JPH0784063A - Dielectric detector - Google Patents

Abstract

PURPOSE:To effectively operate a dielectric detector when a dielectric to be detected is present, CONSTITUTION:A dielectric detector has a detector IC1 having switching means for detecting a change of an electrostatic capacity of a capacitor Cx to repeat charging and discharging of the capacitor Cx to oscillator a pulse signal, and a deciding circuit IC2 for judging presence of a dielectric based on an output of the detector IC1, and outputs end of periods of voltage signals output from the detector IC1 according to a frequency divider FC of detecting timing generating means for generating a signal for indicating a time point of charging and discharging, logic circuits AND, OR, NOT and SRFF. A threshold value VTH3 is decided via resistors R8, R9 of noise deciding means, a voltage signal is compared with the value VTH3 by a comparator CMP3, and its result is decided by the circuit IC2 to detect presence or absence of noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric detecting device for detecting the presence or absence of a dielectric such as a personnel by a change in capacitance between at least a pair of electrodes. For example, when a personnel gets in a vehicle. A seat belt device that operates automatically, a power window or an auto-lock device that automatically closes when a person gets off the vehicle, the presence or absence of personnel, or the presence or absence of the presence of a part of the body of the personnel (hereinafter simply referred to as the presence or absence of personnel. ) It can be used as a sensor for performing control according to.

[0002]

2. Description of the Related Art As a conventional technique, for example, Japanese Unexamined Patent Publication No. 1-
There are dielectric detection devices such as those disclosed in Japanese Patent No. 113692 and Japanese Patent Application Laid-Open No. 4-303790, which detect the presence or absence of personnel depending on the change in capacitance between electrodes. In these devices, a low-pass filter is arranged between the input port of the dielectric detecting means and the output side of the sensor electrode to remove the noise of the signal output from the sensor electrode. As a result, it is possible to reduce only the change in the capacitance due to the intervention of the personnel and reduce the adverse effect on the personnel detection by the dielectric other than the personnel and the malfunction of the dielectric detection device.

[0003]

However, the frequency components of the reference signal and the voltage signal output from the detecting means of the dielectric detecting device are 0 to 20 kHz, and the low frequency noise in question is about 17 kHz, which is very close. , As described above, when a low-pass filter is used to prevent malfunction due to low-frequency noise of the capacitance type sensor, a large attenuation is given to frequencies higher than the cutoff frequency, but noise of signals with a frequency lower than the cutoff frequency is removed. However, it is difficult to remove low-frequency noise using a low-pass filter, and the resistors, inductors, and capacitors become large. Further, the RC and LC filters have problems that not only the circuit element becomes large, but also the characteristic is deteriorated and the detected voltage signal is attenuated. Therefore, it is an object of the present invention to reliably detect low frequency noise in a dielectric detection device and improve the reliability of the device.

[0004]

Means for Solving the Problems At least a pair of electrodes arranged to face each other, switching means for alternately switching between charging and discharging for the pair of electrodes, and after the switching means switches between charging and discharging. Capacitance detection means for obtaining the delay time and estimating the capacitance between the electrodes from the delay time and the switching means, and the output of the capacitance detection means, and the presence of the detected dielectric substance from the magnitude of the capacitance. In a dielectric detecting device having a dielectric presence / absence determining means for determining whether or not there is a potential difference detecting means for detecting a potential difference between electrodes and a time point at which sufficient charging or discharging is performed after the switching means switches to charging or discharging. After the detection timing generation means for issuing the signal shown and the switching means switch to charging or discharging, sufficient charging or discharging is performed corresponding to the signal issued by the detection timing generation means. When the potential difference detected by the potential difference detection means deviates from the potential difference range between the electrodes estimated at the point, noise determination means determines that there is noise, and when the noise determination means determines that there is noise, the presence or absence of a dielectric And a canceling means for invalidating the judgment of the judging means.

[0005]

In the dielectric detecting device having the above-described structure, the switching means alternately repeats charging and discharging between at least one pair of electrodes to generate a pulse signal. Since the electrodes form a capacitor, the voltage generated between the electrodes has a waveform that is delayed with respect to the pulse signal and has a rising and a falling edge. The delay time due to the blunt rise and fall is proportional to the capacitance of the electrode.
Therefore, the capacitance detecting means can measure the capacitance between the electrodes. The capacitance of the electrode changes depending on whether or not there is a dielectric near the electrode. Therefore, the dielectric presence / absence determining means can determine the presence / absence of the dielectric from the capacitance between the electrodes.

The detection timing generation means emits a signal indicating the time when the capacitor is sufficiently charged or discharged after the switching means switches to discharging or charging. When the detection timing generation means emits a signal and the potential difference between the electrodes detected by the potential difference detection means is out of the estimated potential difference range, the noise determination means determines that there is noise.
The canceling means invalidates the judgment of the dielectric presence / absence judging means when there is noise. When the potential difference between the electrodes detected by the potential difference detection means is within the estimated potential difference range, the noise determination means determines that there is no noise, and the signal is used for the dielectric presence / absence determination.

[0007]

1 is a block diagram of the present invention, and FIG. 2 is a concrete circuit diagram of an embodiment of the present invention.

As shown in FIGS. 1 and 2, the capacitor Cx includes a vehicle body 2, a sensor electrode 4 provided on a seat 3, and a vehicle interior space 5 composed of the vehicle body 2 and the sensor electrode 4. The capacitor is formed via the resistor R1 and forms a charging circuit together with the resistor R1 depending on the presence or absence of personnel (dielectric material). In this embodiment, the detection circuit I shown in FIG.
C1 is composed of the switching means, the detection timing generation means, the potential difference detection means, the noise determination means, and the cancellation means shown in FIG. The determination circuit IC2 is composed of capacitance detection means and dielectric presence / absence determination means. Hereinafter, the charging circuit including the capacitor Cx and the detection circuit I
The respective configurations and operations of C1 and the determination circuit IC2 will be described.

The capacitor Cx is a resistor R having a predetermined resistance value.
1 to the output port SEO of the detection circuit IC1. The connection point (b) connected to the capacitor Cx is biased by the resistors R13 and R14. The connection point (b) between the capacitor Cx and the resistor R1 is connected to the inverting input terminal of the first comparator CMP1 via the resistor R11, to the inverting input terminal of the second comparator CMP2 via the resistor R12, and further to the third comparator CMP2. They are connected to the inverting input terminals of CMP3, respectively.

On the other hand, the constant voltage Vcc generated by the power supply circuit PC is divided by the resistors R2 and R3 to set the first threshold value VTH1, which is the first comparator C.
It is input to the non-inverting input terminal of MP1. Similarly, the constant voltage Vcc is divided by the resistors R4 and R5 to set the second threshold value VTH2, which is the second comparator C.
It is input to the non-inverting input terminal of MP2. Further, the constant voltage Vcc is divided by the resistors R8 and R9, the third threshold value VTH3 is set, and the third threshold value VTH3 is input to the non-inverting input terminal of the third comparator CMP3. Note that the first comparator CMP1 is for personnel detection, and the second comparator CM
P2 is for detecting dielectric breakdown and is the third comparator CMP3.
Is for noise detection. The second threshold value VTH2 is set to a higher level than the first threshold value VTH1 and the third threshold value VTH3 is set to a lower level than the first threshold value VTH1. The output terminal of the first comparator CMP1 is connected to the input port SEI of the detection circuit IC1, the output terminal of the second comparator CMP2 is connected to the input port SEH of the detection circuit IC1, and the third comparator CMP3. The output terminal of is connected to the input port SEL of the detection circuit IC1.

The operation of the circuit from the capacitor Cx to the detection circuit IC1 will be described with reference to the timing chart of FIG. In addition, (a) to (e) of the same figure show the pulse of the signal at each point a to e in the circuit. First, when the reference signal (a) of the predetermined frequency pulse signal is output from the output port SEO of the detection circuit IC1, the charging circuit composed of the resistor R1 and the capacitor Cx alternately switches between charging and discharging to generate the voltage signal (b). ) Is formed. The voltage signal (b) is the first threshold value VTH1 set by the resistors R2 and R3 in the first comparator CMP1.
And the signal (c) is output from the output terminal to the detection circuit IC1.
Input port SEI. In addition, the resistance R13,
R14 is used to bias the voltage value of the voltage signal at the low (L) level to about 0.6V. The phase difference To between the signal (c) and the reference signal (a) is proportional to the product of the capacitance of the capacitor Cx and the resistance value of the resistor R1, but since the resistor R1 is a predetermined fixed resistor, the phase difference To is It is proportional to the capacity of Cx. Then, the exclusive OR (EX-OR) of the reference signal (a) and the signal (c) is obtained in the detection circuit IC1. As a result, FIG.
As shown in, a signal (x) having a pulse width corresponding to the phase difference To is obtained, which is digitally processed and output to the determination circuit IC2.

On the other hand, the voltage signal (b) is also supplied to the second comparator CMP2 and compared with the second threshold value VTH2. When the insulation resistance between the sensor electrode 4 and the body 2 of the vehicle is Rx and this is sufficiently larger than the resistance value of the resistance R1, the peak value of the voltage signal (b) becomes the constant voltage Vcc. Therefore, the signal (d) of FIG. 3 is output from the output terminal to the input port SEH of the detection circuit IC1. However, as the resistance value Rx decreases, Vcc.Rx / (Rx + R
The value of the resistor R1 at the peak value obtained in 1) cannot be ignored, and the peak value will decrease. Therefore, when Rx <R1.R5 / R4, the signal (d) is maintained at the high (H) level as shown in FIG. As shown in FIG.
4 and the signal (d) of FIG. 4 is supplied to the input port SEH of the detection circuit IC1 and the signal (d) of FIG. 4 is supplied to the input port SEH, the signal is set in the detection circuit IC1. Dielectric breakdown is detected according to the check timing.

The voltage signal (b) is also supplied to the third comparator CMP3, and in addition to the second threshold value VTH2,
Only for a certain period of time is the third threshold value VTH3 compared.

Here, the threshold value VTH3 is the resistance R8, R.
No. 9 is used so that the voltage is about 0.3V. Also,
As shown in FIG. 3, the voltage signal (b) is Cx, so that the voltage is almost constant during the latter half of t1 for t2 hours.
The values of R1, R8, and R9 are set in advance, and output from the output terminal to the input port SEH of the detection circuit IC1.

Here, at the time of noise detection, the frequency dividing circuit F constituting detection timing generating means for synchronizing with the reference signal (a) and emitting a signal within the range of t2 time in FIG.
FIG. 5 shows a circuit diagram of C, logic circuits OR, AND, NOT, and a flip-flop SRFF which is a canceling means.
Further, FIG. 6 shows a timing chart in which the detection timing generating means composed of the frequency dividing circuit FC and the logic circuits OR, AND, and NOT issues the detection timing. The circuit of FIG. 5 is arranged in the detection circuit IC1. In FIG.
A pulse signal of a predetermined frequency of 8 MHz is input from the oscillating element OS1 to the frequency dividing circuit FC and outputs signals of 2 ¹³ frequency division and 2 ¹⁴ frequency division. This signal is the logic circuit OR, AN
D, NOT, the flip-flop SRFF, and the third comparator CMP3 are input. The reset signal R of the flip-flop SRFF is the decision circuit IC.
Timely input from 2. Here, when both the signals of the 2 ¹³ frequency division and the 2 ¹⁴ frequency division are at the low (L) level, the timing shown in FIGS. 3, 4 and 6 is synchronized with the reference signal (a) by the determination circuit IC2. For the time t2, the third comparator CMP3 causes the third threshold value VTH3 and the voltage signal (b).
I tried to compare.

When no noise is detected, the signal (e) of FIG. 3 is supplied from the output terminal to the input port SEL of the detection circuit IC1. However, there is noise,
The magnitude of noise at time t2 is the third threshold value VTH
When the number reaches 3, the signal (e) in FIG. 4 is supplied from the output terminal to the input port SEL of the detection circuit IC1, and noise is detected. When noise is detected, the judgment of the dielectric detection by the judgment circuit IC2 is canceled by the flip-flop SRFF.

Output ports OT1 and OT of the decision circuit IC2
2, OT3 and OT4 are connected to the input ports SL, SCL, END and INP of the detection circuit IC1, respectively. The output port INE of the detection circuit IC1 is connected to the input port IN2 of the determination circuit IC2 and also connected to the input port CE of the determination circuit IC2 via the resistors R6 and R7 connected in parallel. Furthermore, the detection circuit IC1
Of the determination circuit IC2 is the output port SOT of
It is connected to N3. The output port INE is the determination circuit I
An enable signal for instructing input permission to C2, that is, an input permission signal is output at a predetermined cycle, and output port SOT
Responds to the input permission signal to serially transfer the capacitance data in the detection circuit IC1 to the determination circuit IC2. A signal indicating the output data set in the detection circuit IC1 is input to the input port SL from the determination circuit IC2, and an output clock signal is input to the input port SCL.
Further, an input enable signal is input to the determination circuit I at the input port END.
When it is input to C2, the result is input, whereby it is checked whether the input / output of the input permission signal is executed within the predetermined time, and the personnel presence / absence signal of the determination result is input to the input port INP. To be done.

The input circuit SC is connected to the input port IN1 of the determination circuit IC2 and the output side connection point of the resistors R6 and R7. The power supply circuit PC is connected to the ports VCC of the detection circuit IC1 and the determination circuit IC2, respectively, the constant voltage Vcc is supplied to the detection circuit IC1 and the determination circuit IC2, and the ports RST and RS1 of the detection circuit IC1 and the determination circuit IC2 are supplied. To the detection circuit I
A reset signal is output to each of C1 and the determination circuit IC2. The power supply circuit PC is connected to the power supply B via the diode D1, and is also connected to the battery B via the diodes D2 and D3, the ignition switch IG, and the accessory switch ACC, respectively.
Ignition switch IG, accessory switch AC
C is connected to the input circuit SC via the diodes D4 and D5. Oscillators OS1 and OS2 are connected to the ports XI and XO of the detection circuit IC1 and the determination circuit IC2, respectively, and the detection circuit IC1 and the determination circuit IC2 are installed in the port GND, respectively. Further, a signal indicating the presence or absence of personnel is output to an external system such as a display device through the port OTP of the detection circuit IC1 and the output circuit OC.

7 to 9 are timing charts in this embodiment, and FIG. 7 shows the output to the external system ExECU stopped. FIG. 8 is a timing chart when the output stop state of the external system ExECU is changed to the output operation, and FIG. 9 is a timing chart when the output operation state of the external system ExECU is changed to the output stop. Figure 7
In the above, when the detection circuit IC1 is in the standby state, that is, the standby state, the input permission signal changes from the low (L) level to the high (H) level, and the determination circuit I is output from the output port INE.
When input to C2, the determination circuit IC2 enters the wakeup state, that is, the operable state. Then, the determination circuit IC2
After the clock is stabilized, the capacitance data corresponding to the output of the capacitor Cx is input from the detection circuit IC1, and the presence or absence of the personnel is determined based on this capacitance data. In FIG. 7, since the output to the external system ExECU is stopped, there is no output of the result of determination of the presence or absence of personnel, and the determination circuit IC2 returns to the standby state.

When there is an input from the output port INE when the output stop state to the external system ExECU shown in FIG. 8 shifts to the output operation, the determination circuit IC2 is in the wake-up state as described above. After the clock stabilizes after some delay time, when it is detected that the ignition switch IG or the accessory switch ACC is turned on based on the input signal to the input port IN1, the output for displaying the result of the presence or absence of the personnel is displayed. The operation is started. In wake-up state, output port IN
The signal of the input port IN1 is constantly monitored according to the output of E, and when it is at a high (H) level, the input port IN3
Even after the serial input is made to the person and the presence / absence determination is performed, the result of the presence / absence determination is continuously output.

As shown in FIG. 9, when the input signal from the output port INE becomes a high (H) level when the result of the presence / absence determination is in the output state, according to the serial input of the capacitance data to the input port IN3. The presence or absence of personnel is determined. Then, when both the accessory switch ACC and the ignition switch IG are turned off, the input signal to the input port IN1 changes from the high (H) level to the low (L) level, so that the output of the result of the presence / absence determination is stopped. ,
The standby state is entered, and thereafter the same operation as in FIG. 7 is performed.

Next, the operation of the decision circuit IC2 will be described with reference to the flowchart of FIG.

In the figure, the input port CE is high (H).
When the level signal is input, the judgment circuit IC2 starts to operate, and it is judged in step 101 whether or not it is a cold start. When the determination circuit IC2 is in a cold start state before operation, initialization is performed in step 102, various clocks are cleared, and various data are set to initial values. Then go to step 103
A signal from the input circuit SC is input to the input port IN1, and an input permission signal from the port INE of the detection circuit IC1 is input to the input port IN2. Then, in step 104, the output port OT for outputting the personnel presence / absence signal.
Data is output from 4 and supplied to the input port INP of the detection circuit IC1. Then, in step 105, a watchdog is performed to check the system for abnormality, and in step 106, the state of the random access memory is checked by the ram check, and then in step 107, the state of the input signal to the input port IN2. Is determined. If the input signal is at the high (H) level, the capacitance data is serially input from the output port SOT of the detection circuit IC1 to the input port IN3 in step 108, the presence / absence of personnel is determined in step 109, and the process proceeds to step 110. . On the other hand, when it is determined in step 107 that the input signal to the input port IN2 is at the low (L) level, the process directly proceeds to step 110.

In step 110, the input port I
The state of the input signal to N1 is determined, and if it is at the high (H) level, the output data of the output port OT4 is set and the process returns to step 103. On the other hand, when it is determined that the input signal to the input port IN1 is at the low (L) level, the output data of the output port OT4 is reset in step 112, and then the standby state is set in step 113.

Next, the process of determining the presence / absence of personnel will be described with reference to FIG. 11 regarding the processing of presence / absence determination of personnel performed in step 109. First, in step 201, the flag F
It is determined whether I is set. The flag defines the reset state as (0) and the set state as (1). The flag FI is set (1) when the capacitance data is transferred from the detection circuit IC1 to the determination circuit IC2, and the state of the flag FI is determined every 0.5 seconds. If the flag FI is set, step 202
At, it is determined whether or not the capacity data flag Ferr is set (1). If it is determined that Ferr is reset (0), the process proceeds from step 203 to 205, and the previous value Da of the capacity data stored in the old capacity data holding register and the current value Da stored in the new capacity data holding register. It is determined whether or not the difference from the value Db of is greater than or equal to a predetermined value. That is, in step 203, the difference between the previous value Da and the current value Db is calculated and stored in the capacity change amount holding register as the change amount Dc. In step 204, the previous value Da is stored in the old capacity data holding register as the current value Db.
Is stored and the data is updated, the absolute value of the variation D is compared with a predetermined value X in step 205. Change D
If the absolute value of c is greater than or equal to the predetermined value X, step 2
In step 06, it is determined whether or not the flag FJ indicating the presence / absence of personnel is set. When the flag FJ is set (1), it indicates "there is a manpower", and when it is not set (0), it indicates "there is no manpower". When it is determined in step 206 that the flag FJ is not set,
In step 207, it is determined whether the flag FT1 is set, and if it is set, step 208
Then, the flag FJ is set. Here, the flag FT
1 is set (1) when the timer TM1 that operates in response to the change from "no personnel" to "with personnel" overflows. Similarly, the flag FT2 is
It is set (0) when the timer TM2 that operates in response to the change from "with personnel" to "without personnel" overflows. In step 207, the flag FT
When 1 is set, that is, when a predetermined time or more elapses after changing from "no staff" to "possible", the process proceeds to step 208 and the flag FJ is set to indicate "possible". . On the other hand, when it is determined in step 205 that the absolute value of the fluctuation amount Dc is less than the predetermined value X, the process proceeds to step 209, it is determined whether the flag FJ is set, and if it is set, the step is further stepped. At 210, it is determined whether the flag FT2 is set. When the flag FT2 is set, that is, when a predetermined time or more has elapsed after the change from "personnel present" to "no person", the routine proceeds to step 211, where the flag FJ is reset (0) and "no person" is set. Will be shown. Then, after it is determined to be NO in step 206 or step 209, the flag FJ is set in step 208, or the flag FJ is reset in step 211, the process proceeds from step 212 to 215, and the timer TM1, TM2 is reset, the flags FT1 and FT2 are reset, and the process returns to the main routine. As described above, "personnel available"
From "No staff" or from "No staff" to "Has staff", the state is held for a predetermined time set by the timer TM1 or TM2.

Here, steps 201 and 202 in FIG.
The determination of the defective flag of the capacity data, which is performed during the period, will be described in detail with reference to the flowchart of FIG.

First, a method of measuring capacitance data in the detection circuit IC1 will be described. From the output port SEO of the detection circuit IC1, 2 MHz at 8 MHz of the oscillation circuit OS1
^The signal divided by ¹⁴ is output as the reference signal (a) to the capacitor Cx. Then, when the signal (c) output from the first comparator CMP1 is input to the input port SEI according to the change in the capacitance of the capacitor Cx, the exclusive OR with the reference signal (a) is obtained. , Signal (x) is obtained. While this signal (x) is at a low (L) level, it is logically ORed with a predetermined clock signal and converted into capacitance data, which is counted 16 times and then the average value is obtained. That is, the 1/16 average value of the capacitance data counted here is stored in the determination circuit IC2 at a predetermined timing from the output port SOT as capacitance data.
Bits are transferred serially.

Considering the case where dielectric breakdown or noise occurs, the capacitance data is not always accurate in the above method. Therefore, in the present embodiment, the second
Comparator CMP2, third comparator CMP3
Etc. were used to detect dielectric breakdown and noise as follows. First, when capacitance data is input from the capacitor Cx, initialization is performed in step 301, and the counters C1 and C2 and the memory D are set to zero. Here, the counter C1 is counted when no dielectric breakdown or noise is detected in one pulse, and the counter C2 is always counted once for one pulse. In step 302, the capacity data Do for one pulse is input. In steps 303 and 304, the presence or absence of dielectric breakdown and noise is detected. If no dielectric breakdown or noise is detected in the pulse, the counter C1 is counted in step 305. In step 306, the capacitance data Do for one pulse is added to the capacitance data D. Then, in step 307, the counter C2 is counted. In step 308, it is determined whether the counter C1 is 16 or more. If the counter C1 is less than 16, it is determined in step 314 whether the counter C2 is 32 or more. If it is determined that the counter C2 is lower than 32, the process returns to step 302, and the above operation is repeated until it is determined in step 308 that the counter C1 is 16 or more. In step 308, counter C
If it is determined that 1 is 16 or more, step 309,
At 310 and 311, pulses are input until the counter C2 counts 32 or more. When it is determined in step 311 that the counter C2 counts 32 or more, in step 312, the average value D / 16 of the capacitance data for one pulse is taken, and in step 313, the capacitance data defect flag Ferr = 0 is input to the determination circuit IC2 from the output port SOT at a predetermined timing together with the capacitance data, and the process proceeds to step 203 in FIG.

When dielectric breakdown or noise is detected in 16 or more of the 32 pulses, the counter C2 is determined to be 32 or more in step 314, and step 31 is performed.
At 5, the capacity data defect flag Ferr = 1 is input to the determination circuit IC2 from the output port SOT at a predetermined timing together with the capacity data, and the process returns to the main routine again.

In addition to the dielectric detecting device shown in this embodiment, for example, by providing a low-pass filter in the middle of the capacitance detecting means and the electrodes, it is possible to remove high frequency noise in addition to low frequency noise. The reliability of the dielectric detection device can be further improved.

The dielectric detection device can be used for various controls such as air bag control, audio directivity control, seat position control in a vehicle, and is not limited to the vehicle, and can be used to count the number of people entering the theater or the like. It can be used for aircraft and the like.

[0032]

According to the present invention, noise judgment is performed only when the capacitor is sufficiently charged or discharged. Therefore, since the noise determination is not performed when the waveform has a blunt rising edge and a falling edge, an appropriate noise determination can be performed.
Further, it is effective in preventing malfunction due to noise having a frequency lower than that of the pulse signal, and the reliability of the dielectric detection device is improved.

Further, as compared with the conventional dielectric detecting device using the noise filter, the part of the device for making noise judgment is downsized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a dielectric detection device according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a dielectric detection device according to the present invention.

FIG. 3 is a timing chart of signals of respective parts of the detection circuit of the embodiment of the dielectric detection device according to the present invention.

FIG. 4 is a timing chart of signals of various parts of the detection circuit of the embodiment of the dielectric detection device according to the present invention.

FIG. 5 is a circuit diagram in which timing is output in synchronization with a reference signal according to the present embodiment and only for a fixed time.

6 is a timing chart of signals emitted by the circuit of FIG.

FIG. 7 is a timing chart for explaining the operation of the determination circuit of the embodiment of the dielectric detection device according to the present invention.

FIG. 8 is a timing chart for explaining the operation of the determination circuit of the dielectric detection device according to the embodiment of the present invention.

FIG. 9 is a timing chart for explaining the operation of the determination circuit of the dielectric detection device according to the embodiment of the present invention.

FIG. 10 is a flowchart showing the processing of a main routine in the determination circuit of one embodiment of the dielectric detection device of the present invention.

FIG. 11 is a flowchart showing a process for determining the presence or absence of personnel in a determination circuit of an embodiment of the dielectric detection device according to the present invention.

FIG. 12 is a flowchart showing a process of determining a defective flag of capacitance data in an embodiment of the dielectric detection device of the present invention.

[Explanation of symbols]

1 Person (Dielectric) 2 Vehicle Body 3 Seat 4 Sensor Electrode 5 Vehicle Space ExECU External System Cx Capacitor PC Power Supply Circuit SC Input Circuit OC Output Circuit OS1 Oscillation Circuit 1 OS2 Oscillation Circuit 2 D1, D2, D3, D4, D5 Diode IG Ignition switch ACC Accessory switch B Battery ECU Electronic control unit FC Dividing circuit OR OR OR AND AND AND NOT NOT IC1 detection circuit IC2 judgment circuit CMP1 1st comparator CMP2 2nd
Comparator CMP3 Third Comparator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Eiji Okada Eiji Okada 2-1-1 Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. (72) Inventor Koichi Sugiyama 1-cho, Toyota-cho, Aichi prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. At least a pair of electrodes arranged to face each other, switching means for alternately switching between charging and discharging with respect to the pair of electrodes, and a delay time after the switching means switches to charging or discharging. And a capacitance detecting means for estimating the capacitance between the electrodes from the delay time and the switching means, and an output of the capacitance detecting means, and based on the magnitude of the capacitance, the dielectric to be detected. In the dielectric detection device having a dielectric presence / absence determining means for determining the presence of a potential difference detecting means for detecting a potential difference between the electrodes, and a sufficient charge or discharge is performed after the switching means switches to charging or discharging. The detection timing generation means for outputting a signal indicating the time point of the breakage, and the switching timing means for charging or discharging, and corresponding to the signal issued by the detection timing generation means for sufficiently charging. Alternatively, when the potential difference detected by the potential difference detection means deviates from the potential difference range between the electrodes estimated at the time of discharging, noise determination means for determining that there is noise, and the noise determination means detects noise. A dielectric detection device comprising: a cancellation unit that invalidates the determination of the dielectric presence determination unit when it is determined that there is.