Sensor device

Abstract

Provided is, for example, a sensor device having a structure that can be easily thinned.　For example, a sensor device (100, 200, 300) comprises: a shaft (S); a strain-generating body (101) that has a surface (101a) extending in the radial direction; a bearing (102) that connects the shaft (S) and the strain-generating body (101) in the radial direction; a holder (104) that rotates together with a ring (102r) of the bearing (102); a strain sensor (103) that is attached to the surface (101a); and a substrate (105), wherein the strain sensor (103) and the substrate (105) are electrically connected to each other.

Description

Sensor Device

[0001] The present invention relates to a sensor device.

[0002] A sensor using a Hall element or a magnetoresistive element is known as a sensor for detecting the rotation speed of a shaft. For example, Patent Document 1 discloses a device including an encoder fixed to a member disposed in the space between a bearing and a shaft, and a sensor fixed to a vehicle or the like.

[0003] Japanese Patent Application Publication No. 6-94029

[0004] For example, devices such as the motor drive unit of an electrically assisted bicycle may include a sensor (cadence sensor) for detecting the rotational speed of the shaft, as well as a sensor (torque sensor) for detecting the torque on the shaft. In such devices, multiple sensors each occupy space, which can lead to problems such as increased size and reduced design freedom. One of the objectives of the present invention is to provide a sensor device with a structure that can be easily made thinner.

[0005] A sensor device that is an example of the present invention includes a shaft, a strain element having a surface extending in the radial direction, a bearing that connects the shaft and the strain element in the radial direction, a holder that rotates together with a ring of the bearing, a strain sensor attached to the radially extending surface, and a substrate, wherein the strain sensor and the substrate are electrically connected.

[0006] 1 is a perspective view of a sensor device according to a first embodiment which is an example of the present invention; FIG. 2 is another perspective view of the sensor device according to the first embodiment which is an example of the present invention; FIG. 3 is a cross-sectional view of the sensor device according to the first embodiment which is an example of the present invention; FIG. 4 is a perspective view of a strain-generating body of the sensor device according to the first embodiment which is an example of the present invention; FIG. 5 is a perspective view showing a partial configuration of the sensor device according to the first embodiment which is an example of the present invention; FIG. 6 is a partial cross-sectional view showing a partial configuration of the sensor device according to the first embodiment which is an example of the present invention; FIG. 7 is a perspective view showing an arrangement of a holder and a substrate of the sensor device according to the first embodiment which is an example of the present invention; FIG. 8 is a perspective view showing a part of a shaft of the sensor device according to the first embodiment which is an example of the present invention; FIG. 9 is a partial cross-sectional view of a sensor device according to a modified example; FIG. 10 is a perspective view showing an example of an elastic body of the sensor device according to the modified example; FIG. 11 is a partial cross-sectional view of a sensor device according to another modified example; FIG. 12 is a perspective view showing a part of a configuration of a sensor device according to a second embodiment which is an example of the present invention; FIG. 13 is a partial cross-sectional view of a sensor device according to the second embodiment which is an example of the present invention; FIG. 14 is a perspective view showing a part of a shaft of the sensor device according to the second embodiment which is an example of the present invention; 10A and 10B are diagrams illustrating the arrangement of a flexible substrate, a rigid member, and a bonding member of a sensor device according to a third embodiment, which is one example of the present invention.

[0007] In describing the embodiments of the present invention, for convenience of explanation, the direction along the axis X (the central axis of the shafts S, S4, and S5) will be referred to as the axial direction. In the axial direction, the direction from the strain bodies 101, 401, and 501 to the holders 104, 404, and 504 (the direction of arrow a) will be referred to as one side, and the opposite direction (the direction of arrow b) will be referred to as the other side. Furthermore, the direction of arrows c and d perpendicular to the axis X will be referred to as the radial direction, the direction of arrow c away from the axis X will be referred to as the outer side or one side in the radial direction, and the direction of arrow d approaching the axis X will be referred to as the inner side or other side in the radial direction. In a given member or part, the surface on the outer side in the radial direction (the direction of arrow c) will be referred to as the outer peripheral surface, and the surface on the inner side in the radial direction (the direction of arrow d) will be referred to as the inner peripheral surface. Furthermore, the direction of rotation around the axis X will be referred to as the circumferential direction.

[0008] First Embodiment A first embodiment of the present invention will now be described with reference to the drawings (FIGS. 1 to 8). FIG. 1 is a perspective view of a sensor device 100 according to this embodiment. FIG. 2 is a perspective view of the sensor device 100 from another angle. FIG. 3 is a cross-sectional view of the sensor device 100. FIG. 4 is a perspective view of a strain element 101 included in the sensor device 100. FIG. 5 is a perspective view showing a portion of the configuration of the sensor device 100 (the strain element 101, the bearing 102, the holder 104, and the strain sensor 103). FIG. 6 is a partially cross-sectional perspective view showing a portion of the configuration of the sensor device 100. FIG. 7 is a perspective view showing the arrangement of the holder 104 and the substrate 105 included in the sensor device 100. FIG. 8 is a perspective view showing a portion of a shaft included in the sensor device 100.

[0009] As shown in FIGS. 1 to 3 , the sensor device 100 includes a shaft S, a strain element 101, a bearing 102, a strain sensor 103, a holder 104, and a substrate 105. The strain element 101 has a surface 101a extending in the radial direction, and the strain sensor 103 is attached to the surface 101a. The shaft S and the strain element 101 are connected in the radial direction by a bearing 102. In this embodiment, the bearing 102 is a ball bearing having a ring 102r (an inner ring 102i and an outer ring 102o) and rolling elements 102b. Note that the bearing 102 is not limited to a ball bearing and may be various other bearings, such as a sleeve bearing. Furthermore, although the bearing 102 is illustrated as a shielded bearing in the drawings, the bearing 102 does not necessarily have to have a shield. The holder 104 is configured to rotate together with the inner ring 102i, which is one of the rings 102r of the bearing 102. The strain sensor 103 and the substrate 105 are electrically connected via a connector C. The configuration of the sensor device 100 will be described in detail below.

[0010] As shown in FIGS. 3 and 4 , the strain body 101 has an inner portion (holding portion 110), an outer portion (plurality of mounting portions 120) that surrounds the holding portion 110 in the radial direction, a connecting portion 130 that connects the holding portion 110 and the mounting portion 120, and a tubular (cylindrical) protruding portion 111 that is connected to the other axial side (direction of arrow b) of the holding portion 110 and the inner side in the radial direction (direction of arrow d) and protrudes to the other axial side (direction of arrow b).

[0011] The retaining portion 110 is a cylindrical portion extending in the axial direction and having a cylindrical inner peripheral surface 110i around the axis X. The retaining portion 110 supports the shaft S via the bearing 102. In FIG. 4 , the outer shape (radial outer shape) of the retaining portion 110 is substantially circular when viewed in the axial direction. However, the outer shape of the retaining portion 110 is not limited to this and may be any shape, such as substantially circular, elliptical, polygonal, or a shape including complex irregularities. Two cylindrical protrusions 110b extending in the axial direction protrude outward in the radial direction (in the direction of arrow c) on the outer peripheral surface of the retaining portion 110. When viewed in the axial direction, the two protrusions 110b are arranged in positions that are rotationally symmetric with respect to the axis X (hereinafter also referred to as "dyad symmetry" in this specification), overlapping when rotated 180° around the axis X. Each protrusion 110b is formed with an internally threaded hole 110h extending in the axial direction. The holding portion 110 has an end face 110a at one end in the axial direction (the direction of arrow a). The end face 110a, together with a surface 131 of the connecting portion 130 (described later), constitutes a part of a surface 101a extending in the radial direction of the strain body 101.

[0012] Four plate-shaped connecting portions 130 protrude radially outward (in the direction of arrow c) from the end of the holding portion 110 on one side in the axial direction (in the direction of arrow a). The four connecting portions 130 are arranged in positions that are rotationally symmetric (hereinafter also referred to as "four-fold symmetry"), overlapping when rotated 90° around the axis X. That is, the four connecting portions 130 are arranged at equal intervals (every 90°) in the circumferential direction. However, the arrangement and number of connecting portions 130 may vary depending on the arrangement and number of mounting portions 120. In the radial direction, the outer side (in the direction of arrow c) of each connecting portion 130 is connected to the end of one side in the axial direction (in the direction of arrow a) of the mounting portion 120. Thus, the connecting portions 130 connect the holding portion 110 and the mounting portion 120.

[0013] The connecting portion 130 has elasticity and is prone to deformation accompanied by strain, due in part to the shape of the gap 140 described below. The connecting portion 130 has a surface 131 on one side in the axial direction (the direction of arrow a). The surface 131, together with the end surface 110a of the holding portion 110, constitutes a part of the surface 101a extending in the radial direction of the strain generating body 101.

[0014] The mounting portion 120 is a portion that can be used to mount the flexure element 101 to an external member, and has a substantially L-shaped cross section. As shown in FIG. 3 , the dimensions of the mounting portion 120 in the axial direction are the same or substantially the same as the dimensions of the holding portion 110. In this embodiment, the flexure element 101 includes four mounting portions 120. However, the number of mounting portions 120 on the flexure element 101 is not limited to four, and may be one, two, three, five or more. In this embodiment, the four mounting portions 120 are arranged at positions that are quadrilaterally symmetric about the axis X. That is, the four mounting portions 120 are arranged at predetermined intervals (equally spaced in this embodiment) in the circumferential direction (every 90°). However, the multiple mounting portions 120 do not have to be arranged at equal intervals in the circumferential direction. For example, a configuration may be possible in which a second mounting portion 120 is arranged at a distance of n degrees from a first mounting portion 120, a third mounting portion 120 is arranged at a distance of (180-n) degrees from there, and a fourth mounting portion 120 is arranged at a distance of n degrees from there. The mounting portions 120 are elastically or plastically deformable in response to an external force. Since all four mounting portions 120 have the same configuration, only one mounting portion 120 will be described in detail below, and detailed descriptions of the other mounting portions 120 will be omitted.

[0015] The mounting portion 120 has a surface 122 extending in the axial direction. The strain element 101 has a gap 140, which will be described later, between a portion 121 (portion extending in the axial direction) of the mounting portion 120 having the surface 122 and the holding portion 110. Due to the shape of the gap 140, the portion 121 of the mounting portion 120 having the surface 122 has a thinner wall thickness (thickness in the radial direction) than the other portions of the mounting portion 120, making it more susceptible to deformation accompanied by strain.

[0016] As shown in Fig. 3 , the mounting portion 120 faces the holding portion 110 in the radial direction, with a gap 140 interposed therebetween. In the axial direction, the gap 140 is formed on the other side of the connecting portion 130 (in the direction of arrow b). Due to the presence of the gap 140, the mounting portion 120 and the holding portion 110 are spaced apart by a predetermined distance on the other side of the connecting portion 130 in the axial direction (in the direction of arrow b). The gap 140 penetrates the strain element 101 in the circumferential direction (the depth direction in Fig. 3 ).

[0017] The gap 140 includes two different shaped through holes (holes). The gap 140 includes a first through hole (hole) 141 having a circular or approximately circular cross section and a second through hole (slit) 142 connected to the first through hole 141. In the axial direction, the second through hole (slit) 142 is connected to the other side of the first through hole 141 (the direction of arrow b). The second through hole (slit) 142 has a width (radial dimension) narrower than the size (diameter) of the first through hole 141. However, the shape of the gap 140 is not limited thereto and may be any shape, such as a shape having only the second through hole (slit), a shape having a combination of multiple through holes having circular or approximately circular cross sections, or a shape having the second through hole (slit) extending in the radial direction.

[0018] Due to the formation of the first through hole 141, a recess is formed on the radially inner surface (direction of arrow d) of the mounting portion 120, which is recessed radially outward (direction of arrow c), and a recess is formed on the axially other side (direction of arrow b) of the connecting portion 130, which is recessed axially to one side (direction of arrow a), and a recess is formed on the radially outer surface (direction of arrow c) of the holding portion 110, which is recessed radially inward (direction of arrow d).

[0019] The surface 131 of each connecting portion 130 and the surface 122 extending in the axial direction of each mounting portion 120 are both deformable surfaces. Therefore, the strain element 101 as a whole has a plurality of deformable surfaces (eight in this embodiment). The plurality of deformable surfaces are arranged in positions that are four-fold symmetric (rotationally symmetric) in the circumferential direction ( FIG. 4 ).

[0020] In this embodiment, a strain sensor 103 is attached to the surface 131 of each connecting portion 130, detecting strain on the surface 131. That is, a plurality of strain sensors 103 (four in this embodiment) are attached to the strain body 101. However, it is not necessary for the strain sensors 103 to be attached to all of the plurality of surfaces 131. Furthermore, the directions of strain detected by the individual strain sensors 103 may be different from each other.

[0021] The strain sensor 103 includes a grid 103g (see FIG. 5 ). The grid 103g of the strain sensor 103 is disposed in the most deformable portion of the connecting portion 130, i.e., the portion that overlaps with the gap 140 in the axial direction (the portion whose radial position is the same as the gap 140). The strain sensor 103 is attached to the surface 131 so that the orientation of the grid 103g is in a predetermined direction (which may be either the radial direction or the circumferential direction; in the illustrated example, the radial direction). Note that the orientation of the grids of the multiple strain sensors 103 may be oblique to the circumferential direction or the radial direction. Furthermore, among the multiple strain sensors, the orientation of the grids of two opposing strain sensors 103 may be radial, and the orientation of the grids of the other two opposing strain sensors 103 may be circumferential. Alternatively, among the multiple strain sensors, the grid orientation of two opposing strain sensors 103 may be a direction in which the radial direction and the circumferential direction meet (a diagonal direction (first direction)), and the grid orientation of the other two opposing strain sensors 103 may be a direction in which the radial direction and the circumferential direction meet (a diagonal direction (second direction)), with the first direction and the second direction being different directions, such as intersecting each other. If the strain sensor 103 is a strain gauge, the strain on the surface 131 is detected as a change in resistance value. The strain sensor 103 may also be various other sensors, such as a resistive element or a piezoelectric element.

[0022] As described above, in this embodiment, the strain sensors 103 are attached to the surface 131 of the connecting portion 130. However, the strain sensors 103 may also be attached to the surface 122 extending in the axial direction of the mounting portion 120. Alternatively, some of the strain sensors 103 may be attached to the surface 131 of the connecting portion 130, and other strain sensors 103 may be attached to the surface 122 of the mounting portion 120.

[0023] As shown in FIGS. 3 and 4 , a fixing portion 123 for connection to an external member (not shown), such as a housing, is disposed radially outward (in the direction of arrow c) of the mounting portion 120 relative to the axially extending portion 121. The fixing portion 123 is a rectangular plate-like portion extending radially outward (in the direction of arrow c) from the end of the surface 122 on the other axial side (in the direction of arrow b). A hole 123h having a circular or nearly circular cross section and extending in the axial direction is formed, for example, in the center of the fixing portion 123. The mounting portion 120 is fixed to an external member by a fastening member, such as a bolt (not shown), which is inserted axially through the hole 123h of the fixing portion 123. This fixes the entire strain body 101 to the external member.

[0024] As shown in FIG. 3 , the bearing 102 is disposed radially inside (in the direction of arrow d) the holding portion 110 of the flexure body 101. The bearing 102 is held by the holding portion 110 of the flexure body 101. The inner ring 102i of the bearing 102 is bonded or press-fitted into the outer peripheral surface of the shaft S. This fixes the inner ring 102i of the bearing 102 to the shaft S. The outer ring 102o of the bearing 102 is press-fitted into the inner peripheral surface 110i of the holding portion 110 of the flexure body 101. The bearing 102 rotatably supports the shaft S with respect to the flexure body 101. The inner ring 102i of the bearing 102 may face the outer peripheral surface of the shaft S with a predetermined gap (for example, the gap indicated by symbol P in the modified example shown in FIG. 9 ) in the radial direction, so that the bearing rotatably supports the shaft S (any of a clearance fit, an intermediate fit, or an interference fit may be used). In this embodiment and the following embodiments, it is assumed that the inner ring 102i of the bearing 102 may face the outer peripheral surface of the shaft S with a predetermined radial gap (this may be a clearance fit, an intermediate fit, or an interference fit).

[0025] The shaft S is a substantially cylindrical member extending in the axial direction. The shaft S is supported by a strain body 101 via a bearing 102. In this embodiment, the shaft S is a bicycle crankshaft. In the axial direction, one end Sa and the other end Sb of the shaft S are connected to a crank arm or the like (not shown). In FIGS. 1 and 2 , the one end Sa and the other end Sb of the shaft S are illustrated as parts formed in a rectangular tube shape (a tube with four corners in this embodiment). However, the one end Sa and the other end Sb of the shaft S may have any other shape. In the axial direction, a gear portion Sg is formed near the center of the shaft S. Rotation of a motor or the like (not shown) is transmitted to the gear portion Sg via a reduction gear or the like (not shown), thereby enabling the shaft S to rotate. However, the gear portion Sg does not necessarily have to be formed on the shaft S.

[0026] 3 and 4, a cylindrical (cylindrical) protrusion 111 extending in the other direction (arrow b direction) is connected to the other end of the holding portion 110 of the strain element 101 in the axial direction. The protrusion 111 has a cylindrical outer peripheral surface 111o extending in the axial direction on the radially outer side (arrow c direction), and a cylindrical inner peripheral surface 111i extending in the axial direction on the radially inner side (arrow d direction).

[0027] In the radial direction, the inner circumferential surface 111i of the protrusion 111 has a dimension (inner diameter) smaller than the dimension (inner diameter) of the inner circumferential surface 110i of the holding portion 110, and the outer circumferential surface 111o of the protrusion 111 has a dimension (outer diameter) slightly larger than the dimension of the inner circumferential surface of the holding portion 110. However, the dimension of the outer circumferential surface 111o of the protrusion 111 may be even larger, may be equal to the dimension of the inner circumferential surface 110i of the holding portion 110, or may be smaller than the dimension of the inner circumferential surface 110i of the holding portion 110.

[0028] In this embodiment, an end face of the protrusion 111 on one axial side (direction of arrow a) is in contact with an end face of the outer ring 102o of the bearing 102 on the other axial side (direction of arrow b). As a result, the protrusion 111 supports the bearing 102 while restricting movement of the bearing 102 to the other axial side (direction of arrow b). Also, for example, a structure may be employed in which the protrusion 111 is engaged with a recess of an external member (not shown), such as a housing, so that the protrusion 111 receives part of the external force acting on the sensor device 100, thereby preventing fatigue failure of the mounting portion 120. However, the strain element 101 does not have to have the protrusion 111.

[0029] Next, the details of the holder 104, substrate 105, and flexible substrate 106 in the sensor device 100 will be described mainly with reference to FIGS. 3 and 5 to 7. As shown in FIG. 5, an annular flexible substrate 106 is disposed on the radially extending surface 101a of the strain body 101 (particularly, the end surface 110a of the holding portion 110). The flexible substrate 106 is disposed so as to surround the holder 104 from the radially outer side (in the direction of arrow c). The flexible substrate 106 has a wiring pattern (not shown) and is electrically connected to the strain sensor 103 on the surface 131 of each connecting portion 130 of the strain body 101. The flexible substrate 106 has a portion (hereinafter referred to as a plate-shaped portion) 106c that protrudes radially outward (in the direction of arrow c). The plate-shaped portion 106c of the flexible substrate 106 is connected to a connector C (described later) of the substrate 105.

[0030] 6, the flexible substrate 106 and the bearing 102 overlap in the axial direction. Specifically, the flexible substrate 106 covers the contact portion between the outer ring 102o of the bearing 102 and the inner circumferential surface 110i of the holder 110 of the flexure body 101 from one axial side (the direction of arrow a). In this case, the flexible substrate 106 prevents dust and other particles from entering the contact portion between the outer ring 102o of the bearing 102 and the inner circumferential surface 110i of the holder 110 of the flexure body 101. However, the flexible substrate 106 and the bearing 102 do not have to overlap in the axial direction.

[0031] The substrate 105 is, for example, an arc-shaped, flat printed circuit board (PCB) on which circuits and electronic components (neither of which are shown) are arranged. However, the substrate 105 may have any other shape. As shown by the imaginary lines in FIG. 5 , in this embodiment, the substrate 105 extends parallel or approximately parallel to the surface 101a of the flexure body 101 extending in the radial direction. That is, the surface of the substrate 105 on which circuits are arranged extends in the radial direction. In the radial direction, the dimensions of the substrate 105 are smaller than the dimensions of the flexure body 101. That is, in the radial direction, the entire substrate 105 is located inside (in the direction of arrow d) the outermost end (in the direction of arrow c) of the flexure body 101 (in this embodiment, the outer end of the fixing portion 123 of the flexure body 101). However, in the radial direction, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the projected area of ​​the substrate 105 as viewed from the axial direction may be located outside (in the direction of arrow c) the outermost end of the strain body 101.

[0032] The substrate 105 is disposed on one side in the axial direction (the direction of the arrow a) of the flexure body 101 and the flexible substrate 106. In the axial direction, the substrate 105 is disposed apart from the flexure body 101 and the flexible substrate 106. As shown in FIG. 3 , the distance D between the substrate 105 and the surface 101 a extending in the radial direction of the flexure body 101 is １ is the distance D from the end of the bearing 102 on the other side (in the direction of the arrow b) to the surface 101a. ２ is smaller than the distance D ２ is less than half of the

[0033] As shown in FIG. 5 , the substrate 105 is arranged to overlap the surface 101 a extending in the radial direction of the strain sensor 101 in the axial direction. In this embodiment, the substrate 105 is arranged to overlap two adjacent strain sensors 103 of the four strain sensors 103 in the axial direction. However, the substrate 105 may be arranged to overlap one strain sensor 103 of the four strain sensors 103 in the axial direction, or may be arranged to overlap three or more strain sensors 103 in the axial direction, or may not be arranged to overlap any strain sensor 103 in the axial direction. The substrate 105 is arranged to overlap the plate-shaped portion 106 c of the flexible substrate 106 in the axial direction. A connector C is arranged on a surface 105 b (see FIG. 7 ) on the other side (direction of arrow b) of the substrate 105 in the axial direction, and the substrate 105 is electrically connected to the flexible substrate 106 via the connector C. In this way, the strain sensor 103 is electrically connected to the substrate 105 via the flexible substrate 106. However, the electrical connection between the strain sensor 103 and the substrate 105 may be established by any other method.

[0034] As shown in Fig. 7, circular holes 105h are formed at both ends of the arc-shaped base plate 105. As shown in Fig. 5, bolts B, which are fastening members, are inserted into the holes 105h of the base plate 105 and screwed into the female threaded holes 110h of the convex portions 110b via spacers Bs, thereby fixing the base plate 105 to the strain body 101.

[0035] As shown in FIG. 7 , a sensor 105s is disposed on a surface 105b on the other axial side (in the direction of arrow b) of the substrate 105. The sensor 105s is attached to an edge portion on the inner side (in the direction of arrow d) of the substrate 105 in the radial direction. The sensor 105s is a sensor capable of detecting magnetic flux and may be, for example, a Hall element, a Hall IC, or a magnetoresistive element. The sensor 105s detects, in the radial direction, the magnetic flux or a change in magnetic flux of a magnet M (described later) disposed in the holder 104. The substrate 105 is provided with, for example, a circuit (not shown) for amplifying signals from the sensor 105s and the strain sensor 103 and communicating them with the outside.

[0036] The holder 104 is a cylindrical member that surrounds the shaft S from the outside in the radial direction. As shown in FIGS. 3, 5, and 7, the holder 104 is disposed inside the substrate 105 in the radial direction. The holder 104 and the substrate 105 are spaced apart in the radial direction. The holder 104 and the substrate 105 overlap in their positions in the axial direction. As best shown in FIG. 6, in this embodiment, the holder 104 and the shaft S are spaced apart in the radial direction. However, the holder 104 and the shaft S may be in contact with each other in the radial direction.

[0037] As shown in FIG. 3 , the holder 104 includes, in order from one axial end, a plate portion 104a, a cylindrical portion 104b, and a protruding portion 104c. The cylindrical portion 104b is a cylindrical portion extending in the axial direction. The plate portion 104a is an annular portion connected to the end of the cylindrical portion 104b on one axial side (in the direction of arrow a) and extending radially outward (in the direction of arrow c). The protruding portion 104c is a cylindrical portion with an outer shape (diameter (outside diameter)) smaller than the inner ring 102i of the bearing 102 and connected to the end of the cylindrical portion 104b on the other axial side (in the direction of arrow b). The plate portion 104a, the cylindrical portion 104b, and the protruding portion 104c share the inner circumferential surface 104i of the holder 104 ( FIGS. 6 and 7 ).

[0038] As shown in FIG. 6 , a recess 104k is formed around the axis X in the cylindrical portion 104b of the holder 104 at a corner on the other axial side (in the direction of arrow b) and the outer side in the radial direction (in the direction of arrow c). The recess 104k is formed by a surface 104k1 extending in the radial direction and a surface 104k2 extending in the axial direction. The surface 104k1 of the holder 104 faces the other axial side (in the direction of arrow b), and the surface 104k2 faces the outer side in the radial direction (in the direction of arrow c). In this embodiment, the surface 104k1 of the holder 104 and the surface 105b on the other axial side (in the direction of arrow b) of the substrate 105 are positioned at the same or substantially the same axial position (see FIG. 9 ).

[0039] An annular, plate-shaped magnet M is disposed on the holder 104. As shown in FIG. 6 , the magnet M is attached to a surface 104k1 of the holder 104. The magnet M is disposed coaxially with the holder 104. The magnet M is, for example, alternately magnetized in the circumferential direction, and each magnet M has two different magnetic poles arranged alternately. As shown in FIG. 3 , the magnet M and the sensor 105s disposed on the substrate 105 overlap in the axial direction. The radial distance between the magnet M and the sensor 105s is within a range in which the sensor 105s can detect the magnetic flux of the magnet M. The magnet M does not have to be annular. In that case, the magnet M may be attached to, for example, one or more locations in the circumferential direction of the holder 104. Furthermore, the magnet M may be attached to a surface 104k2 of the holder 104, the outer circumferential surface of the cylindrical portion 104b of the holder 104, or any other location on the holder 104.

[0040] The holder 104 is disposed on one side of the bearing 102 in the axial direction (in the direction of arrow a). The other axial end of the holder 104 (in the direction of arrow b) is fixed to the ring 102r (specifically, the inner ring 102i) of the bearing 102. This allows the holder 104 to rotate together with the ring 102r of the bearing 102. As shown in FIG. 6 , a groove 102g extending in the axial direction is formed at the connection between the holder 104 and the ring 102r of the bearing 102. In this embodiment, the groove 102g is formed in the inner ring 102i of the bearing 102. In this embodiment, the groove 102g is formed as a recess that goes around the axis X at the end of the inner ring 102i on one side in the axial direction (in the direction of arrow a) and on the inner side in the radial direction (in the direction of arrow d).

[0041] The protrusion 104c of the holder 104 engages with a groove 102g formed in the inner ring 102i of the bearing 102. In the axial direction, the dimension of the protrusion 104c of the holder 104 is smaller than the dimension of the groove 102g of the bearing 102. That is, in the axial direction, the other end of the protrusion 104c of the holder 104 (in the direction of arrow b) is spaced apart from the other end of the groove 102g of the bearing 102 (in the direction of arrow b). As shown in FIG. 6 , an annular gap G is formed between the other end of the protrusion 104c of the holder 104 (in the direction of arrow b) and the other end of the groove 102g of the bearing 102 (in the direction of arrow b). When fixing the protrusion 104c of the holder 104 to the groove 102g of the bearing 102, for example, the outer circumferential surface of the protrusion 104c may be fixed to the inner ring 102i of the bearing 102 using an adhesive. 6 , excess adhesive remains in gap G, thereby preventing the adhesive from flowing out toward shaft S. The groove extending in the axial direction formed at the connection between holder 104 and ring 102r of bearing 102 may be formed in holder 104. In that case, holder 104 may have a groove instead of protrusion 104c, and bearing 102 may have a protrusion instead of groove 102g, with the protrusion of bearing 102 engaging with the groove of holder 104.

[0042] The holder 104 has an engaged portion 104e on its inner circumferential surface 104i. As shown in Figures 3, 5, and 7, the engaged portion 104e is formed as a groove extending in the axial direction and recessed radially outward (in the direction of arrow c). The engaged portion 104e extends from one end of the holder 104 in the axial direction (in the direction of arrow a) to the other end of the holder 104 in the axial direction (in the direction of arrow b). However, the engaged portion 104e may extend to a position on the side (upper side) of a protrusion Sf (described later) of the shaft S relative to the other end of the holder 104 (in the direction of arrow b).

[0043] As shown in FIG. 8 , the shaft S is provided with a protrusion (flange portion) Sf, an annular portion Sr, and an engagement portion Se. The flange portion Sf is an annular plate portion (base) that extends radially outward (in the direction of arrow c). The annular portion Sr is connected to the other axial side (in the direction of arrow b) of the flange portion Sf and has a smaller dimension (diameter) than the flange portion Sf. An engagement portion Se having a substantially rectangular parallelepiped shape is disposed on the other axial side (in the direction of arrow b) of the annular portion Sr. The engagement portion Se extends from the annular portion Sr toward the other axial side (in the direction of arrow b) along the shaft S. As shown in FIG. 3 , the engagement portion Se of the shaft S engages with the engaged portion 104e of the holder 104 in the radial direction. That is, the engaging portion Se of the shaft S is inserted into the engaged portion 104e of the holder 104, which is formed as a groove, from one axial side to the other in the direction of arrow b. In this way, the holder 104 is restricted from rotating about the X-axis relative to the shaft S. As shown in Figure 3, the engaging portion Se of the shaft S is slightly spaced from the holder 104 in the radial direction.

[0044] The sensor device 100 according to this embodiment has the above-described configuration. When the sensor device 100 is used on a bicycle, the shaft S is a crankshaft to which a crank arm and a pedal are connected. When one pedal is stepped on, a force acts to tilt the pedal side (end Sa or Sb) of the shaft S, causing the bearing 102 to move radially, pressing a portion of the strain body 101 radially outward (in the direction of arrow c) and pulling another portion of the strain body 101 radially inward (in the direction of arrow d). As a result, stress concentrates in a portion of the strain body 101 near the gap 140 (e.g., the connecting portion 130), causing deformation accompanied by strain.

[0045] The presence of multiple strain sensors 103 makes it possible to detect strain in the strain element 101 in response to tilt of the shaft S in all directions. In particular, in the sensor device 100, the four strain sensors 103 are positioned in quadrilateral symmetry around the axis X, making it possible to more accurately detect strain in all directions. Signals from the strain sensors 103 are transmitted to the substrate 105 via the flexible substrate 106 and the connector C.

[0046] In addition, a sensor 105s is attached to the substrate 105 to detect magnetic flux from the magnet M placed in the holder 104. Because the magnet M rotates together with the shaft S, the magnetic flux detected by the sensor 105s changes with the rotation of the shaft S. Therefore, the sensor 105s can detect the rotation speed of the shaft S. The substrate 105 can amplify signals input from the strain sensor 103 and the sensor 105s and transmit them to an external device.

[0047] In the sensor device 100 according to this embodiment, a torque sensor is formed by attaching a strain sensor 103 to a strain element 101 that holds a bearing 102 arranged on a shaft S. A holder 104 that rotates together with a ring 102r of the bearing 102 is arranged inside a substrate 105, and a cadence sensor is formed by enabling a sensor 105s arranged on the substrate 105 to detect the magnetic flux of a magnet M arranged on the holder 104. This structure makes it easy to make the entire sensor device thin.

[0048] In the sensor device 100 according to this embodiment, the holder 104 and the shaft S are spaced apart in the radial direction. Therefore, it is possible to suppress displacement of the magnet M caused by the stress applied to the shaft S being directly transmitted to the holder 104, thereby improving the detection accuracy of the sensor 105s.

[0049] (Modifications) Although the sensor device of the present invention has been described above with reference to preferred embodiments, the sensor device of the present invention is not limited to the configuration of the above-described embodiment. Below, examples of other configurations that can be adopted by the sensor device of the present invention will be described.

[0050] The sensor device of the present invention may include a sensor device 200 shown in FIG. 9 , in which an elastic body 107 is disposed axially between the protrusion (flange portion) Sf of the shaft S and the plate portion 104a of the holder 104. While FIG. 9 shows the elastic body 107 as a circular member having a rectangular cross section, the elastic body 107 may have any shape. The elastic body 107 may be, for example, a wave washer as shown in FIG. 10 . The elastic body 107 biases the ring 102r (inner ring 102i in the illustrated example) of the bearing 102 toward the other side in the axial direction (the direction of arrow b) via the holder 104. This preloads the ring 102r of the bearing 102, thereby extending the life of the bearing 102. The elastic body 107 may be a wave washer as shown in FIG. 10 , a coil spring, or a member having rubber elasticity. When the elastic body 107 is a member having rubber elasticity, examples of materials that can be used to form the elastic body 107 include thermosetting elastomers such as natural rubber and synthetic rubber, and thermoplastic elastomers such as styrene-based, olefin-based, PVC-based, acrylic-based, polyamide-based, polyester-based, and polyurethane-based. The elastic body 107 may be a single member that surrounds the shaft S from the outside in the radial direction, or multiple members that are arranged in the circumferential direction. The configuration of the sensor device 200 is the same as that of the sensor device 100, except for the points described above.

[0051] Furthermore, the sensor device of the present invention may include a holder 304 instead of the holder 104 and a bearing 302 instead of the bearing 102, as in the sensor device 300 shown in FIG. 11 . The holder 304 includes, in order from one axial end, a plate portion 304a, a cylindrical portion 304b, and a protruding portion 304c. The configurations of the plate portion 304a and the cylindrical portion 304b are similar to those of the plate portion 104a and the cylindrical portion 104b of the holder 104. The protruding portion 304c is a cylindrical portion whose dimensions (diameter (outer diameter)) are smaller than the inner ring 302i of the bearing 302 and which is connected to the end of the cylindrical portion 304b on the other axial side (in the direction of arrow b). The protruding portion 304c has the same length as the axial dimension of the bearing 302. The plate portion 304a, the cylindrical portion 304b, and the protruding portion 304c share the inner circumferential surface 304i of the holder 304. The bearing 302 has a ring 302r (an inner ring 302i and an outer ring 302o). The ring 302r (inner ring 302i in the illustrated example) of the bearing 302 is connected to the shaft S via a protrusion 304c that is a part of the holder 304. That is, in the radial direction, the protrusion 304c of the holder 304 is sandwiched between the inner ring 302i of the bearing 302 and the shaft S. In this modified example, the holder 304 is fixed to the shaft S. The configuration of the sensor device 300 is the same as that of the sensor device 100, except for the points described above. With the above configuration, the sensor device 300 can accommodate shafts S having various dimensions (diameters) simply by preparing multiple holders 304 with different inner diameters (the radial dimension of the inner circumferential surface 304i) without changing the other configurations.

[0052] The sensor device of the present invention does not have to be used on a bicycle. In the sensor device of the present invention, the shaft and the holder do not have to be engaged as in the above-described embodiment. In the sensor device of the present invention, the connection between the holder and the bearing does not have to have a groove or protrusion extending in the axial direction. In the sensor device of the present invention, the holder and the bearing ring may be formed as an integral member. In the sensor device of the present invention, the strain element may have another shape.

[0053] Further embodiments included in the present invention will be described below.

[0054] Second Embodiment A second embodiment, which is an example of the present invention, will now be described with reference to the drawings (FIGS. 12 to 15). FIG. 12 is a perspective view showing a partial configuration of a sensor device 400 according to this embodiment. FIG. 13 is a partial cross-sectional view of the sensor device 400. FIG. 14 is a perspective view showing a portion of the shaft S4 of the sensor device 400. FIG. 15 is another partial cross-sectional view of the sensor device 400.

[0055] The sensor device 400 includes a shaft S4, a strain element 401, a bearing 402, a strain sensor 403, a holder 404, and a substrate 405. FIG. 12 shows the configuration of the sensor device 400 excluding the shaft S4. The strain element 401 has a surface 401a extending in the radial direction, and the strain sensor 403 is attached to the surface 401a. As shown in FIG. 13 , the shaft S4 and the strain element 401 are connected in the radial direction via a bearing 402. In this embodiment, the bearing 402 is a ball bearing including a ring 402r (an inner ring 402i and an outer ring 402o) and rolling elements 402b. The bearing 402 is not limited to a ball bearing and may be various other bearings, such as a sleeve bearing. Although the bearing 402 is illustrated as a bearing with a shield in the drawings, the bearing 402 does not necessarily have to have a shield. The holder 404 is configured to rotate together with an inner ring 402i, which is one of the rings 402r of the bearing 402. The strain sensor 403 and the substrate 405 are electrically connected via a conductive member C4. The configuration of the sensor device 400 will be described in detail below.

[0056] As shown in FIG. 13 , the flexure element 401 has an inner portion (holding portion) 410, an outer portion (plurality of mounting portions 420) that radially surrounds the holding portion 410, and a connecting portion 430 that connects the holding portion 410 and the mounting portion 420. FIG. 13 is a cross-sectional view obtained by cutting along a plane that includes the axis X and is aligned with the direction in which one of the mounting portions 420 extends. The holding portion 410 is a cylindrical portion that extends in the axial direction and has a cylindrical inner circumferential surface 410i around the axis X. The holding portion 410 supports the shaft S4 via a bearing 402. A portion 411 that protrudes radially inward is provided at an end of the holding portion 410 on one axial side (in the direction of arrow a). The surface of the portion 411 facing the one axial side (in the direction of arrow a) constitutes a part of a surface 401a that extends radially of the flexure element 401.

[0057] A plate-shaped, annular connecting portion 430 extends radially outward from an end portion of the holding portion 410 on one axial side (in the direction of arrow a). One axial end portion of the mounting portion 420 is connected to the outer side of the connecting portion 430 in the radial direction. Therefore, the connecting portion 430 connects the holding portion 410 and the mounting portion 420, which are separated from each other in the radial direction. The connecting portion 430 is elastic and easily deforms with distortion, due in part to the shape of the gap 440 (described later). The surface of the connecting portion 430 facing one axial side (in the direction of arrow a) constitutes a part of a surface 401a extending radially of the strain element 401.

[0058] The mounting portions 420 are portions that can be used to mount the flexure element 401 to an external member, and have a substantially L-shaped cross section. The mounting portions 420 are curved so as to bulge outward in the radial direction. As shown in FIG. 12 , the flexure element 401 has three mounting portions 420. In this embodiment, the three mounting portions 420 are arranged at positions that are triangularly symmetric about the axis X. That is, the three mounting portions 420 are arranged at predetermined intervals in the circumferential direction (every 120° in this embodiment).

[0059] 13 , the attachment portion 420 faces the holding portion 410 in the radial direction, with a gap 440 interposed between them. In the axial direction, the gap 440 is formed on the other side of the connecting portion 430 (in the direction of arrow b). Due to the presence of the gap 440, the attachment portion 420 and the holding portion 410 are spaced apart by a predetermined distance on the other axial side (in the direction of arrow b) of the connecting portion 430. The gap 440 is curved along the circumferential direction.

[0060] In this embodiment, strain sensors 403 that detect strain on the surface 401a are attached to the surface 401a extending in the radial direction of the strain element 401. The strain sensors 403 are disposed at the portions where the mounting portions 420 are connected. That is, a plurality of strain sensors 403 (three in this embodiment) are attached to the strain element 401.

[0061] The grid (not shown) of the strain sensor 403 is disposed in the most deformable portion of the connecting portion 430, i.e., the portion that overlaps with the gap 440 in the axial direction (the portion whose radial position is the same as the gap 440). The strain sensor 403 is attached to the surface 401 a so that the orientation of the grid is in a predetermined direction. The strain sensor 403 may be a strain gauge. If the strain sensor 403 is a strain gauge, the strain on the surface 401 a is detected as a change in resistance value. The strain sensor 403 may be various other sensors, such as a resistive element or a piezoelectric element.

[0062] 13 , the bearing 402 is disposed radially inside (in the direction of arrow d) the holder 410 of the flexure body 401. The bearing 402 is held by the holder 410 of the flexure body 401. The inner ring 402i of the bearing 402 is bonded or press-fitted onto the outer peripheral surface of the shaft S4. As a result, the inner ring 402i of the bearing 402 is fixed to the shaft S4. The outer ring 402o of the bearing 402 is press-fitted into the inner peripheral surface 410i of the holder 410 of the flexure body 401. In this embodiment, the portion 411 of the holder 410 is in contact with an end face of the outer ring 402o of the bearing 402 on one axial side (in the direction of arrow a). As a result, the portion 411 of the holder 410 restricts movement of the bearing 402 to one axial side (in the direction of arrow a). With the above configuration, the bearing 402 supports the shaft S4 rotatably relative to the strain element 401.

[0063] An annular substrate 405 is disposed on a surface 401a extending in the radial direction of the flexure element 401. The substrate 405 is, for example, a flat printed circuit board (PCB) on which circuits and electronic components (neither of which are shown) are disposed. The substrate 405 is disposed so as to sandwich the strain sensor 403 between itself and the flexure element 401. The substrate 405 surrounds the holder 404 from the outside in the radial direction (the direction of arrow c). The substrate 405 extends parallel or approximately parallel to the surface 401a extending in the radial direction of the flexure element 401. The substrate 405 has a surface 405b on the strain sensor 403 side and a surface 405a on the opposite side from the strain sensor 403. The surfaces 405a and 405b extend in the radial direction.

[0064] In the radial direction, the dimensions of the substrate 405 are smaller than the dimensions of the flexure body 401. That is, in the radial direction, the entire substrate 405 is located inside (in the direction of arrow d) the outermost end (in the direction of arrow c) of the flexure body 401 (in this embodiment, the outer end of the mounting portion 420 of the flexure body 401). However, in the radial direction, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the projected area of ​​the substrate 405 as viewed from the axial direction may be located outside the outermost end of the flexure body 401.

[0065] A strain sensor 403 and a conductive member C4 that electrically connects the substrate 405 and the strain sensor 403 are disposed between the substrate 405 and the strain element 401. The conductive member C4 is, for example, a flexible conductor. A land 405l to which the conductive member C4 is electrically connected is provided on a surface 405a of the substrate 405 opposite the strain sensor 403. The conductive member C4 has a portion C4a that curves from the strain sensor 403 toward the land 405l of the substrate 405.

[0066] As shown in Fig. 12, a sensor 405s is disposed on a surface 405a of the substrate 405 opposite the strain sensor 403. The sensor 405s is attached to the inner edge of the substrate 405 in the radial direction. The sensor 405s is a sensor capable of detecting magnetic flux, and may be, for example, a Hall element, a Hall IC, or a magnetoresistive element. The sensor 405s detects, in the radial direction, the magnetic flux or a change in magnetic flux of a magnet M (described later) disposed in the holder 404. The substrate 405 is provided with, for example, a circuit (not shown) for amplifying signals from the sensor 405s and the strain sensor 403 and communicating them with the outside.

[0067] The holder 404 is an annular member that surrounds the shaft S4 from the outside in the radial direction. The holder 404 is disposed inside the substrate 405 in the radial direction. The holder 404 and the substrate 405 are spaced apart in the radial direction. The holder 404 and the substrate 405 overlap in position in the axial direction.

[0068] 13 , the holder 404 includes a flange (protruding portion) 404a extending radially outward, a plate portion (plate) 404b extending radially inward, and a cylindrical portion (cylinder) 404c. The cylindrical portion 404c is a cylindrical portion extending axially. The flange 404a and the plate portion 404b are connected to the cylindrical portion 404c. In the axial direction, the flange 404a is disposed on one side (in the direction of arrow a) of the plate portion 404b.

[0069] An annular, plate-shaped magnet M is disposed in the holder 404. The magnet M is attached to one axial side (the direction of arrow a) of the flange 404a of the holder 404. The magnet M is disposed coaxially with the holder 404. The magnet M is, for example, alternately magnetized in the circumferential direction, and each magnet M has two different magnetic poles arranged alternately. The magnet M and the sensor 405s disposed on the substrate 405 overlap in the axial direction. Furthermore, the magnet M and the sensor 405s face each other in the radial direction. The distance between the magnet M and the sensor 405s in the radial direction is within a range in which the sensor 405s can detect the magnetic flux of the magnet M. The magnet M may not be annular, but may be composed of multiple magnets M. In this case, the magnet M may be attached to, for example, one or more locations in the circumferential direction of the holder 404.

[0070] In the axial direction, the holder 404 is disposed on one side (in the direction of arrow a) of the bearing 402. The inner ring 402i of the bearing 402 protrudes further in the axial direction (in the direction of arrow a) than the outer ring 402o. The plate portion 404b and the cylindrical portion 404c of the holder 404 are connected to the ring 402r of the bearing 402 (specifically, the inner ring 402i). This allows the holder 404 to rotate together with the ring 402r of the bearing 402. Alternatively, a spacer may be provided in place of the protruding portion of the inner ring 402i of the bearing 402, and the plate portion 404b and the cylindrical portion 404c of the holder 404 may be connected to this spacer, so that the holder 404 rotates together with the ring 402r of the bearing 402.

[0071] In the axial direction, an annular gap (space) G4 is formed between the plate portion 404b of the holder 404 and the ring 402r (inner ring 402i) of the bearing 402. When adhesive is used to fix the holder 404 and the bearing 402, excess adhesive remains in the gap G4, preventing the adhesive from flowing out toward the shaft S4.

[0072] As shown in FIG. 12 , the plate portion 404b of the holder 404 is provided with an engaged portion 404e. The engaged portion 404e is a convex portion that protrudes radially inward. In the illustrated embodiment, a pair of engaged portions 404e are provided symmetrically with respect to the axis X or at positions facing each other radially. As shown in FIG. 14 , the shaft S4 is provided with an engaging portion S4e. The engaging portion S4e may be a recess, a groove, or a slit. In the illustrated embodiment, four engaging portions S4e, including hidden ones, are formed around the shaft S4. However, the number of engaging portions S4e is not particularly limited as long as it is equal to or greater than the number of engaged portions 404e. As shown in FIG. 15 , the engaging portion S4e of the shaft S4 engages with the engaged portion 404e of the holder 404. In this way, the engaged portion 404e of the holder 404 and the engaging portion S4e of the shaft S4 are engaged, and the rotation of the holder 404 around the X-axis relative to the shaft S4 is restricted.

[0073] According to this embodiment, the sensor device can be made thinner. Furthermore, according to this embodiment, the number of parts is reduced, which improves productivity and reduces costs.

[0074] [Third embodiment] A third embodiment, which is an example of the present invention, will now be described with reference to the drawings (Figs. 16 to 18). Fig. 16 is a perspective view showing a partial configuration of a sensor device 500 according to this embodiment. Fig. 17 is a partial cross-sectional view of the sensor device 500. Fig. 18 is a diagram showing the arrangement of a flexible substrate 506, a rigid member (reinforcing plate 508), and a bonding member 509 of the sensor device 500.

[0075] The sensor device 500 includes a shaft S5, a strain element 501, a bearing 502, a strain sensor 503, a holder 504, and a flexible substrate 506 as a substrate. FIG. 16 shows the configuration of the sensor device 500 excluding the shaft S5. The strain element 501 has a surface 501a extending in the radial direction, and the strain sensor 503 is attached to the surface 501a. As shown in FIG. 17 , the shaft S5 and the strain element 501 are connected in the radial direction via a bearing 502. In this embodiment, the bearing 502 is a ball bearing including a ring 502r (an inner ring 502i and an outer ring 502o) and rolling elements 502b. The bearing 502 is not limited to a ball bearing and may be various other bearings, such as a sleeve bearing. Although the bearing 502 is illustrated as a bearing with a shield in the drawings, the bearing 502 does not necessarily have to have a shield. The holder 504 is configured to rotate together with an inner ring 502i, which is one of the rings 502r of the bearing 502. The strain sensor 503 and the flexible substrate 506 are electrically connected. The configuration of the sensor device 500 will be described in detail below.

[0076] As shown in Fig. 17 , the strain element 501 has an inner portion (holding portion) 510, an outer portion (plurality of mounting portions 520) that radially surrounds the holding portion 510, and a connecting portion 530 that connects the holding portion 510 and the mounting portion 520. Fig. 17 is a cross-sectional view obtained by cutting along a plane that includes the axis X and is along the direction in which one of the mounting portions 520 extends. The holding portion 510 is a cylindrical portion that extends in the axial direction and has a cylindrical inner circumferential surface 510i around the axis X. The holding portion 510 supports the shaft S5 via a bearing 502. A portion 511 that protrudes radially inward is provided at the end of the holding portion 510 on the other axial side (in the direction of arrow b).

[0077] A plate-shaped, annular connecting portion 530 extends radially outward from an end portion of the holding portion 510 on one axial side (in the direction of arrow a). One axial end portion of the mounting portion 520 is connected to the outer side of the connecting portion 530 in the radial direction. Therefore, the connecting portion 530 connects the holding portion 510 and the mounting portion 520, which are separated from each other in the radial direction. The connecting portion 530 is elastic and easily deforms with distortion, due in part to the shape of the gap 540, which will be described later. The surface of the connecting portion 530 facing one axial side (in the direction of arrow a) constitutes a part of a surface 501a extending radially of the strain element 501.

[0078] The mounting portions 520 are portions that can be used to mount the strain element 501 to an external member. The mounting portions 520 are curved so as to bulge outward in the radial direction. As shown in Fig. 16 , the strain element 501 has three mounting portions 520. In this embodiment, the three mounting portions 520 are arranged at positions that are triangularly symmetric about the axis X. That is, the three mounting portions 520 are arranged at predetermined intervals in the circumferential direction (every 120° in this embodiment).

[0079] 17 , the attachment portion 520 faces the holding portion 510 in the radial direction, with a gap 540 interposed between them. In the axial direction, the gap 540 is formed on the other side of the connecting portion 530 (in the direction of arrow b). Due to the presence of the gap 540, the attachment portion 520 and the holding portion 510 are spaced apart by a predetermined distance on the other axial side (in the direction of arrow b) of the connecting portion 530. The gap 540 is curved along the circumferential direction.

[0080] In this embodiment, strain sensors 503 for detecting strain on the surface 501a are attached to the surface 501a extending in the radial direction of the strain element 501. The strain sensors 503 are disposed at the portions where the mounting portions 520 are connected. That is, a plurality of strain sensors 503 (three in this embodiment) are attached to the strain element 501.

[0081] The grid (not shown) of the strain sensor 503 is disposed in the most deformable portion of the connecting portion 530, i.e., the portion that overlaps with the gap 540 in the axial direction (the portion whose radial position is the same as the gap 540). The strain sensor 503 is attached to the surface 501 a so that the orientation of the grid is in a predetermined direction. The strain sensor 503 may be a strain gauge. If the strain sensor 503 is a strain gauge, the strain on the surface 501 a is detected as a change in resistance value. The strain sensor 503 may be various other sensors, such as a resistive element or a piezoelectric element.

[0082] 17 , the bearing 502 is disposed radially inside (in the direction of arrow d) the holder 510 of the flexure body 501. The bearing 502 is held by the holder 510 of the flexure body 501. The inner ring 502i of the bearing 502 is bonded or press-fitted onto the outer peripheral surface of the shaft S5. As a result, the inner ring 502i of the bearing 502 is fixed to the shaft S5. The outer ring 502o of the bearing 502 is press-fitted into the inner peripheral surface 510i of the holder 510 of the flexure body 501. In this embodiment, the portion 511 of the holder 510 is in contact with the end face of the outer ring 502o of the bearing 502 on the other axial side (in the direction of arrow b). As a result, the portion 511 of the holder 510 restricts movement of the bearing 502 to the other axial side (in the direction of arrow b). With the above configuration, the bearing 502 supports the shaft S5 rotatably relative to the strain element 501.

[0083] An annular flexible substrate 506 is disposed on the surface 501a extending in the radial direction of the strain element 501. The flexible substrate 506 is disposed so as to surround the holder 504 from the outside in the radial direction. The flexible substrate 506 has a wiring pattern (not shown). As shown in FIG. 16 , an outer peripheral portion 506o of the flexible substrate 506 includes a protrusion 506c extending radially outward (in the direction of arrow c) and a recess 506r recessed relative to the protrusion 506c. The flexible substrate 506 is electrically connected to the strain sensors 503 at the protrusion 506c. The flexible substrate 506 has one protrusion 506c for each strain sensor 503. The recess 506r is a notch recessed radially inward. In the circumferential direction, the protrusion 506c is disposed between a pair of recesses 506r.

[0084] As shown in FIG. 16 , a sensor 506s is disposed on a surface 506a of the flexible substrate 506 facing one side in the axial direction (the direction of arrow a). Other elements may also be disposed on the surface 506a. The sensor 506s is attached to the inner edge of the flexible substrate 506 in the radial direction. The sensor 506s is a sensor capable of detecting magnetic flux and may be, for example, a Hall element, a Hall IC, or a magnetoresistive element. The sensor 506s detects, in the radial direction, the magnetic flux or a change in magnetic flux of a magnet M (described later) disposed in the holder 504. The flexible substrate 506 is provided with, for example, a circuit (not shown) for amplifying signals from the sensor 506s and the strain sensor 503 and communicating them with the outside.

[0085] 18 , a rigid member (reinforcing plate 508) is attached to a surface 506b of flexible substrate 506 facing the other axial side (direction of arrow b). Flexible substrate 506 and reinforcing plate 508 are attached to a surface 501a extending in the radial direction of strain body 501 by a bonding member 509. Bonding member 509 may be, for example, double-sided tape or an adhesive. In the radial direction, outer periphery 509o of bonding member 509 is located more inward (direction of arrow d) than protruding portion 506c of flexible substrate 506.

[0086] The holder 504 is an annular member that surrounds the shaft S5 from the outside in the radial direction. As shown in Figures 16 and 17, the holder 504 is disposed inside the flexible substrate 506 in the radial direction. The holder 504 and the flexible substrate 506 are spaced apart in the radial direction. The holder 504 and the flexible substrate 506 overlap in their positions in the axial direction.

[0087] 17 , the holder 504 includes a flange (protruding portion) 504a extending radially outward, a plate portion (plate) 504b extending radially inward, and a cylindrical portion (cylinder) 404c. The cylindrical portion 504c is a cylindrical portion extending axially. The flange 504a and the plate portion 504b are connected to the cylindrical portion 504c. The flange 504a and the plate portion 504b form a single continuous surface on one side in the axial direction (the direction of arrow a).

[0088] An annular, plate-shaped magnet M is disposed in the holder 504. The magnet M is attached to the other axial side (the direction of arrow b) of the flange 504a of the holder 504. The magnet M is disposed coaxially with the holder 504. The magnet M is, for example, alternately magnetized in the circumferential direction, and each magnet M has two different magnetic poles arranged alternately. The magnet M and the sensor 506s disposed on the flexible substrate 506 overlap in the axial direction. The magnet M and the sensor 506s face each other in the radial direction. The distance between the magnet M and the sensor 506s in the radial direction is within a range in which the sensor 506s can detect the magnetic flux of the magnet M. The magnet M may not be annular, but may be composed of multiple magnets M. In this case, the magnet M may be attached, for example, to one or more locations in the circumferential direction of the holder 504.

[0089] In the axial direction, the holder 504 is disposed on one side (in the direction of arrow a) of the bearing 502. The inner ring 502i of the bearing 502 protrudes further in the axial direction (in the direction of arrow a) than the outer ring 502o. The plate portion 504b and the cylindrical portion 504c of the holder 504 are connected to the ring 502r of the bearing 502 (specifically, the inner ring 502i). This allows the holder 504 to rotate together with the ring 502r of the bearing 502. Alternatively, a spacer may be provided in place of the protruding portion of the inner ring 502i of the bearing 502, and the plate portion 504b and the cylindrical portion 504c of the holder 504 may be connected to this spacer, so that the holder 504 rotates together with the ring 502r of the bearing 502.

[0090] In the axial direction, an annular gap (space) G5 is formed between the plate portion 504b of the holder 504 and the ring 502r (inner ring 502i) of the bearing 502. When adhesive is used to fix the holder 504 and the bearing 502, excess adhesive remains in the gap G5, preventing the adhesive from flowing out toward the shaft S5.

[0091] As shown in FIG. 16 , an engaged portion 504e is provided on the plate portion 504b of the holder 504. The engaged portion 504e is a convex portion that protrudes radially inward. In the illustrated embodiment, a pair of engaged portions 504e are provided symmetrically with respect to the axis X or at positions facing each other radially. As shown in FIG. 17 , an engaging portion S5e is formed on the shaft S5. The engaging portion S5e of the shaft S5 engages with the engaged portion 504e of the holder 504. In this way, the engaged portion 504e of the holder 504 and the engaging portion S5e of the shaft S5 engage with each other, and rotation of the holder 504 around the X-axis relative to the shaft S5 is restricted.

[0092] According to this embodiment, the sensor device can be made thinner and lighter because the sensor 506s and other elements, circuits, etc. are arranged directly on the flexible substrate 506. Furthermore, because the protruding portion 506c of the flexible substrate 506 is connected to the strain sensor 503 and the joining member 509 is located inside the protruding portion 506c, peeling of the joining member 509 due to the flexible substrate 506 riding up onto the strain sensor 503 is unlikely to occur.

[0093] In addition, those skilled in the art can appropriately modify the sensor device of the present invention and change the shape, dimensions, and combination of various components in accordance with conventionally known knowledge. As long as such modifications still include the components of the present invention, they are of course included in the scope of the present invention.

[0094] 100, 200, 300, 400, 500... sensor device, 101, 401, 501... strain generating body, 101a, 401a, 501a... radially extending surface, 102, 302, 402, 502... bearing, 102g... groove, 102r, 302r, 402r, 502r... ring, 103, 403, 503... strain sensor, 103g... grid, 104, 304, 404, 504... holder, 104e, 404e, 504e... engaged portion, 105, 405... substrate, 105s, 405s , 505s...sensor, 405l...land, 106, 506...flexible substrate, 506c...protrusion, 506s...sensor, 107...elastic body, 508...rigid member, 509...joint member, 110, 410, 510...inner part (holding part), 120, 420, 520...outer part (mounting part), 130, 430, 530...connecting part, S, S4, S5...shaft, Sf...protrusion (flange part), Se, S4e, S5e...engaging part, M...magnet, A...adhesive, C4...conductive member.

Claims

1. A sensor device comprising: a shaft; a strain element having a surface extending in the radial direction; a bearing connecting the shaft and the strain element in the radial direction; a holder rotating together with a ring of the bearing; a strain sensor attached to the surface extending in the radial direction; and a substrate, wherein the strain sensor and the substrate are electrically connected.

2. The sensor device according to claim 1, wherein the holder is disposed radially inside the substrate.

3. The sensor device according to claim 1 or 2, wherein a magnet is disposed in the holder, and a sensor for detecting the magnetic flux of the magnet is disposed on the substrate.

4. A sensor device as described in any one of claims 1 to 3, wherein the shaft has an engaging portion, the holder has an engaged portion, and the engaged portion of the holder and the engaging portion of the shaft engage in a radial direction.

5. A sensor device according to any one of claims 1 to 4, wherein a groove extending in the axial direction is formed at the connection between the holder and the ring of the bearing, and an adhesive is provided in the groove.

6. A sensor device as described in any one of claims 1 to 5, wherein the strain element comprises an inner part that supports the shaft, an outer part that surrounds the inner part, and a connecting part that connects the inner part and the outer part, the connecting part having elasticity, and the strain sensor comprises a grid, and the grid is arranged in the most deformable part of the connecting part.

7. A sensor device as described in any one of claims 1 to 6, wherein a flexible substrate electrically connected to the strain sensor is disposed on the radially extending surface, and the flexible substrate and the bearing overlap in the axial direction.

8. A sensor device as described in any one of claims 1 to 7, wherein the shaft is provided with a protrusion extending in the radial direction, an elastic body is arranged between the protrusion and the holder in the axial direction, and the elastic body biases the ring of the bearing via the holder.

9. A sensor device according to any one of claims 1 to 8, wherein the holder and the shaft are spaced apart in the radial direction.

10. A sensor device according to any one of claims 1 to 8, wherein the ring of the bearing is connected to the shaft via a portion of the holder.

11. A sensor device according to any one of claims 1 to 10, wherein the strain sensor and a conductive member electrically connecting the substrate and the strain sensor are disposed between the substrate and the strain element.

12. A sensor device as described in claim 11, wherein the substrate has a surface facing the strain sensor and a surface opposite the strain sensor, the surface of the substrate opposite the strain sensor is provided with a land to which the conductive member is electrically connected, and the conductive member has a portion curved from the strain sensor toward the land.

13. A sensor device as described in any one of claims 1 to 6, wherein the substrate is a flexible substrate, the flexible substrate is arranged on a surface of the strain generating element that extends in the radial direction, and the flexible substrate has a protrusion electrically connected to the strain sensor.

14. The sensor device according to claim 13, wherein the outer periphery of the flexible substrate in the radial direction includes the protrusion and a recess recessed relative to the protrusion.

15. The sensor device according to claim 14, wherein the flexible substrate is attached to the surface extending in the radial direction by a bonding member, and the outer periphery of the bonding member is located inside the protrusion in the radial direction.

16. A sensor device according to any one of claims 1 to 6, wherein the substrate is a flexible substrate, the flexible substrate is arranged on a surface of the strain-generating body extending in the radial direction, and a sensor for detecting magnetic flux is arranged on the flexible substrate.

17. The sensor device according to claim 16, wherein a rigid member is attached to the flexible substrate.

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