Load Sensor

Abstract

This load sensor comprises: a base member (11); a plurality of conductive elastic bodies (13) which are disposed on an upper surface of the base member (11) and arranged side by side at predetermined intervals in a Y-axis direction; a plurality of linear conductive members (14a) which extend in an X-axis direction and cross the plurality of conductive elastic bodies (13); and dielectric bodies (14b) which are disposed between the conductive elastic bodies (13) and the conductive members (14a).

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 technology]

[0002] Load sensors are widely used in fields such as industrial equipment, robots, and vehicles. In recent years, with the advancement of computer-based control technology and improvements in design, there has been progress in the development of electronic devices that make use of a variety of free-form surfaces, such as humanoid robots and automobile interior fittings. Accordingly, there is a demand for high-performance load sensors to be attached to each free-form surface.

[0003] The following Patent Document 1 describes a pressure-sensitive element (load sensor) including a plurality of first electrodes made of a conductive elastic body, a plurality of second electrodes made of linear conductive members, and a dielectric covering the surfaces of the second electrodes. The plurality of first electrodes and the plurality of second electrodes are arranged so as to intersect with each other in a plan view. Insulating portions made of an insulating elastic body are arranged between the plurality of first electrodes. The plurality of first electrodes and the plurality of insulating portions are integrated to form an elastic sheet.

[0004] In this configuration, when the load applied to each intersection of the first electrode and the second electrode increases, the contact area between the first electrode and the dielectric increases at each intersection, and the capacitance between the first electrode and the second electrode increases accordingly. Therefore, by detecting the value of the capacitance between the first electrode and the second electrode for each intersection, the load applied to each intersection can be detected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 079995 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above configuration, the speed of elastic return of the conductive elastic body (first electrode) when the load is released is usually slower than the elastic deformation of the conductive elastic body when the load is applied. This causes a difference in the relationship between the load and the capacitance when the load is applied and when the load is released. Therefore, when detecting the load both when the load is applied and when the load is released, it becomes difficult to detect the load smoothly and accurately.

[0007] In view of the above problem, an object of the present invention is to provide a load sensor that can suppress deviation in the relationship between load and capacitance between when a load is applied and when the load is released. [Means for solving the problem]

[0008] A load sensor according to a main aspect of the present invention includes a base member, a plurality of conductive elastic bodies arranged on an upper surface of the base member and spaced apart in a first direction with a predetermined gap therebetween, a plurality of linear conductive members extending in a second direction and intersecting the conductive elastic bodies, and a dielectric body arranged between the conductive elastic bodies and the conductive members. The width of the conductive elastic body in a direction perpendicular to the second direction is equal to or less than an upper limit contact width at which the conductive elastic body can come into contact with the conductive member via the dielectric. .

[0009] According to the load sensor of this aspect, the conductive elastic bodies are arranged with gaps between them, thereby reducing the space required for arranging the conductive elastic bodies relative to the upper surface of the base member. This allows the structure consisting of the base member and the conductive elastic bodies to quickly return to its original elastic state when the load is released, thereby enabling the relationship between the load and capacitance when the load is released to approach the relationship between the load and capacitance when the load is applied. This reduces the deviation in the relationship between the load and capacitance when the load is applied and when the load is released. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to provide a load sensor that can suppress the occurrence of a deviation in the relationship between the load and the capacitance when the load is applied and when the load is released.

[0011] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below. [Brief explanation of the drawings]

[0012] [Figure 1] Fig. 1(a) is a perspective view showing a lower base member and a conductor placed on the upper surface of the lower base member according to an embodiment, and Fig. 1(b) is a perspective view showing a state in which a conductive elastic body is disposed on the structure of Fig. 1(a) according to an embodiment. [Figure 2] Fig. 2(a) is a perspective view showing a state in which a conductor wire is arranged on the structure of Fig. 1(b) according to an embodiment, and Fig. 2(b) is a perspective view showing a state in which an upper base member is installed on the structure of Fig. 2(a) according to an embodiment. [Figure 3] 3(a) and 3(b) are diagrams each showing a schematic cross section of a sensor unit according to an embodiment. [Figure 4] FIG. 4 is a plan view schematically showing the internal configuration of the load sensor according to the embodiment. [Figure 5] FIG. 5 is a plan view schematically showing the internal configuration of a load sensor according to a comparative example. [Figure 6] FIG. 6 is a graph showing an example of a change in capacitance over time when a load is applied and released, according to a comparative example. [Figure 7] Fig. 7(a) is a graph showing a relationship between load and capacitance according to a comparative example, and Fig. 7(b) is a graph showing a relationship between load and capacitance according to an embodiment. [Figure 8] 8(a) and 8(b) are diagrams illustrating a preferred range of the conductor wire in the Y-axis direction according to the embodiment. [Figure 9] 9(a) and 9(b) are diagrams illustrating a preferred range of the conductor wire in the Y-axis direction according to the embodiment. [Figure 10]10(a) and 10(b) are diagrams illustrating a preferred relationship between the widths of the conductive elastic body and the conductive body in the X-axis direction according to the embodiment. [Figure 11] FIG. 11 is a plan view schematically showing the internal configuration of a load sensor according to a modified example. [Figure 12] 12(a) and 12(b) are diagrams each showing a schematic cross section of a sensor unit according to a modified example.

[0013] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The load sensor according to the present invention can be applied to a load sensor for a management system or electronic device that performs processing in response to an applied load.

[0015] Examples of management systems include inventory management systems, driver monitoring systems, coaching management systems, security management systems, and nursing care / childcare management systems.

[0016] In an inventory management system, for example, a load sensor installed on a stock shelf detects the weight of the stock piled up, and detects the type and number of products on the stock shelf. This allows for efficient inventory management and labor savings in stores, factories, warehouses, etc. Furthermore, a load sensor installed inside a refrigerator detects the weight of food in the refrigerator, and detects the type, number, and amount of food in the refrigerator. This allows for automatic menu suggestions using the food in the refrigerator.

[0017] In a driver monitoring system, for example, a load sensor provided in the steering device monitors the load distribution of the driver on the steering device (for example, grip force, grip position, and pedal force). Also, a load sensor provided in the vehicle seat monitors the load distribution of the driver on the vehicle seat while seated (for example, center of gravity position). This makes it possible to provide feedback on the driver's driving state (drowsiness, psychological state, etc.).

[0018] In a coaching management system, for example, load sensors installed in the bottom of shoes monitor the load distribution on the soles of the feet, which can correct or guide the wearer to an appropriate walking or running state.

[0019] In a security management system, for example, load sensors installed on the floor detect the load distribution as a person passes through, and detect the person's weight, stride length, passing speed, shoe sole pattern, etc. By comparing this detected information with data, it becomes possible to identify the person who has passed through.

[0020] In a caregiving and childcare management system, for example, load sensors installed on bedding and toilet seats monitor the weight distribution of the human body relative to the bedding and toilet seat. This makes it possible to estimate what actions the person is about to take in relation to the position of the bedding or toilet seat and prevent falls or trips.

[0021] Examples of electronic devices include in-vehicle devices (car navigation systems, audio equipment, etc.), home appliances (electric kettles, induction cooking heaters, etc.), smartphones, electronic paper, electronic book readers, PC keyboards, game controllers, smartwatches, wireless earphones, touch panels, electronic pens, penlights, luminous clothing, musical instruments, etc. In electronic devices, a load sensor is provided in the input unit that receives input from the user.

[0022] The load sensor in the following embodiments is a capacitance type load sensor that is typically provided in the load sensors of the management systems and electronic devices described above. Such load sensors are sometimes called "capacitive pressure-sensitive sensor elements," "capacitive pressure detection sensor elements," "pressure-sensitive switch elements," etc. The load sensors in the following embodiments are connected to a detection circuit, and the load sensor and the detection circuit constitute a load detection device. The following embodiments are one embodiment of the present invention, and the present invention is not limited to the following embodiments in any way.

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing has X, Y, and Z axes which are orthogonal to each other. The Z axis direction is the height direction of the load sensor 1.

[0024] FIG. 1(a) is a perspective view that schematically shows a base member 11 and a conductor 12 that is placed on an upper surface 11a (the surface on the positive side of the Z axis) of the base member 11. FIG.

[0025] The base member 11 is an elastic insulating flat plate. Condition The base member 11 has a rectangular shape in a plan view. The thickness of the base member 11 is constant. When the thickness of the base member 11 is small, the base member 11 is sometimes called a sheet member or a film member. The base member 11 is made of a non-conductive resin material or a non-conductive rubber material.

[0026] The resin material used for the base member 11 is at least one resin material selected from the group consisting of, for example, styrene-based resins, silicone-based resins (such as polydimethylpolysiloxane (PDMS)), acrylic-based resins, rotaxane-based resins, and urethane-based resins. The rubber material used for the base member 11 is at least one rubber material selected from the group consisting of, for example, 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.

[0027] The conductors 12 are arranged on the upper surface 11a of the base member 11. Here, three conductors 12 are arranged on the upper surface 11a of the base member 11 so as to extend in the first direction (Y-axis direction). The conductors 12 are made of a material with lower resistance than the conductive elastic body 13 described below. In this embodiment, the conductors 12 are elastic conductive members, and the thickness of the conductors 12 is smaller than the thickness of the conductive elastic body 13 described below. A cable 12a electrically connected to the conductors 12 is installed at the end of each conductor 12 on the negative side of the Y-axis.

[0028] FIG. 1(b) is a perspective view that schematically shows a state in which a conductive elastic body 13 is arranged in the structure of FIG. 1(a).

[0029] The conductive elastic bodies 13 are formed on the upper surface 11a of the base member 11 so as to cover the conductors 12. The conductive elastic bodies 13 are formed on the upper surface 11a so that the conductors 12 are positioned at approximately the middle of the conductive elastic bodies 13 in the second direction (X-axis direction). The conductive elastic bodies 13 are formed side by side in the first direction (Y-axis direction) with a predetermined gap between them. Here, six conductive elastic bodies 13 are formed in the Y-axis direction. Furthermore, rows each consisting of a plurality of conductive elastic bodies 13 aligned in the Y-axis direction are formed side by side in the X-axis direction with a predetermined gap between them. Here, three rows each consisting of a plurality of conductive elastic bodies 13 aligned in the Y-axis direction are formed in the X-axis direction.

[0030] The conductive elastic body 13 is an elastic, conductive member. The conductive body 12 and a row of the conductive elastic bodies 13 arranged in the Y-axis direction and formed to cover the conductive body 12 are electrically connected to each other.

[0031] Here, the conductor 12 and the conductive elastic body 13 are formed on the upper surface 11a of the base member 11 by a printing method such as screen printing, gravure printing, flexographic printing, offset printing, or gravure offset printing. After the conductor 12 is formed as shown in FIG. 1(a), the conductive elastic body 13 is formed so as to overlap the conductor 12 as shown in FIG. 1(b). These printing methods make it possible to form the conductor 12 and the conductive elastic body 13 on the upper surface 11a of the base member 11 to a thickness of about 0.001 mm to 0.5 mm. However, the method for forming the conductor 12 and the conductive elastic body 13 is not limited to the above printing method.

[0032] The conductor 12 and the conductive elastic body 13 are made of a resin material with a conductive filler dispersed therein, or a rubber material with a conductive filler dispersed therein.

[0033] The resin material used for the conductor 12 and the conductive elastic body 13 is, like the resin material used for the above-described base member 11, at least one resin material selected from the group consisting of styrene-based resins, silicone-based resins (polydimethylpolysiloxane (e.g., PDMS)), acrylic-based resins, rotaxane-based resins, and urethane-based resins. The rubber material used for the conductor 12 and the conductive elastic body 13 is, like the rubber material used for the above-described base member 11, 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.

[0034] The conductive filler used in the conductor 12 and the conductive elastomer 13 is 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 (i.e., a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS)), and conductive fibers such as metal-coated organic fibers and metal wires (in a fibrous state).

[0035] In this embodiment, the conductive filler used in the conductor 12 is Ag (silver). In this case, the resistivity of the conductor 12 is 9×10 -3 The width of the conductor 12 in the X-axis direction is, for example, 10 μm or more, and the conductor 12 is configured so as to be smaller than the width of the conductive elastic body 13 in the X-axis direction. In this embodiment, the conductive filler that forms the conductive elastic body 13 is C (carbon). In this case, the resistivity of the conductive elastic body 13 is 1×10 -2 [Ω·cm] or more.

[0036] FIG. 2(a) is a perspective view that schematically shows a state in which a conductor wire 14 is arranged in the structure of FIG. 1(b).

[0037] The conductor wires 14 have a linear shape and extend in the second direction (X-axis direction). The conductor wires 14 are bent near the end of the base member 11 on the positive side of the X-axis. By bending the conductor wires 14, two conductor wires 14 adjacent to each other in the first direction (Y-axis direction) become a pair of conductor wires 14. Here, three pairs of conductor wires 14 are arranged to extend in the X-axis direction. The conductor wires 14 are arranged overlapping on the top surfaces of the three conductive elastic bodies 13 so as to intersect with the three conductive elastic bodies 13 aligned in the X-axis direction. The conductor wires 14 are made of a linear conductive member and a dielectric formed to cover the surface of the conductive member. The configuration of the conductor wires 14 will be described later with reference to FIGS. 3(a) and 3(b).

[0038] 2(a), each conductor wire 14 is loosely sewn to the base member 11 with thread so that it can move in the longitudinal direction (X-axis direction). The thread in this case is made of chemical fiber, natural fiber, or a mixture of these fibers.

[0039] FIG. 2(b) is a perspective view that schematically shows a state in which a base member 21 is installed on the structure of FIG. 2(a).

[0040] The base member 21 has the same configuration as the base member 11. The base member 21 has the same size and shape as the base member 11 and is made of the same material as the base member 11. The base member 21 is placed from above (the positive side of the Z axis) the structure shown in FIG. 2(a). Then, the outer periphery of the base member 21 is connected to the outer periphery of the base member 11 with, for example, a silicone rubber adhesive or thread. This fixes the base member 11 and the base member 21 together. In this way, the load sensor 1 is completed as shown in FIG. 2(b).

[0041] The load sensor 1 may be used in a state in which it is turned upside down from the state shown in Fig. 2(b). In this case, the base member 21 does not necessarily have to be made of the same material as the base member 11, and may be made of, for example, a hard material that is not easily elastically deformed.

[0042] Here, the load sensor 1 has a plurality of sensor units A1 arranged in a matrix in a plan view. The load sensor 1 has a total of nine sensor units A1 arranged in the second direction (X-axis direction) and the first direction (Y-axis direction). One sensor unit A1 corresponds to a region including an intersection between two conductive elastic bodies 13 adjacent in the Y-axis direction and two conductor wires 14 arranged on the upper surfaces of these two conductive elastic bodies 13. That is, one sensor unit A1 includes the conductor 12, the conductive elastic body 13, the conductor wires 14, and the base members 11 and 21 near the intersection. When the load sensor 1 is installed on a predetermined installation surface and a load is applied to the upper surface 21a (the surface on the positive side of the Z-axis) of the base member 21 constituting the sensor unit A1, the electrostatic capacitance between the conductive elastic bodies 13 and the conductive members in the conductor wires 14 changes, and the load is detected based on the electrostatic capacitance.

[0043] 3(a) and 3(b) are schematic cross-sectional views of the sensor unit A1 taken along a plane parallel to the YZ plane at the center of the sensor unit A1 in the X-axis direction. Fig. 3(a) shows the sensor unit A1 in a state where no load is applied, and Fig. 3(b) shows the sensor unit A1 in a state where a load is applied.

[0044] As shown in Figures 3(a) and 3(b), the conductor wire 14 is composed of a conductive member 14a and a dielectric member 14b formed on the conductive member 14a. The conductive member 14a is a linear member having electrical conductivity, and the dielectric member 14b covers the surface of the conductive member 14a. In Figures 3(a) and 3(b), the surface of the base member 11 on the negative side of the Z axis is placed on a mounting surface.

[0045] 3(a), when no load is applied, the force applied between the conductive elastic body 13 and the conductor wire 14 and the force applied between the base member 21 and the conductor wire 14 are almost zero. From this state, when a load is applied downward to the upper surface 21a of the base member 21 corresponding to the sensor unit A1 as shown in FIG. 3(b), the conductor wire 14 causes the conductive elastic body 13, the conductor 12, and the base members 11 and 21 to deform.

[0046] 3(b), when a load is applied, the conductor wire 14 is brought closer to the conductive elastic body 13 so as to be wrapped in the conductive elastic body 13, and the contact area between the conductor wire 14 and the conductive elastic body 13 increases. This causes a change in the capacitance between the conductive member 14a and the conductive elastic body 13. Then, by detecting the change in capacitance between the pair of conductor wires 14 included in the sensor unit A1, the load acting on the sensor unit A1 can be calculated.

[0047] FIG. 4 is a plan view schematically showing the internal configuration of the load sensor 1. As shown in FIG.

[0048] The three cables 12a are connected to an external circuit (not shown) including a load detection circuit. This connects the three conductors 12 to the external circuit. Furthermore, one end of each conductor wire 14 has the dielectric 14b coating removed, exposing the conductive member 14a. This end of each conductor wire 14 is connected to the external circuit.

[0049] The external circuit detects the capacitance value for each sensor unit A1 while switching between the conductor 12 and conductor wire 14 to be detected. Specifically, the external circuit applies a DC voltage via a resistor to the conductive elastic body 13 and conductor wire 14 that intersect in the sensor unit A1 to be detected, and measures the voltage value at this intersection. The voltage value at the intersection rises with a time constant determined by the resistance and the capacitance at the intersection (the capacitance due to the dielectric 14b between the conductive elastic body 13 and the conductive member 14a).

[0050] Here, the capacitance at the intersection point has a magnitude corresponding to the load applied to the intersection point. That is, the contact area of ​​the dielectric 14b with the conductive elastic body 13 changes depending on the load applied to the intersection point. The capacitance at the intersection point has a value corresponding to this contact area. The external circuit measures the voltage value at the intersection point at a predetermined timing after a certain period of time has elapsed since the start of application of the DC voltage, and obtains the load of the sensor unit A1 corresponding to that intersection point based on the measured voltage value. In this way, the load at each sensor unit A1 is detected.

[0051] Incidentally, the load sensor 1 may be used to detect a load not only when the load is applied but also when the load is released. When the load is released, the external circuit measures the voltage value of the sensor portion A1 (intersection position) at a predetermined timing after the start of DC voltage application, and detects the load at the sensor portion A1 based on the measured voltage value, as described above.

[0052] For example, in a usage mode in which a load sensor 1 is installed on the bottom of a shoe and the load distribution on the sole of the foot is monitored, the load when the shoe lands on the ground and the load when the shoe leaves the ground are monitored from the detection results of the load sensor 1. In this case, the above-mentioned external circuit (load detection circuit) detects the load when the shoe lands on the ground and the load on the top surface of the load sensor 1 increases (load application), and the load when the shoe leaves the ground and the load on the top surface of the load sensor 1 decreases (load release), for each sensor unit A1, and transmits the detection results to the monitoring system. The monitoring system monitors whether the walking or running state is appropriate based on the received load detection results (load distribution on the sole of the foot).

[0053] In such a usage mode, it is preferable that there is as little deviation as possible between the relationship between the load and capacitance when the load is applied and the relationship between the load and capacitance when the load is released, so that the load when the load is applied and the load when the load is released can be detected smoothly and accurately by an external circuit (load detection circuit).

[0054] In this embodiment, as described above, a plurality of conductive elastic bodies 13 are arranged on the upper surface of the base member 11 so as to be aligned in the first direction (Y-axis direction) with a predetermined gap therebetween. As a result, as will be described below, it is possible to suppress the difference between the change in capacitance of the sensor unit A1 when a load is applied and the change in capacitance of the sensor unit A1 when the load is released, and it is possible to smoothly and accurately detect the load when the load is applied and the load when the load is released.

[0055] FIG. 5 is a plan view schematically showing the internal configuration of the load sensor 2 according to the comparative example.

[0056] In the comparative example, the conductive elastic body 13 is formed continuously and without interruption in the Y-axis direction on the upper surface of the base member 11. That is, in the comparative example, the conductive elastic body 13 is not divided into gaps in the Y-axis direction. Even in this configuration, the external circuit (load detection circuit) can calculate the load applied to and released from each sensor unit A1 by processing similar to that in FIG. 4.

[0057] However, in the comparative example, the conductive elastic body 13 is not divided with gaps in the Y-axis direction, so the conductive elastic body 13 requires a large space to be placed relative to the upper surface 11a of the base member 11. On the other hand, since the conductive elastic body 13 contains the conductive filler as described above, it is harder than the base member 11. For this reason, when the conductive elastic body 13 requires a large space to be placed relative to the upper surface 11a of the base member 11 as in the comparative example, it becomes difficult for the structure consisting of the base member 11, the conductor 12, and the conductive elastic body 13 (hereinafter referred to as the "elastic structure") to quickly return to its original elastic state when the load is released, and as a result, the relationship between the load and capacitance when the load is released is likely to deviate from the relationship between the load and capacitance when the load is applied.

[0058] FIG. 6 is a graph showing an example of a change in capacitance over time when a load is applied and released, according to a comparative example.

[0059] In the example shown in Figure 6, a constant load is applied to sensor unit A1 at the load application timing shown in the figure, and this load is released from sensor unit A1 at the load release timing shown in the figure. The fine amplitude waveform in the figure shows fluctuations in capacitance due to noise.

[0060] The capacitance value detected when the load is zero is approximately 400 pF, and the capacitance value detected when the load is stable is approximately 800 pF. When the load is applied at approximately 0.18 s on the time axis, the capacitance value increases with time until approximately 0.24 s. When the load is released at approximately 0.37 s, the capacitance value decreases with time until approximately 0.46 s.

[0061] 6, for a predetermined period after the load is applied, the contact area between the dielectric 14b and the conductive elastic body 13 increases due to the elastic deformation of the elastic structure, and the capacitance of the sensor portion A1 (intersection position) increases in accordance with the increase in the contact area. Also, for a predetermined period after the load is released, the contact area between the dielectric 14b and the conductive elastic body 13 decreases due to the elastic restoration of the elastic structure, and the capacitance of the sensor portion A1 (intersection position) decreases in accordance with the decrease in the contact area.

[0062] In this case, the slope of the change in capacitance immediately after the load is released is gentler than the line L2, which is the left-right inversion of the line L1 that shows the change in capacitance when the load is applied. Furthermore, the slope of the change in capacitance when the load is released becomes even gentler after 0.4 seconds. In other words, the rate at which the capacitance value returns to the zero-load level (near 400 pF) becomes even slower in the latter half of the load release.

[0063] As described above, the change in capacitance when a load is applied and when the load is released is not symmetrical, and the change in capacitance when the load is released is slower than when a load is applied. In other words, in the comparative example, the elastic recovery of the conductive elastic body 13 when the load is released is slow, making it difficult for the capacitance to quickly return to the level when the load is zero.

[0064] FIG. 7(a) is a graph schematically showing the relationship between load and capacitance according to a comparative example.

[0065] The graph in Fig. 7(a) shows a schematic diagram of the change in capacitance of the sensor unit A1 (intersection position) when the load applied to the sensor unit A1 (intersection position) is increased from zero to a constant value at a constant rate and then decreased at the same rate. The horizontal axis of Fig. 7(a) represents the magnitude of the applied load, and the vertical axis of Fig. 7(a) represents the capacitance of the sensor unit A1 (intersection position).

[0066] 5, in the comparative example, the conductive elastic body 13 is formed continuously without gaps in the Y-axis direction so as to straddle all of the conductor wires 14, which makes it difficult for the elastic structure to elastically return to its original state as described above. Therefore, the speed of elastic deformation of the conductive elastic body 13 at the intersection of the conductor wires 14 when a load is applied is slower than the speed of elastic deformation of the conductive elastic body 13 at the intersection when a load is applied.

[0067] As a result, as shown in Figure 7(a), the relationship between the load and capacitance when the load is released deviates from the relationship between the load and capacitance when the load is applied. For example, for the same load F1, different capacitances C1 and C2 are generated when the load is applied and when it is released. Furthermore, even though the same capacitance C2 is obtained when the load is applied and when it is released, different loads F1 and F2 are detected.

[0068] FIG. 7(b) is a graph schematically showing the relationship between load and capacitance according to the embodiment.

[0069] 4, in the embodiment, the conductive elastic bodies 13 are formed spaced apart in the Y-axis direction for each conductor wire 14, so the influence of the conductive elastic bodies 13 on the elastic return of the elastic structure is reduced, making the elastic structure more likely to return to its original state than in the comparative example. As a result, the speed of elastic deformation of the conductive elastic bodies 13 at the intersections of the conductor wires 14 when a load is applied is made closer to the speed of elastic return of the conductive elastic bodies 13 at the intersections when the load is released.

[0070] As a result, as shown in FIG. 7(b), the relationship between the load and capacitance when the load is released can be made closer to the relationship between the load and capacitance when the load is applied. As a result, for example, for the same load F1, the capacitance values ​​C1 and C2 obtained when the load is applied and released are made closer to each other than in FIG. 7(a). Also, the load values ​​F1 and F2 obtained for the same capacitance C2 when the load is applied and released are made closer to each other than in FIG. 7(a). Therefore, according to the configuration of the embodiment, the difference between the detected load when the load is applied and the detected load when the load is released is reduced, allowing for smooth and accurate load detection.

[0071] Next, a preferred range of the width of the conductive elastic body 13 in the Y-axis direction will be described.

[0072] FIG. 8(a) is a diagram schematically showing a cross section of the vicinity of the conductive elastic body 13 and the conductor wire 14 when the sensor unit A1 is cut along a plane parallel to the YZ plane at the center position in the X-axis direction.

[0073] In this embodiment, the cross section of the conductor wire 14 in the YZ plane is circular. In this case, the length La of the periphery of the lower half of the circular cross section of the conductor wire 14 is the upper limit contact width in the Y-axis direction, over which the conductive elastic body 13 can come into contact with the conductive member 14a via the dielectric 14b. It is preferable that the width Lb of the conductive elastic body 13 in the Y-axis direction be equal to or less than the upper limit contact width. In other words, it is preferable that the length La and the width Lb be defined by the following formula (1):

[0074] La ≧ Lb … (1)

[0075] 8(a), if the radius of the circular cross section of the conductor wire 14 is r, then the length La is expressed by πr. Therefore, the upper limit contact width is πr, and it is preferable that the width Lb of the conductive elastic body 13 in the Y-axis direction is set to be equal to or less than πr.

[0076] Setting the width Lb in this manner effectively reduces the space required for arranging the conductive elastic body 13. That is, if the width Lb is greater than the upper limit contact width, the portion of the conductive elastic body 13 that exceeds the upper limit contact width will not come into contact with the conductive member 14a no matter how much the load is increased. Therefore, this portion does not contribute to an increase in the contact area or capacitance. Therefore, by reducing this portion and setting the width Lb of the conductive elastic body 13 in the Y-axis direction to be equal to or less than the upper limit contact width, the space required for arranging the conductive elastic body 13 can be effectively reduced while still properly detecting changes in capacitance corresponding to changes in the contact area.

[0077] The cross section of the conductor wire 14 taken along the YZ plane may have a shape other than a circle. For example, the cross section of the conductor wire 14 may have any of the shapes shown in Fig. 8(b) to Fig. 9(b).

[0078] FIG. 8(b) is a diagram schematically illustrating a modified example in which the cross section of the conductor wire 14 taken along the YZ plane has an elliptical shape.

[0079] In this case, the outer periphery of the lower half of the elliptical cross section of the conductor wire 14 corresponds to the length La in formula (1), which is the upper limit contact width at which the conductive elastic body 13 can come into contact with the conductive member 14a via the dielectric 14b. In this case as well, by setting the width Lb of the conductive elastic body 13 in the Y-axis direction to be equal to or less than the upper limit contact width in accordance with formula (1), the arrangement space for the conductive elastic body 13 can be effectively reduced.

[0080] FIG. 9(a) is a diagram schematically illustrating a modified example in which the cross section of the conductor wire 14 taken along the YZ plane has a triangular shape.

[0081] In this modified example, the conductor wire 14 is disposed between the conductive elastic body 13 and the base member 21 with the apex of the triangular cross section of the conductor wire 14 facing downward so as to contact the conductive elastic body 13. In this case, the sum of the lengths La1 and La2 of the two sides connecting to the apex of the triangular cross section of the conductor wire 14 (La1+La2) corresponds to the length La in equation (1) and is the upper limit contact width at which the conductive elastic body 13 can come into contact with the conductive member 14a via the dielectric 14b. In this case as well, by setting the width Lb of the conductive elastic body 13 in the Y-axis direction to be equal to or less than the upper limit contact width in accordance with equation (1), the arrangement space for the conductive elastic body 13 can be effectively reduced.

[0082] FIG. 9(b) is a diagram schematically illustrating a modified example in which the cross section of the conductor wire 14 taken along the YZ plane has a trapezoidal shape.

[0083] In this modification, the conductor wire 14 is disposed between the conductive elastic body 13 and the base member 21 with the trapezoidal cross section of the conductor wire 14 facing downward. If the length of the side of the trapezoidal cross section of the conductor wire 14 that contacts the conductive elastic body 13 is La1 and the lengths of the two sides connected to the side of length La1 are La2 and La3, respectively, the sum of lengths La1, La2, and La3 (La1 + La2 + La3) corresponds to length La in equation (1) and is the upper limit contact width at which the conductive elastic body 13 can come into contact with the conductive member 14a via the dielectric 14b. In this case, too, by setting the width Lb of the conductive elastic body 13 in the Y-axis direction to be equal to or less than the upper limit contact width in accordance with equation (1), the space required for arranging the conductive elastic body 13 can be effectively reduced.

[0084] Even when the cross-sectional shape of the conductor wire 14 is a shape other than those shown in Figures 8(a) to 9(b), the width Lb of the conductive elastic body 13 in the Y-axis direction can be set to be equal to or less than the upper limit contact width in accordance with formula (1), thereby effectively reducing the space required for arranging the conductive elastic body 13.

[0085] Next, a preferred relationship between the widths of the conductive elastic body 13 and the conductive body 12 in the X-axis direction will be described.

[0086] Fig. 10(a) is a plan view schematically showing the configuration of the conductive elastic body 13 and the conductor 12 near the position where the conductive elastic body 13 and the conductor 12 overlap. Fig. 10(b) is a diagram schematically showing a cross section of the base member 11, the conductor 12, and the conductive elastic body 13 when cut along a plane parallel to the XZ plane near the position where the conductive elastic body 13 and the conductor 12 overlap.

[0087] As shown in Figures 10(a) and 10(b), if the width of the conductive elastic body 13 in the X-axis direction is Wa and the width of the conductive body 12 in the X-axis direction is Wb, the widths Wa and Wb are preferably defined by the following equation (2).

[0088] Wa>Wb …(2)

[0089] When the widths Wa and Wb are defined as in the above formula (2), the conductor 12 is prevented from protruding outside the conductive elastic body 13 in the X-axis direction at the position where the conductor wire 14 passes (near the center position of the conductive elastic body 13 in the Y-axis direction). This makes it possible to prevent the conductor wire 14 from coming into contact with the conductor 12 protruding outside the conductive elastic body 13.

[0090] <Effects of the embodiment> According to the embodiment, the following effects are achieved.

[0091] The conductive elastic bodies 13 are disposed on the upper surface 11a of the base member 11 and are arranged in a first direction (Y-axis direction) with a predetermined gap between them. A plurality of linear conductive members 14a extend in a second direction (X-axis direction) and intersect with the plurality of conductive elastic bodies 13. The dielectric body 14b is disposed between the conductive elastic bodies 13 and the conductive members 14a.

[0092] With this configuration, the conductive elastic bodies 13 are arranged with gaps between them, thereby reducing the space required for arranging the conductive elastic bodies 13 relative to the upper surface 11a of the base member 11. This makes it easier for the elastic structure consisting of the base member 11, the conductors 12, and the conductive elastic bodies 13 to quickly return to their original elastic state when the load is released, and as a result, as shown in Fig. 7(b), the relationship between the load and capacitance when the load is released can be made closer to the relationship between the load and capacitance when the load is applied. In other words, it is possible to reduce the deviation in the relationship between the load and capacitance when the load is applied and when the load is released.

[0093] Furthermore, since the space required for arranging the conductive elastic body 13 can be reduced, the amount of conductive elastic body 13 used can be reduced, thereby reducing the weight of the load sensor 1. Furthermore, when the conductive elastic body 13 is printed on the upper surface 11a of the base member 11, the printing process is simplified, thereby reducing the amount of ink used and printing defects.

[0094] 8(a) to 9(b), the width Lb of the conductive elastic body 13 in the direction (Y-axis direction) perpendicular to the second direction (X-axis direction) is equal to or less than the upper limit contact width (La) at which the conductive elastic body 13 can come into contact with the conductive member 14a via the dielectric 14b. This limits the width of the conductive elastic body 13 within the range of the upper limit contact width, effectively reducing the space required for arranging the conductive elastic body 13 and allowing the elastic structure to elastically return to its original position more quickly when the load is released. Furthermore, because the width of the conductive elastic body 13 is within the range of the upper limit contact width, the load at the intersection of the conductive elastic body 13 and the conductive member 14a can be properly detected.

[0095] The conductor 12 is configured to have a lower resistance than the conductive elastic body 13. The conductor 12 is covered with the conductive elastic body 13 and disposed on the upper surface 11a of the base member 11, and is connected to an external circuit. The presence of the conductor 12 reduces the resistance between the upper surface of the conductive elastic body 13 and the external circuit. This increases the detection sensitivity at each intersection of the conductor wire 14 and the conductive elastic body 13.

[0096] The conductor 12 extends in the first direction (Y-axis direction) so as to cross the multiple conductive elastic bodies 13. This allows the multiple conductive elastic bodies 13 to be connected to an external circuit with one conductor 12, simplifying the configuration.

[0097] The conductor 12 has elasticity, which can prevent the conductor 12 from affecting the elasticity of the conductive elastic body 13. This allows for more accurate detection of the load at each intersection of the conductor wire 14 and the conductive elastic body 13.

[0098] The conductive elastic body 13 contains carbon particles, and the conductor 12 contains metal particles, which allows the conductive elastic body 13 to be made soft and the resistivity of the conductor 12 to be reduced.

[0099] As shown in FIGS. 10(a) and 10(b), the width Wa of the conductive elastic body 13 in the direction (X-axis direction) perpendicular to the first direction (Y-axis direction) is larger than the width Wb of the conductor 12 in the direction perpendicular to the first direction. This prevents the conductive member 14a from coming into contact with the conductor 12 that protrudes from the conductive elastic body 13. This allows for accurate load detection at each intersection between the conductive elastic body 13 and the conductive member 14a. Furthermore, if the dielectric 14b is formed on the outer periphery of the conductive member 14a, contact between the conductor 12 and the dielectric 14b is avoided, preventing the dielectric 14b from peeling off from the conductive member 14a. Furthermore, because the width Wb of the conductor 12 is smaller than the width Wa of the conductive elastic body 13, the influence of the conductor 12 on the elastic structure can be suppressed.

[0100] One conductive member 14a is disposed on the upper surface of one conductive elastic body 13. This minimizes the width of the conductive elastic body 13 in the first direction (Y-axis direction), thereby minimizing the difference in the relationship between load and capacitance when a load is applied and when the load is released.

[0101] A plurality of rows each consisting of a plurality of conductive elastic bodies 13 are arranged in the second direction (X-axis direction). This allows the intersection positions of the conductive elastic bodies 13 and the conductive members 14a to be arranged in a matrix pattern. This allows load detection over a wider range.

[0102] The conductive member 14a is configured to have a circular cross section, which allows the contact area to smoothly change in response to a load.

[0103] The dielectric 14b is formed so as to cover the outer periphery of the conductive member 14a, so that the dielectric 14b can be disposed between the conductive elastic body 13 and the conductive member 14a simply by covering the surface of the conductive member 14a with the dielectric 14b.

[0104] <Example of change> The configuration of the load sensor 1 can be modified in various ways in addition to the configuration shown in the above embodiment.

[0105] For example, in the above embodiment, one conductor wire 14 is arranged on the upper surface of one of the plurality of conductive elastic bodies 13 aligned in the Y-axis direction. However, multiple conductor wires 14 may be arranged on the upper surface of one of the plurality of conductive elastic bodies 13 aligned in the Y-axis direction. For example, as shown in FIG. 11 , two conductor wires 14 may be arranged on the upper surface of one of the plurality of conductive elastic bodies 13 aligned in the Y-axis direction. In this case, the number of divisions of the conductive elastic body 13 in the Y-axis direction is set to three. Furthermore, one conductive elastic body 13 is arranged in one sensor unit A1, and two conductor wires 14 are arranged on the upper surface of the conductive elastic body 13 of each sensor unit A1.

[0106] In this case, too, since the conductive elastic body 13 is divided in the Y-axis direction, the elastic structure is more likely to elastically restore quickly compared to the comparative example shown in Fig. 5. Furthermore, when a plurality of conductive members 14a (conductor wires 14) are arranged on the upper surface of one conductive elastic body 13 in this way, the process of arranging the conductive elastic body 13 can be simplified. Additionally, when the number of sensor units A1 arranged in the Y-axis direction is even, the conductive elastic body 13 may be divided into two and arranged in the Y-axis direction.

[0107] In the above embodiment, the angle formed between the extension direction of the conductor 12 and the extension direction of the conductor wire 14 is 90°, but it may be an angle other than 90°. Even when the angle formed is an angle other than 90°, the multiple conductive elastic bodies 13 are arranged side by side with a predetermined gap between them in the extension direction of the conductor 12.

[0108] In the above embodiment, the conductor 12 is composed of an elastic material and a conductive filler dispersed in the material, but it may also be composed of a conductive material that has almost no elasticity. In this case, the resistivity of the conductor 12 can be further reduced, but the elasticity of the elastic structure consisting of the base member 11, the conductor 12, and the conductive elastic body 13 will decrease. Therefore, it is preferable that the conductor 12 be composed of an elastic material and a conductive filler, as in the above embodiment.

[0109] In the above embodiment, the multiple conductive elastic bodies 13 arranged in the Y-axis direction are electrically connected to each other by the conductors 12 and to an external circuit, but the means for connecting the conductive elastic bodies 13 to an external circuit is not limited to the above. For example, the conductors drawn out from each conductive elastic body 13 may be connected to the external circuit so as not to come into contact with the conductor wires 14.

[0110] In the above embodiment, a pair of conductor wires 14 adjacent in the Y-axis direction are connected at their ends on the positive side of the X-axis, but they may be separated at their ends on the positive side of the X-axis. That is, separate conductor wires 14 may be arranged side by side in the Y-axis direction. In this case, the two conductor wires 14 passing through one sensor unit A1 are connected to each other in a subsequent external circuit.

[0111] In the above embodiment, the load sensor 1 includes three pairs of conductor wires 14, but may include one or more pairs of conductor wires 14. For example, the load sensor 1 may include only one pair of conductor wires 14. Furthermore, the sensor unit A1 of the load sensor 1 includes two conductor wires 14 aligned in the Y-axis direction, but may include one or more conductor wires 14. For example, the sensor unit A1 may include only one conductor wire 14. When the sensor unit A1 of the load sensor 1 includes three or more conductor wires 14 aligned in the Y-axis direction, these conductor wires 14 may be connected at their ends in the X-axis direction, or may be connected to each other in a subsequent external circuit.

[0112] In the above embodiment, the load sensor 1 includes three rows of six conductive elastic bodies 13 aligned in the Y-axis direction, but it is sufficient to include at least one row of conductive elastic bodies 13. For example, the load sensor 1 may include only one row of conductive elastic bodies 13.

[0113] In the above embodiment, the conductive member 14a is composed of a single wire, but it may also be composed of a twisted wire made of multiple twisted wires. In this case, too, the cross section of the twisted wire is preferably approximately circular so that the contact area increases smoothly in response to the load. However, the cross section of the twisted wire may be a shape other than circular.

[0114] In the above embodiment, the sensor section A1 includes the conductive elastic body 13 only below the conductor wire 14, but this is not limiting, and the sensor section A1 may also include a conductive elastic body above the conductor wire 14.

[0115] FIG. 12(a) is a diagram schematically showing the configuration of a modified example in which a conductor 22 and a conductive elastic body 23 are arranged above a conductor wire 14. In FIG.

[0116] In this case, similar to the conductor 12 and conductive elastic body 13 formed on the base member 11, the conductor 22 and conductive elastic body 23 are formed on the lower surface of the base member 21. The size, thickness and material of the conductor 22 are configured similarly to the conductor 12, and the size, thickness and material of the conductive elastic body 23 are configured similarly to the conductive elastic body 13. When viewed in the Z-axis direction, the conductor 22 is disposed in the same position as the conductor 12, and the conductive elastic body 23 is disposed in the same position as the conductive elastic body 13.

[0117] In this configuration example, as shown in Fig. 12(a), a base member 21 (another base member) is disposed opposite an upper surface 11a of the base member 11. A plurality of conductive elastic bodies 23 (another conductive elastic bodies) are disposed on the lower surface of the base member 21 and are lined up in a first direction (Y-axis direction) with a predetermined gap between them. The plurality of conductive elastic bodies 23 are disposed, for example, so as to face the plurality of conductive elastic bodies 13, respectively. A dielectric body 14b is disposed between the plurality of conductive elastic bodies 23 and the conductive member 14a.

[0118] With this configuration, not only the contact area between the conductor wire 14 and the conductive elastic body 13 but also the contact area between the conductor wire 14 and the conductive elastic body 23 changes depending on the load, so the change in contact area when a load is applied is greater than in the cases of Figures 3(a) and (b). This increases the load detection sensitivity of the load sensor 1. Furthermore, like the lower conductive elastic body 13, the upper conductive elastic body 23 is also arranged with a predetermined gap in the Y-axis direction, which makes it easier for the elastic structure consisting of the base member 21, the conductor 22, and the conductive elastic body 23 to quickly return to its original elastic state.

[0119] The upper conductive elastic bodies 23 and the lower conductive elastic bodies 13 do not necessarily have to be arranged in a one-to-one relationship. For example, six lower conductive elastic bodies 13 may be arranged in the Y-axis direction as shown in Fig. 4, and three upper conductive elastic bodies 23 may be arranged in the Y-axis direction, similar to the conductive elastic bodies 13 in Fig. 11.

[0120] In the above embodiment, the dielectric 14b is disposed so as to cover the conductive member 14a, but instead, the dielectric may be disposed on the opposing surface of the conductive elastic body 13.

[0121] FIG. 12(b) is a diagram schematically illustrating a configuration of a modified example in which the dielectric 31 is disposed on the opposing surface (upper surface) of the conductive elastic body 13. In this case, when a load is applied to the sensor unit A1, the conductive member 14a (conductor wire 14) moves relatively toward the conductive elastic body 13, changing the contact area between the conductive member 14a and the dielectric 31. This changes the capacitance between the conductive elastic body 13 and the conductive member 14a, allowing the load to be detected at each sensor unit A1. Note that in the configuration of FIG. 12(b), as in FIG. 12(a), the conductor 22 and the conductive elastic body 23 may be formed on the lower surface of the base member 21, and a dielectric may be disposed on the opposing surface (lower surface) of the conductive elastic body 23.

[0122] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims. [Explanation of symbols]

[0123] 1 Load sensor 11 Base material 11a Top side 12 Conductors 13 Conductive elastic body 14a Conductive member 14b Dielectric 21 Base material (other base material) 22 Conductors 23 Conductive elastic body (other conductive elastic body) 31 Dielectric

Claims

1. A base member; a plurality of conductive elastic bodies arranged on an upper surface of the base member and aligned in a first direction with a predetermined gap therebetween; a plurality of linear conductive members extending in a second direction and intersecting the plurality of conductive elastic bodies; a dielectric disposed between the conductive elastic body and the conductive member, a width of the conductive elastic body in a direction perpendicular to the second direction is equal to or less than an upper limit contact width at which the conductive elastic body can come into contact with the conductive member via the dielectric; A load sensor characterized by:

2. The load sensor according to claim 1, a conductor having a lower resistance than the conductive elastic body is covered by the conductive elastic body and disposed on the upper surface of the base member; The conductor is connected to an external circuit. A load sensor characterized by:

3. The load sensor according to claim 2, The conductor extends in the first direction so as to cross the plurality of conductive elastic bodies. A load sensor characterized by:

4. 4. The load sensor according to claim 2, The conductor has elasticity. A load sensor characterized by:

5. The load sensor according to claim 4, the conductive elastic body contains carbon particles, The conductor includes metal particles. A load sensor characterized by:

6. The load sensor according to any one of claims 2 to 5, a width of the conductive elastic body in a direction perpendicular to the first direction is greater than a width of the conductive body in a direction perpendicular to the first direction; A load sensor characterized by:

7. The load sensor according to any one of claims 1 to 6, one of the conductive members is disposed on the upper surface of the one of the conductive elastic bodies; A load sensor characterized by:

8. The load sensor according to any one of claims 1 to 6, the plurality of conductive members are disposed on an upper surface of the one conductive elastic body; A load sensor characterized by:

9. The load sensor according to any one of claims 1 to 8, A plurality of rows each consisting of the plurality of conductive elastic bodies are arranged in the second direction. A load sensor characterized by:

10. The load sensor according to any one of claims 1 to 9, The conductive member is configured to have a circular cross section. A load sensor characterized by:

11. The load sensor according to any one of claims 1 to 10, The dielectric is formed so as to cover the outer periphery of the conductive member. A load sensor characterized by:

12. The load sensor according to any one of claims 1 to 11, Another base member disposed opposite the upper surface of the base member; a plurality of other conductive elastic bodies arranged on the lower surface of the other base member and aligned in the first direction with a predetermined gap therebetween; a dielectric body disposed between the plurality of other conductive elastic bodies and the conductive member, the conductive member is disposed between the conductive elastic body and the other conductive elastic body; A load sensor characterized by:

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