Force sensor and detection device

Abstract

[Problem] To provide a force sensor capable of detecting the position and magnitude of pressure in the up-down direction, capable of detecting the magnitude of shearing force, and suitable for miniaturization. [Solution] A lower electrode layer 40 has a plurality of grid electrodes 41. An upper electrode layer 60 has one or more isolated electrodes 62. Each of the isolated electrodes 62 straddles at least two adjacent grid electrodes 41 in a top view. This force sensor is capable of detecting the position and magnitude of pressure in the up-down direction, from a change in electrostatic capacity between the upper electrode layer 60 and each grid electrode 41. The force sensor is capable of detecting shearing force in a first direction and in a second direction, from a change in the ratio of electrostatic capacities between the isolated electrode 62 and the two grid electrodes 41 straddled by the isolated electrode 62. Since the number of electrodes for detecting shearing force can be reduced, the force sensor is suitable for miniaturization.

Description

Force Sensor and Detection Device

[0001] The present invention relates to a force sensor and a detection device including the force sensor.

[0002] Conventionally, a force sensor that detects an external force applied to a sheet-like sensor body has been known. The structure of the conventional force sensor is described in, for example, Patent Document 1. The sensor of Patent Document 1 has a lower detection electrode and an upper detection electrode. In the sensor of Patent Document 1, the pressure and shear force applied to the sensor are detected based on the change in capacitance between the lower detection electrode and the upper detection electrode.

[0003] Japanese Patent Application Laid-Open No. 2023-183457

[0004] However, the upper detection electrode of Patent Document 1 is a strip-shaped electrode extending from one end to the other end of the pressure-sensitive region. In such a structure of Patent Document 1, since the range occupied by the upper detection electrode is large, there is a problem that it is not suitable for miniaturization.

[0005] Therefore, an object of the present invention is to provide a force sensor that can detect the position and magnitude of a pressure in the vertical direction, can detect the magnitude of a shear force, and is suitable for miniaturization.

[0006] One aspect of the present invention is a force sensor for detecting an external force, comprising a sensor body having a lower insulating sheet, a lower electrode layer formed on the upper surface of the lower insulating sheet, an upper insulating sheet located above the lower insulating sheet and the lower electrode layer, an upper electrode layer formed on the lower surface of the upper insulating sheet, and a dielectric layer interposed between the lower electrode layer and the upper electrode layer, wherein the lower electrode layer has a plurality of grid electrodes arranged in a grid pattern on the upper surface of the lower insulating sheet in a first direction and a second direction intersecting the first direction, and the upper electrode layer has, in a top view, a planar electrode that overlaps with each of the plurality of grid electrodes and one or more isolated electrodes provided inside the outer shape of the area in which the plurality of grid electrodes are arranged, and the one or more isolated electrodes, in a top view, have at least one of a region spanning at least two adjacent grid electrodes in the first direction and a region spanning at least two adjacent grid electrodes in the second direction.

[0007] Another aspect of the present invention is a force sensor for detecting an external force, comprising a sensor body having a lower insulating sheet, a lower electrode layer formed on the upper surface of the lower insulating sheet, an upper insulating sheet located above the lower insulating sheet and the lower electrode layer, an upper electrode layer formed on the lower surface of the upper insulating sheet, and a dielectric layer interposed between the lower electrode layer and the upper electrode layer, wherein the lower electrode layer has a plurality of grid electrodes arranged in a grid pattern on the upper surface of the lower insulating sheet in a first direction and a second direction intersecting the first direction, the upper electrode layer has a portion that overlaps with each of the plurality of grid electrodes in a top view, and one or more isolated electrodes that overlap only a portion of the plurality of grid electrodes in the first direction and the second direction, and the one or more isolated electrodes have at least one of the following in a top view: a region that spans at least two adjacent grid electrodes in the first direction and a region that spans at least two adjacent grid electrodes in the second direction.

[0008] It is desirable that the upper electrode layer, when viewed from above, has portions that overlap with each of the plurality of grid electrodes and has planar electrodes that are different from the isolated electrodes.

[0009] The one or more isolated electrodes include a first isolated electrode that spans at least two adjacent grid electrodes in the first direction when viewed from above, and a second isolated electrode that spans at least two adjacent grid electrodes in the second direction when viewed from above, and it is desirable that the first isolated electrode and the second isolated electrode do not overlap in the vertical direction.

[0010] It is desirable that the at least two grid electrodes that the first isolated electrode straddles and the at least two grid electrodes that the second isolated electrode straddles are all different grid electrodes.

[0011] It is desirable that the number of the first isolated electrode and the second isolated electrode be the same.

[0012] The force sensor preferably has two or more of the isolated electrodes, and it is desirable that the two or more isolated electrodes are arranged point-symmetrically with respect to each other when viewed from above.

[0013] Preferably, the first isolated electrode and the second isolated electrode each straddle two adjacent grid electrodes in the circumferential direction, centered near the center of the sensor body, when viewed from above.

[0014] It is desirable that the planar electrode and the isolated electrode be arranged on the same plane.

[0015] The force sensor further comprises electrical wiring formed on the upper surface of the upper insulating sheet, wherein the upper insulating sheet has through holes in positions that overlap the isolated electrode in the vertical direction, and the electrical wiring is preferably electrically connected to the isolated electrode through the through holes.

[0016] Furthermore, the present invention may also be a detection device comprising the force sensor described above, and a detection circuit that detects a pressure in the z-axis direction perpendicular to the surface of the sensor body, and shear forces in the x-axis and y-axis directions along the surface of the sensor body, based on a change in capacitance between the lower electrode layer and the upper electrode layer.

[0017] According to the present invention, the position and magnitude of pressure in the vertical direction can be detected by the change in capacitance between the upper electrode layer and each grid electrode. Furthermore, shear forces in the first and second directions can be detected by the change in the ratio of capacitance between an isolated electrode and two grid electrodes that the isolated electrode straddles. In addition, since the number of electrodes required to detect shear forces can be reduced, it is suitable for miniaturizing the force sensor.

[0018] This is a schematic diagram of a detection device equipped with a force sensor. This is a longitudinal cross-sectional view of the sensor body. This is an exploded perspective view of the lower electrode layer and the upper electrode layer. This is a top view of the lower electrode layer and the upper electrode layer. This is a partial longitudinal cross-sectional view of the sensor body when pressure is applied to the upper surface of the cover sheet in the vertical direction (z-axis direction). This is a partial longitudinal cross-sectional view of the sensor body when a shear force is applied to the upper surface of the cover sheet in the first direction (x-axis direction). This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example. This is a top view of the lower electrode layer and the upper electrode layer according to a modified example.

[0019] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the directions along the surface of the sensor body 10 will be referred to as the first direction (x-axis direction) and the second direction (y-axis direction). The first and second directions intersect each other (for example, are orthogonal). The direction perpendicular to the surface of the sensor body 10 will be referred to as the up and down direction (z-axis direction). However, the terms "up" and "down" in the following description are used for convenience in explaining the structure and do not limit the orientation of the force sensor according to the present invention when in use.

[0020] Furthermore, in the following explanation, the shapes and extents of "grid electrodes," "planar electrodes," and "isolated electrodes" will be described without including the electrical wiring connected to these electrodes.

[0021] <1. Configuration of the Detection Device> Figure 1 is a schematic diagram of a detection device 100 equipped with a force sensor 1 according to one embodiment of the present invention. This detection device 100 is a device that detects external forces such as pressure and shear force applied to the force sensor 1. The detection device 100 is used, for example, as an input device for an information processing device. However, the detection device 100 may also be used for other purposes such as a tactile sensor for a robot.

[0022] As shown in Figure 1, the detection device 100 includes a force sensor 1 and a detection circuit 3. The force sensor 1 and the detection circuit 3 are electrically connected by a flexible printed circuit board 2. The force sensor 1 has a sheet-shaped sensor body 10. The detection circuit 3 detects the external force acting on the sensor body 10 by measuring the change in capacitance between electrodes provided inside the sensor body 10.

[0023] <2. Configuration of the Force Sensor> Figure 2 is a longitudinal cross-sectional view of the sensor body 10. As shown in Figure 2, the sensor body 10 has a support sheet 20, a lower insulating sheet 30, a lower electrode layer 40, an upper insulating sheet 50, an upper electrode layer 60, a dielectric layer 70, and a cover sheet 80. The support sheet 20, lower insulating sheet 30, lower electrode layer 40, dielectric layer 70, upper electrode layer 60, upper insulating sheet 50, and cover sheet 80 are stacked in this order from bottom to top.

[0024] The support sheet 20 is located at the bottom layer of the sensor body 10. The support sheet 20 has higher rigidity than the lower insulating sheet 30, the upper insulating sheet 50, and the cover sheet 80. The material used for the support sheet 20 is an insulating resin or glass. Specifically, polyethylene terephthalate (PET), polyimide, or polycarbonate sheets can be used as the material for the support sheet 20. The thickness of the support sheet 20 is, for example, 0.02 to 1 mm.

[0025] The lower insulating sheet 30 is a substrate that holds the lower electrode layer 40. The lower insulating sheet 30 is laminated on the upper surface of the support sheet 20. The material used for the lower insulating sheet 30 is an insulating resin. Specifically, the material used for the lower insulating sheet 30 can be thermoplastic or thermosetting resins such as acrylic, urethane, fluorine compounds, polyester, polycarbonate, polyacetal, polyamide, olefin, silicone rubber, or urethane, or UV-curable resins such as cyanoacrylate. The thickness of the lower insulating sheet 30 is, for example, 0.02 to 0.2 mm.

[0026] The lower electrode layer 40 is formed on the upper surface of the lower insulating sheet 30. A conductive metal is used as the material for the lower electrode layer 40. Specifically, metal oxides such as gold, silver, copper, aluminum, indium oxide, tin oxide, indium tin oxide (ITO), and tin antimonate, as well as platinum, palladium, and rhodium, are used as the material for the lower electrode layer 40. The surface resistance of the lower electrode layer 40 is, for example, several mΩ / □ to several hundred Ω / □.

[0027] The lower electrode layer 40 is formed, for example, by printing silver ink onto the upper surface of the lower insulating sheet 30. However, the lower electrode layer 40 may also be formed by other methods such as sputtering, vacuum deposition, or photolithography. The electrode pattern of the lower electrode layer 40 will be described later.

[0028] The upper insulating sheet 50 is a substrate that holds the upper electrode layer 60. The upper insulating sheet 50 is located above the lower insulating sheet 30 and the lower electrode layer 40. The material used for the upper insulating sheet 50 is an insulating resin. Specifically, the material used for the upper insulating sheet 50 can be thermoplastic or thermosetting resins such as acrylic, urethane, fluorine compounds, polyester, polycarbonate, polyacetal, polyamide, olefin, silicone rubber, or urethane, or UV-curable resins such as cyanoacrylate. The thickness of the lower insulating sheet 30 is, for example, 0.02 to 0.2 mm.

[0029] The upper electrode layer 60 is formed on the lower surface of the upper insulating sheet 50. A conductive metal is used as the material for the upper electrode layer 60. Specifically, metal oxides such as gold, silver, copper, aluminum, indium oxide, tin oxide, indium tin oxide (ITO), and tin antimonate, as well as platinum, palladium, and rhodium, are used as the material for the upper electrode layer 60. The surface resistance of the upper electrode layer 60 is, for example, several mΩ / □ to several hundred Ω / □.

[0030] The upper electrode layer 60 is formed, for example, by printing silver ink onto the lower surface of the upper insulating sheet 50. However, the upper electrode layer 60 may also be formed by other methods such as sputtering, vacuum deposition, or photolithography. The electrode pattern of the upper electrode layer 60 will be described later.

[0031] The dielectric layer 70 is interposed between the lower electrode layer 40 and the upper electrode layer 60. The dielectric layer 70 is provided over the entire surface between the upper surface of the lower insulating sheet 30 on which the lower electrode layer 40 is formed and the lower surface of the upper insulating sheet 50 on which the upper electrode layer 60 is formed. Therefore, the lower electrode layer 40, the upper electrode layer 60, and the dielectric layer 70 constitute a parallel plate capacitor.

[0032] The dielectric layer 70 is made of a material that is an insulator and elastically deformable in response to external forces. Specifically, the dielectric layer 70 can be a silicone-based, acrylic-based, urethane-based, or olefin-based gel sheet, or other foam sheets, rubber sheets, resin sheets, or nonwoven fabric sheets. The thickness of the dielectric layer 70 is, for example, 0.02 to 2 mm. Although the dielectric layer 70 in this embodiment has been described as a single layer, the dielectric layer 70 may be composed of multiple layers made of the same or different materials.

[0033] Furthermore, the upper insulating sheet 50 and the lower insulating sheet 30 are made of a material that is resistant to elastic deformation in order to maintain the shape of the upper electrode layer 60 and the lower electrode layer 40. Specifically, it is preferable that their tensile modulus is 100 MPa or more, and is 100 times or more greater than the tensile modulus of the dielectric layer 70. This allows for accurate detection of changes in the capacitance ratio between the electrode layers 60 and 40.

[0034] The cover sheet 80 is the sheet that receives the external force to be detected. The cover sheet 80 covers the upper surface of the upper insulating sheet 50. In other words, the cover sheet 80 is located in the uppermost layer of the sensor body 10. The upper surface of the cover sheet 80 is the surface exposed to the outside of the sensor body 10. The material used for the cover sheet 80 is an insulating resin. Specifically, polyethylene terephthalate (PET) can be used as the material for the cover sheet 80. The thickness of the cover sheet 80 is, for example, 0.1 to 1 mm.

[0035] The cover sheet 80 may be made of a material that is easily elastically deformable, such as silicone rubber or urethane rubber. However, as will be described later, the force sensor 1 of this embodiment is not intended to detect up to the position where shear force is applied. For this reason, polyethylene terephthalate, which is not easily elastically deformed, can be used for the cover sheet 80. This makes it possible to reduce the material cost of the cover sheet 80.

[0036] <3. Electrode Pattern> Next, the electrode patterns of the lower electrode layer 40 and the upper electrode layer 60 described above will be explained. Figure 3 is an exploded perspective view of the lower electrode layer 40 and the upper electrode layer 60. Note that the dielectric layer 70 between the lower electrode layer 40 and the upper electrode layer 60 is omitted from the illustration in Figure 3. Figure 4 is a top view of the lower electrode layer 40 and the upper electrode layer 60.

[0037] As shown in Figures 3 and 4, the lower electrode layer 40 has a plurality of grid electrodes 41. The plurality of grid electrodes 41 are arranged in a grid pattern in a first direction and a second direction on the upper surface of the lower insulating sheet 30. In this application, "arranged in a grid pattern" means that there are grid-like gaps between each grid electrode 41. However, the shape of the grid electrodes 41 is not limited to a rectangular shape as shown in Figures 3 and 4, but may be circular or other shapes.

[0038] In the examples shown in Figures 3 and 4, three grid electrodes 41 are arranged in the first direction and three in the second direction, for a total of nine grid electrodes 41. The size of the area where the grid electrodes 41 are placed (pressure-sensitive area) is, for example, about 30 mm x 30 mm. However, the size of the pressure-sensitive area is not limited to the above example.

[0039] As shown in Figures 3 and 4, the upper electrode layer 60 has one planar electrode 61. The planar electrode 61 is an electrode for detecting pressure in the vertical direction (z-axis direction). The planar electrode 61 covers the upper surfaces of the multiple grid electrodes 41. That is, in a top view, the planar electrode 61 has a portion that overlaps with each of the multiple grid electrodes 41. In this embodiment, the outer shape of the planar electrode 61 is a rectangle that is slightly larger than the outer shape of the area in which the nine grid electrodes 41 are provided. Therefore, as shown in Figure 4, in a top view, the planar electrode 61 overlaps with all the grid electrodes 41 of the lower electrode layer 40.

[0040] By providing a planar electrode 61 that overlaps with each of the multiple grid electrodes 41, the position where vertical pressure is applied can be detected with high accuracy. Furthermore, the force sensor 1 of this embodiment detects vertical pressure using the planar electrode 61 and detects shear forces in the first and second directions using isolated electrodes 62, which will be described later. This allows for the accurate detection of both vertical pressure and shear forces in the first and second directions.

[0041] Furthermore, as shown in Figures 3 and 4, the upper electrode layer 60 has a plurality of isolated electrodes 62. The isolated electrodes 62 are electrodes for detecting shear force in a first direction (x-axis direction) or a second direction (y-axis direction). The planar electrode 61 has a plurality of rectangular holes 610. The isolated electrodes 62 are arranged within these holes 610. Therefore, although the planar electrode 61 and the isolated electrodes 62 are different electrodes that do not conduct electricity to each other, they are provided on the same plane extending in the first and second directions.

[0042] In this embodiment, the plurality of isolated electrodes 62 have two first isolated electrodes 62x and two second isolated electrodes 62y. The first isolated electrodes 62x are electrodes for detecting shear force in a first direction (x-axis direction). In a top view, the first isolated electrodes 62x are arranged to straddle two adjacent grid electrodes 41 in the first direction. The second isolated electrodes 62y are electrodes for detecting shear force in a second direction (y-axis direction). In a top view, the second isolated electrodes 62y are arranged to straddle two adjacent grid electrodes 41 in the second direction.

[0043] The plurality of isolated electrodes 62 are located inside the outer shape of the range where the plurality of grid electrodes 41 are arranged in a top view. Also, each isolated electrode 62 does not overlap with all of the plurality of grid electrodes 41 arranged in the first direction in a top view. That is, each isolated electrode 62 overlaps with only a part of the plurality of grid electrodes 41 arranged in the first direction in a top view. Further, each isolated electrode 62 does not overlap with all of the plurality of grid electrodes 41 arranged in the second direction in a top view. That is, each isolated electrode 62 overlaps with only a part of the plurality of grid electrodes 41 arranged in the second direction in a top view. As a result, the isolated electrodes 62 necessary for detecting the shearing force can be made smaller, so that the force sensor 1 can be miniaturized.

[0044] FIG. 5 is a partial longitudinal sectional view of the sensor body 10 when a pressure Fz in the vertical direction (z-axis direction) is applied to the upper surface of the cover sheet 80. In this case, a part of the planar electrode 61 to which the pressure Fz is applied is displaced downward. As a result, the vertical distance d between the part of the planar electrode 61 and the grid electrode 41 below it becomes smaller. Then, the capacitance C between the planar electrode 61 and the grid electrode 41 increases. This capacitance C increases as the pressure Fz increases.

[0045] The detection circuit 3 identifies the grid electrode 41 among the plurality of grid electrodes 41 whose capacitance C with the planar electrode 61 has increased. As a result, the detection circuit 3 detects the position where the pressure Fz is applied in the first direction (x-axis direction) and the second direction (y-axis direction). Further, the detection circuit 3 detects the magnitude of the pressure Fz based on the increase amount of the capacitance C between the grid electrode 41 and the planar electrode 61. Then, the detection circuit 3 outputs the detected position and magnitude of the pressure Fz to the outside.

[0046] FIG. 6 is a partial longitudinal sectional view of the sensor body 10 when a shearing force Fx in the first direction (x-axis direction) is applied to the upper surface of the cover sheet 80. In FIG. 5, the symbols of the two grid electrodes 41 straddled by the first isolated electrode 62x are shown separately as 41a and 41b. The grid electrode 41a and the grid electrode 41b are adjacent to each other in the first direction.

[0047] In the no-load state, the first isolated electrode 62x overlaps approximately equally with the grid electrode 41a and the grid electrode 41b. Therefore, the ratio of the capacitance Ca between the first isolated electrode 62x and the grid electrode 41a to the capacitance Cb between the first isolated electrode 62x and the grid electrode 41b is Ca:Cb≈1:1. However, as shown in FIG. 6, when a shearing force Fx in the first direction from the grid electrode 41a toward the grid electrode 41b is applied to the cover sheet 80, the position of the first isolated electrode 62x moves toward the grid electrode 41b side. Then, the capacitance Ca between the first isolated electrode 62x and the grid electrode 41a decreases, and the capacitance Cb between the first isolated electrode 62x and the grid electrode 41b increases. The change in the ratio of these capacitances Ca and Cb becomes larger as the shearing force Fx becomes larger.

[0048] The detection circuit 3 detects the magnitude and direction of the shearing force Fx in the first direction (x-axis direction) based on the change in the ratio of the two capacitances Ca and Cb described above. Then, the detection circuit 3 outputs the detected magnitude and direction of the shearing force Fx to the outside.

[0049] When a shearing force Fy in the second direction (y-axis direction) is applied to the cover sheet 80, similarly to FIG. 6, the two capacitances between the second isolated electrode 62y and the two grid electrodes 41 straddled by the second isolated electrode 62y change. The detection circuit 3 detects the magnitude and direction of the shearing force Fy in the second direction (y-axis direction) based on the change in the ratio of the two capacitances. Then, the detection circuit 3 outputs the detected magnitude and direction of the shearing force Fy to the outside.

[0050] As described above, in this force sensor 1, the position and magnitude of the pressure Fz and the magnitudes and directions of the shearing forces Fx and Fy can be detected. Also, the isolated electrodes 62 for detecting the shearing forces Fx and Fy are arranged inside the outer shape of the range where the plurality of grid electrodes 41 are arranged. Further, the isolated electrodes 62 for detecting the shearing forces Fx and Fy overlap only a part of the plurality of grid electrodes 41 in the first direction and the second direction. Thereby, the size of the electrodes for detecting the shearing force can be suppressed. Therefore, a force sensor 1 suitable for miniaturization can be provided.

[0051] In particular, in the force sensor 1 of this embodiment, the pressure Fz in the vertical direction (z-axis direction) is detected by the planar electrode 61, and the shear forces Fx and Fy in the first direction (z-axis direction) and the second direction (y-axis direction) are detected by the isolated electrode 62. By detecting the pressure Fz and the shear forces Fx and Fy with separate electrodes in this way, the pressure Fz and the shear forces Fx and Fy can be detected with high accuracy.

[0052] Furthermore, in the force sensor 1 of this embodiment, the shear force Fx in the first direction (x-axis direction) is detected by the first isolated electrode 62x, and the shear force Fy in the second direction (y-axis direction) is detected by the second isolated electrode 62y. In other words, the shear force Fx in the first direction (x-axis direction) and the shear force Fy in the second direction (y-axis direction) are detected by separate isolated electrodes 62 that do not overlap in the vertical direction. As a result, the shear force Fx in the first direction (x-axis direction) and the shear force Fy in the second direction (y-axis direction) can be detected with high accuracy.

[0053] Furthermore, in this embodiment, the two grid electrodes 41 that the first isolated electrode 62x straddles and the two grid electrodes 41 that the second isolated electrode 62y straddles are all different grid electrodes 41. In this way, in this embodiment, the shear force Fx in the first direction (x-axis direction) and the shear force Fy in the second direction (y-axis direction) are detected by separate grid electrodes 41. This allows for accurate detection of the shear force Fx in the first direction (x-axis direction) and the shear force Fy in the second direction (y-axis direction).

[0054] Furthermore, in the force sensor 1 of this embodiment, there are two first isolated electrodes 62x and two second isolated electrodes 62y. That is, the number of first isolated electrodes 62x for detecting the shear force Fx in the first direction (x-axis direction) is the same as the number of second isolated electrodes 62y for detecting the shear force Fy in the second direction (y-axis direction). As a result, the detection sensitivity of the shear force Fx in the first direction (x-axis direction) and the detection sensitivity of the shear force Fy in the second direction (y-axis direction) can be made equal.

[0055] Furthermore, in the force sensor 1 of this embodiment, the four isolated electrodes 62 are arranged point-symmetrically with respect to each other when viewed from above. This suppresses bias in the detection sensitivity within the plane of the force sensor 1, enabling more accurate detection of shear forces Fx and Fy.

[0056] Furthermore, in the force sensor 1 of this embodiment, the two first isolated electrodes 62x and the two second isolated electrodes 62y each straddle two adjacent grid electrodes 41 in the circumferential direction, centered near the center of the sensor body 10, when viewed from above. Therefore, the detection circuit 3 can also detect the magnitude and direction of the moment force centered near the center of the sensor body 10 based on the changes in capacitance Ca and Cb between these isolated electrodes 62 and the grid electrodes 41a.

[0057] Furthermore, in the force sensor 1 of this embodiment, the planar electrode 61 and the plurality of isolated electrodes 62 are arranged on the same plane extending in the first and second directions. Therefore, the detection accuracy of pressure Fz, shear force Fx, Fy, or moment force can be improved compared to when the planar electrode 61 and the isolated electrodes 62 are arranged at different heights.

[0058] Furthermore, in the structure of this embodiment, the isolated electrode 62 is surrounded by the planar electrode 61. Therefore, it is not possible to extend the electrical wiring outward from the isolated electrode 62 on the lower surface of the upper insulating sheet 50. To address this, as shown in Figure 2, a through-hole 51 is provided in the upper insulating sheet 50 in this embodiment. The through-hole 51 penetrates the upper insulating sheet 50 vertically at a position that overlaps the isolated electrode 62 in the vertical direction. Electrical wiring 63 is provided on the upper surface of the upper insulating sheet 50, and the isolated electrode 62 and the electrical wiring 63 are electrically connected via the through-hole 51. As a result, even though the isolated electrode 62 is surrounded by other electrodes on the lower surface of the upper insulating sheet 50, the electrical wiring 63 can be drawn out from the isolated electrode 62. The other end of the electrical wiring 63 is electrically connected to the detection circuit 3 via the flexible printed circuit board 2.

[0059] Furthermore, in a top view, the portion of the layer where the electrical wiring 63 is provided, other than the electrical wiring 63, may be further provided with a ground (GND) electrode (not shown). The GND electrode is an electrode connected to the reference potential of the detection circuit 3. This allows the GND electrode to protect the upper electrode layer 60 and reduce noise.

[0060] Furthermore, the electrical wiring 63 extending from multiple isolated electrodes 62 may merge midway and share a common other end. This reduces the number of electrical wirings 63, allowing the force sensor 1 to be miniaturized. When the other ends of the electrical wiring 63 are shared, it is preferable that the grid electrodes 41 that each of the multiple isolated electrodes 62 straddles are all different.

[0061] As described above, according to this embodiment, the position and magnitude of pressure in the vertical direction can be detected by the change in capacitance Ca and Cb between the upper electrode layer 60 and each grid electrode 41. Furthermore, shear forces in the first and second directions can be detected by the change in the ratio of capacitance Ca and Cb between an isolated electrode 62 and the two grid electrodes 41 that the isolated electrode 62 straddles. In addition, since the number of electrodes for detecting shear forces can be reduced, it is suitable for miniaturizing the force sensor 1.

[0062] <4. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Hereinafter, various modifications will be described, focusing on the differences from the above embodiment. Figures 7 to 14 are top views of the lower electrode layer 40 and the upper electrode layer 60 according to the modifications.

[0063] In the example shown in Figure 7, the size of each grid electrode 41 is smaller than in the embodiment described above. By arranging the grid electrodes 41 more finely in this way, the position where the vertical pressure Fz is applied can be detected more precisely.

[0064] In the example in Figure 8, four grid electrodes 41 are arranged in the first direction and four in the second direction, for a total of 16 grid electrodes 41. In the example in Figure 9, five grid electrodes 41 are arranged in the first direction and five in the second direction, for a total of 25 grid electrodes 41. Thus, the number of grid electrodes 41 arranged in each direction may be even or odd. Furthermore, as shown in Figures 8 and 9, it is desirable that, in a top view, all grid electrodes 41 that each isolated electrode 62 straddles are different grid electrodes 41.

[0065] In the example shown in Figure 10, five grid electrodes 41 are arranged in the first direction and three in the second direction, for a total of 15 grid electrodes 41. Thus, the number of grid electrodes 41 arranged in the first direction and the number of grid electrodes 41 arranged in the second direction may be different.

[0066] In the example shown in Figure 11, the isolated electrode 62 is L-shaped. Each isolated electrode 62 has a portion that spans two adjacent grid electrodes 41 in a first direction and a portion that spans two adjacent grid electrodes 41 in a second direction when viewed from above. Thus, the isolated electrode 62 may span three or more grid electrodes 41 when viewed from above. Even in this configuration, it is possible to detect the shear force based on the change in the ratio of capacitance between the isolated electrode 62 and the multiple grid electrodes 41 that the isolated electrode 62 spans.

[0067] In the example shown in Figure 12, the sensor body 10 has only one isolated electrode 62. This single isolated electrode 62 has a portion that spans two adjacent grid electrodes 41 in a first direction and a portion that spans two adjacent grid electrodes 41 in a second direction when viewed from above. Even with this configuration, it is possible to detect shear force based on the change in the ratio of capacitance between the isolated electrode 62 and the multiple grid electrodes 41 that the isolated electrode 62 spans.

[0068] In the example shown in Figure 13, each of the grid electrodes 41 is rectangular in shape when viewed from above. Also, in the example shown in Figure 13, the upper electrode layer 60 does not have a planar electrode 61. Furthermore, each of the multiple isolated electrodes 62 straddles two adjacent rectangular grid electrodes 41 when viewed from above. In this way, even without planar electrodes 61, if the multiple isolated electrodes 62 have portions that overlap with each of the multiple grid electrodes 41 when viewed from above, the pressure in the vertical direction (z-axis direction) can be detected based on the change in capacitance between the isolated electrodes 62 and the grid electrodes 41. Moreover, by making the grid electrodes 41 and isolated electrodes 62 rectangular and straddling each other along their long sides, the capacitance value can be increased, making it easier to detect small changes. In other words, shear force can be detected with high accuracy.

[0069] In the example shown in Figure 14, the upper electrode layer 60 does not have a planar electrode 61. In a top view, the multiple isolated electrodes 62 have portions that overlap with each of the multiple grid electrodes 41. Therefore, pressure in the vertical direction (z-axis direction) can be detected based on the change in capacitance between the isolated electrodes 62 and the grid electrodes 41. In addition, each isolated electrode 62 has a region that spans two adjacent grid electrodes 41 in a first direction and a region that spans two adjacent grid electrodes 41 in a second direction, in a top view. Therefore, shear force can be detected based on the change in the ratio of capacitance between the isolated electrodes 62 and the grid electrodes 41.

[0070] Furthermore, in the above embodiment, the plurality of grid electrodes 41 were arranged in the same orientation as the rectangular lower insulating sheet 30. That is, the lower insulating sheet 30 supporting the plurality of grid electrodes 41 arranged in the first and second directions was rectangular in shape with sides extending in the first and second directions. However, the plurality of grid electrodes 41 may be arranged in an inclined state with respect to the rectangular lower insulating sheet 30. That is, the lower insulating sheet 30 supporting the plurality of grid electrodes 41 arranged in the first and second directions may be rectangular in shape with sides inclined with respect to the first and second directions.

[0071] Furthermore, the elements appearing in the above embodiments and modifications may be combined or partially removed to the extent that no inconsistencies arise. In addition, other elements may be provided between the elements of the force sensor to the extent that no inconsistencies arise.

[0072] 1: Force sensor 2: Flexible printed circuit board 3: Detection circuit 10: Sensor body 20: Support sheet 30: Lower insulating sheet 40: Lower electrode layer 41: Grid electrode 50: Upper insulating sheet 51: Through hole 60: Upper electrode layer 61: Planar electrode 62: Isolated electrode 62x: First isolated electrode 62y: Second isolated electrode 63: Electrical wiring 70: Dielectric layer 80: Cover sheet 100: Detection device 610: Hole C: Capacitance Fx: Shear force Fy: Shear force Fz: Pressure

Claims

1. A force sensor for detecting an external force, comprising: a lower insulating sheet; a lower electrode layer formed on the upper surface of the lower insulating sheet; an upper insulating sheet located above the lower insulating sheet and the lower electrode layer; an upper electrode layer formed on the lower surface of the upper insulating sheet; and a dielectric layer interposed between the lower electrode layer and the upper electrode layer, wherein the lower electrode layer has a plurality of grid electrodes arranged in a grid pattern on the upper surface of the lower insulating sheet in a first direction and a second direction intersecting the first direction; the upper electrode layer, in a top view, has a planar electrode that overlaps with each of the plurality of grid electrodes; and one or more isolated electrodes provided inside the outer shape of the area in which the plurality of grid electrodes are arranged; wherein, in a top view, the one or more isolated electrodes have at least one of the following: a region spanning at least two adjacent grid electrodes in the first direction; and a region spanning at least two adjacent grid electrodes in the second direction.

2. A force sensor for detecting an external force, comprising a sensor body having: a lower insulating sheet; a lower electrode layer formed on the upper surface of the lower insulating sheet; an upper insulating sheet located above the lower insulating sheet and the lower electrode layer; an upper electrode layer formed on the lower surface of the upper insulating sheet; and a dielectric layer interposed between the lower electrode layer and the upper electrode layer, wherein the lower electrode layer has a plurality of grid electrodes arranged in a grid pattern on the upper surface of the lower insulating sheet in a first direction and a second direction intersecting the first direction; the upper electrode layer, in a top view, has a portion that overlaps with each of the plurality of grid electrodes and one or more isolated electrodes that overlap only a portion of the plurality of grid electrodes in the first direction and the second direction; and the one or more isolated electrodes, in a top view, have at least one of the following: a region spanning at least two adjacent grid electrodes in the first direction and a region spanning at least two adjacent grid electrodes in the second direction.

3. The force sensor according to claim 2, wherein the upper electrode layer has a portion that overlaps with each of the plurality of grid electrodes when viewed from above, and has a planar electrode different from the isolated electrode.

4. The force sensor according to any one of claims 1 to 3, wherein the one or more isolated electrodes comprises a first isolated electrode that spans at least two adjacent grid electrodes in the first direction when viewed from above, and a second isolated electrode that spans at least two adjacent grid electrodes in the second direction when viewed from above, and the first isolated electrode and the second isolated electrode do not overlap in the vertical direction.

5. The force sensor according to claim 4, wherein the at least two grid electrodes that the first isolated electrode straddles and the at least two grid electrodes that the second isolated electrode straddles are all different grid electrodes.

6. The force sensor according to claim 4, wherein the number of the first isolated electrode and the second isolated electrode are the same.

7. The force sensor according to claim 1 or claim 3, comprising two or more isolated electrodes, wherein the two or more isolated electrodes are arranged point-symmetrically with respect to each other in a top view.

8. The force sensor according to claim 4, wherein the first isolated electrode and the second isolated electrode each straddle two grid electrodes that are adjacent in the circumferential direction centered near the center of the sensor body when viewed from above.

9. The force sensor according to claim 1 or claim 3, wherein the planar electrode and the isolated electrode are arranged on the same plane.

10. The force sensor according to claim 1 or 2, further comprising electrical wiring formed on the upper surface of the upper insulating sheet, wherein the upper insulating sheet has through holes in positions that overlap the isolated electrode in the vertical direction, and the electrical wiring is electrically connected to the isolated electrode through the through holes.

11. A detection device comprising: a force sensor according to claim 1 or claim 2; and a detection circuit that detects a pressure in the z-axis direction perpendicular to the surface of the sensor body and shear forces in the x-axis and y-axis directions along the surface of the sensor body based on a change in capacitance between the lower electrode layer and the upper electrode layer.

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