Gearing and robots

Abstract

To provide a gear device and a robot that can withstand the stress on a diaphragm even with short distance in a rotation axis direction between the diaphragm and a wave generator.SOLUTION: A gear device 1 includes an internal gear 2, an external gear 3, and a wave generator 4. The external gear 3 includes a cylinder section 31, a diaphragm 32, and a boss section 35. The diaphragm 32 includes a first coupling section 321, a second coupling section 322, and a diaphragm body 323. A ratio of the length from one opening end 34 of the cylinder section 31 to the surface 326 of the diaphragm 32 on the opposite side of the opening end 34 in a rotation axis Ja direction to the length from the inner circumferential surface 351 of the boss section 35 coupled to the second coupling section 322 to the outer circumferential surface 314 of the cylinder section 31 in the radial direction is 1.0 or more and 5.0 or less, and t(C)≥t(A), where t(A) represents the thickness of the inner circumferential end A of the diaphragm 32 and t(C) represents the thickness of the outer circumferential end C.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Patent Document 1 discloses a diaphragm thickness shape for reducing fatigue damage under high load torque in a wave reducer (gear device). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 100701 Summary of the Invention [Problem to be solved by the invention]

[0004] In a wave reducer, when the distance in the rotational axis direction between the diaphragm of the external gear and the wave generator is short, the force acting on the diaphragm is greater than when the distance is long, increasing the possibility of fatigue failure. Patent Document 1 does not take into account the case where the distance in the rotational axis direction between the diaphragm and the wave generator is short. [Means for solving the problem]

[0005] The gear device includes an internal gear, an external gear that is partially meshed with the internal gear and rotates relatively to the internal gear about a rotation axis and has flexibility, and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position between the internal gear and the external gear in a circumferential direction about the rotation axis. The external gear has a cylindrical portion, a diaphragm that extends radially outward from the cylindrical portion, and an annular boss portion that is connected to an outer peripheral end side of the diaphragm. The diaphragm has a first connection portion that is connected to an end of the cylindrical portion, and a second connection portion that is connected to the boss. a second connection portion connected to an inner circumferential surface of a boss portion, and a diaphragm body connected to the first connection portion and the second connection portion, wherein the ratio of the length from one opening end of the cylindrical portion to the surface of the diaphragm opposite to the opening end in the rotational axis direction 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 1.0 or more and 5.0 or less, and when the thickness of the inner end of the diaphragm is t(A) and the thickness of the outer circumferential end is 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 rotates the second member relatively to the first member, and a driving source that outputs the driving force toward the gear device. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a side view showing a schematic configuration of a robot according to an embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a gear device according to an embodiment. [Diagram 3] FIG. [Figure 4] FIG. 4 is a diagram showing the meshing state of teeth of a gear device. [Diagram 5] FIG. 4 is a half cross-sectional view of an external gear cut along a plane including a rotation axis. [Figure 6] FIG. 4 is a diagram showing the relationship between diaphragm thickness and stress. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] FIG. 1 is a side view showing a schematic configuration of a robot 100 according to this embodiment. For convenience of explanation, the upper side in FIG. 1 is referred to as "upper" and the lower side is referred to as "lower". The base 110 side in FIG. 1 is referred to as the "base end side", and the opposite side, i.e., the end effector 150 side, is referred to as the "tip side". The up-down direction in FIG. 1 is referred to as the "vertical direction", and the left-right direction is referred to as the "horizontal direction". Furthermore, the direction in which a rotation axis Ja, which will be described later, extends is referred to as the "axial direction". In this specification, "direction" includes both the direction along the axis and the opposite direction.

[0009] The robot 100 will now be briefly described. The robot 100 shown in Fig. 1 is a robot used for operations such as supplying, removing, transporting, and assembling precision equipment and the parts that constitute the equipment. As shown in Fig. 1, the robot 100 has a base 110, a first arm 120, a second arm 130, a work head 140, an end effector 150, and piping 160. Note that "rotation" includes movement in one direction or in both directions, including the opposite direction, about a certain center point, and rotation about a certain center point.

[0010] Each part of the robot 100 will be briefly described. The base 110 is fixed to a floor surface (not shown) by, for example, bolts or the like. A control device 190 that performs overall control of the robot 100 is installed inside the base 110. A first arm 120 is connected to the base 110 so as to be rotatable about a first axis J1 that is aligned vertically to the base 110. In other words, the first arm 120 rotates relative to the base 110.

[0011] A first driving unit 170 is installed within the base 110. The first driving unit 170 has a motor 171 (driving source) which is a first motor such as a servo motor that generates a driving force for rotating the first arm 120, and a gear device 1 which is a first reducer that reduces the rotation speed of the motor 171. An input shaft of the gear device 1 is connected to a rotating shaft of the motor 171, and an output shaft of the gear device 1 is connected to the first arm 120. Therefore, when the motor 171 is driven and the driving force is transmitted to the first arm 120 via the gear device 1, the first arm 120 rotates within a horizontal plane around the first axis J1.

[0012] A second arm 130 that is rotatable around a second axis J2 relative to the first arm 120 is connected to the tip of the first arm 120. Although not shown, a second drive unit having a second motor that generates a drive force for rotating the second arm 130 and a second reducer that reduces the rotation of the second motor is installed inside the second arm 130. Then, the drive force of the second motor is transmitted to the second arm 130 via the second reducer, so that the second arm 130 rotates around the second axis J2 in a horizontal plane relative to the first arm 120.

[0013] A working head 140 is disposed at the tip of the second arm 130. The working head 140 has a spline shaft 141 inserted through a spline nut and a ball screw nut (not shown) that are coaxially disposed at the tip of the second arm 130. The spline shaft 141 is rotatable about a third axis J3 shown in FIG. 1 with respect to the second arm 130, and is also movable in the up and down directions.

[0014] Although not shown, a rotation motor and a lift motor are disposed within the second arm 130. The driving force of the rotation motor is transmitted to the spline nut by a driving force transmission mechanism, not shown, and when the spline nut rotates forward or backward, the spline shaft 141 rotates forward or backward about the third axis J3 that is aligned in the vertical direction.

[0015] On the other hand, the driving force of the lift motor is transmitted to the ball screw nut by a driving force transmission mechanism (not shown), and when the ball screw nut rotates forward or backward, the spline shaft 141 moves up and down.

[0016] An end effector 150 is connected to the tip of the spline shaft 141. The end effector 150 is not particularly limited, and examples thereof include an end effector that grips a transported object, an end effector that processes a workpiece, and the like.

[0017] A plurality of wires connected to each electronic component arranged in second arm 130, such as the second motor, the rotation motor, and the lift motor, are routed through piping 160 connecting second arm 130 and base 110 to inside base 110. Furthermore, the plurality of wires are gathered together inside base 110 and routed to control device 190 installed in base 110 together with wires connected to motor 171 and an encoder (not shown).

[0018] As described above, the robot 100 comprises the base 110 which is a first member, the first arm 120 which is a second member rotatably mounted on the base 110, the gear device 1 which transmits driving force from one side of the base 110 and the first arm 120 to the other side, and the motor 171 which is a driving source which outputs driving force toward the gear device 1.

[0019] The first arm 120 and the second arm 130 may be collectively regarded as a “second member.” Furthermore, the “second member” may include the work head 140 and the end effector 150 in addition to the first arm 120 and the second arm 130.

[0020] In addition, in this embodiment, the first reducer is configured with the gear device 1, but the second reducer may also be configured with the gear device 1, and further, both the first reducer and the second reducer may be configured with the gear device 1. When the second reducer is configured with 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."

[0021] In this embodiment, the motor 171 and the gear device 1 are provided on the base 110, but 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.

[0022] Although the robot 100 of this embodiment is exemplified as a horizontal multi-joint robot, the robot of the present invention is not limited to this. For example, the number of joints of the robot may be any number, and the robot may also be applied to a vertical multi-joint robot.

[0023] FIG. 2 is an exploded perspective view showing the gear device 1 according to this embodiment. FIG. 3 is a vertical cross-sectional view of the gear device 1. FIG. 4 is a diagram showing the meshing state of the teeth of the gear device 1. In the following drawings, for the sake of convenience, the dimensions of each part are appropriately exaggerated as necessary, and the dimensions of each part do not necessarily correspond to the actual dimensions. In addition, in FIG. 2, for the sake of convenience, part of the external gear 3, specifically the diaphragm 32, is omitted.

[0024] The gear device 1 will now be described. The gear device 1 shown in Fig. 2 is a strain wave gear device and is used, for example, as a reducer. This gear device 1 has an internal gear 2, a top-hat shaped flexible external gear 3 provided inside the internal gear 2, and a wave generator 4 provided inside the external gear 3 and equipped with a bearing 42. Although not shown, lubricant such as grease is appropriately placed in each part of the gear device 1, specifically, the meshing portion between the internal gear 2 and the external gear 3, and the fitting portion between the external gear 3 and the wave generator 4, etc.

[0025] 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 described above, and the other is connected to the first arm 120 of the robot 100 described above. 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 a rotation shaft (not shown) of a motor 171.

[0026] Therefore, when the rotating shaft of the motor 171 rotates, the wave generator 4 rotates at the same rotation speed as the rotating shaft of the motor 171. Since the internal gear 2 and the external gear 3 have different numbers of teeth, their meshing positions move in the circumferential direction and they rotate relatively around the rotation axis Ja due to the difference in the number of teeth. In this embodiment, since the number of teeth of the internal gear 2 is greater than the number of teeth of the external gear 3, it is possible to rotate the external gear 3 at a rotation speed lower than the rotation speed of the rotating shaft of the motor 171. In other words, it is possible to realize a reducer in which the wave generator 4 is on the input shaft side and the external gear 3 is on the output shaft side.

[0027] The connection form of the internal gear 2, external gear 3, and wave generator 4 is not limited to the form described above, and for example, the gear device 1 can be used as a reducer 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 also be used as a reducer even if the external gear 3 is connected to the rotating shaft of the motor 171. In this case, it is sufficient to fix the wave generator 4 to the base 110 and connect the internal gear 2 to the first arm 120.

[0028] The configuration of the gear device 1 will now be briefly described. As shown in Figs. 2 to 4, the internal gear 2 is a gear made of a rigid body that does not substantially bend in the radial direction, and is a ring-shaped gear having 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. The tooth traces of the internal teeth 23 may be inclined with respect to the rotation axis Ja. In other words, the internal gear 2 may be a helical gear or a double-helical gear.

[0029] The external gear 3 is inserted inside the internal gear 2. The external gear 3 is a flexible gear capable of bending and deforming in the radial direction, and has external teeth 33 that mesh with the internal teeth 23 of the internal gear 2. The number of teeth of the external gear 3 is smaller than the number of teeth of the internal gear 2. In this way, the external gear 3 and the internal gear 2 have different numbers of teeth, thereby realizing a speed reducer.

[0030] In this embodiment, the external gear 3 has a so-called top hat shape and has an open end 34 at the axial right end in Fig. 3. Here, the external gear 3 has a cylindrical portion 31 that is cylindrical about the rotation axis Ja. This cylindrical portion 31 has an external teeth forming portion 311 which is a portion on the open end 34 side, and a cylindrical body portion 312 of a constant thickness which is a portion on the opposite side to the open end 34. The external teeth 33 are formed on the outer circumferential surface side of the external teeth forming portion 311.

[0031] In addition to the cylindrical portion 31, the external gear 3 has a diaphragm 32 connected to the cylindrical portion 31 and extending radially outward from the cylindrical portion 31. The external gear 3 also has an annular boss portion 35 connected to the diaphragm 32.

[0032] An output shaft (not shown) is fixed to the boss portion 35 of the external gear 3 by a fastener such as a screw. This connects the output shaft to the external gear 3. Note that the method of connecting the output shaft to the external gear 3 is not limited to this.

[0033] 3 and 4, the wave generator 4 is disposed inside the external gear 3 and is rotatable around the rotation axis Ja. Then, as shown in Fig. 4, the wave generator 4 deforms the cross section of the external gear 3 into an ellipse or oval shape with a major axis La and a minor axis Lb, thereby meshing the external teeth 33 with the internal teeth 23 of the internal gear 2. The external gear 3 and the internal gear 2 are rotatable around the same rotation axis Ja, and are meshed with each other inside and outside.

[0034] As described above, the cylindrical portion 31 of the external gear 3 has the external teeth forming portion 311 and the body portion 312. The external teeth forming portion 311 is the end portion on the open end 34 side shown in FIG. 3, and is the portion where the external teeth 33 are provided. The body portion 312 is the portion of the cylindrical portion 31 located on the diaphragm 32 side. Of these, the external teeth forming portion 311 is the portion where large deformation occurs due to coning. Coning refers to a three-dimensional deformation in which the cylindrical portion 31 opens outward with respect to the rotation axis Ja at the position of the major axis La shown in FIG. 4 and narrows inward with respect to the rotation axis Ja at the position of the minor axis Lb. The external teeth forming portion 311 is deformed more than the body portion 312 when the wave generator 4 is fitted to the external gear 3.

[0035] The wave generator 4 is fitted into the external teeth forming portion 311 of the external gear 3. The wave generator 4 has a cam 41 and a bearing 42 attached to the outer periphery of the cam 41. The cam 41 has a shaft portion 411 that rotates around a rotation axis Ja, and a cam portion 412 that protrudes outward from one end of the shaft portion 411. When viewed from the direction along the rotation axis Ja, the outer periphery of the cam portion 412 has an elliptical or oval shape with a major axis La in the up-down direction and a minor axis Lb in the left-right direction as viewed in FIG. 4. The bearing 42 is fitted into the cam 41, and has a flexible inner ring 421 and an outer ring 423, and a plurality of balls 422 arranged between them.

[0036] The inner ring 421 is fitted onto the outer peripheral surface of the cam portion 412 of the cam 41, and is elastically deformed into an elliptical or oval shape along the outer peripheral surface of the cam portion 412. Accordingly, the outer ring 423 is also elastically deformed into an elliptical or oval shape. The outer peripheral surface of the outer ring 423 abuts against the inner peripheral surface 313 of the cylindrical portion 31, as shown in Fig. 3. The multiple balls 422 are held by a cage (not shown) so as to keep the intervals between them constant in the circumferential direction of the inner ring 421.

[0037] In this type of wave generator 4, as the cam 41 rotates around the rotation axis Ja, the orientation of the cam portion 412 changes, and the outer ring 423 is deformed accordingly. This causes the meshing positions of the internal gear 2 and the external gear 3 to move in the circumferential direction. At this time, since the inner ring 421 is fixedly installed with respect to the outer circumferential surface of the cam portion 412, the deformation state does not change.

[0038] Fig. 5 is a half sectional view of the external gear 3 cut along a plane including the rotation axis Ja. Note that the rotation axis Ja is not shown in Fig. 5. The external gear 3 will now be described in detail. As described above, the cylindrical portion 31 of the external gear 3 includes the external teeth forming portion 311, one end of which is the open end 34, and the body portion 312 of a constant thickness between the external teeth forming portion 311 and the diaphragm 32. The external teeth 33 are formed on the outer circumferential surface side of the external teeth forming portion 311.

[0039] In this embodiment, the thickness of the body portion 312 is constant, but it is also possible to set the cross-sectional shape of the body portion 312 so that the thickness gradually decreases from the diaphragm 32 side toward the external teeth forming portion 311, for example.

[0040] The diaphragm 32 has a first connection portion 321 that is connected to and curved at the end D of the cylindrical portion 31, a second connection portion 322 that is connected to the inner surface 351 of the boss portion 35, and a diaphragm body 323 that is connected to the first connection portion 321 and the second connection portion 322.

[0041] In other words, the first connection portion 321 is continuous with the inner circumferential end A of the diaphragm main body 323 and curves from a direction extending radially inward to a direction along the rotation axis Ja toward the cylindrical portion 31. An 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 an outer circumferential end C of the diaphragm main body 323 and is connected to an inner circumferential surface 351 of the boss portion 35. The diaphragm main body 323 extends in a radial direction that is perpendicular to the rotation axis Ja.

[0042] Here, the end D of the cylindrical portion 31 is a portion where the first connection portion 321 starts to bend on the cylindrical portion 31 side. In particular, the end D of the cylindrical portion 31 is a portion where the concave arc 54 of the first connection portion 321 starts to bend on the cylindrical portion 31 side. The outer peripheral end C of the diaphragm 32 is a portion where the surface of the second connection portion 322 on the side where the boss portion 35 of the diaphragm body 323 protrudes starts to bend from the diaphragm body 323 toward the boss portion 35. The inner peripheral end A of the diaphragm 32 is a portion where the first connection portion 321 starts to bend on the diaphragm body 323 side. In particular, the inner peripheral end A of the diaphragm 32 is a portion where the concave arc 54 of the first connection portion 321 starts to bend on the diaphragm body 323 side.

[0043] In this embodiment, for example, the length L1 in the radial direction relative to the rotation axis Ja from the inner peripheral surface 351 of the boss portion 35 connected to the second connection portion 322 to the outer peripheral surface 314 of the cylindrical portion 31 is 8 mm or more and 20 mm or less. Also, the length L2 in the direction of the rotation axis Ja from one opening end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 (diaphragm main body 323) opposite to the opening end 34 is 20 mm or more and 40 mm or less.

[0044] Therefore, the ratio of the length L2 from one opening end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 (diaphragm main body 323) in the direction of the rotation axis Ja to the length L1 from the inner peripheral surface 351 of the boss portion 35 to the outer peripheral surface 314 of the cylindrical portion 31 in the radial direction is 1.0 or more and 5.0 or less. In this way, the gear device 1 of this embodiment is a small device in a flat form in which the distance between the diaphragm 32 of the external gear 3 and the wave generator 4 is short in the direction of the rotation axis Ja.

[0045] The external gear 3 will now be described in more detail. 5, the outer circumferential surface 314 of the body portion 312 of the cylindrical portion 31 of the external gear 3 is defined by an outer straight line 53 extending parallel to the rotation axis Ja from a portion 51 connected to the external teeth forming portion 311 to an end D of the body portion 312. The inner circumferential surface 313 of the body portion 312 is also defined by an inner straight line 52 extending parallel to the rotation axis Ja when viewed in cross section. Therefore, the outer straight line 53 and the inner straight line 52 define the body portion 312 to have a constant thickness.

[0046] The outer circumferential surface of first connecting portion 321 of diaphragm 32 connected to body portion 312 is defined by a concave arc 54 when viewed in cross section. One end of the concave arc 54 smoothly connects to the outer straight line 53 at the position of end D of body portion 312. The inner circumferential surface of first connecting portion 321 is defined by a straight line portion 52a of the inner straight line 52 extending beyond end D, a convex arc 55 smoothly connected to this straight line portion 52a, and a straight line portion 56a smoothly connected to the other end of the convex arc 55 and extending radially outward.

[0047] Here, in first connection portion 321, the connection portion center position between inner circumferential end A and end portion D is designated as E. In first connection portion 321, the radius of curvature of outer convex arc 55 is smaller than that of inner concave arc 54. The thickness of first connection portion 321 is greatest at connection portion center position E, gradually increases from inner circumferential end A to connection portion center position E, and gradually decreases from connection portion center position E to end portion D.

[0048] A surface 327 of the diaphragm body 323 connected to the first connecting portion 321 on the cylindrical portion 31 side is defined by a concave curve 57 when viewed in cross section, as shown in FIG.

[0049] Here, the approximate center portion between the inner circumferential end A and the outer circumferential end C of the diaphragm body 323 is designated as B. The concave curve 57 is composed of, for example, a concave arc 57a that defines the portion from the inner circumferential end A to the center portion B, and a concave arc 57b that defines the portion from the center portion B to the outer circumferential end C. One end of the concave arc 57a is smoothly connected to the concave arc 54 at the position of the inner circumferential end A, and the other end is smoothly connected to the concave arc 57b.

[0050] 5, a surface 326 of the diaphragm body 323 opposite to the cylindrical portion 31 side, which is connected to the first connecting portion 321, is defined by a straight portion 56 extending from an end of a straight portion 56a beyond the inner circumferential end A. The straight portion 56 extends to the position of the outer circumferential end C along a radial direction perpendicular to the rotation axis Ja.

[0051] The thickness of the diaphragm body 323 defined by the concave curve 57 and the straight line portion 56 is thinnest at the center B, gradually increases from the center B toward the inner circumferential end A, and gradually increases from the center B toward the outer circumferential end C.

[0052] Next, the surface of the second connecting portion 322 on the cylindrical portion 31 side, which is connected to the outer peripheral end C of the diaphragm body 323, is defined by an arc extending beyond the outer peripheral end C of the concave arc 57b of the concave curve 57, when viewed in cross section. The end of the concave arc 57b is connected to a straight line portion 58 which defines the surface on the same side of the boss portion 35, when viewed in cross section.

[0053] 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 circumferential end C. The other end of the concave arc 59 smoothly connects to the inner circumferential surface 351 of the boss portion 35. The concave arc 59 is formed with a predetermined radius of curvature.

[0054] FIG. 6 is a diagram showing the relationship between the thickness and stress of the diaphragm 32. Specifically, in FIG. 6, 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), the horizontal axis is t(A) / t(C), and the vertical axis is the maximum negative load stress applied to the region from the inner peripheral end A to the outer peripheral end C. Note that since the load stress is applied more to the inner peripheral end A than to the outer peripheral end C, the vertical axis can also be regarded as the load stress applied to the inner peripheral end A.

[0055] As shown in FIG. 6, when t(A) / t(C), which is the ratio of the thickness t(A) of the inner peripheral end A of the diaphragm 32 to the thickness t(C) of the outer peripheral end C of the diaphragm 32, ranges from 0.7 to 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) of the inner peripheral end A is greater than the thickness t(C) of the outer peripheral end C, it can be seen that the load stress applied to the inner peripheral end A increases rapidly. Further in other words, when the thickness t(C) of the outer peripheral end C is thinner than the thickness t(A) of the inner peripheral end A, stress is also rapidly applied to the outer peripheral end C. Therefore, the thickness t(A) of the inner peripheral end A of the diaphragm 32 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is t(C)≧t(A), and preferably 0.7 < t(A) / t(C) ≦ 1.0. More preferably, 0.83 ≦ t(A) / t(C) ≦ 0.98.

[0056] 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 t(A), t(B), t(C), and t(D), respectively, it is set such that t(C)≧t(A)>t(D)>t(B).

[0057] Specifically, with reference to the thickness t(C) of the thickest outer peripheral end C among the four parts (inner peripheral end A, central portion B, outer peripheral end C, end portion D), it is preferable to set the thicknesses of the inner peripheral end A, the central portion B, and the end portion D as follows.

[0058] As described above, the thickness t(A) of the inner peripheral end A of the diaphragm 32 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is t(C) ≧ t(A), it is preferable that 0.7 < t(A) / t(C) ≦ 1.0, more preferably, 0.83 ≦ t(A) / t(C) ≦ 0.98.

[0059] The thickness t(B) of the central portion B of the diaphragm 32 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is t(C) ≧ t(A) > t(B), it is preferable that 0.5 < t(B) / t(C) < 0.9, more preferably, 0.55 ≦ t(B) / t(C) ≦ 0.65.

[0060] The thickness t(D) of the end portion D of the cylindrical portion 31 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is t(C) ≧ t(A) > t(D), it is preferable that 0.5 < t(D) / t(C) < 1.0, more preferably, 0.6 ≦ t(D) / t(C) ≦ 0.9.

[0061] Also, 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 t(B) < t(D).

[0062] According to the present embodiment, the following effects can be obtained.

[0063] 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 has a cylindrical portion 31, a diaphragm 32, and a boss portion 35. The diaphragm 32 has a first connection portion 321 connected to the end D of the cylindrical portion 31, a second connection portion 322 connected to the inner peripheral 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. Further, the end D of the cylindrical portion 31 is the starting point of the bend on the cylindrical portion 31 side of the first connection portion 321. Also, the outer peripheral end C of the diaphragm 32 is the starting point of the bend on the diaphragm body 323 side of the second connection portion 322. Further, the inner peripheral end A of the diaphragm 32 is the starting point of the bend on the diaphragm body 323 side of the first connection portion 321. In the radial direction, the ratio of the length from the inner peripheral surface 351 of the boss portion 35 connected to the second connection portion 322 to the outer peripheral surface 314 of the cylindrical portion 31, to the length in the direction of the rotation axis Ja from one open end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 on the side opposite to the open end 34 is 1.0 or more and 5.0 or less. 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). According to this configuration, in the gear device 1, in the radial direction, the ratio of the length from the inner peripheral surface 351 of the boss portion 35 to the outer peripheral surface 314 of the cylindrical portion 31, to the length in the direction of the rotation axis Ja from the open end 34 of the cylindrical portion 31 to the surface 326 of the diaphragm 32 is 1.0 or more and 5.0 or less. Thus, when the distance in the direction of the rotation axis Ja between the diaphragm 32 of the external gear 3 and the wave generator 4 is short, by setting t(C)≥t(A), the diaphragm 32 can withstand the stress applied thereto. Therefore, when the distance in the direction of the rotation axis Ja between the diaphragm 32 and the wave generator 4 is short, since the stress applied to the diaphragm 32 can be accommodated, the gear device 1 can be miniaturized.

[0064] In the gear device 1 of this embodiment, the ratio of the thickness t(A) of the inner peripheral end A of the diaphragm 32 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. According to this configuration, the gear device 1 can further withstand the stress applied to the diaphragm 32.

[0065] In the gear device 1 of the present 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 t(B), t(C) ≧ t(A) > t(B). Also, the thickness t(B) of the central portion B of the diaphragm 32 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is 0.5 < t(B) / t(C) < 0.9, and more preferably, 0.55 ≦ t(B) / t(C) ≦ 0.65. According to this configuration, in addition to the inner peripheral end A and the outer peripheral end C of the diaphragm 32, the central portion B of the gear device 1 also becomes more likely to deform, and by dispersing and reducing the stress concentration on the inner peripheral end A and the outer peripheral end C, fatigue failure of the diaphragm 32 can be suppressed.

[0066] In the gear device 1 of the present embodiment, when the thickness of the end portion D of the cylindrical portion 31 is t(D), t(C) ≧ t(A) > t(D). Also, the thickness t(D) of the end portion D of the cylindrical portion 31 with respect to the thickness t(C) of the outer peripheral end C of the diaphragm 32 is 0.5 < t(D) / t(C) < 1.0, and more preferably, 0.6 ≦ t(D) / t(C) ≦ 0.9. According to this configuration, the gear device 1 makes the end portion D of the cylindrical portion 31 thinner with respect to the outer peripheral end C of the diaphragm 32, so that the end portion D of the cylindrical portion 31 also becomes more likely 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.

[0067] 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). In the gear device 1, a shear stress in the rotational direction due to the load torque is applied to each cross section of the external gear 3. Furthermore, the shear stress becomes large when the radial distance from the rotation axis Ja is small. Therefore, the shear stress is smaller in the center B of the diaphragm 32, which is farther from the rotation axis Ja than the end D of the cylindrical portion 31, than in the end D of the cylindrical portion 31. As a result, even if the thickness t(B) of the center B of the diaphragm 32 is made thinner than the thickness t(D) of the end D of the cylindrical portion 31, the diaphragm 32 can withstand the shear stress.

[0068] The robot 100 of this embodiment includes a first member (base 110), a second member (first arm 120) that rotates relative to the first member (base 110), a gear device 1 that transmits a driving force that rotates the second member (first arm 120) relatively to the first member (base 110), and a driving source (motor 171) that outputs a driving force toward the gear device 1. The first arm 120 and the second arm 130 may be collectively regarded as a "second member." Furthermore, the "second member" may include a working head 140 and an end effector 150 in addition to the first arm 120 and the second arm 130. When the distance in the direction of the rotation axis Ja between the diaphragm 32 of the external gear 3 and the wave generator 4 is short, the gear device 1 can withstand even large stresses applied to the diaphragm 32, and therefore can be made compact. Therefore, the robot 100 including the first member, the second member, the gear device 1, and the drive source can also be made compact. [Explanation of symbols]

[0069] 1...gear device, 2...internal gear, 3...external gear, 4...wave generator, 31...cylindrical portion, 32...diaphragm, 34...open end of cylindrical portion, 35...boss portion, 100...robot, 110...base as first member, 120...first arm as second member, 171...motor as driving source, 313...inner peripheral surface of external gear, 314...outer peripheral surface of cylindrical portion, 321...first connecting portion, 322...second connecting portion, 323...diaphragm body, 326 ...surface of the diaphragm opposite the opening end, 351...inner surface of the boss portion, A...inner end of the diaphragm, t(A)...thickness of the inner end, B...center of the diaphragm, t(B)...thickness of the center portion, C...outer end of the diaphragm, t(C)...thickness of the outer end, D...end of the cylindrical portion, t(D)...thickness of the end, Ja...axis of rotation, L1...length from the inner surface of the boss portion to the outer surface of the cylindrical portion, L2...length from the opening end of the cylindrical portion to the surface of the diaphragm.

Claims

1. An internal gear; an external gear that is partially meshed with the internal gear and rotates relatively to the internal gear about a rotation axis, and has flexibility; a wave generator that comes into contact with an inner peripheral surface of the external gear and moves a meshing position between the internal gear and the external gear in a circumferential direction around the rotation axis; the external gear has a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to an outer circumferential end side of the diaphragm, the diaphragm has a first connection portion connected to an end of the cylindrical portion, a second connection portion connected to an inner circumferential surface of the boss portion, and a diaphragm body connected to the first connection portion and the second connection portion, a ratio of a length from an inner peripheral surface of the boss portion connected to the second connection portion to an outer peripheral surface of the cylindrical portion in the radial direction to a length from one opening end of the cylindrical portion to a surface of the diaphragm opposite to the opening end in the rotation axis direction is equal to or greater than 1.0 and equal to or less than 5.0, When the thickness of the inner peripheral end of the diaphragm is t(A), the thickness of the outer peripheral end is t(C), and the thickness of the central portion between the inner peripheral end and the outer peripheral end is t(B), t(C) ≧ t(A) > t(B), and A gear device characterized in that 0.5<t(B) / t(C)<0.

9.

2. 2. The gear arrangement of claim 1, A gear device characterized in that 0.7<t(A) / t(C)≦1.

0.

3. 2. The gear arrangement of claim 1, A gear device characterized in that 0.83≦t(A) / t(C)≦0.

98.

4. An internal gear; an external gear that is partially meshed with the internal gear and rotates relatively to the internal gear about a rotation axis, and has flexibility; a wave generator that comes into contact with an inner peripheral surface of the external gear and moves a meshing position between the internal gear and the external gear in a circumferential direction around the rotation axis; the external gear has a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to an outer circumferential end side of the diaphragm, the diaphragm has a first connection portion connected to an end of the cylindrical portion, a second connection portion connected to an inner circumferential surface of the boss portion, and a diaphragm body connected to the first connection portion and the second connection portion, a ratio of a length from an inner peripheral surface of the boss portion connected to the second connection portion to an outer peripheral surface of the cylindrical portion in the radial direction to a length from one opening end of the cylindrical portion to a surface of the diaphragm opposite to the opening end in the rotation axis direction is equal to or greater than 1.0 and equal to or less than 5.0, When the thickness of the inner peripheral end of the diaphragm is t(A), the thickness of the outer peripheral end is t(C), and the thickness of the central portion between the inner peripheral end and the outer peripheral end is t(B), t(C) ≧ t(A) > t(B), and A gear device, characterized in that 0.55≦t(B) / t(C)≦0.

65.

5. An internal gear; an external gear that is partially meshed with the internal gear and rotates relatively to the internal gear about a rotation axis, and has flexibility; a wave generator that comes into contact with an inner peripheral surface of the external gear and moves a meshing position between the internal gear and the external gear in a circumferential direction around the rotation axis; the external gear has a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to an outer circumferential end side of the diaphragm, the diaphragm has a first connection portion connected to an end of the cylindrical portion, a second connection portion connected to an inner circumferential surface of the boss portion, and a diaphragm body connected to the first connection portion and the second connection portion, a ratio of a length from an inner peripheral surface of the boss portion connected to the second connection portion to an outer peripheral surface of the cylindrical portion in the radial direction to a length from one opening end of the cylindrical portion to a surface of the diaphragm opposite to the opening end in the rotation axis direction is equal to or greater than 1.0 and equal to or less than 5.0, When the thickness of the inner peripheral end of the diaphragm is t(A), the thickness of the outer peripheral end is t(C), and the thickness of the end of the cylindrical portion is t(D), t(C) ≧ t(A) > t(D), and A gear device characterized in that 0.5<t(D) / t(C)<1.

0.

6. An internal gear; an external gear that is partially meshed with the internal gear and rotates relatively to the internal gear about a rotation axis, and has flexibility; a wave generator that comes into contact with an inner peripheral surface of the external gear and moves a meshing position between the internal gear and the external gear in a circumferential direction around the rotation axis; the external gear has a cylindrical portion, a diaphragm extending radially outward from the cylindrical portion, and an annular boss portion connected to an outer circumferential end side of the diaphragm, the diaphragm has a first connection portion connected to an end of the cylindrical portion, a second connection portion connected to an inner circumferential surface of the boss portion, and a diaphragm body connected to the first connection portion and the second connection portion, a ratio of a length from an inner peripheral surface of the boss portion connected to the second connection portion to an outer peripheral surface of the cylindrical portion in the radial direction to a length from one opening end of the cylindrical portion to a surface of the diaphragm opposite to the opening end in the rotation axis direction is equal to or greater than 1.0 and equal to or less than 5.0, When the thickness of the inner peripheral end of the diaphragm is t(A), the thickness of the outer peripheral end is t(C), and the thickness of the end of the cylindrical portion is t(D), t(C) ≧ t(A) > t(D), and A gear device, characterized in that 0.6≦t(D) / t(C)≦0.

9.

7. A gear device according to claim 1 or 4, When the thickness of the end of the cylindrical portion is t (D), A gear device, characterized in that t(B)<t(D).

8. A gear device according to claim 5 or 6, When the thickness of the central portion between the inner peripheral end and the outer peripheral end is t(B), A gear device, characterized in that t(B)<t(D).

9. A first member; A second member that rotates relative to the first member; A gear device according to any one of claims 1 to 8, which transmits a driving force for rotating the second member relatively to the first member; a drive source that outputs the drive force toward the gear device; A robot comprising:

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