WO2021187342A1

WO2021187342A1 - Torque sensor and robot joint structure

Info

Publication number: WO2021187342A1
Application number: PCT/JP2021/009960
Authority: WO
Inventors: 岡田　亮二
Original assignee: 株式会社グローセル
Priority date: 2020-03-19
Filing date: 2021-03-12
Publication date: 2021-09-23
Also published as: CN115280122A; JP7360542B2; JPWO2021187342A1

Abstract

Provided is a torque sensor with which it is possible to highly precisely detect torque acting around a drive axis. By contriving the positioning of a plurality of resistor elements formed in a strain sensor and also contriving the positioning of four strain sensors including a first strain sensor, a second strain sensor, a third strain sensor, and a fourth strain sensor, only strain originating from torque around a drive axis is extracted, and strain originating from torque around axes other than the drive axis and strain originating from force applied in each axial direction are cancelled out.

Description

Torque sensor and robot joint structure

The present invention relates to a torque sensor and a robot joint structure, and relates to, for example, a technique that is effective when applied to a torque sensor that is a component of the robot joint structure.

Japanese Unexamined Patent Publication No. 2017-80841 (Patent Document 1) describes a technique for correcting a sensor detection error caused by interference of other axes at a joint of a robot arm.

Japanese Unexamined Patent Publication No. 2017-80841

In response to the recent decline in the working population, it is expected that articulated robots will be used in various fields. However, in order to replace articulated robots with human labor, there are various problems to be overcome at present.

For example, when trying to utilize an articulated robot for collaborating with a human beside a human, that is, a robot called a collaborative robot, it is necessary to detect the contact between the human and the articulated robot with high sensitivity. This is because it is necessary to detect a slight contact reaction force with a human and suddenly stop the operation of the articulated robot in order to prevent the articulated robot from accidentally contacting the human and injuring the human. Is.

Therefore, in order to detect a slight contact reaction force with a human, an articulated robot for collaborating with a human acts, in particular, around the drive shaft among the forces (including torque) acting on the robot arm. It is equipped with a torque sensor that detects torque.

This torque sensor is required to detect the torque acting around the drive shaft with high sensitivity in order to detect a slight contact reaction force with a human, but with the current technology, other than the drive shaft As a result of the difficulty in sufficiently reducing the torque around the shaft and the noise caused by the force applied in each axial direction, a torque sensor that detects the torque acting around the drive shaft with high sensitivity is desired. That is, in the torque sensor that detects the torque acting around the drive shaft, it is desired to reduce the noise caused by the torque around the shaft other than the drive shaft and the force applied in each shaft direction.

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

Other issues and new features will become apparent from the description and accompanying drawings herein.

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 capture distortion as a change in resistance value.

Here, the plurality of connecting portions are arranged on the first virtual line passing through the center of the inner ring of the inner ring portion, and the first connecting portion and the third connecting portion arranged on opposite sides to the center of the inner ring, respectively. A second connection portion and a second virtual line that pass through the center of the inner ring of the inner ring portion and are arranged on the second virtual line that is orthogonal to the first virtual line and are arranged on opposite sides to the center of the inner ring. It has 4 connections.

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

At this time, each of the plurality of strain sensors has a semiconductor substrate that overlaps 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 are the first resistance element. , Includes 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 that bisects the first angle.

Here, the first strain sensor among the plurality of strain sensors is arranged on the first connection portion so that the third virtual line coincides with the first virtual line, and the second strain sensor among the plurality of strain sensors is arranged. Is arranged on the second connection portion so that the third virtual line coincides with the second virtual line.

On the other hand, in the third strain sensor among the plurality of strain sensors, the third virtual line coincides with the first virtual line, and the first resistance element of the third strain sensor with respect to the center of the inner ring is the first strain sensor. Arranged on the third connection portion so that the second resistance element of the third strain sensor is point-symmetric with the first resistance element and the second resistance element of the third strain sensor is point-symmetric with respect to the center of the inner ring. In the fourth strain sensor among the plurality of strain sensors, the third virtual line coincides with the second virtual line, and the first resistance element of the fourth strain sensor with respect to the center of the inner ring is the second strain sensor. Arranged on the fourth connection portion so as to be point-symmetric with the first resistance element and point-symmetric with the second resistance element of the second strain sensor with respect to the center of the inner ring. Has been done.

Further, the torque sensor in 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 capture distortion as a change in resistance value.

Here, the plurality of connecting portions are arranged on the first virtual line passing through the center of the inner ring of the inner ring portion, and the first connecting portion and the fourth connecting portion arranged on opposite sides to the center of the inner ring, respectively. A second connection that is a second A virtual line that passes through the center of the inner ring of the inner ring portion and is arranged on the second A virtual line that intersects the center of the inner ring with the first virtual line, and is arranged on opposite sides to the center of the inner ring. The second B virtual line passing through the inner ring center of the inner ring portion and the fifth connecting portion and the second virtual line, which are arranged on the second B virtual line intersecting the first virtual line and the inner ring center, and opposite to each other with respect to the inner ring center. It has a third connection and a sixth connection arranged on the side.

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

Here, the first strain sensor among the plurality of strain sensors is arranged on the first connection portion so that the third virtual line coincides with the first virtual line, and the second strain sensor among the plurality of strain sensors is arranged. Is arranged on the second connection so that the third virtual line coincides with the second A virtual line, and in the third distortion sensor among the plurality of distortion sensors, the third virtual line coincides with the second B virtual line. It is arranged on the second connection portion as described above.

On the other hand, in the fourth strain sensor among the plurality of strain sensors, the third virtual line coincides with the first virtual line, and the first resistance element of the fourth strain sensor with respect to the center of the inner ring is the first strain sensor. Arranged on the fourth connection portion so that the second resistance element of the fourth strain sensor is point-symmetric with the first resistance element and the second resistance element of the fourth strain sensor is point-symmetric with respect to the center of the inner ring. In the fifth strain sensor among the plurality of strain sensors, the third virtual line coincides with the second A virtual line, and the first resistance element of the fifth strain sensor with respect to the center of the inner ring is the second strain sensor. Arranged on the fifth connection so that the second resistance element of the fifth strain sensor is point-symmetric with the first resistance element and the second resistance element of the second strain sensor is point-symmetric with respect to the center of the inner ring. In the sixth distortion sensor among the plurality of distortion sensors, the third virtual line coincides with the second B virtual line, and the first resistance element of the sixth distortion sensor with respect to the center of the inner ring is the third distortion sensor. Arranged on the sixth connection so that the second resistance element of the sixth strain sensor is point-symmetric with the first resistance element and the second resistance element of the sixth strain sensor is point-symmetric with respect to the center of the inner ring. Has been done.

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

It is a schematic diagram which shows an example of a robot system. It is a figure which shows the robot joint structure schematically. It is a schematic diagram which shows the robot joint structure in a related technique. It is a schematic diagram which shows the setting example of a coordinate axis. It is a top view which shows the structure of the torque sensor in embodiment. It is sectional drawing cut along the line AA of FIG. It is a table which explains the basic idea in an embodiment in an easy-to-understand manner. It is a top view which shows the distortion sensor in embodiment. It is a top view which shows the arrangement of four distortion sensors. It is a schematic diagram which shows the distortion applied to the resistance element formed in each of four distortion sensors when the y-axis torque around the y-axis is applied to a torque sensor. It is a schematic diagram which shows the strain applied to the resistance element formed in each of four strain sensors when a force in a y-axis direction is applied to a torque sensor. It is a schematic diagram which shows the distortion applied to the resistance element formed in each of four distortion sensors when the z-axis torque around the z-axis is applied to a torque sensor. It is a functional block diagram of a calculation part. It is a flowchart explaining operation of a calculation part. It is a graph which shows the output from each of four distortion sensors when the y-axis torque around the y-axis is applied. It is a graph which shows the total output from four distortion sensors when the y-axis torque around the y-axis is applied. It is a graph which shows the change of the average value of the output from four distortion sensors when the y-axis torque around the y-axis is further applied in the state where the z-axis torque is applied around the z-axis. It is a figure which shows typically the robot joint structure which applied the torque sensor in embodiment. It is a figure which shows typically the modification of the robot joint structure which applied the torque sensor in embodiment. It is a figure which shows typically the modification of the robot joint structure which applied the torque sensor in embodiment. It is a figure which shows typically the robot joint structure which applied the torque sensor in embodiment. It is an enlarged view of the connection part of a torque sensor and a link. It is a schematic view seen from the arrow direction of FIG. It is a schematic view seen from the AA plane of FIG. 23. It is a schematic view seen from the BB plane of FIG. 23. It is a graph which qualitatively shows the relationship between a surface pressure and a coefficient of static friction. (A) is a diagram showing how the bolt is deformed by applying torque or force to the torque sensor, and (b) is a diagram showing how the "bolt / outer ring portion surface" is slipped. .. FIGS. (A) and (B) are diagrams for explaining a mechanism in which the accuracy of detecting torque around the drive shaft by the torque sensor becomes unstable when the "bolt / outer ring portion surface" slips. It is a figure for demonstrating the device for improving the stability of the torque detection accuracy in a torque sensor. It is a top view which shows the structure of the torque sensor in the modification. It is a table explaining the application example of the basic idea to the modification example.

In all the drawings for explaining the embodiment, the same members are, in principle, given the same reference numerals, and the repeated description thereof will be omitted. In addition, in order to make the drawing easy to understand, hatching may be added even if it is a plan view.

<Robot system>
FIG. 1 is a schematic diagram showing an example of a robot system.

As shown in FIG. 1, the robot system 1 includes, for example, a robot arm 10 configured as an articulated 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, and these plurality of joint structures are configured to be controlled by the robot control unit 11. An end effector composed of, for example, an electric hand is connected to the tip of the robot arm 10. In the robot system 1 configured in this way, the robot control unit 11 controls the operation of the joint structure of the robot arm 10 and the operation of the end effector. As a result, the work can be operated by the robot arm 10.

<Robot joint structure>
Next, the robot joint structure included in the robot arm 10 will be described.

FIG. 2 is a diagram schematically showing a robot joint structure.

In FIG. 2, the robot joint structure 20 is a structure that connects the link 21A of the robot arm 10 and the link 21B of the robot arm 10. Specifically, a motor 22 is arranged inside the link 21A, and a speed reducer 23 is connected to the motor 22. The motor 22 and the speed reducer 23 form a drive 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 in this way, the torque sensor 30 connected to the speed reducer 23 constituting the drive unit 24 and the link 21B are integrated by rotating the motor 22 constituting the drive unit 24. Rotate around the drive shaft.

<Examination of improvement>
Here, the torque sensor 30 has a function of detecting the torque around the drive shaft when the link 21B is rotated around the drive shaft. Specifically, the torque sensor 30 is configured to be deformed when the link 21B is rotated around the drive shaft, and the distortion based on this deformation is detected by a change in the electric resistance value (change in voltage). It is configured to calculate the torque around the drive shaft based on the detected change in the electric resistance value.

However, the deformation of the torque sensor 30 is caused not only by the torque around the drive shaft but also by the torque around other shafts other than the drive shaft and the force applied in each shaft direction. This means that changes in the electrical resistance value detected by the torque sensor 30 include not only changes due to distortion based on torque around the drive shaft, but also torque around other shafts other than the drive shaft and forces applied in each axial direction. It means that the change due to the distortion based on is also included. That is, the change in the electric resistance value due to the torque around the other shafts other than the drive shaft and the strain based on the force applied in each shaft direction becomes noise when calculating the torque around the drive shaft. Therefore, in order for the torque sensor 30 to detect the torque around the drive shaft with high sensitivity, it is necessary to sufficiently reduce the noise caused by the torque around the shaft other than the drive shaft and the force applied in each shaft direction. .. That is, it is desired that the torque sensor 30 for detecting the torque acting around the drive shaft with high accuracy reduces the noise caused by the torque around the shaft other than the drive shaft and the force applied in each shaft direction. ing.

Regarding this point, for example, there are related technologies shown below. The "related technology" referred to in the present specification is a technology having a problem newly found by the inventor, and is not a known conventional technology, but is intended as a prerequisite technology (unknown technology) of a new technical idea. It is a technique described in.

FIG. 3 is a schematic diagram showing a robot joint structure in a related technology.

As shown in FIG. 3, in the robot joint structure 20A in the related technology, a bearing member 26 is provided between the speed reducer 23 constituting the drive unit 24 and the torque sensor 30. The bearing member 26 is configured to rotate around the drive shaft together with the torque sensor 30, while fixing and supporting the torque sensor 30. That is, in the related technology, the torque sensor 30 is fixedly supported by the bearing member 26, so that the torque sensor 30 is not easily deformed except around the drive shaft. As a result, in the related technology, the torque sensor 30 is less likely to be deformed due to the torque around other shafts other than the drive shaft and the force applied in each shaft direction. According to the related technology, when the torque sensor 30 detects the torque around the drive shaft, it is possible to reduce the noise caused by the torque around the other shafts other than the drive shaft and the force applied in each shaft direction. Means. That is, according to the related technology, it is considered that the torque around the drive shaft can be detected with high accuracy.

However, in the related technology, since it is necessary to newly provide a bearing member 26 for fixing and supporting the torque sensor 30, the mass of the robot joint structure 20A becomes large. That is, it is desirable that the mass of the robot joint structure 20A is small, but in the related technology, the mass of the robot joint structure 20A becomes large, and the operation of the robot joint structure 20A may become dull. Further, since it is necessary to newly provide the bearing member 26, the component cost of the robot joint structure 20A will increase. Therefore, it can be seen that the related technology can detect the torque around the drive shaft with high accuracy, but there is room for improvement from the viewpoint of improving the motion agility of the robot joint structure 20A and reducing the component cost. ..

Therefore, in the present embodiment, a device is devised to realize a torque sensor 30 that can detect the torque around the drive shaft with high accuracy without using the bearing member 26. Hereinafter, the technical idea in the present embodiment to which this device has been devised will be described.

<Setting of coordinate axes>
First, an example of setting the coordinate axes will be described.

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

Here, in this specification, the drive shaft is the z-axis. Therefore, the torque around the drive shaft is the z-axis torque around the z-axis, and the torque sensor 30 in the present embodiment aims to detect the z-axis torque around the z-axis with high accuracy.

On the other hand, when the coordinate axes are set in this way, the torque around the other axes other than the drive axis is the x-axis torque "Tx" or the y-axis torque "Ty", and the force applied in each axis direction is the force in the x-axis direction. They are "Fx", a force in the y-axis direction "Fy", and a force in the z-axis direction "Fz".

<Torque sensor configuration>
Subsequently, a schematic configuration of the torque sensor according to 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 composed of a circular ring, an outer ring portion 120 composed of a circular ring having a diameter larger than that of the inner ring portion 110, and an inner ring portion 110 and an outer ring portion 120. It is provided with a plurality of spokes (connection portions) 130 for connecting the above. Here, the plurality of spokes 130 are the spokes 130A and the spokes 130C arranged on the first virtual line VL1 passing through the inner ring center CP of the inner ring portion 110 and arranged on opposite sides to the inner ring center CP. And the second virtual line VL2 passing through the inner ring center CP of the inner ring portion 110 and arranged on the second virtual line VL2 orthogonal to the first virtual line VL1 and opposite to each other with respect to the inner ring center CP. The

spokes

130B and 130D that are arranged are included.

The torque sensor 100 configured in this way is equipped with a plurality of strain sensors 200 that capture distortion as a change in electrical resistance value. Specifically, the torque sensor 100 is equipped with four strain sensors 200. More specifically, the four strain sensors 200 include a first strain sensor 200A arranged on the spokes 130A, a second strain sensor 200B arranged on the spokes 130B, and a second strain sensor 200B arranged on the spokes 130C. A third strain sensor 200C and a fourth strain sensor 200D arranged on the spokes 130D are included.

FIG. 6 is a cross-sectional view taken along the line AA of FIG. As shown in FIG. 6, the inner ring portion 110 and the outer ring portion 120 are connected by the spokes 130B and the spokes 130D, the second strain sensor 200B is arranged on the spokes 130B, and the fourth strain is placed on the spokes 130D. It can be seen that the sensor 200D is arranged.

As described above, the torque sensor 100 according to the present embodiment is configured. The torque sensor 100 is deformed when a torque around each axis or a force in each axial direction is applied. In particular, the spokes 130 of the torque sensor 100 are deformed when a torque around each axis or a force in each axial direction is applied, and the strain sensor 200 arranged on the spokes 130 is distorted due to the deformation of the spokes 130. The strain sensor 200 captures the generated strain as a change in the electrical resistance of the resistance element.

<Basic idea in the embodiment>
Next, the basic idea in this embodiment will be described.

The basic idea in the present embodiment is to devise the arrangement of a plurality of resistance elements formed in the strain sensor 200, and to devise the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor. By devising the arrangement of the four strain sensors 200 made of 200D, only the strain caused by the torque around the drive shaft is extracted, while the strain caused by the torque around other shafts other than the drive shaft and the distortion in each axial direction It is an idea that offsets the distortion caused by the applied force.

That is, the basic idea in the present embodiment is caused not only by the torque around the drive shaft but also by the torque around the drive shaft even when the torque around the other shafts other than the drive shaft and the force in each shaft direction are applied. The idea is to devise the arrangement of a plurality of resistance elements formed in the distortion sensor 200 and to devise the arrangement of the four distortion sensors 200 so as to extract only the distortion and cancel the other distortions. For example, the concept of the basic idea will be explained below.

FIG. 7 is a table for explaining the basic idea in this embodiment in an easy-to-understand manner.

In FIG. 7, in the first strain sensor 200A, by devising the arrangement of the resistance element formed in the first strain sensor 200A and devising the arrangement of the first strain sensor 200A, it is caused by the x-axis torque around the x-axis. The strain to be generated is "zero", the strain caused by the y-axis torque around the y-axis is "ε _Ty ", the strain caused by the z-axis torque around the z-axis is "ε _Tz ", and the strain caused by the force in the x-axis direction. Is "ε _Fx ", the strain caused by the force in the y-axis direction is "zero", and the strain caused by the force in the z-axis direction is "zero".

Further, in the second strain sensor 200B, by devising the arrangement of the resistance element formed in the second strain sensor 200B and devising the arrangement of the second strain sensor 200B, the distortion caused by the x-axis torque around the x-axis is devised. Is "ε _Tx ", the strain caused by the y-axis torque around the y-axis is "zero", the strain caused by the z-axis torque around the z-axis is "ε _Tz ", and the strain caused by the force in the x-axis direction is "". "Zero", the strain caused by the force in the y-axis direction is "ε _Fy ", and the strain caused by the force in the z-axis direction is "zero".

Further, in the third strain sensor 200C, by devising the arrangement of the resistance element formed in the third strain sensor 200C and devising the arrangement of the third strain sensor 200C, the distortion caused by the x-axis torque around the x-axis is devised. Is "zero", the strain caused by the y-axis torque around the y-axis is "-ε _Ty ", the strain caused by the z-axis torque around the z-axis is "ε _Tz ", and the strain caused by the force in the x-axis direction is "-ε Ty". "-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".

Similarly, in the fourth strain sensor 200D, by devising the arrangement of the resistance elements formed in the fourth strain sensor 200D and devising the arrangement of the fourth strain sensor 200D, it is caused by the x-axis torque around the x-axis. The strain is "-ε _Tx ", the strain caused by the y-axis torque around the y-axis is "zero", the strain caused by the z-axis torque around the z-axis is "ε _Tz ", and the strain caused by the force in the x-axis direction. Is "zero", the strain caused by the force in the y-axis direction is "-ε _Fy ", and the strain caused by the force in the z-axis direction is "zero".

Then, in the basic idea of the present embodiment, the strains generated by the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, and the fourth strain sensor 200D are added. Then, for example, the total strain caused by the x-axis torque around the x-axis is "zero", the total strain caused by the y-axis torque around the y-axis is "zero", and the total strain caused by the z-axis torque around the z-axis is "zero". Is "4ε _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". It becomes.

That is, as shown in FIG. 7, the total strain other than the total strain caused by the z-axis torque around the z-axis is "zero". This means that if the basic idea of the present embodiment is adopted, only the strain caused by the torque around the drive shaft is extracted, while the strain caused by the torque around the other shaft other than the drive shaft and the force applied in each axial direction are extracted. It means that the distortion caused by can be offset. Therefore, according to the basic idea in the present embodiment, not only the torque around the drive shaft but also the torque around the drive shaft and the torque around the drive shaft even when the torque around the other shafts other than the drive shaft and the force in each shaft direction are applied. As a result of being able to extract only the resulting strain and offset the other strains, it can be seen that the torque around the drive shaft can be calculated with high accuracy.

<Realization of basic ideas>
Therefore, in the following, a device for embodying the basic idea in the present embodiment will be described. Specifically, this device includes a device for arranging a plurality of resistance elements formed in the strain sensor 200 and four strain sensors 200 (first strain sensor 200A, second strain sensor 200B, and third strain sensor 200C). And the fourth strain sensor 200D) there is a device for the arrangement.

<< Ingenuity for arrangement of multiple resistance elements >>
FIG. 8 is a plan view showing a strain sensor according to the present embodiment.

In FIG. 8, the strain sensor 200 according to the present embodiment has a rectangular semiconductor substrate 210. The semiconductor substrate 210 is made of, for example, silicon (Si). A plurality of resistance elements 300 are formed on the semiconductor substrate 210. Specifically, the semiconductor substrate 210 is formed with four resistance elements 300 including a resistance element 300A, a resistance element 300B, a resistance element 300C, and a resistance element 300D. Each of these plurality of resistance elements 300 is, for example, a diffusion resistance element formed by introducing conductive impurities into the semiconductor substrate 210. 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 overlaps with the semiconductor substrate 210 extends in a direction that bisects the first angle. Similarly, the angle formed by the resistance element 300A and the resistance element 300B is also a right angle, the angle formed by the resistance element 300B and the resistance element 300C is also a right angle, and the angle formed by the resistance element 300C and the resistance element 300D is also a right angle. That is, the four resistance elements 300 are arranged so that the angles formed by each other are at right angles. The term "right angle" as used herein means a case where the idea of intentionally making a right angle is included, and even if the actual value deviates from 90 degrees by an error. If the idea of making a right angle to the root is included, it shall be included in the "right angle" as used herein. To give a specific example of numerical values, for example, if the angle is 88 degrees to 92 degrees, it can be considered that there is an idea of making a right angle to the base, so that it is included in the "right angle" referred to in the present specification. can.

Also, the number of resistance elements is not limited to four. For example, there are a plurality of sets of resistance elements extending in a direction that bisects the first angle with respect to the third virtual line VL3, and the angles formed by the constituent resistance elements are at right angles. However, it is sufficient that these plurality of sets of synthesis circuits are finally equivalent to the form shown in FIG.

<< Ingenuity for arrangement of 4 distortion sensors >>
FIG. 9 is a plan view showing the arrangement of the four strain sensors 200.

As shown in FIG. 9, the first strain sensor 200A out of the four strain sensors 200 is arranged so that the third virtual line VL3 (see FIG. 8) coincides with the first virtual line VL1. On the other hand, the second strain sensor 200B out of the four strain sensors 200 is arranged so that the third virtual line VL3 (see FIG. 8) coincides with the second virtual line VL2. Further, in the third strain sensor 200C out of the four strain sensors 200, the third virtual line VL3 (see FIG. 8) coincides with the first virtual line VL1 and the third distortion sensor with respect to the inner ring center CP. The resistance element 300A of 200C is point-symmetric with the resistance element 300A of the first strain sensor 200A, and the resistance element 300B of the third strain sensor is point-symmetric with the resistance element 300B of the first distortion sensor 200A with respect to the inner ring center CP. The resistance element 300C of the third strain sensor 200C is point-symmetrical to the resistance element 300C of the first strain sensor 200A with respect to the inner ring center CP, and the resistance element of the third strain sensor is point-symmetrical with respect to the inner ring center CP. The 300D is arranged so as to be point-symmetrical with the resistance element 300D of the first strain sensor 200A. Further, in the fourth distortion sensor 200D out of the four strain sensors 200, the third virtual line VL3 (see FIG. 8) coincides with the second virtual line VL2, and the fourth distortion sensor with respect to the inner ring center CP. The resistance element 300A of the 200D is point-symmetrical to the resistance element 300A of the second strain sensor 200B, and the resistance element 300B of the fourth strain sensor 200D is pointed to the resistance element 300B of the second strain sensor 200B with respect to the inner ring center CP. The resistance element 300C of the fourth strain sensor 200D is point-symmetric with respect to the resistance element 300C of the second strain sensor 200B with respect to the inner ring center CP, and the fourth strain sensor 200D is symmetrical with respect to the inner ring center CP. The resistance element 300D is arranged so as to be point-symmetrical with the resistance element 300D of the second distortion sensor 200B.

In the following, the basic idea in the present embodiment is embodied by devising the arrangement of the four resistance elements 300 formed in the strain sensor 200 and devising the arrangement of the four strain sensors 200. Specifically, in the four strain sensors 200 in which the four resistance elements 300 shown in FIG. 8 are formed, these four strain sensors 200 are arranged as shown in FIG. It will be explained that the basic idea (see FIG. 7) in the above is embodied.

<< Specific explanation to offset distortion >>
FIG. 10 is a schematic view showing the strain applied to the resistance element 300 formed in each of the four strain sensors 200 when the y-axis torque (“Ty”) around the y-axis is applied to the torque sensor 100. .. In FIG. 10, the tensile strain is “+”, the compression strain is “−”, and the output strain from the strain sensor 200 based on the strain applied to the four resistance elements 300 formed in each strain sensor 200 is “((. Distortion of the resistance element 300A + distortion of the resistance element 300C)-(distortion of the resistance element 300B + distortion of the resistance element 300D) ”.

Focusing on the first strain sensor 200A in FIG. 10, tensile strain is generated in the resistance element 300A and the resistance element 300C, while compression strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A is set to "+ ε _Ty ".

Subsequently, focusing on the second strain sensor 200B, the same tensile strain occurs in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. As a result, the output distortion output from the second distortion sensor 200B becomes "0".

Next, focusing on the third strain sensor 200C, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the third distortion sensor 200C _{becomes "-ε Ty} ".

Further, focusing on the fourth strain sensor 200D, the same tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. As a result, the output distortion output from the fourth distortion sensor 200D becomes "0".

From the above, the four strain sensors 200 (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) shown in FIG. 10 are used to rotate the y-axis as shown in FIG. It can be seen that the distortion caused by the y-axis torque is realized.

FIG. 11 is a schematic view showing the strain applied to the resistance element 300 formed in each of 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 compression strain is “−”, and the output strain from the strain sensor 200 based on the strain applied to the four resistance elements 300 formed in each strain sensor 200 is “((. Distortion of the resistance element 300A + distortion of the resistance element 300C)-(distortion of the resistance element 300B + distortion of the resistance element 300D) ”.

Focusing on the first strain sensor 200A in FIG. 11, the same tensile strain is generated in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A becomes "0".

Subsequently, focusing on the second strain sensor 200B, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the second distortion sensor 200B is set to "+ ε _Fy ".

Next, focusing on the third strain sensor 200C, the same tensile strain occurs in the resistance element 300A, the resistance element 300B, the resistance element 300C, and the resistance element 300D. As a result, the output distortion output from the third distortion sensor 200C becomes "0".

Further, focusing on the fourth strain sensor 200D, tensile strain is generated in the resistance element 300A and the resistance element 300C, while compression strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the fourth distortion sensor 200D _{becomes "-ε Fy} ".

From the above, the four strain sensors 200 (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) shown in FIG. 11 are used in the y-axis direction shown in FIG. It can be seen that the distortion caused by the applied force is realized.

FIG. 12 is a schematic view showing the strain applied to the resistance element 300 formed in each of the four strain sensors 200 when the z-axis torque (“Tz”) around the z-axis is applied to the torque sensor 100. .. In FIG. 12, the tensile strain is “+”, the compression strain is “−”, and the output strain from the strain sensor 200 based on the strain applied to the four resistance elements 300 formed in each strain sensor 200 is “((. Distortion of the resistance element 300A + distortion of the resistance element 300C)-(distortion of the resistance element 300B + distortion of the resistance element 300D) ”.

Focusing on the first strain sensor 200A in FIG. 12, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A is set to "+ ε _Tz ".

Subsequently, focusing on the second strain sensor 200B, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A _{becomes "+ ε Tz} ".

Next, focusing on the third strain sensor 200C, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A _{becomes "+ ε Tz} ".

Further, focusing on the fourth strain sensor 200D, compression strain is generated in the resistance element 300A and the resistance element 300C, while tensile strain is generated in the resistance element 300B and the resistance element 300D. As a result, the output distortion output from the first distortion sensor 200A _{becomes "+ ε Tz} ".

From the above, the four strain sensors 200 (first strain sensor 200A, second strain sensor 200B, third strain sensor 200C, and fourth strain sensor 200D) shown in FIG. 12 are used to rotate the z-axis as shown in FIG. It can be seen that the distortion caused by the z-axis torque is realized.

Based on FIGS. 10 to 12, in the four strain sensors 200 in which the four resistance elements 300 shown in FIG. 8 are formed, these four strain sensors 200 are arranged as shown in FIG. , It can be seen that the basic idea (see FIG. 7) in this embodiment is embodied.

<Structure of calculation unit>
The torque sensor 100 has a calculation unit that calculates the torque around the normal axis that passes through the inner ring center CP and is perpendicular to the inner ring portion 110 based on the outputs from the four strain sensors 200 described above. That is, the torque sensor 100 is driven around the drive axis (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. ) Z-axis torque is calculated.

The configuration of the calculation unit that calculates the z-axis torque around the z-axis will be described below.

FIG. 13 is a functional block diagram of the calculation unit 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, and a voltage value addition unit 505. It has a drive shaft torque calculation unit 506, an output unit 507, and a data storage unit 508.

The first voltage value input unit 501 is configured to input the output voltage from the first distortion sensor 200A. Specifically, the first strain sensor 200A is configured to be distorted due to deformation of the torque sensor 100 based on torque or force, and the resistance value of the four resistance elements 300 provided inside this distortion. It is configured to be regarded as a change, and the resistance value change is converted into a voltage value and output. The first voltage value input unit 501 is configured to be able to input the output voltage from the first distortion sensor 200A. Then, the first voltage value, which is the output voltage from the first distortion 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 is the difference between the resistance value of the resistance element 300A in the first distortion sensor 200A and the resistance value of the resistance element 300B and the first distortion sensor 200A. It corresponds to the first total value obtained by adding the difference between the resistance value of the resistance element 300C and the resistance value of the resistance element 300D.

The second voltage value input unit 502 is configured to input the output voltage from the second distortion sensor 200B. Specifically, the second strain sensor 200B is also configured to be distorted due to deformation of the torque sensor 100 based on torque or force, and the resistance value of the four resistance elements 300 provided inside this distortion. It is configured to be regarded as a change, and the resistance value change is converted into a voltage value and output. The second voltage value input unit 502 is configured to be able to input the output voltage from the second distortion sensor 200B. Then, the second voltage value, which is the output voltage from the second distortion sensor 200B, is stored in the data storage unit 508.

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

The third voltage value input unit 503 is configured to input the output voltage from the third distortion sensor 200C. Specifically, the third strain sensor 200C is configured to be distorted due to deformation of the torque sensor 100 based on torque or force, and the resistance value of the four resistance elements 300 provided inside this distortion. It is configured to be regarded as a change, and the resistance value change is converted into a voltage value and output. The third voltage value input unit 503 is configured to be able to input the output voltage from the third distortion sensor 200C. Then, the third voltage value, which is the output voltage from the third distortion 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 is the difference between the resistance value of the resistance element 300A in the third distortion sensor 200C and the resistance value of the resistance element 300B and the third distortion sensor 200C. It corresponds to the third total value obtained by adding the difference between the resistance value of the resistance element 300C and the resistance value of the resistance element 300D.

The fourth voltage value input unit 504 is configured to input the output voltage from the fourth distortion sensor 200D. Specifically, the fourth strain sensor 200D is configured to be distorted due to deformation of the torque sensor 100 based on torque or force, and the resistance value of the four resistance elements 300 provided inside this distortion. It is configured to be regarded as a change, and the resistance value change is converted into a voltage value and output. The fourth voltage value input unit 504 is configured to be able to input the output voltage from the fourth distortion sensor 200D. Then, the fourth voltage value, which is the output voltage from the fourth distortion 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 is the difference between the resistance value of the resistance element 300A in the fourth distortion sensor 200D and the resistance value of the resistance element 300B and the fourth distortion sensor 200D. It corresponds to the fourth total value obtained by adding the difference between the resistance value of the resistance element 300C and the resistance value of the resistance element 300D.

Next, the voltage value adding unit 505 uses 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, and the third voltage value input unit. It is configured to calculate the total voltage value by adding the third voltage value input to the 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, for example, calculating the total shown in FIG. 7. That is, the total voltage value calculated by the voltage value addition unit 505 cancels out the distortion caused by the torque around the other shaft and the force applied in each shaft direction, and becomes the distortion caused only by the drive shaft torque around the drive shaft. It becomes the corresponding voltage value.

Subsequently, the drive shaft torque calculation unit 506 is configured to calculate the drive shaft torque around the drive shaft based on the total voltage value calculated by the voltage value addition unit 505. At this time, in the present embodiment, the total voltage value calculated by the voltage value adding unit 505 cancels out the distortion caused by the torque around the other shaft and the force applied in each axial direction, and the drive shaft around the drive shaft. Since the voltage value corresponds to the distortion caused only by the torque, the drive shaft torque calculated based on the total voltage value is highly accurate. For example, there is a correlation between strain and an electrical resistance value, and there is also a correlation between a voltage value based on this electrical resistance value and strain. Since there is also a correlation between strain and torque, the voltage value and torque are also correlated. An equation or table showing the correlation between the voltage value and the torque is stored in the data storage unit 508. As a result, 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 formula or table stored in the data storage unit 508.

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

<Operation of calculation unit>
The calculation unit 500 in the present embodiment is configured as described above, and the operation of the calculation unit 500 will be described below with reference to the drawings.

FIG. 14 is a flowchart illustrating the operation of the calculation unit.

In FIG. 14, the first voltage value input unit 501 inputs the first voltage value which is the output voltage from the first distortion sensor 200A, and the second voltage value input unit 502 outputs from the second distortion sensor 200B. Enter the second voltage value, which is the voltage. Similarly, the third voltage value input unit 503 inputs the third voltage value which is the output voltage from the third distortion sensor 200C, and the fourth voltage value input unit 504 inputs the output voltage from the fourth distortion sensor 200D. The fourth voltage value is input (S101). Next, the voltage value adding unit 505 adds the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value to calculate the total voltage value. After that, the drive shaft torque calculation unit 506 calculates the drive shaft torque based on the total voltage value calculated by the voltage value addition unit 505. Then, the value of the drive shaft torque calculated by the drive shaft torque calculation unit 506 is output from the output unit 507.

As described above, the operation of the calculation unit 500 is realized.

<Verification of effect>
Next, the verification result of the effect in the present embodiment will be described.

FIG. 15 is a graph showing the outputs from each of the four strain sensors when the y-axis torque (“Ty”) around the y-axis is applied.

In FIG. 15, the horizontal axis represents the magnitude of the y-axis torque (“Ty (Nm)”), while the vertical axis represents the output “strain amount (με)” of each strain sensor.

Focusing on the output of the first strain sensor in FIG. 15, it can be seen 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 "100 Nm", the output from the first strain sensor is "15 με", and when the y-axis torque is "200 Nm", the output from the first strain sensor is "35 με". ". When the y-axis torque is "400 Nm", the output from the first strain sensor is "60 με", and when the y-axis torque is "600 Nm", the output from the first strain sensor is "90 με". ".

On the other hand, focusing on the output of the third strain sensor, it can be seen that the output (absolute value) from the third strain sensor increases as the y-axis torque increases. For example, when the y-axis torque is "100 Nm", the output from the first strain sensor is "-15 με", and when the y-axis torque is "200 Nm", the output from the first strain sensor is "-15 με". -35 με ”. When the y-axis torque is "400 Nm", the output from the first strain sensor is "-60 με", and when the y-axis torque is "600 Nm", the output from the first strain sensor is "-60 με". -90 με ”.

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

Focusing on the output from the second strain sensor and the output from the fourth strain sensor, it can be seen that 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 the four strain sensors when the y-axis torque (“Ty”) around the y-axis is applied.

In FIG. 16, the horizontal axis shows the magnitude of the y-axis torque (“Ty (Nm)”), while the vertical axis shows the total output “strain amount (με)” from the four strain sensors. ing.

As shown in FIG. 16, it can be seen that the total output from the four strain sensors is almost "0" regardless of the magnitude of the y-axis torque. That is, from FIG. 16, for example, even if the y-axis torque around the y-axis, which is an example of the torque around the other shaft other than the drive shaft torque (z-axis torque) around the drive shaft, is added, the first one based on the y-axis torque. It can be seen that when the output from the strain sensor, the output from the second strain sensor, the output from the third strain sensor, and the output from the fourth strain sensor are added, the total output becomes almost "0". That is, it can be seen from the results shown in FIGS. 15 and 16 that the total output from the four strain sensors is not affected by the strain caused by the y-axis torque.

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

In FIG. 17, the horizontal axis represents the magnitude of the y-axis torque (“Ty (Nm)”), while the vertical axis represents the average value of the output “strain amount (με)” from the four strain sensors. Is shown. Further, each point indicates the magnitude of the z-axis torque (“Tz”). For example, "*" means that the z-axis torque is clockwise and is 600 (Nm). The "dotted line" has a z-axis torque ("Tz") counterclockwise and is -600 (Nm).

For example, referring to FIG. 7, the output from the first strain sensor 200A is the strain amount obtained by adding the strain amount _{“ε Ty} _{” due to the y-axis torque and the strain amount “ε Tz} ” due to the z-axis torque. It becomes the corresponding output. On the other hand, the output from the second strain sensor 200B is an output corresponding to the sum of the strain amount “ε _Ty _{” caused by the y-axis torque and the strain amount “ε Tz} ” caused by the z-axis torque. However, in the second strain sensor 200B, "ε _Ty " becomes zero. Further, the output from the third strain sensor 200C is an output corresponding to the amount of strain obtained by adding the amount of strain _{"-ε Ty} _{" caused by the y-axis torque and the amount of strain "ε Tz} " caused by the z-axis torque. .. Further, the output from the fourth strain sensor 200D is an output corresponding to the strain amount obtained by adding the strain amount _{“−ε Ty} _{” due to the y-axis torque and the strain amount “ε Tz} ” due to the z-axis torque. .. However, in the second distortion sensor 200D, "-ε _Ty " becomes zero. Therefore, the outputs of the four strain sensors 200 are different, but the average value of the outputs of the four strain sensors 200 is offset except for the strain amount due to the z-axis torque. ε _Tz ”. This is shown in FIG. That is, since the average value of the outputs of the four strain sensors 200 is the strain amount "ε _Tz ", it depends only on the magnitude of the z-axis torque and becomes a constant value regardless of the magnitude of the y-axis torque. .. From FIG. 17, it can be seen that when the magnitude of the z-axis torque is increased, the average value of the outputs of the four strain sensors 200 becomes large, and does not change even if the y-axis torque increases. This can be understood from the fact that the average value of the outputs of the four strain sensors 200 is the strain amount “ε _Tz”.

<Application to robot joint structure>
The torque sensor 100 in this embodiment can be applied to, for example, a robot joint structure of a robot arm. For example, FIG. 18 is a diagram schematically showing a robot joint structure 20 to which the torque sensor 100 according to the present embodiment is applied. In FIG. 18, the torque sensor 100 according to the present embodiment is connected to a drive unit 24 including a motor 22 and a speed reducer 23, and is also connected to a link 21B forming a part of a robot arm. According to the robot joint structure 20 configured in this way, the drive shaft torque around the drive shaft can be detected with high accuracy by the torque sensor 100.

Furthermore, according to the robot joint structure 20 to which the torque sensor 100 is applied, the following advantages can also be obtained. For example, in the related technique shown in FIG. 3, a bearing member 26 is provided between the drive unit 24 and the torque sensor 30. This is because the torque sensor 30 is fixedly supported by the bearing member 26 so that it is less likely to be deformed except around the drive shaft. That is, in the torque sensor 30 in the related technology, when the torque sensor 30 is deformed due to the torque around the other shafts other than the drive shaft and the force applied in each axial direction, the strain caused by this deformation is also detected by the torque sensor 30. As a result, the torque sensor 30 is easily affected by the torque around the other shafts other than the drive shaft and the noise caused by the force applied in each shaft direction. For this reason, in the related technology, 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. As a result, according to the related technology, the torque sensor 30 is less likely to be deformed due to the torque around the other shafts other than the drive shaft and the force applied in each shaft direction. Therefore, the torque sensor 30 detects the torque around the drive shaft. When doing so, it is possible to reduce noise caused by torque around other shafts other than the drive shaft and forces applied in each shaft direction. That is, according to the related technology, the torque sensor 30 is fixedly supported by the bearing member 26 to make the torque sensor 30 less likely to be deformed other than around the drive shaft, so that the torque around the drive shaft can be detected with high accuracy. ing.

In this regard, the torque sensor 100 according to the present embodiment can be used as a torque sensor 100 even if the torque sensor 100 is deformed due to torque around other shafts other than the drive shaft or a force applied in each axial direction. The four strain sensors 200 provided cancel out the distortion caused by the torque around the other shafts other than the drive shaft and the force applied in each axial direction. That is, according to the torque sensor 100 in the present embodiment, even if the torque sensor 100 is deformed due to the torque around the other shaft other than the drive shaft and the force applied in each shaft direction, the other shaft other than the drive shaft Noise caused by the surrounding torque and the force applied in each axial direction is less likely to occur. Therefore, the torque sensor 100 in the present embodiment has torque around the drive shaft without suppressing deformation of the torque sensor 100 due to torque around other shafts other than around the drive shaft and forces applied in each axial direction. Can be detected with high accuracy. This means that according to the torque sensor 100 in the present embodiment, it is not necessary to fix and support the bearing member 26 as in the torque sensor 30 of the related technique shown in FIG. In other words, the torque sensor 100 in the present embodiment cancels out the distortion caused by the torque around the other shafts other than the drive shaft and the force applied in each shaft direction without being fixedly supported by the bearing member 26. , The torque around the drive shaft can be detected with high accuracy. Therefore, according to the present embodiment, since the bearing member 26 is not required, it is possible to suppress an increase in the mass of the robot joint structure 20 itself. Therefore, according to the present embodiment, the motion agility of the robot joint structure can be improved by adopting the torque sensor 100. Furthermore, since it is not necessary to add a new component called the bearing member 26, it is possible to reduce the number of parts of the robot joint structure 20, which has the advantage of reducing the cost of parts.

When the torque sensor 100 in the present embodiment is adopted, not only the robot joint structure 20 shown in FIG. 18 but also the robot joint structure 20B shown in FIG. 19 and the robot joint structure 20C shown in FIG. 20 can be realized, for example. can. In this case as well, the remarkable effect that the detection accuracy of the drive shaft torque around the drive shaft can be improved without sacrificing the motion agility of the robot joint structure and the cost of parts can be obtained.

For these effects, it is necessary that the torque sensor 100 has high rigidity and is not excessively deformed by the moments of the x-axis, y-axis, and z-axis. In order to increase the rigidity of the torque sensor 100, the thickness and width of the spokes 130 shown in FIG. 5 must be increased. Then, 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 z-axis torque at the limit that can be detected becomes large. However, the strain sensor 200 shown in FIG. 8 has a significantly higher sensitivity to a strain gauge that measures based on a general metal resistance change. It is known that when the strain sensor 200 is made of silicon, the gauge ratio indicating the sensitivity for detecting strain is about 25 times that of a general metallic strain gauge. Therefore, by using the strain sensor 200, the rigidity of the torque sensor 100 can be increased, and as a result, the bearing member 26 can be omitted.

<Further study>
The torque sensor 100 in the present embodiment has high accuracy in torque around the drive shaft without suppressing deformation of the torque sensor 100 due to torque around other shafts other than the drive shaft and forces applied in each axial direction. It is useful in that it can be detected in, and is effective, for example, by applying it to the robot joint structure 20. However, as a result of the study by the present inventor, it has been found that it is important to devise a connection structure between the torque sensor 100 and the link 21B when applying the torque sensor 100 to the robot joint structure 20. Explain the findings.

<New findings found by the present inventor>
FIG. 21 is a diagram schematically showing a robot joint structure 20 to which the torque sensor 100 according to the present embodiment is applied. In FIG. 21, the region RA shows the connection portion between the torque sensor 100 and the link 21B. FIG. 22 is an enlarged view of the connection portion between the torque sensor 100 and the link 21B shown in the region RA. As shown in FIG. 22, the torque sensor 100 is formed with a through portion TH, and the link 21B is formed with an opening OP having a thread. The penetrating portion TH formed in the torque sensor 100 and the opening OP formed in the link 21B communicate with each other, and a bolt 600A is inserted into the penetrating portion TH and the opening OP. Then, by using the bolt 600A and the nut 600B, the torque sensor 100 and the link 21B are connected. At this time, an axial force "P" is applied to the bolt 600A.

Next, FIG. 23 is a schematic view seen from the direction of the arrow in FIG. 22. As shown in FIG. 23, the torque sensor 100 and the link 21B are connected by a bolt 600A and a nut 600B. Then, FIG. 24 shows a schematic view seen from the AA plane of FIG. 23, and FIG. 25 shows a schematic view seen from the BB plane of FIG. 23. Here, the AA surface is referred to as a "bolt / outer ring portion surface", and the BB surface is referred to as an "outer ring portion / link surface".

In FIG. 24, the bolt 600A is fixed to the outer ring portion 120 of the torque sensor 100, and the contact surface between the bolt 600A and the outer ring portion 120 is indicated by “S1”. At this time, the surface pressure “σ1” between the bolt 600A and the outer ring portion 120 is given by “σ1 = P / S1”. Here, "P" indicates the axial force applied to the bolt 600A, and "S1" indicates the contact area between the bolt 600A and the outer ring portion 120. As shown in FIG. 24, since the contact area “S1” between the bolt 600A and the outer ring portion 120 is small, the surface pressure “σ1” between the bolt 600A and the outer ring portion 120 becomes large.

In FIG. 25, the outer ring portion 120 of the torque sensor 100 and the link 21B are fixed by bolts 600A, and the contact surface between the outer ring portion 120 and the link 21B is indicated by “S2”. This "S2" corresponds to the entire surface of the outer ring portion 120. At this time, the surface pressure “σ2” between the outer ring portion 120 and the link 21B is given by “σ2 = P / S2”. Here, "P" indicates the axial force applied to the bolt 600A, and "S2" indicates the contact area between the outer ring portion 120 and the link 21B. As shown in FIG. 25, since the contact area “S2” between the outer ring portion 120 and the link 21B is large, the surface pressure “σ2” between the outer ring portion 120 and the link 21B becomes small.

Subsequently, FIG. 26 is a graph qualitatively showing the relationship between the surface pressure and the coefficient of static friction. In FIG. 26, the horizontal axis represents the surface pressure “σ”, while 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, when the surface pressure “σ” becomes large, the static friction coefficient “μ” becomes It can be seen that it tends to be smaller. That is, it can be seen that the larger the surface pressure “σ”, the more slippery it becomes.

Here, since the contact area "S1" between the bolt 600A and the outer ring portion 120 is much smaller than the contact surface "S2" between the outer ring portion 120 and the link 21B, the contact area between the bolt 600A and the outer ring portion 120 The surface pressure "σ1" is much larger than the surface pressure "σ2" between the outer ring portion 120 and the link 21B. This means that the "bolt / outer ring surface", which is the interface between the bolt 600A and the outer ring 120, is more slippery than the "outer ring / link surface", which is the interface between the outer ring 120 and the link 21B. doing.

FIG. 27 is a schematic view showing how slippage occurs on the “bolt / outer ring portion surface”. FIG. 27A shows, for example, how the bolt 600A is deformed by applying torque or force to the torque sensor 100. In FIG. 27A, the deformation of the bolt 600A is largely drawn for the sake of clarity. Here, if the deformation of the bolt 600A becomes too large and exceeds the limit of the static friction force, slippage occurs on the "bolt / outer ring portion surface" as shown in FIG. 27 (b). Then, the present inventor has newly found that when the "bolt / outer ring portion surface" slips, the detection accuracy of the torque around the drive shaft by the torque sensor 100 becomes unstable.

In the following, a mechanism will be described in which the torque detection accuracy around the drive shaft of the torque sensor 100 becomes unstable when slippage occurs on the "bolt / outer ring surface".

28 (a) and 28 (b) are for explaining a mechanism in which the torque detection accuracy around the drive shaft of the torque sensor 100 becomes unstable when the “bolt / outer ring surface” slips. It is a figure. First, in FIG. 28A, a force line in which a torque is applied to the torque sensor 100 and the torque is transmitted from the inner ring portion 110 to the outer ring portion 120 as a shearing force is indicated by an arrow. 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 to the inside of the bolt 600A via the “bolt / outer ring portion surface” (first path). Further, in addition to the first path, the force line of the shearing force is transmitted to the link 21B via the "outer ring portion / link surface" (second path). As described above, the force line of the shearing force flows through both the first path and the second path, and there is a "bolt / outer ring portion surface" in which slip is likely to occur in the first path. Therefore, if slippage occurs on the "bolt / outer ring portion surface", the force line of the shearing force flowing through the spokes 130 is disturbed. Here, a strain sensor 200 is arranged on the spokes 130, and since the strain sensor 200 measures the flow of the shearing force on the spokes 130, the force line of the shearing force flowing through the spokes 130 is disturbed. Then, the output from the distortion sensor 200 arranged on the spoke 130 is also disturbed. As a result, the torque detection accuracy of the torque sensor 100 becomes unstable. This finding is a finding newly found by the present inventor.

Therefore, based on this finding, the present inventor has further devised a method for improving the stability of the torque detection accuracy of the torque sensor 100. In the following, this device will be described.

<Explanation of ingenuity>
FIG. 29 is a diagram for explaining a device for improving the stability of the torque detection accuracy of the torque sensor. In FIG. 29, the ingenuity is that a thread is formed in the penetrating portion TH provided in the outer ring portion 120 of the torque sensor 100, and the torque sensor 100 and the link 21B are fastened with a screw 700 instead of a bolt. be. That is, a screw hole is formed in the outer ring portion 120 of the torque sensor 100, and the outer ring portion 120 is a member (which can rotate integrally with the outer ring portion 120 by screwing a screw 700 into the screw hole). It is configured so that it can be fastened to the link 21B). As a result, the stability of the torque detection accuracy of the torque sensor 100 can be improved. The reason for this will be described below.

As shown in FIG. 29, when the torque sensor 100 and the link 21B are screwed together, the screw holes and the screws 700 provided in the outer ring portion 120 of the torque sensor 100 have frictional forces on the entire surface of the threads and screw valleys. Since it is fixed by, the torque sensor 100 and the link 21B can be mechanically regarded as an integrated product. Therefore, in FIG. 29, the force line of the shearing force is transmitted from the inner ring portion 110 through the spokes 130 to the outer ring portion 120 including the screw 700, and then flows to the link 21B via the “outer ring portion / link surface”. At this time, since the "outer ring portion / link surface" is in contact with the entire outer ring portion 120, the surface pressure "σ" becomes small, and thus the static friction coefficient "μ" becomes large. This means that, according to this device, slippage is less likely to occur between the outer ring portion 120 and the link 21B (first advantage). Further, in this device, there is no "bolt / outer ring surface" where slippage is likely to occur (second advantage). As described above, according to the ingenuity in the present embodiment, the flow of the force line of the shearing force passing through the spoke 130 is stabilized by the synergistic factor of the first advantage and the second advantage described above, and as a result, the torque sensor 100 The stability of torque detection accuracy can be improved.

<Modification example>
The basic idea is to devise the arrangement of multiple strain sensors provided in the torque sensor and the arrangement of multiple resistance elements formed in each of the multiple strain sensors to eliminate only the distortion caused by the torque around the drive shaft. On the other hand, the idea is to offset the distortion caused by the torque around the other shafts other than the drive shaft and the strain caused by the force applied in each axis direction. In this basic idea, in the embodiment, a configuration of a torque sensor 100 including four strain sensors 200 as shown in FIG. 5 is adopted, and a plurality of strain sensors 200 formed in the strain sensor 200 as shown in FIG. 8 are formed. This is realized by adopting the layout arrangement of the resistance element 300.

However, the basic idea is not only the configuration described in the embodiment, but also the configuration of the torque sensor 100A including the six strain sensors 200 as shown in FIG. 30 and the distortion as shown in FIG. This can also be realized by the configuration of this modification in which the layout arrangement of the plurality of resistance elements 300 formed on the sensor 200 is adopted.

In the following, first, the configuration of the torque sensor 100A will be described in this modified example.

FIG. 30 is a plan view showing the configuration of the torque sensor 100A in this modified example. In FIG. 30, the torque sensor 100A connects an inner ring portion 110 composed of a circular ring, an outer ring portion 120 composed of a circular ring having a diameter larger than that of the inner ring portion 110, and the inner ring portion 110 and the outer ring portion 120. It is provided with a plurality of spokes (connection portions) 130.

In this modification, the plurality of spokes 130 are composed of six spokes 130, spokes 130A, spokes 130B, spokes 130C, spokes 130D, spokes 130E, and spokes 130F.

Specifically, the

spokes

130A and 130D are arranged on the first virtual line VL1 and on opposite sides of the inner ring center CP. The

spokes

130B and 130E are arranged on the virtual line VL2A, respectively, and are arranged on opposite sides to the inner ring center CP. The

spokes

130C and 130F are arranged on the virtual line VL2B, respectively, and are arranged on opposite sides 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, and form an intersection angle of about 60 degrees. That is, in this modification, the first virtual line VL1, the virtual line VL2A, and the virtual line VL2B are not orthogonal to each other. Then, in FIG. 30, assuming that the virtual line orthogonal to the first virtual line VL1 is the second virtual line VL2, the second virtual line VL2 is a bisector of the virtual line VL2A and the virtual line VL2B. ..

Next, as shown in FIG. 30, strain sensors 200 are mounted on each of the six spokes 130. Specifically, the first strain sensor 200A is mounted on the spokes 130A, and the second strain sensor 200B is mounted on the spokes 130B. A third strain sensor 200C is mounted on the spokes 130C, and a fourth strain sensor 200D is mounted on the spokes 130D. Further, a fifth distortion sensor 200E is mounted on the spokes 130E, and a sixth distortion sensor 200F is mounted on the spokes 130F.

As shown in FIG. 8, a plurality of resistance elements 300 are formed in the strain sensor 200 mounted on each of the six spokes 130. In this respect, the present modification is the same as that of 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. Similarly, the second strain sensor 200B and the fifth strain sensor 200E are point-symmetric with respect to the inner ring center CP. Further, the third strain sensor 200C and the sixth strain sensor 200F are point-symmetrical with respect to the inner ring center CP.

In this way, the torque sensor 100A is configured.

FIG. 31 is a table for explaining an example of applying the basic idea to a modified example.

In FIG. 31, in the first strain sensor 200A, by adopting the configuration shown in FIG. 30, the strain caused by the x-axis torque around the x-axis is “zero”, and the strain caused by the y-axis torque around the y-axis is set to “zero”. "Ε _Ty ", strain due to z-axis torque around the z-axis is "ε _Tz ", strain due to force in the x-axis direction is "ε _Fx ", strain due to force in the y-axis direction is "zero" , The distortion caused by the force in the z-axis direction becomes "zero".

In the second strain sensor 200B, by employing the configuration shown in FIG. 30, the distortion distortion resulting from x-axis torque about the x-axis is due to the "Ipushiron'_Tx", y-axis torque around the y-axis is "ε '' _Ty ”, the strain caused by the z-axis torque around the z-axis is“ ε _Tz ”, the strain caused by the force in the x-axis direction is“ ε ´ _Fx ”, and the strain caused by the force in the y-axis direction is“ ε Tz ”. '' _Fy ”, the distortion caused by the force in the z-axis direction is“ zero ”.

In the third strain sensor 200C, by adopting the configuration shown in FIG. 30, the distortion caused by the x-axis torque around the x-axis is the strain caused by the "-Ipushiron'_Tx", y-axis torque about the y-axis is "-Ipushiron'' _Ty ", z-axis about the z-axis distortion resulting from torque" epsilon _Tz ", distortion resulting from force in x-axis direction"-Ipushiron' _Fx ", distortion resulting from forces in the y-axis direction Is "-ε" _Fy ", and the distortion caused by the force in the z-axis direction is" zero ".

In the fourth strain sensor 200D, by adopting the configuration shown in FIG. 30, the strain caused by the x-axis torque around the x-axis is "zero", and the strain caused by the y-axis torque around the y-axis is "-ε _Ty". , The strain caused by the z-axis torque around the z-axis is "ε _Tz ", the strain caused by the force in the x-axis direction is "-ε _Fx ", the strain caused by the force in the y-axis direction is "zero", z The distortion caused by the axial force is "zero".

In the fifth strain sensor 200E, by adopting the configuration shown in FIG. 30, the distortion caused by the x-axis torque around the x-axis is the strain caused by the "-Ipushiron'_Tx", y-axis torque about the y-axis is "-Ipushiron'' _Ty ", z-axis about the z-axis distortion resulting from torque" epsilon _Tz ", distortion resulting from force in x-axis direction"-Ipushiron' _Fx ", distortion resulting from forces in the y-axis direction Is "-ε" _Fy ", and the distortion caused by the force in the z-axis direction is" zero ".

In the sixth strain sensor 200F, by adopting the configuration shown in FIG. 30, the distortion distortion resulting from x-axis torque about the x-axis is due to the "Ipushiron'_Tx", y-axis torque around the y-axis is "ε '' _Ty ”, the strain caused by the z-axis torque around the z-axis is“ ε _Tz ”, the strain caused by the force in the x-axis direction is“ ε ´ _Fx ”, and the strain caused by the force in the y-axis direction is“ ε Tz ”. '' _Fy ”, the distortion caused by the force in the z-axis direction is“ zero ”.

Then, also in this modified example, the strains generated by the first strain sensor 200A, the second strain sensor 200B, the third strain sensor 200C, the fourth strain sensor 200D, the fifth strain sensor 200E, and the sixth strain sensor 200F are added. do. Then, for example, the total strain caused by the x-axis torque around the x-axis is "zero", the total strain caused by the y-axis torque around the y-axis is "zero", and the total strain caused by the z-axis torque around the z-axis is "zero". Is "6ε _Tz ", the total strain caused by the force in the x-axis direction is "zero", the total strain caused by the force in the y-axis direction is "zero", and the total strain caused by the force in the z-axis direction is "zero". It becomes.

That is, as shown in FIG. 31, the total strain other than the total strain caused by the z-axis torque around the z-axis is "zero". This means that even in this modification, only the strain caused by the torque around the drive shaft is extracted, while the strain caused by the torque around the other shafts other than the drive shaft and the strain caused by the force applied in each axial direction are offset. It means that you can do it. Therefore, even in this modified example, not only the torque around the drive shaft but also the torque around other shafts other than the drive shaft and the distortion caused by the torque around the drive shaft are applied even when a force in each shaft direction is applied. As a result of being able to extract and offset the other strains, it can be seen that the torque around the drive shaft can be calculated with high accuracy.

As described above, it can be seen that the basic idea can be realized not only by the configuration of the torque sensor 100 in the embodiment shown in FIG. 5, but also by the configuration of the torque sensor 100A in the present modification shown in FIG.

In particular, the advantage of adopting the torque sensor 100 in the embodiment is that the cost can be reduced in that the basic idea can be realized with four strain sensors 200, which is less than the six strain sensors 200 as in this modification. Can be mentioned.

On the other hand, the advantage of adopting the torque sensor 100A in this modification is that the total strain due to the torque around the drive shaft (around the z-axis) is "4ε _Tz " in the embodiment (see FIG. 7). In this modification, the total strain caused by the torque around the drive shaft (around the z-axis) _{can be set to "6 ε Tz} ", and as a result, the magnitude of the detection signal can be increased.

Although the invention made by the present inventor has been specifically described above based on the embodiment thereof, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof. Needless to say.

For example, as shown in FIG. 8, the strain sensor 200 in the present embodiment is composed of four resistance elements 300 (resistance element 300A, resistance element 300B, resistance element 300C, and resistance element 300D) arranged orthogonally to each other. However, the technical idea in the present embodiment is not limited to this, and for example, in FIG. 8, two resistance elements 300 (resistance element 300A and resistance element 300D) arranged at right angles to each other. It can be widely applied to the case of configuring the strain sensor 200.

1 Robot system 10 Robot arm 11 Robot control unit 20 Robot joint structure 20A Robot joint structure 20B Robot joint structure 20C Robot joint structure 21A Link 21B Link 22 Motor 23 Reducer 24 Drive unit 25 Lubricating member 26 Bearing member 30 Torque sensor 100 Torque sensor 110 Inner ring 120 Outer ring 130 Spoke 130A Spoke 130B Spoke 130C Spoke 130D Spoke 200 Strain sensor 200A 1st strain sensor 200B 2nd strain sensor 200C 3rd strain sensor 200D 4th strain sensor 300 Resistance element

300A Resistance element

300B Resistance element 300C Element

300D Resistance element 500 Calculation unit 501 1st voltage value input unit 502 2nd voltage value input unit 503 3rd voltage value input unit 504 4th voltage value input unit 505 Voltage value addition unit 506 Drive shaft torque calculation unit 507 Output unit 508 Data storage 600A Bolt 600B Nut 700 Screw CP Inner ring center OP Opening TH Penetration

Claims

Inner ring part and
With the outer ring
A plurality of connecting portions connecting the inner ring portion and the outer ring portion, and
Multiple distortion sensors that capture distortion as a change in resistance value,
With
The plurality of connections are
The first connection portion and the third connection portion arranged on the first virtual line passing through the inner ring center of the inner ring portion and arranged on opposite sides to the inner ring center, respectively.
A second virtual line passing through the center of the inner ring of the inner ring portion, which is arranged on each of the second virtual lines orthogonal to the first virtual line and arranged on opposite sides to the center of the inner ring. 2 connection part and 4th connection part,
Have,
The plurality of strain sensors
The first distortion sensor arranged on the first connection portion and
The second distortion sensor arranged on the second connection portion and
With the third distortion sensor arranged on the third connection part,
The fourth distortion sensor arranged on the fourth connection portion and
Have,
Each of the plurality of strain sensors
A semiconductor substrate that overlaps the third virtual line in a plan view,
A plurality of resistance elements formed on the semiconductor substrate and
Have,
The plurality of resistance elements
With the first resistance element
With the second resistance element
Including
The first angle formed by the first resistance element and the second resistance element is a right angle.
The third virtual line extends in a direction that bisects the first angle.
The first strain sensor among the plurality of strain sensors is arranged on the first connection portion so that the third virtual line coincides with the first virtual line.
The second strain sensor among the plurality of strain sensors is arranged on the second connection portion so that the third virtual line coincides with the second virtual line.
In the third strain sensor among the plurality of strain sensors, the third virtual line coincides with the first virtual line, and the first resistance element of the third strain sensor is attached to the center of the inner ring. The point symmetry with the first resistance element of the first strain sensor, and the second resistance element of the third strain sensor points with respect to the center of the inner ring with the second resistance element of the first strain sensor. Arranged on the third connection so as to be symmetrical,
In the fourth strain sensor among the plurality of strain sensors, the third virtual line coincides with the second virtual line, and the first resistance element of the fourth strain sensor is attached to the center of the inner ring. The point symmetry with the first resistance element of the second strain sensor, and the second resistance element of the fourth strain sensor points with respect to the center of the inner ring with the second resistance element of the second strain sensor. A torque sensor arranged on the fourth connection portion so as to be symmetrical.
In the torque sensor according to claim 1,
The torque sensor is a torque sensor having a calculation unit that calculates torque around a normal axis that passes through the center of the inner ring and is perpendicular to the inner ring portion based on outputs from the plurality of strain sensors.
In the torque sensor according to claim 2.
The calculation unit
The first difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the first strain sensor, the resistance value of the first resistance element in the second strain sensor, and the second resistance element. The second difference of the resistance value of, the third difference between the resistance value of the first resistance element in the third strain sensor and the resistance value of the second resistance element, and the first resistance element in the fourth strain sensor. A torque sensor that calculates the torque around the normal axis perpendicular to the inner ring portion based on the total output obtained by adding the resistance value of the above and the fourth difference of the resistance value of the second resistance element.
In the torque sensor according to claim 1,
Each of the plurality of resistance elements is a torque sensor which is a diffusion resistance element formed by introducing conductive impurities into the semiconductor substrate.
In the torque sensor according to claim 1,
The plurality of resistance elements
With the third resistance element
With the 4th resistance element
Including
The second angle formed by the third resistance element and the fourth resistance element is a right angle.
The third virtual line is a torque sensor extending in a direction that bisects the second angle.
In the torque sensor according to claim 5.
The torque sensor has a calculation unit that calculates torque around the normal axis with respect to the main surface of the semiconductor substrate based on outputs from the plurality of strain sensors.
The calculation unit
The difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the first strain sensor, the resistance value of the third resistance element in the first strain sensor, and the resistance value of the fourth resistance element. The first total, which is the sum of the difference between
The difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the second strain sensor, the resistance value of the third resistance element in the second strain sensor, and the resistance value of the fourth resistance element. The second total, which is the sum of the difference between
The difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the third strain sensor, the resistance value of the third resistance element in the third strain sensor, and the resistance value of the fourth resistance element. The third total, which is the sum of the difference between
The difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the fourth strain sensor, the resistance value of the third resistance element in the fourth strain sensor, and the resistance value of the fourth resistance element. The fourth total, which is the sum of the difference between
A torque sensor that calculates the torque around the normal axis perpendicular to the inner ring portion based on the total output obtained by adding.
In the torque sensor according to claim 1,
A torque sensor in which a screw hole is formed in the outer ring portion.
In the torque sensor according to claim 7.
The torque sensor is configured such that the outer ring portion can be fastened to a member that can be integrally rotated with the outer ring portion by screwing a screw into the screw hole.
In the torque sensor according to claim 8.
The member is a torque sensor which is a link.
In the torque sensor according to claim 1,
The torque sensor is a torque sensor which is a component constituting a robot joint structure.
The torque sensor according to claim 1 and
A drive unit connected to the inner ring portion of the torque sensor and
It is a robot joint structure with
A robot joint structure in which a bearing member does not intervene between the drive portion and the outer ring portion.
Inner ring part and
With the outer ring
A plurality of connecting portions connecting the inner ring portion and the outer ring portion, and
Multiple distortion sensors that capture distortion as a change in resistance value,
With
The plurality of connections are
The first connection portion and the fourth connection portion arranged on the first virtual line passing through the inner ring center of the inner ring portion and arranged on opposite sides to the inner ring center, respectively.
A second A virtual line passing through the center of the inner ring of the inner ring portion, which is arranged on the second A virtual line intersecting the first virtual line at the center of the inner ring, and arranged on opposite sides to the center of the inner ring. With the 2nd and 5th connections made
A second B virtual line passing through the center of the inner ring of the inner ring portion, which is arranged on the second B virtual line intersecting the first virtual line at the center of the inner ring, and arranged on opposite sides to the center of the inner ring. With the 3rd and 6th connections made
Have,
The plurality of strain sensors
The first distortion sensor arranged on the first connection portion and
The second distortion sensor arranged on the second connection portion and
With the third distortion sensor arranged on the third connection part,
The fourth distortion sensor arranged on the fourth connection portion and
With the fifth distortion sensor arranged on the fifth connection part,
With the sixth distortion sensor arranged on the sixth connection part,
Have,
Each of the plurality of strain sensors
A semiconductor substrate that overlaps the third virtual line in a plan view,
A plurality of resistance elements formed on the semiconductor substrate and
Have,
The plurality of resistance elements
With the first resistance element
With the second resistance element
Including
The first angle formed by the first resistance element and the second resistance element is a right angle.
The third virtual line extends in a direction that bisects the first angle.
The first strain sensor among the plurality of strain sensors is arranged on the first connection portion so that the third virtual line coincides with the first virtual line.
The second strain sensor among the plurality of strain sensors is arranged on the second connection portion so that the third virtual line coincides with the second A virtual line.
The third strain sensor among the plurality of strain sensors is arranged on the second connection portion so that the third virtual line coincides with the second B virtual line.
In the fourth strain sensor among the plurality of strain sensors, the third virtual line coincides with the first virtual line, and the first resistance element of the fourth strain sensor is attached to the center of the inner ring. The point symmetry with the first resistance element of the first strain sensor, and the second resistance element of the fourth strain sensor points with respect to the center of the inner ring with the second resistance element of the first strain sensor. Arranged on the fourth connection so as to be symmetrical,
In the fifth strain sensor among the plurality of strain sensors, the third virtual line coincides with the second A virtual line, and the first resistance element of the fifth strain sensor is attached to the center of the inner ring. The point symmetry with the first resistance element of the second strain sensor, and the second resistance element of the fifth strain sensor points with respect to the center of the inner ring with the second resistance element of the second strain sensor. Arranged on the fifth connection so as to be symmetrical,
In the sixth strain sensor among the plurality of strain sensors, the third virtual line coincides with the second B virtual line, and the first resistance element of the sixth strain sensor is attached to the center of the inner ring. The point symmetry with the first resistance element of the third strain sensor, and the second resistance element of the sixth strain sensor points with respect to the center of the inner ring with the second resistance element of the third strain sensor. A torque sensor arranged on the sixth connection portion so as to be symmetrical.
In the torque sensor according to claim 12,
When the virtual line passing through the center of the inner ring and orthogonal to the first virtual line is defined as the second virtual line, the second virtual line is a combination of the second A virtual line and the second B virtual line. A torque sensor that is a bisector.
In the torque sensor according to claim 12,
The torque sensor is a torque sensor having a calculation unit that calculates torque around a normal axis that passes through the center of the inner ring and is perpendicular to the inner ring portion based on outputs from the plurality of strain sensors.
In the torque sensor according to claim 14,
The calculation unit
The first difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the first strain sensor, the resistance value of the first resistance element in the second strain sensor, and the second resistance element. The second difference of the resistance value of, the third difference between the resistance value of the first resistance element in the third strain sensor and the resistance value of the second resistance element, and the first resistance element in the fourth strain sensor. The fourth difference between the resistance value of the second resistance element and the resistance value of the second resistance element, the fifth difference between the resistance value of the first resistance element and the resistance value of the second resistance element in the fifth strain sensor, and the second. 6 The torque around the normal axis perpendicular to the inner ring portion is calculated based on the total output obtained by adding the resistance value of the first resistance element and the sixth difference of the resistance value of the second resistance element in the distortion sensor. , Torque sensor.