JP2021096126A - Detection circuit and load detector - Google Patents

Abstract

To provide a detection circuit capable of suppressing the circuit configuration from becoming complicated, and a capacitive load detector.SOLUTION: A detection circuit 2 detects the change in capacitance at the intersection of a copper wire of a coated copper wire 13 and a conductive elastic body 12 with respect to a capacitance type load sensor 1. The detection circuit 2 includes: a supply line L1 for supplying a rectangular voltage to a copper wire of the coated copper wire 13; a resistance 22 placed in the supply line L1; a voltage measurement unit 24 for measuring the potential downstream the resistance 22; and a digital control unit 21 that applies a rectangular digital signal separately to multiple conductive elastic bodies 12.SELECTED DRAWING: Figure 5

Description

The present invention includes a detection circuit used for a capacitance type load sensor that detects a load applied from the outside based on a change in capacitance, and a load detection device including the detection circuit and the capacitance type load sensor. Regarding.

Load sensors are widely used in fields such as industrial equipment, robots and vehicles. In recent years, along with the development of computer-based control technology and the improvement of design, the development of electronic devices using various free-form surfaces such as humanoid robots and interior parts of automobiles has been progressing. In line with this, it is required to mount a high-performance load sensor on each free curved surface.

In the following Patent Document 1, eight front-side electrodes, eight back-side electrodes intersecting the eight front-side electrodes, a dielectric layer arranged between the front-side electrodes and the back-side electrodes, and eight front-side electrodes Capacitive sensors are described that include four multiplexers that are electrically connected to and four multiplexers that are electrically connected to eight backside electrodes. At the time of measurement, the four multiplexers connected to the eight front electrodes are sequentially switched, and the four multiplexers connected to the eight back electrodes are sequentially switched. At this time, when the weight of the user is applied, the distance between the front side electrode and the back side electrode in the sensor unit at the position where the load is applied becomes short, and the capacitance of the sensor unit changes. Then, the load applied to the sensor unit is detected based on the change in capacitance.

Japanese Patent No. 6329854

In the above configuration, if an attempt is made to increase the position (sensor unit) for measuring the load, for example, an analog switch (multiplexer or the like) is required according to the number of sensor units, and the circuit configuration becomes complicated. It ends up.

In view of such a problem, an object of the present invention is to provide a detection circuit and a capacitance type load detection device capable of suppressing complicated circuit configuration.

A first aspect of the present invention includes a first electrode, a plurality of second electrodes arranged so as to intersect the first electrode, and a dielectric interposed between the first electrode and the second electrode. The present invention relates to a detection circuit for detecting a change in capacitance at an intersection position between the first electrode and the second electrode with respect to a capacitance type load sensor. The detection circuit according to this embodiment includes a supply line for supplying a rectangular voltage to the first electrode, a resistor arranged on the supply line, a voltage measuring unit for measuring a potential on the downstream side of the resistor, and the above. A digital control unit for individually applying a rectangular digital signal to a plurality of second electrodes is provided.

According to the detection circuit according to this aspect, among the intersection positions of the first electrode and the second electrode, these intersection positions are obtained by applying a digital signal from the digital control unit to the second electrode at the intersection position other than the measurement target. It is possible to suppress the accumulation of electric charge in the battery. Therefore, the voltage corresponding to the capacitance at the intersection position of the measurement target can be appropriately measured. Here, since a signal of a predetermined voltage level is supplied to the second electrode at the intersection position other than the measurement target by digital control, an analog switch (multiplexer or the like) that switches between application and non-application of voltage for each second electrode. ) Does not need to be provided. Therefore, it is possible to suppress the complexity of the circuit configuration, simplify the circuit configuration, and reduce the cost.

A second aspect of the present invention relates to a load detecting device. The load detection device according to this aspect includes the detection circuit according to the first aspect and the capacitance type load sensor.

According to the load detection device according to this aspect, the same effect as that of the first aspect is obtained.

As described above, according to the present invention, it is possible to provide a detection circuit and a capacitance type load detection device capable of suppressing complicated circuit configurations.

The effects or significance of the present invention will be further clarified by the description of the embodiments shown below. However, the embodiments shown below are merely examples when the present invention is put into practice, and the present invention is not limited to those described in the following embodiments.

FIG. 1A is a perspective view schematically showing a base material and a conductive elastic body according to the first embodiment. FIG. 1B is a perspective view schematically showing a coated copper wire according to the first embodiment. FIG. 2A is a perspective view schematically showing the thread according to the first embodiment. FIG. 2B is a perspective view schematically showing the load sensor according to the first embodiment, which has been assembled by installing the base material. 3A and 3B are cross-sectional views schematically showing the periphery of the coated copper wire when viewed in the negative direction of the X-axis according to the first embodiment. FIG. 4 is a plan view schematically showing a load sensor when viewed in the negative direction of the Z axis according to the first embodiment. FIG. 5 is a diagram showing a circuit configuration of the load detection device according to the first embodiment. FIG. 6 is a circuit diagram schematically showing a state after the application of the rectangular voltage and the digital signal according to the first embodiment is started. FIG. 7 is a circuit diagram schematically showing a state in which discharge is performed according to the first embodiment. FIG. 8 is a diagram showing a circuit configuration of the load detection device according to Comparative Example 1. 9 (a) and 9 (b) show the potential (measurement) of the supply line acquired by the voltage measuring unit in a state where a low load and a high load are applied to the sensor unit to be measured according to the first embodiment, respectively. This is the result of calculating the voltage) by simulation. 10 (a) and 10 (b) show the potential (measurement) of the supply line acquired by the voltage measuring unit in a state where a low load and a high load are applied to the sensor unit to be measured according to the second embodiment, respectively. This is the result of calculating the voltage) by simulation. 11 (a) and 11 (b) show the potential (measurement) of the supply line acquired by the voltage measuring unit in a state where a low load and a high load are applied to the sensor unit to be measured according to the third embodiment, respectively. This is the result of calculating the voltage) by simulation. FIG. 12 is a flowchart showing the switching of the operation mode according to the fourth embodiment. FIG. 13 is a diagram showing a circuit configuration of a load detecting device according to a modified example.

The capacitance type load sensor according to the present invention can be applied to a load sensor of a management system or an electronic device that performs processing according to an applied load.

Examples of the management system include an inventory management system, a driver monitoring system, a coaching management system, a security management system, a nursing care / childcare management system, and the like.

In the inventory management system, for example, a load sensor provided on the inventory shelf detects the load of the loaded inventory, and detects the type of product and the number of products existing on the inventory shelf. As a result, inventories can be efficiently managed in stores, factories, warehouses, etc., and labor saving can be realized. In addition, the load sensor provided in the refrigerator detects the load of the food in the refrigerator, and detects the type of food in the refrigerator and the number and amount of foods. As a result, menus using food in the refrigerator can be automatically proposed.

In a driver monitoring system, for example, a load sensor provided in a steering device monitors a load distribution (for example, gripping force, gripping position, pedaling force) of a driver with respect to the steering device. In addition, the load sensor provided on the vehicle-mounted seat monitors the load distribution (for example, the position of the center of gravity) of the driver with respect to the vehicle-mounted seat in the seated state. This makes it possible to feed back the driving state (sleepiness, psychological state, etc.) of the driver.

In the coaching management system, for example, the load distribution on the sole of the foot is monitored by a load sensor provided on the bottom of the shoe. As a result, it is possible to correct or guide the person to a proper walking state or running state.

In a security management system, for example, a load sensor provided on the floor detects a load distribution when a person passes by, and detects weight, stride length, passing speed, sole pattern, and the like. This makes it possible to identify the person who passed by by collating these detection information with the data.

In the long-term care / childcare management system, for example, a load sensor provided on the bedding or the toilet seat monitors the load distribution on the bedding and the toilet seat of the human body. As a result, it is possible to estimate what kind of behavior a person is trying to take at the position of the bedding or the toilet seat and prevent a fall or a fall.

Electronic devices include, for example, in-vehicle devices (car navigation systems, audio equipment, etc.), home appliances (electric pots, IH cooking heaters, etc.), smartphones, electronic paper, e-book readers, PC keyboards, game controllers, smart watches, wireless. Examples include earphones, touch panels, electronic pens, penlights, glowing clothing, and musical instruments. In electronic devices, a load sensor is provided at an input unit that receives input from a user.

The load sensor in the following embodiment is a capacitance type load sensor typically provided in a load sensor of a management system or an electronic device as described above. Such a load sensor may be referred to as a "capacitive pressure-sensitive sensor element", a "capacitive pressure detection sensor element", a "pressure-sensitive switch element", or the like. Further, the detection circuit in the following embodiment is a detection circuit connected to the load sensor as described above, and the load detection device in the following embodiment is a load detection device including the load sensor and the detection circuit as described above. Is. The following embodiments are one embodiment of the present invention, and the present invention is not limited to the following embodiments.

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

<Embodiment 1>
The load sensor 1 will be described with reference to FIGS. 1 (a) to 4 (4).

FIG. 1A is a perspective view schematically showing the base material 11 and the three conductive elastic bodies 12 installed on the upper surface of the base material 11.

The base material 11 is an elastic and insulating member, and has a flat plate shape parallel to the XY plane. The base material 11 is composed of a non-conductive resin material or a non-conductive rubber material. The resin material used for the base material 11 is selected from the group consisting of, for example, a styrene resin, a silicone resin (for example, polydimethylpolysiloxane (PDMS)), an acrylic resin, a rotaxane resin, a urethane resin, and the like. It is at least one kind of resin material to be used. The rubber material used for the base material 11 is, for example, silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, and the like. It is at least one rubber material selected from the group consisting of epichlorohydrin rubber, urethane rubber, natural rubber and the like.

The conductive elastic body 12 is installed on the upper surface (the surface on the positive side of the Z axis) of the base material 11 with an adhesive or the like. In FIG. 1A, three conductive elastic bodies 12 are installed on the upper surface of the base material 11. The conductive elastic body 12 is a conductive member having elasticity. Each conductive elastic body 12 has a long strip shape in the Y-axis direction on the upper surface of the base material 11, and is installed side by side in a state of being separated from each other in the X-axis direction. A cable 12a electrically connected to the conductive elastic body 12 is installed at the end on the negative side of the Y-axis of each conductive elastic body 12. The conductive elastic body 12 is composed of a resin material and a conductive filler dispersed therein, or a rubber material and a conductive filler dispersed therein.

The resin material used for the conductive elastic body 12 is the same as the resin material used for the base material 11 described above, for example, a styrene resin, a silicone resin (polydimethylpolysiloxane (for example, PDMS), etc.), an acrylic resin, and the like. It is at least one resin material selected from the group consisting of a rotaxane-based resin, a urethane-based resin, and the like. The rubber material used for the conductive elastic body 12 is the same as the rubber material used for the base material 11 described above, for example, silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene. It is at least one rubber material selected from the group consisting of propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, natural rubber and the like.

The conductive filler used for the conductive elastic body 12 is, for example, Au (gold), Ag (silver), Cu (copper), C (carbon), ZnO (zinc oxide), In ₂ O ₃ (indium oxide (III)). ), And _{metal materials such as SnO 2} (tin (IV) oxide) and PEDOT: PSS (ie, a composite consisting of poly (3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS)). It is at least one material selected from the group consisting of conductive polymer materials such as, metal-coated organic fibers, and conductive fibers such as metal wire (fiber state).

FIG. 1B is a perspective view schematically showing three coated copper wires 13 mounted on the structure of FIG. 1A.

The coated copper wire 13 is arranged so as to be overlapped on the upper surface of the three conductive elastic bodies 12 shown in FIG. 1 (a). Here, the three coated copper wires 13 are arranged so as to overlap the upper surfaces of the three conductive elastic bodies 12. Each coated copper wire 13 is composed of a conductive wire rod and a dielectric material that coats the surface of the wire rod. The three coated copper wires 13 are arranged side by side along the longitudinal direction (Y-axis direction) of the conductive elastic body 12 so as to intersect the conductive elastic body 12. Each coated copper wire 13 is arranged so as to extend in the X-axis direction so as to straddle the three conductive elastic bodies 12. The configuration of the coated copper wire 13 will be described later with reference to FIGS. 3 (a) and 3 (b).

FIG. 2A is a perspective view schematically showing the thread 14 installed in the structure of FIG. 1B.

After the three coated copper wires 13 are arranged as shown in FIG. 1 (b), each coated copper wire 13 can be moved in the longitudinal direction (X-axis direction) of the coated copper wire 13 by the thread 14. It is connected to the base material 11. In the example shown in FIG. 2A, 12 threads 14 connect the coated copper wire 13 to the base material 11 at a position other than the position where the conductive elastic body 12 and the coated copper wire 13 overlap. .. The thread 14 is made of a conductive material, for example, a fiber and a conductive metal material dispersed therein. The conductive metal material used for the thread 14 is, for example, silver.

FIG. 2B is a perspective view schematically showing the base material 15 installed in the structure of FIG. 1B.

As shown in FIG. 2B, the base material 15 is installed from above the structure shown in FIG. 2A. The base material 15 is an insulating member. The base material 15 is at least one resin material selected from the group consisting of, for example, polyethylene terephthalate, polycarbonate, and polyimide. The base material 15 has a flat plate shape parallel to the XY plane, and the size of the base material 15 in the XY plane is the same as that of the base material 11. The base material 15 is fixed to the base material 11 by connecting the vertices of the four corners of the base material 15 to the vertices of the four corners of the base material 11 with a silicone rubber adhesive, a thread, or the like. In this way, as shown in FIG. 2B, the load sensor 1 is completed.

3A and 3B are cross-sectional views schematically showing the periphery of the coated copper wire 13 when viewed in the negative direction of the X-axis. FIG. 3A shows a state in which no load is applied, and FIG. 3B shows a state in which a load is applied.

As shown in FIG. 3A, the coated copper wire 13 is composed of a copper wire 13a and a dielectric material 13b that covers the copper wire 13a. The copper wire 13a is made of copper, and the diameter of the copper wire 13a is, for example, about 60 μm. The dielectric 13b has an electrical insulating property and is made of, for example, a resin material, a ceramic material, a metal oxide material, or the like. The dielectric 13b is at least one selected from the group consisting of polypropylene resin, polyester resin (for example, polyethylene terephthalate resin), polyimide resin, polyphenylene sulfide resin, polyvinyl formal resin, polyurethane resin, polyamideimide resin, polyamide resin and the like. It may be a kind of resin material, or at least one kind of metal oxide material selected from the group consisting of _{Al 2} O ₃ and Ta ₂ O _{5 and the like.}

When no load is applied to the region shown in FIG. 3A, the force applied between the conductive elastic body 12 and the coated copper wire 13 and the force applied between the base material 15 and the coated copper wire 13 are applied. The force is almost zero. From this state, as shown in FIG. 3B, when a load is applied upward to the lower surface of the base material 11 and a load is applied downward to the upper surface of the base material 15, the coated copper is applied. The conductive elastic body 12 is deformed by the wire 13. Even when the lower surface of the base material 11 or the upper surface of the base material 15 is placed on a stationary object and a load is applied only to the other base material, the load is similarly received from the stationary object side due to the reaction. become.

As shown in FIG. 3B, when a load is applied, the coated copper wire 13 is brought close to the conductive elastic body 12 so as to be wrapped in the conductive elastic body 12, and the coated copper wire 13 and the conductive elastic body 12 The contact area between and is increased. As a result, the capacitance between the copper wire 13a in the coated copper wire 13 and the conductive elastic body 12 changes, the capacitance in this region is detected, and the load applied to this region is calculated.

FIG. 4 is a plan view schematically showing the load sensor 1 when viewed in the negative direction of the Z axis. In FIG. 4, the thread 14 and the base material 15 are not shown for convenience.

As shown in FIG. 4, the sensor units A11, A12, A13, A21, A22, and A23 whose capacitance changes according to the load at the position where the three conductive elastic bodies 12 and the three coated copper wires 13 intersect. , A31, A32, A33 are formed. Each sensor unit includes a conductive elastic body 12 and a coated copper wire 13, the coated copper wire 13 constitutes the other pole of capacitance (for example, an anode), and the conductive elastic body 12 is of capacitance. It constitutes one pole (eg, a cathode).

That is, the copper wire 13a of the coated copper wire 13 constitutes one electrode of the load sensor 1 (capacitance type load sensor), and the conductive elastic body 12 is the load sensor 1 (capacitance type load sensor). The dielectric 13b of the coated copper wire 13 constituting the other electrode corresponds to the dielectric that defines the capacitance in the load sensor 1 (capacitance type load sensor). In this configuration, the copper wire 13a corresponds to the "first electrode" described in the claims, and the conductive elastic body 12 corresponds to the "second electrode" described in the claims, and the dielectric 13b. Corresponds to the "dielectric" described in the claims.

When a load is applied to each sensor unit in the Z-axis direction, the coated copper wire 13 is wrapped in the conductive elastic body 12 by the load. As a result, the contact area between the coated copper wire 13 and the conductive elastic body 12 changes, and the capacitance between the coated copper wire 13 and the conductive elastic body 12 changes. The end of the coated copper wire 13 on the negative side of the X-axis and the end of the cable 12a on the negative side of the Y-axis are connected to the detection circuit 2 described later with reference to FIG.

As shown in FIG. 4, the three coated copper wires 13 are referred to as lines L11, L12, L13, and the cables 12a drawn from the three conductive elastic bodies 12 are referred to as lines L21, L22, L23. The positions where the line L11 intersects the conductive elastic bodies 12 connected to the lines L21, L22, and L23 are the sensor portions A11, A12, and A13, respectively, and the line L12 is connected to the lines L21, L22, and L23. The positions where the line L13 intersects with the conductive elastic bodies 12 connected to the lines L21, L22, and L23 are the sensor units A21, A22, and A23, respectively. is there.

When a load is applied to the sensor unit A11, the contact area between the conductive elastic body 12 and the coated copper wire 13 in the sensor unit A11 increases. Therefore, the load applied by the sensor unit A11 can be calculated by detecting the capacitance between the line L11 and the line L21. Similarly, in the other sensor unit, the load applied in the other sensor unit can be calculated by detecting the capacitance between the two lines intersecting in the other sensor unit.

Next, the configuration of the load detection device 3 will be described.

FIG. 5 is a diagram showing a circuit configuration of the load detection device 3. The load detection device 3 includes the load sensor 1 as described above and a detection circuit 2 electrically connected to the load sensor 1. In FIG. 5, for convenience, only the coated copper wire 13 and the conductive elastic body 12 are shown for the load sensor 1, and the conductive elastic body 12 is shown linearly. Further, in FIG. 5, the number of the coated copper wire 13 and the conductive elastic body 12 is four, unlike the examples shown in FIGS. 1A to 4.

The detection circuit 2 includes a digital control unit 21, a resistor 22, a switching unit 23, a voltage measuring unit 24, a switch 31, and a resistor 32. The detection circuit 2 is a detection circuit for detecting a change in capacitance at the intersection position of the coated copper wire 13 and the conductive elastic body 12 with respect to the load sensor 1.

The digital control unit 21 includes an arithmetic processing circuit and a memory, and is composed of, for example, an FPGA or an MPU. The digital control unit 21 is connected to the resistor 22, the switching unit 23, and the voltage measuring unit 24 via a signal line. Further, the digital control unit 21 is connected to the four conductive elastic bodies 12 via a cable 12a (see FIG. 2B).

The digital control unit 21 outputs a rectangular voltage signal (hereinafter, referred to as “rectangular voltage”) to the supply line L1 via the resistor 22. The supply line L1 is connected to the downstream terminal of the resistor 22 and supplies a rectangular voltage to the copper wire 13a (see FIGS. 3A and 3B) of the coated copper wire 13. The rectangular voltage output to the circuit by the digital control unit 21 is applied to the RC circuit formed by the resistor 22 and the sensor unit of the load sensor 1. The switching unit 23 and the voltage measuring unit 24 are connected to the supply line L1.

The switching unit 23 selectively switches the supply line L1 to or not connected to the copper wire 13a of the coated copper wire 13 under the control of the digital control unit 21. Specifically, the switching unit 23 includes four multiplexers 23a. The four multiplexers 23a are provided corresponding to the four coated copper wires 13 (copper wires 13a), respectively. The copper wire 13a of the coated copper wire 13 is connected to the output side terminal of each multiplexer 23a. Two input side terminals of each multiplexer 23a are provided. A supply line L1 is connected to one of the input side terminals, and a rectangular voltage is applied to the input side terminal from the digital control unit 21 via the supply line L1 and the resistor 22. Nothing is connected to the other input terminal of the multiplexer 23a.

The digital control unit 21 individually applies a rectangular voltage signal (hereinafter, referred to as “digital signal”) to the four conductive elastic bodies 12. That is, a digital signal is directly applied to the four conductive elastic bodies 12 from the substrate of the digital control unit 21 without going through an analog circuit such as a resistor.

The voltage measuring unit 24 measures the potential of the supply line L1, that is, the potential difference between the supply line L1 and the ground, and outputs the potential to the digital control unit 21.

The switch 31 and the resistor 32 are installed between the supply line L1 and the ground. The switch 31 selectively switches the supply line L1 to either connected or unconnected to the ground via the resistor 32 under the control of the digital control unit 21.

The digital control unit 21 switches the switching unit 23 between the voltage value and application timing of the rectangular voltage applied to the copper wire 13a of the coated copper wire 13 and the voltage value and application timing of the digital signal applied to the conductive elastic body 12. The timing and the switching timing of the switch 31 are controlled. The digital control unit 21 calculates the load applied to the target sensor unit based on the potential of the supply line L1 measured by the voltage measurement unit 24.

Next, the control of the digital control unit 21 at the time of load detection will be described.

When the load detection device 3 is activated, the digital control unit 21 performs the capacitance of the sensor unit at the intersection position (16 locations in the case of FIG. 5) between the coated copper wire 13 and the conductive elastic body 12, as shown below. The capacitance is measured in order, and the load applied to each sensor unit is calculated.

For example, a case where the load is measured for the sensor portion A11 at the position where the uppermost coated copper wire 13 and the leftmost conductive elastic body 12 intersect in FIG. 5 will be described.

When the digital control unit 21 starts measuring the sensor unit A11, the digital control unit 21 is connected to the copper wire 13a (see FIGS. 3A and 3B) of the coated copper wire 13 constituting the electrode of the sensor unit A11 to be measured. The multiplexer 23a is switched so that the multiplexer 23a is connected to the supply line L1. Further, the digital control unit 21 switches the other three multiplexers 23a so that the other three multiplexers 23a are not connected to the supply line L1. Further, the digital control unit 21 sets the switch 31 to the non-connected state.

Subsequently, the digital control unit 21 applies a low-level digital signal to the conductive elastic body 12 constituting the sensor unit A11 to be measured, and the other three conductive elastic bodies 12 constituting the sensor unit other than the measurement target. Apply a high level digital signal to. In Embodiment 1, the low level digital signal is a ground level voltage or 0V and the high level digital signal is equal to a rectangular voltage. Then, the digital control unit 21 outputs a rectangular voltage at the same time as the application of the digital signal via the resistor 22.

FIG. 6 is a circuit diagram schematically showing a state after the application of the rectangular voltage and the digital signal is started when the sensor unit A11 is the measurement target. In FIG. 6, the thick line shows the potential and equipotential portion of the supply line L1, and the double line shows the potential and equipotential portion between the digital control unit 21 and the resistor 22.

As shown in FIG. 6, when the application of the rectangular voltage and the digital signal is started, the rectangular voltage is applied to the sensor unit A11 to be measured via the resistor 22, and the sensor unit A11 to be measured is charged. Rectangle. Along with this, the potential of the sensor unit A11 rises due to the time constant defined by the resistance value R of the resistor 22 and the capacity of the sensor unit A11 according to the load. This potential is reflected in the potential of the supply line L1. Then, this potential is measured by the voltage measuring unit 24 and output to the digital control unit 21.

The digital control unit 21 refers to the measured voltage of the voltage measuring unit 24 at a predetermined timing of the application period of the rectangular voltage, and based on the measured voltage and the time constant and the voltage value of the rectangular voltage, the sensor to be measured The capacitance C of the part A11 is calculated. Then, the digital control unit 21 calculates the load applied to the sensor unit A11 based on the capacitance C.

At this time, a high-level digital signal from the digital control unit 21 is applied to the cathode side of the other sensor units A12 to A14 in the same row as the sensor unit A11 to be measured (the same coated copper wire 13). , The potential of the anode and the potential of the cathode are brought close to each other. Therefore, since the electric charge is suppressed from being accumulated in the other sensor units A12 to A14, the electric charge is appropriately accumulated in the sensor unit A11 to be measured, and the voltage of the sensor unit A11 can be measured with high accuracy.

The other 12 sensor units that are not in the same row as the sensor unit A11 to be measured (the same coated copper wire 13) are stored in these other sensor units because the anode is separated from the supply line L1. The electric charge does not affect the measurement of the potential of the sensor unit A11 in the voltage measuring unit 24.

When the digital control unit 21 calculates the load on the sensor unit A11 to be measured, the digital control unit 21 stops applying the rectangular voltage. In this way, the measurement of the load in one sensor unit is completed. After that, the digital control unit 21 applies a low-level digital signal to all the conductive elastic bodies 12 to set the switch 31 to the connected state. As a result, the electric charge stored in each sensor unit is discharged.

FIG. 7 is a circuit diagram schematically showing a state in which discharge is performed.

From the state of FIG. 6, the application of the rectangular voltage is stopped, and the low-level digital signal is applied to the conductive elastic body 12, so that all the sensor units are connected to the ground. As a result, the electric charges accumulated in all the sensor units are discharged. Further, when the switch 31 is set to the connected state, the copper wire 13a of the coated copper wire 13 where the sensor unit A11 to be measured is located is connected to the ground via the supply line L1 and the resistor 32. .. As a result, in addition to the discharge of the conductive elastic body 12, the coated copper wire 13 is also discharged, so that the electric charge can be discharged in a shorter time.

After that, the digital control unit 21 sets the switch 31 to the non-connected state in order to measure the load of the next sensor unit, and sets the connected state of the multiplexer 23a according to the position of the sensor unit to be measured next. Then, a high level or low level digital signal is applied to each conductive elastic body 12. Further, the digital control unit 21 starts applying a rectangular voltage at the same time as applying the digital signal. In this way, the digital control unit 21 sequentially measures the capacitance of each sensor unit and calculates the load applied to each sensor unit.

As described above, according to the detection circuit 2, a high-level digital signal is applied from the digital control unit 21 to the conductive elastic body 12 constituting another sensor unit in the same row as the sensor unit to be measured. To. As a result, it is possible to suppress the accumulation of unintended charges in other sensor units. When a high-level digital signal is supplied to the conductive elastic body 12 constituting the other sensor unit in this way, an analog switch (multiplexer or the like) for switching between application and non-application of voltage is provided for each conductive elastic body 12. There is no need to provide it. This will be described with reference to the circuit configuration of Comparative Example 1 of FIG.

FIG. 8 is a diagram showing a circuit configuration of the load detection device 5 of Comparative Example 1.

The load detection device 5 includes a load sensor 1 similar to that of the first embodiment, and a detection circuit 4 electrically connected to the load sensor 1. An equipotential generation unit 25 and another switching unit 26 are added to the detection circuit 4 of Comparative Example 1 as compared with the detection circuit 2 of the first embodiment shown in FIG.

The equipotential generation unit 25 is an operational amplifier, and outputs a voltage equal to the potential of the supply line L1 to another supply line L2. The other switching unit 26 includes four multiplexers 26a. Each multiplexer 26a is provided corresponding to four conductive elastic bodies 12. A conductive elastic body 12 is connected to the output side terminal of each multiplexer 26a via a cable 12a (see FIG. 2B). Two input side terminals of each multiplexer 26a are provided. A ground is connected to one input side terminal, and another supply line L2 is connected to the other input side terminal.

For example, a case where the load is measured for the sensor portion A11 at the position where the uppermost coated copper wire 13 and the leftmost conductive elastic body 12 intersect in FIG. 8 will be described.

When the digital control unit 21 starts measuring the sensor unit A11, as in the case of the first embodiment, the copper wire 13a of the coated copper wire 13 constituting the electrode of the sensor unit A11 to be measured (FIG. 3 (a), Each multiplexer 23a is switched so that (see (b))) is connected to the supply line L1 and the copper wire 13a of the other coated copper wire 13 is not connected to the supply line L1. Further, in the digital control unit 21, the conductive elastic body 12 constituting the electrode of the sensor unit A11 to be measured is connected to the ground, and the other three conductive elastic bodies 12 are connected to the other supply line L2. Each multiplexer 26a is switched. Further, the digital control unit 21 sets the switch 31 to the non-connected state.

After that, the digital control unit 21 outputs a rectangular voltage via the resistor 22. At this time, a voltage equipotential with the supply line L1 generated by the equipotential generation unit 25 is applied to the other three conductive elastic bodies 12 constituting the sensor units A12 to A14 via the other supply lines L2. Will be done. In this state, the voltage measured by the voltage measuring unit 24 is output to the digital control unit 21, and the load is calculated. After that, the application of the rectangular voltage is stopped. Then, each multiplexer 26a is switched so that all the conductive elastic bodies 12 are connected to the ground, the switch 31 is set to the connected state, and the electric charge accumulated in all the sensor units is discharged.

According to Comparative Example 1, in another sensor unit in the same row as the sensor unit to be measured, the potential on the anode side (potential of the supply line L1) and the potential on the cathode side (potential of the other supply line L2) Can be set to the same potential, so that it is possible to suppress the accumulation of electric charges in other sensor units. However, in Comparative Example 1, it is necessary to provide the equipotential generation unit 25 and another switching unit 26 as compared with the first embodiment, which complicates the circuit configuration. On the other hand, in the first embodiment, since the digital signal is applied from the digital control unit 21 to the four conductive elastic bodies 12, another switching unit 26 (four multiplexers 26a) for switching between application and non-application of voltage. Alternatively, it is not necessary to provide the equipotential generation unit 25 for setting the potential on the cathode side.

Next, the inventors simulated the voltage change in the first embodiment and the second comparative example that produces an ideal voltage change.

In the following simulation, in the first embodiment, the matrix of the load sensor 1 is set to 3 × 3. That is, in the first embodiment, three coated copper wires 13 and three conductive elastic bodies 12 were arranged. In Comparative Example 2, the matrix of the load sensor 1 was set to 1 × 1 as compared with the first embodiment. That is, in Comparative Example 2, only one coated copper wire 13 and one conductive elastic body 12 were arranged, and a low-level digital signal was always applied to the conductive elastic body 12.

Further, in the following simulation, the capacity of the sensor unit when no load is applied (no load state) and when a low load is applied is set to 10 pF, and the capacity of the sensor unit when a high load is applied. Was 100 pF. The resistance value of the resistor 22 was set to 220 kΩ, and the parasitic capacitance contained in the entire circuit was set to 70 pF. The rectangular voltage was set to 3.3V. The high-level digital signal applied from the digital control unit 21 of the first embodiment to the conductive elastic body 12 was set to 3.3 V.

9 (a) and 9 (b) simulate the potential (measured voltage) of the supply line L1 acquired by the voltage measuring unit 24 with a low load and a high load applied to the sensor unit to be measured, respectively. It is a result calculated by.

In FIGS. 9A and 9B, the rectangular voltage is shown by a dotted line, and the high-level digital signal output from the digital control unit 21 in the first embodiment is shown by a thin solid line, which is measured in the first embodiment. The measured voltage on the downstream side of the resistor 22 is shown by a thick solid line, and the measured voltage on the downstream side of the resistor 22 measured in Comparative Example 2 is shown by a broken line. In FIGS. 9A and 9B, the rectangular voltage and the digital signal completely match.

In this simulation, the application of the rectangular voltage and the high-level digital signal was started when 10 μs passed. At this time, in Comparative Example 2, since there is no other sensor unit in the same row as the sensor unit to be measured (copper wire 13a of the coated copper wire 13), after 10 μs without being affected by the other sensor unit. The measured voltage rose smoothly from.

On the other hand, in the first embodiment, since there are two other sensor units in the same row as the sensor unit to be measured, the voltage increases one step after 10 μs due to the influence of the other sensor units, but after that, Comparative Example 2 The measured voltage rose smoothly with a smaller inclination. As described above, the measured voltage of the first embodiment has a shape in line with the measured voltage of Comparative Example 2 which causes an ideal voltage change in both the low load and the high load. Therefore, for example, it was found that an appropriate measured voltage can be obtained even in the first embodiment by reading the measured voltage at a reading time Tr of about 50 μsec.

<Effect of embodiment>
As described above, according to the embodiment, the following effects are achieved.

A digital signal (high-level voltage signal) is applied from the digital control unit 21 to the conductive elastic body 12 at the intersection position other than the measurement target among the intersection positions of the copper wire 13a of the coated copper wire 13 and the conductive elastic body 12. As a result, it is possible to suppress the accumulation of electric charges at these intersecting positions. Therefore, the voltage corresponding to the capacitance at the intersection position of the measurement target can be appropriately measured. Here, since a signal having a predetermined voltage level (high-level digital signal) is supplied to the conductive elastic body 12 at the intersection position other than the measurement target by digital control, as in Comparative Example 1 shown in FIG. For each conductive elastic body 12, it is necessary to provide an analog switch (multiplex 26a, etc.) for switching between application and non-application of voltage, and an equal potential generation unit 25 for applying a voltage equivalent to the supply line L1 to the conductive elastic body 12. There is no. Therefore, it is possible to suppress the complexity of the circuit configuration, simplify the circuit configuration, and reduce the cost.

The digital control unit 21 sets a digital signal (high level voltage signal) at a voltage level equal to the rectangular voltage. As a result, as shown in FIGS. 9A and 9B, the potential generated in the supply line L1 (measured voltage of the first embodiment) approaches the ideal voltage change (change of the measured voltage of Comparative Example 2). Therefore, the load can be measured with high accuracy. The rectangular voltage and the high-level digital signal applied by the digital control unit 21 do not have to completely match, and may be substantially the same level.

The digital control unit 21 starts applying a high-level digital signal at the same timing as the output start timing of the rectangular voltage. As a result, as shown in FIGS. 9A and 9B, the potential (measured voltage of the first embodiment) generated in the supply line L1 is changed to an ideal voltage (change of the measured voltage of Comparative Example 2). ), So the load can be measured accurately. The output start timing of the rectangular voltage and the timing at which the digital control unit 21 starts applying the high-level digital signal do not have to completely coincide with each other, and may be substantially the same timing.

A plurality of coated copper wires 13 (copper wires 13a) are arranged side by side along the extending direction of the conductive elastic body 12, and the conductive elastic bodies 12 intersect with the copper wires 13a via the dielectric 13b. ing. Further, the switching unit 23 selectively switches the supply line L1 to either connected or non-connected to each copper wire 13a. This makes it possible to measure the load (load applied to the sensor unit) at the intersections arranged in a matrix.

<Embodiment 2>
In the first embodiment, as shown in FIGS. 9A and 9B, the high-level digital signal applied by the digital control unit 21 to the conductive elastic body 12 is set to be equal to the rectangular voltage. On the other hand, in the second embodiment, the high-level digital signal applied by the digital control unit 21 to the conductive elastic body 12 is set lower than the rectangular voltage.

10 (a) and 10 (b) show the potential of the supply line L1 acquired by the voltage measuring unit 24 in a state where a low load and a high load are applied to the sensor unit to be measured according to the second embodiment, respectively. This is the result of calculating (measured voltage) by simulation.

As shown in FIGS. 10 (a) and 10 (b), the high-level digital signal is lower than the rectangular voltage and is set to about 1 V, so that the implementation shown in FIGS. 9 (a) and 9 (b) is performed. Compared with the case of the first embodiment, the curve of the measured voltage of the second embodiment moves downward and is closer to the second comparative example. In particular, the rise of the measured voltage at 10 μs is remarkably suppressed to a low level. As a result, the intersection of the measured voltage of the second embodiment and the measured voltage of the comparative example 2 is accelerated as compared with the case of the first embodiment.

As described above, according to the second embodiment, the digital control unit 21 sets the voltage level of the high-level digital signal applied to the conductive elastic body 12 to be lower than the rectangular voltage. As a result, the intersection of the measured voltage of the second embodiment and the measured voltage of the comparative example 2 is accelerated, so that the potential generated in the supply line L1 can be brought closer to the ideal voltage change at an early timing. For example, in the cases of FIGS. 10A and 10B, the ideal measurement voltage can be obtained by setting the reading time Tr to around 18 μsec in both the low load and the high load. Therefore, since the measurement time of the load applied to one sensor unit can be set short, the load can be quickly measured by the load detection device 3.

<Embodiment 3>
In the first embodiment, as shown in FIGS. 9A and 9B, the timing at which the digital control unit 21 starts applying a high-level digital signal to the conductive elastic body 12 is the output start timing of a rectangular voltage. Was set to the same as. On the other hand, in the third embodiment, the digital control unit 21 starts applying the high-level digital signal at a timing delayed by a predetermined time from the output start timing of the rectangular voltage.

11 (a) and 11 (b) show the potential of the supply line L1 acquired by the voltage measuring unit 24 in a state where a low load and a high load are applied to the sensor unit to be measured according to the third embodiment, respectively. This is the result of calculating (measured voltage) by simulation.

As shown in FIG. 11A, in the case of a low load, the application of the high-level digital signal was started about 15 μsec later than the output start timing of the rectangular voltage, so that the measured voltage of the third embodiment was measured. Compared with the case of the first embodiment shown in FIG. 9A, the reading time Tr is closer to that of Comparative Example 2. On the other hand, as shown in FIG. 11B, in the case of a high load, the measured voltage of the third embodiment is slightly higher in the vicinity of the reading time Tr than in the case of the first embodiment shown in FIG. 9B. It is far from the curve of Comparative Example 2. However, in the case of a high load, the measured voltage of the third embodiment is different from that of the first embodiment shown in FIG. 9 (b) by making the delay time for delaying the application of the high-level digital signal smaller than 15 μsec. By comparison, it is possible to further approach Comparative Example 2 in the vicinity of the reading time Tr.

As described above, according to the third embodiment, the digital control unit 21 starts applying the high-level digital signal to the conductive elastic body 12 at a timing delayed by a predetermined time from the output start timing of the rectangular voltage. As a result, the voltage generated in the supply line L1 can be remarkably asymptotic to the ideal voltage value.

<Embodiment 4>
In the second embodiment, the high-level digital signal is set lower than the rectangular voltage, and in the third embodiment, the timing at which the application of the high-level digital signal is started is set later than the output start timing of the rectangular voltage. Was done.

Here, as in the second embodiment, the operation mode for starting the application of the digital signal (high level digital signal) having a voltage level lower than the rectangular voltage at the same timing as the output start timing of the rectangular voltage is set to "first. Called "mode". Further, as in the third embodiment, the operation mode in which the application of the digital signal (high level digital signal) having the same voltage level as the rectangular voltage is started at the timing delayed by a predetermined time from the output start timing of the rectangular voltage is set to ". It is called "second mode". In the fourth embodiment, the above two operation modes are switched depending on the situation.

FIG. 12 is a flowchart showing the switching of the operation mode of the fourth embodiment.

When the load detection device 3 is activated, the digital control unit 21 sets the operation mode to the first mode (S11). As a result, the high-level digital signal is set lower than the rectangular voltage as in the second embodiment. Subsequently, the digital control unit 21 acquires the fluctuation frequency of the load based on the load applied to each sensor unit (S12). In S12, the digital control unit 21 counts, for example, how many times a load fluctuation of a predetermined threshold value or more occurs in each sensor unit within a fixed time, and averages the counts of each sensor unit to obtain a load. Obtained as the fluctuation frequency of.

Subsequently, the digital control unit 21 determines whether or not the fluctuation frequency of the load acquired in S12 is greater than the threshold Th1 (S13). When the fluctuation frequency of the load is greater than the threshold value Th1 (S13: YES), the digital control unit 21 returns the process to S11 and maintains the first mode.

On the other hand, when the fluctuation frequency of the load is equal to or less than the threshold value Th1 (S13: NO), the digital control unit 21 sets the operation mode to the second mode (S14). Subsequently, the digital control unit 21 acquires the total load, which is the total of the loads detected by each sensor unit, and the fluctuation frequency of the load similar to that in S12, based on the load applied to each sensor unit (S15). In S15, instead of the total load, the average of the loads detected by each sensor unit may be acquired.

Subsequently, the digital control unit 21 determines whether or not the total load acquired in S15 is larger than the threshold Th2 (S16). When the total load is equal to or less than the threshold value Th2 (S16: NO), the digital control unit 21 sets the timing of applying the high-level digital signal to the conductive elastic body 12 to the first timing (S17). For example, in the case of FIG. 11A, the first timing is set to 30 μsec. On the other hand, when the total load is larger than the threshold value Th2 (S16: YES), the digital control unit 21 sets the timing of applying the high-level digital signal to the conductive elastic body 12 earlier than the first timing to start outputting the rectangular voltage. The timing is set later than (S18).

Subsequently, the digital control unit 21 determines whether or not the fluctuation frequency of the load acquired in S15 is greater than the threshold Th1 (S19). When the load fluctuation frequency is greater than the threshold Th1 (S19: YES), the digital control unit 21 returns the process to S11 and changes the operation mode to the first mode. On the other hand, when the fluctuation frequency of the load is equal to or less than the threshold value Th1 (S19: NO), the digital control unit 21 returns the process to S14 and maintains the second mode.

As described above, according to the fourth embodiment, the measurement accuracy of the load can be improved by selectively switching between the first mode and the second mode according to the fluctuation cycle of the load and the magnitude of the load. ..

That is, since the first mode is set when the load fluctuates frequently, the measured voltage can be accurately acquired even if the reading time Tr is shortened as shown in FIGS. 10A and 10B. .. As a result, the reading time Tr can be accelerated to perform quick load measurement according to the fluctuation of the load, and the load measurement accuracy can be improved.

Further, as described in the third embodiment, when the start timing of the high-level digital signal is relatively large behind the start timing of the rectangular voltage (as in the case of FIG. 11A), the low load is accurate. Can be measured well. On the other hand, when the start timing of the high-level digital signal is slightly delayed from the start timing of the rectangular voltage, the high load can be measured accurately. Then, according to the fourth embodiment, when the total load is equal to or less than the threshold value Th2, the application timing of the high level digital signal is set to the first timing, and when the total load is larger than the threshold value Th2, the high level digital signal is applied. The application timing is set to the second timing. Therefore, according to the fourth embodiment, since the application timing of the high-level digital signal is set according to the load, the load can be measured more accurately according to the magnitude of the load.

The timing of applying the high-level digital signal can be set to the same timing, the first timing, and the second timing with respect to the output start timing of the rectangular voltage, and the high-level digital signal can be applied. The signal level can be set to the same level and a lower level for the rectangular voltage. Therefore, by appropriately combining these, the digital control unit 21 may have six types of operation modes.

Further, in the fourth embodiment, the operation mode is automatically switched according to the fluctuation cycle of the load and the magnitude of the load, but the user considers the fluctuation frequency of the load and the magnitude of the load, and the operation unit such as a button. The operation mode may be selected via.

<Change example>
The configurations of the load sensor 1, the detection circuit 2, and the load detection device 3 can be variously changed in addition to the configurations shown in the above embodiment.

For example, in the above embodiment, the load sensor 1 includes a plurality of coated copper wires 13, but may include at least one or more coated copper wires 13. For example, the number of coated copper wires 13 provided in the load sensor 1 may be one.

Further, in the above embodiment, the switching unit 23 includes four multiplexers 23a, but the configuration of the switching unit 23 is not limited to this. For example, the switching unit 23 may include only one demultiplexer.

FIG. 13 is a diagram showing a circuit configuration of the load detection device 3 according to a modification example in this case.

The switching unit 23 includes one demultiplexer 23b. One input side terminal of the demultiplexer 23b is provided, and the supply line L1 is connected to this input side terminal. Four output-side terminals of the demultiplexer 23b are provided, and copper wires 13a (see FIGS. 3A and 3B) of the coated copper wire 13 are connected to the four output-side terminals, respectively.

Even when the switching unit 23 is configured by the demultiplexer 23b in this way, the supply line L1 is selected as either connected or unconnected to the copper wire 13a of the coated copper wire 13 as in the above embodiment. Can be switched. Further, since the switching unit 23 is composed of the demultiplexer 23b, the configuration of the switching unit 23 can be simplified.

Further, in the above embodiment, instead of the coated copper wire 13, an electrode composed of a linear conductive member made of a substance other than copper and a dielectric covering the conductive member may be used. .. The conductive member of the electrode in this case is composed of, for example, a metal body, a glass body and a conductive layer formed on the surface thereof, a resin body and a conductive layer formed on the surface thereof.

Further, in the above embodiment, the configuration of the load sensor 1 does not necessarily have to be a configuration in which the coated copper wire 13 and the conductive elastic body 12 are combined. For example, an elastic dielectric material is provided between the upper and lower electrodes. May be sandwiched between them.

Further, in the above embodiment, the copper wire 13a of the coated copper wire 13 is selectively switched to either connected or unconnected to the supply line L1 by the switching unit 23 (four multiplexers 23a). .. However, the switching unit 23 does not have to be configured by the multiplexer, and may be configured by a switching circuit other than the multiplexer.

Further, in the above embodiment, the digital control unit 21 outputs a rectangular voltage to the supply line L1 via the resistor 22, but the digital control unit 21 provides a switch for supplying the voltage from the DC power supply to the resistor 22. By controlling, a rectangular voltage may be supplied to the supply line L1 via the resistor 22.

In addition, various modifications of the embodiment of the present invention can be made as appropriate within the scope of the technical idea shown in the claims.

1 Load sensor (capacitive load sensor)
2 Detection circuit 3 Load detection device 12 Conductive elastic body (second electrode)
13a Copper wire (first electrode)
13b Dielectric 21 Digital control unit 22 Resistance 23 Switching unit 23b Demultiplexer 24 Voltage measurement unit L1 Supply line

Claims (11)

A capacitance type load sensor including a first electrode, a plurality of second electrodes arranged so as to intersect the first electrode, and a dielectric material interposed between the first electrode and the second electrode. On the other hand, it is a detection circuit for detecting a change in capacitance at an intersection position between the first electrode and the second electrode.
A supply line for supplying a rectangular voltage to the first electrode and
With the resistors placed on the supply line,
A voltage measuring unit that measures the potential on the downstream side of the resistor,
A digital control unit that individually applies a rectangular digital signal to the plurality of second electrodes is provided.
A detection circuit characterized by that. In the detection circuit according to claim 1,
The digital control unit sets the digital signal at a voltage level equal to the rectangular voltage.
A detection circuit characterized by that. In the detection circuit according to claim 1,
The digital control unit sets the voltage level of the digital signal lower than the rectangular voltage.
A detection circuit characterized by that. In the detection circuit according to any one of claims 1 to 3,
The digital control unit starts applying the digital signal at the same timing as the output start timing of the rectangular voltage.
A detection circuit characterized by that. In the detection circuit according to any one of claims 1 to 3,
The digital control unit starts applying the digital signal at a timing delayed by a predetermined time from the output start timing of the rectangular voltage.
A detection circuit characterized by that. In the detection circuit according to any one of claims 1 to 5,
The digital control unit
A first mode in which the application of the digital signal having a voltage level lower than the rectangular voltage is started at the same timing as the output start timing of the rectangular voltage.
A second mode is provided in which the application of the digital signal having a voltage level equal to the rectangular voltage is started at a timing delayed by a predetermined time from the output start timing of the rectangular voltage.
A detection circuit characterized by that. In the detection circuit according to claim 6,
In the second mode, the digital control unit sets the start timing of application of the digital signal based on the load measurement result.
A detection circuit characterized by that. In the detection circuit according to any one of claims 1 to 7.
A plurality of the first electrodes are arranged side by side along the second electrode.
The second electrode intersects the plurality of first electrodes with the dielectric material.
A switching unit for selectively switching the supply line to either connected or unconnected to each of the first electrodes is provided.
A detection circuit characterized by that. In the detection circuit according to claim 8,
The switching unit is a demultiplexer that selectively connects the supply line to the plurality of first electrodes.
A detection circuit characterized by that. The detection circuit according to any one of claims 1 to 9.
The capacitance type load sensor is provided.
A load detection device characterized by the fact that. In the load detecting device according to claim 10,
One of the first electrode and the second electrode is a linear conductive member.
The dielectric is coated around the conductive member.
The first electrode and the other of the second electrode are formed of a conductive elastic body.
A load detection device characterized by the fact that.

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