Torque sensor and robot joint structure

Abstract

The present application provides a torque sensor capable of detecting a torque acting on the periphery of a drive shaft with high sensitivity. By providing the configuration of a plurality of resistance elements formed in a strain sensor and the configuration of four strain sensors composed of a first strain sensor, a second strain sensor, a third strain sensor, and a fourth strain sensor, only the strain caused by the torque around the drive shaft can be extracted, and the strain caused by the torque around other shafts other than the drive shaft or the strain caused by the force applied in each shaft direction can be canceled.

Description

Technical Field

[0001] This invention relates to a torque sensor and a robot joint structure, for example, to an effective technology for a torque sensor used as a component of a robot joint structure. Background Technology

[0002] Japanese Patent Application Publication No. 2017-80841 (Patent Document 1) discloses a technique for correcting sensor detection errors caused by interference with other axes at the joints of a robot arm.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-80841 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] Due to the decline in the working-age population in recent years, it is predicted that jointed robots will be applied in many fields. However, there are still many problems to be overcome in order to replace human labor with jointed robots.

[0008] For example, in the case of using a multi-jointed robot, also known as a collaborative robot, to work alongside humans, highly sensitive sensing of contact between the human and the multi-jointed robot is required. This is because, to prevent the multi-jointed robot from accidentally contacting and injuring a human, it is necessary to detect even slight contact reactions and quickly stop the operation of the multi-jointed robot.

[0009] Therefore, multi-jointed robots designed to work alongside humans are equipped with torque sensors to sense slight contact reactions with humans. These torque sensors specifically detect the torque acting around the drive shaft among the forces (including torques) acting on the robot arm.

[0010] The torque sensor is required to detect the torque acting around the drive shaft with high sensitivity in order to sense the slight contact reaction force with a human. However, in the prior art, it is difficult to sufficiently reduce the noise caused by the torque acting around other shafts besides the drive shaft or the forces applied in each axial direction. Therefore, a torque sensor with high sensitivity for detecting the torque acting around the drive shaft is desired. That is, in a torque sensor that detects the torque acting around the drive shaft, it is desirable to find a way to reduce the noise caused by the torque acting around other shafts besides the drive shaft or the forces applied in each axial direction.

[0011] The purpose of this invention is to provide a torque sensor capable of highly sensitively detecting the torque acting around a drive shaft.

[0012] Other topics and new features will be described in the description and accompanying drawings of this specification.

[0013] Solutions for solving technical problems

[0014] One embodiment of the torque sensor includes an inner ring portion, an outer ring portion, multiple connecting portions connecting the inner ring portion and the outer ring portion, and multiple strain sensors that acquire strain as a change in resistance value.

[0015] The plurality of connecting portions include: a first connecting portion and a third connecting portion, respectively disposed on a first virtual line passing through the center of the inner ring portion and disposed on opposite sides of each other with respect to the center of the inner ring portion; and a second connecting portion and a fourth connecting portion, respectively disposed on a second virtual line passing through the center of the inner ring portion and orthogonal to the first virtual line and disposed on opposite sides of each other with respect to the center of the inner ring portion.

[0016] Furthermore, the plurality of strain sensors include a first strain sensor disposed on the first connecting portion, a second strain sensor disposed on the second connecting portion, a third strain sensor disposed on the third connecting portion, and a fourth strain sensor disposed on the fourth connecting portion.

[0017] At this point, each of the multiple strain sensors has a semiconductor substrate that coincides with the third virtual line when viewed from above, and multiple resistive elements formed on the semiconductor substrate. The multiple resistive elements include a first resistive element and a second resistive element. The first angle formed by the first resistive element and the second resistive element is a right angle, and the third virtual line extends along a direction that bisects the first angle.

[0018] Among them, the first strain sensor among the multiple strain sensors is arranged on the first connecting part in such a way that the third virtual line is consistent with the first virtual line, and the second strain sensor among the multiple strain sensors is arranged on the second connecting part in such a way that the third virtual line is consistent with the second virtual line.

[0019] On the other hand, the third strain sensor among the plurality of strain sensors is arranged on the third connecting portion with the third virtual line aligned with the first virtual line, and the first resistive element of the third strain sensor is symmetrical with respect to the center of the inner ring and the first resistive element of the first strain sensor, and the second resistive element of the third strain sensor is symmetrical with respect to the center of the inner ring and the second resistive element of the first strain sensor. The fourth strain sensor among the plurality of strain sensors is arranged on the fourth connecting portion with the third virtual line aligned with the second virtual line, and the first resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring and the first resistive element of the second strain sensor, and the second resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring and the second resistive element of the second strain sensor.

[0020] In addition, the torque sensor in the modified example has an inner ring, an outer ring, multiple connecting parts connecting the inner ring and the outer ring, and multiple strain sensors that obtain strain as a change in resistance value.

[0021] The plurality of connecting portions include: a first connecting portion and a fourth connecting portion, respectively disposed on a first virtual line passing through the center of the inner ring portion and disposed on opposite sides of each other with respect to the center of the inner ring portion; a second connecting portion and a fifth connecting portion, respectively disposed on a second A virtual line passing through the center of the inner ring portion and intersecting the first virtual line at the center of the inner ring portion and disposed on opposite sides of each other with respect to the center of the inner ring portion; and a third connecting portion and a sixth connecting portion, respectively disposed on a second B virtual line passing through the center of the inner ring portion and intersecting the first virtual line at the center of the inner ring portion and disposed on opposite sides of each other with respect to the center of the inner ring portion.

[0022] Furthermore, the plurality of strain sensors include a first strain sensor disposed on the first connecting portion, a second strain sensor disposed on the second connecting portion, a third strain sensor disposed on the third connecting portion, a fourth strain sensor disposed on the fourth connecting portion, a fifth strain sensor disposed on the fifth connecting portion, and a sixth strain sensor disposed on the sixth connecting portion.

[0023] At this point, each of the multiple strain sensors has a semiconductor substrate that coincides with the third virtual line when viewed from above, and multiple resistive elements formed on the semiconductor substrate. The multiple resistive elements include a first resistive element and a second resistive element. The first angle formed by the first resistive element and the second resistive element is a right angle, and the third virtual line extends along a direction that bisects the first angle.

[0024] Among them, the first strain sensor among the multiple strain sensors is arranged on the first connecting part in such a way that the third virtual line is consistent with the first virtual line; the second strain sensor among the multiple strain sensors is arranged on the second connecting part in such a way that the third virtual line is consistent with the second A virtual line; and the third strain sensor among the multiple strain sensors is arranged on the second connecting part in such a way that the third virtual line is consistent with the second B virtual line.

[0025] On the other hand, the fourth strain sensor among the plurality of strain sensors is arranged on the fourth connecting portion in such a manner that the third virtual line is aligned with the first virtual line, and the first resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring and the first resistive element of the first strain sensor, and the second resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring and the second resistive element of the first strain sensor. The fifth strain sensor among the plurality of strain sensors is arranged on the fifth connecting portion in such a manner that the third virtual line is aligned with the second A virtual line, and the first resistive element of the fifth strain sensor is symmetrical with respect to the center of the inner ring and the first resistive element of the second strain sensor, and the second resistive element of the fifth strain sensor is symmetrical with respect to the center of the inner ring and the second resistive element of the second strain sensor. The sixth strain sensor among the plurality of strain sensors is arranged on the sixth connecting portion in such a manner that the third virtual line is aligned with the second B virtual line, and the first resistive element of the sixth strain sensor is symmetrical with respect to the center of the inner ring and the first resistive element of the third strain sensor, and the second resistive element of the sixth strain sensor is symmetrical with respect to the center of the inner ring and the second resistive element of the third strain sensor.

[0026] Invention Effects

[0027] According to one embodiment of the torque sensor, the torque acting around the drive shaft can be detected with high sensitivity. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating an example of a robotic system.

[0029] Figure 2 This is a schematic diagram illustrating the structure of a robot's joints.

[0030] Figure 3 This is a schematic diagram illustrating the structure of a robot joint in the relevant technology.

[0031] Figure 4 This is a schematic diagram showing an example of coordinate axis settings.

[0032] Figure 5 This is a top view showing the configuration of the torque sensor in the embodiment.

[0033] Figure 6 It is along Figure 5 A cross-sectional view after AA line cutting.

[0034] Figure 7 It is a table that concisely and easily explains the basic ideas of the implementation method.

[0035] Figure 8 This is a top view illustrating the strain sensor of an embodiment.

[0036] Figure 9 This is a top view showing the configuration of the four strain sensors.

[0037] Figure 10 This is a schematic diagram showing the strain applied to the resistive elements of the four strain sensors when a y-axis torque around the y-axis is applied to the torque sensor.

[0038] Figure 11 This is a schematic diagram showing the strain applied to the resistive elements of the four strain sensors when a force in the y-axis direction is applied to the torque sensor.

[0039] Figure 12 This is a schematic diagram showing the strain applied to the resistive elements of the four strain sensors when a z-axis torque is applied around the z-axis to the torque sensor.

[0040] Figure 13 This is a functional block diagram of the computing department.

[0041] Figure 14 This is a flowchart explaining the operation of the computing unit.

[0042] Figure 15 This is a graph showing the outputs from four strain sensors when a y-axis torque is applied around the y-axis.

[0043] Figure 16 This is a graph showing the total output from four strain sensors when a y-axis torque is applied around the y-axis.

[0044] Figure 17 This is a graph showing the change in the average value of the outputs from four strain sensors when a z-axis torque is applied around the z-axis, and then a y-axis torque is applied around the y-axis.

[0045] Figure 18 This is a diagram schematically illustrating the structure of a robot joint using a torque sensor in an application implementation.

[0046] Figure 19 This is a diagram illustrating a modified example of a robot joint structure using a torque sensor in an application implementation.

[0047] Figure 20 This is a diagram illustrating a modified example of a robot joint structure using a torque sensor in an application implementation.

[0048] Figure 21 This is a diagram schematically illustrating the structure of a robot joint using a torque sensor in an application implementation.

[0049] Figure 22 This is an enlarged view of the connection between the torque sensor and the connecting rod.

[0050] Figure 23 From Figure 22 The diagram shows the direction of the arrow.

[0051] Figure 24 From Figure 23 A schematic diagram observed from the AA side.

[0052] Figure 25 From Figure 23 A schematic diagram observed from the BB side.

[0053] Figure 26 It is a graph that qualitatively shows the relationship between surface pressure and static friction coefficient.

[0054] Figure 27 (a) is a diagram illustrating the deformation of a bolt by applying torque or force to a torque sensor. Figure 27 (b) is a diagram showing the situation where slippage occurs on the “bolt outer ring surface”.

[0055] Figure 28 Figures (a) and (b) are used to illustrate the mechanism by which the accuracy of the torque sensor in detecting the torque around the drive shaft becomes unstable when slippage occurs on the "bolt-outer ring surface".

[0056] Figure 29 This diagram illustrates the innovative aspects that improve the stability of torque sensor torque detection accuracy.

[0057] Figure 30 This is a top view showing the configuration of the torque sensor in the modified example.

[0058] Figure 31 This is a table that illustrates the application of the basic ideas in variations. Detailed Implementation

[0059] In all the figures describing the embodiments, the same components are generally represented by the same symbols, and therefore will not be described repeatedly. It should be noted that, in order to make the drawings easier to understand, sometimes shaded areas are used in the top view.

[0060] <Robot Systems>

[0061] Figure 1 This is a schematic diagram illustrating an example of a robotic system.

[0062] like Figure 1As shown, the robot system 1 includes, for example, a robot arm 10 configured as a multi-joint robotic arm and a robot control unit 11 for controlling the operation of the robot arm 10. The robot arm 10 has multiple rotatable joint structures, which are configured to be controlled by the robot control unit 11. Furthermore, an end effector, such as an electric manipulator, is connected to the tip of the robot arm 10. In this robot system 1, the robot control unit 11 controls the operation of the joint structures of the robot arm 10 and the operation of the end effector. Therefore, workpieces can be manipulated by the robot arm 10.

[0063] <Robot Joint Structure>

[0064] Next, the robot joint structure included in the robot arm 10 will be described.

[0065] Figure 2 This is a schematic diagram illustrating the structure of a robot's joints.

[0066] exist Figure 2 In this design, the robot joint structure 20 is a structure for connecting link 21A and link 21B of the robot arm 10. Specifically, a motor 22 is internally arranged in link 21A, and a reducer 23 is connected to the motor 22. The motor 22 and the reducer 23 constitute the drive unit 24 of the robot joint structure 20. Furthermore, a torque sensor 30 is connected to the reducer 23, and the link 21B is connected to the torque sensor 30. In addition, a lubrication component 25 is provided between the reducer 23 and the torque sensor 30. In this robot joint structure 20, by rotating the motor 22 constituting the drive unit 24, the torque sensor 30 connected to the reducer 23 constituting the drive unit 24 and the link 21B rotate together around the drive shaft.

[0067] <Discussion on Improvement>

[0068] The torque sensor 30 is configured to detect the torque around the drive shaft when the connecting rod 21B rotates around the drive shaft. Specifically, the torque sensor 30 is configured to deform the connecting rod 21B when it rotates around the drive shaft, and is configured to detect the strain based on the deformation by the change in resistance value (change in voltage), and calculate the torque around the drive shaft based on the detected change in resistance value.

[0069] However, not only torque around the drive shaft causes deformation of the torque sensor 30, but torque around other shafts or forces applied in each axial direction also cause deformation. This means that the change in resistance detected by the torque sensor 30 includes not only the change in strain based on the torque around the drive shaft, but also the change in strain based on torque around other shafts or forces applied in each axial direction. In other words, the change in resistance due to strain from torque around other shafts or forces applied in each axial direction creates noise when calculating the torque around the drive shaft. Therefore, in order to detect the torque around the drive shaft with high sensitivity in the torque sensor 30, it is necessary to sufficiently reduce the noise caused by torque around other shafts or forces applied in each axial direction. That is, in the torque sensor 30 used for high-precision detection of torque acting around the drive shaft, it is desirable to reduce the noise caused by torque around other shafts or forces applied in each axial direction.

[0070] Regarding this, there are related technologies, such as those shown below. The "related technologies" referred to in this specification are technologies concerning a problem recently discovered by the inventor. These technologies are not previously known technologies, but rather technologies described as prerequisites for a novel technical idea (non-publicly known technologies).

[0071] Figure 3 This is a schematic diagram illustrating the structure of a robot joint in the relevant technology.

[0072] like Figure 3 As shown, in the robot joint structure 20A of the related art, a bearing component 26 is provided between the reducer 23 constituting the drive unit 24 and the torque sensor 30. This bearing component 26 is configured to rotate around the drive shaft together with the torque sensor 30, while also providing fixed support for the torque sensor 30. That is, in the related art, the torque sensor 30 is configured to be less prone to deformation outside the drive shaft due to being fixedly supported by the bearing component 26. Therefore, in the related art, deformation of the torque sensor 30 caused by torques outside the drive shaft or forces applied in each axial direction is less likely to occur. This means that, according to the related art, when detecting torque around the drive shaft using the torque sensor 30, noise caused by torques outside the drive shaft or forces applied in each axial direction can be reduced. In other words, it can be considered that, according to the related art, torque around the drive shaft can be detected with high precision.

[0073] However, in related technologies, a new bearing component 26 is required to fix the torque sensor 30, thus increasing the mass of the robot joint structure 20A. That is, a smaller mass for the robot joint structure 20A is desirable, but in related technologies, the increased mass may lead to sluggish operation of the robot joint structure 20A. Furthermore, the need for the new bearing component 26 increases the component cost of the robot joint structure 20A. Therefore, while related technologies can accurately detect torque around the drive shaft, there is still room for improvement from the perspective of enhancing the operational agility of the robot joint structure 20A and reducing component costs.

[0074] Therefore, in this embodiment, an innovation was made to realize a torque sensor 30 that can accurately detect the torque around the drive shaft without using the bearing component 26. The idea behind this innovative embodiment will be explained below.

[0075] <Coordinate Axis Settings>

[0076] First, let's explain an example of how to set up the coordinate axes.

[0077] Figure 4 This is a schematic diagram illustrating an example of coordinate axis setup. For example... Figure 4 As shown, the x-axis, y-axis, and z-axis are set as three-dimensional coordinates and are orthogonal to each other. The force acting along the x-axis is denoted by "Fx", the force acting along the y-axis by "Fy", and the force acting along the z-axis by "Fz". Furthermore, the x-axis torque caused by rotation about the x-axis is denoted by "Tx", the y-axis torque caused by rotation about the y-axis by "Ty", and the z-axis torque caused by rotation about the z-axis by "Tz".

[0078] In this specification, the drive shaft is referred to as the z-axis. Therefore, the torque around the drive shaft is the z-axis torque around the z-axis, and the torque sensor 30 in this embodiment is designed to detect the z-axis torque around the z-axis with high precision.

[0079] On the other hand, if the coordinate axes are set as described above, the torque around the axes other than the drive axis is the x-axis torque "Tx" or the y-axis torque "Ty", and the force applied in each axis direction is the x-axis force "Fx", the y-axis force "Fy", or the z-axis force "Fz".

[0080] <Composition of Torque Sensor>

[0081] Next, a schematic configuration of the torque sensor in this embodiment will be described.

[0082] Figure 5 This is a top view showing the configuration of the torque sensor according to this embodiment. Figure 5 As shown, the torque sensor 100 includes an inner ring portion 110 formed by a circular ring, an outer ring portion 120 formed by a circular ring with a diameter larger than that of the inner ring portion 110, and a plurality of spokes (connecting portions) 130 connecting the inner ring portion 110 and the outer ring portion 120. The plurality of spokes 130 includes: spokes 130A and 130C, respectively disposed on a first virtual line VL1 passing through the inner ring center CP of the inner ring portion 110, and disposed opposite to each other with respect to the inner ring center CP; and spokes 130B and 130D, respectively disposed on a second virtual line VL2 passing through the inner ring center CP of the inner ring portion 110 and orthogonal to the first virtual line VL1, and disposed opposite to each other with respect to the inner ring center CP.

[0083] The torque sensor 100 thus configured includes multiple strain sensors 200 that acquire changes in resistance as strain. Specifically, the torque sensor 100 includes four strain sensors 200. More specifically, the four strain sensors 200 include a first strain sensor 200A disposed on spoke 130A, a second strain sensor 200B disposed on spoke 130B, a third strain sensor 200C disposed on spoke 130C, and a fourth strain sensor 200D disposed on spoke 130D.

[0084] Figure 6 yes Figure 5 A sectional view after cutting with AA line. (Example) Figure 6 As shown, the inner ring 110 and the outer ring 120 are connected by spokes 130B and spokes 130D. A second strain sensor 200B is disposed on spoke 130B, and a fourth strain sensor 200D is disposed on spoke 130D.

[0085] This constitutes the torque sensor 100 of this embodiment. The torque sensor 100 deforms when subjected to torque around its shafts or force in its axial direction. Specifically, the spokes 130 of the torque sensor 100 deform when subjected to torque around its shafts or force in its axial direction. The deformation of the spokes 130 causes strain in the strain sensor 200 disposed on the spokes 130, and the strain sensor 200 acquires the change in resistance of the resistive element as the resulting strain.

[0086] <Basic Idea of ​​Implementation Method>

[0087] Next, the basic idea of ​​this implementation method will be explained.

[0088] The basic idea of ​​this embodiment is that by setting up a configuration of multiple resistive elements formed in the strain sensor 200, and setting up a configuration of four strain sensors 200 consisting of a first strain sensor 200A, a second strain sensor 200B, a third strain sensor 200C, and a fourth strain sensor 200D, only the strain caused by the torque around the drive shaft is extracted, and the strain caused by the torque around other shafts other than the drive shaft or the strain caused by the force applied in each axial direction is offset.

[0089] That is, the basic idea of ​​this embodiment is to configure a plurality of resistive elements formed in the strain sensor 200 and to configure four strain sensors 200 so that even when torque is applied not only around the drive shaft but also around other shafts and forces in each axial direction, only the strain caused by the torque around the drive shaft can be extracted, and other strains can be offset. For example, the concept of the basic idea will be explained below.

[0090] Figure 7 This is a table that concisely and easily explains the basic idea of ​​this implementation method.

[0091] Figure 7 In the first strain sensor 200A, by configuring the resistive element formed in the first strain sensor 200A and configuring the first strain sensor 200A, the strain caused by the x-axis torque around the x-axis is "zero", and the strain caused by the y-axis torque around the y-axis is "ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is ε. Fx The strain caused by the force in the y-axis direction is "zero", and the strain caused by the force in the z-axis direction is "zero".

[0092] Furthermore, in the second strain sensor 200B, by configuring the resistive element formed in the second strain sensor 200B and configuring the second strain sensor 200B, the strain caused by the x-axis torque around the x-axis is set to "ε". Tx The strain caused by the y-axis torque around the y-axis is "zero", and the strain caused by the z-axis torque around the z-axis is "ε". Tz The strain caused by the force along the x-axis is "zero", and the strain caused by the force along the y-axis is "ε". Fy The strain caused by the force in the z-axis direction is "zero".

[0093] Furthermore, in the third strain sensor 200C, by configuring the resistive element formed in the third strain sensor 200C and configuring the third strain sensor 200C, the strain caused by the x-axis torque around the x-axis is set to "zero", and the strain caused by the y-axis torque around the y-axis is set to "-ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is -ε. Fx The strain caused by the force in the y-axis direction is "zero", and the strain caused by the force in the z-axis direction is "zero".

[0094] Similarly, in the fourth strain sensor 200D, by configuring the resistive element formed in the fourth strain sensor 200D and configuring the fourth strain sensor 200D, the strain caused by the x-axis torque around the x-axis is set to "-ε". Tx The strain caused by the y-axis torque around the y-axis is "zero", and the strain caused by the z-axis torque around the z-axis is "ε". Tz The strain caused by the force along the x-axis is "zero", and the strain caused by the force along the y-axis is "-ε". Fy The strain caused by the force in the z-axis direction is "zero".

[0095] Furthermore, in the basic idea of ​​this embodiment, the strains generated by the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D are added together. In this way, for example, the total strain caused by the x-axis torque around the x-axis is "zero", the total strain caused by the y-axis torque around the y-axis is "zero", and the total strain caused by the z-axis torque around the z-axis is "4ε". Tz The total strain caused by the force in the x-axis direction is "zero", the total strain caused by the force in the y-axis direction is "zero", and the total strain caused by the force in the z-axis direction is "zero".

[0096] That is, such as Figure 7 As shown, the total strain other than the total strain caused by the z-axis torque around the z-axis is "zero". This means that, if the basic idea of ​​this embodiment is adopted, it is possible to extract only the strain caused by the torque around the drive shaft and offset the strain caused by the torque around other axes or the strain caused by the force applied in each axial direction. Therefore, it can be seen that, according to the basic idea of ​​this embodiment, even when not only the torque around the drive shaft is applied, but also the torque around other axes and the force in each axial direction are applied, it is possible to extract only the strain caused by the torque around the drive shaft and offset the other strains, thereby enabling high-precision calculation of the torque around the drive shaft.

[0097] <Implementation of the basic idea>

[0098] Therefore, the innovations in realizing the basic idea of ​​this embodiment will be explained below. Specifically, the innovations include: an innovation in the arrangement of the plurality of resistive elements formed in the strain sensor 200; and an innovation in the arrangement of the four strain sensors 200 (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C and fourth strain sensor 200D).

[0099] <<Innovation for the Configuration of Multiple Resistor Elements>>

[0100] Figure 8 This is a top view showing the strain sensor of this embodiment.

[0101] Figure 8 In this embodiment, the strain sensor 200 has a rectangular semiconductor substrate 210. The semiconductor substrate 210 is formed of, for example, silicon (Si). Furthermore, a plurality of resistive elements 300 are formed on the semiconductor substrate 210. Specifically, four resistive elements 300, consisting of resistive elements 300A, 300B, 300C, and 300D, are formed on the semiconductor substrate 210. These plurality of resistive elements 300 are, for example, diffused resistive elements formed by introducing conductive impurities into the semiconductor substrate 210. For example, the first angle formed by resistive elements 300A and 300D is a right angle, and a third virtual line VL3 coinciding with the semiconductor substrate 210 extends in a direction that bisects the first angle. Similarly, the angle formed by resistive elements 300A and 300B is also a right angle, the angle formed by resistive elements 300B and 300C is also a right angle, and the angle formed by resistive elements 300C and 300D is also a right angle. That is, the four resistive elements 300 are arranged at right angles to each other. It should be noted that the term "right angle" in this specification includes cases where the intention is to make them essentially right angles. Even if the actual value deviates from 90 degrees, as long as the intention of making them essentially right angles is included, it falls under the definition of "right angle" in this specification. For example, if the angle is between 88 and 92 degrees, it is considered to have the intention of making them essentially right angles, and therefore can be considered "right angle" in this specification.

[0102] Furthermore, the number of resistive elements is not limited to only four. For example, even if there are multiple groups of resistive elements that extend relative to the third virtual line VL3 along the direction that bisects the first angle, and the angles formed by the resistive elements to each other are right angles, as long as the circuit composed of these multiple groups is ultimately connected to... Figure 8 The form shown is equivalent.

[0103] <<Innovation for the Configuration of Four Strain Sensors>>

[0104] Figure 9 This is a top view showing the configuration of four strain sensors 200.

[0105] like Figure 9 As shown, the first strain sensor 200A of the four strain sensors 200 uses the third virtual line VL3 (see...). Figure 8 The strain sensor 200B of the four strain sensors 200 is configured in a manner consistent with the first virtual line VL1. On the other hand, the second strain sensor 200B is configured with the third virtual line VL3 (see...). Figure 8 The third strain sensor 200C of the four strain sensors 200 is configured in the same manner as the second virtual line VL2. Additionally, the third strain sensor 200C is configured with the third virtual line VL3 (see...). Figure 8 The third strain sensor 200C's resistive element 300A is symmetrical with respect to the inner ring center CP and the resistive element 300A of the first strain sensor 200A. Similarly, the third strain sensor's resistive element 300B is symmetrical with respect to the inner ring center CP and the resistive element 300B of the first strain sensor 200A. The third strain sensor 200C's resistive element 300C is symmetrical with respect to the inner ring center CP and the resistive element 300C of the first strain sensor 200A. The third strain sensor's resistive element 300D is symmetrical with respect to the inner ring center CP and the resistive element 300D of the first strain sensor 200A. Furthermore, the fourth strain sensor 200D of the four strain sensors 200 is arranged in a manner consistent with the first virtual line VL1. (See the third virtual line VL3...) Figure 8 The fourth strain sensor 200D is configured in a manner consistent with the second virtual line VL2, and the resistive element 300A of the fourth strain sensor 200D is symmetrical with respect to the inner ring center CP and the resistive element 300A of the second strain sensor 200B. The resistive element 300B of the fourth strain sensor 200D is symmetrical with respect to the inner ring center CP and the resistive element 300B of the second strain sensor 200B. The resistive element 300C of the fourth strain sensor 200D is symmetrical with respect to the inner ring center CP and the resistive element 300C of the second strain sensor 200B. The resistive element 300D of the fourth strain sensor 200D is configured in a manner symmetrical with respect to the inner ring center CP and the resistive element 300D of the second strain sensor 200B.

[0106] The basic idea of ​​this embodiment is realized below through innovations in the configuration of the four resistive elements 300 formed in the strain sensor 200 and innovations in the configuration of the four strain sensors 200. Specifically, for the four strain sensors 200, the basic idea of ​​this embodiment is realized through innovations in the configuration of the four resistive elements 300 formed in the strain sensor 200. Figure 8 Among the four strain sensors 200 of the four resistive elements 300 shown, by means of the above four strain sensors 200 as follows Figure 9 The configuration shown is used to implement the basic idea of ​​this embodiment (see [reference]). Figure 7 The example is used to illustrate this.

[0107] <<Detailed Explanation of Strain Countermeasures>>

[0108] Figure 10 This is a schematic diagram showing the strain applied to the resistive elements 300 of the four strain sensors 200 when a y-axis torque (“Ty”) around the y-axis is applied to the torque sensor 100. Figure 10 In this context, tensile strain is set as "+", compressive strain is set as "-", and the output strain from strain sensor 200 based on the strain applied to the four resistive elements 300 formed on each strain sensor 200 is set as "(strain of resistive element 300A + strain of resistive element 300C) - (strain of resistive element 300B + strain of resistive element 300D)".

[0109] Figure 10 In this model, tensile strain is generated in the first strain sensor 200A, resistive elements 300A and 300C, while compressive strain is generated in resistive elements 300B and 300D. Therefore, the output strain from the first strain sensor 200A is set to "+ε". Ty ".

[0110] Next, focusing on the second strain sensor 200B, the same tensile strain is generated on the resistive elements 300A, 300B, 300C, and 300D. This results in the output strain of the second strain sensor 200B being "0".

[0111] Next, focusing on the third strain sensor 200C, compressive strain is generated on resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. This results in the output strain of the third strain sensor 200C being "-ε". Ty ".

[0112] Furthermore, focusing on the fourth strain sensor 200D, tensile strain is generated on the resistive elements 300A, 300B, 300C, and 300D. This results in the output strain of the fourth strain sensor 200D being "0".

[0113] Therefore, it can be seen that, through Figure 10 The four strain sensors 200 shown (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) realize Figure 7 The strain caused by the y-axis torque around the y-axis is shown.

[0114] Figure 11 This is a schematic diagram showing the strain applied to the resistive elements 300 of the four strain sensors 200 when a force ("Fy") in the y-axis direction is applied to the torque sensor 100. Figure 11 In this context, tensile strain is set as "+", compressive strain is set as "-", and the output strain from strain sensor 200 based on the strain applied to the four resistive elements 300 formed on each strain sensor 200 is set as "(strain of resistive element 300A + strain of resistive element 300C) - (strain of resistive element 300B + strain of resistive element 300D)".

[0115] Figure 11 In this process, the same tensile strain is generated in the first strain sensor 200A, resistor elements 300A, 300B, 300C, and 300D. This results in the output strain of the first strain sensor 200A being "0".

[0116] Next, focusing on the second strain sensor 200B, compressive strain is generated on resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. This results in the output strain output by the second strain sensor 200B being "+ε". Fy ".

[0117] Next, focusing on the third strain sensor 200C, the same tensile strain is generated on the resistive elements 300A, 300B, 300C, and 300D. This results in the output strain output by the third strain sensor 200C being "0".

[0118] Furthermore, focusing on the fourth strain sensor 200D, tensile strain is generated on resistive elements 300A and 300C, while compressive strain is generated on resistive elements 300B and 300D. This results in the output strain output by the fourth strain sensor 200D being "-ε". Fy ".

[0119] Therefore, it can be seen that, through Figure 11 The four strain sensors 200 shown (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) realize Figure 7 The strain is shown as the result of a force applied in the y-axis direction.

[0120] Figure 12This is a schematic diagram showing the strain applied to the resistive elements 300 of the four strain sensors 200 when a z-axis torque ("Tz") around the z-axis is applied to the torque sensor 100. Figure 12 In this context, tensile strain is set as "+", compressive strain is set as "-", and the output strain from strain sensor 200 based on the strain applied to the four resistive elements 300 formed on each strain sensor 200 is set as "(strain of resistive element 300A + strain of resistive element 300C) - (strain of resistive element 300B + strain of resistive element 300D)".

[0121] Figure 12 In this model, compressive strain is generated on the first strain sensor 200A, resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. Therefore, the output strain output by the first strain sensor 200A is set to +ε. Tz ".

[0122] Next, focusing on the second strain sensor 200B, compressive strain is generated on resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. This results in the output strain output by the first strain sensor 200A being "+ε". Tz ".

[0123] Next, focusing on the third strain sensor 200C, compressive strain is generated on resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. This results in the output strain output by the first strain sensor 200A being "+ε". Tz ".

[0124] Furthermore, focusing on the fourth strain sensor 200D, compressive strain is generated on resistive elements 300A and 300C, while tensile strain is generated on resistive elements 300B and 300D. This results in the output strain output by the first strain sensor 200A being "+ε". Tz ".

[0125] Therefore, it can be seen that, through Figure 12 The four strain sensors 200 shown (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) realize Figure 7 The strain caused by the z-axis torque around the z-axis is shown.

[0126] based on Figures 10-12 It can be seen that, in Figure 8The four strain sensors 200 shown are formed with four resistive elements 300. By means of the above four strain sensors 200 as follows: Figure 9 The configuration shown implements the basic idea of ​​this embodiment (see [reference]). Figure 7 ).

[0127] <Structure of the Computing Unit>

[0128] The torque sensor 100 includes a calculation unit that calculates the torque around a normal axis passing through the center CP of the inner ring and perpendicular to the inner ring portion 110, based on the outputs from the four strain sensors 200. Specifically, the torque sensor 100 calculates the z-axis torque around the drive shaft (around the z-axis) based on the outputs of the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D.

[0129] The following section describes the structure of the calculation unit for calculating the z-axis torque around the z-axis.

[0130] Figure 13 This is the functional block diagram of the Computing Unit 500. Figure 13 In the calculation unit 500, there are a first voltage value input unit 501, a second voltage value input unit 502, a third voltage value input unit 503, a fourth voltage value input unit 504, a voltage value summing unit 505, a drive shaft torque calculation unit 506, an output unit 507, and a data storage unit 508.

[0131] The first voltage value input unit 501 is configured to input the output voltage from the first strain sensor 200A. Specifically, the first strain sensor 200A is configured to generate strain due to the deformation of the torque sensor 100 based on torque or force, and is configured to acquire the resistance value change of the four internal resistive elements 300 as the strain, convert the resistance value change into a voltage value, and output it. The first voltage value input unit 501 is configured to be able to input the output voltage from the first strain sensor 200A. Furthermore, the first voltage value, which is the output voltage from the first strain sensor 200A, is stored in the data storage unit 508.

[0132] It should be noted that, for example, the first voltage value of the input first voltage value input unit 501 corresponds to the first total value. The first total value is the sum of the difference between the resistance values ​​of the resistor element 300A and the resistor element 300B in the first strain sensor 200A, and the difference between the resistance values ​​of the resistor element 300C and the resistor element 300D in the first strain sensor 200A.

[0133] The second voltage value input unit 502 is configured to input the output voltage from the second strain sensor 200B. Specifically, the second strain sensor 200B is also configured to generate strain due to the deformation of the torque sensor 100 based on torque or force, and is configured to acquire the resistance value change of the four internal resistive elements 300 as the strain, convert the resistance value change into a voltage value, and output it. The second voltage value input unit 502 is configured to be able to input the output voltage from the second strain sensor 200B. Furthermore, the second voltage value, which is the output voltage from the second strain sensor 200B, is stored in the data storage unit 508.

[0134] It should be noted that, for example, the second voltage value of the input second voltage value input unit 502 corresponds to the second total value. The second total value is the sum of the difference between the resistance values ​​of the resistive element 300A and the resistive element 300B in the second strain sensor 200B, and the difference between the resistance values ​​of the resistive element 300C and the resistive element 300D in the second strain sensor 200B.

[0135] The third voltage value input unit 503 is configured to input the output voltage from the third strain sensor 200C. Specifically, the third strain sensor 200C is configured to generate strain due to the deformation of the torque sensor 100 based on torque or force, and is configured to acquire the resistance value change of the four internal resistive elements 300 as the strain, convert the resistance value change into a voltage value, and output it. The third voltage value input unit 503 is configured to input the output voltage from the third strain sensor 200C. Furthermore, the third voltage value, which is the output voltage from the third strain sensor 200C, is stored in the data storage unit 508.

[0136] It should be noted that, for example, the third voltage value of the input third voltage value input unit 503 corresponds to the third total value. The third total value is the sum of the difference between the resistance values ​​of the resistive element 300A and the resistive element 300B in the third strain sensor 200C and the difference between the resistance values ​​of the resistive element 300C and the resistive element 300D in the third strain sensor 200C.

[0137] The fourth voltage value input unit 504 is configured to input the output voltage from the fourth strain sensor 200D. Specifically, the fourth strain sensor 200D is configured to generate strain due to the deformation of the torque sensor 100 based on torque or force, and is configured to acquire the resistance value change of the four internal resistive elements 300 as the strain, convert the resistance value change into a voltage value, and output it. The fourth voltage value input unit 504 is configured to be able to input the output voltage from the fourth strain sensor 200D. Furthermore, the fourth voltage value, which is the output voltage from the fourth strain sensor 200D, is stored in the data storage unit 508.

[0138] It should be noted that, for example, the third voltage value of the fourth voltage value input unit 504 corresponds to the fourth total value. The fourth total value is the sum of the difference between the resistance values ​​of the resistive elements 300A and 300B in the fourth strain sensor 200D and the difference between the resistance values ​​of the resistive elements 300C and 300D in the fourth strain sensor 200D.

[0139] Next, the voltage value summing unit 505 is configured to calculate the total voltage value obtained by adding the first voltage value input from the first voltage value input unit 501, the second voltage value input from the second voltage value input unit 502, the third voltage value input from the third voltage value input unit 503, and the fourth voltage value input from the fourth voltage value input unit 504. The voltage value summing unit 505 calculates the total voltage value and, for example... Figure 7 The total calculation shown corresponds to the total voltage value calculated by the voltage value summing unit 505. That is, the total voltage value calculated by the voltage value summing unit 505 is the voltage value that corresponds to the strain caused by the torque around other shafts or the force applied in each shaft direction, which cancels out the strain caused by the torque of the drive shaft only around the drive shaft.

[0140] Next, the drive shaft torque calculation unit 506 is configured to calculate the drive shaft torque around the drive shaft based on the total voltage value calculated by the voltage value summing unit 505. In this embodiment, since the total voltage value calculated by the voltage value summing unit 505 cancels out the strain caused by the torque around other shafts or the force applied in each axial direction, and corresponds only to the strain caused by the drive shaft torque around the drive shaft, the accuracy of the drive shaft torque calculated based on the total voltage value is very high. For example, strain and resistance value are correlated, and the voltage value based on this resistance value is also correlated with strain. Furthermore, since strain and torque are also correlated, the voltage value and torque are also correlated. Formulas and tables representing the correlation between these voltage values ​​and torque are stored in the data storage unit 508. This allows the drive shaft torque calculation unit 506 to calculate the drive shaft torque based on the formulas and tables stored in the data storage unit 508 and the total voltage value calculated by the voltage value summing unit 505.

[0141] The output unit 507 is configured to output the value of the drive shaft torque calculated by the drive shaft torque calculation unit 506 to the outside. For example, the value of the drive shaft torque output from the output unit 507 can be input to the outside. Figure 1 The robot control unit 11 shown is used for the operation control of the robot arm 10 by the robot control unit 11.

[0142] <The Operation of the Computing Department>

[0143] The computing unit 500 of this embodiment is configured as follows. The operation of the computing unit 500 will be described below with reference to the accompanying drawings.

[0144] Figure 14 This is a flowchart explaining the operation of the computing unit.

[0145] Figure 14 In this process, the first voltage value input unit 501 inputs a first voltage value, which is the output voltage from the first strain sensor 200A, and the second voltage value input unit 502 inputs a second voltage value, which is the output voltage from the second strain sensor 200B. Similarly, the third voltage value input unit 503 inputs a third voltage value, which is the output voltage from the third strain sensor 200C, and the fourth voltage value input unit 504 inputs a fourth voltage value, which is the output voltage from the fourth strain sensor 200D (S101). Next, the voltage value summing unit 505 adds the first, second, third, and fourth voltage values ​​to calculate a total voltage value. Then, the drive shaft torque calculation unit 506 calculates the drive shaft torque based on the total voltage value calculated by the voltage value summing unit 505. Finally, the drive shaft torque value calculated by the drive shaft torque calculation unit 506 is output from the output unit 507.

[0146] The following implements the operation of the computing unit 500.

[0147] <Verification of the effect>

[0148] Next, the verification results of the effects of this embodiment will be explained.

[0149] Figure 15 This is a graph showing the outputs from four strain sensors when a y-axis torque (“Ty”) is applied around the y-axis.

[0150] Figure 15 In the diagram, the horizontal axis shows the magnitude of the y-axis torque ("Ty(N·m)"), while the vertical axis represents the output "strain (με)" of each strain sensor.

[0151] Figure 15 Focusing on the output of the first strain sensor, it can be seen that as the y-axis torque increases, the output (absolute value) from the first strain sensor also increases. For example, when the y-axis torque is 100 N·m, the output from the first strain sensor is 15 με; when the y-axis torque is 200 N·m, the output is 35 με. Furthermore, when the y-axis torque is 400 N·m, the output is 60 με; and when the y-axis torque is 600 N·m, the output is 90 με.

[0152] On the other hand, looking at the output of the third strain sensor, it can be seen that as the y-axis torque increases, the output (absolute value) from the third strain sensor also increases. For example, when the y-axis torque is 100 N·m, the output from the first strain sensor is -15 με; when the y-axis torque is 200 N·m, the output from the first strain sensor is -35 με. Furthermore, when the y-axis torque is 400 N·m, the output from the first strain sensor is -60 με; and when the y-axis torque is 600 N·m, the output from the first strain sensor is -90 με.

[0153] Therefore, it can be seen that if the outputs from the first strain sensor and the second strain sensor are added together, the total output of the first strain sensor and the third strain sensor is "0". This means that the outputs from the first strain sensor and the third strain sensor cancel each other out.

[0154] Furthermore, it can be seen that, considering the outputs from the second strain sensor and the fourth strain sensor, regardless of the magnitude of the y-axis torque, the output from any strain sensor is almost "0".

[0155] Figure 16 This is a graph showing the total output from four strain sensors when a y-axis torque (“Ty”) is applied around the y-axis.

[0156] Figure 16 In the diagram, the horizontal axis represents the magnitude of the y-axis torque ("Ty(N·m)"), while the vertical axis represents the total output "strain (με)" from the four strain sensors.

[0157] like Figure 16 As can be seen, regardless of the magnitude of the y-axis torque, the total output from the four strain sensors is almost "0". That is, from Figure 16 It is known that, for example, even if a y-axis torque is applied—an example of the torque around the drive shaft (z-axis torque) other than the drive shaft torque around the drive shaft—the sum of the outputs from the first strain sensor, the second strain sensor, the third strain sensor, and the fourth strain sensor based on the y-axis torque is almost "0". That is, by Figure 15 and Figure 16 The results shown demonstrate that the total output from the four strain sensors is unaffected by the strain caused by the y-axis torque.

[0158] Figure 17 This is a graph showing the change in the average value of the outputs from four strain sensors when a certain amount of z-axis torque is applied around the z-axis, and then a y-axis torque is applied around the y-axis.

[0159] Figure 17 In the diagram, the horizontal axis represents the magnitude of the y-axis torque (“Ty(N·m)”), while the vertical axis represents the average value of the output “strain (με)” from the four strain sensors. Furthermore, each point represents the magnitude of the z-axis torque (“Tz”). For example, “*” indicates a clockwise z-axis torque of 600 (N·m). A “dashed line” indicates a counter-clockwise z-axis torque (“Tz”) of -600 (N·m).

[0160] For example, refer to Figure 7 The output from the first strain sensor 200A is the strain "ε" caused by the y-axis torque. Ty The strain ε caused by the z-axis torque. Tz "The output corresponding to the summed strain. On the other hand, the output from the second strain sensor 200B is the strain ε caused by the y-axis torque." Ty The strain ε caused by the z-axis torque. Tz "The output corresponding to the summed strain. Among them, in the second strain sensor 200B, "ε" Ty "It is zero. Additionally, the output from the third strain sensor 200C is the strain "-ε" caused by the y-axis torque." Ty The strain ε caused by the z-axis torque. Tz "The output corresponding to the summed strain. Furthermore, the output from the fourth strain sensor 200D is the strain caused by the y-axis torque" -ε Ty The strain ε caused by the z-axis torque. Tz "The output corresponding to the summed strain. Among them, in the second strain sensor 200D, "-ε" Ty The value is zero. Therefore, the outputs of the four strain sensors 200 are different, but apart from the strain caused by the z-axis torque, the average value of the outputs of the four strain sensors 200 cancels each other out, thus achieving a strain of "ε". Tz This content is shown in Figure 17 That is, because the average value of the outputs of the four strain sensors 200 reaches the strain "ε" Tz Therefore, it depends only on the magnitude of the z-axis torque, not the y-axis torque, forming a fixed value. Figure 17 It can be seen that increasing the z-axis torque increases the average output of the four strain sensors 200, while increasing the y-axis torque does not change this average value. This can be achieved by using the average output of the four strain sensors 200 to measure the strain "ε". Tz To understand this.

[0161] <Applications to Robot Joint Structures>

[0162] The torque sensor 100 of this embodiment can be applied to, for example, the joint structure of a robot arm. Figure 18 This is a schematic diagram illustrating the robot joint structure 20 to which the torque sensor 100 of this embodiment is applied. Figure 18 In this embodiment, the torque sensor 100 is connected to the drive unit 24, which includes a motor 22 and a reducer 23, and is also connected to the link 21B, which forms part of the robot arm. Based on this configuration of the robot joint structure 20, the torque sensor 100 can accurately detect the torque of the drive shaft around the drive shaft.

[0163] Furthermore, the robot joint structure 20 using the torque sensor 100 offers the following advantages. For example, in Figure 3 In the related technology shown, a bearing component 26 is provided between the drive unit 24 and the torque sensor 30. This is because by using the bearing component 26 to fix and support the torque sensor 30, deformation is less likely to occur outside the drive shaft area. That is, in the torque sensor 30 of the related technology, if the torque sensor 30 is deformed due to torque around other shafts or forces applied in each axial direction other than the drive shaft, the strain caused by this deformation is also detected by the torque sensor 30. As a result, the torque sensor 30 is easily affected by noise caused by torque around other shafts or forces applied in each axial direction other than the drive shaft. Therefore, in the related technology, by fixing and supporting the torque sensor 30 with the bearing component 26, the torque sensor 30 is less likely to deform outside the drive shaft area. Thus, according to the related technology, since the torque sensor 30 is less likely to deform due to torque around other shafts or forces applied in each axial direction other than the drive shaft, the noise caused by torque around other shafts or forces applied in each axial direction other than the drive shaft can be reduced when the torque sensor 30 detects torque around the drive shaft. That is, according to relevant technology, by fixing the torque sensor 30 with the bearing component 26, the torque sensor 30 is not easily deformed except around the drive shaft, thereby enabling high-precision detection of the torque around the drive shaft.

[0164] In related technologies, the mass of the robot joint structure 20A increases because a new bearing component 26 is required to fix the torque sensor 30. While a smaller mass is desirable, the increased mass in related technologies can lead to sluggish operation of the robot joint structure 20A. Furthermore, the need for the new bearing component 26 increases the component cost of the robot joint structure 20A. Therefore, while related technologies can accurately detect torque around the drive shaft, there is still room for improvement in terms of enhancing the operational agility of the robot joint structure 20A and reducing component costs.

[0165] Regarding this point, in the torque sensor 100 of this embodiment, even if the torque around other shafts besides the drive shaft or the force applied in each axial direction causes deformation of the torque sensor 100, the strain caused by the torque around other shafts besides the drive shaft or the force applied in each axial direction will be offset by the four strain sensors 200 provided in the torque sensor 100. That is, according to the torque sensor 100 of this embodiment, even if the torque around other shafts besides the drive shaft or the force applied in each axial direction causes deformation of the torque sensor 100, noise caused by the torque around other shafts besides the drive shaft or the force applied in each axial direction is not easily generated. Therefore, in the torque sensor 100 of this embodiment, even if the deformation of the torque sensor 100 caused by the torque around other shafts besides the drive shaft or the force applied in each axial direction is not suppressed, the torque around the drive shaft can be detected with high accuracy. This means that the torque sensor 100 according to this embodiment does not require... Figure 3 The torque sensor 30 in the related technology is fixedly supported by a bearing component 26. In other words, even if the torque sensor 100 of this embodiment is not fixedly supported by the bearing component 26, the torque around other axes besides the drive shaft or the strain caused by the force applied in each axial direction will cancel each other out, thereby enabling high-precision detection of the torque around the drive shaft. Therefore, according to this embodiment, since the bearing component 26 is not required, the increase in the mass of the robot joint structure 20 itself can be suppressed. Thus, according to this embodiment, by using the torque sensor 100, the operational agility of the robot joint structure can be improved. Furthermore, since the addition of the bearing component 26 is not required, the number of components in the robot joint structure 20 can be reduced, thereby also achieving the advantage of reduced component costs.

[0166] It should be noted that if the torque sensor 100 of this embodiment is used, it can not only achieve... Figure 18 The robot joint structure 20 shown can also achieve, for example... Figure 19 The robot joint structure 20B shown is Figure 20 The robot joint structure 20C is shown. Even in this case, significant effects can be achieved, namely, improved detection accuracy of drive shaft torque around the drive shaft without sacrificing the operational agility of the robot joint structure or component costs.

[0167] It should be noted that these effects require high rigidity of the torque sensor 100, preventing excessive deformation due to torques along the x, y, and z axes. To increase the rigidity of the torque sensor 100, the size must be increased. Figure 5The thickness and width of the spokes 130 are shown. As a result, the strain caused by the z-axis torque decreases, reducing the ability to resolve the z-axis torque to be measured. That is, the detectable critical z-axis torque increases. However, Figure 8 The strain sensor 200 shown has exceptionally high sensitivity compared to strain gauges that measure resistance changes based on ordinary metals. It is known that when the strain sensor 200 is made of silicon, the strain coefficient, which represents the sensitivity to strain detection, is approximately 25 times that of a strain gauge with ordinary metallic properties. Therefore, by using the strain sensor 200, the rigidity of the torque sensor 100 can be increased, thereby eliminating the need for the bearing component 26.

[0168] <Further Exploration>

[0169] The torque sensor 100 of this embodiment is useful for accurately detecting torque around the drive shaft even without suppressing deformation of the torque sensor 100 caused by torque around other axes besides the drive shaft or by forces applied in each axial direction. For example, it can be effectively used in robot joint structure 20. However, the inventors have learned through exploration that it is crucial to innovate the connection structure between the torque sensor 100 and the link 21B when applying the torque sensor 100 to the robot joint structure 20. This insight will be explained below.

[0170] <New insights discovered by the inventor>

[0171] Figure 21 This is a schematic diagram illustrating the robot joint structure 20 to which the torque sensor 100 of this embodiment is applied. Figure 21 In the diagram, area RA represents the connection point between torque sensor 100 and connecting rod 21B. Furthermore, Figure 22 This is an enlarged view of the connection between the torque sensor 100 and the connecting rod 21B shown in area RA. Figure 22 As shown, a through portion TH is formed on the torque sensor 100, and a threaded opening OP is formed on the connecting rod 21B. The through portion TH in the torque sensor 100 communicates with the opening OP in the connecting rod 21B, and a bolt 600A is inserted into both the through portion TH and the opening OP. The torque sensor 100 and the connecting rod 21B are connected using the bolt 600A and the nut 600B. At this time, an axial force "P" is applied to the bolt 600A.

[0172] then, Figure 23 From Figure 22 A schematic diagram showing the direction of the arrow. (See diagram below.) Figure 23 As shown, the torque sensor 100 and the connecting rod 21B are connected by bolts 600A and nuts 600B. Furthermore, Figure 24 Showing from Figure 23A schematic diagram observed from plane AA. Figure 25 Showing from Figure 23 A schematic diagram observed from the BB surface. The AA surface is referred to as the "bolt / outer ring surface," and the BB surface as the "outer ring / connecting rod surface."

[0173] Figure 24 In the torque sensor 100, a bolt 600A is fixed to the outer ring 120. The contact surface between the bolt 600A and the outer ring 120 is denoted by "S1". The surface pressure "σ1" between the bolt 600A and the outer ring 120 is obtained by the formula "σ1 = P / S1". Here, "P" represents the axial force applied to the bolt 600A, and "S1" represents the contact area between the bolt 600A and the outer ring 120. Figure 24 As shown, since the contact area “S1” between bolt 600A and outer ring 120 is small, the surface pressure “σ1” between bolt 600A and outer ring 120 increases.

[0174] Figure 25 In this design, the outer ring 120 of the torque sensor 100 and the connecting rod 21B are fixed by bolts 600A. The contact surface between the outer ring 120 and the connecting rod 21B is represented by "S2". This "S2" is equivalent to the entire surface of the outer ring 120. The surface pressure "σ2" between the outer ring 120 and the connecting rod 21B is obtained by the formula "σ2 = P / S2". Here, "P" represents the axial force applied to bolt 600A, and "S2" represents the contact area between the outer ring 120 and the connecting rod 21B. Figure 25 As shown, since the contact area “S2” between the outer ring 120 and the connecting rod 21B is large, the surface pressure “σ2” between the outer ring 120 and the connecting rod 21B is reduced.

[0175] then, Figure 26 It is a graph that qualitatively shows the relationship between surface pressure and static friction coefficient. Figure 26 In the diagram, the horizontal axis represents the surface pressure "σ", while the vertical axis represents the static friction coefficient "μ". For example... Figure 26 As shown, in Figure 24 The axial force (“P”) shown and Figure 25 When the axial force ("P") is equal, if the surface pressure "σ" increases, the static friction coefficient "μ" tends to decrease. Therefore, it can be seen that if the surface pressure "σ" increases, slippage is more likely to occur.

[0176] In this case, since the contact area "S1" between bolt 600A and outer ring 120 is very small compared to the contact area "S2" between outer ring 120 and connecting rod 21B, the surface pressure "σ1" between bolt 600A and outer ring 120 becomes very large compared to the surface pressure "σ2" between outer ring 120 and connecting rod 21B. This means that the "bolt-outer ring surface," which is the interface between bolt 600A and outer ring 120, is more prone to sliding than the "outer ring-connecting rod surface," which is the interface between outer ring 120 and connecting rod 21B.

[0177] Figure 27 This is a schematic diagram showing the situation where sliding occurs on the "bolt outer ring surface". Figure 27 (a) illustrates, for example, the deformation of bolt 600A by applying torque or force to torque sensor 100. It should be noted that... Figure 27 In (a), for ease of understanding, the deformation of bolt 600A is shown to be relatively large. However, if the deformation of bolt 600A becomes excessive, exceeding the limit of static friction, then... Figure 27 As shown in (b), slippage occurs on the "bolt outer ring surface". Furthermore, the inventors have newly discovered that when slippage occurs on the "bolt outer ring surface", the accuracy of the torque sensor 100 in detecting the torque around the drive shaft becomes unstable.

[0178] The mechanism by which the accuracy of the torque sensor 100 in detecting the torque around the drive shaft becomes unstable when slippage occurs on the "bolt outer ring surface" will be explained below.

[0179] Figure 28 (a) and Figure 28 (b) is a diagram illustrating the mechanism by which the accuracy of the torque sensor 100 in detecting the torque around the drive shaft becomes unstable when slippage occurs at the "bolt / outer ring surface". First, Figure 28 In (a), arrows indicate the force lines through which torque, after being applied to torque sensor 100, is transmitted as shear force from inner ring 110 to outer ring 120. For example... Figure 28As shown in (a), the shear force line originates from the inner ring 110, passes through the spoke 130, and is transmitted within the bolt 600A via the "bolt-outer ring surface" (first path). Furthermore, in addition to the first path, the shear force line is also transmitted to the connecting rod 21B via the "outer ring-connecting rod surface" (second path). Thus, the shear force line flows through both the first and second paths, and the "bolt-outer ring surface" is prone to slippage on the first path. Therefore, when slippage occurs on the "bolt-outer ring surface," the shear force line flowing through the spoke 130 becomes disordered. Since a strain sensor 200 is disposed on the spoke 130 to measure the flow of shear force on the spoke 130, if the shear force line flowing through the spoke 130 is disordered, the output from the strain sensor 200 disposed on the spoke 130 will also become disordered. This results in unstable torque detection accuracy of the torque sensor 100. This insight is a new discovery by the inventors.

[0180] Therefore, based on this insight, the inventors have made further innovations to improve the stability of the torque detection accuracy of the torque sensor 100. This innovation will be explained below.

[0181] <Explanation of Innovation Points>

[0182] Figure 29 This diagram illustrates the innovative aspects that improve the stability of torque sensor torque detection accuracy. Figure 29 The innovation lies in forming a thread on the through portion TH of the outer ring portion 120 of the torque sensor 100, and using a screw 700 instead of a bolt to fasten the torque sensor 100 and the connecting rod 21B. Specifically, a threaded hole is formed on the outer ring portion 120 of the torque sensor 100, and this outer ring portion 120 is configured to be fastened to a component (connecting rod 21B) that can rotate integrally with the outer ring portion 120 by inserting a screw 700 into the threaded hole. This improves the stability of the torque detection accuracy of the torque sensor 100. The reasons for this will be explained below.

[0183] like Figure 29 As shown, when the torque sensor 100 and connecting rod 21B are fastened with screws, the screw hole and screw 700 in the outer ring portion 120 of the torque sensor 100 are fixed to the entire surface of the thread and thread groove by friction. Therefore, mechanically, the torque sensor 100 and connecting rod 21B can be considered as a single unit. Figure 29In this embodiment, the shear force line originates from the inner ring portion 110, passes through the spokes 130, and is transmitted to the outer ring portion 120, which includes the screw 700. Then, it flows to the connecting rod 21B via the "outer ring portion-connecting rod surface." Since the "outer ring portion-connecting rod surface" is in overall contact with the outer ring portion 120, the surface pressure "σ" decreases, increasing the static friction coefficient "μ." This means that, according to this innovation, slippage is easily generated between the outer ring portion 120 and the connecting rod 21B (first advantage). Furthermore, in this innovation, there is no "bolt-outer ring portion surface" where slippage is easily generated (second advantage). Thus, according to the innovation of this embodiment, through the synergistic effect of the first and second advantages, the flow of the shear force line through the spokes 130 is stabilized, thereby improving the stability of the torque detection accuracy of the torque sensor 100.

[0184] <Variation Example>

[0185] The basic idea is to extract only the strain caused by the torque around the drive shaft by innovating the configuration of multiple strain sensors in the torque sensor and the configuration of multiple resistive elements formed in the multiple strain sensors, while offsetting the strain caused by the torque around other shafts or the strain caused by the force applied in each axial direction. In the implementation, this basic idea is achieved by employing, for example... Figure 5 The torque sensor 100 is configured as shown, having four strain sensors 200, and employs a configuration such as... Figure 8 This is achieved through the arrangement of multiple resistive elements 300 formed in the strain sensor 200 as shown.

[0186] However, the basic idea can also be realized through the configuration of this variant example, that is, not only adopting the configuration described in the implementation method, but further adopting, as... Figure 30 The torque sensor 100A, as shown, has six strain sensors 200 and employs a configuration such as... Figure 8 The arrangement of multiple resistive elements 300 formed in the strain sensor 200 is shown.

[0187] Next, the configuration of the torque sensor 100A in this modified example will be explained.

[0188] Figure 30 This is a top view showing the configuration of the torque sensor 100A in this modified example. Figure 30 In the torque sensor 100A, there is an inner ring portion 110 composed of a circular ring, an outer ring portion 120 composed of a circular ring with a diameter larger than that of the inner ring portion 110, and a plurality of spokes (connecting portions) 130 connecting the inner ring portion 110 and the outer ring portion 120.

[0189] In this modified example, the multiple spokes 130 are composed of six spokes 130: spoke 130A, spoke 130B, spoke 130C, spoke 130D, spoke 130E and spoke 130F.

[0190] Specifically, spokes 130A and 130D are respectively disposed on the first virtual line VL1, and are arranged on opposite sides of each other relative to the inner ring center CP. Spokes 130B and 130E are respectively disposed on virtual line VL2A, and are arranged on opposite sides of each other relative to the inner ring center CP. Spokes 130C and 130F are respectively disposed on virtual line VL2B, and are arranged on opposite sides of each other relative to the inner ring center CP.

[0191] The first virtual lines VL1, VL2A, and VL2B intersect at the center CP of the inner ring of the inner ring portion 110, forming an intersection angle of approximately 60 degrees. That is, in this modified example, the first virtual lines VL1, VL2A, and VL2B are not orthogonal to each other. Furthermore, Figure 30 If the virtual line orthogonal to the first virtual line VL1 is taken as the second virtual line VL2, then the second virtual line VL2 forms the bisection line of virtual lines VL2A and VL2B.

[0192] Next, as Figure 30 Each of the six spokes 130 is equipped with a strain sensor 200. Specifically, a first strain sensor 200A is mounted on spoke 130A, and a second strain sensor 200B is mounted on spoke 130B. Furthermore, a third strain sensor 200C is mounted on spoke 130C, and a fourth strain sensor 200D is mounted on spoke 130D. Additionally, a fifth strain sensor 200E is mounted on spoke 130E, and a sixth strain sensor 200F is mounted on spoke 130F.

[0193] like Figure 8 As shown, a plurality of resistive elements 300 are formed on the strain sensors 200 mounted on the six spokes 130 respectively. In this respect, this variation is the same as the embodiment.

[0194] Figure 30 In this configuration, the first strain sensor 200A and the fourth strain sensor 200D are symmetrical with respect to the inner ring center point CP. Similarly, the second strain sensor 200B and the fifth strain sensor 200E are symmetrical with respect to the inner ring center point CP. Additionally, the third strain sensor 200C and the sixth strain sensor 200F are symmetrical with respect to the inner ring center point CP.

[0195] This constitutes the torque sensor 100A.

[0196] Figure 31 This is a table that illustrates the application of the basic ideas in variations.

[0197] Figure 31 In the first strain sensor 200A, by employing Figure 30 The configuration shown makes the strain caused by the x-axis torque around the x-axis "zero", and the strain caused by the y-axis torque around the y-axis "ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is ε. Fx The strain caused by the force in the y-axis direction is "zero", and the strain caused by the force in the z-axis direction is "zero".

[0198] In the second strain sensor 200B, by using Figure 30 The configuration shown makes the strain caused by the x-axis torque around the x-axis "ε′" Tx The strain caused by the y-axis torque around the y-axis is denoted as ε″. Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is ε′. Fx The strain caused by the force along the y-axis is ε. Fy The strain caused by the force in the z-axis direction is "zero".

[0199] In the third strain sensor 200C, by adopting Figure 30 The configuration shown makes the strain caused by the x-axis torque around the x-axis "-ε′" Tx The strain caused by the y-axis torque around the y-axis is "-ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is -ε′. Fx The strain caused by the force along the y-axis is -ε. Fy The strain caused by the force in the z-axis direction is "zero".

[0200] In the fourth strain sensor 200D, by adopting Figure 30 The configuration shown makes the strain caused by the x-axis torque around the x-axis "zero", and the strain caused by the y-axis torque around the y-axis "-ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is -ε. Fx The strain caused by the force in the y-axis direction is "zero", and the strain caused by the force in the z-axis direction is "zero".

[0201] In the fifth strain sensor 200E, by adopting Figure 30The configuration shown makes the strain caused by the x-axis torque around the x-axis "-ε′" Tx The strain caused by the y-axis torque around the y-axis is "-ε". Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is -ε′. Fx The strain caused by the force along the y-axis is -ε. Fy The strain caused by the force in the z-axis direction is "zero".

[0202] In the sixth strain sensor 200F, by adopting Figure 30 The configuration shown makes the strain caused by the x-axis torque around the x-axis "ε′" Tx The strain caused by the y-axis torque around the y-axis is denoted as ε″. Ty The strain caused by the z-axis torque around the z-axis is ε. Tz The strain caused by the force in the x-axis direction is ε′. Fx The strain caused by the force along the y-axis is ε. Fy The strain caused by the force in the z-axis direction is "zero".

[0203] Furthermore, in this modified example, the strains generated by the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, the fourth strain sensor 200D, the fifth strain sensor 200E, and the sixth strain sensor 200F are added together. In this way, for example, the total strain caused by the x-axis torque around the x-axis is "zero", the total strain caused by the y-axis torque around the y-axis is "zero", and the total strain caused by the z-axis torque around the z-axis is "6ε". Tz The total strain caused by the force in the x-axis direction is "zero", the total strain caused by the force in the y-axis direction is "zero", and the total strain caused by the force in the z-axis direction is "zero".

[0204] That is, such as Figure 31 As shown, the total strain other than the total strain caused by the z-axis torque around the z-axis is "zero". This means that, in this modified example, it is also possible to extract only the strain caused by the torque around the drive shaft and offset the strain caused by the torque around other axes or the strain caused by the force applied in each axial direction. Therefore, it can be seen that, in this modified example, even when not only the torque around the drive shaft is applied, but also the torque around other axes or the force in each axial direction is applied, it is possible to extract only the strain caused by the torque around the drive shaft and offset the other strains, thereby enabling high-precision calculation of the torque around the drive shaft.

[0205] In summary, the basic idea can be achieved not only through, for example... Figure 5 The torque sensor 100 of the illustrated embodiment can also be implemented by... Figure 30 The torque sensor 100A shown in this modified example is implemented using the configuration of this embodiment.

[0206] In particular, the advantages of the torque sensor 100 using the embodiment can be listed: as in this modified example, the basic idea can be realized with four strain sensors 200, which is less than six strain sensors 200, thus reducing costs.

[0207] On the other hand, the advantages of using the torque sensor 100A of this modified example can be listed as follows: In the embodiment, the total strain caused by the torque around the drive shaft (around the z-axis) is "4ε". Tz (See) Figure 7 In this modified example, the total strain caused by the torque around the drive shaft (around the z-axis) is 6ε. Tz This increases the magnitude of the detection signal.

[0208] The invention of the inventor has been specifically described above through the embodiments, but the invention is not limited to the embodiments described, and various modifications can be made without departing from its spirit.

[0209] For example, such as Figure 8 As shown, an example of the strain sensor 200 of this embodiment consisting of four resistive elements 300 (resistive element 300A, resistive element 300B, resistive element 300C, and resistive element 300D) arranged orthogonally to each other has been described. However, the technical concept of this embodiment is not limited to this, and it can be widely applied to, for example... Figure 8 The strain sensor 200 is composed of two resistive elements 300 (resistive element 300A and resistive element 300D) arranged orthogonally to each other.

[0210] Symbol Explanation

[0211] 1… Robot system; 10… Robot arm; 11… Robot control unit; 20… Robot joint structure; 20A… Robot joint structure; 20B… Robot joint structure; 20C… Robot joint structure; 21A… Link; 21B… Link; 22… Motor; 23… Reducer; 24… Drive unit; 25… Lubrication components; 26… Bearing components; 30… Torque sensor; 100… Torque sensor; 110… Inner ring; 120… Outer ring; 130… Spoke; 130A… Spoke; 130B… Spoke; 130C… Spoke; 130D… Spoke; 200… Strain sensor; 200A… First strain sensor; 200B… Second strain sensor Strain sensor; 200C… Third strain sensor; 200D… Fourth strain sensor; 300… Resistor; 300A… Resistor; 300B… Resistor; 300C… Resistor; 300D… Resistor; 500… Calculation unit; 501… First voltage value input unit; 502… Second voltage value input unit; 503… Third voltage value input unit; 504… Fourth voltage value input unit; 505… Voltage value summing unit; 506… Drive shaft torque calculation unit; 507… Output unit; 508… Data storage unit; 600A… Bolt; 600B… Nut; 700… Screw; CP… Inner ring center; OP… Opening; TH… Through part.

Claims

1. A torque sensor, comprising: Inner ring; Outer ring section; Multiple connecting portions for connecting the inner ring portion and the outer ring portion; and Multiple strain sensors acquire strain as a change in resistance. The plurality of connecting parts have: The first connecting portion and the third connecting portion are respectively disposed on a first virtual line passing through the center of the inner ring portion, and are disposed on opposite sides of each other relative to the center of the inner ring portion; and The second connecting portion and the fourth connecting portion are respectively disposed on a second virtual line that passes through the center of the inner ring portion and is orthogonal to the first virtual line, and are disposed on opposite sides of each other with respect to the center of the inner ring portion. The plurality of strain sensors have: A first strain sensor is disposed on the first connecting part; A second strain sensor is disposed on the second connecting part; A third strain sensor is disposed on the third connecting part; as well as A fourth strain sensor is disposed on the fourth connecting part. The plurality of strain sensors each have: The semiconductor substrate has a diagonal line that coincides with the third virtual line when viewed from above; as well as Multiple resistive elements are formed on the semiconductor substrate. The plurality of resistive elements include: First resistive element; and Second resistive element, The first angle formed by the first resistive element and the second resistive element is a right angle. The third virtual line extends along the direction that bisects the first angle. The first strain sensor among the plurality of strain sensors is configured on the first connecting portion in such a manner that the third virtual line coincides with the first virtual line. The second strain sensor among the plurality of strain sensors is arranged on the second connection portion in such a manner that the third virtual line coincides with the second virtual line. The third strain sensor among the plurality of strain sensors is arranged on the third connecting portion such that the third virtual line coincides with the first virtual line, and the first resistive element of the third strain sensor is symmetrical with respect to the center of the inner ring with respect to the first resistive element of the first strain sensor, and the second resistive element of the third strain sensor is symmetrical with respect to the center of the inner ring with respect to the second resistive element of the first strain sensor. The fourth strain sensor among the plurality of strain sensors is aligned with the third virtual line and the second virtual line. Furthermore, the first resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring to the first resistive element of the second strain sensor, and the second resistive element of the fourth strain sensor is symmetrical with respect to the center of the inner ring to the second resistive element of the second strain sensor, all arranged on the fourth connecting portion. The plurality of resistive elements include: The third resistive element; and Fourth resistive element, The second angle formed by the third resistive element and the fourth resistive element is a right angle. The third virtual line extends along the direction that bisects the second angle. The torque sensor has the following characteristics: The calculation unit is used to calculate the torque around the normal axis relative to the main surface of the semiconductor substrate based on the outputs from the plurality of strain sensors. The calculation unit calculates the torque around the normal axis based on the total output, which is obtained by adding the following results: The first total is obtained by adding the difference between the resistance values ​​of the first and second resistive elements in the first strain sensor and the difference between the resistance values ​​of the third and fourth resistive elements in the first strain sensor. The second total is obtained by adding the difference between the resistance values ​​of the first and second resistive elements in the second strain sensor and the difference between the resistance values ​​of the third and fourth resistive elements in the second strain sensor. The third sum is obtained by adding the difference between the resistance values ​​of the first and second resistive elements in the third strain sensor and the difference between the resistance values ​​of the third and fourth resistive elements in the third strain sensor, and... The fourth sum is obtained by adding the difference between the resistance values ​​of the first and second resistive elements in the fourth strain sensor and the difference between the resistance values ​​of the third and fourth resistive elements in the fourth strain sensor.

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