Sensor Unit

Abstract

To provide a sensor unit having excellent detection accuracy.SOLUTION: A sensor unit 10 comprises a first sensor part 11 for detecting deformation of an object to be measured, and a second sensor part 12 for detecting the deformation of the object to be measured. The first sensor part and the second sensor part are fixed to the object to be measured in such a manner that the object to be measured is arranged between the first sensor part and the second sensor part in a first direction when they are attached to the object to be measured. A physical property value of the first sensor part and a physical property value of the second sensor part change in accordance with first deformation of the object to be measured.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor unit for detecting changes in the shape of an object to be measured and a method for attaching the sensor unit. [Background technology]

[0002] As an example of an invention relating to a conventional sensor unit and a sensor unit mounting method, the swing analysis device, swing analysis method, and swing analysis system described in Patent Document 1 are known. The swing analysis device described in Patent Document 1 includes an information input unit that accepts input of acceleration information, angular velocity information, and shaft distortion information detected by a sensor attached to the shaft of a golf club, a posture calculation unit that calculates posture information of the golf club during the swing period based on the acceleration information and angular velocity information, a correction unit that corrects the posture information of the golf club at the time of impact based on the shaft distortion information, and a display control unit that displays the posture information of the golf club corrected by the correction unit on a display. Such a swing analysis device can analyze the swing of a golf club. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6342034 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there is a demand for improving the detection accuracy of the sensor in the swing analysis device described in Patent Document 1.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sensor unit and a sensor unit mounting method that are excellent in detection accuracy. [Means for solving the problem]

[0006] A sensor unit according to one aspect of the present invention includes: A sensor unit for detecting deformation of an object to be measured, The sensor unit includes: a first sensor unit for detecting deformation of the object to be measured; a second sensor unit that detects deformation of the object to be measured, the first sensor unit and the second sensor unit are fixed to the object to be measured such that, when attached to the object to be measured, the object to be measured is disposed between the first sensor unit and the second sensor unit in a first direction; The physical property value of the first sensor unit and the physical property value of the second sensor unit change in response to the first deformation of the object to be measured.

[0007] A sensor unit attachment method according to one aspect of the present invention includes: A sensor unit mounting method for mounting a first sensor unit and a second sensor unit to an object to be measured, the cross section of which is perpendicular to a third direction and has a shape that is point-symmetric, The first sensor unit and the second sensor unit are fixed to the object to be measured so that the object to be measured is positioned between the first sensor unit and the second sensor unit, and so that the physical property values ​​of the first sensor unit and the physical property values ​​of the second sensor unit change in accordance with the deformation of the object to be measured.

[0008] In this specification, an axis or member extending in the third direction does not necessarily refer only to an axis or member that is parallel to the third direction. An axis or member extending in the third direction refers to an axis or member that is inclined within a range of ±45 degrees with respect to the third direction. Similarly, an axis or member extending in the front-to-back direction refers to an axis or member that is inclined within a range of ±45 degrees with respect to the front-to-back direction. An axis or member extending in the left-to-right direction refers to an axis or member that is inclined within a range of ±45 degrees with respect to the left-to-right direction. An axis or member extending in the up-down direction refers to an axis or member that is inclined within a range of ±45 degrees with respect to the up-to-down direction.

[0009] In this specification, directions are defined as follows. In the golf clubs 20, 20a to 20d, the shafts 21, 21a to 21d, which are the objects to be measured, are cylindrical, and the direction of the central axis of the cylinder is defined as the third direction. The circumference of the third direction is defined as the circumferential direction. The direction perpendicular to the third direction is defined as the first direction. The direction perpendicular to the third direction and different from the first direction is defined as the second direction. Furthermore, when the sheets 13, 13a to 13d are laid out on a plane, the normal direction to the main surface of each of the sheets 13, 13a to 13d is defined as the front-rear direction. When the sheets 13, 13a to 13d are laid out on a plane, as viewed in the front-rear direction, the direction in which the first sensor units 11, 11a to 11d and the second sensor units 12, 12a to 12d are aligned is defined as the left-right direction. The direction perpendicular to the front-rear direction and the left-right direction is defined as the up-down direction.

[0010] In this specification, unless otherwise specified, the various parts of the first member are defined as follows: The front part of the first member means the front half of the first member. The rear part of the first member means the rear half of the first member. The left part of the first member means the left half of the first member. The right part of the first member means the right half of the first member. The upper part of the first member means the upper half of the first member. The lower part of the first member means the lower half of the first member. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a sensor unit and a sensor unit mounting method that are excellent in detection accuracy. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view of a sensor unit 10 according to the first embodiment, in a state where a sheet 13 is laid out flat. [Figure 2] FIG. 2 is a plan view and a cross-sectional view of the first sensor unit 11 in a state where the sheet 13 according to the first embodiment is laid out flat. [Figure 3] FIG. 3 is a plan view and a cross-sectional view of the second sensor unit 12 in a state where the sheet 13 according to the first embodiment is laid out flat. [Figure 4] FIG. 4 is a perspective view of the sensor unit 10 according to the first embodiment attached to the shaft 21. FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line AA of the sensor unit 10 according to the first embodiment attached to the shaft 21. As shown in FIG. [Figure 6] FIG. 6 is a plan view of sensor unit 10a in a state where sheet 13a according to the first modified example is laid out flat. [Figure 7] FIG. 7 is a plan view of sensor unit 10b according to the second embodiment, in which sheet 13b is laid out flat. [Figure 8] FIG. 8 is a plan view and a cross-sectional view of a third sensor unit 15b in a state where a sheet 13b according to the second embodiment is laid out flat. [Figure 9] FIG. 9 is a plan view and a cross-sectional view of a fourth sensor unit 16b in a state where a sheet 13b according to the second embodiment is laid out flat. [Figure 10] FIG. 10 is a perspective view of a sensor unit 10b according to the second embodiment attached to a shaft 21b. [Figure 11] FIG. 11 is a cross-sectional view taken along the line AA of a sensor unit 10b according to the second embodiment attached to a shaft 21b. [Figure 12] FIG. 12 is a plan view of sensor unit 10c in a state where sheet 13c according to the second modification is laid out flat. [Figure 13] FIG. 13 is a plan view of a sensor unit 10d according to the third embodiment in a state where a sheet 13d is laid out flat. [Figure 14] FIG. 14 is a plan view and a cross-sectional view of a fifth sensor unit 18d in a state where a sheet 13d according to the third embodiment is laid out flat. [Figure 15] FIG. 15 is a perspective view of a sensor unit 10d according to the third embodiment attached to a shaft 21d. [Figure 16]FIG. 16 is a cross-sectional view taken along line AA of a sensor unit 10d according to the third embodiment attached to a shaft 21d. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] A sensor unit 10 according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of the sensor unit 10 according to the first embodiment, with the sheet 13 laid out flat. FIG. 2 is a plan view and a cross-sectional view of the first sensor unit 11 according to the first embodiment, with the sheet 13 laid out flat. FIG. 3 is a plan view and a cross-sectional view of the second sensor unit 12 according to the first embodiment, with the sheet 13 laid out flat. FIG. 4 is a perspective view of the sensor unit 10 according to the first embodiment, attached to the shaft 21. FIG. 5 is a cross-sectional view taken along line AA of the sensor unit 10 according to the first embodiment, attached to the shaft 21.

[0014] The sensor unit 10 is a sensor unit that detects deformation of a shaft 21, which will be described later. As shown in Fig. 1, the sensor unit 10 includes a first sensor section 11, a second sensor section 12, and a sheet 13. The first sensor section 11 and the second sensor section 12 are arranged in this order from left to right.

[0015] The first sensor unit 11 detects deformation of the shaft 21 (described below) and includes a film shape. The first sensor unit 11 includes a front main surface and a rear main surface. As shown in FIG. 2, the first sensor unit 11 includes a piezoelectric film 113, a first electrode 114a, a second electrode 114b, a charge amplifier 115, and a voltage amplifier circuit 116.

[0016] The piezoelectric film 113 is an example of a piezoelectric body. The piezoelectric film 113 has a film shape. Therefore, the piezoelectric film 113 (first piezoelectric body) includes a front main surface S111 (first piezoelectric body first main surface) and a rear main surface S112 (first piezoelectric body second main surface). The main surfaces of the piezoelectric film 113 (first piezoelectric body) have a rectangular shape when viewed in the normal direction to the main surface of the sheet 13 (first sheet) in a state in which the piezoelectric film 113 (first piezoelectric body) is unfolded into a plane. In this embodiment, when the sheet 13 (first sheet) is unfolded into a plane, the front main surface S111 and the rear main surface S112 of the piezoelectric film 113 (first piezoelectric body) have a rectangular shape with long sides extending in the up-down direction and short sides extending in the left-right direction in a front-rear direction. In this embodiment, the longitudinal direction of the piezoelectric film 113 (first piezoelectric element) is the up-down direction, and the lateral direction of the piezoelectric film 113 (first piezoelectric element) is the left-right direction. In this embodiment, the piezoelectric film 113 is a PLA film.

[0017] The second sensor unit 12 detects deformation of the shaft 21 (described later) and includes a film shape. However, the direction of deformation of the shaft 21 (described later) detected by the first sensor unit 11 and the direction of deformation of the shaft 21 (described later) detected by the second sensor unit 12 are the same. The second sensor unit 12 includes a front principal surface and a rear principal surface. As shown in FIG. 3, the second sensor unit 12 includes a piezoelectric film 123, a third electrode 124a, and a fourth electrode 124b.

[0018] The piezoelectric film 123 is an example of a piezoelectric body. The piezoelectric film 123 has a film shape. Therefore, the piezoelectric film 123 (second piezoelectric body) includes a front main surface S121 (first main surface of the second piezoelectric body) and a rear main surface S122 (second main surface of the second piezoelectric body). The main surfaces of the piezoelectric film 123 (second piezoelectric body) have a rectangular shape when viewed in the normal direction to the main surface of the sheet 13 (first sheet) in a state in which the piezoelectric film 123 (second piezoelectric body) is unfolded into a plane. In this embodiment, when the sheet 13 (first sheet) is unfolded into a plane, the front main surface S121 and the rear main surface S122 of the piezoelectric film 123 (second piezoelectric body) have a rectangular shape with long sides extending in the up-down direction and short sides extending in the left-right direction in a front-rear direction. In this embodiment, the longitudinal direction of the piezoelectric film 123 (second piezoelectric body) is the up-down direction, and the lateral direction of the piezoelectric film 123 (second piezoelectric body) is the left-right direction. In this embodiment, the piezoelectric film 123 is a PLA film. Piezoelectric film 113 and piezoelectric film 123 will be described in more detail below.

[0019] Piezoelectric films 113 and 123 generate electric charges corresponding to the differential values ​​of the deformations of piezoelectric films 113 and 123, respectively. Piezoelectric films 113 and 123 have the characteristic that the polarity of the electric charges generated when they are stretched in the vertical direction is opposite to the polarity of the electric charges generated when they are stretched in the horizontal direction, respectively. Specifically, piezoelectric films 113 and 123 are each films formed from a chiral polymer. An example of a chiral polymer is polylactic acid (PLA), particularly poly-L-lactic acid (PLLA). PLLA, which is made of a chiral polymer, has a helical main chain structure. PLLA has piezoelectric properties in which the molecules are oriented when stretched uniaxially. Piezoelectric films 113 and 123 each have a piezoelectric constant of d14.

[0020] The uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) forms a 45-degree angle clockwise with respect to the vertical direction and a 45-degree angle counterclockwise with respect to the horizontal direction. That is, the piezoelectric film 113 (first piezoelectric element) is stretched in at least one axial direction. This 45-degree angle includes, for example, an angle of approximately 45 degrees ±10 degrees. As a result, the piezoelectric film 113 generates electric charge when the piezoelectric film 113 is deformed so as to be expanded or compressed in the vertical direction. For example, when the piezoelectric film 113 is deformed so as to be expanded in the vertical direction, the piezoelectric film 113 generates a negative electric charge. When the piezoelectric film 113 is deformed so as to be compressed in the vertical direction, the piezoelectric film 113 generates a positive electric charge. The magnitude of the electric charge depends on the differential value of the deformation of the piezoelectric film 113 due to expansion or compression.

[0021] The uniaxial stretching axis OD2 of the piezoelectric film 123 (second piezoelectric element) forms a 45-degree counterclockwise angle with respect to the vertical direction and a 45-degree clockwise angle with respect to the horizontal direction. That is, the piezoelectric film 123 (second piezoelectric element) is stretched in at least one axial direction. This 45-degree angle includes, for example, an angle of approximately 45 degrees ±10 degrees. As a result, the uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) forms an angle of 90 degrees clockwise with respect to the uniaxial stretching axis OD2 of the piezoelectric film 123 (second piezoelectric element) when the sheet 13 (first sheet) is laid out flat. This 90 degrees includes, for example, an angle of approximately 90 degrees ±10 degrees. Furthermore, the piezoelectric film 123 generates electric charges when the piezoelectric film 123 is deformed so as to be expanded or compressed in the vertical direction. For example, the piezoelectric film 123 generates positive electric charges when it is deformed so as to be expanded in the vertical direction. For example, when the piezoelectric film 123 is deformed so as to be compressed in the vertical direction, it generates a negative charge. The magnitude of the charge depends on the differential value of the deformation amount of the piezoelectric film 123 due to expansion or compression.

[0022] The first electrode 114a is a signal electrode. As shown in Fig. 2, the first electrode 114a is provided on the rear main surface S112 (the second main surface of the first piezoelectric element). The first electrode 114a covers the rear main surface S112. The first electrode 114a is, for example, an organic electrode made of ITO (indium tin oxide), ZnO (zinc oxide), or the like, a metal film formed by vapor deposition or plating, or a printed electrode film made of silver paste.

[0023] The second electrode 114b is a ground electrode. The second electrode 114b is connected to a ground potential. As shown in FIG. 2, the second electrode 114b is provided on the front main surface S111 (first main surface of the first piezoelectric element). As a result, the piezoelectric film 113 is located between the first electrode 114a and the second electrode 114b. The second electrode 114b covers the front main surface S111. The second electrode 114b is, for example, an organic electrode made of ITO (indium tin oxide), ZnO (zinc oxide), or the like, a metal film formed by vapor deposition or plating, or a printed electrode film made of silver paste.

[0024] The first sensor unit 11 is attached to the sheet 13 (first sheet) via an adhesive layer (not shown). More specifically, the adhesive layer is conductive. Specifically, the adhesive layer fixes the first electrode 114a to the front main surface of the sheet 13 (first sheet). That is, the rear main surface of the first sensor unit 11 is fixed to the front main surface of the sheet 13.

[0025] The third electrode 124a is a signal electrode. As shown in Fig. 3, the third electrode 124a is provided on the rear main surface S122 (the second main surface of the second piezoelectric element). The third electrode 124a covers the rear main surface S122. The third electrode 124a is, for example, an organic electrode made of ITO (indium tin oxide), ZnO (zinc oxide), or the like, a metal film formed by vapor deposition or plating, or a printed electrode film made of silver paste.

[0026] The fourth electrode 124b is a ground electrode. The fourth electrode 124b is connected to a ground potential. As shown in FIG. 3, the fourth electrode 124b is provided on the front main surface S121 (the first main surface of the second piezoelectric body). As a result, the piezoelectric film 123 is located between the third electrode 124a and the fourth electrode 124b. The fourth electrode 124b covers the front main surface S121. The fourth electrode 124b is, for example, an organic electrode made of ITO (indium tin oxide), ZnO (zinc oxide), or the like, a metal film formed by vapor deposition or plating, or a printed electrode film made of silver paste.

[0027] The second sensor unit 12 is attached to the sheet 13 (first sheet) via an adhesive layer (not shown). More specifically, the adhesive layer is conductive. Specifically, the adhesive layer secures the third electrode 124a to the front main surface of the sheet 13 (first sheet). That is, the rear main surface of the second sensor unit 12 is secured to the front main surface of the sheet 13.

[0028] The sheet 13 is attached to the shaft 21, which will be described later. The sheet 13 (first sheet) is conductive. As a result, the sheet 13 (first sheet) electrically connects the first electrode 114a and the third electrode 124a of the second sensor unit 12. Therefore, the third electrode 124a is connected to the charge amplifier 115 via the first electrode 114a.

[0029] Charge amplifier 115 converts the charges generated by piezoelectric film 113 and piezoelectric film 123 into a detection signal, which is a voltage signal, and outputs it to voltage amplifier circuit 116. Voltage amplifier circuit 116 amplifies the detection signal and outputs it.

[0030] Returning to the description of the sheet 13, the sheet 13 includes a front main surface and a rear main surface. The front and rear main surfaces of the sheet 13 are rectangular. The front main surface of the sheet 13 has a rectangular shape with a left short side extending in the vertical direction, a right short side extending in the vertical direction, an upper long side extending in the horizontal direction, and a lower long side extending in the horizontal direction. The rear main surface of the sheet 13 has a left short side extending in the vertical direction, a right short side extending in the vertical direction, an upper long side extending in the horizontal direction, and a lower long side extending in the horizontal direction. The lengths of the upper long side and the lower long side of the front main surface of the sheet 13 and the upper long side and the lower long side of the rear main surface of the sheet 13 are equal to or greater than the circumference of the cross-sectional circle of the shaft 21 (described below) when the sheet 13 is unfolded flat. An adhesive layer (not shown) is provided on the rear main surface of the sheet 13. The adhesive layer is insulating.

[0031] 1, when the sheet 13 is unfolded on a plane, the front main surface of the first sensor unit 11 is disposed at a position that does not overlap with the front main surface of the second sensor unit 12 when viewed in the front-rear direction. That is, when the sheet 13 is unfolded on a plane, the front main surface of the first sensor unit 11 has a portion that does not overlap with the front main surface of the second sensor unit 12 when viewed in the front-rear direction. The front main surface of the second sensor unit 12 is disposed at a position that does not overlap with the front main surface of the first sensor unit 11 when viewed in the front-rear direction. That is, when the sheet 13 is unfolded on a plane, the front main surface of the second sensor unit 12 has a portion that does not overlap with the front main surface of the first sensor unit 11 when viewed in the front-rear direction.

[0032] 1, when sheet 13 (first sheet) is laid out flat, the left and right short sides of the front main surface of sheet 13, the long sides of first sensor unit 11 (the longitudinal direction of the first piezoelectric element), and the long sides of second sensor unit 12 (the longitudinal direction of the second piezoelectric element) are parallel to one another. Furthermore, when sheet 13 is laid out flat, the upper and lower long sides of the front main surface of sheet 13, the short sides of first sensor unit 11, and the short sides of second sensor unit 12 are parallel to one another.

[0033] As shown in FIG. 1 , when the seat 13 is unfolded flat, a first center point CP1 of the first sensor unit 11 is defined when viewed in the front-to-back direction. The first center point CP1 is, for example, the center of gravity of the front main surface of the first sensor unit 11. The first center point CP1 may also be, for example, the center of gravity of the rear main surface of the first sensor unit 11. The first center point CP1 may also be, for example, the center of the front main surface of the first sensor unit 11. In this case, for example, if two diagonals are defined on the front main surface of the first sensor unit 11, the two diagonals intersect at the first center point CP1. For example, if a line connecting the midpoints of two short sides and a line connecting the midpoints of two long sides are defined on the front main surface of the first sensor unit 11, the line connecting the midpoints of the two short sides and the line connecting the midpoints of the two long sides intersect at the first center point CP1. The first center point CP1 may also be, for example, the center of the rear main surface of the first sensor unit 11. In this case, for example, if two diagonals are defined on the rear principal surface of the first sensor unit 11, the two diagonals intersect at the first center point CP1. Also, for example, if a line connecting the midpoints of the two short sides and a line connecting the midpoints of the two long sides are defined on the rear principal surface of the first sensor unit 11, the line connecting the midpoints of the two short sides and the line connecting the midpoints of the two long sides intersect at the first center point CP1.

[0034] Similarly, when the seat 13 is laid out flat, a second center point CP2 of the second sensor unit 12 is defined as viewed in the front-to-rear direction. Note that the definition of the second center point CP2 is similar to the definition of the first center point CP1, and therefore a detailed description thereof will be omitted.

[0035] As shown in FIG. 1, when the seat 13 is unfolded on a plane, an arbitrary straight line L1 extending in the left-right direction is defined as the line L1 when viewed in the front-to-back direction. When the seat 13 is unfolded on a plane, a perpendicular line drawn from the first center point CP1 to the line L1 when viewed in the front-to-back direction is defined as the first intersection point P1. When viewed in the front-to-back direction, a perpendicular line drawn from the second center point CP2 to the line L1 is defined as the second intersection point P2. The distance between the first intersection point P1 and the second intersection point P2 is defined as the first distance D1. In this embodiment, the first distance D1 is equal to half the circumference of the cross-sectional circle of the shaft 21 (described below) when the seat 13 is unfolded on a plane.

[0036] As shown in FIG. 4, the golf club 20 includes a shaft 21 and a head 22. The shaft 21 is cylindrical. The central axis of the cylinder is aligned with the third direction DIR3. That is, the shaft 21 extends in the third direction DIR3. A cross section of the shaft 21 perpendicular to the third direction DIR3 has a circular shape. The circumferential direction of the cross-sectional circle of the shaft 21 is aligned with the circumferential direction DIRC. The shaft 21 has a first end and a second end in the third direction DIR3. The head 22 is provided at the first end of the shaft 21. The grip is provided near the second end of the shaft 21. In this embodiment, the object to be measured is the shaft 21.

[0037] The sensor unit 10 is attached to the circumferential surface of the shaft 21. Specifically, the rear main surface of the sheet 13 is fixed to the shaft 21 by an adhesive layer (not shown) provided on the rear main surface of the sheet 13. In the example of FIG. 4, the sensor unit 10 is attached near the grip of the shaft 21, but the attachment position of the sensor unit 10 to the shaft 21 is not limited to this. When the sensor unit 10 is attached to the shaft 21, the direction in which the upper long side and the lower long side of the front main surface of the sheet 13 extend is the same as the circumferential direction DIRC.

[0038] As described above, the direction in which the upper long side and the lower long side of the front main surface of the seat 13 extend is the same as the circumferential direction DIRC. Therefore, the first distance D1 is equal to the distance in the circumferential direction DIRC between the first center point CP1 of the first sensor unit 11 and the second center point CP2 of the second sensor unit 12. Also, as described above, the first distance D1 is equal to half the circumference of the cross-sectional circle of the shaft 21 when the seat 13 is unfolded on a plane. Therefore, the first center point CP1 of the first sensor unit 11 and the second center point CP2 of the second sensor unit 12 are disposed 180 degrees apart in the circumferential direction DIRC of the shaft 21. That is, as shown in FIG. 5, when the sensor unit 10 is attached to the shaft 21, the first sensor unit 11 and the second sensor unit 12 are fixed to the shaft 21 such that the shaft 21 is disposed between the first sensor unit 11 and the second sensor unit 12 in the first direction DIR1. As a result, the first sensor unit 11 detects deformation in the first direction DIR1 of the shaft 21. Similarly, the second sensor unit 12 detects deformation in the first direction DIR1 of the shaft 21. In this embodiment, the deformation of the shaft 21 detected by the first sensor unit 11 is deformation (bending) of the shaft 21 in the first direction DIR1, and the deformation of the shaft 21 detected by the second sensor unit 12 is deformation (bending) of the shaft 21 in the first direction DIR1.

[0039] For example, when shaft 21 is deformed in first direction DIR1, piezoelectric film 113 generates an electric charge and piezoelectric film 123 generates an electric charge in response to the deformation of shaft 21. That is, the electrical characteristics of piezoelectric film 113 and the electrical characteristics of piezoelectric film 123 change in response to the deformation (first deformation) of shaft 21. Piezoelectric film 113 is compressed in the vertical direction and generates a positive electric charge, and piezoelectric film 123 is stretched in the vertical direction and generates a positive electric charge. That is, the polarity of the electric charge generated by piezoelectric film 113 and the polarity of the electric charge generated by piezoelectric film 123 become equal.

[0040] However, when the shaft 21 is deformed in the second direction DIR2, the piezoelectric film 113 generates no charge or generates almost no charge, and the piezoelectric film 123 generates no charge or generates almost no charge, in response to the deformation of the shaft 21. That is, the electrical characteristics of the piezoelectric film 113 and the electrical characteristics of the piezoelectric film 123 do not change or change almost only in response to the deformation (second deformation) of the shaft 21.

[0041] [effect] The sensor unit 10 can improve detection accuracy. More specifically, a cross section of the shaft 21 perpendicular to the third direction DIR3 has a circular shape. The first sensor unit 11 and the second sensor unit 12 are fixed to the shaft 21 such that the shaft 21 is disposed between the first sensor unit 11 and the second sensor unit 12 in the first direction DIR1 when attached to the shaft 21. The electrical characteristics of the first sensor unit 11 and the second sensor unit 12 change in response to deformation of the shaft 21. As a result, when the shaft 21 is deformed (bent) in the first direction DIR1, the piezoelectric film 113 compresses and the piezoelectric film 123 expands, causing both the piezoelectric film 113 and the piezoelectric film 123 to generate electric charges. Therefore, the potential of the detection signal of the first sensor unit 11 changes, and the potential of the detection signal of the second sensor unit 12 changes. As a result, the detection signal of the first sensor unit 11 and the detection signal of the second sensor unit 12 can be used to detect deformation of the shaft 21. As a result, the sensor unit 10 can improve the accuracy of detecting the deformation of the shaft 21.

[0042] The sensor unit 10 facilitates generation of detection signals from the first sensor section 11 and the second sensor section 12. More specifically, the uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) forms a 45-degree angle clockwise with respect to the up-down direction and a 45-degree angle counterclockwise with respect to the left-right direction. The uniaxial stretching axis OD2 of the piezoelectric film 123 (second piezoelectric element) forms a 45-degree angle counterclockwise with respect to the up-down direction and a 45-degree angle clockwise with respect to the left-right direction. As a result, when the sheet 13 (first sheet) is unfolded on a plane, the uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) forms a 90-degree angle clockwise with respect to the uniaxial stretching axis OD2 of the piezoelectric film 123 (second piezoelectric element). As a result, when the shaft 21 is deformed (bent) in the first direction DIR1, the polarity of the charge generated by the piezoelectric film 113 and the polarity of the charge generated by the piezoelectric film 123 become equal. Therefore, a detection signal can be generated by adding the charge generated by piezoelectric film 113 and the charge generated by piezoelectric film 123. As a result, it becomes easy to generate the detection signals of first sensor unit 11 and second sensor unit 12.

[0043] In the sensor unit 10, the sheet 13 (first sheet) electrically connects the first electrode 114a and the third electrode 124a. This allows the detection signals of the first sensor section 11 and the second sensor section 12 to be generated by one charge amplifier 115 and one voltage amplifier circuit 116. As a result, the circuit configuration of the sensor unit 10 is simplified.

[0044] [First Modification] A sensor unit 10a according to a first modified example of the present invention will be described below with reference to the drawings. Fig. 6 is a plan view of sensor unit 10a according to the first modified example in a state where sheet 13a according to the first modified example is laid out flat. Regarding sensor unit 10a according to the first modified example, only the parts that differ from the arrangement structure of sensor unit 10 according to the first embodiment will be described, and the rest will be omitted.

[0045] As shown in FIG. 6, the sensor unit 10a further includes a sheet 14a. The sheet 13a (first sheet) is insulating. The sheet 14a (second sheet) is conductive. The sheet 14a has a strip shape extending in the left-right direction when viewed in the front-rear direction. The sheet 14a is attached to the first sensor unit 11a and the second sensor unit 12a. Specifically, the sheet 14a (second sheet) electrically connects the first electrode 114a and the third electrode 124a. The left portion of the sheet 14a is attached to the top of the first electrode 114a. The right portion of the sheet 14a is attached to the top of the third electrode 124a.

[0046] The sensor unit 10a as described above also has the same effects as the sensor unit 10.

[0047] In this modification, sheet 14a electrically connects first electrode 114a and third electrode 124a, but sheet 14a may also electrically connect second electrode 114b and fourth electrode 124b.

[0048] Furthermore, sensor unit 10a may further include conductive sheet 14e, and first sensor unit 11a and second sensor unit 12a may be connected by sheet 14e. Specifically, sheet 14a may connect first electrode 114a and third electrode 124a, and sheet 14e may connect second electrode 114b and fourth electrode 124b. That is, sheet 14a (second sheet) may electrically connect first electrode 114a and third electrode 124a, and sheet 14e (third sheet) may electrically connect second electrode 114b and fourth electrode 124b.

[0049] [Second embodiment] A sensor unit 10b according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is a plan view of the sensor unit 10b according to the second embodiment, with the sheet 13b laid out flat. FIG. 8 is a plan view and a cross-sectional view of the third sensor unit 15b according to the second embodiment, with the sheet 13b laid out flat. FIG. 9 is a plan view and a cross-sectional view of the fourth sensor unit 16b according to the second embodiment, with the sheet 13b laid out flat. FIG. 10 is a perspective view of the sensor unit 10b according to the second embodiment, attached to the shaft 21b. FIG. 11 is a cross-sectional view of the sensor unit 10b according to the second embodiment, attached to the shaft 21b, taken along line AA. Note that only the differences between the sensor unit 10b according to the second embodiment and the sensor unit 10 according to the first embodiment will be described, and the rest will be omitted.

[0050] As shown in Fig. 7, sensor unit 10b further includes sheet 14b, third sensor unit 15b, fourth sensor unit 16b, and sheet 17b. When sheet 13b is laid out flat, first sensor unit 11b, second sensor unit 12b, third sensor unit 15b, and fourth sensor unit 16b are arranged in this order from left to right. Sheet 13b (first sheet) is insulating. Sheet 14b (second sheet) and sheet 17b (fourth sheet) are conductive.

[0051] The third sensor unit 15b detects deformation of the shaft 21b, which is the object to be measured, and includes the shape of the film. However, the direction of deformation of the shaft 21b, which is the object to be measured, detected by the first sensor unit 11b and the second sensor unit 12b (first direction) is different from the direction of deformation of the shaft 21b, which is the object to be measured, detected by the third sensor unit 15b (second direction). The third sensor unit 15b includes a front principal surface and a rear principal surface.

[0052] As shown in FIG. 8, the third sensor unit 15b includes a piezoelectric film 153, a fifth electrode 154a, a sixth electrode 154b, a charge amplifier 155, and a voltage amplification circuit 156.

[0053] The piezoelectric film 153 is an example of a piezoelectric body. The piezoelectric film 153 has a film shape. Therefore, the piezoelectric film 153 (third piezoelectric body) includes a front main surface S151 (first main surface of the third piezoelectric body) and a rear main surface S152 (second main surface of the third piezoelectric body). The main surfaces of the piezoelectric film 153 (third piezoelectric body) have a rectangular shape when viewed in the normal direction to the main surface of the sheet 13b (first sheet) in a state in which the piezoelectric film 153 (third piezoelectric body) is spread out on a plane. In this embodiment, when the sheet 13b (first sheet) is spread out on a plane, the front main surface S151 and the rear main surface S152 of the piezoelectric film 153 (third piezoelectric body) have a rectangular shape with long sides extending in the up-down direction and short sides extending in the left-right direction in a front-rear direction. In this embodiment, the longitudinal direction of the piezoelectric film 153 (third piezoelectric element) is the up-down direction, and the lateral direction of the piezoelectric film 153 (third piezoelectric element) is the left-right direction. In this embodiment, the piezoelectric film 153 is a PLA film. The PLA film is the same as in the first embodiment, and therefore a description thereof will be omitted. In this embodiment, the uniaxial stretching axis OD3 of the piezoelectric film 153 (third piezoelectric element) forms a 45-degree angle clockwise with respect to the up-down direction and a 45-degree angle counterclockwise with respect to the left-right direction. That is, the piezoelectric film 153 (third piezoelectric element) is stretched in at least one axial direction. This 45-degree angle includes, for example, an angle of approximately 45 degrees ±10 degrees. Note that the fifth electrode 154a, the sixth electrode 154b, the charge amplifier 155, and the voltage amplifier circuit 156 have the same structures as the first electrode 114a, the second electrode 114b, the charge amplifier 115, and the voltage amplifier circuit 116, and therefore a description thereof will be omitted.

[0054] The third sensor unit 15b is attached to the sheet 13b (first sheet) via an adhesive layer (not shown). Specifically, the adhesive layer fixes the fifth electrode 154a to the front main surface of the sheet 13b (first sheet). That is, the rear main surface of the third sensor unit 15b is fixed to the front main surface of the sheet 13b.

[0055] The fourth sensor unit 16b detects deformation of the shaft 21b, which is the object to be measured, and includes the shape of the film. However, the direction of deformation of the shaft 21b, which is the object to be measured, detected by the third sensor unit 15b is the same as the direction of deformation of the shaft 21b, which is the object to be measured, detected by the fourth sensor unit 16b. The fourth sensor unit 16b includes a front principal surface and a rear principal surface.

[0056] As shown in FIG. 9, the fourth sensor unit 16b includes a piezoelectric film 163, a seventh electrode 164a, and an eighth electrode 164b.

[0057] The piezoelectric film 163 is an example of a piezoelectric element. The piezoelectric film 163 has a film shape. Therefore, the piezoelectric film 163 (fourth piezoelectric element) includes a front main surface S161 (first main surface of the fourth piezoelectric element) and a rear main surface S162 (second main surface of the fourth piezoelectric element). The main surfaces of the piezoelectric film 163 (fourth piezoelectric element) have a rectangular shape when viewed in the normal direction to the main surface of the sheet 13b (first sheet) in a state in which the piezoelectric film 163 (fourth piezoelectric element) is unfolded into a plane. In this embodiment, when the sheet 13b (first sheet) is unfolded into a plane, the front main surface S161 and the rear main surface S162 of the piezoelectric film 163 (fourth piezoelectric element) have a rectangular shape with long sides extending in the up-down direction and short sides extending in the left-right direction in a front-rear direction. In this embodiment, the longitudinal direction of the piezoelectric film 163 (piezoelectric element) of the fourth sensor unit 16b is the up-down direction, and the lateral direction of the piezoelectric film 163 (piezoelectric element) of the fourth sensor unit 16b is the left-right direction. Furthermore, in this embodiment, the piezoelectric film 163 is a PLA film. The PLA film is the same as in the first embodiment, and a description thereof will be omitted. In this embodiment, the uniaxial stretching axis OD4 of the piezoelectric film 163 (fourth piezoelectric element) forms a 45-degree angle counterclockwise with respect to the up-down direction and a 45-degree angle clockwise with respect to the left-right direction. That is, the piezoelectric film 163 (fourth piezoelectric element) is stretched in at least one axial direction. This 45 degrees includes, for example, an angle of approximately 45 degrees ±10 degrees. As a result, when the sheet 13b (first sheet) is laid out flat, the uniaxially stretched axis OD3 of the piezoelectric film 153 (third piezoelectric element) forms an angle of 90 degrees clockwise with respect to the uniaxially stretched axis OD4 of the piezoelectric film 163 (fourth piezoelectric element). This 90 degrees includes, for example, an angle of approximately 90 degrees ±10 degrees. Note that the seventh electrode 164a and the eighth electrode 164b have the same structure as the first electrode 114a and the second electrode 114b, and therefore a description thereof will be omitted.

[0058] The fourth sensor unit 16b is attached to the sheet 13b (first sheet) via an adhesive layer (not shown). Specifically, the adhesive layer secures the seventh electrode 164a to the front main surface of the sheet 13b (first sheet). That is, the rear main surface of the fourth sensor unit 16b is secured to the front main surface of the sheet 13b.

[0059] 7, sheet 14b (second sheet) is attached to first sensor unit 11b and second sensor unit 12b. Specifically, sheet 14b (second sheet) electrically connects first electrode 114a and third electrode 124a. The left portion of sheet 14b is attached to the top of first electrode 114a. The right portion of sheet 14b is attached to the top of third electrode 124a.

[0060] 7, sheet 17b (fourth sheet) is attached to third sensor unit 15b and fourth sensor unit 16b. Specifically, sheet 17b (fourth sheet) electrically connects fifth electrode 154a and seventh electrode 164a. The left portion of sheet 17b is attached to the lower portion of fifth electrode 154a. The right portion of sheet 17b is attached to the lower portion of seventh electrode 164a.

[0061] As shown in Fig. 7, when sheet 13b is unfolded flat, the front main surface of third sensor unit 15b is disposed at a position that does not overlap with the front main surface of fourth sensor unit 16b when viewed in the front-rear direction. That is, when sheet 13b is unfolded flat, the front main surface of third sensor unit 15b has a portion that does not overlap with the front main surface of fourth sensor unit 16b when viewed in the front-rear direction. The front main surface of fourth sensor unit 16b is disposed at a position that does not overlap with the front main surface of third sensor unit 15b when viewed in the front-rear direction. That is, when sheet 13b is unfolded flat, the front main surface of fourth sensor unit 16b has a portion that does not overlap with the front main surface of third sensor unit 15b when viewed in the front-rear direction.

[0062] 7, when sheet 13b (first sheet) is laid out flat, the left and right short sides of the front main surface of sheet 13b, the long sides of first sensor unit 11b (the longitudinal direction of the first piezoelectric element), the long sides of second sensor unit 12b (the longitudinal direction of the second piezoelectric element), the long sides of third sensor unit 15b (the longitudinal direction of the third piezoelectric element), and the long sides of fourth sensor unit 16b (the longitudinal direction of the fourth piezoelectric element) are parallel to one another. Also, when sheet 13b is laid out flat, the upper and lower long sides of the front main surface of sheet 13b, the short sides of first sensor unit 11b, the short sides of second sensor unit 12b, the short sides of third sensor unit 15b, and the short sides of fourth sensor unit 16b are parallel to one another.

[0063] 7, when the sheet 13b is laid out flat, a third center point CP3b of the third sensor unit 15b and a fourth center point CP4b of the fourth sensor unit 16b are defined as viewed in the front-to-rear direction. Note that the definitions of the third center point CP3b and the fourth center point CP4b are the same as those of the first center point CP1, and therefore detailed description thereof will be omitted.

[0064] As shown in FIG. 7, when the sheet 13b is unfolded on a plane, as viewed in the front-to-rear direction, the intersection of a perpendicular line drawn from the third center point CP3b to the line L1 and the line L1 is defined as a third intersection P3b. Also, as viewed in the front-to-rear direction, the intersection of a perpendicular line drawn from the fourth center point CP4b to the line L1 and the line L1 is defined as a fourth intersection P4b. The distance between the third intersection P3b and the fourth intersection P4b is defined as a second distance D2b. The distance between the first intersection P1b and the third intersection P3b is defined as a third distance D3b. The distance between the first intersection P1b and the fourth intersection P4b is defined as D4b. The distance between the second intersection P2b and the third intersection P3b is defined as D5b. The distance between the second intersection P2b and the fourth intersection P4b is defined as D6b.

[0065] In this embodiment, the first distance D1b is equal to half the circumference of the cross-sectional circle of the shaft 21b to be measured when the sheet 13b is unfolded on a plane. The second distance D2b is equal to half the circumference of the cross-sectional circle of the shaft 21b to be measured when the sheet 13b is unfolded on a plane. The third distance D3b is equal to one-fourth the circumference of the cross-sectional circle of the shaft 21b to be measured when the sheet 13b is unfolded on a plane. The fourth distance D4b is equal to three-fourths the circumference of the cross-sectional circle of the shaft 21b to be measured when the sheet 13b is unfolded on a plane. The fifth distance D5b is equal to one-fourth the circumference of the cross-sectional circle of the shaft 21b to be measured when the sheet 13b is unfolded on a plane. Furthermore, the sixth distance D6b in this embodiment is equal to one-fourth the length of the circumference of the cross-sectional circle of the shaft 21b, which is the object to be measured, when the sheet 13b is laid out flat.

[0066] As shown in FIGS. 10 and 11, the sensor unit 10b is attached to the circumferential surface of the shaft 21b. Specifically, the rear main surface of the sheet 13b is fixed to the shaft 21b by an adhesive layer (not shown) provided on the rear main surface of the sheet 13b. As described above, the second distance D2b is equal to half the circumference of the cross-sectional circle of the shaft 21b when the sheet 13b is unfolded flat. As a result, the third center point CP3b of the third sensor unit 15b and the fourth center point CP4b of the fourth sensor unit 16b are disposed 180 degrees apart in the circumferential direction DIRC of the shaft 21b. That is, as shown in FIG. 11, when the sensor unit 10b is attached to the shaft 21b, the third sensor unit 15b and the fourth sensor unit 16b are fixed to the shaft 21b such that the shaft 21b is disposed between the third sensor unit 15b and the fourth sensor unit 16b in the second direction DIR2. As a result, the third sensor unit 15b detects deformation of the shaft 21b in the second direction DIR2. Similarly, the fourth sensor unit 16b detects deformation of the shaft 21b in the second direction DIR2. In this embodiment, the deformation of the shaft 21b detected by the third sensor unit 15b is deformation (bending) of the shaft 21b in the second direction DIR2, and the deformation of the shaft 21b detected by the fourth sensor unit 16b is deformation (bending) of the shaft 21b in the second direction DIR2.

[0067] As described above, the third distance D3b is equal to one-fourth the circumference of the cross-sectional circle of the shaft 21b when the sheet 13b is unfolded on a plane. As a result, the first center point CP1b of the first sensor unit 11b and the third center point CP3b of the third sensor unit 15b are disposed 90 degrees apart in the circumferential direction DIRC of the shaft 21b. In other words, the first direction DIR1 and the second direction DIR2 are 90 degrees apart when viewed from the third direction DIR3.

[0068] For example, when shaft 21b is deformed in first direction DIR1, piezoelectric film 113 generates an electric charge and piezoelectric film 123 generates an electric charge in response to the deformation of shaft 21b. That is, the electrical characteristics of piezoelectric film 113 and the electrical characteristics of piezoelectric film 123 change in response to the deformation (first deformation) of shaft 21b. Piezoelectric film 113 is compressed in the vertical direction and generates a positive electric charge, and piezoelectric film 123 is stretched in the vertical direction and generates a positive electric charge. That is, the polarity of the electric charge generated by piezoelectric film 113 and the polarity of the electric charge generated by piezoelectric film 123 become equal.

[0069] However, when shaft 21b is deformed in the first direction DIR1, piezoelectric film 153 generates no or almost no charge, and piezoelectric film 163 generates no or almost no charge, in response to the deformation of shaft 21b. That is, the electrical characteristics of piezoelectric film 153 and the electrical characteristics of piezoelectric film 163 do not change or change almost only in response to the deformation (first deformation) of shaft 21b.

[0070] For example, when shaft 21b is deformed in second direction DIR2, piezoelectric film 153 generates an electric charge and piezoelectric film 163 generates an electric charge in response to the deformation of shaft 21b. That is, the electrical characteristics of piezoelectric film 153 and the electrical characteristics of piezoelectric film 163 change in response to the deformation (second deformation) of shaft 21b. Piezoelectric film 153 is stretched in the vertical direction and generates a negative electric charge, and piezoelectric film 163 is compressed in the vertical direction and generates a negative electric charge. That is, the polarity of the electric charge generated by piezoelectric film 153 and the polarity of the electric charge generated by piezoelectric film 163 become equal.

[0071] However, when shaft 21b is deformed in the second direction DIR2, piezoelectric film 113 generates no or almost no charge, and piezoelectric film 123 generates no or almost no charge, in response to the deformation of shaft 21b. That is, the electrical characteristics of piezoelectric film 113 and the electrical characteristics of piezoelectric film 123 do not change or change almost only in response to the deformation (second deformation) of shaft 21b.

[0072] The sensor unit 10b described above also achieves the same effects as the sensor unit 10. It also improves the detection accuracy of deformation of the shaft 21b in the first direction DIR1 and the second direction DIR2, which is different from the first direction DIR1. More specifically, the cross section of the shaft 21b perpendicular to the third direction DIR3 has a circular shape. The third sensor unit 15b and the fourth sensor unit 16b are fixed to the shaft 21b such that the shaft 21b is positioned between the third sensor unit 15b and the fourth sensor unit 16b in the second direction DIR2, which is different from the first direction DIR1, when attached to the shaft 21b. The electrical characteristics of the third sensor unit 15b and the fourth sensor unit 16b change in response to the deformation of the shaft 21b. As a result, when shaft 21b is deformed (bent) in the second direction DIR2, piezoelectric film 153 compresses and piezoelectric film 163 expands, causing both piezoelectric film 153 and piezoelectric film 163 to generate electric charges. This changes the potential of the detection signal of third sensor unit 15b and the potential of the detection signal of fourth sensor unit 16b. This allows the detection signals of third sensor unit 15b and fourth sensor unit 16b to be used to detect deformation of shaft 21b. As a result, sensor unit 10b can improve the accuracy of detecting deformation of shaft 21b.

[0073] The sensor unit 10b facilitates generation of detection signals from the third sensor unit 15b and the fourth sensor unit 16b. More specifically, the uniaxial stretching axis OD3 of the piezoelectric film 153 (third piezoelectric element) forms a 45-degree angle clockwise with respect to the up-down direction and a 45-degree angle counterclockwise with respect to the left-right direction. The uniaxial stretching axis OD4 of the piezoelectric film 163 (fourth piezoelectric element) forms a 45-degree angle counterclockwise with respect to the up-down direction and a 45-degree angle clockwise with respect to the left-right direction. As a result, when the sheet 13 (first sheet) is unfolded on a plane, the uniaxial stretching axis OD3 of the piezoelectric film 153 (third piezoelectric element) forms a 90-degree angle clockwise with respect to the uniaxial stretching axis OD4 of the piezoelectric film 163 (fourth piezoelectric element). As a result, when the shaft 21b is deformed (bent) in the second direction DIR2, the polarity of the charge generated by the piezoelectric film 153 becomes equal to the polarity of the charge generated by the piezoelectric film 163. Therefore, a detection signal can be generated by adding the charge generated by piezoelectric film 153 and the charge generated by piezoelectric film 163. As a result, it becomes easier to generate the detection signals of third sensor unit 15b and fourth sensor unit 16b.

[0074] In sensor unit 10b, sheet 17b (fourth sheet) electrically connects fifth electrode 154a and seventh electrode 164a. This allows detection signals of third sensor section 15b and fourth sensor section 16b to be generated by one charge amplifier 155 and one voltage amplifier circuit 156. As a result, the circuit configuration of sensor unit 10b is simplified.

[0075] In this embodiment, the sheet 17b electrically connects the fifth electrode 154a and the seventh electrode 164a, but the sheet 17b may also electrically connect the sixth electrode 154b and the eighth electrode 164b.

[0076] Sensor unit 10b may further include conductive sheet 17e, and third sensor unit 15b and fourth sensor unit 16b may be connected by sheet 17e. Specifically, sheet 17b may connect fifth electrode 154a and seventh electrode 164a, and sheet 17e may connect sixth electrode 154b and eighth electrode 164b. That is, sheet 17b (fourth sheet) may electrically connect fifth electrode 154a and seventh electrode 164a, and sheet 17e (fifth sheet) may electrically connect sixth electrode 154b and eighth electrode 164b.

[0077] [Second Modification] A sensor unit 10c according to a second modified example of the present invention will be described below with reference to the drawings. Fig. 12 is a plan view of the sensor unit 10c according to the second modified example, with the sheet 13c according to the second modified example laid out flat. Regarding the sensor unit 10c according to the second modified example, only the differences in the arrangement structure of the sensor unit 10b according to the second embodiment will be described, and the rest will be omitted.

[0078] As shown in FIG. 12, when the sheet 13c is laid out flat, the first sensor unit 11c and the second sensor unit 12c are aligned from left to right. When the sheet 13c is laid out flat, the third sensor unit 15c and the fourth sensor unit 16c are aligned from left to right. The left side of the third sensor unit 15c is located below the right side of the first sensor unit 11c. The right side of the third sensor unit 15c is located below the left side of the second sensor unit 12c. The left side of the fourth sensor unit 16c is located below the right side of the second sensor unit 12c.

[0079] 12, when the sheet 13c is unfolded flat, the first sensor unit 11c has a portion that overlaps with the third sensor unit 15c when viewed in the vertical direction. When the sheet 13c is unfolded flat, the second sensor unit 12c has a portion that overlaps with the third sensor unit 15c and the fourth sensor unit 16c when viewed in the vertical direction. When the sheet 13c is unfolded flat, the third sensor unit 15c has a portion that overlaps with the first sensor unit 11c and the second sensor unit 12c when viewed in the vertical direction. When the sheet 13c is unfolded flat, the fourth sensor unit 16c has a portion that overlaps with the second sensor unit 12c when viewed in the vertical direction.

[0080] The sensor unit 10c described above also achieves the same effects as the sensor unit 10b. Furthermore, the areas of the front and rear principal surfaces of the first sensor unit 11c, the second sensor unit 12c, the third sensor unit 15c, and the fourth sensor unit 16c can be increased, thereby increasing the areas over which the first sensor unit 11c, the second sensor unit 12c, the third sensor unit 15c, and the fourth sensor unit 16c detect electric charges. This increases the voltage fluctuations of the detection signals of the first sensor unit 11c and the second sensor unit 12c. Furthermore, the voltage fluctuations of the detection signals of the third sensor unit 15c and the fourth sensor unit 16c also increase. As a result, the detection accuracy of the sensor unit 10c can be improved.

[0081] [Third embodiment] A sensor unit 10d according to a third embodiment of the present invention will be described below with reference to the drawings. FIG. 13 is a plan view of the sensor unit 10d according to the third embodiment, with the sheet 13d laid out flat. FIG. 14 is a plan view and a cross-sectional view of a fifth sensor section 18d according to the third embodiment, with the sheet 13d laid out flat. FIG. 15 is a perspective view of the sensor unit 10d according to the third embodiment, attached to the shaft 21d. FIG. 16 is a cross-sectional view of the sensor unit 10d according to the third embodiment, attached to the shaft 21d, taken along line AA. Note that only the differences between the sensor unit 10d according to the third embodiment and the sensor unit 10 according to the first embodiment will be described, and the rest will be omitted.

[0082] 13, sensor unit 10d further includes fifth sensor unit 18d and sheet 19d. When sheet 13d is laid out flat, first sensor unit 11d and fifth sensor unit 18d are arranged in this order from front to back.

[0083] The fifth sensor unit 18d detects deformation of the shaft 21d, which is the object to be measured, and includes a film shape. However, the direction of deformation of the shaft 21d, which is the object to be measured, detected by the first sensor unit 11d and the second sensor unit 12d is the same as the direction of deformation of the shaft 21d, which is the object to be measured, detected by the fifth sensor unit 18d. The fifth sensor unit 18d includes a front principal surface and a rear principal surface. Furthermore, the area of ​​the front principal surface of the fifth sensor unit 18d is smaller than the area of ​​the front principal surface of the first sensor unit 11d.

[0084] As shown in FIG. 14, the fifth sensor unit 18d includes a piezoelectric film 183, a ninth electrode 184a, a tenth electrode 184b, a charge amplifier 185, and a voltage amplification circuit 186.

[0085] The piezoelectric film 183 is an example of a piezoelectric body. The piezoelectric film 183 has a film shape. Therefore, the piezoelectric film 183 includes a front main surface S181 and a rear main surface S182. When the piezoelectric film 183 (fifth piezoelectric body) is unfolded on a plane, the main surface of the piezoelectric film 183 (fifth piezoelectric body) has a rectangular shape when viewed in the normal direction to the main surface of the sheet 13d (first sheet). In this embodiment, when the sheet 13d (first sheet) is unfolded on a plane, the front main surface S181 and the rear main surface S182 of the piezoelectric film 183 (fifth piezoelectric body) have a rectangular shape with long sides extending in the up-down direction and short sides extending in the left-right direction when viewed in the front-rear direction. In this embodiment, the longitudinal direction of the piezoelectric film 183 (fifth piezoelectric body) is the up-down direction, and the short side direction of the piezoelectric film 183 (fifth piezoelectric body) is the left-right direction. In this embodiment, the piezoelectric film 183 is a PLA film. The PLA film is the same as in the first embodiment, and therefore a description thereof will be omitted. In this embodiment, the uniaxial stretching axis OD5 of the piezoelectric film 183 (fifth piezoelectric element) forms a 45-degree angle clockwise with respect to the up-down direction and a 45-degree angle counterclockwise with respect to the left-right direction. That is, the piezoelectric film 183 (fifth piezoelectric element) is stretched in at least one axial direction. The uniaxial stretching axis OD5 of the piezoelectric film 183 (fifth piezoelectric element) and the uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) are in the same direction. The ninth electrode 184a, the tenth electrode 184b, the charge amplifier 185, and the voltage amplification circuit 186 have the same structures as the first electrode 114a, the second electrode 114b, the charge amplifier 115, and the voltage amplification circuit 116, and therefore a description thereof will be omitted.

[0086] The fifth sensor unit 18d is attached to the sheet 19d (sixth sheet) via an adhesive layer (not shown). Specifically, the adhesive layer secures the ninth electrode 184a to the front main surface of the sheet 19d. That is, the rear main surface of the fifth sensor unit 18d is secured to the front main surface of the sheet 19d.

[0087] The fifth sensor unit 18d is attached to the sheet 13d via an adhesive layer (not shown). The adhesive layer has insulating properties. Specifically, the adhesive layer fixes the tenth electrode 184b to the rear main surface of the sheet 13d. That is, the front main surface of the fifth sensor unit 18d is fixed to the rear main surface of the sheet 13d.

[0088] Sheet 19d is attached to shaft 21d, which is the object to be measured. Sheet 19d (sixth sheet) is insulating. Sheet 19d includes a front main surface and a rear main surface. The front and rear main surfaces of sheet 19d are rectangular. The front main surface of sheet 19d has a rectangular shape with a left short side extending in the vertical direction, a right short side extending in the vertical direction, an upper long side extending in the horizontal direction, and a lower long side extending in the horizontal direction. The rear main surface of sheet 19d has a left short side extending in the vertical direction, a right short side extending in the vertical direction, an upper long side extending in the horizontal direction, and a lower long side extending in the horizontal direction. The lengths of the upper long side and the lower long side of the front main surface of sheet 19d are shorter than the lengths of the upper long side and the lower long side of the front main surface of sheet 13d. Furthermore, the lengths of the left short side and the right short side of the front main surface of sheet 19d are shorter than the lengths of the left short side and the right short side of the front main surface of sheet 13d.

[0089] Sheet 19d (sixth sheet) is attached to sheet 13d (first sheet) via an adhesive layer (not shown). More specifically, the adhesive layer has insulating properties. Specifically, the adhesive layer fixes a portion of the front main surface of sheet 19d to the rear main surface of sheet 13d. When viewed in the front-to-rear direction with sheet 19d laid out flat, the portion of the front main surface of sheet 19d is a portion where the front main surface of sheet 19d does not overlap with the front main surface of fifth sensor unit 18d and where the rear main surface of sheet 13d overlaps with the front main surface of sheet 19d, as viewed in the front-to-rear direction with sheet 19d laid out flat. In other words, a portion of the front main surface of sheet 19d is fixed to a portion of the rear main surface of sheet 13d.

[0090] 13, when sheet 13d (first sheet) is laid out flat, the left and right short sides of the front main surface of sheet 13d, the long sides of first sensor unit 11d (the longitudinal direction of the first piezoelectric element), the long sides of second sensor unit 12d (the longitudinal direction of the second piezoelectric element), and the long sides of fifth sensor unit 18d (the longitudinal direction of the fifth piezoelectric element) are parallel to one another. Also, when sheet 13d is laid out flat, the upper and lower long sides of the front main surface of sheet 13d, the short sides of first sensor unit 11d, the short sides of second sensor unit 12d, and the short sides of fifth sensor unit 18d are parallel to one another.

[0091] 13, when the sheet 13d is laid out flat, a fifth center point CP5d of the fifth sensor unit 18d is defined as viewed in the front-to-rear direction. Note that the definition of the fifth center point CP5d conforms to the definition of the first center point CP1, and therefore detailed description thereof will be omitted.

[0092] In this embodiment, the first center point CP1d of the first sensor unit 11d and the fifth center point CP5d of the fifth sensor unit 18d coincide with each other, so that the front main surface of the fifth sensor unit 18d has a portion that overlaps with the front main surface of the first sensor unit 11d when viewed in the front-rear direction when the sheet 13d is unfolded flat.

[0093] As shown in FIGS. 15 and 16 , the sensor unit 10d is attached to the circumferential surface of the shaft 21d. Specifically, a portion of the rear main surface of the sheet 13d and a portion of the rear main surface of the sheet 19d are fixed to the shaft 21d by adhesive layers (not shown) provided on a portion of the rear main surface of the sheet 13d and a portion of the rear main surface of the sheet 19d. With the sensor unit 10d attached to the shaft 21d, the fifth sensor unit 18d is fixed to the shaft 21d so as to be positioned between the first sensor unit 11d and the shaft 21d in the first direction DIR1. As a result, the fifth sensor unit 18d detects deformation of the shaft 21d in the first direction DIR1, similar to the first sensor unit 11d and the second sensor unit 12d. In this embodiment, the deformation of the shaft 21d detected by the first sensor unit 11d, the second sensor unit 12d, and the fifth sensor unit 18d is deformation (bending) of the shaft 21d in the first direction DIR1. Furthermore, the polarity of the charge generated by the piezoelectric film 183 of the fifth sensor unit 18d is the same as the polarity of the charge generated by the piezoelectric film 113 of the first sensor unit 11d and the piezoelectric film 123 of the second sensor unit 12d.

[0094] For example, when shaft 21d deforms in first direction DIR1, piezoelectric film 113 generates an electric charge, piezoelectric film 123 generates an electric charge, and piezoelectric film 183 generates an electric charge in response to the deformation of shaft 21d. That is, the electrical characteristics of piezoelectric film 113, piezoelectric film 123, and piezoelectric film 183 change in response to the deformation of shaft 21d. Furthermore, piezoelectric film 113 generates a positive electric charge because it is compressed in the vertical direction, piezoelectric film 123 generates a positive electric charge because it is stretched in the vertical direction, and piezoelectric film 183 generates a positive electric charge because it is compressed in the vertical direction. That is, the polarity of the electric charge generated by piezoelectric film 113, the polarity of the electric charge generated by piezoelectric film 123, and the polarity of the electric charge generated by piezoelectric film 183 become equal.

[0095] However, when shaft 21d is deformed in the second direction DIR2, piezoelectric film 113 generates no charge or generates almost no charge, piezoelectric film 123 generates no charge or generates almost no charge, and piezoelectric film 183 generates no charge or generates almost no charge, in response to the deformation of shaft 21d (second deformation). That is, the electrical characteristics of piezoelectric film 113, the electrical characteristics of piezoelectric film 123, and the electrical characteristics of piezoelectric film 183 do not change or change almost no.

[0096] The sensor unit 10d described above also achieves the same effects as the sensor unit 10. More specifically, the cross section of the shaft 21d perpendicular to the third direction DIR3 has a circular shape. The fifth sensor unit 18d is fixed to the shaft 21d so that it is disposed between the first sensor unit 11d and the shaft 21d in the first direction DIR1 when attached to the shaft 21d. The electrical characteristics of the first sensor unit 11d, the second sensor unit 12d, and the fifth sensor unit 18d change in response to deformation of the shaft 21d. As a result, when the shaft 21d is deformed (bent) in the first direction DIR1, the piezoelectric films 113 and 183 compress, and the piezoelectric film 123 expands, causing the piezoelectric films 113, 123, and 183 to generate electric charges. Therefore, the potential of the detection signal of the first sensor unit 11d and the potential of the detection signal of the second sensor unit 12d change, and the potential of the detection signal of the fifth sensor unit 18d also changes. This allows the detection signals of the first sensor unit 11d and the second and fifth sensor units 12d and 18d to be used to detect deformation of the shaft 21d. As a result, the sensor unit 10d can improve the accuracy of detecting deformation of the shaft 21d.

[0097] According to the sensor unit 10d, the area of ​​the front main surface of the fifth sensor portion 18d is smaller than the area of ​​the front main surface of the first sensor portion 11d, so that the adhesion of the sensor unit 10d to the shaft 21d can be improved.

[0098] [Other embodiments] The sensor unit according to the present invention is not limited to sensor units 10, 10a to 10d, and can be modified within the scope of the gist thereof. Furthermore, the configurations of sensor units 10, 10a to 10d may be combined in any manner.

[0099] In addition, when sheets 13, 13a to 13d are unfolded on a plane, uniaxial stretching axis OD1 of piezoelectric film 113, uniaxial stretching axis OD3 of piezoelectric film 153, and uniaxial stretching axis OD5 of piezoelectric film 183 are not limited to an angle of 45 degrees clockwise with respect to the up-down direction and an angle of 45 degrees counterclockwise with respect to the left-right direction, but may be at other angles. Furthermore, uniaxial stretching axis OD2 of piezoelectric film 123 and uniaxial stretching axis OD4 of piezoelectric film 163 are not limited to an angle of 45 degrees counterclockwise with respect to the up-down direction and an angle of 45 degrees clockwise with respect to the left-right direction, but may be at other angles.

[0100] For example, when sheets 13, 13a to 13d (first sheets) are laid out flat, the uniaxial stretching axis OD1 of piezoelectric film 113 (first piezoelectric element), the uniaxial stretching axis OD3 of piezoelectric film 153 (third piezoelectric element), and the uniaxial stretching axis OD5 of piezoelectric film 183 (fifth piezoelectric element) may each form a 45-degree angle counterclockwise with respect to the up-down direction and a 45-degree angle clockwise with respect to the left-right direction, and the uniaxial stretching axis OD2 of piezoelectric film 123 (second piezoelectric element) and the uniaxial stretching axis OD4 of piezoelectric film 163 (fourth piezoelectric element) may each form a 45-degree angle clockwise with respect to the up-down direction and a 45-degree angle counterclockwise with respect to the left-right direction. In this configuration, when shafts 21, 21a to 21d are deformed (bent) in first direction DIR1, piezoelectric films 113 and 183 are compressed in the vertical direction and generate negative charges, and piezoelectric film 123 is stretched in the vertical direction and generates negative charges. Also, when shafts 21b and 21c are deformed (bent) in second direction DIR2, piezoelectric film 153 is stretched in the vertical direction and generates positive charges, and piezoelectric film 163 is compressed in the vertical direction and generates positive charges.

[0101] The uniaxial stretching axis OD1 of the piezoelectric film 113 (first piezoelectric element) and the uniaxial stretching axis OD3 of the piezoelectric film 153 (third piezoelectric element) may form an angle of 90 degrees counterclockwise with the uniaxial stretching axis OD2 of the piezoelectric film 123 (second piezoelectric element) and the uniaxial stretching axis OD4 of the piezoelectric film 163 (fourth piezoelectric element) when the sheets 13, 13a-13d (first sheets) are laid out flat. This 90 degrees includes, for example, an angle of about 90 degrees ±10 degrees.

[0102] In addition, when the sheet 13d is unfolded flat, the front main surface of the fifth sensor unit 18d has a portion that overlaps with the front main surface of the second sensor unit 12d when viewed in the front-to-back direction, and the uniaxial stretching axis OD5 of the piezoelectric film 183 and the uniaxial stretching axis OD2 of the piezoelectric film 123 may be in the same direction.

[0103] The first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b and 15c, the fourth sensor units 16b and 16c, and the fifth sensor unit 18d may each include a material having other piezoelectric properties. Also, the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b and 15c, the fourth sensor units 16b and 16c, and the fifth sensor unit 18d may each include a material that does not have piezoelectric properties.

[0104] For example, the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d may each have a piezoelectric constant of d31. The first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d having a piezoelectric constant of d31 are each, for example, a PVDF (polyvinylidene fluoride) film.

[0105] The deformation of the object to be measured may be detected by detecting the amount of deformation itself.

[0106] The detection of deformation of the object to be measured may be detection of bending of the object to be measured or detection of twist of the object to be measured.

[0107] For example, the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d may each include a strain gauge.

[0108] The characteristics of the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d that change in response to deformation of the shafts 21, 21a to 21d may be physical properties other than electrical properties. For example, the physical properties of the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d that change in response to deformation of the shafts 21, 21a to 21d may be mechanical properties, thermal properties, optical properties, and chemical properties.

[0109] The first electrode 114a may be provided on the front principal surface S111, the second electrode 114b may be provided on the rear principal surface S112, the third electrode 124a may be provided on the front principal surface S121, and the fourth electrode 124b may be provided on the rear principal surface S122. As a result, the second electrode 114b and the fourth electrode 124b may be electrically connected.

[0110] Furthermore, the fifth electrode 154a may be provided on the front principal surface S151, the sixth electrode 154b may be provided on the rear principal surface S152, the seventh electrode 164a may be provided on the front principal surface S161, and the eighth electrode 164b may be provided on the rear principal surface S162. As a result, the sixth electrode 154b and the eighth electrode 164b may be electrically connected.

[0111] The ninth electrode 184a may be provided on the front principal surface S181, and the tenth electrode 184b may be provided on the rear principal surface S182.

[0112] The ninth electrode 184a may be electrically connected to the first electrode 114a or the third electrode 124a. The tenth electrode 184b may be electrically connected to the second electrode 114b or the fourth electrode 124b. This allows the charge amplifier 185 and the voltage amplifier circuit 186 to be omitted.

[0113] Each of the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b and 15c, the fourth sensor units 16b and 16c, and the fifth sensor unit 18d may include a charge amplifier and a voltage amplification circuit.

[0114] The second sensor units 12, 12a to 12d may include a charge amplifier 115 and a voltage amplification circuit 116. The fourth sensor units 16b, 16c may include a charge amplifier 155 and a voltage amplification circuit 156.

[0115] It should be noted that each of the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d does not necessarily have to have a film shape.

[0116] It should be noted that the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, the fourth sensor units 16b, 16c, and the fifth sensor unit 18d do not necessarily have to be attached to the sheets 13, 13a to 13d and the sheet 19d, respectively. In this case, an insulating adhesive layer may be provided on the front or rear main surface of each of the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, and the fourth sensor units 16b, 16c, and the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, and the fourth sensor units 16b, 16c may be fixed to the shaft 21, 21a to 21d or the fifth sensor unit 18d by the adhesive layer. Also, an insulating adhesive layer may be provided on the front or rear main surface of the fifth sensor unit 18d, and the fifth sensor unit 18d may be fixed to the shaft 21d by the adhesive layer.

[0117] In addition, when the sheets 13, 13a to 13d are unfolded flat, the front and rear main surfaces of the first sensor units 11, 11a to 11d, the front and rear main surfaces of the second sensor units 12, 12a to 12d, the front and rear main surfaces of the third sensor units 15b, 15c, the front and rear main surfaces of the fourth sensor units 16b, 16c, and the front and rear main surfaces of the fifth sensor unit 18d may each have a rectangular shape with short sides extending in the vertical direction and long sides extending in the horizontal direction when viewed in the front-to-back direction.

[0118] In addition, the lengths of the upper and lower long sides of the front main surface of sheets 13, 13a to 13d and the lengths of the upper and lower long sides of the rear main surface of sheets 13, 13a to 13d may each be longer than the circumference of the cross-sectional circle of shaft 21, 21a to 21d when sheets 13, 13a to 13d are unfolded on a plane.

[0119] In addition, when the sensor units 10, 10a to 10d are attached to the shafts 21, 21a to 21d, respectively, when viewed in the third direction DIR3, there may be three or more intersections between any straight line perpendicular to the third direction DIR3 and the front main surface of the sheets 13, 13a to 13d.

[0120] In addition, the lengths of the upper and lower long sides of the front main surface of sheets 13, 13a to 13d and the lengths of the upper and lower long sides of the rear main surface of sheets 13, 13a to 13d may each be equal to the circumference of the cross-sectional circle of shaft 21, 21a to 21d when sheets 13, 13a to 13d are unfolded on a plane.

[0121] The front and rear main surfaces of sheets 13, 13a to 13d and sheet 19d do not have to be rectangular. A rectangular shape includes a rectangle and a shape obtained by slightly modifying a rectangle. An example of a slightly modified rectangle is a rectangle with chamfered corners. The front and rear main surfaces of sheets 13, 13a to 13d and sheet 19d may have shapes that are completely different from a rectangle.

[0122] The thickness of sheets 13, 13a to 13d and sheet 19d (the distance between the front and rear main surfaces of sheets 13, 13a to 13d and sheet 19d) may or may not be uniform.

[0123] In addition, when the sheets 13, 13a to 13d are unfolded flat, the front and rear main surfaces of the first sensor units 11, 11a to 11d, the front and rear main surfaces of the second sensor units 12, 12a to 12d, the front and rear main surfaces of the third sensor units 15b, 15c, the front and rear main surfaces of the fourth sensor units 16b, 16c, and the front and rear main surfaces of the fifth sensor unit 18d do not have to have a rectangular shape.

[0124] For example, when the sheets 13, 13a to 13d are unfolded flat, the front and rear main surfaces of the first sensor units 11, 11a to 11d, the front and rear main surfaces of the second sensor units 12, 12a to 12d, the front and rear main surfaces of the third sensor units 15b, 15c, the front and rear main surfaces of the fourth sensor units 16b, 16c, and the front and rear main surfaces of the fifth sensor unit 18d may each have an elliptical shape.

[0125] For example, when the sheets 13, 13a to 13d are laid out flat, the front and rear main surfaces of the first sensor units 11, 11a to 11d, the front and rear main surfaces of the second sensor units 12, 12a to 12d, the front and rear main surfaces of the third sensor units 15b, 15c, the front and rear main surfaces of the fourth sensor units 16b, 16c, and the front and rear main surfaces of the fifth sensor unit 18d may each have a square shape.

[0126] When sheets 13, 13a to 13d are unfolded on a plane, the positions of first center points CP1, CP1a, CP1b, CP1c, and CP1d in the vertical direction, second center points CP2, CP2a, CP2b, CP2c, and CP2d in the vertical direction, and fifth center point CP5d in the vertical direction may be different from each other.Furthermore, when sheets 13b and 13c are unfolded on a plane, the positions of first center points CP1b and CP1c in the vertical direction, second center points CP2b and CP2c in the vertical direction, third center points CP3b and CP3c in the vertical direction, and fourth center points CP4b and CP4c in the vertical direction may be different from each other.

[0127] When the sheets 13, 13a to 13d are unfolded on a plane, the rear main surfaces of the first sensor units 11, 11a to 11d may have portions that do not overlap with the rear main surfaces of the second sensor units 12, 12a to 12d when viewed in the front-to-rear direction. When the sheets 13b, 13c are unfolded on a plane, the rear main surfaces of the third sensor units 15b, 15c may have portions that do not overlap with the rear main surfaces of the fourth sensor units 16b, 16c.

[0128] Furthermore, when the sheet 13d is laid out flat, the front and rear principal surfaces of the first sensor unit 11d may have portions that do not overlap with the front and rear principal surfaces of the fifth sensor unit 18d.

[0129] In addition, when the sensor units 10, 10a to 10d are attached to the shafts 21, 21a to 21d, respectively, the first sensor units 11, 11a to 11d, the second sensor units 12, 12a to 12d, the third sensor units 15b, 15c, and the fourth sensor units 16b, 16c may be arranged between the shafts 21, 21a to 21d and the sheets 13, 13a to 13d, respectively. In this case, an insulating adhesive layer may be provided on the front main surface of the first sensor unit 11, 11a to 11d, the front main surface of the second sensor unit 12, 12a to 12d, the front main surface of the third sensor unit 15b, 15c, and the front main surface of the fourth sensor unit 16b, 16c, and the first sensor unit 11, 11a to 11d, the second sensor unit 12, 12a to 12d, the third sensor unit 15b, 15c, and the fourth sensor unit 16b, 16c may be fixed to the shaft 21, 21a to 21d by the adhesive layer, respectively.

[0130] In addition, in a state where the sensor unit 10d is attached to the shaft 21d, the first sensor section 11d may be disposed between the fifth sensor section 18d and the shaft 21d.

[0131] In addition, the front main surfaces of the first sensor units 11b and 11c may have portions that overlap with the front main surfaces of the third sensor units 15b and 15c or the front main surfaces of the fourth sensor units 16b and 16c when viewed in the front-to-back direction when the sheets 13b and 13c are unfolded flat.

[0132] In addition, the front main surfaces of the second sensor units 12b and 12c may have portions that overlap with the front main surfaces of the third sensor units 15b and 15c or the front main surfaces of the fourth sensor units 16b and 16c when viewed in the front-to-back direction when the sheets 13b and 13c are unfolded flat.

[0133] The sheet 19d may be attached to the first sensor unit 11d or the second sensor unit 12d.

[0134] The area of ​​the front principal surface of the fifth sensor portion 18d may be equal to or larger than the area of ​​the front principal surface of the first sensor portion 11d.

[0135] The cross section of the object to be measured perpendicular to the third direction DIR3 is not limited to a circle as long as it has a point-symmetric shape. For example, the cross section of the object to be measured perpendicular to the third direction DIR3 may be an ellipse, a parallelogram, a rectangle, or a regular even-numbered polygon.

[0136] The shape of the object to be measured may not extend in the third direction DIR3.

[0137] The object to be measured is not limited to a shaft, but may be, for example, a baseball bat, a tennis racket, or a robot arm.

[0138] The number of sensor units may be three or more.

[0139] Two or more sensor units 10, 10a to 10d may be stacked. [Explanation of symbols]

[0140] 10, 10a, 10b, 10c, 10d: sensor unit 11, 11a, 11b, 11c, 11d: first sensor unit 12, 12a, 12b, 12c, 12d: second sensor unit 13, 13a, 13b, 13c, 13d: Sheets 14a, 14b, 14e: Sheets 15b, 15c: Third sensor section 16b, 16c: Fourth sensor section 17b, 17e: Sheet 18d: 5th sensor section 19d: Sheet 20, 20a, 20b, 20c, 20d: Golf clubs 21, 21a, 21b, 21c, 21d: shaft 22: Head 113, 123, 153, 163, 183: Piezoelectric film 114a: 1st electrode 114b: 2nd electrode 124a: 3rd electrode 124b: 4th electrode 154a: 5th electrode 154b: 6th electrode 164a: 7th electrode 164b: 8th electrode 184a: 9th electrode 184b: 10th electrode 115, 155, 185: Charge amplifier 116, 156, 186: Voltage amplifier circuit OD1, OD2, OD3, OD4, OD5: Uniaxial stretching axis S111, S121, S151, S161, S181: Front main surface S112, S122, S152, S162, S182: Rear main surface CP1, CP1a, CP1b, CP1d: 1st center point CP2, CP2a, CP2b: 2nd center point CP3b: 3rd center point CP4b: 4th center point CP5d: 5th center point P1, P1b: 1st intersection P2, P2b: 2nd intersection P3b: 3rd intersection P4b: 4th intersection D1, D1b: First distance D2b: 2nd distance D3b: 3rd distance D4b: 4th distance D5b: 5th distance D6b: 6th distance

Claims

1. A sensor unit for detecting deformation of a shaft of a golf club, The sensor unit includes: a first sensor unit that detects deformation of the shaft; a second sensor unit that detects deformation of the shaft; a first sheet to which both the first sensor unit and the second sensor unit are attached, the first sheet being a separate member from the first sensor unit and the second sensor unit and having electrical conductivity; the first sensor unit includes a first electrode and a second electrode; the second sensor unit includes a third electrode and a fourth electrode, the first sheet electrically connects the first electrode and the third electrode; when the first sheet is unfolded on a plane, a length of the main surface of the first sheet along a direction in which the first sensor unit and the second sensor unit are aligned is equal to or greater than half of a circumferential length of a cross-sectional circle of the shaft, as viewed in a normal direction of the main surface of the first sheet; the first seat is attached to the circumferential surface of the shaft; the first sensor unit and the second sensor unit are fixed to the shaft such that, when attached to the shaft, the shaft is disposed between the first sensor unit and the second sensor unit in a first direction and are spaced apart from each other by 180 degrees in a circumferential direction of the shaft; a physical property value of the first sensor unit and a physical property value of the second sensor unit change in response to a first deformation of the shaft; Sensor unit.

2. A sensor unit for detecting deformation of a shaft of a golf club, The sensor unit includes: a first sensor unit that detects deformation of the shaft; a second sensor unit that detects deformation of the shaft; a first sheet to which both the first sensor unit and the second sensor unit are attached, the first sheet being a separate member from the first sensor unit and the second sensor unit and having insulating properties; a first conductor having electrical conductivity; Equipped with the first sensor unit includes a first electrode and a second electrode; the second sensor unit includes a third electrode and a fourth electrode, the first conductor electrically connects the first electrode and the third electrode; when the first sheet is unfolded on a plane, a length of the main surface of the first sheet along a direction in which the first sensor unit and the second sensor unit are aligned is equal to or greater than half of a circumferential length of a cross-sectional circle of the shaft, as viewed in a normal direction of the main surface of the first sheet; the first seat is attached to the circumferential surface of the shaft; the first sensor unit and the second sensor unit are fixed to the shaft such that, when attached to the shaft, the shaft is disposed between the first sensor unit and the second sensor unit in a first direction and are spaced apart from each other by 180 degrees in a circumferential direction of the shaft; a physical property value of the first sensor unit and a physical property value of the second sensor unit change in response to a first deformation of the shaft; Sensor unit.

3. the first sensor unit includes a film shape, The second sensor unit includes a film shape. The sensor unit according to claim 1 or 2.

4. a main surface of the first sensor unit has a rectangular shape when viewed in a normal direction to the main surface of the first sensor unit in a state in which the first sensor unit is developed on a plane; a main surface of the second sensor unit has a rectangular shape when viewed in a normal direction to the main surface of the second sensor unit in a state in which the second sensor unit is developed on a plane; The sensor unit according to claim 3 .

5. The first sensor unit has a first sensor unit first main surface and a first sensor unit second main surface, the second sensor unit has a second sensor unit first main surface and a second sensor unit second main surface; the first electrode is provided on a second main surface of the first sensor portion, the second electrode is provided on a first main surface of the first sensor unit, the third electrode is provided on a second main surface of the second sensor portion, the fourth electrode is provided on a first main surface of the second sensor unit; The sensor unit according to claim 2 .

6. The sensor unit includes: A second conductor having conductivity, Further preparation, the second conductor electrically connects the second electrode and the fourth electrode. The sensor unit according to claim 5 .

7. The first sensor unit has a first sensor unit first main surface and a first sensor unit second main surface, the second sensor unit has a second sensor unit first main surface and a second sensor unit second main surface; the first electrode is provided on a second main surface of the first sensor portion, the second electrode is provided on a first main surface of the first sensor unit, the third electrode is provided on a second main surface of the second sensor portion, the fourth electrode is provided on a first main surface of the second sensor unit; The sensor unit according to claim 1 .

8. The sensor unit includes: a third sensor unit that detects deformation of the shaft, Further preparation, the third sensor unit is attached to the first seat, The physical property value of the third sensor unit changes in response to the second deformation of the shaft, the third sensor unit is located between the first sensor unit and the second sensor unit when the first sheet is laid out flat. The sensor unit according to any one of claims 2, 5 and 6.

9. The sensor unit includes: a fourth sensor unit that detects deformation of the shaft, Further preparation, the fourth sensor unit is attached to the first seat, a physical property value of the fourth sensor unit changes in response to the second deformation; the second sensor unit is located between the third sensor unit and the fourth sensor unit when the first sheet is laid out flat. The sensor unit according to claim 8 .

10. The sensor unit includes: a third conductor having electrical conductivity, Further preparation, the third sensor unit includes a fifth electrode; the fourth sensor unit includes a seventh electrode; the third conductor electrically connects the fifth electrode and the seventh electrode; The sensor unit according to claim 9 .

11. When the first sheet is unfolded on a plane, the first conductor has a band shape extending in the direction in which the first sensor unit and the second sensor unit are aligned when viewed in the normal direction of the main surface of the first sheet, and connects the end of the first electrode and the end of the third electrode in a direction perpendicular to the direction in which the first sensor unit and the second sensor unit are aligned. The sensor unit according to any one of claims 2, 5, 6, and 8 to 10.

12. The sensor unit includes: a third sensor unit that detects deformation of the shaft; a fourth sensor unit that detects deformation of the shaft; Further preparation, the third sensor unit and the fourth sensor unit are attached to the first seat, the third sensor unit and the fourth sensor unit are fixed to the shaft such that, when attached to the shaft, the shaft is located between the third sensor unit and the fourth sensor unit in the second direction; a physical property value of the third sensor unit and a physical property value of the fourth sensor unit change in response to a second deformation of the shaft; the third sensor unit includes a film shape, the fourth sensor unit includes a film shape, The first direction and the second direction are different directions. The sensor unit according to any one of claims 2, 5 and 6.

13. The sensor unit includes: a third conductor having electrical conductivity, Further preparation, the third sensor unit has a third sensor unit first main surface and a third sensor unit second main surface, the fourth sensor unit has a fourth sensor unit first main surface and a fourth sensor unit second main surface, the third sensor unit includes a fifth electrode provided on a second main surface of the third sensor unit and a sixth electrode provided on a first main surface of the third sensor unit, the fourth sensor unit includes a seventh electrode provided on a second main surface of the fourth sensor unit and an eighth electrode provided on a first main surface of the fourth sensor unit, the third conductor electrically connects the fifth electrode and the seventh electrode; The sensor unit according to claim 12.

14. The sensor unit includes: a fourth conductor having electrical conductivity, Further preparation, the fourth conductor electrically connects the sixth electrode and the eighth electrode; The sensor unit according to claim 13.

15. The third sensor unit and the fourth sensor unit are fixed to the shaft so that, when attached to the shaft, they are spaced 180 degrees apart from each other in the circumferential direction of the shaft; the first sensor unit and the third sensor unit are fixed to the shaft so as to be spaced apart from each other by 90 degrees in a circumferential direction of the shaft when attached to the shaft, When viewed in a normal direction to a main surface of the first sheet in a state in which the first sheet is laid out on a plane, the first conductor has a band shape extending in a direction in which the first sensor unit and the second sensor unit are arranged, and connects an end of the first electrode and an end of the third electrode in a direction perpendicular to the direction in which the first sensor unit and the second sensor unit are arranged. The sensor unit according to any one of claims 9, 10 and 12 to 14.

16. The sensor unit includes: a fifth sensor unit that detects deformation of the shaft; an insulator having insulating properties; Further preparation, the insulator is attached to the first sensor unit or the first sheet, the fifth sensor unit is attached to the insulator, the fifth sensor unit is fixed to the shaft so as to be disposed between the first sensor unit and the shaft in the first direction when attached to the shaft; a main surface of the fifth sensor unit has a portion that overlaps with a main surface of the first sensor unit when viewed in a normal direction of the main surface of the first sheet in a state in which the first sheet is spread out flat, a physical property value of the fifth sensor unit changes in response to the first deformation; the fifth sensor unit includes a film shape, a main surface of the fifth sensor unit has a rectangular shape when viewed in a normal direction of the main surface of the first sheet when the first sheet is unfolded on a plane; a longitudinal direction of the fifth sensor unit is parallel to a longitudinal direction of the first sensor unit when the first sheet is unfolded on a plane; The sensor unit according to claim 1 or 7.

17. When the first sheet is laid out flat, the insulator is surrounded by the first sensor unit, and the fifth sensor unit is surrounded by the insulator when viewed in a normal direction of a main surface of the first sheet. The sensor unit according to claim 16.

18. the fifth sensor unit is located between the first sensor unit and the insulator; The sensor unit according to claim 16 or 17.

19. The shaft has a shape extending in a third direction perpendicular to both the first direction and a second direction different from the first direction. The sensor unit according to any one of claims 1 to 18.

20. A cross section of the shaft perpendicular to a third direction orthogonal to both the first direction and a second direction different from the first direction includes a point-symmetric shape.

20. The sensor unit according to claim 1.

21. the deformation of the shaft detected by the first sensor unit is bending of the shaft, The deformation of the shaft detected by the second sensor unit is bending of the shaft. The sensor unit according to any one of claims 1 to 20.

22. In response to the first deformation, the first sensor unit compresses and the second sensor unit expands.

22. The sensor unit according to claim 1.

23. The sensor unit includes: a first adhesive layer that attaches the first sensor unit to the first sheet; a second adhesive layer that attaches the second sensor unit to the first sheet; Further comprising:

23. The sensor unit according to claim 1.

Images