Reduction drive
Patent Information
- Application Number
- JP2024051642
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-10-09
Smart Images
Figure 2025150645000001_ABST
Abstract
Description
[Technical Field]
[0001] An embodiment of the present invention relates to a reducer that is applied to a joint of a robot arm, for example. [Background technology]
[0002] The reducer is connected to the rotation shaft of the motor at the joint of the robot arm, reduces the rotation speed of the motor, and supplies torque to the robot arm (see, for example, Patent Document 1). [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-006337 Summary of the Invention [Problem to be solved by the invention]
[0004] A torque sensor is attached to the reducer to detect the torque supplied to the robot arm. For example, if the torque sensor is annular, the torque sensor is attached to the reducer case with the center of the torque sensor aligned with the axis of the reducer. If the reducer is, for example, a wave reducer, the case is deformed due to the operation of an elliptical wave generator provided inside the reducer. This deformation of the case is transmitted to the torque sensor. As a result, the detection output signal of the torque sensor contains ripples other than torque, reducing the torque detection accuracy. Therefore, it is desirable to prevent deformation of the reducer case.
[0005] The embodiments of the present invention provide a reducer capable of preventing deformation of the case. [Means for solving the problem]
[0006] The reducer of this embodiment includes an annular first case having a first surface, a second surface parallel to the first surface, a first side surface connecting the peripheries of the first surface and the second surface, and a first opening penetrating the first surface and the second surface; an annular second case having a second opening sharing an axis passing through the center of the first opening; an annular internal gear fixed to the second case and having internal teeth; and an annular internal gear having external teeth arranged inside the internal gear, one end of which in the axial direction is fixed to the first case and a portion of which is meshed with the internal gear. the third surface, a fourth surface parallel to the third surface, a second side surface connecting the periphery of the third surface and the fourth surface, and a third opening penetrating the third surface and the fourth surface, the fourth surface being fixed to the first surface of the first case with the center of the third opening coinciding with the center of the first opening, and the reinforcing member having a higher surface rigidity than the first case. [Brief explanation of the drawings]
[0007] [Figure 1] FIG. 1 is a plan view showing a reducer according to a first embodiment. [Figure 2] Side view of Figure 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a diagram schematically showing a cross section taken along line IV-IV in FIG. 3. [Figure 5] FIG. 2 is a plan view showing the reinforcing member of the first embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing a part of a reducer according to a second embodiment. [Figure 7] FIG. 10 is a plan view showing a reinforcing member according to a second embodiment. [Figure 8] FIG. 11 is a cross-sectional view showing a part of a reducer according to a third embodiment. [Figure 9] FIG. 10 is a plan view showing a reinforcing member according to a third embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a part of a reducer according to a fourth embodiment. [Figure 11] FIG. 10 is a plan view showing a reinforcing member according to a fourth embodiment. [Figure 12] FIG. 10 is a cross-sectional view showing a modified example of the first case. [Figure 13] 13 is a cross-sectional view showing a case where the first case shown in FIG. 12 is applied to the first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION
[0008] Hereinafter, embodiments will be described with reference to the drawings, in which the same parts are designated by the same reference numerals. (First embodiment) 1 to 3, a torque sensor 30 is disposed on the surface of the reducer 10, and a reinforcing member (hereinafter referred to as a plate) 40 is disposed between the reducer 10 and the torque sensor 30.
[0009] (Torque sensor configuration) 1, the torque sensor 30 includes an annular first structure 31, an annular second structure 32, a plurality of third structures 33 as beams, and a plurality of strain sensors 34. The first structure 31 and the second structure 32 function as a torque input section or output section, and the plurality of third structures 33 function as a torque transmission section. In this embodiment, the first structure 31 functions, for example, as a torque output section, and the second structure 32 functions as a torque input section.
[0010] The first structure 31, the second structure 32, and the third structure 33 are elastic bodies made of metal, for example, stainless steel. However, they are not limited to stainless steel, and other metals can also be used.
[0011] 1 and 3, the first structure 31 has a plurality of screw holes 31a that penetrate from the front surface to the back surface around the periphery. A robot arm (not shown) is fixed to the first structure 31 by screws (not shown) that are inserted into each of the screw holes 31a in the first structure 31.
[0012] The second structure 32 of the torque sensor 30 is concentric with the axis Z passing through the center of the first structure 31 and is disposed at a predetermined distance from the first structure 31. The axial thickness of the outer surface of the second structure 32 is equal to the axial thickness of the inner surface of the first structure 31, and the axial thickness of the inner surface of the second structure 32 is thicker than the axial thickness of the outer surface. However, this is not limited thereto, and the overall thickness of the second structure 32 may be equal to the thickness of the first structure 31.
[0013] The second structure 32 has a circular opening 32a in the center and a plurality of openings 32b around the opening 32a.
[0014] The plurality of third structures 33 are arranged radially with respect to the first structure 31 and the second structure 32, and connect the first structure 31 and the second structure 32 together.
[0015] The plurality of strain sensors 34 are disposed between the first structure 31 and the second structure 32. In this embodiment, the number of strain sensors 34 is, for example, eight, but is not limited to this and may be four or two.
[0016] As shown in FIG. 1, each strain sensor 34 includes a strain element 34a made of an elastic material, such as a metal, and a plurality of strain gauges 34b arranged on the strain element 34a via an insulating film (not shown).
[0017] One end of the flexure body 34a is disposed on the first structure 31, for example, on the rear surface of the first structure 31, and the other end is disposed on the second structure 32, for example, on the rear surface of the second structure 32. One end of the flexure body 34a is fixed to the rear surface of the first structure 31 by a fixing member (not shown) and a screw (not shown). The other end of the flexure body 34a is fixed to the rear surface of the second structure 32 by a fixing member (not shown) and a screw (not shown).
[0018] The plurality of strain sensors 34 constitute, for example, a plurality of bridge circuits (not shown), and torque is detected by these bridge circuits.
[0019] (Configuration of the reducer) As shown in Figures 3 and 4, the reducer 10 is, for example, a wave reducer, and includes an annular first case 11, an annular second case 12, an annular internal gear 13, a flexible cylindrical external gear 14, bearings 15, 16, 17, and 18, and an elliptical wave generator 19.
[0020] The annular first case 11 has a first surface (front surface) 11a, a second surface 11b parallel to the first surface 11a, and a first side surface 11c connecting the periphery of the first surface 11a and the second surface 11b. The first case 11 has a circular first opening 11d in the center that penetrates the first surface 11a and the second surface 11b, and a plurality of openings 11e that penetrate the first surface 11a and the second surface 11b around the periphery. Furthermore, a plurality of screw holes 11f are provided between the plurality of openings 11e and the first opening 11d. The positions of the plurality of screw holes 11f coincide with the positions of a plurality of openings 32b provided in the second structure 32 of the torque sensor 30.
[0021] Furthermore, the center of the first opening 11d is aligned with the axis Z, and the diameter of the first opening 11d is equal to the diameter of the opening 32a provided in the second structure 32 of the torque sensor 30.
[0022] The annular second case 12 has a second opening 12a in the center thereof. The center of the second opening 12a is aligned with the axis Z, and the diameter of the second opening 12a is larger than the diameter of the first opening 11d.
[0023] The bearing 15 is, for example, a rolling bearing, and includes an inner ring 15a, an outer ring 15b, and, for example, a roller 15c disposed between the inner ring 15a and the outer ring 15b. The diameter of the inner ring 15a is larger than the diameter of the first opening 11d of the first case 11, and part of the periphery of the outer ring 15b of the bearing 15 is in contact with the inside of the side surface 11c of the first case 11. In this state, the outer ring 15b is fixed to the second surface 11b of the first case 11 together with the external gear 14, which will be described later.
[0024] The annular internal gear 13 has internal teeth 13a on its inside. The internal gear 13 is fixed to the second case 12 together with the inner ring 15a of the bearing 15. That is, the second case 12 has a plurality of openings 12b, and the internal gear 13 and the inner ring 15a of the bearing 15 have a plurality of openings or screw holes at the same positions as the plurality of openings 12b. The internal gear 13 is fixed to the inner ring 15a of the bearing 15 and the second case 12 by being fixed with screws (not shown) inserted into the openings or screw holes, including the openings 12b.
[0025] The cylindrical, flexible external gear 14 is disposed inside the internal gear 13. Specifically, the longitudinal direction of the cylinder is disposed along the axis Z. One end of the external gear 14 (the end on the second case 12 side) has external teeth 14a that can mesh with the internal teeth 13a, and the other end (the end on the first case 11 side) is bent outward perpendicular to the axis Z and is fixed to the first case 11 together with the outer ring 15b of the bearing 15.
[0026] Specifically, an annular fixing member 21 is provided on the other end of the outer ring 15b, and the other end of the outer ring 15b is connected to the fixing member 21. The fixing member 21 has a plurality of openings 11e in the first case 11 and a plurality of openings or screw holes at the same positions as the plurality of openings 11e in the outer ring 15b, for example, the screw holes, and screws (not shown) are inserted into the openings 11e, the openings or screw holes in the fixing member 21, and the screw holes in the outer ring 15b, thereby fixing the other end of the external gear 14 together with the outer ring 15b of the bearing 15 to the first case 11.
[0027] Furthermore, a flexible bearing 16 is disposed inside one end of the external gear 14. The bearing 16 includes an outer ring 16a, an inner ring 16b, and a plurality of balls disposed between the outer ring 16a and the inner ring 16b. The outer ring 16a of the bearing 16 is fixed to the inside of one end (the end on the second case side) of the external gear 14, and the external gear 14 is movable together with the outer ring 16a of the bearing 16. The inner ring 16b of the bearing 16 is fixed to a wave generator 19.
[0028] The wave generator 19 is arranged, for example, within the opening 32a of the torque sensor 30, the first opening 11d of the first case 11, the second opening 12a of the second case, and the inner ring 16b of the bearing 16, and is rotatably held by a bearing 17 provided on the second surface 11b of the first case 11 and a bearing 18 provided on the second case 12.
[0029] The cross section of wave generator 19 is elliptical at the portion where inner ring 16b of bearing 16 is fixed, and is circular at the portions corresponding to bearings 17 and 18. For example, a through hole 19a is provided in the center of wave generator 19 along axis Z, and the shaft of a motor (not shown) is inserted into this through hole 19a. Wave generator 19 is fixed to the motor shaft and rotated by the motor.
[0030] (Configuration of reinforcing member) The plate 40 is disposed between the first surface 11a of the first case 11 of the reducer 10 and the second structure 32 of the torque sensor 30, and has a diameter (outer diameter) substantially equal to the diameter of the second structure 32.
[0031] As shown in FIG. 5 , the plate 40 has a flat annular shape and includes a third surface 40a, a fourth surface 40b parallel to the third surface 40a, and a second side surface 40c connecting the peripheries of the third surface 40a and the fourth surface 40b. The plate 40 also includes a third opening 40d in the center that penetrates the third surface 40a and the fourth surface 40b, and multiple fourth openings 40e around the third opening 40d. The diameter of the third opening 40d is the same as the diameters of the opening 32a of the torque sensor 30 and the first opening 11d of the first case 11, but is preferably the same as the diameter of the opening 32a of the torque sensor 30. The multiple fourth openings 40e are located at the same positions as the multiple openings 32b provided in the second structure 32 of the torque sensor 30. The diameter of the fourth opening 40e is the same as the diameter of the opening 32b of the second structure 32.
[0032] In the first embodiment, the diameter of the plate 40 is set to be the same as, for example, the diameter of the second structure 32 of the torque sensor 30. It is desirable that the thickness of the plate 40 be thin in order to make the robot arm small and lightweight. However, the diameter and thickness of the plate 40 are not limited to these, as will be described below.
[0033] The plate 40 is made of a material having a higher specific strength (tensile strength divided by density) than the material of the first case 11 of the reducer 10. Specifically, if the first case 11 of the reducer 10 is made of, for example, an aluminum alloy, the plate 40 is made of an iron-based material such as high-strength steel or a titanium alloy. However, the material of the plate 40 is not limited to these, and it is sufficient that the plate 40 has a higher surface rigidity than the first case 11.
[0034] The minimum dimensions of the plate 40 are as follows:
[0035] D≧1.5d Where, D: diameter of plate 40 d: diameter of the third opening 40d The optimum range for the diameter D of the plate 40 is 1.8d to 2.2d.
[0036]
number
[0037] where t is the thickness of plate 40 Ics: Moment of inertia of internal gear 13
[0038]
number
[0039] Then, The optimum range of the thickness t of the plate 40 is t=2.2A to 2.6A. In other words, the thickness of the plate 40 in the direction of the axis Z may be within the range of the thickness of the first case 11.
[0040] 3, the plate 40 is disposed between the first surface 11a of the first case 11 and the second structure 32 of the torque sensor 30. The center of the third opening 40d of the plate 40 is aligned with the centers of the first opening 11d of the first case 11 and the opening 32a of the torque sensor 30. In this state, screws 20 are inserted into the multiple openings 32b of the torque sensor 30, the fourth opening 40e of the plate 40, and the multiple screw holes 11f of the first case 11, and the plate 40 is fixed between the first surface 11a of the first case 11 and the torque sensor 30.
[0041] (action) As shown in FIG. 4, when the motor rotates, for example, in the direction of arrow A, the wave generator 19 of the reducer 10 also rotates in the direction of arrow A. As the wave generator 19 rotates, the external gear 14 rotates while deforming via the flexible bearing 16, and the meshing position between the external teeth 14a and the internal teeth 13a of the internal gear 13 moves in the direction of arrow A. The number of teeth of the external gear 14 is smaller than the number of teeth of the internal gear 13. Therefore, the rotation speed of the external gear 14 is reduced relative to the rotation of the wave generator 19. Because the external gear 14 is fixed to the first case 11, the first case 11 rotates together with the external gear 14 in the direction of arrow A relative to the second case 12.
[0042] When the external gear 14 rotates and deforms via the flexible bearing 16 in accordance with the rotation of the wave generator 19, the internal gear 13 expands in the major axis direction (directions of arrows B and C in the figure) of the elliptical wave generator 19 and contracts in the minor axis direction (directions of arrows D and E in the figure). These expanding and contracting portions move in the direction of arrow A in the figure as the wave generator 19 rotates. The internal gear 13 is fixed to the inner ring 15a of the rolling bearing 15, and the outer ring 15b of the rolling bearing 15 is fixed to the first case 11. For this reason, like the internal gear 13, the expanding and contracting portions of the first case 11 also move in the direction of arrow A in the figure as the wave generator 19 rotates.
[0043] However, a plate 40 having higher surface rigidity than the first case 11 is disposed between the first surface 11a of the first case 11 and the second structure 32 of the torque sensor 30. This makes it possible to prevent the deformation of the first case 11 from being transmitted to the second structure 32 of the torque sensor 30. Therefore, the torque sensor 30 can prevent the deformation of the first case 11 from being detected as a ripple, and can accurately detect torque.
[0044] The reducer 10 is not limited to a wave reducer, but may be a reducer using a planetary gear that may affect the torque detection of the torque sensor 30 as the speed reducing operation proceeds.
[0045] (Effects of the first embodiment) According to the first embodiment, the plate 40, which has higher surface rigidity than the first case 11 of the reducer 10, is connected between the torque sensor 30 and the reducer 10. Therefore, the plate 40 can prevent deformation of the first case 11 from being transmitted to the torque sensor 30. Therefore, the torque sensor 30 can detect torque with high accuracy.
[0046] Generally, in order to increase the surface rigidity of first case 11, it is conceivable to increase the thickness of first case 11 or use a harder material, but in this case, there is a concern that the reducer will become larger and heavier.
[0047] However, according to the first embodiment, the thickness of the plate 40 in the axial Z direction is thinner than the thickness of the first case 11 and the thickness of the torque sensor 30, and the weight of the plate 40 is lighter than the thickness of the first case 11 and the weight of the torque sensor 30. This makes it possible to make the reducer 10 thinner and lighter, and further allows for high-speed operation.
[0048] Furthermore, since the reducer 10 can be made thinner, the arm length of the robot arm can be shortened, and the moment of inertia can be reduced by making the reducer 10 lighter. Therefore, the robot arm can be made smaller, lighter, and operate at higher speeds.
[0049] (Second embodiment) 6 and 7 show a portion of a reducer 10 according to a second embodiment. In the first embodiment, the plate 40 is flat and annular, but in the second embodiment, the plate 50 serving as a reinforcing member has a first protrusion 50f, a second protrusion 50g, a plurality of third protrusions 50h, and a plurality of fourth protrusions 50i.
[0050] Specifically, the plate 50 is annular with a diameter (outer diameter) equal to the diameter of the second structure 32 of the torque sensor 30, and includes a third surface 50a, a fourth surface 50b parallel to the third surface 50a, and a second side surface 50c connecting the peripheries of the third surface 50a and the fourth surface 50b.
[0051] Furthermore, the plate 50 includes a first annular protrusion 50f provided on the third surface 50a, a second annular protrusion 50g provided on the fourth surface 50b, and a third opening 50d that penetrates the first protrusion 50f and the second protrusion 50g. The first protrusion 50f and the second protrusion 50g each protrude in the axial Z direction, and the diameter of the third opening 50d is equal to the diameter of the opening 32a of the torque sensor 30 and approximately equal to the diameter of the first opening 11d of the first case 11.
[0052] The plate 50 includes a plurality of fourth openings 50e penetrating the third surface 50a and the fourth surface 50b around its periphery. Each of the fourth openings 50e is disposed at a position corresponding to a screw hole 11f of the first case 11 and an opening 32b of the torque sensor 30.
[0053] 7, the first protrusion 50f of the plate 50 includes a plurality of third protrusions 50h spaced apart at a predetermined interval around its periphery, and the second protrusion 50g includes a plurality of fourth protrusions 50i spaced apart at a predetermined interval around its periphery. The third protrusions 50h and the fourth protrusions 50i each protrude in a direction perpendicular to the axis Z. For example, four third protrusions 50h and four fourth protrusions 50i are provided, and are arranged at equal intervals, for example, 90° apart, around the first protrusion 50f and the second protrusion 50g.
[0054] The material of the plate 50 and the first case 11 is the same as that of the first embodiment, but the thickness of the first protrusion 50f and the second protrusion 50g of the plate 50 is increased compared to that of the first embodiment, so that the plate 50 has higher surface rigidity compared to the plate 40 of the first embodiment.
[0055] 6, in the torque sensor 30, the back surface of the second structure 32 includes a first annular recess 32c around the opening 32a. The first recess 32c has a diameter and depth sufficient to accommodate the first protrusion 50f of the plate 50.
[0056] The first surface 11a of the first case 11 of the reducer 10 includes a second annular recess 11g around the first opening 11d. The second recess 11g has a diameter and depth sufficient to accommodate the second protrusion 50g of the plate 50.
[0057] When the plate 50 is disposed between the first case 11 and the torque sensor 30, the first protrusion 50f is housed in the first recess 32c of the torque sensor 30, and the second protrusion 50g is housed in the second recess 11g of the first case 11. In this state, the torque sensor 30, the plate 50, and the first case 11 are fixed together by the screws 20 inserted into the openings 32b, the fourth openings 50e, and the screw holes 11f, as in the first embodiment.
[0058] The side surface of the first recess 32c of the torque sensor 30 is in line contact with the tips of the multiple third protrusions 50h provided on the side surface of the first protrusion 50f of the plate 50, and the side surface of the second recess 11g of the first case 11 is in line contact with the tips of the multiple fourth protrusions 50i provided on the side surface of the second protrusion 50g of the plate 50. Therefore, the torque sensor 30, the plate 50, and the first case 11 can be easily centered, and interference of the torque sensor 30 with other axes can be suppressed.
[0059] (Effects of the second embodiment) According to the second embodiment, the plate 50 has a first protrusion 50f and a second protrusion 50g. Therefore, the plate 50 of the second embodiment can be made thicker in the direction of axis Z than the plate 50 of the first embodiment, and can have higher surface rigidity than the plate 50 of the first embodiment. Therefore, it is possible to further prevent deformation of the first case 11 caused by operation of the wave generator 19 from being transmitted to the torque sensor 30.
[0060] Moreover, the torque sensor 30 has a first recess 32c that accommodates the first protrusion 50f and the third protrusion 50h of the plate 50, and the first case 11 of the reducer 10 has a second recess 11g that accommodates the second protrusion 50g and the fourth protrusion 50i of the plate 50. Therefore, the plate 50 is reliably positioned between the torque sensor 30 and the first case 11 of the reducer 10. This makes it possible to prevent deformation of the first case 11 from being transmitted to the torque sensor 30, thereby improving the accuracy of torque detection by the torque sensor 30.
[0061] Furthermore, the torque sensor 30 has a first recess 32c that accommodates the first protrusion 50f and the third protrusion 50h of the plate 50, and the first case 11 of the reducer 10 has a second recess 11g that accommodates the second protrusion 50g and the fourth protrusion 50i of the plate 50. Therefore, even if the thickness of the plate 50 is increased by the first protrusion 50f and the second protrusion 50g, the thickness of the reducer 10 and the torque sensor 30 can be prevented from increasing. This makes it possible to reduce the size and weight of the robot arm.
[0062] (Third embodiment) 8 and 9 show a part of the third embodiment. In the first and second embodiments, the torque sensor 30, plates 40 and 50, and first case 11 are fixed together by a plurality of screws 20 inserted therein, as in the first embodiment. In the third embodiment, the plate 60 serving as a reinforcing member is fixed only to the first case 11.
[0063] The plate 60 has a flat annular shape, and the diameter (outer diameter) of the plate 60 is smaller than the diameter of the second structure 32 of the torque sensor 30 and larger than the diameter of the opening 32a of the second structure 32. The thickness of the plate 60 in the axial Z direction is larger than the thickness of the plate 40 of the first embodiment and approximately equal to the thickness of the plate 50 of the second embodiment, and the material of the plate 60 is the same as that of the first embodiment. Therefore, the plate 60 has approximately the same surface rigidity as the plate 50 of the second embodiment. The material of the first case 11 is the same as that of the first embodiment.
[0064] The diameter of the third opening 60a of the plate 60 is approximately equal to the diameter of the first opening 11d of the first case 11 and the diameter of the opening 32a of the torque sensor 30. The plate 60 includes a plurality of fourth openings 60b around the third opening 60a. Each fourth opening 60b is shaped to be able to accommodate a screw and its head (not shown).
[0065] 8, the first surface 11a of the first case 11 has a fifth recess 11i around the first opening 11d. The diameter of the fifth recess 11i is approximately equal to the diameter of the plate 60, and the depth is approximately equal to the thickness of the plate 60. The bottom of the fifth recess 11i includes a plurality of screw holes 11j, for example. Each screw hole 11j is disposed at a position corresponding to each fourth opening 60b of the plate 60. The material of the first case 11 is the same as that of the first embodiment.
[0066] The first surface 11a of the first case 11 includes a ring-shaped fifth protrusion 11k around the fifth recess 11i. The fifth protrusion 11k protrudes slightly in the axial Z direction from the first surface 11a of the first case 11. The thickness of the fifth protrusion 11k from the first surface 11a in the axial Z direction is smaller than the width of the fifth protrusion 11k in a direction perpendicular to the axial Z direction. The outer diameter of the fifth protrusion 11k is slightly larger than the diameter of the fifth recess 11i.
[0067] Additionally, the rear surface of the second structure 32 of the torque sensor 30 includes a sixth recess 32e. The diameter of the sixth recess 32e is approximately equal to the outer diameter of the fifth protrusion 11k, and the depth thereof is approximately equal to the thickness of the fifth protrusion 11k in the axial Z direction.
[0068] The plate 60 is housed in the fifth recess 11i of the first case 11. In this state, the plate 60 is fixed in the fifth recess 11i of the first case 11 by a screw (not shown) inserted into the fourth opening 60b of the plate 60 and the screw hole 11j of the first case 11.
[0069] The second structure 32 of the torque sensor 30 has a sixth recess 32e on the back surface thereof fitted into the annular fifth protrusion 11k of the first case 11. In this state, a screw (not shown) is inserted into the opening 32b of the torque sensor 30 and the screw hole 11f of the first case 11, and the torque sensor 30 is fixed to the first case 11 by this screw.
[0070] (Effects of the third embodiment) The third embodiment can also provide the same effects as the first and second embodiments.
[0071] Moreover, the plate 60 is housed in the fifth recess 11i of the first case 11, and the plate 60 is not interposed between the torque sensor 30 and the first case 11. This prevents the reducer 10 from becoming larger in size due to the thickness of the plate 60.
[0072] Furthermore, the first case 11 has a fifth protrusion 11k around the fifth recess 11i, and the second structure 32 of the torque sensor 30 has a sixth recess 32e that houses the fifth protrusion 11k. This strengthens the connection between the first case 11 and the second structure 32 and suppresses deformation of the first case 11 by the plate 60, thereby improving the torque detection accuracy.
[0073] (Fourth embodiment) 10 and 11 show a part of the fourth embodiment. In the first to third embodiments, the plates 40, 50, and 60 are attached to the first surface 11a of the first case 11. In the fourth embodiment, the plate 70 is attached to the second surface 11b of the first case 11.
[0074] The materials of the plate 70 and the first case 11 are the same as those in the first embodiment. The plate 70 has a flat annular shape, and the diameter (outer diameter) of the plate 70 is smaller than the diameter of the second structure 32 of the torque sensor 30 and larger than the diameter of the opening 32a of the second structure 32. The thickness of the plate 70 in the axial Z direction is larger than the thickness of the plate 40 of the first embodiment and is approximately equal to the thickness of the plate 50 of the second embodiment.
[0075] The diameter of the opening 70a of the plate 70 is approximately equal to the diameter of the first opening 11d of the first case 11 and the opening 32a of the torque sensor 30. The plate 70 includes, for example, a plurality of screw holes 70b spaced apart at predetermined intervals around the periphery of the opening 70a.
[0076] Meanwhile, the first surface 11a of the first case 11 includes an annular sixth protrusion 11l around the first opening 11d. The sixth protrusion 11l protrudes in the Z-axis direction, and its thickness is approximately equal to the thickness of the fifth protrusion 11k of the third embodiment. The diameter of the sixth protrusion 11l is smaller than the diameter of the plate 70 and larger than the diameter of the opening 70a of the plate 70. The sixth protrusion 11l of the first case 11 includes a plurality of openings 11m spaced apart at predetermined intervals around the first opening 11d. Each opening 11m is positioned corresponding to a screw hole 70b in the plate 70 and is shaped to accommodate a screw and its head.
[0077] The back surface of the second structure 32 of the torque sensor 30 includes a seventh recess 32f. The seventh recess 32f is substantially the same as the sixth recess 32e of the third embodiment, and has a shape that allows the sixth protrusion 11l of the first case 11 to fit therein.
[0078] When the plate 70 is placed on the second surface 11b of the first case 11, it is fixed to the second surface 11b of the first case 11 by screws (not shown) inserted into the openings 11m of the first case 11 and the screw holes 70b of the plate 70.
[0079] The torque sensor 30 has a seventh recess 32f provided on the back surface thereof fitted into the annular sixth protrusion 11l of the first case 11. In this state, a screw (not shown) is inserted into the opening 32b of the torque sensor 30 and the screw hole 11f of the first case 11, and the torque sensor 30 and the first case 11 are fixed together by this screw.
[0080] (Effects of the fourth embodiment) The fourth embodiment can also achieve the same effects as the first to third embodiments. Moreover, in the fourth embodiment, the plate 70 is directly connected to the second surface 11b of the first case 11, so deformation of the first case 11 can be suppressed and the size of the reducer 10 can be prevented from increasing due to the thickness of the plate 60.
[0081] Furthermore, the first case 11 has an annular sixth protrusion 11l, and the second structure 32 of the torque sensor 30 has a seventh recess 32f that accommodates the sixth protrusion 11l. This strengthens the connection between the first case 11 and the second structure 32 and prevents deformation of the first case 11 by the plate 60, thereby improving the torque detection accuracy.
[0082] (Modification of the first case) 12 and 13 show a modified example of the first case 11, which is applied to, for example, the first embodiment. However, this modification can also be applied to the second to fourth embodiments.
[0083] The second surface 11b of the first case 11 includes a cylindrical holding portion 11n that holds the bearing 17, and includes a plurality of fins 11o spaced a predetermined distance apart around the holding portion 11n. The fins 11o are arranged radially about the axis Z from the periphery of the holding portion 11n near the fixed member 21. The thickness of each fin 11o in the direction of the axis Z is less than the distance between the second surface 11b of the first case 11 and the other end of the external gear 14, and each fin 11o does not come into contact with the other end of the external gear 14 or the fixed member 21.
[0084] A lubricant such as grease 80 is filled into the space formed by the second surface 11b of the first case 11 of the reducer 10, the fixed member 21, the external gear 14, the flexible bearing 16, the wave generator 19, the cylindrical holding portion 11n, and the bearing 17.
[0085] The function of the multiple fins 11o is to increase the fluidity of the grease 80. When the wave generator 19 is rotated by a motor (not shown), the first case 11 fixed to the external gear 14 is rotated together with the external gear 14. When the first case 11 is rotated, the grease 80 is agitated by the multiple fins 11o. Therefore, the grease 80 is supplied to the external gear 14, the bearing 16, and the bearing 17.
[0086] (Transformation effect) According to the above modification, the second surface 11b of the first case 11 has a plurality of fins 11o, and these fins 11o increase the fluidity of the grease 80 inside the reducer 10. This allows the grease 80 to be filled into the external gear 14, bearing 16, and bearing 17 inside the reducer 10. This makes it possible to ensure stable operation of the reducer 10 over a long period of time.
[0087] Moreover, the multiple fins 11o of the first case 11 also function as ribs, and can increase the rigidity in the planar direction of the first case 11. This makes it possible to further prevent deformation of the reducer 10, and therefore further improve the torque detection accuracy of the torque sensor 30.
[0088] In each embodiment, the plates 40, 50, 60, 70 and the torque sensor 30 are fixed to the first case 11 with screws, but the fixing method is not limited to this, and other means such as pins, adhesive, or welding can also be used. When fixing means other than screws or pins are used, the openings or screw holes into which they are inserted can be omitted.
[0089] Furthermore, the present invention is not limited to the above-described embodiments, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]
[0090] 10... reducer, 11... first case, 11a... first surface, 11b... second surface, 11c... first side surface, 11d... first opening, 11g... second recess, 11i... fifth recess, 11k... fifth protrusion, 11l... sixth protrusion, 12... second case, 12a... second opening, 13... internal gear, 13a... internal teeth, 14... external gear, 14a... external teeth, 19... wave generator, 20... screw, 30... torque sensor, 32c... first recess , 32e...6th recess, 32f...7th recess, 40...plate (reinforcing member), 40a...3rd surface, 40b...4th surface, 40c...2nd side surface, 40d...3rd opening, 40e...4th opening, 50...plate (reinforcing member), 50f...1st protrusion, 50g...2nd protrusion, 50h...3rd protrusion, 50i...4th protrusion, 60...plate (reinforcing member), 70...plate (reinforcing member), 80...grease (lubricant).
Claims
1. an annular first case having a first surface, a second surface parallel to the first surface, a first side surface connecting the peripheries of the first surface and the second surface, and a first opening penetrating the first surface and the second surface; an annular second case having a second opening that shares an axis passing through the center of the first opening; an annular internal gear fixed to the second case and having internal teeth; a flexible cylindrical external gear disposed inside the internal gear, one end of which in the axial direction is fixed to the first case, and which has external teeth a portion of which meshes with the internal gear; an elliptical wave generator disposed inside the external gear and rotating the external gear; an annular reinforcing member having a third surface, a fourth surface parallel to the third surface, a second side surface connecting the peripheries of the third surface and the fourth surface, and a third opening penetrating the third surface and the fourth surface, the fourth surface being fixed to the first surface of the first case with the center of the third opening aligned with the center of the first opening; wherein the reinforcing member has a surface rigidity higher than that of the first case.
2. 2. The reducer according to claim 1, wherein the reinforcing member is disposed between one of the torque input and output portions of the torque sensor and the first surface of the first case, and is fixed to one of the input and output portions and the first surface of the first case.
3. the third surface of the reinforcing member has a first protrusion protruding in the axial direction around the third opening, the fourth surface of the reinforcing member has a second protrusion protruding in the axial direction around the third opening, the torque sensor has a first recess that accommodates the first protrusion of the reinforcing member, The first surface of the first case has a second recess that accommodates the second protrusion of the reinforcing member.
3. The reducer according to claim 2, wherein:
4. the first protrusion of the reinforcing member has a plurality of third protrusions around the first protrusion, The reducer according to claim 3 , wherein the second protrusion of the reinforcing member has a plurality of fourth protrusions around it.
5. the first surface of the first case has a fifth recess that accommodates the reinforcing member, 2. The reducer according to claim 1, wherein the reinforcing member is fixed in the fifth recess, and one of the input portion and the output portion of the torque sensor is fixed to the first surface of the first case.
6. the first surface of the first case has a fifth protrusion around the fifth recess, 6. The reducer according to claim 5, wherein one of the input portion and the output portion of the torque sensor has a sixth recess that accommodates the fifth protrusion.
7. the reinforcing member is fixed to the second surface of the first case, 2. The reducer according to claim 1, wherein one of the input portion and the output portion of the torque sensor is fixed to the first surface of the first case.
8. the first surface of the first case has a sixth protrusion around the first opening, the sixth protrusion having a diameter smaller than the reinforcing member and larger than the diameter of the first opening; 8. The reducer according to claim 7, wherein one of the input portion and the output portion of the torque sensor has a seventh recess that houses the sixth protrusion.
9. a plurality of fins provided on the second surface of the first case; a lubricant filled at least between the second surface of the first case and the cylindrical external gear; 2. The reducer according to claim 1, further comprising: