Patent ID: 12222252

It should be noted that the drawings are solely for description and do not limit the scope of the present invention in any way.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is applicable to a load sensor of a management system or an electronic apparatus that performs processing in accordance with an applied load.

Examples of the management system include a stock management system, a driver monitoring system, a coaching management system, a security management system, and a caregiving/nursing management system.

In the stock management system, for example, by a load sensor provided to a stock shelf, the load of a placed stock is detected, and the kinds of commodities and the number of commodities present on the stock shelf are detected. Accordingly, in a store, a factory, a warehouse, and the like, the stock can be efficiently managed, and manpower saving can be realized. In addition, by a load sensor provided in a refrigerator, the load of food in the refrigerator is detected, and the kinds of the food and the quantity and amount of the food in the refrigerator are detected. Accordingly, a menu that uses food in a refrigerator can be automatically proposed.

In the driver monitoring system, by a load sensor provided to a steering device, the distribution of a load (e.g., gripping force, grip position, tread force) applied on the steering device by a driver is monitored, for example. In addition, by a load sensor provided to a vehicle-mounted seat, the distribution of a load (e.g., the position of the center of gravity) applied on the vehicle-mounted seat by the driver in a seated state is monitored. Accordingly, the driving state (sleepiness, mental state, and the like) of the driver can be fed back.

In the coaching management system, for example, by a load sensor provided to the bottom of a shoe, the load distribution at a sole is monitored. Accordingly, correction or leading to an appropriate waking state or running state can be realized.

In the security management system, for example, by a load sensor provided to a floor, the load distribution is detected when a person passes, and the body weight, stride, passing speed, shoe sole pattern, and the like are detected. Accordingly, the person who has passed can be identified by checking these pieces of detection information against data.

In the caregiving/nursing management system, for example, by load sensors provided to bedclothes and a toilet seat, the distributions of loads applied by a human body onto the bedclothes and the toilet seat are monitored. Accordingly, at the positions of the bedclothes and the toilet seat, what action the person is going to take is estimated, whereby tumbling or falling can be prevented.

Examples of the electronic apparatus include a vehicle-mounted apparatus (car navigation system, audio apparatus, etc.), a household electrical appliance (electric pot, IH cooking heater, etc.), a smartphone, an electronic paper, an electronic book reader, a PC keyboard, a game controller, a smartwatch, a wireless earphone, a touch panel, an electronic pen, a penlight, lighting clothes, and a musical instrument. In an electronic apparatus, a load sensor is provided to an input part that receives an input from a user.

The embodiments below are of load sensors that are typically provided in a management system or an electronic apparatus as described above. Such a load sensor may be referred to as a “capacitance-type pressure-sensitive sensor element”, a “capacitive pressure detection sensor element”, a “pressure-sensitive switch element”, or the like. The embodiments below are examples of embodiments of the present invention, and the present invention is not limited to the embodiments below in any way.

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 provided in the drawings. The Z-axis direction is the height direction of a load sensor1.

Embodiment 1

With reference toFIG.1AtoFIG.3B, a procedure of assembling a load sensor1of Embodiment 1 is described.

FIG.1Ais a perspective view schematically showing a base member11and three electrically-conductive elastic bodies12set on the upper face of the base member11.

The base member11is an insulative member having elasticity. The base member11has a flat plate shape parallel to an X-Y plane. The base member11is formed from a non-electrically-conductive resin material or a non-electrically-conductive rubber material. The resin material used in the base member11is a resin material of at least one type selected from the group consisting of a styrene-based resin, a silicone-based resin (e.g., polydimethylpolysiloxane (PDMS)), an acrylic resin, a rotaxane-based resin, a urethane-based resin, and the like, for example. The rubber material used in the base member11is a rubber material of at least one type 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, natural rubber, and the like, for example.

The electrically-conductive elastic bodies12are set on the upper face (the face on the Z-axis positive side) of the base member11with an adhesive or the like. InFIG.1A, three electrically-conductive elastic bodies12are set on the upper face of the base member11. Each electrically-conductive elastic body12is an electrically-conductive member having elasticity. The electrically-conductive elastic bodies12each have a band-like shape that is long in the Y-axis direction on the upper face of the base member11, and are set so as to be separated from each other. Each electrically-conductive elastic body12is formed from a resin material and an electrically-conductive filler dispersed therein, or from a rubber material and an electrically-conductive filler dispersed therein.

Similar to the resin material used in the base member11described above, the resin material used in the electrically-conductive elastic body12is a resin material of at least one type selected from the group consisting of a styrene-based resin, a silicone-based resin (polydimethylpolysiloxane (e.g., PDMS)), an acrylic resin, a rotaxane-based resin, a urethane-based resin, and the like, for example. Similar to the rubber material used in the base member11described above, the rubber material used in the electrically-conductive elastic body12is a rubber material of at least one type 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, natural rubber, and the like, for example.

The electrically-conductive filler used in the electrically-conductive elastic body12is a material of at least one type selected from the group consisting of: metal materials such as Au (gold), Ag (silver), Cu (copper), C (carbon), ZnO (zinc oxide), In2O3(indium oxide (III)), and SnO2(tin oxide (IV)); electrically-conductive macromolecule materials such as PEDOT:PSS (i.e., a complex composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate (PSS)); electrically-conductive fibers such as a metal-coated organic matter fiber and a metal wire (fiber state); and the like, for example.

FIG.1Bis a perspective view schematically showing three covered copper wires13, threads14provided to each covered copper wire13, a wiring fixation base member15, and a circuit connection terminal16, which are set on the structure shown inFIG.1A.

Each covered copper wire13has a shape in which a pair of covered copper wires are connected at a connection part13aon the Y-axis negative side. The covered copper wire13is composed of a copper wire and a covering member that is insulative and that covers the copper wire. The covering member of the covered copper wire13is polyurethane, for example. The covering member has been removed from the connection part13a, which is one end portion of the covered copper wire13. For example, the covering member of the connection part13ais removed as a result of the connection part13abeing subjected to soldering. That is, as a result of the connection part13abeing immersed in a bath containing a high temperature molten solder, the covering member is melted and removed by heat, the connection part13ais exposed, and the solder is attached to the exposed connection part13a. The three covered copper wires13are set with threads14in the vicinities of end portions on the Y-axis positive side of the respective three electrically-conductive elastic bodies12.

FIG.2AandFIG.2Bare perspective views schematically showing an end portion on the Y-axis positive side of an electrically-conductive elastic body12, a connection part13aof a covered copper wire13, and threads.

As described above, the connection part13aof the covered copper wire13is in a state where the covering member has been removed and the inner copper wire is exposed. The connection part13aof the covered copper wire13is wound a predetermined number of times (e.g., once) in a circular shape. The thread14is formed from an electrically-conductive material, and is composed of a fiber and an electrically-conductive metal material dispersed therein. The electrically-conductive metal material used in the thread14is silver, for example. The diameter of the connection part13ais about 3 mm, and the width in the X-axis direction of the electrically-conductive elastic body12is about 10 mm.

At the time of assembly, as shown inFIG.2A, the connection part13ais pressed from above (the Z-axis negative direction) against the vicinity of the end portion on the Y-axis positive side of the electrically-conductive elastic body12. Then, as shown inFIG.2B, the connection part13ais fixed to the electrically-conductive elastic body12by four threads14. Four threads14are set at four places on the X-axis positive side, the X-axis negative side, the Y-axis positive side, and the Y-axis negative side of the connection part13awound in a circular shape. Here, the connection part13ais fixed by the threads14at an interval of 90° in the circumferential direction.

FIG.2Cis a side view schematically showing a cross-section obtained when the configuration shown inFIG.1Bis cut along a plane parallel to a Y-Z plane passing through the center of the connection part13a. InFIG.2C, for convenience, the covered copper wire13extending on the X-axis positive side and the covered copper wire13extending on the X-axis negative side are shown so as to be shifted in the Z-axis direction.

Each thread14is fastened to the electrically-conductive elastic body12and the base member11by embroidering so as to extend across, between the inner side and the outer side of, the copper wire exposed in the connection part13a, and so as to penetrate the electrically-conductive elastic body12and the base member11. Accordingly, as indicated by each white arrow, the thread14presses and fixes the connection part13ato the surface of the electrically-conductive elastic body12such that the connection part13ais movable with respect to the surface of the electrically-conductive elastic body12.

With reference back toFIG.1B, the wiring fixation base member15and the circuit connection terminal16are set on the Y-axis positive side of the base member11. Covered portions13bof the covered copper wires13are connected, in a state of being bundled by a thread15a, to the upper face of the wiring fixation base member15. Each covered portion13bis a portion where the covering member is provided in the covered copper wire13. That is, the portion in which the covering member of the covered copper wire13remains without being removed by the above-described soldering is the covered portion13b.

Here, the “state of being bundled” is a state where the positions of the wires are restricted such that the wires are concentrated with the intervals therebetween suppressed. In the description below as well, the “state of being bundled” has the same meaning.

InFIG.1B, three threads15aconnect the covered portions13b, at respective three positions, to the wiring fixation base member15. That is, the covered copper wires13drawn from the respective electrically-conductive elastic bodies12are bundled at three places and fixed to the upper face of the wiring fixation base member15. A plurality of covered copper wires13may be tied by another thread to be bundled, and then, these covered copper wires13may be fixed by the thread15ato the wiring fixation base member15.

End portions on the side opposite to the connection part13aof each covered copper wire13is connected to the circuit connection terminal16. Then, other three covered copper wires17are disposed on the upper face of the three electrically-conductive elastic bodies12so as to perpendicularly cross the electrically-conductive elastic bodies12.

FIG.3Ais a perspective view schematically showing three covered copper wires17set on the structure shown inFIG.1B.

Each covered copper wire17is bent at an end portion on the X-axis positive side. That is, the covered copper wire17has a shape in which a pair of covered copper wires are connected at an end portion on the X-axis positive side. Three covered copper wires17are disposed so as to be superposed on the three electrically-conductive elastic bodies12. InFIG.3A, the three covered copper wires17are disposed so as to be superposed on the upper face of the three electrically-conductive elastic bodies12.

Each covered copper wire17is composed of a wire member that is electrically conductive, and a dielectric body that covers the surface of the wire member. The three covered copper wires17are disposed so as to be arranged along the longitudinal direction (the Y-axis direction) of the electrically-conductive elastic bodies12. Each covered copper wire17is disposed, extending in the X-axis direction, so as to extend across the three electrically-conductive elastic bodies12. End portions on the X-axis negative side of each covered copper wire17are bent in the Y-axis positive direction along the upper face of the base member11, and are connected to the circuit connection terminal16. That is, the portion, of the covered copper wire17, that is drawn from the region where the covered copper wire17is superposed on the electrically-conductive elastic body12is directly connected to the circuit connection terminal16without being connected to another wiring. The configuration of the covered copper wire17will be described later with reference toFIG.4AandFIG.4B.

After the three covered copper wires17have been disposed, each covered copper wire17is connected to the base member11by threads11aso as to be movable relative to the surface of each electrically-conductive elastic body12. InFIG.3A,12threads11aconnect the covered copper wires17to the base member11at positions other than the positions where the electrically-conductive elastic bodies12and the covered copper wires17overlap each other.

Subsequently, in the vicinity of an end portion on the X-axis negative side of the base member11, the covered copper wires17extending in the Y-axis direction are connected, in a state of being bundled by threads11b, to the base member11. InFIG.3A, three threads11bconnect the covered copper wires17, at respective three positions, to the base member11. Accordingly, a structure1ashown inFIG.3Ais assembled using the three threads11b.

Subsequently, as shown inFIG.3B, a base member20is set from above the structure1ashown inFIG.3A. The base member is an insulative member. The base member20is a resin material of at least one type selected from the group consisting of polyethylene terephthalate, polycarbonate, polyimide, and the like, for example. The base member20has a flat plate shape parallel to the X-Y plane. Four corners of the base member20are connected to the base member11by a silicone rubber-based adhesive, a thread, or the like, whereby the base member20is fixed to the structure1a. Accordingly, the load sensor1is completed as shown inFIG.3B.

FIG.4AandFIG.4Bare each a cross-sectional view schematically showing the periphery of a covered copper wire17when viewed in the X-axis negative direction.FIG.4Ashows a state where no load is applied, andFIG.4Bshows a state where loads are applied.

As shown inFIG.4A, the covered copper wire17is composed of a copper wire17aand a dielectric body17bcovering the copper wire17a. The diameter of the copper wire17ais about 60 μm, for example. The dielectric body17bhas an electric insulation property, and is formed from a resin material, a ceramic material, a metal oxide material, or the like, for example. The dielectric body17bmay be a resin material of at least one type selected from the group consisting of a polypropylene resin, a polyester resin (e.g., polyethylene terephthalate resin), a polyimide resin, a polyphenylene sulfide resin, a polyvinyl formal resin, a polyurethane resin, a polyamide imide resin, a polyamide resin, and the like, or may be a metal oxide material of at least one type selected from the group consisting of Al2O3, Ta2O5, and the like.

When no load is applied to the region shown inFIG.4A, the force applied between the electrically-conductive elastic body12and the covered copper wire17, and the force applied between the base member20and the covered copper wire17are substantially zero. From this state, when a load is applied in the upward direction to the lower face of the base member11, and a load is applied in the downward direction to the upper face of the base member20as shown inFIG.4B, the electrically-conductive elastic body12is deformed by the covered copper wire17. It should be noted that, when the lower face of the base member11or the upper face of the base member20is placed on a stationary object and a load is applied only to the other base member as well, a load will be similarly received from the stationary object side due to reaction.

As shown inFIG.4B, when the loads are applied, the covered copper wire17is brought close to the electrically-conductive elastic body12so as to be wrapped by the electrically-conductive elastic body12, and the contact area between the covered copper wire17and the electrically-conductive elastic body12increases. Accordingly, the capacitance between the copper wire17ain the covered copper wire17and the electrically-conductive elastic body12changes, the capacitance between two lines corresponding to this region is detected, and the load applied to this region is calculated.

FIG.5is a plan view schematically showing the load sensor1when viewed in the Z-axis negative direction. InFIG.5, for convenience, only the vicinity of the three electrically-conductive elastic bodies12is shown, and the threads14,11a,11b, the wiring fixation base member15, the circuit connection terminal16, and the base member20are not shown.

As shown inFIG.5, element parts A11, A12, A13, A21, A22, A23, A31, A32, A33in which capacitance changes in accordance with a load are formed at positions where the three electrically-conductive elastic bodies12and the three covered copper wires17cross each other. Each element part includes an electrically-conductive elastic body12and a covered copper wire17, the electrically-conductive elastic body12forms one pole (e.g., positive pole) for capacitance, and the covered copper wire17forms the other pole (e.g., negative pole) for capacitance. When a load is applied in the Z-axis direction to each element part, the covered copper wire17is wrapped by the electrically-conductive elastic body12due to the load. Accordingly, the contact area between the electrically-conductive elastic body12and the covered copper wire17changes, and the capacitance between the electrically-conductive elastic body12and the covered copper wire17changes.

As described above, the three covered copper wires13and the three covered copper wires17are connected to the circuit connection terminal16. The circuit connection terminal16is a terminal for connecting each element part described above to an external electronic circuit. When the load sensor1is used, the circuit connection terminal16is connected to the external electronic circuit.

As shown inFIG.5, the covered copper wires13drawn from the three electrically-conductive elastic bodies12are referred to as lines L11, L12, L13, and the three covered copper wires17drawn from the three electrically-conductive elastic bodies12are referred to as lines L21, L22, L23. The positions at which the line L21crosses the electrically-conductive elastic bodies12connected to the lines L11, L12, L13are the element parts A11, A12, A13, respectively. The positions at which the line L22crosses the electrically-conductive elastic bodies12connected to the lines L11, L12, L13are the element parts A21, A22, A23, respectively. The positions at which the line L23crosses the electrically-conductive elastic bodies12connected to the lines L11, L12, L13are the element parts A31, A32, A33, respectively.

When a load is applied to the element part A11, the contact area between the electrically-conductive elastic body12and the covered copper wire17increases in the element part A11. Therefore, when the capacitance between the line L11and the line L21is detected, the load applied to the element part A11can be calculated. Similarly, in another element part as well, when the capacitance between the two lines crossing each other in the other element part is detected, the load applied to the other element part can be calculated.

As described above, the three lines L11, L12, L13and the three lines L21, L22, L23are connected to the circuit connection terminal16. By an external device connected to the circuit connection terminal16, the capacitance according to combinations of the three electrically-conductive elastic bodies12and the three covered copper wires17can be detected.

For example, when one of the three lines L11, L12, L13is selectively connected to the ground, and the voltage between the line connected to the ground and one of the three lines L21, L22, L23is detected, the capacitance in the element part to which the two lines are connected and in which the covered copper wire17and the electrically-conductive elastic body12cross each other, can be detected. Specifically, on the basis of the time until a predetermined amount of electric charge is accumulated in an element part, the capacitance in the element part is detected. On the basis of this capacitance, the load applied to the element part is calculated.

Next, the inventors conducted an experiment of verifying effects brought about by pressing and fixing the connection part13aof the covered copper wire13to the electrically-conductive elastic body12by threads14, as shown inFIG.2C.

In the present experiment, as shown inFIG.6AandFIG.6B, the inventors used a configuration that corresponds to only the vicinity of the connection part13ashown inFIG.2B. InFIG.6AandFIG.6B, for convenience, out of the wound connection part13a, a portion on the Y-axis positive side is shown. InFIG.6AandFIG.6B, the configurations similar to those in the load sensor1above are denoted by the same reference characters.

FIG.6Ais a cross-sectional view schematically showing a configuration (Embodiment 1) in which the connection part13aof the covered copper wire13is pressed against the electrically-conductive elastic body12in advance by the thread14. In the configuration of Embodiment 1 inFIG.6A, the connection part13ais pressed and fixed to the surface of the electrically-conductive elastic body12such that not less than 30% of the surface area of the connection part13ais in contact with the electrically-conductive elastic body12. Accordingly, as shown inFIG.6A, the connection part13asinks in the electrically-conductive elastic body12. On the other hand,FIG.6Bis a cross-sectional view schematically showing a configuration (comparative example) in which the connection part13aof the covered copper wire13is placed on the surface of the electrically-conductive elastic body12without being fixed to the electrically-conductive elastic body12.

In the configurations inFIG.6AandFIG.6B, the inventors applied an external force from the upper base member20to the position of the connection part13a, and measured the resistance value between the connection part13aand the electrically-conductive elastic body12.

FIG.6Cis a graph showing experimental results regarding a relationship between external force and resistance value with respect to the configurations (Embodiment 1/comparative example) shown inFIG.6AandFIG.6B. The horizontal axis represents the magnitude of the external force applied to the connection part13a, and the vertical axis represents the resistance value between the connection part13aand the electrically-conductive elastic body12.

In the case of the comparative example, in a range in which the external force applied to the connection part13ais not greater than 4 N, variation in the resistance value is very large, and when the load exceeds 4 N, variation in the resistance value becomes small. In the case of the comparative example, when the external force applied to the connection part13ais small, the contact between the connection part13aand the electrically-conductive elastic body12is unstable, and thus, variation in the resistance value becomes very large. On the other hand, in the configuration of the comparative example, when the external force applied to the connection part13abecomes large, the connection part13asinks in the electrically-conductive elastic body12, and the contact between the connection part13aand the electrically-conductive elastic body12is stabilized, and thus, variation in the resistance value becomes small. Thus, in the case of the comparative example, the resistance value changes to a great extent in accordance with the magnitude of the external force applied to the connection part13a.

In contrast to this, in the case of Embodiment 1, regardless of the magnitude of the external force applied to the connection part13a, variation in the resistance value is small. In the case of Embodiment 1, even in a state where the external force applied the connection part13ais zero, the connection part13ais pressed against the electrically-conductive elastic body12by the thread14, and not less than 30% of the surface area of the connection part13ais in contact with the electrically-conductive elastic body12, as shown inFIG.6A. Therefore, regardless of the magnitude of the external force, the connection part13ais always sunk in the electrically-conductive elastic body12, and the contact between the connection part13aand the electrically-conductive elastic body12is in a stable state. Thus, variation in the resistance value can be suppressed to be small.

As described above, in the load sensor1, on the basis of the time until a predetermined amount of electric charge is accumulated in an element part, the capacitance in the element part is detected. However, when the load sensor1is to be set, a mechanism, a member, or the like other than the load sensor1may come into contact with the position, in the base member20, that corresponds to the connection part13a, whereby an external force may be applied to the connection part13a. In such a case, when variation in the resistance value between the connection part13aand the electrically-conductive elastic body12with respect to the external force is large as in the comparative example above, the time until a predetermined amount of electric charge is accumulated in the element part will be unintentionally varied in accordance with the magnitude of the external force. In this case, the capacitance in the element part cannot be appropriately detected, and thus, the load applied to the element part cannot be appropriately calculated.

In contrast to this, according to the configuration of Embodiment 1, even when an external force is applied to the connection part13a, variation in the resistance value between the connection part13aand the electrically-conductive elastic body12with respect to the magnitude of the external force is suppressed to be small. Thus, unintended time variation until the predetermined amount of electric charge is accumulated in the element part is suppressed. Therefore, according to the configuration of Embodiment 1, the capacitance in the element part can be appropriately detected, and thus, the load applied to the element part can be appropriately calculated.

Effects of Embodiment 1

According to Embodiment 1, the following effects are exhibited.

The covered copper wire13is movable while being in contact with the electrically-conductive elastic body12, in accordance with elastic deformation of the electrically-conductive elastic body12. Therefore, even when the electrically-conductive elastic body12has been elastically deformed due to stretch and contraction, etc., the connection between the covered copper wire13and the electrically-conductive elastic body12is maintained. In addition, since drawing with respect to the electrically-conductive elastic body12is realized by means of the covered copper wire13, the electric resistance of wiring for drawing is not increased. Further, since the connection part13aof the covered copper wire13is pressed and fixed to the surface of the electrically-conductive elastic body12, even when an external force is applied to the connection place between the covered copper wire13and the electrically-conductive elastic body12, i.e., the position of the connection part13a, change due to this external force in the resistance value at the connection place, i.e., the resistance value between the connection part13aand the electrically-conductive elastic body12, can be suppressed. Therefore, while the resistance value of the wiring drawn from each element part A11to A13, A21to A23, A31to A33shown inFIG.5can be suppressed to be small, change due to an external force in the resistance value at the connection place of the wiring (the covered copper wire13) to the element part can be suppressed, and reliability in the connection between the element part and the wiring can be enhanced.

The connection part13aof the covered copper wire13is pressed and fixed to the surface of the electrically-conductive elastic body12such that not less than 30% of the surface area of the connection part13ais in contact with the electrically-conductive elastic body12. Accordingly, as shown inFIG.6C, even when the external force changes, variation in the resistance value between the connection part13aand the electrically-conductive elastic body12is small, and thus, unintended time variation until a predetermined amount of electric charge is accumulated in the element part is suppressed. Therefore, the capacitance in the element part can be appropriately detected, and thus, the load applied to the element part can be appropriately calculated. In the following embodiments and modifications as well, it is preferable that the connection part connected to the electrically-conductive elastic body is pressed and fixed to the surface of the electrically-conductive elastic body such that not less than 30% of the surface area of the connection part is in contact with the electrically-conductive elastic body.

As shown inFIG.2AtoFIG.2C, the covered copper wire13is sewn to the electrically-conductive elastic body12by threads14in a state where the covered copper wire13is placed on the surface of the electrically-conductive elastic body12. Accordingly, the regions where the threads14are provided to the electrically-conductive elastic body12are significantly small, and thus, the covered copper wire13can be connected to the electrically-conductive elastic body12while original properties of the electrically-conductive elastic body12are maintained.

As shown inFIG.2B, the connection part13aof the covered copper wire13is fixed to the surface of the electrically-conductive elastic body12by threads14, in a state where the connection part13aextends along a looped shape on the surface of the electrically-conductive elastic body12. Accordingly, the contact area between the covered copper wire13and the surface of the electrically-conductive elastic body12can be increased. Therefore, the contact resistance between the covered copper wire13and the electrically-conductive elastic body12can be reduced, and change in the capacitance can be more accurately detected.

Each thread14is formed by an electrically-conductive metal material being attached to the surface of a fiber. Therefore, the thread14has electrical conductivity, and thus, the contact resistance between the covered copper wire13and the electrically-conductive elastic body12can be reduced. Therefore, change in the capacitance can be more accurately detected.

The covered copper wire13is a covered copper wire that is covered by a covering member that is insulative, and the covering member has been removed in the connection part13aof the covered copper wire13. Therefore, even when the covered copper wire13drawn from each element part comes into contact with another material that is electrically conductive, the covered copper wire13and the other material are electrically insulated from each other by the insulative covering member. Therefore, at the time of setting or the like of the load sensor1, handling of the covered copper wire13can be easily performed.

As a result of the connection part13aof the covered copper wire13being subjected to soldering, the covering member is removed from the connection part13a. Thus, when soldering is used, the covering member can be smoothly removed.

As shown inFIG.5, in the load sensor1, a plurality of element parts A11to A13, A21to A23, A31to A33in each of which capacitance changes in accordance with a load are provided, and a plurality of covered copper wires13respectively drawn from the plurality of element parts are fixed, in a state of being bundled, to the wiring fixation base member15. Accordingly, the covered copper wires13can be put together in a compact manner, and the volume occupied by the covered copper wires13can be reduced. Therefore, handling of the covered copper wires13can be easily performed.

Since each covered copper wire17also serves as wiring for drawing from an element part, there is no need to separately provide wiring for drawing. In addition, since the covered copper wire17is in a state of being in contact with the electrically-conductive elastic body12, when the electrically-conductive elastic body12has been elastically deformed, the covered copper wire17moves relative to the surface of the electrically-conductive elastic body12while being in contact with the surface of the electrically-conductive elastic body12. Therefore, even when the electrically-conductive elastic body12has been elastically deformed due to stretch and contraction, etc., the connection between the covered copper wire17and the electrically-conductive elastic body12is maintained. Since the covered copper wire17is also used as wiring for drawing, the electric resistance of the wiring for drawing is not increased. Therefore, while the resistance value of the wiring drawn from the element part is suppressed to be small, reliability in the connection between the electrically-conductive elastic body12and the wiring can be enhanced.

As shown inFIG.5, in the load sensor1, a plurality of element parts A11to A13, A21to A23, A31to A33in each of which capacitance changes in accordance with a load are provided, and a plurality of covered copper wires17respectively drawn from the plurality of element parts are fixed, in a state of being bundled, to the base member11. Accordingly, the covered copper wire17can be put together in a compact manner, and the volume occupied by the covered copper wires17can be reduced. Therefore, handling of the covered copper wires17can be easily performed.

A plurality of electrically-conductive elastic bodies12that are long in the Y-axis direction are disposed so as to be arranged in the X-axis direction, and a plurality of covered copper wires17that extend across the plurality of electrically-conductive elastic bodies12are disposed so as to be arranged in the Y-axis direction. Accordingly, as shown inFIG.5, a plurality of element parts A11to A13, A21to A23, A31to A33can be disposed in a matrix shape.

Each covered copper wire17is fastened by threads11ato the base member11in the load sensor1so as to be movable relative to the surface of each electrically-conductive elastic body12. Therefore, in a case where the electrically-conductive elastic body12has been elastically deformed due to stretch and contraction, etc., while the covered copper wire17is allowed to move relative to the electrically-conductive elastic body12, the disposition of the covered copper wire17in the load sensor1can be maintained at a predetermined position.

Modification of Embodiment 1

In Embodiment 1 above, the connection part13aof the covered copper wire13is connected to the electrically-conductive elastic body12by threads14. However, the means for connecting the connection part13aand the electrically-conductive elastic body12together is not limited thereto.

FIG.7AtoFIG.7Ceach show a modification in which an eyelet21is used instead of the threads14.

As shown inFIG.7A, the eyelet21is a tubular member provided with a hole penetrating the eyelet21in the up-down direction. The eyelet21is formed from aluminum or copper, which is electrically conductive. At each of an upper end portion21aand a lower end portion21b, an opening continuous to the inner cavity thereof is formed. The height (the length in the Z-axis direction) of the eyelet21is slightly greater than the thickness obtained by adding the thickness of the electrically-conductive elastic body12and the thickness of the base member11. When the eyelet21is used, a hole12apenetrating the electrically-conductive elastic body12in the up-down direction and a hole11cpenetrating the base member11in the up-down direction (seeFIG.7C) are formed at the position at which the eyelet21is to be set. The diameter of the hole12a,11cis substantially the same as the outer diameter of the eyelet21.

As shown inFIG.7A, at the time of assembly, the connection part13ais caused to have a shape extending along the outer periphery of the eyelet21, and the eyelet21is inserted into the inside of the connection part13ain a looped shape. Then, the eyelet21is passed through the hole12aof the electrically-conductive elastic body12and the hole11cof the base member11. At this time, the eyelet21is positioned with respect to the electrically-conductive elastic body12and the base member11such that the upper end portion21aslightly protrudes in the upward direction from the upper face of the electrically-conductive elastic body12and the lower end portion21bslightly protrudes in the downward direction from the lower face of the base member11.

In this state, the upper end portion21ais crimped onto the upper face of the electrically-conductive elastic body12, and the lower end portion21bis crimped onto the lower face of the base member11. At this time, the upper end portion21ais bent in the downward direction while being outwardly widened as shown inFIG.7BandFIG.7C, and the lower end portion21bis bent in the upward direction while being outwardly widened as shown inFIG.7C. As a result, the eyelet21presses and fixes the connection part13ato the surface of the electrically-conductive elastic body12, as indicated by a white arrow, such that the connection part13ais movable with respect to the surface of the electrically-conductive elastic body12. Accordingly, similar to Embodiment 1, the connection part13ais connected to the electrically-conductive elastic body12.

Therefore, when the eyelet21is used as well, similar to Embodiment 1 above, the covered copper wire13is movable while being in contact with the electrically-conductive elastic body12, in accordance with elastic deformation of the electrically-conductive elastic body12. Therefore, even when the electrically-conductive elastic body12has been elastically deformed due to stretch and contraction, etc., the connection between the covered copper wire13and the electrically-conductive elastic body12is maintained. Therefore, reliability in the connection between the element part and the wiring can be enhanced. When the eyelet21is used, the covered copper wire13can be easily fixed to the electrically-conductive elastic body12, compared with the case where threads14are sewn.

In Embodiment 1 above, the connection part13aof the covered copper wire13is in a looped shape wound in a circular shape. However, the shape of the connection part13ais not limited thereto, and may be a U-shape, a rectangular shape, a spiral shape, or the like.

FIG.8Ashows a modification in which the shape of the connection part13ais a U-shape. In this modification, the connection part13aof the covered copper wire13is in a U-shape. In this case, three places on the X-axis positive side, the X-axis negative side, and the Y-axis negative side of the connection part13aare fastened to the electrically-conductive elastic body12by three threads14. In this case as well, reliability in the connection between the element part and the wiring can be enhanced. However, in the case ofFIG.8A, the contact area between the connection part13aand the electrically-conductive elastic body12is reduced when compared with that of Embodiment 1 above. Therefore, from the viewpoints of increase of the contact area and reduction of the contact resistance, it is preferable that the connection part13ais in a looped shape wound in a circular shape, as in Embodiment 1 above.

In Embodiment 1 above, the connection part13aof the covered copper wire13is fixed only to the electrically-conductive elastic body12and the base member11which are positioned on the lower side. However, the connection part13amay be fixed also to the base member20which is positioned on the upper side.

FIG.8Bshows a modification in which, when threads14are used, the threads14are fixed also to the base member20on the upper side.

As shown inFIG.8B, each thread14of the present modification is fixed so as to penetrate, in the up-down direction, the base member11, the electrically-conductive elastic body12, and the base member20, by passing through the inner side and the outer side of the connection part13a. In this case, the base member20is disposed so as to be in close contact with the electrically-conductive elastic body12, and the thread14brings the two base members11,20into close contact with each other. Accordingly, as indicated by each white arrow, the thread14indirectly, via the base members11,20, presses and fixes the connection part13ato the surface of the electrically-conductive elastic body12such that the connection part13ais movable with respect to the surface of the electrically-conductive elastic body12. As a result, the connection part13ais connected to the electrically-conductive elastic body12.

FIG.8Cshows a modification in which, when an eyelet21is used, the eyelet21is fixed also to the base member20on the upper side.

As shown inFIG.8C, the height (the length in the Z-axis direction) of the eyelet21of the present modification is slightly greater than the thickness from the lower face of the base member11to the upper face of the base member20. A hole20apenetrating the base member20in the up-down direction, a hole12apenetrating the electrically-conductive elastic body12in the up-down direction, and a hole11cpenetrating the base member11in the up-down direction are formed at the position at which the eyelet21is to be set. The diameter of the hole20a,12a,11cis substantially the same as the outer diameter of the eyelet21.

In this case as well, the eyelet21is positioned such that the upper end portion21aslightly protrudes in the upward direction from the upper face of the base member20and the lower end portion21bslightly protrudes in the downward direction from the lower face of the base member11. In this state, the upper end portion21ais crimped onto the upper face of the base member20, and the lower end portion21bis crimped onto the lower face of the base member11.

Then, similar toFIG.8B, as indicated by a white arrow, the eyelet21indirectly, via the base members11,20, presses and fixes the connection part13ato the surface of the electrically-conductive elastic body12such that the connection part13ais movable with respect to the surface of the electrically-conductive elastic body12. That is, as a result of the eyelet21being crimped, the connection part13ais sandwiched and fixed by the base members11,20while receiving certain pressing forces in the up-down direction. As a result, the connection part13ais connected to the electrically-conductive elastic body12.

Embodiment 2

In Embodiment 1, the base member20is set on the upper face of the structure1ashown inFIG.3A. However, in Embodiment 2, another structure30that has three electrically-conductive elastic bodies32is set on the upper face of the structure1ashown inFIG.3A.

FIG.9Ais a perspective view schematically showing a configuration of the structure30.

The structure30includes a base member31, three electrically-conductive elastic bodies32, three covered copper wires33, and a plurality of threads34for fixing each covered copper wire33to a corresponding electrically-conductive elastic body32. The base member31is formed from the same material as that of the base member11, and the thickness of the base member31is similar to the thickness of the base member11. Electrically-conductive elastic bodies32similar to the electrically-conductive elastic bodies12set on the base member11are set on the face on the Z-axis negative side of the base member31. The three electrically-conductive elastic bodies32are disposed so as to be superposed on the three electrically-conductive elastic bodies12, when the structure30is superposed on the structure1a. Each covered copper wire33is connected to the vicinity of an end portion on the Y-axis positive side of a corresponding electrically-conductive elastic body32. The covered copper wire33has a configuration similar to that of the covered copper wire13, and the thread34has a configuration similar to that of the thread14. A connection part33aof the covered copper wire33is connected by four threads34to the electrically-conductive elastic body32in a manner similar to that by the threads14. As a result, the structure30shown inFIG.9Ais assembled.

Subsequently, from above the structure1ashown inFIG.3A, the structure30inFIG.9Ais set in a state of being reversed in the up-down direction, as shown inFIG.9B. Four corners of the base member31are connected to the base member11by a silicone rubber-based adhesive, a thread, or the like, whereby the structure30is fixed to the base member11. At this time, covered portions33bof the covered copper wires33are fixed in a state of being bundled by threads15a, to the upper face of the wiring fixation base member15, as in the case of the covered portions13bof the covered copper wires13. In this case, the covered portions33bof the covered copper wires33and the covered portions13bof the covered copper wires13may be bundled together. End portions on the side opposite to the connection part33aof each covered copper wire33is connected to the circuit connection terminal16. Then, as shown inFIG.9B, a load sensor1of Embodiment 2 is completed.

FIG.10AandFIG.10Bare each a cross-sectional view schematically showing the periphery of a covered copper wire17when viewed in the X-axis negative direction.FIG.10Ashows a state where no load is applied, andFIG.10Bshows a state where loads are applied.

When no load is applied to the region shown inFIG.10A, the force applied between the electrically-conductive elastic body12and the covered copper wire17and the force applied between the covered copper wire17and the electrically-conductive elastic body32are substantially zero. From this state, as shown inFIG.10B, when a load is applied in the upward direction to the lower face of the base member11, and a load is applied in the downward direction to the upper face of the base member31, the two electrically-conductive elastic bodies12,32having elasticity are deformed by the covered copper wire17.

As shown inFIG.10B, when the loads are applied, the covered copper wire17is brought close to the two electrically-conductive elastic bodies12,32so as to be wrapped by the two electrically-conductive elastic bodies12,32, and the contact area between the covered copper wire17and the electrically-conductive elastic body12and the contact area between the covered copper wire17and the electrically-conductive elastic body32increase. Accordingly, the capacitance between the copper wire17ain the covered copper wire17and the electrically-conductive elastic body12and the capacitance between the copper wire17ain the covered copper wire17and the electrically-conductive elastic body32change. Then, the load applied to this region is calculated on the basis of the sum of the two capacitances.

Effects of Embodiment 2

According to Embodiment 2, the following effects are exhibited in addition to effects similar to those in Embodiment 1.

As shown inFIG.9AandFIG.9B, the structure30is disposed on the upper side of the structure1asuch that each electrically-conductive elastic body32is superposed on the covered copper wires17. Then, on the basis of the sum of the capacitance between the copper wire17aof the covered copper wire17and the electrically-conductive elastic body12and the capacitance between the copper wire17ain the covered copper wire17and the electrically-conductive elastic body32, the load is calculated. Accordingly, when compared with Embodiment 1, the capacitance is increased, and thus, sensitivity of the load sensor1can be enhanced. Therefore, load detection accuracy of the load sensor1can be enhanced. In addition, since the upper and lower sides of the covered copper wire17are shielded by the electrically-conductive elastic bodies12,32, respectively, noise occurring in the copper wire17aof the covered copper wire17can be suppressed.

Modification of Embodiment 2

In Embodiment 2 above, separate covered copper wires13,33are drawn from the electrically-conductive elastic body12on the structure1aside and the electrically-conductive elastic body32on the structure30side, respectively. However, a common covered copper wire may be drawn from the two electrically-conductive elastic bodies12,32superposed on each other in the up-down direction.

FIG.11Ashows a modification in which, in Embodiment 2 above, a common covered copper wire13is drawn from two electrically-conductive elastic bodies12,32superposed on each other in the up-down direction, and the covered copper wire13is fixed by threads14.

As shown inFIG.11A, in this modification, in the vicinity of end portions on the Y-axis positive side of the electrically-conductive elastic bodies12,32, each thread14is sewn so as to penetrate the upper and lower members, as in the case of the modification described with reference toFIG.8B. Accordingly, the connection part13aof the covered copper wire13is sandwiched by the two electrically-conductive elastic bodies12,32, and is pressed and fixed to the surfaces of the two electrically-conductive elastic bodies12,32so as to be movable with respect to the surfaces of the two electrically-conductive elastic bodies12,32.

As a result, the load sensor1of this modification is completed as shown inFIG.11B. In this modification, when viewed from the upper face side of the base member31, four threads14are provided at each of three positions corresponding to the electrically-conductive elastic bodies12,32superposed on each other in the up-down direction, and each covered copper wire13is fixed by four threads14.

FIG.12Ashows a modification in which, in Embodiment 2 above, a common covered copper wire13is drawn from two electrically-conductive elastic bodies12,32superposed on each other in the up-down direction, and the covered copper wire13is fixed by an eyelet21.

As shown inFIG.12A, in this modification, similar to the modification described with reference toFIG.8C, in the vicinity of end portions on the Y-axis positive side of the electrically-conductive elastic bodies12,32, an eyelet21is passed through a hole31aof the base member31, a hole32aof the electrically-conductive elastic body32, a hole12aof the electrically-conductive elastic body12, and a hole11cof the base member11, and is set so as to penetrate each member in the up-down direction. Accordingly, the connection part13aof the covered copper wire13is sandwiched by the two electrically-conductive elastic bodies12,32, and is pressed and fixed to the surfaces of the two electrically-conductive elastic bodies12,32so as to be movable with respect to the surfaces of the two electrically-conductive elastic bodies12,32.

As a result, the load sensor1of this modification is completed as shown inFIG.12B. In this modification, when viewed from the upper face side of the base member31, an eyelet21is provided at each of three positions corresponding to the electrically-conductive elastic bodies12,32superposed on each other in the up-down direction, and each covered copper wire13is fixed by one eyelet21.

In Embodiment 2 above, the two covered copper wires13,33respectively connected to the electrically-conductive elastic body12and the electrically-conductive elastic body32are each fixed by threads, but may be each fixed by an eyelet. Alternatively, one of the two covered copper wires13,33may be fixed by threads, and the other may be fixed by an eyelet.

Embodiment 3

In Embodiments 1, 2, as shown inFIG.3A, the end portions on the X-axis negative side of each covered copper wire17set on the electrically-conductive elastic bodies12are directly fixed to the base member11by threads11b. However, in Embodiment 3, a shield layer41is set between the covered copper wire17and the base member11.

FIG.13Ais a perspective view schematically showing the shield layer41, a covered copper wire42, and threads43, which are set to the structure inFIG.1B. When compared withFIG.1B, the base member11inFIG.13Ais configured to be long in the X-axis direction.

The shield layer41is formed from a material similar to that of the electrically-conductive elastic body12, and the thickness of the shield layer41is similar to the thickness of the electrically-conductive elastic body12. The shield layer is configured to have a size, in the X-Y plane, that can substantially include the covered copper wires17positioned to the left of the left-end electrically-conductive elastic body12. The shield layer41is set on the upper face of the base member11with an adhesive or the like. The covered copper wire42is set, by the threads43, in the vicinity of an end portion on the Y-axis positive side of the shield layer41. The covered copper wire42has a configuration similar to that of the covered copper wire13, and the thread43has a configuration similar to that of the thread14. A connection part42aof the covered copper wire42is connected to the shield layer41by the threads43, similar to the connection part13aof the covered copper wire13. End portions on the side opposite to the connection part42aof the covered copper wire42are connected to the circuit connection terminal16.

Then, similar to Embodiment 1, three covered copper wires17and threads11a,11bare set to the structure inFIG.13A. In the vicinity of an end portion on the X-axis negative side of the base member11, the covered copper wires17extending in the Y-axis direction are connected, in a state of being bundled by threads11b, to the upper face of the shield layer41. As a result, the structure1aof Embodiment 3 is assembled as shown inFIG.13B.

FIG.14Ais a perspective view schematically showing a shield layer51, a covered copper wire52, and threads53set to the structure inFIG.9A. When compared withFIG.9A, the base member31inFIG.14Ais configured to be long in the X-axis direction.

The shield layer51is formed from a material similar to that of the electrically-conductive elastic body32, and the thickness of the shield layer51is similar to the thickness of the electrically-conductive elastic body32. The shield layer51is configured to have a size, in the X-Y plane, similar to that of the shield layer41inFIG.13A. The shield layer51is set on the face on the Z-axis negative side of the base member31with an adhesive or the like. The covered copper wire52is set, by the threads53, in the vicinity of an end portion on the Y-axis positive side of the shield layer51. The covered copper wire52has a configuration similar to that of the covered copper wire33, and the thread53has a configuration similar to that of the thread34. A connection part52aof the covered copper wire52is connected to the shield layer51by the threads53, similar to the connection part33aof the covered copper wire33. As a result, the structure30of Embodiment 3 is assembled as shown inFIG.14A.

Subsequently, as shown inFIG.14B, from above the structure1ainFIG.13B, the structure30inFIG.14Ais set in a state of being reversed in the up-down direction. Four corners of the base member31are connected to the base member11by a silicone rubber-based adhesive, a thread, or the like, whereby the structure30is fixed to the base member11. At this time, end portions on the side opposite to the connection part52aof the covered copper wire52are connected to the circuit connection terminal16. Then, as shown inFIG.14B, a load sensor1of Embodiment 3 is completed.

When the load sensor1is used, an electric potential having the same polarity as that of the electrically-conductive elastic body12is applied to the shield layer41, and an electric potential having the same polarity as that of the electrically-conductive elastic body32is applied to the shield layer51. Accordingly, occurrence of noise in the covered copper wires17in the ranges of the shield layers41,51is suppressed.

Effects of Embodiment 3

According to Embodiment 3, the following effects are exhibited in addition to effects similar to those in Embodiments 1, 2.

The shield layers41,51shield each covered copper wire17drawn from an element part, from external noise. Accordingly, noise superposed on the covered copper wire17can be reduced. The shield layer41is disposed on the same face as that of the base member11on which the electrically-conductive elastic bodies12are disposed, and the shield layer51is disposed on the same face as that of the base member31on which the electrically-conductive elastic bodies32are disposed. Therefore, setting of the shield layers41,51is facilitated.

Other Modifications

Various modifications of the configuration of the load sensor1can be made in addition to the configurations shown in Embodiments 1 to 3 above.

For example, in Embodiments 1 to 3 above, three electrically-conductive elastic bodies12are set on the surface of the base member11. However, the number of electrically-conductive elastic bodies12disposed on the load sensor1is not limited thereto. For example, on the entire surface of the base member11, one electrically-conductive elastic body12may be disposed, or four or more electrically-conductive elastic bodies12may be disposed. In addition, although three covered copper wires17are disposed with respect to three electrically-conductive elastic bodies12, the numbers of electrically-conductive elastic bodies12and covered copper wires17that are disposed are not limited thereto. For example, a plurality of covered copper wires17extending in the X-axis direction may be disposed so as to be arranged in the Y-axis direction, with respect to one electrically-conductive elastic body12extending in the Y-axis direction. Alternatively, the load sensor1may be provided with one electrically-conductive elastic body12and one covered copper wire17only.

In association with changes in the number of electrically-conductive elastic bodies12and the number of covered copper wires17, the number of element parts in each of which capacitance changes in accordance with a load is also changed. That is, the number of element parts provided in the load sensor1is not limited to the number shown in Embodiments 1 to 3 above, and another number of element parts may be provided in the load sensor1.

In Embodiments 1 to 3 above, a plurality of covered copper wires13are bundled by the threads15asuch that the cross-section of the concentrated space thereof has a planar shape. However, not limited thereto, the plurality of covered copper wires13may be bundled by the threads15asuch that the cross-section of the concentrated space has another shape (e.g., a quadrangular shape or a triangular shape). Similarly, the plurality of covered copper wires17may also be bundled by the threads11bsuch that the cross-section of the concentrated space thereof has another shape. In addition, the plurality of covered copper wires33may be bundled by the threads15asuch that, not limited to a planar shape, the cross-section of the concentrated space thereof has another shape.

In Embodiment 1 above, as shown inFIG.2C, the thread14sews the covered copper wire13to the electrically-conductive elastic body12and the base member11. However, not limited thereto, the thread14may sew the covered copper wire13only to the electrically-conductive elastic body12. In Embodiment 2 above, the thread34sews the covered copper wire33to the electrically-conductive elastic body32and the base member31, but not limited thereto, the thread34may sew the covered copper wire33only to the electrically-conductive elastic body32. Similarly, the thread43may also sew the covered copper wire42only to the shield layer41, and the thread53may also sew the covered copper wire52only to the shield layer51.

In Embodiments 1 to 3 and the modifications above, the threads14,34,43,53and the eyelet21are formed from a material that has electrical conductivity, but need not necessarily have electrical conductivity. However, from the viewpoint of reduction of contact resistance, it is preferable that the threads14,34,43,53and the eyelet21are configured to have electrical conductivity, as described above.

In Embodiment 3 above, the shield layer is disposed on the upper and lower sides of the covered copper wires17, but may be disposed only on the upper side or the lower side of the covered copper wires17. The shield layer may also be provided so as to cover the entirety of the outer side of the load sensor1.

In Embodiment 1 above, the base member20may be an insulative member having elasticity. In this case, the base member20is formed from a material similar to that of the base member11, for example.

In Embodiments 1 to 3 above, the covered copper wires13,17,33,42,52are directly connected to the circuit connection terminal16. However, not limited thereto, the covered copper wires13,17,33,42,52may be connected to another terminal connected to the circuit connection terminal16, thereby being connected indirectly, via the other terminal, to the circuit connection terminal16.

In Embodiments 1 to 3 above, the covering member of the connection part13aof each covered copper wire13is removed by soldering, but not limited thereto, may be removed by another means. For example, the covering member of the connection part13amay be removed by a chemical processing technique such as immersing the connection part13ainto an ammonia-based reagent, potassium hydroxide, or the like. Similarly, the covering member of the connection part of the covered copper wires33,42,52may be removed by another means, not limited to soldering.

In Embodiments 1 to 3 above, instead of each covered copper wire17, a covered copper wire60implemented as a stranded wire obtained by bundling a plurality of covered copper wires17may be used.

FIG.15Ais an enlarged diagram schematically showing a configuration of the covered copper wire60.FIG.15Bis a cross-sectional view schematically showing a configuration of the covered copper wire60.

As shown inFIG.15A, the covered copper wire60is a stranded wire obtained by stranding the covered copper wires17used in Embodiments 1 to 3 above. As shown inFIG.15B, a plurality of covered copper wires17forming the covered copper wire60are gathered in a substantially circular shape, thereby forming a bundle. The diameter of the covered copper wire60is 0.3 mm, for example.

As shown inFIG.15AandFIG.15B, since the covered copper wire60is implemented as a stranded wire, the diameter of one covered copper wire60is greater than the diameter of one covered copper wire17. Accordingly, the contact area between the covered copper wire60and the electrically-conductive elastic body12, and the contact area between the covered copper wire60and the electrically-conductive elastic body32increase when compared with those in Embodiments 1 to 3. Therefore, the capacitance between the covered copper wire60and the electrically-conductive elastic body12and the capacitance between the covered copper wire60and the electrically-conductive elastic body32are increased, and thus, the sensitivity of the load sensor1can be enhanced. In addition, since the covered copper wire60is implemented as a stranded wire, flexibility can be enhanced and strength against bending can be enhanced, when compared with those in Embodiments 1 to 3.

Instead of each of the covered copper wires13,33,42,52, a covered copper wire implemented as a stranded wire obtained by bundling a plurality of covered copper wires may be used. In this case as well, in the covered copper wire implemented as a stranded wire, flexibility can be enhanced and strength against bending can be enhanced.

In Embodiments 1 to 3 above, the three covered copper wires13and the three covered copper wires17may be connected to an electronic circuit18outside the load sensor1, through the following configuration, for example.

FIG.16Ais a plan view schematically showing a configuration of a connection substrate70according to a modification in this case.

The connection substrate70includes six metal island parts71, six patterns72, six electrodes73, and a connector74.

The metal island parts71are provided on the connection substrate70. Three covered copper wires13and three covered copper wires17are respectively connected to the metal island parts71by soldering. The covering member of a connection part13cof each covered copper wire13and the covering member of a connection part17cof each covered copper wire17are each removed in advance, before being connected to a corresponding metal island part71. The covering member is removed by the connection part13c,17cbeing immersed in a bath containing a high temperature molten solder, as in the case of the connection part13aabove.

Each metal island part71is connected to a corresponding electrode73via a pattern72. The patterns72and the electrodes73are provided on the connection substrate70. The connector74is provided on the connection substrate70so as to cover the electrodes73. Six terminals of the connector74are electrically connected the six electrodes73, respectively. The connector74is a circuit connection terminal for connecting each element part of the load sensor1to the external electronic circuit18.

The electronic circuit18is set on a main substrate (not shown). A connector18aand cables18bare connected to this main substrate. The connector18aincludes six terminals to be respectively connected to the six terminals on the connector74side. Each terminal of the connector18ais connected to the electronic circuit18via a cable18b. The connector18ais set to an end portion of each cable18b. As a result of the connector18abeing connected to the connector74of the connection substrate70, the three electrically-conductive elastic bodies and the three covered copper wires17are electrically connected to the electronic circuit18.

When the connection substrate70is configured in this manner, the connection substrate70and the electronic circuit can be smoothly connected to each other. In addition, terminal portions (the electrodes73and the connector74) for connecting the covered copper wires13and the covered copper wires17to an external device can be configured to be compact.

Instead of the connection substrate70shown inFIG.16A, another connector such as a box connector or a crimp connector may be used to connect the covered copper wires13,17to the electronic circuit18.

Alternatively, as shown inFIG.16B, a main substrate19to which the electronic circuit18is mounted may be provided with six metal island parts71, and the covered copper wires13and the covered copper wires17may be directly connected to these metal island parts71by soldering.

In Embodiments 1 to 3 above, the thread11a,11b,14,15a,34,43,53is sewn to a target object by embroidering, but not limited thereto, may be sewn to the target object by machine sewing. When the thread is sewn to the target object by machine sewing, the seam of the thread becomes strong.

FIG.17Ais a perspective view schematically showing a state where the covered copper wires17are fixed to the base member11by the thread11awhen the thread11ais sewn by machine sewing. In this case, for example, the thread11ais sewn in the Y-axis direction by machine sewing so as to extend across all of the three covered copper wires17arranged in the Y-axis direction.

FIG.17Bis a side view schematically showing a cross-section obtained when the structure1ais cut along a plane parallel to the Y-Z plane at the position of the thread11aextending in the Y-axis direction inFIG.17A. When the thread11ais sewn to the base member11by machine sewing, a needle thread81and a bobbin thread82of the thread11aare connected to each other in the vicinity of the center in the up-down direction of the base member11. When the needle thread81and the bobbin thread82are sewn to the base member11by machine sewing from the upper and lower sides, each covered copper wire17disposed on the upper face side of the base member11is pressed and fixed to the base member11by the needle thread81of the thread11a.

FIG.18AandFIG.18Bare each a plan view schematically showing a state where the connection part13aof the covered copper wire13is fixed to the electrically-conductive elastic body12and the base member11by the thread14when the thread is sewn by machine sewing.FIG.18Ashows a case where, similar to the case ofFIG.2B, four places of the connection part13aare fixed by the thread14.FIG.18Bshows a case where the shape of the seam has 16 vertexes.FIG.18Cis a perspective view schematically showing a configuration of the load sensor1when the seam is provided over the entire periphery as inFIG.18B.

As shown inFIG.18AandFIG.18B, in the case of machine sewing, the thread14is sewn in a single sewing operation from the sewing start position to the sewing end position. Therefore, the seam seems to be continuous when viewed from the upper face side. In the case ofFIG.18A, the number of times the seam extends across the connection part13ais 6. In the case ofFIG.18B, the number of times the seam extends across the connection part13ais 32. As in the case ofFIG.18B, when the entire periphery of the connection part13ais sewn by the thread14and the number of times the thread14extends across the connection part13ais increased, the connection part13ais more assuredly connected to the electrically-conductive elastic body12.

It should be noted that, when the thread14is sewn over the entire periphery as shown inFIG.18BandFIG.18C, the thread14need not necessarily be sewn by machine sewing, but may be sewn by embroidery.

In addition to the above, various modifications can be made as appropriate to the embodiments of the present invention without departing from the scope of the technical idea defined by the claims.