Joint mechanisms of construction machinery

Abstract

To reduce the stress on the joints of construction machinery. [Solution] The device includes a first drive unit 101 that includes an electric motor 110 and outputs torque, a first member having a first connecting wall 64 and a second connecting wall 66 that are aligned in a direction along the rotation axis 21J of the torque output by the first drive unit 101, a second member having a first connecting wall 33 and a second connecting wall 35 that are located between the first connecting wall 64 and the second connecting wall 66, and a pin 71 that connects the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other in the circumferential direction about the rotation axis 21J, wherein the first drive unit 101 connects the second connecting wall 66 and the second connecting wall 35 and rotates the second connecting wall 66 and the second connecting wall 35 relative to each other in the circumferential direction about the rotation axis 21J.

Description

Technical Field

[0001] This invention relates to a joint mechanism of construction machinery.

Background Art

[0002] The excavator disclosed in Patent Document 1 includes a vehicle body, a boom, an arm, and a bucket. The boom is connected to the front end of the vehicle body. The boom is rotatable vertically with respect to the vehicle body. The arm is connected to the tip of the boom. The arm is rotatable vertically with respect to the boom. The bucket is connected to the tip of the arm. The bucket is rotatable vertically with respect to the arm.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology such as Patent Document 1, it is desired to reduce the burden acting on each joint portion, such as the connection portion between the boom and the arm or the connection portion between the arm and the bucket.

Means for Solving the Problems

[0005] The joint mechanism for a construction machine to solve the above problems includes a drive device that includes an electric motor and outputs torque, a first member having a first connecting wall and a second connecting wall arranged in a direction along the rotation axis of the torque output by the drive device, a second member having at least a portion located between the first connecting wall and the second connecting wall in a direction along the rotation axis, and a connecting member that connects the first connecting wall and the second member so as to be rotatable relative to each other in the circumferential direction about the rotation axis, wherein the drive device connects the second connecting wall and the second member and rotates the second connecting wall and the second member relative to each other in the circumferential direction about the rotation axis.

[0006] In the above configuration, the load acting on the first member can be borne by the two wall sections, the first connecting wall and the second connecting wall. Therefore, this load is distributed between the first and second connecting walls. This reduces the load acting on each connecting wall and on the connection between the first and second members.

[0007] In the joint mechanism of a construction machine, the second member has a connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, the connecting member connects the first connecting wall and the connecting wall, and the drive device may have a base portion fixed to one of the second connecting wall and the connecting wall, and an output portion fixed to the other of the second connecting wall and the connecting wall, which rotates relative to the base portion in a circumferential direction about the axis of rotation.

[0008] In the joint mechanism of a construction machine, the second member has a first connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, and a second connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, the connecting member connects the first connecting wall and the first connecting wall, and the drive device may have a base portion fixed to one of the second connecting wall and the second connecting wall, and an output portion fixed to the other of the second connecting wall and the second connecting wall, which rotates relative to the base portion in a circumferential direction about the axis of rotation.

[0009] In the joint mechanism of a construction machine, the base portion of the drive device may be located between the first connecting wall and the second connecting wall in a direction along the axis of rotation. In the joint mechanism of a construction machine, the second member has a third connecting wall located on the opposite side of the second connecting wall from the first connecting wall in the direction along the axis of rotation, and the drive device may penetrate the third connecting wall.

[0010] In the joint mechanism of a construction machine, the first member may be a bucket having an opening. In the joint mechanism of a construction machine, the second member has a first connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, and a second connecting wall located on the opposite side of the second connecting wall from the first connecting wall in a direction along the axis of rotation, and when the connecting member is the first connecting member, the first connecting member connects the first connecting wall and the first connecting wall, and further comprises a second connecting member that connects the second connecting wall and the second connecting wall so as to be rotatable relative to each other in a circumferential direction about the axis of rotation, and the drive device may have a base portion fixed to one of the second connecting wall and the first connecting wall, and an output portion fixed to the other of the second connecting wall and the first connecting wall and rotating relative to the base portion in a circumferential direction about the axis of rotation.

[0011] In the joint mechanism of a construction machine, the drive device has a base portion fixed to one of the second connecting wall and the second member, and an output portion fixed to the other of the second connecting wall and the second member, which rotates relative to the base portion in a circumferential direction about the rotation axis, wherein the output portion has a spline groove formed along the rotation axis and may be fixed to the second connecting wall or the second member via the spline groove.

[0012] A joint mechanism for a construction machine to solve the above problems comprises a drive device including an electric motor that outputs torque, a first member, and a second member aligned with the first member in a direction along the rotation axis of the torque output by the drive device, wherein the drive device has a base portion fixed to the first member and an output portion fixed to the second member and rotating relative to the base portion in a circumferential direction about the rotation axis, and the output portion has a spline groove formed along the rotation axis and is fixed to the second member via the spline groove.

[0013] As shown in the above configuration, when the output unit is fixed to the second member using a so-called spline joint, the torque of the output unit is more easily transmitted to the second member compared to, for example, when the output unit is fixed to the second member with bolts. In this way, by efficiently transmitting force between members, the load acting on the connecting parts of each member can be reduced. [Effects of the Invention]

[0014] The above technical concept can reduce the stress acting on the joints of construction mechanisms. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic side view of an excavator. [Figure 2] Figure 2 is a schematic cross-sectional view of the first joint mechanism. [Figure 3] Figure 3 is a schematic cross-sectional view of the second joint mechanism. [Figure 4] Figure 4 is a schematic cross-sectional view of the third joint mechanism. [Figure 5] Figure 5 is a schematic cross-sectional view illustrating an example of a modification to the joint mechanism. [Figure 6] Figure 6 is a schematic cross-sectional view illustrating an example of a modification to the joint mechanism. [Figure 7] Figure 7 is a schematic cross-sectional view illustrating an example of a modification to the joint mechanism. [Figure 8] Figure 8 is a schematic cross-sectional view illustrating an example of a modification to the joint mechanism.

Embodiment for Carrying out the Invention

[0016] Hereinafter, an embodiment of a joint mechanism of a construction machine will be described with reference to the drawings. Note that the drawings may show the components enlarged for easy understanding. Also, the dimensional ratios of the components may be different from the actual ones or those in other drawings. In this specification, when collectively describing members with a common name employed in a plurality of joint mechanisms, the reference signs may be omitted when explaining them collectively.

[0017] <Overall Configuration> As shown in FIG. 1, an excavator 10 which is a construction machine includes a vehicle body 12 and a pair of traveling devices 14. The vehicle body 12 houses various mechanisms, devices, and components necessary for operating the excavator 10. The vehicle body 12 may include a passenger seat. The pair of traveling devices 14 are located on both the left and right sides of the vehicle body 12. The traveling device 14 includes a crawler for traveling and an operating mechanism for rotating the crawler.

[0018] The excavator 10 includes a support 60, a boom 30, and an arm 40. Further, the excavator 10 includes a bucket 50 as an attachment. [[ID=十九]]The support 60 is located on the front side with respect to the vehicle body 12. The support 60 includes a support body 62 and a wall portion for connecting the support body 62 to the boom 30. The support body 62 is connected to the vehicle body 12.

[0019] The boom 30 is connected to the support 60. The boom 30 comprises a boom body 31 and a wall portion for connecting the boom body 31 to the support 60 and the arm 40. The boom body 31 is a long plate or column. For example, the boom body 31 is bent in the middle of its longitudinal direction. The boom body 31 is rotatable relative to the support 60 about a first rotation axis 21J. The first rotation axis 21J extends in a direction perpendicular to the virtual axis extending vertically from the vehicle body 12. The first rotation axis 21J is the central axis of the torque output by the first drive unit 101, which will be described later.

[0020] The arm 40 is connected to the end of the boom body 31 opposite to the connection point with the vehicle body 12. The arm 40 comprises an arm body 41 and a wall portion for connecting the arm body 41 to the boom 30 and the bucket 50. The arm body 41 is a long, plate-like or columnar shape. The arm body 41 is rotatable relative to the boom 30 about a second rotation axis 22J. The second rotation axis 22J is approximately parallel to the first rotation axis 21J. The second rotation axis 22J is the central axis of the torque output by the second drive unit 102, which will be described later.

[0021] The bucket 50 is connected to the end of the arm 40 opposite to the point where it connects to the boom 30. The bucket 50 comprises a bucket body 51 and a wall portion for connecting the bucket body 51 to the arm 40. The bucket body 51 is box-shaped with an opening. The bucket body 51 is rotatable relative to the arm 40 about a third rotation axis 23J. The third rotation axis 23J is approximately parallel to the first rotation axis 21J. The third rotation axis 23J is the central axis of the torque output by the third drive unit 103, which will be described later.

[0022] <First joint mechanism> The first joint mechanism 21, which connects the support 60 and the boom 30, will now be described. As shown in Figure 2, the excavator 10 is equipped with a first drive unit 101, a first brake unit 130, a pin 71, and a cover 72 in the first connecting portion, which is the connecting part between the support 60 and the boom 30. The first joint mechanism 21 in this embodiment is composed of these members and the support 60 and boom 30, which are the objects to be connected. The support 60 is the first member of the first joint mechanism 21. The boom 30 is the second member of the first joint mechanism 21. The pin 71 is a connecting member of the first joint mechanism 21. Note that in Figure 2, the cross-sectional structure of some members of the first joint mechanism 21 is omitted and shown as a plan view.

[0023] As shown in Figure 2, at the first joint section, the support body 62 and the boom body 31 are located on opposite sides of the first rotation axis 21J. The end face 62A of the support body 62 and the first end face 31A of the boom body 31 face each other across the first rotation axis 21J. The first end face 31A of the boom body 31 is the end face of the elongated boom body 31 that is closer to the vehicle body 12. With respect to the direction along the first rotation axis 21J, the dimension of the end face 62A of the support body 62 is larger than the dimension of the first end face 31A of the boom body 31. Hereinafter, in the description of the first joint mechanism 21, one of the two directions along the first rotation axis 21J will be referred to as the first direction A1, and the other as the second direction A2. The end face 62A of the support body 62 on the first direction A1 side is located on the first direction A1 side relative to the end face 31A of the boom body 31 on the first direction A1 side. The end face 62A of the support body 62 on the second direction A2 side is located on the second direction A2 side relative to the end face 31A of the boom body 31 on the second direction A2 side.

[0024] The support 60 comprises a first connecting wall 64 and a second connecting wall 66 as a configuration for connecting the support body 62 to the boom body 31. The first connecting wall 64 protrudes from the end face 62A of the support body 62 toward the boom body 31. In detail, the first connecting wall 64 protrudes from the end face 62A of the support body 62 toward the first direction A1. The first connecting wall 64 is plate-shaped. In the direction along the first rotation axis 21J, the entire length of the first connecting wall 64, from the connecting end connected to the end face 62A to the protruding end opposite the connecting end, is located at approximately the same position as the end face 62A toward the first direction A1. The protruding end of the first connecting wall 64 is located toward the boom body 31 than the first rotation axis 21J. The first rotation axis 21J passes through the main surface of the first connecting wall 64. The main surface of the first connecting wall 64 is approximately perpendicular to the first rotation axis 21J. The main surface is the surface with the largest area among the outer surfaces of the plate-shaped object. The first connecting wall 64 is provided with a through hole 64A. The through hole 64A penetrates the first connecting wall 64 in a direction along the first rotation axis 21J. The central axis of the through hole 64A is approximately coincident with the first rotation axis 21J.

[0025] The second connecting wall 66 protrudes from the end face 62A of the support body 62 toward the boom body 31. More specifically, the second connecting wall 66 protrudes from the end face 62A of the support body 62 toward the second direction A2. The second connecting wall 66 has the same shape and dimensions as the first connecting wall 64. That is, the second connecting wall 66 is plate-shaped. In the direction along the first rotation axis 21J, the entire length of the second connecting wall 66, from the connecting end connected to the end face 62A to the protruding end opposite the connecting end, is located at approximately the same position as the end face 62A toward the second direction A2. The second connecting wall 66 is aligned with the first connecting wall 64 in the direction along the first rotation axis 21J. Similar to the first connecting wall 64, the second connecting wall 66 is positioned where the first rotation axis 21J passes. The main surface of the second connecting wall 66 is approximately perpendicular to the first rotation axis 21J. The second connecting wall 66 is provided with a through hole 66A. Details of the through hole 66A will be described later.

[0026] The boom 30 includes a first connecting wall 33 and a second connecting wall 35 as a configuration for connecting the boom body 31 to the support body 62. The first connecting wall 33 protrudes from the first end face 31A of the boom body 31 toward the support body 62. More specifically, the first connecting wall 33 protrudes from the end of the first end face 31A toward the first direction A1. The first connecting wall 33 is plate-shaped. In the direction along the first rotation axis 21J, the entire length of the first connecting wall 33, from the connecting end connected to the first end face 31A to the protruding end opposite the connecting end, is located at approximately the same position as the end of the first end face 31A toward the first direction A1. The protruding end of the first connecting wall 33 is located toward the support body 62 than the first rotation axis 21J. The first rotation axis 21J passes through the main surface of the first connecting wall 33. The main surface of the first connecting wall 33 is approximately perpendicular to the first rotation axis 21J. In the direction along the first rotation axis 21J, the first connecting wall 33 is located between the first connecting wall 64 and the second connecting wall 66. The first connecting wall 33 is located immediately next to the first connecting wall 64. There is a small gap between the first connecting wall 33 and the first connecting wall 64. The first connecting wall 33 is provided with a through hole 33A. The through hole 33A penetrates the first connecting wall 33 in the direction along the first rotation axis 21J. The central axis of the through hole 33A is approximately the same as the diameter of the through hole 64A of the first connecting wall 64 in the support 60.

[0027] The second connecting wall 35 protrudes from the first end face 31A of the boom body 31 toward the support body 62. More specifically, the second connecting wall 35 protrudes from the end of the first end face 31A on the second direction A2 side. The second connecting wall 35 has the same shape and dimensions as the first connecting wall 33. That is, the second connecting wall 35 is plate-shaped. In the direction along the first rotation axis 21J, the entire length of the second connecting wall 35, from the connecting end connected to the first end face 31A to the protruding end opposite the connecting end, is located at approximately the same position as the end of the first end face 31A on the second direction A2 side. Similar to the first connecting wall 33, the second connecting wall 35 is positioned where the first rotation axis 21J passes through. The main surface of the second connecting wall 35 is approximately perpendicular to the first rotation axis 21J. The second connecting wall 35 is aligned with the first connecting wall 33 in the direction along the first rotation axis 21J. In the direction along the first rotation axis 21J, the second connecting wall 35 is located between the first connecting wall 33 and the second connecting wall 66 in the support 60. The second connecting wall 35 is separated from both the first connecting wall 33 and the second connecting wall 66. In the direction along the first rotation axis 21J, the distance between the second connecting wall 35 and the first connecting wall 33 is longer than the distance between the second connecting wall 35 and the second connecting wall 66. Note that in Figure 2, the distance between the second connecting wall 35 and the second connecting wall 66 is exaggerated and shown as larger. The second connecting wall 35 has a through hole 35A. The through hole 35A penetrates the second connecting wall 35. The central axis of the through hole 35A approximately coincides with the first rotation axis 21J. The diameter of the through-hole 35A is larger than the diameter of the through-hole 33A in the first connecting wall 33.

[0028] The pin 71 is positioned to straddle the first connecting wall 64 of the support 60 and the first connecting wall 33 of the boom 30. Specifically, the pin 71 is located inside the through-hole 64A of the first connecting wall 64 and the through-hole 33A of the first connecting wall 33. The pin 71 penetrates both the through-hole 64A of the first connecting wall 64 and the through-hole 33A of the first connecting wall 33. The pin 71 is cylindrical. The central axis of the pin 71 is approximately the same as the first rotation axis 21J. The diameter of the pin 71 is approximately the same as the diameter of the through-hole 64A of the first connecting wall 64. As a result of the pin 71 penetrating both the through-hole 64A of the first connecting wall 64 and the through-hole 33A of the first connecting wall 33, the pin 71 connects the first connecting wall 64 and the first connecting wall 33. Furthermore, the outer surface of the pin 71 is in slidable contact with the inner surface of the through-hole 64A of the first connecting wall 64. Similarly, the outer surface of the pin 71 is in slidable contact with the inner surface of the through-hole 33A of the first connecting wall 33. As a result, the pin 71 supports the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other. At the same time, the pin 71 connects the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other in the circumferential direction about the first rotation axis 21J. A bearing may be placed between the through-hole 64A of the first connecting wall 64 and the pin 71. Similarly, a bearing may be placed between the through-hole 33A of the first connecting wall 33 and the pin 71. The bearing may be a rolling bearing or a sliding bearing. When a bearing is placed in each through-hole, the diameter of the pin 71 or the through-hole may be adjusted as appropriate.

[0029] The cover 72 is located on the opposite side of the first connecting wall 33 from the first connecting wall 64. The cover 72 is, for example, disc-shaped. The main surface of the cover 72 faces the main surface of the first connecting wall 64. The diameter of the circle of the cover 72 is larger than the diameter of the through hole 64A in the first connecting wall 64. The cover 72 covers the through hole 64A. In this embodiment, the cover 72 is fixed to a pin 71. For example, the cover 72 is integrally molded with the pin 71. The cover 72 is fixed to the first connecting wall 64 by bolts B.

[0030] The first drive unit 101 is located between the second connecting wall 66 of the support 60 and the first connecting wall 33 of the boom 30, in a direction along the first rotation axis 21J. The first drive unit 101 includes an electric motor 110 and a reduction gear 120. In Figure 2, the convenient boundary between the electric motor 110 and the reduction gear 120 is shown by a dashed line.

[0031] The electric motor 110 is the drive source for the first drive unit 101. The electric motor 110 is electrically connected to a battery (not shown). The electric motor 110 comprises a housing 112 and an output shaft 114. The housing 112 is cylindrical. The central axis of the housing 112 is approximately coincident with the first rotation axis 21J. The housing 112 is fixed to the second connecting wall 35 of the boom 30 via the fixing structure of the reduction gear 120, which will be described later. The housing 112 is located on the first direction A1 side with respect to the second connecting wall 35. That is, the housing 112 is located between the first connecting wall 33 and the second connecting wall 35 in the direction along the first rotation axis 21J. The housing 112 constitutes the base portion of the first drive unit 101.

[0032] The output shaft 114 is located inside the housing 112. The output shaft 114 is cylindrical. The central axis of the output shaft 114 approximately coincides with the first rotation axis 21J. The output shaft 114 is rotatable relative to the housing 112. The output shaft 114 rotates circumferentially around the first rotation axis 21J. The output shaft 114 can rotate in both forward and reverse directions in response to the power supply to the housing 112. That is, the output shaft 114 can output torque in both forward and reverse directions with respect to the circumferential direction around the first rotation axis 21J. Both ends of the output shaft 114 protrude outside the housing 112 in the direction along the first rotation axis 21J.

[0033] The reduction gear 120 is located on the second direction A2 side relative to the electric motor 110. The reduction gear 120 comprises a case 122, a reduction mechanism 123, and an output member 124. The case 122 is cylindrical. The central axis of the case 122 substantially coincides with the first rotation axis 21J. The end face of the case 122 on the first direction A1 side is fixed to the end face of the housing 112 of the electric motor 110 on the second direction A2 side. For example, flange walls protrude from both the outer circumferential surface of the housing 112 and the outer circumferential surface of the case 122. The housing 112 and the case 122 are fixed by fixing these flange walls with bolts. In the direction along the first rotation axis 21J, the case 122 is located in substantially the same position as the second connecting wall 35 of the boom 30. The case 122 is located inside the through hole 35A of the second connecting wall 35. Case 122 penetrates the second connecting wall 35. The outer diameter of case 122 is approximately the same as the diameter of the through-hole 35A in the second connecting wall 35. Case 122 is fixed to the second connecting wall 35. For example, the gearbox 120 has a flange wall that protrudes from the outer circumferential surface of case 122. By bolting this flange wall to the second connecting wall 35, case 122 is fixed to the second connecting wall 35.

[0034] The reduction gear 123 is located inside the case 122. The reduction gear 123 is connected to the output shaft 114 of the electric motor 110. The reduction gear 123 amplifies the torque output by the output shaft 114 of the electric motor 110 at a predetermined ratio and outputs it to the output member 124. The reduction gear 123 can be, for example, an eccentric oscillating gear type or a planetary gear type. The reduction gear 123 can be of any type as long as it is configured to amplify and output the torque from the electric motor 110.

[0035] The output member 124 protrudes from inside the case 122 toward the second direction A2 relative to the case 122. The output member 124 is cylindrical. The central axis of the output member 124 constitutes the first rotation axis 21J. Although not shown in the figures, the output member 124 is rotatably supported inside the case 122, for example by a rolling bearing. The output member 124 is rotatable relative to the case 122 and, consequently, to the housing 112 of the electric motor 110. The output member 124 rotates in the circumferential direction about the first rotation axis 21J. That is, the output member 124 rotates relative to the base in the circumferential direction about the first rotation axis 21J. The output member 124 is fixed to the second connecting wall 66 of the support 60. This fixing structure will be described later. The output member 124 constitutes the output section of the first drive unit 101.

[0036] As described above, the housing 112 of the electric motor 110 and the case 122 of the reduction gear 120 are fixed to the second connecting wall 35 of the boom 30. On the other hand, the output member 124 of the reduction gear 120 is fixed to the second connecting wall 66 of the support 60. The output member 124 of the reduction gear 120 rotates relative to the case 122 of the reduction gear 120 in the circumferential direction about the first rotation axis 21J. In other words, the first drive unit 101 outputs torque that causes the second connecting wall 35 and the second connecting wall 66 to rotate relative to each other in the circumferential direction about the first rotation axis 21J.

[0037] As described above, pin 71 connects the first connecting wall 64 of the support 60 to the first connecting wall 33 of the boom 30. Also, the first drive unit 101 connects the second connecting wall 66 of the support 60 to the second connecting wall 35 of the boom 30. In other words, the boom 30 is connected to the first connecting wall 64 of the support 60 via pin 71, and is also connected to the second connecting wall 66 of the support 60 via the first drive unit 101.

[0038] The fixing structure between the output member 124 of the reduction gear 120 and the second connecting wall 66 of the support 60 will now be described. As a premise for this fixing structure, the second connecting wall 66 is provided with a through hole 66A. The through hole 66A penetrates the second connecting wall 66 in a direction along the first rotation axis 21J. The central axis of the through hole 66A is approximately coincident with the first rotation axis 21J. Multiple spline teeth 66S protrude from the inner surface of the through hole 66A. The multiple spline teeth 66S are arranged at equal intervals in the circumferential direction around the first rotation axis 21J. The spline teeth 66S extend along the first rotation axis 21J. In the direction along the first rotation axis 21J, the spline teeth 66S continue across both ends of the second connecting wall 66. On the other hand, on the outer circumferential surface of the portion of the output member 124 of the reduction gear 120 that is exposed from the case 122, there are multiple spline grooves 124S. The multiple spline grooves 124S are arranged at equal intervals in the circumferential direction around the first rotation axis 21J. The spline grooves 124S extend along the first rotation axis 21J. In other words, the spline grooves 124S are formed along the first rotation axis 21J. The spline grooves 124S extend to the end of the output member 124 on the second direction A2 side. Note that the groove depth of the spline grooves 124S in Figure 2 is for convenience only. The same applies to the spline grooves in other drawings.

[0039] The output member 124 of the speed reducer 120 is fixed to the second connecting wall 66 by spline coupling. That is, the output member 124 of the speed reducer 120 is located inside the through hole 66A of the second connecting wall 66. The spline groove 124S of the output member 124 is fitted into the spline teeth 66S of the second connecting wall 66. As a result, the output member 124 is fixed to the second connecting wall 66. That is, the output member 124 is fixed to the second connecting wall 66 via the spline groove 124S. Note that the opening of the through hole 66A of the second connecting wall 66 on the side opposite to the speed reducer 120 may be covered with a cover.

[0040] The first brake device 130 is located on the opposite side of the electric motor 110 from the reduction gear 120. That is, in the direction along the first rotation axis 21J, the first brake device 130 is located between the electric motor 110 and the first connecting wall 33 of the boom 30. The first brake device 130 is fixed to the housing 112 of the electric motor 110. For example, flange walls protrude from the outer circumferential surfaces of both the first brake device 130 and the housing 112 of the electric motor 110. The first brake device 130 and the housing 112 of the electric motor 110 are fixed by fixing these flange walls with bolts. The first brake device 130 is connected to the output shaft 114 of the electric motor 110. The first brake device 130 is electrically connected to a battery (not shown). When the first brake device 130 is receiving power from the battery, it does not apply braking force to the output shaft 114 of the electric motor 110. Therefore, in this case, the output shaft 114 of the electric motor 110 is freely rotatable. On the other hand, when the power supply from the battery is cut off, the first brake device 130 applies a braking force to the output shaft 114. At the same time, the first brake device 130 makes the output shaft 114 of the electric motor 110 unable to rotate.

[0041] An example of the procedure for connecting each component in the first joint mechanism 21 will be described. First, the worker positions the support 60 and the boom 30 in an aligned state. Specifically, the worker positions the support 60 and the boom 30 so that the through hole 64A of the first connecting wall 64 of the support 60 and the through hole 33A of the first connecting wall 33 of the boom 30 are coaxial. After this, the worker attaches the first drive unit 101 to each wall. Specifically, the worker first passes the case 122 of the reducer 120 through the through hole 35A of the second connecting wall 35 of the boom 30. Then, the worker inserts the output member 124 of the reducer 120 into the through hole 66A of the second connecting wall 66 of the support 60. In this way, the worker spline-connects the output member 124 of the reducer 120 and the second connecting wall 66. Next, the worker fixes the case 122 of the reduction gear 120 to the second connecting wall 35. Furthermore, the worker fixes the housing 112 of the electric motor 110 to the case 122 of the reduction gear 120. After this, the worker fixes the first brake device 130 to the housing 112 of the electric motor 110. After this, the worker passes the pin 71 through the through hole 64A of the first connecting wall 64 in the support 60 and the through hole 33A of the first connecting wall 33 in the boom 30. Then, the worker fixes the cover 72, which is integrated with the pin 71, to the first connecting wall 64. In this way, each component is connected. Note that the procedure for connecting each component described here is just one example, and the procedure for connecting each component can be changed as appropriate.

[0042] The first joint mechanism 21 is configured as described above. In the first joint mechanism 21, when the output shaft 114 of the electric motor 110 in the first drive unit 101 rotates, the output member 124 of the reduction gear 120 outputs torque in accordance with that rotation. Along with this torque output, the second connecting wall 35 of the boom 30 rotates relative to the second connecting wall 66 of the support body 60 around the first rotation axis 21J. At the same time, the boom 30 rotates relative to the support body 60. At this time, the pin 71 becomes the axis of relative rotation between the first connecting wall 64 of the support body 60 and the first connecting wall 33 of the boom 30.

[0043] <Second joint mechanism> The second joint mechanism 22, which connects the boom 30 and the arm 40, will now be described. As shown in Figure 3, the excavator 10 is equipped with a second drive unit 102, a second brake unit 132, a first pin 81, a second pin 82, a first cover 83, and a second cover 84 in the second connecting portion, which is the connection part between the boom 30 and the arm 40. The second joint mechanism 22 is composed of these members and the boom 30 and arm 40 that are to be connected. The boom 30 is the first member of the second joint mechanism 22. The arm 40 is the second member of the second joint mechanism 22. The first pin 81 is the first connecting member of the second joint mechanism 22, and the second pin 82 is the second connecting member of the second joint mechanism 22. Note that in Figure 3, the cross-sectional structure of some members of the second joint mechanism 22 is omitted and shown as a plan view.

[0044] As shown in Figure 3, at the second joint section, the boom body 31 and the arm body 41 are located on opposite sides of the second rotation axis 22J. The second end face 31B of the boom body 31 and the first end face 41A of the arm body 41 face each other across the second rotation axis 22J. The second end face 31B of the boom body 31 is the end face of the elongated boom body 31 opposite to the first end face 31A. The first end face 41A of the arm body 41 is the end face of the elongated arm body 41 closer to the boom 30. Hereinafter, in the description of the second joint mechanism 22, one of the two directions along the second rotation axis 22J will be referred to as the first direction B1, and the other as the second direction B2.

[0045] The end of the boom body 31 closest to the arm body 41 protrudes toward the first direction B1 relative to the main portion 31M of the boom body 31. As a result, with respect to the direction along the second rotation axis 22J, the dimension of the second end face 31B of the boom body 31 is larger than the dimension of the main portion 31M of the boom body 31. Conversely to the boom body 31, the end of the arm body 41 closest to the boom body 31 protrudes toward the second direction B2 relative to the main portion 41M of the arm body 41. As a result, with respect to the direction along the second rotation axis 22J, the dimension of the first end face 41A of the arm body 41 is larger than the dimension of the main portion 41M of the arm body 41. With respect to the direction along the second rotation axis 22J, the dimension of the first end face 41A of the arm body 41 is approximately the same as the dimension of the second end face 31B of the boom body 31. Furthermore, with respect to the direction along the second rotation axis 22J, the dimensions of the main portion 41M of the arm body 41 are approximately the same as the dimensions of the main portion 31M of the boom body 31.

[0046] Under the dimensional relationship described above, the boom body 31 and the arm body 41 are arranged as follows: In the direction along the second rotation axis 22J, the main portion 31M of the boom body 31 and the main portion 41M of the arm body 41 are located at approximately the same position. As a result of the end of the boom body 31 protruding toward the first direction B1, the end of the second end face 31B of the boom body 31 toward the first direction B1 is located toward the first direction B1 relative to the end of the first end face 41A of the arm body 41 toward the first direction B1. On the other hand, as a result of the end of the arm body 41 protruding toward the second direction B2, the end of the first end face 41A of the arm body 41 toward the second direction B2 is located toward the second direction B2 relative to the end of the second end face 31B of the boom body 31 toward the second direction B2.

[0047] The boom 30 includes a first connecting wall 37 and a second connecting wall 39 as a configuration for connecting the boom body 31 to the arm body 41. The first connecting wall 37 protrudes from the second end face 31B of the boom body 31 toward the arm body 41. More specifically, the first connecting wall 37 protrudes from the end of the second end face 31B toward the first direction B1. The first connecting wall 37 is plate-shaped. In the direction along the second rotation axis 22J, the entire length of the first connecting wall 37, from the connecting end connected to the second end face 31B to the protruding end opposite the connecting end, is located approximately at the same position as the end of the second end face 31B toward the first direction B1. The protruding end of the first connecting wall 37 is located toward the arm body 41 than the second rotation axis 22J. The second rotation axis 22J passes through the main surface of the first connecting wall 37. The main surface of the first connecting wall 37 is approximately perpendicular to the second rotation axis 22J. The first connecting wall 37 is provided with a through hole 37A. The through hole 37A penetrates the first connecting wall 37 in a direction along the second rotation axis 22J. The central axis of the through hole 37A is approximately coincident with the second rotation axis 22J.

[0048] The second connecting wall 39 protrudes from the second end face 31B of the boom body 31 toward the arm body 41. More specifically, the second connecting wall 39 protrudes from the end of the second end face 31B on the second direction B2 side. The second connecting wall 39 has the same shape and dimensions as the first connecting wall 37. That is, the second connecting wall 39 is plate-shaped. In the direction along the second rotation axis 22J, the entire length of the second connecting wall 39, from the connecting end connected to the second end face 31B to the protruding end opposite the connecting end, is located at approximately the same position as the end of the second end face 31B on the second direction B2 side. Similar to the first connecting wall 37, the second connecting wall 39 is positioned where the second rotation axis 22J passes through. The main surface of the second connecting wall 39 is approximately perpendicular to the second rotation axis 22J. The second connecting wall 39 is aligned with the first connecting wall 37 in a direction along the second rotation axis 22J. The second connecting wall 39 is provided with a through hole 39A. The through hole 39A penetrates the second connecting wall 39 in a direction along the second rotation axis 22J. The central axis of the through hole 39A is approximately the same as the second rotation axis 22J. The diameter of the through hole 39A is approximately the same as the diameter of the through hole 37A of the first connecting wall 37.

[0049] The arm 40 includes a first connecting wall 43 and a second connecting wall 44 as a configuration for connecting the arm body 41 to the boom body 31. The first connecting wall 43 protrudes from the first end face 41A of the arm body 41 toward the boom body 31. More specifically, the first connecting wall 43 protrudes from the end of the first end face 41A toward the first direction B1. The first connecting wall 43 is plate-shaped. In the direction along the second rotation axis 22J, the entire length of the first connecting wall 43, from the connecting end connected to the first end face 41A to the protruding end opposite the connecting end, is located at approximately the same position as the end of the first end face 41A toward the first direction B1. The protruding end of the first connecting wall 43 is located toward the boom body 31 than the second rotation axis 22J. The second rotation axis 22J passes through the main surface of the first connecting wall 43. The main surface of the first connecting wall 43 is approximately perpendicular to the second rotation axis 22J. In the direction along the second rotation axis 22J, the first connecting wall 43 is located between the first connecting wall 37 and the second connecting wall 39 on the boom 30. The first connecting wall 43 is located immediately next to the first connecting wall 37. There is a small gap between the first connecting wall 43 and the first connecting wall 37. The first connecting wall 43 is provided with a through hole 43A. The through hole 43A penetrates the first connecting wall 43 in the direction along the second rotation axis 22J. The central axis of the through hole 43A is approximately the same as the diameter of the through hole 37A in the first connecting wall 37 on the boom 30.

[0050] The second connecting wall 44 protrudes from the first end face 41A of the arm body 41 toward the boom body 31. More specifically, the second connecting wall 44 protrudes from the end of the first end face 41A on the second direction B2 side. The second connecting wall 44 has the same shape and dimensions as the first connecting wall 43. That is, the second connecting wall 44 is plate-shaped. In the direction along the second rotation axis 22J, the entire length of the second connecting wall 44, from the connecting end connected to the first end face 41A to the protruding end opposite the connecting end, is located at approximately the same position as the end of the first end face 41A on the second direction B2 side. Similar to the first connecting wall 43, the second connecting wall 44 is positioned where the second rotation axis 22J passes through. The main surface of the second connecting wall 44 is approximately perpendicular to the second rotation axis 22J. In the direction along the second rotation axis 22J, the second connecting wall 44 is located on the opposite side of the first connecting wall 43 from the second connecting wall 39 of the boom 30. The second connecting wall 44 is located immediately next to the second connecting wall 39. There is a small gap between the second connecting wall 44 and the second connecting wall 39. The second connecting wall 44 is provided with a through hole 44A. The through hole 44A penetrates the second connecting wall 44 in the direction along the second rotation axis 22J. The central axis of the through hole 44A is approximately the same as the second rotation axis 22J. The diameter of the through hole 44A is approximately the same as the diameter of the through hole 43A of the first connecting wall 43.

[0051] The first pin 81 is positioned to straddle the first connecting wall 37 of the boom 30 and the first connecting wall 43 of the arm 40. Specifically, the first pin 81 is located inside the through hole 37A of the first connecting wall 37 and the through hole 43A of the first connecting wall 43. The first pin 81 penetrates both the through hole 37A of the first connecting wall 37 and the through hole 43A of the first connecting wall 43. The first pin 81 is cylindrical. The central axis of the first pin 81 is approximately the same as the second rotation axis 22J. The diameter of the first pin 81 is approximately the same as the diameter of the through hole 43A of the first connecting wall 43. As a result of the first pin 81 penetrating both the first connecting wall 37 and the first connecting wall 43, the first pin 81 connects these two walls. The outer surface of the first pin 81 is in slidable contact with the inner surface of the through hole 37A of the first connecting wall 37. Similarly, the outer surface of the first pin 81 is in slidable contact with the inner surface of the through hole 43A of the first connecting wall 43. As a result, the first pin 81 supports the first connecting wall 37 and the first connecting wall 43 so that they can rotate relative to each other. At the same time, the first pin 81 connects the first connecting wall 37 and the first connecting wall 43 so that they can rotate relative to each other in the circumferential direction about the second rotation axis 22J. In addition, similar to the first joint mechanism 21, a bearing may be placed between the inner surface of the through hole 37A of the first connecting wall 37 and the first pin 81. Similarly, a bearing may be placed between the inner surface of the through hole 43A of the first connecting wall 43 and the first pin 81.

[0052] The first cover 83 is located on the opposite side of the first connecting wall 43 from the first connecting wall 37. The first cover 83 is, for example, disc-shaped. The main surface of the first cover 83 faces the main surface of the first connecting wall 37. The diameter of the circle of the first cover 83 is larger than the diameter of the through hole 37A in the first connecting wall 37. The first cover 83 covers the through hole 37A. In this embodiment, the first cover 83 is fixed to the first pin 81. For example, the first cover 83 is integrally molded with the first pin 81. The first cover 83 is fixed to the first connecting wall 37 by bolts B.

[0053] The second pin 82 is positioned to straddle the second connecting wall 39 of the boom 30 and the second connecting wall 44 of the arm 40. Specifically, the second pin 82 is located inside the through-hole 39A of the second connecting wall 39 and the through-hole 44A of the second connecting wall 44. The second pin 82 penetrates both the through-hole 39A of the second connecting wall 39 and the through-hole 44A of the second connecting wall 44. The second pin 82 is cylindrical. The central axis of the second pin 82 is approximately the same as the second rotation axis 22J. The diameter of the second pin 82 is approximately the same as the diameter of the through-hole 39A of the second connecting wall 39. As a result of the second pin 82 penetrating both the second connecting wall 39 and the second connecting wall 44, the second pin 82 connects these two walls. The outer surface of the second pin 82 is in slidable contact with the inner surface of the through-hole 39A of the second connecting wall 39. Similarly, the outer surface of the second pin 82 is in slidable contact with the inner surface of the through-hole 44A of the second connecting wall 44. As a result, the second pin 82 supports the second connecting wall 39 and the second connecting wall 44 so that they can rotate relative to each other. At the same time, the second pin 82 connects the second connecting wall 39 and the second connecting wall 44 so that they can rotate relative to each other in the circumferential direction about the second rotation axis 22J. As explained in relation to the first pin 81, a bearing may be placed between the inner surface of the through-hole 39A of the second connecting wall 39 and the second pin 82. Similarly, a bearing may be placed between the inner surface of the through-hole 44A of the second connecting wall 44 and the second pin 82.

[0054] The second cover 84 is located on the opposite side of the second connecting wall 39 from the second connecting wall 44. The second cover 84 is, for example, disc-shaped. The main surface of the second cover 84 faces the main surface of the second connecting wall 44. The diameter of the circle of the second cover 84 is larger than the diameter of the through hole 44A in the second connecting wall 44. The second cover 84 covers the through hole 44A. In this embodiment, the second cover 84 is fixed to the second pin 82. For example, the second cover 84 is integrally molded with the second pin 82. The second cover 84 is fixed to the second connecting wall 44 by bolts B.

[0055] The second drive unit 102 is located between the first connecting wall 43 of the arm 40 and the second connecting wall 39 of the boom 30 in a direction along the second rotation axis 22J. The configuration of the second drive unit 102 is substantially the same as that of the first drive unit 101. Therefore, only a brief explanation of the second drive unit 102 is given here. The second drive unit 102 comprises an electric motor 110 and a reduction gear 120. The electric motor 110 comprises a housing 112 and an output shaft 114 that rotates relative to the housing 112. The reduction gear 120 comprises a case 122 fixed to the housing 112 of the electric motor 110, a reduction mechanism 123 that amplifies the torque of the electric motor 110, and an output member 124 that outputs the torque from the reduction mechanism 123 to the outside. The housing 112 of the electric motor 110 constitutes the base portion of the second drive unit 102. The output member 124 of the reduction gear 120 constitutes the output section of the second drive unit 102. In the second drive unit 102, the second rotation axis 22J replaces the first rotation axis 21J in the first drive unit 101, becoming the central axis of the torque output by the output member 124. In other words, the central axis of the output member 124 of the reduction gear 120 in the second drive unit 102 constitutes the second rotation axis 22J. The output member 124 of the reduction gear 120 rotates relative to the case 122 of the reduction gear 120 and, consequently, the housing 112 of the electric motor 110, in the circumferential direction around the second rotation axis 22J. Further explanation of the configuration of the second drive unit 102 is omitted. Note that, with respect to the second drive unit 102 shown in Figure 3, parts that function identically or substantially identically to those of the first drive unit 101 shown in Figure 2 are denoted by the same reference numerals as in Figure 2.

[0056] The second drive unit 102 is fixed to the first connecting wall 43 of the arm 40 and the second connecting wall 39 of the boom 30. Specifically, the housing 112 of the electric motor 110 is fixed to the first connecting wall 43 via the second brake device 132. This will be described later. The output member 124 of the reduction gear 120 is fixed to the second connecting wall 39. For example, the reduction gear 120 has a flange wall 124F that protrudes from the output member 124. The output member 124 is fixed to the second connecting wall 39 by fixing this flange wall 124F to the second connecting wall 44 with bolts B. Unlike the first drive unit 101, the output member 124 of the second drive unit 102 does not have a spline groove 124S.

[0057] As described above, the housing 112 of the electric motor 110 is fixed to the first connecting wall 43 of the arm 40. On the other hand, the output member 124 of the reduction gear 120 is fixed to the second connecting wall 39 of the boom 30. The output member 124 of the reduction gear 120 rotates relative to the case 122 of the reduction gear 120 and, consequently, the housing 112 of the electric motor 110, in the circumferential direction about the second rotation axis 22J. In other words, the second drive unit 102 outputs torque that causes the first connecting wall 43 and the second connecting wall 39 to rotate relative to each other in the circumferential direction about the second rotation axis 22J.

[0058] As described above, the first pin 81 connects the first connecting wall 37 of the boom 30 to the first connecting wall 43 of the arm 40. The second drive unit 102 connects the second connecting wall 39 of the boom 30 to the first connecting wall 43 of the arm 40. In other words, the first connecting wall 43 of the arm 40 is connected to the first connecting wall 37 of the boom 30 via the first pin 81, and is also connected to the second connecting wall 39 of the boom 30 via the second drive unit 102.

[0059] The second brake device 132 is located on the first direction B1 side relative to the second drive device 102. The second brake device 132 is located between the first connecting wall 43 of the arm 40 and the electric motor 110 of the second drive device 102. The second brake device 132 is fixed to the housing 112 of the electric motor 110. The function of the second brake device 132 is the same as that of the first brake device 130. The second brake device 132 is also fixed to the first connecting wall 43 of the arm 40. For example, the second brake device 132 has a flange wall 132F. This flange wall 132F is fixed to the first connecting wall 43 by bolts B, thereby fixing the second brake device 132 to the second connecting wall 44. At the same time, the electric motor 110 of the second drive device 102, which is fixed to the second brake device 132, is also fixed to the second connecting wall 44.

[0060] An example of the procedure for connecting each component in the second joint mechanism 22 will be described. First, the worker positions the boom 30 and the arm 40 in an aligned state. Specifically, the worker positions the boom 30 and the arm 40 so that the through hole 37A of the first connecting wall 37 of the boom 30 and the through hole 43A of the first connecting wall 43 of the arm 40 are coaxial. After this, the worker fixes the second drive unit 102 to the first connecting wall 43 of the arm 40 and the second connecting wall 39 of the boom 30. Specifically, the worker first positions the reducer 120 of the second drive unit 102 between the first connecting wall 43 and the second connecting wall 39. Then, the worker fixes the output member 124 of the reducer 120 to the second connecting wall 39. After this, the worker fixes the housing 112 of the electric motor 110 to the case 122 of the reducer 120. Next, the worker fixes the second brake device 132 to the housing 112 of the electric motor 110. Then, the worker fixes the second brake device 132 to the first connecting wall 43 of the arm 40. After that, the worker passes the first pin 81 through the through hole 37A of the first connecting wall 37 on the boom 30 and the through hole 43A of the first connecting wall 43 on the arm 40. Then, the worker fixes the first cover 83, which is integrated with the first pin 81, to the first connecting wall 37. After that, the worker passes the second pin 82 through the through hole 44A of the second connecting wall 44 on the arm 40 and the through hole 39A of the second connecting wall 39 on the boom 30. Then, the worker fixes the second cover 84, which is integrated with the second pin 82, to the second connecting wall 44. In this way, each component is connected. The procedure for connecting the components described here is just one example, and the procedure for connecting the components can be modified as needed.

[0061] The second joint mechanism 22 is configured as described above. In the second joint mechanism 22, when the output shaft 114 of the electric motor 110 in the second drive unit 102 rotates, the output member 124 of the reduction gear 120 outputs torque in accordance with that rotation. Along with this torque output, the first connecting wall 43 of the arm 40 rotates relative to the second connecting wall 39 of the boom 30 around the second rotation axis 22J. At the same time, the boom 30 and the arm 40 rotate relative to each other. At this time, the first pin 81 supports the relative rotation between the first connecting wall 37 of the boom 30 and the first connecting wall 43 of the arm 40. Similarly, the second pin 82 supports the relative rotation between the second connecting wall 39 of the boom 30 and the second connecting wall 44 of the arm 40.

[0062] <Third joint mechanism> The third joint mechanism 23, which connects the arm 40 and the bucket 50, will now be described. As shown in Figure 4, the excavator 10 is equipped with a third drive unit 103, a third brake unit 133, a pin 91, and a cover 92 at the third connecting portion, which is the connection part between the arm 40 and the bucket 50. The third joint mechanism 23 is composed of these members and the arm 40 and bucket 50 that are to be connected. The bucket 50 is the first member of the third joint mechanism 23. The arm 40 is the second member of the third joint mechanism 23. The third brake unit 133 is a specific member of the third joint mechanism 23. The pin 91 is a connecting member of the third joint mechanism 23. Note that in Figure 4, the cross-sectional structure of some members of the third joint mechanism 23 is omitted and shown as a plan view.

[0063] As shown in Figure 4, at the third joint section, the bucket body 51 and the arm body 41 are located on opposite sides of the third rotation axis 23J. The end face 51A of the bucket body 51 and the second end face 41B of the arm body 41 face each other across the third rotation axis 23J. The end face 51A of the bucket body 51 is one of the outer surfaces of the box-shaped bucket body 51. The second end face 41B of the arm body 41 is the end face of the elongated arm body 41 opposite to the first end face 41A. With respect to the direction along the third rotation axis 23J, the dimension of the end face 51A of the bucket body 51 is larger than the dimension of the second end face 41B of the arm body 41. Hereinafter, in the description of the third joint mechanism 23, one of the two directions along the third rotation axis 23J will be referred to as the first direction C1, and the other as the second direction C2. The end face 51A of the bucket body 51 on the first direction C1 side is located on the first direction side relative to the end face 41B of the arm body 41 on the first direction C1 side. The end face 51A of the bucket body 51 on the second direction C2 side is located on the second direction C2 side relative to the end face 41B of the arm body 41 on the second direction C2 side.

[0064] The bucket 50 includes a first connecting wall 53 and a second connecting wall 55 as a configuration for connecting the bucket body 51 to the arm body 41. The first connecting wall 53 protrudes from the end face 51A of the bucket body 51 toward the arm body 41. In detail, the first connecting wall 53 protrudes from the end face 51A toward the first direction C1. The first connecting wall 53 is plate-shaped. In the direction along the third rotation axis 23J, the entire length of the first connecting wall 53, from the connecting end connected to the end face 51A to the protruding end opposite the connecting end, is located at approximately the same position as the end face 51A toward the first direction C1. The protruding end of the first connecting wall 53 is located toward the arm body 41 than the third rotation axis 23J. The third rotation axis 23J passes through the main surface of the first connecting wall 53. The main surface of the first connecting wall 53 is approximately perpendicular to the third rotation axis 23J.

[0065] The second connecting wall 55 protrudes from the end face 51A of the bucket body 51 toward the arm body 41. More specifically, the second connecting wall 55 protrudes from the end face 51A on the second direction C2 side. The second connecting wall 55 has the same shape and dimensions as the first connecting wall 53. That is, the second connecting wall 55 is plate-shaped. In the direction along the third rotation axis 23J, the entire length of the second connecting wall 55, from the connecting end connected to the end face 51A to the protruding end opposite the connecting end, is located at approximately the same position as the end face 51A on the second direction C2 side. The second connecting wall 55 is aligned with the first connecting wall 53 in the direction along the third rotation axis 23J. Similar to the first connecting wall 53, the second connecting wall 55 is positioned where the third rotation axis 23J passes. The main surface of the second connecting wall 55 is approximately perpendicular to the third rotation axis 23J. The second connecting wall 55 is provided with a through hole 55A. The through hole 55A penetrates the second connecting wall 55 in a direction along the third rotation axis 23J. The central axis of the through hole 55A is approximately coincident with the third rotation axis 23J.

[0066] The arm 40 is equipped with a specific connecting wall 47 for connecting the arm body 41 to the bucket body 51. The specific connecting wall 47 protrudes from the second end face 41B of the arm body 41 toward the bucket body 51. More specifically, the specific connecting wall 47 protrudes from approximately the center of the second end face 41B in the direction along the third rotation axis 23J. The specific connecting wall 47 is plate-shaped. In the direction along the third rotation axis 23J, the entire specific connecting wall 47, from the connecting end connected to the second end face 41B to the protruding end opposite the connecting end, is located approximately at the same position as the center of the second end face 41B. The protruding end of the specific connecting wall 47 is located on the bucket body 51 side of the third rotation axis 23J. The third rotation axis 23J passes through the main surface of the specific connecting wall 47. The main surface of the specific connecting wall 47 is approximately perpendicular to the third rotation axis 23J. In the direction along the third rotation axis 23J, the specific connecting wall 47 is located between the first connecting wall 53 and the second connecting wall 55. More specifically, in the direction along the third rotation axis 23J, the specific connecting wall 47 is located approximately in the center between the first connecting wall 53 and the second connecting wall 55. The specific connecting wall 47 is provided with a through hole 47A. The through hole 47A penetrates the specific connecting wall 47 in the direction along the third rotation axis 23J. The central axis of the through hole 47A is approximately coincident with the third rotation axis 23J.

[0067] The third drive unit 103 is located between the first connecting wall 53 and the second connecting wall 55 of the bucket 50 in a direction along the third rotation axis 23J. The configuration of the third drive unit 103 is substantially the same as that of the first drive unit 101. Therefore, only a brief explanation of the third drive unit 103 is provided here. The third drive unit 103 comprises an electric motor 110 and a reduction gear 120. The electric motor 110 comprises a housing 112 and an output shaft 114 that rotates relative to the housing 112. The reduction gear 120 comprises a case 122 fixed to the housing 112 of the electric motor 110, a reduction mechanism 123 that amplifies the torque of the electric motor 110, and an output member 124 that outputs the torque from the reduction mechanism 123 to the outside. The housing 112 of the electric motor 110 constitutes the base portion of the third drive unit 103. The output member 124 constitutes the output portion of the third drive unit 103. In the third drive unit 103, the third rotation axis 23J replaces the first rotation axis 21J in the first drive unit 101, becoming the central axis of the torque output by the output member 124. In other words, the central axis of the output member 124 of the reduction gear 120 in the third drive unit 103 constitutes the third rotation axis 23J. The output member 124 of the reduction gear 120 then rotates relative to the case 122 of the reduction gear 120 and, consequently, the housing 112 of the electric motor 110, in the circumferential direction around the third rotation axis 23J. Further explanation of the configuration of the third drive unit 103 is omitted. Note that, with respect to the third drive unit 103 shown in Figure 5, parts that function identically or substantially identically to those of the first drive unit 101 shown in Figure 2 are denoted by the same reference numerals as in Figure 2.

[0068] The third drive unit 103 is fixed to a specific connecting wall 47 of the arm 40. Specifically, the housing 112 of the electric motor 110 is located inside the through hole 47A of the specific connecting wall 47. The housing 112 passes through the through hole 47A. The diameter of the housing 112 is approximately the same as the diameter of the through hole 47A. The central axis of the housing 112 is approximately the same as the third rotation axis 23J. The housing 112 is fixed to the specific connecting wall 47. For example, the housing 112 is fixed to the specific connecting wall 47 by bolts using an L-shaped bracket or the like. The housing 112 may have a flange wall that protrudes from the outer circumferential surface of the housing 112. This flange wall and the specific connecting wall 47 may then be fixed by bolts. As a result of the housing 112 of the electric motor 110 being fixed to the specific connecting wall 47, the case 122 of the reduction gear 120 is also fixed to the specific connecting wall 47.

[0069] The third drive unit 103 is fixed to the second connecting wall 55 of the bucket 50. Specifically, the output member 124 of the reduction gear 120 is fixed to the second connecting wall 55 of the bucket 50 using spline coupling. That is, the output member 124, like the first drive unit 101, has a plurality of spline grooves 124S. The plurality of spline grooves 124S are arranged at equal intervals in the circumferential direction around the third rotation axis 23J. The spline grooves 124S extend along the third rotation axis 23J. The spline grooves 124S reach the end of the output member 124 on the first direction C1 side. The second connecting wall 55 of the bucket 50 is provided with a through hole 55A to receive these spline grooves 124S. The central axis of the through hole 55A is approximately coincident with the third rotation axis 23J. A plurality of spline teeth 55S protrude from the inner surface of the through hole 55A. Multiple spline teeth 55S are arranged at equal intervals in the circumferential direction around the third rotation axis 23J. The spline teeth 55S extend along the third rotation axis 23J. In the direction along the third rotation axis 23J, the spline teeth 55S continue across both ends of the second connecting wall 55. The output member 124 of the reduction gear 120 is located inside the through hole 55A. The spline teeth 55S of the through hole 55A are fitted into the spline grooves 124S of the output member 124. As a result, the output member 124 is fixed to the second connecting wall 55. That is, the output member 124 is fixed to the second connecting wall 55 via the spline grooves 124S. The opening of the through hole 55A in the second connecting wall 55 on the side opposite to the reduction gear 120 may be covered by a cover. In Figure 4, the gap between the case 122 of the reduction gear 120 and the second connecting wall 55 is exaggerated and shown as larger.

[0070] As described above, the housing 112 of the electric motor 110 and the case 122 of the reduction gear 120 are fixed to the specific connecting wall 47 of the arm 40. On the other hand, the output member 124 of the reduction gear 120 is fixed to the second connecting wall 55 of the bucket 50. The output member 124 of the reduction gear 120 rotates relative to the case 122 of the reduction gear 120 in the circumferential direction about the third rotation axis 23J. In other words, the third drive unit 103 outputs torque that causes the specific connecting wall 47 and the second connecting wall 55 to rotate relative to each other in the circumferential direction about the third rotation axis 23J. At the same time, the third drive unit 103 connects the specific connecting wall 47 and the second connecting wall 55.

[0071] The third brake device 133 is located on the first direction C1 side relative to the third drive device 103. The third brake device 133 is located between the first connecting wall 53 of the bucket 50 and the electric motor 110 of the third drive device 103. It can also be said that the third brake device 133 is located between the first connecting wall 53 and the specific connecting wall 47 of the arm 40. The third brake device 133 is fixed to the housing 112 of the electric motor 110. The function of the third brake device 133 is the same as that of the first brake device 130. The third brake device 133 is fixed to the first connecting wall 53 of the bucket 50. For example, the third brake device 133 may have a flange wall 133F similar to that of the second brake device 132. The third brake device 133 is fixed to the first connecting wall 53 by bolts B on this flange wall 133F.

[0072] As described above, the third brake device 133 is fixed to the first connecting wall 53 of the bucket 50 and to the housing 112 of the electric motor 110. The housing 112 is fixed to the specific connecting wall 47. In other words, the third brake device 133 is interposed between the first connecting wall 53 and the specific connecting wall 47.

[0073] The pin 91 is positioned to straddle the first connecting wall 53 of the bucket 50 and the third brake device 133. The pin 91 is cylindrical. The central axis of the pin 91 is approximately coincident with the third rotation axis 23J. The diameter of the pin 91 is approximately coincident with the diameter of the through hole 53A in the first connecting wall 53. The pin 91 passes through the through hole 53A in the first connecting wall 53 and is inserted into the interior of the third brake device 133. That is, the pin 91 connects the first connecting wall 53 and the third brake device 133. The outer surface of the pin 91 and the inner surface of the through hole 53A in the first connecting wall 53 are in slidable contact. The portion of the pin 91 located inside the third brake device 133 is rotatably supported, for example, by a rolling bearing 133G. As a result, the pin 91 supports the first connecting wall 53 and the third brake device 133 so that they can rotate relative to each other. In addition, the pin 91 connects the first connecting wall 53 and the third brake device 133 so that they can rotate relative to each other in the circumferential direction about the third rotation axis 23J. A bearing may be placed between the inner surface of the through hole 53A in the first connecting wall 53 and the pin 91.

[0074] As described above, pin 91 connects the first connecting wall 53 of the bucket 50 to the third brake device 133. The third brake device 133 is connected to a specific connecting wall 47 of the arm 40 via the electric motor 110 of the third drive device 103. In other words, pin 91 connects the first connecting wall 53 and the specific connecting wall 47. From a different perspective, the specific connecting wall 47 is connected to the first connecting wall 53 of the bucket 50 via the electric motor 110, the third brake device 133, and pin 91. On the other hand, the specific connecting wall 47 is connected to the second connecting wall 55 of the bucket 50 via the third drive device 103. In other words, the specific connecting wall 47 and thus the arm 40 are connected to both the first connecting wall 53 and the second connecting wall 55 of the bucket 50.

[0075] The cover 92 is located on the opposite side of the first connecting wall 53 from the specific connecting wall 47. The cover 92 is, for example, disc-shaped. The main surface of the cover 92 faces the main surface of the first connecting wall 53. The diameter of the circle of the cover 92 is larger than the diameter of the through hole 53A in the first connecting wall 53. The cover 92 covers the through hole 53A. In this embodiment, the cover 92 is fixed to a pin 91. For example, the cover 92 is integrally molded with the pin 91. The cover 92 is fixed to the first connecting wall 53 by bolts B.

[0076] An example of the procedure for connecting each component in the third joint mechanism 23 will be described. First, the worker positions the bucket 50 and the arm 40 in an aligned state. Specifically, the worker positions the bucket 50 and the arm 40 so that the through hole 53A of the first connecting wall 53 of the bucket 50 and the through hole 47A of the specific connecting wall 47 of the arm 40 are coaxial. After this, the worker fixes the third drive unit 103 to the second connecting wall 55 of the bucket 50 and the specific connecting wall 47 of the arm 40. Specifically, the worker first positions the reducer 120 of the third drive unit 103 between the specific connecting wall 47 and the second connecting wall 55. Then, the worker inserts the output member 124 of the reducer 120 into the through hole 55A of the second connecting wall 55. In this way, the worker spline-couples the output member 124 of the reducer 120 to the second connecting wall 55. Next, the worker inserts the electric motor 110 into the specific connecting wall 47 of the arm 40 from the first direction C1 side. Then, the worker fixes the housing 112 of the electric motor 110 to the specific connecting wall 47, and also fixes the housing 112 of the electric motor 110 to the case 122 of the reduction gear 120. Furthermore, the worker positions the third brake device 133 between the electric motor 110 and the first connecting wall 53 of the bucket 50. Then, the worker fixes the third brake device 133 to the electric motor 110 and the first connecting wall 53. After this, the worker inserts the pin 91 into the first connecting wall 53 and the third brake device 133. Then, the worker fixes the cover 92, which is integrated with the pin 91, to the first connecting wall 53. In this way, each component is connected. The procedure for connecting the components described here is just one example, and the procedure for connecting the components can be modified as needed.

[0077] The third joint mechanism 23 is configured as described above. In the third joint mechanism 23, when the output shaft 114 of the electric motor 110 in the third drive unit 103 rotates, the output member 124 of the reduction gear 120 outputs torque in accordance with that rotation. Along with this torque output, the second connecting wall 55 of the bucket 50 rotates relative to the specific connecting wall 47 of the arm 40 around the third rotation axis 23J. At the same time, the arm 40 and the bucket 50 rotate relative to each other. At this time, the pin 91 supports the relative rotation between the first connecting wall 53 of the bucket 50 and the third brake unit 133 and, consequently, the third drive unit 103.

[0078] <Effects and Effects of the Embodiment> (1) Now, in the third joint mechanism 23 shown in Figure 4, suppose the bucket 50 is rotated relative to the arm 40. At this time, a first load acts on the wall portion connecting the bucket 50 to the arm 40, which is a load corresponding to the weight of the bucket 50 and the excavated material excavated by the bucket 50, and is a load in the circumferential direction centered on the third rotation axis 23J. In the configuration of this embodiment, the bucket 50 is connected to the arm 40 via two wall portions, the first connecting wall 53 and the second connecting wall 55. Therefore, the first load is distributed between the first connecting wall 53 and the second connecting wall 55. In other words, in the configuration of this embodiment, the first load can be borne by the two wall portions, the first connecting wall 53 and the second connecting wall 55, thus reducing the load on each connecting wall portion.

[0079] Furthermore, when the bucket 50 rotates relative to the arm 40, or when the bucket 50 strikes the object to be excavated, the bucket 50 may move in any direction perpendicular to the third rotation axis 23J, for example, as shown by arrow U in Figure 4. This movement is called orthogonal movement. Here, a pin 91 passes through the first connecting wall 53 of the bucket 50. The pin 91 receives the first connecting wall 53 when the bucket 50 moves orthogonally. In other words, the pin 91 and the bearing 133G supporting the pin 91 are responsible for absorbing the load acting on the first connecting wall 53. By receiving this load, the impact acting from the second connecting wall 55 to the output member 124 of the reduction gear 120 due to the orthogonal movement of the bucket 50 can be reduced.

[0080] Although the third joint mechanism 23 is used as an example here, the same applies to the first joint mechanism 21 and the second joint mechanism 22. For example, in the first joint mechanism 21 shown in Figure 2, the support 60 is connected to the boom 30 by two walls, a first connecting wall 64 and a second connecting wall 66. This reduces the load on the connecting walls compared to, for example, the case where the support 60 and the boom 30 are connected by a single wall. Also, in the first joint mechanism 21, the first connecting wall 64 is connected to the first connecting wall 33 of the boom 30 by a pin 71. For example, when the boom 30 and thus the first connecting wall 33 move in any direction perpendicular to the first rotation axis 21J, the pin 71 receives the first connecting wall 33. By the pin 71 receiving the first connecting wall 33, the impact acting on the second drive unit 102 from the second connecting wall 35 can be reduced.

[0081] (2) In the third joint mechanism 23 shown in Figure 4, the arm 40 has only one wall portion, which is composed of a specific connecting wall 47, as a wall portion for connecting with the bucket 50. In this case, the structure of the arm 40 can be simplified compared to a configuration in which multiple connecting walls are provided. Furthermore, the specific connecting wall 47 is located approximately in the center between the first connecting wall 64 and the second connecting wall 66 in the direction along the third rotation axis 23J. By positioning the specific connecting wall 47 approximately in the center between the first connecting wall 64 and the second connecting wall 66, the force supporting the bucket 50 in the direction along the third rotation axis 23J becomes equal. As a result, the support state of the bucket 50 is stabilized.

[0082] (3) In the first joint mechanism 21 shown in Figure 2, the boom 30 has two walls, a first connecting wall 33 and a second connecting wall 35, which serve as walls for connecting to the support 60. The first connecting wall 33 and the second connecting wall 35 individually support the pin 71 and the first drive unit 101. By supporting the pin 71 and the first drive unit 101 with separate walls in this way, the load acting on the pin 71 and the load acting on the first drive unit 101 can be relieved independently. Therefore, for example, when the boom 30 moves in any direction perpendicular to the first rotation axis 21J, the load received by the pin 71 is not transmitted to the first drive unit 101. This contributes to reducing the load on the first drive unit 101.

[0083] (4) In the first joint mechanism 21 shown in Figure 2, the housing 112 of the electric motor 110 is located between the first connecting wall 33 and the second connecting wall 35 of the boom 30. Furthermore, the first connecting wall 33 and the second connecting wall 35 of the boom 30 are located between the first connecting wall 64 and the second connecting wall 66 of the support 60. In other words, in the direction along the first rotation axis 21J, the housing 112 of the electric motor 110, and by extension the entire electric motor 110, is sandwiched between two double walls on both sides. In this case, the electric motor 110 is not exposed to the outside in the direction along the first rotation axis 21J. Adopting this arrangement makes it difficult for soil and sand to get on the electric motor 110, and is therefore suitable for protecting the electric motor 110.

[0084] (5) With respect to the third joint mechanism 23 shown in Figure 4, the bucket 50 is removed more often than the arm 40 or boom 30, for example, for maintenance. Therefore, it is preferable that the number of steps required to attach and detach the bucket 50 from the arm 40 be kept to a minimum. In this regard, in the third joint mechanism 23, there is only one pin 91, which is a connecting member that supports the bucket 50 and the arm 40 so that they can rotate relative to each other. If there were multiple pins connecting the bucket 50 and the arm 40, the number of steps required to attach the pins would increase by the number of pins. In this regard, in the configuration of this embodiment, since there is only one pin 91, the number of steps required to attach and detach the bucket 50 from the arm 40 can be minimized in terms of attaching or removing the pins.

[0085] (6) In the second joint mechanism 22 shown in Figure 3, the boom 30 has two walls, a first connecting wall 37 and a second connecting wall 39, which serve as walls for connecting with the arm 40. The arm 40 has a first connecting wall 43 that pairs with the first connecting wall 37 and a second connecting wall 44 that pairs with the second connecting wall 39. A first pin 81 passes through the first connecting wall 37 and the first connecting wall 43. A second pin 82 passes through the second connecting wall 39 and the second connecting wall 44. Thus, in the second joint mechanism 22, there are two pins as connecting members. In this case, for example, when the arm 40 moves in a direction perpendicular to the second rotation axis 22J, both the first pin 81 and the second pin 82 receive the movement of the arm 40. Therefore, the load on each of the first pin 81 and the second pin 82 can be reduced. Furthermore, because there are two pins to absorb the impact, the impact reaching the second drive unit 102 can be suppressed.

[0086] (7) In the third joint mechanism 23 shown in Figure 4, the output member 124 of the speed reducer 120 is fixed to the second connecting wall 55 of the bucket 50 by spline coupling. When using spline coupling, in order to fix the speed reducer 120 to the second connecting wall 55, it is only necessary to move the output member 124 of the speed reducer 120 in a direction along the third rotation axis 23J relative to the second connecting wall 55. Therefore, in the configuration of this embodiment using spline coupling, the speed reducer 120 can be easily attached to the second connecting wall 55 and, consequently, to the bucket 50. The same can be said for the attachment of the speed reducer 120 to the second connecting wall 66 in the first joint mechanism 21 shown in Figure 2. Although attachment has been described here, in the configuration of this embodiment, removal is also easy, just as with attachment.

[0087] As explained below, when the output member 124 of the reducer 120 and the second connecting wall 55 are fixed using spline coupling, the torque of the output member 124 can be reliably transmitted to the second connecting wall 55. Here, of the spline groove 124S of the output member 124, the surface facing the circumferential direction around the third rotation axis 23J is referred to as the side surface. Similarly, of the spline teeth 55S of the second connecting wall 55, the surface facing the above circumferential direction is also referred to as the side surface. The side surface of the spline groove 124S and the side surface of the spline teeth 55S face each other. At the same time, the side surface of the spline groove 124S and the side surface of the spline teeth 55S are in contact. Now, suppose the output member 124 rotates in the above circumferential direction. Then, torque is transmitted from the side surface of the spline groove 124S to the side surface of the spline teeth 55S. And the second connecting wall 55 rotates together with the spline teeth 55S. Here, the third joint mechanism 23 is used as an example, but even in the first joint mechanism 21 shown in Figure 2, the torque output by the output member 124 of the reduction gear 120 can be reliably transmitted to the second connecting wall 66.

[0088] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0089] Regarding the first joint mechanism 21, the method of forming the spline groove 124S in the output member 124 of the reducer 120 is not limited to the example of the above embodiment. The part of the outer circumferential surface of the output member 124 other than the part in which the irregularities related to the spline coupling are formed is called the general surface. When forming the spline groove 124S on the outer circumferential surface of the output member 124, multiple spline teeth may be made to protrude from the general surface. The spline groove 124S may then be partitioned by adjacent spline teeth. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the method of forming the spline groove 124S for the third joint mechanism 23 is not limited to the example of the above embodiment.

[0090] The method for fixing the two members at various points in the first joint mechanism 21 is not limited to the example of the above embodiment. Any method is acceptable as long as it can fix the two members. For example, when fixing the output member 124 of the reducer 120 to the second connecting wall 66 of the support 60, means other than spline coupling may be used. Similar to the first joint mechanism 21, the method for fixing the two members of the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example of the above embodiment.

[0091] If spline coupling is not used to fix the two members together, the configuration related to spline coupling may be eliminated. In other words, the spline groove 124S may be eliminated from the output member 124 of the reducer 120, and the spline teeth 66S may be eliminated from the second connecting wall 66 of the support 60.

[0092] Regarding the first joint mechanism 21, the cover 72 and the pin 71 do not need to be fixed to each other. If the cover 72 and the pin 71 are not fixed, a cover can be provided on the second direction A2 side relative to the first connecting wall 33 to block the through hole 33A of the first connecting wall 33. This cover and the cover 72 prevent the pin 71 from coming out of the through hole 64A of the first connecting wall 64 and the through hole 33A of the first connecting wall 33. Even in this case, the pin 71 functions as an axial member that supports the relative rotation between the first connecting wall 64 and the first connecting wall 33. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the covers and pins of the second joint mechanism 22 and the third joint mechanism 23 do not need to be fixed to each other.

[0093] Regarding the first joint mechanism 21, it is not essential that the pin 71 penetrates the first connecting wall 64 and the first connecting wall 33. For example, the pin 71 may be positioned in a range from the middle of the through-hole 64A in the first connecting wall 64 to the middle of the through-hole 33A in the first connecting wall 33, in the direction along the first rotation axis 21J. Even in this case, since the pin 71 straddles both the first connecting wall 64 and the first connecting wall 33, the pin 71 can support the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other. Furthermore, in order to connect the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other, the following connecting member may be used instead of the pin 71. That is, a cylindrical connecting member may be made to protrude from the side surface of the first connecting wall 33 on the first direction A1 side, and a recess for accommodating this connecting member may be provided on the side surface of the first connecting wall 64 on the second direction A2 side. In this case, the central axis of the connecting member should be approximately aligned with the central axis of the torque output by the first drive unit 101. Even with this configuration, the connecting member can support the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other. Thus, the connecting member is not limited to the example of the above embodiment. The connecting member only needs to be able to connect the first connecting wall 64 and the first connecting wall 33 so that they can rotate relative to each other about the central axis of the torque output by the first drive unit 101. Here, the first joint mechanism 21 was used as an example, but similar to the first joint mechanism 21, the configuration of the connecting member for the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example of the above embodiment.

[0094] Regarding the first joint mechanism 21, the position of the first drive unit 101 relative to the second connecting wall 35 in the direction along the first rotation axis 21J is not limited to the example of the above embodiment. In other words, it is not essential that the base portion of the first drive unit 101 is positioned between the first connecting wall 33 and the second connecting wall 35. For example, as will be explained in the modified example of Figure 5 below, the base portion may be located on the second direction A2 side relative to the second connecting wall 35. Similar to the first joint mechanism 21, the position of the third drive unit 103 relative to the specific connecting wall 47 in the direction along the third rotation axis 23J is not limited to the example of the above embodiment. As will be explained in the modified example of Figure 7 below, the entire second drive unit 102 may be located on the second direction C2 side relative to the specific connecting wall 47.

[0095] Regarding the first joint mechanism 21, the wall portion to which the base portion and the fixed portion of the first drive unit 101 are fixed is not limited to the example of the above embodiment. That is, the wall portion to which the base portion of the first drive unit 101 is fixed and the wall portion to which the output portion is fixed may be swapped from the example of the above embodiment. Specifically, the housing 112 of the electric motor 110 may be fixed to the second connecting wall 66 of the support 60, while the output member 124 of the reduction gear 120 may be fixed to the second connecting wall 35 of the boom 30. The first drive unit 101 only needs to have its base portion fixed to one of the second connecting wall 66 and the second connecting wall 35, and its output portion fixed to the other of the second connecting wall 66 and the second connecting wall 35. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the wall portion to which the base portion and the wall portion to which the output portion are fixed may also be swapped from the example of the above embodiment for the second joint mechanism 22 and the third joint mechanism 23.

[0096] As shown in the above modification example, when the wall portion that fixes the output section of the first drive unit 101 is the second connecting wall 35, the method of fixing the output section and the second connecting wall 35 is not limited. For example, the output section may be fixed to the second connecting wall 35 using a spline connection, or it may be fixed to the second connecting wall 35 using other methods. The same applies to the second drive unit 102 and the third drive unit 103.

[0097] Regarding the first joint mechanism 21, the configuration of the first drive unit 101 is not limited to the example of the above embodiment. The first drive unit 101 includes an electric motor 110 and only needs to be able to output torque around a specific rotation axis. In the above embodiment, this specific axis corresponds to the first rotation axis 21J. For example, in the first drive unit 101, the output shaft 114 of the electric motor 110 and the reduction mechanism 123 of the reduction gear 120 may be connected via a shock absorption mechanism. The shock absorption mechanism can transmit the rotation of the output shaft 114 of the electric motor 110 to the reduction mechanism 123 and has the function of mitigating the shock transmitted from the reduction mechanism 123 to the output shaft 114 of the electric motor 110. For example, the shock absorption mechanism may be made of rubber or resin material. For example, the shock absorption mechanism may be made of a spring. In the first drive unit 101, the shape of the housing 112 of the electric motor 110 may differ from the example of the above embodiment. The shape of the case 122 of the reduction gear 120 may differ from that of the example in the above embodiment. The reduction gear 120 may be omitted in the first drive unit 101. If the reduction gear 120 is omitted from the first drive unit 101, the output shaft 114 of the electric motor 110 outputs torque to the outside of the first drive unit 101. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the configuration of the drive unit for the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example in the above embodiment. The drive unit includes an electric motor and only needs to be able to output torque around a specific rotation axis.

[0098] Regarding the first joint mechanism 21, the handling of the components constituting the base portion of the first drive unit 101 is not limited to the example of the above embodiment. The base portion can be any component that does not output power itself but supports the rotation of the output portion. For example, in addition to the housing 112 of the electric motor 110, the case 122 of the reduction gear 120 may also be treated as the base portion. Here, the first joint mechanism 21 was used as an example, but similar to the first joint mechanism 21, the handling of the base portions of the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example of the above embodiment.

[0099] Similar to the above examples of modifications to the base section, the handling of the components constituting the output section of the first drive unit 101 is not limited to the examples of the above embodiments. The output section can be any component that rotates relative to the base section and outputs torque to the outside of the first drive unit 101. For example, if the reduction gear 120 is removed from the first drive unit 101, the output shaft 114 of the electric motor 110 constitutes the output section. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the handling of the output sections of the second joint mechanism 22 and the third joint mechanism 23 is not limited to the examples of the above embodiments.

[0100] • In the first joint mechanism 21, the first brake device 130 is not essential. The same applies to the second joint mechanism 22 and the third joint mechanism 23. In the first joint mechanism 21, the arrangement of the first connecting wall 64 and the second connecting wall 66 with respect to the support body 62 is not limited to the example of the above embodiment. That is, in the direction along the first rotation axis 21J, the first connecting wall 64 may be located anywhere within the range of the end face 62A of the support body 62. For example, in the direction along the first rotation axis 21J, the first connecting wall 64 may be located near the center of the end face 62A of the support body 62. Similarly, in the direction along the first rotation axis 21J, the second connecting wall 66 may be located anywhere within the range of the end face 62A of the support body 62. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the arrangement of each connecting wall with respect to the body of the first member in the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example of the above embodiment.

[0101] In the first joint mechanism 21, it is not essential that the first connecting wall 64 and the second connecting wall 66 have the same shape and dimensions. The shape and dimensions of the first connecting wall 64 may be appropriately designed so that it can be positioned through the first rotation axis 21J. The same applies to the second connecting wall 66. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the shape and dimensions of each connecting wall in the second joint mechanism 22 and the third joint mechanism 23 are not limited to the examples in the above embodiment.

[0102] In the first joint mechanism 21, the arrangement of the first connecting wall 33 and the second connecting wall 35 with respect to the boom body 31 is not limited to the example of the above embodiment. That is, in the direction along the first rotation axis 21J, the first connecting wall 33 may be located anywhere within the range of the first end face 31A of the boom body 31. Similarly, in the direction along the first rotation axis 21J, the second connecting wall 35 may be located anywhere within the range of the second end face 31B of the boom body 31. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the arrangement of each connecting wall with respect to the second member of the second joint mechanism 22 and the third joint mechanism 23 is not limited to the example of the above embodiment.

[0103] In the first joint mechanism 21, it is not essential that the first connecting wall 33 and the second connecting wall 35 have the same shape and dimensions. The shape and dimensions of the first connecting wall 33 may be appropriately designed so that it can be positioned through the first rotation axis 21J. The same applies to the second connecting wall 35. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the shape and dimensions of each connecting wall in the second joint mechanism 22 and the third joint mechanism 23 are not limited to the examples in the above embodiment.

[0104] In the first joint mechanism 21, the connection configuration in the above embodiment may be applied by swapping the support and the boom. That is, in the first joint mechanism 21, the configuration of each wall portion provided on the boom and the support may be changed so that the boom constitutes the first member and the support constitutes the second member. Specifically, the boom is provided with a first connecting wall and a second connecting wall that are aligned in the direction along the first rotation axis 21J. On the other hand, the support is provided with a first connecting wall located between the first connecting wall and the second connecting wall in the direction along the first rotation axis 21J, and a second connecting wall located between the first connecting wall and the second connecting wall. The first connecting wall of the boom and the first connecting wall of the support are connected by a connecting member, and the second connecting wall of the boom and the second connecting wall of the support are connected by the first drive device 101. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the configuration of the second joint mechanism 22 and the third joint mechanism 23 may also be applied by swapping the first and second members.

[0105] The connection configuration applied to the first joint mechanism 21 may also be applied to parts of the excavator 10 other than the connection between the support 60 and the boom 30. For example, the same configuration may be applied to the connection between the boom 30 and the arm 40, or to the connection between the bucket 50 and the arm 40. Here, the first joint mechanism 21 is used as an example, but similar to the first joint mechanism 21, the configurations of the second joint mechanism 22 and the third joint mechanism 23 may also be applied to locations different from those in the above embodiment.

[0106] As described in the above embodiment, in the first joint mechanism 21, the first member has two connecting walls aligned in a direction along a specific rotation axis. The second member also has two connecting walls aligned in a direction along a specific rotation axis. The two connecting walls are located between the two connecting walls. Two examples of configurations different from the above embodiment will be described as ways in which the first member and the second member, which have these walls, are connected for relative rotation by a connecting member and a drive device. The two examples described here will focus on the connection between the bucket 50 and the arm 40. The bucket 50 and the arm 40 are connected so as to be able to rotate relative to each other around the third rotation axis 23J shown in Figure 1.

[0107] First, the first example will be explained using Figure 5. This first example differs from the example in Figure 2 in that the arrangement of the drive unit relative to the second connecting wall is changed, and the base part of the drive unit is fixed to the second connecting wall while the output part is fixed to the second connecting wall. In Figure 5, parts that function the same or substantially the same as those in Figures 1 to 4 are denoted by the same reference numerals as in Figures 1 to 4. In addition, in Figure 5, the configuration of parts that function the same or substantially the same as the first joint mechanism 21 will be omitted or simplified as appropriate.

[0108] The joint mechanism 223 shown in Figure 5 comprises a first member consisting of a bucket 50 and a second member consisting of an arm 40. The bucket 50 and the arm 40 are located on one side and the other side of the third rotation axis 23J. A first connecting wall 253 and a second connecting wall 255 protrude from the end face 51A of the bucket body 51. The first connecting wall 253 and the second connecting wall 255 are aligned in a direction along the third rotation axis 23J. The second connecting wall 255 is located on the second direction C2 side relative to the first connecting wall 253. The first connecting wall 253 and the second connecting wall 255 are located near the center of the end face 51A of the bucket body 51 in a direction along the third rotation axis 23J.

[0109] On the other hand, the first connecting wall 233 and the second connecting wall 235 protrude from the second end face 41B of the arm body 41. The first connecting wall 233 and the second connecting wall 235 are aligned in a direction along the third rotation axis 23J. The first connecting wall 233 is located between the first connecting wall 253 and the second connecting wall 255 of the bucket 50. The second connecting wall 235 is located between the first connecting wall 233 and the second connecting wall 255 of the bucket 50. In the example in Figure 5, the first connecting wall 233 and the second connecting wall 235 are separated in a direction along the third rotation axis 23J. However, the first connecting wall 233 and the second connecting wall 235 may be a single unit.

[0110] The first connecting wall 253 of the bucket 50 and the first connecting wall 233 of the arm 40 are connected by a pin 71 so as to be able to rotate relative to each other. That is, the pin 71 passes through the through hole 253A of the first connecting wall 253 of the bucket 50 and the through hole 233A of the first connecting wall 233 of the arm 40.

[0111] The second connecting wall 255 of the bucket 50 and the second connecting wall 235 of the arm 40 are connected by a drive unit 104. In the drive unit 104, the case 122 of the reduction gear 120 is located on the second direction C2 side relative to the second connecting wall 255. The case 122 is fixed to the second connecting wall 255 via a flange wall 122F that protrudes from the outer circumferential surface of the case 122. The electric motor 110 is located on the second direction C2 side relative to the reduction gear 120. In other words, unlike the example in Figure 2, the case 122 of the reduction gear 120 and the housing 112 of the electric motor 110 are not located in the space between the first connecting wall 233 and the second connecting wall 235, but are exposed to the outside. A brake device 134 is located on the second direction C2 side relative to the electric motor 110. The brake device 134 is fixed to the housing 112 of the electric motor 110. The function of the brake device 134 is the same as that of the embodiment described above.

[0112] The output member 124 of the reduction gear 120 passes through the through hole 255A of the second connecting wall 255 of the bucket 50. The output member 124 is slidable against the inner surface of the through hole 255A. The end of the output member 124 on the first direction C1 side is located inside the through hole 235A of the second connecting wall 235 of the arm 40. Inside the through hole 235A, the spline groove 124S of the output member 124 meshes with the spline teeth 235S formed in the through hole 235A. That is, the output member 124 is spline-coupled to the second connecting wall 235 via a plurality of spline grooves 124S. The output member 124 rotates relative to the case 122 of the reduction gear 120 and, consequently, the housing 112 of the electric motor 110, in the circumferential direction about the third rotation axis 23J.

[0113] As shown in Figure 5, in this example, the housing 112 of the electric motor 110, which is the base of the drive unit 104, is fixed to the second connecting wall 255. On the other hand, the output member 124 of the reduction gear 120, which is the output section of the drive unit 104, is fixed to the second connecting wall 235. When the electric motor 110 is driven, the second connecting wall 235 fixed to the output member 124 and the second connecting wall 255 fixed to the housing 112 of the electric motor 110 rotate relative to each other in the circumferential direction around the third rotation axis 23J.

[0114] In the example shown in Figure 5, the electric motor 110 and the reduction gear 120 are exposed to the outside. In this configuration, the electric motor 110 and the reduction gear 120 can be easily attached to or removed from the second connecting wall 255. Therefore, maintenance is less time-consuming.

[0115] Next, a second example will be explained using Figure 6. This second example differs from the example in Figure 2 in that the second member has three connecting walls. In Figure 6, parts that function the same or substantially the same as those in Figures 1 to 5 are denoted by the same reference numerals as in Figures 1 to 5. In addition, in Figure 6, the configuration of parts that function the same or substantially the same as the first joint mechanism 21 will be omitted or simplified as appropriate.

[0116] The joint mechanism 330 shown in Figure 6, similar to the example in Figure 5, comprises a first member consisting of a bucket 50 and a second member consisting of an arm 40. The bucket 50 and the arm 40 are located on one side and the other side of the third rotation axis 23J. A first connecting wall 353 and a second connecting wall 355 protrude from the end face 51A of the bucket body 51. The first connecting wall 353 and the second connecting wall 355 are aligned in a direction along the third rotation axis 23J. The second connecting wall 355 is located on the second direction C2 side relative to the first connecting wall 353.

[0117] On the other hand, three connecting walls, a first connecting wall 333, a second connecting wall 335, and a third connecting wall 337, protrude from the second end face 41B of the arm body 41. The first connecting wall 333, the second connecting wall 335, and the third connecting wall 337 are aligned in a direction along the third rotation axis 23J. The first connecting wall 333, the second connecting wall 335, and the third connecting wall 337 are separated from each other in a direction along the third rotation axis 23J. The first connecting wall 333 is located between the first connecting wall 353 and the second connecting wall 355 of the bucket 50. The second connecting wall 335 is located between the first connecting wall 333 and the second connecting wall 355 of the bucket 50. The third connecting wall 337 is located between the second connecting wall 335 and the second connecting wall 355. In other words, the third connecting wall 337 is located on the opposite side of the second connecting wall 335 from the first connecting wall 333.

[0118] The first connecting wall 353 of the bucket 50 and the first connecting wall 333 of the arm 40 are connected by a pin 71 so as to be able to rotate relative to each other. That is, the pin 71 passes through the through hole 353A of the first connecting wall 353 of the bucket 50 and the through hole 333A of the first connecting wall 333 of the arm 40.

[0119] The second connecting wall 335 of the arm 40 and the second connecting wall 355 of the bucket 50 are connected by a drive unit 104. Specifically, the housing 112 of the electric motor 110 is located inside the through hole 335A in the second connecting wall 335. The housing 112 passes through the through hole 335A. The housing 112 is fixed to the second connecting wall 335. A brake device 134 is located on the first direction C1 side relative to the housing 112. On the other hand, a reduction gear 120 is located on the second direction C2 side relative to the housing 112. The output member 124 of the reduction gear 120 passes through the through hole 337A in the third connecting wall 337. The output member 124 is slidable against the inner surface of the through hole 337A. The end of the output member 124 on the second direction C2 side extends to the second direction C2 side relative to the third connecting wall 337. The end of the output member 124 on the second direction C2 side is located inside the through hole 355A of the second connecting wall 355. Inside the through hole 355A, the spline groove 124S of the output member 124 meshes with the spline teeth 355S formed in the through hole 355A. That is, the output member 124 is spline-coupled to the second connecting wall 355 via a plurality of spline grooves 124S. The output member 124 rotates relative to the case 122 of the reduction gear 120 and, consequently, the housing 112 of the electric motor 110, in the circumferential direction about the third rotation axis 23J. Therefore, when the electric motor 110 is driven, the second connecting wall 355 fixed to the output member 124 and the second connecting wall 335 fixed to the housing 112 of the electric motor 110 rotate relative to each other in the circumferential direction about the third rotation axis 23J. Furthermore, the portion of the output member 124 that penetrates, for example, the third connecting wall 337, may be made of the above-mentioned shock mitigation mechanism. In other words, the entire output member 124 in the direction along the third rotation axis 23J does not have to be made of the same material, and the material or configuration may be changed along the way.

[0120] In the configuration shown in Figure 6, the drive unit 104 is supported by three walls: the second connecting wall 355 of the bucket 50, the second connecting wall 335 of the arm 40, and the third connecting wall 337 of the arm 40. Therefore, the load on each wall in supporting the drive unit 104 can be distributed. Thus, the load on each wall can be reduced. In addition, in the configuration shown in Figure 6, the output member 124 of the drive unit 104 penetrates the third connecting wall 337. In this case, there are the following advantages. As explained in the effects of the above embodiment, when the bucket 50 rotates relative to the arm 40, or when the bucket 50 hits the object to be excavated, the bucket 50 may move in any direction perpendicular to the third rotation axis 23J, for example, as shown by arrow V in Figure 6. Along with this movement of the bucket 50, the output member 124 of the reduction gear 120 may also move in any direction perpendicular to the third rotation axis 23J, together with the second connecting wall 355. The third connecting wall 337, through which the output member 124 passes, can withstand the movement of the output member 124. This reduces the impact that reaches the electric motor 110.

[0121] Furthermore, in the configuration described above where the second member has three connecting walls, the third connecting wall 337 may be positioned on the opposite side of the second connecting wall 355 of the bucket 50 from the second connecting wall 335. In this configuration, the drive unit 104 may be connected to the third connecting wall 337.

[0122] As described in the above embodiment, in the second joint mechanism 22, the first member has two connecting walls aligned in a direction along a specific axis of rotation. The second member also has two connecting walls aligned in a direction along a specific axis of rotation. One of the two connecting walls is located between the two connecting walls, and the other is located outside the two connecting walls. When connecting the first member and the second member, which have these walls, to relative rotation by the drive device and the two connecting members, the overall configuration of the first member and the second member may be changed from the example of the above embodiment. For example, with respect to the second joint mechanism 22 of the above embodiment, the dimensions of the main part 31M of the boom body 31 and the dimensions of the second end face 31B of the boom body 31 may be substantially the same in the direction along the second axis of rotation 22J. Also, with respect to the second joint mechanism 22 of the above embodiment, the second end face 31B of the boom body 31 may protrude toward the second direction B2 side relative to the main part 31M of the boom body 31. Here, we used boom 30 as an example, but the overall shape of arm 40 may also be changed.

[0123] Regarding the third joint mechanism 23, the specific member is not limited to the brake device. Furthermore, in a configuration where the second member has only one connecting wall, such as the third joint mechanism 23, it is not essential to interpose the specific member between the specific connecting wall 47 and the first connecting wall 53.

[0124] As described in the above embodiment, in the third joint mechanism 23, the first member has two connecting walls aligned in a direction along a specific axis of rotation. On the other hand, the second member has a specific connecting wall located between the two connecting walls in a direction along a specific axis of rotation. An example of a configuration different from the above embodiment, in which the first member and the second member, which have these walls, are connected for relative rotation by a connecting member and a drive device, will be described with reference to Figure 7. The joint mechanism 23A shown in Figure 7 differs from the example in Figure 4 in that the first connecting wall 53 and the specific connecting wall 47 are directly connected by a pin 91.

[0125] Specifically, in the joint mechanism 23A, the specific connecting wall 47 protrudes from the end of the second end face 41B of the arm body 41 on the side of the first direction C1. In the direction along the third rotation axis 23J, the specific connecting wall 47 is located immediately next to the first connecting wall 53 of the bucket 50. In the direction along the third rotation axis 23J, there is a small gap between the specific connecting wall 47 and the first connecting wall 53. A pin 91 passes through the through hole 53A of the first connecting wall 53 and the through hole 47A of the specific connecting wall 47. The pin 91 supports the first connecting wall 53 and the specific connecting wall 47 so that they can rotate relative to each other.

[0126] On the other hand, a third brake device 133 is located on the second direction C2 side relative to the specific connecting wall 47. The third brake device 133 is fixed to the specific connecting wall 47 via a flange wall 133F. A third drive device 103 is located on the second direction C2 side relative to the third brake device 133. The housing 112 of the electric motor 110 in the third drive device 103 is fixed to the third brake device 133. In other words, the housing 112 is fixed to the specific connecting wall 47 via the third brake device 133. On the other hand, the output member 124 of the reduction gear 120 is fixed to the second connecting wall 55 of the bucket 50 via a spline groove 124S, similar to the third joint mechanism 23 in the above embodiment. Note that in Figure 7, parts that function the same or substantially the same as those in Figures 1 to 6 are denoted by the same reference numerals as in Figures 1 to 6, and redundant explanations are omitted.

[0127] In the joint mechanism 23A shown in Figure 7, the arm 40 has only one wall portion, which is composed of a specific connecting wall 47, as a wall portion for connecting with the bucket 50. Therefore, in the example of Figure 7, the structure of the arm 40 can be simplified compared to a configuration in which, for example, multiple connecting wall portions are provided, as in (2) above. In addition, in the joint mechanism 23A shown in Figure 7, there is only one pin 91, which is a connecting member that supports the bucket 50 and the arm 40 so that they can rotate relative to each other. Therefore, as in (5), the number of steps required to attach and detach the bucket 50 to the arm 40 can be minimized in terms of attaching or detaching the pin.

[0128] Regarding the configuration shown in Figure 7, the first connecting wall 53 may be eliminated from the bucket 50, and the pin 91 that penetrates the first connecting wall 53 may also be eliminated. That is, as in the joint mechanism 350 shown in Figure 8, the bucket 50, which is the first member, has only one connecting wall 55. This connecting wall 55 is connected to a specific connecting wall 47 of the arm 40, which is the second member, by a drive device 103. As described above, the housing 112 of the electric motor 110 is fixed to the specific connecting wall 47 via a brake device 133. That is, the base part of the drive device is fixed to the first member. However, it is not essential that the brake device 133 is interposed between the base part and the first member. On the other hand, the output member 124 of the reduction gear 120 is fixed to the connecting wall 55 by spline coupling. That is, the output part is fixed to the second member by spline coupling. In Figure 8, parts that function identically or substantially identically to those in Figures 1 to 7 are denoted by the same reference numerals as in Figures 1 to 7, thereby omitting redundant explanations.

[0129] Here, in technologies such as that described in Patent Document 1, it is necessary to simplify the work involved in assembling the components at each joint, such as the connection point between the boom and the arm, or the connection point between the arm and the bucket. In this regard, the configuration shown in Figure 8 utilizes a spline coupling as the structure for fixing the output member 124 of the reduction gear 120 to the connecting wall 55. By using a spline coupling, as described in (7) above, when fixing the output member 124 to the connecting wall 55, it is only necessary to insert the output member 124 into the through hole 55A of the connecting wall 55. Therefore, the work involved in fixing the output member 124 to the connecting wall 55 is not time-consuming.

[0130] As shown in the example in Figure 8 above, in a configuration where the bucket 50 has only one connecting wall 55, the arrangement of the connecting wall 55 with respect to the bucket body 51 in the direction along the third rotation axis 23J is not limited to the example in Figure 8 and can be changed as appropriate. Similarly, the arrangement of the specific connecting wall 47 with respect to the arm body 41 in the direction along the third rotation axis 23J is not limited to the example in Figure 8 and can be changed as appropriate. In addition, in the joint mechanism 350 shown in Figure 8, the wall that fixes the base part of the drive unit 103 and the wall that fixes the output part may be swapped. In this case, the arm 40 is treated as the first member, and the specific connecting wall 47 in Figure 8 is treated as the connecting wall. At the same time, the bucket 50 is treated as the second member, and the connecting wall 55 in Figure 8 is treated as the connecting wall. That is, the base of the drive unit is fixed to the first member, and the output part is fixed to the second member. Thus, in a configuration in which the first member has only one connecting wall, the first member is not limited to an attachment such as a bucket 50. Furthermore, when the first member is changed from an attachment, the second member that is connected to the first member is also changed. A connecting structure in which the first member has only one connecting wall may also be applied to parts of the excavator 10 other than the connection point between the bucket 50 and the arm 40.

[0131] The overall configuration of the excavator 10 is not limited to the examples of the above embodiments. For example, attachments other than a bucket may be used. The attachments may be devices, mechanisms, tools, etc. that are effective in various tasks using the excavator 10. Furthermore, the excavator 10 may have two rotatably connected members other than the boom 30, arm 40, and attachments. Various joint mechanisms described in the above embodiments may be applied to the connection point of such two members.

[0132] The construction machinery to which the various joint mechanisms described in the above embodiments are applied is not limited to the excavator 10. Regardless of the type of construction machinery, applying the various joint mechanisms described in the above embodiments and modifications can reduce the load acting on the joints.

[0133] In the above embodiment, a structure composed of multiple objects may be integrated, or conversely, a structure composed of a single object may be divided into multiple objects. Whether or not the objects are integrated, the structure should be configured in a way that achieves the objective of the invention.

[0134] This section describes the technical concepts that can be understood from the above embodiments and modified examples. An articulation mechanism for a construction machine comprising: a drive device including an electric motor that outputs torque; a first member having a first connecting wall and a second connecting wall arranged in a direction along the rotation axis of the torque output by the drive device; a second member having at least a portion located between the first connecting wall and the second connecting wall in a direction along the rotation axis; a specific member interposed between the first connecting wall and the second member; and a connecting member that connects the first connecting wall and the specific member so as to be rotatable relative to each other in the circumferential direction about the rotation axis, wherein the drive device connects the second connecting wall and the second member and rotates the second connecting wall and the second member relative to each other in the circumferential direction about the rotation axis. [Explanation of Symbols]

[0135] 10... Excavator 21...First joint mechanism 22...Second joint mechanism 23...Third joint mechanism 30... Boom 40...arm 50...bucket 60...Support 33,43,233,333…First connecting wall 35, 44, 235, 335… Second connecting wall 37,53,64,253,353…1st connecting wall 39,55,66,255,355…Second connecting wall 47...Specific connection wall 71...pin 81...1st pin 82...2nd pin 101...First drive unit 102...Second drive unit 103...Third drive unit 110… Electric motor 337...Third connecting wall

Claims

1. A drive unit that includes an electric motor and outputs torque, A first member having a first connecting wall and a second connecting wall that are aligned in a direction along the rotation axis of the torque output by the drive device, A second member having at least a portion of its length located between the first connecting wall and the second connecting wall in the direction along the rotation axis, The first connecting wall and the second member are connected so as to be rotatable relative to each other in the circumferential direction about the axis of rotation, The drive device connects the second connecting wall and the second member, and rotates the second connecting wall and the second member relative to each other in the circumferential direction about the axis of rotation. Joint mechanisms of construction machinery.

2. The second member has a connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, The connecting member connects the first connecting wall and the connecting wall. The drive unit comprises a base portion fixed to one of the second connecting wall and the connecting wall, and an output portion fixed to the other of the second connecting wall and the connecting wall, which rotates relative to the base portion in a circumferential direction about the rotation axis. The joint mechanism for a construction machine according to claim 1.

3. The second member has a first connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, and a second connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, The connecting member connects the first connecting wall and the first connecting wall. The drive unit comprises a base portion fixed to one of the second connecting wall and the second linking wall, and an output portion fixed to the other of the second connecting wall and the second linking wall, which rotates relative to the base portion in a circumferential direction about the rotation axis. The joint mechanism for a construction machine according to claim 1.

4. The base portion of the drive device is located between the first connecting wall and the second connecting wall in a direction along the axis of rotation. The joint mechanism for a construction machine according to claim 3.

5. The second member has a third connecting wall located on the opposite side of the second connecting wall from the first connecting wall in the direction along the axis of rotation, The drive device penetrates the third connecting wall. The joint mechanism for a construction machine according to claim 4.

6. The first member is a bucket having an opening. The joint mechanism for a construction machine according to claim 2 or 3.

7. The second member has a first connecting wall located between the first connecting wall and the second connecting wall in a direction along the axis of rotation, and a second connecting wall located on the opposite side of the second connecting wall from the first connecting wall in a direction along the axis of rotation. When the aforementioned connecting member is designated as the first connecting member, The first connecting member connects the first connecting wall and the first connecting wall. Furthermore, the second connecting wall and the second linking wall are provided with a second connecting member that connects them so as to be rotatable relative to each other in the circumferential direction about the axis of rotation, The drive unit comprises a base portion fixed to one of the second connecting wall and the first connecting wall, and an output portion fixed to the other of the second connecting wall and the first connecting wall, which rotates relative to the base portion in a circumferential direction about the rotation axis. The joint mechanism for a construction machine according to claim 1.

8. The drive device comprises a base portion fixed to one of the second connecting wall and the second member, and an output portion fixed to the other of the second connecting wall and the second member, which rotates relative to the base portion in a circumferential direction about the rotation axis. The output unit has a spline groove formed along the rotation axis and is fixed to the second connecting wall or the second member via the spline groove. The joint mechanism for a construction machine according to claim 1.

9. A drive unit that includes an electric motor and outputs torque, First member and The drive device comprises a second member which is aligned with the first member in a direction along the rotation axis of the torque output by the drive device, The drive device comprises a base portion fixed to the first member and an output portion fixed to the second member and rotating relative to the base portion in a circumferential direction about the rotation axis, The output unit has a spline groove formed along the rotation axis and is fixed to the second member via the spline groove. Joint mechanisms of construction machinery.

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