Gears and robots

Abstract

Provided are a gear device and a robot that can withstand stress applied to a diaphragm even when the distance between the diaphragm and a wave generator in the direction of the rotation axis is short. The gear device (1) comprises an internal gear (2), an external gear (3), and a wave generator (4). The external gear (3) comprises a cylindrical portion (31), a diaphragm (32), a boss portion (35), and the diaphragm (32) comprises a first connecting portion (321), a second connecting portion (322), and a diaphragm body (323). The ratio of the length from the open end (34) on one side of the cylindrical portion (31) to the surface (326) of the diaphragm (32) on the opposite side of the open end (34) in the direction of the rotation axis Ja to the length from the inner peripheral surface (351) of the boss portion (35) connected to the second connecting portion (322) to the outer peripheral surface (314) of the cylindrical portion (31) in the radial direction is greater than 1.0 and less than 5.0. Furthermore, when the thickness of the inner peripheral end A of the diaphragm (32) is t(A) and the thickness of the outer peripheral end C is t(C), t(C)≥t(A).

Description

Technical Field

[0001] The present invention relates to a gear device and a robot equipped with the gear device. Background Art

[0002] Patent Document 1 discloses the thickness and shape of a diaphragm for reducing fatigue failure under high load torque in a wave reducer (gear device).

[0003] Patent Document 1: International Publication No. 2018 / 100701

[0004] In a wave reducer, when the distance between the diaphragm of the external gear and the wave generator in the direction of the rotation axis is short, the force applied to the diaphragm increases compared to when the distance is long, increasing the possibility of fatigue failure. Patent Document 1 does not consider the case where the distance between the diaphragm and the wave generator in the direction of the rotation axis is short. Summary of the Invention

[0005] The gear device comprises: an internal gear; an external gear partially meshing with the internal gear and rotating relative to the internal gear around a rotation axis, the external gear having flexibility; and a wave generator contacting the inner peripheral surface of the external gear so as to move the meshing position of the internal gear and the external gear in the circumferential direction around the rotation axis, wherein the external gear has a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to one side of the outer peripheral end of the diaphragm, the diaphragm having a first connecting portion connected to the end of the cylindrical portion, and a first connecting portion connected to the outer peripheral end of the diaphragm. The second connection portion connected to the inner circumferential surface of the boss portion, and the diaphragm body connected to the first connection portion and the second connection portion, the ratio of the length of the surface of the diaphragm from the open end of one side of the cylindrical portion to the opposite side of the open end in the direction of the rotation axis to the length from the inner circumferential surface of the boss portion connected to the second connection portion to the outer circumferential surface of the cylindrical portion in the radial direction is greater than 1.0 and less than 5.0, when the thickness of the inner circumferential end of the diaphragm is set to t(A) and the thickness of the outer circumferential end is set to t(C), t(C)≥t(A).

[0006] The robot includes: a first member; a second member that rotates relative to the first member; a gear device that transmits a driving force that causes the second member to rotate relative to the first member; and a driving source that outputs the driving force to the gear device. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a side view showing a schematic configuration of a robot according to the embodiment.

[0008] Figure 2 It is an exploded perspective view showing a gear device according to the embodiment.

[0009] Figure 3 It is a longitudinal cross-sectional view of the gear unit.

[0010] Figure 4 It is a diagram showing the meshing state of the teeth of the gear device.

[0011] Figure 5 This is a half-sectional view of the external gear cut along a plane including the rotation axis.

[0012] Figure 6 It is a graph showing the relationship between the thickness of the separator and the stress.

[0013] Description of Reference Numerals

[0014] 1…gear device, 2…internal gear, 3…external gear, 4…wave generator, 31…cylindrical portion, 32…diaphragm, 34…open end of the cylindrical portion, 35…boss portion, 100…robot, 110…base serving as the first component, 120…first arm serving as the second component, 171…motor serving as a drive source, 313…inner circumferential surface of the external gear, 314…outer circumferential surface of the cylindrical portion, 321…first connecting portion, 322…second connecting portion, 323…diaphragm body, 326…the surface of the diaphragm on the opposite side of the opening end, 351…the inner circumferential surface of the boss portion, A…the inner circumferential end of the diaphragm, t(A)…the thickness of the inner circumferential end, B…the central portion of the diaphragm, t(B)…the thickness of the central portion, C…the outer circumferential end of the diaphragm, t(C)…the thickness of the outer circumferential end, D…the end portion of the cylindrical portion, t(D)…the thickness of the end portion, Ja…the axis of rotation, L1…the length from the inner circumferential surface of the boss portion to the outer circumferential surface of the cylindrical portion, L2…the length from the opening end of the cylindrical portion to the surface of the diaphragm. DETAILED DESCRIPTION

[0015] Figure 1 1 is a side view showing the schematic structure of the robot 100 according to the present embodiment. Figure 1 In the drawings, the upper side is referred to as "upper" and the lower side is referred to as "lower". Figure 1 The base 110 side is referred to as the "base end side" and the opposite side, that is, the end effector 150 side is referred to as the "front end side". Figure 1 In the drawings, the vertical direction is referred to as the "vertical direction," and the horizontal direction is referred to as the "horizontal direction." Furthermore, the direction in which the rotation axis Ja, described later, extends is referred to as the "axial direction." It should be noted that the term "direction" in this specification includes both directions along one side of the axis and the opposite direction.

[0016] The robot 100 will be briefly described.

[0017] Figure 1The robot 100 shown is, for example, a robot used for feeding, removing, transporting, and assembling precision equipment or parts constituting precision equipment. Figure 1 As shown, robot 100 includes a base 110, a first arm 120, a second arm 130, a work head 140, an end effector 150, and piping 160. It should be noted that "rotation" includes movement in one direction or in opposite directions relative to a certain center point, as well as rotation relative to a certain center point.

[0018] Each part of the robot 100 will be briefly described.

[0019] The base 110 is fixed to the ground (not shown) with bolts, for example. A control device 190 is provided within the base 110 to centrally control the robot 100. Furthermore, a first arm 120 is coupled to the base 110. The first arm 120 is rotatable relative to the base 110 about a first axis J1 extending in the vertical direction. In other words, the first arm 120 rotates relative to the base 110.

[0020] A first drive unit 170 is provided within the base 110. The first drive unit 170 includes a motor 171 (drive source), such as a servo motor, which generates the driving force for rotating the first arm 120, and a gear unit 1, which serves as a first speed reducer for reducing the speed of the motor 171. The input shaft of the gear unit 1 is coupled to the rotational axis of the motor 171, while the output shaft of the gear unit 1 is coupled to the first arm 120. Therefore, when the driving force of the motor 171 is transmitted to the first arm 120 via the gear unit 1, the first arm 120 rotates in a horizontal plane about the first axis J1.

[0021] A second arm 130 is connected to the front end of the first arm 120, capable of rotating relative to the first arm 120 about the second axis J2. Although not shown, a second drive unit is provided within the second arm 130. This second drive unit includes a second motor that generates a driving force to rotate the second arm 130, and a second speed reducer that reduces the rotation of the second motor. Furthermore, the driving force from the second motor is transmitted to the second arm 130 via the second speed reducer, allowing the second arm 130 to rotate relative to the first arm 120 about the second axis J2 within a horizontal plane.

[0022] The working head 140 is arranged at the front end of the second arm 130. The working head 140 has a spline shaft 141, and the spline shaft 141 is inserted into a spline nut and a ball screw nut (not shown) coaxially arranged at the front end of the second arm 130. The spline shaft 141 can rotate relative to the second arm 130. Figure 1 The third axis J3 shown rotates and is movable in the up and down directions.

[0023] Although not shown, a rotary motor and a lifting motor are disposed within the second arm 130. The driving force of the rotary motor is transmitted to the spline nut via a driving force transmission mechanism (not shown). When the spline nut rotates forward and reverse, the spline shaft 141 rotates forward and reverse about the third axis J3 along the vertical direction.

[0024] On the other hand, the driving force of the lifting motor is transmitted to the ball screw nut via a driving force transmission mechanism (not shown). When the ball screw nut rotates forward and reverse, the spline shaft 141 moves up and down.

[0025] An end effector 150 is connected to the front end of the spline shaft 141. The end effector 150 is not particularly limited, and examples thereof include an end effector for gripping a conveyed object and an end effector for processing a workpiece.

[0026] A plurality of wires connected to the various electronic components arranged in the second arm 130, such as the second motor, the rotary motor, and the lifting motor, are routed into the base 110 through the piping 160 connecting the second arm 130 and the base 110. Furthermore, the plurality of wires are collected in the base 110 and, together with wires connected to the motor 171 and an encoder (not shown), are routed to the control device 190 provided in the base 110.

[0027] As described above, the robot 100 includes: a base 110 as a first component; a first arm 120 as a second component configured to be rotatable relative to the base 110; a gear device 1 that transmits driving force from one side of the base 110 and the first arm 120 to the other side; and a motor 171 as a driving source that outputs driving force to the gear device 1.

[0028] It should be noted that the first arm 120 and the second arm 130 may be collectively referred to as a “second component.” Furthermore, the “second component” may include, in addition to the first arm 120 and the second arm 130 , the working head 140 and the end effector 150 .

[0029] In this embodiment, the first speed reducer is constituted by the gear device 1. However, the second speed reducer may also be constituted by the gear device 1. Furthermore, both the first speed reducer and the second speed reducer may be constituted by the gear device 1. When the second speed reducer is constituted by the gear device 1, the first arm 120 may be regarded as the "first member" and the second arm 130 may be regarded as the "second member."

[0030] In this embodiment, the motor 171 and the gear device 1 are provided on the base 110 . However, the motor 171 and the gear device 1 may be provided on the first arm 120 . In this case, the output shaft of the gear device 1 may be connected to the base 110 .

[0031] It should be noted that the robot 100 of this embodiment illustrates a horizontal multi-joint robot, but the robot of the present invention is not limited thereto. For example, the number of joints of the robot is arbitrary, and the robot can also be applied to a vertical multi-joint robot.

[0032] Figure 2 It is an exploded perspective view showing the gear device 1 according to the present embodiment. Figure 3 It is a longitudinal sectional view of the gear device 1 . Figure 4 It is a diagram showing the meshing state of the teeth of the gear device 1. It should be noted that in the following figures, for the sake of convenience, the dimensions of each part are appropriately exaggerated as needed, and the dimensions of each part are not necessarily consistent with the actual dimensions. Figure 2 In FIG, for convenience of illustration, a portion of the external gear 3 is omitted, specifically, the diaphragm 32 is omitted.

[0033] The gear device 1 will be described.

[0034] Figure 2 The illustrated gear device 1 is a wave gear device used, for example, as a speed reducer. This gear device 1 includes an internal gear 2, a flexible, top-hat-shaped external gear 3 disposed inside the internal gear 2, and a wave generator 4 disposed inside the external gear 3 and equipped with a bearing 42. Although not shown, lubricants such as lubricating oil are appropriately disposed in various parts of the gear device 1, specifically, in the meshing portion between the internal gear 2 and the external gear 3, and in the mating portion between the external gear 3 and the wave generator 4.

[0035] One of the internal gear 2, the external gear 3, and the wave generator 4 is connected to the base 110 of the robot 100, and the other is connected to the first arm 120 of the robot 100. In this embodiment, the internal gear 2 is fixed to the base 110, the external gear 3 is connected to the first arm 120, and the wave generator 4 is connected to the rotating shaft of the motor 171 (not shown).

[0036] Therefore, when the rotating shaft of motor 171 rotates, wave generator 4 rotates at the same speed as the rotating shaft of motor 171. Furthermore, because the internal gear 2 and the external gear 3 have different numbers of teeth, the difference in their tooth numbers causes relative rotation around the rotation axis Ja as their meshing positions shift circumferentially. In this embodiment, the internal gear 2 has a greater number of teeth than the external gear 3, allowing the external gear 3 to rotate at a speed lower than the rotation speed of the rotating shaft of motor 171. In other words, a speed reducer can be realized with the wave generator 4 as the input shaft and the external gear 3 as the output shaft.

[0037] It should be noted that the connection method between the internal gear 2, the external gear 3, and the wave generator 4 is not limited to the method described above. For example, even if the external gear 3 is fixed to the base 110 and the internal gear 2 is connected to the first arm 120, the gear device 1 can still be used as a speed reducer. Furthermore, even if the external gear 3 is connected to the rotating shaft of the motor 171, the gear device 1 can still be used as a speed reducer. In this case, the wave generator 4 can also be fixed to the base 110 and the internal gear 2 can be connected to the first arm 120.

[0038] The structure of the gear device 1 will be briefly described.

[0039] like Figures 2 to 4 As shown, the internal gear 2 is a ring-shaped gear made of a rigid body that is substantially indestructible in the radial direction and has internal teeth 23. In this embodiment, the internal gear 2 is a spur gear. Therefore, the internal teeth 23 have tooth traces parallel to the rotation axis Ja. It should be noted that the tooth traces of the internal teeth 23 may also be inclined relative to the rotation axis Ja. In other words, the internal gear 2 may also be a helical gear or a herringbone gear.

[0040] External gear 3 is inserted inside internal gear 2. External gear 3 is a flexible gear capable of radially flexing and deforming, and has external teeth 33 that mesh with internal teeth 23 of internal gear 2. Furthermore, external gear 3 has fewer teeth than internal gear 2. This difference in the number of teeth between external gear 3 and internal gear 2 allows for a speed reducer to be implemented.

[0041] In this embodiment, the external gear 3 is a so-called top hat type. Figure 3 The axial right end of the external gear 3 has an open end 34. Here, the external gear 3 has a cylindrical portion 31 that is cylindrical about the rotation axis Ja. This cylindrical portion 31 includes an external tooth forming portion 311, which is located on the side of the open end 34, and a cylindrical main body portion 312, which is located on the opposite side of the open end 34 and has a constant thickness. It should be noted that external teeth 33 are formed on the outer circumferential surface of the external tooth forming portion 311.

[0042] In addition to the cylindrical portion 31, the external gear 3 includes a diaphragm 32 connected to the cylindrical portion 31 and extending radially outward from the cylindrical portion 31. The external gear 3 also includes an annular boss portion 35 connected to the diaphragm 32.

[0043] The output shaft (not shown) is fixed to the boss portion 35 of the external gear 3 by a fixing member such as a screw. Thus, the output shaft is connected to the external gear 3. It should be noted that the method of connecting the output shaft and the external gear 3 is not limited to this.

[0044] like Figure 3 、 Figure 4 As shown in FIG. 1 , the wave generator 4 is arranged inside the external gear 3 and is rotatable around the rotation axis Ja. Figure 4 As shown, the wave generator 4 deforms the cross-section of the external gear 3 into an elliptical or oblong shape with a major axis La and a minor axis Lb, thereby causing the external teeth 33 to mesh with the internal teeth 23 of the internal gear 2. The external gear 3 and the internal gear 2 are rotatable about the same rotation axis Ja and mesh internally and externally with each other.

[0045] As described above, the cylindrical portion 31 of the external gear 3 includes an external tooth forming portion 311 and a main body portion 312. The external tooth forming portion 311 is Figure 3 The end portion on the side of the open end 34 shown is the portion where the external teeth 33 are provided. In addition, the main body portion 312 is the portion of the cylindrical portion 31 located on the side of the diaphragm 32. Among them, the external tooth forming portion 311 is the portion that produces a large deformation caused by coning. Coning means a three-dimensional deformation as described below: Figure 4 At the position of the major axis La shown, the cylindrical portion 31 expands outward relative to the rotation axis Ja, and at the position of the minor axis Lb, the cylindrical portion 31 narrows inward relative to the rotation axis Ja. When the wave generator 4 is fitted into the external gear 3, the external tooth forming portion 311 deforms more than the main body portion 312.

[0046] The wave generator 4 is embedded in the outer tooth forming portion 311 of the external gear 3. The wave generator 4 includes a cam 41 and a bearing 42 mounted on the outer periphery of the cam 41. The cam 41 includes a shaft 411 that rotates around the rotation axis Ja and a cam portion 412 that protrudes outward from one end of the shaft 411. When viewed from the direction along the rotation axis Ja, Figure 4 In the drawing, the outer circumference of the cam portion 412 has an elliptical or oblong shape with the vertical major axis La and the horizontal minor axis Lb. The bearing 42 includes a flexible inner ring 421 and outer ring 423 that fit into the cam 41, and a plurality of balls 422 disposed therebetween.

[0047] The inner ring 421 is embedded in the outer peripheral surface of the cam portion 412 of the cam 41 and elastically deforms into an elliptical or oblong shape along the outer peripheral surface of the cam portion 412. Subsequently, the outer ring 423 is also elastically deformed into an elliptical or oblong shape. Figure 3 As shown, the outer peripheral surface of the outer ring 423 contacts the inner peripheral surface 313 of the cylindrical portion 31. The plurality of balls 422 are retained by a retainer (not shown) so that the intervals between them in the circumferential direction of the inner ring 421 are kept constant.

[0048] As the cam 41 rotates about the rotation axis Ja, the wave generator 4 changes the orientation of the cam portion 412, causing the outer ring 423 to deform accordingly. This causes the meshing position of the internal gear 2 and the external gear 3 to shift circumferentially. Since the inner ring 421 is fixedly attached to the outer circumference of the cam portion 412, the deformation pattern remains unchanged.

[0049] Figure 5 This is a half-section view of the external gear 3 cut along a plane including the rotation axis Ja. Figure 5 In the figure, the rotation axis Ja is omitted.

[0050] The outer gear 3 will be described in detail.

[0051] As described above, the cylindrical portion 31 of the external gear 3 includes the external teeth forming portion 311 having an open end 34 at one end and a main body portion 312 of constant thickness between the external teeth forming portion 311 and the diaphragm 32. External teeth 33 are formed on the outer peripheral surface of the external teeth forming portion 311.

[0052] In the present embodiment, the thickness of the main body portion 312 is set to be constant. However, for example, the cross-sectional shape of the main body portion 312 may be set to have a gradually decreasing thickness from the diaphragm 32 side toward the external teeth forming portion 311 .

[0053] The diaphragm 32 includes a curved first connection portion 321 connected to the end D of the cylindrical portion 31 , a second connection portion 322 connected to the inner circumferential surface 351 of the boss portion 35 , and a diaphragm body 323 connected to the first connection portion 321 and the second connection portion 322 .

[0054] In other words, the first connection portion 321 is continuous with the inner circumferential end A of the diaphragm body 323 and curves from the radially inward direction along the rotation axis Ja toward the cylindrical portion 31. Furthermore, the end D of the cylindrical portion 31 is connected to the first connection portion 321. In other words, the second connection portion 322 extends radially outward from the outer circumferential end C of the diaphragm body 323 and is connected to the inner circumferential surface 351 of the boss portion 35. The diaphragm body 323 extends in the radial direction, which is a direction orthogonal to the rotation axis Ja.

[0055] Here, end D of the cylindrical portion 31 is the portion of the first connecting portion 321 on the cylindrical portion 31 side where the curvature begins. Specifically, end D of the cylindrical portion 31 is the portion of the first connecting portion 321 on the cylindrical portion 31 side where the curvature begins. At the outer peripheral end C of the diaphragm 32, the surface of the diaphragm body 323 of the second connecting portion 322 on the side where the boss portion 35 protrudes is the portion that begins to bend from the diaphragm body 323 toward the boss portion 35. The inner peripheral end A of the diaphragm 32 is the portion of the first connecting portion 321 on the diaphragm body 323 side where the curvature begins. Specifically, the inner peripheral end A of the diaphragm 32 is the portion of the first connecting portion 321 on the diaphragm body 323 side where the curvature begins.

[0056] In this embodiment, for example, the length L1 from the inner circumferential surface 351 of the boss portion 35 connected to the second connecting portion 322 to the outer circumferential surface 314 of the cylindrical portion 31 in the radial direction relative to the rotation axis Ja is 8 mm or more and 20 mm or less. Furthermore, the length L2 from the open end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 (diaphragm body 323) on the opposite side of the open end 34 in the direction of the rotation axis Ja is 20 mm or more and 40 mm or less.

[0057] Therefore, the ratio of the length L2 from the open end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 (diaphragm body 323) in the direction of the rotation axis Ja to the length L1 from the inner circumferential surface 351 of the boss portion 35 to the outer circumferential surface 314 of the cylindrical portion 31 in the radial direction is 1.0 or greater and 5.0 or less. Thus, the gear device 1 of this embodiment is a compact, flat device in which the distance between the diaphragm 32 of the external gear 3 and the wave generator 4 in the direction of the rotation axis Ja is shortened.

[0058] The outer gear 3 will be described in more detail.

[0059] When observing on a cross section, Figure 5 As shown, the outer circumferential surface 314 of the main body 312 of the cylindrical portion 31 of the external gear 3, from the portion 51 connected to the external tooth-forming portion 311 to the end D of the main body 312, is defined by an outer straight line 53 extending parallel to the rotation axis Ja. When viewed in cross section, the inner circumferential surface 313 of the main body 312 is also defined by an inner straight line 52 extending parallel to the rotation axis Ja. Thus, the main body 312 of constant thickness is defined by the outer straight line 53 and the inner straight line 52.

[0060] When viewed in cross section, the outer circumferential surface of the first connecting portion 321 of the diaphragm 32 connected to the main body 312 is defined by a concave arc 54. One end of the concave arc 54 smoothly connects to the outer straight line 53 at the position of the end D of the main body 312. When viewed in cross section, the inner circumferential surface of the first connecting portion 321 is defined by a straight portion 52a of the inner straight line 52 extending beyond the end D, a convex arc 55 smoothly connected to the straight portion 52a, and a straight portion 56a smoothly connected to the other end of the convex arc 55 and extending radially outward.

[0061] Here, in the first connecting portion 321, the center position of the connecting portion between the inner peripheral end A and the end D is set to E. In the first connecting portion 321, the curvature radius of the outer convex arc 55 is smaller than the curvature radius of the inner concave arc 54. The wall thickness of the first connecting portion 321 is the largest at the center position E of the connecting portion, gradually increases from the inner peripheral end A to the center position E of the connecting portion, and gradually decreases from the center position E to the end D.

[0062] When observing on a cross section, Figure 5 As shown, a surface 327 of the diaphragm body 323 on the cylindrical portion 31 side connected to the first connecting portion 321 is defined by a concave curve 57 .

[0063] Here, the approximate center portion between the inner peripheral end A and the outer peripheral end C of the diaphragm body 323 is designated as B. The concave curve 57 is composed of, for example, a concave arc 57a defining the distance from the inner peripheral end A to the center portion B, and a concave arc 57b defining the distance from the center portion B to the outer peripheral end C. One end of the concave arc 57a smoothly connects to the concave arc 54 at the position of the inner peripheral end A, and the other end smoothly connects to the concave arc 57b.

[0064] When observing on a cross section, Figure 5 As shown, the surface 326 of the diaphragm body 323 opposite the cylindrical portion 31 side connected to the first connecting portion 321 is defined by a straight portion 56 extending from the end of the straight portion 56a beyond the inner peripheral end A. The straight portion 56 extends in a radial direction perpendicular to the rotation axis Ja to the position of the outer peripheral end C.

[0065] The thickness of the diaphragm body 323 defined by the concave curve 57 and the straight portion 56 is thinnest at the center portion B, gradually increases from the center portion B toward the inner peripheral end A, and further increases from the center portion B toward the outer peripheral end C.

[0066] Then, when viewed in cross section, the surface of the second connecting portion 322 on the cylindrical portion 31 side connected to the outer peripheral end C of the diaphragm body 323 is defined by the arc of the concave arc 57b of the concave curve 57 that extends beyond the outer peripheral end C. When viewed in cross section, the end of the concave arc 57b is connected to the straight line portion 58 that defines the surface on the same side of the boss portion 35.

[0067] When viewed in cross section, the surface of the second connecting portion 322 opposite to the surface on the cylindrical portion 31 side is defined by a concave arc 59 that smoothly connects to the end of the straight portion 56 at the position of the outer peripheral end C. The other end of the concave arc 59 smoothly connects to the inner peripheral surface 351 of the boss portion 35. The concave arc 59 is formed with a predetermined radius of curvature.

[0068] Figure 6 32 is a graph showing the relationship between the thickness and stress of the diaphragm 32. Figure 6 In FIG, t(A) / t(C) is plotted on the horizontal axis, and the vertical axis represents the maximum load stress applied to the region from the inner peripheral end A to the outer peripheral end C, assuming that the thickness at the inner peripheral end A of the diaphragm 32 is t(A) and the thickness at the outer peripheral end C is t(C). It should be noted that since the load stress applied to the inner peripheral end A is greater than that applied to the outer peripheral end C, the vertical axis can also represent the load stress applied to the inner peripheral end A.

[0069] like Figure 6As shown, when the ratio t(A) / t(C) of the thickness t(A) at the inner peripheral end A of the diaphragm 32 to the thickness t(C) at the outer peripheral end C of the diaphragm 32 is between 0.7 and 1, the load stress applied to the inner peripheral end A increases, but not extremely. However, when t(A) / t(C) is greater than 1, in other words, when the thickness t(A) at the inner peripheral end A is greater than the thickness t(C) at the outer peripheral end C, the load stress applied to the inner peripheral end A increases sharply. In other words, when the thickness t(C) at the outer peripheral end C is less than the thickness t(A) at the inner peripheral end A, stress is also applied sharply to the outer peripheral end C.

[0070] Therefore, the thickness t(A) of the inner peripheral end A of the diaphragm 32 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is:

[0071] t(C)≥t(A),

[0072] Furthermore, it is preferred that 0.7<t(A) / t(C)≤1.0.

[0073] More preferably, 0.83≤t(A) / t(C)≤0.98.

[0074] It should be noted that in this embodiment, when the thicknesses of the inner peripheral end A, the central portion B, the outer peripheral end C, and the end portion D of the diaphragm 32 are set to t(A), t(B), t(C), and t(D), respectively,

[0075] t(C)≥t(A)>t(D)>t(B).

[0076] Specifically, it is preferred to use the thickness t(C) of the thickest outer peripheral end C among the four parts (inner peripheral end A, central part B, outer peripheral end C, end part D) as a reference, and set the thicknesses of the inner peripheral end A, central part B, and end part D as follows.

[0077] As described above, the thickness t(A) of the inner peripheral end A of the diaphragm 32 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is:

[0078] t(C)≥t(A),

[0079] Preferably, 0.7<t(A) / t(C)≤1.0,

[0080] More preferably, 0.83≤t(A) / t(C)≤0.98.

[0081] The thickness t(B) of the central portion B of the diaphragm 32 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is:

[0082] t(C)≥t(A)>t(B),

[0083] Preferably, 0.5<t(B) / t(C)<0.9,

[0084] More preferably, 0.55≤t(B) / t(C)≤0.65.

[0085] The thickness t(D) of the end portion D of the cylindrical portion 31 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is:

[0086] t(C)≥t(A)>t(D),

[0087] Preferably, 0.5<t(D) / t(C)<1.0,

[0088] More preferably, 0.6≤t(D) / t(C)≤0.9.

[0089] Furthermore, the thickness t(B) of the central portion B of the diaphragm 32 and the thickness t(D) of the end portion D of the cylindrical portion 31 are:

[0090] t(B)<t(D).

[0091] According to this embodiment, the following effects can be obtained.

[0092] The gear device 1 of this embodiment includes an internal gear 2, an external gear 3, and a wave generator 4. The external gear 3 also includes a cylindrical portion 31, a diaphragm 32, and a boss portion 35. The diaphragm 32 includes a first connection portion 321 connected to the end D of the cylindrical portion 31, a second connection portion 322 connected to the inner circumferential surface 351 of the boss portion 35, and a diaphragm body 323 connected to the first connection portion 321 and the second connection portion 322. The end D of the cylindrical portion 31 is the point where the first connection portion 321 on the cylindrical portion 31 side begins to bend. The outer circumferential end C of the diaphragm 32 is the point where the second connection portion 322 on the diaphragm body 323 side begins to bend. The inner circumferential end A of the diaphragm 32 is the point where the first connection portion 321 on the diaphragm body 323 side begins to bend. It should be noted that the ratio of the length from one open end 34 of the cylindrical portion 31 to the surface of the diaphragm 32 on the opposite side of the open end 34 in the direction of the rotation axis Ja to the length from the inner circumferential surface 351 of the boss portion 35 connected to the second connecting portion 322 to the outer circumferential surface 314 of the cylindrical portion 31 in the radial direction is greater than or equal to 1.0 and less than or equal to 5.0. Furthermore, when the thickness at the inner circumferential end A of the diaphragm 32 is t(A) and the thickness at the outer circumferential end C is t(C), t(C) ≥ t(A).

[0093] With this configuration, in the gear device 1, the ratio of the length from the open end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 in the direction of the rotation axis Ja to the length from the inner circumferential surface 351 of the boss portion 35 to the outer circumferential surface 314 of the cylindrical portion 31 in the radial direction is 1.0 to 5.0. Thus, when the distance between the diaphragm 32 of the external gear 3 and the wave generator 4 in the direction of the rotation axis Ja is short, t(C) ≥ t(A) and the diaphragm 32 can withstand stress. Therefore, when the distance between the diaphragm 32 and the wave generator 4 in the direction of the rotation axis Ja is short, the stress applied to the diaphragm 32 can be mitigated, allowing the gear device 1 to be miniaturized.

[0094] In the gear device 1 of this embodiment, the thickness t(A) of the inner peripheral end A of the diaphragm 32 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is 0.7<t(A) / t(C)≤1.0, and more preferably 0.83≤t(A) / t(C)≤0.98.

[0095] According to this configuration, the gear device 1 can further withstand the stress applied to the diaphragm 32 .

[0096] In the gear device 1 of this embodiment, when the thickness of the central portion B between the inner peripheral end A and the outer peripheral end C of the diaphragm 32 is represented by t(B), t(C) ≥ t(A) > t(B). Furthermore, the thickness t(B) of the central portion B of the diaphragm 32 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is such that 0.5 < t(B) / t(C) < 0.9, and more preferably 0.55 ≤ t(B) / t(C) ≤ 0.65.

[0097] According to this configuration, in the gear device 1 , not only the inner peripheral end A and the outer peripheral end C of the diaphragm 32 but also the central portion B is easily deformed, thereby dispersing and reducing stress concentration on the inner peripheral end A and the outer peripheral end C, thereby suppressing fatigue failure of the diaphragm 32 .

[0098] In the gear device 1 of this embodiment, when the thickness of the end portion D of the cylindrical portion 31 is t(D), t(C) ≥ t(A) > t(D). Furthermore, the thickness t(D) of the end portion D of the cylindrical portion 31 relative to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is such that 0.5 < t(D) / t(C) < 1.0, and more preferably 0.6 ≤ t(D) / t(C) ≤ 0.9.

[0099] According to this structure, in the gear device 1, by making the end D of the cylindrical portion 31 thinner than the outer peripheral end C of the diaphragm 32, the end D of the cylindrical portion 31 is also easy to deform, and by dispersing and reducing the stress concentration on the inner peripheral end A and the outer peripheral end C of the diaphragm, fatigue failure of the diaphragm 32 can be suppressed.

[0100] In the gear device 1 of the present embodiment, the thickness t(B) of the central portion B of the diaphragm 32 and the thickness t(D) of the end portion D of the cylindrical portion 31 satisfy t(B)<t(D).

[0101] In the gear device 1, shear stress in the rotational direction is applied to each cross-section of the external gear 3 based on the load torque. Furthermore, the shear stress increases as the radial distance from the rotation axis Ja decreases. Therefore, the shear stress is reduced in the central portion B of the diaphragm 32, which is farther from the rotation axis Ja than the end portion D of the cylindrical portion 31, compared to the end portion D of the cylindrical portion 31. This allows the diaphragm 32 to withstand shear stress even when the thickness t(B) of the central portion B is thinner than the thickness t(D) of the end portion D of the cylindrical portion 31.

[0102] The robot 100 of this embodiment includes: a first component (base 110); a second component (first arm 120) that rotates relative to the first component (base 110); a gear unit 1 that transmits a driving force to rotate the second component (first arm 120) relative to the first component (base 110); and a drive source (motor 171) that outputs the driving force to the gear unit 1. It should be noted that the first arm 120 and the second arm 130 can be collectively referred to as the "second component." Furthermore, the "second component" may include, in addition to the first arm 120 and the second arm 130, a work head 140 and an end effector 150.

[0103] In the gear device 1, when the distance between the diaphragm 32 of the external gear 3 and the rotation axis Ja of the wave generator 4 is short, even if the stress applied to the diaphragm 32 increases, the device can withstand it, thereby achieving miniaturization. Consequently, the robot 100 including the first component, the second component, the gear device 1, and the drive source can also be miniaturized.

Claims

1. A gear device, characterized in that: have: Internal gear; an external gear partially meshing with the internal gear and relatively rotating with respect to the internal gear around a rotation axis, the external gear being flexible; and a wave generator that contacts the inner peripheral surface of the external gear and moves the meshing position of the internal gear and the external gear in the circumferential direction around the rotation axis; The external gear includes a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to one side of the outer peripheral end of the diaphragm. The diaphragm includes a first connection portion connected to the end of the cylindrical portion, a second connection portion connected to the inner peripheral surface of the boss portion, and a diaphragm body connected to the first connection portion and the second connection portion. The ratio of the length of the surface of the diaphragm from one open end of the cylindrical portion to the opposite side of the open end in the direction of the rotation axis to the length from the inner peripheral surface of the boss portion connected to the second connecting portion to the outer peripheral surface of the cylindrical portion in the radial direction is 1.0 or more and 5.0 or less. When the thickness of the inner peripheral end of the diaphragm is t(A) and the thickness of the outer peripheral end is t(C), t(C)≥t(A), 0.83≤t(A) / t(C)≤0.

98.

2. The gear device according to claim 1, characterized in that When the thickness of the center portion between the inner peripheral end and the outer peripheral end of the diaphragm is t(B), t(C)≥t(A)>t(B), and, 0.5<t(B) / t(C)<0.

9.

3. The gear device according to claim 1, characterized in that When the thickness of the center portion between the inner peripheral end and the outer peripheral end of the diaphragm is t(B), t(C)≥t(A)>t(B), and, 0.55≤t(B) / t(C)≤0.

65.

4. The gear device according to claim 1, characterized in that When the thickness of the end portion of the cylindrical portion is t(D), t(C)≥t(A)>t(D), and 0.5<t(D) / t(C)<1.

0.

5. The gear device according to claim 1, characterized in that When the thickness of the end portion of the cylindrical portion is t(D), t(C)≥t(A)>t(D), and 0.6≤t(D) / t(C)≤0.

9.

6. The gear device according to claim 4 or 5, characterized in that t(B)<t(D).

7. A robot, characterized in that: have: first component; a second component, rotating relative to the first component; The gear device according to any one of claims 1 to 6, which transmits a driving force causing the second member to rotate relative to the first member; as well as A driving source outputs the driving force to the gear device.

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