electrostatic detection device

Abstract

The present invention provides an electrostatic detector capable of determining which of a plurality of wirings connected to a shield electrode has an fault such as a disconnection.　This electrostatic detector comprises: a plurality of sensor electrodes; a shield electrode coupled to the plurality of sensor electrodes; a signal output unit that outputs an AC signal; a plurality of first wirings that are connected to the plurality of sensor electrodes; a plurality of second wirings that are connected between the shield electrode and the signal output unit, and that supply the AC signal to the shield electrode, the plurality of second wirings having different resistance values from each other between the shield electrode and the signal output unit; and a determination unit that is connected to the plurality of sensor electrodes via the plurality of first wirings, and that determines whether an abnormality has occurred in any of the plurality of second wirings on the basis of the capacitance of the plurality of sensor electrodes.

Description

Technical Field

[0001] This disclosure relates to an electrostatic detection device.

Background Art

[0002] Conventionally, there is a capacitance detection device capable of determining that a part of a plurality of wirings connected to a shield electrode is disconnected by detecting the phase difference between the detection signal of a plurality of detection electrodes and the drive signal (sine wave signal) (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <l By the way, a conventional capacitance detection device (electrostatic detection device) does not determine which of a plurality of wirings connected to a shield electrode has an abnormality such as disconnection.

[0005] Therefore, an object is to provide an electrostatic detection device capable of determining which of a plurality of wirings connected to a shield electrode has an abnormality such as disconnection.

Means for Solving the Problems

[0006] The electrostatic detection device of the embodiment of the present disclosure includes a plurality of sensor electrodes, a shield electrode coupled to the plurality of sensor electrodes, a signal output unit that outputs an AC signal, a plurality of first wirings connected to the plurality of sensor electrodes, a plurality of second wirings that connect the shield electrode and the signal output unit and supply the AC signal to the shield electrode, wherein the resistance values ​​between the shield electrode and the signal output unit are different from each other, and a determination unit connected to the plurality of sensor electrodes via the plurality of first wirings that determines whether an abnormality has occurred in any of the plurality of second wirings based on the capacitance of the plurality of sensor electrodes. [Effects of the Invention]

[0007] This invention provides an electrostatic detection device capable of determining which of the multiple wires connected to the shield electrode has experienced an abnormality such as a broken wire. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of the configuration of the electrostatic detection device according to the embodiment. [Figure 2] This figure shows an example of the circuit configuration of the electrostatic detection device according to the embodiment. [Figure 3] This diagram shows a detailed example of a circuit configuration corresponding to a single sensor electrode. [Figure 4] This figure shows an example of how real and imaginary signals change depending on the state of the electrostatic detection device of the embodiment. [Figure 5] This figure shows the simulation results (Part 1). [Figure 6A] This figure shows the simulation results (Part 2). [Figure 6B] This figure shows the simulation results (Part 2). [Figure 6C] This figure shows the simulation results (Part 2). [Figure 7] This flowchart shows an example of the process performed by the electrostatic detection device 100. [Modes for carrying out the invention]

[0009] The following describes embodiments to which the electrostatic detection device of this disclosure is applied.

[0010] <Embodiment> Figure 1 shows an example of the configuration of the electrostatic detection device 100 according to the embodiment. As an example, Figure 1 shows the electrostatic detection device 100 mounted on the steering wheel 10 of a vehicle.

[0011] The steering wheel 10 is mounted on a vehicle, and the sensor electrode 110 and shield electrode 120 of the electrostatic detection device 100 are mounted inside the outer surface (cover) of the rim 11. The rim 11 is formed in an annular shape, and a core made of a metal material such as iron is provided in an annular shape around its entire circumference inside its outer surface. The electrostatic detection device 100 determines whether the driver's hand H is in contact with the rim 11 of the steering wheel 10. The hand H is an example of an object. The electrostatic detection device 100 also determines whether there is an abnormality such as a break in the wiring 125 connected to the shield electrode 120. The annular rim 11 of the steering wheel 10 is an example of an object to which the sensor electrode 110 and shield electrode 120 are fixed. An example of an object to which the objects are fixed is not limited to the annular rim 11 of the steering wheel 10, but may be, for example, an object with a non-annular shape, such as an aircraft control stick, that is gripped by the hand H. A break in wiring 125 is not limited to a complete break, but also includes a change in impedance due to cracks or other damage. Hereafter, this will simply be referred to as an abnormality in wiring 125.

[0012] Hereinafter, the driver of the vehicle will be referred to as the operator of the electrostatic detection device 100. The electrostatic detection device 100 will be described in which the operator's hand H, which is the target of detection, is in contact with the surface of the rim 11 of the steering wheel 10 on which the sensor electrode 110 is provided. The operator's touch to the rim 11 of the steering wheel 10 on which the sensor electrode 110 is provided will be referred to as the operator's operation.

[0013] The steering wheel 10 has a rim 11, a hub 12, and spokes 13. In FIG. 1, in order to show the sensor electrode 110 and the shield electrode 120, the sensor electrode 110 and the shield electrode 120 are shown outside, separated from the rim 11.

[0014] The ground terminal of the steering wheel 10 is electrically connected to the core metal of the rim 11 of the steering wheel 10. By connecting the core metal and the ground terminal of the ECU 130 via a connector not shown, the ground potential of the ECU 130 becomes equal to the ground potential of the steering wheel 10.

[0015] <Configuration of the Capacitive Detection Device 100> The capacitive detection device 100 includes a sensor electrode 110, a shield electrode 120, and an ECU 130 (Electronic Control Unit). The ECU 130 has an interface circuit 140 and a capacitive MCU (Microcontroller Unit) 150 The interface circuit 140 is connected to the sensor electrode 110 and the shield electrode 120 via wirings 115 and 125. The wiring 115 is an example of at least a part of the first wiring, and the wiring 125 is an example of at least a part of the second wiring. The wiring 115 is a part of the first wiring located outside the ECU 130, and the wiring 125 is a part of the second wiring located outside the ECU 130.

[0016] <Sensor Electrode 110> The sensor electrodes 110 are arranged in four in the left-right and front-back directions of the rim 11 of the steering wheel 10, and include sensor electrodes 110LF, 110LB, 110RF, and 110RB. Here, the left-right and up-down directions in FIG. 1 will be used for explanation. In FIG. 1, to show the steering wheel 10 as seen from the operator (driver), the left-right and up-down directions in FIG. 1 correspond to the left-right and up-down directions of the vehicle. Also, the direction perpendicular to and passing through FIG. 1 corresponds to the front-back direction of the vehicle. Further, when explaining the sensor electrodes 110 etc., the left-right and up-down directions mean the left-right and up-down directions of the steering wheel 10 in a state where the steering angle of the vehicle is in a neutral state.

[0017] The sensor electrodes 110LF, 110LB, 110RF, and 110RB are configured to be respectively arranged in the left-right and front-back directions around the rim 11. The sensor electrodes 110LF, 110LB, 110RF, and 110RB are respectively arranged on the left-front (LF) side, left-back (LB) side, right-front (RF) side, and right-back (RB) side of the rim 11.

[0018] In FIG. 1, the sensor electrodes 110LF, 110LB, 110RF, and 110RB are shown arranged side by side around the rim 11 so that the connection relationship with the wirings 115 and 125 described later can be easily understood. However, actually, the sensor electrode 110LF is located on the front side of the left half of the circumference of the rim 11, and the sensor electrode 110LB is located on the rear side of the left half of the circumference of the rim 11. The sensor electrode 110RF is located on the front side of the right half of the circumference of the rim 11, and the sensor electrode 110RB is located on the rear side of the right half of the circumference of the rim 11.

[0019] The sensor electrodes 110LF, 110LB, 110RF, and 110RB are provided so as to overlap the shield electrode 120 over substantially the entire circumference of the rim 11 of the steering wheel 10 in a state insulated from the core metal of the rim 11 of the steering wheel 10.

[0020] The sensor electrodes 110LF, 110LB, 110RF, and 110RB are connected to the ECU 130 via wiring 115LF, 115LB, 115RF, and 115RB, respectively. The sensor electrodes 110LF, 110LB, 110RF, and 110RB are thin, sheet-like, strip-shaped electrodes provided around the entire circumference of the annular rim 11, and can be manufactured, for example, by applying a conductive material such as silver paste to the surface of a resin film.

[0021] Furthermore, wires 115LF, 115LB, 115RF, and 115RB are signal lines, and are enclosed and shielded by wires 125LF, 125LB, 125RF, and 125RB, which will be described later, to form a four-wire harness.

[0022] In the following, unless otherwise specified, the sensor electrodes 110LF, 110LB, 110RF, and 110RB will simply be referred to as sensor electrode 110. Similarly, unless otherwise specified, the wiring 115LF, 115LB, 115RF, and 115RB will simply be referred to as wiring 115.

[0023] <Shield electrode 120> The shield electrode 120 is provided around the entire circumference of the annular rim 11 of the steering wheel 10, in an insulated state from the core metal of the rim 11 and the sensor electrode 110. The shield electrode 120, like the sensor electrode 110, is a thin, sheet-like, strip-shaped electrode, and is provided around the entire circumference of the rim 11 of the steering wheel 10, overlapping with the sensor electrode 110.

[0024] The shield electrode 120 is provided to reduce noise by shielding the sensor electrode 110 from structures at the ground potential of the vehicle, and also to reduce parasitic capacitance between the sensor electrode and the structures at the ground potential. The shield electrode 120 is supplied with an AC signal from an AC signal source described later and functions as an active shield electrode. By making the shield electrode 120 function as an active shield electrode, a function that reduces noise and parasitic capacitance (hereinafter referred to as the active shield function) is obtained.

[0025] Four wires, 125LF, 125LB, 125RF, and 125RB, are connected to the shield electrode 120. The number of wires 125LF to 125RB is equal to the number of sensor electrodes 110LF to 110RB and the number of wires 115LF to 115RB. Wires 125LF, 125LB, 125RF, and 125RB are connected to the left front (LF), left rear (LB), right front (RF), and right rear (RB) of the shield electrode 120, respectively.

[0026] The shield electrode 120 is connected to the ECU 130 via wirings 125LF, 125LB, 125RF, and 125RB. The thin, sheet-like, strip-shaped electrode used as the shield electrode 120 can be manufactured, for example, by applying a conductive material such as silver paste to the surface of a resin film.

[0027] Wires 125LF, 125LB, 125RF, and 125RB, for example, have a configuration that encloses and shields the signal wires 115LF, 115LB, 115RF, and 115RB, respectively. Wires 125LF to 125RB shield each other in a relationship where wires 115LF to 115RB correspond to the core wires of the coaxial cable, and wires 125LF to 125RB correspond to the shield wires of the coaxial cable. Wires 115LF and 125LF constitute one wire harness, and wires 115LB and 125LB constitute one wire harness. Wires 115RF and 125RF constitute one wire harness, and wires 115RB and 125RB constitute one wire harness.

[0028] By supplying an AC signal to such a shield electrode 120, parasitic capacitance with other components besides the hand H to be detected is reduced, and current outflow from the sensor electrode 110 to components other than the hand H is suppressed, thereby improving detection accuracy.

[0029] In the following, unless otherwise specified, wirings 125LF, 125LB, 125RF, and 125RB will simply be referred to as wiring 125.

[0030] The number of wires 125 is, for example, equal to the number of wires 115. Therefore, by positioning the part of wire 125LF that connects to the shield electrode 120 and the part of wire 115LF that connects to the sensor electrode 110LF close together, it becomes easier to shield wire 115LF with wire 125LF. The same applies to wires 125LB~125RB and wires 115LB~115RB. Therefore, it becomes easier to shield wires 115LF~115RB with wires 125LF~125RB, respectively.

[0031] Furthermore, wirings 125LF, 125LB, 125RF, and 125RB are connected to the left front (LF), left rear (LB), right front (RF), and right rear (RB) of the shield electrode 120, respectively. Therefore, if a malfunction occurs in any of the wirings 125LF to 125RB, the active shielding function for any of the sensor electrodes 110LF to 110RB will malfunction. Since wirings 125LF to 125RB shield wirings 115LF to 115RB respectively, a malfunction in wirings 125LF to 125RB will cause a malfunction in the shielding of wirings 115LF to 115RB, resulting in a malfunction in the active shielding function. A malfunction in the active shielding function is a deviation from the ideal active shielding state.

[0032] <ecu130> The ECU130 is, for example, located inside the instrument panel of a vehicle. The ECU130 includes an interface circuit 140 and an electrostatic MCU 150.

[0033] <Interface circuit 140> The interface circuit 140 is connected to the sensor electrodes 110LF~110RB and the shield electrode 120 via wiring 115LF~115RB and wiring 125LF~125RB. Based on commands input from the electrostatic MCU 150, the interface circuit 140 inputs a sine wave (input sine wave) to the sensor electrode 110 and the shield electrode 120, and acquires the sine wave (output sine wave) output from the sensor electrodes 110LF~110RB. The interface circuit 140 acquires the capacitance value of the sensor electrodes 110LF~110RB from the input sine wave and the output sine wave, performs digital conversion, and removes noise using a low-pass filter, and outputs the amplitude AD value to the electrostatic MCU 150. The amplitude AD value is expressed as a unitless count value, for example. The amplitude AD value is also a value that represents the difference with respect to a predetermined reference value representing the noise floor.

[0034] <Electrostatic MCU150> The electrostatic MCU 150 is implemented by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interfaces, and an internal bus. As an example, the electrostatic MCU 150 is connected to an ECU (not shown) that controls the electronic equipment of the vehicle on which the steering wheel 10 is mounted. The vehicle's ECU may be, for example, electronic equipment related to autonomous driving of the vehicle.

[0035] The electrostatic MCU 150 includes a determination unit 151 and a memory 152. The determination unit 151 represents the functions of the program executed by the electrostatic MCU 150 as functional blocks. The memory 152 functionally represents the memory of the electrostatic MCU 150.

[0036] The determination unit 151 determines whether the driver's hand H is in contact with the rim 11 of the steering wheel 10, and also determines whether there is an abnormality such as a break in the wiring 125. Details of the determination process performed by the determination unit 151 will be described later.

[0037] Memory 152 stores programs and data necessary for the determination unit 151 to perform processing.

[0038] <Circuit Configuration> Next, the circuit configuration of the electrostatic detection device 100 will be described. In the following explanation, Figures 2 and 3 will be used in addition to Figure 1. Figure 2 is a diagram showing an example of the circuit configuration of the electrostatic detection device 100. Figure 3 is a diagram showing in detail an example of the circuit configuration corresponding to the sensor electrode 110.

[0039] <Sensor electrode 110 and shield electrode 120> Figure 2 shows the circuit 113LF to 113RB for four sensor electrodes 110LF to 110RB, four wires 115LF to 115RB, one shield electrode 120, and four wires 125LF to 125RB.

[0040] Circuit 113LF includes a sensor electrode 110LF, wiring 115LF, shield electrode 120, and wiring 125LF. Circuit 113LB includes a sensor electrode 110LB, wiring 115LB, shield electrode 120, and wiring 125LB. Circuit 113RF includes a sensor electrode 110RF, wiring 115RF, shield electrode 120, and wiring 125RF. Circuit 113RB includes a sensor electrode 110RB, wiring 115RB, shield electrode 120, and wiring 125RB. In Figure 2, one shield electrode 120 is shown divided within the four circuits 113LF to 113RB, but the shield electrode 120 is a single electrode, and the shield electrodes 120 of circuits 113LF to 113RB are connected to each other. Hereafter, unless otherwise specified, circuits 113LF to 113RB will simply be referred to as circuit 113. Figure 3 shows a detailed example of the configuration of circuit 113.

[0041] In the circuits shown in Figures 2 and 3, the ground (ground potential point) is the part of the vehicle body that is at ground potential, and is at the same potential as the core metal of the steering wheel 10. Ground potential is an example of a reference potential, and the ground potential point is an example of a reference potential point. Figure 3 also shows the operator's hand H.

[0042] Here, let Chg be the capacitance between hand H and sensor electrode 110, Crs be the capacitance between sensor electrode 110 and shield electrode 120, Crgl be the capacitance (stray capacitance) between sensor electrode 110 and ground, and Csg be the capacitance between shield electrode 120 and ground.

[0043] <Interface circuit 140> The interface circuit 140 includes a filter circuit 141, a charge amplifier 142, an AC signal source 143, a waveform adjustment unit 144, an ADC (Analog to Digital Converter) 145, multipliers 146A and 146B, integrators 147A and 147B, and wiring 148A and 148B. The interface circuit 140 can be implemented as an IC (Integrated Circuit) chip, for example. The AC signal source 143 is an example of a signal output unit. Here, as an example, a configuration in which the interface circuit 140 has multipliers 146A, 146B, integrators 147A and 147B will be described. However, multipliers 146A and 146B, integrators 147A and 147B may be included in the electrostatic MCU 150.

[0044] Furthermore, Figure 2 shows four circuits 113LF to 113RB, but since the configurations of the four circuits 113LF to 113RB are identical, we will explain the configuration of circuit 113 shown in Figure 3.

[0045] <Filter circuit 141> The filter circuit 141 is an RC-type low-pass filter provided between the sensor electrode 110, the shield electrode 120, the inverting input terminal of the charge amplifier 142, and the connection point A of the AC signal source 143 and the waveform adjustment unit 144. In practice, four filter circuits 141 are provided, corresponding to circuits 113LF to 113RB shown in Figure 2.

[0046] The filter circuit 141, as an example, consists of resistors R1 and R2 and a capacitor C. Capacitor C is connected between the inverting input terminal of the charge amplifier 142 and connection point A of the AC signal source 143 and the waveform adjustment unit 144. Resistor R1 is inserted in series between the sensor electrode 110 and one end of capacitor C (the upper terminal in Figures 2 and 3). Resistor R2 is inserted in series between the shield electrode 120 and the other end of capacitor C (the lower terminal in Figures 2 and 3).

[0047] Resistor R2 is sometimes referred to as resistor 141A. Resistor R1 is part of wiring 148A, and resistor R2 (resistor 141A) is part of wiring 148B. Filter circuit 141 uses resistor R1, which is part of wiring 148A, and resistor R2 (resistor 141A), which is part of wiring 148B, as the resistance components of an RC type low-pass filter. The resistance values ​​of resistor 141A in the four filter circuits 141 included in interface circuit 140 are different from each other. The reason for this will be explained later.

[0048] <Charge Amplifier 142> The charge amplifier 142 has a non-inverting input terminal (+) connected to the output terminal of the waveform adjustment unit 144, an inverting input terminal (-) connected to one end (upper terminal) of capacitor C of the filter circuit 141 and resistor R1, and an output terminal connected to the input terminal of the ADC 145. The inverting input terminal (-) of the charge amplifier 142 is an example of a first terminal, and the non-inverting input terminal (+) is an example of a second terminal. The charge amplifier 142 is a differential amplifier that amplifies the difference between the input of the non-inverting input terminal (+) and the input of the inverting input terminal (-) to output an output signal.

[0049] <AC signal source 143> The AC signal source 143 outputs an AC signal to drive the shield electrode 120. The output terminal of the AC signal source 143 is connected to the other end (lower terminal) of capacitor C of the filter circuit 141 and resistor 141A, and to the input terminal of the waveform adjustment unit 144. The AC signal is supplied to the shield electrode 120 and the waveform adjustment unit 144 through the filter circuit 141. In addition, since the shield electrode 120 is electromagnetically coupled to the sensor electrode 110, the AC signal is also supplied to the sensor electrode 110. Both the sensor electrode 110 and the shield electrode 120 are supplied with AC signals in phase.

[0050] In this description, we will explain a configuration in which the AC signal source 143 is connected to the shield electrode 120 via the filter circuit 141. However, the positions of the sensor electrode 110 and the shield electrode 120 may be reversed. In this case, the AC signal output by the AC signal source 143 will be supplied to the sensor electrode 110 via the filter circuit 141, and then supplied to the shield electrode 120 via the sensor electrode 110.

[0051] <Waveform adjustment section 144> The waveform adjustment unit 144 adjusts the amplitude and phase of the AC signal supplied from the AC signal source 143 and outputs it so that the voltage of the output signal of the charge amplifier 142 becomes approximately zero when the operator's hand H or the like is not in contact with the rim 11 in the initial state. Even after the adjustment has been made in the initial state, the waveform adjustment unit 144 maintains the state in which the amplitude and phase of the AC signal have been adjusted and continues to output the AC signal to the non-inverting input terminal (+) of the charge amplifier 142.

[0052] <adc145> The ADC145 has an input terminal connected to the output terminal of the charge amplifier 142 and an output terminal connected to one of the input terminals of the multipliers 146A and 146B. The ADC145 digitally converts the signal output from the charge amplifier 142 and outputs it to the multipliers 146A and 146B.

[0053] <Multiplier 146A> The multiplier 146A has one input terminal connected to the output terminal of the ADC 145, another input terminal to which a demodulated sine wave is input, and an output terminal connected to the integrator 147A. The demodulated sine wave input to the other input terminal is phase-adjusted so that it is in phase with the AC signal output by the AC signal source 143. The multiplier 146A multiplies the output of the ADC 145 (the signal obtained by digitally converting the output signal of the charge amplifier 142) and the AC signal as a demodulated sine wave, demodulates the signal, and generates a signal corresponding to the amplitude of the AC component having the same frequency as the AC signal output by the AC signal source 143, and outputs it to the integrator 147A. The AC signal as a demodulated sine wave is an example of a first AC signal.

[0054] <Multiplier 146B> The multiplier 146B has one input terminal connected to the output terminal of the ADC 145, another input terminal to which the demodulated cosine wave is input, and an output terminal connected to the integrator 147B. The demodulated cosine wave input to the other input terminal is 90 degrees out of phase (90 degrees ahead) of the AC signal output by the AC signal source 143, and its phase is adjusted so that it is 90 degrees out of phase (90 degrees ahead) of the AC signal output by the AC signal source 143. The multiplier 146B multiplies the output of the ADC 145 (the signal obtained by digitally converting the output signal of the charge amplifier 142) and the AC signal as a demodulated cosine wave and demodulates it to generate a signal corresponding to the amplitude of the AC component that has a phase 90 degrees different from the AC signal output by the AC signal source 143, and outputs it to the integrator 147B. The AC signal as a demodulated cosine wave is an example of a second AC signal.

[0055] <Integrator 147A> The integrator 147A has an input terminal connected to the output terminal of the multiplier 146A and an output terminal connected to one of the input terminals of the electrostatic MCU 150. It integrates the output of the multiplier 146A and outputs it to the electrostatic MCU 150 as a real number signal. The real number signal represents the count value obtained by integrating the output of the multiplier 146A. The real number signal is an example of the first converted value and is input to the electrostatic MCU 150.

[0056] <Integrator 147B> The integrator 147B has an input terminal connected to the output terminal of the multiplier 146B and an output terminal connected to the other input terminal of the electrostatic MCU 150. It integrates the output of the multiplier 146B and outputs it to the electrostatic MCU 150 as an imaginary signal. The imaginary signal represents the count value obtained by integrating the output of the multiplier 146B. The imaginary signal is an example of a second transformed value and is input to the electrostatic MCU 150.

[0057] <Wiring 148A> Wiring 148A has a resistor R1 inserted in series and connects wiring 115 to the non-inverting input terminal of charge amplifier 142. Resistor R1 is part of wiring 148A. Wiring 115 and wiring 148A are examples of the first wiring. Wiring 115 is connected to the sensor electrode 110, and wiring 148A is connected to the electrostatic MCU 150 via charge amplifier 142, ADC 145, multipliers 146A and 146B, and integrators 147A and 147B.

[0058] <Wiring 148B> Wiring 148B has a resistor R2 (resistor 141A) inserted in series and connects wiring 125 to the AC signal source 143. Resistor R2 (resistor 141A) is part of wiring 148B. Wiring 125 and wiring 148B are examples of second wiring connecting the shield electrode 120 to the AC signal source 143.

[0059] <Judgment section 151> The determination unit 151 shown in Figure 1 determines whether there is an abnormality such as a break in the wiring 125 based on real and imaginary signals, and also determines whether the object to be detected is in contact with the surface of the steering wheel 10. Details of the determination process will be described later.

[0060] <Real and imaginary signals> Figure 4 shows an example of how the real and imaginary signals change depending on the state of the electrostatic detection device 100. In Figure 4, the horizontal axis is the real axis Re, and the vertical axis is the imaginary axis Im. The coordinates determined by the real and imaginary signals of the electrostatic detection device 100 can be set according to the state of the electrostatic detection device 100, as shown in Figure 4 as an example, by adjusting the impedance of each part of the circuit 113LF to 113RB.

[0061] In Figure 4, the initial coordinates are approximately on the imaginary axis Im and are very close to the origin. In such initial coordinates, the values ​​of the real and imaginary signals are very small. The initial coordinates are obtained in the initial state of the electrostatic detection device 100. The initial state is when there are no abnormalities such as broken wires in the wiring 125 and when the hand H is not touching the surface of the steering wheel 10. Such initial coordinates can be obtained by adjusting the impedance of each part of the circuit 113LF to 113RB.

[0062] Furthermore, the coordinates during touch operation (no abnormalities) are those obtained when a touch operation is performed, provided that there are no abnormalities such as disconnections in the wiring 125. Touch operation refers to the state where the hand H is in contact with the surface of the steering wheel 10 (the state in which a touch operation is performed). The coordinates during touch operation (no abnormalities) are those where the value of the real signal is very large and the value of the imaginary signal is very small. In other words, these are coordinates obtained by increasing almost exclusively the value of the real signal compared to the initial state. By adjusting the impedance of each part of circuit 113LF~113RB, such coordinates during touch operation (no abnormalities) can be obtained.

[0063] Furthermore, the coordinates for the abnormal state of wiring 125 (no touch) are obtained when no touch operation is performed and an abnormality such as a break in the wiring 125 of the electrostatic detection device 100 has occurred. The coordinates for the abnormal state of wiring 125 (no touch) are those in which the value of the real signal is very small and the value of the imaginary signal is very large. In other words, these coordinates are obtained when almost only the value of the imaginary signal increases compared to the initial state. By adjusting the impedance of each part of circuit 113LF~113RB, such coordinates for the abnormal state of wiring 125 (no touch) can be obtained.

[0064] <Setting the resistance value of resistor 141A in circuit 113LF~113RB> As shown in Figure 4, there is an abnormality in wiring 125. none Time coordinates (touch) can be ) indicates an abnormality in wiring 125. none The coordinates at time (without touch) can be distinguished. Similarly, the coordinates when a touch operation is performed while wiring 125 is malfunctioning can also be distinguished from the coordinates when wiring 125 is malfunctioning (without touch).

[0065] The electrostatic detection device 100 determines whether an abnormality such as a break in the wiring 125LF to 125RB has occurred by setting the resistance values ​​of the resistors 141A connected to circuits 113LF to 113RB to different values. Here, we will describe a configuration in which the resistance values ​​of the four resistors 141A connected to circuits 113LF to 113RB are set to different values. However, instead of setting the resistance values ​​of the resistors 141A to different values, for example, the resistance values ​​of the four wires 148B connected to circuits 113LF to 113RB may be set to different values. For example, the resistance values ​​of the four wires 148B may be set to different values ​​by having different wire widths, thicknesses, or materials for the four wires 148B.

[0066] <Simulation Results (Part 1)> Figure 5 shows the simulation results (Part 1). Figure 5 shows an example of the simulation results for the coordinates (no touch) when wiring 125 is abnormal. In Figure 5, the horizontal axis shows the value of the real signal (count value), and the vertical axis shows the value of the imaginary signal (count value). Figure 5 shows the coordinates (no touch) when wiring 125LF~125RB is abnormal, obtained by setting the resistance value of resistor 141A in circuits 113LF~113RB to 200Ω, 250Ω, 350Ω, and 677Ω as examples.

[0067] The real and imaginary signals obtained when an abnormality occurs in each of the wirings 125LF to 125RB are the real and imaginary signals obtained in the interface circuit 140 shown in Figure 3, which is connected to each of the circuits 113LF to 113RB. That is, the real and imaginary signals obtained when an abnormality occurs in wiring 125LF are the real and imaginary signals obtained in the interface circuit 140 shown in Figure 3, which is connected to circuit 113LF. The real and imaginary signals obtained when an abnormality occurs in wiring 125LB are the real and imaginary signals obtained in the interface circuit 140 shown in Figure 3, which is connected to circuit 113LB. The same applies to wirings 125RF and 125RB.

[0068] In Figure 5, the real and imaginary signals when there is a malfunction in wiring 125LF are shown as white circles (○), and the real and imaginary signals when there is a malfunction in wiring 125LB are shown as black circles (●). Furthermore, the real and imaginary signals when there is a malfunction in wiring 125RF are shown as white diamonds (◇), and the real and imaginary signals when there is a malfunction in wiring 125LB are shown as black diamonds (◆).

[0069] Here, wirings 125LF, 125LB, 125RF, and 125RB shield wirings 115LF, 115LB, 115RF, and 115RB, which are connected to sensor electrodes 110LF, 110LB, 110RF, and 110RB, respectively. Therefore, a malfunction in wiring 125LF corresponds to a malfunction in the active shielding function to sensor electrode 110LF. Similarly, a malfunction in wiring 125LB corresponds to a malfunction in the active shielding function to sensor electrode 110LB. A malfunction in wiring 125RF corresponds to a malfunction in the active shielding function to sensor electrode 110RF. A malfunction in wiring 125RB corresponds to a malfunction in the active shielding function to sensor electrode 110RB.

[0070] Because the resistance values ​​of resistors 141A in circuits 113LF to 113RB are different, as shown in Figure 5, if an abnormality such as a break occurs in each of the wirings 125LF to 125RB, the values ​​of the real and imaginary signals will be different. The four markers shown in Figure 5 show examples of the values ​​of the real and imaginary signals when an abnormality occurs in each of the wirings 125LF to 125RB.

[0071] The values ​​of the real and imaginary signals show the smallest value when a malfunction occurs in wiring 125LF, and the second smallest value when a malfunction occurs in wiring 125LB. Furthermore, the values ​​of the real and imaginary signals show the third smallest value (second largest value) when a malfunction occurs in wiring 125RF, and the largest value when a malfunction occurs in wiring 125RB.

[0072] The impedance of wiring 125LF~125RB changes depending on the condition of the break. As an example, when the resistance value of resistor 141A in circuit 113LF~113RB is changed by ±10%, the range of values ​​that the real and imaginary signals can take depending on the abnormality of wiring 125LF~125RB is shown by four dashed ellipses.

[0073] The dashed lines of the four ellipses are separated by straight lines (1) to (5), and there are no overlapping regions. Therefore, by using straight lines (1) to (5), it is possible to determine which of the wirings 125LF to 125RB has experienced an abnormality.

[0074] The resistance value of resistor 141A in circuit 113LF~113RB should be set to a value that allows you to determine whether an abnormality such as a break in the wiring 125LF~125RB has occurred using lines (1)~(5).

[0075] By determining whether an abnormality such as a break in the wiring 125LF, 125LB, 125RF, or 125RB has occurred, it is possible to determine whether an abnormality has occurred in the active shielding function for any of the sensor electrodes 110LF, 110LB, 110RF, or 110RB.

[0076] Here, we describe the results of simulations performed by setting the resistance value of resistor 141A in circuits 113LF~113RB to 200Ω, 250Ω, 350Ω, and 677Ω as examples. The resistance values ​​of 200Ω, 250Ω, 350Ω, and 677Ω were calculated as examples to achieve a combined resistance of 75Ω. However, the actual resistance value of resistor 141A in circuits 113LF~113RB should be set to an appropriate value that allows for the determination of whether an abnormality such as a break in wiring 125LF, 125LB, 125RF, or 125RB has occurred, taking into account the impedance of each part of the actual circuits 113LF~113RB and the impedance of the interface circuit 140.

[0077] <Simulation Results (Part 2)> Figures 6A to 6C show the simulation results (Part 2). Figures 6A to 6C show an example of the simulation results for the coordinates (with touch) when wiring 125 is abnormal. The coordinates (with touch) when wiring 125 is abnormal are the coordinates when a touch operation is performed when wiring 125 is abnormal. Figures 6A to 6C show the coordinates (with touch) when wiring 125 is abnormal, obtained by setting the resistance value of resistor 141A in circuits 113LF to 113RB to 200Ω, 250Ω, 350Ω, and 677Ω as examples.

[0078] Figures 6A to 6C show the coordinates obtained from the real and imaginary signal values ​​obtained by the four interface circuits 140 (see Figure 3) connected to circuits 113LF to 113RB, in the event of a fault in each of the wirings 125LF to 125RB. Specifically, in the case of a fault in wiring 125LF, the coordinates are shown, obtained from the real and imaginary signal values ​​obtained by the four interface circuits 140 (see Figure 3) connected to circuits 113LF to 113RB. The same applies to wirings 125RF to 125RB. In other words, each of Figures 6A to 6C shows 16 coordinates.

[0079] In Figures 6A to 6C, the real and imaginary signals obtained by the four interface circuits 140 when an abnormality occurs in wiring 125LF are shown as white circles (○), and the real and imaginary signals obtained by the four interface circuits 140 when an abnormality occurs in wiring 125LB are shown as black circles (●). Furthermore, the real and imaginary signals obtained by the four interface circuits 140 when an abnormality occurs in wiring 125RF are shown as white diamonds (◇), and the real and imaginary signals obtained by the four interface circuits 140 when an abnormality occurs in wiring 125LB are shown as black diamonds (◆).

[0080] Figure 6A shows an example of coordinates when an abnormality occurs in each of the wirings 125LF to 125RB while two fingers are touching the surface of the rim 11 of the steering wheel 10. As shown in Figure 6A, when an abnormality occurs in wiring 125LF, the coordinates obtained by the four interface circuits 140 were all approximately the same. Similarly, for wirings 125LB to 125RB, the coordinates obtained by the four interface circuits 140 were all approximately the same.

[0081] The coordinates obtained when an abnormality occurred in each of the wirings 125LF to 125RB were completely separated into four groups. From this, it was found that, with two fingers touching the surface of the rim 11 of the steering wheel 10, it is possible to determine which of the four interface circuits 140 is experiencing an abnormality, regardless of which of the wirings 125LF to 125RB is being used for the coordinates obtained.

[0082] Figure 6B shows an example of coordinates when the surface of the steering wheel 10 at the 2 o'clock position is gripped (touched) with one hand, and when an abnormality such as a break occurs in each of the wires 125LF to 125RB. In Figure 6B, as with the results shown in Figure 6A, the coordinates obtained by the four interface circuits 140 when an abnormality occurs in wire 125LF were all approximately the same. Furthermore, the coordinates obtained by the four interface circuits 140 for wires 125LB to 125RB showed some variation compared to Figure 6A, but were all approximately the same.

[0083] The coordinates obtained when an abnormality occurred in each of the wirings 125LF to 125RB were completely separated into four groups. From this, it was found that even when the surface of the steering wheel 10 is held with one hand (touched), it is possible to determine which of the four interface circuits 140 has an abnormality, from wiring 125LF to 125RB, using the coordinates obtained from any of them.

[0084] Figure 6C shows an example of coordinates when the surface of the steering wheel 10 at the 10 o'clock and 2 o'clock positions is gripped (touched) with both hands, and when an abnormality such as a break occurs in each of the wires 125LF to 125RB. In Figure 6C, as is substantially the same as the results shown in Figure 6A, when an abnormality occurs in wire 125LF, the coordinates obtained by the four interface circuits 140 were all approximately equal. Similarly, for wires 125LB to 125RB, the coordinates obtained by the four interface circuits 140 were all approximately equal, as is the case in Figure 6A.

[0085] The coordinates obtained when an abnormality occurred in each of the wirings 125LF to 125RB were completely separated into four groups. From this, it was found that, when the surface of the steering wheel 10 is held with both hands (touched), it is possible to determine which of the four interface circuits 140 is experiencing an abnormality, regardless of which of the four wirings 125LF to 125RB is being used for the coordinates obtained.

[0086] <Flowchart> Figure 7 is a flowchart showing an example of the process performed by the electrostatic detection device 100. Here, we describe the process in which the determination unit 151 determines whether an abnormality has occurred in any of the wirings 125LF to 125RB based on the real and imaginary signals output from any one of the four interface circuits 140. However, it is also possible to determine whether an abnormality has occurred in any of the wirings 125LF to 125RB based on the real and imaginary signals output from any two or more of the four interface circuits 140.

[0087] When the processing is started, the determination unit 151 determines whether an abnormality has occurred in any of the wirings 125LF to 125RB (step S1).

[0088] If the determination unit 151 determines that an abnormality has occurred in any of the wirings 125LF to 125RB (S1: YES), it identifies the sensor electrode 110 corresponding to the wiring where the abnormality has occurred and notifies the higher-level device that an abnormality has occurred in the active shielding function for the identified sensor electrode 110 (step S2A). Sensor electrode 110LF corresponds to wiring 125LF, sensor electrode 110LB corresponds to wiring 125LB, sensor electrode 110RF corresponds to wiring 125RF, and sensor electrode 110RB corresponds to wiring 125RB.

[0089] If the determination unit 151 determines that no abnormality has occurred in any of the wirings 125LF to 125RB (S1:NO), it notifies the higher-level device that no abnormality has occurred (step S2B).

[0090] When the determination unit 151 completes the processing in step S2A or S2B, it terminates the series of processes (end).

[0091] As an example, the determination unit 151 repeatedly executes the process shown in Figure 7 at a predetermined control cycle from the time the ignition or power of the vehicle equipped with the electrostatic detection device 100 is turned on until the ignition or power is turned off. The determination unit 151 also determines whether a hand H is touching the rim 11 of the steering wheel 10 based on the real and imaginary signals output from at least one of the four interface circuits 140.

[0092] <Effects> The electrostatic detection device 100 includes a plurality of sensor electrodes 110, a shield electrode 120 coupled to the plurality of sensor electrodes 110, an AC signal source 143 that outputs an AC signal, a plurality of first wires (115, 148A) connected to the plurality of sensor electrodes 110, a plurality of second wires (125, 148B) that connect the shield electrode 120 and the AC signal source 143 and supply an AC signal to the shield electrode 120, wherein the resistance values ​​between the shield electrode 120 and the AC signal source 143 are different from each other, and a determination unit 151 connected to the plurality of sensor electrodes 110 via the plurality of first wires (115, 148A) and determining whether an abnormality has occurred in any of the plurality of second wires (125, 148B) based on the capacitance of the plurality of sensor electrodes 110.

[0093] Therefore, it is possible to provide an electrostatic detection device 100 that can determine which of the multiple wires 125 connected to the shield electrode 120 has an abnormality such as a break in the wire.

[0094] Furthermore, at least a portion of the second wiring (125, 148B) (wiring 125) may be shielded wiring that shields at least a portion of the first wiring (115, 148A) (wiring 115). This allows wiring 125 to shield wiring 115 from noise, thereby improving noise immunity.

[0095] Furthermore, the number of second wirings (125, 148B) may be equal to the number of first wirings (115, 148A). This makes it easier to shield wiring 115LF with wiring 125LF by arranging the portion of wiring 125LF connected to the shield electrode 120 and the portion of wiring 115LF connected to the sensor electrode 110LF close together. The same applies to wirings 125LB~125RB and wirings 115LB~115RB. In addition, it is possible to determine that an abnormality has occurred in the active shielding function to the sensor electrode 110 connected to wiring 115 corresponding to the abnormal wiring 125.

[0096] Furthermore, at least a portion (125) of the second wiring (125, 148B) may be shielded by covering at least a portion (115) of the first wiring (115, 148A). This allows wiring 115 to be shielded more effectively from noise by wiring 125, thereby improving noise immunity.

[0097] Furthermore, the determination unit 151 may determine whether an abnormality has occurred in any of the multiple second wirings (125, 148B) based on the real and imaginary components obtained by digitally converting the capacitance of the multiple sensor electrodes 110 and demodulating it with a demodulated signal of the same frequency as the AC signal. In this case, it is possible to determine which wiring 125 has an abnormality based on the change in impedance of any of the multiple wirings 125.

[0098] Furthermore, the determination unit 151 may determine, based on the real and imaginary components, whether the hand H is in contact with the surface covering the multiple sensor electrodes 110. This makes it possible to provide an electrostatic detection device 100 that can determine, based on the real and imaginary components, whether the hand H is in contact with the surface of the rim 11 of the steering wheel 10, and also determine which of the multiple wirings 125 has an abnormality such as a broken wire.

[0099] Although exemplary embodiments of electrostatic detection devices of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0100] This international application claims priority based on Japanese Patent Application No. 2023-043466, filed on 17 March 2023, the entire contents of which are incorporated herein by reference. [Explanation of Symbols]

[0101] 10 Steering Wheel 11 rim 12 hubs 13 spokes 100 Electrostatic detection device 110, 110LF, 110LB, 110RF, 110RB sensor electrodes 113, 113LF, 113LB, 113RF, 113RB circuits 115, 115LF, 115LB, 115RF, 115RB wiring (an example of the first wiring, an example of at least a part of the first wiring) 120 Shielded electrodes 125, 125LF, 125LB, 125RF, 125RB wiring (an example of second wiring, an example of at least a part of second wiring) 140 Interface Circuits 141 Filter Circuit 141A resistor 142 Charge Amplifier 143 AC signal source (an example of a signal output section) 144 Waveform adjustment section 146A, 146B multiplier 147A, 147B Integrator 148A Wiring (Example of the first wiring) 148B Wiring (Example of the second wiring) 150 Electrostatic MCUs 151 Judgment section 152 memory

Claims

1. Multiple sensor electrodes, A shield electrode coupled to the plurality of sensor electrodes, A signal output section that outputs AC signals, Multiple first wires connected to the multiple sensor electrodes, A plurality of second wirings that connect the shield electrode and the signal output unit and supply the AC signal to the shield electrode, wherein the plurality of second wirings have different resistance values ​​between the shield electrode and the signal output unit, A determination unit connected to the plurality of sensor electrodes via the plurality of first wirings, which determines whether an abnormality has occurred in any of the plurality of second wirings based on the capacitance of the plurality of sensor electrodes. An electrostatic detection device, including one.

2. The electrostatic detection device according to claim 1, wherein at least a portion of the second wiring is a shielding wire that shields at least a portion of the first wiring.

3. The electrostatic detection device according to claim 2, wherein the number of second wirings is equal to the number of first wirings.

4. The electrostatic detection device according to claim 2, wherein at least a portion of the second wiring shields at least a portion of the first wiring.

5. The electrostatic detection device according to any one of claims 1 to 4, wherein the determination unit determines whether an abnormality has occurred in any of the plurality of second wirings, based on the real and imaginary components obtained by digitally converting the capacitance of the plurality of sensor electrodes and demodulating it with a demodulated signal of the same frequency as the AC signal.

6. The electrostatic detection device according to claim 5, wherein the determination unit determines whether an object is in contact with the cover covering the plurality of sensor electrodes based on the real component and the imaginary component.

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