Tactile sensor

Abstract

The tactile sensor includes a sensor unit of the electrostatic capacitance method, and the sensor unit of the electrostatic capacitance method has a stacked structure in which a first electrode layer, an elastic layer, and a second electrode layer are stacked. The first electrode layer has a plurality of first electrodes, and the second electrode layer is composed of one or more second electrodes as a single layer. Two or more of the plurality of first electrodes are partially overlapping electrodes that partially overlap with the second electrode when viewed in the normal direction of the contact surface of the sensor unit, and the number of one or more openings formed in one second electrode, or the number of one or more island portions formed by one or more second electrodes is smaller than the number of the plurality of first electrodes.

Description

Technical Field

[0001] The technology disclosed in the present application relates to a tactile sensor. Background Art

[0002] As a tactile sensor capable of detecting the pressure distribution and shear force of a contact surface in contact with an object, for example, the following technologies are known.

[0003] That is, the tactile sensor described in Patent Document 1 includes a support substrate, a first insulator, a second insulator, a plurality of electrodes, a plurality of first strip electrodes, and a plurality of second strip electrodes. The support substrate, the second insulator, and the first insulator are sequentially arranged and stacked from the side opposite to the side where pressure is input to the tactile sensor.

[0004] The plurality of electrodes are provided so as to cover the entire area between the second insulator and the support substrate. The plurality of first strip electrodes are provided to extend in a first direction on the side of the first insulator opposite to the second insulator. The plurality of first strip electrodes extend between adjacent electrodes in a direction intersecting the first direction among the plurality of electrodes, so that in a plan view, they only overlap a part of each of the adjacent electrodes.

[0005] The plurality of second strip electrodes are provided to extend in a second direction intersecting the first direction between the first insulator and the second insulator. The plurality of second strip electrodes extend between adjacent electrodes in a direction intersecting the second direction among the plurality of electrodes, so that in a plan view, they only overlap a part of each of the adjacent electrodes.

[0006] The tactile sensor is connected to a capacitance measurement circuit. The capacitance measurement circuit can detect the capacitance generated between the electrode and the first strip electrode that overlaps the electrode in a plan view. In addition, the capacitance measurement circuit can detect the capacitance generated between the electrode and the second strip electrode that overlaps the electrode in a plan view.

[0007] The tactile sensor described in Patent Document 2 includes a first substrate, a second substrate, and a dielectric. The first substrate includes a plurality of first electrodes. The second substrate includes a plurality of second electrodes respectively corresponding to the plurality of first electrodes. The dielectric is provided between the first substrate and the second substrate.

[0008] The second electrode corresponding to any one of the plurality of first electrodes is arranged to be offset in one direction in the second substrate with respect to any one of the first electrodes. The other second electrodes corresponding to the other first electrodes adjacent to any one of the first electrodes are arranged to be offset in other directions in the second substrate with respect to the other first electrodes.

[0009] The plurality of first electrodes are matched one-to-one with the plurality of second electrodes. The plurality of first electrodes are arranged to be isolated from each other, and the plurality of second electrodes are arranged to be isolated from each other.

[0010] Prior art documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Publication No. 6280579

[0013] Patent Document 2: Japanese Unexamined Patent Application Publication No. 6488414 Summary of the invention

[0014] Problems to be solved by the invention

[0015] In the tactile sensor described in Patent Document 1, the counter electrode facing a plurality of electrodes has a two-layer structure of a plurality of first strip electrodes and a plurality of second strip electrodes. Therefore, the structure of the tactile sensor becomes complicated, and the manufacturing process of the tactile sensor also becomes complicated.

[0016] In the tactile sensor described in Patent Document 2, a plurality of first electrodes are paired one-to-one with a plurality of second electrodes. In addition, in order to detect a shearing force, the plurality of first electrodes are arranged separately from each other, and the plurality of second electrodes are also arranged separately from each other. Therefore, the intervals between the plurality of first electrodes become wider, and the intervals between the plurality of second electrodes become wider. Therefore, the number of the plurality of first electrodes and the plurality of second electrodes cannot be increased, and the resolution of the pressure distribution is reduced.

[0017] Therefore, there is room for improvement in terms of being able to detect a shearing force and ensuring the resolution of the pressure distribution even with a simple structure and manufacturing process.

[0018] As one aspect, an object of the technology disclosed in the present application is to obtain a tactile sensor that can detect a shearing force and ensure the resolution of the pressure distribution even with a simple structure and manufacturing process.

[0019] Means for solving the problems

[0020] In order to achieve the above object, according to one aspect of the technology disclosed in the present application, there is provided a tactile sensor including a capacitive sensor unit. The capacitive sensor unit has a contact surface with an object, and has a laminated structure in which an elastic layer and a first electrode layer and a second electrode layer located on both sides sandwiching the elastic layer are laminated in the normal direction of the contact surface. The first electrode layer has a plurality of first electrodes, the second electrode layer is composed of one or more second electrodes as a single layer, and two or more of the plurality of first electrodes are a plurality of partially overlapping electrodes that are partially overlapped with the second electrode when viewed in the normal direction. The number of one or more openings formed in one of the second electrodes, or the number of one or more island portions formed by one or more of the second electrodes is less than the number of the plurality of first electrodes.

[0021] Advantages of the Invention

[0022] The tactile sensor according to one aspect of the technology disclosed in the present application can detect a shear force and ensure the resolution of a pressure distribution even with a simple structure and manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a perspective view showing an example of a robot system.

[0024] Figure 2 is a view showing Figure 1 an example of a pair of tactile sensors.

[0025] Figure 3 is a longitudinal sectional view of the tactile sensor according to the first embodiment.

[0026] Figure 4 is Figure 3 a top view of the substrate of

[0027] Figure 5 is Figure 3 a top view of the second electrode layer of

[0028] Figure 6 is a view showing a state where the second electrode, the elastic layer, and the substrate of Figure 3 are overlapped.

[0029] Figure 7 is Figure 3 a bottom view of the substrate of

[0030] Figure 8 is a view for explaining Figure 3 an example of a manufacturing method of the tactile sensor of

[0031] Figure 9 is a view for explaining Figure 3A top view of an example of displacement Δx and displacement Δy in the tactile sensor.

[0032] Figure 10 It illustrates Figure 3 A diagram of an example of displacement Δx and displacement Δz in the tactile sensor.

[0033] Figure 11 It illustrates Figure 3 A diagram of an example of displacement Δy and displacement Δz in the tactile sensor.

[0034] Figure 12 A longitudinal cross-sectional view of the tactile sensor of the second embodiment.

[0035] Figure 13 It is Figure 12 A top view of the second electrode layer of

[0036] Figure 14 It shows the state where Figure 12 The second electrode, the elastic layer, and the substrate of are overlapped. A top view.

[0037] Figure 15 A longitudinal cross-sectional view of the tactile sensor of the third embodiment.

[0038] Figure 16 It is Figure 15 A top view of the second electrode layer of

[0039] Figure 17 It shows the state where Figure 15 The second electrode, the elastic layer, and the substrate of are overlapped. A top view.

[0040] Figure 18 A longitudinal cross-sectional view of the tactile sensor of the fourth embodiment.

[0041] Figure 19 It is Figure 18 A top view of the second electrode layer of

[0042] Figure 20 It shows the state where Figure 18 The second electrode, the elastic layer, and the substrate of are overlapped. A top view. Detailed Description of the Embodiment

[0043] Hereinafter, an embodiment of the technology disclosed in the present application will be described in detail with reference to the drawings.

[0044] (An example of the robot system 100)

[0045] First, an overview of an example of the robot system 100 will be described.

[0046] Figure 1This is a perspective view showing an example of the robot system 100. The robot system 100 includes a robot 102 and a controller 104. The robot 102 is, for example, an articulated robot and includes a robot arm 106 and a robot hand 108. The robot arm 106 includes a plurality of joint portions 110. The robot hand 108 is provided at the distal end portion of the robot arm 106. The robot hand 108 is connected to the distal end portion of the robot arm 106 via a wrist joint portion 112.

[0047] A pair of gripping portions 114 are provided on the robot hand 108. The pair of gripping portions 114 are arranged to face each other. The pair of gripping portions 114 approach and separate in the direction in which they face each other by the drive of a drive portion (not shown). In a state where the workpiece W is arranged between the pair of gripping portions 114, if the pair of gripping portions 114 move in the direction of approaching each other, the workpiece W is gripped by the pair of gripping portions 114.

[0048] The controller 104 controls the robot 102 and is electrically connected to the robot 102. In Figure 1 this case, as an example, the controller 104 is connected to the robot 102 by wire, but the controller 104 may also be connected to the robot 102 wirelessly.

[0049] (An example of the tactile sensing system 1)

[0050] Next, an outline of an example of the tactile sensing system 1 will be described.

[0051] The tactile sensing system 1 is mounted in the robot system 100. The tactile sensing system 1 includes a pair of tactile sensors 10 and an output unit 12. The pair of tactile sensors 10 are respectively provided on the opposing surfaces 114A of the pair of gripping portions 114 facing each other. The pair of tactile sensors 10 are provided at positions where they come into contact with the workpiece W in a state where the workpiece W is gripped by the pair of gripping portions 114, that is, as an example, at the mutually opposing portions at the distal ends of the pair of gripping portions 114.

[0052] The output unit 12 is electrically connected to the pair of tactile sensors 10. The output unit 12 may be connected to the pair of tactile sensors 10 by wire or wirelessly. As will be described in detail later, the output unit 12 has the following functions: performing various processes based on the data output from the pair of tactile sensors 10 and outputting the data based on the result of the process to the controller 104. As an example, the output unit 12 is provided at the wrist joint portion 112.

[0053] Figure 2 Shows Figure 1Stereogram of an example of a pair of tactile sensors 10. As an example, the pair of tactile sensors 10 are symmetric in the direction facing each other. The X-axis direction corresponds to the first direction orthogonal to the direction facing the pair of tactile sensors 10, the Y-axis direction corresponds to the second direction orthogonal to the direction facing the pair of tactile sensors 10, and the Z-axis direction corresponds to the direction facing the pair of tactile sensors 10. The X-axis direction is orthogonal to the Y-axis direction. As an example, the X-axis direction corresponds to the longitudinal direction of the tactile sensor 10, and the Y-axis direction corresponds to the lateral direction of the tactile sensor 10.

[0054] The tactile sensor 10 includes a support plate 14, a substrate 16, and a sensor unit 18. The support plate 14 is formed separately from the above-mentioned holding part 114 (refer to Figure 1 ) and is fixed to the holding part 114. The support plate 14 may also be formed integrally with the holding part 114. The substrate 16 is fixed to the support plate 14, and the sensor unit 18 is provided on the substrate 16. Details of the sensor unit 18 will be described in detail later.

[0055] Next, the first to fourth embodiments of the tactile sensing system 1 will be described.

[0056] [First Embodiment]

[0057] First, the first embodiment will be described.

[0058] (Structure of Tactile Sensor 10)

[0059] Figure 3 is a longitudinal sectional view of the tactile sensor 10 of the first embodiment. The tactile sensor 10 of the first embodiment includes a sensor unit 18 and a substrate 16.

[0060] The sensor unit 18 is an electrostatic capacitance type. More specifically, the sensor unit 18 is a self-capacitance type and has a laminated structure formed by laminating a plurality of layers. That is, the sensor unit 18 has an insulating layer 20, an elastic layer 22, a first electrode layer 24, and a second electrode layer 26 as the plurality of layers. The first electrode layer 24 and the second electrode layer 26 are located on both sides sandwiching the elastic layer 22.

[0061] The insulating layer 20 is located on the side opposite to the elastic layer 22 with respect to the second electrode layer 26. The insulating layer 20 forms the surface layer portion of the sensor unit 18. The surface of the insulating layer 20 is formed as a contact surface 28 that contacts the workpiece W (refer to Figure 1 ). In addition, the insulating layer 20 may be omitted. In the case where the insulating layer 20 is omitted, the second electrode layer 26 and the surface of the surface layer formed on the second electrode layer 26 become the contact surface 28.

[0062] The elastic layer 22 is a dielectric. The elastic layer 22 has flexibility and elasticity. The elastic layer 22 is formed of, for example, a gel. The insulating layer 20, the elastic layer 22, the first electrode layer 24, and the second electrode layer 26 are stacked in the Z-axis direction. The Z-axis direction corresponds to the normal direction of the contact surface 28. The insulating layer 20, the elastic layer 22, the first electrode layer 24, and the second electrode layer 26 are bonded to each other by, for example, an adhesive. In order to improve the overall bonding strength of the sensor unit 18, the insulating layer 20 preferably has a size that covers the entire surface of the second electrode layer 26.

[0063] The first electrode layer 24 has a plurality of first electrodes 34. The plurality of first electrodes 34 are formed on the first surface 16A of the substrate 16 on the sensor unit 18 side. A plurality of electrostatic capacitance detection ICs (Integrated Circuit) 44 are mounted on the second surface 16B of the substrate 16 on the side opposite to the sensor unit 18. The plurality of first electrodes 34 and the plurality of electrostatic capacitance detection ICs 44 are connected by through-holes 46 extending in the thickness direction of the substrate 16.

[0064] Figure 4 is Figure 3 A top view of the substrate 16. The plurality of first electrodes 34 formed on the first surface 16A of the substrate 16 are arranged in a matrix along the X-Y plane. That is, the plurality of first electrodes 34 are arranged with the X-axis direction as the longitudinal direction and the Y-axis direction as the lateral direction. The X-Y plane is a plane parallel to the above-described contact surface 28 (refer to Figure 2 ).

[0065] The plurality of first electrodes 34 are independent of each other. The plurality of first electrodes 34 have the same shape. As an example, the plurality of first electrodes 34 are formed in a square shape in a top view. The top view corresponds to observation in the Z-axis direction. As an example, six first electrodes 34 are arranged in the X-axis direction and six first electrodes 34 are arranged in the Y-axis direction. That is, the number of the plurality of first electrodes 34 is 36. The plurality of first electrodes 34 are arranged at equal intervals in the X-axis direction and the Y-axis direction, respectively.

[0066] Figure 5 is Figure 3 A top view of the second electrode layer 26. The second electrode layer 26 is composed of a plurality of second electrodes 36 as a single layer. The plurality of second electrodes 36 are formed of, for example, conductive rubber. The plurality of second electrodes 36 are each formed in a flat plate shape. The plurality of second electrodes 36 can be connected to the ground of the substrate 16 or can be floating with respect to the ground.

[0067] The plurality of second electrodes 36 form a plurality of independent island portions. The plurality of second electrodes 36 are arranged in a matrix along the X-Y plane. That is, the plurality of second electrodes 36 are arranged with the X-axis direction as the longitudinal direction and the Y-axis direction as the lateral direction.

[0068] The plurality of second electrodes 36 are of the same shape. As an example, the plurality of second electrodes 36 are each formed in a square shape when viewed from above. The number of the plurality of second electrodes 36 is greater than the number of the plurality of first electrodes 34 (see Figure 4 As an example, the plurality of second electrodes 36 are arranged in three in the X-axis direction and three in the Y-axis direction. That is, the number of the plurality of second electrodes 36 is nine. The plurality of second electrodes 36 are arranged at equal intervals in the X-axis direction and the Y-axis direction.

[0069] Figure 6 It shows that Figure 3 FIG. 1 is a top view of a state in which a plurality of second electrodes 36, an elastic layer 22, and a substrate 16 overlap. The plurality of second electrodes 36 are arranged so as to overlap all of the plurality of first electrodes 34 in a top view. The plurality of second electrodes 36 are respectively formed so as to partially overlap four first electrodes 34 adjacent in the X-axis direction and the Y-axis direction among the plurality of first electrodes 34 in a top view. Each second electrode 36 is located at the center of the four first electrodes 34 in a top view and partially overlaps the four first electrodes 34.

[0070] Thus, in the first embodiment, all of the plurality of first electrodes 34 partially overlap with the plurality of second electrodes 36. In the first embodiment, all of the plurality of first electrodes 34 are equivalent to an example of "a plurality of partially overlapping electrodes partially overlapping with the plurality of second electrodes", and a plurality of signals output from the plurality of first electrodes 34 are equivalent to an example of "a plurality of locally overlapping electrode signals".

[0071] In the first embodiment, all of the plurality of first electrodes 34 correspond to an example of “a plurality of partially overlapping electrodes partially overlapping the second electrode”, and a plurality of signals output from the plurality of first electrodes 34 correspond to an example of “a plurality of partially overlapping electrode signals”.

[0072] The electrostatic capacitance C [F] between the first electrode 34 and the second electrode 36 is obtained by the following equation.

[0073] C=ε×A / d

[0074] ε is the dielectric constant of the elastic layer 22 [Fm -1 ], A is the overlapping area of ​​the first electrode 34 and the second electrode 36 when viewed from above [m 2 ], d is the distance [m] between the first electrode 34 and the second electrode 36 along the Z-axis direction.

[0075] In the sensor unit 18, when pressure is applied to the contact surface 28, the distance d between each first electrode 34 and the second electrode 36 changes, and the capacitance C changes according to the change in the distance d. Further, in the sensor unit 18, when a shearing force is applied to the contact surface 28, the overlapping area A between each first electrode 34 and the second electrode 36 changes, and the capacitance C changes according to the change in the area A.

[0076] In addition, the pressure applied to the contact surface 28 is equivalent to the force applied to the contact surface 28 along the Z-axis direction, which will be described in detail later. Further, the shearing force applied to the contact surface 28 is equivalent to the force applied to the contact surface 28 along the direction orthogonal to the Z-axis direction. Among the directions orthogonal to the Z-axis direction, there are the X-axis direction, the Y-axis direction, and the direction formed by combining the X-axis direction and the Y-axis direction.

[0077] The plurality of first electrodes 34 are driven by a capacitance detection IC 44 (see Figure 3 , Figure 7 ) described later, and respectively output signals corresponding to the capacitance C between them and the second electrode 36. That is, the sensor unit 18 outputs a plurality of signals corresponding to the plurality of first electrodes 34 respectively. These plurality of signals are analog signals.

[0078] Figure 7 is Figure 3 a bottom view of the substrate 16. The plurality of capacitance detection ICs 44 are arranged in a matrix along the X-Y plane. That is, the plurality of capacitance detection ICs 44 are arranged with the X-axis direction as the longitudinal direction and the Y-axis direction as the lateral direction. The plurality of capacitance detection ICs 44 have the same structure. As an example, three capacitance detection ICs 44 are arranged in the X-axis direction respectively, and three capacitance detection ICs 44 are arranged in the Y-axis direction respectively. That is, the number of the plurality of capacitance detection ICs 44 is nine.

[0079] Four first electrodes 34 that overlap with the capacitance detection IC 44 in a top view are connected to each capacitance detection IC 44. Each capacitance detection IC 44 has a structure capable of driving the four first electrodes 34 and outputting data corresponding to the signals output from the four first electrodes 34.

[0080] (Manufacturing method of the tactile sensor 10)

[0081] Figure 8 is a diagram showing an example of the manufacturing method of the tactile sensor 10 of Figure 3 . The tactile sensor 10 is manufactured, for example, by the following procedure. That is, a plurality of capacitance detection ICs 44 are mounted on the second surface 16B of the substrate 16 on which a plurality of first electrodes 34 are formed by patterning on the first surface 16A. A plurality of through holes 46 are formed in the substrate 16, and the plurality of capacitance detection ICs 44 are connected to the plurality of first electrodes 34 via the plurality of through holes 46.

[0082] Next, an elastic layer 22 is laminated on the first electrode layer 24 having a plurality of first electrodes 34. Further, a second electrode layer 26 composed of a plurality of second electrodes 36 (see Figure 5 ) is laminated on the elastic layer 22, and further, an insulating layer 20 is laminated on the second electrode layer 26. The insulating layer 20, the elastic layer 22, the first electrode layer 24, and the second electrode layer 26 are bonded to each other by an adhesive or the like, for example. By the above procedure, the tactile sensor 10 is manufactured.

[0083] In addition, as Figure 5 shown, as a processing method for forming a plurality of openings 38 in the second electrode 36, punching, cutting, injection molding, die stamping, etc. can be cited.

[0084] (Explanation of displacements Δx, Δy, Δz)

[0085] Figure 9 is a top view showing an example of the displacements Δx and Δy in the tactile sensor 10 of Figure 3 . Further, in Figure 9 , the electrostatic capacitances C 00 ~C 55 between each of the plurality of first electrodes 34 and the second electrode 36 are shown corresponding to each of the plurality of first electrodes 34.

[0086] Figure 10 is a diagram showing an example of the displacements Δx and Δz in the tactile sensor 10 of Figure 3 . In Figure 10 , cases of (A) no vertical load Fz', (B) having a vertical load Fz', (C) having a shear force Fx, and (D) having a vertical load Fz' + shear force Fx are shown respectively.

[0087] Figure 11 is a diagram showing an example of the displacements Δy and Δz in the tactile sensor 10 of Figure 3 . In Figure 11 , cases of (A) no vertical load Fz', (B) having a vertical load Fz', (C) having a shear force Fy, and (D) having a vertical load Fz' + shear force Fy are shown respectively.

[0088] As Figure 9 , Figure 10 shown, the displacement Δx corresponds to the distance by which the second electrode 36 moves in the X-axis direction as the shear force Fx acts. Similarly, as Figure 9 , Figure 11 shown, the displacement Δy corresponds to the distance by which the second electrode 36 moves in the Y-axis direction as the shear force Fy acts.

[0089] AsFigure 10 and Figure 11 As shown, the distance Z0 is the distance along the Z-axis direction between the first electrode 34 and the second electrode 36 when no vertical load Fz' is applied. The displacement Δz is the distance that the second electrode 36 moves toward the first electrode 34 side along the Z-axis direction under the action of the vertical load Fz'.

[0090] Hereinafter, a calculation example of the displacements Δx, Δy, and Δz will be described using the adjacent first electrode 34 that partially overlaps with one second electrode 36 as an example.

[0091] (When no vertical load Fz' is applied: Δx, Δy, Δz = 0)

[0092] As shown in (A) of Figure 10 and (A) of Figure 11 when no vertical load Fz' is applied, Δx, Δy, Δz = 0, and Equation 1 holds for the adjacent first electrode 34 that partially overlaps with the second electrode 36.

[0093] [Equation 1]

[0094] C 00_0 = K1 / Z0

[0095] C 01_0 = K2 / Z0

[0096] C 00_0 and C 01_0 are the electrostatic capacitances between the adjacent first electrode 34 and the second electrode 36 when no vertical load Fz' is applied, and K1 and K2 are constants.

[0097] For the electrostatic capacitances between other adjacent first electrodes 34 and second electrodes 36, equations similar to Equation 1 also hold.

[0098] (When only vertical load Fz' is applied: Δx, Δy = 0, Δz ≠ 0)

[0099] As shown in (B) of Figure 10 and (B) of Figure 11 when only vertical load Fz' is applied, Δx, Δy = 0, Δz ≠ 0, and Equation 2 holds for the adjacent first electrode 34 that partially overlaps with the second electrode 36.

[0100] [Equation 2]

[0101] C 00_z = K1 / (Z0 - Δz)

[0102] C 01_z = K2 / (Z0 - Δz)

[0103] C 00_z and C01_z is the electrostatic capacitance between the adjacent first electrode 34 and second electrode 36 when only the vertical load Fz’ acts thereon.

[0104] Based on Equation 2, the following is obtained.

[0105] C 00_z / K1 = 1 / (Z0 - Δz)

[0106] Z0 - Δz = K1C 00_z

[0107] Δz = Z0 - K1 / C 00_z

[0108] Based on Equation 1, the displacement Δz of the second electrode 36 relative to one of the first electrodes 34 is obtained as follows.

[0109] Z0 = K1 / C 00_0

[0110] ∴Δz = K1(1 / C 00_0 - 1 / C 00_z )

[0111] Similarly, the displacement Δz of the second electrode 36 relative to the other first electrode 34 is obtained as follows.

[0112] Δz = K2(1 / C 01_0 - 1 / C 01_z )

[0113] Regarding the displacement Δz of the second electrode 36 relative to the other first electrode 34, it is also obtained in the same manner as above.

[0114] (When only the shear force Fx acts: Δy, Δz = 0, Δx ≠ 0)

[0115] As Figure 10 shown in (C) below, when only the shear force Fx acts, Δy, Δz = 0, Δx ≠ 0, and Equation 3 holds for the adjacent first electrode 34 that partially overlaps with the second electrode 36.

[0116] [Equation 3]

[0117] C 00_x = K1 / Z0 + Δx·Kp / Z0

[0118] C 01_x = K2 / Z0 - Δx·Kp / Z0

[0119] C 00_ｘ 、C 01_x are the electrostatic capacitances between the first electrode 34 and the second electrode 36 adjacent in the x - direction when only the shear force Fx acts, and Kp is a constant.

[0120] Calculate the following according to Equation 3.

[0121] Δx·Kp / Z0 = C 00_x -K1 / Z0

[0122] Δx·Kp = Z0·C 00_x -K1

[0123] Δx = (Z0·C 00_x -K1) / Kp

[0124] According to Equation 1, since K1 = Z0 × C 00_0 , the displacement Δx of the second electrode 36 relative to one of the first electrodes 34 is calculated as follows.

[0125] Δx = (Z0·C 00_x -Z0×C 00_0 ) / Kp

[0126] Δx = Z0 / Kp×(C 00_x -C 00_0 )

[0127] Similarly, the displacement Δx of the second electrode 36 relative to the other first electrode 34 is calculated as follows.

[0128] Δx = Z0 / Kp×(C 01_0 -C 01_x )

[0129] Regarding the displacement Δx of the second electrode 36 relative to the other first electrode 34, it is calculated in the same manner as above.

[0130] (When only the shear force Fy acts: Δx, Δz = 0, Δy ≠ 0)

[0131] As Figure 11 (C) shows, when only the shear force Fy acts, the displacement Δy of the second electrode 36 relative to the first electrode 34 is calculated by the same calculation as when only the shear force Fx acts.

[0132] (When only the vertical load Fz’ and the shear force Fx act: Δy = 0, Δx, Δz ≠ 0)

[0133] As Figure 10 (D) shows, when only the vertical load Fz’ and the shear force Fx act, Δy = 0, Δx, Δz ≠ 0, and Equation 4 holds for the first electrode 34 adjacent to and partially overlapping with the second electrode 36.

[0134] [Equation 4]

[0135] C 00_zx= K1 / (Z0 - Δz) + Δx·Kp / (Z0 - Δz)

[0136] C 01_zx = K2 / (Z0 - Δz) + Δx·Kp / (Z0 - Δz)

[0137] C 00_zx 、C 01_zx is the electrostatic capacitance between the first electrode 34 and the second electrode 36 when only the vertical load Fz’ and the shear force Fx act.

[0138] According to Equation 4, the displacements Δz and Δx of the second electrode 36 relative to the first electrode 34 are obtained as follows.

[0139] Δz = (K1 + K2){1 / (C 00_0 + C 01_0 ) - 1 / (C 00_zx + C 01_zx )}

[0140] Δx = (K1 + K2) / 2Kp·(C 00_zx - C 01_zx ) / (C 00_zx + C 01_zx )

[0141] Regarding the displacements Δz and Δx of the second electrode 36 relative to the other first electrode 34, they are also obtained in the same manner as above.

[0142] (When only the vertical load Fz’ and the shear force Fy act: Δx = 0, Δy, Δz ≠ 0)

[0143] As Figure 11 shown in (D) of, when only the vertical load Fz’ and the shear force Fy act, the displacements Δz and Δy of the second electrode 36 relative to the adjacent first electrode 34 are obtained by the same calculation as when only the vertical load Fz’ and the shear force Fx act.

[0144] (When the vertical load Fz’ and the shear forces Fx and Fy act: Δx, Δy, Δz ≠ 0)

[0145] When the vertical load Fz’ and the shear forces Fx and Fy act, the displacements Δx, Δy, and Δz of the second electrode 36 relative to the first electrode 34 can be obtained as follows. In the range of the four first electrodes 34 that partially overlap with one second electrode 36, the values of the displacement Δz in each first electrode 34 are often approximately the same. Therefore, it is assumed that the values of the displacement Δz are the same. In this case, the magnitude of the signal (electrostatic capacitance value) corresponding to each first electrode 34 is proportional to the overlapping area of each first electrode 34 with the second electrode 36. Therefore, the electrostatic capacitance values C 00 、C01 , C 10 , C 11 The ratio of and the overlapping area S 00 , S 01 , S 10 , S 11 are equal. That is, Equation 5 holds.

[0146] [Equation 5]

[0147] C 00 : C 01 : C 10 : C 11 = S 00 : S 01 : S 10 : S 11

[0148] If the square root of the overlapping area in the no-load state is set as a, then the overlapping areas S 00 , S 01 , S 10 , S 11 are shown by Equation 6.

[0149] [Equation 6]

[0150] S 00 = (a - Δx) × (a - Δy), S 01 = (a - Δx) × (a + Δy), S 10 = (a + Δx) × (a - Δy), S 11 = (a + Δx) × (a + Δy)

[0151] According to Equation 6, the sum of the 4 overlapping areas is 4a 2 , which is a constant. Therefore, based on the sum 4a of the 4 overlapping areas 2 and Equation 5, the overlapping areas S 00 , S 01 , S 10 , S 11 become known values. Based on the above, the unknown displacements Δx, Δy can be calculated through the simultaneous equations of Equation 6.

[0152] It is also possible to, after calculating the displacements Δx, Δy, use them as known values and correct the displacement Δz assumed to be the same value to the respective displacements Δz in each first electrode 34. For example, it is possible to obtain the correlation between the displacements Δx, Δy and the 4 displacements Δz in advance in an environment where the true values of the 4 displacements Δz can be measured by other means, and use this correlation for this correction. It is also possible to obtain this correlation through machine learning.

[0153] When it is known that the four electrostatic capacitance values corresponding to each of the first electrodes 34 are approximately equal, that is, the displacements Δx and Δy are close to zero, the displacement Δz in the four first electrodes 34 can also be calculated individually by the method described for the case of Δx, Δy = 0, Δz ≠ 0. The case of Δx, Δy = 0, Δz ≠ 0 means, for example, the case where the workpiece W placed on the table is held and the weight of the workpiece W is not applied to the contact surface 28. If the workpiece W is lifted from the workbench from this state, the displacement Δz hardly changes, and mainly the displacements Δx and Δy change. Therefore, the displacements Δx and Δy can be obtained more accurately by taking the displacement Δz as a known value.

[0154] In this specification, "calculating the pressure value at each of a plurality of pressure detection positions" includes: when it is assumed that the displacements Δz at a plurality of pressure detection positions such as the four first electrodes 34 are the same, treating the pressure values based on the calculated same displacement Δz as the pressure values at each pressure detection position. In addition, "calculating the aggregated pressure value by calculating the representative value for the pressure values at each of the plurality of pressure detection positions" includes: when it is assumed that the displacements Δz at a plurality of pressure detection positions such as the four first electrodes 34 are the same, calculating the aggregated pressure value by taking the pressure values based on the calculated same displacement Δz as the representative value.

[0155] As described above, the output unit 12 calculates the respective shear force Fx and Fy values in a manner that removes the influence of pressure on the plurality of signals based on the plurality of signals respectively corresponding to the plurality of first electrodes 34 including at least one partially overlapping electrode that is the first electrode 34 partially overlapping with the second electrode 36.

[0156] Next, the operation and effects of the first embodiment will be described.

[0157] In the tactile sensor 10 (refer to Figures 3 to 7 ), the second electrode layer 26 is composed of a plurality of second electrodes 36 as a single layer. Therefore, the structure and manufacturing process of the tactile sensor 10 can be simplified.

[0158] In addition, by detecting the electrostatic capacitance that changes according to the distance between the first electrode 34 and the second electrode 36, the pressure can be detected at the positions of the plurality of first electrodes 34 respectively. And each second electrode 36 partially overlaps with four first electrodes 34 adjacent in the X-axis direction and the Y-axis direction. Therefore, by detecting the electrostatic capacitance that changes according to the overlapping area where the four first electrodes 34 overlap with the second electrode 36, the shear force can also be detected at the position of each second electrode 36.

[0159] Moreover, the number of the plurality of second electrodes 36 is less than the number of the plurality of first electrodes 34, whereby the plurality of first electrodes 34 are matched with one second electrode 36. Therefore, for example, compared with the case where the plurality of first electrodes 34 and the plurality of second electrodes 36 are matched one by one, the interval between the plurality of first electrodes 34 can be reduced. Thereby, the number of the plurality of first electrodes 34 can be ensured, and thus the resolution of the pressure distribution can be ensured.

[0160] Thus, according to the tactile sensor 10 according to the first embodiment, even with a simple structure and manufacturing process, the shear force can be detected and the resolution of the pressure distribution can be ensured.

[0161] Next, a modified example of the first embodiment will be described.

[0162] The tactile sensor 10 has 36 first electrodes 34, but the number of the plurality of first electrodes 34 can be any number.

[0163] The number of the plurality of second electrodes 36 can be any number as long as it is less than the number of the plurality of first electrodes 34.

[0164] The plurality of first electrodes 34 are preferably arranged in a matrix along the contact surface 28, but may be arranged in a manner other than a matrix as long as a desired pressure distribution can be obtained within the contact surface 28.

[0165] [Second Embodiment]

[0166] Next, the second embodiment will be described.

[0167] (Structure of the Tactile Sensor 10)

[0168] Figure 12 is a longitudinal sectional view of the tactile sensor 10 according to the second embodiment. The tactile sensor 10 according to the second embodiment is different from the above-described tactile sensor 10 (refer to Figures 3 to 6 ), and the structure of the second electrode layer 26 is changed as follows.

[0169] Figure 13 is Figure 12 a top view of the second electrode layer 26 of

[0170] Figure 14 is a view showing Figure 12A plan view of the state where the second electrode 36, the elastic layer 22, and the substrate 16 overlap. As an example, the number of the plurality of first electrodes 34 is 36. In contrast, the second electrode 36 forms one island portion. Therefore, in the second embodiment, the number of island portions formed by the second electrode 36 is smaller than the number of the plurality of first electrodes 34.

[0171] As an example, the second electrode 36 is formed as a square smaller than the contact surface 28 (see Figure 12 ). The second electrode 36 has a size that overlaps all of the plurality of first electrodes 34 in plan view. Specifically, the second electrode 36 has a size such that the first electrodes 34 arranged along the outer peripheral portion of the second electrode 36 among the plurality of first electrodes 34 overlap the outer peripheral portion of the second electrode 36 in plan view. Thus, the first electrodes 34 arranged along the outer peripheral portion of the second electrode 36 partially overlap the second electrode 36 in plan view, and the entirety of the first electrodes 34 located inside the outer peripheral portion of the second electrode 36 among the plurality of first electrodes 34 overlap the second electrode 36.

[0172] In the second embodiment, the first electrodes 34 among the plurality of first electrodes 34 that partially overlap the second electrode 36 are an example of "a plurality of partial overlap electrodes that partially overlap the second electrode", and the plurality of signals output from the first electrodes 34 that partially overlap the second electrode 36 are an example of "a plurality of partial overlap electrode signals".

[0173] In Figure 12 the sensor unit 18 of the tactile sensor 10 shown, when pressure is applied to the contact surface 28 and the distance d between each first electrode 34 and the second electrode 36 changes, the capacitance C changes according to the change in the distance d. Further, in the sensor unit 18, when a shearing force is applied to the contact surface 28, the overlapping area A between the first electrode 34 (see Figure 14 ) that partially overlaps the second electrode 36 and the second electrode 36 changes, and the capacitance C changes according to the change in the area A.

[0174] The tactile sensor 10 having such a structure is manufactured in the same manner as the tactile sensor 10 of the above-described first embodiment (see Figures 3 to 6 ).

[0175] Further, in the second embodiment, the displacements Δx, Δy, and Δz are calculated based on the same concept as in the case of the first embodiment.

[0176] Next, the operation and effects of the second embodiment will be described.

[0177] In the tactile sensor 10 (see Figures 12 to 14)In [the structure], the second electrode layer 26 is composed of one second electrode 36 as a single layer. Therefore, the structure and manufacturing process of the tactile sensor 10 can be simplified.

[0178] In addition, by detecting the capacitance that changes according to the distance between the first electrode 34 and the second electrode 36, pressure can be detected at the positions of the respective first electrodes 34. And a part of the plurality of first electrodes 34, that is, the first electrodes 34 arranged along the outer peripheral portion of the second electrode 36 partially overlap the second electrode 36 in a top view. Therefore, by detecting the capacitance that changes according to the overlapping area where the first electrode 34 overlaps the second electrode 36, shear force can also be detected at the positions of the first electrodes 34 arranged along the outer peripheral portion of the second electrode 36.

[0179] Moreover, the number of the second electrodes 36 is 1, which is less than the number of the plurality of first electrodes 34. Thus, the plurality of first electrodes 34 are matched with one second electrode 36. Therefore, for example, compared with the case where the plurality of first electrodes 34 and the plurality of second electrodes 36 are matched one by one, the interval between the plurality of first electrodes 34 can be reduced. Thereby, the number of the plurality of first electrodes 34 can be ensured, and thus the resolution of the pressure distribution can be ensured.

[0180] In this way, according to the tactile sensor 10 of the second embodiment, even with a simple structure and manufacturing process, shear force can be detected and the resolution of the pressure distribution can be ensured.

[0181] In addition, since the second electrode 36 has a single structure, for example, compared with the case where the second electrode 36 is composed of a plurality of components, the manufacturing efficiency can be improved and the number of components can be reduced.

[0182] Next, a modified example of the second embodiment will be described.

[0183] The tactile sensor 10 has 36 first electrodes 34, but the number of the plurality of first electrodes 34 can be any number.

[0184] The number of the second electrodes 36 is 1, but as long as it is less than the number of the plurality of first electrodes 34, the number of the second electrodes 36 can be any number.

[0185] The plurality of first electrodes 34 are preferably arranged in a matrix along the contact surface 28, but as long as a desired pressure distribution can be obtained within the contact surface 28, they can also be arranged in a manner other than a matrix.

[0186] [Third Embodiment]

[0187] Next, the third embodiment will be described.

[0188] (Structure of the tactile sensor 10)

[0189] Figure 15 is a longitudinal sectional view of the tactile sensor 10 of the third embodiment. The tactile sensor 10 of the third embodiment is different from the tactile sensor 10 of the first embodiment described above (refer to Figures 3 to 6 ) in that the structure of the second electrode layer 26 is changed as follows.

[0190] Figure 16 is Figure 15 a top view of the second electrode layer 26. The second electrode layer 26 is composed of a single second electrode 36. The second electrode 36 is formed of, for example, conductive rubber. The second electrode 36 is formed in a flat plate shape. As an example, the second electrode 36 is formed in a square shape in a top view. The second electrode 36 may be grounded to the substrate 16 (refer to Figure 3 ) or may be floating with respect to the ground.

[0191] A plurality of openings 38 are formed in the second electrode 36. The plurality of openings 38 penetrate in the thickness direction of the second electrode 36, that is, in the Z-axis direction. The plurality of openings 38 are arranged in a matrix along the X-Y plane. That is, the plurality of openings 38 are arranged with the X-axis direction as the longitudinal direction and the Y-axis direction as the lateral direction.

[0192] The plurality of openings 38 have the same shape. As an example, the plurality of openings 38 are formed in a square shape in a top view. The number of the plurality of openings 38 is smaller than the number of the plurality of first electrodes 34 described above (refer to Figure 4 ). As an example, three of the plurality of openings 38 are arranged in the X-axis direction and three are arranged in the Y-axis direction. That is, the number of the plurality of openings 38 is nine. The plurality of openings 38 are arranged at equal intervals in the X-axis direction and the Y-axis direction, respectively.

[0193] Figure 17 is a top view showing a state in which the second electrode 36, the elastic layer 22, and the substrate 16 of Figure 15 are overlapped. The second electrode 36 has a size that completely overlaps all of the plurality of first electrodes 34 in a top view. Specifically, the second electrode 36 has a size such that all of the plurality of first electrodes 34 are received inside the outer shape portion of the second electrode 36 in a top view.

[0194] The plurality of openings 38 are each formed to partially overlap four first electrodes 34 that are adjacent in the X-axis direction and the Y-axis direction among the plurality of first electrodes 34. Specifically, each opening 38 is located at the center of the four first electrodes 34 and partially overlaps the four first electrodes 34 in a top view.

[0195] Thus, in the third embodiment, all of the plurality of first electrodes 34 are received inside the outer shape portion of the second electrode 36 in a plan view, and in addition, all of the plurality of first electrodes 34 partially overlap with the opening 38. All of the plurality of first electrodes 34 partially overlapping with the opening 38 is equivalent to all of the plurality of first electrodes 34 partially overlapping with the second electrode 36.

[0196] In the third embodiment, all of the plurality of first electrodes 34 are an example of "a plurality of partially overlapping electrodes that partially overlap with the second electrode", and the plurality of signals output from the plurality of first electrodes 34 are an example of "a plurality of partially overlapping electrode signals".

[0197] In Figure 15 In the sensor unit 18 of the tactile sensor 10 shown, when pressure is applied to the contact surface 28 and the distance d between each first electrode 34 and the second electrode 36 changes, the capacitance C changes according to the change in the distance d. In addition, in the sensor unit 18, when a shearing force is applied to the contact surface 28 and the overlapping area A where each first electrode 34 overlaps with the second electrode 36 changes, the capacitance C changes according to the change in the area A.

[0198] The tactile sensor 10 having such a structure is manufactured in the same manner as the tactile sensor 10 of the first embodiment described above (refer to Figures 3 to 6 ).

[0199] In addition, in the third embodiment, the calculation of the displacements Δx, Δy, and Δz is performed based on the same concept as in the case of the first embodiment.

[0200] Next, the operation and effects of the third embodiment will be described.

[0201] In the tactile sensor 10 (refer to Figures 15 to 17 ), the second electrode layer 26 is composed of one second electrode 36 as a single layer. Therefore, the structure and manufacturing process of the tactile sensor 10 can be simplified.

[0202] In addition, by detecting the capacitance that changes according to the distance between the first electrode 34 and the opening 38, pressure can be detected at the positions of the plurality of first electrodes 34. And each opening 38 partially overlaps with four first electrodes 34 adjacent in the X-axis direction and the Y-axis direction, so by detecting the capacitance that changes according to the overlapping area where the four first electrodes 34 overlap with the plurality of openings 38, shearing force can also be detected at the position of each opening 38.

[0203] Moreover, the number of openings 38 formed in the second electrode 36 is smaller than the number of the plurality of first electrodes 34, such that the plurality of first electrodes 34 are matched with one opening 38. Therefore, for example, compared with the case where the plurality of first electrodes 34 are matched with the plurality of openings 38 one by one, the interval between the plurality of first electrodes 34 can be reduced. Thus, the number of the plurality of first electrodes 34 can be ensured, and the resolution of the pressure distribution can be ensured.

[0204] Thus, according to the tactile sensor 10 according to the third embodiment, even with a simple structure and manufacturing process, the shear force can be detected and the resolution of the pressure distribution can be ensured.

[0205] In addition, the second electrode 36 is a single structure having a plurality of openings 38. Therefore, for example, compared with the case where the second electrode 36 is composed of a plurality of components, the manufacturing efficiency can be improved and the number of components can be reduced.

[0206] The tactile sensor 10 has 36 first electrodes 34, but the number of the plurality of first electrodes 34 can be any number.

[0207] The number of the plurality of second electrodes 36 can be any number as long as it is smaller than the number of the plurality of first electrodes 34.

[0208] The plurality of first electrodes 34 are preferably arranged in a matrix along the contact surface 28, but may be arranged in a manner other than a matrix as long as a desired pressure distribution can be obtained within the contact surface 28.

[0209] [Fourth Embodiment]

[0210] Next, the fourth embodiment will be described.

[0211] (Structure of the Tactile Sensor 10)

[0212] Figure 18 is a longitudinal sectional view of the tactile sensor 10 according to the fourth embodiment. The tactile sensor 10 according to the fourth embodiment is different from the tactile sensor 10 according to the above-described first embodiment (refer to Figures 3 to 6 ) in that the structure of the second electrode layer 26 is changed as follows.

[0213] Figure 19 is Figure 18 a top view of the second electrode layer 26 of . The second electrode layer 26 is composed of one second electrode 36 as a single layer. The second electrode 36 is formed in a flat plate shape. The second electrode 36 can be connected to the ground of the substrate 16 or can be floating with respect to the ground. The second electrode 36 is formed of, for example, conductive rubber.

[0214] One opening 38 is formed in the second electrode 36. As an example, the opening 38 is formed in the central portion of the second electrode 36. The second electrode 36 is square in plan view, and the opening 38 is also square in plan view.

[0215] Figure 20 It shows the state where Figure 18 the second electrode 36, the elastic layer 22, and the substrate 16 are overlapped. As an example, the number of the plurality of first electrodes 34 is 36. In contrast, one opening 38 is formed in the second electrode 36. Therefore, in the fourth embodiment, the number of openings 38 formed in the second electrode 36 is smaller than the number of the plurality of first electrodes 34.

[0216] The second electrode 36 has a size that overlaps all of the plurality of first electrodes 34 in plan view. Specifically, the second electrode 36 has a size such that all of the plurality of first electrodes 34 are accommodated inside the outer shape portion of the second electrode 36 in plan view.

[0217] As an example, the opening 38 is formed as a square smaller than the smallest square that can accommodate all of the four central first electrodes 34 adjacent in the X-axis direction and the Y-axis direction in plan view. The opening 38 is located at the center of the four central first electrodes 34 in plan view and partially overlaps with the four first electrodes 34. Thus, the four central first electrodes 34 among the plurality of first electrodes 34 partially overlap with the second electrode 36 in plan view, and the first electrodes 34 other than the four central first electrodes 34 among the plurality of first electrodes 34 overlap with the second electrode 36 as a whole.

[0218] In the second embodiment, the four central first electrodes 34 among the plurality of first electrodes 34 are an example of the "plurality of partially overlapping electrodes that partially overlap with the second electrode", and the plurality of signals output from the four central first electrodes are an example of the "plurality of partially overlapping electrode signals".

[0219] The tactile sensor 10 having such a structure is manufactured in the same manner as the tactile sensor 10 of the above-described first embodiment (refer to Figures 3 to 6 ).

[0220] In the fourth embodiment, the displacements Δx, Δy, and Δz are calculated based on the same idea as in the case of the first embodiment.

[0221] Next, the operation and effects of the fourth embodiment will be described.

[0222] In the tactile sensor 10 (refer to Figures 18 to 20 ), the second electrode layer 26 is composed of one second electrode 36 as a single layer. Therefore, the structure and manufacturing process of the tactile sensor 10 can be simplified.

[0223] In addition, by detecting the capacitance that changes according to the distance between the first electrode 34 and the second electrode 36, the pressure can be detected at the positions of the respective first electrodes 34. Further, four central first electrodes 34 among the plurality of first electrodes 34 partially overlap with the opening 38 formed at the center of the second electrode 36 in a plan view. Therefore, by detecting the capacitance that changes according to the overlapping area where the four first electrodes 34 overlap with the second electrode 36, the shearing force can also be detected at the position of the opening 38.

[0224] Moreover, the number of openings 38 formed in the second electrode 36 is one, which is smaller than the number of the plurality of first electrodes 34. As a result, the plurality of first electrodes 34 are matched with one opening 38. Therefore, for example, compared with the case where the plurality of first electrodes 34 are matched one-to-one with a plurality of openings 38, the intervals between the plurality of first electrodes 34 can be reduced. Thereby, the number of the plurality of first electrodes 34 can be ensured, and thus the resolution of the pressure distribution can be ensured.

[0225] As described above, according to the tactile sensor 10 according to the fourth embodiment, even with a simple structure and manufacturing process, the shearing force can be detected and the resolution of the pressure distribution can be ensured.

[0226] In addition, since the second electrode 36 has a single structure, for example, compared with the case where the second electrode 36 is composed of a plurality of components, the manufacturing efficiency can be improved and the number of components can be reduced.

[0227] Next, a modified example of the fourth embodiment will be described.

[0228] The tactile sensor 10 has 36 first electrodes 34, but the number of the plurality of first electrodes 34 can be any number.

[0229] One opening 38 is formed in the second electrode 36, but as long as the number of the openings 38 is smaller than the number of the plurality of first electrodes 34, the number of the openings 38 can be any number.

[0230] The plurality of first electrodes 34 are preferably arranged in a matrix along the contact surface 28, but as long as a desired pressure distribution can be obtained within the contact surface 28, they may be arranged in a manner other than a matrix.

[0231] As described above, the first to fourth embodiments of the technology disclosed in the present application have been described, but the technology disclosed in the present application is not limited to the above, and of course, various modifications can be made without departing from the gist thereof.

[0232] In addition, the entire disclosure of Japanese Patent Application No. 2020-140395 is incorporated herein by reference.

[0233] In addition, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and separately recited.

Claims

1. A tactile sensor, wherein, the tactile sensor includes a sensor unit using the capacitance method, the sensor unit using the capacitance method has a contact surface with an object, and has a laminated structure in which an elastic layer and a first electrode layer and a second electrode layer located on both sides sandwiching the elastic layer are laminated in the normal direction of the contact surface, the first electrode layer has a plurality of first electrodes, the second electrode layer is composed of a single second electrode formed with a plurality of openings, two or more of the plurality of first electrodes are partially overlapping electrodes that partially overlap the second electrode when viewed in the normal direction, the number of the plurality of openings is smaller than the number of the plurality of first electrodes, each of the plurality of openings is formed to partially overlap adjacent first electrodes among the plurality of first electrodes when viewed in the normal direction.

Images