Load sensor

Abstract

A load sensor (1) comprises: base materials (11, 21) disposed so as to face each other; conductive elastic bodies (12, 22) respectively disposed on the facing surfaces of the base materials (11, 21); a conductive member (31) disposed between the base material (11) and the conductive elastic body (22); a dielectric (32) disposed between the conductive elastic bodies (12, 22) and the conductive member (31); and a configuration in which a contact area of the dielectric (32) changes in association with an increase in a load such that a change in capacitance between the conductive elastic bodies (12, 22) and the conductive member (31) in association with a change in the load becomes close to a straight line.

Description

Technical Field

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

Background Art

[0002] Load sensors are widely used in fields such as industrial equipment, robots, and vehicles. In recent years, with the development of computer control technology and the improvement of design quality, the development of electronic devices that use a variety of free-form surfaces, such as humanoid robots and automotive interior parts, has advanced. Along with this, it is required to mount high-performance load sensors on each free-form surface.

[0003] Patent Document 1 below describes a pressure-sensitive element including a first conductive member made of sheet-like conductive rubber, a linear second conductive member sandwiched between the first conductive member and a base material, and a dielectric formed so as to cover the second conductive member. In this configuration, as the load increases, the contact area between the first conductive member and the dielectric increases, and accordingly, the capacitance between the first conductive member and the second conductive member increases. Therefore, by detecting the value of the capacitance between the first conductive member and the second conductive member, the load applied to the pressure-sensitive element can be detected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above configuration, since the second conductive member is linear, the contact area does not increase linearly in response to an increase in load, and the relationship between the load and the capacitance is defined by a curved waveform. Therefore, when obtaining the load from the value of the capacitance, it is necessary to take this waveform into account, resulting in a problem that the load detection process becomes complicated.

[0006] In view of such problems, an object of the present invention is to provide a load sensor capable of more easily detecting a load applied to the load sensor.

Means for Solving the Problems

[0007] The main aspect of the present invention relates to a load sensor. The load sensor according to this aspect includes a first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, and the capacitance between the conductive elastic body and the conductive member changes linearly as the load changes. The dielectric has a plurality of micropores whose density changes in a tangential direction in which contact of the dielectric progresses as the load increases. 。

[0008] According to the load sensor according to this aspect, the change in the capacitance between the conductive elastic body and the conductive member as the load changes can be approximated to a straight line. Therefore, by measuring the value of the capacitance between the conductive elastic body and the conductive member and applying a simple process based on a proportional relationship to the measured capacitance value, the load applied to the load sensor can be properly detected. Thus, the load applied to the load sensor can be detected more easily.

Effects of the Invention

[0009] As described above, according to the present invention, it is possible to provide a load sensor capable of more easily detecting a load applied to the load sensor.

[0010] The effects or significance of the present invention will become clearer from the description of the embodiments shown below. However, the embodiments shown below are merely examples when implementing the present invention, and the present invention is not limited to those described in the following embodiments at all.

Brief Description of the Drawings

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[0012] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

Mode for Carrying Out the Invention

[0013] The load sensor according to the present invention is applicable to a load sensor of a management system or an electronic device that performs processing according to an applied load.

[0014] Examples of the management system include an inventory management system, a driver monitoring system, a coaching management system, a security management system, a caregiving and childcare management system, and the like.

[0015] In the inventory management system, for example, a load sensor provided on a storage shelf detects the load of the stocked inventory, and the type and quantity of the products present on the storage shelf are detected. As a result, inventory can be efficiently managed and labor saving can be achieved in stores, factories, warehouses, etc. Also, a load sensor provided inside a refrigerator detects the load of the food inside the refrigerator, and the type, quantity, and amount of the food inside the refrigerator are detected. As a result, a menu using the food inside the refrigerator can be automatically proposed.

[0016] In the driver monitoring system, for example, a load sensor provided on a steering device monitors the load distribution (e.g., gripping force, gripping position, stepping force) on the steering device by the driver. Also, a load sensor provided on a vehicle seat monitors the load distribution (e.g., center of gravity position) on the vehicle seat by the driver in the seated state. As a result, the driving state (such as drowsiness and mental state) of the driver can be fed back.

[0017] In the coaching management system, for example, a load sensor provided on the sole of a shoe monitors the load distribution on the sole of the foot. As a result, it is possible to correct or guide to an appropriate walking state or running state.

[0018] In the security management system, for example, a load sensor provided on the floor detects the load distribution when a person passes through, and the body weight, stride, passing speed, and shoe sole pattern are detected. As a result, it becomes possible to identify the person who has passed by comparing these detected information with data.

[0019] In a nursing and childcare management system, for example, the load distribution of the human body on bedding and toilet seats is monitored by load sensors provided on the bedding and toilet seats. Thereby, it is possible to estimate what kind of action a person is trying to take at the position of the bedding and toilet seat, and prevent falls and drops.

[0020] Examples of electronic devices include in-vehicle devices (such as car navigation systems and audio devices), home appliances (such as electric kettles and IH cooking heaters), smartphones, electronic paper, e-book readers, PC keyboards, game controllers, smartwatches, wireless earphones, touch panels, electronic pens, penlights, illuminated clothing, musical instruments, etc. In an electronic device, a load sensor is provided in an input unit that receives an input from a user.

[0021] The load sensor in the following embodiments is a capacitance-type load sensor typically provided in the load sensors of the above-described management systems and electronic devices. Such load sensors may also be referred to as "capacitance-type pressure-sensitive sensor elements", "capacitive pressure detection sensor elements", "pressure-sensitive switch elements", etc. Further, the load sensor in the following embodiments is connected to a detection circuit, and a load detection device is constituted by the load sensor and the detection circuit. The following embodiments are one embodiment of the present invention, and the present invention is not limited to the following embodiments in any way.

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, X, Y, and Z axes orthogonal to each other are added to each figure. The Z-axis direction is the height direction of the load sensor 1.

[0023] <Embodiment 1> FIG. 1(a) is a perspective view schematically showing a base material 11 and three conductive elastic bodies 12 installed on a facing surface 11a (the surface on the positive Z-axis side) of the base material 11.

[0024] The base material 11 is an insulating member having elasticity and has a flat plate shape parallel to the X-Y plane. The base material 11 is composed of a non-conductive resin material or a non-conductive rubber material. The resin material used for the base material 11 is, for example, at least one resin material selected from the group consisting of styrene resins, silicone resins (such as polydimethylpolysiloxane (PDMS)), acrylic resins, rotaxane resins, and urethane resins. The rubber material used for the base material 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-propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, and natural rubber.

[0025] The conductive elastic body 12 is formed on the opposing surface 11a (the surface on the positive Z-axis side) of the base material 11. In FIG. 1(a), three conductive elastic bodies 12 are formed on the opposing surface 11a of the base material 11. The conductive elastic body 12 is a conductive member having elasticity. Each conductive elastic body 12 has a strip shape that is long in the Y-axis direction and is formed side by side at a predetermined interval in the X-axis direction. A cable 12a electrically connected to the conductive elastic body 12 is installed at the end of each conductive elastic body 12 on the negative Y-axis side.

[0026] The conductive elastic body 12 is formed on the opposing surface 11a of the base material 11 by a printing method such as screen printing, gravure printing, flexographic printing, offset printing, and gravure offset printing. According to these printing methods, it is possible to form the conductive elastic body 12 on the opposing surface 11a of the base material 11 with a thickness of about 0.001 mm to 0.5 mm. However, the forming method of the conductive elastic body 12 is not limited to the printing method.

[0027] 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.

[0028] The resin material used for the conductive elastic body 12 is the same as the resin material used for the base material 11 described above. For example, it is at least one resin material selected from the group consisting of styrene resins, silicone resins (such as polydimethylpolysiloxane (e.g., PDMS)), acrylic resins, rotaxane resins, and urethane resins. The rubber material used for the conductive elastic body 12 is the same as the rubber material used for the base material 11 described above. For example, it is 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-propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, and natural rubber.

[0029] The conductive filler used for the conductive elastic body 12 is, for example, at least one material selected from the group consisting of 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 (that is, a composite composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS)), and conductive fibers such as metal-coated organic fibers and metal wires (in fibrous state).

[0030] FIG. 1(b) is a perspective view schematically showing a state in which three pairs of conductor lines 13 are installed on the base material 11.

[0031] A pair of conductor lines 13 is formed by bending one conductor line extending in the X-axis direction, and includes two conductor lines 13a extending in the negative X-axis direction from the bending position. The two conductor lines 13a constituting the pair of conductor lines 13 are arranged side by side with a predetermined interval. The pair of conductor lines 13 is arranged on the upper surfaces of the three conductive elastic bodies 12 shown in FIG. 1(a). Here, three pairs of conductor lines 13 are arranged on the upper surfaces of the three conductive elastic bodies 12.

[0032] The three pairs of conductor lines 13 are arranged so as to intersect the conductive elastic body 12, and are arranged side by side at a predetermined interval along the longitudinal direction (Y-axis direction) of the conductive elastic body 12. The pair of conductor lines 13 extends in the X-axis direction so as to straddle the three conductive elastic bodies 12. The conductor line 13a is composed of a linear conductive member and a dielectric formed on the surface of the conductive member. The configuration of the conductor line 13a will be described later with reference to FIGS. 3(a) and (b).

[0033] After the three pairs of conductor lines 13 are arranged as shown in FIG. 1(b), each pair of conductor lines 13 is installed on the base material 11 with the thread 14 so as to be movable in the extending direction (X-axis direction) of the pair of conductor lines 13. In the example shown in FIG. 1(b), twelve threads 14 connect the pair of conductor lines 13 to the base material 11 at positions other than the positions where the conductive elastic body 12 and the pair of conductor lines 13 overlap. The thread 14 is composed of chemical fiber, natural fiber, or a mixed fiber thereof.

[0034] FIG. 2(a) is a perspective view schematically showing a base material 21 disposed on top of the base material 11 and three conductive elastic bodies 22 installed on the facing surface 21a (the surface on the negative Z-axis side) of the base material 21.

[0035] The base material 21 has the same size and shape as the base material 11 and is composed of the same material as the base material 11. The conductive elastic body 22 is formed at a position facing the conductive elastic body 12 on the facing surface 21a (the surface on the negative Z-axis side) of the base material 21 and is formed side by side at a predetermined interval in the X-axis direction. The conductive elastic body 22 has the same size and shape as the conductive elastic body 12 and is composed of the same material as the conductive elastic body 12. The conductive elastic body 22 is formed on the surface on the negative Z-axis side of the base material 21 by a predetermined printing method in the same manner as the conductive elastic body 12. The formation method of the conductive elastic body 22 is not limited to the printing method. A cable 22a electrically connected to the conductive elastic body 22 is installed at the end on the negative Y-axis side of each conductive elastic body 22.

[0036] FIG. 2(b) is a perspective view schematically showing a state in which the structure of FIG. 2(a) is installed on the structure of FIG. 1(b).

[0037] From above (the positive Z-axis side) of the structure shown in FIG. 1(b), the structure shown in FIG. 2(a) is disposed. At this time, the base material 11 and the base material 21 are disposed such that the opposing surface 11a and the opposing surface 21a face each other, and the conductive elastic body 12 and the conductive elastic body 22 are disposed so as to overlap. Then, the outer peripheral four sides of the base material 21 are connected to the outer peripheral four sides of the base material 11 with a silicone rubber-based adhesive, a thread, or the like, whereby the base material 11 and the base material 21 are fixed. Thereby, the three pairs of conductor lines 13 are sandwiched by the three conductive elastic bodies 12 and the three conductive elastic bodies 22. Thus, as shown in FIG. 2(b), the load sensor 1 is completed.

[0038] FIGS. 3(a) and 3(b) are cross-sectional views schematically showing the periphery of the conductor line 13a when viewed in the negative X-axis direction. FIG. 3(a) shows a state where no load is applied, and FIG. 3(b) shows a state where a load is applied.

[0039] As shown in FIGS. 3(a) and 3(b), the conductor line 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.

[0040] The conductive member 31 is composed of, for example, a conductive metal material. In addition, the conductive member 31 may be composed of a core wire made of glass and a conductive layer formed on the surface thereof, or may be composed of a core wire made of resin and a conductive layer formed on the surface thereof. In Embodiment 1, the conductive member 31 is composed of aluminum. The dielectric 32 has electrical insulation properties and is composed of, for example, a resin material, a ceramic material, a metal oxide material, or the like.

[0041] In addition, as the conductive member 31, valve metals such as titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and tungsten (W), molybdenum (Mo), copper (Cu), nickel (Ni), silver (Ag), gold (Au), etc. are used. Also, the diameter of the conductive member 31 may be, for example, 10 μm or more and 1500 μm or less, or may be 50 μm or more and 800 μm or less. Such a configuration of the conductive member 31 is preferable from the viewpoints of the strength and resistance of the conductive member. The thickness of the dielectric 32 is preferably 5 nm or more and 100 μm or less, and can be appropriately selected according to the design of sensor sensitivity and the like.

[0042] As shown in FIG. 3(a), when no load is applied, the forces applied between the conductive elastic body 12 and the conductor line 13a, and between the conductive elastic body 22 and the conductor line 13a are substantially zero. From this state, as shown in FIG. 3(b), when an upward load is applied to the lower surface of the base material 11 and a downward load is applied to the upper surface of the base material 21, the conductive elastic bodies 12 and 22 are deformed by the conductor line 13a.

[0043] As shown in FIG. 3(b), when a load is applied, the conductor line 13a is brought closer to the conductive elastic bodies 12 and 22 so as to be wrapped by the conductive elastic bodies 12 and 22, and the contact area between the conductor line 13a and the conductive elastic bodies 12 and 22 increases. Thereby, the capacitance between the conductive member 31 and the conductive elastic body 12 and the capacitance between the conductive member 31 and the conductive elastic body 22 change. Then, by detecting the capacitance of the region of the conductor line 13a, the load applied to this region is calculated.

[0044] FIG. 4 is a plan view schematically showing the inside of the load sensor 1 when viewed in the negative Z-axis direction. In FIG. 4, for convenience, the illustration of the thread 14 is omitted.

[0045] In the measurement area R of the load sensor 1, nine sensor units arranged in the X-axis direction and the Y-axis direction are set. Specifically, nine regions obtained by dividing the measurement area R into three equal parts in the X-axis direction and three equal parts in the Y-axis direction are assigned to the nine sensor units. The boundary of each sensor unit is in contact with the boundary of the adjacent sensor unit. The nine sensor units correspond to nine positions where the conductive elastic bodies 12 and 22 intersect with a pair of conductor lines 13. At these nine positions, nine sensor units A11, A12, A13, A21, A22, A23, A31, A32, and A33 whose capacitance changes according to the load are formed.

[0046] Each sensor unit includes the conductive elastic bodies 12 and 22 and a pair of conductor lines 13. The pair of conductor lines 13 constitutes one electrode (for example, the anode) of the capacitance, and the conductive elastic bodies 12 and 22 constitute the other electrode (for example, the cathode) of the capacitance. That is, the conductive member 31 (see FIGS. 3(a) and 3(b)) in the pair of conductor lines 13 constitutes one electrode of the load sensor 1 (capacitance type load sensor), the conductive elastic bodies 12 and 22 constitute the other electrode of the load sensor 1 (capacitance type load sensor), and the dielectric 32 (see FIGS. 3(a) and 3(b)) in the pair of conductor lines 13 corresponds to the dielectric that defines the capacitance in the load sensor 1 (capacitance type load sensor).

[0047] When a load is applied to each sensor unit in the Z-axis direction, the pair of conductor lines 13 (two conductor lines 13a) are pressed against and embedded in the conductive elastic bodies 12 and 22 by the load. As a result, the contact area between the pair of conductor lines 13 and the conductive elastic bodies 12 and 22 changes, and the capacitance between the pair of conductor lines 13 and the conductive elastic bodies 12 and 22 changes.

[0048] The end portion on the negative X-axis side of the pair of conductor lines 13, the end portion on the negative Y-axis side of the cable 12a, and the end portion on the negative Y-axis side of the cable 22a are connected to a detection circuit installed for the load sensor 1.

[0049] In Fig. 4, the cables 12a and 22a drawn from the three sets of conductive elastic bodies 12 and 22 are shown as lines L11, L12, and L13, and the conductive members 31 in the three pairs of conductor lines 13 are shown as lines L21, L22, and L23. The positions where the conductive elastic bodies 12 and 22 connected to line L11 intersect with lines L21, L22, and L23 are sensor parts A11, A12, and A13 respectively. The positions where the conductive elastic bodies 12 and 22 connected to line L12 intersect with lines L21, L22, and L23 are sensor parts A21, A22, and A23 respectively. The positions where the conductive elastic bodies 12 and 22 connected to line L13 intersect with lines L21, L22, and L23 are sensor parts A31, A32, and A33 respectively.

[0050] When a load is applied to sensor part A11, the contact area between the pair of conductor lines 13 and the conductive elastic bodies 12 and 22 at sensor part A11 increases. Therefore, by detecting the capacitance between line L11 and line L21, the load applied to sensor part A11 can be calculated. Similarly, for other sensor parts, by detecting the capacitance between two intersecting lines at the other sensor part, the load applied to the other sensor part can be calculated.

[0051] By the way, as shown in Figs. 3(a) and 3(b), when the dielectric 32 is formed so as 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 in response to the increase in load. As a result, the relationship between the load and the capacitance is defined by a curved waveform as shown by the solid line in Fig. 5. In Fig. 5, point P0 indicates 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 part. When obtaining the load from the capacitance value, the curve in the inner part from point P0 is used. However, as shown in Fig. 5, this part has a curved waveform. For this reason, when obtaining the load from the capacitance value, it is necessary to take this waveform into account, resulting in the problem that the load detection process becomes complicated.

[0052] Here, let the capacitance of the sensor unit be C, the permittivity of vacuum be ε0, the relative permittivity of the dielectric 32 be ε r , the contact area between the conductive elastic bodies 12 and 22 and the dielectric 32 be S, and the thickness of the dielectric 32 be d. Then, the capacitance C is calculated by the following formula (1).

[0053] C = ε0·ε r ·S / d …(1)

[0054] The inventors focused on the fact that the capacitance C changes according to the values of ε r , S, and d as shown in the above formula (1), and considered that by adjusting the values of ε r , S, and d, the relationship between the capacitance and the load can be set in a linear shape.

[0055] In this embodiment, among the values of ε r , S, and d, attention is paid to the contact area S, and the load sensor 1 is configured as shown in FIGS. 6(a) to 7(a) below. According to this configuration, as the load changes, the contact area S of the dielectric 32 changes as the load increases so that the change in the capacitance between the conductive elastic body 12 、22 and the conductive member 31 approaches a straight line. As a result, the load applied to the load sensor 1 can be detected more easily.

[0056] FIG. 6(a) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before the load is applied, and FIG. 6(b) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the state where the load is applied. For convenience, only the configuration on the conductive elastic body 22 side is shown in FIGS. 6(a) and 6(b), and the illustration on the conductive elastic body 12 side is omitted. However, also on the conductive elastic body 12 side, the same phenomena as on the conductive elastic body 22 side occur according to the change in the load.

[0057] In FIG. 6(a), D1 indicates the contact surface direction in which the contact of the dielectric 32 progresses as the load increases. In the initial state of FIG. 6(a), among the dielectrics 32 formed around the conductive member 31, only the position of the dielectric 32 where the conductive member 31 and the conductive elastic body 22 are closest (the position closest to the positive Z-axis) contacts the conductive elastic body 22. Thereafter, when a load is applied to the load sensor 1, as shown in FIG. 6(b), while the conductive elastic body 22 deforms, the contact between the dielectric 32 and the conductive elastic body 22 progresses in the contact surface direction D1. θ in FIG. 6(b) defines the circumferential contact range between the dielectric 32 and the conductive elastic body 22 by the circumferential angle (hereinafter referred to as the "contact angle"). The contact angle θ increases as the load increases.

[0058] Here, the dielectric 32 is composed of, for example, alumina (aluminum oxide). The dielectric 32 made of alumina is formed on the surface of the aluminum conductive member 31 by anodic oxidation treatment (anodizing treatment). Thereby, a film of aluminum oxide (alumina) is formed on the surface of the conductive member 31. The anodic oxidation treatment (anodizing treatment) is carried out by applying an appropriate voltage (1 to 500 V) under the conditions of 0°C to 80°C using an inorganic acid solution such as sulfuric acid, oxalic acid, phosphoric acid, boric acid, or an organic acid solution.

[0059] At this time, by adjusting the conditions of the anodic oxidation 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 or microcracks. The diameter of the micropores 33 is, for example, 1 nm or more and 100 nm or less. Also, by adjusting the conditions of the anodic oxidation treatment, the density of the micropores 33 is set lower in the region near the second position P2 away from the first position P1 in the contact surface direction D1 than in the region near the first position P1 sandwiched between the conductive elastic body 22 and the conductive member 31 in the initial state before the load is applied. The second position P2 is, for example, the upper limit position of the range where the dielectric 32 can contact the conductive elastic body 22 when the load is applied (the position farthest from the first position P1 in the range).

[0060] When forming the dielectric 32 and the micropores 33, for example, when the conductive member 31 is immersed in the treatment liquid used in the anodizing treatment by half in the radial direction, while the conductive member 31 is pulled up from the treatment liquid at a predetermined speed, the temperature and voltage are adjusted. Thereby, the dielectric 32 is formed on the surface of the conductive member 31, and the micropores 33 are formed in the dielectric 32 such that the density gradually changes in the junction surface direction D1.

[0061] FIG. 7(a) is a side view schematically showing the configuration when the conductor line 13a is viewed in the negative Y-axis direction. FIG. 7(a) also shows an enlarged view schematically showing the micropores 33 formed in the dielectric 32.

[0062] As shown in FIG. 7(a), a large number of micropores 33 are formed in the dielectric 32. The micropores 33 are formed in the dielectric 32 such that the density (degree of concentration) decreases along the junction surface direction D1. Thereby, along the junction surface direction D1, the surface area of the dielectric 32 per unit area excluding the micropores 33 (hereinafter referred to as "surface density") gradually increases. The density of the micropores 33 is set by adjusting the conditions of the anodic oxidation treatment (anodizing treatment) when forming the dielectric 32.

[0063] As shown in FIG. 6(a), when the cross-section of the conductive member 31 is circular, if the surface density of the dielectric 32 is uniform over the entire circumference, in the range where the load is small, as the load increases, the contact area between the dielectric 32 and the conductive elastic body 22 rapidly increases, and in the range where the load is large, as the load increases, the contact area gradually increases. In this case, in the range where the load is small, the change in capacitance accompanying the change in load becomes rapid, and in the range where the load is large, the change in capacitance accompanying the change in load becomes gentle.

[0064] On the other hand, as described above, when a plurality of micropores 33 are formed in the dielectric 32 and the areal density of the dielectric 32 is set to be larger in the region near the second position P2 than in the region near the first position P1, in a range where the load is small, the change amount of the contact area between the dielectric 32 and the conductive elastic body 22 that changes within a predetermined load range is small, so that the change in capacitance can be suppressed. In a range where the load is large, the change amount of the contact area between the dielectric 32 and the conductive elastic body 22 that changes within a predetermined load range is large, so that the change in capacitance can be increased. As a result, the change in the contact area accompanying the change in the load can be made closer to a linear state, and as a result, the relationship between the load and the capacitance can be made closer to a linear relationship.

[0065] <Effect of Embodiment 1> According to Embodiment 1, the following effects can be obtained.

[0066] As described above, since the contact area between the dielectric 32 and the conductive elastic bodies 12 and 22 changes as the load changes, as shown by the broken line in FIG. 5, the change in capacitance between the conductive elastic body 22 and the conductive member 31 accompanying the change in the load can be made closer to a straight line. Therefore, by measuring the capacitance value between the conductive elastic bodies 12 and 22 and the conductive member 31 and applying a simple process based on a proportional relationship to the measured capacitance value, the load applied to the load sensor 1 can be appropriately detected. Thus, the load applied to the load sensor 1 can be detected more simply.

[0067] As shown in FIG. 7(a), the dielectric 32 has a plurality of micropores 33 whose density changes in the contact surface direction D1. As a result, as described above, the change in the contact area accompanying the change in the load can be made closer to a linear state, and as a result, the relationship between the load and the capacitance can be made closer to a linear relationship.

[0068] As shown in FIGS. 3(a) and 3(b), the dielectric 32 is installed so as to cover the surface of the conductive member 31. According to this configuration, the dielectric 32 can be installed between the conductive elastic bodies 12 and 22 and the conductive member 31 simply by covering the surface of the conductive member 31 with the dielectric 32.

[0069] As shown in FIGS. 3(a) and 3(b), the conductive elastic bodies 12 are also arranged on the opposing surface 11a of the base material 11 together with the opposing surface 21a of the base material 21. As the load increases, the contact area of the dielectric 32 changes so that the change in capacitance between the conductive elastic bodies 12, 22 and the conductive member 31 accompanying the change in load approaches a straight line. Thus, by arranging the conductive elastic bodies 12, 22 on both of the base materials 11, 21, the change in capacitance due to the change in load can be made larger than when only one of the conductive elastic bodies 12, 22 is arranged, and the detection accuracy of the load can be improved. Further, since the contact area of the dielectric 32 with the conductive elastic bodies 12, 22 changes as the load increases so that the change in capacitance between the conductive elastic bodies 12, 22 and the conductive member 31 accompanying the change in load approaches a straight line, the load applied to the load sensor 1 can be detected simply and accurately.

[0070] <Modification Example of Embodiment 1> In Embodiment 1, as shown in FIG. 7(a), a plurality of fine holes 33 are formed in the dielectric 32, so that the contact area of the dielectric 32 with the conductive elastic bodies 12, 22 changes as the load increases. However, instead of forming the fine holes 33, the surface roughness of the dielectric 32 may be adjusted in the contact surface direction D1 so that the surface density of the dielectric 32 changes.

[0071] FIG. 7(b) is a diagram schematically showing a cross section when the dielectric 32 is cut in the Y-Z plane.

[0072] In this modification example, the dielectric 32 is made of a resin material or the like, and is typically made of urethane. After the dielectric 32 is formed on the surface of the conductive member 31, the conductive member 31 coated with the dielectric 32 is passed through a ring-shaped mold having fine irregularities on its inner surface. Then, by sliding the ring-shaped mold in the longitudinal direction of the conductive member 31, fine grooves 34 are formed 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 ring-shaped mold so that the interval between the grooves 34 formed on the surface of the dielectric 32 increases according to the contact surface direction D1. The surface roughness is defined by, for example, the depth s1, pitch s2, and surface interval s3 of the grooves 34 formed on the surface of the dielectric 32. At this time, even when the dielectric 32 is in close contact with the conductive elastic bodies 12 and 22, the depth s1, pitch s2, and surface interval s3 of the grooves 34 are set so that the conductive elastic bodies 12 and 22 do not enter the grooves 34.

[0073] In this way, by setting the surface roughness, the area corresponding to the surface interval s3 of the grooves 34 per unit area is set as the surface density of the dielectric 32. In this modification example, the surface roughness of the surface of the dielectric 32 is adjusted so that the surface density of the dielectric 32 gradually increases in the contact surface direction D1.

[0074] As described above, in this modification example, the surface density of the dielectric 32 is set to increase according to the contact surface direction D1, and the surface density of the dielectric 32 is set to be larger near the second position P2 than near the first position P1. Thus, similar to the first embodiment, in the range where the load is small, the change amount of the contact area between the dielectric 32 and the conductive elastic body 22 that changes within a predetermined load range is small, so the change in capacitance can be suppressed. In the range where the load is large, the change amount of the contact area between the dielectric 32 and the conductive elastic body 22 that changes within a predetermined load range is large, so the change in capacitance can be increased. As a result, the change in the contact area accompanying the change in the load can be made closer to a linear state, and consequently, the relationship between the load and the capacitance can be made closer to a linear relationship.

[0075] Note that the method of changing the contact area of the dielectric 32 in the contact surface direction D1 is not limited to the method of changing the density and surface roughness of the micropores 33. For example, other methods may be used, such as forming depressions or protrusions on the surface of the dielectric 32 and increasing the interval between the depressions or protrusions in accordance with the contact surface direction D1.

[0076] In addition, the change in the contact area does not necessarily have to be continuously changed in the contact surface direction D1, and may be changed stepwise in the contact surface direction D1.

[0077] <Embodiment 2> In the above Embodiment 1, regarding the relative permittivity ε of the dielectric r , among the values of the contact area S and the thickness d, only the contact area S was focused on, and the relationship between the load and the capacitance was made close to a linear relationship. In contrast, in Embodiment 2, by focusing on all the values of ε r , S, and d, the relationship between the load and the capacitance is made close to a linear relationship.

[0078] FIG. 8(a) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before the load is applied according to Embodiment 2, and FIG. 8(b) is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the state where the load is applied according to Embodiment 2. For convenience, only the configuration on the conductive elastic body 22 side is shown in FIGS. 8(a) and 8(b), and the illustration of the conductive elastic body 12 side is omitted. However, also on the conductive elastic body 12 side, the same phenomena as on the conductive elastic body 22 side occur in response to the change in the load.

[0079] In the configuration of FIG. 8(a), the dielectric 32 is composed of dielectrics 32a and 32b. The dielectric 32a is formed on the surface of the conductive member 31 within a range of a predetermined contact angle θ1, and the dielectric 32b is formed on the surface of the conductive member 31 within a range larger than the contact angle θ1. The thickness of the dielectric 32a is larger than the thickness of the dielectric 32b. The relative permittivity of the dielectric 32b is set higher than the relative permittivity of the dielectric 32a.

[0080] 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 urethane, and the dielectric 32b is made of alumina.

[0081] A notch C1 is formed at the first position P1 of the dielectric 32a. The notch C1 is formed along the X-axis direction on the surface of the dielectric 32a and is a notch that does not penetrate the dielectric 32a in the thickness direction. For example, the notch C1 is formed at least in a range where the conductive member 31 and the conductive elastic body 22 overlap in a plan view. By forming the notch C1, the sudden increase in the contact area from the initial state of load application front can be suppressed, and the sudden increase in capacitance can be suppressed.

[0082] Similar to the dielectric 32 shown in FIG. 7(b), the dielectric 32a has grooves 34 formed on its surface. That is, the surface roughness of the dielectric 32a is adjusted so that the surface density of the dielectric 32a gradually increases according to the contact surface direction D1. Therefore, similar to the case of FIG. 7(b), in the range where the contact angle is θ1, when the load is small, the change amount of the contact area between the dielectric 32a and the conductive elastic body 22 that changes within a predetermined load range is small, so the change in capacitance can be suppressed. When the load is large, the change amount of the contact area between the dielectric 32a and the conductive elastic body 22 that changes within a predetermined load range is large, so the change in capacitance can be increased.

[0083] Similar to the dielectric 32 shown in FIG. 7(a), the dielectric 32b has micropores 33 formed on its surface. The density of the micropores 33 gradually decreases along the contact surface direction D1, and the surface density of the dielectric 32b gradually increases along the contact surface direction D1. Thereby, similar to the case of FIG. 7(a), in the range larger than the contact angle θ1, when the load is small, the change amount of the contact area between the dielectric 32b and the conductive elastic body 22 that fluctuates within a predetermined load range is small, so the change in capacitance can be suppressed. When the load is large, the change amount of the contact area between the dielectric 32b and the conductive elastic body 22 that changes within a predetermined load range is large, so the change in capacitance can be increased.

[0084] FIG. 9(a) shows the relationship between the contact angle θ and the value of ε r ·S / d. FIG. 9(b) is a graph showing the relationship between pressure and capacitance.

[0085] In FIG. 9(a), the contact angle θ1 (see FIGS. 8(a) and 8(b)) is set to be around 55°. In the load sensor 1 in this case, when the contact angle is around 90°, the upper conductive elastic body 22 and the lower conductive elastic body 12 come into contact with each other. The angle range Rd11 is the range where the contact angle is from 0° to θ1, and the angle range Rd12 is the range where the contact angle is θ1 or more.

[0086] In the angle range Rd11, ε r / d is set to 1, and the surface density changes from 0% to 100% along the contact surface direction D1. When the contact angle is near 0°, as shown in FIGS. 8(a) and 8(b), since the notch C1 is formed at the position of the first position P1, the surface density becomes 0%. In the angle range Rd12, ε r / d is set to 3, and the surface density changes from 33% to 100% along the contact surface direction D1. Thus, by changing the value of ε r / d and the value of the surface density, up to the contact angle (90°) at which the upper and lower conductive elastic bodies 12 and 22 come into contact with each other, ε r ·S / d can be set linearly.

[0087] As shown in FIG. 9(a), when the value of ε r ·S / d is set linearly, as shown by the dashed line in FIG. 9(b), a curve showing the relationship between pressure and capacitance can be set linearly from the point where the load is 0 to the point P0. In FIG. 9(b), the point P0 corresponds to the state where the upper and lower conductive elastic bodies 12 and 22 start to contact around the conductor line 13a, that is, the state around 90° in FIG. 9(a).

[0088] <Effect of Embodiment 2> According to Embodiment 2, the following effects are achieved.

[0089] The dielectric 32a is provided with a notch C1 in the initial contact region (the first position P1). As a result, it is possible to suppress a sharp increase in the contact area in a range where the load is small, and it is possible to suppress a sharp increase in the capacitance in a range where the load is small. Therefore, in a range where the load is small, the relationship between the load and the capacitance can be made closer to a simpler linear relationship.

[0090] As the load increases, the relative permittivity of the dielectric 32 changes in the contact surface direction D1. That is, in the dielectric 32, the relative permittivity of the dielectric 32b located in a range larger than the contact angle θ1 is larger than the relative permittivity of the dielectric 32a located in the range of the contact angle θ1. In this way, by adjusting the relative permittivity of the dielectric 32 in the contact surface direction D1 together with the contact area, the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 accompanying the change in load can be made closer to a smooth and accurate straight line.

[0091] Since the material of the dielectric 32 is different in the contact surface direction D1, the relative permittivity of the dielectric 32 changes in the contact surface direction D1. That is, the dielectric 32 is composed of a dielectric 32a made of urethane and a dielectric 32b made of alumina having a relative permittivity larger than that of urethane. As a result, the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 accompanying the change in load can be smoothly made closer to a straight line.

[0092] The thickness of the dielectric 32a is large than the thickness of the dielectric 32b. That is, the thickness of the dielectric 32 changes in the contact surface direction D1. The capacitance per unit area of the dielectric 32 is inversely proportional to the thickness. Therefore, by further adjusting the thickness of the dielectric 32a in this way, the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 accompanying the change in load can be made even smoother and more accurately closer to a straight line.

[0093] <Modification Example 1 of Embodiment 2> In Embodiment 2, as shown in FIGS. 8(a) and 8(b), the dielectric 32 is composed of four (two pairs) of dielectrics, but it may be composed of other numbers of dielectrics. In this modified example, the dielectric 32 is composed of eight dielectrics 32a, 32b, 32c, 32d (four pairs). Also, in this modified example, the curve showing the relationship between the pressure and the capacitance approaches two straight lines with different slopes.

[0094] FIG. 10 is a diagram schematically showing the relationship between the dielectric 32 and the conductive elastic body 22 in the initial state before the load is applied according to this modified example. For convenience, only the configuration on the conductive elastic body 22 side is shown in FIG. 10.

[0095] In the configuration of FIG. 10, the dielectric 32a is formed on the surface of the conductive member 31 in the range where the contact angle θ2 or less, the dielectric 32b is formed on the surface of the conductive member 31 in the range where the contact angle is larger than θ2 and the contact angle θ3 or less, the dielectric 32c is formed on the surface of the conductive member 31 in the range where the contact angle is larger than θ3 and the contact angle θ4 or less, and the dielectric 32d is formed on the surface of the conductive member 31 in the range where the contact angle is larger than θ4.

[0096] The thicknesses of the dielectrics 32a and 32c are equal to each other, and the thicknesses of the dielectrics 32b and 32d are equal to each other. The thicknesses of the dielectrics 32a and 32c are larger than the thicknesses of the dielectrics 32b and 32d. The relative dielectric constants of the dielectrics 32a and 32c are equal to each other, and the relative dielectric constants of the dielectrics 32b and 32d are equal to each other. The relative dielectric constants of the dielectrics 32b and 32d are higher than the relative dielectric constants of the dielectrics 32a and 32c.

[0097] The dielectrics 32a and 32c are formed of, for example, resin, and the dielectrics 32b and 32d are formed of, for example, metal oxide. For example, the dielectrics 32a and 32c are formed of urethane, and the dielectrics 32b and 32d are formed of alumina. A notch C1 is formed at the first position P1 of the dielectric 32a, similar to FIGS. 8(a) and 8(b).

[0098] Dielectrics 32a and 32c have grooves 34 formed on their surfaces, similar to the dielectric 32 shown in Fig. 7(b). That is, the surface roughness of dielectrics 32a and 32c is adjusted such that the surface density of dielectrics 32a and 32c gradually increases along the contact surface direction D1. Therefore, similar to the case of Fig. 7(b), in the range of the contact angle θ2 and the range from θ3 to θ4, as the load increases, the change amount of the contact area between the dielectric 32a and the conductive elastic body 22 that changes within a predetermined load range becomes larger, so that the change in capacitance can be enhanced.

[0099] Dielectrics 32b and 32d have micropores 33 formed on their surfaces, similar to the dielectric 32 shown in Fig. 7(a). The surface density of dielectric 32b gradually increases along the contact surface direction D1. Thereby, similar to the case of Fig. 7(a), in the range of the contact angle from θ2 to θ3 and the range where the contact angle is larger than θ4, as the load increases, the change amount of the contact area between the dielectric 32b and the conductive elastic body 22 that changes within a predetermined load range becomes larger, so that the change in capacitance can be enhanced.

[0100] Fig. 11(a) is a graph showing the relationship between the contact angle θ and the value of ε r ·S / d. Fig. 11(b) is a graph showing the relationship between pressure and capacitance.

[0101] In Fig. 11(a), the contact angles θ2, θ3, θ4 (see Fig. 10) are set to be around 16°, around 35°, and around 80°, respectively. In the load sensor 1 in this case, the upper conductive elastic body 22 and the lower conductive elastic body 12 come into contact when the contact angle is around 90°. The angle range Rd21 is the range where the contact angle is 0° to θ2, and the angle range Rd22 is the range where the contact angle is larger than θ2 and less than or equal to θ3. Also, the angle range Rd23 is the range where the contact angle is larger than θ3 and less than or equal to θ4, and the angle range Rd24 is the range where the contact angle is larger than θ4.

[0102] In the angle ranges Rd21 and Rd23, ε r / d is set to 1, and in the angle ranges Rd22 and Rd24, ε rIt is set to / d = 3. In the angular range Rd21, the areal density changes from 0% to 100% along the tangential direction D1. In the angular range Rd22, the areal density changes from 33% to 66% along the tangential direction D1. In the angular range Rd23, the areal density changes from 50% to 100% along the tangential direction D1. In the angular range Rd24, the areal density changes from 33% to 100% along the tangential direction D1.

[0103] As shown in Fig. 11(a), ε r ·When the value of S / d is set, as shown by the dashed line in Fig. 11(b), the curve showing the relationship between pressure and capacitance can be approximated by two straight lines with different slopes from the point where the load is 0 to the point P0.

[0104] <Effect of Modification Example 1 of Embodiment 2> According to this modification example, the following effects are achieved.

[0105] As shown by the dashed line in Fig. 11(b), the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 associated with the change in load can be approximated by two straight lines. Therefore, also in this case, by measuring the capacitance value between the conductive elastic bodies 12 and 22 and the conductive member 31 and applying a simple process based on a proportional relationship to the measured capacitance value, the load applied to the load sensor 1 can be properly detected. Thus, the load applied to the load sensor 1 can be detected more simply.

[0106] <Modification Example 2 of Embodiment 2> In Embodiment 2, as shown in Figs. 8(a) and (b), since the dielectric 32 is composed of dielectrics 32a and 32b with different relative permittivities, the relative permittivity of the dielectric 32 changes in the tangential direction D1. However, the relative permittivity of the dielectric 32 may be changed in the tangential direction D1 by other methods. In this modification example, since the dielectric 32 contains the filler 35, the relative permittivity of the dielectric 32 changes in the tangential direction D1.

[0107] FIG. 12 is a diagram schematically showing 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 example. For convenience, only the configuration on the conductive elastic body 22 side is shown in FIG. 12.

[0108] In the configuration of FIG. 12, the dielectric 32 is made of, for example, resin or metal oxide. The dielectric 32 is made of, for example, urethane or alumina. 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. When the dielectric 32 is made of a material other than alumina, the filler 35 may be alumina. In this modification example, the fillers 35 are included in the dielectric 32 such that the density of the fillers 35 changes in the junction surface direction D1. In this modification example, the density of the fillers 35 is adjusted so that the relative dielectric constant of the dielectric 32 gradually increases in the junction surface direction D1.

[0109] Also, in the dielectric 32, the micropores 33 shown in FIG. 7(a) or the grooves 34 shown in FIG. 7(b) are formed while the density is adjusted in the junction surface direction D1, whereby the areal density of the dielectric 32 gradually increases according to the junction surface direction D1.

[0110] As described above, according to this modification example, since the density of the fillers 35 changes in the junction surface direction D1, the relative dielectric constant of the dielectric 32 increases in the junction surface direction D1. Thereby, also in this modification example, the relationship between the load and the capacitance can be made closer to a straight line.

[0111] Note that the thickness of the dielectric 32 may change so as to gradually decrease in the junction surface direction D1. In this case, the capacitance per unit area by the dielectric 32 gradually increases in the junction surface direction D1. Therefore, by further adjusting the thickness of the dielectric 32 in this way, the change in capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31 accompanying the change in load can be made even smoother and more accurately closer to a straight line. The thickness of the dielectric 32 may change stepwise in the junction surface direction D1.

[0112] <Embodiment 3> In the above-described Embodiments 1 and 2 and the modification example, the dielectric 32 is disposed on the surface of the conductive member 31. However, in Embodiment 3, a dielectric is formed on the surfaces of the conductive elastic bodies 12 and 22.

[0113] FIG. 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 the load is applied according to Embodiment 3, and FIG. 13(b) is a diagram schematically showing the relationship between the dielectrics 15 and 23 and the conductive member 31 in the state where the load is applied according to Embodiment 3.

[0114] As shown in FIGS. 13(a) and 13(b), in Embodiment 3, dielectrics 15 and 23 are respectively formed on the surfaces of the conductive elastic bodies 12 and 22. In FIG. 13(a), D2 indicates the tangential direction in which the contact of the dielectrics 15 and 23 progresses as the load increases.

[0115] In the initial state of FIG. 13(a), only the position where the conductive member 31 and the conductive elastic bodies 12 and 22 are closest to each other in the regions of the dielectrics 15 and 23 contacts the conductive member 31. Thereafter, when a load is applied to the load sensor 1, as shown in FIG. 13(b), while the conductive elastic bodies 12 and 22 are deforming, the contact between the dielectrics 15 and 23 and the conductive member 31 progresses in the tangential direction D2. θ in FIG. 13(b) is the contact angle. The contact angle θ increases as the load increases.

[0116] Here, the dielectrics 15 and 23 are made of a resin material or the like, typically urethane, like the dielectric 32 in the modification example of Embodiment 1. A plurality of grooves similar to the groove 34 in the modification example of Embodiment 1 are formed in the dielectrics 15 and 23. When the position of the dielectrics 15 and 23 sandwiched between the conductive elastic bodies 12 and 22 and the conductive member 31 in the initial state before the load is applied is defined as the first position P1, the surface roughness of the dielectrics 15 and 23 is adjusted so that the surface density of the dielectrics 15 and 23 gradually increases in the tangential direction D2.

[0117] According to Embodiment 3, since the surface density of the dielectrics 15 and 23 increases along the junction surface direction D2, similar to Embodiment 1, when a load is applied, the change in the contact area accompanying the change in the load can be made closer to a linear state. As a result, the relationship between the load and the capacitance can be made closer to a linear relationship. Therefore, similar to Embodiment 1, by measuring the value of the capacitance between the conductive elastic bodies 12 and 22 and the conductive member 31, and applying a simple process based on a proportional relationship to the measured capacitance value, the load applied to the load sensor 1 can be appropriately detected, and the load applied to the load sensor 1 can be detected more simply.

[0118] Note that also in this embodiment, the dielectric 15 may be configured such that a plurality of dielectrics having different relative permittivities are arranged in the junction surface direction D2, and the dielectric 23 may be configured such that a plurality of dielectrics having different relative permittivities are arranged in the junction surface direction D2. Further, the thicknesses of the dielectrics 15 and 23 may change in the junction surface direction D2, and a notch C1 may be formed at the first position P1 of the dielectrics 15 and 23. Also, similar to Modification Example 2 of Embodiment 2, the dielectrics 15 and 23 may contain a filler, and the relative permittivity of the dielectrics 15 and 23 may be adjusted in the junction surface direction D2 according to the density of the filler.

[0119] <Embodiment 4> In the above Embodiments 1, 2 and Modification Examples, the conductive elastic body is arranged on the linear conductive member 31, but in Embodiment 4, the conductive elastic body is arranged on a conductive member having a spherical shape.

[0120] FIG. 14(a) is a plan view schematically showing the configuration of the load sensor 1 according to Embodiment 4 when viewed in the negative Z-axis direction, and FIG. 14(b) is a view schematically showing a cross section of the load sensor 1 according to Embodiment 4 by the Y-Z plane. In FIG. 14(a), for convenience, only the base material 41 and the conductive member 42 are shown.

[0121] The load sensor 1 includes a base material 41, a conductive member 42, a dielectric 43, a base material 44, and a conductive elastic body 45. The base materials 41 and 44 have a square shape when viewed in the Z-axis direction and are made of the same materials as the base materials 11 and 21 in the first and second embodiments 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 the sphere and is disposed on the upper surface of the base material 41. The conductive member 42 is made of the same material as the conductive member 31 in the first and second embodiments and the modified examples. The dielectric 43 is disposed 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, urethane or alumina. The conductive elastic body 45 is made of the same material as the conductive elastic bodies 12 and 22 in the first and second embodiments and the modified examples. The conductive elastic body 45 is disposed on the surface of the base material 44 on the negative side of the Z-axis.

[0122] In the fourth embodiment, the first position P1 is the central position of the conductive member 42 when viewed in the Z-axis direction. In the fourth embodiment, the direction extending radially along the curved surface of the conductive member 42 from the first position P1 is the contact surface direction D1. In the fourth embodiment, a plurality of micropores are formed in the dielectric 43 along the contact surface direction D1, similar to the micropores 33 in the first embodiment. The density of the micropores in the dielectric 43 decreases along the contact surface direction D1. As a result, the areal density of the dielectric 43 increases along the contact surface direction D1.

[0123] Also in the fourth embodiment, when a load is applied from the outside of the base materials 41 and 44, the conductive elastic body 45 is pressed against the conductive member 42 via the dielectric 43. Thereby, the capacitance between the dielectric 43 and the conductive elastic body 45 changes according to the load, and the load is calculated according to the capacitance. Further, in the fourth embodiment, similar to the first embodiment, since the areal density of the dielectric 43 increases along the contact surface direction D1, the graph showing the relationship between the load and the capacitance can be approximated to a straight line.

[0124] Note that, also in Embodiment 4, similar to the modification example of Embodiment 1 shown in FIG. 7(b), grooves may be formed in the dielectric 43 instead of micropores, and the surface roughness of the dielectric 43 may be adjusted so that the surface density of the dielectric 43 increases along the tangential direction D1.

[0125] Also, in Embodiment 4, similar to Embodiment 2 and Modification Example 1 of Embodiment 2, the dielectric 43 may have a configuration in which a plurality of dielectrics having different relative permittivities are arranged in the tangential direction D1, and the thickness of the dielectric 43 may vary in the tangential direction D1. Further, a circular notch may be formed at the first position P1 of the dielectric 43. Furthermore, similar to Modification Example 2 of Embodiment 2, the dielectric 43 may contain a filler, and the relative permittivity of the dielectric 43 may be adjusted in the tangential direction D1 according to the density of the filler.

[0126] <Other Modification Examples> In the above-described Embodiments 1 to 3, the dielectric 32 is composed of one type of material in the thickness direction, but may have a structure in which two or more types of materials are laminated in the thickness direction. That is, the number of layers of the dielectric 32 is not limited to one layer, and may be two or more layers. Also, the number of laminated layers of the dielectric 32 may vary according to the positions in the tangential directions D1 and D2. For example, the number of laminated layers may be two layers near the first position P1 and one layer near the second position P2. Also, in Embodiment 4, the number of laminated layers of the dielectric 43 is not limited to one layer.

[0127] Also, in the above-described Embodiments 1 to 4, micropores were provided in the alumina-based dielectric to change the surface density in the tangential directions D1 and D2. However, as shown in FIG. 7(b), the surface density may vary in the tangential directions D1 and D2 by adjusting the surface roughness of the surface of the alumina-based dielectric.

[0128] In the above-described Embodiments 1 and 2, as a configuration for changing the contact area between the dielectric 32 and the conductive elastic bodies 12 and 22 in accordance with a load, micropores 33 or grooves 34 are formed in the dielectric 32. However, the present invention is not limited to this, and neither micropores 33 nor grooves 34 are formed in the dielectric 32, and micropores or grooves may be formed in the conductive elastic bodies 12 and 22 so that the density decreases in the contact surface direction D2 (see FIGS. 13(a) and (b)). In this case, since the surface density of the conductive elastic bodies 12 and 22 increases in the contact surface direction D2, the same effects as those in the above-described embodiments are achieved. Similarly, in the above-described Embodiment 3 as well, micropores or grooves may be formed in the conductive elastic bodies 12 and 22, and in the above-described Embodiment 4 as well, micropores or grooves may be formed in the conductive elastic body 45.

[0129] In the above-described 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 a circular shape, and other shapes such as an ellipse or a pseudo-circular shape may be used. Further, the conductive member 31 may be constituted by a stranded wire in which a plurality of conductive members are stranded.

[0130] In the above-described Embodiments 1 to 3, as shown in FIG. 2(b), the load sensor 1 includes three pairs of conductor lines 13, but at least one pair of conductor lines 13 may be provided. For example, the pair of conductor lines 13 included in the load sensor 1 may be one pair.

[0131] In the above-described Embodiments 1 to 3, as shown in FIG. 2(b), the load sensor 1 includes three pairs of conductive elastic bodies 12 and 22 facing each other vertically, but at least one pair of conductive elastic bodies 12 and 22 may be provided. For example, the pair of conductive elastic bodies 12 and 22 included in the load sensor 1 may be one pair.

[0132] In the above-described Embodiments 1 to 3, the conductive elastic body 22 on the base material 21 side may be omitted. In this case, the pair of conductor lines 13 is sandwiched between the conductive elastic body 12 on the base material 11 side and the opposing surface 21a of the base material 21, and the pair of conductor lines 13 sinks into the conductive elastic body 12 according to the load, thereby changing the capacitance in each sensor unit. Further, when the conductive elastic body 22 on the base material 21 side is omitted, a sheet-like base material may be installed instead of the base material 21.

[0133] In the above-described Embodiments 1 to 3, the pair of conductor lines 13 has a shape in which two conductor lines 13a arranged in the Y-axis direction are connected at the ends in the X-axis direction. However, instead of the pair of conductor lines 13, one conductor line may be arranged, or three or more conductor lines may be arranged. Further, the shape of the pair of conductor lines 13 may not be a straight line shape in a plan view, and may be a waveform shape.

[0134] In addition, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

Explanation of Reference Numerals

[0135] 1 Load sensor 11, 21 Base materials (first base material, second base material) 11a, 21a Opposing surfaces 12, 22 Conductive elastic bodies 15, 23, 32 Dielectrics 31 Conductive member 33 Micro holes 35 Filler 41, 44 Base materials (first base material, second base material) 42 Conductive member 43 Dielectric 45 Conductive elastic body C1 Chip

Claims

1. A first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, The dielectric has a plurality of micropores whose density changes in the tangential direction in which the contact of the dielectric progresses as the load increases, so that the change in capacitance between the conductive elastic body and the conductive member accompanying the change in load approaches a straight line. A load sensor characterized by the above.

2. A first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, The surface roughness of the dielectric is adjusted so that the surface density of the dielectric changes in the tangential direction in which the contact of the dielectric progresses as the load increases, so that the change in capacitance between the conductive elastic body and the conductive member accompanying the change in load approaches a straight line. A load sensor characterized by the above.

3. A first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, The dielectric is provided with a notch in the initial contact region so that the change in capacitance between the conductive elastic body and the conductive member accompanying the change in load approaches a straight line. A load sensor characterized by the above.

4. A first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, The relative permittivity of the dielectric changes in the tangential direction in which the contact of the dielectric progresses as the load increases, so that the change in capacitance between the conductive elastic body and the conductive member accompanying the change in load approaches a straight line. A load sensor characterized by the above.

5. In the load sensor according to claim 4, By making the materials of the dielectric different in the tangential direction, the relative permittivity of the dielectric changes in the tangential direction. A load sensor characterized by the above.

6. In the load sensor according to claim 4 or 5, The dielectric includes a filler, and the density of the filler changes in the junction surface direction, whereby the relative permittivity of the dielectric changes in the junction surface direction. A load sensor characterized by this.

7. A first base material and a second base material arranged to face each other, a conductive elastic body arranged on the facing surface of the first base material, a conductive member arranged between the second base material and the conductive elastic body, a dielectric arranged between the conductive elastic body and the conductive member, the thickness of the dielectric changes in the junction surface direction in which the contact of the dielectric progresses as the load increases so that the change in capacitance between the conductive elastic body and the conductive member accompanying the change in load approaches a straight line. A load sensor characterized by this.

8. In the load sensor according to any one of Claims 1 to 7, the conductive member is a conductive wire. A load sensor characterized by this.

9. In the load sensor according to Claim 8, the dielectric is installed so as to cover the surface of the wire. A load sensor characterized by this.

10. In the load sensor according to any one of Claims 1 to 7, the conductive member is a conductive member having a spherical shape. A load sensor characterized by this.

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