Torque sensor, torque detection unit, and method for manufacturing torque sensor

Abstract

The invention provides a torque sensor, a torque detection unit, and a method for manufacturing the torque sensor. A torque detection unit (30) of a torque sensor (1) is columnar, one end of the torque detection unit (30) is sandwiched between the bottom surfaces of a first frame section (10A) and a second frame section (10B), the other end of the torque detection unit (30) is sandwiched between the bottom surfaces of a first core section (20A) and a second core section (20B), and film-like strain gauges (40) are disposed on both side surfaces orthogonal to the bottom surface of the first frame section (10A).

Description

Technical Field

[0001] The present disclosure relates to a torque sensor, a torque detection unit, and a method for manufacturing the torque sensor. Background Art

[0002] In recent years, torque sensors for measuring output torque of an actuator, etc. have been developed. Patent Document 1 discloses a torque sensor having an inner structure, an outer structure, and a bridge connecting the two structures.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-73177 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In a torque sensor, a strain gauge is arranged at a strain generating portion that generates strain according to an applied torque. The strain generated by the applied torque is apparent on the side of the beam of the torque sensor. However, it is difficult to accurately arrange a strain gauge at a predetermined position on the side of the beam.

[0008] An object of one aspect of the present disclosure is to provide a torque sensor capable of measuring torque with high accuracy.

[0009] Solutions for solving problems

[0010] In order to solve the above-mentioned problems, a torque sensor of one embodiment of the present disclosure includes a first frame part, a second frame part, a first core part, a second core part, and a torque detection part. The first frame part has a cylindrical shape. The second frame part is arranged at a position opposite to the bottom surface of the first frame part, and has a cylindrical shape concentric with the first frame part. The first core part is arranged in the hollow of the first frame part, and has a cylindrical or columnar shape concentric with the first frame part. The second core part is arranged in the hollow of the second frame part and is at a position opposite to the bottom surface of the first core part, and has a cylindrical or columnar shape concentric with the first frame part. The torque detection part is columnar, one end of which is clamped between the bottom surfaces of the first frame part and the second frame part, and the other end of which is clamped between the bottom surfaces of the first core part and the second core part, and a film-shaped strain gauge is arranged on two side surfaces orthogonal to the bottom surface of the first frame part.

[0011] In order to solve the above-mentioned problems, a torque detection part of one scheme of the present disclosure is used for a torque sensor having a first frame part, a second frame part, a first core part and a second core part. The first frame part has a cylindrical shape. The second frame part is arranged at a position opposite to the bottom surface of the first frame part, and has a cylindrical shape concentric with the first frame part. The first core part is arranged in the hollow of the first frame part, and has a cylindrical or columnar shape concentric with the first frame part. The second core part is arranged in the hollow of the second frame part and is at a position opposite to the bottom surface of the first core part, and has a cylindrical or columnar shape concentric with the first frame part. The torque detection part is columnar, one end of which is clamped between the bottom surfaces of the first frame part and the second frame part, and the other end of which is clamped between the bottom surfaces of the first core part and the second core part, and film-shaped strain gauges are arranged on two side surfaces orthogonal to the bottom surface of the first frame part.

[0012] In order to solve the above-mentioned problems, a method for manufacturing a torque sensor according to one embodiment of the present disclosure is a method for manufacturing a torque sensor having a first frame portion, a second frame portion, a first core portion, a second core portion, and a torque detection portion. The first frame portion has a cylindrical shape. The second frame portion is arranged at a position opposite to the bottom surface of the first frame portion, and has a cylindrical shape concentric with the first frame portion. The first core portion is arranged in the hollow of the first frame portion, and has a cylindrical or columnar shape concentric with the first frame portion. The second core portion is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion, and has a cylindrical or columnar shape concentric with the first frame portion. The method for manufacturing a torque sensor includes a first step, a second step, and a third step. In the first step, a film-shaped strain gauge is formed on the side of the torque detection portion formed into a columnar shape. In the second step, one end of the torque detection part is clamped between the bottom surfaces of the first frame part and the second frame part, and the other end of the torque detection part is clamped between the bottom surfaces of the first core part and the second core part. In the third step, the first frame part and the second frame part are fastened, and the first core part and the second core part are fastened. The side surface of the torque detection part forming the film-shaped strain gauge in the first step is the side surface orthogonal to the bottom surfaces of the first frame part and the second frame part in the second step.

[0013] Effects of the Invention

[0014] According to an aspect of the present disclosure, it is possible to provide a torque sensor capable of measuring torque with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view showing the structure of the torque sensor according to the first embodiment of the present disclosure.

[0016] Figure 2 It is a plan view showing the structure of the torque sensor according to the first embodiment of the present disclosure.

[0017] Figure 3 It is a plan view showing the structure of a torque sensor according to Embodiment 2 of the present disclosure. DETAILED DESCRIPTION

[0018] [Implementation method 1]

[0019] (Torque sensor)

[0020] Figure 1 It is a cross-sectional view showing the structure of the torque sensor according to the first embodiment of the present disclosure. Figure 1 The torque sensor 1 shown in the figure includes a first frame portion 10A, a second frame portion 10B, a first core portion 20A, a second core portion 20B, and a plurality of torque detection portions 30. Figure 1 The X-axis direction, the Y-axis direction, and the Z-axis direction are defined as shown by arrows.

[0021] The first frame portion 10A and the second frame portion 10B have concentric cylindrical shapes. Here, the cylindrical shape refers to a columnar shape having a hollow through hole between the bottom surface and the upper surface, and is not limited to a cylindrical shape. Figure 1 In the figure, the bottom surfaces of the first frame portion 10A and the second frame portion 10B are parallel to the XY plane. The first frame portion 10A and the second frame portion 10B are arranged at positions where the bottom surfaces are opposite to each other. The first frame portion 10A has a recess 11A sunken in the Z-axis direction around the inner edge of its bottom surface. On the other hand, the second frame portion 10B has a recess 11B sunken in the Z-axis direction around the inner edge of its bottom surface. When the first frame portion 10A and the second frame portion 10B are arranged at positions where the bottom surfaces are opposite to each other, the recesses 11A and 11B are formed by overlapping the positions of the openings with the bottoms facing each other.

[0022] The first core 20A and the second core 20B have a cylindrical shape. The first core 20A and the second core 20B are concentric with the first frame 10A and the second frame 10B. Figure 1In the embodiment, the bottom surfaces of the first core portion 20A and the second core portion 20B are parallel to the XY plane. The first core portion 20A is arranged in the hollow of the first frame portion 10A. The second core portion 20B is arranged in the hollow of the second frame portion 10B. The first core portion 20A and the second core portion 20B are arranged so that their bottom surfaces are opposite to each other. The first core portion 20A has a recess 21A that is recessed in the Z-axis direction around the outer edge of its bottom surface. On the other hand, the second core portion 20B has a recess 21B that is recessed in the Z-axis direction around the outer edge of its bottom surface. When the first core portion 20A and the second core portion 20B are arranged in positions where their bottom surfaces are opposite to each other, the recesses 21A and 21B are opposite to each other through the bottoms and the positions of the openings overlap, thereby forming the second recess 21.

[0023] The torque detection portion 30 has a columnar shape. In the torque detection portion 30, the first end 31 as one end thereof is clamped in the first recess 11 between the bottom surfaces of the first frame portion 10A and the second frame portion 10B. In addition, in the torque detection portion 30, the second end 32 as the other end is clamped in the second recess 21 between the bottom surfaces of the first core portion 20A and the second core portion 20B. The dimension of the torque detection portion 30 in the Z-axis direction is greater than the depth of the first recess 11 and the second recess 21 in the Z-axis direction. Figure 1 , the dimension of the torque detection portion 30 in the Z-axis direction is consistent with the sum of the depths of the first recess 11 and the second recess 21 in the Z-axis direction. The depths of the first recess 11 and the second recess 21 in the Z-axis direction are each half of the dimension of the torque detection portion 30 in the Z-axis direction.

[0024] Figure 2 It is a plan view showing the structure of the torque sensor according to the first embodiment of the present disclosure. Figure 2 The first frame portion 10A is viewed from the side Figure 1 1 is a top view of the A-A section of the torque sensor 1 shown. The first frame portion 10A and the second frame portion 10B have first recesses 11 on radial axes R1 and R2 extending radially from the center axis of the first frame portion 10A. In addition, the first core portion 20A and the second core portion 20B have second recesses 21 on radial axes R1 and R2 extending radially from the center axis of the first frame portion 10A. The number of first recesses 11 provided in the torque sensor 1 is the same as the number of second recesses 21. The torque sensor 1 has the same number of torque detection portions 30 as the first recesses 11 and the second recesses 21. The plurality of torque detection portions 30 are arranged on radial axes R1 and R2 extending radially from the center axis of the first frame portion 10A. Each torque detection portion 30 has a shape that is line-symmetrical with respect to the radial axes R1 and R2. The plurality of first recessed portions 11 , the plurality of second recessed portions 21 , and the plurality of torque detection portions 30 are arranged at equal intervals on a circumference centered on the central axis of the first frame portion 10A.

[0025] The first end 31 and the second end 32 of the torque detection portion 30 have a shape wider than the beam portion between the first end 31 and the second end 32 when viewed from above. The first recess 11 formed between the bottom surfaces of the first frame portion 10A and the second frame portion 10B has a shape that fits with the first end 31. The second recess 21 formed between the bottom surfaces of the first core portion 20A and the second core portion 20B has a shape that fits with the second end 32.

[0026] In the torque detection unit 30, a film-shaped strain gauge 40 is arranged on the side surfaces 33 and 34 that are orthogonal to the bottom surface of the first frame portion 10A. For example, the output shaft of the actuator is inserted into the hollow 22 of the first core portion 20A and the second core portion 20B. The output shaft of the actuator extends in the Z-axis direction. The film-shaped strain gauge 40 detects the strain of the torque detection unit 30 generated by the rotation of the output shaft of the actuator.

[0027] The first frame portion 10A and the second frame portion 10B have holes 51 on radial axes extending radially from the central axis of the first frame portion 10A, which are threadedly engaged with the fastening member 50. The first core portion 20A and the second core portion 20B have holes 52 on radial axes extending radially from the central axis of the first frame portion 10A, which are threadedly engaged with the fastening member 50.

[0028] (Manufacturing method of torque sensor)

[0029] The first frame portion 10A, the second frame portion 10B, the first core portion 20A, and the second core portion 20B are formed of various materials such as metal materials such as stainless steel, aluminum, and magnesium, resin materials, and ceramics. The first frame portion 10A, the second frame portion 10B, the first core portion 20A, and the second core portion 20B can be manufactured by casting using a mold or cutting, for example.

[0030] The torque detection part 30 is formed into a columnar shape using various materials such as metal materials such as stainless steel, aluminum, and magnesium, resin materials, and ceramics. The film strain gauge 40 is formed of, for example, a thin layer of chromium nitride (NCr). The film strain gauge 40 is formed on the side surfaces 33 and 34 of the torque detection part 30 formed into a columnar shape using a thin film forming technique such as sputtering and evaporation (first process). Since the film strain gauge 40 can be formed in a state where the torque detection part 30 is separated from the first frame part 10A, etc., the accuracy of the position where the film strain gauge 40 is formed can be improved compared to the past.

[0031] The following describes the assembly of the torque sensor 1. The first end 31 of the torque detection part 30 is arranged in the recess 11B of the second frame part 10B and fits in the recess 11B. The second end 32 of the torque detection part 30 is arranged in the recess 21B of the second core part 20B and fits in the recess 21B. The first frame part 10A is arranged on the first end 31 of the torque detection part 30 in such a manner that the recess 11A fits in the first end 31. The first core part 20A is arranged on the second end 32 of the torque detection part 30 in such a manner that the recess 21A fits in the second end 32. As a result, the bottom surfaces of the first frame part 10A and the second frame part 10B are opposite to each other, and the first end 31 of the torque detection part 30 is sandwiched by the first recess 11 between the bottom surfaces of the first frame part 10A and the second frame part 10B. The bottom surfaces of the first core 20A and the second core 20B are opposite to each other, and the second end 32 of the torque detection unit 30 is sandwiched by the second recess 21 between the bottom surfaces of the first core 20A and the second core 20B (second step). The side surfaces 33 and 34 of the torque detection unit 30 on which the film-shaped strain gauge 40 is formed are the side surfaces orthogonal to the bottom surfaces of the first frame 10A and the second frame 10B in the second step.

[0032] Next, the fastening member 50 is screwed into the holes 51 of the first frame portion 10A and the second frame portion 10B, thereby fastening the first frame portion 10A and the second frame portion 10B. In addition, the fastening member 50 is screwed into the holes 52 of the first core portion 20A and the second core portion 20B, thereby fastening the first core portion 20A and the second core portion 20B (third step).

[0033] The torque detection unit 30 can be provided in a plurality of types with different sizes, materials, and arrangement positions of the film-shaped strain gauge 40, etc., depending on the application of the torque sensor 1. For example, a torque detection unit 30 with changed materials and thickness and changed sensitivity to deformation, detection accuracy, output response characteristics, etc. can be provided. The user of the torque sensor 1 can remove the fastening member 50 from the torque sensor 1 and replace the torque detection unit 30 with a torque detection unit 30 that matches the desired application.

[0034] [Implementation method 2]

[0035] Embodiment 2 of the present disclosure will be described below. In addition, for convenience of description, components having the same functions as those described in Embodiment 1 above are denoted by the same reference numerals, and description thereof will not be repeated.

[0036] Figure 3 1 is a top view showing the structure of a torque sensor according to Embodiment 2 of the present disclosure. Figure 1 and Figure 2 The difference of the torque sensor 1 shown is that Figure 3The torque sensor 2 shown in the figure has a through hole 36 on the side of the torque detection part 30. More specifically, the torque detection part 30 of the torque sensor 2 has a through hole 36 at the center of a side surface 35 parallel to the bottom surface of the first frame part 10A when the torque sensor 2 is mounted. Figure 3 The side surface 35 of the torque detection unit 30 shown in the figure penetrates to the side surface on the opposite side to the side surface 35. The center of gravity G of the torque detection unit 30 is located inside the opening of the through hole 36 in a plan view.

[0037] The opening of the through hole 36 is shaped such that the length along the direction R3 which is orthogonal to the radial axis R1 or R2 and parallel to the bottom surface of the first frame portion 10A is smaller than the length along the direction parallel to the radial axis R1 or R2 on which the torque detection portion 30 is arranged. For example, the through hole 36 is formed by cutting or the like when the torque detection portion 30 is formed. The opening of the through hole 36 is shaped like a rectangle with rounded corners. The method for forming the through hole 36 is not limited to cutting. The opening of the through hole 36 may also be shaped like a rectangle without rounded corners, an ellipse, or the like.

[0038] In the case where the through hole 36 is provided on the side surface 35 of the torque detection part 30, the strain generated in the central part of the side surfaces 33 and 34 of the torque detection part 30 due to the rotation of the output shaft of the actuator or the like inserted into the hollow part 22 becomes larger than the case where the through hole 36 is not provided. The central part of the side surfaces 33 and 34 is, for example, a range of a predetermined distance from the center of the side surfaces 33 and 34. Here, the predetermined distance refers to, for example, the length of the through hole 36 along the direction R3. When the shape of the through hole 36 is changed to a perfect circle, and when the long side direction and the short side direction of the through hole 36 are switched, the effect of increasing the strain generated in the central part of the side surfaces 33 and 34 is not confirmed.

[0039] In the torque sensor 2, the film-shaped strain gauge 40 is arranged in the center of the side surfaces 33 and 34 of the torque detection unit 30. That is, the film-shaped strain gauge 40 is arranged in the side surfaces 33 and 34 of the torque detection unit 30 at a location where strain is output to a large extent due to the provision of the through hole 36 on the side surface 35 of the torque detection unit 30. Thus, the torque sensor 2 can improve the measurement sensitivity compared with the torque sensor 1.

[0040] In addition, in the torque sensor 2, the through holes 36 are arranged so that the center of gravity G of the torque detection unit 30 is located inside the opening of the through holes 36 when viewed from above, thereby suppressing the number of through holes 36 arranged in the torque detection unit 30 to a minimum. The allowable load and measurement sensitivity of the torque sensor are in a trade-off relationship. By suppressing the number of through holes 36 arranged in the torque detection unit 30 to a minimum, the measurement sensitivity can be improved without excessively reducing the allowable load of the torque sensor 2.

[0041] [Variation]

[0042] In the above embodiment, the first core portion 20A and the second core portion 20B are set to be cylindrical, but as long as they have a hole in the center for the output shaft to be inserted, they are not limited to the cylindrical shape, and the hole for the output shaft to be inserted may not be a through hole. For example, when the torque sensor 1 is mounted on the front end of the output shaft, the first core portion 20A and the second core portion 20B may also be a columnar shape without a through hole.

[0043] In the above-mentioned embodiment, the first end 31 of the torque detection part 30 is clamped in the first recess 11 between the bottom surfaces of the first frame part 10A and the second frame part 10B. However, the first end 31 of the torque detection part 30 may be clamped by any method as long as it is fixed in a state of being clamped between the bottom surfaces of the first frame part 10A and the second frame part 10B. For example, the depth of the recess 11A forming the first recess 11 may be made consistent with the dimension of the torque detection part 30 in the Z-axis direction, and the depth of the recess 11B may be set to zero. In addition, the second end 32 of the torque detection part 30 may be clamped by any method as long as it is fixed in a state of being clamped between the bottom surfaces of the first core part 20A and the second core part 20B.

[0044] In the above embodiment, in the torque sensors 1 and 2, four torque detection units 30 are arranged at 90-degree intervals on a circumference centered on the central axis of the first frame portion 10A. However, the number of torque detection units 30 arranged in the torque sensors 1 and 2 is not limited to four. For example, the torque sensors 1 and 2 may also be arranged with eight torque detection units 30 at 45-degree intervals on a circumference centered on the central axis of the first frame portion 10A.

[0045] In the above embodiment, in the torque detection section 30, the film-shaped strain gauge 40 is arranged on the side surfaces 33 and 34 that are orthogonal to the bottom surface of the first frame section 10A when the torque detection section 30 is mounted on the torque sensor 1. However, the position where the film-shaped strain gauge 40 is arranged is not limited to the side surfaces 33 and 34 of the torque detection section 30. For example, in the torque detection section 30, the film-shaped strain gauge 40 may also be arranged on the side surface that is parallel to the bottom surface of the first frame section 10A when the torque detection section 30 is mounted on the torque sensor 1.

[0046] 〔plan〕

[0047] (Scheme 1) A torque sensor, wherein the torque sensor comprises: a first cylindrical frame portion; a second frame portion, which is arranged at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is arranged in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; a second core portion, which is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion and has a cylindrical or columnar shape concentric with the first frame portion; and a torque detection portion, which is columnar, one end of which is clamped between the bottom surfaces of the first frame portion and the second frame portion, and the other end of which is clamped between the bottom surfaces of the first core portion and the second core portion, and a membrane strain gauge is arranged on two side surfaces orthogonal to the bottom surface of the first frame portion.

[0048] According to the above configuration, since the film-shaped strain gauge 40 is formed on the torque detection section 30 while the torque detection section 30 is separated from the first frame section 10A, etc., the film-shaped strain gauge 40 can be accurately arranged. Therefore, the torque sensor 1 capable of measuring torque with high accuracy can be provided.

[0049] (Solution 2) The torque sensor according to Solution 1, wherein the torque detection portion is arranged on a radial axis extending radially from a central axis of the first frame portion, and has a shape that is line-symmetrical with respect to the radial axis.

[0050] According to the above configuration, the torque detector 30 can accurately measure the torque in the positive direction and the torque in the negative direction under the same conditions, with respect to the torque generated by the rotation around the central axis (Z axis) of the first frame portion 10A.

[0051] (Solution 3) The torque sensor according to Solution 1 or 2, wherein the torque sensor includes a plurality of the torque detection parts, and the plurality of the torque detection parts are arranged at equal intervals on a circumference centered on the central axis of the first frame part.

[0052] According to the above structure, the film-like strain gauge 40 is equally affected by the external force around the Z axis, and thus is advantageous from the viewpoint of accurately detecting the torque.

[0053] (Scheme 4) A torque sensor according to any one of schemes 1 to 3, wherein the bottom surfaces of the first frame portion and the second frame portion have a first recessed portion recessed in a shape that fits with the one end of the torque detecting portion, and the bottom surfaces of the first core portion and the second core portion have a second recessed portion recessed in a shape that fits with the other end of the torque detecting portion.

[0054] According to the above configuration, the first end 31 and the second end 32 of the torque detection unit 30 can be stably fixed.

[0055] (Solution 5) The torque sensor according to any one of Solutions 1 to 4, wherein, in a plan view, the end portions of the one end and the other end of the torque detection portion have a shape that is wider than a beam portion between the one end and the other end.

[0056] According to the above structure, when viewed from the bottom surface side of the first frame portion 10A, the first end 31 and the second end 32 of the torque detection portion 30 have a shape wider than the beam portion therebetween. By configuring in this way, the first end 31 is fitted into the first recess 11, and the second end 32 is fitted into the second recess 21, and compared with providing a flange portion perpendicular to the bottom surface of the first frame portion 10A and fitting it, it is possible to reduce the shaking in the direction of the torque to be detected.

[0057] (Solution 6) The torque sensor according to any one of Solutions 1 to 5, wherein the film-like strain gauge is further arranged on two side surfaces of the torque detection portion that are parallel to the bottom surface of the first frame portion.

[0058] According to the above configuration, the torque sensor 1 can be used as a six-axis torque sensor.

[0059] (Scheme 7) A torque detection portion, which is used for a torque sensor, comprises: a cylindrical first frame portion; a second frame portion, which is arranged at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is arranged in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; and a second core portion, which is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion and has a cylindrical or columnar shape concentric with the first frame portion, wherein the torque detection portion has a columnar shape, one end of which is clamped between the bottom surfaces of the first frame portion and the second frame portion, and the other end of which is clamped between the bottom surfaces of the first core portion and the second core portion, and a membrane strain gauge is arranged on two side surfaces orthogonal to the bottom surface of the first frame portion.

[0060] According to the above configuration, the film strain gauge 40 can be formed on the torque detection unit 30 while the torque detection unit 30 is separated from the first frame unit 10A, etc., so the film strain gauge 40 can be accurately arranged. Therefore, the torque sensor 1 capable of measuring torque with high accuracy can be provided.

[0061] (Scheme 8) A method for manufacturing a torque sensor, the torque sensor comprising: a first cylindrical frame portion; a second frame portion, which is arranged at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is arranged in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; a second core portion, which is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion and has a cylindrical or columnar shape concentric with the first frame portion; and a torque detecting portion, wherein the method for manufacturing the torque sensor comprises: a first step , in which a film-like strain gauge is formed on the side of the torque detecting portion formed into a columnar shape; a second step, in which one end of the torque detecting portion is clamped between the bottom surfaces of the first frame portion and the second frame portion, and the other end of the torque detecting portion is clamped between the bottom surfaces of the first core portion and the second core portion; and a third step, in which the first frame portion and the second frame portion are fastened, and the first core portion and the second core portion are fastened, and the side of the torque detecting portion on which the film-like strain gauge is formed in the first step is the side that is orthogonal to the bottom surfaces of the first frame portion and the second frame portion in the second step.

[0062] According to the above configuration, in the first step, the film strain gauge 40 can be formed on the torque detection section 30 while the torque detection section 30 is separated from the first frame section 10A, etc., so the film strain gauge 40 can be accurately arranged. Therefore, a torque sensor 1 capable of measuring torque with high accuracy can be provided.

[0063] (Scheme 9) A torque sensor according to Scheme 2, wherein the torque detecting portion has a through hole that passes through two side surfaces parallel to the bottom surface of the first frame portion, and the opening of the through hole is shaped such that the length along a direction orthogonal to the radial axis on which the torque detecting portion is arranged and parallel to the bottom surface of the first frame portion is longer than the length along a direction parallel to the radial axis.

[0064] According to the above configuration, in the area of ​​the side surfaces 33 and 34 of the torque detection unit 30 corresponding to the position where the through hole 36 is provided on the side surface 35, the strain caused by the rotation of the output shaft becomes larger than when no through hole 36 is provided. This can improve the measurement sensitivity of the torque sensor.

[0065] (Solution 10) A torque sensor according to Solution 9, wherein the center of gravity of the torque detection portion is located inside the opening of the through hole when viewed from above.

[0066] According to the above structure, by setting the through hole 36 in a manner such that the center of gravity G of the torque detection part 30 is located on the inner side of the opening of the through hole 36 when viewed from above, the number of through holes 36 provided in the torque sensor 2 can be suppressed to a minimum, and the measurement sensitivity can be improved without excessively reducing the allowable load of the torque sensor.

[0067] (Scheme 11) A torque detection portion according to Scheme 7, wherein the torque detection portion has a through hole that passes through two side surfaces parallel to the bottom surface of the first frame portion, and the torque detection portion is arranged on a radial axis extending radially from the central axis of the first frame portion, and has a shape that is line-symmetrical with respect to the radial axis, and the opening of the through hole is a shape in which the length along the direction orthogonal to the radial axis and parallel to the bottom surface of the first frame portion is longer than the length along the direction parallel to the radial axis.

[0068] By using the torque detection unit of the above structure in the torque sensor, the strain generated by the rotation of the output shaft in the area corresponding to the position where the through hole 36 is provided on the side surface 35 of the torque detection unit 30 is larger than when the through hole 36 is not provided. As a result, the measurement sensitivity of the torque sensor can be improved.

[0069] [Additional Notes]

[0070] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

Claims

1. A torque sensor, wherein: The torque sensor has: A first cylindrical frame portion; a second frame portion, which is disposed at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is disposed in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; A second core portion, which is disposed in the hollow of the second frame portion and is located opposite to the bottom surface of the first core portion, and has a cylindrical or columnar shape concentric with the first frame portion; as well as The torque detection part is columnar, one end of which is clamped between the bottom surface of the first frame part and the bottom surface of the second frame part, and the other end of which is clamped between the bottom surface of the first core part and the bottom surface of the second core part, and a membrane strain gauge is arranged on two side surfaces orthogonal to the bottom surface of the first frame part.

2. The torque sensor according to claim 1, wherein: The torque detection portion is disposed on a radial axis extending radially from a central axis of the first frame portion, and has a shape that is line-symmetrical with respect to the radial axis.

3. The torque sensor according to claim 1, wherein: The torque sensor includes a plurality of the torque detection units. The plurality of torque detection parts are arranged at equal intervals on a circumference centered on the central axis of the first frame part.

4. The torque sensor according to claim 1, wherein: The bottom surface of the first frame portion and the bottom surface of the second frame portion have a first recessed portion recessed in a shape that fits with the one end of the torque detection portion. A second recessed portion recessed in a shape to fit with the other end of the torque detector is provided on the bottom surface of the first core portion and the bottom surface of the second core portion.

5. The torque sensor according to claim 1, wherein: In a plan view, the end portions of the one end and the other end of the torque detection portion have a shape wider than a beam portion between the one end and the other end.

6. The torque sensor according to claim 1, wherein: The film-like strain gauge is further arranged on two side surfaces of the torque detection portion that are parallel to the bottom surface of the first frame portion.

7. The torque sensor according to claim 2, wherein: The torque detection portion has a through hole that penetrates between two side surfaces parallel to the bottom surface of the first frame portion. The opening of the through hole has a shape in which a length along a direction perpendicular to the radial axis where the torque detection portion is arranged and parallel to the bottom surface of the first frame portion is longer than a length along a direction parallel to the radial axis.

8. The torque sensor according to claim 7, wherein: The center of gravity of the torque detection portion is located inside the opening of the through hole in a plan view.

9. A torque detection unit, which is used for a torque sensor, and the torque sensor comprises: a first cylindrical frame portion; a second frame portion, which is arranged at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is arranged in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; and a second core portion, which is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion and has a cylindrical or columnar shape concentric with the first frame portion, wherein: The torque detection portion has a columnar shape, one end of which is clamped between the bottom surface of the first frame portion and the bottom surface of the second frame portion, and the other end of which is clamped between the bottom surface of the first core portion and the bottom surface of the second core portion. In the torque detection section, film-shaped strain gauges are arranged on two side surfaces perpendicular to the bottom surface of the first frame portion.

10. The torque detection unit according to claim 9, wherein: The torque detection portion has a through hole that penetrates between two side surfaces parallel to the bottom surface of the first frame portion. The torque detection portion is arranged on a radial axis extending radially from the central axis of the first frame portion and has a shape that is line-symmetrical with respect to the radial axis. The opening of the through hole has a shape in which a length in a direction perpendicular to the radiation axis and parallel to the bottom surface of the first frame portion is longer than a length in a direction parallel to the radiation axis.

11. A method for manufacturing a torque sensor, the torque sensor comprising: a first cylindrical frame portion; a second frame portion, which is arranged at a position opposite to the bottom surface of the first frame portion and has a cylindrical shape concentric with the first frame portion; a first core portion, which is arranged in the hollow of the first frame portion and has a cylindrical or columnar shape concentric with the first frame portion; a second core portion, which is arranged in the hollow of the second frame portion and is at a position opposite to the bottom surface of the first core portion and has a cylindrical or columnar shape concentric with the first frame portion; and a torque detection unit, wherein: The manufacturing method of the torque sensor has the following features: A first step of forming a film-shaped strain gauge on a side surface of the torque detection portion formed in a columnar shape; A second step, in which one end of the torque detection portion is sandwiched between the bottom surface of the first frame portion and the bottom surface of the second frame portion, and the other end of the torque detection portion is sandwiched between the bottom surface of the first core portion and the bottom surface of the second core portion; as well as A third step is to fasten the first frame portion and the second frame portion, and to fasten the first core portion and the second core portion. The side surface of the torque detection portion on which the film-shaped strain gauge is formed in the first step is a side surface orthogonal to the bottom surface of the first frame portion and the bottom surface of the second frame portion in the second step.

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