JP2019174327A - Torque sensor - Google Patents

Abstract

To provide a torque sensor with which it is possible to prevent the degradation of a strain gauge and improve the accuracy of detecting torque.SOLUTION: A plurality of third structures 13 connect a first structure 11 and a second structure 12. A first strain sensor 19 is connected between the first and the second structures, and a second strain sensor 20 is connected between the first and the second structures. At least one stopper 16 is fixed at one end to one of the first and the second structures and is engageable at other end with an engaging part 14f provided in the other of the first and the second structures.SELECTED DRAWING: Figure 16

Description

  Embodiments described herein relate generally to a torque sensor provided at a joint of a robot arm, for example.

  The torque sensor has a first structure to which torque is applied, a second structure to which torque is output, and a plurality of strain generating portions as beams that connect the first structure and the second structure. In addition, a plurality of strain gauges as sensor elements are arranged in these strain generating portions. These strain gauges constitute a bridge circuit (see, for example, Patent Documents 1, 2, and 3).

JP 2013-096735 A Japanese Patent Laying-Open No. 2015-049209 JP 2017-172983 A

  If the torque sensor can detect the torque up to the allowable strain of the strain gauge, the sensitivity can be increased, and a torque sensor with high resolution or high accuracy can be obtained.

  However, when a large force exceeding the rated torque is applied to the strain gauge, it is necessary to consider the safety factor against fatigue of the strain gauge. For this reason, the safety factor is designed to be a value larger than 1, for example, in the range of about 3 to 5. Safety and sensitivity are in a trade-off relationship, and when the safety factor is set large, the rated torque becomes small and the torque detection accuracy (sensitivity) decreases. Therefore, the accuracy of the torque sensor is reduced.

  Embodiments of the present invention are intended to provide a torque sensor that can improve the accuracy of torque detection by preventing deterioration of a strain gauge.

  The torque sensor according to the embodiment includes a first structure, a second structure, a plurality of third structures that connect the first structure and the second structure, the first structure, and the first structure. At least one strain sensor connected between two structures, one end is fixed to one of the first structure and the second structure, and the other end is the first structure and the second And at least one stopper that can be engaged with an engaging portion provided on the other side of the structure.

The top view which shows the torque sensor to which each embodiment is applied. The top view shown except for a part of FIG. The top view which concerns on 1st Embodiment and is shown except a part of FIG. FIG. 4 is a perspective view of FIG. 3. The top view which expands and shows the A section shown with a broken line in FIG. The top view shown in order to demonstrate operation | movement at the time of applying the force of a torque (Mz) direction to the torque sensor shown in FIG. The side view shown in order to demonstrate operation | movement at the time of applying the force of directions other than a torque (Fz, Mx) to the torque sensor shown in FIG. The perspective view which shows the structure shown in FIG. FIG. 8 is a cross-sectional view taken along the line VIIIA-VIIIA shown in FIG. 7 and is a view shown to explain a cross-sectional secondary moment in a direction other than torque (Fz, Mx). FIG. 8 is a cross-sectional view taken along line VIIIB-VIIIB shown in FIG. 7, and is a view shown for explaining a cross-sectional secondary moment in a direction other than torque (Fz, Mx). The figure shown in order to demonstrate the cross-section secondary moment of a general structure. The figure shown in order to demonstrate the cross-sectional secondary moment of the structure different from FIG. 8C. The figure shown in order to demonstrate the cross-sectional secondary moment of the torque (Mz) direction of FIG. 8A. The figure shown in order to demonstrate the cross-sectional secondary moment of the torque (Mz) direction of FIG. 8B. The figure shown in order to demonstrate the cross-sectional secondary moment of the structure different from FIG. 8C and FIG. 8D. The figure shown in order to demonstrate the positional relationship of a structure and a strain body. The top view which shows the torque sensor which concerns on the comparative example of 1st Embodiment. The top view shown in order to demonstrate operation | movement at the time of applying the force of a torque (Mz) direction to the torque sensor shown in FIG. The side view shown in order to demonstrate operation | movement at the time of applying the force of directions other than a torque (Fz, Mx) to the torque sensor shown in FIG. The figure which shows the distortion at the time of applying the same force to each axial direction of the torque sensor of 1st Embodiment, and the torque sensor of a comparative example. The top view which shows 2nd Embodiment and shows a 1st strain sensor and a 2nd strain sensor. The circuit diagram which shows an example of the bridge circuit of a 1st distortion sensor. The figure shown in order to demonstrate the mode of the strain body in the case where the force of a torque direction is applied to the torque sensor of 2nd Embodiment, and the case where the force of directions other than a torque direction is applied. The figure which shows schematically the torque sensor which concerns on the comparative example of 2nd Embodiment. The top view which shows 3rd Embodiment and expands and shows the part shown by B of FIG. The figure which shows operation | movement of a stopper and shows a part of FIG. FIG. 17A is a diagram schematically illustrating a part of FIG. 16, illustrating the operation of a stopper different from that of FIG. 17A. The figure shown in order to demonstrate the relationship between the torque applied to a torque sensor, and the operation | movement of a stopper. The figure which shows the relationship between the distortion of a strain gauge, and stress. The top view which shows the 1st modification of 3rd Embodiment, and expands and shows a part. The top view which shows the 2nd modification of 3rd Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.

  FIG. 1 shows an example of a torque sensor 10 to which the present embodiment is applied.

  In FIG. 1, the torque sensor 10 includes a first structure 11, a second structure 12, a plurality of third structures 13, a fourth structure 14, a fifth structure 15, stoppers 16 and 17, and a cover 18. is doing.

  The first structure 11 and the second structure 12 are formed in an annular shape, and the diameter of the second structure 12 is smaller than the diameter of the first structure 11. The second structure 12 is arranged concentrically with the first structure 11, and the first structure 11 and the second structure 12 are connected by a third structure 13 as a plurality of beam portions arranged radially. Has been. The second structure 12 has a hollow portion 12a, and, for example, a wiring (not shown) is passed through the hollow portion 12a.

  For example, the first structure 11 is connected to a measurement target, and the plurality of third structures 13 transmit torque from the first structure 11 to the second structure 12. Conversely, the second structure 12 may be connected to the measurement target, and torque may be transmitted from the second structure 12 to the first structure 11 via the plurality of third structures 13.

  The first structure 11, the second structure 12, and the plurality of third structures 13 are made of metal, for example, stainless steel. However, if sufficient mechanical strength can be obtained with respect to applied torque. It is also possible to use materials other than metals.

  FIG. 2 shows a state where the stoppers 16 and 17 of FIG. 1 are removed. A first strain sensor 19 and a second strain sensor 20 are provided between the first structure 11 and the second structure 12. That is, as will be described later, one end portions of the first strain sensor 19 and the second strain sensor 20 are joined to the first structure 11, and the other end portions of the first strain sensor 19 and the second strain sensor 20 are The two structures 12 are joined.

  Further, the first strain sensor 19 and the second strain sensor 20 are arranged at positions symmetrical with respect to the centers (the center of torque action) of the first structure 11 and the second structure 12. In other words, the first strain sensor 19 and the second strain sensor 20 are arranged on the diameters of the annular first structure body 11 and second structure body 12.

  The thicknesses of the first strain sensor 19 and the second strain sensor 20, that is, the thickness of the strain generating body to be described later are smaller than the thickness of the third structure 13. The mechanical strength of the torque sensor 10 is set by the thickness and width of the third structure 13. The strain body is provided with a plurality of strain gauges as sensor elements, and a bridge circuit is constituted by these sensor elements.

  The stoppers 16 and 17 protect the mechanical deformation of the first strain sensor 19 and the second strain sensor 20 and have a function as a cover for the first strain sensor 19 and the second strain sensor 20. Details of the stoppers 16 and 17 will be described later.

The first strain sensor 19 is connected to the flexible substrate 21, and the second strain sensor 20 is connected to the flexible substrate 22. The flexible boards 21 and 22 are connected to a printed board (not shown) covered by the cover 18. An operational amplifier that amplifies an output voltage of a bridge circuit, which will be described later, is disposed on the printed circuit board. Since the circuit configuration is not the essence of this embodiment, the description is omitted.
(First embodiment)
3 and 4 show the first embodiment. The first strain sensor 19 and the second strain sensor 20, the flexible substrates 21 and 22, the cover 18 and the like are removed from FIGS. Only the structure 11, the second structure 12, the plurality of third structures 13, the fourth structure 14, and the fifth structure 15 are shown.

  In the first embodiment, when a force in a direction other than the torque direction Mz, in particular, in the illustrated arrow Fz direction and Mx direction is applied to the torque sensor 10, the strain generating bodies of the first strain sensor 19 and the second strain sensor 20 are used. In this structure, strain is not concentrated on a plurality of strain gauges as sensor elements.

  Specifically, the fourth structure 14 and the fifth structure 15 are provided at positions symmetrical with respect to the centers of the first structure 11 and the second structure 12, and the fourth structure 14 includes the first structure 14 and the first structure 11. The structure 11 has a recess 14 f continuous from the second structure 12, and the fifth structure 15 has a recess 15 f continuous from the first structure 11 to the second structure 12. As will be described later, the first strain sensor 19 is disposed in the recess 14 f of the fourth structure 14, and the second strain sensor 20 is disposed in the recess 15 f of the fifth structure 15.

  In addition, although 1st Embodiment has shown about the case where two strain sensors, the 1st strain sensor 19 and the 2nd strain sensor, are provided, the number of strain sensors may be three or more. In this case, the number of structures may be increased according to the number of strain sensors.

  Since the fourth structure 14 and the fifth structure 15 have the same configuration, only the fourth structure 14 will be specifically described.

  As shown in FIG. 5, the fourth structure 14 includes a first connection part 14 a and a second connection part 14 b as joint parts for joining the first strain sensor 19, and a third connection part 14 c and a fourth part as beams. It has the connection part 14d and the opening part 14e enclosed by the 1st connection part 14a, the 2nd connection part 14b, the 3rd connection part 14c, and the 4th connection part 14d.

  In other words, the fourth structure 14 is a beam having an opening 14 e provided between the first structure 11 and the second structure 12.

  The first connection portion 14a extends from the first structure 11 to the second structure 12 side. The second connection portion 14b extends from the second structure 12 to the first structure 11 side.

  The 3rd connection part 14c and the 4th connection part 14d as a beam are provided between the 1st connection part 14a and the 2nd connection part 14b.

  The length L1 of the third connection portion 14c and the fourth connection portion 14d is shorter than the length L2 (also shown in FIG. 1) of the third structure 13 as a beam. A width W1 in the torque (Mz) direction of the third connection portion 14c and the fourth connection portion 14d is narrower than a width W2 in the torque direction of the first connection portion 14a and the second connection portion 14b, and the third connection portion 14c and the fourth connection portion 14c. The total width W1 of the connecting portion 14d is narrower than the width W3 (shown in FIG. 1) of the third structure 13 in the torque (Mz) direction. For this reason, the stiffness in the torque direction of the third connection portion 14c and the fourth connection portion 14d is lower than the stiffness in the torque direction of the first connection portion 14a, the second connection portion 14b, and the third structure 13.

  The thicknesses of the third connection portion 14c and the fourth connection portion 14d in the Fz direction are equal to the thicknesses of the first structure, the second structure, and the third structure in the Fz direction. Furthermore, the sum of the length L11 of the first connection portion 14a, the length L12 of the second connection portion 14b, and the length L1 of the third connection portion 14c and the fourth connection portion 14d is the length of the third structure 13. Is equal to For this reason, the rigidity in the Fz direction of the third connection part 14c and the fourth connection part 14d is slightly smaller than the rigidity of the third structure 13 in the Fz direction.

  That is, as shown in FIG. 6A described later, in the torque (Mz) direction, the first connection portion 14a and the first structure 11 constitute a high-rigidity portion HS1, and the second connection portion 14b and the second structure 12 Constitutes the high-rigidity portion HS2. Furthermore, in the torque (Mz) direction, the third connection portion 14c constitutes the low rigidity portion LS1, and the fourth connection portion 14d constitutes the low rigidity portion LS2.

  The total of the length L11 of the first connection portion 14a, the length L12 of the second connection portion 14b, and the length L1 of the third connection portion 14c and the fourth connection portion 14d is the length of the third structure 13. Is not limited to the case of being equal to each other.

  The 1st connection part 14a has the recessed part 14f mentioned above. The thickness of the recess 14 f is thinner than the thickness of the first to third structures 11, 12, and 13.

  One end of the first strain sensor 19 is connected to the recess 14f of the first connection portion 14a, and the other end is connected to the recess 14f of the second connection portion 14b. For this reason, the first strain sensor 19 straddles the opening 14e. As will be described later, the bottom of the recess 14f is positioned below the center of the thickness of the fourth structure 14, and the surface of the strain-generating body constituting the first strain sensor 19 is the first structure 11 and the second structure. 12, a plane including the center of gravity of the structure including the plurality of third structures 13, the fourth structure 14, and the fifth structure 15.

  6A and 6B are diagrams schematically showing FIG. 5, FIG. 6A shows a case where a force in the torque (Mz) direction is applied to the torque sensor 10, and FIG. 6B shows a case other than torque on the torque sensor 10. The case where the force of the direction of (Fz, Mx) is applied is shown.

  As shown in FIG. 6A, when a torque (Mz) direction force is applied to the torque sensor 10, the third connecting portion 14c and the fourth connecting portion 14d as the low-rigidity portions LS1 and LS2 are deformed, thereby The first strain sensor 19 (second strain sensor 20) is deformed and torque can be detected.

  On the other hand, as shown in FIG. 6B, when a force in a direction other than torque (Fz, Mx) is applied to the torque sensor 10, that is, the first structure 11 is in the direction indicated by the arrow with respect to the second structure 12. In the case of displacement, the rigidity of the first connection part 14a and the second connection part 14b is substantially equal to the rigidity of the third connection part 14c and the fourth connection part 14d. For this reason, the total length L2 of the length L11 of the first connecting portion 14a, the length L12 of the second connecting portion 14b, and the length L1 of the third connecting portion 14c and the fourth connecting portion 14d serves as an effective length. Since the length L2 is longer than the length L1 of the third connection portion 14c and the fourth connection portion 14d, the first strain sensor 19 (second strain) is applied when a force in a direction other than torque (Fz, Mx) is applied. The deformation of the sensor 20) occurs in the range of the length L2, and the strain can be prevented from concentrating on a plurality of strain gauges as sensor elements provided on the strain generating body of the first strain sensor 19. It is possible to prevent a decrease in detection accuracy of the sensor 19 (second strain sensor 20).

  FIG. 7 schematically shows the fourth structure 14. With reference to FIG. 7, the secondary moment of inertia (ease of deformation) of the fourth structure 14 and the conditions required for the fourth structure 14 (fifth structure 15) will be described.

  When the high rigidity portion HS2 of the fourth structure 14 is fixed and a force in the torque (Mz) direction is applied to the high rigidity portion HS1, the cross-sectional secondary moment is represented by Js, and the torque (Mz) is applied to the low rigidity portions LS1 and LS2. ) When the force in the direction is applied, the cross-sectional secondary moment is expressed by Jw, and when the force in the direction other than the torque (Fz) is applied to the highly rigid portion HS1, the cross-sectional secondary moment is expressed by Is, and the low-rigidity portion LS1 , Suppose that Iw represents the secondary moment of section when a force in a direction other than torque (Fz) is applied to LS2.

  The ratio of the cross-sectional secondary moment of the high-rigidity portion HS1 in the torque (Mz) direction to the cross-sectional secondary moments of the low-rigidity portions LS1 and LS2 is expressed by the following equation (1).

Js / Jw (1)
The ratio of the cross-sectional secondary moment of the high-rigidity portion HS1 in the direction other than torque (Fz) and the cross-sectional secondary moments of the low-rigidity portions LS1 and LS2 is expressed by the following equation (2).

  The ratio of the cross-sectional secondary moment of the high-rigidity portion HS1 in the direction other than torque (Fz) and the cross-sectional secondary moments of the low-rigidity portions LS1 and LS2 is expressed by the following equation (2).

Is / Iw (2)
If the values of the expressions (1) and (2) are both “1”, the cross-sectional secondary moments of the high-rigidity portion HS1 and the low-rigidity portions LS1, LS2 are equal, and the deformation does not concentrate on the low-rigidity portions LS1, LS2. As the values of the expressions (1) and (2) are both larger than “1”, the deformation is concentrated on the low rigidity portions LS1 and LS2.

  When a force in the torque (Mz) direction is applied, strain is concentrated on a plurality of strain gauges as sensor elements provided on the strain-generating body of the first strain sensor 19, and directions other than torque (Fz, Mx) In order to shift the strain concentration location from the strain gauge when the force of 1 is applied, one deformation concentration level (α) is close to 1 (α → 1) and the other deformation concentration level (β) is deformation concentration. It is desired that it is very large (β >> α) compared to the degree (α).

  The deformation concentration level of the low rigidity portions LS1 and LS2 when a force in the torque (Mz) direction is applied is greater than the deformation concentration level of the low rigidity portions LS1 and LS2 when a force in a direction other than the torque (Fz) is applied. Thus, it is easy to deform with respect to a force in the torque direction, and difficult to deform with respect to a force in a direction other than the torque. That is, the condition required for the fourth structure 14 (the fifth structure 15) is that the relationship represented by the following expression (3) is satisfied.

Js / Jw> Is / Iw (3)
Specifically, FIG. 8A is a cross-sectional view along the line VIIIA-VIIIA shown in FIG. 7 and shows an example of the dimension of the high-rigidity portion HS1. FIG. 8B is a cross-sectional view taken along line VIIIB-VIIIB shown in FIG. 7 and shows an example of dimensions of the low-rigidity portions LS1 and LS2.

  As shown in FIG. 8A, in the high-rigidity portion HS1 having a U-shaped cross section, the cross-sectional secondary moment Is regarding the axis N1-N1 when a force in a direction other than torque (Fz) is applied is as follows. It is. Here, the axis N1-N1 is an axis that passes through the center in the thickness direction of the high-rigidity portion HS1.

As shown in FIG. 8C, in general, when the dimensions of the structure having an L-shaped cross section and the structure having a U-shaped cross section satisfy the relationship of b = B−a and h = e ₁ −t, The cross-sectional secondary moment Is of the structure having an L-shaped cross section and the structure having a U-shaped cross section is the same, and is expressed by the following equation (4).

Is = (Be ₁ ³ -bh ³ + ae ₂ ³ ) / 3 (4)
Where h = e ₁ −t,
e ₁ = (aH ² + bt ² ) / (2 (aH + bt))
e ₂ = H−e ₁
For this reason, the cross-sectional secondary moment Is regarding the axis N1-N1 when a force in a direction other than the torque (Fz) is applied to the high-rigidity portion HS1 shown in FIG. 8A can be obtained by Expression (4).

Note that e ₁ is the position of the center of gravity in the structure as an elastic body including the first structure 11, the second structure 12, the plurality of third structures 13, the fourth structure 14, and the fifth structure 15. Is half the thickness of the structure. For this reason, e ₁ ≈6 with respect to the thickness H = 12. Therefore, e ₂ ≈6.

  Substituting the dimensions shown in FIG. 8A into equation (4) results in the following.

Is = (Be ₁ ³ -bh ³ + ae ₂ ³ ) / 3
= (14 × 6 ³ −8 × (6-5.8) ³ + 6 × 6 ³ ) / 3
= 1440
As shown in FIG. 8B, when a force in a direction other than torque (Fz) is applied to the low-rigidity portions LS1 and LS2 having a rectangular cross section, the cross-sectional secondary moment Is regarding the axis N2-N2 is It is as follows. Here, the axis N2-N2 is an axis passing through the center in the thickness direction of the low-rigidity portions LS1, LS2.

  As shown in FIG. 8D, generally, the cross-sectional secondary moment Iw ′ of the structure having a rectangular cross section is expressed by the following equation (5).

^{Iw '= bh 3/12 ...} (5)
Substituting the dimensions shown in FIG. 8B into equation (5) yields the following.

^{Iw '= 2 × 12 3/} 12
= 288
Since the low-rigidity portions LS1 and LS2 shown in FIG. 8B have two rectangular cross sections, the cross-sectional secondary moment Iw in the direction other than the torque (Fz) related to the axis N2-N2 is expressed by the following equation (6). .

Iw = 2 × Iw ′ (6)
Therefore, the cross-sectional secondary moment Iw in the direction other than the torque (Fz) related to the axis N2-N2 is as follows.

Iw = 576
On the other hand, as shown in FIG. 8E, when a force in the torque (Mz) direction is applied in the high-rigidity portion HS1 having a U-shaped cross section, the cross-sectional secondary moment Js regarding the axis N3-N3 is as follows. is there. Here, the axis N3-N3 is an axis that passes through the center in the width direction of the high-rigidity portion HS1.

  As shown in FIG. 8G, in general, when the dimensions of a structure having an I-shaped cross section and a structure having a U-shaped cross section satisfy the relationship of b = Ba, h = H-2t, The cross-sectional secondary moments of the structure having a letter-shaped cross section and the structure having a U-shaped cross section are the same, and are expressed by the following equation (7).

Js = (BH ³ −bh ³ ) / 12 (7)
Substituting the dimensions shown in FIG. 8A into Equation (7) yields the following.

Js = (12 × 14 ³ −6.2 × 8 ³ ) / 12
= 2479
8F, when a force in the torque (Mz) direction is applied to the low-rigidity portions LS1 and LS2 having a rectangular cross section, the cross-sectional secondary moment Jw ′ with respect to the axis N4-N4 is as shown in FIG. 8D. As described above, it is expressed by the following formula (8). Here, the axis N4-N4 is an axis passing through the center in the width direction of the low-rigidity portion LS1.

^{Jw '= bh 3/12 ...} (8)
Substituting the dimensions shown in FIG. 8B into equation (8) results in the following.

^{Jw '= 12 × 2 3/} 12
= 8
Since the low-rigidity portions LS1 and LS2 shown in FIG. 8F have two rectangular cross sections, the cross-sectional secondary moment Jw in the direction of the torque (Mz) with respect to the axis N4-N4 is expressed by the following equation (9).

Jw = 2 × Jw ′ (9)
Therefore, the cross-sectional secondary moment Iw in the direction other than the torque (Fz) related to the axis N2-N2 is as follows.

Jw = 16
The cross-sectional secondary moments Is = 1440, Iw = 576 in the direction other than the torque (Fz) determined as described above, Iw = 576, the cross-sectional secondary moments Js = 2479, Jw = 16 in the torque (Mz) direction are expressed by the above equation (3). When substituting into, it becomes as follows, and it can be seen that the condition of Expression (3) is satisfied.

Js / Jw> Is / Iw
2479/16> 1440/576
155> 2.5
Therefore, it can be seen that the fourth structure 14 and the fifth structure 15 are easily deformed with respect to the force in the torque (Mz) direction and are not easily deformed with respect to the force in the direction other than the torque (Fz).

FIG. 8H shows the positional relationship between the recess 14f and the first strain sensor 19 (strain body). As described above, the bottom of the recess 14f is located at the center H / 2 or less of the thickness of the fourth structure 14. Specifically, the surface of the strain-generating body constituting the first strain sensor 19 has the first structure 11, the second structure 12, the plurality of third structures 13, the fourth structure 14, and the fifth structure. Therefore, the bottom of the recess 14f is lower than the surface CG including the center of gravity of the fourth structure 14 by the thickness of the strain generating body. This position is a neutral plane, and no compressive force or tensile force is applied to the strain generating body. For this reason, it is possible to reduce the strain in the bending direction of the strain generating body, that is, in the direction other than the torque (Fz).
(Effects of the first embodiment)
According to the first embodiment, the fourth structure 14 provided with the first strain sensor 19 and the fifth structure 15 provided with the second strain sensor 20 are in the torque (Mz) direction and other than the torque (Fz, respectively). , Mx) acts as a high rigidity portion with respect to the force in the direction of Mx), and acts as a low rigidity portion with respect to the force in the torque (Mz) direction, and other than torque (Fz , Mx) is provided with a third connection portion 14c and a fourth connection portion 14d that act as a highly rigid portion with respect to the force in the direction of Mx). For this reason, it is possible to prevent the strain generated by the force in the direction other than the torque from being concentrated on the strain gauges 51, 52, 53, 54 of the first strain sensor 19 and the second strain sensor 20. Therefore, the absolute amount of strain applied to the strain gauges 51, 52, 53, 54 can be reduced, and the detection voltage for forces in directions other than the torque of the first strain sensor 19 and the second strain sensor 20 can be greatly reduced. Therefore, it is possible to prevent torque and other shaft interference other than torque to prevent an increase in size, and to provide a highly accurate torque sensor.

  Hereinafter, the effect of the first embodiment will be specifically described with reference to a comparative example.

  FIG. 9 shows a comparative example of the torque sensor 10. The torque sensor 30 shown in FIG. 9 is different from the torque sensor 10 shown in the first embodiment in the configuration of the connecting portion between the first strain sensor 19 and the second strain sensor 20, and other configurations are the same as those in the first embodiment. It is the same.

  In the torque sensor 30, one end of the first strain sensor 19 and the second strain sensor 20 is connected to the protrusion 11-1 provided on the first structure 11, and the other end is connected to the second structure 12. Each is connected to the provided protrusion 12-1. The protrusions 11-1 and 12-1 have the same thickness as the first structure 11 and the second structure 12, for example. The distance between the protrusion 11-1 and the protrusion 12-1 is equal to the length L1 of the third connection portion 14c and the fourth connection portion 14d shown in FIG.

  In the torque sensor 30 as a comparative example, only the third structure 13 acts as a high-rigidity part with respect to forces in the torque direction and directions other than torque, and the first strain sensor 19 and the second strain sensor 20 are the first Only the strain body is provided between the structure 11 and the second structure 12. For this reason, the first strain sensor 19 and the second strain are applied to the torque sensor 30 in either direction when a force in the torque (Mz) direction is applied or when a force in a direction other than the torque (Fz, Mx) is applied. The strain is concentrated on the strain gauge provided on the strain body of the strain sensor 20.

  FIG. 10A and FIG. 10B are diagrams schematically showing FIG. 9, FIG. 10A shows a case where a torque (Mz) direction force is applied to the torque sensor 30, and FIG. The case where the force of the direction of (Fz, Mx) is applied is shown.

  FIG. 11 shows distortions when the same force is applied in the respective axial directions of the torque sensor 10 according to the first embodiment and the torque sensor 30 according to the comparative example.

  As is clear from FIG. 11, in the case of the torque sensor 10 according to the first embodiment, the distortion with respect to the force in the torque (Mz) direction is larger than in the comparative example, and other than the torque (Fx, Fy, Fz, Mx, My ) Is less strained than the comparative example. In particular, it can be seen that the strain with respect to forces in the Fz and Mx directions can be significantly reduced compared to the comparative example. Therefore, according to the first embodiment, the first strain sensor 19 and the second strain sensor 20 can be reduced in distortion due to a force in a direction other than the torque, and the detection accuracy of the first strain sensor 19 and the second strain sensor 20 can be reduced. It is possible to prevent the decrease.

The surface of the strain generating body constituting the first strain sensor 19 includes the first structure 11, the second structure 12, the plurality of third structures 13, the fourth structure 14, and the fifth structure 15. It is located on the plane CG including the center of gravity of the structure. For this reason, it is possible to reduce the strain in the bending direction of the strain generating body, that is, in the direction other than the torque (Fz).
(Second Embodiment)
FIG. 12 shows a second embodiment.

  As described above, the first strain sensor 19 is provided in the fourth structure 14, and the second strain sensor 20 is provided in the fifth structure 15. Since the first strain sensor 19 and the second strain sensor 20 have the same configuration, only the configuration of the first strain sensor 19 will be described.

  The first strain sensor 19 includes a strain generating body 41 and a plurality of strain gauges 51, 52, 53, and 54 as sensor elements disposed on the surface of the strain generating body 41.

  The strain body 41 is made of a rectangular metal plate, for example, stainless steel (SUS). The thickness of the strain body 41 is thinner than the thickness of the third structure 13.

  The strain gauges 51, 52, 53, and 54 are constituted by, for example, Cr—N thin film resistors provided on the strain generating body 41. The material of the thin film resistor is not limited to Cr-N.

  The strain generating body 41 has one end connected to the first connecting portion 14a and the other end connected to the second connecting portion 14b. As a connection method between the strain body 41 and the first connection portion 14a and the second connection portion 14b, for example, a connection method using welding, screwing, or an adhesive can be used.

  As for the strain body 41, the part between the location welded to the 1st connection part 14a and the location welded to the 2nd connection part 14b functions as a substantial strain generation body, for example. For this reason, the effective length of the strain body 41 corresponds to the length between the location connected to the first connection portion 14a and the location connected to the second connection portion 14b.

  The plurality of strain gauges 51, 52, 53, 54 are arranged in the region AR <b> 1 on the second structure 12 side from the central portion CT of the effective length of the strain generating body 41 in the strain generating body 41. This region AR1 is a region where a large strain is generated in the strain generating body 41 within the range of the opening 14e. As will be described later, this area AR1 is an area where the sensitivity of the first strain sensor 19 with respect to forces in directions other than torque, for example, Fx and My directions, and the sensitivity of the first strain sensor 19 in the torque (Mz) direction are the same. It is.

  The strain gauges 51, 52, 53, 54 are arranged along the two diagonal lines DG 1, DG 2 of the strain body 41 in the longitudinal direction of the strain gauges 51, 52, 53, 54 in the area AR 1. That is, the strain gauges 51 and 52 are arranged along one diagonal line DG1 whose longitudinal direction is indicated by a broken line, and the strain gauges 53 and 54 are arranged along the other diagonal line DG2 whose longitudinal direction is indicated by a broken line. . The diagonal lines DG1 and DG2 correspond to rectangular regions located in the opening 14e of the strain generating body 41.

  The strain gauges 51, 52, 53, 54 of the first strain sensor 19 constitute one bridge circuit, and the strain gauges 51, 52, 53, 54 of the second strain sensor 20 also constitute one bridge circuit. For this reason, the torque sensor 10 includes two bridge circuits.

  FIG. 13 shows an example of the bridge circuit 50 of the first strain sensor 19. The second strain sensor 20 also includes a bridge circuit having the same configuration as the bridge circuit 50. Each of the output voltage of the bridge circuit 50 of the first strain sensor 19 and the output voltage of the bridge circuit 50 of the second strain sensor 19 is compensated for offset, temperature, and the like using software (not shown), for example. Thereafter, the output voltage of the bridge circuit 50 of the first strain sensor 19 and the output voltage of the bridge circuit 50 of the second strain sensor 19 are integrated and output as a detection voltage of the torque sensor 10. Compensation for offset, temperature, etc. is not limited to software, but can also be performed by hardware.

  In the bridge circuit 50, a series circuit of a strain gauge 52 and a strain gauge 53 and a series circuit of a strain gauge 54 and a strain gauge 51 are arranged between the power supply Vo and the ground GND. An output voltage Vout + is output from a connection node between the strain gauge 52 and the strain gauge 53, and an output voltage Vout− is output from a connection node between the strain gauge 54 and the strain gauge 51. The output voltage Vout + and the output voltage Vout− are supplied to the operational amplifier OP, and the output voltage Vout is output from the output terminal of the operational amplifier OP.

  When a force in the torque (Mz) direction is applied to the torque sensor 10, the torque sensor represented by Expression (5) is obtained from the output voltage Vout + of one connection node of the bridge circuit 50 and the output voltage Vout− of the other connection node. Ten output voltages Vout are obtained.

Vout = (Vout + −Vout−)
= (R3 / (R2 + R3) -R1 / (R1 + R4)). Vo (5)
Here, R1 is the resistance value of the strain gauge 51, R2 is the resistance value of the strain gauge 52, R3 is the resistance value of the strain gauge 53, and R4 is the resistance value of the strain gauge 54.

  In a state where no torque is applied to the torque sensor 10, ideally, R1 = R2 = R3 = R4 = R. However, in actuality, there is a variation in resistance value, and a voltage associated with the variation in resistance value is output in a state where no torque is applied. This voltage is made zero by offset adjustment.

  On the other hand, when a force in a direction other than torque, for example, Fx and My directions, is applied to the torque sensor 10, the output voltage Vout is output from the bridge circuit 50 by changing the resistance values of R1 to R4. However, the output voltage of the bridge circuit 50 of the second strain sensor 20 is a voltage whose polarity is opposite to that of the bridge circuit 50 of the first strain sensor 19. For this reason, the output voltage in each bridge circuit 50 has the same absolute value and is different in positive and negative, so that they are canceled out and the detected voltage becomes 0V.

  When the strain gauges 51, 52, 53, and 54 as the sensor elements have the same displacement amount in the torque (Mz) direction and the directions other than the torque (Fx, My), they can output the same voltage. preferable. For this reason, the strain gauges 51, 52, 53, and 54 are regions in which the strain of the strain generating body 41 is equal in the torque (Mz) direction and directions other than the torque (Fx, My) (regions in which the sensitivity of measurement is equal). It is preferable to arrange | position.

  FIG. 14 schematically shows the state of the strain generating body 41 when a torque (Mz) direction force is applied to the torque sensor 10 and when a force other than the torque (Fx, My) direction is applied. ing.

  When the movement of the strain generating body 41 provided between the first structure 11 and the second structure 12 is observed macroscopically, when a torque (Mz) direction force is applied to the torque sensor 10, the torque In any case where a force in a direction other than (Fx, My) is applied, it appears that the strain generating body 41 is changed in the shear direction.

  However, when the movement of the strain generating body 41 provided between the first structure 11 and the second structure 12 is observed microscopically, when a force in the torque (Mz) direction is applied to the torque sensor 10, A rotational force acts on the strain body 41. On the other hand, when a force in a direction other than torque (Fx, My) is applied to the torque sensor 10, a translational force acts on the strain generating body 41. For this reason, there is a difference in deformation of the strain generating body 41 between when a force in the torque (Mz) direction is applied and when a force in a direction other than the torque (Fx, My) is applied.

  That is, there is a difference between the deformation of the region AR1 of the strain body 41 on the second structure 12 side and the deformation of the region AR2 of the strain body 41 on the first structure 11 side. Specifically, in the area AR1 of the strain generating body 41, the strain of the strain generating body 41 when the force in the torque (Mz) direction is applied and the force in the direction other than the torque (Fx, My) are applied. The difference from the strain of the strain generating body 41 in the case is that in the region AR2 of the strain generating body 41, the strain of the strain generating body 41 when a force in the torque (Mz) direction is applied and other than the torque (Fx, My) It is smaller than the difference from the strain of the strain generating body 41 when a force in the direction of is applied.

  That is, in the region AR1 on the second structure 12 side, when the force in the torque direction (Mz) is applied, the strain of the strain generating body 41 and the force in the direction other than the torque (Fx, My) are applied. The difference from the strain of the strain generating body 41 is small.

For this reason, when a plurality of strain gauges 51, 52, 53, 54 are arranged in the area AR1, the difference between the detection sensitivity of torque (Mz) and the detection sensitivity of other than torque (Fx, My) is as small as less than 1%. . On the other hand, when a plurality of strain gauges 51, 52, 53, and 54 are arranged in the area AR2, the difference between the detection sensitivity of torque and the detection sensitivity other than torque is several percent. Therefore, it is preferable to arrange a plurality of strain gauges 51, 52, 53, 54 in the area AR1 on the second structure 12 side.
(Effect of 2nd Embodiment)
According to the second embodiment, each of the first strain sensor 19 and the second strain sensor 20 includes the first structure 11 and the strain body 41 connected between the second structure 12 and A plurality of strain gauges 51, 52, 53, 54 as sensor elements provided on the strain generating body 41 are provided, and the plurality of strain gauges 51, 52, 53, 54 are in the longitudinal center of the strain generating body 41. It arrange | positions to area | region AR1 of the 2nd structure 12 side from CT. The region AR1 of the strain generating body 41 includes strain (sensitivity) (a1, a2) when a force in the torque direction is applied to each of the first strain sensor 19 and the second strain sensor 20, and a direction other than the torque. This is a region where the difference in strain (sensitivity) (b1, b2) when a force is applied is small (a1≈b1, a2≈b2, a1 ≠ a2). Therefore, by adjusting the torque sensitivity for each of the first strain sensor 19 and the second strain sensor 20, the processing accuracy of the first structure 11, the second structure 12, and the third structure 13, A decrease in torque detection accuracy can be prevented without depending on the placement accuracy of the first strain sensor 19 and the second strain sensor 20 with respect to the first structure 11 and the second structure 12.

  Moreover, since the bridge circuit 50 arranged in the region AR1 of the strain generating body 41 has a small difference in detection sensitivity with respect to the force in the torque direction and the force in the direction other than the torque, the first strain sensor 19 and the second strain sensor 20 The output voltage error is also small. For this reason, when the voltages output from the two bridge circuits 50 are calibrated, the detection errors other than the torque can be calibrated only by calibrating the detection error with respect to the torque. Therefore, since it is not necessary to provide another strain sensor to detect a force in a direction other than torque (Fx, My), the calibration time can be shortened and a high-speed response can be realized.

  The effects of the second embodiment will be specifically described below.

  FIG. 15 schematically shows a torque sensor 60 according to a comparative example. The torque sensor 60 includes a first strain sensor 61 and a second strain sensor 62 between the first structure 11 and the second structure 12. The first strain sensor 61 and the second strain sensor 62 each have a strain body 63, and each of the strain bodies 63 includes a plurality of strain gauges 51, 52, 53, and 54 that form a bridge circuit shown in FIG. Is arranged. Since FIG. 15 is a schematic diagram, the third structure 13 is omitted.

  In the comparative example, the arrangement of the strain gauges 51, 52, 53, 54 is different from that of the second embodiment. That is, the strain gauges 52 and 53 are disposed in the region of the strain body 63 on the first structure 11 side, and the strain gauges 51 and 54 are disposed in the region of the strain body 63 on the second structure 12 side. Yes.

  In the case of the configuration shown in FIG. 15, the strain gauges 52 and 53 arranged in the region on the first structure 11 side are arranged in the torque (Mz) direction and the directions other than the torque (Fx, My). Distortion is different. Therefore, the sensitivity of the first strain sensor 61 and the sensitivity of the second strain sensor 62 when a force in the torque (Mz) direction is applied, and the force in a direction other than the torque (Fx, My) are applied. The difference between the sensitivity of the first strain sensor 61 and the sensitivity of the second strain sensor 62 is large.

  Specifically, when a force in a direction other than torque (Fx, My) is applied to the torque sensor 60, the sensitivity in the direction other than torque (Fx, My) differs from the sensitivity in the torque (Mz) direction. The output voltage value (positive value) of the first strain sensor 61 and the output voltage value (negative value) of the second strain sensor 62 are different from each other. For this reason, the torque sensor 60 outputs an error consisting of an average value of the first strain sensor 61 and the second strain sensor 62.

  On the other hand, in the case of the torque sensor 10 of the second embodiment, when a force in a direction other than torque (Fx, My) is applied to the torque sensor 10, the sensitivity in the direction other than torque (Fx, My) is torque (Mz ) Coincides with the direction sensitivity. Therefore, the output voltage value (positive value) (Vout1) of the first strain sensor 19 and the output voltage value (negative value) (−Vout2) of the second strain sensor 20 are substantially equal (| Vout1 |). ≈ | −−Vout2 |). For this reason, the output of the torque sensor 10 becomes substantially zero because the output voltages of the first strain sensor 61 and the second strain sensor 62 are offset. Therefore, in the case of the second embodiment, it is possible to reduce a detection error for a force in a direction other than torque (Fx, My).

  In the case of the torque sensor 60 according to the comparative example, the errors in the output voltages of the first strain sensor 61 and the second strain sensor 62 are large (| Vout1 |) between the direction of torque (Mz) and the direction other than torque (Fx, My). ≠ | −Vout2 |). Therefore, in order to calibrate these errors, it is necessary to perform calibration for correcting the detection error in the torque direction and calibration for correcting the detection error in the direction other than the torque. Therefore, the torque sensor 60 according to the comparative example needs to be separately provided with a bridge circuit including a strain gauge for detecting a force in a direction other than the torque. For this reason, in the torque sensor 60 according to the comparative example, the circuit board is increased in size and the calculation processing time by software is increased, so that the adjustment work is complicated as compared with the second embodiment, and the responsiveness is lowered.

  On the other hand, in the case of the second embodiment, there is almost no error in the output voltages of the first strain sensor 19 and the second strain sensor 20 in the torque (Mz) direction and the directions other than torque (Fx, My). For this reason, it is only necessary to correct the detection error in the torque direction. Therefore, the calibration time can be shortened and the response performance of the torque sensor can be improved.

Moreover, 2nd Embodiment is not limited to the structure of the torque sensor 10, The strain gauges 51, 52, 53, 54 should just be arrange | positioned in area | region AR1. For this reason, even if the arrangement according to the second embodiment is applied to a torque sensor 30 having a structure as shown in FIG. 9, for example, the same effect as that of the second embodiment can be obtained.
(Third embodiment)
FIG. 16 shows a third embodiment, and shows an enlarged portion indicated by B in FIG.

  As described with reference to FIG. 2, the first strain sensor 19 is covered with the stopper 16, and the second strain sensor 20 is covered with the stopper 17. The stopper 16 and the stopper 17 are made of, for example, stainless steel or an iron-based alloy. The stopper 16 and the stopper 17 prevent mechanical deformation of the first strain sensor 19 and the second strain sensor 20, and protect the strain gauges 51, 52, 53, and 54. Further, the stopper 16 and the stopper 17 also serve as a waterproof cover for the first strain sensor 19 and the second strain sensor 20. Description of a specific waterproof structure is omitted.

  Since the stopper 16 and the stopper 17 have the same configuration, only the stopper 16 will be described.

  As shown in FIG. 16, the stopper 16 has one end portion 16a and the other end portion 16b, and the width of the other end portion 16b of the stopper 16 is narrower than the width of the one end portion 16a. One end 16a of the stopper 16 is, for example, press-fitted and fixed in a recess 14f as an engaging portion formed on the second structure 12 side of the fourth structure 14. The other end 16 b of the stopper 16 is disposed in a recess 14 f formed on the first structure 11 side of the fourth structure 14. The width of the other end portion 16b of the stopper 16 is narrower than the width of the concave portion 14f provided on the first structure 11 side, and there is a gap between both sides of the other end portion 16b of the stopper 16 and the side surface of the concave portion 14f. Each GP is provided.

  The gap GP is determined by the rigidity of the third structure 13 and the rated torque.

  Specifically, when a torque of, for example, 1000 N · m is applied to the torque sensor 10, when the first structure 11 is deformed by, for example, 10 μm with respect to the second structure 12, the gap GP is set to, for example, 10 μm. The

  17A and 17B show the operation of the stopper, and schematically show a part of FIG.

  As shown in FIG. 17A, when no torque is applied to the torque sensor 10, a predetermined gap GP is provided between both sides of the other end 16b of the stopper 16 and the recess 14f. In this state, when a torque equal to or lower than the rated torque is applied to the torque sensor 10, the first structure 11 moves relative to the second structure 12, and a voltage corresponding to the torque applied from the first strain sensor 19. Is output. When the application of torque to the torque sensor 10 is removed, the first strain sensor 19 returns due to elastic deformation.

  On the other hand, as shown in FIG. 17B, when a torque larger than the rated torque is applied to the torque sensor 10, the side surface of the concave portion 14f of the first structure 11 is brought into contact with the other end portion 16b of the stopper 16, and the second structure The movement of the first structure 11 with respect to the body 12 is restricted. For this reason, the first strain sensor 19 is protected within a range of elastic deformation. When the application of torque to the torque sensor 10 is removed, the first strain sensor 19 returns due to elastic deformation. The second strain sensor 20 is also protected by the same configuration.

  FIG. 18 is a diagram for explaining the relationship between the torque as a load applied to the torque sensor 10 and the operation of the stopper 16. The torque applied to the torque sensor 10 and the detected distortion (bridge circuit 50). The output voltage is schematically shown.

  As shown in FIG. 18, when a torque equal to or lower than the rated torque is applied to the torque sensor 10, the first strain body 11 of the first strain sensor 19 (second strain sensor 20) has the second structure. A voltage corresponding to the applied torque is output from the first strain sensor 19 (second strain sensor 20) while moving relative to the body 12.

On the other hand, when a torque larger than the rated torque is applied to the torque sensor 10, the side surface of the recess 14f comes into contact with the stopper 16, and the deformation of the plurality of third structures 13 is suppressed by the rigidity of the stopper 16 (stopper 17). Accordingly, deformation of the strain generating body 41 is suppressed. That is, the operating point Op of the stopper 16 is set equal to the rated torque of the torque sensor 10, and the stopper 16 protects the strain generating body 41 against a torque larger than the rated torque.
(Effect of the third embodiment)
According to the third embodiment, the first strain sensor 19 and the second strain sensor 20 are provided with the stopper 16 as a cover, and the one end 16a of the stopper 16 is fixed in the recess 14f on the second structure 12 side. When the torque sensor 10 is applied with a torque larger than the rated torque, the other end portion 16b contacts the side surface of the recess 14f on the first structure 11 side. For this reason, it is possible to protect the first strain sensor 19 and the second strain sensor 20. Further, the structures other than the first strain sensor 19 and the second strain sensor 20 are also protected from plastic deformation and the like, similarly to the first strain sensor 19 and the second strain sensor 20.

  Moreover, the rated torque of the torque sensor 10 can be brought close to the 0.2% proof stress of the strain gauge. For this reason, the output voltage of the bridge circuit 50 at the rated torque can be increased. Therefore, it is possible to provide a high resolution and high accuracy torque sensor.

  FIG. 19 shows the relationship between strain and stress of the strain gauge. The rated torque of the torque sensor according to the third embodiment and the rated torque of the torque sensor without the stopper 16 and the stopper 17 as a comparative example. , Shows.

  In the case of a general torque sensor not having the stopper 16 and the stopper 17 as a comparative example, the strain gauge is designed with a safety factor against impact and fatigue set to about 3 to 5. For example, when the safety factor is 3, the stress of the strain gauge is set to 1/3 of the 0.2% proof stress. For this reason, the rated torque is also set to 1/3 of the breaking torque.

  On the other hand, in the case of the third embodiment, since the first strain sensor 19 and the second strain sensor 20 are protected by the stopper 16 and the stopper 17, it is necessary to set the safety factor of the strain gauge to 1 or more. Absent. For this reason, the rated torque of the strain gauge can be set larger than that of a general torque sensor that does not have the stopper 16 and the stopper 17. Therefore, it is possible to provide a high resolution and high accuracy torque sensor.

Furthermore, by increasing the rigidity of the stopper 16, a torque sensor having a high allowable load (high maximum torque) can be provided.
(Modification)
FIG. 20 shows a first modification of the third embodiment. In the third embodiment, the stopper 16 protects the first strain sensor 19 by the other end portion 16b coming into contact with the side surface of the recess 14f on the first structure 11 side.

  In the first modification, the other end 16b of the stopper 16 has an opening 16b-1, and is inserted into the opening 16b-1 on the first structure 11 side of the fourth structure 14. A protrusion 14g is provided. A gap GP1 is provided between the opening 16b-1 and the protrusion 14g. The dimension of the gap GP1 is, for example, smaller than the dimension of the gap GP. For this reason, when a torque larger than the allowable torque is applied to the torque sensor 10, the first strain sensor 19 can be protected by the protrusion 14 g coming into contact with the opening 16 b-1 of the stopper 16.

  The stopper 17 of the second strain sensor 20 has the same configuration as the stopper 16.

  According to the first modified example, the same effect as that of the third embodiment can be obtained. In addition, according to the first modification, the first strain sensor 19 (second strain sensor 20) can be further protected by the protrusion 14g coming into contact with the opening 16b-1 of the stopper 16. .

  FIG. 21 shows a second modification of the third embodiment.

  While the third embodiment includes the stopper 16 and the stopper 17, the second modification further includes four stoppers 16-1, 16-2, 17-1, 17-2. It has. That is, the structures of the stoppers 16-1, 16-2, 17-1, and 17-2 are the same as the stoppers 16 and 17.

  The effect similar to 3rd Embodiment can be acquired also by a 2nd modification. In addition, according to the second modification, since the number of stoppers is larger than that in the third embodiment, the first strain sensor 19 and the second strain sensor 20 can be further protected.

  In addition, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 10 ... Torque sensor, 11 ... 1st structure, 12 ... 2nd structure, 13 ... 3rd structure, 14 ... 4th structure, 14a ... 1st connection part, 14b ... 2nd connection part, 14c ... 1st 3 connection part, 14d ... 4th connection part, 14e ... opening part, 14f ... recessed part (engagement part), 14g ... protrusion, 15 ... 5th structure, 16, 16-1, 16-2 ... stopper, 16b- DESCRIPTION OF SYMBOLS 1 ... Opening part, 17, 17-1, 17-2 ... Stopper, 19 ... 1st strain sensor, 20 ... 2nd strain sensor, 41 ... Strain body, GP, GP1 ... Gap, 51, 52, 53, 54 ... Strain gauge as a sensor element.

Claims (4)

A first structure;
A second structure;
A plurality of third structures connecting the first structure and the second structure;
At least one strain sensor connected between the first structure and the second structure;
One end is fixed to one of the first structure and the second structure, and the other end is engageable with an engaging portion provided on the other of the first structure and the second structure. At least one stopper,
A torque sensor comprising:   The torque sensor according to claim 1, wherein the engaging portion is a recess, and the other end of the stopper is disposed in the recess.   The other end of the stopper has an opening, and the other of the first structure and the second structure includes a protrusion provided in the opening. Torque sensor.   The torque sensor according to claim 1, wherein the stopper is a waterproof cover that covers the strain sensor.

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