Electrostatic detection device

Abstract

Provided is an electrostatic detection device capable of detecting, in a case where a plurality of wiring lines are connected to a shield electrode, abnormality of the shield electrode or the plurality of wiring lines.　This electrostatic detection device comprises: an interface circuit having N (N is an integer greater than or equal to 4) sensor electrodes, a shield electrode disposed so as to face the N sensor electrodes, N first wiring lines respectively connected to the N sensor electrodes, N second wiring lines connected to the shield electrode, N input terminals to which the N first wiring lines are respectively connected, and N input / output terminals to which the N second wiring lines are respectively connected; and a control unit that detects abnormality of the shield electrode and the N second wiring lines on the basis of combinations of, when an output voltage is output to the shield electrode from two or more input / output terminals among the N input / output terminals, an input voltage input from two or more remaining input / output terminals among the N input / output terminals and the output voltage output to the shield electrode from the two or more input / output terminals.

Description

Electrostatic detection device

[0001] The present disclosure relates to an electrostatic detection device.

[0002] A steering wheel release detection device has been proposed that includes a sensor electrode of an electrostatic sensor located inside a steering wheel of a vehicle, the electrostatic sensor detecting capacitance when a person grips or releases the steering wheel, a heater having one end grounded to the vehicle body and configured to maintain the steering wheel at a predetermined temperature, a grounded shield electrode interposed between the sensor electrode and the heater to shield the sensor electrode from the heater, and an insulator for insulating the sensor electrode, the shield electrode, and the heater, and a detection unit that applies an AC voltage to the electrostatic sensor, detects a voltage value from a current generated in the electrostatic sensor in response to the application of the AC voltage, and determines that the steering wheel is gripped if the voltage value exceeds a predetermined threshold, and that the steering wheel is released if the voltage value is equal to or less than the threshold. The sensor electrode may be separated into multiple parts (see, for example, Patent Document 1).

[0003] JP 2014-190856 A

[0004] However, conventional steering wheel release detection devices do not detect abnormalities such as disconnections in the shield electrode or the wiring connected to the shield electrode, etc. When there are multiple wirings connected to the shield electrode, it becomes a challenge to be able to determine which wiring has an abnormality.

[0005] Therefore, an object of the present invention is to provide an electrostatic detection device that can detect an abnormality in a shield electrode or a plurality of wires when there are a plurality of wires connected to a shield electrode.

[0006] An electrostatic detection device according to an embodiment of the present disclosure includes: N (N is an integer of 4 or greater) sensor electrodes; a shield electrode disposed opposite the N sensor electrodes; N first wires connected to the N sensor electrodes, respectively; N second wires connected to the shield electrode; N input terminals to which the N first wires are connected, respectively; and N input / output terminals to which the N second wires are connected, respectively; and a control unit that detects an abnormality between the shield electrode and the N second wires based on a combination of an input voltage input from two or more remaining input / output terminals of the N input / output terminals when an output voltage is output from two or more input / output terminals of the N input / output terminals to the shield electrode, and the output voltage output from the two or more input / output terminals to the shield electrode.

[0007] When there are multiple wires connected to a shield electrode, an electrostatic detection device can be provided that can detect an abnormality in the shield electrode or the multiple wires.

[0008] 1 is a diagram illustrating an example of the configuration of an electrostatic detection device 100 according to an embodiment; FIG. 2 is a diagram illustrating an example of the circuit configuration of the electrostatic detection device 100; FIG. 3 is a diagram illustrating in detail an example of the circuit configuration corresponding to the sensor electrode 110; FIG. 4 is a diagram illustrating an example of the relationship between four sensor electrodes 110LF to 110RB, four wires 115LF to 115RB, a shield electrode 120, and four wires 125LF to 125RB; FIG. 5 is a diagram illustrating a modified example of the four wires 125LF to 125RB connected to the shield electrode 120; FIG. 6 is a diagram illustrating an example of a method for determining an abnormality location in the electrostatic detection device 100; FIG. 7 is a diagram illustrating an example of calculation of voltage values ​​of two input terminals when ports (1) to (4) are assigned in five ways; and FIG. 8 is a flowchart illustrating an example of an abnormality diagnosis process executed by a determination unit 151.

[0009] Hereinafter, an embodiment to which the electrostatic detection device of the present disclosure is applied will be described.

[0010] 1 is a diagram showing an example of the configuration of an electrostatic detection device 100 according to an embodiment of the present invention, which shows, as an example, the electrostatic detection device 100 mounted on a steering wheel 10 of a vehicle.

[0011] A steering wheel 10 is mounted on a vehicle, and a sensor electrode 110 and a shield electrode 120 of an electrostatic detection device 100 are mounted on the inside of a cover (surface) 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 around the entire circumference inside the cover. The electrostatic detection device 100 constitutes a hands-off detection (HoD) system and determines whether a driver's hand H is in contact with the rim 11 of the steering wheel 10. The hand H is an example of a detection target. The electrostatic detection device 100 also determines whether an abnormality, such as a break, has occurred in the shield electrode 120 and the wiring 125 connected to the shield electrode 120. The annular rim 11 of the steering wheel 10 is an example of a fixed target to which the sensor electrode 110 and the shield electrode 120 are fixed. An example of the fixed object is not limited to the annular rim 11 of the steering wheel 10, but may also be a part that has a non-annular shape and is gripped by the hand H, such as the control stick of an aircraft. A break or the like in the shield electrode 120 and the wiring 125 does not necessarily mean a complete break, but also includes a change in impedance due to the occurrence of a crack or the like. Hereinafter, this will be simply referred to as an abnormality in the shield electrode 120 or the wiring 125. An abnormality in the shield electrode 120 or the wiring 125 means that the shield electrode 120 or the wiring 125 has failed.

[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, which determines whether an abnormality has occurred in the wiring 125 and whether the operator's hand H, as a detection target, 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 touching 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 Figure 1, the sensor electrode 110 and the shield electrode 120 are shown on the outside and away from the rim 11 in order to show the sensor electrode 110 and the shield electrode 120.

[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 electrostatic detection device 100> The electrostatic 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 an electrostatic MCU (Microcontroller Unit) 150. The interface circuit 140 is connected to the sensor electrode 110 and the shield electrode 120 via wiring 115 and 125. The wiring 115 is an example of a first wiring, and the wiring 125 is an example of a second wiring. The electrostatic MCU 150 is an example of a control unit.

[0016] <Sensor Electrode 110> Four sensor electrodes 110 are arranged in the left-right and front-rear directions on 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. Since FIG. 1 shows the steering wheel 10 as seen by an operator (driver), the left-right and up-down directions in FIG. 1 correspond to the left-right and up-down directions of the vehicle. Furthermore, the direction vertically penetrating FIG. 1 corresponds to the front-rear direction of the vehicle. Furthermore, in explaining the sensor electrodes 110, the left-right and up-down directions refer to the left-right and up-down directions of the steering wheel 10 when the steering angle of the vehicle is in a neutral state.

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

[0018] 1, the sensor electrodes 110LF, 110LB, 110RF, and 110RB are shown lined up around the rim 11 to make it easier to understand the connection relationship with wiring 115 and 125 (described later). However, in reality, 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 over the shield electrode 120 over substantially the entire circumference of the rim 11 of the steering wheel 10 while being insulated from the core metal of the rim 11 of the steering wheel 10. "Over the shield electrode 120" means that the shield electrode 120 is provided on the rim 11, and then the sensor electrodes 110LF, 110LB, 110RF, and 110RB are provided to cover the shield electrode 120.

[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, band-like electrodes provided over substantially the entire circumference of the annular rim 11, and can be produced, for example, by applying a conductor such as silver paste to the surface of a resin film.

[0021] Wires 115LF, 115LB, 115RF, and 115RB are signal wires, and are wrapped and shielded by wires 125LF, 125LB, 125RF, and 125RB, respectively, which will be described later, to form four wire harnesses.

[0022] In the following description, when there is no need to distinguish between the sensor electrodes 110LF, 110LB, 110RF, and 110RB, they will be simply referred to as sensor electrodes 110. Similarly, when there is no need to distinguish between the wirings 115LF, 115LB, 115RF, and 115RB, they will be simply referred to as wirings 115.

[0023] <Shield electrode 120> The shield electrode 120 is provided over approximately the entire circumference of the annular rim 11 of the steering wheel 10, insulated from the core metal of the rim 11 and the sensor electrode 110. Similar to the sensor electrode 110, the shield electrode 120 is a thin sheet-like, band-like electrode, and is provided over approximately 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 shield the sensor electrode 110 from structures at the vehicle ground potential, thereby reducing noise and reducing parasitic capacitance between the sensor electrode 110 and the structures at the ground potential. An AC signal is supplied to the shield electrode 120 from an AC signal source (described later), and the shield electrode 120 functions as an active shield electrode. By making the shield electrode 120 function as an active shield electrode, a function of reducing noise and parasitic capacitance (hereinafter referred to as the active shield function) can be obtained.

[0025] Four wirings 125LF, 125LB, 125RF, and 125RB are connected to the shield electrode 120. The number of wirings 125LF to 125RB is equal to the number of sensor electrodes 110LF to 110RB and the number of wirings 115LF to 115RB. The 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.

[0026] The shield electrode 120 is connected to the ECU 130 via wiring 125LF, 125LB, 125RF, and 125RB. The thin sheet-like, strip-shaped electrode used as the shield electrode 120 can be fabricated, for example, by applying a conductor such as silver paste to the surface of a resin film. The shield electrode 120 fabricated in this manner has a substantially uniform thickness and a substantially uniform resistance value at every portion.

[0027] As an example, the wires 125LF, 125LB, 125RF, and 125RB are configured to respectively wrap and shield the wires 115LF, 115LB, 115RF, and 115RB that serve as signal lines. The wires 115LF to 115RB correspond to the core wires of coaxial cables, and the wires 125LF to 125RB correspond to the shield wires of the coaxial cables, so that the wires 125LF to 125RB shield the wires 115LF to 115RB, respectively. The wires 115LF and 125LF form one wire harness, and the wires 115LB and 125LB form another wire harness. The wires 115RF and 125RF form one wire harness, and the wires 115RB and 125RB form another wire harness.

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

[0029] In the following description, when there is no need to distinguish between the wirings 125LF, 125LB, 125RF, and 125RB, they will be simply referred to as wirings 125.

[0030] For example, the number of wirings 125 is equal to the number of wirings 115. Therefore, by arranging the portion where wiring 125LF is connected to shield electrode 120 close to the portion where wiring 115LF is connected to sensor electrode 110LF, it becomes easier to shield wiring 115LF with wiring 125LF. The same applies to wirings 125LB to 125RB and wirings 115LB to 115RB. Therefore, it becomes easier to shield wirings 115LF to 115RB with wirings 125LF to 125RB, respectively.

[0031] Furthermore, the 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 an abnormality occurs in any of the wirings 125LF to 125RB, an abnormality occurs in the active shield function for any of the sensor electrodes 110LF to 110RB. Because the wirings 125LF to 125RB shield the wirings 115LF to 115RB, an abnormality in the wirings 125LF to 125RB causes an abnormality in the shielding of the wirings 115LF to 115RB, resulting in an abnormality in the active shield function. An abnormality in the active shield function occurs when the active shield state deviates from the ideal state.

[0032] The ECU 130 is provided, for example, inside an instrument panel of a vehicle. The ECU 130 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. The interface circuit 140 inputs a sine wave (input sine wave) to the sensor electrode 110 and the shield electrode 120 based on a command input from the electrostatic MCU 150, and acquires a sine wave (output sine wave) output from the sensor electrodes 110LF-110RB. The interface circuit 140 acquires the capacitance values ​​(electrostatic capacitance) of the sensor electrodes 110LF-110RB from the input sine wave and output sine wave, converts them into digital data, removes noise using a low-pass filter, and outputs the digital data as an amplitude AD value to the electrostatic MCU 150. The amplitude AD value is expressed, for example, as a unitless count value.

[0034] <Electrostatic MCU 150> The electrostatic MCU 150 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. As an example, the electrostatic MCU 150 is connected to electronic devices (such as a host ECU) of a vehicle in which the steering wheel 10 is mounted. The electronic devices of the vehicle may be, for example, electronic devices related to automatic driving of the vehicle.

[0035] The electrostatic MCU 150 has a determination unit 151 and a memory 152. The determination unit 151 represents, as a functional block, the functions of a program executed by the electrostatic MCU 150. 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 whether an abnormality such as a break has occurred in the wiring 125. Details of the determination process executed by the determination unit 151 will be described later. Note that the determination (detection) of an abnormality by the determination unit 151 is synonymous with the electrostatic MCU 150 determining (detecting) an abnormality.

[0037] The memory 152 stores programs, data, etc. required for the determination unit 151 to perform processing.

[0038] <Circuit Configuration> Next, the circuit configuration of the electrostatic detection device 100 will be described. The following description will be made with reference to Figs. 2 and 3 in addition to Fig. 1. Fig. 2 is a diagram showing an example of the circuit configuration of the electrostatic detection device 100. Fig. 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> FIG. 2 shows circuits 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] The circuit 113LF includes a sensor electrode 110LF, a wiring 115LF, a shield electrode 120, and a wiring 125LF, and the circuit 113LB includes a sensor electrode 110LB, a wiring 115LB, a shield electrode 120, and a wiring 125LB. The circuit 113RF includes a sensor electrode 110RF, a wiring 115RF, a shield electrode 120, and a wiring 125RF, and the circuit 113RB includes a sensor electrode 110RB, a wiring 115RB, a shield electrode 120, and a wiring 125RB. Although one shield electrode 120 is shown separated into the four circuits 113LF to 113RB in FIG. 2 , the shield electrode 120 is a single electrode, and the shield electrodes 120 of the circuits 113LF to 113RB are connected to each other. Hereinafter, when there is no need to distinguish between the circuits 113LF to 113RB, they will be simply referred to as circuits 113. An example of the configuration of the circuit 113 is shown in detail in FIG.

[0041] 2 and 3, the ground (ground potential point) is a part of the vehicle body or the like that has ground potential, and is at the same potential as the core metal of the steering wheel 10. The ground potential is an example of a reference potential, and the ground potential point is an example of a reference potential point. Also shown in FIG. 3 is the operator's hand H.

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

[0043] 3, 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, switches 146A to 146C, a power supply 147, wiring 148A and 148B, and an ADC 149. The interface circuit 140 also includes input terminals IN1 to IN4 and input / output terminals I / O-1 to I / O-4. The AC signal source 143 is an example of a signal output unit.

[0044] Fig. 3 shows a circuit corresponding to one wiring 115 and one wiring 125. In reality, the interface circuit 140 has four circuits shown in Fig. 3 corresponding to four wirings 115LF to 115RB and four wirings 125LF to 125RB. The interface circuit 140 can be realized, for example, by an IC (Integrated Circuit) chip.

[0045] The input terminals IN1 to IN4 are input terminals through which signals are input to the interface circuit 140. The input / output terminals I / O-1 to I / O-4 are terminals that can be used as input terminals through which signals are input to the interface circuit 140 and as output terminals through which signals are output from the interface circuit 140. Hereinafter, the input / output terminals I / O-1 to I / O-4 may be referred to as ports (1) to (4), and therefore, in FIG. 2, I / O-1 to I / O-4 and (1) to (4) are shown together.

[0046] As shown in FIG. 2, a line 115LF is connected to input terminal IN1. A line 115LB is connected to input terminal IN2. A line 115RF is connected to input terminal IN3. A line 115RB is connected to input terminal IN4. A line 125LF is connected to input / output terminal I / O-1. A line 125LB is connected to input / output terminal I / O-2. A line 125RF is connected to input / output terminal I / O-3. A line 125RB is connected to input / output terminal I / O-4.

[0047] When the judgment unit 151 judges that an object to be detected has come into contact with the surface of the steering wheel 10, the input / output terminals I / O-1 to I / O-4 become output terminals that output the AC signal output from the AC signal source 143 to the shield electrode 120.

[0048] Furthermore, when the determination unit 151 detects an abnormality in the shield electrode 120 and the wiring 125LF to 125RB (125LF, 125LB, 125RF, 125RB), any two of the four input / output terminals I / O-1 to I / O-4 become output terminals that output an H-level voltage and an L-level voltage from the interface circuit 140, and any two remaining terminals become input terminals that input the voltage of the shield electrode 120 to the interface circuit 140. Details of this will be described later.

[0049] Although FIG. 2 shows four circuits 113LF to 113RB, the configuration of the four circuits 113LF to 113RB is the same, and therefore only the configuration of the circuit 113 shown in FIG. 3 will be described here.

[0050] <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 a connection point A between the AC signal source 143 and the waveform adjustment unit 144. In reality, four filter circuits 141 are provided corresponding to the circuits 113LF to 113RB shown in FIG.

[0051] As an example, the filter circuit 141 is composed of resistors R1 and R2 and a capacitor C. The capacitor C is connected between the inverting input terminal of the charge amplifier 142 and a connection point A of the AC signal source 143 and the waveform adjustment unit 144. The resistor R1 is inserted in series between the sensor electrode 110 and one end of the capacitor C (the upper terminal in FIGS. 2 and 3). The resistor R2 is inserted in series between the shield electrode 120 and the other end of the capacitor C (the lower terminal in FIGS. 2 and 3).

[0052] <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 the capacitor C of the filter circuit 141 and to the 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 to the non-inverting input terminal (+) and the input to the inverting input terminal (-) and outputs an output signal.

[0053] <AC Signal Source 143> The AC signal source 143 outputs an AC signal that drives the shield electrode 120. The output terminal of the AC signal source 143 is connected to the other end (lower terminal) of the capacitor C of the filter circuit 141, resistor R2, and an input terminal of the waveform adjustment unit 144 via the switch 146A. When the determination unit 151 determines that an object to be detected has come into contact with the surface of the steering wheel 10, the switch 146A is turned on, and the AC signal is supplied to the shield electrode 120 via the filter circuit 141 and also to the waveform adjustment unit 144. In addition, because the shield electrode 120 is electromagnetically coupled to the sensor electrode 110, the AC signal is also supplied to the sensor electrode 110. AC signals of the same phase are supplied to the sensor electrode 110 and the shield electrode 120.

[0054] Although the following describes a configuration in which AC signal source 143 is connected to shield electrode 120 via filter circuit 141, the positions of sensor electrode 110 and shield electrode 120 may be reversed. In this case, the AC signal output from AC signal source 143 is supplied to sensor electrode 110 via filter circuit 141, and is then supplied to shield electrode 120 via sensor electrode 110.

[0055] <Waveform Adjustment Unit 144> The waveform adjustment unit 144 adjusts and outputs the amplitude and phase of the AC signal supplied from the AC signal source 143 so that the voltage of the output signal from the charge amplifier 142 becomes approximately zero when the operator's hand H or the like is not in contact with the rim 11, which is the initial state. Even after adjustment in the initial state, the waveform adjustment unit 144 maintains the adjusted state of the amplitude and phase of the AC signal and continues to output the AC signal to the non-inverting input terminal (+) of the charge amplifier 142.

[0056] <ADC 145> The ADC 145 has an input terminal connected to the output terminal of the charge amplifier 142, and an output terminal connected to the electrostatic MCU 150. The ADC 145 digitally converts the signal output from the charge amplifier 142 and outputs it to the electrostatic MCU 150 as an amplitude AD value.

[0057] <Switch 146A> The switch 146A is connected between the wiring 148B and the AC signal source 143, and is controlled to be switched on and off by the determination unit 151. The switch 146A is turned on when the determination unit 151 determines that an object to be detected has come into contact with the surface of the steering wheel 10.

[0058] <Switch 146B> Switch 146B is connected between the positive terminal of power supply 147 and wiring 148B, and is controlled to be switched on and off by determination unit 151. Switch 146B is turned off when determination unit 151 determines that an object to be detected has contacted the surface of steering wheel 10, and may be turned on when determination unit 151 detects an abnormality in wiring 125 and shield electrode 120. This will be described in detail later.

[0059] <Switch 146C> The switch 146C is connected between the wiring 148B and the ground (ground potential point), and is controlled to be switched on and off by the determination unit 151. The switch 146C is turned off when the determination unit 151 determines that an object to be detected has contacted the surface of the steering wheel 10, and may be turned on when the determination unit 151 detects an abnormality in the wiring 125 and the shield electrode 120. This will be described in detail later.

[0060] <Power supply 147> The power supply 147 is a DC power supply. The power supply 147 is connected between the switch 146B and the ground (ground potential point). As an example, the power supply 147 outputs a voltage of 5 V from the positive terminal on the switch 146B side. The voltage of 5 V output from the power supply 147 is an example of an H (High) level voltage. Furthermore, 0 V, which is the voltage of the ground (ground potential point), is an example of an L (Low) level voltage.

[0061] <Wiring 148A> The wiring 148A has a resistor R1 inserted in series, and is a wiring that connects the wiring 115 and the non-inverting input terminal of the charge amplifier 142. The resistor R1 is a part of the wiring 148A. The wiring 115 is connected to the sensor electrode 110, and the wiring 148A is connected to the electrostatic MCU 150 via the charge amplifier 142 and the ADC 145.

[0062] <Wiring 148B> Wiring 148B has a resistor R2 inserted in series and is a wiring that connects between wiring 125 and the electrostatic MCU 150. Resistor R2 is a part of wiring 148B. Between resistor R2 and the electrostatic MCU 150, the other end of capacitor C (lower terminal in FIGS. 2 and 3), the input terminal of waveform adjustment unit 144 (lower terminal in FIG. 3), and switches 146A to 146C are connected to wiring 148B. In addition, an ADC 149 is inserted between connection point A and the electrostatic MCU 150 on wiring 148B. A switch (not shown) can be provided between the input terminal of waveform adjustment unit 144 and wiring 148B, and can be turned off when performing abnormality diagnosis processing.

[0063] <ADC 149> The ADC 149 is inserted into the wiring 148B and is provided closer to the electrostatic MCU 150 than the switch 146C. If the switch closest to the electrostatic MCU 150 is the switch 146A or the switch 146B, the ADC 149 may be provided closer to the electrostatic MCU 150 than the switch 146A or the switch 146B. The ADC 149 has an input terminal connected to the shield electrode 120 via the resistor R2 and an output terminal connected to the electrostatic MCU 150. That is, the input terminal of the ADC 149 is connected to the input / output terminal I / O of the interface circuit 140. The ADC 149 digitally converts an input voltage input to the input / output terminal I / O and outputs the digital signal to the electrostatic MCU 150.

[0064] <Determination Unit 151> The determination unit 151 shown in FIG. 1 determines whether an object to be detected has contacted the surface of the steering wheel 10 based on a difference value obtained by subtracting a reference value from the amplitude AD value input from the ADC 145. The determination unit 151 also detects abnormalities in the shield electrode 120 and the wiring 125LF-125RB based on the H-level voltage and L-level voltage output from any two of the input / output terminals I / O-1 to I / O-4 and the voltage of the shield electrode 120 input to any two of the remaining terminals. The determination unit 151 selects two input / output terminals to be used as input terminals and two input / output terminals to be used as output terminals from among the input / output terminals I / O-1 to I / O-4, and detects abnormalities in the shield electrode 120 and the wiring 125LF-125RB while switching the selection method. This will be described in more detail below.

[0065] <Four Sensor Electrodes 110LF-110RB, Four Wires 115LF-115RB, Shield Electrode 120, and Four Wires 125LF-125RB> Figure 4A is a diagram showing an example of the relationship between the four sensor electrodes 110LF-110RB, the four wires 115LF-115RB, the shield electrode 120, and the four wires 125LF-125RB. Figure 4A shows the four sensor electrodes 110LF-110RB and the shield electrode 120 in an extended state. In Figure 4A, the horizontal direction is the longitudinal direction of the shield electrode 120. The shield electrode 120 is attached to the rim 11 of the steering wheel 10 so that its longitudinal direction follows the outer periphery of the rim 11.

[0066] In FIG. 4A , the four sensor electrodes 110LF-110RB are arranged along the longitudinal direction. The four wires 115LF-115RB connected to the sensor electrodes 110LF-110RB are also arranged along the longitudinal direction. The four wires 125LF-125RB connected to the shield electrode 120 are arranged at the same positions as the four wires 115LF-115RB in the longitudinal direction. The wires 115LF-115RB are each surrounded and shielded by the wires 125LF-125RB to form a four-wire harness. Note that FIG. 4A shows, as an example, a configuration in which the wires 115LF-115RB and the wires 125LF-125RB are arranged on the same side. The wires 125LF-125RB are arranged at equal intervals along the longitudinal direction. However, the arrangement of the wirings 115LF-115RB and the wirings 125LF-125RB is not limited to this arrangement. For example, the wirings 115LF and 115RF and the wirings 125LF and 125RF may be provided on the same side, and the wirings 115LB and 115RB and the wirings 125LB and 125RB may be provided on opposite sides. Furthermore, the spacing between the wirings 125LF-125RB in the longitudinal direction does not have to be equal. For example, if the ratio of the spacing between the wirings 125LF-125RB in the longitudinal direction is known, an abnormality in the shield electrode 120 or the plurality of wirings 125 can be identified by taking the ratio of the spacing into consideration.

[0067] Four wirings 125LF, 125LB, 125RF, and 125RB are connected between both ends (one end and the other end) of the shield electrode 120 in the longitudinal direction. Wiring 125LF is an example of the first second wiring. Wiring 125LB is an example of the second second wiring. Wiring 125RF is an example of the third second wiring. Wiring 125RB is an example of the fourth second wiring. For convenience of explanation, wiring 125LF may be referred to as the first wiring. Similarly, wiring 125LB may be referred to as the second wiring, wiring 125RF may be referred to as the third wiring, and wiring 125RB may be referred to as the fourth wiring.

[0068] The four wirings 125LF to 125RB connected to the shield electrode 120 may have a configuration as shown in Fig. 4B. Fig. 4B is a diagram showing a modified example of the four wirings 125LF to 125RB connected to the shield electrode 120. As shown in Fig. 4B, the four wirings 125LF to 125RB may be connected to the shield electrode 120 alternately in the short-side direction of the shield electrode 120. The short-side direction is a direction perpendicular to the long-side direction in a plan view.

[0069] <Method of Determining Abnormal Location> Fig. 5 is a diagram illustrating an example of a method of determining abnormal locations in the electrostatic detection device 100. Fig. 5 shows the shield electrode 120 and the wiring 125LF to 125RB. The wiring 125LF to 125RB are connected to ports (1) to (4), respectively. The ports (1) to (4) are input / output terminals I / O-1 to I / O-4 of the interface circuit 140.

[0070] 2 and 3, two of the ports (1) to (4) are used as output terminals, and by turning on one of the switches 146B and 146C while turning off the switch 146A corresponding to the two output terminals, it is possible to output an H-level voltage or an L-level voltage to the shield electrode 120. Furthermore, by using the remaining two of the ports (1) to (4) as input terminals and turning off the switches 146A to 146C corresponding to the two input terminals, it is possible to obtain the voltage value of the shield electrode 120 by the electrostatic MCU 150 via the two wires 125 connected to the two input terminals.

[0071] Two of the ports (1) to (4) can be assigned as output terminals that output H-level voltage and L-level voltage, respectively, and the remaining two can be assigned as input terminals.

[0072] For example, if port (1) shown in FIG. 5 is assigned as an output terminal for an H-level voltage, port (4) as an output terminal for an L-level voltage, and ports (2) and (3) as two input terminals, it is possible to obtain the voltage value of the shield electrode 120 at ports (2) and (3) while outputting an H-level voltage from port (1) and an L-level voltage from port (4). The voltage value of the shield electrode 120 at ports (2) and (3) is generated by connecting the wiring 125LF to 125RB to the shield electrode 120 at equal intervals in the longitudinal direction and by having the shield electrode 120 have a substantially constant resistance value at every portion. For the voltage values ​​of ports (2) and (3), setting the H-level voltage to 5 V and the L-level voltage to 0 V creates a sufficient difference for determining the location of an abnormality. The H-level voltage and the L-level voltage do not have to be 5 V and 0 V, but may be, for example, 4 V and 1 V, as long as the difference in voltage between the two input terminals is sufficient to determine the location of an abnormality.

[0073] 5, an x ​​mark indicating a break in wiring 125LF is shown as an example. When there is no break in wiring 125LF, ports (2) and (3) obtain a voltage obtained by dividing the voltage value of the H-level voltage output from port (1) to shield electrode 120 and the L-level voltage output from port (4) to shield electrode 120. As an example, when there is no break in wiring 125LF and 5 V is applied to port (1) and 0 V is applied to port (4), the voltage values ​​of ports (2) and (3) become 3.3 V and 1.6 V.

[0074] However, if a break occurs in the wiring 125LF, the 5V voltage is not supplied to the shield electrode 120 through port (1), and the voltage values ​​obtained at ports (2) and (3) differ from the voltage values ​​obtained when no abnormality occurs in the wiring 125LF. As an example, if 5V is applied to port (1) and 0V is applied to port (4) when a break occurs in the wiring 125LF, the voltage values ​​at ports (2) and (3) will be 0V, 0V. In this way, if a break occurs in the wiring 125LF, the voltage value at at least one of ports (2) and (3) will change to a value different from the normal value.

[0075] When two of the ports (1) to (4) are used as output terminals to output an H-level voltage and an L-level voltage, and the remaining two are used as input terminals, there are five ways to assign the ports (1) to (4): Here, the output terminal that outputs an H-level voltage is denoted as H, the output terminal that outputs an L-level voltage is denoted as L, and the two input terminals to which the voltage of the shield electrode 120 is input are denoted as A, and the assignment is written in the order of ports (1) to (4).

[0076] The five allocation methods for ports (1) to (4) are HAAL, AHLA, HALA, AAHL, and ALAH. In this way, while setting the allocation method for ports (1) to (4) in five ways in order, the voltage values ​​of the two input terminals are obtained in advance for the wirings 125LF to 125RB and the shield electrode 120 in a state where no abnormalities occur in any of them, a state where a break occurs in any one of them, a state where two or more abnormalities occur, and a state where even more abnormalities exist.

[0077] 6 is a diagram showing an example of calculation of voltage values ​​of two input terminals when ports (1) to (4) are assigned in five ways. FIG. 6 also shows voltage values ​​of two input terminals when ports (1) to (4) are assigned to HAAL, AHLA, HALA, AAHL, and ALAH in each of abnormal patterns (A) to (N). For example, abnormal pattern (A) indicates that ports (1) to (4) are assigned to HAAL, and the voltage values ​​(0,0) of the two input terminals corresponding to AA are 0V, 0V. Also, in FIG. 6, wiring 125LF to 125RB connected to ports (1) to (4) are referred to as wiring (1) to (4).

[0078] FIG. 6 also shows 14 abnormality patterns (A) to (N) for cases where there is a single abnormality. Abnormal pattern (A) is an abnormality pattern in which there is a single break in wiring (1). Similarly, abnormal patterns (B) to (D) are abnormality patterns in which there is a single break in wiring (2) to (4), respectively. Abnormal pattern (E) is an abnormality pattern in which there is a break in the shield electrode 120. The break in the shield electrode 120 is, for example, an abnormality in which the shield electrode 120 is split in the longitudinal direction between the portions of the shield electrode 120 where wirings (3) and (4) are connected. The voltage values ​​of the two input terminals shown here are, for example, an abnormality in which there is a break in the shield electrode 120 between the portions of the shield electrode 120 where wirings (3) and (4) are connected. However, the same applies to the portions of the shield electrode 120 where wirings (1) and (2) are connected and where wirings (2) and (3) are connected, as will be described later.

[0079] Abnormal patterns (F) to (H) are abnormal patterns in which a single crack has occurred in the shield electrode 120. Because the crack location differs between abnormal patterns (F) to (H), they are distinguished by being labeled as shield electrode crack 1 location-1, shield electrode crack 1 location-2, and shield electrode crack 1 location-3.

[0080] Abnormal pattern (I) is an abnormal pattern in which a short circuit has occurred at one location between wires (1) and (2). Similarly, abnormal patterns (J) to (N) are abnormal patterns in which a short circuit has occurred at one location between wires (1) and (3), between wires (1) and (4), between wires (2) and (3), between wires (2) and (4), and between wires (3) and (4), respectively.

[0081] Although FIG. 6 does not show the voltage values ​​of the two input terminals when abnormalities occur at two or more locations in the wirings 125LF to 125RB and the shield electrode 120, they can be calculated in the same way.

[0082] Of the abnormal patterns (A) to (N) shown in FIG. 6, abnormal patterns (A) to (D) and (F) to (N) have unique combinations of voltage values ​​at the two input terminals obtained by assigning ports (1) to (4) in five ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH, and there are no combinations of voltage values ​​that are the same as other abnormal patterns.

[0083] That is, for example, in the case of abnormal pattern (A), when ports (1) to (4) are assigned in the order of five ways, HAAL, AHLA, HALA, AAHL, and ALAH, there is no abnormal pattern other than abnormal pattern (A) in which the combinations of voltage values ​​of two input terminals obtained in five assignments are (0,0), (0,0), (0,0), (0,5), and (0,2.5). Of the combinations of voltage values ​​of two input terminals in the five assignments of HAAL, AHLA, HALA, AAHL, and ALAH, (0,0), (0,0), (0,0), (0,5), and (0,2.5), the first to fourth times (0,0), (0,0), (0,0), and (0,5) are different from the voltage values ​​when no abnormality occurs (normal), while the fifth time (0,2.5) is equal to the voltage values ​​in normal times. From this combination of voltage values, it is possible to identify abnormal pattern (A) in which a break has occurred at one point in the wiring (1).

[0084] Similarly, for abnormal patterns (B) to (D) and (F) to (N), it is possible to identify which of abnormal patterns (B) to (D) and (F) to (N) the abnormal pattern is, based on the combination of voltage values ​​of two input terminals obtained by allocating ports (1) to (4) in the order of five different patterns: HAAL, AHLA, HALA, AAHL, and ALAH. Note that, depending on the abnormal pattern, there may be some abnormal patterns that can be identified before the allocation of ports (1) to (4) is performed five times.

[0085] However, in the case of abnormal pattern (E) in which a break has occurred in the shield electrode 120, the combination of voltage values ​​of the two input terminals obtained by five allocations is equal to one or more abnormal patterns among the abnormal patterns in which abnormalities have occurred in two or more locations, and therefore it is not possible to identify abnormal pattern (E) based on the combination of voltage values ​​of the two input terminals obtained by five allocations. Note that this also applies to abnormal patterns in which a break has occurred between the portion of the shield electrode 120 where wires (1) and (2) are connected and between the portion where wires (2) and (3) are connected.

[0086] Furthermore, in the case of abnormality patterns in which two or more abnormalities occur, the combination of voltage values ​​of the two input terminals obtained by five allocations is equal to one or more of the abnormality patterns in which two or more abnormalities occur, and therefore it is not possible to identify two or more abnormal locations based on the combination of voltage values ​​of the two input terminals obtained by five allocations.

[0087] Note that under the rule that abnormality diagnosis is performed while allocating ports (1) to (4) in five ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH, in the case of abnormal pattern (A), it is possible to identify abnormal pattern (A) by performing measurement with the fifth allocation of ALAH. In other words, there are other combinations of voltage values ​​of two input terminals, such as (0,0), (0,0), (0,0), and (0,5), obtained with the first through fourth allocations of HAAL, AHLA, HALA, and AAHL, but there are no other combinations of voltage values ​​of two input terminals, such as (0,0), (0,0), (0,0), (0,5), and (0,2.5), obtained with the first through fifth allocations.

[0088] Similarly, under the same rules, in the case of abnormal patterns (B) to (D), it is possible to identify abnormal patterns (B) to (D) by performing measurements with HALA allocation up to the third time, ALAH allocation up to the fifth time, and HALA allocation up to the third time, respectively.

[0089] 6 are assigned in five different ways, table data representing the voltage values ​​of the two input terminals may be stored in memory 152. Furthermore, in order to determine whether the voltage values ​​of the two input terminals are normal, table data representing the voltage values ​​of the two input terminals when ports (1) to (4) are assigned in five different ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH under normal conditions may be stored in memory 152.

[0090] Furthermore, under the same rules, in the case of abnormal patterns (F) to (H), it is possible to identify abnormal patterns (F) to (H) by performing measurements with AHLA assignments up to the second time, HAAL assignments up to the first time, and HAAL assignments up to the first time, respectively.

[0091] Furthermore, under the same rules, in the case of abnormal patterns (I) to (K), it is possible to identify abnormal patterns (I) to (K) by performing measurements with HAAL assignment up to the first time, ALAH assignment up to the fifth time, and AHLA assignment up to the second time, respectively.

[0092] Furthermore, under the same rules, in the case of abnormal patterns (L) to (N), it is possible to identify abnormal patterns (L) to (N) by performing measurements with HAAL assignment up to the first time, HALA assignment up to the third time, and AHLA assignment up to the second time, respectively.

[0093] Note that, here, the explanation is based on the rule that the ports (1) to (4) are assigned in five ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH while performing the abnormality diagnosis, but the order in which the ports (1) to (4) are assigned is not limited to HAAL, AHLA, HALA, AAHL, and ALAH. If the order is changed, the number of times until the abnormality pattern can be identified will differ.

[0094] The electrostatic detection device 100 performs an abnormality diagnosis while sequentially allocating the ports (1) to (4) in five different patterns, and identifies which of the abnormality patterns (A) to (D) or (F) to (N) corresponds to a single abnormality. If it is determined that two or more abnormalities have occurred, the electrostatic detection device 100 notifies the vehicle's host ECU that an abnormality has occurred in the HoD system. It should be noted that the notification may be sent not only to the host ECU but also to other related ECUs (examples of external devices).

[0095] <Flowchart> FIG. 7 is a flowchart showing an example of an abnormality diagnosis process executed by the determining unit 151.

[0096] When the determination unit 151 starts the abnormality diagnosis process, it switches the allocation of ports (1) to (4) and acquires the voltage values ​​of the two input terminals (step S1). Steps S1 to S3 are repeated up to five times, so as an example, each time step S1 is repeated, the allocation of ports (1) to (4) is switched in five ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH, and the voltage values ​​of the two input terminals are acquired.

[0097] Note that, before switching the allocation of ports (1) to (4) and acquiring the voltage values ​​of the two input terminals, the determination unit 151 preferably sets the potential of the shield electrode 120 to the ground potential by turning off all of the switches 146A and 146B and turning on all of the switches 146C. This is because if an abnormality diagnosis is performed in a state in which the potential of the shield electrode 120 deviates from the ground potential due to the influence of noise or the like, accurate voltage values ​​of the two input terminals may not be acquired.

[0098] The determination unit 151 determines whether the voltage values ​​of the two input terminals are normal (step S2). Whether the voltage values ​​of the two input terminals are normal can be determined by comparing the voltage values ​​corresponding to the current number of times step S2 is being performed with the voltage values ​​from the first to fifth times included in table data representing the voltage values ​​of the two input terminals in a normal state stored in memory 152. For example, when step S2 is being performed for the second time, it is possible to determine whether the voltage values ​​of the two input terminals are normal by comparing the voltage values ​​of the two input terminals acquired in step S1 for the second time with the voltage values ​​for the second time included in table data representing the voltage values ​​of the two input terminals in a normal state stored in memory 152.

[0099] If the determining unit 151 determines that the voltage values ​​of the two input terminals are normal (S2: Yes), it determines whether the measurement of the voltage values ​​of the two input terminals for the five allocations has been completed (step S3).

[0100] When the determination unit 151 determines that the measurement of the voltage values ​​of the two input terminals for the five allocations has been completed (S3: Yes), it starts electrostatic scanning (step S4). Electrostatic scanning is a process in which the electrostatic detection device 100, as an HoD system, uses the sensor electrode 110 to determine whether the operator's hand H, as the detection object, is in contact with the surface of the rim 11 of the steering wheel 10. The determination unit 151 turns on all switches 146A and turns off all switches 146B and 146C, and then determines whether the detection object is in contact with the surface of the rim 11 of the steering wheel 10 based on the difference value obtained by subtracting a reference value from the amplitude AD value input from the ADC 145. When the determination unit 151 completes the process of step S4, the flow returns to step S1.

[0101] If the determining unit 151 determines in step S3 that the measurement of the voltage values ​​of the two input terminals in the five allocations has not been completed (S3: No), the flow returns to step S1.

[0102] Furthermore, if the determination unit 151 determines in step S2 that the voltage values ​​of the two input terminals are not normal (S2: No), it determines that an abnormality has occurred in the wiring 125LF to 125RB or the shield electrode 120 (step S5).

[0103] The determination unit 151 determines whether the voltage values ​​of the two input terminals acquired in step S1 up to that point correspond to any of the abnormal patterns (A) to (D) or (F) to (N) (step S6). For example, if it is determined that the voltage values ​​are abnormal in the second step S2, the determination unit 151 may determine whether the voltage values ​​of the two input terminals acquired in the two steps S1 match the voltage values ​​of the two input terminals in the first and second times of any of the abnormal patterns (A) to (D) and (F) to (N) stored in the memory 152.

[0104] If the determination unit 151 determines that the voltage values ​​of the two input terminals acquired in step S1 correspond to any of the abnormal patterns (A) to (D) or (F) to (N) (S6: Yes), it calibrates the output voltage of the sensor electrode 110 (step S7). The determination unit 151 turns on all switches 146A and turns off all switches 146B and 146C, and then stores the amplitude AD value input from the ADC 145 in a state where the detection object is not touching the surface of the rim 11 of the steering wheel 10 as a reference value in the memory 152. After completing the process of step S7, the determination unit 151 proceeds to step S4. Thereafter, unless calibration is performed again in step S7, the determination unit 151 performs the determination process of step S4 using the reference value stored in the memory 152. The determination unit 151 determines whether the detection object is touching the surface of the steering wheel 10 based on a difference value obtained by subtracting the reference value from the amplitude AD value input from the ADC 145.

[0105] Furthermore, if the determination unit 151 determines in step S6 that the voltage values ​​of the two input terminals acquired in step S1 up to that point do not correspond to any of the abnormal patterns (A) to (D) or (F) to (N) (S6: No), it switches the assignment of ports (1) to (4) and acquires the voltage values ​​of the two input terminals (step S8). Since steps S1 to S3 are repeated a maximum of five times, for example, each time step S1 is repeated, the assignment of ports (1) to (4) is switched in five ways in the order of HAAL, AHLA, HALA, AAHL, and ALAH, and the voltage values ​​of the two input terminals are acquired.

[0106] In step S8, before switching the allocation of ports (1) to (4) and acquiring the voltage values ​​of the two input terminals, the determination unit 151 preferably sets the potential of the shield electrode 120 to the ground potential by turning off all the switches 146A and 146B and turning on all the switches 146C, as in step S1, in order to acquire accurate voltage values ​​of the two input terminals.

[0107] The determination unit 151 determines whether or not the measurement of the voltage values ​​of the two input terminals in step 8 for the five allocations has been completed (step S9). That is, the determination unit 151 determines whether or not the processing of step 8 has been repeated five times to measure the voltage values ​​of five sets of two input terminals.

[0108] If the determination unit 151 determines that the measurement of the voltage values ​​of the two input terminals in step 8 has not been completed for the five allocations (S9: No), it determines whether the voltage values ​​of the two input terminals acquired in step S8 up to that point correspond to any of the abnormal patterns (A) to (D) or (F) to (N) (step S10). The process of step S10 is the same as that of step S6.

[0109] If the judgment unit 151 determines that the voltage values ​​of the two input terminals acquired in step S8 up to that point correspond to any of abnormal patterns (A) to (D) or (F) to (N) (S10: Yes), the flow proceeds to step S7 and calibration is performed.

[0110] Furthermore, if the determination unit 151 determines in step S10 that the voltage values ​​of the two input terminals acquired in step S1 up to that point do not correspond to any of the abnormal patterns (A) to (D) or (F) to (N) (S10: No), the flow returns to step S8.

[0111] Furthermore, when the determination unit 151 determines in step S9 that the measurement of the voltage values ​​of the two input terminals in step 8 for the five allocations has been completed (S9: Yes), it determines whether the five sets of voltage values ​​of the two input terminals acquired in the five times of step S8 correspond to any of abnormal patterns (A) to (D) or (F) to (N) (step S11). The process of step S11 is a process that performs the same processes as steps S6 and S10 on the voltage values ​​of the five sets of two input terminals.

[0112] If the judgment unit 151 determines that the voltage values ​​of the five sets of two input terminals acquired in five times of step S8 correspond to any of abnormal patterns (A) to (D) or (F) to (N) (S11: Yes), the flow proceeds to step S7 and calibration is performed.

[0113] Furthermore, if the determination unit 151 determines in step S11 that the five sets of voltage values ​​of the two input terminals acquired in the five iterations of step S8 do not correspond to any of abnormality patterns (A) to (D) or (F) to (N) (S11: No), it determines that two or more abnormalities have occurred and notifies the host ECU that two or more abnormalities have occurred (step S12). In this case, the electrostatic detection device 100 enters a state in which it does not perform electrostatic scanning. After completing the process of step S12, the determination unit 151 ends the series of processes.

[0114] <Effects> The electrostatic detection device 100 includes N (N is an integer greater than or equal to 4) sensor electrodes 110, a shield electrode 120 arranged opposite the N sensor electrodes 110, N wires 115 connected to the N sensor electrodes 110, N wires 125 connected to the shield electrode 120, N input terminals to which the N wires 115 are respectively connected, and N input / output terminals I / O to which the N wires 125 are respectively connected. When an output voltage is output from two or more of the N input / output terminals I / O to the shield electrode 120, the ECU 130 detects an abnormality between the shield electrode 120 and the N wires 125 based on a combination of an input voltage input from the remaining two or more input / output terminals I / O of the N input / output terminals I / O and the output voltage output from the two or more input / output terminals I / O to the shield electrode 120. Therefore, an abnormality in the shield electrode 120 or the plurality of wirings 125 can be appropriately identified based on the combination of the input voltage and the output voltage.

[0115] Therefore, when there are multiple wirings 125 connected to the shield electrode 120 , it is possible to provide an electrostatic detection device 100 that can detect an abnormality in the shield electrode 120 or the multiple wirings 125 .

[0116] Furthermore, the ECU 130 may change the combination of two or more of the N input / output terminals I / O, and detect an abnormality between the shield electrode 120 and the N wirings 125 based on the combination of the input voltage input from the remaining two or more input / output terminals I / O and the output voltage output from the two or more input / output terminals I / O to the shield electrode 120. By performing an abnormality diagnosis while changing the combination of two or more input / output terminals I / O, it is possible to detect abnormalities in various patterns.

[0117] Furthermore, the ECU 130 may output an L-level voltage (reference voltage) from the N input / output terminals I / O every time the combination of two or more input / output terminals I / O among the N input / output terminals I / O is changed. By setting the potential of the shield electrode 120 to the ground potential, accurate voltage values ​​of the two input terminals can be obtained.

[0118] Furthermore, the ECU 130 may determine whether a detection target is in proximity to at least one of the N sensor electrodes 110 based on voltages input to the N input terminals from the N wires 115. This can be used in a system that determines the proximity of a detection target, such as an HoD system.

[0119] Furthermore, N may be 4, the number of the two or more input / output terminals I / O may be 2, and the number of the remaining two or more input / output terminals I / O may be 2, and the ECU 130 may detect an abnormality between the shield electrode 120 and the four wirings 125 based on a combination of two types of input voltages input from the two input / output terminals I / O and two types of output voltages output from the two input / output terminals I / O to the shield electrode 120.

[0120] Furthermore, the four wirings 125 are connected to the shield electrode 120 in the order of the first wiring 125 to the fourth wiring 125 between one end and the other end of the shield electrode 120, and there are five combinations of the two types of output voltages and the two types of input voltages output from the two input / output terminals I / O to the shield electrode 120, from the first combination to the fifth combination shown below. In the first combination, the input / output terminal I / O to which the first wiring 125 is connected outputs an H level voltage as the output voltage, and the input voltage is input to the input / output terminal I / O to which the second wiring 125 is connected. , an input voltage is input to the input / output terminal I / O to which the third wiring 125 is connected, and the input / output terminal I / O to which the fourth wiring 125 is connected outputs an L level voltage as an output voltage. The second combination is a combination in which an input voltage is input to the input / output terminal I / O to which the first wiring 125 is connected, and the input / output terminal I / O to which the second wiring 125 is connected outputs an H level voltage as an output voltage. The input / output terminal I / O to which the third wiring 125 is connected outputs an L level voltage as an output voltage. The third combination is a combination in which an input voltage is input to the input / output terminal I / O to which the first wiring 125 is connected, outputs an H-level voltage as the output voltage, the input voltage is input to the input / output terminal I / O to which the second wiring 125 is connected, the input / output terminal I / O to which the third wiring 125 is connected outputs an L-level voltage as the output voltage, and the input voltage is input to the input / output terminal I / O to which the fourth wiring 125 is connected. The fourth combination is a combination in which an input voltage is input to the input / output terminal I / O to which the first wiring 125 is connected, and the second wiring 125 outputs an L-level voltage as the output voltage. The fifth combination is a combination in which an input voltage is input to the input / output terminal I / O to which the third wiring 125 is connected, an H level voltage is output as the output voltage, and an L level voltage is output as the output voltage of the input / output terminal I / O to which the fourth wiring 125 is connected, and the fifth combination is a combination in which an input voltage is input to the input / output terminal I / O to which the first wiring 125 is connected, an L level voltage is output as the output voltage of the input / output terminal I / O to which the second wiring 125 is connected, and an input voltage is input to the input / output terminal I / O to which the third wiring 125 is connected,The input / output terminal I / O to which the fourth wiring 125 is connected may be a combination that outputs an H-level voltage as the output voltage. By using four wirings 125 and five combinations of two types of output voltages output from two input / output terminals I / O to the shield electrode 120 and two types of input voltages, it is possible to detect abnormalities due to various patterns with high accuracy.

[0121] Furthermore, the ECU 130 may perform an abnormality diagnosis by setting the combinations of the two types of output voltages and the two types of input voltages to the first to fifth combinations upon startup or upon updating the reference value for determining whether an object to be detected has approached the N sensor electrodes 110 based on the capacitance of the N sensor electrodes 110. By performing an abnormality diagnosis upon startup or upon updating the reference value, it is possible to provide an electrostatic detection device 100 that can detect an abnormality with high accuracy.

[0122] Furthermore, the four sensor electrodes 110 and the shield electrode 120 may be provided along the circumferential direction of the rim 11 of the vehicle steering wheel 10. An electrostatic detection device 100 capable of constructing an HoD system can be provided.

[0123] The shield electrode 120 may be provided along the circumferential direction on the rim 11 of the vehicle steering wheel 10, and two of the four sensor electrodes 110 may be provided on the front side of the rim 11 of the steering wheel 10 along the circumferential direction, overlapping the shield electrode 120, and the remaining two may be provided on the rear side of the rim 11 of the steering wheel 10 along the circumferential direction, overlapping the shield electrode 120. An electrostatic detection device 100 capable of constructing an HoD system can be provided.

[0124] Furthermore, if the ECU 130 determines that two or more abnormalities have occurred, it may notify an external device. Since it is difficult to identify abnormalities in two or more locations, by notifying an external device, safety can be ensured.

[0125] The above describes an electrostatic detection device according to an exemplary embodiment of the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0126] This international application claims priority based on Japanese Patent Application No. 2024-130747, filed on August 7, 2024, the entire contents of which are incorporated herein by reference.

[0127] 10 Steering wheel 11 Rim 100 Electrostatic detection device 110, 110LF, 110LB, 110RF, 110RB Sensor electrodes 113, 113LF, 113LB, 113RF, 113RB Circuit 115, 115LF, 115LB, 115RF, 115RB Wiring (an example of first wiring) 120 Shield electrode 125, 125LF, 125LB, 125RF, 125RB Wiring (an example of second wiring) 140 Interface circuit 150 Electrostatic MCU (an example of a control unit) 151 Determination unit 152 Memory

Claims

1. An electrostatic detection device comprising: N (N is an integer of 4 or greater) sensor electrodes; a shield electrode arranged opposite the N sensor electrodes; N first wires connected to the N sensor electrodes, respectively; N second wires connected to the shield electrode; an interface circuit having N input terminals to which the N first wires are connected, and N input / output terminals to which the N second wires are connected, respectively; and a control unit that detects an abnormality between the shield electrode and the N second wires based on a combination of input voltages input from the remaining two or more input / output terminals of the N input / output terminals when output voltages are output from two or more input / output terminals of the N input / output terminals to the shield electrode, and the output voltages output from the two or more input / output terminals to the shield electrode.

2. The electrostatic detection device according to claim 1, further comprising a signal output unit that outputs an AC signal, wherein the N second wirings supply the AC signal to the shield electrode.

3. The electrostatic detection device described in claim 1, wherein the control unit detects an abnormality between the shield electrode and the N second wirings based on a combination of an input voltage input from the remaining two or more input / output terminals and an output voltage output from the two or more input / output terminals to the shield electrode while changing the combination of the two or more input / output terminals among the N input / output terminals.

4. The electrostatic detection device according to claim 3, wherein the control unit outputs a reference voltage from the N input / output terminals each time the combination of the two or more input / output terminals among the N input / output terminals is changed.

5. An electrostatic detection device as described in any one of claims 1 to 4, wherein the control unit determines whether an object to be detected is in proximity to at least one of the N sensor electrodes based on the voltages input from the N first wirings to the N input terminals.

6. An electrostatic detection device according to any one of claims 1 to 5, wherein N is 4, the number of the two or more input / output terminals is 2, the number of the remaining two or more input / output terminals is 2, and the control unit detects an abnormality between the shield electrode and the four second wirings based on a combination of two types of input voltages input from the two input / output terminals and two types of output voltages output from the two input / output terminals to the shield electrode.

7. The four second wirings are connected to the shield electrode between one end and the other end of the shield electrode in the order of the first second wiring to the fourth second wiring, and there are five combinations of the two types of output voltages output from the two input / output terminals to the shield electrode and the two types of input voltages, namely, the first combination to the fifth combination below, and the first combination is a combination in which the input / output terminal to which the first second wiring is connected outputs an H level voltage as the output voltage, the input / output terminal to which the second second wiring is connected receives the input voltage, the input voltage is input to the input / output terminal to which the third second wiring is connected receives the input voltage, and the input / output terminal to which the fourth second wiring is connected outputs an L level voltage as the output voltage, the second combination is a combination in which the input voltage is input to the input / output terminal to which the first second wire is connected, the input / output terminal to which the second second wire is connected outputs an H-level voltage as the output voltage, the input / output terminal to which the third second wire is connected outputs an L-level voltage as the output voltage, and the input voltage is input to the input / output terminal to which the fourth second wire is connected; the third combination is a combination in which the input / output terminal to which the first second wire is connected outputs an H-level voltage as the output voltage, the input voltage is input to the input / output terminal to which the second second wire is connected, the input / output terminal to which the third second wire is connected outputs an L-level voltage as the output voltage, and the input voltage is input to the input / output terminal to which the fourth second wire is connected; the fourth combination is a combination in which the input voltage is input to the input / output terminal to which the first second wiring is connected, the input voltage is input to the input / output terminal to which the second second wiring is connected, the input / output terminal to which the third second wiring is connected outputs an H-level voltage as the output voltage, and the input / output terminal to which the fourth second wiring is connected outputs an L-level voltage as the output voltage,7. The electrostatic detection device according to claim 6, wherein the fifth combination is a combination in which the input voltage is input to the input / output terminal to which the first second wiring is connected, the input / output terminal to which the second second wiring is connected outputs an L-level voltage as the output voltage, the input voltage is input to the input / output terminal to which the third second wiring is connected, and the input / output terminal to which the fourth second wiring is connected outputs an H-level voltage as the output voltage.

8. The electrostatic detection device according to claim 7, wherein the control unit, upon startup or upon updating a reference value for determining the proximity of an object to be detected to the N sensor electrodes based on the capacitance of the N sensor electrodes, sets the combinations of the two types of output voltages and the two types of input voltages to any of the first to fifth combinations and performs abnormality diagnosis.

9. The electrostatic detection device according to any one of claims 6 to 8, wherein the four sensor electrodes and the shield electrode are provided along the circumferential direction of a steering wheel for a vehicle.

10. An electrostatic detection device as described in claim 9, wherein the shield electrode is provided along the circumferential direction of a steering wheel for a vehicle, and two of the four sensor electrodes are provided on top of the shield electrode along the circumferential direction on the front side of the steering wheel, and the remaining two are provided on top of the shield electrode along the circumferential direction on the rear side of the steering wheel.

11. An electrostatic detection device according to any one of claims 1 to 10, wherein the control unit notifies an external device when it determines that the abnormality has occurred in two or more locations.

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