Wave gear device comprising strain gauge type torque sensor

Abstract

To provide a wave gear device provided with a strain gauge type torque sensor without causing increase in device dimension.SOLUTION: In a wave gear device 1, a communication board 12 of a strain gauge type torque sensor 10 is attached to a flat board mounting surface 55 formed by cutting a part of a circular outer peripheral surface 54 of an outer ring 51 of a cross roller bearing 5 (support bearing) into a D-shape. A part of an outer peripheral side of an installation space of the outer ring 51 is used as an installation space for the communication board 12. The communication board 12 can be assembled to the wave gear device 1 without causing increase in device dimension. Unlike when the communication board 12 is incorporated inside the device, the communication board 12 is not exposed to high-temperature environments or lubricant, ensuring the life of the torque sensor 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a strain gauge type torque sensor. [Background technology]

[0002] Strain wave gearing is used as a reducer in the drive units of various devices, for example, in robot machines such as the joints of a work robot system 100A as shown in Fig. 1B. In this case, a strain gauge torque sensor 10A may be used to detect the load torque. The strain gauge torque sensor 10A is composed of a strain gauge torque detection unit 11A incorporated in the strain wave gearing 1A, a communication board 12A installed outside the robot, and a torque detection signal processing unit 14A mounted on a robot control panel 110.

[0003] Torque detection unit 11A includes a strain gauge wiring board that includes multiple strain gauges, a wiring pattern that connects the strain gauges to form a bridge circuit, solder lands for gauge lead wires drawn from the strain gauges, and other wiring parts. The analog output from the bridge circuit, which is the detection output of the strain gauges, is output to communication board 12A via cable wiring 13A drawn outside the robot, and after A / D conversion in communication board 12A, is transmitted to signal processing unit 14A, where the load torque is calculated.

[0004] Wave gearing devices equipped with strain gauge-type torque sensors have been proposed, for example, in Patent Documents 1 and 2. The strain gauges are attached to flexible deformation sites such as the diaphragm of a cup-shaped or top-hat-shaped external gear, which is a component of the wave gearing device. In addition, a flexible printed circuit board attached to the diaphragm is used as the strain gauge wiring board. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2024-16800 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-16799 Summary of the Invention [Problem to be solved by the invention]

[0006] In a wave gear device equipped with a strain gauge-type torque sensor, the communication board is installed outside the device. The cabling (analog signal line) running from the inside to the outside has problems with disconnections and noise generation. To avoid or suppress disconnections and noise generation, it is desirable to incorporate the communication board inside the device so that the analog signal line can be short. This requires securing space inside the device to install the communication board, which creates other problems such as an increase in the overall length. Furthermore, when the communication board is installed inside the device, measures must be taken to prevent the communication board from being exposed to the high-temperature environment inside the device or to lubricants such as grease.

[0007] In view of the above, an object of the present invention is to provide a strain gauge type torque sensor having a communication board for the torque sensor incorporated therein, without increasing the size of the device and without exposing the device to the high temperature environment or lubricant inside the device. [Means for solving the problem]

[0008] The strain gauge type torque sensor of the present invention is provided in a wave gear device. a rigid internal gear; a flexible external gear; a wave generator that deflects the external gear in a radial direction to partially mesh the external gear with the internal gear; a support bearing that supports the internal gear and the external gear so that they can rotate relative to each other; a torque sensor that detects a load torque based on the output of a strain gauge attached to the external gear; It is equipped with The support bearing is an outer ring attached coaxially to the external gear or the internal gear; a flat substrate mounting surface formed by D-cutting a portion of the circular outer peripheral surface of the outer ring; It is equipped with The torque sensor is characterized in that it includes a communication board that A / D converts the sensor output and transmits it to the outside, and the communication board is attached to the board attachment surface.

[0009] Here, it is desirable to provide a flat surface on the outer peripheral surface of the outer ring by D-cutting part of the circular outer peripheral surface so that it is point symmetrical with the board mounting surface. This makes it possible to suppress bias in the outer ring's center of gravity and stress distribution caused by the formation of the board mounting surface, and avoids adverse effects such as reduced torque detection accuracy.

[0010] In the case of a cup-shaped or top-hat shaped external gear, a strain gauge can be attached to its diaphragm. In this case, a flexible printed circuit board attached to the diaphragm can be used as a strain gauge wiring board having wiring including a wiring pattern that forms a bridge circuit of the strain gauge. [Effects of the Invention]

[0011] In the wave gear device of the present invention, a communication board for the torque sensor is attached to a flat board mounting surface formed by D-cutting part of the circular outer peripheral surface of the outer ring of the support bearing. Part of the outer peripheral side of the installation space for the outer ring is used as the installation space for the communication board for the torque sensor. The present invention has the following advantages. (1) A communication board can be mounted on the strain wave gear device without increasing the size of the device. (2) Compared to installing the communication board outside the device, the torque detection unit and communication board can be located closer to each other inside the device. This allows the wiring (analog signal transmission path) connecting them to be shorter, avoiding problems such as wire breakage and noise in the detection signal. (3) Because the communication board is mounted on the outer peripheral surface of the outer ring of the support bearing, the communication board is not exposed to the high temperature environment or lubricant inside the device, ensuring the life of the torque sensor. In addition, since the communication board is easier to access from the outside than when it is built inside the device, maintenance and inspection are easier. [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 1 is an explanatory diagram showing an example of a robot system incorporating a strain gauge type torque sensor to which the present invention is applied. [Figure 1B] FIG. 1 is an explanatory diagram showing a robot system incorporating a conventional strain gauge type torque sensor. [Figure 2] 1A is a schematic longitudinal sectional view of a strain wave gear device to which the present invention is applied, and FIG. 1B is an explanatory diagram showing a portion of the strain wave gear device where a communication board for a torque sensor is attached. [Figure 3] 1A is a plan view of a cross roller bearing (support bearing) with a communication board attached, as seen from the outside in the radial direction, and FIG. 1B is a side view as seen from the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1A is an explanatory diagram showing an example of a robot system equipped with a strain gauge-type torque sensor to which the present invention is applied. The strain gauge gear device 1 is incorporated as a reducer into a robot machine, such as a joint of a work robot system 100, for use. A strain gauge-type torque sensor 10 is used to detect the load torque. The strain gauge-type torque sensor 10 is composed of a strain gauge-type torque detection unit 11, a communication board 12 and a wiring unit 13, which are incorporated into the strain gauge gear device 1, and a torque detection signal processing unit 14 mounted on a robot control panel 110.

[0014] (Harmonic gearing) 2(A) is a schematic longitudinal cross-sectional view of the strain wave gear device 1, and FIG. 2(B) is an explanatory diagram showing a portion of the strain wave gear device 1 where a communication board 12 of a torque sensor 10 is attached. Referring to these figures, the strain wave gear device 1 comprises a rigid internal gear 2, a flexible external gear 3 coaxially arranged inside the rigid internal gear 2, a wave generator 4 with an elliptical contour fitted coaxially inside the flexible external gear 3, a cross roller bearing 5 serving as a support bearing that supports the internal gear 2 and the external gear 3 in a state where they can rotate freely relative to each other, a hollow input shaft 6, a fixed end plate 7 arranged on one axial side, and an output shaft end plate 8 arranged on the other axial side. Both shaft ends of the hollow input shaft 6 are supported by the end plates 7 and 8 via ball bearings 9a and 9b, which serve as input shaft support bearings.

[0015] The external gear 3 is shaped like a top hat and comprises a cylindrical body 32 on which external teeth 31 are formed, a diaphragm 33 that is continuous with one end of the cylindrical body 32 and extends radially outward, and an annular boss 34 formed on the outer periphery of the diaphragm 33. The cylindrical body 32 is bent into an elliptical shape by the wave generator 4, and the external teeth 31 partially mesh with the internal teeth 21 of the internal gear 2. The wave generator 4 comprises a cam plate 41 of a constant width that is formed integrally with the hollow input shaft 6, and a wave bearing 42 that is fitted onto the elliptical outer periphery of the cam plate 41.

[0016] When the wave generator 4 rotates in conjunction with the rotation of the hollow input shaft 6, the meshing positions of the gears 2, 3 move circumferentially, causing relative rotation between the two gears according to the difference in the number of teeth between them. The internal gear 2 is sandwiched between the inner ring 52 of the cross roller bearing 5 and the end plate 7, and these three members are fastened and fixed coaxially in this state. The boss 34 of the external gear 3 is sandwiched between the outer ring 51 of the cross roller bearing 5 and the other end plate 8, and these three members are fastened and fixed coaxially in this state. In this example, the internal gear 2 is fixed so as not to rotate, and the external gear 3 rotates, outputting reduced rotation to the load member (not shown) via the end plate 8, which functions as the output shaft.

[0017] (Strain gauge torque sensor) As described above (see FIG. 1A), the strain gauge torque sensor 10 comprises a torque detection unit 11, a communication board 12, and a wiring unit 13 that are assembled to the strain gear device 1, and a signal processing unit 14 that is mounted on a robot control panel 110 outside the device. The torque detection unit 11 comprises multiple sets of strain gauges 15 and a strain gauge wiring board 16 that are attached to the diaphragm 33 of the external gear 3.

[0018] The strain gauges 15 are attached with an adhesive to an end face 35 of the diaphragm 33 of the external gear 3, which is connected to the inner circumferential surface of the cylindrical body 32. A strain gauge wiring board 16 is also attached to the end face 35 via a spacer 17, which may be made of double-sided tape or the like. Wiring, including a wiring pattern that interconnects the strain gauges 15 to form a bridge circuit, lead terminals, and the like are printed on the strain gauge wiring board 16. The areas where the strain gauges 15 are arranged are coated with a coating agent to protect the wiring.

[0019] Here, the communication board 12 is attached to the outer peripheral surface of the outer ring 51 of the cross roller bearing 5. A sensor output output from a bridge circuit made up of multiple strain gauges 15 in accordance with the deflection of the diaphragm 33 of the external gear 3 is supplied to the communication board 12 via wiring section 13. The sensor output is A / D converted in the communication board 12 and transmitted to a signal processing section 14 outside the device.

[0020] FIG. 3(A) is a plan view of the cross roller bearing 5 (support bearing) with the communication board 12 attached, as seen from the outside in the radial direction, and (B) is a side view as seen from the axial direction.

[0021] Explaining with reference to Figure 3, the cross roller bearing 5 to which the communication board 12 is attached comprises an outer ring 51, an inner ring 52, and a plurality of rollers 53 inserted between them in a rollable state. A portion of the circular outer peripheral surface 54 of the outer ring 51 is D-cut to form a flat board mounting surface 55. In this example, a portion of the circular outer peripheral surface 54 that is point-symmetrical to the board mounting surface 55 is also D-cut to form a flat surface 56 that is point-symmetrical to the board mounting surface 55. This prevents imbalances in the center of gravity and load distribution of the outer ring 51. The D-cut formed on the outer ring 51 is appropriately set based on the required strength of the outer ring 51, etc.

[0022] A communication board 12 having a rectangular outline that is slightly smaller than the board mounting surface 55 is attached to a board mounting surface 55 having a flat rectangular outline formed on the outer peripheral surface of the outer ring 51. The communication board 12 is mounted with connection terminals 12a of a wiring unit 13, a communication module 12b including an A / D conversion circuit, a wiring pattern, etc. The wiring unit 13 is made of, for example, a flexible printed wiring board, and is arranged through a radially extending wiring groove 36 formed in the end face of the boss 34 of the external gear 3 on the side of the end plate 8. The wiring unit 13 outputs detection signals from a strain gauge wiring board 16, which is arranged inside the device surrounded by the end plate 8, the external gear 3, and the hollow input shaft 6, to the communication board 12 attached to the board mounting surface 55 formed on the outer peripheral surface of the outer ring that is exposed to the outside of the device.

[0023] As described above, the torque sensor 10 of the strain wave gear device 1 includes the communication board 12 attached to the board attachment surface 55 formed on the outer peripheral surface of the outer ring 51 of the cross roller bearing 5 that faces the outside of the device. The board attachment surface 55 is a flat surface formed by D-cutting part of the circular outer peripheral surface 54 of the outer ring 51. Part of the outer peripheral side of the installation space of the outer ring 51 is used as installation space for the communication board 12 of the torque sensor 10.

[0024] Unlike when the installation space for the communication board 12 is secured inside the device, the overall length and outer diameter of the strain wave gear device 1 can be made close to those of a standard product that does not have a torque detection unit. Furthermore, unlike when the communication board 12 is installed outside the device, the wiring section 13 (analog signal transmission path) connecting the torque detection section 11 inside the device and the communication board 12 can be short, thereby avoiding problems such as wire breakage and noise in the detection signal. Furthermore, when the communication board 12 is installed inside a device, it may be exposed to a lubricant such as grease that is filled or applied inside the device, and the communication board 12 is exposed to the high-temperature environment inside the device. In this example, the communication board 12 is attached to the outer peripheral surface of the outer ring that faces the outside of the device, which prevents the communication board 12 from being exposed to a lubricant such as grease and being corroded. In addition, because the communication board 12 is not exposed to high temperatures, there is no risk of damage to the electronic components mounted on it. Furthermore, compared to when the communication board 12 is installed inside a device, the communication board 12 is easier to access from outside the device, making maintenance and inspection easier.

[0025] (Other embodiments) In the above example, the present invention is applied to a strain wave gear device equipped with a top-hat shaped external gear, but the present invention can also be applied to a cup-type strain wave gear device equipped with a cup-shaped external gear, or a flat-type strain wave gear device equipped with a cylindrical external gear. [Explanation of symbols]

[0026] 1 Strain wave gearing 2 Internal gear 3 External gear 4. Wave Generator 5 Cross roller bearing (support bearing) 6 hollow input shaft 7, 8 End plates 9a, 9b ball bearings 10 Torque sensor 11 Torque detection unit 12 Communication board 12a Connection terminal 12b communication module 13 Wiring section 14 Signal processing section 15 Strain gauge 16 Strain gauge wiring board 17 Spacer 21 Inner teeth 31 Outer teeth 32 Cylindrical body 33 Diaphragm 34 Boss 35 End face 36 Wiring groove 41 Cam plate 42 Wave bearing 51 outer ring 52 Inner circle 53 Laura 54 Circular outer surface 55 PCB mounting surface 56 Flat surface 100 Robot Systems 110 Robot control panel

Claims

1. a rigid internal gear; a flexible external gear; a wave generator that deflects the external gear in a radial direction to partially mesh the external gear with the internal gear; a support bearing that supports the internal gear and the external gear so that they can rotate relative to each other; a torque sensor that detects a load torque based on the output of a strain gauge attached to the external gear; In a wave gear device comprising: The support bearing is an outer ring attached coaxially to the external gear or the internal gear; a flat substrate mounting surface formed by D-cutting a portion of the circular outer peripheral surface of the outer ring; It is equipped with A strain gauge type strain gear device comprising a strain gauge type torque sensor, wherein the torque sensor is provided with a communication board that A / D converts the sensor output and transmits it to the outside, and the communication board is attached to the board mounting surface.

2. 2. A strain gauge type strain wave gear device equipped with a strain gauge type torque sensor according to claim 1, wherein the circular outer peripheral surface of the outer ring has a flat surface formed by D-cutting a portion of the circular outer peripheral surface so as to be point symmetrical with the board mounting surface.

3. the external gear includes a cylindrical body portion on which external teeth are formed and which is flexible in the radial direction, and a disk-shaped diaphragm extending radially outward or inward from one end of the cylindrical body portion, the strain gauge is attached to the diaphragm, The torque sensor includes a sensor substrate having wiring including a wiring pattern that configures a bridge circuit of the strain gauges, and the sensor output, which is the output of the bridge circuit, is converted into a digital signal by an A / D converter of the communication substrate.

3. A strain gauge type strain wave gear device equipped with a strain gauge type torque sensor according to claim 1 or 2, wherein the sensor substrate is a rigid substrate arranged coaxially facing the diaphragm in the axial direction, or a flexible printed circuit board attached to the diaphragm.

4. the external gear is top hat shaped, the diaphragm extends radially outward from one end of the cylindrical body, and an annular boss is integrally formed on the outer circumferential edge of the diaphragm; 4. A strain gauge type strain wave gear device equipped with a strain gauge type torque sensor according to claim 3, wherein the boss is attached coaxially to the outer ring of the support bearing.

5. the external gear is cup-shaped, the diaphragm extends radially inward from one end of the cylindrical body portion, and a disk-shaped or annular boss is integrally formed on the inner peripheral edge of the diaphragm, 4. A strain gauge type strain wave gear device equipped with a strain gauge type torque sensor according to claim 3, wherein the boss is attached coaxially to the inner ring of the support bearing.

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