Bearing device and harmonic gear device

Abstract

The bearing device (1) is provided with a strain inducer (6) for detecting torque. The strain inducer (6) includes: a first ring portion (7) that is mounted on a rotating-side member; a second ring portion (8) that is mounted on a load-side member; and a plurality of ribs (9) serving as strain inducing portions that connect between the first ring portion (7) and the second ring portion (8). One of the inner ring (4) and the outer ring (3) is integrally formed with the first ring portion (7) of the strain inducer (6). The deformation generated in the ribs (9) of the strain inducer (6) due to the torque acting from the load-side member on the rotating-side member is detected by a strain gauge or the like and converted into torque. The strain inducer for detecting torque can be assembled to a rotary drive device such as a motor or a speed reducer without a dedicated installation space and without fastening connecting metal parts or the like.

Description

Technical Field

[0001] The present invention relates to a bearing device including a strain inducer for detecting torque and a harmonic gear device assembled with the bearing device. Background Art

[0002] Regarding a torque detector including a strain inducer, a strain inducer having a predetermined elastic characteristic is provided, for example, between a rotating shaft and a load-side member, and a strain generated in the strain inducer is measured by a detection element such as a strain gauge, thereby detecting the torque applied to the rotating shaft from the load-side member. Such a torque detector is well known and is described in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2009-288198) and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2018-132154).

[0003] The torque sensor described in Patent Document 2 is assembled in a speed reducer with a motor. A harmonic gear is used in the speed reducer, and an internal gear and an external gear are supported by a crossed roller bearing so as to be rotatable relative to each other. The strain inducer of the torque sensor is installed between the internal gear as a fixed-side member and the device housing. The strain inducer generates a strain due to the displacement of the internal gear in the circumferential direction caused by the torque applied to the internal gear, and the strain is detected by a strain gauge. The strain inducer is sandwiched between an annular fixing member installed on the internal gear and the device housing, and in this state, the internal gear, the fixing member, the strain inducer, and the device housing are fixedly connected and fixed by fastening connection bolts.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-288198

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-132154 Summary of the Invention

[0008] Conventionally, in order to assemble a torque detector having a strain inducer structure in a rotary drive device such as a motor, a speed reducer, or a rotary actuator, it has been necessary to machine an installation portion for installing the supply strain inducer on rotating components such as the device housing and gears, and in addition, additional components for installation, fastening connection metal parts such as bolts and screws have been required. In order to achieve weight reduction, compactification, and reduction in the number of components of the device, it has been desired to reduce the space for installing the torque detection portion having a strain inducer structure and to be able to reduce additional components for installation.

[0009] Focusing on bearings assembled in rotary drive devices such as motors, speed reducers, and rotary actuators, an object of the present invention is to provide a bearing device having a race ring with a strain inducer in which a torque detector is assembled in a small and compact installation space. Another object of the present invention is to provide a harmonic gear device assembled with the above-described bearing device.

[0010] To achieve the above object, the bearing device of the present invention is characterized by having:

[0011] a bearing including an outer ring, an inner ring, and a plurality of rolling elements inserted in a race formed between the outer ring and the inner ring so as to be able to roll; and

[0012] a strain inducer including a first annular portion, a second annular portion coaxially disposed with respect to the first annular portion, and a strain inducing portion connecting between the first annular portion and the second annular portion,

[0013] wherein one of the inner ring and the outer ring is integrally formed with the first annular portion of the strain inducer or coaxially fixed to the first annular portion.

[0014] In rotary drive devices such as motors, speed reducers, and rotary actuators, the bearing device of the present invention is assembled as a bearing for rotatably supporting a rotary shaft. One of the race rings of the bearing device for supporting the rotary shaft is integrated with or fixed to a strain inducer for detecting torque. In the device, there is no need to separately secure a space for assembling the strain inducer for detecting torque. In addition, there is no need for mounting components and fastening connecting metal parts for assembling the strain inducer. Therefore, the torque detection portion having the strain inducer can be assembled in the device in a smaller installation space and in a more compact manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a perspective view and a perspective cross-sectional view showing the bearing device to which the present invention is applied.

[0016] Figure 2 is showing Figure 1 a perspective view and a perspective cross-sectional view of a modified example of the bearing device.

[0017] Figure 3 is a perspective cross-sectional view showing another example of the bearing device to which the present invention is applied.

[0018] Figure 4 is a cross-sectional view and a perspective cross-sectional view showing an example of a harmonic gear device assembled with the bearing device to which the present invention is applied. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of a bearing device and a harmonic gear device to which the present invention is applied will be described with reference to the accompanying drawings. In addition, the present invention is not limited to the configuration of the embodiments.

[0020] Figure 1 (a) is a perspective view showing an example of a bearing device to which the present invention is applied, Figure 1 (b) is a perspective cross-sectional view thereof. The bearing device 1 is assembled, for example, between a rotating shaft (not shown) and a device housing (not shown) in a rotary drive device such as a motor, a speed reducer, a rotary actuator, etc., and supports the rotating shaft in a rotatable state. The load side component (not shown) is rotationally driven by the output rotation of the rotating shaft.

[0021] The bearing device 1 includes a crossed roller bearing 2 and a strain inducer 6 for detecting torque. The crossed roller bearing 2 includes: an outer ring 3; an inner ring 4; and a plurality of cylindrical rollers 5, which are inserted between the outer ring and the inner ring in a rotatable state. For example, in a rotary drive device, the outer ring 3 is fixed to the device housing as a fixed side component, and the inner ring 4 of the crossed roller bearing 2 is coaxially fixed to the rotating shaft. A rectangular cross-section circular ring-shaped track is formed by a V-shaped track groove 3a formed on the inner peripheral surface of the outer ring 3 and a V-shaped track groove 4a formed on the outer peripheral surface of the inner ring 4. Here, the cylindrical rollers 5 are inserted in a rotatable state.

[0022] In this example, the inner ring 4 and the strain inducer 6 for detecting torque are integrally formed. In other words, the above components are made into a single component. The strain inducer 6 includes: a first ring portion 7; a second ring portion 8, which is concentrically arranged inside the first ring portion 7; and a plurality of ribs 9 as strain inducing portions, which connect between the circular inner peripheral surface 4b of the first ring portion 7 and the circular outer peripheral surface 8a of the second ring portion 8. A track groove 4a is formed on the circular outer peripheral surface of the first ring portion 7, and the first ring portion 7 functions as the inner ring 4. The ribs 9 are formed at equal angular intervals in the circumferential direction. The circular end face 8b of the second ring portion 8 is a load mounting surface for coaxially fixing the load side component. Here, a plurality of bolt holes 8c for fastening and connecting the load side component are formed.

[0023] The first ring portion 7 that functions as the inner ring 4 and is mounted on the rotating shaft of the rotary drive device, and the second ring portion 8 that is mounted on the load side component are both rigid bodies. In contrast, the ribs 9 have preset elastic characteristics. The torque acting on the rotating shaft from the load side component is transmitted via the strain inducer 6. By appropriately presetting the elastic characteristics of the ribs 9, the ribs 9 are deformed corresponding to the magnitude of the transmitted torque. A strain detection element such as a strain gauge 10 is attached to the surface of the ribs 9. The torque is detected based on the detection signal output from the strain gauge 10.

[0024] Conventionally, when a strain inducer for torque detection is assembled to a rotary drive device such as a motor, a speed reducer, or a rotary actuator, it is necessary to secure a space for installing the strain inducer around components such as a rotary shaft, and additional components for installation, fastening connection metal parts such as bolts and screws are required. If the bearing device 1 of this example is used, there is no need to separately secure a space for installing the strain inducer 6, and there is also no need for additional components or fastening connection metal parts. Therefore, it is beneficial for the device to be small, compact, and lightweight.

[0025] Moreover, the strain inducer 6 and the inner ring 4 are integrated, so there are no drawbacks such as a decrease in the assembly accuracy of the strain inducer 6. In addition, there is no thermal strain between components due to different materials. Therefore, an improvement in torque detection accuracy can be expected.

[0026] Here, in the above bearing device 1, the strain inducer 6 and the inner ring 4 are made into a single component. The strain inducer 6 and the inner ring 4 can also be made as separate components and formed into a structure in which the inner ring 4 is fixedly fastened and connected to the first ring portion 7 of the strain inducer 6. Figure 2 The bearing device 1A in this case is shown.

[0027] Figure 2 (a) is a perspective view of the bearing device 1A, Figure 2 (b) is a perspective sectional view thereof. The basic structure of the bearing device 1A is the same as that of the above bearing device 1, so the corresponding parts are denoted by the same reference numerals and their description is omitted. In the bearing device 1A of this example, a strain inducer mounting portion 4d is formed in advance in a part on the inner peripheral side of the annular end face 4c of the inner ring 4. The strain inducer mounting portion 4d includes: an annular stepped portion with a constant depth; and a plurality of bolt holes formed at equal angular intervals in the circumferential direction on the end face of the bottom of the specified stepped portion. The first ring portion 7 on the outer peripheral side of the strain inducer 6 is coaxially assembled to the strain inducer mounting portion 4d of the inner ring 4 and fixedly fastened and connected by a fastening connection bolt 6a.

[0028] Figure 3 is a perspective sectional view showing another example of the bearing device to which the present invention is applied. In the bearing device 11, the outer ring and the strain inducer are made into a single component. In a rotary drive device (not shown) such as a motor, a speed reducer, or a rotary actuator, the bearing device 11 is assembled between its rotary side component (not shown) and its fixed side component (not shown), and the rotary side component is supported in a rotatable state. The load side component (not shown) is rotationally driven by the output rotation of the rotary side component.

[0029] The bearing device 11 includes a ball bearing 12 and a strain inducer 16 for detecting torque. The inner ring 14 of the ball bearing 12 is fixed to a fixed-side member (not shown). A load-side member (not shown) is coaxially fixed to the outer ring 13 of the ball bearing 12. An annular race is formed by a raceway groove 13a formed on the inner peripheral surface of the outer ring 13 and a raceway groove 14a formed on the outer peripheral surface of the inner ring 14. Here, the balls 15 are inserted in a freely rolling state.

[0030] In this example, the outer ring 13 and the strain inducer 16 are integrally formed. In other words, the above components are made into a single component. The strain inducer 16 includes: a first annular portion 17 that functions as the outer ring 13; a second annular portion 18 that is concentrically arranged outside the first annular portion 17; and a plurality of ribs 19 as strain inducing portions that connect between the circular outer peripheral surface 13b (17b) of the first annular portion 17 and the circular inner peripheral surface 18a of the second annular portion 18. A raceway groove 13a is formed on the circular inner peripheral surface 13a (17a) of the first annular portion 17. The ribs 19 are formed at equal angular intervals in the circumferential direction. The load-side member is mounted on the annular end face 13c (17c) of the first annular portion 17 (outer ring 13). The annular end face 18b of the second annular portion 18 is coaxially fixed to the rotating-side member.

[0031] The first annular portion 17 (outer ring 13) mounted on the load-side member and the second annular portion 18 mounted on the rotating-side member are each a rigid body. The ribs 19 have preset elastic characteristics. The torque acting from the load-side member on the rotating-side member is transmitted via the strain inducer 16. By appropriately presetting the elastic characteristics of the ribs 19, the ribs 19 generate strain corresponding to the magnitude of the transmitted torque. A strain detection element such as a strain gauge (not shown) is adhered to the surface of the ribs 19. The torque is detected based on the detection signal output from the strain gauge.

[0032] Figure 4 (a) is a cross-sectional view showing an example of a harmonic gear device assembled with the bearing device to which the present invention is applied. Figure 4 (b) is a perspective cross-sectional view thereof.

[0033] The harmonic gear device 30 includes: a rigid internal gear 31 formed in an annular shape; a flexible external gear 32 formed in a top hat shape; a wave generator 33 that flexes the external gear 32 into a non-circular shape and meshes it locally with the internal gear 31; and a bearing device 41 that supports the internal gear 31 and the external gear 32 so as to be relatively rotatable. For example, the wave generator 33 is a rotational input member, and rotation is input from a rotating shaft 34 such as a motor. The external gear 32 is a fixed-side member, and the internal gear 31 is a rotating-side member. The load-side member 35 is rotationally driven by the output rotation from the internal gear 31. In addition, Figure 4(b) Omit the vibration generator 33.

[0034] The external gear 32 includes: a cylindrical main body 32a; a diaphragm 32b that extends radially outward from one end of the main body 32a; and an annular boss 32c that is integrally formed on the outer peripheral edge of the diaphragm 32b. External teeth 32d are formed on the outer peripheral surface of the cylindrical main body 32a. The portion where the external teeth 32d are formed is flexed into a non-circular shape, such as an elliptical shape, by the vibration generator 33 and is locally engaged with the internal teeth 31d of the internal gear 31.

[0035] The bearing device 41 includes a crossed roller bearing 42 and a strain inducer 46. The crossed roller bearing 42 includes: an outer ring 43; an inner ring 44; and a plurality of cylindrical rollers 45 that are inserted between the outer ring and the inner ring in a freely rotatable state. The outer ring 43 is coaxially fixed to the annular boss 32c of the external gear 32, which is a fixed-side member. A V-shaped raceway groove 43a formed on the inner peripheral surface of the outer ring 43 and a V-shaped raceway groove 44a formed on the outer peripheral surface of the inner ring 44 form an annular raceway with a rectangular cross section, where the cylindrical rollers 45 are inserted in a freely rotatable state.

[0036] The strain inducer 46 includes: a first annular portion 47; a second annular portion 48 that is concentrically arranged inside the first annular portion 47; and a plurality of ribs 49 as strain inducing portions that connect between the circular inner peripheral surface of the first annular portion 47 and the circular outer peripheral surface of the second annular portion 48. The ribs 49 are formed at equal angular intervals in the circumferential direction. The annular end face 48b of the second annular portion 48 is a load mounting surface for coaxially fixing the load-side member 35, and bolt holes for fastening and connecting the load-side member are formed.

[0037] Here, the internal gear 31, the inner ring 44, and the first annular portion 47 of the strain inducer 46 are integrally formed. In other words, the above three components are made into a single component. That is, the raceway groove 44a of the inner ring 44 is formed on the circular outer peripheral surface of the first annular portion 47 of the strain inducer 46. In the circular inner peripheral surface of the first annular portion 47, one end side portion in the direction of the central axis 30a is connected to the rib 49, and internal teeth 31d are formed at the other end side portion.

[0038] The first annular portion 47 that functions as the internal gear 31 and the inner ring 44 of the rotating side member, and the second annular portion 48 mounted on the load side member are each rigid bodies. In contrast, the rib 49 has a preset elastic characteristic. The torque acting on the internal gear 31 from the load side member is transmitted via the strain inducer 46. By appropriately presetting the elastic characteristic of the rib 49, the rib 49 generates a strain corresponding to the magnitude of the transmitted torque. A strain detection element such as a strain gauge 50 is attached to the surface of the rib 49. The torque is detected based on the detection signal output from the strain gauge 50.

[0039] Thus, in the harmonic gear device 30 of this example, the first annular portion 47, which is a part on the inner peripheral side of the strain inducer 46, is the inner ring 4 having a V-shaped raceway groove 44a formed in the circular outer peripheral surface, and is also the internal gear 31 having internal teeth 31d formed in the circular inner peripheral surface. The three components of the strain inducer 46, the inner ring 44, and the internal gear 31 are made into a single component.

[0040] Therefore, when using the bearing device 41 of this example, there is no need to separately secure a space for mounting the strain inducer 46. In addition, since the strain inducer 46, the inner ring 44, and the internal gear 31 are integrated, there is also no need for additional components for assembling the strain inducer 46 and fastening connection metal parts. Thus, it is beneficial for the device to be small, compact, and lightweight.

[0041] Moreover, the strain inducer 46, the inner ring 44, and the internal gear 31 are made into a single component, which can avoid drawbacks such as a decrease in assembly accuracy that occur when assembling the three components. In addition, the thermal strain between components due to material differences also disappears. Thus, an improvement in the torque detection accuracy can be expected.

Claims

1. A wave gear device, characterized in that: The wave gear device has: A rigid internal gear; A flexible external gear; A wave generator that flexes the external gear into a non-circular shape and meshes it locally with the internal gear; And A bearing device that supports the internal gear and the external gear in a relatively rotatable state, The external gear includes: a cylindrical main body; A diaphragm that extends radially outward from one end of the cylindrical main body; and an annular boss that is a rigid body integrally formed on the outer periphery of the diaphragm, and external teeth are formed on the outer peripheral surface of the cylindrical main body, The portion of the cylindrical main body where the external teeth are formed is flexed into a non-circular shape by the wave generator and meshes locally with the internal teeth of the internal gear, The wave generator is a rotation input member, the external gear is a fixed-side member, and the internal gear is a rotation-side member, The bearing device includes a bearing and a strain inducer, The bearing includes: an outer ring; an inner ring; and a plurality of rolling elements that are inserted between the outer ring and the inner ring in a freely rolling state, The outer ring is coaxially fixed to the boss of the external gear as the fixed-side member, The strain inducer includes: A first annular portion; A second annular portion that is concentrically arranged inside the first annular portion; and A plurality of ribs as strain inducing portions that connect between the circular inner peripheral surface of the first annular portion and the circular outer peripheral surface of the second annular portion, The internal gear and the inner ring are integrally formed on the first annular portion, An orbital groove of the inner ring is formed on the circular outer peripheral surface of the first annular portion, and in the circular inner peripheral surface of the first annular portion, one end side portion in the direction of the central axis is connected to the rib, and the internal teeth of the internal gear are formed on the other end side portion, The circular end face of the second annular portion is a load mounting surface for coaxially fixing a load-side member.

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