deceleration device

Abstract

To vary rigidity of a reduction gear.SOLUTION: A reduction gear (1) includes: a variable rigidity part (50) capable of varying rigidity of the reduction gear (1); and a first internal tooth gear (31G) and an external tooth gear (30) engaging each other. The variable rigidity part (50) causes the first internal tooth gear (31G) to displace toward the external tooth gear (30) to increase rigidity of the reduction gear (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reduction gear transmission. [Background technology]

[0002] BACKGROUND ART Conventionally, a reduction gear device used to drive a joint of a robot is known (see, for example, Patent Document 1). This type of reduction gear may require different rigidity depending on the situation, for example, high rigidity to suppress vibration during movement, while low rigidity is required to provide soft contact when gripping a workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-97363 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above circumstances, and has an object to change the rigidity of a reduction gear transmission. [Means for solving the problem]

[0005] The present invention provides a reduction gear transmission, a variable stiffness unit that varies the stiffness of the reduction gear device while the reduction gear device is in operation, and a pair of gears that mesh with each other; the pair of gears is an internal gear and an external gear, The variable stiffness portion is The internal gear is Towards the gears Radially inward The rigidity is improved by displacing the member. [Effects of the Invention]

[0006] According to the present invention, the rigidity of the reduction gear transmission can be changed. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing a schematic configuration of a robot to which a reduction gear transmission according to an embodiment is applied; [Figure 2] FIG. 2A is a cross-sectional view of the reduction gear transmission according to the present embodiment, and FIG. 2B is a cross-sectional view taken along line AA in FIG. [Figure 3] 2(a) is an enlarged view of part B in FIG. 2(a), illustrating the configuration and operation of the variable stiffness section of the embodiment. FIG. [Figure 4] 10A and 10B are diagrams illustrating modified examples of the variable stiffness portion of the embodiment. [Figure 5] 10A and 10B are diagrams illustrating modified examples of the variable stiffness portion of the embodiment. [Figure 6] 10A and 10B are diagrams illustrating modified examples of the variable stiffness portion of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0009] [Robot configuration] FIG. 1 is a diagram showing a schematic configuration of a robot 100 to which a reduction gear transmission 1 according to this embodiment is applied. As shown in this figure, the reduction gear 1 according to this embodiment is incorporated into a joint 102 that connects arms 101 (101a, 101b) of a robot 100, and drives the joint 102. The robot 100 is, for example, a collaborative robot that performs a predetermined task in collaboration with a human, and its operation is controlled by a control unit 110. Note that the use of the reduction gear 1 according to this embodiment is not limited to robots, and the reduction gear 1 can be applied to various applications in which changing the rigidity of the reduction gear 1 provides an advantage, such as machine tools.

[0010] [Configuration of reduction gear] FIG. 2(a) is a cross-sectional view showing the reduction gear transmission 1 according to this embodiment, and FIG. 2(b) is a cross-sectional view taken along line AA in (a). As shown in Figures 2(a) and (b), the reduction gear 1 is a cylindrical flexible mesh type reduction gear, and includes an exciter shaft 10, an external gear 30, a first internal gear 31G and a second internal gear 32G, an exciter bearing 12, a casing 33, a first cover 34, and a second cover 35.

[0011] The vibrator shaft 10 is a hollow cylindrical shaft that rotates around a rotation axis O1, and includes a vibrator 10A whose cross section perpendicular to the rotation axis O1 has a non-circular (e.g., elliptical) outer shape, and shaft portions 10B and 10C provided on both sides of the vibrator 10A in the axial direction. The elliptical shape is not limited to a geometrically strict ellipse, but also includes an approximate ellipse. The shaft portions 10B and 10C are shafts whose cross section perpendicular to the rotation axis O1 has a circular outer shape. In the following description, the direction along the rotation axis O1 is referred to as the "axial direction," the direction perpendicular to the rotation axis O1 is referred to as the "radial direction," and the direction of rotation about the rotation axis O1 is referred to as the "circumferential direction." Additionally, within the axial direction, the side (left side in the drawing) that is connected to an external driven member and outputs decelerated motion to the driven member is referred to as the "output side," and the side opposite the output side (right side in the drawing) is referred to as the "anti-output side."

[0012] The external gear 30 is a flexible cylindrical member centered on the rotation axis O1, and has teeth on its outer periphery.

[0013] The first internal gear 31G and the second internal gear 32G rotate around the rotation axis O1 around the vibrator shaft 10. Of these, the first internal gear 31G is configured by providing internal teeth at a corresponding location on the inner periphery of the first internal gear member 31. The second internal gear 32G is configured by providing internal teeth at a corresponding location on the inner periphery of the second internal gear member 32. The first internal gear 31G and the second internal gear 32G are arranged side by side in the axial direction and mesh with the external gear 30. Specifically, the first internal gear 31G meshes with teeth of the external gear 30 on the opposite side from the axial center to the output side, and the second internal gear 32G meshes with teeth of the external gear 30 on the output side from the axial center.

[0014] The vibrator bearing 12 is, for example, a roller bearing, and is arranged between the vibrator 10A and the external gear 30. The vibrator bearing 12 has a plurality of rolling elements (rollers) 12b and a cage 12c that holds the plurality of rolling elements 12b. The plurality of rolling elements 12b roll on the outer circumferential surface of the vibrator 10A and the inner circumferential surface of the external gear 30 as rolling surfaces. The vibrator bearing 12 may have an inner ring separate from the vibrator 10A and an outer ring separate from the external gear 30.

[0015] Spacer rings 41 and 42 are provided on both axial sides of the vibrator bearing 12 and the external gear 30, respectively, as restricting members that come into contact with them and restrict their axial movement.

[0016] The casing 33 is connected to the first internal gear member 31 and covers the outer diameter side of the second internal gear 32G. A main bearing 38 (e.g., a ball bearing) is disposed between the casing 33 and the second internal gear member 32, and the casing 33 rotatably supports the second internal gear member 32 via the main bearing 38. When the reduction gear transmission 1 is incorporated into a mating device (robot 100), the casing 33 and the first internal gear member 31 are connected by co-fastening to a fixed member (arm 101a) of the mating device that is different from a driven member (arm 101b) (see FIG. 1).

[0017] The first cover 34 is connected to the first internal gear member 31, and covers the meshing portion between the external gear 30 and the first internal gear 31G from the non-output side in the axial direction. A first bearing 36 (e.g., a ball bearing) is arranged between the first cover 34 and the shaft portion 10B of the vibrator shaft 10, and the first cover 34 rotatably supports the vibrator shaft 10 via the first bearing 36.

[0018] The second cover 35 is connected to the second internal gear member 32 and covers the meshing portion between the external gear 30 and the second internal gear 32G from the axial output side. The second cover 35 and the second internal gear member 32 are connected to a driven member (arm 101b of the robot 100) that outputs decelerated motion (see FIG. 1). A second bearing 37 (e.g., a ball bearing) is arranged between the second cover 35 and the shaft portion 10C of the vibrator shaft 10, and the second cover 35 rotatably supports the vibrator shaft 10 via the second bearing 37.

[0019] [Materials of each component] The material of each member is not particularly limited, but in this embodiment, they are configured as follows. The vibrator shaft 10, external gear 30, casing 33, first cover 34, second cover 35, and spacer rings 41, 42 are made of metal materials such as steel. Specifically, for example, the vibrator shaft 10 is made of steel materials such as chromium-molybdenum steel, the external gear 30 is made of steel materials such as nickel-chromium-molybdenum steel, and the spacer rings 41, 42 are made of steel materials such as high-carbon chromium bearing steel. The casing 33, the first cover 34, and the second cover 35 are not limited to being made of metal, and may be made of resin, similar to the internal gear member.

[0020] The first internal gear member 31 and the second internal gear member 32 are made of resin. Such resins include not only natural resins, but also composite materials such as CFRP (Carbon Fiber Reinforced Plastics), composite materials of resin and other materials, and baked goods (paper baked goods, cloth baked goods, etc.). By using resin instead of metal for these members, the weight of the reduction gear transmission 1 can be reduced. Furthermore, the self-lubricating properties of the material itself allow for a reduction in the amount of lubricant required for the sliding parts. These members are not limited to being made of resin, but may be made of steel or metal such as aluminum.

[0021] [Variable stiffness section] The reduction gear 1 includes a variable stiffness section 50 that varies the stiffness of the reduction gear 1. 3(a) and (b) are enlarged views of part B in FIG. 2(a) and are diagrams for explaining the configuration and operation of the variable stiffness unit 50. In FIG. 3(a), the external gear 30 and the first internal gear 31G are depicted separated in the radial direction to make them easier to recognize. In reality, the two are closer in the radial direction than in the state shown in FIG. 3(a) and overlap (mesh) in the circumferential direction. In FIG. 3(b), deformation of each part is exaggerated for ease of understanding. The variable stiffness unit 50 of this embodiment changes the stiffness of the reduction gear 1 (more specifically, the connection stiffness connecting the two arms 101) by changing the meshing ratio between the first internal gear 31G and the external gear 30. The meshing ratio refers to the number of teeth in contact, and is generally counted to the nearest decimal point.

[0022] Specifically, as shown in FIG. 3( a ), the variable stiffness section 50 is configured to include a pressure ring 51 and a solenoid (actuator) 52 . The pressure ring 51 is formed in a cylindrical shape and is incorporated into the outer diameter side (radially outward) of the first internal gear 31G. More specifically, the first internal gear member 31 has an annular recess 31a that opens to the output side in the axial direction on the outer diameter side of the first internal gear 31G, and the inner diameter side of this recess 31a forms a cylindrical portion 31b that has the first internal gear 31G on its inner circumferential surface and is cantilevered on the anti-output side. The pressure ring 51 is arranged in the recess 31a so as to be fitted onto the cylindrical portion 31b. The pressure ring 51 has an internal storage space 51a in which a pressure medium (oil, air, etc.) is sealed. The storage space 51a is located on the outer diameter side of the first internal gear 31G and is formed to be relatively wide in the axial direction. The storage space 51a is also provided on the inner diameter side (inside in the radial direction) of the pressure ring 51, and an inner wall portion 51b on the inner diameter side is formed to be thin so that it can be deformed by the pressure inside the storage space 51a.

[0023] The solenoid 52 is fixed to the outer diameter side of the pressure ring 51, and has a plunger 52a (movable iron core) inserted into the storage space 51a of the pressure ring 51. The solenoid 52 is an example of a pressure changer according to the present invention, and changes the pressure of the pressure medium in the pressure ring 51 (storage space 51a) by driving the plunger 52a. The solenoid 52 is also electrically connected to the control unit 110 (see FIG. 1) via a cable 52b that is taken out to the outside through holes drilled in the axial direction in the first internal gear member 31 and the first cover 34, and its operation is controlled by the control unit 110.

[0024] Next, the operation of the variable stiffness section 50 will be described. As shown in Figure 3(a), when the solenoid 52 is not pushing out the plunger 52a, the pressure ring 51 is not deformed, and the first internal gear 31G and the external gear 30 are in a meshed state as per the design drawings, excluding other deformation factors.

[0025] In this state, when the solenoid 52 is driven to push the plunger 52a into the storage space 51a of the pressure ring 51, the pressure medium in the storage space 51a is pressurized, and the inner wall portion 51b of the pressure ring 51 is deformed toward its inner diameter, as shown in FIG. 3(b). Then, the cylindrical portion 31b of the first internal gear member 31, pressed against the inner wall portion 51b, is deformed toward its inner diameter, with the non-output side (fixed end side) serving as a fulcrum and tilting significantly at the unsupported output side (free end side). This causes the first internal gear 31G on the inner circumferential surface of the cylindrical portion 31b to displace toward the external gear 30, improving the meshing ratio between the first internal gear 31G and the external gear 30. This ultimately improves the rigidity of the reduction gear 1, i.e., the connection rigidity of the two arms 101 connected via the reduction gear 1. In this way, by controlling the amount of movement of the plunger 52a (advancing and retreating member) with the variable stiffness section 50, the meshing ratio between the first internal gear 31G and the external gear 30 can be changed, and the stiffness of the reduction gear 1 can be adjusted.

[0026] The variable stiffness section 50 of this embodiment is not particularly limited in its specific configuration as long as it can vary the meshing ratio between the first internal gear 31G and the external gear 30. For example, as shown in Fig. 4(a), instead of the solenoid 52, a tube 52c communicating with the storage space 51a of the pressure ring 51 may be provided, and the pressure within the storage space 51a may be changed by controlling the amount of pressure medium supplied to the storage space 51a through this tube 52c. The tube 52c is connected to an external pressure medium supply mechanism (not shown), and the operation of the supply mechanism is controlled by the control unit 110 (see Fig. 1). In this case, a flange may be provided on the pressure ring 51, and the tube 52c may be attached to this flange, as shown in Fig. 4(b). Alternatively, as shown in FIG. 5(a), instead of the solenoid 52, a screw 53 (movable member) may be provided in the storage space 51a (or in a space connected to the storage space 51a), and the pressure in the storage space 51a may be changed by moving the screw 53 forward and backward relative to the enclosed pressure medium. Alternatively, as shown in FIG. 5(b), a storage space 51a may be provided in the first internal gear member 31, and the pressure in this storage space 51a may be changed to directly displace the first internal gear 31G.

[0027] Alternatively, as shown in Figure 6(a), the outer surface of the cylindrical portion 31b of the first internal gear member 31 may be tapered, and a pressure ring 54 having a corresponding tapered surface on its inner surface may be fitted onto the cylindrical portion 31b, and the cylindrical portion 31b may be displaced by moving this pressure ring 54 back and forth in the axial direction. Alternatively, as shown in Figure 6(b), a clamp ring 55 having a C-shape in plan view may be placed on the outer diameter side of the cylindrical portion 31b of the first internal gear member 31 instead of the pressure ring 51, and the cylindrical portion 31b may be displaced by moving a bolt 55a tightening the opening of this clamp ring 55 back and forth.

[0028] [Operation of the reduction gear] Next, the operation of the reduction gear 1 will be described. When the vibrator shaft 10 is driven to rotate by a drive source such as a motor, the motion of the vibrator 10A is transmitted to the external gear 30. At this time, the external gear 30 is constrained to a shape that follows the outer circumferential surface of the vibrator 10A and is bent into an elliptical shape having a major axis portion and a minor axis portion when viewed from the axial direction. Furthermore, the external gear 30 is meshed with the fixed first internal gear 31G at its major axis portion. Therefore, the external gear 30 does not rotate at the same rotational speed as the vibrator 10A, and the vibrator 10A rotates relatively inside the external gear 30. Then, with this relative rotation, the external gear 30 is bent and deformed so that the major axis position and the minor axis position move circumferentially. The period of this deformation is proportional to the rotation period of the vibrator shaft 10.

[0029] When the external gear 30 flexes and deforms, the position of its major axis moves, causing the meshing position between the external gear 30 and the first internal gear 31G to change in the rotational direction. Here, for example, if the number of teeth of the external gear 30 is 100 and the number of teeth of the first internal gear 31G is 102, the meshing teeth of the external gear 30 and the first internal gear 31G will shift with each rotation of the meshing position, causing the external gear 30 to rotate (spin on its axis). With the above number of teeth, the rotational motion of the vibrator shaft 10 is transmitted to the external gear 30 after being decelerated at a reduction ratio of 100:2.

[0030] Meanwhile, because the external gear 30 also meshes with the second internal gear 32G, the meshing position between the external gear 30 and the second internal gear 32G also changes in the rotational direction due to the rotation of the vibrator shaft 10. Here, because the number of teeth of the second internal gear 32G is the same as the number of teeth of the external gear 30, the external gear 30 and the second internal gear 32G do not rotate relative to each other, and the rotational motion of the external gear 30 is transmitted to the second internal gear 32G at a reduction ratio of 1:1. As a result, the rotational motion of the vibrator shaft 10 is decelerated at a reduction ratio of 100:2 and transmitted to the second internal gear member 32 and the second cover 35, and this rotational motion is output to the driven member (the arm 101b of the robot 100).

[0031] Here, when the reduction gear 1 is operated while the robot 100 is being driven, the control unit 110 changes the stiffness of the reduction gear 1 using the variable stiffness unit 50. Specifically, for example, the control unit 110 increases the rigidity of the reduction gear 1 to suppress vibration when the robot 100 is moving, and decreases the rigidity of the reduction gear 1 so that it can make soft contact with a workpiece around the area where it may come into contact with the workpiece. Alternatively, the rigidity of the reduction gear 1 may be decreased to increase the tolerance for contact (with people or objects) when the robot 100 is moving, and may be increased to accurately determine the position when the robot 100 is stopped.

[0032] [Technical effect of this embodiment] As described above, according to the reduction gear transmission 1 of this embodiment, the rigidity of the reduction gear transmission 1 can be changed by the variable rigidity section 50. This makes it possible to achieve an appropriate rigidity according to the operating state of the driven device.

[0033] Furthermore, according to the reduction gear 1 of this embodiment, the variable stiffness unit 50 has a storage space 51a in which a pressure medium is sealed, and a pressure change unit (solenoid 52) that changes the pressure of the pressure medium in the storage space 51a. The variable stiffness unit 50 displaces the first internal gear 31G toward the external gear 30 in accordance with the pressure in the storage space 51a, thereby changing the meshing ratio between the first internal gear 31G and the external gear 30 and suitably changing the stiffness of the reduction gear 1. Note that, in this embodiment, an example has been described in which stiffness is improved by deforming one gear toward the other gear, but the method for improving stiffness is not limited as long as it can be improved. For example, a method may be used in which a pressure medium whose stiffness is improved by being pressurized is used.

[0034] [others] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, in the above embodiment, the variable stiffness unit 50 is incorporated into the first internal gear member 31 on the counter-output side to displace the first internal gear 31G. However, it may also be incorporated into the second internal gear member 32 on the output side to displace the second internal gear 32G. However, because the second internal gear member 32 rotates relative to the casing, it is preferable to provide the variable stiffness unit on a gear that does not rotate relative to the casing, as in the above embodiment, because this facilitates connection between the variable stiffness unit and the outside of the device (cable 52b or tube 52c). Note that the "casing" in this case refers to a housing component that is fixed to a fixed member different from the driven member of the mating device, and corresponds to the first internal gear member 31, casing 33, and first cover 34 in the above embodiment. In other words, it is preferable that the variable stiffness unit be provided on a member that does not rotate relative to a member to which the other end of the wiring or piping for driving the variable stiffness unit is connected.

[0035] Furthermore, the variable stiffness unit according to the present invention may be configured to displace at least one of a pair of meshing gears toward the other to improve the stiffness of the reduction gear transmission. Therefore, the variable stiffness unit may displace the external gear, or may displace both the internal gear and the external gear. However, when the pair of gears are made of materials with different Young's moduli, as in the above embodiment, it is preferable that the variable stiffness unit displace the gear with the lower Young's modulus.

[0036] Furthermore, in the above embodiment, the variable stiffness section 50 changes the stiffness by changing the meshing ratio of the gears, but the variable stiffness section of the present invention may be one that changes the stiffness of the reduction gear device, and is not limited to one that changes the meshing ratio of the gears. For example, the variable stiffness section may be a section that changes the physical properties (those that affect stiffness, such as the elastic coefficient) of the components of the reduction gear (those that contribute to the connecting stiffness between the two arms of the robot) by applying electricity, temperature changes, or a magnetic field.

[0037] Furthermore, the reduction gear according to the present invention is not limited to a flexible mesh reduction gear, but can be suitably applied to other types of reduction gears such as an eccentric oscillating reduction gear, a simple planetary gear, etc. Furthermore, it is not limited to reduction gears that use gears, but may also be a traction drive, for example. In addition, the details shown in the above embodiment can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0038] 1 Reducer 10A vibrator 30 External gear 31 first internal gear member 31a Recess 31b Cylindrical part 31G 1st internal gear 32 second internal gear member 32G Second internal gear 33 Casing 50 Variable stiffness section 51 Pressure ring 51a Storage space 51b Inner wall 52 Solenoid 52a plunger 52b cable 52c tube 53 screws 54 Pressure ring 55 Clamp ring 55a bolt 100 robots 101 Arm 102 Joints 110 control section O1 Rotational Axis

Claims

1. A reduction gear device, a variable stiffness unit that varies the stiffness of the reduction gear device while the reduction gear device is in operation, and a pair of gears that mesh with each other; the pair of gears is an internal gear and an external gear, the variable stiffness portion improves the stiffness by displacing the internal gear radially inward toward the external gear. Reduction device.

2. the variable stiffness portion has a storage space in which a pressure medium is sealed, and a pressure change portion that changes the pressure of the pressure medium in the storage space, The storage space displaces at least the internal gear of the pair of gears in accordance with the internal pressure. The reduction gear according to claim 1 .

3. the pressure change unit changes the pressure by moving an advancing / retracting member forward and backward relative to the pressure medium sealed in the storage space; The reduction gear according to claim 2 .

4. the variable stiffness portion is provided on one of the pair of gears that does not rotate relative to the casing, The reduction gear transmission according to any one of claims 1 to 3.

5. The variable stiffness portion is disposed radially outward of the internal gear. The reduction gear transmission according to any one of claims 1 to 4.

6. The reduction gear device is a flexible mesh reduction gear device that has a vibration exciter and in which the external gear is flexibly deformed by the vibration exciter. The reduction gear transmission according to any one of claims 1 to 5.

7. the pair of gears are made of materials having different Young's moduli, the variable stiffness unit displaces the gear with a lower Young's modulus; The reduction gear transmission according to any one of claims 1 to 6.

8. The variable stiffness portion has a storage space in which a pressure medium is sealed, and a pressure change portion that changes the pressure of the pressure medium in the storage space. The reduction gear according to claim 1 .

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