Load Cell

Abstract

The load sensor (1) comprises: substrates (11, 21) arranged to face each other; conductive elastic bodies (12, 22) arranged on opposite surfaces of the substrates (11, 21); a conductive member (31) arranged between the substrate (11) and the conductive elastic body (22); a dielectric (32) arranged between the conductive elastic body (12, 22) and the conductive member (31); and a structure in which the contact area of ​​the dielectric (32) changes with an increase in load, so that a change in electrostatic capacitance between the conductive elastic body (12, 22) and the conductive member (31) as the load changes is close to a straight line.

Description

Technical Field

[0001] The present invention relates to a load sensor that detects a load applied from the outside based on a change in electrostatic capacitance. Background Art

[0002] Load sensors are widely used in fields such as industrial equipment, robotics, and vehicles. In recent years, with the advancement of computer-based control technology and improvements in aesthetics, a wide variety of electronic devices, such as humanoid robots and automotive interiors, have been developed that utilize free-form surfaces. Consequently, high-performance load sensors are required to be incorporated into each free-form surface.

[0003] Patent Document 1 below describes a pressure-sensitive element comprising a first conductive member made of a sheet of conductive rubber, a linear second conductive member sandwiched between the first conductive member and a substrate, and a dielectric formed to cover the second conductive member. In this structure, as the load increases, the contact area between the first conductive member and the dielectric increases, and this increases the electrostatic capacitance between the first and second conductive members. Therefore, by detecting the electrostatic capacitance between the first and second conductive members, it is possible to detect the load applied to the pressure-sensitive element.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 096901 Summary of the Invention

[0007] -Problems to be solved by the invention-

[0008] However, in the above-described structure, since the second conductive member is linear, the contact area does not increase linearly with increasing load, and the relationship between load and capacitance is defined by a curved waveform. Therefore, when calculating the load from the capacitance value, this waveform must be taken into account, complicating the load detection process.

[0009] In view of this problem, an object of the present invention is to provide a load sensor that can more easily detect a load applied to the load sensor.

[0010] -Methods for solving the problem-

[0011] The main aspect of the present invention relates to a load sensor. The load sensor includes: a first substrate and a second substrate disposed so as to face each other; a conductive elastic body disposed on the opposing surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and a structure that varies the contact area of ​​the dielectric with increasing load, such that the change in electrostatic capacitance between the conductive elastic body and the conductive member as the load changes approximates a linear relationship.

[0012] According to the load sensor of this embodiment, the change in capacitance between the conductive elastic body and the conductive member as the load changes is close to a linear curve. Therefore, by measuring the capacitance between the conductive elastic body and the conductive member and applying a simple proportionality-based processing to the measured capacitance, the load applied to the load sensor can be appropriately detected. This makes it possible to more easily detect the load applied to the load sensor.

[0013] -Effects of the Invention-

[0014] As described above, according to the present invention, it is possible to provide a load sensor that can more easily detect a load applied to the load sensor.

[0015] The effects and significance of the present invention will become more apparent through the description of the following embodiments. However, the following embodiments are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described in the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 (a) is a perspective view schematically showing the conductive elastic body provided on the lower substrate and the facing surface of the lower substrate according to the first embodiment. Figure 1 (b) is a perspective view schematically showing a state in which a conductor wire is provided on a substrate according to the first embodiment.

[0017] Figure 2 (a) is a perspective view schematically showing the conductive elastic body provided on the upper substrate and the facing surface of the upper substrate according to the first embodiment. Figure 2 (b) is a perspective view schematically showing the assembled load sensor according to the first embodiment.

[0018] Figure 3 (a) and (b) are cross-sectional views schematically showing the periphery of the conductor line according to the first embodiment when viewed in the negative direction of the X-axis.

[0019] Figure 4It is a plan view schematically showing the interior of the load sensor according to the first embodiment when viewed in the negative direction of the Z axis.

[0020] Figure 5 This is a graph schematically showing the relationship between load and capacitance according to the first embodiment.

[0021] Figure 6 (a) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in the initial state before a load is applied according to the first embodiment. Figure 6 (b) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in a state where a load is applied according to the first embodiment.

[0022] Figure 7 (a) is a side view schematically showing the structure of the conductor line according to the first embodiment when viewed in the negative direction of the Y axis. Figure 7 (b) is a diagram schematically showing a cross section of a dielectric material according to a modification of the first embodiment when it is cut along the YZ plane.

[0023] Figure 8 (a) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in the initial state before a load is applied according to the second embodiment. Figure 8 (b) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in a state where a load is applied according to the second embodiment.

[0024] Figure 9 (a) shows the contact angle θ and ε involved in the second embodiment. r · A graph showing the relationship between the S / d values. Figure 9 (b) is a graph showing the relationship between pressure and electrostatic capacitance according to the second embodiment.

[0025] Figure 10 This is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in the initial state before a load is applied according to Modification 1 of Embodiment 2.

[0026] Figure 11 (a) shows the contact angle θ and ε involved in the modification example 1 of the second embodiment. r · A graph showing the relationship between the S / d values. Figure 11 (b) is a graph showing the relationship between pressure and electrostatic capacitance according to Modification 1 of Embodiment 2.

[0027] Figure 12 This is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in the initial state before a load is applied according to Modification 2 of Embodiment 2.

[0028] Figure 13 (a) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in the initial state before a load is applied according to the third embodiment. Figure 13 (b) is a diagram schematically showing the relationship between the dielectric and the conductive elastic body in a state where a load is applied according to the third embodiment.

[0029] Figure 14 (a) is a plan view schematically showing the structure of the load sensor according to the fourth embodiment when viewed in the negative direction of the Z axis. Figure 14 (b) is a diagram schematically showing a cross section of the load sensor according to the fourth embodiment, taken along the YZ plane.

[0030] However, the accompanying drawings are mainly for explanation and are not intended to limit the scope of the present invention. DETAILED DESCRIPTION

[0031] The load sensor according to the present invention can be applied to a management system that performs processing according to an applied load, or a load sensor of an electronic device.

[0032] Examples of the management system include an inventory management system, a driver monitoring system, a guidance management system, a safety management system, and a nursing / childcare management system.

[0033] In an inventory management system, for example, load sensors installed on inventory racks detect the load of loaded inventory and the types and quantities of goods on the racks. This allows for efficient inventory management and labor savings in stores, factories, warehouses, and the like. Furthermore, load sensors installed in refrigerators detect the load of food within the refrigerator and the types, quantity, and quantity of food within. This allows for the automatic presentation of menus using food from the refrigerator.

[0034] In the driver monitoring system, for example, a load sensor installed in the steering system monitors the driver's load distribution on the steering system (e.g., grip force, grip position, pedal force). Furthermore, a load sensor installed in the vehicle seat monitors the load distribution of the driver on the vehicle seat (e.g., center of gravity position) when seated. This provides feedback on the driver's driving state (e.g., drowsiness, psychological state, etc.).

[0035] In the guidance management system, for example, load sensors installed on the soles of shoes monitor the load distribution on the soles of the feet, thereby correcting or guiding the user to an appropriate walking or running state.

[0036] In a safety management system, for example, load sensors installed on the floor can detect the load distribution, weight, stride length, speed, and shoe pattern of people passing through. By comparing this detection information with the data, the person passing through can be identified.

[0037] In nursing and childcare management systems, for example, load sensors placed on bedding and toilets monitor the distribution of the human body's load on the bedding and toilets. This allows the user to infer their intended actions based on their position on the bedding and toilets, preventing falls and rolls.

[0038] Examples of electronic devices include in-vehicle devices (car navigation systems, audio equipment, etc.), home appliances (electric kettles, IH cooking heaters, etc.), smartphones, electronic paper, e-book readers, PC keyboards, game controllers, smart watches, wireless headphones, touch panels, electronic pens, penlights, luminous clothing, musical instruments, etc. In electronic devices, load sensors are provided in the input section that receives input from the user.

[0039] The load sensor in the following embodiments is a typical electrostatic capacitance load sensor included in the aforementioned management system and electronic equipment. Such load sensors may also be referred to as "electrostatic capacitance pressure sensor elements," "capacitive pressure detection sensor elements," "pressure-sensitive switch elements," etc. Furthermore, the load sensor in the following embodiments is connected to a detection circuit, and the load sensor and detection circuit together constitute a load detection device. The following embodiment is one embodiment of the present invention and is not limited to the following embodiment.

[0040] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For convenience, mutually orthogonal X, Y, and Z axes are indicated in each drawing. The Z axis is the height direction of the load cell 1.

[0041] <Implementation Method 1>

[0042] Figure 1 (a) is a perspective view schematically showing a substrate 11 and three conductive elastic bodies 12 provided on an opposing surface 11 a (surface on the positive side of the Z axis) of the substrate 11 .

[0043] The substrate 11 is an elastic, insulating member having a flat plate shape parallel to the XY plane. The substrate 11 is made of a non-conductive resin material or a non-conductive rubber material. The resin material used for the substrate 11 is, for example, at least one resin material selected from the group consisting of styrene resins, silicone resins (e.g., polydimethylpolysiloxane (PDMS)), acrylic resins, rotaxane resins, and polyurethane resins. The rubber material used for the substrate 11 is, for example, at least one rubber material selected from the group consisting of silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene-butadiene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, polyurethane rubber, and natural rubber.

[0044] The conductive elastic body 12 is formed on the facing surface 11a (the surface on the positive side of the Z axis) of the substrate 11. Figure 1 In (a), three conductive elastic bodies 12 are formed on the opposing surface 11a of the substrate 11. The conductive elastic bodies 12 are elastic and electrically conductive members. Each conductive elastic body 12 has a strip-like shape that is elongated in the Y-axis direction and is arranged side by side at predetermined intervals in the X-axis direction. A cable 12a electrically connected to the conductive elastic body 12 is provided at the end of each conductive elastic body 12 on the negative side of the Y-axis.

[0045] The conductive elastic body 12 is formed on the facing surface 11a of the substrate 11 by a printing method such as screen printing, gravure printing, flexographic printing, offset printing, or gravure offset printing. These printing methods can form the conductive elastic body 12 on the facing surface 11a of the substrate 11 to a thickness of approximately 0.001 mm to 0.5 mm. However, the method for forming the conductive elastic body 12 is not limited to printing methods.

[0046] The conductive elastic body 12 is composed of a resin material and a conductive filler dispersed therein, or a rubber material and a conductive filler dispersed therein.

[0047] The resin material used for the conductive elastomer 12 is similar to the resin material used for the substrate 11 described above, and is, for example, at least one resin material selected from the group consisting of styrene-based resins, silicone-based resins (such as polydimethylpolysiloxane (PDMS)), acrylic resins, rotaxane-based resins, and polyurethane-based resins. The rubber material used for the conductive elastomer 12 is similar to the rubber material used for the substrate 11 described above, and is, for example, at least one rubber material selected from the group consisting of silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene-butadiene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, polyurethane rubber, and natural rubber.

[0048] The conductive filler used for the conductive elastomer 12 is, for example, at least one material selected from a group of conductive fibers including metal materials such as Au (gold), Ag (silver), Cu (copper), C (carbon), ZnO (zinc oxide), In2O3 (indium (III) oxide), and SnO2 (tin (IV) oxide), conductive polymer materials such as PEDOT:PSS (i.e., a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS)), metal-coated organic fibers, metal wires (in fiber state), etc.

[0049] Figure 1 (b) is a perspective view schematically showing a state in which three pairs of conductor wires 13 are provided on the substrate 11 .

[0050] The pair of conductor lines 13 is formed by bending a conductor line extending in the X-axis direction, and includes two conductor lines 13a extending from the bending position in the negative direction of the X-axis. The two conductor lines 13a constituting the pair of conductor lines 13 are arranged side by side with a predetermined interval. Figure 1 Here, three pairs of conductor wires 13 are arranged so as to overlap with the upper surfaces of the three conductive elastic bodies 12 shown in (a).

[0051] The three pairs of conductor wires 13 are arranged to cross the conductive elastic body 12 and are arranged side by side with a predetermined interval along the longitudinal direction (Y-axis direction) of the conductive elastic body 12. The pair of conductor wires 13 are arranged along the X-axis direction so as to cross the three conductive elastic bodies 12. The conductor wire 13a includes a linear conductive member and a dielectric formed on the surface of the conductive member. For the structure of the conductor wire 13a, refer to Figure 3 (a) and (b) are used to illustrate.

[0052] like Figure 1 As shown in (b), after arranging three pairs of conductor wires 13, each pair of conductor wires 13 is provided on the substrate 11 through the wire 14 so as to be movable in the extending direction (X-axis direction) of the pair of conductor wires 13. Figure 1 In the example shown in (b), twelve wires 14 connect the pair of conductor wires 13 to the substrate 11 at positions other than where the conductive elastic body 12 overlaps the pair of conductor wires 13. The wires 14 are made of chemical fibers, natural fibers, or mixed fibers thereof.

[0053] Figure 2 (a) is a perspective view schematically showing a substrate 21 arranged to overlap the upper side of the substrate 11 and three conductive elastic bodies 22 provided on the facing surface 21 a (surface on the negative side of the Z axis) of the substrate 21 .

[0054] The substrate 21 has the same size and shape as the substrate 11 and is made of the same material as the substrate 11. The conductive elastomer 22 is formed on the opposite surface 21a of the substrate 21 (the surface on the negative side of the Z axis) at a position opposite to the conductive elastomer 12, and is formed side by side with a prescribed interval in the X-axis direction. The conductive elastomer 22 has the same size and shape as the conductive elastomer 12 and is made of the same material as the conductive elastomer 12. The conductive elastomer 22 is formed on the surface on the negative side of the Z axis of the substrate 21 by a prescribed printing method, similar to the conductive elastomer 12. The method for forming the conductive elastomer 22 is not limited to the printing method. At the end of each conductive elastomer 22 on the negative side of the Y axis, a cable 22a electrically connected to the conductive elastomer 22 is provided.

[0055] Figure 2 (b) is schematically shown in Figure 1 The structure of (b) is provided with Figure 2 (a) is a three-dimensional diagram of the state of the structure.

[0056] from Figure 1 Above the structure shown in (b) (Z-axis positive side), configure Figure 2 The structure shown in (a). At this time, the opposing surfaces 11a and 21a of the substrate 11 and the substrate 21 are configured to face each other, and the conductive elastomer 12 and the conductive elastomer 22 are configured to overlap. Moreover, the substrate 11 and the substrate 21 are fixed by connecting the outer four sides of the substrate 21 relative to the outer four sides of the substrate 11 using a silicone rubber adhesive, wire, etc. Thus, three groups of a pair of conductor wires 13 are sandwiched by three conductive elastomers 12 and three conductive elastomers 22. In this way, as Figure 2 As shown in (b), the load sensor 1 is completed.

[0057] Figure 3 (a) and (b) are cross-sectional views schematically showing the periphery of the conductor line 13a when viewed in the negative direction of the X-axis. Figure 3 (a) indicates the state where no load is applied. Figure 3 (b) shows a state where a load is applied.

[0058] like Figure 3 As shown in (a) and (b) of FIG. 1 , the conductor wire 13a is composed of a conductive member 31 and a dielectric 32 formed on the conductive member 31. The conductive member 31 is a wire having a linear shape.

[0059] The conductive member 31 is made of, for example, a conductive metal material. Alternatively, the conductive member 31 may be made of a core wire made of glass and a conductive layer formed on its surface, or a core wire made of resin and a conductive layer formed on its surface. In the first embodiment, the conductive member 31 is made of aluminum. The dielectric 32 has electrical insulating properties and is made of, for example, a resin material, a ceramic material, or a metal oxide material.

[0060] In addition, as the conductive member 31, valve action metals such as titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), tungsten (W), molybdenum (Mo), copper (Cu), nickel (Ni), silver (Ag), gold (Au), etc. can be used. In addition, the diameter of the conductive member 31 can be, for example, not less than 10 μm and not more than 1500 μm, or not less than 50 μm and not more than 800 μm. The structure of the conductive member 31 as described above is preferred from the perspective of the strength and resistance of the conductive member. The thickness of the dielectric 32 is preferably not less than 5 nm and not more than 100 μm, and can be appropriately selected according to the design of the sensor sensitivity, etc.

[0061] like Figure 3 As shown in (a), when no load is applied, the force applied between the conductive elastic body 12 and the conductor line 13a and the force applied between the conductive elastic body 22 and the conductor line 13a are almost zero. Figure 3 As shown in (b) of FIG. 2 , when an upward load is applied to the lower surface of the substrate 11 and a downward load is applied to the upper surface of the substrate 21 , the conductive elastic bodies 12 and 22 are deformed by the conductor wires 13 a .

[0062] like Figure 3 As shown in (b), when a load is applied, the conductor wire 13a approaches the conductive elastic bodies 12 and 22, becoming surrounded by them. This increases the contact area between the conductor wire 13a and the conductive elastic bodies 12 and 22. Consequently, the electrostatic capacitance between the conductive member 31 and the conductive elastic body 12, as well as the electrostatic capacitance between the conductive member 31 and the conductive elastic body 22, changes. Furthermore, by detecting the electrostatic capacitance of the region of the conductor wire 13a, the load applied to that region can be calculated.

[0063] Figure 4 : is a top view schematically showing the interior of the load cell 1 when viewed in the negative direction of the Z axis. Figure 4 In the figure, the wire 14 is omitted for convenience.

[0064] The load sensor 1 has nine sensor sections arranged side by side in the X- and Y-axis directions within its measurement region R. Specifically, the nine sensor sections are divided into three regions in the X- and Y-axis directions, respectively. The boundary of each sensor section abuts the boundary of the adjacent sensor section. These nine sensor sections correspond to the nine locations where the conductive elastic bodies 12 and 22 intersect with the pair of conductor lines 13. At these nine locations, nine sensor sections A11, A12, A13, A21, A22, A23, A31, A32, and A33 are formed, whose capacitance varies depending on the load.

[0065] Each sensor portion includes a conductive elastic body 12, 22 and a pair of conductive wires 13. The pair of conductive wires 13 constitute one electrode (e.g., anode) of the electrostatic capacitor, and the conductive elastic body 12, 22 constitutes the other electrode (e.g., cathode) of the electrostatic capacitor. That is, the conductive member 31 (see Figure 3 (a), (b)) constitute one electrode of the load sensor 1 (capacitive load sensor), the conductive elastic bodies 12 and 22 constitute the other electrode of the load sensor 1 (capacitive load sensor), and the dielectric 32 in the pair of conductor wires 13 (refer to Figure 3 (a) and (b) correspond to the dielectric that specifies the capacitance in the load sensor 1 (capacitive load sensor).

[0066] When a load is applied to each sensor unit in the Z-axis direction, the pair of conductor wires 13 (two conductor wires 13a) are pressed by the load and sink into the conductive elastic bodies 12 and 22. As a result, the contact area between the pair of conductor wires 13 and the conductive elastic bodies 12 and 22 changes, and the electrostatic capacitance between the pair of conductor wires 13 and the conductive elastic bodies 12 and 22 changes.

[0067] The ends of the pair of conductor wires 13 on the negative side of the X axis, the ends of the cable 12 a on the negative side of the Y axis, and the ends of the cable 22 a on the negative side of the Y axis are connected to a detection circuit provided in the load sensor 1 .

[0068] exist Figure 4In the figure, the cables 12a and 22a extending from the three sets of conductive elastic bodies 12 and 22 are represented as lines L11, L12, and L13, and the conductive members 31 within the three pairs of conductive wires 13 are represented as lines L21, L22, and L23. The locations where the conductive elastic bodies 12 and 22 connected to line L11 intersect with lines L21, L22, and L23 are sensor portions A11, A12, and A13, respectively. The locations where the conductive elastic bodies 12 and 22 connected to line L12 intersect with lines L21, L22, and L23 are sensor portions A21, A22, and A23, respectively. The locations where the conductive elastic bodies 12 and 22 connected to line L13 intersect with lines L21, L22, and L23 are sensor portions A31, A32, and A33, respectively.

[0069] When a load is applied to sensor section A11, the contact area between the pair of conductor lines 13 and the conductive elastic bodies 12 and 22 in sensor section A11 increases. Therefore, by detecting the capacitance between line L11 and line L21, the load applied to sensor section A11 can be calculated. Similarly, in other sensor sections, the load applied to those other sensor sections can be calculated by detecting the capacitance between two intersecting lines in those other sensor sections.

[0070] However, if Figure 3 As shown in (a) and (b), if the dielectric 32 is formed to cover the periphery of the conductive member 31, the contact area between the dielectric 32 and the conductive elastic bodies 12 and 22 does not increase linearly with the increase of the load. As a result, the relationship between the load and the electrostatic capacitance is as follows: Figure 5 It is defined by a curved waveform as shown by the solid line. Figure 5 In FIG. 1 , point P0 represents the inflection point where the upper conductive elastic body 22 and the lower conductive elastic body 12 begin to contact around the conductor line 13a when a load is applied to the sensor portion. When the load is calculated based on the capacitance value, the curve further inward than point P0 is used. However, as shown in FIG. Figure 5 Therefore, when calculating the load from the capacitance value, it is necessary to take this waveform into consideration, which complicates the load detection process.

[0071] Here, if the capacitance of the sensor portion is C, the dielectric constant of a vacuum is ε0, and the relative dielectric constant of the dielectric 32 is ε r , assuming that the contact area between the conductive elastic bodies 12 and 22 and the dielectric 32 is S, and the thickness of the dielectric 32 is d, the electrostatic capacitance C is calculated by the following formula (1).

[0072] C=ε0·ε r ·S / d...(1)

[0073] The inventors believe that the capacitance C is proportional to ε as shown in the above formula (1). r , S, d values, by adjusting ε r By adjusting the values ​​of S and d, the relationship between electrostatic capacitance and load can be set to a linear shape.

[0074] In this embodiment, we focus on ε r The contact area S among the values ​​of , S, and d is as follows Figure 6 (a)~ Figure 7 The load sensor 1 is configured as shown in (a). With this configuration, as the load increases, the contact area S of the dielectric 32 changes, so that the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 as the load changes approximates a linear relationship. This makes it easier to detect the load applied to the load sensor 1.

[0075] Figure 6 (a) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before a load is applied. Figure 6 (b) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in a state where a load is applied. Figure 6 In (a) and (b), only the structure on the conductive elastic body 22 side is shown, and the illustration of the conductive elastic body 12 side is omitted. However, on the conductive elastic body 12 side, the same phenomenon as that on the conductive elastic body 22 side occurs due to changes in load.

[0076] exist Figure 6 In (a), D1 represents the direction of contact of the dielectric 32 as the load increases. Figure 6 In the initial state of (a), among the dielectrics 32 formed around the conductive member 31, only the position of the dielectric 32 closest to the conductive elastic body 22 (the position on the most positive side of the Z axis) is in contact with the conductive elastic body 22. Then, if a load is applied to the load sensor 1, Figure 6 As shown in (b), the conductive elastic body 22 is deformed, and the contact between the dielectric 32 and the conductive elastic body 22 advances in the interface direction D1. Figure 6 The angle θ in (b) defines the circumferential contact range between the dielectric 32 and the conductive elastic body 22 by the circumferential angle (hereinafter referred to as "contact angle"). The contact angle θ increases as the load increases.

[0077] Here, the dielectric 32 is composed of, for example, aluminum oxide. The dielectric 32 composed of aluminum oxide is formed on the surface of the aluminum conductive member 31 through an anodic oxidation treatment (aluminum treatment). As a result, an aluminum oxide (aluminum oxide) film is formed on the surface of the conductive member 31. The anodic oxidation treatment (aluminum treatment) is performed by using an inorganic acid solution such as sulfuric acid, oxalic acid, phosphoric acid, or boric acid, or an organic acid solution, at a temperature of 0°C to 80°C, and applying an appropriate voltage (1 to 500V).

[0078] At this time, by adjusting the conditions of the anodizing treatment, a plurality of micropores 33 described later are formed in the dielectric 32 formed on the surface of the conductive member 31. The micropores 33 include, for example, micropores, microcracks, etc. The diameter of the micropores 33 is, for example, greater than 1 nm and less than 100 nm. In addition, by adjusting the conditions of the anodizing treatment, the density of the micropores 33 in the area near the second position P2 away from the first position P1 in the interface direction D1 is set lower than the area near the first position P1 sandwiched between the conductive elastomer 22 and the conductive member 31 in the initial state before the load is applied. The second position P2 is set, for example, to the upper limit position of the range in which the dielectric 32 can contact the conductive elastomer 22 when the load is applied (the position farthest from the first position P1 in the range).

[0079] To form dielectric 32 and micropores 33, for example, conductive member 31 is immersed only halfway in the radial direction in the treatment solution used for alumite treatment. Conductive member 31 is then pulled out of the treatment solution at a predetermined speed while adjusting the temperature and voltage. This forms dielectric 32 on the surface of conductive member 31, and micropores 33 are formed in dielectric 32 so that the density gradually changes along the interface direction D1.

[0080] Figure 7 (a) is a side view schematically showing the structure of the conductor line 13a when viewed in the negative direction of the Y axis. Figure 7 (a) of FIG. 1 also shows an enlarged view schematically showing the micropores 33 formed in the dielectric 32 .

[0081] like Figure 7 As shown in (a), most of the micropores 33 are formed in the dielectric 32. The micropores 33 are formed in the dielectric 32 so that their density (degree of concentration) decreases along the interface direction D1. As a result, the surface area per unit area of ​​the dielectric 32 excluding the micropores 33 (hereinafter referred to as "area density") gradually increases along the interface direction D1. The density of the micropores 33 is set by adjusting the conditions of the anodizing treatment (aluminum treatment) during the formation of the dielectric 32.

[0082] like Figure 6As shown in (a), when the cross-section of the conductive member 31 is circular, if the surface density of the dielectric 32 is uniform throughout the entire circumference, then within a light load range, the contact area between the dielectric 32 and the conductive elastic body 22 increases rapidly as the load increases, while within a heavy load range, the contact area increases slowly as the load increases. In this case, within a light load range, the change in electrostatic capacitance with load changes is rapid, while within a heavy load range, the change in electrostatic capacitance with load changes is slow.

[0083] In contrast, as described above, if a plurality of fine pores 33 are formed in the dielectric 32 and the surface density of the dielectric 32 in the region near the second position P2 is set to be greater than that in the region near the first position P1, then in a light load range, the amount of change in the contact area between the dielectric 32 and the conductive elastic body 22 with a predetermined load amplitude is small, thereby suppressing changes in capacitance. In a heavy load range, the amount of change in the contact area between the dielectric 32 and the conductive elastic body 22 with a predetermined load amplitude is large, thereby increasing changes in capacitance. This allows the change in contact area with changes in load to be made closer to a linear state, and as a result, the relationship between load and capacitance can be made closer to a linear relationship.

[0084] <Effects of Implementation Method 1>

[0085] According to the first embodiment, the following effects are achieved.

[0086] As described above, the contact area between the dielectric 32 and the conductive elastic bodies 12 and 22 changes with the change in load. Figure 5 As shown by the dashed line, the change in capacitance between the conductive elastic body 22 and the conductive member 31 as the load changes is close to a straight line. Therefore, by measuring the capacitance between the conductive elastic bodies 12, 22 and the conductive member 31 and applying a simple proportionality-based process to the measured capacitance, the load applied to the load sensor 1 can be appropriately detected. Consequently, the load applied to the load sensor 1 can be more easily detected.

[0087] like Figure 7 As shown in (a), the dielectric 32 has a plurality of micropores 33 whose density varies in the contact direction D1. As described above, the change in contact area accompanying the change in load can be made close to a linear state, and as a result, the relationship between load and electrostatic capacitance can be made close to a linear relationship.

[0088] like Figure 3As shown in (a) and (b) of FIG. , the dielectric 32 is provided to cover the surface of the conductive member 31. With this structure, the dielectric 32 can be provided between the conductive elastic body 12, 22 and the conductive member 31 simply by covering the surface of the conductive member 31 with the dielectric 32.

[0089] like Figure 3 As shown in (a) and (b), the conductive elastic body 12 is also arranged on the opposing surface 21a of the substrate 21 and the opposing surface 11a of the substrate 11. As the load increases, the contact area of ​​the dielectric 32 changes so that the change in electrostatic capacitance between the conductive elastic bodies 12, 22 and the conductive member 31 as the load changes is close to a straight line. In this way, by arranging the conductive elastic bodies 12, 22 on both substrates 11 and 21, the change in electrostatic capacitance caused by the change in load can be made greater than when only one of the conductive elastic bodies 12, 22 is arranged, thereby improving the load detection accuracy. Furthermore, since the contact area of ​​the dielectric 32 changes as the load increases so that the change in electrostatic capacitance between the conductive elastic bodies 12, 22 and the conductive member 31 as the load changes is close to a straight line, the load applied to the load sensor 1 can be detected simply and accurately.

[0090] <Modification of Implementation Example 1>

[0091] In embodiment 1, as Figure 7 As shown in (a), by forming a plurality of micropores 33 in the dielectric 32, the contact area of ​​the dielectric 32 relative to the conductive elastomer 12, 22 changes with the increase of the load, but the formation of the micropores 33 can also be changed to adjust the surface roughness of the dielectric 32 in the interface direction D1 so that the surface density of the dielectric 32 changes.

[0092] Figure 7 (b) is a diagram schematically showing a cross section of the dielectric 32 when it is cut along the YZ plane.

[0093] In this variation, the dielectric 32 is made of a resin material, typically polyurethane. After the dielectric 32 is formed on the surface of the conductive member 31, the conductive member 31, covered by the dielectric 32, is passed through an annular die having fine irregularities on its inner surface. The annular die then slides along the longitudinal direction of the conductive member 31, forming fine grooves 34 on the surface of the dielectric 32. The surface roughness of the dielectric 32 is set by adjusting the density of the fine irregularities on the inner surface of the annular die so that the spacing of the grooves 34 formed on the surface of the dielectric 32 increases along the interface direction D1. The surface roughness is determined, for example, by the depth s1, spacing s2, and surface spacing s3 of the grooves 34 formed on the surface of the dielectric 32. The depth s1, spacing s2, and surface spacing s3 of the grooves 34 are set so that, even when the dielectric 32 is in close contact with the conductive elastomers 12 and 22, the grooves 34 do not penetrate into the conductive elastomers 12 and 22.

[0094] By setting the surface roughness in this manner, the area corresponding to the surface spacing s3 of the grooves 34 per unit area is set to the surface density of the dielectric 32. In this modification, the surface roughness of the dielectric 32 is adjusted so that the surface density of the dielectric 32 gradually increases in the interface direction D1.

[0095] As described above, in this modified example, the surface density of the dielectric 32 is set to increase along the contact direction D1, with the surface density of the dielectric 32 near the second position P2 being set higher than that near the first position P1. Consequently, similar to the first embodiment described above, in a light load range, the change in the contact area between the dielectric 32 and the conductive elastic body 22 is small when the load is varied within a predetermined range, thereby suppressing changes in capacitance. In a heavy load range, the change in the contact area between the dielectric 32 and the conductive elastic body 22 is large when the load is varied within a predetermined range, thereby increasing changes in capacitance. This allows the change in contact area with changes in load to be made closer to a linear state, resulting in a closer linear relationship between load and capacitance.

[0096] In addition, the method of changing the contact area of ​​the dielectric 32 in the interface direction D1 is not limited to the method of changing the density and surface roughness of the micropores 33. For example, it can also be other methods such as forming depressions or protrusions on the surface of the dielectric 32 and increasing the spacing between the depressions or protrusions along the interface direction D1.

[0097] Furthermore, the change in the contact area does not necessarily need to be continuous in the interface direction D1 , and may also be stepwise in the interface direction D1 .

[0098] <Implementation Method 2>

[0099] In the first embodiment, only the relative dielectric constant ε related to the dielectric is considered. r , contact area S, and thickness d, the relationship between load and capacitance is close to a linear relationship. In contrast, in the second embodiment, attention is paid to ε r For all values ​​of , S, and d, the relationship between load and electrostatic capacitance is close to a linear relationship.

[0100] Figure 8 (a) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before a load is applied according to the second embodiment. Figure 8 (b) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in a state where a load is applied according to the second embodiment. Figure 8 In (a) and (b), only the structure of the conductive elastic body 22 side is shown, and the illustration of the conductive elastic body 12 side is omitted. On the conductive elastic body 12 side, the same phenomenon as that on the conductive elastic body 22 side also occurs according to the change in load.

[0101] exist Figure 8 In the structure (a), dielectric 32 is composed of dielectrics 32a and 32b. Dielectric 32a is formed on the surface of conductive member 31 within a predetermined contact angle θ1, and dielectric 32b is formed on the surface of conductive member 31 within a range greater than contact angle θ1. Dielectric 32a is thicker than dielectric 32b. The relative dielectric constant of dielectric 32b is set to be higher than that of dielectric 32a.

[0102] The dielectric 32a is made of, for example, resin, and the dielectric 32b is made of, for example, metal oxide. For example, the dielectric 32a is made of polyurethane, and the dielectric 32b is made of aluminum oxide.

[0103] A notch C1 is formed at a first position P1 in the dielectric 32a. The notch C1 is formed along the X-axis on the surface of the dielectric 32a, not penetrating the dielectric 32a in the thickness direction. For example, the notch C1 is formed at least within the region where the conductive member 31 and the conductive elastic body 22 overlap when viewed from above. Forming the notch C1 prevents a sudden increase in contact area from the initial state before a load is applied, thereby preventing a sudden increase in capacitance.

[0104] Dielectric 32a and Figure 7 Similarly to the dielectric 32 shown in (b), grooves 34 are formed on the surface. That is, the surface roughness of the dielectric 32a is adjusted so that the surface density of the dielectric 32a gradually increases along the interface direction D1. Figure 7Similarly to case (b), in the range of contact angle θ1, in the range of smaller load, the change in the contact area between the dielectric 32a and the conductive elastomer 22 that changes with the specified load amplitude is smaller, so the change in electrostatic capacitance can be suppressed. In the range of larger load, the change in the contact area between the dielectric 32a and the conductive elastomer 22 that changes with the specified load amplitude is larger, so the change in electrostatic capacitance can be increased.

[0105] Dielectric 32b and Figure 7 Similarly to the dielectric 32 shown in (a), micropores 33 are formed on the surface. The density of the micropores 33 gradually decreases along the interface direction D1, and the surface density of the dielectric 32b gradually increases along the interface direction D1. Figure 7 Similarly to case (a), in a range larger than the contact angle θ1, in a range with smaller loads, the change in the contact area between the dielectric 32b and the conductive elastomer 22 that changes with a specified load amplitude is smaller, so the change in electrostatic capacitance can be suppressed. In a range with larger loads, the change in the contact area between the dielectric 32b and the conductive elastomer 22 that changes with a specified load amplitude is larger, so the change in electrostatic capacitance can be increased.

[0106] Figure 9 (a) represents the contact angle θ and ε r · A graph showing the relationship between the S / d values. Figure 9 (b) is a graph showing the relationship between pressure and electrostatic capacitance.

[0107] exist Figure 9 In (a), the contact angle θ1 (refer to Figure 8 (a) and (b) are set to approximately 55°. In this case, in load sensor 1, the upper conductive elastic body 22 contacts the lower conductive elastic body 12 at a contact angle of approximately 90°. Angle range Rd11 is the contact angle range of 0° to θ1, and angle range Rd12 is the contact angle range of θ1 or greater.

[0108] In the angle range Rd1 1, set to ε r / d=1, along the interface direction D1, the surface density changes from 0% to 100%. When the contact angle is near 0°, such as Figure 8 As shown in (a) and (b), a notch C1 is formed at the first position P1, so the surface density is 0%. In the angle range Rd12, it is set to ε r / d=3, along the interface direction D1, the surface density varies from 33% to 100%. r The value of / d and the value of the surface density change, and ε can be set linearly r The value of S / d is adjusted to a contact angle (90°) at which the upper and lower conductive elastic bodies 12 and 22 come into contact with each other.

[0109] like Figure 9 As shown in (a), if ε r The value of S / d is set linearly, then Figure 9 As shown by the dotted line in (b), the curve representing the relationship between pressure and electrostatic capacitance can be set to a straight line from the point when the load is 0 to point P0. Figure 9 In (b), point P0 corresponds to the state where the upper and lower conductive elastic bodies 12 and 22 begin to contact around the conductor line 13a, that is, Figure 9 The state near 90° in (a).

[0110] <Effects of Implementation Method 2>

[0111] According to the second embodiment, the following effects are achieved.

[0112] In dielectric 32a, a notch C1 is provided in the initial contact area (first position P1). This prevents a sharp increase in contact area in a light load range, and prevents a sharp increase in capacitance in a light load range. Therefore, in a light load range, the relationship between load and capacitance can be more easily made close to a linear relationship.

[0113] As the load increases, the relative permittivity of dielectric 32 changes in the interface direction D1. Specifically, within dielectric 32, the relative permittivity of dielectric 32b within the range larger than contact angle θ1 is greater than the relative permittivity of dielectric 32a within the range of contact angle θ1. By adjusting the contact area and the relative permittivity of dielectric 32 in interface direction D1, the change in capacitance between conductive elastic bodies 12, 22 and conductive member 31 as the load changes can be more smoothly and accurately adjusted to approximate a linear line.

[0114] By varying the material of dielectric 32 in the interface direction D1, the relative permittivity of dielectric 32 varies in the interface direction D1. Specifically, dielectric 32 is composed of dielectric 32a made of polyurethane and dielectric 32b made of aluminum oxide, which has a greater relative permittivity than polyurethane. This allows the capacitance between conductive elastic bodies 12 and 22 and conductive member 31 to change more smoothly with changes in load, resulting in a near-linear change.

[0115] The thickness of dielectric 32a is greater than that of dielectric 32b. That is, the thickness of dielectric 32 varies in the interface direction D1. The capacitance per unit area of ​​dielectric 32 is inversely proportional to its thickness. Therefore, by further adjusting the thickness of dielectric 32a, the change in capacitance between conductive elastic bodies 12, 22 and conductive member 31 accompanying changes in load can be smoothed and accurately made closer to a straight line.

[0116] <Modification Example 1 of Implementation Example 2>

[0117] In embodiment 2, as Figure 8 As shown in (a) and (b), dielectric 32 is composed of four (two pairs) dielectrics, but may also be composed of another number of dielectrics. In this modified example, dielectric 32 is composed of eight dielectrics 32a, 32b, 32c, and 32d (four pairs). In addition, in this modified example, the curve representing the relationship between pressure and electrostatic capacitance is close to two straight lines with different slopes.

[0118] Figure 10 Schematically shows the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before the load is applied according to this modification. Figure 10 Only the structure on the conductive elastic body 22 side is shown.

[0119] exist Figure 10 In the structure, the dielectric 32a is formed on the surface of the conductive component 31 in a range below the contact angle θ2, the dielectric 32b is formed on the surface of the conductive component 31 in a range greater than the contact angle θ2 and less than the contact angle θ3, the dielectric 32c is formed on the surface of the conductive component 31 in a range greater than the contact angle θ3 and less than the contact angle θ4, and the dielectric 32d is formed on the surface of the conductive component 31 in a range greater than the contact angle θ4.

[0120] The thicknesses of dielectrics 32a and 32c are equal, and the thicknesses of dielectrics 32b and 32d are equal. The thicknesses of dielectrics 32a and 32c are greater than the thicknesses of dielectrics 32b and 32d. The relative permittivity of dielectrics 32a and 32c is equal, and the relative permittivity of dielectrics 32b and 32d is equal. The relative permittivity of dielectrics 32b and 32d is higher than the relative permittivity of dielectrics 32a and 32c.

[0121] The dielectrics 32a and 32c are formed of resin, for example, and the dielectrics 32b and 32d are formed of metal oxide, for example. For example, the dielectrics 32a and 32c are formed of polyurethane, and the dielectrics 32b and 32d are formed of aluminum oxide. Figure 8 Similarly to (a) and (b), a notch C1 is formed.

[0122] Dielectrics 32a, 32c and Figure 7 Similarly to the dielectric 32 shown in (b), grooves 34 are formed on the surface. That is, the surface roughness of the dielectrics 32a and 32c is adjusted so that the surface density of the dielectrics 32a and 32c gradually increases along the interface direction D1. Figure 7Similarly to case (b), in the range of contact angle θ2 and in the range from θ3 to θ4, the change in the contact area between the dielectric 32a and the conductive elastic body 22, which changes with a predetermined load amplitude, becomes larger as the load increases, thereby increasing the change in electrostatic capacitance.

[0123] Dielectrics 32b, 32d and Figure 7 The surface density of the dielectric 32b gradually increases along the interface direction D1. Figure 7 Similarly to case (a), in the range of contact angles from θ2 to θ3 and in the range of contact angles greater than θ4, the change in contact area between the dielectric 32b and the conductive elastomer 22, which changes at a prescribed load amplitude, increases as the load increases, thereby increasing the change in electrostatic capacitance.

[0124] Figure 11 (a) represents the contact angle θ and ε r · A graph showing the relationship between the S / d values. Figure 11 (b) is a graph showing the relationship between pressure and electrostatic capacitance.

[0125] exist Figure 11 In (a), the contact angles θ2, θ3, and θ4 (see Figure 10 ) are set to approximately 16°, approximately 35°, and approximately 80°, respectively. In this case, in the load sensor 1, the upper conductive elastic body 22 contacts the lower conductive elastic body 12 at a contact angle of approximately 90°. Angle range Rd21 covers the contact angle range of 0° to θ2, while angle range Rd22 covers the contact angle range greater than θ2 and not greater than θ3. Furthermore, angle range Rd23 covers the contact angle range greater than θ3 and not greater than θ4, and angle range Rd24 covers the contact angle range greater than θ4.

[0126] In the angle ranges Rd21 and Rd23, set to ε r / d=1, in the angle range Rd22 and Rd24, set to ε r / d = 3. In the angle range Rd21, the areal density varies along the junction direction D1 from 0% to 100%, in the angle range Rd22, the areal density varies along the junction direction D1 from 33% to 66%, in the angle range Rd23, the areal density varies along the junction direction D1 from 50% to 100%, and in the angle range Rd24, the areal density varies along the junction direction D1 from 33% to 100%.

[0127] like Figure 11 As shown in (a), if ε r ·The value of S / d is set, then Figure 11As shown by the dotted line in (b), from the point where the load is 0 to the point P0, the curve representing the relationship between pressure and electrostatic capacitance can be made close to two straight lines with different slopes.

[0128] <Effects of Modification Example 1 of Implementation Example 2>

[0129] According to this modification example, the following effects are achieved.

[0130] like Figure 11 As shown by the dotted lines in (b), the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 as the load changes is close to two straight lines. Therefore, even in this case, by measuring the capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 and applying a simple proportionality-based process to the measured capacitance, the load applied to the load sensor 1 can be appropriately detected. This makes it possible to more easily detect the load applied to the load sensor 1.

[0131] <Modification Example 2 of Implementation Example 2>

[0132] In embodiment 2, as Figure 8 As shown in (a) and (b), the dielectric 32 is composed of dielectrics 32a and 32b having different relative permittivities, so that the relative permittivity of the dielectric 32 varies in the interface direction D1. However, other methods can also be used to vary the relative permittivity of the dielectric 32 in the interface direction D1. In this modified example, the dielectric 32 includes a filler 35, so that the relative permittivity of the dielectric 32 varies in the interface direction D1.

[0133] Figure 12 Schematically shows the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before the load is applied according to this modification. Figure 12 Only the structure on the conductive elastic body 22 side is shown.

[0134] exist Figure 12 In the structure, the dielectric 32 is made of, for example, resin or metal oxide. The dielectric 32 is made of, for example, polyurethane or aluminum oxide. The dielectric 32 includes a plurality of fillers 35. The fillers 35 are, for example, Au (gold), Ag (silver), Cu (copper), C (carbon), resin, etc. In the case where the dielectric 32 is made of a material other than aluminum oxide, the fillers 35 may also be aluminum oxide. In this modification, the fillers 35 are included in the dielectric 32 so that the density of the fillers 35 changes in the junction direction D1. In this modification, the density of the fillers 35 is adjusted so that the relative dielectric constant of the dielectric 32 gradually increases in the junction direction D1.

[0135] also, Figure 7 The micropore 33 shown in (a) or Figure 7 The density of the grooves 34 shown in (b) is adjusted in the junction direction D1 and formed in the dielectric 32 , whereby the surface density of the dielectric 32 gradually increases along the junction direction D1 .

[0136] As described above, according to this modification, the density of the filler 35 changes in the interface direction D1, thereby increasing the relative permittivity of the dielectric 32 in the interface direction D1. Therefore, in this modification, the relationship between load and capacitance can be made close to a straight line.

[0137] Alternatively, the thickness of the dielectric 32 can be varied so as to gradually decrease in the interface direction D1. In this case, the capacitance per unit area of ​​the dielectric 32 gradually increases in the interface direction D1. Therefore, by further adjusting the thickness of the dielectric 32 in this manner, the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 as the load changes can be smoothed and accurately made to approximate a linear line. The thickness of the dielectric 32 can also be varied in a stepwise manner in the interface direction D1.

[0138] <Implementation Method 3>

[0139] In the first and second embodiments and the modified examples, the dielectric 32 is arranged on the surface of the conductive member 31 . However, in the third embodiment, the dielectric is formed on the surfaces of the conductive elastic bodies 12 and 22 .

[0140] Figure 13 (a) is a diagram schematically showing the relationship between the dielectrics 15 and 23 and the conductive member 31 in the initial state before a load is applied according to the third embodiment. Figure 13 (b) is a diagram schematically showing the relationship between the dielectrics 15 and 23 and the conductive member 31 in a state where a load is applied according to the third embodiment.

[0141] like Figure 13 As shown in (a) and (b), in the third embodiment, dielectrics 15 and 23 are formed on the surfaces of the conductive elastic bodies 12 and 22, respectively. Figure 13 In (a), D2 represents the interface direction in which the dielectrics 15 and 23 come into contact with each other as the load increases.

[0142] exist Figure 13 In the initial state of (a), only the closest position of the conductive member 31 and the conductive elastic body 12, 22 in the area of ​​the dielectric 15, 23 is in contact with the conductive member 31. Then, if a load is applied to the load sensor 1, Figure 13 As shown in (b), the conductive elastic bodies 12 and 22 are deformed, and the contact between the dielectrics 15 and 23 and the conductive member 31 advances in the interface direction D2. Figure 13(b) θ is the contact angle. The contact angle θ increases as the load increases.

[0143] Here, dielectrics 15 and 23, like dielectric 32 in the modified example of Embodiment 1, are made of a resin material, typically polyurethane. Dielectrics 15 and 23 are formed with a plurality of grooves, similar to groove 34 in the modified example of Embodiment 1. In the initial state before load application, if the position of dielectrics 15 and 23 sandwiched between conductive elastic bodies 12 and 22 and conductive member 31 is set to first position P1, the surface roughness of dielectrics 15 and 23 is adjusted so that the surface density of dielectrics 15 and 23 gradually increases in the interface direction D2.

[0144] In the third embodiment, the surface density of the dielectrics 15 and 23 increases along the contact direction D2. Therefore, similar to the first embodiment, when a load is applied, the change in contact area accompanying the change in load can be made close to a linear state. As a result, the relationship between load and capacitance can be made close to a linear relationship. Therefore, similar to the first embodiment, by measuring the capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 and applying a simple proportionality-based processing to the measured capacitance, the load applied to the load sensor 1 can be appropriately detected, making it easier to detect the load applied to the load sensor 1.

[0145] Furthermore, in this embodiment, dielectric 15 may be configured such that multiple dielectrics having different relative permittivities are arranged in the interface direction D2, and dielectric 23 may be configured such that multiple dielectrics having different relative permittivities are arranged in the interface direction D2. Furthermore, the thickness of dielectrics 15 and 23 may vary in the interface direction D2, and notches C1 may be formed at first positions P1 of dielectrics 15 and 23. Furthermore, similar to Modification 2 of Embodiment 2, dielectrics 15 and 23 may contain fillers, and the relative permittivities of dielectrics 15 and 23 may be adjusted in the interface direction D2 by adjusting the density of the fillers.

[0146] <Implementation Method 4>

[0147] In the first and second embodiments and the modified examples, the conductive elastic body is disposed on the linear conductive member 31 . However, in the fourth embodiment, the conductive elastic body is disposed on the conductive member having a spherical shape.

[0148] Figure 14 (a) is a plan view schematically showing the structure of the load sensor 1 according to the fourth embodiment when viewed in the negative direction of the Z axis. Figure 14 (b) is a diagram schematically showing a cross section of the load sensor 1 according to the fourth embodiment, taken along the YZ plane. Figure 14In (a), for convenience, only the base material 41 and the conductive member 42 are shown.

[0149] The load sensor 1 includes a substrate 41, a conductive member 42, a dielectric 43, a substrate 44, and a conductive elastic body 45. The substrates 41 and 44 have a square shape when viewed in the Z-axis direction and are made of the same material as the substrates 11 and 21 of the above-mentioned embodiments 1 and 2 and the modified examples. The conductive member 42 is a conductive member having a spherical shape. The conductive member 42 has a dome shape formed by the upper part of a sphere and is arranged on the upper surface of the substrate 41. The conductive member 42 is made of the same material as the conductive member 31 of the above-mentioned embodiments 1 and 2 and the modified examples. The dielectric 43 is arranged on the upper surface of the conductive member 42 and is made of a resin or a metal oxide. The dielectric 43 is made of, for example, polyurethane or aluminum oxide. The conductive elastic body 45 is made of the same material as the conductive elastic bodies 12 and 22 of the above-mentioned embodiments 1 and 2 and the modified examples. The conductive elastic body 45 is arranged on the surface of the substrate 44 on the negative side of the Z-axis.

[0150] In the fourth embodiment, the first position P1 is the center of the conductive member 42 when viewed in the Z-axis direction. In the fourth embodiment, the direction extending radially from the first position P1 along the curved surface of the conductive member 42 is the interface direction D1. In the fourth embodiment, a plurality of micropores are formed in the dielectric 43 along the interface direction D1, similar to the micropores 33 in the first embodiment. The density of the micropores in the dielectric 43 decreases along the interface direction D1. Consequently, the surface density of the dielectric 43 increases along the interface direction D1.

[0151] In the fourth embodiment, when a load is applied from outside the substrates 41 and 44, the conductive elastic body 45 is pressed against the conductive member 42 via the dielectric 43. Consequently, the capacitance between the dielectric 43 and the conductive elastic body 45 changes according to the load, and the load is calculated based on the capacitance. Furthermore, in the fourth embodiment, as in the first embodiment described above, the surface density of the dielectric 43 increases along the interface direction D1, thereby allowing the graph representing the relationship between load and capacitance to approximate a straight line.

[0152] In addition, in the fourth embodiment, Figure 7 Similarly to the modification of the first embodiment shown in (b), grooves are formed in the dielectric 43 instead of the micropores, and the surface roughness of the dielectric 43 can be adjusted so that the surface density of the dielectric 43 increases along the interface direction D1.

[0153] Furthermore, in Embodiment 4, similar to Embodiment 2 and Modification 1 of Embodiment 2, dielectric 43 may also be configured such that a plurality of dielectrics having different relative permittivities are arranged in the interface direction D1, and the thickness of dielectric 43 may vary in the interface direction D1. Furthermore, a circular notch may be formed at the first position P1 of dielectric 43. Furthermore, similar to Modification 2 of Embodiment 2, dielectric 43 may include a filler, and the relative permittivity of dielectric 43 in the interface direction D1 may be adjusted by adjusting the density of the filler.

[0154] <Other Changes>

[0155] In the above-described first to third embodiments, dielectric 32 is composed of a single material in the thickness direction. However, it may also have a structure in which two or more materials are stacked in the thickness direction. That is, the number of layers of dielectric 32 is not limited to one; it may be two or more. Furthermore, the number of stacked layers of dielectric 32 may vary depending on the position in the interface directions D1 and D2. For example, near the first position P1, the number of stacked layers may be two, while near the second position P2, the number of stacked layers may be one. Furthermore, in the above-described fourth embodiment, the number of stacked layers of dielectric 43 is not limited to one.

[0156] Furthermore, in the above-mentioned first to fourth embodiments, micropores are provided in the dielectric material containing aluminum oxide in order to change the surface density in the interface directions D1 and D2. However, it is also possible to Figure 7 As shown in (b), by adjusting the surface roughness of the dielectric material containing aluminum oxide, the surface density changes in the interface directions D1 and D2.

[0157] In the above-mentioned first and second embodiments, the contact area between the dielectric 32 and the conductive elastic bodies 12 and 22 is changed according to the load, and the dielectric 32 is provided with micropores 33 or grooves 34. However, the present invention is not limited thereto, and the dielectric 32 may not have micropores 33 or grooves 34, or the conductive elastic bodies 12 and 22 may have micropores or grooves so that the density is increased in the interface direction D2 (see FIG. Figure 13 (a) and (b)) are reduced. In this case, since the surface density of the conductive elastic bodies 12 and 22 increases in the interface direction D2, the same effects as those of the above-mentioned embodiments can be achieved. Similarly, in the above-mentioned embodiment 3, micropores or grooves can be formed in the conductive elastic bodies 12 and 22, and in the above-mentioned embodiment 4, micropores or grooves can be formed in the conductive elastic body 45.

[0158] In the above-mentioned embodiments 1 to 3, the cross-sectional shape of the conductive member 31 is circular, but the cross-sectional shape of the conductive member 31 is not limited to circular and may be elliptical, quasi-circular, etc. Furthermore, the conductive member 31 may be composed of stranded wires formed by twisting a plurality of conductive members.

[0159] In addition, in the above-mentioned embodiments 1 to 3, if Figure 2 As shown in (b) of FIG. 1 , the load sensor 1 includes three pairs of conductor wires 13. However, the load sensor 1 only needs to include at least one pair of conductor wires 13. For example, the load sensor 1 may include only one pair of conductor wires 13.

[0160] In addition, in the above-mentioned embodiments 1 to 3, if Figure 2 As shown in (b), the load sensor 1 includes three sets of conductive elastic bodies 12, 22 facing each other vertically, but it is sufficient to include at least one set of conductive elastic bodies 12, 22. For example, the load sensor 1 may include only one set of conductive elastic bodies 12, 22.

[0161] Furthermore, in the above-described first to third embodiments, the conductive elastic body 22 on the substrate 21 side can be omitted. In this case, the pair of conductor wires 13 are sandwiched between the conductive elastic body 12 on the substrate 11 side and the opposing surface 21a of the substrate 21. Depending on the load, the pair of conductor wires 13 sink into the conductive elastic body 12, causing the capacitance in each sensor section to change. Furthermore, when the conductive elastic body 22 on the substrate 21 side is omitted, a sheet-like substrate can be provided in place of the substrate 21.

[0162] Furthermore, in the first to third embodiments described above, the pair of conductor lines 13 is configured such that two conductor lines 13a are arranged side by side in the Y-axis direction and connected at their ends in the X-axis direction. However, a single conductor line may be provided instead of a pair of conductor lines 13, or three or more conductor lines may be provided. Furthermore, the shape of the pair of conductor lines 13 in plan view may not be a straight line, but may be a wavy shape.

[0163] Furthermore, various modifications can be appropriately made to the embodiments of the present invention within the scope of the technical concept described in the claims.

[0164] -Explanation of symbols-

[0165] 1 load cell

[0166] 11, 21 base materials (first base material, second base material)

[0167] 1 1a, 21a facing surfaces

[0168] 12, 22 conductive elastomer

[0169] 15, 23, 32 dielectrics

[0170] 31 conductive components

[0171] 33 micropores

[0172] 35 fillers

[0173] 41, 44 base materials (first base material, second base material)

[0174] 42 conductive components

[0175] 43 dielectric

[0176] 45 conductive elastomer

[0177] C1 gap.

Claims

1. A load sensor comprising: The first substrate and the second substrate are arranged to face each other; a conductive elastic body disposed on the opposite surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and The contact area of ​​the dielectric changes with an increase in load so that the change in electrostatic capacitance between the conductive elastic body and the conductive member with a change in load is close to a linear structure. The dielectric has a plurality of fine pores whose density changes in a junction direction in which contact of the dielectric progresses as a load increases.

2. A load sensor comprising: The first substrate and the second substrate are arranged to face each other; a conductive elastic body disposed on the opposite surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and The contact area of ​​the dielectric changes with an increase in load so that the change in electrostatic capacitance between the conductive elastic body and the conductive member with a change in load is close to a linear structure. The surface roughness of the dielectric surface is adjusted so that the surface density of the dielectric changes in a contact direction of the dielectric as the load increases.

3. A load sensor comprising: The first substrate and the second substrate are arranged to face each other; a conductive elastic body disposed on the opposite surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and The contact area of ​​the dielectric changes with an increase in load so that the change in electrostatic capacitance between the conductive elastic body and the conductive member with a change in load is close to a linear structure. A notch is provided in the dielectric in the initial contact region.

4. A load sensor comprising: The first substrate and the second substrate are arranged to face each other; a conductive elastic body disposed on the opposite surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and The contact area of ​​the dielectric changes with an increase in load so that the change in electrostatic capacitance between the conductive elastic body and the conductive member with a change in load is close to a linear structure. In the interface direction as the contact of the dielectric progresses with an increase in load, the relative dielectric constant of the dielectric changes.

5. The load sensor according to claim 4, wherein By making the material of the dielectric different in the junction direction, the relative dielectric constant of the dielectric changes in the junction direction.

6. The load sensor according to claim 4, wherein The dielectric comprises a filler, By varying the density of the filler in the interface direction, the relative dielectric constant of the dielectric varies in the interface direction.

7. A load sensor comprising: The first substrate and the second substrate are arranged to face each other; a conductive elastic body disposed on the opposite surface of the first substrate; a conductive member disposed between the second substrate and the conductive elastic body; a dielectric disposed between the conductive elastic body and the conductive member; and The contact area of ​​the dielectric changes with an increase in load so that the change in electrostatic capacitance between the conductive elastic body and the conductive member with a change in load is close to a linear structure. The thickness of the dielectric changes in the junction direction as the contact of the dielectric progresses with an increase in load.

8. The load sensor according to any one of claims 1 to 7, wherein: The conductive member is a conductive wire.

9. The load sensor according to claim 8, wherein The dielectric is provided to cover the surface of the wire.

10. The load sensor according to any one of claims 1 to 7, wherein The conductive member is a conductive member having a spherical shape.

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