CN115280122A

CN115280122A - Torque sensor and robot joint structure

Info

Publication number: CN115280122A
Application number: CN202180021441.8A
Authority: CN
Inventors: 冈田亮二
Original assignee: Senior Director Of Co ltd
Current assignee: Senior Director Of Co ltd
Priority date: 2020-03-19
Filing date: 2021-03-12
Publication date: 2022-11-01
Also published as: WO2021187342A1; JP7360542B2; JPWO2021187342A1

Abstract

The invention provides a torque sensor capable of detecting torque acting around a drive shaft with high sensitivity. By providing an arrangement of a plurality of resistance elements formed in the strain sensor and providing an arrangement of four strain sensors including the first strain sensor, the second strain sensor, the third strain sensor, and the fourth strain sensor, it is possible to extract only the strain caused by the torque around the drive shaft and cancel out the strain caused by the torque around the other shaft than the drive shaft or the strain caused by the force applied in each axial direction.

Description

Torque sensor and robot joint structure

Technical Field

The present invention relates to a torque sensor and a robot joint structure, and for example, to an effective technique applied to a torque sensor as a member of a robot joint structure.

Background

Jp 2017-80841 a (patent document 1) describes a technique of correcting a detection error of a sensor caused by interference with another axis at a joint of a robot arm.

Documents of the prior art

Patent literature

Patent document 1: japanese laid-open patent publication No. 2017-80841

Disclosure of Invention

Technical problem to be solved by the invention

Due to the reduction in labor population in recent years, it is predicted that articulated robots will be applied in many fields. However, there are still many problems to be overcome to replace human labor with a multi-joint robot.

For example, when it is desired to use a robot called a cooperative robot, which is an articulated robot for working together with a human being beside the human being, it is necessary to sense contact between the human being and the articulated robot with high sensitivity. This is because, in order to prevent the articulated robot from erroneously contacting the human being to injure the human being, it is necessary to detect a slight contact reaction force with the human being and to stop the operation of the articulated robot quickly.

Therefore, a multi-joint robot for working together with a human being is mounted with a torque sensor for sensing a slight contact reaction force with the human being, and the torque sensor detects a torque acting around a drive shaft among forces (including torques) acting on a robot arm in particular.

The torque sensor is required to detect the torque acting around the drive shaft with high sensitivity so as to sense a slight contact reaction force with a human being, but in the prior art, it is difficult to sufficiently reduce noise caused by the torque acting around the shaft other than the drive shaft or the force applied in each axial direction, and therefore a torque sensor that detects the torque acting around the drive shaft with high sensitivity is desired. That is, in the torque sensor for detecting the torque acting around the drive shaft, it is desirable to reduce noise caused by the torque around the shaft other than the drive shaft and the force applied in each axial direction.

The purpose of the present invention is to provide a torque sensor capable of detecting torque acting around a drive shaft with high sensitivity.

Other objects and novel features will be apparent from the description and drawings.

Means for solving the technical problem

The torque sensor in one embodiment includes an inner ring portion, an outer ring portion, a plurality of connection portions connecting the inner ring portion and the outer ring portion, and a plurality of strain sensors that acquire strain as a change in resistance value.

Wherein the plurality of connecting portions have: a first connection portion and a third connection portion which are respectively arranged on a first virtual line passing through an inner ring center of the inner ring portion and are arranged on opposite sides of the inner ring center; and a second connection portion and a fourth connection portion which are respectively arranged on a second virtual line passing through the inner ring center of the inner ring portion and orthogonal to the first virtual line, and are arranged on opposite sides with respect to the inner ring center.

The plurality of strain sensors include a first strain sensor disposed on the first connection portion, a second strain sensor disposed on the second connection portion, a third strain sensor disposed on the third connection portion, and a fourth strain sensor disposed on the fourth connection portion.

In this case, each of the plurality of strain sensors includes a semiconductor substrate overlapping with the third virtual line in a plan view and a plurality of resistance elements formed on the semiconductor substrate, and the plurality of resistance elements include a first resistance element and a second resistance element. The first angle formed by the first resistance element and the second resistance element is a right angle, and the third virtual line extends in a direction bisecting the first angle.

Wherein a first strain sensor of the plurality of strain sensors is arranged on the first connection portion such that the third virtual line coincides with the first virtual line, and a second strain sensor of the plurality of strain sensors is arranged on the second connection portion such that the third virtual line coincides with the second virtual line.

On the other hand, a third strain sensor of the plurality of strain sensors is disposed on the third connection portion such that the third virtual line coincides with the first virtual line, and the first resistance element of the third strain sensor is point-symmetric to the first resistance element of the first strain sensor with respect to the center of the inner ring, and the second resistance element of the third strain sensor is point-symmetric to the second resistance element of the first strain sensor with respect to the center of the inner ring, and a fourth strain sensor of the plurality of strain sensors is disposed on the fourth connection portion such that the third virtual line coincides with the second virtual line, and the first resistance element of the fourth strain sensor is point-symmetric to the first resistance element of the second strain sensor with respect to the center of the inner ring, and the second resistance element of the fourth strain sensor is point-symmetric to the second resistance element of the second strain sensor with respect to the center of the inner ring.

The torque sensor according to the modified example includes an inner ring portion, an outer ring portion, a plurality of connection portions connecting the inner ring portion and the outer ring portion, and a plurality of strain sensors that acquire strain as a change in resistance value.

Wherein the plurality of connecting portions have: a first connection portion and a fourth connection portion which are respectively arranged on a first virtual line passing through an inner ring center of the inner ring portion and are arranged on opposite sides with respect to the inner ring center; a second connection portion and a fifth connection portion which are respectively arranged on a second virtual line A passing through the inner ring center of the inner ring portion and intersecting with the first virtual line at the inner ring center, and are arranged on opposite sides with respect to the inner ring center; and a third connection portion and a sixth connection portion which are respectively disposed on a second B virtual line passing through an inner ring center of the inner ring portion and intersecting the first virtual line at the inner ring center, and which are disposed on opposite sides with respect to the inner ring center.

The plurality of strain sensors include a first strain sensor disposed on the first connection portion, a second strain sensor disposed on the second connection portion, a third strain sensor disposed on the third connection portion, a fourth strain sensor disposed on the fourth connection portion, a fifth strain sensor disposed on the fifth connection portion, and a sixth strain sensor disposed on the sixth connection portion.

Wherein a first strain sensor of the plurality of strain sensors is disposed on the first connection portion such that the third virtual line coincides with the first virtual line, a second strain sensor of the plurality of strain sensors is disposed on the second connection portion such that the third virtual line coincides with the second a virtual line, and a third strain sensor of the plurality of strain sensors is disposed on the second connection portion such that the third virtual line coincides with the second B virtual line.

On the other hand, a fourth strain sensor of the plurality of strain sensors is disposed on the fourth connection portion so that the third virtual line coincides with the first virtual line and the first resistance element of the fourth strain sensor is point-symmetric with respect to the center of the inner ring to the first resistance element of the first strain sensor and the second resistance element of the fourth strain sensor is point-symmetric with respect to the center of the inner ring to the second resistance element of the first strain sensor, a fifth strain sensor of the plurality of strain sensors is disposed on the fifth connection portion so that the third virtual line coincides with the second a virtual line and the second resistance element of the fifth strain sensor is point-symmetric with respect to the center of the inner ring to the second resistance element of the second strain sensor, a sixth strain sensor of the plurality of strain sensors is disposed on the fifth connection portion so that the third virtual line coincides with the second B virtual line and the first resistance element of the sixth strain sensor coincides with respect to the center of the inner ring to the second resistance element of the second strain sensor and the sixth strain sensor is disposed on the connection portion so that the point-symmetric with respect to the center to the second resistance element of the inner ring to the third strain sensor.

Effects of the invention

According to the torque sensor in one embodiment, the torque acting around the drive shaft can be detected with high sensitivity.

Drawings

Fig. 1 is a schematic diagram showing one example of a robot system.

Fig. 2 is a diagram schematically showing the structure of a robot joint.

Fig. 3 is a schematic diagram showing a joint structure of a robot in the related art.

Fig. 4 is a schematic diagram showing an example of setting of coordinate axes.

Fig. 5 is a plan view showing the configuration of the torque sensor in the embodiment.

Fig. 6 isbase:Sub>A sectional view taken along linebase:Sub>A-base:Sub>A of fig. 5.

Fig. 7 is a table for explaining the basic idea of the embodiment in a concise and understandable manner.

Fig. 8 is a plan view showing a strain sensor of the embodiment.

Fig. 9 is a plan view showing the configuration of four strain sensors.

Fig. 10 is a schematic diagram showing strains applied to resistive elements respectively formed on four strain sensors when a y-axis torque around the y-axis is applied to the torque sensor.

Fig. 11 is a schematic diagram showing applied strains respectively formed on the resistive elements of the four strain sensors when a force in the y-axis direction is applied to the torque sensor.

Fig. 12 is a schematic diagram showing applied strains respectively formed on resistive elements of four strain sensors when a z-axis torque around the z-axis is applied to a torque sensor.

Fig. 13 is a functional block diagram of the calculation section.

Fig. 14 is a flowchart for explaining the operation of the calculation unit.

Fig. 15 is a graph showing outputs from four strain sensors, respectively, when a y-axis torque around the y-axis is applied.

FIG. 16 is a graph showing the total output from four strain sensors when a y-axis torque about the y-axis is applied.

Fig. 17 is a graph showing changes in the average values of the outputs from the four strain sensors when the y-axis torque around the y-axis is further applied in a state where the z-axis torque is applied around the z-axis.

Fig. 18 is a diagram schematically showing a robot joint structure to which a torque sensor according to an embodiment is applied.

Fig. 19 is a diagram schematically showing a modification of the robot joint structure to which the torque sensor according to the embodiment is applied.

Fig. 20 is a diagram schematically showing a modification of the robot joint structure to which the torque sensor according to the embodiment is applied.

Fig. 21 is a diagram schematically showing a robot joint structure to which a torque sensor of the embodiment is applied.

Fig. 22 is an enlarged view of a connection portion of the torque sensor and the link.

Fig. 23 is a schematic view as viewed from the arrow direction of fig. 22.

Fig. 24 isbase:Sub>A schematic view seen from thebase:Sub>A-base:Sub>A plane of fig. 23.

Fig. 25 is a schematic view seen from the B-B plane of fig. 23.

Fig. 26 is a graph qualitatively showing the relationship between the surface pressure and the static friction coefficient.

Fig. 27 (a) is a view showing a case where a bolt is deformed by applying torque or force to the torque sensor, and fig. 27 (b) is a view showing a case where a slip occurs on the "bolt/outer ring surface".

Fig. 28 (a) and (b) are diagrams for explaining a mechanism in which the accuracy of the torque sensor detecting the torque around the drive shaft becomes unstable when the slip occurs on the "bolt/outer ring portion surface".

Fig. 29 is a diagram for explaining a new point of improving the stability of the torque detection accuracy of the torque sensor.

Fig. 30 is a plan view showing a configuration of a torque sensor in a modification.

Fig. 31 is a table illustrating an application example of the basic idea in the modification.

Detailed Description

In all the figures illustrating the embodiments, in principle, the same components have the same reference numerals and will not be described in detail. Note that, in order to facilitate understanding of the drawings, the top view may be shaded.

< robot System >

Fig. 1 is a schematic diagram showing one example of a robot system.

As shown in fig. 1, the robot system 1 includes, for example, a robot arm 10 configured as a multi-joint robot arm, and a robot control unit 11 that controls the operation of the robot arm 10. The robot arm 10 has a plurality of rotatable joint structures configured to be controlled by the robot control section 11. An end effector, which is configured by, for example, an electric robot hand, is connected to the distal end portion of the robot arm 10. In the robot system 1 configured as described above, the robot control unit 11 controls the operation of the joint structure of the robot arm 10 and the operation of the end effector. Thereby, the workpiece can be operated by the robot arm 10.

< robot Joint Structure >

Next, a robot joint structure included in the robot arm 10 will be described.

Fig. 2 is a diagram schematically showing a joint structure of the robot.

In fig. 2, the robot joint structure 20 is a structure for connecting the link 21A of the robot arm 10 and the link 21B of the robot arm 10. Specifically, a motor 22 is disposed inside the link 21A, and a speed reducer 23 is connected to the motor 22. The motor 22 and the speed reducer 23 constitute a driving unit 24 of the robot joint structure 20. A torque sensor 30 is connected to the speed reducer 23, and a link 21B is connected to the torque sensor 30. Further, a lubricating member 25 is provided between the speed reducer 23 and the torque sensor 30. In the robot joint structure 20 configured as described above, the motor 22 constituting the driving unit 24 is rotated, whereby the torque sensor 30 and the link 21B connected to the speed reducer 23 constituting the driving unit 24 are rotated as a whole about the driving shaft.

< investigation on improvement >

Among them, the torque sensor 30 has a function of detecting torque around the drive shaft when the connecting rod 21B is rotated around the drive shaft. Specifically, the torque sensor 30 is configured to generate deformation when the link 21B rotates about the drive shaft, and is configured to detect strain based on the deformation by a change in resistance value (a change in voltage), and to calculate torque around the drive shaft based on the detected change in resistance value.

However, not only the torque around the drive shaft but also the torque sensor 30 is deformed by the torque around the other shaft other than the drive shaft or the force applied in each axial direction. This means that the change in the resistance value detected by the torque sensor 30 includes not only a change in strain from the torque around the drive shaft but also a change in strain from the torque around the drive shaft or the force applied to each axial direction. That is, a change in resistance value from a strain based on a torque around the drive shaft or a force applied in each axial direction may cause 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 noise caused by the torque around the drive shaft and the forces applied in the respective axial directions. That is, in the torque sensor 30 for detecting the torque acting around the drive shaft with high accuracy, it is desirable to reduce noise caused by the torque acting around the drive shaft or the force acting in each axial direction.

In this regard, there are related techniques as shown below, for example. The "related art" described in the present specification refers to a technology having a problem newly found by the inventors, which is not a conventionally known technology but a prerequisite technology (non-known technology) describing it as a novel technical idea.

Fig. 3 is a schematic view showing a joint structure of a robot of the related art.

As shown in fig. 3, in the robot joint structure 20A of the related art, a bearing member 26 is provided between a reduction gear 23 and a torque sensor 30 that constitute a driving portion 24. The bearing member 26 is configured to be rotatable about the drive shaft together with the torque sensor 30 while fixedly supporting the torque sensor 30. That is, in the related art, the torque sensor 30 is configured to be less likely to be deformed other than around the drive shaft by being fixedly supported by the bearing member 26. Therefore, in the related art, the torque sensor 30 is not easily deformed by the peripheral torque other than the drive shaft or the force applied in each axial direction. This means that, according to the related art, when the torque around the drive shaft is detected by the torque sensor 30, noise caused by the torque around the drive shaft or the force applied to each axial direction can be reduced. That is, it is considered that, according to the related art, the torque around the drive shaft can be detected with high accuracy.

However, in the related art, since the bearing member 26 for fixedly supporting the torque sensor 30 needs to be newly provided, the mass of the robot joint structure 20A increases. That is, it is desirable that the mass of the robot joint structure 20A is smaller, but in the related art, the mass of the robot joint structure 20A is increased, which may cause the operation of the robot joint structure 20A to be sluggish. Further, since the bearing member 26 needs to be newly provided, the cost of the components of the robot joint structure 20A increases. Therefore, it is understood that, in the related art, although the torque around the drive shaft can be detected with high accuracy, there is room for improvement from the viewpoint of improving the operational agility of the robot joint structure 20A and reducing the member cost.

Therefore, in the present embodiment, a novel idea has been created to realize a torque sensor 30 capable of detecting a torque around a drive shaft with high accuracy without using the bearing member 26. Next, the idea of the technique of the present embodiment adopting such innovation will be described.

< setting of coordinate axes >

First, an example of setting the coordinate axis will be described.

Fig. 4 is a schematic diagram showing an example of setting of coordinate axes. As shown in fig. 4, an x-axis, a y-axis, and a z-axis orthogonal to each other are set as three-dimensional coordinates. The force acting in the x-axis direction is denoted by "Fx", the force acting in the y-axis direction is denoted by "Fy", and the force acting in the z-axis direction is denoted by "Fz". Further, an x-axis torque caused by rotation about the x-axis is denoted by "Tx", a y-axis torque caused by rotation about the y-axis is denoted by "Ty", and a z-axis torque caused by rotation about the z-axis is denoted by "Tz".

In this specification, the drive axis 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 of the present embodiment is intended to detect the z-axis torque around the z-axis with high accuracy.

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

< construction of Torque sensor >

Next, a schematic configuration of the torque sensor of the present embodiment will be described.

Fig. 5 is a plan view showing the configuration of the torque sensor according to the present embodiment. As shown in fig. 5, the torque sensor 100 includes an inner ring portion 110 formed of a ring, an outer ring portion 120 formed of a ring having a larger diameter than 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. Wherein the plurality of spokes 130 comprises: the

spokes

130A and 130C are respectively disposed on a first virtual line VL1 passing through the inner ring center CP of the inner ring portion 110, and are disposed on opposite sides with respect to the inner ring center CP; and a spoke 130B and a spoke 130D that are respectively disposed on a second virtual line VL2 that passes through the inner ring center CP of the inner ring portion 110 and is orthogonal to the first virtual line VL1, and that are disposed on opposite sides of the inner ring center CP.

The torque sensor 100 configured as described above is mounted with a plurality of strain sensors 200 that acquire changes in resistance values as strains. Specifically, four strain sensors 200 are mounted on the torque sensor 100. In detail, the four strain sensors 200 include a first strain sensor 200A disposed on the spoke 130A, a second strain sensor 200B disposed on the spoke 130B, a third strain sensor 200C disposed on the spoke 130C, and a fourth strain sensor 200D disposed on the spoke 130D.

Fig. 6 isbase:Sub>A cross-sectional view taken along linebase:Sub>A-base:Sub>A of fig. 5. As shown in fig. 6, the inner ring portion 110 and the outer ring portion 120 are connected by a spoke 130B and a spoke 130D, a second strain sensor 200B is disposed on the spoke 130B, and a fourth strain sensor 200D is disposed on the spoke 130D.

The torque sensor 100 of the present embodiment is thus configured. The torque sensor 100 is deformed when a torque around each axis or a force in each axis direction is applied thereto. In particular, the spokes 130 of the torque sensor 100 are deformed by applying a torque around each axis or a force in each axial direction, and the strain sensor 200 arranged on the spokes 130 is deformed by the spokes 130 to generate a strain, and the strain sensor 200 acquires a change in the resistance of the resistance element as the generated strain.

< basic idea of embodiment >

Next, the basic idea of the present embodiment will be explained.

The basic idea of the present embodiment is to extract only strain caused by torque around the drive shaft and cancel strain caused by torque around the other shaft than the drive shaft or strain caused by force applied in each shaft direction by providing an arrangement of a plurality of resistance elements formed in the strain sensor 200 and an arrangement of four strain sensors 200 including the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D.

That is, the basic idea of the present embodiment is to provide an arrangement of a plurality of resistance elements formed in the strain sensors 200 and an arrangement of four strain sensors 200 so that even when not only the torque around the drive shaft but also the torque around the other shafts other than the drive shaft and the force in each shaft direction are applied, only the strain caused by the torque around the drive shaft is extracted and the other strains are cancelled. For example, the concept of the basic idea is explained below.

Fig. 7 is a table for explaining the basic idea of the present embodiment in a concise and understandable manner.

In fig. 7, in the first strain sensor 200A, the arrangement of the resistance elements formed in the first strain sensor 200A is set, and the arrangement of the first strain sensor 200A is set so thatThe strain resulting from the torque of the x-axis around the x-axis is "zero", and the strain resulting from the torque of the y-axis around the y-axis is "epsilon_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain caused by the force in the direction of the x-axis 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 ".

In the second strain sensor 200B, the arrangement of the resistance element formed in the second strain sensor 200B is set, and the arrangement of the second strain sensor 200B is set so that the strain due to the x-axis torque around the x-axis becomes "e ∈_Tx", the strain due to the y-axis torque around the y-axis is" zero ", and the strain due to the z-axis torque around the z-axis is" ε_Tz", the strain caused by the force in the x-axis direction is" zero ", and the strain caused by the force in the y-axis direction is" ε_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the third strain sensor 200C, the arrangement of the resistive elements formed in the third strain sensor 200C and the arrangement of the third strain sensor 200C are arranged so that the strain due to the x-axis torque around the x-axis is "zero" and the strain due to the y-axis torque around the y-axis is "-epsilon_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain caused by the force in the direction of the x-axis is". Epsilon. "_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 ".

Similarly, in the fourth strain sensor 200D, the arrangement of the resistance elements formed in the fourth strain sensor 200D is provided, and the arrangement of the fourth strain sensor 200D is provided, so that the strain due to the x-axis torque around the x-axis is set to — "epsilon ∈_Tx", the strain due to the torque of the y-axis around the y-axis is" zero ", and the strain due to the torque of the z-axis around the z-axis is" epsilon_Tz", the strain caused by the force in the x-axis direction is" zero ", and the strain caused by the force in the y-axis direction is". Epsilon. "_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the basic idea of the present embodiment, the strains generated in the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D are added. Thus, for example, the total strain due to the x-axis torque around the x-axis becomes "zero", the total strain due to the y-axis torque around the y-axis becomes "zero", and the total strain due to the z-axis torque around the z-axis becomes "4 ∈_Tz"the total strain due to the force in the x-axis direction is" zero ", the total strain due to the force in the y-axis direction is" zero ", and the total strain due to the force in the z-axis direction is" zero ".

That is, as shown in fig. 7, the total strain other than the total strain due to the z-axis torque around the z-axis becomes "zero". This means that, according to the basic idea of the present embodiment, it is possible to extract only the strain due to the torque around the drive shaft and cancel out the strain due to the torque around the other shaft than the drive shaft or the strain due to the force applied in each axial direction. Therefore, according to the basic idea of the present embodiment, even when not only the torque around the drive shaft but also the torque around the other shaft other than the drive shaft and the force in each shaft direction are applied, it is possible to extract only the strain due to the torque around the drive shaft and cancel the other strain, thereby calculating the torque around the drive shaft with high accuracy.

< implementation of the basic idea >

Therefore, innovations for realizing the basic idea of the present embodiment will be described below. Specifically, the innovation includes: innovations for the configuration of the multiple resistive elements formed in the strain sensor 200; and innovation with respect to the configuration of the four strain sensors 200 (the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D).

< creation of arrangement of plural resistance elements >)

Fig. 8 is a plan view showing the strain sensor of the present embodiment.

In fig. 8, the strain sensor 200 of the present embodiment has a rectangular semiconductor substrate 210. The semiconductor substrate 210 is formed of, for example, silicon (Si). A plurality of resistive elements 300 are formed on the semiconductor substrate 210. Specifically, four resistance elements 300 including a resistance element 300A, a resistance element 300B, a resistance element 300C, and a resistance element 300D are formed on the semiconductor substrate 210. Each of the plurality of resistance elements 300 is a diffused resistance element formed by introducing a conductivity type impurity into the semiconductor substrate 210, for example. Here, for example, the first angle formed by the resistance element 300A and the resistance element 300D is a right angle, and the third virtual line VL3 that coincides with the semiconductor substrate 210 extends in a direction that bisects the first angle. Similarly, the angle formed by the resistor element 300A and the resistor element 300B is also a right angle, the angle formed by the resistor element 300B and the resistor element 300C is also a right angle, and the angle formed by the resistor element 300C and the resistor element 300D is also a right angle. That is, the four resistance elements 300 are arranged so that the angles formed by the resistance elements are perpendicular to each other. The term "right angle" as used herein means a case including a concept of intentionally making a right angle, and even if an actual value is out of 90 degrees, the term "right angle" as used herein includes a concept of making a substantially right angle. Specific examples of numerical values include an idea of forming a substantially right angle as long as the angle is 88 to 92 degrees, for example, and thus the term "right angle" as used herein can be included.

The number of resistance elements is not limited to only 4. For example, even if a plurality of groups of resistance elements extending in a direction bisecting the first angle with respect to the third virtual line VL3 and forming a right angle with each other are provided, the above-described multiple combination circuit may be finally equivalent to the form shown in fig. 8.

< Innovation of configuration for four Strain Sensors > <

Fig. 9 is a plan view showing the configuration of four strain sensors 200.

As shown in fig. 9, the first strain sensor 200A of the four strain sensors 200 is configured in such a manner that the third virtual line VL3 (see fig. 8) coincides with the first virtual line VL 1. On the other hand, the second strain sensor 200B of the four strain sensors 200 is configured in such a manner that the third virtual line VL3 (see fig. 8) coincides with the second virtual line VL 2. Further, the third strain sensor 200C among the four strain sensors 200 is arranged such that the third virtual line VL3 (see fig. 8) coincides with the first virtual line VL1, the resistive element 300A of the third strain sensor 200C is point-symmetric to the resistive element 300A of the first strain sensor 200A with respect to the inner ring center CP, the resistive element 300B of the third strain sensor is point-symmetric to the resistive element 300B of the first strain sensor 200A with respect to the inner ring center CP, the resistive element 300C of the third strain sensor 200C is point-symmetric to the resistive element 300C of the first strain sensor 200A with respect to the inner ring center CP, and the resistive element 300D of the third strain sensor is point-symmetric to the resistive element 300D of the first strain sensor 200A with respect to the inner ring center CP. The fourth strain sensor 200D of the four strain sensors 200 is arranged such that the third virtual line VL3 (see fig. 8) coincides with the second virtual line VL2, the resistive element 300A of the fourth strain sensor 200D is point-symmetric to the resistive element 300A of the second strain sensor 200B with respect to the inner ring center CP, the resistive element 300B of the fourth strain sensor 200D is point-symmetric to the resistive element 300B of the second strain sensor 200B with respect to the inner ring center CP, the resistive element 300C of the fourth strain sensor 200D is point-symmetric to the resistive element 300C of the second strain sensor 200B with respect to the inner ring center CP, and the resistive element 300D of the fourth strain sensor 200D is point-symmetric to the resistive element 300D of the second strain sensor 200B with respect to the inner ring center CP.

Next, the basic idea of the present embodiment is realized by innovations in the arrangement of the four resistance elements 300 formed in the strain sensor 200 and in the arrangement of the four strain sensors 200. Specifically, an example will be described in which, in four strain sensors 200 in which four resistance elements 300 shown in fig. 8 are formed, the basic idea of the present embodiment (see fig. 7) is realized by arranging the above four strain sensors 200 as shown in fig. 9.

< description of canceling Strain >

Fig. 10 is a schematic diagram showing applied strains respectively formed on 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. In fig. 10, "+" is given to tensile strain and "-" is given to compressive strain, and "(strain of the resistive element 300A + strain of the resistive element 300C) - (strain of the resistive element 300B + strain of the resistive element 300D)" is given to output strain from the strain sensor 200 based on strain applied to the four resistive elements 300 formed on each strain sensor 200.

In fig. 10, focusing on the first strain sensor 200A, tensile strain is generated in the resistance element 300A and the resistance element 300C, and compressive strain is generated in the resistance element 300B and the resistance element 300D. Thereby setting the output strain output from the first strain sensor 200A to "+ epsilon_Ty”。

Focusing on the second strain sensor 200B, the same tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. Thereby causing the output strain output from the second strain sensor 200B to become "0".

Next, focusing on the third strain sensor 200C, compressive strain is generated in the

resistance elements

300A and 300C, and tensile strain is generated in the

resistance elements

300B and 300D. Such that the output of the third strain sensor 200C is strained to — "epsilon_Ty”。

Focusing on the fourth strain sensor 200D, tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. Thereby causing the output strain of the fourth strain sensor 200D to become "0".

As can be seen, the strain due to the y-axis torque around the y-axis shown in fig. 7 is realized by the four strain sensors 200 (the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D) shown in fig. 10.

Fig. 11 is a schematic diagram showing strains applied to the resistive elements 300 respectively formed on the four strain sensors 200 when a force ("Fy") in the y-axis direction is applied to the torque sensor 100. In fig. 11, the tensile strain is "+", the compressive strain is "-", and the output strain from the strain sensor 200 based on the strains applied to the four resistance elements 300 formed on each strain sensor 200 is set to "(the strain of the resistance element 300A + the strain of the resistance element 300C) - (the strain of the resistance element 300B + the strain of the resistance element 300D)".

In fig. 11, focusing on the first strain sensor 200A, the same tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. Thereby causing the output strain output from the first strain sensor 200A to become "0".

Next, focusing on the second strain sensor 200B, compressive strain is generated in the resistance element 300A and the resistance element 300C, and tensile strain is generated in the resistance element 300B and the resistance element 300D. Thereby causing the output strain output by the second strain sensor 200B to be "+ epsilon_Fy”。

Next, focusing on the third strain sensor 200C, the same tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. Thereby causing the output strain output by the third strain sensor 200C to become "0".

Further, focusing on the fourth strain sensor 200D, tensile strain is generated in the

resistance elements

300A and 300C, and compressive strain is generated in the

resistance elements

300B and 300D. Thereby causing the output from the fourth strain sensor 200D to be strained to — "epsilon_Fy”。

As can be seen, the strain caused by the force applied in the y-axis direction shown in fig. 7 is realized by the four strain sensors 200 (the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D) shown in fig. 11.

Fig. 12 is a schematic diagram showing applied strains respectively formed on the resistive elements 300 of the four strain sensors 200 when z-axis torque ("Tz") around the z-axis is applied to the torque sensor 100. In fig. 12, the tensile strain is "+", the compressive strain is "-", and the output strain from the strain sensor 200 based on the strains applied to the four resistance elements 300 formed on each strain sensor 200 is set to "(the strain of the resistance element 300A + the strain of the resistance element 300C) - (the strain of the resistance element 300B + the strain of the resistance element 300D)".

In fig. 12, focusing on the first strain sensor 200A, compressive strain is generated in the resistance element 300A and the resistance element 300C, and tensile strain is generated in the resistance element 300B and the resistance element 300D. Thereby setting the output strain output by the first strain sensor 200A to "+ epsilon_Tz”。

Next, focusing on the second strain sensor 200B, compressive strain is generated in the resistance element 300A and the resistance element 300C, and tensile strain is generated in the resistance element 300B and the resistance element 300D. So that the output strain output by the first strain sensor 200A becomes "+ epsilon_Tz”。

resistance elements

300A and 300C, and tensile strain is generated in the

resistance elements

300B and 300D. So that the output strain output by the first strain sensor 200A becomes "+ epsilon_Tz”。

Further, focusing on the fourth strain sensor 200D, compressive strain is generated in the

resistance elements

300A and 300C, and tensile strain is generated in the

resistance elements

As can be seen, the strain due to the z-axis torque around the z-axis shown in fig. 7 is realized by the four strain sensors 200 (the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D) shown in fig. 12.

As is apparent from fig. 10 to 12, in the four strain sensors 200 having the four resistance elements 300 formed therein shown in fig. 8, the basic idea of the present embodiment is realized by disposing the four strain sensors 200 as shown in fig. 9 (see fig. 7).

< construction of calculating section >

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

Next, a configuration of a calculation unit that calculates z-axis torque around the z-axis will be described.

Fig. 13 is a functional block diagram of the calculation section 500. In fig. 13, the calculation unit 500 includes 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 addition unit 505, a drive shaft torque calculation unit 506, an output unit 507, and a data storage unit 508.

The first voltage value input section 501 is configured to input an output voltage from the first strain sensor 200A. Specifically, the first strain sensor 200A is arranged to generate strain due to deformation of the torque sensor 100 by torque or force, and is arranged to acquire a resistance value change of the four resistance elements 300 provided inside as the strain, convert the resistance value change into a voltage value, and output the voltage value. The first voltage value input portion 501 is configured to be able to input the output voltage from the first strain sensor 200A. Then, a first voltage value, which is an output voltage from the first strain sensor 200A, is stored in the data storage unit 508.

For example, the first voltage value input to the first voltage value input unit 501 corresponds to a first total value obtained by adding the difference between the resistance value of the resistive element 300A and the resistance value of the resistive element 300B in the first strain sensor 200A and the difference between the resistance value of the resistive element 300C and the resistance value of the resistive element 300D in the first strain sensor 200A.

The second voltage value input section 502 is configured to input the output voltage from the second strain sensor 200B. Specifically, the second strain sensor 200B is also arranged to generate strain due to deformation of the torque sensor 100 by torque or force, and is arranged to acquire a change in resistance value of the four resistance elements 300 provided inside as the strain, convert the change in resistance value into a voltage value, and output the voltage value. The second voltage value input section 502 is configured to be able to input the output voltage from the second strain sensor 200B. Then, a second voltage value, which is an output voltage from the second strain sensor 200B, is stored in the data storage portion 508.

For example, the second voltage value input to the second voltage value input unit 502 corresponds to a second total value obtained by adding the difference between the resistance value of the resistive element 300A and the resistance value of the resistive element 300B in the second strain sensor 200B and the difference between the resistance value of the resistive element 300C and the resistance value of the resistive element 300D in the second strain sensor 200B.

The third voltage value input section 503 is configured to input the output voltage from the third strain sensor 200C. Specifically, the third strain sensor 200C is arranged to generate strain due to deformation of the torque sensor 100 by torque or force, and is arranged to acquire a resistance value change of the four resistance elements 300 provided inside as the strain, convert the resistance value change into a voltage value, and output the voltage value. The third voltage value input section 503 is configured to input the output voltage from the third strain sensor 200C. Then, a third voltage value, which is an output voltage from the third strain sensor 200C, is stored in the data storage unit 508.

For example, the third voltage value input to the third voltage value input unit 503 corresponds to a third total value obtained by adding the difference between the resistance value of the resistive element 300A and the resistance value of the resistive element 300B in the third strain sensor 200C and the difference between the resistance value of the resistive element 300C and the resistance value of the resistive element 300D in the third strain sensor 200C.

The fourth voltage value input section 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 deformation of the torque sensor 100 by torque or force, acquire a change in resistance value of the four resistance elements 300 provided inside as the strain, convert the change in resistance value into a voltage value, and output the voltage value. The fourth voltage value input portion 504 is configured to be able to input the output voltage from the fourth strain sensor 200D. A fourth voltage value, which is an output voltage from the fourth strain sensor 200D, is stored in the data storage unit 508.

For example, the third voltage value input to the fourth voltage value input unit 504 corresponds to a fourth total value obtained by adding the difference between the resistance value of the resistive element 300A and the resistance value of the resistive element 300B in the fourth strain sensor 200D and the difference between the resistance value of the resistive element 300C and the resistance value of the resistive element 300D in the fourth strain sensor 200D.

Next, the voltage value adder 505 is configured to calculate a total voltage value obtained by adding the first voltage value input to the first voltage value input unit 501, the second voltage value input to the second voltage value input unit 502, the third voltage value input to the third voltage value input unit 503, and the fourth voltage value input to the fourth voltage value input unit 504. The calculation of the total voltage value by the voltage value adding unit 505 corresponds to the calculation of the total voltage value shown in fig. 7, for example. That is, the total voltage value calculated by the voltage value adding unit 505 is a voltage value corresponding to the strain caused only by the drive shaft torque around the drive shaft, in which the strains caused by the torque around the other shafts or the force applied in each shaft direction are cancelled out.

Next, the drive shaft torque calculation section 506 is configured to calculate the drive shaft torque around the drive shaft based on the total voltage value calculated by the voltage value addition section 505. In this case, in the present embodiment, the total voltage value calculated by the voltage value adding unit 505 is a voltage value corresponding to the strain caused only by the drive shaft torque around the drive shaft, since the torque around the other shaft or the strain caused by the force applied in each shaft direction is cancelled, and the drive shaft torque calculated based on the total voltage value is highly accurate. For example, the strain and the resistance value have a correlation, and the voltage value based on the resistance value also has a correlation with the strain. Further, since strain and torque also have a correlation, a voltage value and torque also have a correlation. An equation and a table indicating the correlation between the voltage value and the torque are stored in the data storage unit 508. Thus, the drive shaft torque calculation unit 506 can calculate the drive shaft torque from the total voltage value calculated by the voltage value addition unit 505 based on the equation and the table stored in the data storage unit 508.

The output portion 507 is configured to output the value of the drive shaft torque calculated by the drive shaft torque calculation portion 506 to the outside. For example, the value of the drive shaft torque output from the output unit 507 can be input to the robot control unit 11 shown in fig. 1 and used by the robot control unit 11 to control the operation of the robot arm 10.

< operation of calculating section >

The calculation unit 500 of the present embodiment is configured as follows, and the operation of the calculation unit 500 will be described below with reference to the drawings.

Fig. 14 is a flowchart for explaining the operation of the calculation unit.

In fig. 14, the first voltage value input section 501 inputs a first voltage value as an output voltage from the first strain sensor 200A, and the second voltage value input section 502 inputs a second voltage value as an output voltage from the second strain sensor 200B. Similarly, the third voltage value input section 503 inputs a third voltage value as an output voltage from the third strain sensor 200C, and the fourth voltage value input section 504 inputs a fourth voltage value as an output voltage of the fourth strain sensor 200D (S101). Next, the voltage value addition unit 505 adds the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value to calculate a total voltage value. Then, the drive shaft torque calculation portion 506 calculates the drive shaft torque based on the total voltage value calculated by the voltage value addition portion 505. Next, the value of the drive shaft torque calculated by drive shaft torque calculation unit 506 is output from output unit 507.

The operation of the calculation section 500 is realized as follows.

< verification of Effect >

Next, the result of verifying the effect of the present embodiment will be described.

Fig. 15 is a graph showing outputs from four strain sensors, respectively, when a y-axis torque ("Ty") around the y-axis is applied.

In fig. 15, the horizontal axis shows the magnitude of the y-axis torque ("Ty (N · m)"), and the vertical axis shows the output "strain amount (μ ∈)" of each strain sensor.

In fig. 15, focusing on the output of the first strain sensor, it is understood that the output (absolute value) from the first strain sensor increases as the y-axis torque increases. For example, when the y-axis torque is "100N · m", the output from the first strain sensor is "15 μ ∈", and when the y-axis torque is "200N · m", the output from the first strain sensor is "35 μ ∈". Further, when the y-axis torque is "400N · m", the output from the first strain sensor is "60 μ ∈", and when the y-axis torque is "600N · m", the output from the first strain sensor is "90 μ ∈".

On the other hand, focusing on the output of the third strain sensor, it is known 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 "100N · m", the output from the first strain sensor is "-15 μ ε", and when the y-axis torque is "200N · m", the output from the first strain sensor is "-35 μ ε". Further, when the y-axis torque is "400N · m", the output from the first strain sensor is "-60 μ ∈", and when the y-axis torque is "600N · m", the output from the first strain sensor is "-90 μ ∈".

Therefore, it is understood that when the output from the first strain sensor and the output from the second strain sensor are added, the total output of the output from the first strain sensor and the output from the third strain sensor becomes "0". That is, the output from the first strain sensor and the output from the third strain sensor cancel each other out.

Further, it is also known that, with a view to the output from the second strain sensor and the output from the fourth strain sensor, the output from any strain sensor is almost "0" regardless of the magnitude of the y-axis torque.

FIG. 16 is a graph showing the total output from four strain sensors when a y-axis torque ("Ty") about the y-axis is applied.

In fig. 16, the horizontal axis represents the magnitude of the y-axis torque ("Ty (N · m)") and the vertical axis represents the total output "strain amount (μ ∈)" from the four strain sensors.

As can be seen from fig. 16, the total output from the four strain sensors is almost "0" regardless of the magnitude of the y-axis torque. That is, as is clear from fig. 16, even if a y-axis torque around the y-axis, which is an example of a torque around the other axis than a drive axis torque around the drive axis (z-axis torque), is applied, when the output from the first strain sensor, the output from the second strain sensor, the output from the third strain sensor, and the output from the fourth strain sensor based on the y-axis torque are added, the total of the outputs is almost "0". That is, as is evident from the results shown in fig. 15 and 16, the total output from the four strain sensors is not affected by the strain due to the y-axis torque.

Fig. 17 is a graph showing changes in the average values of outputs from the four strain sensors when a certain amount of z-axis torque is applied around the z-axis and y-axis torque around the y-axis is further applied.

In fig. 17, the horizontal axis represents the magnitude of the y-axis torque ("Ty (N · m)"), and the vertical axis represents the average value of the outputs "strain amount (μ ∈)" from the four strain sensors. Also, each point represents the magnitude of the z-axis torque ("Tz"). For example, ". Delta." indicates that the z-axis torque is clockwise and 600 (N.m). The "dashed line" indicates that the z-axis torque ("Tz") is counterclockwise and-600 (N m).

For example, referring to FIG. 7, the output from the first strain sensor 200A is the amount of strain "ε" caused by the torque on the y-axis_Ty"amount of strain due to Z-axis torque ∈_Tz"output corresponding to the added dependent variable. On the other hand, the output from the second strain sensor 200B is the amount of strain "ε" caused by the y-axis torque_Ty"amount of strain due to Z-axis torque ∈_Tz"output corresponding to the added dependent variable. Wherein, in the second strain sensor 200B, "ε_Ty"is zero. In addition, the output from the third strain sensor 200C is the amount of strain- ε caused by the y-axis torque_Ty"amount of strain due to Z-axis torque ∈_Tz"output corresponding to the added dependent variable. And, the output from the fourth strain sensor 200D is related to the y-axis torqueAmount of strain caused — "epsilon_Ty"amount of strain due to Z-axis torque ∈_Tz"outputs corresponding to the added dependent variables. Wherein in the second strain sensor 200D, "-. Epsilon."_Ty"is zero. Therefore, the outputs of the four strain sensors 200 are different from each other, but the average values of the outputs of the four strain sensors 200 are cancelled out in addition to the amount of strain due to the z-axis torque, and the amount of strain "epsilon ∈ is achieved_Tz". This is shown in figure 17. That is, the average value of the outputs of the four strain sensors 200 reaches the strain amount "ε_TzTherefore, a fixed value is formed independently of the magnitude of the y-axis torque and only depending on the magnitude of the z-axis torque. As can be seen from fig. 17, when the magnitude of the z-axis torque is increased, the average value of the outputs of the four strain sensors 200 is increased, and the average value does not change even if the y-axis torque is increased. This can be achieved by the average of the outputs of the four strain sensors 200 to the strain amount "epsilon ∈_Tz"to understand.

< application to robot Joint Structure >

The torque sensor 100 of the present embodiment can be applied to a robot joint structure of a robot arm, for example. For example, fig. 18 is a diagram schematically showing a robot joint structure 20 to which the torque sensor 100 of the present embodiment is applied. In fig. 18, the torque sensor 100 of the present embodiment is connected to a driving unit 24 including a motor 22 and a speed reducer 23, and is connected to a link 21B constituting a part of a robot arm. According to the robot joint structure 20 configured as described above, the drive shaft torque around the drive shaft can be detected with high accuracy by the torque sensor 100.

Further, according to the robot joint structure 20 to which the torque sensor 100 is applied, the following advantages can be obtained. For example, in the related art shown in fig. 3, a bearing member 26 is provided between the driving portion 24 and the torque sensor 30. This is because the torque sensor 30 is fixedly supported by the bearing member 26, and thus is less likely to be deformed beyond the periphery of the drive shaft. That is, in the torque sensor 30 of the related art, when the torque sensor 30 is deformed by the torque around the other shaft than the drive shaft or the force applied in each axial direction, the strain caused by the deformation is also detected by the torque sensor 30, and as a result, the torque sensor 30 is susceptible to the influence of the noise caused by the torque around the other shaft or the force applied in each axial direction. As can be seen, in the related art, the torque sensor 30 is fixedly supported by the bearing member 26 so that the torque sensor 30 is less likely to be deformed except around the drive shaft. Thus, according to the related art, since the torque sensor 30 is less likely to be deformed by the torque around the drive shaft or the force applied in each axial direction, when the torque around the drive shaft is detected by the torque sensor 30, the noise caused by the torque around the drive shaft or the force applied in each axial direction can be reduced. That is, according to the related art, the torque sensor 30 is fixed and supported by the bearing member 26, so that the torque sensor 30 is less likely to be deformed except for the periphery of the drive shaft, thereby detecting the torque around the drive shaft with high accuracy.

In the related art, the mass of the robot joint structure 20A increases because a new bearing member 26 for fixedly supporting the torque sensor 30 needs to be provided. That is, it is desirable that the mass of the robot joint structure 20A is small, but in the related art, the mass of the robot joint structure 20A is increased, which may cause the operation of the robot joint structure 20A to be sluggish. Further, since the bearing member 26 needs to be newly provided, the cost of the components of the robot joint structure 20A increases. Therefore, it is known that, in the related art, although the torque around the drive shaft can be detected with high accuracy, there is room for improvement from the viewpoint of improving the operational agility of the robot joint structure 20A and reducing the component cost.

In this regard, in the torque sensor 100 of the present embodiment, even if the torque sensor 100 is deformed by the torque around the other shaft than the drive shaft or the force applied in each axial direction, the four strain sensors 200 provided in the torque sensor 100 cancel out the strain caused by the torque around the other shaft than the drive shaft or the force applied in each axial direction. That is, according to the torque sensor 100 of the present embodiment, even if the torque sensor 100 is deformed by the torque around the other shaft than the drive shaft or the force applied in each axial direction, noise is less likely to be generated by the torque around the other shaft than the drive shaft or the force applied in each axial direction. Therefore, in the torque sensor 100 of the present embodiment, the torque around the drive shaft can be detected with high accuracy without suppressing the deformation of the torque sensor 100 due to the torque around the shaft other than the drive shaft and the force applied in each axial direction. This means that the torque sensor 100 according to the present embodiment does not need to be fixedly supported by the bearing member 26 as in the torque sensor 30 of the related art shown in fig. 3. In other words, the torque sensor 100 of the present embodiment can detect the torque around the drive shaft with high accuracy by canceling out the torque around the shaft other than the drive shaft and the strain caused by the force applied in each axial direction, even if the torque sensor is not fixedly supported by the bearing member 26. Therefore, according to the present embodiment, since the bearing member 26 is not required, an increase in the mass of the robot joint structure 20 itself can be suppressed. Thus, according to the present embodiment, the operation agility of the robot joint structure can be improved by using the torque sensor 100. Further, since it is not necessary to add a new member such as the bearing member 26, the number of components of the robot joint structure 20 can be reduced, and thus the cost of the components can be reduced.

In addition, according to the torque sensor 100 of the present embodiment, not only the robot joint structure 20 shown in fig. 18 but also, for example, a robot joint structure 20B shown in fig. 19 and a robot joint structure 20C shown in fig. 20 can be realized. Even in this case, a remarkable effect can be obtained that the detection accuracy of the drive shaft torque around the drive shaft can be improved without sacrificing the operation agility of the robot joint structure and the member cost.

These effects require that the torque sensor 100 have high rigidity and not be excessively deformed by the moments in the x, y, and z axes. To increase the rigidity of the torque sensor 100, the thickness and width of the spokes 130 shown in fig. 5 must be increased. In this way, the strain generated by the z-axis torque becomes small, and the resolution of the z-axis torque to be measured is reduced. That is, the detectable critical z-axis torque increases. However, the strain sensor 200 shown in fig. 8 has particularly high sensitivity compared to a strain gauge that measures based on a change in resistance of a common metal. It is understood that when the strain sensor 200 is made of silicon, the strain coefficient indicating the sensitivity for detecting strain is about 25 times that of a normal metallic strain gauge. Therefore, by using the strain sensor 200, the rigidity of the torque sensor 100 can be increased, and the bearing member 26 can be omitted.

< further discussion >

The torque sensor 100 according to the present embodiment is useful in that it can detect the torque around the drive shaft with high accuracy without suppressing the deformation of the torque sensor 100 due to the torque around the other shafts than the drive shaft and the force applied in each axial direction, and can be effectively used in the robot joint structure 20, for example. However, the inventors of the present invention have found, through research, that when the torque sensor 100 is applied to the robot joint structure 20, it is important to innovate the connection structure between the torque sensor 100 and the link 21B, and the following description will discuss this finding.

< novel findings found by the inventors >

Fig. 21 is a diagram schematically showing a robot joint structure 20 to which the torque sensor 100 of the present embodiment is applied. In fig. 21, a region RA indicates a connection portion between the torque sensor 100 and the link 21B. Also, fig. 22 is an enlarged view of a connection portion of the torque sensor 100 and the link 21B shown in the region RA. As shown in fig. 22, torque sensor 100 has through portion TH, and link 21B has opening OP formed with a thread. Through portion TH formed in torque sensor 100 communicates with opening OP formed in link 21B, and bolt 600A is inserted into through portion TH and opening OP. Then, the torque sensor 100 and the link 21B are connected by using the bolt 600A and the nut 600B. At this time, an axial force "P" is applied to bolt 600A.

Next, fig. 23 is a schematic view as seen from the arrow direction of fig. 22. As shown in fig. 23, torque sensor 100 and link 21B are connected by bolt 600A and nut 600B. Also, fig. 24 showsbase:Sub>A schematic view as viewed from thebase:Sub>A-base:Sub>A plane of fig. 23, and fig. 25 showsbase:Sub>A schematic view as viewed from the B-B plane of fig. 23. The surface A-A is referred to asbase:Sub>A "bolt/outer ring surface", and the surface B-B is referred to as an "outer ring/link surface".

In fig. 24, bolt 600A is fixed to outer ring portion 120 of torque sensor 100, and the contact surface between bolt 600A and outer ring portion 120 is denoted by "S1". At this time, the surface pressure "σ 1" between the bolt 600A and the outer ring portion 120 is obtained by "σ 1= p/S1". Where "P" denotes an axial force applied to bolt 600A, and "S1" denotes a contact area of bolt 600A and outer ring portion 120. As shown in fig. 24, since the contact area "S1" of bolt 600A and outer ring portion 120 is small, the surface pressure "σ 1" between bolt 600A and outer ring portion 120 becomes large.

In fig. 25, outer ring portion 120 and link 21B of torque sensor 100 are fixed by bolt 600A, and the contact surface between outer ring portion 120 and link 21B is denoted by "S2". The "S2" corresponds to the entire outer ring portion 120. At this time, the surface pressure "σ 2" between the outer ring portion 120 and the link 21B is obtained by "σ 2= p/S2". Where "P" represents an axial force applied to bolt 600A, and "S2" represents a contact area of outer ring portion 120 and link 21B. As shown in fig. 25, since the contact area "S2" of the outer ring portion 120 and the link 21B is large, the surface pressure "σ 2" between the outer ring portion 120 and the link 21B is reduced.

Next, fig. 26 is a graph qualitatively showing a relationship between the surface pressure and the static friction coefficient. In fig. 26, the horizontal axis represents the surface pressure "σ", and the vertical axis represents the static friction coefficient "μ". As shown in fig. 26, when the axial force ("P") shown in fig. 24 and the axial force ("P") shown in fig. 25 are equal to each other, the static friction coefficient "μ" tends to decrease as the surface pressure "σ" increases. That is, it is found that, when the surface pressure "σ" increases, the slip is likely to occur.

Here, since the contact area "S1" of bolt 600A and outer ring portion 120 is very small compared to the contact surface "S2" of outer ring portion 120 and connecting rod 21B, the surface pressure "σ 1" between bolt 600A and outer ring portion 120 becomes very large compared to the surface pressure "σ 2" between outer ring portion 120 and connecting rod 21B. This means that the "bolt outer ring surface" as the interface between bolt 600A and outer ring 120 slides more easily than the "outer ring link surface" as the interface between outer ring 120 and link 21B.

Fig. 27 is a schematic view showing a case where sliding occurs on the "bolt/outer ring surface". Fig. 27 (a) shows a case where bolt 600A is deformed by applying torque or force to torque sensor 100, for example. In fig. 27 (a), bolt 600A is drawn so as to be largely deformed for easy understanding. However, if the deformation of bolt 600A becomes too large and exceeds the limit of the static frictional force, a slip occurs on the "bolt outer ring surface" as shown in fig. 27 (b). The present inventors have newly found that when a slip occurs on the "bolt/outer ring surface", the accuracy with which the torque sensor 100 detects the torque around the drive shaft becomes unstable.

Next, a mechanism in which the accuracy of the torque sensor 100 detecting the torque around the drive shaft becomes unstable when the slip occurs on the "bolt/outer ring portion surface" will be described.

Fig. 28 (a) and 28 (b) are diagrams for explaining a mechanism in which the accuracy of the torque sensor 100 detecting the torque around the drive shaft becomes unstable when the "bolt/outer ring surface" slips. First, in fig. 28 (a), the force lines of the torque transmitted from the inner ring portion 110 to the outer ring portion 120 as shear forces after the torque is applied to the torque sensor 100 are indicated by arrows. As shown in fig. 28 (a), the force line of the shearing force is transmitted from the inner ring portion 110 through the spokes 130 and then through the "bolt outer ring portion surface" inside the bolt 600A (first path). In addition to the first path, the line of force of the shearing force is transmitted to the link 21B (second path) via the "outer ring portion/link surface". In this way, the line of force of the shearing force flows through both the first path and the second path, and there is a "bolt-outer ring surface" that is likely to slide on the first path. Therefore, when the "bolt/outer ring surface" slides, the lines of force of the shearing force flowing through the spokes 130 are disturbed. Since the spoke 130 is provided with the strain sensor 200, and the strain sensor 200 measures the flow of the shear force on the spoke 130, if the line of force of the shear force flowing through the spoke 130 is disordered, the output from the strain sensor 200 provided on the spoke 130 is also disordered. Thereby causing the accuracy with which the torque sensor 100 detects the torque to become unstable. This finding is a new finding of the present inventors.

Therefore, the present inventors innovated based on this finding to improve the stability of the torque detection accuracy of the torque sensor 100. This innovative point will be explained below.

< description of the points of innovation >

Fig. 29 is a diagram for explaining a new point of improving the stability of the torque detection accuracy of the torque sensor. In fig. 29, the innovation point is that a screw thread is formed in a through portion TH provided in an outer ring portion 120 of a torque sensor 100, and the torque sensor 100 and a link 21B are fastened by a screw 700 instead of a bolt. That is, the outer ring portion 120 of the torque sensor 100 is formed with a screw hole, and the outer ring portion 120 is disposed so as to be fastened to a member (link 21B) that can rotate integrally with the outer ring portion 120 by inserting a screw 700 into the screw hole. This can improve the stability of the torque detection accuracy of the torque sensor 100. The reason for this will be explained below.

As shown in fig. 29, when the torque sensor 100 and the link 21B are screwed together, the screw hole and the screw 700 provided in the outer ring portion 120 of the torque sensor 100 are fixed to the entire surface of the screw and the screw groove by friction force, and therefore, the torque sensor 100 and the link 21B can be considered as a single unit in terms of mechanics. Therefore, in fig. 29, the force line of the shearing force is transmitted from the inner ring portion 110 to the outer ring portion 120 including the screw 700 through the spokes 130, and then flows to the link 21B through the "outer ring portion/link face". At this time, since the "outer ring portion and the connecting rod face" are in contact with each other entirely through the outer ring portion 120, the face pressure "σ" is reduced, and the static friction coefficient "μ" is increased. This means that, according to the innovative point, sliding is easily generated between the outer ring portion 120 and the link 21B (first advantage). In addition, in this innovation, there is no "bolt/outer ring surface" where sliding is likely to occur (second advantage). In this way, according to the innovative aspect of the present embodiment, the flow of the line of force of the shearing force passing through the spokes 130 is stabilized by the synergistic factor of the first advantage and the second advantage, and the stability of the torque detection accuracy of the torque sensor 100 can be improved.

< modification example >

The basic idea is to extract only the strain caused by the torque around the drive shaft and cancel out the strain caused by the torque around the other shaft than the drive shaft or the strain caused by the force applied in each axial direction by the innovation of the arrangement of the plurality of strain sensors provided in the torque sensor and the innovation of the arrangement of the plurality of resistance elements formed in the plurality of strain sensors, respectively. In the embodiment, the basic idea is realized by adopting the configuration of the torque sensor 100 including four strain sensors 200 as shown in fig. 5 and by adopting the layout arrangement of the plurality of resistance elements 300 formed in the strain sensors 200 as shown in fig. 8.

However, the basic idea can be realized by the configuration of the present modification, that is, not only the configuration described in the embodiment, but also the configuration of the torque sensor 100A including six strain sensors 200 as shown in fig. 30, and the layout arrangement of the plurality of resistance elements 300 formed in the strain sensors 200 as shown in fig. 8.

Next, first, the structure of the torque sensor 100A in the present modification will be described.

Fig. 30 is a plan view showing the structure of a torque sensor 100A according to this modification. In fig. 30, the torque sensor 100A includes an inner ring portion 110 formed of a ring, an outer ring portion 120 formed of a ring having a larger diameter than 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.

In the present modification, the plurality of spokes 130 includes six spokes 130, namely, a spoke 130A, a spoke 130B, a spoke 130C, a spoke 130D, a spoke 130E, and a spoke 130F.

Specifically, the spokes 130A and the spokes 130D are disposed on the first virtual line VL1 and on the opposite sides with respect to the inner ring center CP. The spokes 130B and the spokes 130E are disposed on the virtual line VL2A, respectively, and are disposed on opposite sides with respect to the inner ring center CP. The

spokes

130C and 130F are disposed on the virtual line VL2B, respectively, and are disposed on opposite sides with respect to the inner ring center CP.

The first virtual line VL1, the virtual line VL2A, and the virtual line VL2B intersect at the inner ring center CP of the inner ring portion 110, forming an intersection angle of approximately 60 degrees. That is, in the present modification, the first virtual line VL1, the virtual line VL2A, and the virtual line VL2B are not orthogonal to each other. In fig. 30, when a virtual line orthogonal to the first virtual line VL1 is defined as a second virtual line VL2, the second virtual line VL2 forms a bisector of the virtual line VL2A and the virtual line VL 2B.

Next, as shown in fig. 30, strain sensors 200 are mounted on the six spokes 130, respectively. Specifically, the spoke 130A is mounted with a first strain sensor 200A, and the spoke 130B is mounted with a second strain sensor 200B. A third strain sensor 200C is mounted on the spoke 130C, and a fourth strain sensor 200D is mounted on the spoke 130D. A fifth strain sensor 200E is mounted on the spoke 130E, and a sixth strain sensor 200F is mounted on the spoke 130F.

As shown in fig. 8, a plurality of resistance elements 300 are formed on the strain sensors 200 respectively mounted on the six spokes 130. In this regard, the present modification is the same as the embodiment.

In fig. 30, the first strain sensor 200A and the fourth strain sensor 200D are point-symmetric with respect to the inner ring center CP. Likewise, the second strain sensor 200B and the fifth strain sensor 200E are point-symmetric with respect to the inner ring center CP. In addition, the third strain sensor 200C and the sixth strain sensor 200F are point-symmetric with respect to the inner ring center CP.

Thereby constituting the torque sensor 100A.

In fig. 31, in the first strain sensor 200A, the strain due to the x-axis torque around the x-axis is set to "zero" and the strain due to the y-axis torque around the y-axis is set to "epsilon" by the configuration shown in fig. 30_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" zeroIs "zero".

In the second strain sensor 200B, the strain due to the x-axis torque around the x-axis is "∈" by using the configuration shown in fig. 30'_Tx", the strain caused by the torque of the y-axis around the y-axis is" ε_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain resulting from the force in the x-axis direction is" ε'_Fx", the strain caused by the force in the y-axis direction is" ε_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the third strain sensor 200C, the strain due to the x-axis torque around the x-axis is — 'epsilon'_Tx", the strain caused by the torque of the y-axis around the y-axis is". Epsilon ""_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain resulting from force in the x-axis direction is". Epsilon'_Fx", the strain caused by the force in the y-axis direction is". Epsilon ""_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the fourth strain sensor 200D, the configuration shown in fig. 30 is adopted, and the strain due to the x-axis torque around the x-axis is set to "zero", and the strain due to the y-axis torque around the y-axis is set to "-epsilon ∈_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain resulting from a force in the x-axis direction is". Epsilon. "_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 ".

In the fifth strain sensor 200E, the strain due to the x-axis torque around the x-axis is — 'epsilon'_Tx", the strain caused by the torque of the y-axis around the y-axis is". Epsilon ""_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain due to force in the x-axis direction is". Epsilon. ')'_Fx", the strain caused by the force in the y-axis direction is". Epsilon ""_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the sixth strain sensor 200F, by samplingWith the configuration shown in FIG. 30, the strain due to the x-axis torque around the x-axis is "ε'_Tx", the strain caused by the torque of the y-axis around the y-axis is" ε_Ty", the strain caused by the z-axis torque around the z-axis is" ε_Tz", the strain due to the force in the x-axis direction is" ε'_Fx", the strain caused by the force in the y-axis direction is" ε_Fy", the strain caused by the force in the z-axis direction is" zero ".

In the present modification, the strains generated in 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. In this way, for example, the total strain due to the x-axis torque around the x-axis is "zero", the total strain due to the y-axis torque around the y-axis is "zero", and the total strain due to the z-axis torque around the z-axis is "6 ∈_Tz"the total strain due to the force in the x-axis direction is" zero ", the total strain due to the force in the y-axis direction is" zero ", and the total strain due to the force in the z-axis direction is" zero ".

That is, as shown in fig. 31, the total strain other than the total strain due to the z-axis torque around the z-axis becomes "zero". This means that, in the present modification, it is possible to extract only the strain due to the torque around the drive shaft and cancel out the strain due to the torque around the other shaft than the drive shaft or the strain due to the force applied in each axial direction. Therefore, in the present modification, even when not only the torque around the drive shaft but also the torque around the other shaft other than the drive shaft or the force in each axial direction is applied, it is possible to extract only the strain due to the torque around the drive shaft and cancel out the other strain, thereby calculating the torque around the drive shaft with high accuracy.

As described above, the basic idea can be realized not only by the configuration of the torque sensor 100 according to the embodiment shown in fig. 5, but also by the configuration of the torque sensor 100A according to the present modification shown in fig. 30.

In particular, the advantages of the torque sensor 100 according to the embodiment include: as in the present modification, the basic idea can be realized by four strain sensors 200, and cost reduction can be achieved in this respect, in comparison with six strain sensors 200.

On the other hand, the torque sensor 100A according to the present modification has advantages such as: in an embodiment, the sum of the strains due to the torque around the drive shaft (around the z-axis) is "4 ε_Tz"(see fig. 7), in the present modification, the total of the strains due to the torque around the drive shaft (around the z-axis) can be made" 6 ∈_Tz", so that the magnitude of the detection signal can be increased.

The present invention is not limited to the above embodiments, and it is needless to say that various modifications can be made without departing from the scope of the invention.

For example, as shown in fig. 8, an example in which the strain sensor 200 of the present embodiment is configured by four resistance elements 300 (the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D) arranged orthogonally to each other has been described, but the technical idea of the present embodiment is not limited thereto, and can be widely applied to a case in which the strain sensor 200 is configured by two resistance elements 300 (the resistance element 300A and the resistance element 300D) arranged orthogonally to each other in fig. 8, for example.

Description of the symbols

1 \ 8230a robot system; 10 \ 8230and a robot arm; 11 8230and a robot control part; 20\8230thejoint structure of a robot; 20A \8230andjoint structure of robot; 20B \8230anda robot joint structure; 20C 8230and a robot joint structure; 21A 8230and connecting rod; 21 B\8230aconnecting rod; 22 \ 8230and motor; 23 \ 8230and a speed reducer; 24\8230anda driving part; 25 8230a lubricated part; 26 \ 8230and bearing parts; 30 \ 8230and a torque sensor; 100 \ 8230and a torque sensor; 110 \ 8230and an inner ring part; 120 \ 8230and an outer ring part; 130 \ 8230a spoke; 130A 8230; 130B \8230aspoke; 130C 8230; 130D 8230; 200 \ 8230and strain sensor; 200A \8230afirst strain sensor; 200B \ 8230a second strain sensor; 200C 8230and a third strain sensor; 200D 8230a fourth strain sensor; 300, 8230and a resistor element; 300A \8230anda resistive element; 300B 8230and a resistor element; 300C 8230and a resistor element; 300D 8230and a resistor element; 500 \ 8230and a calculating part; 501 \ 8230and a first voltage value input part; 502 \ 8230and a second voltage value input part; 503 8230and a third voltage input part; 504 \ 8230and a fourth voltage value input part; 505 \ 8230a voltage value adding part; 506, 8230and a driving shaft torque calculating part; 507 8230and an output part; 508 \ 8230and a data storage part; 600A 8230and bolt; 600B \ 8230and a nut; 700 \ 8230and screws; CP 823060, inner ring center; OP 8230and an opening part; TH 8230and a through part.

Claims

1. A torque sensor is provided with:

an inner ring portion;

an outer ring portion;

a plurality of connecting portions for connecting the inner ring portion and the outer ring portion; and

a plurality of strain sensors for acquiring strain as a change in resistance value,

the plurality of connection portions have:

first and third connection portions that are respectively disposed on a first virtual line passing through an inner ring center of the inner ring portion and are disposed on opposite sides of the inner ring center; and

a second connection portion and a fourth connection portion that are respectively arranged on a second virtual line that passes through the inner ring center of the inner ring portion and is orthogonal to the first virtual line, and that are arranged on opposite sides of the inner ring center,

the plurality of strain sensors have:

a first strain sensor disposed on the first connection portion;

a second strain sensor disposed on the second connection portion;

a third strain sensor disposed on the third connection portion; and

a fourth strain sensor disposed on the fourth connection portion,

the plurality of strain sensors each have:

a semiconductor substrate that coincides with the third virtual line when viewed from above; and

a plurality of resistance elements formed on the semiconductor substrate,

the plurality of resistive elements includes:

a first resistance element; and

a second resistance element for a second one of the resistor elements,

the first angle formed by the first resistive element and the second resistive element is a right angle,

the third virtual line extends in a direction that bisects the first angle,

the first strain sensor of the plurality of strain sensors is arranged on the first connection portion such that the third virtual line coincides with the first virtual line,

the second strain sensor of the plurality of strain sensors is disposed on the second connection portion such that the third virtual line coincides with the second virtual line,

the third strain sensor of the plurality of strain sensors is disposed on the third connection portion such that the third virtual line coincides with the first virtual line, the first resistance element of the third strain sensor is point-symmetric with respect to the inner ring center with respect to the first resistance element of the first strain sensor, and the second resistance element of the third strain sensor is point-symmetric with respect to the inner ring center with respect to the second resistance element of the first strain sensor,

the fourth strain sensor of the plurality of strain sensors is disposed on the fourth connection portion such that the third virtual line coincides with the second virtual line, the first resistance element of the fourth strain sensor is point-symmetric with respect to the inner ring center with respect to the first resistance element of the second strain sensor, and the second resistance element of the fourth strain sensor is point-symmetric with respect to the inner ring center with respect to the second resistance element of the second strain sensor.

2. The torque sensor according to claim 1,

the torque sensor has:

a calculating section for calculating a torque around a normal axis passing through a center of the inner ring and perpendicular to the inner ring portion based on outputs from the plurality of strain sensors.

3. The torque sensor according to claim 2,

the calculation section calculates a torque around a normal axis perpendicular to the inner ring portion based on a total output obtained by adding:

a first difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the first strain sensor, a second difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the second strain sensor, a third difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the third strain sensor, and a fourth difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the fourth strain sensor.

4. The torque sensor according to claim 1,

the plurality of resistance elements are diffusion resistance elements formed by introducing a conductivity type impurity into the semiconductor substrate, respectively.

5. The torque sensor according to claim 1,

the plurality of resistive elements includes:

a third resistance element; and

a fourth resistance element for a second one of the resistance elements,

the second angle formed by the third resistive element and the fourth resistive element is a right angle,

the third virtual line extends in a direction that bisects the second angle.

6. The torque sensor of claim 5,

the torque sensor has:

a calculation section for calculating a torque around a normal axis with respect to the main surface of the semiconductor substrate based on outputs from the plurality of strain sensors,

a first sum obtained by adding a difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the first strain sensor and a difference between the resistance value of the third resistance element and the resistance value of the fourth resistance element in the first strain sensor,

a second sum obtained by adding a difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the second strain sensor and a difference between the resistance value of the third resistance element and the resistance value of the fourth resistance element in the second strain sensor,

a third sum obtained by adding a difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the third strain sensor and a difference between the resistance value of the third resistance element and the resistance value of the fourth resistance element in the third strain sensor, and

a fourth sum of a difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the fourth strain sensor and a difference between the resistance value of the third resistance element and the resistance value of the fourth resistance element in the fourth strain sensor.

7. The torque sensor according to claim 1,

the outer ring part is provided with a screw hole.

8. The torque sensor according to claim 7,

the outer ring portion is configured to be able to be fastened to a member that is integrally rotatable with the outer ring portion by screwing a screw into the screw hole.

9. The torque sensor according to claim 8,

the component is a connecting rod.

10. The torque sensor according to claim 1,

the torque sensor is a component constituting a joint structure of the robot.

11. A robot joint structure having:

the torque sensor of claim 1; and

a drive unit connected to the inner ring portion of the torque sensor,

there is no bearing member between the drive portion and the outer ring portion.

12. A torque sensor is provided with:

an inner ring portion;

an outer ring portion;

the plurality of connection portions have:

a first connection portion and a fourth connection portion that are respectively arranged on a first virtual line passing through an inner ring center of the inner ring portion and are arranged on opposite sides with respect to the inner ring center;

a second connection portion and a fifth connection portion, which are respectively disposed on a second virtual line A passing through the inner ring center of the inner ring portion and intersecting the first virtual line at the inner ring center, and which are disposed on opposite sides of the inner ring center with respect to each other; and

a third connecting portion and a sixth connecting portion which are respectively arranged on a second imaginary line B passing through the inner ring center of the inner ring portion and intersecting the first imaginary line at the inner ring center, and which are arranged on opposite sides with respect to the inner ring center,

the plurality of strain sensors have:

a first strain sensor disposed on the first connection portion;

a second strain sensor disposed on the second connection portion;

a third strain sensor disposed on the third connection portion;

a fourth strain sensor disposed on the fourth connection portion;

a fifth strain sensor disposed on the fifth connection portion; and

a sixth strain sensor disposed on the sixth connection portion,

the plurality of strain sensors each have:

a plurality of resistance elements formed on the semiconductor substrate,

the plurality of resistive elements includes:

a first resistance element; and

a second resistance element for a second one of the resistance elements,

the third virtual line extends in a direction that bisects the first angle,

the second strain sensor of the plurality of strain sensors is disposed on the second connection portion such that the third virtual line coincides with the second a virtual line,

the third strain sensor of the plurality of strain sensors is disposed on the second connection portion such that the third virtual line coincides with the second B virtual line,

the fourth strain sensor of the plurality of strain sensors is disposed on the fourth connection portion such that the third virtual line coincides with the first virtual line, the first resistance element of the fourth strain sensor is point-symmetric with respect to the inner ring center with respect to the first resistance element of the first strain sensor, and the second resistance element of the fourth strain sensor is point-symmetric with respect to the inner ring center with respect to the second resistance element of the first strain sensor,

the fifth strain sensor of the plurality of strain sensors is disposed on the fifth connection portion so that the third virtual line coincides with the second virtual line a, the first resistance element of the fifth strain sensor is point-symmetric with respect to the inner ring center with respect to the first resistance element of the second strain sensor, and the second resistance element of the fifth strain sensor is point-symmetric with respect to the inner ring center with respect to the second resistance element of the second strain sensor,

the sixth strain sensor of the plurality of strain sensors is disposed on the sixth connection portion such that the third virtual line coincides with the second B virtual line, the first resistance element of the sixth strain sensor is point-symmetric with respect to the inner ring center with respect to the first resistance element of the third strain sensor, and the second resistance element of the sixth strain sensor is point-symmetric with respect to the inner ring center with respect to the second resistance element of the third strain sensor.

13. The torque sensor according to claim 12,

if the virtual line passing through the center of the inner ring and orthogonal to the first virtual line is defined as a second virtual line, the second virtual line is a bisector of the second a virtual line and the second B virtual line.

14. The torque sensor according to claim 12,

the torque sensor has:

15. The torque sensor according to claim 14, wherein the calculating portion calculates the torque around a normal axis perpendicular to the inner ring portion based on a total output obtained by adding:

a first difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the first strain sensor, a second difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the second strain sensor, a third difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the third strain sensor, a fourth difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the fourth strain sensor, a fifth difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the fifth strain sensor, and a sixth difference between a resistance value of the first resistance element and a resistance value of the second resistance element in the sixth strain sensor.