JP7296603B2 - Detection circuit and load detection device - Google Patents

Description

The present invention provides a detection circuit used in a capacitance load sensor that detects an externally applied load based on a change in capacitance, and a load detection device including the detection circuit and the capacitance load sensor. Regarding.

Load sensors are widely used in fields such as industrial equipment, robots and vehicles. 2. Description of the Related Art In recent years, along with the development of computer control technology and the improvement of design, the development of electronic devices such as humanoid robots and interior parts of automobiles that use free-form surfaces in various ways is progressing. Accordingly, it is required to mount high-performance load sensors on each free-form surface.

Patent Document 1 below describes eight front electrodes, eight back electrodes intersecting the eight front electrodes, a dielectric layer disposed between the front electrodes and the back electrodes, and eight front electrodes. A capacitive sensor is described comprising four multiplexers electrically connected to , and four multiplexers electrically connected to eight backside electrodes. During measurement, the four multiplexers connected to the eight front electrodes are switched in sequence, and the four multiplexers connected to the eight back electrodes are switched in sequence. At this time, when the user's weight is applied, the distance between the front side electrode and the back side electrode becomes shorter in the sensor section at the position where the load is applied, and the capacitance of the sensor section changes. Then, the load applied to the sensor section is detected based on the change in capacitance.

Japanese Patent No. 6329854

In the above configuration, if you try to increase the number of positions (sensor units) for measuring the load, for example, analog switches (multiplexers, etc.) are required according to the number of sensor units, which complicates the circuit configuration. put away.

In view of such problems, it is an object of the present invention to provide a detection circuit and a capacitive load detection device capable of suppressing complication of the circuit configuration.

A first aspect of the present invention includes a first electrode, a plurality of second electrodes intersecting 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 a position where the first electrode and the second electrode intersect, in a capacitive load sensor. The detection circuit according to this aspect includes a supply line for supplying a rectangular voltage to the first electrode, a resistor arranged in the supply line, a voltage measurement unit for measuring a potential downstream of the resistor, and the a digital controller for applying rectangular digital signals individually to the plurality of second electrodes.

According to the detection circuit according to this aspect, by applying a digital signal from the digital control unit to the second electrodes at the crossing positions other than those to be measured among the crossing positions of the first electrode and the second electrode, these crossing positions It is possible to suppress the accumulation of electric charge in the Therefore, it is possible to appropriately measure the voltage corresponding to the capacitance at the crossing position of the object to be measured. Here, since a signal of a predetermined voltage level is supplied to the second electrodes at the crossing positions other than those to be measured by digital control, an analog switch (such as a multiplexer) that switches between application and non-application of voltage is applied to each second electrode. ) need not be provided. Therefore, complication of the circuit configuration can be suppressed, and simplification of the circuit configuration and cost reduction can be achieved.

A second aspect of the present invention relates to a load detection device. A 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 effects as those of the first aspect can be obtained.

As described above, according to the present invention, it is possible to provide a detection circuit and a capacitive load detection device capable of suppressing complication of the circuit configuration.

The effects and significance of the present invention will become clearer from the description of the embodiments shown below. However, the embodiment shown below is merely one example of the implementation of the present invention, and the present invention is not limited to the embodiments described below.

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

INDUSTRIAL APPLICABILITY The capacitive load sensor according to the present invention can be applied to a management system that performs processing according to the applied load and a load sensor for electronic equipment.

Management systems include, for example, an inventory management system, a driver monitoring system, a coaching management system, a security management system, a care/childcare management system, and the like.

In an inventory management system, for example, a load sensor provided on an inventory shelf detects the load of the loaded inventory, and detects the types and number of products present on the inventory shelf. As a result, it is possible to efficiently manage inventory in stores, factories, warehouses, etc., and to save labor. A 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 the food. As a result, it is possible to automatically propose a menu using the food in the refrigerator.

In the driver monitoring system, for example, a load sensor provided in the steering device monitors the load distribution (for example, gripping force, gripping position, pedaling force) of the driver on the steering device. A load sensor provided on the vehicle seat monitors the load distribution (for example, the position of the center of gravity) of the driver on the vehicle seat while the driver is seated. As a result, the driver's driving state (drowsiness, psychological state, etc.) can be fed back.

In the coaching management system, for example, the load distribution on the sole is monitored by a load sensor provided on the sole of the shoe. As a result, it is possible to correct or guide the user to an appropriate 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 through, and detects the weight, stride length, passing speed, shoe sole pattern, and the like. This makes it possible to identify a passing person by collating this detection information with the data.

In a care/childcare management system, for example, load sensors provided on bedding and a toilet seat monitor the load distribution of the human body on the bedding and the toilet seat. As a result, it is possible to estimate what kind of action the person is trying to take at the position of the bedding and toilet seat, and prevent overturning and falling.

Examples of electronic devices include 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 clothes, and musical instruments. An electronic device is provided with a load sensor in an input section that receives an input from a user.

A load sensor in the following embodiments is a capacitive load sensor that is typically provided in the above management system or load sensor for electronic equipment. Such a load sensor may also be called a "capacitive pressure sensor element", a "capacitive pressure detection sensor element", a "pressure sensitive switch element", or the like. Further, the detection circuit in the following embodiments is a detection circuit connected to the load sensor as described above, and the load detection device in the following embodiments is a load detection device including the load sensor and the detection circuit as described above. is. The following embodiment is one embodiment of the present invention, and the present invention is not limited to the following embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each figure is labeled with mutually orthogonal X, Y, and Z axes. 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. FIG.

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

The base material 11 is an elastic insulating member and has a flat plate shape parallel to the XY plane. The base material 11 is made 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, styrene-based resins, silicone-based resins (for example, polydimethylpolysiloxane (PDMS), etc.), acrylic-based resins, rotaxane-based resins, urethane-based resins, and the like. is at least one resin material. Examples of rubber materials used for the base material 11 include silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, 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 (surface on the Z-axis positive side) 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. In FIG. The conductive elastic body 12 is a conductive member having elasticity. Each conductive elastic body 12 has a belt-like shape elongated in the Y-axis direction on the upper surface of the base material 11, and is arranged side by side in the X-axis direction while being spaced apart from each other. A cable 12 a electrically connected to the conductive elastic body 12 is installed at the Y-axis negative side end of each conductive elastic body 12 . The conductive elastic body 12 is composed of a resin material and conductive filler dispersed therein, or a rubber material and conductive filler dispersed therein.

The resin material used for the conductive elastic body 12 is the same as the resin material used for the substrate 11 described above, for example, styrene resin, silicone resin (polydimethylpolysiloxane (eg, PDMS), etc.), acrylic resin, At least one resin material selected from the group consisting of rotaxane-based resins, urethane-based resins, and the like. The rubber material used for the conductive elastic body 12 is the same as the rubber material used for the substrate 11 described above, for example, silicone rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene, ethylene. 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.

Conductive fillers used for the conductive elastic body 12 include, 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 (that is, a composite 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 metal wires (fiber state).

FIG. 1(b) is a perspective view schematically showing three coated copper wires 13 placed on the structure of FIG. 1(a).

The coated copper wire 13 is placed on top of the three conductive elastic bodies 12 shown in FIG. 1(a). Here, three coated copper wires 13 are arranged on top of three conductive elastic bodies 12 . Each coated copper wire 13 is composed of a conductive wire and a dielectric covering the surface of the wire. The three coated copper wires 13 are arranged side by side so as to intersect the conductive elastic body 12 along the longitudinal direction (Y-axis direction) of the conductive elastic body 12 . Each coated copper wire 13 is arranged extending in the X-axis direction so as to straddle 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. 2(a) is a perspective view schematically showing the thread 14 installed in the structure of FIG. 1(b).

After the three coated copper wires 13 are arranged as shown in FIG. It is connected to the base material 11 . In the example shown in FIG. 2(a), 12 threads 14 connect the coated copper wire 13 to the substrate 11 at positions other than the position where the conductive elastic body 12 and the coated copper wire 13 overlap. . The thread 14 is made of an electrically conductive material, for example, made of fibers and an electrically conductive metal material dispersed therein. The conductive metallic material used for thread 14 is, for example, silver.

FIG. 2(b) is a perspective view schematically showing the substrate 15 installed in the structure of FIG. 1(b).

As shown in FIG. 2(b), the base material 15 is installed from above the structure shown in FIG. 2(a). The base material 15 is an insulating member. Base material 15 is, for example, at least one resin material selected from the group consisting of polyethylene terephthalate, polycarbonate, polyimide, and the like. The base material 15 has a flat plate shape parallel to the XY plane, and the size of the base material 15 on 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, threads, or the like. Thus, the load sensor 1 is completed as shown in FIG. 2(b).

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. 3(a) shows a state in which no load is applied, and FIG. 3(b) 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 13b covering the copper wire 13a. Copper wire 13a is made of copper and has a diameter of, for example, about 60 μm. Dielectric 13b has electrical insulation and is made of, for example, a resin material, a ceramic material, a metal oxide material, or the like. Dielectric 13b is made of at least one resin selected from the group consisting of polypropylene resin, polyester resin (eg, 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 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. Force is almost zero. From this state, as shown in FIG. The conductive elastic body 12 is deformed by the wire 13 . 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 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 are separated. The contact area between the 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 area is detected, and the load applied to this area is calculated.

FIG. 4 is a plan view schematically showing the load sensor 1 when viewed in the Z-axis negative direction. In FIG. 4, illustration of the thread 14 and the base material 15 is omitted for convenience.

As shown in FIG. 4, sensor portions A11, A12, A13, A21, A22, and A23 whose capacitance changes according to the load are located at the intersections of the three conductive elastic bodies 12 and the three coated copper wires 13. , 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 (for example, the anode) of the capacitance, and the conductive elastic body 12 is the capacitance. It constitutes one pole (eg the cathode).

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

When a load is applied to each sensor portion 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 X-axis negative side end of the coated copper wire 13 and the Y-axis negative side end of the cable 12a are connected to the detection circuit 2, which will be described later with reference to FIG.

As shown in FIG. 4, the three coated copper wires 13 are called lines L11, L12 and L13, and the cables 12a pulled out from the three conductive elastic bodies 12 are called lines L21, L22 and L23. The positions where the line L11 intersects with the conductive elastic body 12 connected to the lines L21, L22, and L23 are the sensor portions A11, A12, and A13, respectively, and the line L12 is the conductive elastic body connected to the lines L21, L22, and L23. 12 are the sensor portions A21, A22, and A23, respectively, and the positions where the line L13 intersects the conductive elastic bodies 12 connected to the lines L21, L22, and L23 are the sensor portions A31, A32, and A33, respectively. be.

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

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

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

The detection circuit 2 includes a digital control section 21 , a resistor 22 , a switching section 23 , a voltage measurement section 24 , a switch 31 and a resistor 32 . The detection circuit 2 is a detection circuit for detecting a change in capacitance at the crossing 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 has an arithmetic processing circuit and memory, and is configured by, for example, an FPGA or MPU. The digital control unit 21 is connected to the resistor 22, the switching unit 23, and the voltage measuring unit 24 via signal lines. The digital control unit 21 is also connected to the four conductive elastic bodies 12 via cables 12a (see FIG. 2(b)).

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 of the coated copper wire 13 (see FIGS. 3(a) and 3(b)). The rectangular voltage output to the circuit by the digital control section 21 is applied to the RC circuit formed by the resistor 22 and the sensor section of the load sensor 1 . A switching unit 23 and a voltage measuring unit 24 are connected to the supply line L1.

The switching unit 23 selectively switches the supply line L1 between connection and non-connection with respect 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 terminal of each multiplexer 23a. Two input terminals are provided for each multiplexer 23a. A supply line L1 is connected to one of the input terminals, and a rectangular voltage is applied to this input 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 applies rectangular voltage signals (hereinafter referred to as “digital signals”) individually 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 passing through an analog circuit such as a resistor.

The voltage measurement 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 it to the digital control unit 21 .

A switch 31 and a resistor 32 are installed between the supply line L1 and ground. The switch 31 selectively switches the supply line L1 between connection and non-connection to the ground via the resistor 32 under the control of the digital control unit 21 .

The digital control unit 21 controls the voltage value and application timing of the rectangular voltage applied to the copper wire 13a of the coated copper wire 13, the voltage value and application timing of the digital signal applied to the conductive elastic body 12, and the switching of the switching unit 23. Timing and 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 section 21 at the time of load detection will be described.

When the load detection device 3 is activated, the digital control unit 21 detects the static electricity of the sensor unit at the crossing positions (16 points in the case of FIG. 5) of the coated copper wire 13 and the conductive elastic body 12, for example, as shown below. The capacitance is measured in order, and the load applied to each sensor portion is calculated.

For example, in FIG. 5, 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 will be described.

When the digital control unit 21 starts measuring the sensor unit A11, it 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 disconnected from the supply line L1. Also, the digital control unit 21 sets the switch 31 to a non-connection state.

Subsequently, the digital control unit 21 applies a low-level digital signal to the conductive elastic bodies 12 constituting the sensor part A11 to be measured, and the other three conductive elastic bodies 12 constituting the sensor parts other than the measurement target. Apply a high level digital signal to In Embodiment 1, the low level digital signal is the ground level voltage, ie 0V, and the high level digital signal is equal to the square voltage. Then, the digital control unit 21 causes the rectangular voltage to be output through the resistor 22 simultaneously with the application of the digital signal.

FIG. 6 is a circuit diagram schematically showing a state after application of the rectangular voltage and the digital signal is started when the sensor unit A11 is the object of measurement. In FIG. 6 , the thick line indicates a portion equipotential to the potential of the supply line L1, and the double line indicates a portion equipotential to the potential between the digital control section 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 section A11 to be measured via the resistor 22, and the sensor section A11 to be measured is charged. be. Along with this, the potential of the sensor section A11 rises due to the time constant defined by the resistance value R of the resistor 22 and the capacitance of the sensor section A11 corresponding to the load. This potential is reflected in the potential of the supply line L1. This potential is measured by the voltage measuring section 24 and output to the digital control section 21 .

The digital control unit 21 refers to the voltage measured by the voltage measurement unit 24 at a predetermined timing during the application period of the rectangular voltage, and based on this measured voltage, the time constant, and the voltage value of the rectangular voltage, the sensor to be measured Calculate the capacitance C of the portion A11. Then, based on the capacitance C, the digital control unit 21 calculates the load applied to the sensor unit A11.

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 (same coated copper wire 13) as the sensor unit A11 to be measured. , the potential of the anode and the potential of the cathode are brought closer. Therefore, the accumulation of electric charges in the other sensor units A12 to A14 is suppressed, so that electric charges are appropriately accumulated in the sensor unit A11 to be measured, and the voltage of the sensor unit A11 can be measured with high accuracy.

Note that the other 12 sensor units that are not in the same row (same coated copper wire 13) as the sensor unit A11 to be measured have their anodes separated from the supply line L1, so they are stored in these other sensor units. The electric charge generated does not affect the measurement of the potential of the sensor section A11 in the voltage measurement section 24. FIG.

When the digital control unit 21 calculates the load on the sensor unit A11 to be measured, the application of the rectangular voltage is stopped. 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 and sets the switches 31 to the connected state. As a result, the charge accumulated in each sensor section is discharged.

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

From the state of FIG. 6, the application of the rectangular voltage is stopped, and a low-level digital signal is applied to the conductive elastic body 12, which is equivalent to a state in which all sensor units are connected to the ground. As a result, electric charges accumulated in all the sensor units are discharged. Also, by setting the switch 31 to the connected state, the copper wire 13a of the coated copper wire 13 where the sensor part 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 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 connection state of the multiplexer 23a according to the position of the next sensor unit to be measured. Then, a high-level or low-level digital signal is applied to each conductive elastic body 12 . In addition, the digital control unit 21 starts applying the rectangular voltage at the same time as applying the digital signal. Thus, 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 bodies 12 constituting other sensor units in the same row as the sensor unit to be measured. be. 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 bodies 12 constituting other sensor units in this manner, an analog switch (such as a multiplexer) for switching between application and non-application of voltage is provided for each conductive elastic body 12. No need to set. This will be described with reference to the circuit configuration of Comparative Example 1 in FIG.

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

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 . Compared to the detection circuit 2 of Embodiment 1 shown in FIG. 5, the detection circuit 4 of Comparative Example 1 additionally includes an equipotential generator 25 and another switching unit 26 .

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

For example, in FIG. 8, the case where the load is measured for the sensor portion A11 at the position where the uppermost covered copper wire 13 and the leftmost conductive elastic body 12 intersect 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), (b))) is connected to the supply line L1, and each multiplexer 23a is switched so that the copper wire 13a of the other covered copper wire 13 is disconnected from the supply line L1. In addition, the digital control unit 21 is configured so that the conductive elastic body 12 constituting the electrode of the sensor part 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. Also, the digital control unit 21 sets the switch 31 to a non-connection state.

After that, the digital control section 21 outputs a rectangular voltage through the resistor 22 . At this time, a voltage equal in potential to 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 line L2. be done. In this state, the voltage measured by the voltage measuring section 24 is output to the digital control section 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 electric charges accumulated in all the sensor portions are discharged.

According to Comparative Example 1, the potential on the anode side (the potential of the supply line L1) and the potential on the cathode side (the potential of the other supply line L2) are different in the other sensor section in the same row as the sensor section to be measured. can be set to the same potential, it is possible to suppress accumulation of charge in other sensor portions. However, in Comparative Example 1, it is necessary to provide the equipotential generation section 25 and another switching section 26 as compared with Embodiment 1, and the circuit configuration becomes complicated. In contrast, in Embodiment 1, since a digital signal is applied from the digital control unit 21 to the four conductive elastic bodies 12, another switching unit 26 (four multiplexers 26a) that switches between voltage application and non-application. Also, it is not necessary to provide the equipotential generator 25 for setting the potential on the cathode side.

Next, the inventors performed simulations of voltage changes in the first embodiment and a comparative example 2 in which an ideal voltage change occurs.

In the following simulation, the matrix of the load sensors 1 is set to 3×3 in the first embodiment. That is, in Embodiment 1, three coated copper wires 13 and three conductive elastic bodies 12 are arranged. In Comparative Example 2, the matrix of the load sensors 1 is 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 constantly applied to the conductive elastic body 12 .

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

FIGS. 9A and 9B show simulations of the potential (measured voltage) of the supply line L1 acquired by the voltage measuring unit 24 in a state in which a low load and a high load are applied to the sensor unit to be measured, respectively. This is the result calculated by

In FIGS. 9A and 9B, rectangular voltages are indicated by dotted lines, high-level digital signals output from the digital control unit 21 in the first embodiment are indicated by thin solid lines, and are measured in the first embodiment. A thick solid line indicates the measured voltage downstream of the resistor 22, and a dashed line indicates the measured voltage downstream of the resistor 22 measured in Comparative Example 2. FIG. In addition, in FIGS. 9A and 9B, the rectangular voltage and the digital signal are completely the same.

In this simulation, when 10 microseconds passed, the application of the rectangular voltage and the high level digital signal was started. At this time, in Comparative Example 2, since there is no other sensor unit in the same row (copper wire 13a of the coated copper wire 13) as the sensor unit to be measured, there is no influence of other sensor units, and after 10 μs The measured voltage rose smoothly from

On the other hand, in Embodiment 1, there are two other sensor units in the same row as the sensor unit to be measured. The measured voltage rose smoothly with a smaller slope. Thus, the measured voltage of Embodiment 1 has a shape along the measured voltage of Comparative Example 2, which produces an ideal voltage change in both cases of low load and high load. Therefore, it was found that, for example, a proper measured voltage can be obtained even in the first embodiment by reading the measured voltage at a reading time Tr of around 50 μs.

<Effects of Embodiment>
As described above, according to the embodiment, the following effects can be obtained.

A digital signal (high-level voltage signal) is applied from the digital control unit 21 to the conductive elastic bodies 12 at the intersection positions other than those to be measured among the intersection positions of the copper wire 13 a of the coated copper wire 13 and the conductive elastic bodies 12 . Accordingly, it is possible to suppress the accumulation of charges at these intersection positions. Therefore, it is possible to appropriately measure the voltage corresponding to the capacitance at the crossing position of the object to be measured. Here, since a signal of a predetermined voltage level (high-level digital signal) is supplied to the conductive elastic bodies 12 at the crossing positions other than the object to be measured, as in Comparative Example 1 shown in FIG. It is necessary to provide an analog switch (multiplexer 26a, etc.) for switching between application and non-application of voltage for each conductive elastic body 12, and an equipotential generator 25 for applying a voltage equivalent to that of the supply line L1 to the conductive elastic body 12. There is no Therefore, complication of the circuit configuration can be suppressed, and simplification of the circuit configuration and cost reduction can be achieved.

The digital control unit 21 sets the digital signal (high-level voltage signal) to 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 in Embodiment 1) approaches the ideal voltage change (measured voltage change in Comparative Example 2). Therefore, the load can be measured with high accuracy. It should be noted that the rectangular voltage and the high-level digital signal applied by the digital control unit 21 do not have to be completely the same as long as they are substantially at the same level.

The digital control unit 21 starts applying a high-level digital signal at the same timing as the rectangular voltage output start timing. As a result, as shown in FIGS. 9A and 9B, the potential generated in the supply line L1 (the measured voltage in the first embodiment) is changed to the ideal voltage change (the measured voltage change in the comparative example 2). ), the load can be measured with high accuracy. Note that the output start timing of the rectangular voltage and the timing at which the digital control section 21 starts applying the high-level digital signal may not be completely the same as long as they are substantially the same timing.

A plurality of coated copper wires 13 (copper wires 13a) are arranged side by side along the direction in which the conductive elastic body 12 extends. ing. In addition, the switching unit 23 selectively switches the supply line L1 to either connection or non-connection with respect to each copper wire 13a. This makes it possible to measure the load (the load applied to the sensor section) at the crossing positions arranged in a matrix.

<Embodiment 2>
In Embodiment 1, as shown in FIGS. 9A and 9B, the high-level digital signal applied to the conductive elastic body 12 by the digital control section 21 is set equal to the rectangular voltage. In contrast, in the second embodiment, the high-level digital signal applied to the conductive elastic body 12 by the digital controller 21 is set lower than the rectangular voltage.

10A and 10B respectively show the potential of the supply line L1 obtained by the voltage measurement unit 24 in a state in which a low load and a high load are applied to the sensor unit to be measured, according to the second embodiment. It is the result of calculating (measured voltage) by simulation.

As shown in FIGS. 10(a) and 10(b), the high-level digital signal is set to about 1 V, which is lower than the rectangular voltage. Compared with the case of form 1, the curve of the measured voltage of the embodiment 2 moves downward and approaches the comparative example 2. FIG. In particular, the rise of the measured voltage at 10 μs is remarkably suppressed. As a result, the intersection point between the measured voltage in the second embodiment and the measured voltage in the comparative example 2 is earlier than in 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 to be applied to the conductive elastic body 12 to be lower than the rectangular voltage. As a result, the intersection point of the measured voltage in the second embodiment and the measured voltage in the comparative example 2 is advanced, so that the potential generated in the supply line L1 can approach the ideal voltage change at an early timing. For example, in the case of FIGS. 10(a) and 10(b), an ideal measured voltage can be obtained by setting the reading time Tr to around 18 μs for both low load and high load. Therefore, since the measurement time of the load applied to one sensor section can be set short, the load detection device 3 can quickly measure the load.

<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 rectangular voltage output start timing. was set to the same as On the other hand, in the third embodiment, the digital control unit 21 starts applying a high-level digital signal at a timing delayed by a predetermined time from the rectangular voltage output start timing.

FIGS. 11A and 11B respectively show the potential of the supply line L1 obtained by the voltage measurement unit 24 when a low load and a high load are applied to the sensor unit to be measured, according to the third embodiment. It is the result of calculating (measured voltage) by simulation.

As shown in FIG. 11(a), in the case of a low load, the application of the high-level digital signal was started about 15 μs later than the output start timing of the rectangular voltage. Compared with the case of Embodiment 1 shown in FIG. 9A, it is closer to Comparative Example 2 near the reading time Tr. On the other hand, as shown in FIG. 11(b), in the case of a high load, the measured voltage in the third embodiment is slightly lower near the reading time Tr than in the case of the first embodiment shown in FIG. 9(b). It is away from the curve of Comparative Example 2. However, in the case of a high load, by setting the delay time for delaying the application of the high-level digital signal to less than 15 μs, the measured voltage in Embodiment 3 is different from that in Embodiment 1 shown in FIG. By comparison, it is possible to get even closer to Comparative Example 2 near the reading time Tr.

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

<Embodiment 4>
In Embodiment 2, the high-level digital signal is set lower than the rectangular voltage, and in Embodiment 3, the timing to start applying the high-level digital signal is set later than the output start timing of the rectangular voltage. was done.

Here, as in the second embodiment, the operation mode in which application of a digital signal having a voltage level lower than that of the rectangular voltage (high-level digital signal) is started at the same timing as the output start timing of the rectangular voltage is set to "first mode." mode”. Further, as in the third embodiment, the operation mode in which application of a digital signal having a voltage level equal to the rectangular voltage (high-level digital signal) is started at a timing delayed by a predetermined time from the output start timing of the rectangular voltage is set to " 2nd mode”. In Embodiment 4, the above two operation modes are switched depending on the situation.

FIG. 12 is a flowchart showing switching of operation modes according to the fourth embodiment.

When the load detection device 3 is activated, the digital control section 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 load fluctuation frequency based on the load applied to each sensor unit (S12). In S12, the digital control unit 21 counts, for example, for each sensor unit, how many times a load variation equal to or greater than a predetermined threshold occurs within a certain period of time, and averages the counted number of each sensor unit as a load. obtained as the fluctuation frequency of

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

On the other hand, when the load variation frequency is equal to or less than the threshold 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 sum of the loads detected by the sensors, and the frequency of change in the load similar to that in S12, based on the loads applied to the sensors (S15). In addition, in S15, instead of the total load, the average of the loads detected by the sensors may be obtained.

Subsequently, the digital control unit 21 determines whether or not the total load obtained in S15 is greater than the threshold Th2 (S16). If the total load is equal to or less than the threshold 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). The first timing is set to 30 μs in the case of FIG. 11(a), for example. On the other hand, if 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 to the rectangular voltage output start timing earlier than the first timing. is set to a later timing (S18).

Subsequently, the digital control unit 21 determines whether or not the load variation frequency acquired in S15 is greater than the threshold Th1 (S19). If the load variation 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, if the load variation frequency is equal to or less than the threshold 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 load measurement accuracy can be improved by selectively switching between the first mode and the second mode according to the load fluctuation cycle and the magnitude of the load. .

That is, when the load fluctuates frequently, the first mode is set. Therefore, as shown in FIGS. 10A and 10B, even if the reading time Tr is shortened, the measured voltage can be obtained with high accuracy. . As a result, it is possible to speed up the reading time Tr so that the load can be measured quickly in accordance with the fluctuation of the load, and the accuracy of the load measurement can be improved.

Also, as described in the third embodiment, when the start timing of the high-level digital signal lags relatively far behind the start timing of the rectangular voltage (case like FIG. 11(a)), the low load can be accurately can be measured well. On the other hand, when the start timing of the high-level digital signal is slightly delayed with respect to the start timing of the rectangular voltage, a high load can be measured with high accuracy. Then, according to the fourth embodiment, when the total load is equal to or less than the threshold Th2, the application timing of the high-level digital signal is set to the first timing, and when the total load is greater than the threshold Th2, the high-level digital signal is applied. The application timing is set to the second timing. Therefore, according to Embodiment 4, the application timing of the high-level digital signal is set according to the load, so the load can be measured with higher accuracy according to the magnitude of the load.

As for the timing of applying the high-level digital signal, there are three types of settings that are the same as the output start timing of the rectangular voltage, the first timing, and the second timing. There are two types of settings for the signal level, the same level and a lower level, with respect to the rectangular voltage. Therefore, by appropriately combining these, the digital control section 21 may have six types of operation modes.

In addition, in the fourth embodiment, the operation mode is automatically switched according to the load fluctuation cycle and the magnitude of the load. You may select an operation mode via .

<Change example>
The configurations of the load sensor 1, the detection circuit 2, and the load detection device 3 can be modified in various ways other than the configurations shown in the above embodiments.

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

Moreover, 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 have only one demultiplexer.

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

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

Even when the switching unit 23 is composed of the demultiplexer 23b in this way, the supply line L1 is selected to be either connected or not connected to the copper wire 13a of the coated copper wire 13, as in the above-described embodiment. can be switched. Moreover, since the switching unit 23 is configured by 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. . In this case, the conductive member of the electrode is composed of, for example, a metal body, a glass body and a conductive layer formed on its surface, a resin body and a conductive layer formed on its surface, or the like.

Further, in the above embodiment, the configuration of the load sensor 1 does not necessarily have to be a combination of the coated copper wire 13 and the conductive elastic body 12. For example, a stretchable dielectric may be sandwiched.

In the above embodiment, the copper wire 13a of the coated copper wire 13 is selectively switched between connection and non-connection with respect to the supply line L1 by the switching unit 23 (four multiplexers 23a). . However, the switching unit 23 may not be configured by a multiplexer, and may be configured by a switching circuit other than the multiplexer.

In the above embodiment, the digital control unit 21 outputs the rectangular voltage to the supply line L1 through the resistor 22. A rectangular voltage may be supplied to the supply line L<b>1 via the resistor 22 by controlling.

In addition, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea indicated in the scope of 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 resistor 23 switching unit 23b demultiplexer 24 voltage measurement unit L1 supply line

Claims (11)

A capacitive load sensor comprising a first electrode, a plurality of second electrodes intersecting the first electrode, and a dielectric interposed between the first electrode and the second electrode On the other hand, 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;
a resistor placed in the supply line;
a voltage measuring unit that measures a potential on the downstream side of the resistor;
a digital control unit that individually applies rectangular digital signals to the plurality of second electrodes;
A detection circuit characterized by: 2. The detection circuit of claim 1, wherein
The digital controller sets the digital signal to a voltage level equal to the rectangular voltage.
A detection circuit characterized by: 2. The detection circuit of claim 1, wherein
The digital control unit sets a voltage level of the digital signal lower than the rectangular voltage.
A detection circuit characterized by: 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: 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: 6. The detection circuit according to any one of claims 1 to 5,
The digital control unit
a first mode in which application of the digital signal having a voltage level lower than that of the rectangular voltage is started at the same timing as the output start timing of the rectangular voltage;
a second mode in which 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: 7. The detection circuit of claim 6, wherein
The digital control unit, in the second mode, sets the start timing of the application of the digital signal based on the load measurement result.
A detection circuit characterized by: A detection circuit according to any one of claims 1 to 7,
a plurality of the first electrodes arranged side by side along the second electrode;
the second electrode intersects the plurality of first electrodes through the dielectric;
a switching unit that selectively switches between connection and non-connection of the supply line to each of the first electrodes;
A detection circuit characterized by: 9. The detection circuit of claim 8, wherein
The switching unit is a demultiplexer that selectively connects the supply line to the plurality of first electrodes,
A detection circuit characterized by: a detection circuit according to any one of claims 1 to 9;
and the capacitive load sensor,
A load detection device characterized by: In the load detection 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 other of the first electrode and the second electrode is formed of a conductive elastic body,
A load detection device characterized by:

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