Load sensor

Abstract

This load sensor (1) comprises: a plate-shaped member (10) that receives a load on an upper surface (11); a conductive elastic body (20) that protrudes from a lower surface (12) of the plate-shaped member (10); a recess part (RS1) that receives the conductive elastic body (20); a plurality of electrodes (41) that are installed along the inner surface of the recess part (RS1); and a dielectric body (50) that is disposed between the conductive elastic body (20) and the plurality of electrodes (41). The plate-shaped member (10) is disposed so as to be movable in a direction parallel to the central axis of the conductive elastic body (20) and in a direction perpendicular to said central axis with respect to a member (structure (ST1)) having the recess part (RS1), and non-contact regions are present between the conductive elastic body (20) and the plurality of electrodes (41) with the dielectric body (50) therebetween.

Description

Load Sensor

[0001] The present invention relates to a load sensor that detects an externally applied load based on a change in capacitance.

[0002] Load sensors for detecting applied loads have been used in various fields. For example, a load sensor may include a first electrode having an elastic conductive protrusion, a second electrode facing the first electrode across the protrusion, and a dielectric disposed on the opposing surface of the second electrode. When a load is applied to the first electrode or the second electrode, the protrusion contracts in response to the load. This changes the contact area between the dielectric and the protrusion, and also reduces the distance between the dielectric and the first electrode. As a result, the capacitance between the first electrode and the second electrode changes. The load is detected from this change in capacitance.

[0003] Japanese Patent Application Laid-Open No. 2003-144994 describes this type of load sensor.

[0004] JP 2016-118545 A

[0005] The load sensor having the above configuration can be disposed, for example, on a finger of a robot hand. In this case, the load sensor is disposed on the finger so that the surface receiving the load is perpendicular to the gripping direction of the finger. This allows the gripping force of the finger gripping an object to be obtained from the detection result of the load sensor.

[0006] However, in this usage mode, it is preferable that the load in a direction parallel to the load receiving surface can also be detected, so that the weight of the article gripped by the fingers can be further obtained from the detection result of the load in this direction.

[0007] In view of the above problem, an object of the present invention is to provide a load sensor capable of detecting three directional components of a load, that is, a direction perpendicular to a surface receiving the load and two directions parallel to this surface.

[0008] A load sensor according to a main aspect of the present invention comprises a plate-shaped member that receives a load on one surface, a conductive elastic body that protrudes from the other surface of the plate-shaped member, a recess that receives the conductive elastic body, multiple electrodes installed along the inner surface of the recess, and a dielectric body that is arranged between the conductive elastic body and the multiple electrodes. The plate-shaped member is arranged so as to be movable relative to a member having the recess in directions parallel to and perpendicular to a central axis of the conductive elastic body, and there is a region between the conductive elastic body and the multiple electrodes that does not come into contact with each other via the dielectric body.

[0009] According to the load sensor of this aspect, the conductive elastic body deforms within the recess in response to the load.

[0010] For example, when a load is applied perpendicular to one surface of the plate-like member, the conductive elastic body is compressed, causing it to expand in a direction perpendicular to the direction of protrusion. As a result, in the region where the conductive elastic body and the multiple electrodes do not contact each other via a dielectric (non-contact region), the conductive elastic body and the multiple electrodes come into contact via a dielectric, increasing the contact area between the conductive elastic body and the multiple electrodes via the dielectric. Therefore, the vertical load can be detected based on the magnitude of the capacitance corresponding to the sum of these contact areas.

[0011] Furthermore, when a load is applied in a direction parallel to one surface of the plate-like member, the conductive elastic body moves relative to the recess in the direction of the load. As a result, the contact area between the conductive elastic body and the multiple electrodes via the dielectric changes depending on the direction of the load and the magnitude of the load. Accordingly, the capacitance between each electrode and the conductive elastic body changes depending on the direction of the load and the magnitude of the load. Therefore, a load in a direction parallel to one surface of the plate-like member can be detected based on the balance of these capacitances.

[0012] Therefore, the load sensor according to this aspect can detect three-directional components of the load applied to the load sensor.

[0013] As described above, according to the present invention, it is possible to provide a load sensor capable of detecting three directional components of a load, that is, a direction perpendicular to a surface receiving the load and two directions parallel to this surface.

[0014] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0015] FIG. 1 is an exploded perspective view schematically illustrating the configuration of a load sensor according to the first embodiment. FIG. 2 is a perspective view schematically illustrating a state in which a structure, four electrode members, and four dielectrics according to the first embodiment are combined. FIG. 3 is a perspective view schematically illustrating the configuration of a load sensor according to the first embodiment. FIG. 4 is a diagram schematically illustrating a cross section of the load sensor according to the first embodiment, taken along a plane parallel to a horizontal plane passing through the vicinity of the center in the vertical direction of the conductive elastic body. FIG. 5( a) is a diagram schematically illustrating a C11-C12 cross section of the load sensor according to the first embodiment. FIG. 5( b) is a diagram schematically illustrating a C21-C22 cross section of the load sensor according to the first embodiment. FIGS. 6( a) and 6( b) are cross-sectional views schematically illustrating the shape of the conductive elastic body according to the first embodiment when a horizontal load is applied to the plate-like member. FIGS. 7( a) and 7( b) are cross-sectional views schematically illustrating the shape of the conductive elastic body according to the first embodiment when a vertical load is applied to the plate-like member. FIG. 8( a) is a graph showing a load profile according to a simulation. FIG. 8( b) is a graph showing changes in contact area when the load in the positive X-axis direction is increased stepwise according to a simulation. FIG. 9 is a graph showing various calculated values ​​based on the contact area for four electrodes according to a simulation. FIGS. 10( a) and 10(b) are perspective views schematically showing the configuration of a conductive elastic body according to a modified example of the shape of the conductive elastic body. FIG. 11 is a perspective view schematically showing the configuration of an electrode member according to a modified example of the electrode. FIG. 12 is a diagram schematically showing a cross section of a load sensor cut along a plane parallel to a horizontal plane passing near the center in the vertical direction of the conductive elastic body according to a modified example of the shape of the conductive elastic body and the electrode. FIG. 13 is a diagram schematically showing a cross section of a load sensor cut along a plane parallel to a horizontal plane passing near the center in the vertical direction of the conductive elastic body according to a modified example of the electrode arrangement. FIG. 14 is an exploded perspective view schematically showing the configuration of a load sensor according to a second embodiment. Fig. 15 is an exploded perspective view schematically showing the configuration of an electrode holder and four electrodes according to embodiment 2. Fig. 16 is a perspective view schematically showing a state in which a structure, four electrode members, a dielectric, and an electrode pad are combined according to embodiment 2. Fig. 17 is a perspective view schematically showing the configuration of a load sensor according to embodiment 2.Fig. 18(a) is a diagram schematically showing a cross section of a load sensor according to embodiment 2, taken along a plane parallel to a horizontal plane passing near the center in the up-down direction of the conductive elastic body. Fig. 18(b) is a diagram schematically showing a C41-C42 cross section of the load sensor according to embodiment 2. Fig. 19 is a diagram schematically showing a C11-C12 cross section of a load sensor according to another modified example of embodiment 1. Fig. 20 is a diagram schematically showing a cross section of a load sensor according to another modified example of embodiment 1, taken along a plane parallel to a horizontal plane passing near the center in the up-down direction of the conductive elastic body.

[0016] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0017] The load sensor according to the present invention can be applied to systems and electronic devices that perform processing in response to loads applied in planar and vertical directions.

[0018] An example of such a system is a transfer system using a robot hand. In this case, a load sensor is installed on the gripping surface of the robot hand to detect loads in two-dimensional directions parallel to the gripping surface and in directions perpendicular to the gripping surface. From the detection results, the weight, posture, etc. of the object gripped by the robot hand can be obtained.

[0019] Examples of electronic devices include game controllers, touch panels, electronic pens, etc. In electronic devices, a load sensor is provided in an input unit that receives input from a user in a planar direction and a vertical direction.

[0020] The load sensor in the following embodiments is a capacitance type load sensor that is typically provided in the load sensors of the above-mentioned systems and electronic devices. Such load sensors are also sometimes called "capacitive pressure sensor elements," "capacitive pressure detection sensor elements," "pressure-sensitive switch elements," etc.

[0021] The load sensor in the following embodiment is connected to a detection circuit, and the load sensor and the detection circuit constitute a load detection device. The following embodiment is one embodiment of the present invention, and the present invention is not limited to the following embodiment.

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with X, Y, and Z axes that are orthogonal to one another. The Z axis direction is the height direction of the load sensor. For convenience, the X-Y plane will be referred to as the horizontal plane, the negative direction of the Z axis will be referred to as the upward direction, the positive direction of the Z axis will be referred to as the downward direction, and the Z axis direction will be referred to as the vertical direction.

[0023] First Embodiment FIG. 1 is an exploded perspective view schematically showing the configuration of a load sensor 1 according to a first embodiment.

[0024] The load sensor 1 includes a plate-shaped member 10, a conductive elastic body 20, an electrode holder 30, four electrode members 40, four dielectric members 50, a base member 60, and an axis member 70. A central axis CA parallel to the Z-axis direction is illustrated in Fig. 1. The central axis CA is an axis parallel to the Z-axis direction that passes through the center of the load sensor 1 in a plan view.

[0025] The plate-shaped member 10 has a square shape with rounded corners in a plan view. The plate-shaped member 10 is symmetrical in the X-axis direction and the Y-axis direction about a central axis CA. The top surface 11 and the bottom surface 12 of the plate-shaped member 10 are parallel to a horizontal plane. The plate-shaped member 10 is made of an electrically insulating material, such as polyethylene terephthalate, polycarbonate, or polyimide.

[0026] The conductive elastic body 20 has a truncated cone shape obtained by cutting a predetermined cone shape at the top surface 21. The cross-sectional area of ​​the conductive elastic body 20 decreases upward. The conductive elastic body 20 has a rotationally symmetric shape about a central axis CA. That is, the central axis CA coincides with the central axis of the conductive elastic body 20. The top surface 21 and bottom surface 22 of the conductive elastic body 20 are parallel to the horizontal plane. The conductive elastic body 20 is composed of a non-conductive elastic material and a conductive filler mixed into the elastic material. In the conductive elastic body 20, the conductive filler is dispersed within the elastic material. This gives the conductive elastic body 20 both electrical conductivity and elasticity.

[0027] The elastic material constituting the conductive elastic body 20 is composed of a resin material and a rubber material. Examples of the resin material include styrene-based resin, silicone-based resin (such as polydimethylpolysiloxane (PDMS)), acrylic-based resin, rotaxane-based resin, and urethane-based resin. Examples of the rubber material include silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene-propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, and natural rubber. The elastic material in the first embodiment is silicone rubber.

[0028] The conductive filler constituting the conductive elastic body 20 may be, for example, Au (gold), Ag (silver), Cu (copper), C (carbon), ZnO (zinc oxide), In (inorganic), or the like. ２ O ３ (indium (III) oxide), SnO ２ (tin (IV) oxide), etc. The conductive filler in the first embodiment is C (carbon).

[0029] The electrode holder 30 has a square shape in a plan view. The electrode holder 30 has a shape symmetrical in the X-axis direction and the Y-axis direction about the central axis CA. The upper surface 31 and the lower surface 32 of the electrode holder 30 are parallel to a horizontal plane. The electrode holder 30 has a predetermined thickness. A through hole 30a is formed in the electrode holder 30 at the position of the central axis CA, penetrating the electrode holder 30 from top to bottom. The through hole 30a has a substantially square shape in a plan view. The inner surface 30b of the through hole 30a includes a pair of surfaces parallel to the X-Z plane and a pair of surfaces parallel to the Y-Z plane. The material constituting the electrode holder 30 is an electrically insulating material, and is, for example, the same as the material constituting the plate-like member 10.

[0030] The four electrode members 40 are arranged on the four inner surfaces 30b of the electrode holder 30, respectively. The four electrode members 40 have the same shape. Each electrode member 40 is composed of an electrode 41 arranged on the inner surface 30b and a relay portion 42 connected to the lower end of the electrode 41 and extending in a direction away from the central axis CA. The electrode 41 has a flat plate shape parallel to the Z-axis direction, and the relay portion 42 has a flat plate shape parallel to a horizontal plane. The relay portion 42 functions as wiring for connecting the electrode 41 to an external circuit. The electrode members 40 are formed in the electrode holder 30 by, for example, insert molding. The material constituting the electrode members 40 is a conductive metal, such as gold (Au), silver (Ag), copper (Cu), or platinum (Pt). The material of the electrode member 40 in the first embodiment is copper (Cu).

[0031] The electrode member 40 may be formed as a film separately from the electrode holder 30 and then attached to the electrode holder 30 with an adhesive or the like.

[0032] The dielectric 50 is placed on the inner surface of the electrode 41 after the four electrode members 40 are placed on the electrode holder 30. The dielectric 50 is formed on the inner surface of the electrode 41 by, for example, insert molding. Since the inner surface of the electrode 41 is a surface parallel to the Z-axis direction, the inner surface of the dielectric 50 is also a surface parallel to the Z-axis direction. The material constituting the dielectric 50 is an electrically insulating material, such as polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, or Al. ２ O ３ , Ta ２ O ５ etc.

[0033] The base member 60 has a square shape in a plan view. The base member 60 has a shape symmetrical in the X-axis direction and the Y-axis direction around the central axis CA. The upper surface 61 and the lower surface 62 of the base member 60 are parallel to a horizontal plane. The base member 60 has a predetermined thickness. A through hole 60a is formed in the base member 60 at the position of the central axis CA, penetrating the base member 60 from top to bottom. The through hole 60a has a substantially square shape in a plan view. The through hole 60a is configured to a size that allows the shaft portion 72 of the shaft member 70 to pass through. The material that constitutes the base member 60 is an electrically insulating material, and is, for example, the same as the material that constitutes the plate-like member 10.

[0034] The shaft member 70 includes a flat plate portion 71 and a rectangular prism-shaped shaft portion 72 formed at the center of the upper surface of the plate portion 71. The shaft member 70 is symmetrical in the X-axis direction and the Y-axis direction about a central axis CA. The plate portion 71 and the shaft portion 72 are integrally formed. The material constituting the plate portion 71 and the shaft portion 72 is a conductive metal, for example, similar to the material constituting the electrode member 40.

[0035] During assembly, a pair of electrode members 40 are formed on the electrode holder 30 so as to face each other in the X-axis direction, and a pair of electrode members 40 are formed on the electrode holder 30 so as to face each other in the Y-axis direction. At this time, the electrodes 41 are formed on the inner surface 30b of the electrode holder 30, and the relay portions 42 are formed on the lower surface 32 of the electrode holder 30. Then, a dielectric 50 is formed on the inner surface of each electrode 41. The lower surface 32 of the electrode holder 30 is attached to the upper surface 61 of the base member 60 with an adhesive or the like. The electrode holder 30 and the base member 60 constitute a structure ST1.

[0036] FIG. 2 is a perspective view schematically showing a state in which the structure ST1, four electrode members 40, and four dielectrics 50 according to the first embodiment are combined.

[0037] The structure ST1 is composed of the electrode holder 30 and the base member 60. This forms a recess RS1 in the structure ST1. The recess RS1 is formed in the structure ST1 by the inner surface 30b of the electrode holder 30 and the upper surface 61 of the base member 60.

[0038] Returning to FIG. 1 , after the structure ST1, the four electrode members 40, and the four dielectrics 50 are combined, the lower surface 22 of the conductive elastic body 20 is placed on the upper surface 61 of the base member 60 via the through-hole 30a of the electrode holder 30. Then, the shaft member 70 is placed on the lower surface 62 of the base member 60 with an adhesive or the like so that the shaft portion 72 protrudes above the upper surface 61 of the base member 60 via the through-hole 60a of the base member 60. As a result, the shaft portion 72 is inserted into the lower surface 22 of the conductive elastic body 20, and the conductive elastic body 20 is fixed to the base member 60 together with the shaft member 70, establishing electrical conduction between the conductive elastic body 20 and the shaft member 70. The lower surface of the shaft member 70 is connected to an external circuit.

[0039] Thereafter, the lower surface 12 of the plate-like member 10 is attached to the upper surface 21 of the conductive elastic body 20 with an adhesive or the like. In this way, the load sensor 1 is completed.

[0040] FIG. 3 is a perspective view schematically illustrating the configuration of the load sensor 1 according to the first embodiment.

[0041] The lower surface of the load sensor 1 (the lower surface 62 of the base member 60) is placed on a mounting surface parallel to a horizontal plane. When a load is applied to the upper surface of the load sensor 1 (the upper surface 11 of the plate-shaped member 10) in the Z-axis direction or horizontally, the plate-shaped member 10 moves in response to the load. As a result, the conductive elastic body 20 fixed to the plate-shaped member 10 comes into contact with the dielectric 50 and deforms, thereby detecting the load.

[0042] FIG. 4 is a diagram schematically illustrating a cross section of the load sensor 1 according to the first embodiment, taken along a plane parallel to a horizontal plane passing through the vicinity of the center in the vertical direction of the conductive elastic body 20. As shown in FIG.

[0043] As described above, the four electrodes 41 and the four dielectrics 50 are formed on the inner surface of the recess RS1, and the conductive elastic body 20 is positioned inside the recess RS1. Fig. 4 shows the conductive elastic body 20 in a state where no load is applied to the load sensor 1, i.e., in a no-load state (initial state).

[0044] The four electrodes 41 are arranged on the inner surface 30b at 90-degree angular intervals around the central axis CA. Each dielectric 50 is arranged on the inner surface of the corresponding electrode 41. Each dielectric 50 has a region that is not in contact with the conductive elastic body 20 in the no-load state.

[0045] Furthermore, in a plan view, the conductive elastic body 20 is larger than the shape of the accommodation space for the conductive elastic body 20 in the recess RS1 (the space formed by the inner surfaces of the four dielectrics 50 and the inner surface of the recess RS1). Specifically, the conductive elastic body 20 is larger than the shape inscribed in the dielectrics 50 in the recess RS1. That is, as shown in FIG. 4 , the diameter R1 of the conductive elastic body 20 before being placed in the recess RS1 is larger than the length W1 of one side of the area surrounded by each dielectric 50. As a result, the conductive elastic body 20 contacts the four dielectrics 50 in the no-load state, and therefore the load can be detected without any play when a load is applied.

[0046] 5A is a diagram schematically illustrating the C11-C12 cross section of the load sensor 1 according to embodiment 1. As shown in FIG. 4, the C11-C12 cross section is a cross section of the load sensor 1 cut along a plane parallel to the X-Z plane passing through the central axis CA.

[0047] The depth H1 of the recess RS1 is smaller than the length H2 in the Z-axis direction of the conductive elastic body 20. As a result, a gap of H2-H1 is formed in the height direction (the direction parallel to the central axis of the conductive elastic body 20) between the lower surface 12 of the plate-shaped member 10 and the upper end of the recess RS1 (the upper surface of the structure ST1). Therefore, when a load is applied perpendicularly to the upper surface 11 of the plate-shaped member 10, the plate-shaped member 10 can move downward by H2-H1.

[0048] Furthermore, the size of the conductive elastic body 20 and the recess RS1 and the thickness of the electrode 41 and the dielectric 50 are set so that, in the no-load state, the side of the conductive elastic body 20 contacts the dielectric 50 near the lower end of the electrode 41, but does not contact the dielectric 50 near the upper end of the electrode 41.

[0049] Fig. 5(b) is a diagram schematically illustrating the C21-C22 cross section of the load sensor 1 according to embodiment 1. As shown in Fig. 4, the C21-C22 cross section is a cross section obtained by cutting the load sensor 1 along a plane that is parallel to the Z-axis direction and passes through a diagonal line of the electrode holder 30 in a plan view.

[0050] 4, in the no-load state, each dielectric 50 has a region that is not in contact with the conductive elastic body 20. Such a non-contact region is formed between the conductive elastic body 20 and the inner surface of the recess RS1 in the cross section of FIG.

[0051] As shown in FIGS. 5A and 5B, the conductive elastic body 20 is connected to a shaft member 70 at the position of the central axis CA, and its horizontal position is fixed by the shaft member 70.

[0052] Next, with reference to FIGS. 6(a) to 7(b), the deformation of the conductive elastic body 20 when a load is applied to the load sensor 1 according to the first embodiment will be described.

[0053] 6(a) and 6(b) are cross-sectional views schematically illustrating the shape of the conductive elastic body 20 when a horizontal load is applied to the plate-like member 10 according to the first embodiment. The examples shown in 6(a) and 6(b) illustrate a state in which a load is applied in the positive direction of the X-axis. 6(a) and 6(b) correspond to 5(a) and 4, respectively.

[0054] As shown in FIG. 6A , when a load is applied to the plate-shaped member 10 in the positive direction of the X-axis, the plate-shaped member 10 moves in the positive direction of the X-axis, and the upper surface 21 of the conductive elastic body 20 also moves in the positive direction of the X-axis accordingly. At this time, as shown in FIGS. 6A and 6B , the contact area between the side surface of the conductive elastic body 20 on the positive side of the X-axis and the dielectric 50 increases compared to the no-load state shown in FIGS. 5A and 4 . Meanwhile, the contact area between the side surface of the conductive elastic body 20 on the negative side of the X-axis and the dielectric 50 decreases compared to the no-load state shown in FIGS. 5A and 4 . Therefore, the amount of movement of the plate-shaped member 10 in the X-axis direction can be determined based on the difference in capacitance between the electrode 41 on the positive side of the X-axis and the conductive elastic body 20 and the capacitance between the electrode 41 on the negative side of the X-axis and the conductive elastic body 20. Therefore, the load applied in the X-axis direction can be detected based on this capacitance difference.

[0055] Similarly, when a load is applied in the Y-axis direction, the amount of movement of the plate-like member 10 in the Y-axis direction can be determined based on the difference in capacitance between the electrode 41 on the positive side of the Y-axis and the conductive elastic body 20 and the capacitance between the electrode 41 on the negative side of the Y-axis and the conductive elastic body 20. Therefore, the load applied in the Y-axis direction can be detected based on this difference in capacitance.

[0056] 7(a) and 7(b) are cross-sectional views schematically showing the shape of the conductive elastic body 20 when a load in the vertical direction is applied to the plate-like member 10 according to embodiment 1. Fig. 7(a) is a view corresponding to Fig. 4, and Fig. 7(b) is a view schematically showing the C31-C32 cross section of Fig. 7(a).

[0057] When a load is applied to the plate-shaped member 10 in the vertical direction (Z-axis direction), the plate-shaped member 10 moves in the positive Z-axis direction, and the upper surface 21 of the conductive elastic body 20 also moves in the positive Z-axis direction accordingly. This causes the conductive elastic body 20 to contract in the Z-axis direction over its entire periphery. At this time, as shown in Figure 7(a), the contact area between the dielectric 50 and the side surfaces of the conductive elastic body 20 on the positive X-axis side, negative X-axis side, positive Y-axis side, and negative Y-axis side increases compared to the no-load state shown in Figure 4.

[0058] Therefore, the amount of movement of the plate-like member 10 in the Z-axis direction can be determined based on the capacitance between each electrode 41 and the conductive elastic body 20. Therefore, the load applied in the Z-axis direction can be detected based on this capacitance. Load detection in the Z-axis direction will be described in detail later with reference to a simulation.

[0059] In the example shown in Fig. 7(b), since there is a non-contact area between the conductive elastic body 20 and the inner side surface of the recess RS1 in the diagonal direction of the recess RS1, the conductive elastic body 20 contracts without the side surface of the conductive elastic body 20 coming into contact with the inner surface of the recess RS1. At this time, the conductive elastic body 20 contracts so as to spread outward at the lower part. A method for detecting a vertical load that utilizes this phenomenon in which the conductive elastic body 20 spreads outward at the lower part when a vertical load is applied will be described later with reference to a modified example shown in Fig. 11.

[0060] <Simulation of Separate Detection> Next, the inventors performed the following simulation to verify that even when loads in the X-, Y-, and Z-axis directions are mixed, the loads in each direction can be detected separately.

[0061] 8A is a graph showing the load profile of this simulation. In this simulation, a constant load of 0.05 N was applied in the positive direction of the Y-axis, and a constant load of 0.20 N was applied in the positive direction of the Z-axis. The load in the positive direction of the X-axis was increased stepwise until the final load in the positive direction of the X-axis was adjusted to 0.05 N. In this simulation, the horizontal width of the electrode 41 was set to 0.8 mm, and the vertical height of the electrode 41 was set to 0.5 mm. Therefore, the area of ​​the inner surface of one electrode 41 was 0.4 mm. ２ is.

[0062] Hereinafter, the electrode 41 located on the positive side of the X-axis will be referred to as "electrode E4," the electrode 41 located on the positive side of the Y-axis will be referred to as "electrode E3," the electrode 41 located on the negative side of the X-axis will be referred to as "electrode E2," and the electrode 41 located on the negative side of the Y-axis will be referred to as "electrode E1."

[0063] Furthermore, the contact area between the dielectric 50 formed at the position of electrode E1 and the conductive elastic body 20 is defined as A1, the contact area between the dielectric 50 formed at the position of electrode E2 and the conductive elastic body 20 is defined as A2, the contact area between the dielectric 50 formed at the position of electrode E3 and the conductive elastic body 20 is defined as A3, and the contact area between the dielectric 50 formed at the position of electrode E4 and the conductive elastic body 20 is defined as A4. The capacitance between the electrode E1 and the conductive elastic body 20 is defined as C1, the capacitance between the electrode E2 and the conductive elastic body 20 is defined as C2, the capacitance between the electrode E3 and the conductive elastic body 20 is defined as C3, and the capacitance between the electrode E4 and the conductive elastic body 20 is defined as C4.

[0064] FIG. 8B is a graph showing the change in contact areas A1 to A4 when the load in the positive direction of the X axis is increased stepwise from 0.00 N to 0.05 N in this simulation.

[0065] In this simulation, a constant load is applied in the positive direction of the Y axis, so the contact area A3 for the electrode E3 on the positive side of the Y axis is 0.12 mm ２ On the other hand, the contact area A1 for the electrode E1 on the negative side of the Y axis is smaller than the contact area for the electrode E3, and is 0.03 mm ２ In this simulation, the load is applied in stages in the positive direction of the X-axis, so the contact area A4 for the electrode E4 on the positive side of the X-axis increases from approximately 0.08 N to approximately 0.12 N. Meanwhile, the contact area A2 for the electrode E2 on the negative side of the X-axis decreases from approximately 0.08 N to approximately 0.02 N.

[0066] From the results shown in Figure 8(b), it can be seen that the difference between the contact areas A4 and A2 for the electrodes E4 and E2 arranged in the X-axis direction corresponds to a change in contact area proportional to the load in the X-axis direction. Therefore, it can be seen that the load in the X-axis direction can be obtained based on the difference between the capacitance C4 between the electrode E4 and the conductive elastic body 20 and the capacitance C2 between the electrode E2 and the conductive elastic body 20. Alternatively, it can be seen that the load in the X-axis direction can be obtained based on either the difference between the capacitance C4 between the electrode E4 and the conductive elastic body 20 or the capacitance C2 between the electrode E2 and the conductive elastic body 20. Meanwhile, it can be seen that the difference between the contact areas A3 and A1 for the electrodes E3 and E1 arranged in the Y-axis direction is approximately constant, which corresponds to a constant load in the Y-axis direction.

[0067] In this simulation, the load in the X-axis direction was increased in stages and the load in the Y-axis direction was constant. However, it is believed that the same results would be obtained if the load in the Y-axis direction was increased in stages and the load in the X-axis direction was constant. That is, the difference between the contact areas A3 and A1 of the electrodes E3 and E1 arranged in the Y-axis direction is believed to correspond to the change in contact area proportional to the load in the Y-axis direction. Therefore, it is believed that the load in the Y-axis direction can be obtained based on the difference between the capacitance C3 between the electrode E3 and the conductive elastic body 20 and the capacitance C1 between the electrode E1 and the conductive elastic body 20.

[0068] Furthermore, even when a load is applied horizontally in a direction that has an angle in both the X-axis direction and the Y-axis direction, the load component in the X-axis direction can be detected based on both electrodes E4 and E2 arranged in the X-axis direction, or either one of electrodes E4 or E2, and the load component in the Y-axis direction can be detected based on both electrodes E3 and E1 arranged in the Y-axis direction, or either one of electrodes E3 or E1.

[0069] Next, the inventors investigated whether it is possible to properly detect the load in the Z-axis direction based on the contact areas A1 to A4, even when a load is applied in the X-axis and Y-axis directions in addition to the Z-axis direction, as shown in Figure 8(a).

[0070] FIG. 9 is a graph showing various calculated values ​​based on the contact areas of the electrodes E1 to E4 in this simulation.

[0071] First, the inventors set other conditions in which the load in the X-axis direction and the Y-axis direction is 0 and a constant load of 0.2 N is applied in the positive direction of the Z-axis, since when a load is applied only in the Z-axis direction, the conductive elastic body 20 contacts the dielectric body 50 on the four electrodes E1 to E4 evenly as shown in Figure 7(a). Under these conditions, the sum of the contact areas A1 to A4 was obtained as the calculated value V1. As a result, the calculated value V1 was about 0.34 mm, as shown in Figure 9. ２ It became a constant value of .

[0072] Next, the inventors obtained the sum of the contact areas A1 to A4 as the calculated value V2 under the load conditions shown in Figure 8(a). As a result, it was found that the calculated value V2 slightly decreases as the load in the X-axis direction increases, as shown in Figure 9, and furthermore, it does not become a value similar to the calculated value V1, and does not become a constant value like the calculated value V1.

[0073] Therefore, the inventors conducted the following study on the influence of the loads in the X-axis and Y-axis directions on the calculated value V2.

[0074] First, the inventors investigated why the calculated value V2 when a load in the Z-axis direction as well as loads in the X-axis and Y-axis directions is applied is smaller than the calculated value V1 when only a load in the Z-axis direction is applied. As a result, the inventors inferred that the reason for this is that the increase and decrease in the contact area between two opposing electrodes are not the same. For example, for two electrodes opposing each other in the X-axis direction, it is inferred that the decrease in the contact area of ​​the electrode on the opposite side is greater than the increase in the contact area of ​​the electrode in the X-axis load application direction. Similarly, for two electrodes opposing each other in the Y-axis direction, it is inferred that the decrease in the contact area of ​​the electrode on the opposite side is greater than the increase in the contact area of ​​the electrode in the Y-axis load application direction. The inventors inferred that the difference between these decrease and increase amounts caused the calculated value V2 to be smaller than the calculated value V1.

[0075] Furthermore, it is estimated that this difference changes depending on the magnitude of the load in the X-axis direction or the Y-axis direction. The inventors estimated that, due to this change in the difference, the calculated value V2 does not remain constant, and that the calculated value V2 decreases as the load in the X-axis direction increases.

[0076] Based on the above estimation, the inventors thought that by adding the influence of the difference between contact areas A4 and A2 based on the load in the X-axis direction and the influence of the difference between contact areas A3 and A1 based on the load in the Y-axis direction to the sum of contact areas A1 to A4 (calculated value V2), it would be possible to obtain the sum of contact areas A1 to A4 based only on the load in the Z-axis direction.

[0077] According to the above considerations, if the difference between contact areas A4 and A2 is taken as calculated value V3, the difference between contact areas A3 and A1 is taken as calculated value V4, and the sum of contact areas A1 to A4 based only on the load in the Z-axis direction when loads in the X-axis direction, as well as the load in the Y-axis direction, is taken as calculated value V5, then calculated value V5 can be expressed by the following formula (1): Here, α is the rate of influence of the load in the X-axis direction on the load in the Z-axis direction, and β is the rate of influence of the load in the Y-axis direction on the load in the Z-axis direction.

[0078] V5=V2+αV3+βV4…(1)

[0079] According to the inventor's investigation, it was found that in the configuration of this simulation, it is preferable to set both of the influence rates α and β to approximately 0.5. When the influence rates α and β in formula (1) are set to 0.5, the calculated value V5 is expressed by the following formula (2).

[0080] V5=0.5(A1+A2)+1.5(A3+A4)...(2)

[0081] As a result, as shown in FIG. 9, the calculated value V5 is a substantially constant value regardless of the increase in the load in the X-axis direction, and is a value similar to the calculated value V1.

[0082] Therefore, in the configuration of this simulation, by obtaining the calculated value V6 of the following equation (3) based on the electrostatic capacitances C1 to C4 corresponding to the electrodes E1 to E4, respectively, it can be seen that the load in the Z-axis direction can be obtained based on the calculated value V6.

[0083] V6=C1+C2+C3+C4+α(C4-C2)+β(C3-C1) =0.5(C1+C2)+1.5(C3+C4)...(3)

[0084] From the above results, it was found that even when loads are applied in the X-axis and Y-axis directions in addition to the Z-axis direction, the load in the Z-axis direction can be properly obtained based on the above formula (3).

[0085] It is assumed that the influence rates α and β change depending on the configuration of the load sensor 1. Therefore, the influence rates α and β may be determined appropriately depending on the configuration of the load sensor 1.

[0086] <Effects of First Embodiment> According to the first embodiment, the following effects are achieved.

[0087] As shown in FIGS. 1 and 2 , the load sensor 1 includes a plate-shaped member 10 that receives a load on its upper surface 11 (one of its surfaces), a conductive elastic body 20 that protrudes from the lower surface 12 (the other surface) of the plate-shaped member 10, a recess RS1 that receives the conductive elastic body 20, a plurality of electrodes 41 installed along the inner surface of the recess RS1, and a dielectric 50 disposed between the conductive elastic body 20 and the plurality of electrodes 41. As shown in FIG. 5( a), the plate-shaped member 10 is disposed relative to a member (structure ST1) having the recess RS1 so as to be movable in a direction parallel to the central axis of the conductive elastic body 20 (Z-axis direction) and in directions perpendicular to this central axis (X-axis direction, Y-axis direction). As shown in FIGS. 4 to 5( b), there is a region between the conductive elastic body 20 and the plurality of electrodes 41 that does not contact each other via the dielectric 50.

[0088] According to this configuration, the conductive elastic body 20 deforms within the recess RS1 in response to the load.

[0089] 7( a) and 7(b), when a load is applied vertically to the top surface 11 of the plate-like member 10, the conductive elastic body 20 is compressed, causing the conductive elastic body 20 to expand in a direction (horizontal direction) perpendicular to the protruding direction (Z-axis direction) of the conductive elastic body 20. As a result, in regions (non-contact regions) where the conductive elastic body 20 and the plurality of electrodes 41 do not contact each other via the dielectric 50, the conductive elastic body 20 and the plurality of electrodes 41 come into contact with each other via the dielectric 50, and the contact area between the conductive elastic body 20 and the plurality of electrodes 41 via the dielectric 50 increases. Therefore, a load in the vertical direction can be detected based on the magnitude of the electrostatic capacitance corresponding to the sum of these contact areas.

[0090] 6( a) and 6(b), when a load is applied in a direction parallel to the top surface 11 of the plate-like member 10 (horizontal direction), the conductive elastic body 20 moves relative to the recess RS1 in the direction of the load application. As a result, the contact area between the conductive elastic body 20 and the multiple electrodes 41 via the dielectric 50 changes depending on the direction of the load application and the magnitude of the load. Accordingly, the capacitance between each electrode 41 and the conductive elastic body 20 changes depending on the direction of the load application and the magnitude of the load. Therefore, a load in a direction parallel to the top surface 11 of the plate-like member 10 (horizontal direction) can be detected based on the balance of these capacitances.

[0091] Therefore, with the above configuration, the load sensor 1 can detect three-directional components of the load applied thereto.

[0092] When a load is applied in both the vertical and horizontal directions, the change in the horizontal contact area affects the total contact area, and as a result, the total contact area (calculated value V2) deviates from the total contact area (calculated value V1) based on a load applied only in the vertical direction, as shown in the simulation results of FIG. 9. In contrast, the calculated value V5 shown in equation (2) above approaches the total contact area (calculated value V1) based on a load applied only in the vertical direction, as shown in the simulation results of FIG. 9. Therefore, according to the calculated capacitance value V6 shown in equation (3) above, the load applied in the vertical direction can be properly detected even when a load is applied in both the vertical and horizontal directions.

[0093] As shown in FIG. 4, the dielectric 50 is disposed on the surfaces of the plurality of electrodes 41 .

[0094] According to this configuration, the dielectric 50 can be easily formed.

[0095] As shown in FIG. 2, the plurality of electrodes 41 are arranged at angular intervals of 90 degrees around the central axis CA of the recess RS1.

[0096] According to this configuration, two horizontal components of the load applied to the load sensor 1 can be efficiently detected.

[0097] As shown in FIG. 2, four electrodes 41 are provided on the inner surface 30b of the electrode holder 30 (the inner surface of the recess RS1).

[0098] According to this configuration, the two horizontal components of the load applied to the load sensor 1 can be detected most efficiently.

[0099] 1 and 2, the structure ST1 (member having the recess RS1) has a through-hole 60a that penetrates from the upper surface 61 (bottom surface of the recess RS1) of the base member 60 to the outside. As shown in FIGS. 5(a) and 5(b), a conductive shaft member 70 is connected to the conductive elastic body 20 via the through-hole 60a.

[0100] According to this configuration, the conductive elastic body 20 can be smoothly connected to an external circuit via the shaft member 70 while being positioned horizontally in the recessed portion RS1.

[0101] As shown in FIG. 2, the inner surface 30b of the electrode holder 30 (the inner surface of the recess RS1) is substantially parallel to the central axis CA of the recess RS1.

[0102] According to this configuration, non-contact areas between the conductive elastic body 20 and the plurality of electrodes 41 can be smoothly formed.

[0103] As shown in Figure 4, the recess RS1 has a rectangular outline in a plan view, and electrodes 41 are respectively installed on the inner surface 30b of the electrode holder 30 (the inner surface of the recess RS1) corresponding to at least two adjacent sides of the rectangle.

[0104] According to this configuration, the angle formed by two adjacent electrodes 41 is substantially 90 degrees, so that two horizontal components of the load applied to the load sensor 1 can be efficiently detected.

[0105] As shown in FIG. 4, electrodes 41 are provided on the inner surface 30b of the electrode holder 30 (the inner surface of the recess RS1) corresponding to all sides of the rectangle that defines the outline of the recess RS1.

[0106] According to this configuration, the two horizontal components of the load applied to the load sensor 1 can be detected most efficiently.

[0107] The conductive elastic body 20 has a columnar shape.

[0108] With this configuration, the contact area between the conductive elastic body 20 and the multiple electrodes 41 via the dielectric 50 is more likely to change depending on the load, so the load applied to the load sensor 1 can be detected with high sensitivity.

[0109] As shown in Figure 4, when viewed in a plan view, the conductive elastic body 20 is larger than the shape of the space for accommodating the conductive elastic body 20 in the recess RS1 (the space formed by the inner surfaces of the four dielectrics 50 and the inner surface of the recess RS1).

[0110] With this configuration, the conductive elastic body 20 and the plurality of electrodes 41 are in contact via the dielectric 50 in the no-load state, so that the load can be detected without any play when a load is applied. Furthermore, in the no-load state, the elastic restoring force of the conductive elastic body 20 centers the conductive elastic body 20 with respect to the accommodation space, and the contact areas between the electrodes 41 and the conductive elastic body 20 via the dielectric 50 tend to be balanced. Therefore, when a load is applied in a direction parallel to the top surface 11 of the plate-like member 10 (horizontal direction), the direction of the load can be easily and smoothly detected from the capacitance detected for each electrode 41.

[0111] As shown in FIG. 4, the cross section of the conductive elastic body 20 is a circle.

[0112] When the cross section of the conductive elastic body 20 is circular, the conductive elastic body 20 is easily formed.

[0113] As shown in FIGS. 5A and 5B, the cross-sectional area of ​​the conductive elastic body 20 changes in the Z-axis direction (projection direction).

[0114] According to this configuration, the outer surface of the conductive elastic body 20 is inclined with respect to the electrode 41, which makes it easier to adjust the FC curve that represents the relationship between the load and the capacitance.

[0115] <Examples of changes to the shape of the conductive elastic body> In the first embodiment, the conductive elastic body 20 has a truncated cone shape, but it may have any other shape as long as it is a columnar shape. For example, the conductive elastic body 20 may have a truncated pyramid shape as shown in Fig. 10(a). Furthermore, the conductive elastic body 20 may have a cylindrical shape as shown in Fig. 10(b), or a rectangular column shape.

[0116] In this way, since the conductive elastic body 20 has a columnar shape, as in the above-mentioned embodiment 1, the contact area between the dielectric 50 and the conductive elastic body 20 is more likely to change depending on the load, so that the load applied to the load sensor 1 can be detected with high sensitivity.

[0117] Furthermore, when the conductive elastic body 20 has a truncated pyramid or prism shape, the cross section of the conductive elastic body 20 is polygonal. In this case, adjusting the shape of the conductive elastic body 20 makes it easier to adjust the FC curve.

[0118] <Modification of Electrode> In the first embodiment, the electrode 41 is disposed on the inner surface of the recess RS1 so as to cover the entire inner surface of the recess RS1 in the direction of the central axis CA (Z-axis direction). However, this is not limited thereto, and each electrode 41 may be divided into multiple parts in the direction of the central axis CA of the recess RS1. For example, the electrode member 40 shown in FIG. 1 may be configured as shown in FIG.

[0119] FIG. 11 is a perspective view schematically showing the configuration of an electrode member 40 according to this modified example.

[0120] 1 , the electrode 41 of the electrode member 40 is composed of electrodes 41a and 41b, and the relay portion 42 of the electrode member 40 is composed of relay portions 42a and 42b. That is, in the electrode member 40 of this modified example, the electrode 41 is divided into two in the Z-axis direction to form the electrodes 41a and 41b, and the relay portion 42 is divided into two in the horizontal direction to form the relay portions 42a and 42b. The electrode 41a and the relay portion 42a are integrally formed, and the electrode 41b and the relay portion 42b are integrally formed.

[0121] When forming the electrode member 40, masking is performed on the inner surface of the recess RS1 where the gap between the electrodes 41a and 41b and the gap between the relay portions 42a and 42b are located, and the material of the electrode member 40 is formed by insert molding. Thereafter, the dielectric 50 is formed individually on the inner surfaces of the four electrodes 41.

[0122] The relay portion 42a may be formed on the upper end of the electrode 41a. In this case, the electrode 41a is connected to an external circuit from above the recess RS1 via the relay portion 42a, and the electrode 41b is connected to the external circuit from below the recess RS1 via the relay portion 42b. When the electrode member 40 is configured in this manner, only the electrode 41a can be arranged in the upper region of the inner surface of the recess RS1, and only the electrode 41b can be arranged in the lower region of the inner surface of the recess RS1.

[0123] As described above, as shown in FIG. 11, each electrode 41 is divided into a plurality of parts in the direction of the central axis CA (Z-axis direction) of the recess RS1.

[0124] 7(b), when a load is applied in the vertical direction (Z-axis direction), the lower portion of the conductive elastic body 20 expands in a direction away from the central axis CA. Therefore, a vertical load is likely to appear as a change in the contact area of ​​the lower electrode 41b (away from the plate-shaped member 10), and a horizontal load is likely to appear as a change in the contact area of ​​the upper electrode 41a (closer to the plate-shaped member 10). Therefore, by dividing each electrode 41 vertically as described above and selectively using the divided electrodes 41 (electrodes 41a, 41b) to detect vertical and horizontal loads, it is possible to smoothly and accurately detect vertical and horizontal loads.

[0125] <Examples of Modifications to the Shape of the Conductive Elastic Body and the Electrode> In the first embodiment, the recess RS1 is substantially rectangular in plan view (as viewed in the Z-axis direction) as shown in Fig. 4, but is not limited to this and may be other shapes. For example, the recess RS1 may be circular in plan view as shown in Fig. 12.

[0126] FIG. 12 is a diagram schematically showing a cross section of the load sensor 1 according to this modified example, taken along a plane parallel to a horizontal plane passing through the vicinity of the center in the up-down direction of the conductive elastic body 20. In FIG.

[0127] In this modified example, compared to the first embodiment shown in Fig. 4, the inner surface of the recess RS1, i.e., the inner surface 30b of the electrode holder 30, is circular in plan view. The shape of the inner surface 30b is the side shape of a cylinder centered on the central axis CA and extending in the Z-axis direction. In this modified example, as in the first embodiment, four electrodes 41 are arranged at 90-degree intervals around the central axis CA of the recess RS1, and dielectrics 50 are arranged on the inner surfaces of the four electrodes 41, respectively.

[0128] Furthermore, in this modified example, the conductive elastic body 20 has a truncated quadrangular pyramid shape, as compared to the first embodiment shown in Fig. 4. In this case, the conductive elastic body 20 is installed on the plate-like member 10 and the base member 60 so as not to rotate around the central axis CA. Furthermore, by configuring the conductive elastic body 20 to be larger than the shape inscribed in the dielectric body 50 within the recess RS1, the conductive elastic body 20 contacts the dielectric body 50 in the no-load state, and therefore the load can be detected without play when a load is applied.

[0129] <Modification of Electrode Arrangement> In the first embodiment, the electrodes 41 are arranged on all of the two inner surfaces parallel to the X-Z plane and the two inner surfaces parallel to the Y-Z plane of the recessed portion RS1, as shown in Fig. 4. However, the present invention is not limited to this, and the electrodes 41 do not have to be arranged on all of the four inner surfaces of the recessed portion RS1.

[0130] FIG. 13 is a diagram schematically showing a cross section of the load sensor 1 according to this modified example, taken along a plane parallel to a horizontal plane passing through the vicinity of the center in the up-down direction of the conductive elastic body 20.

[0131] 4, in this modified example, electrodes 41 are arranged only on two adjacent inner surfaces of the four inner surfaces of the recess RS1. In this case as well, the load in the X-axis direction can be detected based on the capacitance between the electrode 41 on the positive side of the X-axis and the conductive elastic body 20, and the load in the Y-axis direction can be detected based on the capacitance between the electrode 41 on the negative side of the Y-axis and the conductive elastic body 20.

[0132] However, as in the above-described first embodiment, arranging a pair of electrodes 41 in the X-axis direction and a pair of electrodes 41 in the Y-axis direction allows for more sensitive detection of the load applied to the load sensor 1.

[0133] In the first embodiment and the modified example, the inner surface of the recess RS1 is parallel to the central axis CA. In contrast, in the second embodiment, the upper side of the inner surface of the recess RS2 is inclined with respect to the central axis CA so as to be farther away from the central axis CA than the lower side of the inner surface of the recess RS2.

[0134] FIG. 14 is an exploded perspective view schematically illustrating the configuration of the load sensor 2 according to the second embodiment.

[0135] The load sensor 2 comprises a plate-shaped member 110, a conductive elastic body 120, an electrode holder 130, four electrode members 140, a dielectric 150, a base member 160, one electrode pad 171, and four electrode pads 172.

[0136] The plate-shaped member 110 has a square shape in a plan view. The plate-shaped member 110 is symmetrical in the X-axis direction and the Y-axis direction about the central axis CA. The peripheral portions of the upper surface 111 and the lower surface 112 of the plate-shaped member 110 are parallel to the horizontal plane. The central portion of the plate-shaped member 110 rises upward relative to the peripheral portions. The plate-shaped member 110 is made of a flexible material.

[0137] The conductive elastic body 120 has a shape obtained by cutting a predetermined spherical shape at the position of an upper surface 121 and the position of a lower surface 122, which pass through the center of the spherical shape. The cross-sectional area of ​​the conductive elastic body 120 decreases as it goes upward. The conductive elastic body 120 has a shape that is rotationally symmetrical about a central axis CA. The upper surface 121 and the lower surface 122 of the conductive elastic body 120 are parallel to a horizontal plane. The material constituting the conductive elastic body 120 is the same as that of the conductive elastic body 20 of the first embodiment.

[0138] The electrode holder 130 has a square shape in a plan view, and is symmetrical in the X-axis direction and the Y-axis direction about a central axis CA.

[0139] FIG. 15 is an exploded perspective view schematically illustrating the configuration of an electrode holder 130 and four electrode members 140 according to the second embodiment.

[0140] The electrode holder 130 includes a holding member 210 and a frame member 220 .

[0141] The holding member 210 has a cylindrical shape. An upper surface 211 and a lower surface 212 of the holding member 210 are parallel to a horizontal plane. A through-hole 210a that passes through the holding member 210 from top to bottom is formed at the center lower end of the holding member 210. A curved inner surface 213 is formed between the upper surface 211 and the through-hole 210a. The inner surface 213 has an inwardly convex curved shape. The holding member 210 has a rotationally symmetric shape about a central axis CA.

[0142] The frame member 220 has a square prism shape. An upper surface 221 and a lower surface 222 of the frame member 220 are parallel to the horizontal plane. A through-hole into which the holding member 210 fits is formed in the center of the frame member 220, and this through-hole has an inner surface 220a.

[0143] The materials constituting the holding member 210 and the frame member 220 are the same as those of the electrode holder 30 of embodiment 1. The holding member 210 is fitted into the inner surface 220a of the frame member 220, and the side surface of the holding member 210 and the inner surface 220a of the frame member 220 are fixed together with an adhesive or the like. In this way, the electrode holder 130 is completed.

[0144] The upper surface 131 of the electrode holder 130 is composed of upper surfaces 211 and 221, the lower surface 132 of the electrode holder 130 is composed of lower surfaces 212 and 222, the through hole 130a of the electrode holder 130 is composed of the through hole 210a, and the inner surface 130b of the electrode holder 130 is composed of the inner surface 213.

[0145] The four electrode members 140 are each formed across the inner surface 130b and the lower surface 132 of the electrode holder 130. The four electrode members 140 have the same shape. Each electrode member 140 is composed of an electrode 141 disposed on the inner surface 130b and a relay portion 142 connected to the lower end of the electrode 141 and extending outward from the central axis CA. The electrode 141 has a curved shape that conforms to the inner surface 130b, and the relay portion 142 has a flat plate shape that is parallel to the horizontal plane. The relay portion 142 functions as wiring for connecting the electrode 141 to an external circuit. The material constituting the electrode member 140 is the same as that of the electrode member 40 of the first embodiment.

[0146] The electrode members 140 are formed on the electrode holder 130 by, for example, insert molding. At this time, four electrode members 140 are formed on the inner surface 130b at 90-degree angular intervals. The four electrode members 140 are formed on the inner surface 130b with a predetermined gap GP (see FIG. 14) between them so that two adjacent electrode members 140 do not contact each other. For convenience, FIG. 15 shows the shape of the electrode members 140 after they have been formed. Note that the electrode members 140 may be formed as films separately from the electrode holder 130 and then attached to the electrode holder 130 with an adhesive or the like. In this way, a structure in which four electrode members 140 are attached to the electrode holder 130 is completed as shown in FIG. 14.

[0147] 14 , the dielectric 150 is disposed so as to straddle the inner surfaces of the four electrodes 141. The material constituting the dielectric 150 is the same as that of the dielectric 50 in the first embodiment. The dielectric 150 is formed on the inner surfaces of the electrodes 141 by, for example, insert molding.

[0148] The base member 160 is composed of multiple substrates and has a square shape in a plan view. The base member 160 has a shape that is symmetrical in the X-axis direction and the Y-axis direction about a central axis CA. An upper surface 161 and a lower surface 162 of the base member 160 are parallel to the horizontal plane. The material that constitutes the base member 160 is the same as that of the base member 60 of the first embodiment.

[0149] The electrode pad 171 is placed at the center of the upper surface 161 of the base member 160. Four electrode pads 172 are placed on the upper surface 161 so as to sandwich the electrode pad 171 in the X-axis direction and the Y-axis direction. The electrode pads 171 and 172 are connected to an external circuit through the gaps between the substrates that make up the base member 160.

[0150] During assembly, the lower surface 132 of the electrode holder 130, on which the electrode members 140 and the dielectric 150 are formed, is attached to the upper surface 161 of the base member 160 with adhesive or the like. At this time, the relay portions 142 (see FIG. 15 ) of each electrode member 140 are connected to the electrode pads 172 located below. The electrode holder 130 and the base member 160 constitute a structure ST2.

[0151] FIG. 16 is a perspective view schematically showing a state in which the structure ST2, four electrode members 140, a dielectric 150, an electrode pad 171, and four electrode pads 172 according to the second embodiment are combined.

[0152] The structure ST2 is composed of the electrode holder 130 and the base member 160. This forms a recess RS2 in the structure ST2. The recess RS2 is formed in the structure ST2 by the inner surface 130b (see FIG. 15 ) of the electrode holder 130 and the upper surface 161 of the base member 60.

[0153] 14 , the center of the lower surface 112 of the plate-shaped member 110 and the upper surface 121 of the conductive elastic body 120 are fixed together with an adhesive or the like, and the peripheral portion of the lower surface 112 of the plate-shaped member 110 and the peripheral portion of the upper surface 131 of the electrode holder 130 are fixed together with an adhesive or the like. At this time, the lower surface 122 of the conductive elastic body 120 is placed on the upper surface 161 of the base member 160 through the through-hole 130a of the electrode holder 130. In this way, the load sensor 2 is completed.

[0154] FIG. 17 is a perspective view schematically illustrating the configuration of a load sensor 2 according to the second embodiment.

[0155] The lower surface of the load sensor 2 (the lower surface 162 of the base member 160) is placed on a placement surface parallel to a horizontal plane. When a load is applied to the upper surface of the load sensor 2 (the upper surface 111 of the plate-like member 110) in the Z-axis direction or horizontally, the center of the plate-like member 110 moves in response to the load. As a result, the conductive elastic body 120 fixed to the plate-like member 110 comes into contact with the dielectric 50 and deforms, thereby detecting the load.

[0156] FIG. 18A is a diagram schematically illustrating a cross section of the load sensor 2 according to the second embodiment, taken along a plane parallel to a horizontal plane passing through the vicinity of the center in the vertical direction of the conductive elastic body 120.

[0157] The four electrodes 141 are formed on the inner surface 130b of the electrode holder 130 so that a gap GP is provided between two adjacent electrodes 141. The dielectric 150 is formed so as to straddle the four electrodes 141.

[0158] Fig. 18(b) is a diagram schematically illustrating the C41-C42 cross section shown in Fig. 18(a) according to embodiment 2. Fig. 18(b) illustrates the conductive elastic body 120 in a state where no load is applied to the load sensor 2, i.e., in a no-load state (initial state).

[0159] In the no-load state, there is a region of the dielectric 150 that is not in contact with the conductive elastic body 120. The depth H1 of the recess RS2 is smaller than the length H2 of the conductive elastic body 120 in the Z-axis direction. As a result, a gap H2-H1 is formed in the height direction (the direction parallel to the central axis of the conductive elastic body 120) between the lower surface 112 of the plate-shaped member 110 and the upper end of the recess RS2 (structure ST2). Furthermore, because the plate-shaped member 110 is made of a flexible material, when a load is applied perpendicularly to the upper surface 111 of the plate-shaped member 110, the central portion of the lower surface of the plate-shaped member 110 can move smoothly downward.

[0160] Furthermore, the size of the conductive elastic body 120 and the recess RS2 and the thickness of the electrode 141 and the dielectric 150 are set so that, in the no-load state, the side of the conductive elastic body 120 contacts the dielectric 150 near the lower end of the electrode 141, but does not contact the dielectric 150 near the upper end of the electrode 141.

[0161] <Effects of Second Embodiment> According to the second embodiment, the following effects are achieved.

[0162] 14 and 16, the load sensor 2 includes a plate-shaped member 110 that receives a load on its upper surface 111 (one surface), a conductive elastic body 120 that protrudes from the lower surface 112 (the other surface) of the plate-shaped member 110, a recess RS2 that receives the conductive elastic body 120, a plurality of electrodes 141 installed along the inner surface of the recess RS2, and a dielectric 150 disposed between the conductive elastic body 120 and the plurality of electrodes 141. As shown in FIG. 18(b), the plate-shaped member 110 is disposed relative to a member (structure ST2) having the recess RS2 so as to be movable in a direction parallel to the central axis of the conductive elastic body 120 (Z-axis direction) and in directions perpendicular to this central axis (X-axis direction, Y-axis direction). A region where the conductive elastic body 120 and the plurality of electrodes 141 do not contact each other exists via the dielectric 150.

[0163] According to this configuration, the conductive elastic body 120 deforms in the recess RS2 in response to the load.

[0164] For example, when a load is applied vertically to the upper surface 111 of the plate-like member 110, the conductive elastic body 120 is compressed, causing the conductive elastic body 120 to expand in a direction (horizontal direction) perpendicular to the protruding direction (Z-axis direction) of the conductive elastic body 120. As a result, in regions (non-contact regions) where the conductive elastic body 120 and the plurality of electrodes 141 do not contact each other via the dielectric 150, the conductive elastic body 120 and the plurality of electrodes 141 come into contact with each other via the dielectric 150, and the contact areas between the conductive elastic body 120 and the plurality of electrodes 141 via the dielectric 150 increase. Therefore, a load in the vertical direction can be detected based on the magnitude of the electrostatic capacitance corresponding to the sum of these contact areas.

[0165] Furthermore, when a load is applied in a direction parallel to the top surface 111 of the plate-like member 110 (horizontal direction), the conductive elastic body 120 moves relative to the recess RS2 in the direction of the load application. As a result, the contact area between the conductive elastic body 120 and the multiple electrodes 141 via the dielectric 150 changes depending on the direction of the load application and the magnitude of the load. Accordingly, the capacitance between each electrode 141 and the conductive elastic body 120 changes depending on the direction of the load application and the magnitude of the load. Therefore, a load in a direction parallel to the top surface 111 of the plate-like member 110 (horizontal direction) can be detected based on the balance of these capacitances.

[0166] Therefore, with the above configuration, the load sensor 2 can detect three-directional components of the load applied thereto.

[0167] As shown in Figure 18 (b), the inner surface of the recess RS2 is inclined with respect to the central axis CA so that the upper side (the side toward the plate-shaped member 110) is farther away from the central axis CA of the recess RS2 than the lower side (the side opposite the plate-shaped member 110).

[0168] According to this configuration, non-contact areas can be smoothly formed between the conductive elastic body 120 and the plurality of electrodes 141 via the dielectric 150 .

[0169] The inner surface of the recess RS2 is curved, and the conductive elastic body 120 has a hemispherical shape that is convex toward the recess RS2.

[0170] With this configuration, the contact area between the conductive elastic body 120 and the multiple electrodes 141 via the dielectric 150 is more likely to change depending on the load, so the load applied to the load sensor 2 can be detected with high sensitivity.

[0171] The load sensor 2 of embodiment 2 may also have a configuration similar to the modified example of embodiment 1. That is, in the load sensor 2, the electrode 141 may be divided into multiple parts in the direction of the central axis CA of the recess RS2, similar to the configuration in Fig. 11 . In the load sensor 2, the electrodes 141 may be arranged only on two adjacent inner surfaces of the four inner surfaces of the recess RS2, similar to the configuration in Fig. 13 .

[0172] <Other Modifications> The configurations of the load sensors 1 and 2 can be modified in various ways in addition to the configurations shown in the first and second embodiments and the modified examples.

[0173] In the first embodiment, as shown in FIG. 5A , the depth H1 of the recess RS1 is set to be smaller than the length H2 of the conductive elastic body 20 in the Z-axis direction, thereby providing a gap between the plate-shaped member 10 and the member (structure ST1) having the recess RS1 in the direction parallel to the central axis of the conductive elastic body 20 (the Z-axis direction). However, the configuration for providing this gap is not limited to this. For example, as shown in FIG. 19 , a protrusion 13 may be provided on the lower surface 12 of the plate-shaped member 10, and the conductive elastic body 20 may protrude from the lower surface of this protrusion 13. The length of the conductive elastic body 20 in the Z-axis direction is smaller than the depth H1 of the recess RS1. Even with this configuration, a gap of the difference H3-H1 between the distance H3 from the bottom surface of the recess RS1 to the lower surface 12 of the plate-shaped member 10 and the depth H1 of the recess RS1 is formed between the plate-shaped member 10 and the member (structure ST1) having the recess RS1.

[0174] 19, a spacer having a thickness similar to the protrusion amount of the protrusion 13 may be integrated with the lower surface 12. In this case, the member in which the plate-shaped member 10 and the spacer are integrated corresponds to the plate-shaped member described in the claims.

[0175] Also, in embodiment 2, with a configuration similar to that described above, a gap may be provided between the plate-like member 110 and the member having the recess RS2 (structure ST2) in a direction parallel to the central axis of the conductive elastic body 120 (Z-axis direction).

[0176] The gap between the plate-like member 10 and the member having the recess RS1 (structure ST1) does not necessarily have to be an empty space, and a soft elastic member such as a sponge may be interposed or filled in this gap. In this case, too, the plate-like member 10 can be arranged to be movable relative to the member having the recess RS1 (structure ST1) in directions parallel to the central axis of the conductive elastic body 20 and in directions perpendicular to this central axis.

[0177] In the first embodiment, four electrodes 41 are arranged along the inner surface of the recess RS1, and in the modified example shown in Fig. 13, two electrodes 41 are arranged along the inner surface of the recess RS1. However, the number of electrodes 41 arranged in the recess RS1 is not limited to four or two, and may be three, five, or more. In the second embodiment, four electrodes 141 are arranged along the inner surface of the recess RS2, but the number of electrodes 41 arranged in the recess RS2 is not limited to four, and may be two, three, five, or more.

[0178] However, when only two electrodes 41 are arranged in the recessed portion RS1, it is preferable that the two electrodes 41 are not arranged in positions facing each other across the central axis CA. In other words, it is preferable that the two electrodes 41 are not arranged at an angular interval of 180 degrees around the central axis CA. By not arranging the two electrodes 41 in positions facing each other across the central axis CA, load components in two parallel horizontal directions can be detected based on the two electrodes 41. Similarly, when only two electrodes 141 are arranged in the recessed portion RS2, it is preferable that the two electrodes 141 are not arranged in positions facing each other across the central axis CA.

[0179] In the first embodiment, the recess RS1 has a substantially rectangular shape in a plan view, and the four electrodes 41 are arranged at angular intervals of 90 degrees around the central axis CA. However, this is not limiting, and the recess RS1 may have a shape other than a rectangular shape in a plan view. In this case, the multiple electrodes 41 arranged on the inner surface of the recess RS1 are arranged at angular intervals other than 90 degrees around the central axis CA. Similarly, in the second embodiment, the multiple electrodes 141 may be arranged at angular intervals other than 90 degrees around the central axis CA.

[0180] In the first embodiment, two sets of electrodes 41 are arranged on either side of the central axis CA, but the number of sets of electrodes 41 is not limited to two and may be three or more. Similarly, in the second embodiment, two sets of electrodes 141 are arranged on either side of the central axis CA, but the number of sets of electrodes 141 is not limited to two and may be three or more.

[0181] In the first embodiment, four dielectrics 50 are arranged on the inner surface of the recess RS1 so as to correspond to the four electrodes 41, respectively, but this is not limited thereto, and the dielectrics 50 may be arranged so as to straddle the four electrodes 41. In the second embodiment, the dielectrics 150 are arranged on the inner surface of the recess RS2 so as to straddle the four electrodes 141, but this is not limited thereto, and four dielectrics 150 may be arranged so as to correspond to the four electrodes 141, respectively.

[0182] In the first embodiment, the dielectric 50 is disposed on the surfaces of the plurality of electrodes 41, but this is not limiting. For example, as shown in FIG. 20 , the dielectric 50 may be disposed on the surface of the conductive elastic body 20 so as to cover the entire periphery of the side surface of the conductive elastic body 20. In this case, there is a region of each electrode 41 that is not in contact with the dielectric 50 in the no-load state. The material that constitutes the dielectric 50 is electrically insulating and is deformable together with the conductive elastic body 20. For example, the material that constitutes the dielectric 50 is polyurethane rubber, silicone rubber, natural rubber, or the like. The dielectric 50 is formed on the surface of the conductive elastic body 20 with a film thickness of, for example, about 8 μm to 30 μm.

[0183] In this case, the conductive elastic body 20 is larger in plan view than the shape of the accommodation space for the conductive elastic body 20 in the recess RS1 (the space formed by the inner surfaces of the four electrodes 41 and the inner surface of the recess RS1). Specifically, the conductive elastic body 20 is larger than the shape inscribed in each electrode 41 in the recess RS1. That is, as shown in FIG. 20 , the diameter R2 of the conductive elastic body 20 before being placed in the recess RS1 is larger than the length W2 of one side of the area surrounded by each electrode 41.

[0184] As a result, similar to embodiment 1, the conductive elastic body 20 contacts the four electrodes 41 via the dielectric 50 in the no-load state, so that the load can be detected without play when a load is applied. Also, similar to embodiment 1, in the no-load state, the conductive elastic body 20 is centered in the accommodation space due to the elastic restoring force of the conductive elastic body 20, and the contact areas between the electrodes 41 and the conductive elastic body 20 via the dielectric 50 tend to be balanced.

[0185] Also, in embodiment 2, the dielectric 150 is arranged on the surface of the multiple electrodes 141, but this is not limited to this, and the dielectric 150 may be arranged on the surface of the conductive elastic body 120 so as to cover the entire side surface of the conductive elastic body 120.

[0186] In the first embodiment, the configuration for connecting the conductive elastic body 20 to an external circuit is not limited to the shaft member 70. For example, the conductive elastic body 20 may be connected to an external circuit by an electrode pad disposed on the bottom surface of the recessed portion RS1, as in the second embodiment. Also, in the second embodiment, the configuration for connecting the conductive elastic body 120 to an external circuit is not limited to the electrode pad 171. For example, the conductive elastic body 120 may be connected to an external circuit by an axis member disposed in the center of the recessed portion RS2, as in the first embodiment.

[0187] In embodiment 1, the cross-sectional area of ​​the conductive elastic body 120 becomes smaller as it moves in the negative direction of the Z axis, but from the viewpoint of adjusting the FC curve, the cross-sectional area of ​​the conductive elastic body 120 may change in other ways.

[0188] In the second embodiment, the inner surface of the recess RS2 has an inwardly convex curved shape, but it may have a truncated cone shape or a truncated quadrangular pyramid shape. Furthermore, the conductive elastic body 120 has a hemispherical shape with the lower end cut off at the lower surface 122, but this is not limited thereto and the conductive elastic body 120 may have a shape other than a hemispherical shape. For example, the conductive elastic body 120 may have a truncated cone shape or a truncated pyramid shape. The shape of the conductive elastic body 120 is determined so that the FC curve has a desired shape relative to the shape of the recess RS2.

[0189] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims.

[0190] <Supplementary Notes> The above description of the embodiments discloses the following techniques.

[0191] (Technology 1) A load sensor comprising: a plate-shaped member that receives a load on one surface; a conductive elastic body that protrudes from the other surface of the plate-shaped member; a recess that receives the conductive elastic body; a plurality of electrodes that are installed along the inner surface of the recess; and a dielectric that is arranged between the conductive elastic body and the plurality of electrodes, wherein the plate-shaped member is arranged to be movable relative to a member having the recess in directions parallel to and perpendicular to a central axis of the conductive elastic body, and wherein there is an area between the conductive elastic body and the plurality of electrodes that does not come into contact via the dielectric.

[0192] According to this technique, the conductive elastic body deforms in the recess in response to a load.

[0193] For example, when a load is applied perpendicular to one surface of the plate-like member, the conductive elastic body is compressed, causing it to expand in a direction perpendicular to the direction of protrusion. As a result, in the region where the conductive elastic body and the multiple electrodes do not contact each other via a dielectric (non-contact region), the conductive elastic body and the multiple electrodes come into contact via a dielectric, increasing the contact area between the conductive elastic body and the multiple electrodes via the dielectric. Therefore, the vertical load can be detected based on the magnitude of the capacitance corresponding to the sum of these contact areas.

[0194] Furthermore, when a load is applied in a direction parallel to one surface of the plate-like member, the conductive elastic body moves relative to the recess in the direction of the load. As a result, the contact area between the conductive elastic body and the multiple electrodes via the dielectric changes depending on the direction of the load and the magnitude of the load. Accordingly, the capacitance between each electrode and the conductive elastic body changes depending on the direction of the load and the magnitude of the load. Therefore, a load in a direction parallel to one surface of the plate-like member can be detected based on the balance of these capacitances.

[0195] Therefore, according to the above technology, it is possible to detect three-directional components of the load applied to the load sensor.

[0196] (Technology 2) The load sensor according to Technology 1, wherein the dielectric is disposed on the surfaces of the plurality of electrodes.

[0197] This technique allows the dielectric to be easily formed.

[0198] (Technology 3) The load sensor according to Technology 1 or 2, wherein the plurality of electrodes are arranged at predetermined angular intervals around the central axis of the recess.

[0199] (Technology 4) The load sensor according to Technology 3, wherein the predetermined angular interval is set to about 90 degrees.

[0200] According to the techniques 3 and 4, two horizontal components of the load applied to the load sensor can be efficiently detected.

[0201] (Technology 5) The load sensor according to Technology 3 or 4, wherein four of the electrodes are provided on the inner surface of the recess.

[0202] This technology makes it possible to most efficiently detect two horizontal components of the load applied to the load sensor.

[0203] (Technology 6) A load sensor according to any one of technologies 1 to 5, characterized in that the member having the recess has a through hole penetrating from a bottom surface of the recess to the outside, and a conductive shaft member is connected to the conductive elastic body via the through hole.

[0204] According to this technique, the conductive elastic body can be smoothly connected to an external circuit via the shaft member while being positioned horizontally in the recess.

[0205] (Technology 7) The load sensor according to any one of Technologies 1 to 6, characterized in that an inner surface of the recess is substantially parallel to a central axis of the recess.

[0206] This technique makes it possible to smoothly form non-contact areas between the conductive elastic body and the plurality of electrodes.

[0207] (Technology 8) The load sensor according to Technology 7, wherein the recess has a rectangular outline in a plan view, and the electrodes are respectively installed on inner surfaces of the recess corresponding to at least two adjacent sides of the rectangle.

[0208] According to this technology, the angle formed by two adjacent electrodes is substantially 90 degrees, so that two horizontal components of the load applied to the load sensor can be efficiently detected.

[0209] (Technology 9) The load sensor according to Technology 8, wherein the electrodes are provided on inner surfaces of the recesses corresponding to all sides of the rectangle.

[0210] This technology makes it possible to most efficiently detect two horizontal components of the load applied to the load sensor.

[0211] (Technology 10) The load sensor according to Technology 8 or 9, characterized in that the conductive elastic body has a columnar shape.

[0212] According to this technology, the contact area between the conductive elastic body and the plurality of electrodes via the dielectric material is easily changed depending on the load, so that the load applied to the load sensor can be detected with high sensitivity.

[0213] (Technology 11) The load sensor according to Technology 10, wherein the conductive elastic body is larger than a shape of a space for accommodating the conductive elastic body in the recess in a plan view.

[0214] According to this technology, the conductive elastic body and the multiple electrodes are in contact with each other via a dielectric when no load is applied, allowing for load detection without play. Furthermore, when no load is applied, the conductive elastic body's elastic restoring force centers the conductive elastic body relative to the housing space, facilitating balancing of the contact areas between each electrode and the conductive elastic body via the dielectric. Therefore, when a load is applied in a direction parallel to one surface of the plate-like member, the direction of the load can be easily and smoothly detected from the capacitance detected for each electrode.

[0215] (Technology 12) The load sensor according to Technology 10 or 11, wherein the cross section of the conductive elastic body is circular or polygonal.

[0216] According to this technique, when the cross section of the conductive elastic body is circular, it is easy to form the conductive elastic body, and when the cross section of the conductive elastic body is polygonal, it is easy to adjust the FC curve by adjusting the shape.

[0217] (Technology 13) The load sensor according to any one of Techniques 10 to 12, wherein the conductive elastic body has a cross-sectional area that changes in the protruding direction.

[0218] According to this technique, the outer surface of the conductive elastic body is inclined relative to the electrode, making it easier to adjust the FC curve.

[0219] (Technology 14) The load sensor according to any one of Technologies 7 to 13, wherein each of the electrodes is divided into a plurality of parts in a central axis direction of the recess.

[0220] A vertical load is likely to appear as a change in the contact area of ​​the lower electrode (away from the plate-like member), while a horizontal load is likely to appear as a change in the contact area of ​​the upper electrode (closer to the plate-like member). Therefore, according to this technology, by dividing each electrode and selectively using the divided electrodes to detect the vertical load and the horizontal load, it is possible to smoothly and accurately detect the vertical load and the horizontal load.

[0221] (Technology 15) In the load sensor described in any one of Technologies 1 to 6, the inner surface of the recess is inclined with respect to the central axis so that the side facing the plate-like member is farther away from the central axis of the recess than the side facing the plate-like member.

[0222] This technique makes it possible to smoothly form non-contact areas between the conductive elastic body and the plurality of electrodes.

[0223] (Technology 16) The load sensor according to Technology 15, wherein an inner surface of the recess has a curved shape, and the conductive elastic body has a hemispherical shape that is convex toward the recess.

[0224] According to this technology, the contact area between the conductive elastic body and the plurality of electrodes via the dielectric material is easily changed depending on the load, so that the load applied to the load sensor can be detected with high sensitivity.

[0225] 1, 2 Load sensor 10 Plate-shaped member 11 Top surface (one surface) 12 Bottom surface (other surface) 20 Conductive elastic body 30b Inner surface 41 Electrode 50 Dielectric 60a Through hole 70 Shaft member 61 Top surface (bottom surface) 110 Plate-shaped member 111 Top surface (one surface) 112 Bottom surface (other surface) 120 Conductive elastic body 130b Inner surface 141 Electrode 150 Dielectric 161 Top surface (bottom surface) CA Central axis RS1, RS2 Recess ST1, ST2 Structure (member having recess)

Claims

1. A load sensor comprising: a plate-shaped member receiving a load on one surface, a conductive elastic body protruding from the other surface of the plate-shaped member, a recess receiving the conductive elastic body, a plurality of electrodes installed along the inner surface of the recess, and a dielectric arranged between the conductive elastic body and the plurality of electrodes, wherein the plate-shaped member is arranged so as to be movable relative to a member having the recess in directions parallel to a central axis of the conductive elastic body and in directions perpendicular to the central axis, and there is an area between the conductive elastic body and the plurality of electrodes that is not in contact via the dielectric.

2. A load sensor according to claim 1, characterized in that the dielectric material is disposed on the surfaces of the plurality of electrodes.

3. A load sensor as claimed in claim 1, characterized in that the plurality of electrodes are arranged at predetermined angular intervals around the central axis of the recess.

4. A load sensor according to claim 3, wherein the predetermined angular interval is set to approximately 90 degrees.

5. The load sensor according to claim 3, wherein four of the electrodes are provided on the inner surface of the recess.

6. A load sensor as described in claim 1, wherein the member having the recess has a through hole penetrating from the bottom surface of the recess to the outside, and a conductive shaft member is connected to the conductive elastic body via the through hole.

7. A load sensor according to any one of claims 1 to 6, characterized in that an inner surface of the recess is substantially parallel to a central axis of the recess.

8. A load sensor as claimed in claim 7, characterized in that the recess has a rectangular outline in a plan view, and the electrodes are respectively provided on the inner surfaces of the recess corresponding to at least two adjacent sides of the rectangle.

9. A load sensor according to claim 8, characterized in that the electrodes are provided on the inner surfaces of the recesses corresponding to all sides of the rectangle.

10. The load sensor according to claim 8, wherein the conductive elastic body has a columnar shape.

11. A load sensor according to claim 10, wherein the conductive elastic body is larger than the shape of the space in the recess where the conductive elastic body is accommodated, in a plan view.

12. A load sensor according to claim 10, wherein the cross section of the conductive elastic body is circular or polygonal.

13. A load sensor according to claim 10, wherein the conductive elastic body has a cross-sectional area that changes in the protruding direction.

14. A load sensor as claimed in claim 7, characterized in that each of said electrodes is divided into a plurality of parts in the direction of the central axis of said recess.

15. A load sensor as claimed in any one of claims 1 to 6, characterized in that the inner surface of the recess is inclined with respect to the central axis so that the side facing the plate-like member is farther away from the central axis of the recess than the side opposite the plate-like member.

16. A load sensor according to claim 15, wherein the inner surface of the recess is curved, and the conductive elastic body is hemispherical in shape and convex toward the recess.

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