751 through the communication opening 751P of the fourth wall 751D. As shown in FIG. 16, the pinion gear 758 includes a gear body 758A and a plurality of pinion teeth 758B. The gear body 758A is cylindrical. The central axis of the gear body 758A substantially coincides with the rotational central axis 756V of the electric motor 756. A transmission shaft 757B of the reducer 757 is disposed in the central hole of the gear body 758A. The gear body 758A is fixed to the transmission shaft 757B. The gear body 758A rotates integrally with the transmission shaft 757B. That is, the gear body 758A is rotatable about an axis substantially perpendicular to the reference axis 751V. The gear body 758A is also driven to rotate by the electric motor 756. A plurality of pinion teeth 758B protrude from the outer peripheral surface of the gear body 758A. The plurality of pinion teeth 758B are arranged at equal intervals in the circumferential direction around the central axis of the gear body 758A. Some of the plurality of pinion teeth 758B mesh with rack teeth 752B of the second member 752. Note that a gap called backlash exists between the pinion teeth 758B and the rack teeth 752B.

[0278] The arrangement of the drive mechanism 755 will be described in detail. As shown in FIG. 17, with respect to the reference axial direction 751L, an imaginary line segment connecting an end 751W of the first member 751 on the negative side and an end 752W of the second member 752 on the positive side is referred to as a second line segment 680Y. When the backhoe 680 is viewed from above in a direction parallel to the central axis of rotation 610V, the central axis 756V of the electric motor 756, and therefore the central axis of the pinion gear 758, is located between the first line segment 680X and the second line segment 680Y. As shown in FIG. 16, the negative side end of the first member 751 is the end of the first member 751 opposite the side where the second member 752 is inserted. The power unit 750 is configured as described above.

[0279] The operation of the power unit 750 will be described. In the power unit 750, when the output shaft 756B of the electric motor 756 rotates, the pinion gear 758 rotates in response to the rotation of the output shaft 756B. The pinion gear 758 rotates in either the forward or reverse direction depending on the rotation direction of the output shaft 756B of the electric motor 756. The rotation of the pinion gear 758 is transmitted to the second member 752 through the meshing of the pinion teeth 758B and the rack teeth 752B. When the pinion gear 758 rotates, the second member 752 moves relative to the first member 751 in the reference axial direction 751L. In other words, the second member 752 moves due to the force received from the pinion gear 758. As indicated by arrow 750V in FIG. 16 , the second member 752 moves in the forward or reverse direction relative to the first member 751 depending on the rotation direction of the pinion gear 758. As the second member 752 moves in this way, the amount by which the second member 752 protrudes relative to the first member 751 increases or decreases. That is, the power unit 750 expands or contracts in the reference axial direction 751L. The expansion and contraction of the power unit 750 drives the left and right swing of the swing bracket 610 and therefore the boom 530, in the same way as described with reference to Figures 11 to 14.

[0280] Adopting the power unit 750 in the excavator 680 has the following advantages. As described in (4-3) above, an external load may be input to the boom 530 when the bucket 550 collides with an excavation target. This load is referred to as a collision load. When the power unit 750 is adopted, the collision load may be transmitted to the second member 752 via the swing bracket 610 and the extension member 685. However, this collision load is hardly transmitted to the pinion gear 758, the reducer 757, or even the electric motor 756 for the following two reasons. The first reason is the presence of a gap between the rack teeth 752B of the second member 752 and the pinion teeth 758B of the pinion gear 758. The presence of this gap allows the collision load to escape without being transmitted from the rack teeth 752B to the pinion teeth 758B. The second reason is that the extension direction of the second member 752 and the central axis of the pinion gear 758 are substantially perpendicular to each other. Here, the collision load acting on the second member 752 mainly has a component in the reference axial direction 751L, which is the extension direction of the second member 752. This collision load is unlikely to act as a force that moves each component in a direction intersecting the reference axial direction 751L. Therefore, the collision load acting on the second member 752 is unlikely to be transmitted as a force that moves the pinion gear 758 in a direction along its central axis. Therefore, the collision load acting on the second member 752 is unlikely to act as a force that moves the pinion gear 758, the reducer 757, and the electric motor 756 in a direction along their central axes. As such, the configuration shown in FIGS. 16 to 18 can prevent the collision load acting on the second member 752 from reaching the reducer 757 and the electric motor 756. 16 to 18, it is not necessary to provide a structure for withstanding a collision load to the reducer 757 and the electric motor 756. Therefore, as in the second embodiment, it is possible to prevent the reducer 757 from becoming too large.

[0281] Furthermore, in power unit 750, drive mechanism 755 is located between first line segment 680X and second line segment 680Y. In other words, drive mechanism 755 is disposed closer to the center of housing section 607 in the Y direction. In this case, even if the diameter of electric motor 756 or reducer 757 becomes somewhat large, electric motor 756 or reducer 757 can be housed within housing section 607. Therefore, the overall size of backhoe 680 can be made compact.

[0282] The configuration of power unit 750 is not limited to the example shown in FIGS. 16 to 18. Power unit 750 may be configured to move second member 752 relative to first member 751 using a so-called rack-and-pinion mechanism. For example, in power unit 750, the location of drive mechanism 755 may be changed from the example shown in FIGS. 16 to 18. For example, drive mechanism 755 may be fixed to housing portion 607 on the positive-side side of the positive-side end of first member 751. Pinion gear 758 may be engaged with rack teeth 752B of second member 752 at a position spaced apart from first member 751 in reference axial direction 751L. Furthermore, drive mechanism 755 may be located on the opposite side of housing portion 607 from the center in the Y direction across first member 751. In the drive mechanism 755, the central axis of the pinion gear 758 and the central rotation axis 756V of the electric motor 756 may intersect. The reducer 757 may be eliminated from the drive mechanism 755, and the pinion gear 758 may be attached to the output shaft 756B of the electric motor 756. The first member 751 is not limited to a rectangular cylindrical shape, but may be cylindrical overall. The second member 752 is not limited to a rectangular columnar shape, but may be columnar extending in the reference axial direction 751L and have rack teeth 752B on its outer surface.

[0283] Fifth Embodiment A fifth embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to FIG. 19. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from the actual components or from those in other drawings. In FIG. 19, parts that are the same as or function substantially the same as those in FIGS. 1 to 18 are given the same reference numerals as those in FIGS. 1 to 18. In the following description, parts that overlap with the first to fourth embodiments may be omitted or simplified as appropriate.

[0284] As shown in FIG. 19, a backhoe 770, which is a construction machine, includes a lower body 602, an upper body 606, which is a vehicle body, a pair of traveling devices 510, and a swivel bearing 603. The configurations of the lower body 602, the pair of traveling devices 510, and the swivel bearing 603 are the same as those in the second embodiment. Therefore, their description will be omitted. The upper body 606 is the same as that in the second embodiment except that it does not include a support wall portion. Note that the riding section is not shown in FIG. 19. The upper body 606 is located on the opposite side of the ground from the lower body 602. In this embodiment, up, down, left, right, front, and rear are defined in the same way as in the second embodiment. For convenience of explanation, FIG. 19 shows some members of the backhoe 770 in cross section.

[0285] The backhoe 770 is equipped with an excavation machine including a boom 530, an arm 540, and a bucket 550. The boom 530, the arm 540, and the bucket 550 are located forward of the upper body 606. The configurations of the boom 530, the arm 540, and the bucket 550 are the same as those in the second embodiment, and therefore, a description thereof will be omitted.

[0286] <Boom swing mechanism> 19, the excavator 770 is equipped with a boom swing mechanism 770A. The boom swing mechanism 770A is a mechanism for swinging the boom 530 left and right relative to the upper body 606. The boom swing mechanism 770A constitutes an electric actuator.

[0287] The boom swing mechanism 770A has a mounting wall 772. The mounting wall 772 is, for example, in the shape of a rectangular plate. The mounting wall 772 is located forward with respect to the storage section 607 of the upper body 606. The mounting wall 772 protrudes forward from the front surface 607F of the storage section 607. The mounting wall 772 is fixed to the front surface 607F of the storage section 607. The main surface of the mounting wall 772 faces up and down. The main surface is the surface of a plate-shaped object with the largest area. The mounting wall 772 has a through hole 772A. The through hole 772A passes through the mounting wall 772 from top to bottom. The central axis of the through hole 772A extends approximately in the Z direction.

[0288] The boom swing mechanism 770A includes a swing bracket 774. The swing bracket 774 is located above the mounting wall 772. The swing bracket 774 is shaped like a circular plate. The swing bracket 774 is located on the upper surface of the mounting wall 772. The main surface of the swing bracket 774 faces up and down. The area of the main surface of the swing bracket 774 is larger than the opening area of the through-hole 772A of the mounting wall 772. The swing bracket 774 covers the through-hole 772A of the mounting wall 772. The swing bracket 774 is slidable relative to the mounting wall 772. The swing bracket 774 is located at a position away from the front surface 607F of the storage section 607. The base wall 534 of the boom 530 is fixed to the upper surface of the swing bracket 774. As in the second embodiment, the boom main body 531 is connected to the base wall 534 via a connecting shaft 532. The boom body 531 is rotatable up and down around a connecting shaft 532 as the center of rotation.

[0289] The boom swing mechanism 770A includes a drive device 780. The drive device 780 is located below the mounting wall 772. The drive device 780 includes an electric motor 781 and a reducer 782.

[0290] The electric motor 781 includes a housing 781A and an output shaft 781B. The electric motor 781 is operated by receiving power from a battery (not shown). The housing 781A has a cylindrical outer shape. The central axis of the housing 781A extends substantially in the Z direction. The output shaft 781B protrudes upward from the housing 781A. The central axis of the output shaft 781B substantially coincides with the central axis of the housing 781A. The output shaft 781B is rotatable relative to the housing 781A. The output shaft 781B rotates around its own central axis. The output shaft 781B is rotatable in both forward and reverse directions in response to the power supply to the housing 781A.

[0291] The reducer 782 is located above the electric motor 781. The reducer 782 includes a reducer main body 782A, an output member 782B, and a protruding portion 782C. The reducer main body 782A has a cylindrical outer shape. The central axis of the reducer main body 782A substantially coincides with the central axis of the housing 781A of the electric motor 781. The reducer main body 782A is connected to the output shaft 781B of the electric motor 781. The torque of the output shaft 781B of the electric motor 781 is input to the reducer main body 782A. The reducer main body 782A amplifies the torque of the output shaft 781B of the electric motor 781 by a predetermined ratio and outputs the amplified torque to the output member 782B. The output member 782B is located above the reducer main body 782A. The output member 782B is cylindrical. The diameter of the output member 782B is smaller than the diameter of the reducer body 782A. The central axis of the output member 782B substantially coincides with the central axis of the reducer body 782A. The output member 782B is rotatable relative to the reducer body 782A. The output member 782B rotates about its own central axis. The central axis of the output member 782B constitutes the rotational central axis 780V of the drive unit 780. In other words, the output member 782B, and therefore the drive unit 780, outputs torque centered on the rotational central axis 780V. The protruding portion 782C protrudes from the outer peripheral surface of the reducer body 782A. The protruding portion 782C is located in an upper portion of the reducer body 782A. The protruding portion 782C extends across the entire area of the reducer body 782A in the circumferential direction centered on the central axis of the reducer body 782A. That is, the protruding portion 782C is annular. The reducer 782 may be, for example, an eccentric oscillating gear type or a planetary gear type. Any type of reducer may be used as the reducer 782 as long as it is configured to amplify and output the torque from the electric motor 781.

[0292] The boom swing mechanism 770A includes a transmission member 783. The transmission member 783 is located above the reducer 782. The transmission member 783 is located inside a through-hole 772A in the mounting wall 772. The transmission member 783 is cylindrical. The diameter of the transmission member 783 is smaller than the diameter of the through-hole 772A. The central axis of the transmission member 783 substantially coincides with a rotational central axis 780V of the drive unit 780. A lower end surface of the transmission member 783 is fixed to an upper end surface of an output member 782B of the reducer 782. An upper end surface of the transmission member 783 is fixed to a lower surface of the swing bracket 774. In other words, the transmission member 783 and the swing bracket 774 are aligned with the drive unit 780 in the direction along the rotational central axis 780V and are disposed on the rotational central axis 780V of the drive unit 780. The transmission member 783 rotates integrally with both the output member 782B and the swing bracket 774. In this way, the transmission member 783 is interposed between the driving device 780 and the swing bracket 774, and transmits the torque of the driving device 780 to the swing bracket 774. The swing bracket 774 receives torque from the driving device 780 via the transmission member 783, and rotates about the rotation central axis 780V. As described above, the transmission member 783 connects the driving device 780 and the swing bracket 774. The swing bracket 774 is supported on the upper surface of the mounting wall 772. As a result, the driving device 780 is suspended from the lower surface of the swing bracket 774. At the same time, the driving device 780 is supported from above by the swing bracket 774. The driving device 780 is attached to the accommodation section 607 via the swing bracket 774 and the mounting wall 772. From another perspective, the swing bracket 774 can also be said to be connected to the accommodating portion 607 so as to be rotatable about the rotation center axis 780V by being supported on the upper surface of the mounting wall 772.

[0293] The boom swing mechanism 770A includes a first bearing 776. The first bearing 776 is located within a through-hole 772A in the mounting wall 772. The first bearing 776 is interposed between the inner surface of the through-hole 772A and the transmission member 783. The first bearing 776 is located in a lower portion of the through-hole 772A. The first bearing 776 is annular as a whole. The first bearing 776 is a so-called rolling bearing. Although not shown, the first bearing 776 includes an annular inner ring, an annular outer ring, and multiple rolling elements. The outer diameter of the inner ring is smaller than the inner diameter of the outer ring. The central axis of the inner ring substantially coincides with the central axis of the outer ring. The inner ring is located inside the outer ring in the radial direction centered on its own central axis. The multiple rolling elements are interposed between the inner ring and the outer ring. The multiple rolling elements are, for example, spherical or cylindrical. The multiple rolling elements guide the rotation of the inner ring relative to the outer ring. A transmission member 783 passes through a central hole in the inner ring. The inner peripheral surface of the inner ring is fixed to the transmission member 783. The inner ring rotates integrally with the transmission member 783. The outer peripheral surface of the outer ring is fixed to the inner surface of the through-hole 772A of the mounting wall 772. In other words, the first bearing 776 is attached to the accommodating portion 607 of the upper body 606 via the mounting wall 772. At the same time, the first bearing 776 rotatably supports the transmission member 783 relative to the mounting wall 772.

[0294] The boom swing mechanism 770A includes a second bearing 777. Similar to the first bearing 776, the second bearing 777 is interposed between the inner surface of the through-hole 772A of the mounting wall 772 and the transmission member 783. The second bearing 777 is located above the first bearing 776. The second bearing 777 is aligned with the first bearing 776 in the Z direction and in the direction along the rotation center axis 780V of the drive unit 780. The configuration of the second bearing 777 is the same as the configuration of the first bearing 776. Therefore, details of the second bearing 777 will be omitted. The second bearing 777 rotatably supports the transmission member 783.

[0295] The boom swing mechanism 770A includes a holding member 784. The holding member 784 is located below the mounting wall 772. In other words, in the direction along the rotational center axis 780V of the electric motor 781, the holding member 784 is located on the opposite side of the swing bracket 774 across the first bearing 776 and the second bearing 777. The holding member 784 is located away from the mounting wall 772. The holding member 784 is also located away from the front surface 607F of the storage section 607. The holding member 784 is shaped like a rectangular plate. The main surfaces of the holding member 784 face up and down. The holding member 784 includes a storage hole 784A. The storage hole 784A passes through the holding member 784 from top to bottom. The central axis of the storage hole 784A substantially coincides with the rotational center axis 780V of the drive unit 780. The diameter of the accommodation hole 784A is approximately the same as the diameter of the reducer body 782A of the driving device 780. The reducer body 782A passes through the accommodation hole 784A. The upper surface of the holding member 784 faces the protruding portion 782C of the reducer 782. The holding member 784 and the protruding portion 782C of the reducer 782 are fixed together with a bolt 789.

[0296] Boom swing mechanism 770A includes a buffer member 786. The buffer member 786 is located between a front surface 607F of the storage portion 607 and a rear end surface 784N of the holding member 784. The buffer member 786 is a coil spring. The elastic modulus of the buffer member 786 is smaller than that of the holding member 784. That is, the buffer member 786 is made of a softer material than the holding member 784. One end of the buffer member 786 is attached to the front surface 607F of the storage portion 607. The other end of the buffer member 786 is attached to a rear end surface 784N of the holding member 784. That is, the buffer member 786 connects the holding member 784 and the storage portion 607. The buffer member 786 is attached to an object using a mounting tool such as a hook.

[0297] <Operation of the Fifth Embodiment> In the excavator 770, when the output shaft 781B of the electric motor 781 rotates, the swing bracket 774 rotates together with the transmission member 783. When the swing bracket 774 rotates, the boom 530 swings left and right.

[0298] <Effects of the Fifth Embodiment> (5-1) As described in the operation of the above embodiment, in the back shovel 770 of this embodiment, the electric motor 781 can be used as a drive source to swing the boom 530 left and right.

[0299] As described in the first embodiment, an external load may be input to the boom 530 when the bucket 550 collides with an object to be excavated. This load is referred to as a collision load. In the excavator 770 of this embodiment, the collision load may be transmitted to the transmission member 783 via the swing bracket 774. The collision load transmitted to the transmission member 783 may act as a force that moves the transmission member 783 radially outward about its central axis. Such a collision load may basically be transmitted to the storage portion 607 via the first bearing 776 and the second bearing 777. The collision load may then be absorbed by the storage portion 607.

[0300] Meanwhile, a portion of the collision load transmitted to transmission member 783 may also be transmitted from transmission member 783 to drive device 780. In addition to this collision load, the following reaction torque also acts on drive device 780. That is, when electric motor 781 is driven to swing bracket 774 and thereby boom 530, a reaction force caused by rotating swing bracket 774 is applied to drive device 780. Hereinafter, the collision load and reaction torque input to drive device 780 will be collectively referred to as a specific load.

[0301] Here, drive device 780 is held by holding member 784. Let us assume that holding member 784 is fixed to front surface 607F of accommodation section 607. In this case, when drive device 780 attempts to operate in response to a specific load input to drive device 780, drive device 780 cannot move, and therefore the specific load cannot be released from drive device 780.

[0302] In contrast, in the configuration of this embodiment, the holding member 784 is disposed at a position away from the accommodation portion 607. Therefore, when the drive device 780 attempts to operate in response to the input of a specific load, the holding member 784 allows the drive device 780 to operate. That is, in the configuration of this embodiment, the drive device 780 operates in response to the specific load, thereby dissipating the specific load from the drive device 780. Furthermore, in the configuration of this embodiment, a buffer member 786 is located between the holding member 784 and the accommodation portion 607. The buffer member 786 damps the operation of the drive device 780 in response to the specific load by its own elastic force. This configuration of this embodiment can effectively reduce the burden on the drive device 780. As a result, the configuration of this embodiment does not require the reducer 782 and the electric motor 781 to be provided with a structure for withstanding the specific load. This contributes to preventing the reducer 782 from becoming larger, for example.

[0303] (5-2) The excavator 770 of this embodiment is equipped with two bearings, a first bearing 776 and a second bearing 777. These two bearings support the transmission member 783. Therefore, when a collision load acts on the transmission member 783 via the boom 530 and thus the swing bracket 774, the collision load is distributed to these two bearings. Therefore, the collision load input to each bearing can be reduced, and the individual bearings are less likely to be burdened.

[0304] <Modification of the fifth embodiment> The fifth embodiment can be modified as follows: The first to fifth embodiments and the following modifications can be combined and implemented as long as no technical contradiction occurs.

[0305] The configuration of the transmission member 783 is not limited to the example of the above embodiment. The transmission member 783 only needs to be able to transmit the torque of the drive unit 780 to the swing bracket 774. For example, the shape of the transmission member 783 may be changed from that of the above embodiment. For example, the transmission member 783 may be a stepped column. The transmission member 783 may be treated as a single member together with the output member 782B of the reducer 782. In other words, the output member 782B of the reducer 782 may be treated as the transmission member 783, or the transmission member 783 may be treated as the output member 782B of the reducer 782.

[0306] The number of bearings that support the transmission member 783 is not limited to the example in the above embodiment. The number of bearings may be one, or may be three or more. The configuration of the bearing is not limited to the example of the above embodiment. For example, the bearing may be a plain bearing. When a plain bearing is used as the bearing, the through-hole 772A of the mounting wall 772 itself may function as the sliding surface of the bearing. In this case, the mounting wall 772 is configured to include the bearing.

[0307] The configuration for attaching the bearing to the accommodation portion 607 is not limited to the example of the above embodiment. For example, the shape of the attachment wall 772 may be changed from the example of the above embodiment. The attachment wall 772 may be configured to be able to hold the bearing and to be able to fix it to the accommodation portion 607. The bearing may be attached to the accommodation portion 607 using a configuration other than a wall portion categorized as the attachment wall 772. In other words, the attachment wall 772 is not essential.

[0308] The bearing may not be attached to the housing 607. The bearing may be attached anywhere on the vehicle body. The buffer member 786 is not limited to the example of the above embodiment. The buffer member 786 may be made of any material softer than the holding member 784. For example, the buffer member 786 may be made of rubber. A rubber object such as this may be interposed between the holding member 784 and the front surface 607F of the storage section 607. Alternatively, for example, the buffer member 787 shown in FIG. 20 may be used. The material of the buffer member 787 may be softer than the holding member 784, and may be, for example, metal or resin. The buffer member 787 is configured in an L-shape when viewed from the Y direction. That is, the buffer member 787 includes a bottom plate portion 787A corresponding to the horizontal side of the L shape and a contact portion 787B corresponding to the vertical side of the L shape. The bottom plate portion 787A is, for example, a rectangular plate. The main surfaces of the bottom plate portion 787A face up and down. The rear end of the bottom plate portion 787A is fixed to the front surface 607F of the storage section 607. The contact portion 787B rises upward from the end of the bottom plate portion 787A opposite the accommodation portion 607. The contact portion 787B is, for example, a rectangular plate. The main surface of the contact portion 787B faces forward and backward. An upper portion of the contact portion 787B is fixed to the rear end surface 784N of the holding member 784. When such a buffer member 787 is used, when a specific load is input to the drive device 780 and the holding member 784 attempts to operate together with the drive device 780, the contact portion 787B moves forward and backward from the connection point with the bottom plate portion 787A. This allows the specific load input to the drive device 780 to be attenuated, as in (5-1) above. Note that in FIG. 20, parts that are the same as or function substantially the same as those in FIG. 19 are denoted by the same reference numerals as those in FIG. 19. Also, in FIG. 20, as in FIG. 19, some components are shown in cross section.

[0309] The connection destination of the buffer member 786 on the opposite side to the holding member 784 may be a part of the vehicle body other than the accommodation section 607. The buffer member 786 may be connected to any part of the vehicle body.

[0310] The configuration of the swing bracket 774 is not limited to the example of the above embodiment. The swing bracket 774 may be fixed to the boom 530 and configured to rotate by receiving torque from the drive unit 780. For example, the shape of the swing bracket 774 may be changed from that of the example of the above embodiment. For example, the swing bracket 774 may be in the shape of a polygonal plate.

[0311] The location where the boom 530 is fixed to the swing bracket 774 is not limited to the example in the above embodiment. The boom 530 may be fixed to any location on the swing bracket 774.

[0312] The configuration of the holding member 784 is not limited to the example of the above embodiment. The holding member 784 only needs to have an accommodating hole 784A through which the drive unit 780 passes. The holding member 784 may be in the form of a circular plate or a polygonal plate other than a square.

[0313] The components of the drive device 780 that pass through the accommodating hole 784A of the holding member 784 are not limited to the examples in the above embodiment. That is, a portion of the drive device 780 other than the reducer main body 782A may pass through the accommodating hole 784A. For example, the electric motor 781 may pass through the accommodating hole 784A.

[0314] The positional relationship between the holding member 784 and the swing bracket 774 is not limited to the example in the above embodiment. The holding member 784 and the swing bracket 774 may be located on opposite sides of the bearing that supports the transmission member 783. For example, the overall configuration of the boom swing mechanism 770A may be changed so that the holding member 784 is located above the bearing and the swing bracket 774 is located below the bearing.

[0315] The configuration of the drive device 780 is not limited to the example of the above embodiment. For example, in the drive device 780, the outer shape of the housing 781A of the electric motor 781 may be changed from that of the example of the above embodiment. The reducer 782 may be eliminated from the drive device 780. When the reducer 782 is eliminated from the drive device 780, the central axis of the output shaft 781B of the electric motor 781 forms the central axis of rotation of the drive device 780. The drive device 780 includes the electric motor 781 and outputs torque centered on the central axis of rotation. The central axis of rotation of the torque output by the drive device 780 may extend overall in the vertical direction of the vehicle body, and may be inclined with respect to the Z direction within a range of, for example, approximately 15 degrees.

[0316] The driving device 780 may be cylindrical. When the driving device 780 is configured cylindrically, the bearing and mounting wall 772 can be eliminated and a columnar member that penetrates the driving device 780 can be used to obtain the same effect as in (5-1). An example of a boom swing mechanism 770B that employs such a configuration will be described below with reference to FIG. 21. As in the above embodiment, the boom swing mechanism 770B constitutes an electric actuator. Note that in FIG. 21, parts that are the same as or function substantially the same as those in FIG. 19 are denoted by the same reference numerals as in FIG. 19. Also, as in FIG. 19, some parts in FIG. 21 are shown in cross section.

[0317] As shown in Fig. 21, the boom swing mechanism 770B includes a flange wall 794. The flange wall 794 protrudes forward from the front surface 607F of the storage section 607 in the upper body 606. The flange wall 794 is fixed to the front surface 607F of the storage section 607. The flange wall 794 is, for example, in the shape of a rectangular plate. The main surfaces of the flange wall 794 face up and down.

[0318] Boom swing mechanism 770B includes a slide plate 796. Slide plate 796 is located on the upper surface of flange wall 794. Slide plate 796 is in the shape of an annular plate. The central axis of slide plate 796 extends substantially in the Z direction. The outer surface of slide plate 796 is processed to reduce frictional resistance.

[0319] The boom swing mechanism 770B includes a drive device 790. The drive device 790 is located above the slide plate 796. The drive device 790 includes an electric motor 791 and a reducer 792.

[0320] The electric motor 791 receives power from a battery (not shown). The electric motor 791 includes a housing 791A and an output shaft 791B. The housing 791A is cylindrical. The inner diameter of the housing 791A approximately matches the inner diameter of the slide plate 796. The outer diameter of the housing 791A approximately matches the outer diameter of the slide plate 796. The central axis of the housing 791A approximately matches the central axis of the slide plate 796. The lower end face of the housing 791A is fixed to the upper surface of the slide plate 796. The output shaft 791B protrudes upward from the housing 791A. The output shaft 791B is cylindrical. The inner diameter of the output shaft 791B is slightly larger than the inner diameter of the housing 791A. The outer diameter of the output shaft 791B is smaller than the outer diameter of the housing 791A. The central axis of output shaft 791B substantially coincides with the central axis of housing 791A. Output shaft 791B is rotatable relative to housing 791A. Output shaft 791B rotates around its own central axis. Output shaft 791B can rotate in both forward and reverse directions depending on the power supply to housing 791A.

[0321] The reducer 792 is located above the electric motor 791. The reducer 792 includes a reducer body 792A, an output member 792B, and a protruding portion 792C. The reducer body 792A is cylindrical. The inner diameter of the reducer body 792A approximately matches the inner diameter of the housing 791A of the electric motor 791. The outer diameter of the reducer body 792A approximately matches the outer diameter of the housing 791A of the electric motor 791. The central axis of the reducer body 792A approximately matches the central axis of the electric motor 791. A lower end face of the reducer body 792A is fixed to an upper end face of the housing 791A of the electric motor 791. The reducer body 792A is connected to an output shaft 791B of the electric motor 791. The torque of the output shaft 791B of the electric motor 791 is input to the reducer body 792A. The reducer body 792A amplifies the torque of the output shaft 791B of the electric motor 791 at a predetermined ratio and outputs the amplified torque to the output member 792B.

[0322] The output member 792B is located above the reducer body 792A. The output member 792B constitutes the output member of the drive unit 780. The output member 792B is cylindrical. The inner diameter of the output member 792B is approximately the same as the inner diameter of the reducer body 792A. The outer diameter of the output member 792B is smaller than the outer diameter of the reducer body 792A. The central axis of the output member 792B is approximately the same as the central axis of the reducer body 792A. The output member 782B is rotatable relative to the reducer body 792A. The output member 792B rotates about its own central axis. The central axis of the output member 792B constitutes the rotational central axis 790V of the drive unit 790. In other words, the output member 792B, and therefore the drive unit 790, outputs torque centered on the rotational central axis 790V.

[0323] The protruding portion 792C protrudes from the outer peripheral surface of the reducer body 792A. The protruding portion 792C is located in an upper portion of the reducer body 792A. The protruding portion 792C extends over the entire area of the reducer body 792A in the circumferential direction centered on the central axis of the reducer body 792A. In other words, the protruding portion 792C is annular.

[0324] The reducer 792 is configured as described above. The reducer 792 may be, for example, an eccentric oscillating gear type or a planetary gear type. Any type of reducer may be used as the reducer 792 as long as it is configured to amplify and output the torque from the electric motor 791. The drive device 790 including the reducer 792 and the electric motor 791 is located above the flange wall 794. At the same time, the drive device 790 is supported from below by the flange wall 794.

[0325] The boom swing mechanism 770B includes a swing bracket 774. The swing bracket 774 is located above the output member 792B of the reducer 792. The swing bracket 774 is plate-shaped. The outer shape of the swing bracket 774 may be circular or polygonal. The main surfaces of the swing bracket 774 face up and down. The swing bracket 774 extends so as to straddle the drive unit 790 from front to back. The front end of the swing bracket 774 extends further forward than the front end of the drive unit 790. A rearward portion of the lower surface of the swing bracket 774 faces the upper end face of the output member 792B of the reducer 792. The lower surface of the swing bracket 774 is fixed to the output member 792B of the reducer 792. Therefore, the swing bracket 774 rotates integrally with the output member 792B. That is, the swing bracket 774 receives torque from the driving device 790 and rotates about a rotational center axis 790V. Furthermore, the base wall 534 of the boom 530 is fixed to a front portion of the upper surface of the swing bracket 774. The swing bracket 774 has a through hole 774H. The through hole 774H is located in a rearward portion of the swing bracket 774. The central axis of the through hole 774H substantially coincides with the rotational center axis 790V of the driving device 790. The diameter of the through hole 774H substantially coincides with the inner diameter of the output member 792B of the reducer 792. As described above, the swing bracket 774 is located upward relative to the driving device 790. That is, the swing bracket 774 is located on the opposite side of the flange wall 794 from the driving device 790 in the direction along the rotational center axis 790V of the driving device 790.

[0326] The boom swing mechanism 770B includes a fixed wall 795. The fixed wall 795 is located above the swing bracket 774. The fixed wall 795 is located away from the swing bracket 774. The fixed wall 795 protrudes forward from the front surface 607F of the storage section 607 in the upper body 606. The fixed wall 795 is fixed to the front surface 607F of the storage section 607. The fixed wall 795 is, for example, in the shape of a rectangular plate. The main surfaces of the fixed wall 795 face up and down.

[0327] As described above, in boom swing mechanism 770B, flange wall 794, slide plate 796, drive unit 790, swing bracket 774, and fixed wall 795 are aligned in a direction along central axis of rotation 790V of drive unit 790. Each of these members is located on central axis of rotation 790V of drive unit 790.

[0328] The boom swing mechanism 770B is provided with a pin 797. The pin 797 extends downward from the fixed wall 795. The pin 797 is cylindrical. The diameter of the pin 797 is smaller than the diameter of the through-hole 774H of the swing bracket 774. The central axis of the pin 797 extends in the Z direction. The upper end of the pin 797 penetrates the fixed wall 795. The pin 797 is fixed to the fixed wall 795. That is, the pin 797 cannot move or rotate relative to the fixed wall 795. The lower end of the pin 797 penetrates the flange wall 794. The pin 797 is fixed to the flange wall 794. That is, the pin 797 cannot move or rotate relative to the flange wall 794. A portion of the pin 797 in the direction along the central axis passes through the through-hole 774H of the swing bracket 774, the central hole 792H of the reducer 792, the central hole 791H of the electric motor 791, and the central hole of the slide plate 796. As a result of this structure, the driving device 790 is attached to the accommodation portion 607 via the pin 797, the flange wall 794, and the fixed wall 795. From another perspective, it can be said that the swing bracket 774 is connected to the accommodation portion 607 via the pin 797, the driving device 790, and the flange wall 794 so as to be rotatable about the rotation central axis 780V.

[0329] The boom swing mechanism 770B includes a holding member 784. The holding member 784 is located between the swing bracket 774 and a flange wall 794. The holding member 784 is disposed at a position away from the front surface 607F of the storage section 607. The configuration of the holding member 784 is the same as that described in relation to FIG. 19 . That is, the holding member 784 is plate-shaped and includes a storage hole 784A. A reducer main body 792A of the drive unit 790 passes through the storage hole 784A. The holding member 784 is fixed to a protruding portion 792C of the reducer 792 by a bolt 789.

[0330] The boom swing mechanism 770B includes a buffer member 786. The buffer member 786 connects a rear end surface 784N of the holding member 784 and a front surface 607F of the storage section 607. The configuration of the buffer member 786 is the same as that described in relation to FIG.

[0331] Boom swing mechanism 770B can swing boom 530 left and right using electric motor 791 as a drive source. That is, when output shaft 791B of electric motor 791 rotates, swing bracket 774 rotates. Then, boom 530 swings left and right together with swing bracket 774.

[0332] As described in relation to FIG. 19 , a specific load, including a collision load of the boom 530 and a reaction torque from the swing bracket 774, may be input to the drive unit 790. Similar to the configuration shown in FIG. 19 , the boom swing mechanism 770B can release this specific load from the drive unit 790. That is, in the boom swing mechanism 770B, the holding member 784 that holds the drive unit 790 is positioned away from the accommodation portion 607. At the same time, there is a gap between the outer circumferential surface of the pin 797 that penetrates the drive unit 790 and the inner circumferential surface of the drive unit 790. Therefore, when the drive unit 790 attempts to operate in response to the input of the specific load, the holding member 784 allows the drive unit 790 to operate. Specifically, the holding member 784 allows the drive unit 790 to rotate around the pin 797. Meanwhile, this operation of the drive unit 790 is gradually damped by the elastic force of the buffer member 786. Therefore, even when the boom swing mechanism 770B is employed, the same effect as (5-1) can be obtained.

[0333] The configuration of the boom swing mechanism 770B is not limited to the example shown in FIG. 21 . The boom swing mechanism 770B may be configured so as to hold the driving device 790 and the swing bracket 774 with the pin 797. For example, the electric motor 791 may be cylindrical, but is not limited to a cylindrical shape. Similarly, the reducer 792 may be cylindrical, but is not limited to a cylindrical shape. The relationship in diameter between the electric motor 791 and the reducer 792 is not limited to the example described above. The electric motor 791 and the reducer 792 may have inner diameters that allow the pin 797 to be inserted therein. The reducer 792 may be eliminated from the driving device 790. The output shaft 791B of the electric motor 791 may be treated as an output member of the driving device 790. The central axis of rotation of the torque output by the driving device 790 may be inclined with respect to the Z direction. The fixed wall 795 and the flange wall 794 may not be fixed to the front surface 607F of the accommodation section 607. The fixed wall 795 and the flange wall 794 may be fixed somewhere on the vehicle body. The shape of the flange wall 794 may be modified as appropriate as long as it is configured to support the drive unit 790. The pin 797 is not limited to being cylindrical, and may be any shape that can pass through the drive unit 780. In addition, the modifications described in relation to FIG. 19 may be applied to the boom swing mechanism 770B as appropriate. For example, the configurations of the buffer member 786, the holding member 784, and the swing bracket 774 are not limited to the examples shown in FIG. 21. Note that the slide plate 796 and the fixed wall 795 may be eliminated from the boom swing mechanism 770B. Furthermore, the buffer member 786 may be eliminated from the boom swing mechanism 770B.

[0334] The swivel bearing 603 is not essential for the excavator 770. That is, depending on the configuration of the excavator 770, the upper body 606 may not be able to swivel relative to the lower body 602, and the upper body 606 and the lower body 602 may be integrated. In this case, the upper body 606 and the lower body 602 constitute the vehicle body. That is, the vehicle body is not limited to the example of the above embodiment.

[0335] The construction machinery to which the boom swing mechanisms 770A and 770B, which are electric actuators, can be applied is not limited to the excavator 770. In the above embodiment, various means may be used to fasten the two members together, such as bolting, welding, integral molding, spline connection, etc.

[0336] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved.

[0337] Sixth Embodiment A sixth embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to Figures 22 and 23. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from those in the actual product or from those in other drawings. In Figures 22 and 23, parts that are the same as or function substantially the same as those in Figures 1 to 21 are given the same reference numerals as in Figures 1 to 21. In Figure 23, for convenience of explanation, some components are shown in cross section. In the following explanation, explanations of parts that overlap with those of the first to fifth embodiments may be omitted or simplified as appropriate.

[0338] As shown in FIG. 22 , a backhoe 800, which is a construction machine, includes a lower body 602, an upper body 606, which is a vehicle body, a pair of traveling devices 510, and a swivel bearing 603. The configurations of the lower body 602, the pair of traveling devices 510, and the swivel bearing 603 are the same as those in the second embodiment. Therefore, their description will be omitted. The configuration of the upper body 606 is the same as that in the second embodiment. That is, the upper body 606 includes a rectangular parallelepiped storage section 607, a riding section located above the storage section 607, and a support wall section 609 protruding forward from a front surface 607F of the storage section 607. The support wall section 609 includes a through-hole 609A that penetrates substantially in the Z direction. The central axis of the through-hole 609A forms a rotation central axis 610V of the boom 530. Note that the riding section is not shown in FIG. 22 . The upper body 606 is located on the opposite side of the ground from the lower body 602. In this embodiment, up, down, left, right, front and back are defined in the same manner as in the second embodiment.

[0339] The backhoe 800 is equipped with an excavation machine including a boom 530, an arm 540, and a bucket 550. The boom 530, the arm 540, and the bucket 550 are located forward of the upper body 606. The configurations of the boom 530, the arm 540, and the bucket 550 are the same as those in the second embodiment, and therefore, a description thereof will be omitted.

[0340] <Boom swing mechanism> 22, the backhoe 800 is provided with a boom swing mechanism 800A. The boom swing mechanism 800A is a mechanism for swinging the boom 530 left and right relative to the upper body 606. The boom swing mechanism 800A constitutes an electric actuator.

[0341] The boom swing mechanism 800A includes a swing bracket 610 and a pin 620. The configurations of the swing bracket 610 and the pin 620 are basically the same as those of the second embodiment. That is, as shown in FIG. 22 , the swing bracket 610 includes an upper wall 611, a lower wall 612 located below the upper wall 611, and a connecting wall 613 connecting the upper wall 611 and the lower wall 612. A base wall 534 of the boom 530 is fixed to the connecting wall 613. The swing bracket 610 of this embodiment differs from that of the second embodiment in the following respect. That is, in the swing bracket 610 of this embodiment, the dimension of the lower wall 612 in the Z direction is larger than the dimension of the upper wall 611 in the Z direction. At the same time, a lower surface 612D of the lower wall 612 is located below a lower surface 607D of the storage section 607 of the upper body 606 in the Z direction. Except for the features of the lower wall 612, the configuration of the swing bracket 610 is the same as that of the second embodiment, so further description of the swing bracket 610 will be omitted.

[0342] The swing bracket 610 is connected to the support wall portion 609 of the upper body 606 via a pin 620. That is, the pin 620 penetrates the upper wall 611 and the lower wall 612 as well as the through-hole 609A of the support wall portion 609. In FIG. 22, the gap between the pin 620 and the through-hole 609A is exaggerated. As in the second embodiment, the pin 620 is rotatable with respect to the through-hole 609A. The pin 620 is supported by the through-hole 609A so as to rotate about a rotation center axis 610V, which is the central axis of the pin 620. Meanwhile, the pin 620 is fixed to the upper wall 611 and the lower wall 612. Therefore, when the pin 620 rotates about the rotation center axis 610V, the upper wall 611 and the lower wall 612 rotate integrally with the pin 620. That is, the swing bracket 610 is rotatable about the rotation center axis 610V.

[0343] Boom swing mechanism 800A includes a drive unit 615. The drive unit 615 is located entirely inside the storage unit 607. The drive unit 615 is located in the front portion of the storage unit 607. The configuration of the drive unit 615 is the same as that of the second embodiment. Therefore, only an outline of the drive unit 615 will be described below.

[0344] The driving device 615 includes an electric motor 616, a reducer 617, and a transmission shaft 618. The electric motor 616 includes a housing 616A and an output shaft 616B. The housing 616A is fixed to the inner wall of the accommodation portion 607. The output shaft 616B protrudes downward from the housing 616A. The output shaft 616B is cylindrical. The central axis of the output shaft 616B extends substantially in the Z direction. The central axis of the output shaft 616B is substantially parallel to the rotation central axis 610V of the swing bracket 610. The output shaft 616B is rotatable relative to the housing 616A.

[0345] The reducer 617 is located below the electric motor 616. The reducer 617 is fixed to the inner wall of the accommodation section 607. The torque of the output shaft 616B of the electric motor 616 is input to the reducer 617. The reducer 617 amplifies the torque of the output shaft 616B of the electric motor 616 at a predetermined ratio and outputs the amplified torque. The reducer 617 may be, for example, an eccentric oscillating gear type or a planetary gear type. Any type of reducer may be used as the reducer 617 as long as it is configured to amplify and output the torque from the electric motor 616.

[0346] The transmission shaft 618 is located below the reducer 617. A portion of the transmission shaft 618 protrudes downward from the lower surface 607D of the accommodation portion 607. The transmission shaft 618 is cylindrical. The central axis of the transmission shaft 618 substantially coincides with the central axis of the output shaft 616B of the electric motor 616. The transmission shaft 618 receives torque from the reducer 617 and rotates about its own central axis. In other words, when the central axis of the transmission shaft 618 is set as a rotational central axis 615V, the transmission shaft 618, and therefore the drive device 615, outputs torque centered about the rotational central axis 615V.

[0347] The boom swing mechanism 800A includes a pinion gear 809. The pinion gear 809 is attached to a transmission shaft 618. As shown in FIG. 23 , the pinion gear 809 includes a main body 809A and a plurality of teeth 809B. The main body 809A is cylindrical. The central axis of the main body 809A substantially coincides with the rotation central axis 615V. The transmission shaft 618 is disposed in a central hole of the main body 809A. The main body 809A is fixed to the transmission shaft 618. The main body 809A rotates integrally with the transmission shaft 618. In other words, the main body 809A receives torque from the drive unit 615 and rotates about the rotation central axis 615V. The plurality of teeth 809B protrude from the outer circumferential surface of the main body 809A. The plurality of teeth 809B are arranged at equal intervals in the circumferential direction around the rotation central axis 615V. 23 shows the pinion gear 809 only schematically, and the number and shape of the teeth 809B shown in Fig. 23 do not necessarily correspond to the actual ones. The same applies to the gear wall 810 described later.

[0348] <Gear Wall> As shown in FIG. 22, the boom swing mechanism 800A includes a gear wall 810. The gear wall 810 is located downward relative to a lower wall 612 of the swing bracket 610. The gear wall 810 is located forward relative to a pinion gear 809. As shown in FIG. 23, the gear wall 810 includes a main body 811 and a plurality of teeth 812. The main body 811 is plate-shaped. The largest surface of the outer surface of the main body 811 is referred to as the main surface 811A. As shown in FIG. 22, the two main surfaces 811A face up and down. The upper surface of the two main surfaces 811A is fixed to a lower surface 612D of the lower wall 612. As shown in FIG. 23, the main surface 811A is semicircular. The central axis of the semicircular arc of the main surface 811A substantially coincides with the central axis 610V of rotation. The portion of the main body 811 corresponding to its thickness is composed of an arcuate surface 811B and a flat surface 811C. The arcuate surface 811B follows the arcuate portion of the main surface 811A. That is, the arcuate surface 811B is arc-shaped with the turning center axis 610V as its center. The arcuate surface 811B extends over approximately 180 degrees in the circumferential direction around the turning center axis 610V. The diameter of the arc of the arcuate surface 811B is larger than the outer diameter of the main body 809A of the pinion gear 809. The flat surface 811C follows the linear portion of the semicircle of the main surface 811A. The flat surface 811C connects both ends of the arc of the arcuate surface 811B. In a plan view facing the turning center axis 610V, the flat surface 811C extends linearly. 22, when the gear wall 810 is fixed to the lower wall 612, the flat surface 811C forms the forefront of the gear wall 810. In the X direction, the flat surface 811C is located at approximately the same position as the turning center axis 610V. The arcuate surface 811B extends rearward from the flat surface 811C. The arcuate surface 811B faces the pinion gear 809.

[0349] The plurality of teeth 812 protrude from the arc surface 811B. The plurality of teeth 812 are arranged at equal intervals in the circumferential direction around the central axis of rotation 610V. Some of the plurality of teeth 812 mesh with some of the plurality of teeth 809B of the pinion gear 809. Note that a gap called backlash is formed between the teeth 812 of the gear wall 810 and the teeth 809B of the pinion gear 809.

[0350] <Operation of the Sixth Embodiment> In the boom swing mechanism 800A, when the output shaft 616B of the electric motor 616 rotates, the pinion gear 809 rotates. Then, the rotation of the pinion gear 809 is transmitted to the gear wall 810 through the meshing of the teeth of the pinion gear 809 and the gear wall 810. Then, the gear wall 810 rotates about the rotation central axis 610V. At the same time, the swing bracket 610 integrated with the gear wall 810 and the boom 530 rotate. The boom 530 rotates either to the left or to the right depending on the rotation direction of the output shaft 616B of the electric motor 616.

[0351] <Effects of the Sixth Embodiment> (6-1) As described in the operation of the above embodiment, in the back shovel 800 of this embodiment, the electric motor 616 can be used as a drive source to swing the boom 530 left and right.

[0352] The diameter of the arcuate surface 811B of the gear wall 810 is larger than the outer diameter of the main body 809A of the pinion gear 809. As a result of this size relationship, the gear wall 810 amplifies the torque of the pinion gear 809 and transmits it to the swing bracket 610. That is, in the configuration of this embodiment, the gear wall 810 and the pinion gear 809 form a type of speed reduction mechanism. If the gear wall 810 and the pinion gear 809 can form a speed reduction mechanism, it is permissible to suppress the torque amplification ability of the reducer 617 of the drive unit 615. If it is acceptable to suppress the torque amplification ability, it is possible to avoid an increase in the size of the components of the reducer 617. That is, in the configuration of this embodiment, it is possible to suppress an increase in the size of the reducer 617 and, ultimately, the entire drive unit 615.

[0353] As described in the first embodiment, an external load may be input to the boom 530 when the bucket 550 collides with an excavation target. This load is referred to as a collision load. When the boom swing mechanism 800A of the present embodiment is employed, the collision load may be transmitted from the swing bracket 610 to the gear wall 810. However, this collision load is released through the gap between the gear wall 810 and the pinion gear 809, and is therefore hardly transmitted to the pinion gear 809 and ultimately to the drive unit 615. Therefore, the configuration of the present embodiment can prevent the collision load acting on the gear wall 810 from reaching the reducer 617 and the electric motor 616. Therefore, the configuration of the present embodiment, as with the other embodiments, does not require the reducer 617 and the electric motor 616 to be provided with a structure for withstanding the collision load. This also contributes to preventing the drive unit 615 from becoming larger, as described above.

[0354] (6-2) In this embodiment, the angular range of the arc of the arc surface 811B of the gear wall 810 is approximately 180 degrees. In other words, the gear wall 810 is semicircular. By making the gear wall 810 semicircular rather than perfectly circular in this way, the dimensions of the gear wall 810 can be made smaller than if the gear wall 810 were perfectly circular. In this case, the space occupied by the gear wall 810 can be made smaller. Therefore, with the configuration of this embodiment, providing the gear wall 810 is unlikely to require changes to the layout of other components.

[0355] <Modification of the Sixth Embodiment> The sixth embodiment can be modified as follows: The first to sixth embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0356] The configuration of the gear wall 810 is not limited to the example of the above embodiment. The gear wall 810 only needs to have an arc-shaped arc surface 811B centered on the rotation central axis 610V and a plurality of teeth 812 protruding from the arc surface 811B. The diameter of the arc of the arc surface 811B needs only to be larger than the outer diameter of the pinion gear 809. For example, in the gear wall 810, the angular range of the arc of the arc surface 811B may be changed from that of the above embodiment. Adopting a configuration in which the angular range of the arc of the arc surface 811B is 165 degrees or more and 195 degrees or less, and in which both ends of the arc of the arc surface 811B are connected by a flat surface 811C extending linearly, is effective in reducing the dimensions of the gear wall 810, as described in (6-2) above. The angular range of the arc of the arc surface 811B can be changed as appropriate. Furthermore, it is not essential that both ends of the arc of the arc surface 811B be connected by linear flat surfaces 811C. As long as the swing bracket 610 can rotate through the meshing of the gear wall 810 and the pinion gear 809, the central axis of the arc of the arc surface 811B of the gear wall 810 does not have to coincide with the turning central axis 610V. Even in this case, it is sufficient that the central axis of the arc of the arc surface 811B is parallel to the rotation central axis 615V of the drive unit 615.

[0357] The arrangement of the gear wall 810 is not limited to the example in the above embodiment. The gear wall 810 only needs to be arranged so that the teeth 812 of the pinion gear 809 face the teeth 809B of the pinion gear 809. The gear wall 810 only needs to be arranged so that it can rotate about the central axis of rotation 610V. For example, the pin 620 may extend downward beyond the bottom wall 612 of the swing bracket 610, and the gear wall 810 may be fixed to the pin 620 at a position spaced apart from the bottom wall 612 in the Z direction.

[0358] The configuration, arrangement, and manner of connection to the vehicle body of the swing bracket 610 are not limited to those of the above embodiment. The swing bracket 610 only needs to be fixed to the boom 530 and connected to the vehicle body so as to be rotatable about the central axis of rotation 610V. Furthermore, the configuration of the vehicle body for supporting the swing bracket 610 is not limited to those of the above embodiment. For example, it is also possible to adopt a configuration such as that shown in FIG. 24, which will be described later. Note that the vehicle body is not limited to the storage section 607, but may be any part of the upper body 606. Furthermore, as will be described in modified examples below, the vehicle body is not limited to the upper body 606.

[0359] The swivel bearing 603 is not essential for the backhoe 800. That is, depending on the configuration of the backhoe 800, the upper body 606 may not be able to swivel relative to the lower body 602, and the upper body 606 and the lower body 602 may be integrated. In this case, the upper body 606 and the lower body 602 constitute the vehicle body. That is, the vehicle body is not limited to the example of the above embodiment.

[0360] The location where the boom 530 is fixed to the swing bracket 610 is not limited to the example in the above embodiment. The boom 530 may be fixed to any location on the swing bracket 610.

[0361] The arrangement of the pinion gear 809 is not limited to the example in the above embodiment. The arrangement of the pinion gear 809 may vary depending on the configuration and arrangement of the drive device 615. The pinion gear 809 only needs to be provided so as to receive torque from the drive device 615 and be rotatable about the central axis of rotation of the drive device 615.

[0362] The configuration of the drive unit 615 is not limited to the example of the above embodiment. The drive unit 615 may include the electric motor 616 and output torque centered on the central axis of rotation. For example, the reducer 617 and the transmission shaft 618 may be eliminated from the drive unit 615. The pinion gear 809 may be directly attached to the output shaft 616B of the electric motor 616. The drive unit 615 may also be configured so that the central axis of the output shaft 616B of the electric motor 616 and the central axis of rotation of the torque output by the drive unit 615 to the outside are positioned at different positions. Such a configuration is possible if the drive unit 615 is provided with a mechanism for converting the rotation direction of the electric motor 616. The central axis of rotation of the torque output by the drive unit 615 may extend in the vertical direction of the vehicle body as a whole, and may be tilted within a range of approximately 15 degrees with respect to the Z direction, for example.

[0363] The location of the drive unit 615 is not limited to the example of the above embodiment. The drive unit 615 may be fixed somewhere in the housing 607. Furthermore, the drive unit 615 may be fixed somewhere in the vehicle body, not just the housing 607. Furthermore, as long as the drive unit 615 can be rotated using the drive unit 615 as a power source through the meshing of the pinion gear 809 and the gear wall 810, the drive unit 615 and the gear wall 810 may be fixed to the vehicle body or the swing bracket 610, interchangeably. An example of such a modification will be described with reference to FIG. 24. In FIG. 24, parts that are the same as or function substantially the same as those in FIGS. 22 and 23 are denoted by the same reference numerals as those in FIGS. 22 and 23. Also, in FIG. 24, as in FIG. 22, some components are shown in cross section.

[0364] The following describes the excavator 800 shown in FIG. 24, focusing mainly on the differences from FIG. 23. In the excavator 800, the upper body 606 includes a first support wall 805 and a second support wall 806 instead of the support wall 609. The first support wall 805 and the second support wall 806 protrude forward from the front surface 607F of the storage section 607. The first support wall 805 and the second support wall 806 are fixed to the front surface 607F of the storage section 607. In the Y direction, the first support wall 805 and the second support wall 806 straddle the center of the storage section 607. The first support wall 805 and the second support wall 806 are plate-shaped with thicknesses in the top and bottom. The first support wall 805 and the second support wall 806 are, for example, rectangular. The outer dimensions of the first support wall portion 805 and the second support wall portion 806 are approximately the same. The first support wall portion 805 is located above the second support wall portion 806. The lower surface of the first support wall portion 805 faces the upper surface of the second support wall portion 806.

[0365] The upper body 606 also includes a third support wall portion 807. The third support wall portion 807 is located upward relative to the first support wall portion 805. The third support wall portion 807 protrudes forward from the front surface 607F of the storage portion 607. The third support wall portion 807 is fixed to the front surface 607F of the storage portion 607. For example, the third support wall portion 807 has a rectangular parallelepiped shape that is elongated in the Y direction. In the Y direction, the third support wall portion 807 straddles the center of the storage portion 607. The front end of the third support wall portion 807 is located rearward relative to the front ends of the first support wall portion 805 and the second support wall portion 806.

[0366] The backhoe 800 is equipped with a boom swing mechanism 800B, which is an electric actuator. The boom swing mechanism 800B includes a swing bracket 610 and a pin 620. The configurations of the swing bracket 610 and the pin 620 are basically the same as those described in relation to FIG. 22 . However, the upper wall 611 and the lower wall 612 of the swing bracket 610 have different outer dimensions. The lower wall 612 of the swing bracket 610 is located between the first support wall portion 805 and the second support wall portion 806 of the upper body 606. The through-hole 612A of the lower wall 612 is positioned such that the front end of the third support wall portion 807 is located on the central axis of the through-hole 612A. The diameter of the through-hole 612A in the lower wall 612 is larger than the diameter of the pin 620. In the boom swing mechanism 800B, the pin 620 penetrates the first support wall portion 805 and the second support wall portion 806 together with the through-hole 612A. The pin 620 is fixed to the first support wall portion 805 and the second support wall portion 806. Meanwhile, due to the relationship in diameter between the through-hole 612A and the pin 620, a gap is formed between the through-hole 612A and the pin 620. Therefore, the pin 620 and the lower wall 612 are rotatable relative to each other. In other words, the lower wall 612 is rotatable around the pin 620 as a central axis. The central axis of the pin 620 forms a rotation central axis 610V, which is the rotation center of the lower wall 612 and, ultimately, the swing bracket 610. The rotation central axis 610V extends substantially in the Z direction. 24, the gap between pin 620 and through-hole 612A of lower wall 612 is exaggerated. Note that in boom swing mechanism 800B, the central axis of through-hole 611A of upper wall 611 is misaligned with the central axis of through-hole 612A of lower wall 612. Specifically, the central axis of through-hole 611A of upper wall 611 is positioned closer to connecting wall 613 than the central axis of through-hole 612A of lower wall 612.

[0367] The boom swing mechanism 800B includes a drive unit 615. Most of the drive unit 615 is located above the upper wall 611 of the swing bracket 610. The configuration of the drive unit 615 is the same as that described in relation to FIG. 22 . That is, the drive unit 615 includes an electric motor 616, a reducer 617, and a transmission shaft 618. The electric motor 616, the reducer 617, and the transmission shaft 618 are arranged in this order from top to bottom. The central axis of the output shaft 616B of the electric motor 616 substantially coincides with the central axis of the transmission shaft 618. The central axis of the transmission shaft 618 forms a rotation central axis 615V of the drive unit 615. The rotation central axis 615V of the drive unit 615 is substantially parallel to the swing central axis 610V. The drive unit 615 is fixed to the upper wall 611 of the swing bracket 610. Specifically, reducer 617 of drive device 615 is fixed to the upper surface of upper wall 611. Transmission shaft 618 passes through through-hole 611A of upper wall 611. A lower portion of transmission shaft 618 protrudes downward from the lower surface of upper wall 611. As described above, the central axis of through-hole 611A of upper wall 611 is offset from the central axis of through-hole 612A of lower wall 612. In consideration of this, rotation central axis 615V of drive device 615 is offset from swing central axis 610V.

[0368] The boom swing mechanism 800B includes a pinion gear 809. The configuration of the pinion gear 809 is the same as that described in relation to FIG. 22 . That is, the pinion gear 809 includes a cylindrical main body 809A and a plurality of teeth 809B protruding from the outer circumferential surface of the main body 809A. The pinion gear 809 is located below the upper wall 611 of the swing bracket 610. A portion of the transmission shaft 618 that protrudes from the lower surface of the upper wall 611 is disposed in a central hole in the main body 809A of the pinion gear 809. The main body 809A of the pinion gear 809 is fixed to the transmission shaft 618. That is, the pinion gear 809 rotates integrally with the transmission shaft 618.

[0369] The boom swing mechanism 800B includes a gear wall 810. The configuration of the gear wall 810 is the same as that described in relation to FIGS. 22 and 23. That is, as shown in FIG. 23, the gear wall 810 includes an arcuate surface 811B, a flat surface 811C connecting both ends of the arc of the arcuate surface 811B, and a plurality of teeth 812 protruding from the arcuate surface 811B. As shown in FIG. 24, the gear wall 810 is located between the pinion gear 809 and the third support wall portion 807 of the upper body 606. The gear wall 810 is fixed to the front end of the third support wall portion 807. More specifically, the flat surface 811C of the gear wall 810 is fixed to the front end of the third support wall portion 807. The arcuate surface 811B of the gear wall 810 protrudes forward from the flat surface 811C. The central axis of the arc of the arc surface 811B substantially coincides with the turning central axis 610V. The arc surface 811B faces the pinion gear 809. Some of the teeth 812 protruding from the arc surface 811B mesh with some of the teeth 809B of the pinion gear 809. A gap called backlash is formed between the teeth 812 of the gear wall 810 and the teeth 809B of the pinion gear 809. The gear wall 810 may be fixed directly to the front surface 607F of the accommodation section 607 without using the third support wall portion 807. In this case, it is possible to appropriately change the shape of the gear wall 810 so that the central axis of the arc of the arc surface 811B substantially coincides with the turning central axis 610V by, for example, changing the angle range of the arc of the arc surface 811B or changing the shape of the portion connecting both ends of the arc of the arc surface 811B.

[0370] The operation of the boom swing mechanism 800B will now be described. When the output shaft 616B of the electric motor 616 rotates, the pinion gear 809 rotates about the rotation center axis 615V of the drive unit 615. At the same time, the pinion gear 809 revolves around the arc surface 811B of the gear wall 810 about the swing center axis 610V through meshing with the teeth 812 of the gear wall 810. As a result of this revolution, the swing bracket 610 rotates about the swing center axis 610V. This causes the boom 530 to rotate.

[0371] In boom swing mechanism 800B, gear wall 810 and pinion gear 809 form a speed reduction mechanism due to the relationship in size between the arc diameter of arc surface 811B of gear wall 810 and the outer diameter of pinion gear 809. Therefore, boom swing mechanism 800B can also obtain the same effect as (6-1) above. Furthermore, in boom swing mechanism 800B, since gear wall 810 is semicircular, it can also obtain the same effect as (6-2) above.

[0372] The construction machinery to which the boom swing mechanisms 800A and 800B, which are electric actuators, can be applied is not limited to the excavator 800. In the above embodiment, various means may be used to fasten the two members together, such as bolting, welding, integral molding, spline connection, etc.

[0373] In the above embodiments, if an object is made up of multiple objects, the multiple objects may be integrated, and conversely, if an object is made up of a single object, it may be divided into multiple objects. Regardless of whether the objects are integrated or not, it is sufficient that the object of the invention can be achieved.

[0374] Seventh Embodiment A seventh embodiment of a construction machine and an electric actuator for the construction machine will be described below with reference to FIG. 25. Note that the drawings may show components enlarged to facilitate understanding. The dimensional ratios of the components may differ from the actual ones or from those in other drawings. In FIG. 25, parts that are the same as or function substantially the same as those in FIGS. 1 to 24 are given the same reference numerals as in FIGS. 1 to 24. In the following description, parts that overlap with the first to sixth embodiments may be omitted or simplified as appropriate.

[0375] <Overall structure> As shown in FIG. 25, a backhoe 830, which is a construction machine, includes a lower body 602, an upper body 606 which is a vehicle body, a pair of traveling devices 510, and a swivel bearing 603. The configurations of the lower body 602, the pair of traveling devices 510, and the swivel bearing 603 are the same as those in the second embodiment. Therefore, a description thereof will be omitted. The upper body 606 will be described later. The upper body 606 is located on the opposite side of the ground from the lower body 602. Note that in this embodiment, up, down, left, right, front, and rear are defined in the same way as in the second embodiment. For convenience of explanation, some members of the backhoe 830 are shown in cross section in FIG. 25.

[0376] The upper body 606 includes a storage section 607, a first support wall section 831, a second support wall section 832, and a riding section. Note that the riding section is not shown in Fig. 25. The configurations of the storage section 607 and the riding section are the same as those in the second embodiment.

[0377] The first support wall portion 831 protrudes forward from the front surface 607F of the storage portion 607. The first support wall portion 831 is fixed to the front surface 607F of the storage portion 607. The first support wall portion 831 is, for example, a rectangular plate. The main surface of the first support wall portion 831 faces up and down. The main surface is the surface of a plate-shaped object with the largest area. The first support wall portion 831 straddles the center of the storage portion 607 in the Y direction.

[0378] The second support wall portion 832 is located above the first support wall portion 831. The second support wall portion 832 is located away from the first support wall portion 831 in the Z direction. The second support wall portion 832 protrudes forward from the front surface 607F of the accommodation portion 607. The second support wall portion 832 is fixed to the front surface 607F of the accommodation portion 607. The second support wall portion 832 is, for example, in the shape of a rectangular plate. The main surface of the second support wall portion 832 faces up and down. The length and width dimensions of the main surface of the second support wall portion 832 are smaller than the length and width dimensions of the main surface of the first support wall portion 831. As a result of this size relationship, the front end of the second support wall portion 832 is located rearward of the front end of the first support wall portion 831. The second support wall portion 832 has a through-hole 832A. The through-hole 832A passes vertically through the second support wall portion 832. The central axis of the through-hole 832A extends substantially in the Z direction.

[0379] The backhoe 830 is equipped with an excavation machine including a boom 530, an arm 540, and a bucket 550. The boom 530, the arm 540, and the bucket 550 are located forward of the storage section 607 of the upper body 606. The configurations of the boom 530, the arm 540, and the bucket 550 are the same as those in the second embodiment. Therefore, a description thereof will be omitted.

[0380] <Boom swing mechanism> The backhoe 830 is equipped with a boom swing mechanism 830A. The boom swing mechanism 830A is a mechanism for swinging the boom 530 left and right relative to the upper body 606. The boom swing mechanism 830A constitutes an electric actuator.

[0381] Boom swing mechanism 830A includes a bearing 840. Bearing 840 includes an inner ring 841, a rolling element 842, and an outer ring 843. Bearing 840 is located above first support wall portion 831 in upper body 606.

[0382] The inner ring 841 is annular. The central axis of the inner ring 841 extends substantially in the Z direction. A lower end surface of the inner ring 841, which is an end surface on one side in the direction along the central axis, faces the upper surface of the first support wall portion 831. The lower end surface of the inner ring 841 is fixed to the upper surface of the first support wall portion 831. In other words, the inner ring 841 is attached to the first support wall portion 831, which is part of the vehicle body.

[0383] The outer ring 843 includes a main body 843A, an upper wall 843B, and a plurality of teeth 843C. The main body 843A is annular. The central axis of the main body 843A substantially coincides with the central axis of the inner ring 841. That is, the main body 843A is provided coaxially with the inner ring 841. Hereinafter, the central axis of the main body 843A will be referred to as the turning center axis 840V. The dimension of the main body 843A in the direction along the turning center axis 840V is smaller than the dimension of the inner ring 841 in the direction along the turning center axis 840V. The inner diameter of the main body 843A is larger than the outer diameter of the inner ring 841. In addition, in the radial direction (hereinafter simply referred to as the radial direction) centered on the turning center axis 840V, the main body 843A is located outward relative to the inner ring 841. The main body 843A surrounds the inner ring 841 from the radially outer side.

[0384] The upper wall 843B is located above the main body 843A. The upper wall 843B is disk-shaped. The center of the circle of the upper wall 843B is located on the turning center axis 840V. The diameter of the upper wall 843B is approximately the same as the outer diameter of the main body 843A. The upper wall 843B is connected to the upper end surface, which is the end surface of the main body 843A on one side of the turning center axis 840V. The upper wall 843B closes an opening defined by the inner peripheral edge of the upper end surface of the main body 843A. A portion of the lower surface of the upper wall 843B that is located radially inward with respect to the main body 843A faces the upper end surface of the inner ring 841. The lower surface of the upper wall 843B and the upper end surface of the inner ring 841 are in slidable contact. The lower surface of the upper wall 843B and the upper end surface of the inner ring 841 may be separated from each other. As a result of the dimensional relationship between the main body 843A and the inner ring 841 in the direction along the turning center axis 840V, the lower end surface of the main body 843A is located away from the upper surface of the first support wall portion 831.

[0385] The teeth 843C protrude radially outward from the outer circumferential surface of the main body 843A and are arranged at equal intervals in the circumferential direction (hereinafter simply referred to as the circumferential direction) about the central axis of rotation 840V.

[0386] The rolling elements 842 are balls. The rolling elements 842 are located between the inner ring 841 and a main body 843A of the outer ring 843. The rolling elements 842 are arranged at equal intervals in the circumferential direction. The rolling elements 842 support the outer ring 843 rotatably with respect to the inner ring 841. In other words, the rolling elements 842 guide the relative rotation of the outer ring 843 with respect to the inner ring 841. As a result of the presence of the rolling elements 842 between the inner ring 841 and the outer ring 843, the outer ring 843 is rotatable about the turning central axis 840V. The entire bearing 840 is located forward of the front end of the second support wall portion 832.

[0387] The boom swing mechanism 830A includes a swing bracket 845. The swing bracket 845 is located above the outer wheel 843. The swing bracket 845 is, for example, a rectangular plate. The main surfaces of the swing bracket 845 face up and down. The lower surface, which is one of the two main surfaces of the swing bracket 845, faces the upper surface of the upper wall 843B of the outer wheel 843. The lower surface of the swing bracket 845 is fixed to the upper surface of the upper wall 843B of the outer wheel 843. Therefore, when the outer wheel 843 rotates, the swing bracket 845 rotates integrally with the outer wheel 843. In other words, the swing bracket 845 is rotatable around the rotation central axis 840V. The base wall 534 of the boom 530 is fixed to the upper surface of the swing bracket 845. As a result of the swing bracket 845 being fixed to the outer wheel 843, the swing bracket 845 is connected to the first support wall portion 831, which is the vehicle body, via the bearing 840 so as to be rotatable around the turning center axis 840V.

[0388] Boom swing mechanism 830A includes a drive device 834. In the X direction, drive device 834 is located between front surface 607F of storage section 607 and bearing ...

Claims

1. The car body and a drive device including an electric motor and outputting torque centered on a rotation central axis extending vertically of the vehicle body; a swing bracket connected to the vehicle body, which receives torque from the drive unit and rotates about a turning center axis parallel to the rotation center axis or the rotation center axis; a boom fixed to the swing bracket; Construction machinery.

2. a drive device including an electric motor and outputting torque about a central axis of rotation; a swing bracket that receives torque from the drive device, rotates around a central axis of rotation that is parallel to the central axis of rotation, or the central axis of rotation, and is fixed to the boom. Electric actuators for construction machinery.

3. The drive device is a transmission shaft that is disposed in a first through hole provided in a vehicle body of the construction machine and is rotatable around the central rotation axis; the electric motor having an output shaft connected to the transmission shaft and attached to the vehicle body; a reducer that is attached to the vehicle body at a position opposite to the electric motor across the first through hole, the reducer having an input shaft connected to the transmission shaft and that amplifies and outputs torque output by the output shaft of the electric motor; an output member that receives torque from the reducer and rotates about the rotation central axis, and that is connected to the swing bracket; The swing bracket receives torque from the output member and rotates about the central axis of rotation. The electric actuator for a construction machine according to claim 2.

4. a cylindrical member having the transmission shaft disposed therein and a pin disposed in the first through hole together with the transmission shaft; The swing bracket is in contact with the pin. The electric actuator for a construction machine according to claim 3.

5. the swing bracket has an opposing wall having a third through hole at a position facing the second through hole provided in the output member, a connecting member connecting the output member and the opposing wall, The connecting member is a base portion disposed in the second through hole and the third through hole; a buffer portion that is cylindrical and has the base portion disposed therein, is disposed in the second through hole and the third through hole together with the base portion, and has an elastic modulus smaller than that of the base portion; The electric actuator for a construction machine according to claim 3.

6. the swing bracket has an opposing wall facing the output member, a connecting member connecting the opposing wall and the output member, There is a gap between the opposing wall and the output member. The electric actuator for a construction machine according to claim 3.

7. The drive device is attached to a body of a construction machine, the swing bracket is connected to the vehicle body so as to be rotatable about the central axis of rotation, a driving member that receives torque from the driving device and rotates about the central axis of rotation; a transmission receiving member attached to the swing bracket and rotating about the central axis of rotation; a transmission mechanism that rotates the driving member and the driven member in conjunction with each other. The electric actuator for a construction machine according to claim 2.

8. the drive member is a drive sprocket that is annular and has a plurality of teeth on its outer circumferential surface, the drive member being centered on the central axis of rotation; the driven member is a driven sprocket that is annular and has a plurality of teeth on its outer circumferential surface, the driven sprocket being centered on the central axis of rotation, The transmission mechanism is a chain wound around the driving sprocket and the driven sprocket. The electric actuator for a construction machine according to claim 7.

9. the driving member is an annular driving pulley centered on the central axis of rotation, the driven member is an annular driven pulley centered on the central axis of rotation, The transmission mechanism is a belt wound around the drive pulley and the driven pulley. The electric actuator for a construction machine according to claim 7.

10. The outer diameter of the driving member is smaller than the outer diameter of the driven member. The electric actuator for a construction machine according to claim 8 or 9.

11. the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is supported by a swivel bearing so as to be rotatable relative to the lower body, When the direction in which the central axis of rotation of the upper body is located as viewed from the central axis of rotation of the upper body is defined as a first direction, and the location of the slewing bearing that is closest to the central axis of rotation in the first direction is defined as a specific location, At least a portion of the drive member is located on an imaginary line segment connecting the specific location and the central axis of rotation. The electric actuator for a construction machine according to claim 7.

12. the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is supported by a swivel bearing so as to be rotatable relative to the lower body, one or more intermediate members attached to the vehicle body and rotating about a central axis parallel to the central axis of rotation; the transmission mechanism is configured to rotate all of the intermediate members, the driving members, and the transmitted members in conjunction with one another; When viewed from the central axis of rotation of the upper body, a direction in which the central axis of rotation is located is defined as a first direction, and a direction opposite to the first direction is defined as a second direction, all of the intermediate members are located on the first direction side as viewed from the driving member, The drive member and the drive device are located on the second direction side as viewed from the central axis of rotation of the upper body. The electric actuator for a construction machine according to claim 7.

13. The drive device is attached to a body of a construction machine, The swing bracket is fixed to an output member of the drive unit, and receives torque from the drive unit to rotate about the central axis of rotation. The electric actuator for a construction machine according to claim 2.

14. the drive device has a reducer that amplifies and outputs torque output by the electric motor, The reducer outputs torque centered on the rotational central axis, which is output by the electric motor, to the swing bracket coaxially with the electric motor. The electric actuator for a construction machine according to claim 13.

15. The drive device is located below the swing bracket, The swing bracket is fixed to the output member of the drive device with a bolt. The electric actuator for a construction machine according to claim 13.

16. the swing bracket is aligned with the drive device in a direction along the rotation central axis, a transmission member interposed between the drive device and the swing bracket and configured to transmit torque of the drive device to the swing bracket; an annular bearing attached to the body of the construction machine, through which the transmission member passes and which rotatably supports the transmission member; a holding member, the holding member being positioned on the opposite side of the swing bracket with respect to the bearing in the direction along the rotation central axis, and through which the drive device passes; a buffer member that connects the holding member and the vehicle body and has a smaller elastic modulus than the holding member, The swing bracket receives torque from the drive unit via the transmission member and rotates around the rotation center axis. The electric actuator for a construction machine according to claim 2.

17. A plurality of the bearings are provided, The plurality of bearings are arranged in a direction along the central axis of rotation. The electric actuator for a construction machine according to claim 16.

18. the drive device is cylindrical with the rotation central axis as its center, the swing bracket is aligned with the drive device in a direction along the rotation central axis, is fixed to an output member of the drive device, receives torque from the drive device, and rotates about the rotation central axis; a flange wall that is located on the opposite side of the swing bracket with respect to the drive device in a direction along the rotation central axis, supports the drive device, and is fixed to a body of the construction machine; a holding member positioned between the swing bracket and the flange wall, the holding member having the driving device passing therethrough; a buffer member that connects the holding member and the vehicle body and has a smaller elastic modulus than the holding member; a pin extending through the drive device and secured to the flange wall. R The electric actuator for a construction machine according to claim 2.

19. the swing bracket is connected to the body of the construction machine so as to be rotatable about the central axis of rotation, a pinion gear that receives torque from the drive device and rotates about the central axis of rotation; a gear wall provided at a position facing the pinion gear, the gear wall has an arc-shaped surface having an arc centered on a central axis parallel to the central axis of rotation, and a plurality of teeth protruding from the arc-shaped surface and meshing with teeth of the pinion gear, a diameter of the arc of the arc surface is larger than an outer diameter of the pinion gear, One of the gear wall and the drive device is fixed to the swing bracket, and the other is fixed to the vehicle body. The electric actuator for a construction machine according to claim 2.

20. the arcuate surface extends over a range of 165 degrees or more and 195 degrees or less in a circumferential direction around a central axis parallel to the central axis of rotation, In the gear wall, both ends of the arc of the arc surface are connected by a flat surface extending linearly. The electric actuator for a construction machine according to claim 19.

21. an annular inner ring attached to a body of the construction machine and centered on the central axis of rotation; an outer ring that is annular and coaxial with the inner ring, has a plurality of teeth on its outer peripheral surface, is fixed to the swing bracket, and rotates together with the swing bracket about the central axis of rotation; a rolling element interposed between the inner ring and the outer ring and configured to guide relative rotation between the inner ring and the outer ring; a pinion gear that is disposed at a position facing the outer peripheral surface of the outer ring, that receives torque output from the drive device and rotates about the central rotation axis, and that has teeth on its outer peripheral surface that mesh with the teeth of the outer ring; The electric actuator for a construction machine according to claim 2.

22. The car body and a cylindrical first member; a second member inserted into the first member from one end of the first member in a direction along the central axis thereof and capable of reciprocating in a direction along the central axis of the first member; an electric motor that drives the reciprocating movement of the second member relative to the first member; a swing bracket connected to the vehicle body so as to be rotatable about a central axis of rotation extending vertically along the vehicle body; a boom fixed to the swing bracket, the first member is connected to one of the vehicle body and the swing bracket in a state in which the first member can rotate about a central axis parallel to the central axis of rotation, The second member is connected to the other of the vehicle body and the swing bracket in a state in which the second member can rotate about a central axis parallel to the central axis of rotation. Construction machinery.

23. a cylindrical first member; a second member inserted into the first member from one end of the first member in a direction along the central axis thereof and capable of reciprocating in a direction along the central axis of the first member; an electric motor that drives the reciprocating movement of the second member relative to the first member; a swing bracket connected to the body of the construction machine so as to be rotatable about a central axis of rotation and fixed to the boom, the first member is connected to one of the vehicle body and the swing bracket in a state in which the first member can rotate about a central axis parallel to the central axis of rotation, The second member is connected to the other of the vehicle body and the swing bracket in a state in which the second member can rotate about a central axis parallel to the central axis of rotation. Electric actuators for construction machinery.

24. the second member is cylindrical and extends along the central axis of the first member, and has an internal thread formed on its inner circumferential surface; a screw shaft that is inserted into the second member from an end of the second member opposite to the one side, has a male thread formed on an outer peripheral surface, and rotates about a central axis of the second member in response to rotation of the electric motor; a ball interposed between the screw shaft and the second member. The electric actuator for a construction machine according to claim 23.

25. a rotational center axis of the electric motor extends parallel to the center axis of the second member at a position different from the center axis of the second member, A transmission mechanism is provided to transmit the rotation of the electric motor to the screw shaft. The electric actuator for a construction machine according to claim 24.

26. the first member defines a fluid chamber into which a fluid is supplied and discharged, The second member is a piston that divides the fluid chamber into two in a direction along the central axis of the first member; a rod extending from the piston to the one side, A fluid circuit is provided that supplies and discharges fluid to each of the two divided fluid chambers in response to the driving of a pump driven by the electric motor. The electric actuator for a construction machine according to claim 23.

27. the second member has a columnar shape extending in a direction along the central axis of the first member, and has a plurality of rack teeth on an outer surface thereof arranged in a direction along the central axis of the first member, a pinion gear that is rotatable about an axis that intersects with the central axis of the second member, has teeth on its outer circumferential surface that mesh with the rack teeth, and is rotationally driven by the electric motor; The electric actuator for a construction machine according to claim 23.

28. the vehicle body is an upper body that is located on the opposite side of the ground from the lower body of the construction machine and is supported by a swivel bearing so as to be rotatable relative to the lower body, a rotational center axis of the electric motor coincides with a center axis of the pinion gear; When viewed in a plan view in a direction along the turning central axis, a virtual line segment connecting the turning central axis of the upper body and the turning central axis is defined as a first line segment, When a virtual line segment connecting an end of the first member opposite to the side where the second member is inserted and an end of the second member on one side in a direction along the central axis of the first member is defined as a second line segment, The rotational center axis of the electric motor is located between the first line segment and the second line segment. The electric actuator for a construction machine according to claim 27.

29. The car body and an electric motor attached to the vehicle body and configured to output torque centered on a rotational central axis; a swing bracket connected to the vehicle body so as to be rotatable about a central turning axis that intersects the rotation central axis and extends vertically of the vehicle body; a conversion mechanism for converting torque of the electric motor centered on the rotation central axis into torque centered on the swivel central axis; a transmission member that transmits the torque converted by the conversion mechanism to the swing bracket; a boom fixed to the swing bracket; Construction machinery.

30. an electric motor that outputs torque centered on a central axis of rotation; a swing bracket connected to the body of the construction machine so as to be rotatable about a central axis of rotation extending in a direction intersecting the central axis of rotation and fixed to the boom; a conversion mechanism for converting torque of the electric motor centered on the rotation central axis into torque centered on the swivel central axis; a transmission member that transmits the torque converted by the conversion mechanism to the swing bracket. Electric actuators for construction machinery.

Images