Torque sensor
By adopting a combined structure of holder, bearing and strain sensor in the torque sensor, the elastic deformation of the strain body is used to detect stress, and the problem of the magnetostrictive sensor device is solved, miniaturized and high-sensitivity stress detection is achieved .
Patent Information
- Application Number
- CN202280095907.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-13
- Publication Date
- 2024-12-20
AI Technical Summary
The existing magnetostrictive torque sensors have caused the device to be larger in configurations such as detection coils, making it difficult to achieve miniaturization.
A torque sensor structure including a retainer, bearing and strain sensor is designed, wherein the strain sensor is installed in the elastic part, and the stress in the axis direction is detected by the elastic deformation of the strain body, and the strain sensor is used to detect the strain in the form of a change in resistance value to avoid The magnetic layer and detection coil configuration of the magnetostrictive sensor are provided.
The device is miniaturized, the sensitivity and accuracy of stress detection are improved, the manufacturing process is simplified, and the magnetic layer attachment processing is avoided.
Smart Images
Figure CN119173746A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a torque sensor. Background Art
[0002] As a torque sensor for detecting a force applied to a shaft, a magnetostrictive torque sensor is known. For example, Patent Document 1 discloses a strain detection device including a magnetic layer fixed to the outer peripheral surface of the shaft and a detection coil for detecting a change in magnetic permeability of the magnetic layer.
[0003] Prior art literature
[0004] Patent Literature
[0005] Patent Document 1: Japanese Patent Laid-Open No. 5-52679 Summary of the invention
[0006] Problems to be solved by the invention
[0007] When a magnetostrictive torque sensor is used, it is necessary to arrange a detection coil and the like, so there is a tendency for the entire device around the shaft to become larger. One example of the subject of the present invention is to miniaturize the torque sensor.
[0008] Technical means of solving problems
[0009] The torque sensor of the present invention includes: a retainer, including an inner peripheral component and an outer peripheral component; a bearing, arranged on the inner peripheral component; and a strain sensor, the outer peripheral component includes an elastic part, the strain sensor is installed on the elastic part, and the elastic part and the strain sensor extend respectively along planes parallel to the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] [ Figure 1 ] is a three-dimensional view of a retainer and a strain sensor of a torque sensor according to a first embodiment as an example of the present invention.
[0011] [ Figure 2 ] is a cross-sectional view of a torque sensor according to a first embodiment as an example of the present invention.
[0012] [ Figure 3 ] is a cross-sectional view of a torque sensor according to a second embodiment as an example of the present invention.
[0013] [ Figure 4 ] is a cross-sectional view of a torque sensor according to a third embodiment as an example of the present invention.
[0014] [ Figure 5 ] is a cross-sectional view of a torque sensor according to a fourth embodiment as an example of the present invention.
[0015] [ Figure 6 ] is a plan view of a retainer and a strain sensor of a torque sensor according to a fifth embodiment as an example of the present invention.
[0016] [ Figure 7 ] is a cross-sectional view of a torque sensor according to a fifth embodiment of the present invention, and corresponds to Figure 6 Cross-sectional view of section AA in FIG.
[0017] [ Figure 8 ] is a plan view of a retainer and a strain sensor of a torque sensor according to a sixth embodiment as an example of the present invention.
[0018] [ Fig. 9 ] is a cross-sectional view of a torque sensor according to a sixth embodiment of the present invention, and corresponds to Figure 6 Cross-sectional view of section BB in FIG.
[0019] [ Fig.10 ] is a stereoscopic view of a retainer and a strain sensor of a torque sensor according to the seventh embodiment as an example of the present invention.
[0020] [ Fig.11 ] is a plan view of a retainer and a strain sensor of a torque sensor according to an eighth embodiment as an example of the present invention. DETAILED DESCRIPTION
[0021] In the description of each embodiment of the present invention, for the convenience of description, the arrow a direction along the center axis (axis X) of the axis S is set to the upper side or one side of the axis direction. The arrow b direction along the axis X is set to the lower side or the other side of the axis direction. Here, the arrow ab directions are referred to as the up-down directions or the axis directions. However, the up-down directions are not necessarily consistent with the vertical direction. Moreover, the arrow cd direction is referred to as the radial direction, the arrow c direction away from the axis X is referred to as the outer side or one side of the radial direction, and the arrow d direction close to the axis X is referred to as the inner side or the other side of the radial direction. Furthermore, the direction along the tangent of the circle around the axis X is referred to as the tangent direction.
[0022] [First embodiment]
[0023] Hereinafter, a first embodiment as an example of the present invention will be described with reference to the drawings. Figure 1 It is a perspective view of a holder 101 and a strain sensor 103 used in the torque sensor 100 of the present embodiment. Figure 2 It is a cross-sectional view showing a state where the torque sensor 100 is mounted on the shaft S and the external device 10 .
[0024] The torque sensor 100 includes a retainer 101, a bearing 102, and a strain sensor 103. In the present embodiment, the bearing 102 is a ball bearing including an inner ring 102i, an outer ring 102o, and rolling elements. In addition, the bearing 102 is not limited to a ball bearing, and may be other various bearings such as a sleeve bearing.
[0025] like Figure 1 As shown, the retainer 101 is a substantially square cylindrical shape in a plan view, and includes an inner peripheral member 110 and an outer peripheral member 120. The inner peripheral member 110 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 110a around the axis X. The outer peripheral member 120 is a member arranged at the outer side (one side in the radial direction, the direction of arrow c) of the inner peripheral member 110 in the radial direction.
[0026] In the axial direction, the size of the inner peripheral member 110 is the same as that of the outer peripheral member 120. In the axial direction, the end face on the upper side (one side in the axial direction, the direction of arrow a) and the end face on the lower side (the other side in the axial direction, the direction of arrow b) of the inner peripheral member 110 are respectively on the same plane as the upper end face and the lower end face of the outer peripheral member 120. At the radially outer side and axially upper end of the inner peripheral member 110, four connecting parts 130 that are roughly rectangular in top view protrude radially from the inner peripheral member 110 to the radially outer side. The four connecting parts 130 are arranged at positions that overlap when rotated 90° around the axis X to become rotationally symmetrical (hereinafter referred to as "four-fold symmetry").
[0027] A strain body 121 that is rectangular in a plan view and roughly L-shaped in a side view is connected to each connection portion 130. The strain body 121 is a deformation portion that is deformed due to stress, and elastic deformation or plastic deformation occurs due to stress. The four strain bodies 121 become the peripheral member 120 in this embodiment. Therefore, the connection portion 130 connects the inner peripheral member 110 with the peripheral member 120. The four strain bodies 121 all have the same structure, so only one strain body 121 is described in detail below, and detailed descriptions of the other strain bodies 121 are omitted.
[0028] like Figure 2As shown, in the radial direction, the strain body 121 (peripheral member 120) and the inner peripheral member 110 face each other with a gap 140 extending in the tangential direction. The gap 140 includes a through hole 141 that is circular or substantially circular in a side view, and a slit 142 that is connected to the lower side of the through hole 141 in the axial direction and has a width (radial width) narrower than the diameter of the through hole 141. Due to the presence of the through hole 141, a concave portion 141a that is concave outward in the radial direction is formed on the surface of the inner side in the radial direction (the other side in the radial direction, the direction of arrow d) of the strain body 121 (peripheral member 120), a concave portion 141b that is concave inward in the axial direction is formed on the surface of the lower side in the axial direction of the connecting portion 130, and a concave portion 141c that is concave inward in the radial direction is formed on the surface of the outer side in the radial direction of the inner peripheral member 110. In addition, the concave portion 141 a , the concave portion 141 b , and the concave portion 141 c do not define a boundary portion, and are connected to form a smooth and continuous curved surface.
[0029] The strain body 121 (peripheral member 120) includes an elastic portion 122. That is, a part of the strain body 121 (peripheral member 120) functions as the elastic portion 122. The region slightly above the center in the axial direction of the portion of the strain body 121 extending along a plane perpendicular to the radial direction (the region where the recess 141a is formed) becomes the elastic portion 122. In addition, the portion extending along a plane perpendicular to the radial direction may also be a portion extending in the axial direction. In the radial direction, the elastic portion 122 faces the inner peripheral member 110 across the gap 140. The elastic portion 122 includes a recess 141a that is recessed outward in the radial direction on the surface facing the inner peripheral member 110. The elastic portion 122 is formed with the recess 141a, and the wall thickness (thickness in the radial direction) becomes thinner than other portions of the strain body 121 (peripheral member 120), and elastic strain deformation is easily caused.
[0030] Each strain body 121 of the torque sensor 100 includes an elastic portion 122, and thus the entire torque sensor 100 includes a plurality of (four in this embodiment) elastic portions 122. In the circumferential direction, the plurality of elastic portions 122 are arranged at positions that are four-fold symmetrical ( Figure 1 ).
[0031] In the radial direction, a strain sensor 103 is installed on the outer surface of the elastic part 122. The elastic part 122 and the strain sensor 103 extend along a plane parallel to the axial direction (extend along a plane perpendicular to the radial direction). The strain sensor 103 is installed in a manner that can detect the strain of the elastic part 122 along the plane perpendicular to the tangential direction. Therefore, in the case where the strain sensor 103 is a strain gauge, it is installed on the elastic part 122 in a manner that the direction of the grid (gauge) (typically the length direction of the strain gauge) is along the axial direction. In the case where the strain sensor 103 is a strain gauge, the strain of the elastic part 122 is detected in the form of a change in resistance value. In addition, the strain sensor 103 is not limited to a strain gauge, and can also be various other sensors such as a piezoelectric element.
[0032] In the radial direction, a fixing portion 123 connected to the external device 10 is arranged at the outer side of the strain body 121 relative to the elastic portion 122. The fixing portion 123 is a square plate-shaped portion extending from the lower end of the elastic portion 122 in the axial direction to the outer side in the radial direction. A circular through hole 123h is formed near the center of the fixing portion 123. The strain body 121 is fixed to the external device 10 via the spacer 105 by the bolt 104 inserted into the through hole 123h. Thus, the retainer 101 is fixed to the external device 10.
[0033] In the radial direction, the bearing 102 is arranged inside the inner peripheral member 110 of the retainer 101. The bearing 102 is retained by the inner peripheral member 110 of the retainer 101. The inner ring 102i of the bearing 102 is attached or pressed into the outer peripheral surface (the surface on the outer side in the radial direction) of the cylindrical shaft S. Thus, the inner ring 102i of the bearing 102 is fixed to the shaft S. The outer ring 102o of the bearing 102 is pressed into the inner peripheral surface 110a of the inner peripheral member 110 of the retainer 101. The bearing 102 supports the shaft S in a rotatable manner relative to the retainer 101. The lower end of the shaft S in the axial direction protrudes from the through hole 11 of the external device 10 to the outside of the external device 10.
[0034] The retainer 101 includes an annular contact portion 111 protruding radially inwardly at the end portion on the lower side in the axial direction. In the present embodiment, the contact portion 111 protrudes radially inwardly from the inner peripheral member 110 of the retainer 101. In the axial direction, the contact portion 111 contacts the lower end surface of the outer ring 102o of the bearing 102. Thus, the contact portion 111 supports the bearing 102 in a state where the downward movement is restricted in the axial direction.
[0035] When the torque sensor 100 is used for an electric bicycle, the shaft S is a crankshaft including pedals. When one of the pedals is stepped on, a force that tilts the shaft S downward in the vertical direction is exerted, so that the bearing 102 tends to move in the radial direction, and a portion of the retainer 101 is pushed toward the radial outer side. In the retainer 101, stress is easily concentrated on the elastic portion 122 of the strain body 121, so the elastic portion 122 undergoes elastic strain deformation. The strain deformation can be detected by the strain sensor 103.
[0036] If a plurality of elastic portions 122 to which the strain sensors 103 are attached are arranged, it is possible to detect stresses corresponding to the inclinations in all directions of the axis S. In particular, in the torque sensor 100 of this embodiment, the four strain bodies 121 are arranged at positions that are four-fold symmetrical about the axis X, so it is possible to more accurately detect stresses in all directions of the axis S. The output of the motor of the electric assist bicycle can be adjusted based on the detected stresses.
[0037] The torque sensor 100 of this embodiment does not use a magnetostrictive sensor, but has a simple structure including a holder 101, a bearing 102, and a strain sensor 103. It is not necessary to arrange the detection coil etc. required in the case of using a magnetostrictive sensor around the shaft S, so that the device can be miniaturized. In addition, since it is not necessary to process such as attaching a magnetic layer to the shaft S, the torque sensor 100 can be easily manufactured.
[0038] In the torque sensor 100 of the present embodiment, in the radial direction, the strain body 121 (outer peripheral member 120) faces the inner peripheral member 110 with a gap 140 therebetween, and the elastic portion 122 includes a concave portion 141a that is concave in the radial direction on the surface facing the inner peripheral member 110, and a concave portion 141b that is concave in the axial direction is formed on the axial lower side surface of the connecting portion 130. Thus, in the torque sensor 100 of the present embodiment, the elastic portion 122 of the strain body 121 is easily strained and deformed, and stress can be detected with high sensitivity.
[0039] [Second embodiment]
[0040] Next, a second embodiment as an example of the present invention will be described with reference to the drawings. Figure 32 is a cross-sectional view showing a state where the torque sensor 200 of the present embodiment is mounted on the shaft S and the external device 10. The torque sensor 200 includes a retainer 201 instead of the retainer 101, and has the same structure as the torque sensor 100 of the first embodiment. The retainer 201 includes an inner peripheral member 210 instead of the inner peripheral member 110, and includes a gap 240 having a slightly different shape from the gap 140, and has the same structure as the retainer 101 of the first embodiment. Hereinafter, for components and assemblies having the same functions and structures as those of the first embodiment, the same symbols as those of the first embodiment are marked, and their detailed description is omitted.
[0041] The retainer 201 is a cylindrical shape of a square when viewed from above, and includes an inner peripheral member 210 and an outer peripheral member 120. The inner peripheral member 210 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 210a around the axis X. In the axial direction, the size of the inner peripheral member 210 is the same as that of the outer peripheral member 120. In the axial direction, the upper end face and the lower end face of the inner peripheral member 210 are respectively on the same plane as the upper end face and the lower end face of the outer peripheral member 120. At the radially outer side and axially upper end of the inner peripheral member 210, four connecting parts 130 that are roughly rectangular in a top view protrude radially from the inner peripheral member 210 toward the radially outer side. The four connecting parts 130 are arranged at positions that are four-fold symmetrical around the axis X.
[0042] like Figure 3 As shown, in the radial direction, the strain body 121 (outer peripheral member 120) faces the inner peripheral member 210 via a gap 240 extending in the tangential direction. The gap 240 includes a through hole 241 that is circular or substantially circular in a side view, and a slit 242 that is connected to the lower side of the through hole 241 in the axial direction and slightly radially inward and has a width (diameter) narrower than the diameter of the through hole 241. In the radial direction, the size of the slit 242 is larger than the size of the slit 142 of the first embodiment.
[0043] Due to the presence of the through hole 241, a concave portion 241a that is concave toward the outside in the radial direction is formed on the surface of the strain body 121 (outer peripheral member 120) on the radial inner side (the other side in the radial direction, the direction of arrow d), a concave portion 241b that is concave toward the upper side in the axial direction is formed on the surface of the lower side in the axial direction of the connecting portion 130, and a concave portion 241c that is concave toward the inside in the radial direction is formed on the surface of the inner peripheral member 210 on the radial outer side. In addition, the concave portion 241a, the concave portion 241b, and the concave portion 241c do not define a boundary portion, and are connected to form a smooth and continuous curved surface. In the radial direction, the elastic portion 122 and the inner peripheral member 210 face each other with a gap 240 between them.
[0044] In the radial direction, the bearing 102 is arranged inside the inner peripheral member 210 of the retainer 201. The bearing 102 is retained by the inner peripheral member 210 of the retainer 201. The outer ring 102o of the bearing 102 is press-fitted into the inner peripheral surface 210a of the inner peripheral member 210 of the retainer 201. The bearing 102 supports the shaft S in a rotatable manner relative to the retainer 201.
[0045] The retainer 201 includes an annular contact portion 211 protruding radially inwardly at the end portion on the lower side in the axial direction. In the present embodiment, the contact portion 211 protrudes radially inwardly from the inner peripheral member 210 of the retainer 201. In the axial direction, the contact portion 211 contacts the lower end surface of the outer ring 102o of the bearing 102. Thus, the contact portion 211 supports the bearing 102 in a state where the downward movement is restricted in the axial direction.
[0046] In the present embodiment, a concave portion 212 having a semicircular or substantially semicircular shape in a side view is formed near the end portion on the lower side in the axial direction of the inner circumferential surface 210a of the inner circumferential member 210. The concave portion 212 is formed in a circular ring shape around the axis X on the upper side of the contact portion 211. The end portion on the lower side in the axial direction of the concave surface of the concave portion 212 is smoothly connected to the upper end face of the contact portion 211 in the axial direction.
[0047] The torque sensor 200 of this embodiment has the same characteristics as those described above with respect to the torque sensor 100 of the first embodiment. In addition, in the torque sensor 200 of this embodiment, the recess 212 is formed in addition to the gap 240, and the radial width of the slit 242 is wider than that of the slit 142 ( Figure 2 ), so that the wall thickness of the inner peripheral member 210 near the end portion on the lower side in the axial direction becomes thinner, so that the contact portion 211 is easily elastically deformed toward the lower side in the axial direction. Therefore, even if a preload is applied to the bearing 102 toward the lower side in the axial direction, the contact portion 211 can be elastically deformed to absorb the influence of the preload.
[0048] Therefore, in the torque sensor 200 of the present embodiment, it is possible to suppress the preload of the bearing 102 from appearing as strain in the elastic portion 122 , and the strain sensor 103 can detect stress with high sensitivity.
[0049] [Third Embodiment]
[0050] Next, a third embodiment as an example of the present invention will be described with reference to the drawings. Figure 41 is a cross-sectional view showing a state where the torque sensor 300 of the present embodiment is mounted on the shaft S and the external device 10. The torque sensor 300 includes a retainer 301 instead of the retainer 101, and has the same structure as the torque sensor 100 of the first embodiment. Hereinafter, for components and assemblies having the same functions and structures as those of the first embodiment, the same reference numerals as those of the first embodiment are given, and their detailed description is omitted.
[0051] The retainer 301 is a substantially square cylindrical shape in a plan view, and includes an inner peripheral member 310 and an outer peripheral member 320. The inner peripheral member 310 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 310a around the axis X. The outer peripheral member 320 is a member arranged at the outer side of the inner peripheral member 310 in the radial direction.
[0052] In the axial direction, the size of the inner peripheral member 310 is smaller than that of the outer peripheral member 320. In the axial direction, the upper end surface of the inner peripheral member 310 and the upper end surface of the outer peripheral member 320 are on the same plane. At the radially outer side and axially upper end of the inner peripheral member 310, four substantially rectangular connection parts 330 in a plan view protrude radially from the inner peripheral member 310 toward the radially outer side. Similar to the torque sensor 100 of the first embodiment, the four connection parts 330 are arranged at positions that are four-fold symmetrical around the axis X.
[0053] A strain body 321 that is rectangular in a plan view and roughly in an inverted T-shape in a side view is connected to each connection portion 330. The strain body 321 is a deformation portion that is deformed due to stress, and elastic deformation or plastic deformation occurs due to stress. The four strain bodies 321 become the peripheral member 320 in this embodiment. Therefore, the connection portion 330 connects the inner peripheral member 310 with the peripheral member 320. The four strain bodies 321 all have the same structure, so only one strain body 321 is described in detail below, and detailed descriptions of the other strain bodies 321 are omitted.
[0054] like Figure 4 As shown, in the radial direction, the strain body 321 (outer peripheral member 320) faces the inner peripheral member 310 via a gap 340 extending in the tangential direction. The gap 340 includes a first through hole 341 that is circular or substantially circular in side view, a second through hole 342 that is connected to the lower side of the first through hole 341 in the axial direction and has a diameter equal to or slightly smaller than that of the first through hole 341, and a slit 343 that extends from the lower end of the second through hole 342 in the axial direction toward the inner side of the radial direction to the bearing 102.
[0055] Due to the existence of the first through hole 341, a concave portion 341a that is concave outward in the radial direction is formed on the radially inner surface of the strain body 321 (outer peripheral member 320), a concave portion 341b that is concave inward in the axial direction is formed on the axially lower surface of the connecting portion 330, and a concave portion 341c that is concave inward in the radial direction is formed on the radially outer surface of the inner peripheral member 310. In addition, the concave portions 341a, 341b, and 341c do not define a boundary portion, and are connected to form a smooth and continuous curved surface.
[0056] The strain body 321 (peripheral member 320) includes an elastic portion 322. The region slightly above the center of the axial direction in the portion of the strain body 321 extending along a plane perpendicular to the radial direction (the region where the recess 341a is formed) becomes the elastic portion 322. In the radial direction, the elastic portion 322 faces the inner peripheral member 310 with a gap 340 therebetween. The elastic portion 322 includes a recess 341a that is recessed outward in the radial direction on the surface facing the inner peripheral member 310. The elastic portion 322 has a thinner wall thickness (thickness in the radial direction) than other portions of the strain body 321 (peripheral member 320) due to the formation of the recess 341a, and is prone to elastic strain deformation.
[0057] As with the torque sensor 100 of the first embodiment, each strain body 321 of the torque sensor 300 includes an elastic portion 322, and thus the entirety includes a plurality (four in this embodiment) of elastic portions 322. In the circumferential direction, the plurality of elastic portions 322 are arranged at positions that are four-fold symmetrical on the outside of the retainer 301 (outward in the radial direction relative to the inner peripheral member 310).
[0058] In the radial direction, a strain sensor 103 is installed on the outer surface of the elastic part 322. The elastic part 322 and the strain sensor 103 extend along a plane parallel to the axial direction (extend along a plane perpendicular to the radial direction). The strain sensor 103 is installed in a manner that can detect the strain of the elastic part 322 along the plane perpendicular to the tangential direction. Therefore, in the case where the strain sensor 103 is a strain gauge, it is installed on the elastic part 322 in a manner that the direction of the grid (gauge) (typically the length direction of the strain gauge) is along the axial direction. In the case where the strain sensor 103 is a strain gauge, the strain of the elastic part 322 is detected in the form of a change in resistance value. In addition, the strain sensor 103 is not limited to a strain gauge, and can also be various other sensors such as a piezoelectric element.
[0059] In the radial direction, the bearing 102 is arranged inside the inner peripheral member 310 of the retainer 301. The bearing 102 is retained by the inner peripheral member 310 of the retainer 301. The outer ring 102o of the bearing 102 is press-fitted into the inner peripheral surface 310a of the inner peripheral member 310 of the retainer 301. The bearing 102 supports the shaft S in a rotatable manner relative to the retainer 301.
[0060] The retainer 301 includes a plate-shaped contact portion 324 protruding radially inwardly at the end portion on the lower side in the axial direction of the retainer 301. In the present embodiment, the contact portion 324 protrudes radially inwardly from the end portion on the lower side in the axial direction of the strain body 321 (peripheral member 320) of the retainer 301. In the axial direction, the contact portion 324 faces the inner peripheral member 310 across the slit 343. The tangential dimension of the contact portion 324 is the same as the tangential dimension of the elastic portion 322 and the fixing portion 123. However, the contact portion 324 may also be formed in a circular ring around the axis X. In the axial direction, the contact portion 324 contacts the lower end surface of the outer ring 102o of the bearing 102. Thus, the contact portion 324 supports the bearing 102 in the axial direction in a state where the downward movement is restricted.
[0061] The torque sensor 300 of this embodiment also has the characteristics described in relation to the torque sensor 100 of the first embodiment. In addition, in the torque sensor 300 of this embodiment, the plate-shaped contact portion 324 protruding radially inward from the outer peripheral member 320 of the retainer 301 supports the bearing 102 along the axial direction. Thus, even when a preload is applied to the bearing 102 downward in the axial direction, the contact portion 324 can be elastically deformed to absorb the influence of the preload. Furthermore, since the contact portion 324 is not provided on the inner peripheral member, the influence of the preload is not transmitted to the elastic portion 322 via the connecting portion 330.
[0062] Therefore, in the torque sensor 300 of the present embodiment, the preload of the bearing 102 that appears as strain in the elastic portion 322 can be further suppressed, so that the strain sensor 103 can detect stress with higher sensitivity.
[0063] [Fourth Embodiment]
[0064] Next, a fourth embodiment as an example of the present invention will be described with reference to the drawings. Figure 54 is a cross-sectional view showing a state where the torque sensor 400 of this embodiment is mounted on the shaft S and the external device 40. The torque sensor 400 includes a retainer 401 instead of the retainer 101, and the external device 10 is replaced by the external device 40, and has the same structure as the torque sensor 100 of the first embodiment. The retainer 401 includes an inner peripheral member 410 instead of the inner peripheral member 110, and the gap 140 is replaced by a gap 440 with a different shape, and has the same structure as the retainer 101 of the first embodiment. Hereinafter, for the components and assemblies having the same functions and structures as those of the first embodiment, the same reference numerals as those of the first embodiment are marked, and their detailed description is omitted.
[0065] The retainer 401 is a cylindrical shape of a square in a top view, and includes an inner peripheral member 410 and an outer peripheral member 120. The inner peripheral member 410 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 410a around the axis X. In the axial direction, the size of the inner peripheral member 410 is smaller than the size of the outer peripheral member 120. In the axial direction, the upper end surface of the inner peripheral member 410 and the upper end surface of the outer peripheral member 120 are on the same plane. At the radially outer side and axially upper end of the inner peripheral member 410, four connecting parts 130 that are roughly rectangular in a top view protrude radially from the inner peripheral member 410 to the radially outer side. The four connecting parts 130 are arranged at positions that are four-fold symmetrical around the axis X.
[0066] like Figure 5 As shown, in the radial direction, the strain body 121 (outer peripheral member 120) faces the inner peripheral member 410 via a gap 440 extending in the tangential direction. The gap 440 includes a through hole 441 that is circular or substantially circular in a side view, and a slit 442 that is connected to the lower side of the through hole 441 in the axial direction and has a width (dimension in the radial direction) narrower than the diameter of the through hole 441. The slit 442 expands in a manner that is concave in a circular arc shape in a side view toward the radial inner side as it moves toward the lower side in the axial direction.
[0067] Due to the presence of the through hole 441, a concave portion 441a that is concave outward in the radial direction is formed on the surface of the strain body 121 (peripheral member 120) on the radial inner side (the other side in the radial direction, the direction of arrow d), a concave portion 441b that is concave inward in the axial direction is formed on the surface of the lower side in the axial direction of the connecting portion 130, and a concave portion 441c that is concave inward in the radial direction is formed on the surface of the radial outer side of the inner peripheral member 410. In addition, the concave portion 441a, the concave portion 441b, and the concave portion 441c do not define a boundary portion, and are connected to form a smooth and continuous curved surface. In the radial direction, the elastic portion 122 and the inner peripheral member 410 face each other with a gap 440 between them.
[0068] In the radial direction, the bearing 102 is arranged inside the inner peripheral member 410 of the retainer 401. The bearing 102 is retained by the inner peripheral member 410 of the retainer 401. The outer ring 102o of the bearing 102 is press-fitted into the inner peripheral surface 410a of the inner peripheral member 410 of the retainer 401. The bearing 102 supports the shaft S in a rotatable manner relative to the retainer 401.
[0069] The external device 40 includes a protrusion 42 that protrudes upward in the axial direction toward the bearing 102 and is formed in a circular ring around the axis X. However, the protrusion 42 may also be a plurality of convex portions arranged on the circumference around the axis X. In the axial direction, the protrusion 42 contacts the lower end surface of the bearing 102. Thus, the protrusion 42 supports the bearing 102 in a state where the downward movement is restricted in the axial direction. More specifically, in the axial direction, the protrusion 42 supports the bearing 102 by contacting the lower end surface of the outer ring 102o.
[0070] The torque sensor 400 of this embodiment also has the characteristics described in relation to the torque sensor 100 of the first embodiment. In addition, in the torque sensor 400 of this embodiment, the protrusion 42 supports the bearing 102 along the axial direction, so there is no situation where the preload in the axial direction of the bearing 102 is expressed as strain of the elastic portion 122, and the strain sensor 103 can detect stress with higher sensitivity.
[0071] [Fifth Embodiment]
[0072] Next, a fifth embodiment as an example of the present invention will be described with reference to the drawings. Figure 6 It is a plan view of a holder 501 and a strain sensor 503 of a torque sensor 500 according to the present embodiment. Figure 7 The torque sensor 500 is mounted on the shaft S and the external device 50. Figure 6 Cross-sectional view of the cross section corresponding to the AA cross section.
[0073] The torque sensor 500 includes a retainer 501, a bearing 502, and a strain sensor 503. In the present embodiment, the bearing 502 is a ball bearing including an inner ring 502i, an outer ring 502o, and rolling elements. In addition, the bearing 502 is not limited to a ball bearing, and may be other various bearings such as a sleeve bearing.
[0074] The retainer 501 is a substantially square cylindrical shape in a plan view, and includes an inner peripheral member 510 and an outer peripheral member 520. The inner peripheral member 510 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 510a around the axis X. The outer peripheral member 520 is a member arranged at the outer side of the inner peripheral member 510 in the radial direction.
[0075] In the axial direction, the size of the inner peripheral member 510 is the same as that of the outer peripheral member 520. In the axial direction, the upper and lower end surfaces of the inner peripheral member 510 are on the same plane as those of the outer peripheral member 520.
[0076] In the radial direction, two strain bodies 521 are connected to the outer side of the inner peripheral member 510 in a mirror-symmetrical manner relative to the plane including the axis X. The strain body 521 is a deformation portion that is deformed due to stress, and undergoes elastic deformation or plastic deformation due to stress. The strain body 521 is a roughly rectangular parallelepiped with the tangent direction set as the length direction, and is formed in the central part of the length direction along the outer shape of the inner peripheral member 510 to form an arc-shaped shape that lacks about half of the radial dimension. The two strain bodies 521 become the peripheral member 520 in this embodiment. The two strain bodies 521 have the same structure, and therefore, only one strain body 521 is described in detail below, and detailed descriptions of the other strain bodies 521 are omitted.
[0077] like Figure 6 As shown in the figure, two through holes 541 are formed in the axial direction, one each near the middle of the longitudinal center and the two ends of the strain body 521, and are circular or substantially circular in plan view. In addition, two slits 542 are formed in the strain body 521, extending from the vicinity of the connection portion with the inner peripheral member 510 in the surface facing the inner peripheral member 510 to the through hole 541 along the tangential direction. The width of the slit 542 is narrower than the diameter of the through hole 541. The through hole 541 and the slit 542 constitute the gap 540.
[0078] The strain body 521 (peripheral member 520) includes an elastic portion 522. The area near the through hole 541 in the portion of the strain body 521 extending along a plane perpendicular to the radial direction becomes the elastic portion 522. In the radial direction, the elastic portion 522 faces the inner peripheral member 510 with the gap 540 therebetween. The elastic portion 522 includes a recessed portion (a portion of the through hole 541) that is recessed in the radial direction on the surface facing the inner peripheral member 510. Due to the presence of the through hole 541, the elastic portion 522 has a thinner wall thickness than other portions of the strain body 521 (peripheral member 520), and is prone to elastic strain deformation.
[0079] Each strain body 521 of the torque sensor 500 includes an elastic portion 522, and thus the entire torque sensor 500 includes a plurality of (four in this embodiment) elastic portions 522. The plurality of elastic portions 522 are arranged circumferentially outside the retainer 501 (outward in the radial direction relative to the inner peripheral member 510).
[0080] Two strain sensors 503 are installed on the surface of each strain body 521 which is opposite to the side connected to the inner peripheral member 510. The strain sensor 503 is installed on the elastic part 522 of the strain body 521. The elastic part 522 and the strain sensor 503 extend along a plane extending in the axial direction and the length direction of the strain body 521. The strain sensor 503 is installed in a manner that can detect the strain of the elastic part 522 along the plane perpendicular to the axial direction. Therefore, in the case where the strain sensor 503 is a strain gauge, it is installed in the elastic part 522 in a manner that the direction of the grid (gauge) (typically the length direction of the strain gauge) is along the length direction of the strain body 521. In the case where the strain sensor 503 is a strain gauge, the strain of the elastic part 522 is detected in the form of a change in resistance value. In addition, the strain sensor 503 is not limited to a strain gauge, and can also be various other sensors such as a piezoelectric element.
[0081] The strain body 521 has a fixing portion 523 connected to the external device 50 at both ends in the longitudinal direction of the elastic portion 522. A through hole 523h is formed near the center of the fixing portion 523 and is circular in plan view and penetrates along the axial direction. Figure 7 As shown, the strain body 521 is fixed to the external device 50 via the spacer 505 by the bolt 504 inserted into the through hole 523h from the upper side in the axial direction. Thus, the holder 501 is fixed to the external device 50.
[0082] In the radial direction, the bearing 502 is arranged on the inner side of the inner peripheral member 510 of the retainer 501. The bearing 502 is retained by the inner peripheral member 510 of the retainer 501. The inner ring 502i of the bearing 502 is attached or pressed into the outer peripheral surface (the surface on the outer side in the radial direction) of the cylindrical shaft S. Thus, the inner ring 502i of the bearing 502 is fixed to the shaft S. The outer ring 502o of the bearing 502 is pressed into the inner peripheral surface 510a of the inner peripheral member 510 of the retainer 501. The bearing 502 supports the shaft S in a rotatable manner relative to the retainer 501. The lower end of the shaft S in the axial direction protrudes from the through hole 51 of the external device 50 to the outside of the external device 50.
[0083] The retainer 501 includes an annular contact portion 511 protruding radially inwardly at the end portion on the lower side in the axial direction. In the present embodiment, the contact portion 511 protrudes radially inwardly from the inner peripheral member 510 of the retainer 501. In the axial direction, the contact portion 511 contacts the lower end surface of the outer ring 502o of the bearing 502. Thus, the contact portion 511 supports the bearing 502 in a state where the downward movement is restricted in the axial direction.
[0084] When the torque sensor 500 is used for an electric bicycle, the shaft S is a crankshaft including a pedal. When one of the pedals is stepped on, a force that tilts the pedal side of the shaft S downward in the vertical direction acts, so that the bearing 502 tends to move in the radial direction, and a part of the retainer 501 is pushed toward the radial outer side. In the retainer 501, stress is easily concentrated on the elastic part 522 of the strain body 521, so the elastic part 522 undergoes elastic strain deformation. The strain deformation can be detected by the strain sensor 503.
[0085] In the torque sensor 500 of this embodiment, four elastic parts 522 on which the strain sensors 503 are mounted are arranged in a row on the outside of the holder 501 in the circumferential direction, so that stresses in all directions can be detected more accurately. In particular, in the torque sensor 500, two strain bodies 521 are arranged in a mirror-symmetrical manner with respect to a plane including the axis X, so stresses in two directions with respect to the arrangement of the strain bodies 521 can be detected with higher sensitivity. The output of the motor of the electric assist bicycle can be adjusted according to the detected stress.
[0086] The torque sensor 500 of this embodiment does not use a magnetostrictive sensor, and has a simple structure including a retainer 501, a bearing 502, and a strain sensor 503. It is not necessary to arrange the detection coils and the like required in the case of using a magnetostrictive sensor around the shaft S, so that the device can be miniaturized. In particular, in the torque sensor 500, the number of strain bodies is as small as two, and the structure can be compact, so the device can be further miniaturized. In addition, since there is no need for processing such as attaching a magnetic layer to the shaft S, the torque sensor 500 is easy to manufacture.
[0087] In the torque sensor 500 of the present embodiment, in the radial direction, the elastic portion 522 faces the inner peripheral member 510 with the gap 140 therebetween, and the elastic portion 522 includes a recessed portion recessed in the radial direction on the surface facing the inner peripheral member 510. Therefore, in the torque sensor 500 of the present embodiment, the elastic portion 522 of the strain body 521 is easily strained and deformed, and stress can be detected with high sensitivity.
[0088] [Sixth Embodiment]
[0089] Next, a sixth embodiment as an example of the present invention will be described with reference to the drawings. Figure 8 It is a plan view of the holder 601 and the strain sensor 503 of the torque sensor 600 according to the present embodiment. Fig. 9 The torque sensor 600 is mounted on the shaft S and the external device 60. Figure 8BB section in FIG. 6 is a cross-sectional view of a section corresponding to the BB section in FIG. 6. The torque sensor 600 includes a retainer 601 instead of the retainer 501, and has the same structure as the torque sensor 500 of the fifth embodiment. Hereinafter, for components and assemblies having the same functions and structures as those of the fifth embodiment, the same reference numerals as those of the fifth embodiment are given, and their detailed description is omitted.
[0090] The torque sensor 600 includes a retainer 601, a bearing 502, and a strain sensor 503. The retainer 601 is a substantially square cylindrical shape in a plan view, and includes an inner peripheral member 610 and an outer peripheral member 620. The inner peripheral member 610 is a cylindrical member extending along the axial direction and including a cylindrical inner peripheral surface 610a around the axis X. The outer peripheral member 620 is a member arranged at a position further outside than the inner peripheral member 610 in the radial direction. The general structure of the retainer 601 is similar to the retainer 501 of the torque sensor 500 of the fifth embodiment, but the inner peripheral member 610 is long in the axial direction, and the inner peripheral member 610 and the outer peripheral member 620 are connected in a manner that deviates from each other in the axial direction, which are different from the retainer 501 of the torque sensor 500 of the fifth embodiment.
[0091] like Fig. 9 As shown, in the axial direction, the size of the inner peripheral member 610 is larger than that of the outer peripheral member 620. In the axial direction, the upper end face and the lower end face of the inner peripheral member 610 are respectively arranged above the upper end face and the lower end face of the outer peripheral member 620. The upper end of the outer peripheral member 620 in the axial direction is connected to the vicinity of the lower end of the inner peripheral member 610 in the axial direction.
[0092] The retainer 601 includes a circular ring-shaped contact portion 611 protruding inward in the radial direction slightly above the central portion in the axial direction. In the axial direction, the contact portion 611 is arranged at a position higher than the upper end portion of the outer peripheral member 620 in the axial direction. In the present embodiment, the contact portion 611 protrudes inward in the radial direction from the inner peripheral member 610 of the retainer 601. In the axial direction, the contact portion 611 contacts the lower end surface of the outer ring 502o of the bearing 502. Thus, the contact portion 611 supports the bearing 502 in the axial direction in a state where the downward movement is restricted.
[0093] In the axial direction, the portion of the inner peripheral member 610 that is lower than the contact portion 611 penetrates the external device 60 and extends to the lower side of the external device 60. In the axial direction, the outer peripheral member 620 is arranged on the lower side of the external device 60 (outside the external device 60). The bolt 504 is inserted into the through hole 523h of the fixing portion 523 formed in the strain body 521 of the outer peripheral member 620 from the lower side in the axial direction. The strain body 521 is screwed to the external device 60 via the spacer 505.
[0094] The torque sensor 600 of this embodiment also has the characteristics described in relation to the torque sensor 500 of the fifth embodiment. In addition, in the torque sensor 600 of this embodiment, the peripheral member 620 is disposed outside the external device 60, so that the internal structure of the external device 60 can be further simplified, thereby enabling further miniaturization of the device.
[0095] [Seventh Embodiment]
[0096] Next, a seventh embodiment as an example of the present invention will be described with reference to the drawings. Fig.10 It is a perspective view of a holder 701 and a strain sensor 703 of the torque sensor according to the present embodiment.
[0097] The torque sensor of this embodiment includes a holder 701, a bearing (not shown), and a strain sensor 703. The holder 701 is in the shape of a plate and includes an inner peripheral member 710 and an outer peripheral member 720. The inner peripheral member 710 is a plate-shaped member having a substantially square shape in a plan view and including a cylindrical inner peripheral surface 710a around the axis X. The outer peripheral member 720 is a member arranged at a radially outer side of the inner peripheral member 710.
[0098] In the two surfaces facing each other across the axis X in the outer peripheral surface (the surface on the outer side in the radial direction) of the inner peripheral member 710, a strain body 721 is connected to each of the central parts. The strain body 721 is a member whose end on the outer side in the radial direction is roughly semicircular when viewed from above and extends with the radial direction as the length direction. In the tangential direction, the size of the strain body 721 is smaller than the size of the inner peripheral member 710. The two strain bodies 721 become the outer peripheral members 720 in this embodiment. The two strain bodies 721 have the same structure, and therefore, only one strain body 721 is described in detail below, and detailed descriptions of the other strain bodies 721 are omitted.
[0099] In the strain body 721 (outer peripheral member 720), a through hole (gap) 740 is formed that penetrates along the axial direction near the connection portion with the inner peripheral member 710. The through hole 740 is a shape in which two circular or substantially circular holes arranged along the tangential direction in plan view are connected by a rectangular hole in plan view.
[0100] The strain body 721 (peripheral member 720) includes an elastic portion 722. In the strain body 721, two portions facing each other in the tangential direction across the through hole 740 become the elastic portion 722. By forming the through hole 740, the elastic portion 722 has a thinner wall thickness than other portions of the strain body 721 (peripheral member 720), and is more susceptible to elastic strain deformation.
[0101] Each strain body 721 of the retainer 701 includes two elastic portions 722, so the entire retainer 701 includes a plurality of (four in this embodiment) elastic portions 722. The plurality of elastic portions 722 are arranged on the outside of the retainer 701 (outside in the radial direction relative to the inner peripheral member 710) in the circumferential direction.
[0102] Two strain sensors 703 are installed on the outer peripheral surface of each strain body 721. The strain sensor 703 is installed on the elastic part 722. The elastic part 722 and the strain sensor 703 extend along the axial direction and the protruding direction (length direction) of the strain body 721. The strain sensor 703 is installed in a manner that can detect the strain of the elastic part 722 along the direction of the plane perpendicular to the axial direction. Therefore, in the case where the strain sensor 703 is a strain gauge, it is installed on the elastic part 722 in a manner that the direction of the grid (gauge) (typically the length direction of the strain gauge) is along the protruding direction (length direction) of the strain body 721. In the case where the strain sensor 703 is a strain gauge, the strain of the elastic part 722 is detected in the form of a change in resistance value. In addition, the strain sensor 703 is not limited to a strain gauge, and can also be various other sensors such as a piezoelectric element.
[0103] In the radial direction, the outer side of the strain body 721 relative to the elastic portion 722 forms a fixing portion 723 connected to an external device (not shown). A circular through hole 723h is formed near the center of the fixing portion 723. The retainer 701 can be fixed to the external device by bolts or the like through the through hole 723h.
[0104] In the radial direction, a bearing not shown is arranged inside the inner peripheral member 710 of the retainer 701. The retainer 701 includes an annular contact portion 711 protruding inwardly in the radial direction at the end portion on the lower side in the axial direction. In the present embodiment, the contact portion 711 protrudes inwardly in the radial direction from the inner peripheral member 710 of the retainer 701. In the axial direction, the contact portion 711 contacts the lower end surface of the bearing. Thus, the contact portion 711 can support the bearing along the axial direction.
[0105] When the torque sensor including the retainer 701 is used in an electric assisted bicycle, the shaft S is a crankshaft including a pedal. When one of the pedals is stepped on, the force of the pedal side of the shaft S tilting downward in the vertical direction acts, so the bearing tends to move in the radial direction, and a part of the retainer 701 is pushed toward the radial outer side. In the retainer 701, stress is easily concentrated on the elastic part 722 of the strain body 721, so the elastic part 722 undergoes elastic strain deformation. The strain deformation can be detected by the strain sensor 703.
[0106] The torque sensor of this embodiment does not use a magnetostrictive sensor, and has a simple structure including a retainer 701, a bearing, and a strain sensor 703. It is not necessary to configure a detection coil or the like around the shaft, which is required when using a magnetostrictive sensor, so the device can be miniaturized. In addition, it is not necessary to process the magnetic layer of the shaft, so it is easy to manufacture the torque sensor. In particular, the retainer 701 of the torque sensor of this embodiment is in the shape of a flat plate, and is fixed to an external device only by two fixing parts 723, so the structure is simple, and the device can be further miniaturized.
[0107] [Eighth Embodiment]
[0108] Next, an eighth embodiment as an example of the present invention will be described with reference to the drawings. Fig.11 It is a plan view of a holder 801 and a strain sensor 803 of the torque sensor according to the present embodiment.
[0109] The torque sensor of this embodiment includes a retainer 801, a bearing (not shown), and a strain sensor 803. The retainer 801 is flat and generally rhombus-shaped in a plan view, and includes an inner peripheral member 810 and an outer peripheral member 820. The inner peripheral member 810 is an annular member including a cylindrical inner peripheral surface 810a around the axis X. The outer peripheral member 820 is a member arranged at a radially outer side than the inner peripheral member 810.
[0110] In the radial direction, on the outer side of the inner peripheral member 810, at a position that is twice symmetrical around the axis X, two small annular fixing portions 823 are arranged slightly separated from the inner peripheral member 810. Near the four tangents circumscribed to the inner peripheral member 810 and the two fixing portions 823, four beam-shaped elastic portions 822 connect the inner peripheral member 810 and the two fixing portions 823. The two fixing portions 823 and the elastic portion 822 form the outer peripheral member 820 in this embodiment. In the circumferential direction, the four elastic portions 822 are arranged in an array on the outer side of the retainer 801 (closer to the outer side in the radial direction than the inner peripheral member 810). A gap 840 is formed between the inner peripheral member 810 and the fixing portion 823. In the radial direction, the elastic portion 822 and the inner peripheral member 810 face each other across the gap 840.
[0111] A strain sensor 803 is installed on the surface of each elastic part 822 that is opposite to the surface facing the inner peripheral member 810. The elastic part 822 and the strain sensor 803 extend along planes parallel to the axial direction, respectively. The strain sensor 803 is installed in a manner that can detect the strain of the elastic part 822 along the plane perpendicular to the axial direction. Therefore, in the case where the strain sensor 803 is a strain gauge, it is installed on the elastic part 822 in a manner that the direction of the grid (gauge) (typically the length direction of the strain gauge) is along the length direction of the elastic part 822. In the case where the strain sensor 803 is a strain gauge, the strain of the elastic part 822 is detected in the form of a change in resistance value. In addition, the strain sensor 803 is not limited to a strain gauge, and can also be various other sensors such as a piezoelectric element.
[0112] The fixing portion 823 is a portion connected to an external device (not shown). In the radial direction, the fixing portion 823 is arranged outside the elastic portion 822. A circular through hole 823h is formed near the center of the fixing portion 823. The retainer 801 can be fixed to the external device by a bolt or the like through the through hole 823h.
[0113] In the radial direction, a bearing not shown is arranged inside the inner peripheral member 810 of the retainer 801. The retainer 801 includes an annular contact portion 811 protruding inwardly in the radial direction at the end portion on the lower side in the axial direction. In the present embodiment, the contact portion 811 protrudes inwardly in the radial direction from the inner peripheral member 810 of the retainer 801. In the axial direction, the contact portion 811 contacts the lower end surface of the bearing. Thus, the contact portion 811 can support the bearing along the axial direction.
[0114] The torque sensor of this embodiment has the same characteristics as those described for the torque sensor of Embodiment 7. Furthermore, the holder 801 of the torque sensor of this embodiment is lightweight, so that the weight of the device can be reduced.
[0115] The torque sensor of the present invention has been described above by way of preferred embodiments, but the torque sensor of the present invention is not limited to the structures of the embodiments. For example, each torque sensor of the embodiments is used for an electric assisted bicycle, but the torque sensor of the present invention is not limited to being used for an electric assisted bicycle.
[0116] In addition, the industry can appropriately change the torque sensor of the present invention or change the combination of various structures according to the existing known knowledge. As long as the structure of the present invention is still provided through the above changes, it is naturally included in the scope of the present invention.
[0117] Explanation of symbols
[0118] 10, 40, 50, 60: External device
[0119] 42: Protrusion
[0120] 100, 200, 300, 400, 500, 600: Torque sensor
[0121] 101, 201, 301, 401, 501, 601, 701, 801: Retainer
[0122] 102, 202, 302, 402, 502, 602, 702, 802: bearings
[0123] 103, 203, 303, 403, 503, 603, 703, 803: Strain sensors
[0124] 110, 210, 310, 410, 510, 610, 710, 810: Inner peripheral components
[0125] 111, 211, 324, 511, 611, 711, 811: Contact Department
[0126] 120, 220, 320, 420, 520, 620, 720, 820: Peripheral components
[0127] 122, 222, 322, 422, 522, 622, 722, 822: elastic part
[0128] 123, 223, 323, 423, 523, 623, 723, 823: Fixed part
[0129] 140, 240, 340, 440, 540, 640, 740, 840: gap
Claims
1. A torque sensor, include: A retainer, comprising an inner peripheral component and an outer peripheral component; A bearing, disposed on the inner peripheral member; and Strain sensors, The peripheral member includes an elastic portion, The strain sensor is mounted on the elastic part, The elastic portion and the strain sensor extend along planes parallel to the axial direction respectively.
2. The torque sensor according to claim 1, include: a plurality of elastic parts, including said elastic part, The plurality of elastic portions are arranged side by side on the outer side of the retainer in the circumferential direction. 3 . The torque sensor according to claim 1 , wherein in a radial direction, the elastic portion faces the inner peripheral member of the holder with a gap therebetween. 4 . The torque sensor according to claim 3 , wherein the elastic portion includes a recessed portion recessed in a radial direction on a surface facing the inner peripheral member.
5. The torque sensor according to claim 3, include: The connecting portion connects the inner peripheral member and the outer peripheral member, and the connecting portion includes a recessed portion recessed in the axial direction. 6 . The torque sensor according to claim 1 , wherein the holder includes a contact portion that contacts the bearing along an axial direction. 7 . The torque sensor according to claim 6 , wherein the contact portion protrudes from the inner peripheral member of the holder in a radial direction. 8 . The torque sensor according to claim 6 , wherein the contact portion protrudes from the outer peripheral member of the holder in a radial direction.
9. The torque sensor according to claim 1, include: The fixing portion is connected to an external device and is arranged outside the elastic portion in a radial direction. 10 . The torque sensor according to claim 9 , wherein the external device includes a protrusion which protrudes toward the bearing.