Power transmission mechanism for robot for transmitting rotational force and drive device for robot

Abstract

A power transmission mechanism of a robot includes a wave gear reducer including: a wave generating member including an elliptical cam; the elastic cylindrical part is provided with a first tooth part; and an annular member having a second tooth section that engages with the first tooth section. A shaft for transmitting the rotational force of a motor has a spline shaft portion having a convex portion formed on the outer peripheral surface thereof. The fluctuation generating member includes an insertion hole having a shape of a recess corresponding to a shape of a protrusion of the spline shaft portion. There is a gap between the spline shaft portion and the insertion hole such that the fluctuation generating member is moved and aligned by the elasticity of the elastic cylindrical member.

Description

Technical Field

[0001] The present invention relates to a power transmission mechanism of a robot for transmitting rotational force and a driving device of the robot. Background Art

[0002] The robot can change the position and posture of the working tool by driving components such as arms. The robot is equipped with a driving device including an electric motor for moving the components. For example, when the robot has a joint, the driving device for moving the components is arranged at the joint. The driving device includes a power transmission mechanism for transmitting rotational force from one component to other components.

[0003] It is known that a speed reducer is arranged in a power transmission mechanism in order to amplify the rotational force of the motor. As a speed reducer, in addition to a gear speed reducer having a structure in which a plurality of gears mesh with each other, a wave gear speed reducer having an elliptical component to which a rotational force is input is also known (for example, Japanese Patent Publication No. 2021-175916). The wave gear speed reducer has the characteristics of a small number of parts and a small size. It is known that a wave gear speed reducer is used in a driving device of a robot (for example, Japanese Patent Publication No. 3-202292).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-175916

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 3-202292 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The driving device transmits the rotational force of the shaft output from the motor to the input component of the reducer. In the case where the reducer is a wave gear reducer, the rotational force of the shaft output from the motor is transmitted to the wave generator (wave generating component) as the input component. For example, a keyway is formed on the outer circumferential surface of the output shaft of the motor and the inner circumferential surface of the insertion hole of the input component of the reducer. A key having a shape that fits into the keyway is inserted. In addition, by fixing the key with a hexagon socket set screw or the like, a key connection can be implemented. In the key connection, it is possible to suppress the connected components from sliding in the circumferential direction with respect to each other.

[0010] However, in the key connection, there is a case where the key deteriorates due to long-term use. As a result, there is a possibility that the rotational force cannot be transmitted reliably. That is, there is a problem of low reliability in maintaining the function of transmitting the rotational force. In addition, in the key connection, the hexagon socket set screw or the like is inserted in one radial direction. As a result, sometimes a deviation occurs between the rotation axis of the input part of the reducer and the rotation axis of the output shaft of the motor. In addition, when the drive device is driven, vibration sometimes occurs. In order to prevent the occurrence of this vibration, it is necessary to perform an operation of aligning the input part or the output shaft of the reducer so that the rotation axis of the input part of the reducer is consistent with the rotation axis of the output shaft of the motor.

[0011] Alternatively, in order to omit the adjustment of the position of the rotating shaft, a cross coupling may be configured between the output shaft of the motor and the input component of the reducer. By configuring a cross coupling, even if there is a deviation of the rotating shaft, the rotational force can be reliably transmitted while aligning the center, and the generation of vibration can be suppressed. However, if a cross coupling is used, there is a problem that the number of parts increases and the drive device becomes expensive. In addition, since space is required to configure the cross coupling, there is a problem that the drive device becomes longer in the axial direction.

[0012] Solutions to Solve Problems

[0013] The power transmission mechanism of the robot of the disclosed method includes: a shaft that transmits the rotational force of the motor; and a wave gear reducer that amplifies the rotational force of the motor. The wave gear reducer includes: a wave generating component that includes a cam having an elliptical shape when viewed from the direction of the rotating shaft; an elastic cylindrical component that has a plurality of first teeth on the outer peripheral surface and is elastically deformable; and an annular component that has a plurality of second teeth on the inner peripheral surface. The first teeth of a part of the elastic cylindrical component and the second teeth of a part of the annular component engage with each other. The shaft has a spline shaft portion having a plurality of convex portions formed in the circumferential direction of the outer peripheral surface. The wave generating component includes an insertion hole, which inserts the spline shaft portion and has a shape of a concave portion corresponding to the shape of the convex portion of the spline shaft portion. The spline shaft portion and the insertion hole have a shape in which a radial gap exists between the spline shaft portion and the insertion hole. The gap has a size that the rotation center axis of the wave generating component can always move and adjust in a direction to offset the eccentricity relative to the center axis of the elastic cylindrical component by utilizing the elasticity of the elastic cylindrical component.

[0014] A driving device for a robot according to an aspect of the present disclosure includes the power transmission mechanism described above and an electric motor for shaft rotation.

[0015] Effects of the Invention

[0016] According to the aspects of the present disclosure, it is possible to provide a power transmission mechanism of a robot and a driving device of a robot that suppress vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a perspective view of a robot in the embodiment.

[0018] Figure 2 It is a schematic cross-sectional view of a drive device including a power transmission mechanism in the embodiment.

[0019] Figure 3 It is an enlarged schematic cross-sectional view of the power transmission mechanism.

[0020] Figure 4 It is a schematic partial cross-sectional view of the speed reducer in the embodiment.

[0021] Figure 5 It is an enlarged schematic cross-sectional view of a portion where the shaft and the wave generating member engage with each other in the embodiment.

[0022] Figure 6 It is an enlarged schematic cross-sectional view of a power transmission mechanism in a comparative example. DETAILED DESCRIPTION

[0023] Reference Figures 1 to 6 , a power transmission mechanism of a robot in an embodiment and a driving device of a robot having the power transmission mechanism are described. The power transmission mechanism of this embodiment transmits the rotational force of a motor from one component to another component. The driving device of this embodiment causes other components of the robot to rotate relative to one component.

[0024] Figure 1 1 is a perspective view of a robot according to the present embodiment. The robot 1 according to the present embodiment is a multi-joint robot including a plurality of joints. The robot 1 includes a plurality of rotatable components. Each component is formed to rotate around drive axes J1 to J6. The drive device according to the present embodiment is arranged at the joints of the robot in order to drive the components of the robot.

[0025] The robot 1 includes a base portion 14 fixed to a setting surface and a rotating base 13 supported by the base portion 14. The rotating base 13 rotates around a driving axis J1 relative to the base portion 14. The robot 1 includes a forearm 11 and an upper arm 12. The upper arm 12 rotates around a driving axis J2 relative to the rotating base 13. The forearm 11 rotates around a driving axis J3 relative to the upper arm 12. Moreover, the forearm 11 rotates around a driving axis J4. The robot 1 includes a wrist 15 supported by the forearm 11. The wrist 15 rotates around a driving axis J5. In addition, the wrist 15 includes a flange 16 that rotates around a driving axis J6. A working tool is fixed to the flange 16 according to the work performed by the robot device equipped with the robot 1.

[0026] The robot 1 of this embodiment includes a base 14, a rotating base 13, an upper arm 12, a forearm 11, and a wrist 15 as components. The robot of this embodiment has six drive axes, but is not limited to this. A robot that changes position and posture by an arbitrary mechanism can be adopted.

[0027] Figure 2 A cross-sectional view showing a driving device according to this embodiment. Figure 1 and Figure 2 In this embodiment, a driving device 2 for rotating the forearm 11 around the driving axis J4 is cited as an example for description. The driving device 2 is arranged at the end of the forearm 11 on the side opposite to the side where the wrist 15 is arranged. The driving device 2 is arranged in a manner such that the direction indicated by the arrow 96 is the direction where the wrist 15 is arranged.

[0028] The drive device 2 includes a motor 45 including a rotor 45a and a stator 45b. The rotor 45a is fixed to the shaft 21. The shaft 21 functions as an output shaft of the motor 45. The shaft 21 is formed to extend slenderly. The shaft 21 of the present embodiment has a hollow hole. That is, the shaft 21 of the present embodiment is a hollow shaft with a cylindrical shape. The shaft 21 rotates with the drive shaft J4 as the rotation axis.

[0029] The rotational force of the shaft 21 is transmitted to the flange 25 via the speed reducer 31. The flange 25 and the flange 26 are fixed to each other by bolts 56. The flange 26 and the flange 27 are fixed to each other by bolts 57. The flanges 25, 26, and 27 rotate integrally. The flange 27 is fixed to a frame that rotates around the drive shaft J4 of the forearm 11, for example.

[0030] The drive device 2 includes a frame 22 in which a motor 45 is arranged. A shaft 21 that transmits the rotational force of the motor 45 is supported to rotate by bearings 51 and 52. The bearing 51 is fixed to the frame 22. The drive device 2 includes a frame 23 in which an electromagnetic brake 46 is arranged, and a frame 24 in which an encoder 47 as a rotation position detector is arranged. The electromagnetic brake 46 brakes the shaft 21. The encoder 47 detects the rotation position of the motor 45.

[0031] The frame 22 of this embodiment is fixed to a frame that does not rotate around the drive axis J4 in the frame of the forearm 11. The frame 22, the frame 23, and the frame 24 are fixed to each other by fastening members such as bolts. In addition, a bearing fixing member 28 for fixing the bearing 52 is arranged between the frame 22 and the frame 23. The bearing fixing member 28 is fixed to the frame 23 by fastening members such as bolts. By removing the fastening member, the frame 24, 23, 22 and the bearing fixing member 28 can be removed from the side opposite to the direction indicated by the arrow 96.

[0032] A protective tube 66 formed of resin is disposed inside the shaft 21. The protective tube 66 is formed in a cylindrical shape along the inner surface of the shaft 21. Line bodies such as electric wires, air tubes, or optical communication cables are inserted into the protective tube 66. The protective tube 66 is clamped by the flange 26 and the flange 27 through the clamping portion 66a and fixed. By disposing the protective tube 66, the line body can be disposed inside the joint portion of the robot 1.

[0033] The shaft 21 of this embodiment has step portions 21a and 21b for limiting the movement of the shaft 21 in the direction in which the rotation axis extends. Bearings 51 and 52 are engaged with the step portions 21a and 21b. The bearing 51 is fixed by the frame 22, and the bearing 52 is fixed by the bearing fixing member 28.

[0034] Oil seals 61 and 62 are arranged on the outer peripheral surface of the shaft 21 to prevent the lubricating oil inside from leaking out and to prevent the intrusion of foreign matter from the outside. In addition, an oil seal 63 is arranged to prevent the lubricating oil inside the main bearing 41 from leaking out and to prevent the intrusion of foreign matter from the outside.

[0035] Figure 3 FIG. 2 is an enlarged schematic cross-sectional view showing a power transmission mechanism of the drive device according to the present embodiment. Figure 2 and Figure 3 The drive device 2 includes a power transmission mechanism 5 that transmits the rotational force outputted from the motor 45 to the flanges 25, 26, and 27. The power transmission mechanism 5 includes a shaft 21 and a speed reducer 31 that amplifies the rotational force of the shaft 21.

[0036] Figure 4 It is a schematic partial cross-sectional view showing the speed reducer according to the present embodiment. Figure 4 9 is a partial cross-sectional view of the speed reducer 31 when viewed in the direction opposite to the arrow 96 in the direction of the rotation axis. Figures 2 to 4 The speed reducer 31 of the present embodiment is a wave gear speed reducer. The speed reducer 31 has a wave generating component 32 as an input portion of the input rotational force. The wave generating component 32 is called a wave generator. The wave generating component 32 includes a hub 36 whose shape (planar shape) is an ellipse as viewed from the direction of the rotation axis and a ball bearing 37 arranged on the outer peripheral surface of the hub 36. The hub 36 functions as a cam whose planar shape is an ellipse. In particular, the hub 36 of the wave generating component 32 functions as an input portion of the speed reducer 31. The inner ring of the ball bearing 37 is fixed to the elliptical hub 36. The outer ring of the ball bearing 37 is formed so as to be elastically deformable according to the rotation of the hub 36 via the ball.

[0037] The reducer 31 has an elastic tubular component 33 that can be elastically deformed. The elastic tubular component 33 is an external gear, which is called a flexible gear. The elastic tubular component 33 is arranged on the outer side of the wave generating component 32. The elastic tubular component 33 has a plurality of first tooth portions 33a formed on the outer peripheral surface. The elastic tubular component 33 is formed to deform with the rotation of the wheel hub 36. The elastic tubular component 33 of this embodiment is fixed to the frame 22 by a bolt 55. The elastic tubular component 33 is fixed to be non-rotating relative to the rotation of the wave generating component 32.

[0038] The reducer 31 has an annular component 34. The annular component 34 is an internal gear, which is called a rigid gear. The annular component 34 has rigidity so that it is difficult to deform elastically. The annular component 34 is arranged on the outer side of the elastic cylindrical component 33. A plurality of second tooth portions 34a are formed on the inner circumferential surface of the annular component 34. Since the wheel hub 36 has an elliptical shape, the first tooth portion 33a and the second tooth portion 34a are engaged with each other in the direction of the major axis of the ellipse. That is, the first tooth portion 33a of a part of the elastic cylindrical component 33 is engaged with the second tooth portion 34a of a part of the annular component 34.

[0039] Here, the number of teeth of the first tooth portion 33a of the elastic cylindrical member 33 is less than the number of teeth of the second tooth portion 34a of the annular member 34. For example, the number of teeth differs by two. When the wave generating member 32 rotates one circle, the annular member 34 rotates slightly according to the difference in the number of teeth of the tooth portions 33a and 34a. In the present embodiment, the annular member 34 functions as an output portion of the speed reducer 31. The speed reducer 31 can reduce speed at a reduction ratio corresponding to the number of teeth of the elastic cylindrical member 33 and the number of teeth of the annular member 34.

[0040] The decelerated rotational force is output from the annular member 34. A main bearing 41 is arranged on the side of the annular member 34. The main bearing 41 of this embodiment is a cross roller bearing. The main bearing 41 has an inner ring 41a and an outer ring 41b. The outer ring 41b is fixed to the frame 22 together with the elastic cylindrical member 33 by bolts 55. The outer ring 41b is a member that does not rotate relative to the frame 22. In contrast, the inner ring 41a is fixed to the flange 25 and the annular member 34 by bolts 39. Therefore, the inner ring 41a, the annular member 34, the flanges 25, 26, 27 and the protective tube 66 rotate integrally. The rotational force of the annular member 34 is transmitted to the frame rotating around the drive shaft J4 of the forearm 11 via the flanges 25, 26, 27.

[0041] Figure 5 This is an enlarged cross-sectional view showing the engagement portion between the shaft and the hub of the wave generating member. Figures 3 to 5 The power transmission mechanism 5 transmits the rotational force of the shaft 21 to the hub 36 of the wave generating member 32 as the input portion of the speed reducer 31. In the present embodiment, the rotational force of the shaft 21 is transmitted to the hub 36 by spline connection.

[0042] The shaft 21 has a spline shaft portion 21e formed with a plurality of protrusions 21d at predetermined intervals in the circumferential direction of the outer peripheral surface. The spline shaft portion 21e is a portion extending in the axial direction. The spline shaft portion 21e is formed in the area indicated by the arrow 97. The spline shaft portion 21e is formed in the area opposite to the hub 36. The protrusion 21d is formed to protrude toward the outside. The protrusion 21d extends in the axial direction. The protrusion 21d and the recessed portion corresponding to the tooth portion of the gear are formed in the circumferential direction.

[0043] The hub 36 of the wave generating member 32 has an insertion hole 36b into which the spline shaft portion 21e is inserted. In the present embodiment, the insertion hole 36b penetrates from one axial end face of the hub 36 to the other end face. The insertion hole 36b has a shape corresponding to the shape of the spline shaft portion 21e. A recess 36a is formed on the inner circumferential surface of the insertion hole 36b. The recess 36a extends in the axial direction.

[0044] In addition, the convex portion 21d on the outer circumferential surface of the spline shaft portion 21e and the concave portion 36a on the inner circumferential surface of the insertion hole 36b are formed along a perfect circle in the cross-sectional shape. In this way, a plurality of teeth are formed on the outer circumferential surface of the shaft 21, and a plurality of teeth engaging with the teeth of the shaft 21 are formed on the inner circumferential surface of the hub 36. A spline-coupled engaging portion is formed in the region where the plurality of teeth are opposed to each other. By adopting the spline coupling, the rotational force can be reliably transmitted.

[0045] The power transmission mechanism 5 of the present embodiment includes a movement limiting portion that limits the axial movement (direction of the rotation axis) of the wave generating component 32. In order to apply a load in the thrust direction to the wave generating component 32 by the elasticity of the elastic tubular component 33, it is necessary to limit the movement. The movement limiting portion of the present embodiment limits the axial movement of the wave generating component 32 in two directions. The movement limiting portion in the present embodiment includes a C-ring 35 as a retaining ring configured in a manner to contact the axial end face of the hub 36. The C-ring 35 has a shape that limits the axial movement of the wave generating component 32. The C-ring 35 limits the movement of the hub 36 in the direction indicated by the arrow 96.

[0046] A recess 21f corresponding to the shape of the C-ring 35 is formed on the spline shaft portion 21e of the shaft 21. The C-ring 35 is embedded in the recess 21f extending in the circumferential direction. By adopting the C-ring as the movement limiting portion, the axial movement of the wave generating component 32 can be limited with a simple structure. In addition, the C-ring 35 can be easily removed. Therefore, the power transmission mechanism can be easily disassembled and the reducer 31 can be removed. The retaining ring is not limited to the C-ring, and a component with an arbitrary ring shape can be used. For example, an E-ring can be used as a retaining ring. As long as the movement can be limited, a structure other than a ring can also be used.

[0047] In addition, the movement limiting portion of the present embodiment includes a step portion 21c formed on the shaft 21 and having a changed outer diameter of the shaft 21. The step portion 21c can be formed in a region of the spline shaft portion 21e where the convex portion 21d is formed. That is, the step portion 21c can be formed in a manner such that the height of the convex portion 21d becomes higher. The step portion 21c is formed to contact the axial end surface of the wave generating component 32. The step portion 21c has a shape that limits the axial movement of the wave generating component 32. The step portion 21c limits the movement of the wave generating component 32 in the direction opposite to the direction indicated by the arrow 96. By constituting the movement limiting portion with a step portion, the axial movement of the wave generating component can be limited without using another component that limits the movement.

[0048] The step portion is not limited to this method, and may be formed by the terminal end of the spline shaft portion 21e. That is, the step portion may be formed at the boundary between the region where the convex portion is formed and the region where the convex portion is not formed. In addition, as the movement limiting portion, any component that limits the axial movement of the wave generating component may be used. For example, the wave generating component may be fixed to the shaft by bolts or adhesives. Alternatively, the step portion may be replaced by a C-shaped ring.

[0049] Reference Figure 5 The spline shaft portion 21e and the insertion hole 36b have a shape in which a gap 91 is present as a narrow space between the spline shaft portion 21e and the insertion hole 36b. In particular, in the cross-sectional shape when cut along a plane perpendicular to the axial direction, the gap 91 is formed in the radial direction. That is, the insertion hole 36b is formed in a shape having a concave portion 36a corresponding to the shape of the convex portion 21d of the spline shaft portion 21e, and is slightly larger than the width of the teeth in the circumferential direction of the spline shaft portion 21e.

[0050] The shaft 21 is supported by bearings 51 and 52 fixed to the frame 22. The rotation axis of the shaft 21 is determined by the positions of the bearings 51 and 52. In contrast, the outer ring of the ball bearing 37 contacts the inner circumferential surface of the elastic tubular component 33. In the direction of the major axis of the elliptical shape of the hub 36, the tooth portion 33a of the elastic tubular component 33 contacts the tooth portion 34a of the annular component 34. Here, the wave generating component 32 is assembled in a manner of being submerged in the elastic tubular component 33, and the elastic tubular component 33 is elastically deformed in a manner of pushing and expanding. The function of automatically aligning the rotation center axis of the wave generating component 32 and the center axis of the elastic tubular component 33 occurs through the force of the elastic tubular component 33 to restore.

[0051] The shape of the elastic tubular member 33 when viewed from the direction of the rotation axis is an ellipse. A force acts on the elastic tubular member 33 to restore the shape viewed from the direction of the rotation axis to a perfect circle. The hub 36 is supported only by the elastic tubular member 33 in the radial direction and is suspended relative to the shaft 21. In addition, in a state where the rotation center axis of the wave generating member 32 is always aligned, the torque is transmitted in a dispersed manner by the multiple teeth of the spline. That is, the rotation center axis is aligned at all rotational positions of the wave generating member 32. At this time, although the thrust acts on the axial direction of the wave generating member 32, the wave generating member 32 will not move in the axial direction due to the function of the aforementioned movement limiting portion.

[0052] Here, the position of the rotation axis of the hub 36 of the wave generating member 32 and the position of the rotation axis of the shaft 21 may be slightly different due to processing errors, etc. In the present embodiment, a gap 91 is formed between the inner peripheral surface of the insertion hole 36b of the hub 36 and the outer peripheral surface of the spline shaft portion 21e of the shaft 21. Therefore, the above-mentioned error in the position of the rotation axis can be absorbed by the gap 91.

[0053] The gap 91 has a size such that the rotation center axis of the wave generating member 32 can be adjusted by always moving in a direction to offset the eccentricity relative to the center of the elastic tubular member 33 due to the elasticity of the elastic tubular member 33. More specifically, the gap 91 is preferably formed larger so as not to hinder the function of adjusting the wave generating member 32. If the gap 91 is too small, the wave generating member 32 may not be able to move sufficiently due to the elastic force of the elastic tubular member 33, and the adjustment is insufficient, causing vibration.

[0054] On the other hand, when the rotational component of the gap 91 between the spline shaft portion 21e and the insertion hole 36b of the hub 36 is large, the angular transmission error reflected in the output portion of the speed reducer 31 becomes large. The angular transmission error corresponds to a value obtained by dividing the magnitude of the rotational component of the gap 91 by the reduction ratio of the speed reducer 31. In this way, it is preferable to suppress the gap 91 to a small level that does not substantially adversely affect the function of the speed reducer, that is, the movement of the robot.

[0055] Figure 6 An enlarged schematic cross-sectional view of a power transmission mechanism of a comparative example is shown. The power transmission mechanism of the comparative example includes a shaft 84 that transmits the rotational force of the motor. The power transmission mechanism of the comparative example transmits the rotational force of the shaft 84 to the hub 83 of the wave generating member 82 through a key connection. A key groove 84a is formed in the shaft 84. In addition, a key groove 83a is formed in the hub 83. In addition, a rectangular parallelepiped key 85 is inserted into the regions of the key grooves 83a and 84a that are opposed to each other.

[0056] A fixing screw (hexagon socket set screw) 86 is inserted into the hub 36. The key 85 is fixed by the fixing screw 86. As shown by the arrow 98, the fixing screw 86 is inserted toward the radial inner side. Therefore, the shaft 84 is pressed in the direction shown by the arrow 98. On the other hand, due to the reaction force of the axial force of the fixing screw 86, a force on the side opposite to the direction shown by the arrow 98 acts on the wave generating component 82. Due to the influence of the gap between the shaft 84 and the hub 83, the wave generating component 82 is sometimes configured to rotate with a rotation axis that deviates from the inherent rotation axis of the reducer 31. In this case, if the reducer is driven, vibration sometimes occurs.

[0057] Alternatively, in order to suppress vibration caused by the deviation of the position of the rotating shaft, a cross coupling may be arranged between the shaft 84 and the wave generating component 82. The cross coupling has a structure in which an insert that can move in the radial direction is arranged between one component and the other component. For example, one component of the cross coupling can be fixed to the shaft 84, and the other component can be fixed to the wave generating component 82. The speed reducer can be driven smoothly while maintaining the state in which the position of the rotating shaft of the shaft 84 and the position of the rotating shaft of the wave generating component 82 are deviated.

[0058] However, by configuring the cross coupling, the axial length of the power transmission mechanism becomes longer, and the power transmission mechanism becomes larger. In addition, in the power transmission mechanism of the comparative example, a key connection is used as a connection method for reliably transmitting the rotational force. In the key connection, if used for a long time, the key may be partially worn due to the increase of the surface pressure caused by the contact of one end, so the reliability is low.

[0059] Reference Figures 3 to 5 In contrast, in the power transmission mechanism of the present embodiment, the elastic force of the elastic tubular member 33 can be used to align the wave generating member 32. The wave generating member 32 can rotate around the rotation axis at the optimal position. In addition, when the position of the rotation axis of the wave generating member 32 is slightly different from the position of the rotation axis of the shaft 21, the difference in the position of the rotation axis can be absorbed by the gap 91 between the inner circumferential surface of the wave generating member 32 and the outer circumferential surface of the shaft 21. As a result, the drive can be performed smoothly while suppressing the vibration of the reducer 31. In the power transmission mechanism of the present embodiment, since other parts such as a cross coupling are not used, the number of parts can be reduced.

[0060] In addition, in the power transmission mechanism of the present embodiment, since a key groove and a key are not used, damage of the key does not occur even if it is used continuously for a long period of time, and the reliability of the speed reducer can be maintained for a long period of time.

[0061] The shaft 21 in this embodiment is a cylindrical component with a hollow hole. Since the hollow shaft has a thin wall thickness, it is difficult to ensure the depth of the keyway (the area for torque transmission) that can transmit sufficient torque. In this embodiment, by forming the convex portion of the spline shaft to be smaller and providing a larger number of teeth, it is possible to form a structure that can reliably transmit rotational force even if it is a hollow shaft. In this way, even if the shaft that outputs the rotational force of the motor is a hollow shaft, it is possible to provide a power transmission mechanism that reliably transmits rotational force while ensuring long-term reliability.

[0062] Reference Figure 5 , it is preferred that the cross-sectional shape of the convex portion 21d of the shaft 21 and the concave portion 36a of the hub 36 is composed of an involute curve. That is, it is preferred that the rotational force is transmitted through the involute spline. By adopting this structure, the strength of the spline shaft and the teeth inserted into the hole can be improved. The axial sliding and the swinging in the radial direction become stronger. In addition, the torque can be evenly distributed to each convex portion. Moreover, the involute spline has the advantage of automatic centering when transmitting torque. However, in order to prevent wear caused by poor lubrication, it is preferred to apply a sufficient amount of lubricating oil to the meshing portion of the teeth of the spline, which is the same as the lubricating oil applied to the meshing portion of the teeth of the reducer during assembly. In addition, as a spline, it is not limited to an involute spline, and a spline with a convex portion of any shape can be used. For example, a square spline with a convex portion having a cross-sectional shape that is approximately a quadrilateral can be used.

[0063] Reference Figure 2 and Figure 3 The drive device 2 of this embodiment can be disassembled and the speed reducer 31 can be removed for replacement. When the drive device 2 is disassembled, the flange 27 can be removed from the flange 26 by removing the bolts 57. In addition, the fixing of the protection tube 66 is released, and the protection tube 66 can be taken out in the direction indicated by the arrow 96. Then, the flange 26 can be removed from the flange 25 by removing the bolts 56. Then, the flange 25 can be removed by removing the bolts 39.

[0064] Next, by removing the C-ring 35 and the bolt 55, the reducer 31 and the main bearing 41 can be removed. In this way, the drive device 2 can be disassembled and the reducer 31 can be replaced. In addition, the bearings 51, 52 and the oil seals 61, 62, 63 and the like can also be replaced. When assembling the drive device 2, it can be assembled in the reverse order of the disassembly. The drive device 2 in this embodiment can be easily disassembled by removing the fastening components, and the parts can be replaced.

[0065] In the above-mentioned embodiment, the power transmission mechanism for driving the components around the driving axis J4 of the robot 1 and the driving device of the robot are described, but the present invention is not limited to this method. The power transmission mechanism and the driving device of the present embodiment can be used in the power transmission mechanism for transmitting the rotational force of any component of the robot and the driving device for driving any component of the robot.

[0066] The above-mentioned embodiments can be combined appropriately. In the above-mentioned figures, the same or equivalent parts are marked with the same reference numerals. In addition, the above-mentioned embodiments are examples and do not limit the invention. In addition, in the embodiments, changes of the embodiments shown in the claims are included.

[0067] Explanation of symbols

[0068] 1—robot; 2—driving device; 5—power transmission mechanism; 21—shaft; 21c—step portion; 21d—convex portion; 21e—spline shaft portion; 31—reducer; 32—wave generating component; 36—hub; 36a—recess; 36b—insertion hole; 37—ball bearing; 33—elastic cylindrical component; 33a—tooth portion; 34—annular component; 34a—tooth portion; 35—C-ring; 45—motor; 91—gap.

Claims

1. A power transmission mechanism of a robot, characterized in that: have: a shaft that transmits the rotational force of the motor; and a wave gear reducer that amplifies the rotational force of the motor, The wave gear reducer comprises: a wave generating member including a cam having an elliptical shape when viewed from the direction of the rotation axis; an elastic tubular member having a plurality of first teeth on an outer peripheral surface and capable of elastic deformation; and an annular member having a plurality of second teeth on an inner peripheral surface thereof, The first teeth of a part of the elastic tubular member and the second teeth of a part of the annular member are engaged with each other. The shaft has a spline shaft portion having a plurality of convex portions formed in the circumferential direction of the outer peripheral surface. The wave generating member includes an insertion hole into which the spline shaft portion is inserted and has a shape of a concave portion corresponding to a shape of the convex portion of the spline shaft portion. The spline shaft portion and the insertion hole have a shape in which a radial gap exists between the spline shaft portion and the insertion hole. The gap has a size such that the rotation center axis of the wave generating member can always be moved and centered in a direction that cancels out the eccentricity with respect to the center axis of the elastic tubular member by utilizing the elasticity of the elastic tubular member.

2. The power transmission mechanism of the robot according to claim 1, characterized in that: A movement restricting portion is provided, the movement restricting portion restricting movement of the wave generating member in two axial directions.

3. The power transmission mechanism of the robot according to claim 1, characterized in that: The shaft includes a step portion that contacts an axial end surface of the wave generating member and changes in outer diameter. The step portion has a shape that restricts axial movement of the wave generating member.

4. The power transmission mechanism of a robot according to any one of claims 1 to 3, characterized in that: The shaft is a hollow shaft having a cylindrical shape.

5. The power transmission mechanism of the robot according to any one of claims 1 to 4, characterized in that: The cross-sectional shapes of the convex portion and the concave portion are formed of involute curves.

6. A driving device of a robot, characterized in that: have: The power transmission mechanism of the robot according to claim 1; and An electric motor that rotates a shaft.

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