Work machine

Abstract

The present invention improves durability. In a motive power transmission mechanism 40 of a multi-tool 10, a connecting piece 50 is formed in a cylindrical shape with a longitudinal direction as an axial direction, and a front side of the connecting piece 50 is closed by a lid part 51. Specifically, both lateral-direction end parts at the front-end part of the connecting piece 50 are connected to each other by the lid part 51. Thus, the lid part 51 functions as a reinforcement part, and any lateral-direction deformation of the connecting piece 50 can be effectively suppressed by the lid part 51. As a result, a connection state between the connecting piece 50 and a reception-side motive power transmission part 64 can be satisfactorily maintained. Therefore, the durability of the multi-tool 10 can be improved.

Description

Work equipment

[0001] The present invention relates to a work machine.

[0002] In the work machine disclosed in Patent Document 1, a power transmission mechanism transmits the driving force of a motor to an output shaft, which rotates back and forth around its own axis, causing a tool attached to the output shaft to oscillate (vibrate). This allows cutting or other processing to be performed on a workpiece. Such work machines are sometimes called multi-tools because of their ability to attach and detach various tool bits, or vibration tools because they perform work by vibrating the tool bit.

[0003] The power transmission mechanism includes an eccentric shaft that rotates eccentrically about an axis extending in the front-rear direction, a bearing mounted on the eccentric shaft, and a swing arm. The front end of the swing arm is fixed to the output shaft so as to be rotatable together with the output shaft, and the arm portion of the swing arm is disposed adjacent to the outer side of the bearing in the left-right direction. As a result, when the bearing rotates eccentrically with the eccentric shaft, the swing arm swings around the axis of the output shaft, and the tool bit attached to the output shaft swings. In other words, power in the left-right direction generated by the eccentric rotation of the eccentric shaft is transmitted from the bearing to the arm portion, and the power is transmitted to the output shaft by the swing arm.

[0004] Japanese Patent Application Laid-Open No. 2021-70100

[0005] Here, durability is an issue with the above-described work machine. First, there is a durability issue due to the workload. For example, if the load acting on the power transmission unit (e.g., the eccentric unit, bearing, swing arm, etc.) during operation of the work machine increases due to the tool attached to the output shaft, the power transmission unit may wear out and deform prematurely, making it difficult to continue working. Second, there is a durability issue due to a decrease in the lubrication performance of the power transmission unit. For example, if the grease (lubricant) applied to the power transmission unit is depleted due to some influence, vibrations and heat may be generated in the power transmission unit, which may cause premature wear and deformation of the power transmission unit. Third, there is a durability issue due to dimensional changes during assembly. That is, the bearing and arm function as power transmission units that transmit the lateral power generated by the eccentric shaft to the output shaft. Therefore, for example, if the lateral dimensions of the power transmission unit, such as the bearing and arm, change during assembly, there is a possibility that a poor connection between the bearing and the arm may occur. Specifically, if the gap between the bearing and the arm becomes large, rattle occurs between them, which may reduce the durability of the work machine, whereas if the gap between the bearing and the arm becomes small, the sliding ability between the bearing and the arm becomes excessively poor, which may reduce the durability of the work machine.

[0006] SUMMARY OF THE INVENTION In consideration of the above, an object of the present invention is to provide a work machine that can improve durability.

[0007] One or more embodiments of the present invention are a work machine including: a motor; an eccentric shaft that extends in a predetermined direction and rotates eccentrically about a predetermined axis extended in the predetermined direction by a driving force of the motor transmitted from an end on one side in the predetermined direction; an output shaft that rotates back and forth about its own axis by transmitting power from the eccentric shaft; a power transmission unit that is formed in a cylindrical shape with its axial direction in the predetermined direction and that transmits orthogonal power that is generated by the eccentric rotation of the eccentric shaft and is perpendicular to the predetermined direction to the output shaft; and a connection unit that covers at least a portion of one end side of the cylindrical power transmission unit in the predetermined direction and is configured to be able to operate integrally with the power transmission unit, and that connects both ends of the power transmission unit in the orthogonal direction.

[0008] In one or more embodiments of the present invention, the power transmission unit is a connecting piece made of a single member, and a rolling member that is supported by the eccentric shaft and transmits the power to the power transmission unit is provided inside the connecting piece, and the connecting unit is integrally formed at one end of the connecting piece in the specified direction, or the connecting unit is made of a separate member from the connecting piece and is attached to one end of the connecting piece in the specified direction.

[0009] One or more embodiments of the present invention are directed to a work machine, wherein the connection portion closes an opening on one side of the connecting piece in the predetermined direction.

[0010] In one or more embodiments of the present invention, the connection portion is a work machine having a regulating surface that faces the rolling member in the predetermined direction and regulates movement of the rolling member to one side in the predetermined direction, and a recess that is positioned on one side of the regulating surface in the predetermined direction and is open to the other side in the predetermined direction.

[0011] One or more embodiments of the present invention are a work machine in which the motor has a rotating shaft, and the eccentric shaft has an insertion hole into which the rotating shaft is inserted, and an axial space portion that communicates with the insertion hole and is open to one side in the specified direction.

[0012] One or more embodiments of the present invention are a work machine in which the inner surface of the connecting piece is configured to include an intermediate groove portion that is open radially inward of the connecting piece and supported surfaces that are arranged on both sides of the intermediate groove portion in the specified direction and are supported by the rolling members, and in which a lubricant is filled in the intermediate groove portion.

[0013] One or more embodiments of the present invention are a work machine in which an end groove portion that is open radially inward of the connecting piece is formed on the inner surface of the connecting piece at one end on one side in the specified direction.

[0014] One or more embodiments of the present invention are a work machine in which the eccentric shaft is inserted into the connecting piece from the other side in the specified direction, and a blocking member is provided on the other side of the connecting piece in the specified direction, radially outside the eccentric shaft, to block the opening on the other side of the connecting piece in the specified direction.

[0015] In one or more embodiments of the present invention, the closing member is a balance weight configured to be rotatable integrally with the eccentric shaft about the predetermined axis.

[0016] In one or more embodiments of the present invention, the balance weight is a working machine configured to include a balance main body portion connected to the eccentric shaft, and a regulating portion that protrudes from the balance main body portion to one side in the predetermined direction and is positioned on the other side of the rolling member in the predetermined direction to regulate movement of the rolling member to the other side in the predetermined direction.

[0017] In one or more embodiments of the present invention, the regulating portion blocks the opening on the other side of the connecting piece in the specified direction, and the tip portion is positioned inside the connecting piece from the other side of the specified direction.

[0018] One or more embodiments of the present invention are directed to a work machine in which the eccentric shaft is coupled to the power transmission part so as to be rotatable relative to the power transmission part.

[0019] One or more embodiments of the present invention are a work machine in which a power transmission member having the power transmission unit is connected to the output shaft so as to be rotatable integrally therewith, and the eccentric shaft rotates eccentrically, causing the power transmission unit to move back and forth in the perpendicular direction and the output shaft to rotate back and forth.

[0020] One or more embodiments of the present invention are a work machine comprising: a motor; an eccentric shaft that extends in a predetermined direction and rotates eccentrically about an axis extending in the predetermined direction by a driving force of the motor transmitted from an end on one side in the predetermined direction; an output shaft that rotates back and forth about its own axis by transmitting power from the eccentric shaft; and a connecting piece that is formed as a single container-shaped part that has a cylindrical portion whose axial direction is in the predetermined direction and a lid portion that closes the end on one side in the predetermined direction of the cylindrical portion and that opens on the other side in the predetermined direction, and that transmits power in an orthogonal direction that is perpendicular to the predetermined direction and is generated by the eccentric rotation of the eccentric shaft to the output shaft.

[0021] One or more embodiments of the present invention are a work machine in which a needle bearing is provided between the eccentric shaft and the cylindrical portion, a swing arm is provided on the output shaft for transmitting the orthogonal power from the connecting piece to the output shaft, the connecting piece is arranged around the needle bearing so as to be movable relative to the eccentric shaft in the predetermined direction, and the movement in the predetermined direction is restricted by the swing arm, and the needle bearing is configured so as to be movable relative to the eccentric shaft in the predetermined direction, and the movement in the predetermined direction is restricted by the cover portion.

[0022] One or more embodiments of the present invention may provide improved durability.

[0023] 8A is a cross-sectional view from the right side showing the interior of the multi-tool according to the first embodiment; FIG. 8B is a cross-sectional view from the right side showing the periphery of the power transmission mechanism shown in FIG. 1; FIG. 8C is a cross-sectional view from above showing the power transmission mechanism shown in FIG. 2 (cross-sectional view along line 3-3 in FIG. 2); FIG. 8D is an exploded perspective view of the power transmission mechanism shown in FIG. 3 as viewed from the front right; FIG. 8A is a cross-sectional view from above showing the swing arm of the power transmission mechanism shown in FIG. 3 as viewed most to the left, and FIG. 8B is a cross-sectional view from above showing the swing arm of the power transmission mechanism shown in FIG. 3 as viewed most to the right; FIG. 8C is a cross-sectional view from the right side showing a first modified example of the power transmission mechanism shown in FIG. 2; FIG. 8D is a cross-sectional view from above showing a second modified example of the power transmission mechanism shown in FIG. 3; FIG. 8A is a cross-sectional view from the rear side showing the interior of a cylindrical power transmission part of the power transmission mechanism of the multi-tool according to the second embodiment (cross-sectional view along line 8A-8A in FIG. 8B); and FIG. 8B is a cross-sectional view from the right side showing the power transmission mechanism of the multi-tool according to the second embodiment. 10 is a cross-sectional view (cross-sectional view taken along line 9-9 in FIG. 8) of the power transmission mechanism shown in FIG. 8 from above. 11 is a cross-sectional view (viewed from the right side) of the interior of the front part of a multi-tool according to a third embodiment. 12 is a plan view (viewed from above) of the swing arm shown in FIG. 10. 13A is a cross-sectional view showing the connection state between the tubular power transmission unit of the swing arm and the connecting piece when the eccentric shaft is at its most upwardly eccentric position relative to the axis of the spindle. 13B is a cross-sectional view showing the connection state between the tubular power transmission unit and the connecting piece when the axes of the eccentric shaft and the spindle are aligned in the vertical direction. 13C is a cross-sectional view showing the connection state between the tubular power transmission unit and the connecting piece when the eccentric shaft is at its most downwardly eccentric position relative to the axis of the spindle. 13A is a plan view showing a modified version of the swing arm shown in FIG. 9, and 13B is a plan view showing a modified version of the swing arm shown in FIG. 11.

[0024] First Embodiment A multi-tool 10 as a work machine according to a first embodiment will be described below with reference to Figures 1 to 5. Note that the arrows UP, FR, and RH shown as appropriate in the drawings indicate the upper side, front side, and right side of the multi-tool 10, respectively. In the following description, when the up / down, front / rear, and left / right directions are used, they refer to the up / down, front / rear, and left / right directions of the multi-tool 10 unless otherwise specified.

[0025] 1, the multi-tool 10 is a power tool that performs cutting or other processing on a workpiece by swinging a tool bit T attached to the front end of the multi-tool 10 about an axial direction that is the up-down direction. The multi-tool 10 includes a housing 12, a motor 24, an output shaft 30, and a power transmission mechanism 40.

[0026] (Regarding the Housing 12) The housing 12 forms the outer shell of the multi-tool 10. The housing 12 is formed as a hollow column extending in the front-rear direction as a whole. A trigger 14 is provided at the upper end of the housing 12 in the middle in the front-rear direction. The trigger 14 is connected to the housing 12 so as to be slidable in the front-rear direction and is exposed upward from the housing 12 so as to be operable. A trigger switch 16 is provided inside the housing 12 behind the trigger 14 and is connected to the trigger 14 by a switch lever 18. The trigger switch 16 is electrically connected to a controller 20, which is housed in the rear end portion of the housing 12. The trigger 14 is positioned in the OFF position shown in FIG. 1 . By sliding the trigger 14 from the OFF position to the ON position at the front, the trigger switch 16 is switched from OFF to ON, and a motor 24 (described later) is driven by the controller 20. A battery 22 is attached from above to the rear end of the housing 12. The battery 22 is located at the rear of the housing 12. The battery 22 is electrically connected to the controller 20 .

[0027] (Regarding the Motor 24) The motor 24 is housed in a motor case 26 provided in the front portion of the housing 12 and is held by the motor case 26. The motor 24 has a rotating shaft 24A, which is disposed with its axial direction aligned with the front-to-rear direction. That is, the axis AL1 of the rotating shaft 24A extends along the front-to-rear direction and corresponds to the predetermined axis of the present invention. The rear end of the rotating shaft 24A is rotatably supported by a motor bearing 28 held in the motor case 26. The motor 24 is a brushless motor.

[0028] (Regarding the output shaft 30) The axial direction of the output shaft 30 is the vertical direction. The output shaft 30 is formed in a generally stepped cylindrical shape, and the diameter of the upper end of the output shaft 30 is set to be smaller than the diameter of the remaining portions. The output shaft 30 is provided within the front end portion of the housing 12, and the lower end of the output shaft 30 protrudes downward from the housing 12. The upper end of the output shaft 30 is rotatably supported by a bearing 32, and the vertical intermediate portion of the output shaft 30 is swingably supported by a bearing 34. The bearings 32 and 34 are held in a head case 36 housed within the housing 12.

[0029] The output shaft 30 is provided with a clamp mechanism 38 for attaching the tool bit T. The clamp mechanism 38 includes a clamp shaft 38A, a clamp lever 38B, and a clamp portion 38C. The clamp shaft 38A is disposed inside the output shaft 30 with the vertical direction as its axial direction. The clamp shaft 38A is connected to the output shaft 30 so as to be movable relative to the output shaft 30 in the vertical direction and to be rotatable integrally therewith. The clamp lever 38B extends in the front-rear direction, and the front end of the clamp lever 38B is connected to the housing 12 above the clamp shaft 38A so as to be rotatable about the left-right direction as its axial direction. The clamp portion 38C is provided at the lower end of the clamp shaft 38A. When the clamp lever 38B is rotated, the clamp shaft 38A is moved up and down by the clamp lever 38B, thereby switching the clamp portion 38C between a state in which the tool bit T is clamped and a state in which the tool bit T is released from its clamp state. When the tool bit T is clamped by the clamp portion 38C, the tool bit T protrudes forward from the lower end of the output shaft 30. The output shaft 30 is connected to a power transmission mechanism 40 (described later) and is configured to rotate back and forth around its own axis within a predetermined rotation angle by the power transmission mechanism 40. As a result, when the multi-tool 10 is in operation, the tool bit T held by the clamp shaft 38A swings left and right with the vertical direction as the axial direction by the power transmitted to the output shaft 30, and performs cutting or other processing on a workpiece with the tool bit T. The orientation of the tool bit T is changeable, and tool bits other than the tool bit T can be attached and detached.

[0030] 1 to 5, the power transmission mechanism 40 is housed within the housing 12 and is located between the motor 24 and the output shaft 30. The power transmission mechanism 40 includes a spindle 42, an eccentric shaft 48, a connecting piece 50 as a power transmission section, a swing arm 60, and a balance weight 70 as a blocking member.

[0031] The spindle 42 is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction and is positioned coaxially with the rotary shaft 24A of the motor 24, in front of the rotary shaft 24A. A spindle hole 42A serving as an insertion hole is formed in the axial center of the spindle 42. The spindle hole 42A penetrates the spindle 42 and the eccentric shaft 48 (described later) in the front-to-rear direction and is formed in a generally stepped hole shape. Specifically, the diameter of the front portion of the spindle hole 42A is set smaller than the diameter of the rear portion of the spindle hole 42A. The front end of the rotary shaft 24A is press-fitted into the rear end of the spindle hole 42A from the rear side, so that the spindle 42 is coupled to the rotary shaft 24A so as to be rotatable together with it.

[0032] The spindle 42 is rotatably supported at its front-rear intermediate portion by a bearing 44. The bearing 44 is held by a bearing holder 46 housed within the housing 12. A notch 42B is formed in the lower portion of the front end of the outer periphery of the spindle 42, and the notch 42B forms the front end of the spindle 42 into a generally D-shape when viewed from the front.

[0033] The eccentric shaft 48 is formed integrally with the spindle 42. The eccentric shaft 48 is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction and protruding forward from the front end of the spindle 42. The eccentric shaft 48 is disposed eccentrically with respect to the axis AL1 (in FIGS. 1 and 2, the axis AL2 of the eccentric shaft 48 is illustrated as being eccentrically positioned above the axis AL1). The internal space of the eccentric shaft 48 is defined as a shaft space 48A. As described above, because the rotating shaft 24A of the motor 24 is press-fitted into the spindle hole 42A from the rear, the shaft space 48A is formed in a recessed shape that is open to the front. The shaft space 48A is filled with a lubricant GR, such as grease.

[0034] A needle bearing 52 serving as a rolling member is provided radially outward of the eccentric shaft 48. The needle bearing 52 is formed in a generally cylindrical shape with its axial direction aligned in the front-to-rear direction. The needle bearing 52 includes cylindrical rollers 52A (rolling elements) and a cage 52B that holds the rollers 52A. The cage 52B holds the rollers 52A so that they do not move relative to each other in the front-to-rear and circumferential directions. The eccentric shaft 48 is inserted into the needle bearing 52, and the needle bearing 52 is rotatably supported by the eccentric shaft 48. As a result, when the eccentric shaft 48 rotates eccentrically about the axis line AL1, the needle bearing 52 also rotates eccentrically about the axis line AL1. Note that forward movement of the needle bearing 52 is restricted by a cover portion 51 of a connecting piece 50 (described later), and rearward movement of the needle bearing 52 is restricted by a balance weight 70 (described later). The rollers 52A are cylindrical and configured to be able to make line contact with the eccentric shaft 48. Therefore, compared to using spherical rolling elements such as ball bearings, the rollers tend to have a higher load-bearing capacity. Furthermore, when using ball bearings with inner and outer rings, they are often attached by press-fitting. However, press-fitting can cause dimensional changes in the parts, which can adversely affect their service life. In this embodiment, the rollers 52A are inserted to be positioned radially outward of the eccentric shaft 48, and their axial movement along the eccentric shaft 48 is determined by the lid portion 51 of the connecting piece 50 and the balance weight 70 (described later). This allows the rolling elements to be positioned without adverse effects such as dimensional changes.

[0035] The connecting piece 50 has a substantially cylindrical portion whose axial direction is the front-to-rear direction (the axial direction of the eccentric shaft 48). In other words, the connecting piece 50 has a cylindrical portion that partially penetrates in the front-to-rear direction. A needle bearing 52 is inserted into the connecting piece 50, and the connecting piece 50 is rotatably supported by the needle bearing 52. In other words, the connecting piece 50 is configured to be rotatable relative to the eccentric shaft 48 around the axial direction of the eccentric shaft 48 (axis line AL2). When the spindle 42 rotates, the connecting piece 50 eccentrically rotates together with the eccentric shaft 48 around the axis line AL1. When the connecting piece 50 is connected to the needle bearing 52, the rear end of the connecting piece 50 protrudes rearward from the needle bearing 52.

[0036] The outer peripheral surface of the connecting piece 50 is a spherical portion 50A. The spherical portion 50A has a partially spherical structure, as if one end and the other end of a sphere in a predetermined direction were cut in a direction perpendicular to the predetermined direction. The center of the spherical portion 50A is located at the center of the connecting piece 50 in the front-to-rear direction and on the axis AL2 of the eccentric shaft 48. Note that the center point of the spherical portion 50A does not necessarily have to be located on the axis AL2. For example, the eccentric momentum of the connecting piece 50 can be changed by shifting the position of the center point of the spherical portion 50A from the axis AL2.

[0037] An intermediate groove portion 50B is formed in the inner peripheral surface of the connecting piece 50 in the middle in the front-to-rear direction. The intermediate groove portion 50B is formed as a groove that opens radially inward of the connecting piece 50 and extends circumferentially of the connecting piece 50. The intermediate groove portion 50B is located radially outward of the rollers 52A of the needle bearing 52. The intermediate groove portion 50B is filled with lubricant GR. This allows the lubricant GR held in the intermediate groove portion 50B to be supplied to the rollers 52A.

[0038] In the connecting piece 50, the inner circumferential surfaces on both front-to-rear directions of the intermediate groove portion 50B serve as supported surfaces 50C, and the supported surfaces 50C are supported by the needle bearings 52. An end groove portion 50D is formed at the front end portion of the inner circumferential surface of the connecting piece 50. The end groove portion 50D is formed in the shape of a groove that opens radially inward of the connecting piece 50 and extends circumferentially of the connecting piece 50. The end groove portion 50D is located radially outward of the front end portion of the needle bearing 52.

[0039] A lid portion 51 serving as a connection portion is integrally formed at the front opening of the connecting piece 50. The lid portion 51 is formed in a generally circular plate shape with its thickness direction in the front-to-rear direction, and the lid portion 51 closes the front opening of the connecting piece 50. In other words, the lid portion 51 connects both left and right ends of the connecting piece 50 to each other.

[0040] The outer periphery of the rear surface of the lid portion 51 forms a restricting surface 51A, which is annular when viewed from the rear. The restricting surface 51A is located adjacent to the front side of the needle bearing 52 and restricts the needle bearing 52 from moving forward. That is, the needle bearing 52 is inserted into the eccentric shaft 48 so as to be movable relative to the eccentric shaft 48 in the front-rear direction, but this relative movement is restricted by the restricting surface 51A. A lid-side recess 51B is formed on the rear surface of the lid portion 51 radially inward of the restricting surface 51A. The lid-side recess 51B is formed in a concave shape that opens to the rear, and the open end of the lid-side recess 51B is connected to the radially inner end of the restricting surface 51A. The lid-side recess 51B is located in front of the eccentric shaft 48, and the lid-side recess 51B communicates with the axial space 48A of the eccentric shaft 48. The lid-side recess 51B is filled with lubricant GR. The front surface of the lid portion 51 is formed in a flat shape.

[0041] The swing arm 60 includes a fixed cylinder portion 61 and a pair of left and right arm portions 62. The fixed cylinder portion 61 is formed in a generally cylindrical shape with its axial direction extending vertically. The upper end portion of the output shaft 30 is fitted into the fixed cylinder portion 61, and the fixed cylinder portion 61 (swing arm 60) is connected to the output shaft 30 so as to be rotatable integrally therewith.

[0042] The pair of arm portions 62 extend rearward from the outer periphery of the fixed cylinder portion 61, with the rear end (tip) of the arm portion 62 positioned outside the connecting piece 50 in the left-right direction. An arm connecting portion 63 is provided between the pair of arm portions 62 on the front side of the connecting piece 50. The arm connecting portion 63 extends in the left-right direction and connects the pair of arm portions 62. As a result, a receiving-side power transmission portion 64 made up of the pair of arm portions 62 and the arm connecting portion 63 is formed at the rear end of the swing arm 60, and the receiving-side power transmission portion 64 is formed in a generally C-shape that is open rearward in plan view (viewed from above).

[0043] A pair of left and right receiving power transmission surfaces 64A are formed on the inner peripheral surface of the receiving power transmission portion 64. The receiving power transmission surfaces 64A extend in the vertical direction and are formed in a generally arc-like shape (C-shaped when viewed from above) that opens inward in the left-right direction in plan view to correspond to the spherical portion 50A of the connecting piece 50. The receiving power transmission surfaces 64A are disposed adjacent to the outer side of the connecting piece 50 in the left-right direction. The receiving power transmission surfaces 64A are curved (albeit slightly) more gently than the spherical portion 50A. Specifically, the curvature of the curved portion of the receiving power transmission surface 64A is greater than that of the spherical portion 50A, and the centers of the arcs (centers of circles that draw the same shape) are configured to be different between the receiving power transmission surface 64A and the spherical portion 50A. This is to prevent assembly difficulties that may occur when the inner arc is curved more gently outward due to manufacturing errors or the like when the arcs contact each other. Therefore, the spherical portion 50A is configured to be able to contact the receiving-side power transmission surface 64A only near the center in the fore-and-aft direction. That is, the spherical portion 50A is configured to be in point contact with the receiving-side power transmission surface 64A. As a result, when the eccentric shaft 48 eccentrically rotates about the axis AL1, the lateral power generated by the eccentric rotation of the eccentric shaft 48 is transmitted to the receiving-side power transmission portion 64 by the connecting piece 50, causing the receiving-side power transmission portion 64 to reciprocate in the lateral direction. As a result, the swing arm 60 swings in the lateral direction (clockwise and counterclockwise) about the axis AL3 of the output shaft 30, causing the output shaft 30 to reciprocate within a predetermined rotation angle (see the arrows in FIG. 3 ). That is, the connecting piece 50 and the receiving-side power transmission portion 64 of the swing arm 60 function as a portion for transmitting the power of the eccentric shaft 48 to the output shaft 30. The front end of the receiving-side power transmission surface 64A is located forward of the connecting piece 50.

[0044] The reason why the connecting piece 50 and the swing arm 60 are connected to each other by a curved structure (the receiving-side power transmission surface 64A and the spherical portion 50A) so as to be able to transmit power is to restrict the movement of the connecting piece 50 in the fore-and-aft direction (the axial direction of the eccentric shaft 48) relative to the eccentric shaft 48 by the swing arm 60. In other words, the connecting piece 50 is inserted onto the outer periphery of the needle bearing 52 so as to be able to move relative to the eccentric shaft 48 in the fore-and-aft direction, but this relative movement is restricted by the swing arm 60. This eliminates the need for a fixing means, such as press-fitting, which may result in dimensional changes, to position the connecting piece 50. In this embodiment, the movement of the connecting piece 50 is restricted by the swing arm 60 fixed to the output shaft 30. Furthermore, the movement of the needle bearing 52 is restricted by the connecting piece 50. Furthermore, the movement of the needle bearing 52 is restricted by a balance weight 70 (described below). Furthermore, movement of the connecting piece 50 is restricted by a balance weight 70 (described later).

[0045] A relief surface 64B is formed on the inner peripheral surface of the receiving power transmission portion 64 at the front (between the pair of receiving power transmission surfaces 64A). In a plan view, the relief surface 64B is formed in an arc shape that opens to the front, and is located one step lower radially outward of the connecting piece 50 than the receiving power transmission surfaces 64A. When the swing arm 60 swings, the spherical portion 50A of the connecting piece 50 slides on the receiving power transmission surfaces 64A and is not located radially inward of the relief surface 64B (see FIGS. 5A and 5B). Note that in FIGS. 5A and 5B, the swing arm 60 shown in FIG. 3 is indicated by a two-dot chain line.

[0046] The balance weight 70 is made of metal. The balance weight 70 has a balance main body 70A, which is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction. Specifically, the balance main body 70A has a hole 70B that penetrates in the front-to-rear direction, and the hole 70B is formed in a generally D-shape corresponding to the front end of the spindle 42 when viewed from the front-to-rear direction. The front end of the spindle 42 is fitted into the hole 70B, and the balance weight 70 is connected to the spindle 42 so as to be rotatable integrally therewith.

[0047] A weight portion 70C protruding radially outward is formed on the outer periphery of the lower portion of the balance main body 70A, and the weight portion 70C extends along the circumferential direction of the balance main body 70A. In other words, the weight portion 70C is located on the opposite side of the axis AL1 from the eccentric shaft 48. This allows the balance weight 70 to reduce vibrations caused by the eccentric rotation of the eccentric shaft 48 when the spindle 42 rotates. In addition, the front end of the balance main body 70A protrudes slightly forward of the spindle 42.

[0048] A restricting tube portion 70D serving as a restricting portion is provided at the front end of the balance main body 70A on the edge of the hole 70B. The restricting tube portion 70D is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction, protrudes forward from the balance main body 70A, and is disposed radially outward from the rear end of the eccentric shaft 48 with a predetermined gap therebetween. The front end of the restricting tube portion 70D is inserted into the rear end of the connecting piece 50 and disposed rearward of the needle bearing 52. As a result, the restricting tube portion 70D restricts rearward movement of the needle bearing 52 and closes the rear opening of the connecting piece 50.

[0049] (Operation and Effect) Next, the operation and effect of this embodiment will be described.

[0050] In the multi-tool 10 configured as described above, when the trigger switch 16 is turned on by sliding the trigger 14, the motor 24 is driven by the controller 20. When the motor 24 is driven, the spindle 42 rotates together with the rotary shaft 24A of the motor 24, and the eccentric shaft 48 rotates eccentrically about the axis AL1. As a result, the swing arm 60 swings left and right about the axis AL3 of the output shaft 30, the output shaft 30 rotates back and forth about its own axis, and the tool bit T swings left and right about the axis AL3 of the output shaft 30. Therefore, the tool bit T can perform cutting or other operations on the workpiece.

[0051] In the power transmission mechanism 40 of the multi-tool 10, the lateral power generated by the eccentric rotation of the eccentric shaft 48 is transmitted from the connecting piece 50 to the receiving power transmission portion 64 of the swing arm 60, and is also transmitted by the swing arm 60 to the output shaft 30. Therefore, if a part of the power transmission mechanism 40 (e.g., a part of the connecting piece 50 or the swing arm 60) is deformed in the lateral direction, a poor connection may occur, potentially reducing the durability of the power transmission mechanism 40 (the multi-tool 10).

[0052] Here, the connecting piece 50 is formed in a cylindrical shape with its axial direction extending in the front-to-rear direction, and the front opening of the connecting piece 50 is closed by the lid portion 51. That is, the lid portion 51 connects both left and right ends of the front end of the connecting piece 50. This allows the lid portion 51 to function as a reinforcing portion, effectively suppressing deformation of the connecting piece 50 in the left and right direction. As a result, the connection between the connecting piece 50 and the receiving-side power transmission portion 64 can be maintained in a good state. This improves the durability of the multi-tool 10.

[0053] In addition, by improving the connection between the connecting piece 50 and the receiving side power transmission part 64, it is possible to suppress the generation of vibrations and noise when the multi-tool 10 is in operation, and it is possible to efficiently transmit the left-right power from the eccentric shaft 48 to the output shaft 30.

[0054] Furthermore, a needle bearing 52 supported by the eccentric shaft 48 is provided inside the connecting piece 50, and the front opening of the connecting piece 50 is closed by the lid 51. This prevents the lubricant GR inside the connecting piece 50 from scattering from the front opening of the connecting piece 50 to the outside of the connecting piece 50. Therefore, the durability of the needle bearing 52 can be improved while improving the retention performance of the lubricant GR supplied to the needle bearing 52.

[0055] The lid portion 51 also has a restricting surface 51A and a lid-side recess 51B. The restricting surface 51A faces the needle bearing 52 in the front-rear direction and restricts the needle bearing 52 from moving forward. The lid-side recess 51B is located forward of the restricting surface 51A and is open to the rear. This allows the lid portion 51 to restrict the needle bearing 52 from moving forward while retaining the lubricant GR in the lid-side recess 51B. In other words, the volume of the connecting piece 50 that can be filled with the lubricant GR can be increased. As a result, the amount of lubricant GR in the connecting piece 50 can be increased, further improving the durability of the needle bearing 52. Note that when the eccentric shaft 48 rotates, the temperature inside the connecting piece 50 rises, causing the lubricant GR to liquefy and flow to the needle bearing 52 radially outward of the eccentric shaft 48. As a result, the lubricant GR in the cover-side recess 51B is supplied to the needle bearing 52.

[0056] Furthermore, a shaft space 48A that is open to the front is formed inside the eccentric shaft 48, and a cover-side recess 51B is disposed in front of the eccentric shaft 48. This allows the shaft space 48A to be connected to the cover-side recess 51B, and the lubricant GR can be held in the cover-side recess 51B. This further increases the volume of the connecting piece 50 that can be filled with the lubricant GR. As a result, the amount of lubricant GR in the connecting piece 50 is further increased, further improving the durability of the needle bearing 52. As described above, when the eccentric shaft 48 rotates, the temperature inside the connecting piece 50 increases, causing the lubricant GR in the shaft space 48A to liquefy and be discharged from the shaft space 48A to the front side of the eccentric shaft 48. The discharged lubricant GR then flows to the needle bearing 52 radially outward of the eccentric shaft 48. This allows the lubricant GR in the cover-side recess 51B to be supplied to the needle bearing 52. In addition, because the shaft space 48A communicates with the spindle hole 42A, the spindle hole 42A can also be used as a filling space for the lubricant GR. Because the shaft space 48A communicates with the spindle hole 42A, both can be formed by boring in one process, which also leads to reduced manufacturing costs.

[0057] The inner peripheral surface of the connecting piece 50 is configured to include an intermediate groove portion 50B that opens radially inward of the connecting piece 50, and supported surfaces 50C that are located on both front-to-rear sides of the intermediate groove portion 50B. The intermediate groove portion 50B is filled with lubricant GR, and the supported surfaces 50C are supported by the needle bearings 52. This allows the needle bearings 52 to support the supported surfaces 50C, while efficiently supplying the lubricant GR in the intermediate groove portion 50B to the needle bearings 52.

[0058] An end groove portion 50D is formed at the front end portion of the inner circumferential surface of the connecting piece 50. As a result, for example, when the lubricant GR in the cover-side recess 51B or the shaft space portion 48A of the eccentric shaft 48 flows radially outward of the eccentric shaft 48, the flowed lubricant GR can be held by the end groove portion 50D. Therefore, the lubricant GR held in the end groove portion 50D can be supplied to the needle bearing 52.

[0059] A balance weight 70 is provided on the rear side of the connecting piece 50, and the balance weight 70 closes the rear opening of the connecting piece 50 radially outward from the eccentric shaft 48. Specifically, a restricting cylindrical portion 70D of the balance weight 70 protrudes forward from the balance main body portion 70A, and the tip of the restricting cylindrical portion 70D is inserted into the rear end portion of the connecting piece 50. This prevents the lubricant GR inside the connecting piece 50 from scattering outside the connecting piece 50 through the rear opening of the connecting piece 50. This further improves the lubricant GR retention performance of the connecting piece 50.

[0060] Furthermore, the tip of the restricting tube portion 70D is disposed within the rear end of the needle bearing 52, restricting its rearward movement. This allows the restricting tube portion 70D, which closes the rear opening of the connecting piece 50, to be used to restrict the rearward movement of the needle bearing 52. This contributes to reducing the number of parts and assembly steps compared to a configuration in which a separate member is provided to restrict the movement of the needle bearing 52. Furthermore, because the rearward movement of the connecting piece 50 is restricted by the needle bearing 52, whose rearward movement is restricted by the restricting tube portion 70D, a positioning member for the connecting piece 50 is not required. In other words, because the longitudinal movement of the needle bearing 52 is restricted by the connecting piece 50 and the balance weight 70, a positioning member for the needle bearing 52 is not required. Note that with this positioning structure, the lid portion 51 does not necessarily need to completely cover the front opening of the connecting piece 50. That is, when the positioning structure of the needle bearing 52 according to the present invention is employed, the cover-side recess 51B may be omitted.

[0061] (Regarding Modification 1 of Power Transmission Mechanism 40) Modification 1 of the power transmission mechanism 40 will be described below with reference to Fig. 6. Modification 1 of the power transmission mechanism 40 is configured similarly to the power transmission mechanism 40 of the first embodiment, except for the following points. Note that in Fig. 6, the same reference numerals are used to designate members configured similarly to the power transmission mechanism 40 of the first embodiment.

[0062] As shown in this figure, in the first modification of the power transmission mechanism 40, a first washer 80 serving as a connecting portion is attached to the front end of the connecting piece 50 instead of the cover portion 51. That is, the first washer 80 and the connecting piece 50 are separate members. The first washer 80 is formed in a generally circular plate shape with its thickness extending in the front-to-rear direction. The first washer 80 is inserted into the front end of the connecting piece 50, and the outer periphery of the first washer 80 is inserted into a front locking groove 50E formed in the inner circumferential surface of the connecting piece 50 to be locked to the connecting piece 50. The front locking groove 50E extends circumferentially around the connecting piece 50. As a result, the first washer 80 closes the front opening of the connecting piece 50 and restricts the needle bearing 52 from moving forward.

[0063] Furthermore, in the first modified example of the power transmission mechanism 40, the restricting cylindrical portion 70D is omitted from the balance weight 70, and a second washer 82 serving as a blocking member is attached to the rear end of the connecting piece 50. The second washer 82 is formed in a generally annular plate shape with its thickness in the front-to-rear direction. The second washer 82 is inserted into the rear end of the connecting piece 50, and the outer periphery of the second washer 82 is inserted into a rear locking groove 50F formed in the inner circumferential surface of the connecting piece 50 to be locked to the connecting piece 50. The rear locking groove 50F extends circumferentially around the connecting piece 50. As a result, the second washer 82 blocks the rear opening of the connecting piece 50 and restricts rearward movement of the needle bearing 52.

[0064] In the first modification, the first washer 80 also closes the front opening of the connecting piece 50 and connects both left and right ends of the front end of the connecting piece 50 together. This effectively prevents the connecting piece 50 from deforming inward in the left and right direction. As a result, the connection between the connecting piece 50 and the receiving power transmission part 64 can be maintained in a good condition. This improves the durability of the multi-tool 10.

[0065] As described above, in the first modification, the first washer 80 closes the front opening of the connecting piece 50, and the second washer 82 closes the rear opening of the connecting piece 50. Therefore, the first washer 80 and the second washer 82 can prevent the lubricant GR from scattering outside the connecting piece 50. This allows the lubricant GR to be well retained within the connecting piece 50. As a result, similar to the first embodiment, the durability of the needle bearing 52 can be improved, and ultimately the durability of the multi-tool 10 can be improved.

[0066] (Second Modification of Power Transmission Mechanism 40) Hereinafter, a second modification of the power transmission mechanism 40 will be described with reference to Fig. 7. The second modification of the power transmission mechanism 40 is configured similarly to the power transmission mechanism 40 of the first embodiment, except for the following points. In Fig. 7, the same reference numerals are used to designate members that are configured similarly to the power transmission mechanism 40 of the first embodiment.

[0067] As shown in this figure, in Modification 2 of the power transmission mechanism 40, a protruding protrusion 51C is formed in the central portion of the lid portion 51 of the connecting piece 50, and the lid-side recess 51B of the lid portion 51 is formed on the protrusion 51C. That is, the depth of the lid-side recess 51B is greater than that of the first embodiment. As a result, in Modification 2, the amount of lubricant GR retained in the lid-side recess 51B can be increased compared to the first embodiment. Therefore, the durability of the needle bearing 52 can be further improved. Furthermore, the leading end (front end) of the protrusion 51C is located within the rear end of the clearance surface 64B of the swing arm 60. This allows the protrusion 51C to be provided on the lid portion 51 by utilizing the area of ​​the clearance surface 64B that does not come into contact with the connecting piece 50 when the swing arm 60 swings.

[0068] In the second modification of the power transmission mechanism 40, a shaft groove 48B is formed on the outer periphery of the eccentric shaft 48. The shaft groove 48B extends circumferentially around the eccentric shaft 48 and is formed around the entire circumference of the eccentric shaft 48. The longitudinal position of the shaft groove 48B coincides with the longitudinal position of the intermediate groove 50B of the connecting piece 50. That is, the shaft groove 48B and the intermediate groove 50B are radially opposed to each other across the needle bearing 52, and the shaft groove 48B is located radially inside the rollers 52A of the needle bearing 52. The lubricant GR is held in the shaft groove 48B. This allows the lubricant GR to be supplied to the needle bearing 52 from the radially inner side of the needle bearing 52. This more effectively improves the durability of the needle bearing 52.

[0069] In the second modification, the raised portion 51C is formed on the cover portion 51 and the shaft side groove portion 48B is formed on the eccentric shaft 48, but one of the raised portion 51C and the shaft side groove portion 48B may be omitted.

[0070] Second Embodiment A multi-tool 100 as a work tool according to a second embodiment will be described below with reference to Figures 8 and 9. The second embodiment is configured similarly to the first embodiment, except for the following points. In Figures 8 and 9, the same reference numerals are used to designate components that are similar to those in the first embodiment.

[0071] As shown in these figures, in the multi-tool 100, a power transmission mechanism 140 is housed in the housing 12 instead of the power transmission mechanism 40 of the first embodiment. The power transmission mechanism 140 includes the spindle 42 (not shown in FIGS. 8 and 9 ) used in the first embodiment, an eccentric shaft 48 formed integrally with the spindle 42, a needle bearing 152 as a rolling member, and a swing arm 160 as a power transmission member.

[0072] In the second embodiment, the eccentric shaft 48 does not include the shaft space 48A, and the eccentric shaft 48 is formed in a substantially cylindrical shape. A connecting piece 150 is provided radially outward of the eccentric shaft 48. The connecting piece 150 is formed in a substantially cylindrical shape with its axial direction extending in the front-to-rear direction. The eccentric shaft 48 is press-fitted into the connecting piece 150, and the connecting piece 150 is fixed to the eccentric shaft 48 so as to be rotatable integrally therewith. As a result, when the spindle 142 rotates, the eccentric shaft 48 and the connecting piece 150 eccentrically rotate about the axis AL1. When the connecting piece 150 is fixed to the eccentric shaft 48, the front end of the eccentric shaft 48 protrudes slightly forward from the connecting piece 150. The outer peripheral surface of the connecting piece 150 is formed as a spherical surface portion 150A. The center point of the spherical portion 150A is located at the center of the connecting piece 150 in the front-rear direction and on the axis AL2 of the eccentric shaft 48. Note that the center point of the spherical portion 150A does not necessarily have to be located on the axis AL2. For example, the eccentric momentum of the connecting piece 150 can be changed by shifting the position of the center point of the spherical portion 150A from the axis AL2.

[0073] The needle bearing 152 is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction. The needle bearing 152 includes rollers 152A (rolling elements) and a cage 152B that holds the rollers 152A. The connecting piece 150 is inserted into the needle bearing 152, and the needle bearing 152 is rotatably supported by the connecting piece 150. In other words, the needle bearing 152 is indirectly rotatably supported by the eccentric shaft 48. As a result, when the eccentric shaft 48 and the connecting piece 150 rotate eccentrically about the axis line AL1, the needle bearing 152 also rotates eccentrically about the axis line AL1. The needle bearing 152 is housed in a cylindrical power transmission portion 164 of the swing arm 160, which will be described later, and the needle bearing 152 and the swing arm 160 are unitized.

[0074] The swing arm 160 is configured to include a fixed cylindrical portion 161 as a fixed portion that forms the front portion of the swing arm 160, a pair of left and right intermediate arm portions 162 that form the intermediate portion of the swing arm 160 in the front-to-rear direction, and a cylindrical power transmission portion 164 that forms the rear end portion of the swing arm 160. The fixed cylindrical portion 161 is formed in a substantially cylindrical shape with the axial direction extending in the up-down direction. The upper end portion of the output shaft 30 is press-fitted into the fixed cylindrical portion 161, and the fixed cylindrical portion 161 (swing arm 160) is fixed to the output shaft 30 so as to be rotatable integrally therewith.

[0075] The pair of left and right intermediate arms 162 are respectively disposed on the left and right outer sides of the left and right center of the fixed cylinder 161, and extend rearward from the outer periphery of the fixed cylinder 161. The rear ends of the intermediate arms 162 are connected to a cylindrical power transmission part 164, which will be described later.

[0076] The cylindrical power transmission part 164 is formed in a generally cylindrical shape with its axial direction extending in the front-rear direction. The rear end of the intermediate arm part 162 described above is connected to a vertically intermediate part of the outer end of the cylindrical power transmission part 164 in the left-right direction. FIG. 8A shows a cross section taken along line 8A-8A in FIG. 8B. Note that FIG. 8A is a schematic cross-sectional view comparing the shapes of the connecting piece 150 and the cylindrical power transmission part 164. The outer diameter position of the needle bearing 152 is indicated by a two-dot chain line, and specific illustrations of the lubricant GR, lubricant supply groove 164A, rollers 152A, and retainer 152B are omitted. As shown in FIG. 8A, the cylindrical power transmission part 164 has a shape close to an ellipse, like a perfect circle extended in the vertical direction, when viewed from the front-rear direction, and is formed in a generally track-like shape with the vertical direction as the longitudinal direction. In other words, when viewed from the front-to-rear direction, the cylindrical power transmission part 164 has a shape in which a perfect circle is divided into upper and lower parts from the center, and the ends are connected by a gentle curve. In other words, when viewed from the front-to-rear direction, the cylindrical power transmission part 164 has a circular shape in which the upper and lower parts are circles with a small curvature in parts, and the middle part is a part of a circle with a larger curvature than the upper and lower parts. The upper, lower, and middle parts have portions with a constant curvature, which makes it different from an ellipse. The left-to-right dimension of the inner peripheral part of the cylindrical power transmission part 164 is set to be slightly larger than the diameter of the needle bearing 152, and the up-to-down dimension of the inner peripheral part of the cylindrical power transmission part 164 is set to be larger than the diameter of the needle bearing 152. The needle bearing 152 is inserted into the cylindrical power transmission part 164 from the rear and accommodated so as to be rotatable relative to the cylindrical power transmission part 164. When the needle bearing 152 is housed in the cylindrical power transmission portion 164, the dimensions of the eccentric shaft 48 and the cylindrical power transmission portion 164 in the front-to-rear direction are set so that the eccentric shaft 48 does not protrude forward beyond the cylindrical power transmission portion 164.

[0077] Furthermore, when the needle bearing 152 is housed in the cylindrical power transmission part 164, relative movement of the needle bearing 152 with respect to the cylindrical power transmission part 164 in the left-right direction is restricted, but relative movement of the needle bearing 152 with respect to the cylindrical power transmission part 164 in the up-down direction is permitted. In other words, the needle bearing 152 is connected to the cylindrical power transmission part 164 so as to be immovable relative to the cylindrical power transmission part 164 in the left-right direction but movable relative to the cylindrical power transmission part 164 in the up-down direction.

[0078] As a result, when the eccentric shaft 48 and the connecting piece 150 rotate eccentrically about the axis line AL1, the needle bearing 152 reciprocates left and right together with the cylindrical power transmission part 164 and also moves up and down relative to the cylindrical power transmission part 164. That is, the cylindrical power transmission part 164 receives only the left and right power generated by the eccentric rotation of the eccentric shaft 48 and moves reciprocally left and right. As a result, the swing arm 160 swings left and right (clockwise and counterclockwise) about the axis line AL3 of the output shaft 30, and the output shaft 30 rotates reciprocally within a predetermined rotation angle (see arrows in FIG. 9 ). That is, the swing arm 160 receives the left and right power generated by the eccentric rotation of the eccentric shaft 48 and transmits the power to the output shaft 30. The vertical dimension of the cylindrical power transmission part 164 is set so as to allow the needle bearing 152 to move relative to the cylindrical power transmission part 164 in the vertical direction during eccentric rotation of the eccentric shaft 48 .

[0079] A lubricant supply groove 164A is formed in the inner periphery of the cylindrical power transmission part 164. The lubricant supply groove 164A is located in the middle of the cylindrical power transmission part 164 in the front-rear direction, extends circumferentially of the cylindrical power transmission part 164, and is formed over the entire circumferential direction of the cylindrical power transmission part 164. The lubricant supply groove 164A is located radially outward of the rollers 152A of the needle bearing 152. The lubricant supply groove 164A is filled with lubricant GR. This allows the lubricant GR in the lubricant supply groove 164A to be supplied to the rollers 152A.

[0080] A retaining ring 166 is provided as a sealing member on the inner periphery of the cylindrical power transmission part 164, rearward of the lubricant supply groove 164A. The retaining ring 166 is formed in a generally circular plate shape with its thickness aligned in the front-to-rear direction and partially open. The outer periphery of the retaining ring 166 is engaged with a locking groove 164B formed in the inner periphery of the cylindrical power transmission part 164, and the inner periphery of the retaining ring 166 protrudes radially inward from the inner periphery of the cylindrical power transmission part 164. This restricts rearward movement of the needle bearing 152 housed in the cylindrical power transmission part 164. The retaining ring 166 also prevents the lubricant GR filled in the lubricant supply groove 164A from leaking out toward the rear opening of the cylindrical power transmission part 164.

[0081] A lid portion 165 serving as a connection portion is integrally formed at the front opening of the cylindrical power transmission portion 164. The lid portion 165 is formed in a generally circular plate shape with its thickness direction in the front-to-rear direction, and the lid portion 165 closes the front opening of the cylindrical power transmission portion 164. In other words, both left and right ends of the cylindrical power transmission portion 164 are connected to each other by the lid portion 165. In addition, the lid portion 165 restricts the forward movement of the needle bearing 152 housed in the cylindrical power transmission portion 164.

[0082] In the power transmission mechanism 140 of the second embodiment, the cylindrical power transmission part 164 receives the power in the left-right direction generated by the eccentric rotation of the eccentric shaft 48 and transmits it to the output shaft 30. Specifically, the cylindrical power transmission part 164 receives the power via the needle bearings 152 inside the cylindrical power transmission part 164 and transmits it to the output shaft 30. Therefore, if the cylindrical power transmission part 164 were to deform outward in the left-right direction, backlash in the left-right direction would occur between the needle bearings 152 and the cylindrical power transmission part 164, which could reduce the durability of the power transmission mechanism 140 (multi-tool 100).

[0083] Here, the cylindrical power transmission part 164 is formed in a cylindrical shape with its axial direction extending in the front-to-rear direction. This allows for less deformation of the cylindrical power transmission part 164 in the left-to-right direction compared to, for example, a structure in which the power transmission part of a swing arm is configured with a pair of left and right arm parts. Furthermore, the front opening of the cylindrical power transmission part 164 is closed by the lid part 165. That is, the lid part 165 connects both left and right ends of the front end of the cylindrical power transmission part 164 to each other. This allows the lid part 165 to function as a reinforcing part, effectively suppressing left-to-right deformation of the cylindrical power transmission part 164. As a result, left-to-right play between the needle bearing 152 and the cylindrical power transmission part 164 can be suppressed. This improves the durability of the multi-tool 100.

[0084] In addition, by suppressing the occurrence of left-right play between the needle bearing 152 and the cylindrical power transmission part 164, the generation of vibration and noise when the multi-tool 100 is in operation can be suppressed, and the left-right power from the eccentric shaft 48 can be efficiently transmitted to the output shaft 30.

[0085] In the power transmission mechanism 140 of the multi-tool 100, the connecting piece 150 is disposed radially outward of the eccentric shaft 48 and is fixed to the eccentric shaft 48 so as to be rotatable therewith. Furthermore, a needle bearing 152 is rotatably supported on the connecting piece 150 and transmits power generated by the eccentric rotation of the eccentric shaft 48 to the swing arm 160. This allows the use of a larger diameter needle bearing 152 compared to a configuration in which the needle bearing 152 is disposed between the eccentric shaft 48 and the connecting piece 150 (hereinafter referred to as the comparative configuration). This allows the needle bearing 152 of the second embodiment to have a larger number of rollers 152A and a higher load rating than the needle bearing of the comparative configuration. This improves the durability of the needle bearing 152 and ultimately the durability of the multi-tool 100.

[0086] Furthermore, the cylindrical power transmission part 164 is formed in a generally track shape with the vertical direction as the longitudinal direction, and the needle bearing 152 is housed within the cylindrical power transmission part 164 so as to be able to rotate relative to the cylindrical power transmission part 164. Specifically, the needle bearing 152 is connected to the cylindrical power transmission part 164 so as to be immovable relative to the cylindrical power transmission part 164 in the left-right direction but movable relative to the cylindrical power transmission part 164 in the up-down direction. As a result, even though the cylindrical power transmission part 164 is formed in a cylindrical shape, the cylindrical power transmission part 164 receives only left-right power from the needle bearing 152, and the swing arm 160 can be swung in the left-right direction.

[0087] A lubricant supply groove 164A is formed in the inner periphery of the cylindrical power transmission part 164. The lubricant supply groove 164A extends circumferentially around the cylindrical power transmission part 164 and is located radially outward of the needle bearing 152. The lubricant supply groove 164A is filled with the lubricant GR. This allows the lubricant GR to be efficiently supplied to the needle bearing 152. This further improves the durability of the multi-tool 100.

[0088] Furthermore, when the eccentric shaft 48 is housed in the cylindrical power transmission portion 164, the eccentric shaft 48 is inserted into the cylindrical power transmission portion 164 from the rear side and does not protrude forward beyond the cylindrical power transmission portion 164. In other words, the front end of the eccentric shaft 48 is located rearward of the front end of the cylindrical power transmission portion 164. As a result, even if lubricant GR adheres to the front end of the eccentric shaft 48, the lubricant GR is scattered toward the inner circumferential surface of the cylindrical power transmission portion 164 due to centrifugal force when the eccentric shaft 48 rotates. Therefore, the lubricant GR adhered to the eccentric shaft 48 can be circulated again to the inner circumferential surface of the cylindrical power transmission portion 164.

[0089] Furthermore, in the swing arm 160, the front opening of the cylindrical power transmission part 164 is closed by the lid part 165. This makes it possible to prevent the lubricant GR from scattering forward from the cylindrical power transmission part 164. This improves the ability of the cylindrical power transmission part 164 to retain the lubricant GR, and also makes it possible to prevent the lubricant GR from scattering toward the output shaft 30.

[0090] Furthermore, a retaining ring 166 is provided on the inner periphery of the cylindrical power transmission part 164, behind the lubricant supply groove 164A. The retaining ring 166 protrudes radially inward from the inner periphery of the cylindrical power transmission part 164, and restricts rearward movement of the needle bearing 152. This makes it possible to utilize the retaining ring 166, which prevents the needle bearing 152 from falling out of the cylindrical power transmission part 164, to block the lubricant GR from flowing toward the rear opening of the cylindrical power transmission part 164. This further improves the lubricant GR retention performance of the cylindrical power transmission part 164.

[0091] Third Embodiment A multi-tool 200 according to a third embodiment will now be described with reference to Figures 10 to 12. The multi-tool 200 has the same configuration as the multi-tool 100 according to the second embodiment, except for the following points. In Figures 10 to 12, the same reference numerals are used to designate components that are similar to those of the multi-tool 100 according to the second embodiment.

[0092] In the third embodiment, the swing arm 160 of the power transmission mechanism 140 is divided into two parts, front and rear. Specifically, the swing arm 160 is composed of a fixed cylinder portion 161 that forms the front portion of the swing arm 160 and a cylindrical power transmission portion 164 that forms the rear portion of the swing arm 160. A support pillar 161A is provided at the rear end of the fixed cylinder portion 161 to rotatably support the cylindrical power transmission portion 164. The support pillar 161A is formed in a substantially rectangular pillar shape that extends in the front-rear direction and extends rearward from the rear end of the fixed cylinder portion 161. A support hole 161B is formed in the rear end of the support pillar 161A and penetrates in the left-right direction.

[0093] A pair of left and right supported portions 164C are integrally formed on the front surface of the lid portion 165 of the cylindrical power transmission portion 164. The supported portions 164C are formed in the shape of a substantially rectangular block extending in the left-right direction and are disposed adjacent to the outer left-right sides of the support pillar 161A. A support shaft 167, whose axial direction is the left-right direction, spans the pair of supported portions 164C. The support shaft 167 is inserted into the support hole 161B and is rotatably supported by the support hole 161B. This allows the cylindrical power transmission portion 164 to be rotatably connected to the fixed cylindrical portion 161 with the left-right direction as its axial direction.

[0094] In the third embodiment, the cylindrical power transmission part 164 is formed in a perfect circular shape when viewed from the front-rear direction, and the needle bearing 152 is housed in the cylindrical power transmission part 164 so as not to move relatively in the radial direction. In other words, the needle bearing 152 is connected to the cylindrical power transmission part 164 so as not to move relatively in the up-down direction or the left-right direction.

[0095] When the eccentric shaft 48 is driven by the motor 24 to rotate eccentrically, as in the second embodiment, the cylindrical power transmission portion 164 of the swing arm 160 reciprocates left and right, the swing arm 160 swings left and right about the axis line AL3 of the output shaft 30, and the output shaft 30 rotates reciprocally within a predetermined rotation angle. When the eccentric shaft 48 rotates eccentrically, the cylindrical power transmission portion 164, together with the needle bearing 152, swings up and down around the axis of the support shaft 167 relative to the fixed cylindrical portion 161, while receiving power from the eccentric shaft 48. Specifically, when the eccentric shaft 48 rotates once from an eccentric position upward, the state transitions from the state shown in FIG. 12(A) to the state shown in FIG. 12(B) via the state shown in FIG. 12(C), and from the state shown in FIG. 12(C) to the state shown in FIG. 12(B) via the state shown in FIG. 12(A). As a result, the fixed cylindrical portion 161 receives power only in the left-right direction from the cylindrical power transmission portion 164, and the swing arm 160 as a whole swings left-right.

[0096] In the third embodiment, the tubular power transmission part 164 is also formed in a tubular shape with its axial direction extending in the front-to-rear direction. The front opening of the tubular power transmission part 164 is closed by the cover part 165. This effectively prevents the tubular power transmission part 164 from deforming in the left-to-right direction in the third embodiment. Therefore, the durability of the multi-tool 200 can be improved in the third embodiment.

[0097] In the swing arm 160 of the second and third embodiments, the front end of the cylindrical power transmission part 164 is closed by the cover part 165. However, the cover part 165 may be omitted from the swing arm 160. In this case, as shown in FIG. 13A , in the swing arm 160 of the second embodiment, the intermediate arm part 162 is formed in a generally U-shaped block shape that is open toward the rear in a plan view. The left and right ends of the intermediate arm part 162 are connected to the left and right ends of the cylindrical power transmission part 164, and the left and right middle part of the intermediate arm part 162 is connected to the rear end of the fixed cylindrical part 161. As a result, the left and right ends of the cylindrical power transmission part 164 are connected to each other by the intermediate arm part 162. Therefore, in the example shown in FIG. 13A , the intermediate arm part 162 corresponds to the connecting part of the present invention.

[0098] 13B, in the swing arm 160 of the third embodiment, the outer left-right end portions of the supported portion 164C are connected to both left-right ends of the cylindrical power transmission portion 164. As a result, both left-right ends of the cylindrical power transmission portion 164 are connected to each other by the supported portion 164C and the support shaft 167. Therefore, in the example shown in FIG. 13B, the supported portion 164C and the support shaft 167 correspond to the connecting portion of the present invention.

[0099] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the motor is arranged so that its rotation shaft is aligned in the front-rear direction, but it may be arranged so that it is aligned in the up-down direction, or it may be arranged at an angle using a bevel gear or the like.

[0100] 10... Multi-tool (work machine), 24... Motor, 30... Output shaft, 42... Spindle, 42A... Spindle hole (insertion hole), 48... Eccentric shaft, 48A... Shaft space portion, 50... Connecting piece (power transmission portion), 50B... Intermediate groove portion, 50C... Supported surface, 50D... End groove portion, 51... Lid portion (connection portion), 51A... Regulating surface, 51B... Lid side recess (recess), 52... Needle bearing (rolling member), 70... Balance weight (blocking member), 70A... Balance main body portion, 7 0D...Regulating cylindrical portion (regulating portion), 80...First washer (connecting portion), 82...Second washer (blocking member), 100...Multi-tool (working machine), 152...Needle bearing (rolling member), 160...Swing arm (power transmission member), 161...Fixed cylindrical portion (fixing portion), 164...Cylindrical power transmission portion (power transmission portion), 164A...Lubricant supply groove (groove portion), 165...Cover portion (connecting portion), 166...Retaining ring (sealing portion), 200...Multi-tool (working machine), AL1...Axis (predetermined axis)

Claims

1. A work machine comprising: a motor; an eccentric shaft that extends in a predetermined direction and rotates eccentrically about a predetermined axis extended in the predetermined direction by a driving force of the motor transmitted from one end of the motor in the predetermined direction; an output shaft that rotates back and forth about its own axis by transmitting power from the eccentric shaft; a power transmission unit that is formed in a cylindrical shape with its axial direction in the predetermined direction and that transmits orthogonal power that is generated by the eccentric rotation of the eccentric shaft and is perpendicular to the predetermined direction to the output shaft; and a connection unit that covers at least a portion of one end of the cylindrical power transmission unit in the predetermined direction and is configured to be operable integrally with the power transmission unit, and that connects both ends of the power transmission unit in the orthogonal direction.

2. The work machine according to claim 1, wherein the power transmission unit is a connecting piece made up of a single member, a rolling member supported by the eccentric shaft is provided inside the connecting piece and transmits the power to the power transmission unit, and the connecting unit is formed integrally with one end of the connecting piece in the specified direction, or the connecting unit is made up of a separate member from the connecting piece and is attached to one end of the connecting piece in the specified direction.

3. A work machine according to claim 2, wherein the connection portion closes an opening on one side of the connecting piece in the predetermined direction.

4. A work machine as described in claim 3, wherein the connection portion has a regulating surface that faces the rolling member in the specified direction and regulates movement of the rolling member to one side in the specified direction, and a recess that is positioned to one side of the regulating surface in the specified direction and is open to the other side in the specified direction.

5. A work machine as described in claim 4, wherein the motor has a rotating shaft, and the eccentric shaft has an insertion hole into which the rotating shaft is inserted, and an axial space portion that communicates with the insertion hole and is open to one side in the predetermined direction.

6. A work machine as described in claim 2, wherein the inner peripheral surface of the connecting piece is configured to include an intermediate groove portion that is open radially inward of the connecting piece, and supported surfaces that are arranged on both sides of the intermediate groove portion in the specified direction and are supported by the rolling members, and wherein a lubricant is filled in the intermediate groove portion.

7. A work machine as described in claim 2, wherein an end groove portion that opens radially inward of the connecting piece is formed on the inner peripheral surface of the connecting piece at one end on one side in the predetermined direction.

8. A work machine as described in claim 3, wherein the eccentric shaft is inserted into the connecting piece from the other side in the specified direction, and a blocking member is provided on the other side in the specified direction of the connecting piece, radially outside the eccentric shaft, to block the opening on the other side in the specified direction of the connecting piece.

9. A work machine according to claim 8, wherein the blocking member is a balance weight configured to be rotatable integrally with the eccentric shaft about the predetermined axis.

10. A work machine as described in claim 9, wherein the balance weight comprises: a balance main body portion connected to the eccentric shaft; and a regulating portion that protrudes from the balance main body portion to one side in the specified direction and is positioned on the other side of the rolling member in the specified direction to regulate movement of the rolling member to the other side in the specified direction.

11. A work machine as described in claim 10, wherein the restricting portion closes the opening on the other side of the connecting piece in the specified direction, and the tip portion is positioned inside the connecting piece from the other side in the specified direction.

12. A work machine according to claim 1, wherein the eccentric shaft is connected to the power transmission section so as to be capable of relative rotation.

13. A work machine as described in claim 1, wherein a power transmission member having the power transmission unit is connected to the output shaft so as to be rotatable integrally therewith, and when the eccentric shaft rotates eccentrically, the power transmission unit moves back and forth in the perpendicular direction and the output shaft rotates back and forth.

14. A work machine comprising: a motor; an eccentric shaft that extends in a predetermined direction and rotates eccentrically about an axis extending in the predetermined direction by the driving force of the motor transmitted from one end of the motor in the predetermined direction; an output shaft that rotates back and forth about its own axis by transmitting power from the eccentric shaft; and a connecting piece that is formed as a single container-like part that has a cylindrical portion whose axial direction is in the predetermined direction and a lid portion that closes the end of the cylindrical portion in the predetermined direction and is open on the other side of the predetermined direction, and that transmits power in a direction perpendicular to the predetermined direction that is generated by the eccentric rotation of the eccentric shaft to the output shaft.

15. A work machine as described in claim 14, wherein a needle bearing is provided between the eccentric shaft and the cylindrical portion, a swing arm is provided on the output shaft for transmitting the orthogonal power from the connecting piece to the output shaft, the connecting piece is arranged around the needle bearing so as to be movable relative to the eccentric shaft in the predetermined direction, and movement in the predetermined direction is restricted by the swing arm, and the needle bearing is configured so as to be movable relative to the eccentric shaft in the predetermined direction, and movement in the predetermined direction is restricted by the cover portion.

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