JPS61184449A - Waterdrop detection sensor - Google Patents

Abstract

PURPOSE:To perform control matching with the actual visual sensation reaction of a person, by performing the driving of a control object at a speed faster than that at a bright time in the daytime when the outside is dark on the night or at the time of a clouded sky and an illumination apparatus was lighted. CONSTITUTION:The output of the titled waterdrop detection sensor is used in automatically driving a control object such as the wiper of a car. When a waterdrop is adhered, the electrostatic capacity of a detection electrode part 1 changes and the oscillation amplitude of an oscillation circuit 2 also changes. A discriminator circuit 14 outputs a drive pulse signal to the control object when the data from the oscillation circuit 2 on the basis of the adhesion of a waterdrop to a detection electrode part 1 generated predetermined numbers of 3 times or more within a predetermined time is a reference value or more. When the outside becomes dark and an illumination apparatus was lighted, a lighting detection circuit 24 detects this state and a reference value variable circuit 25 reduces the reference value of the discriminator circuit 14 on the basis of the detection signal of the lighting detection circuit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a water droplet detection sensor used to detect water droplets and automatically drive a controlled object such as the wiper of a vehicle, ship, or airplane. In particular, the present invention relates to a technology that copes with the fact that when the object to be detected is small water droplets, visibility is worse when the outside world is darker than during the day, such as at night or on cloudy days.

(Summary of the Invention) The present invention drives a controlled object based on multiple detections of water droplets when the water droplets are small, and also drives a controlled object when the outside world is dark such as at night or on a cloudy day when a lighting device is turned on. By performing the drive earlier than in bright daytime, control is performed that matches the practical visual reactions of humans.

(Prior art and its problems) Conventionally, a water drop detection sensor that detects rain drops and automatically drives the wiper of a vehicle has been used, for example, in "Nissan Giho" [December 1982 issue (No. 19)] Page 97 - 1st
02 page] is known.

Its structure is as follows.

That is, falling raindrops cause the diaphragm to vibrate, the piezoelectric element converts the vibration into voltage, and the voltage charges a charging circuit including a capacitor. When the charging voltage reaches the reference value, a wiper drive signal is output to drive the wiper. On the other hand, this wiper drive signal is input to the reset terminal of the charging circuit to instantly discharge the capacitor and stop the wiper drive once.

According to this conventional example, when there is a lot of rain and large raindrops collide with the diaphragm, the charging speed of the capacitor is fast (and the wiper is immediately activated). , the charging speed of the capacitor is slow, and the wiper is activated only when a plurality of small raindrops collide within a predetermined time and the charging voltage reaches a reference value.

That is, the drive timing of the wiper is automatically advanced or delayed in accordance with changes in the size of raindrops.

However, the conventional example having such a configuration has the following problems.

In other words, if small raindrops adhere to the cockpit window glass when the outside world is dark, such as at night or on a cloudy day, and a lighting device such as a flashlight is turned on, the amount of water droplets adhering to the cockpit window will be lower than when it is bright during the day. The fact is that visibility becomes worse.

However, in the conventional example, control that distinguishes between nighttime and daytime is not performed.

Therefore, the number of times raindrops are detected to drive the wipers etc. based on the detection of small raindrops is always the same, and there is a problem that the wiper drive timing is too slow for human vision at night, resulting in poor visibility through the window glass.

(Purpose of the Invention) The present invention was made in view of the above circumstances, and the difference between daytime and nighttime/cloudy weather is that the presence or absence of lighting and the adhesion of water droplets under illumination are visually impaired. The purpose is to perform appropriate control in response to the reduction in the amount of water.

(Configuration and Effects of the Invention) In order to achieve the above object, the present invention has the following configuration.

That is, the water droplet detection sensor of the present invention includes a detection electrode section that detects adhesion of water droplets based on a change in capacitance, and an oscillation circuit that is connected to the detection electrode section and changes the oscillation amplitude based on the change in capacitance. , a discrimination circuit that outputs a drive pulse signal to a controlled object when data from the oscillation circuit based on water droplets adhering to the sensing electrode part a predetermined number of times, three or more times within a predetermined time, is equal to or higher than a reference value; This device includes a lighting detection circuit and a reference value variable circuit that reduces the reference value based on a detection signal from the lighting detection circuit.

The effects of this configuration are as follows.

(i) When water droplets adhere to the sensing electrode directly or indirectly through glass, etc. (hereinafter simply referred to as adhesion, whether directly or indirectly), the capacitance of the sensing electrode changes, resulting in , the oscillation amplitude of the oscillation circuit is varied.

When water droplets are attached a predetermined number of times and as a result, data from the oscillation circuit exceeds a reference value, the discrimination circuit outputs a drive pulse signal to drive the controlled object.

(ii) When the lighting device is not lit, the lighting detection circuit of the lighting device does not operate, and therefore the reference value variable circuit also does not operate.

Therefore, the reference value for the data from the oscillation circuit for the discrimination circuit to output the drive pulse signal is the initial reference value, and only when water droplets are attached to the detection electrode part a predetermined number of times within a predetermined time. The controlled object is driven.

(iii) When the lighting device is turned on, the lighting detection circuit operates, the reference value variable circuit operates, and the reference value is decreased to be equal to or less than the initial reference value.

Therefore, the drive pulse signal is outputted from the discrimination circuit to the controlled object in a state where the number of times of water droplet adhesion is less than the predetermined number of times.

As described above, according to the present invention, the following effects are achieved.

When the lighting device is not turned on because it is bright, the reference value in the discrimination circuit is the initial reference value, so the control target is driven only when water droplets have adhered a predetermined number of times.
In addition, when the lighting device is turned on because it is dark, the reference value of the discriminator circuit is reduced to below the initial reference value, and the number of times water droplets are attached is less than the predetermined number, in other words, at an earlier point in time. Drive the controlled object.

Therefore, appropriate control can be performed that takes into account ergonomic factors that deal with the fact that the adhesion of water droplets under illumination degrades visual acuity.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

First Embodiment FIG. 1 is a circuit diagram of a water droplet detection sensor according to a first embodiment of the present invention.

Circuit explanation> The water droplet adhesion detection electrode part l is a capacitor cl.

It is composed of a C2 series circuit. This series circuit is
Although not shown, it actually consists of an elongated elliptical sensing electrode in the center, an annular sub-electrode surrounding it, and an annular grounding electrode surrounding this sub-electrode. The capacitor C1 and the sub-electrode and the ground electrode constitute a capacitor C2, respectively.

In the case of a vehicle, the sensing electrode section 1 is usually attached to the inner surface of the windshield.

The oscillation circuit 2 includes transistors T r + and T rz connected in series to form an amplifier circuit, and resistors R1-Rh.
etc., capacitor C1, and field effect transistor (F
ET) 3.

The capacitors C1 and C2 of the sensing electrode section 1 are connected in parallel to the resistors R+ and Rz, respectively, and the transistors Tr, Tr
The collector of z is connected to a DC power supply Vcc. A series circuit of a capacitor C1 and a resistor R1 is connected between the emitters of the transistors Tr, Tr, and Tr2, and the emitter of the transistor Tr is grounded via a resistor R3. The emitter of the transistor Tr2 is connected via the resistor R1 to the base of the transistor Tr and the connection point between the capacitors C+ and Cz of the sensing electrode section 1, and the emitter of the transistor Tr2 is
The base of rl is grounded via resistor R2.

A connection point between the capacitor C3 and the resistor R4 is connected to the drain of the FET3 via the resistor Rs, and the source of the FET3 is grounded via the resistor R6.

The oscillation frequency of the oscillation circuit 2 is set to IMHz.

The detection circuit 4 includes a transistor T'r3 and a capacitor 0.
4~C5 and resistance R? , R11, etc., and an inverting amplifier circuit 5.

The capacitor C4 is connected to the emitter of the transistor Tri, which is the output terminal of the oscillation circuit 2, is grounded via the resistor R1, and is also connected to the base of the transistor Tr3. The collector of the transistor Tr3 is connected to the DC power supply Vcc, and the emitter is grounded.

Capacitor CS.

C6 and resistor R6 constitute a smoothing circuit, and this smoothing circuit is
The input terminal is connected to the collector of the transistor Tr3,
The output terminal is connected to the positive input terminal of the inverting amplifier circuit 5. The output terminal of the inverting amplifier circuit 5 is connected to the negative input terminal.

The integrating circuit 6 includes an operational amplifier 7 for integration, a capacitor C7, and resistors R7 to R1.

The output terminal of the inverting amplifier circuit 5 of the detection circuit 4 is connected to the negative input terminal of the operational amplifier 7 via a resistor R7, and is also connected to the output terminal of the operational amplifier 7 via a capacitor C1. Resistance R1°.

The series circuit of R1+ is connected to the DC power supply Vcc, and the resistor R
The connection point of IO+R11 is connected to the positive input terminal of operational amplifier 7 to create its threshold.

The output terminal of the operational amplifier 7 is connected to the gate of the FET 3 of the oscillation circuit 2.

That is, the output of the detection circuit 4 is fed back to the oscillation circuit 2 via the integration circuit 6.

The amplifier circuit 8 includes an inverting amplifier circuit 9, a capacitor C6, and a resistor RI2.

The capacitor C8 is connected to the output terminal of the inverting amplifier circuit 5 of the detection circuit 4, and is connected to the negative input terminal of the inverting amplifier circuit 9 via the resistor RI2. The positive input terminal of the inverting amplifier circuit 9 is connected to the DC power supply Vcc via a resistor R9° to create its threshold.

The first discrimination circuit 10 has a comparator 11 and a one-shot circuit 12. Resistor Rrsr R141RI
The series circuit of S is connected to a DC power supply Vcc to form a voltage dividing circuit.

The negative input terminal of the comparator 11 is connected to the output terminal of the inverting amplifier circuit 9, and the positive input terminal is connected to the resistor R1.

It is connected to the connection point of RI4 to create its threshold, that is, the first reference value Vtb1. The output terminal of the comparator 11 is connected to a one-shot circuit 12, and the output terminal of the one-shot circuit 12 is connected to the input terminal of the NAND gate 3.

The second discrimination circuit 14 generates a drive pulse to the controlled object when the data from the oscillation circuit based on water droplets adhering to the sensing electrode section a predetermined number of times, three or more times within a predetermined time, is equal to or greater than the reference i value, as stated in the constitution of the invention. This category corresponds to "discrimination circuit that outputs a signal."

The second discrimination circuit 14 includes a comparator 15, a programmable counter 16, and a one-shot circuit 17.

The negative input terminal of the comparator 5 is connected to the output terminal of the inverting amplifier circuit 9, and the positive input terminal is connected to the connection point of the resistors R11RI5 to set its threshold, that is, the second reference value vt.
h, is being created. The output terminal of comparator 15 is connected to the input terminal of programmable counter 16.

18 is a hendride relay in a lighting device (not shown), 19 is a tail ride relay, and 20 is a lighting switch. The lighting switch 20 is associated with an off contact 21, a taillight contact 22, and a headlight contact 23, and is connected to the taillight contact 22 when it is connected to the headlight contact 23.

These headlight relays 18 and headlight contacts 2
3 and the lighting switch 20 constitute a lighting detection circuit 24 of the lighting device according to the configuration of the invention.

The reference value variable circuit 25, which decreases the reference value when the second discrimination circuit 14 outputs the drive pulse signal to the wiper drive circuit, is constituted by a data selector.

This data selector 25 has select terminals s, sz, s, which select data corresponding to 1, 2, and 3 water droplets.
and are each connected to a DC power supply Vcc. In addition, the select terminals S'+ and St are connected to the headlight contact 2 via the selector switch Sw and the diodes D, , D.
Connected to 3.

26 is a manually operated select switch, select terminal S
It can be selectively connected to contacts T1°Tz and Ti connected to +, Sz, and Sz.

Three data output terminals of the data selector 25 are connected to the programmable counter 16, and an output terminal of the programmable counter 16 is connected to an input terminal of the one-shot circuit 17 via the data selector 25.

The output terminal of the one-shot circuit 17 is the NAND gate 13
is connected to the input terminal of

The output terminal of the NAND gate 13 is connected to the base of the switching transistor Tr4 of the wiper drive circuit, and is also connected to the counter reset circuit 27.

The counter reset circuit 27 includes a one-shot circuit 28 connected to the DC power supply Vcc. The output terminal of this one-shot circuit 28 is connected to the reset terminal of the programmable counter 16.

A clear circuit 29 clears and initializes the one-shot circuit 12 of the first discrimination circuit 10, the programmable counter 16 and the one-shot circuit 17 in the second discrimination circuit 14 when the water droplet detection sensor is powered on.

This clear circuit 29 is connected to the DC power supply V via the resistor R1&.
Transistor Trs connected to cc and capacitor C
, and a Zener diode ZD.

Note that 30 is a regulator of the DC power supply Vc.

Explanation of Operation> Next, the operation of the first embodiment will be explained based on the time chart of FIG. 2.

(A) to (1) in FIG. 2 show the voltages at points a to i in the circuit of FIG. 1, respectively.

■ When the power is turned on, the resistor RIM of the clear circuit 29 is connected to the DC power supply VCC, and the one-shot circuit 12.1
7 and the programmable counter 16 are cleared to initialize them. That is, the voltage e of the ζ output of the one-shot circuit 12 is at the "H" level, the output voltage f of the programmable counter 16 is at the "L" level, and the voltage g of the ζ output of the one-shot circuit 17 is at the "H" level.

When capacitor C9 is charged and the charging voltage makes Zener diode ZD conductive, transistor Trs is turned on and there is no clear output.

- When the power is turned on, the oscillation circuit 2 operates and starts oscillation. The voltage a at the output terminal of the detection circuit 4 maintains a constant oscillation amplitude in the absence of water droplets (period up to time 1).

Further, when the power is turned on, a voltage is generated across the resistor RI+ of the integrating circuit 6, which operates the operational amplifier 7 and outputs it to the gate of the FET 3. The integrated output of the operational amplifier 7 is the result of integrating the output of the oscillation circuit 2 over a long period of time, that is, up to time t, and is proportional to the average oscillation amplitude of the oscillation circuit 2 during normal operation. . This integrated output is applied to the gate of the FET 3, making the on-resistance of the FET 3 proportional to the integrated output and, in turn, to the oscillation amplitude of the oscillation circuit 2.

As a result, capacitor C3 and resistor R in oscillation circuit 2
6, R, and the time constant determined by the on-resistance of the FET 3 corresponds to the oscillation amplitude of the oscillation circuit 2.

Therefore, even if the oscillation amplitude changes from large to small due to the initial capacitance of the capacitors C, Ct differing depending on the conditions and temperature conditions, the mounting of the sensing electrode part 1 is actually as described above. Since the amplification gain of the transistor Tr, that is, the oscillation gain of the oscillation circuit 2 changes from small to large due to a change in the time constant of the oscillation circuit 2, changes in the oscillation amplitude are absorbed and the oscillation amplitude is always constant as long as there are no water droplets attached. maintain.

■When large water droplets adhere to the detection electrode part 1■ Time 1. When one large water droplet adheres to the detection electrode section 1, the capacitances of the capacitors C+ and Ct change, and as a result, the oscillation amplitude of the oscillation circuit 2 is varied.

The high frequency output from the oscillation circuit 2 with variable oscillation amplitude is detected, amplified and smoothed by the detection circuit 4, and the output voltage a of the inverting amplifier circuit 5 has a sinusoidal waveform as shown in FIG.

■ The output voltage a from the inverting amplifier circuit 5 is input to the negative input terminal of the operational amplifier 7 of the integrating circuit 6, but since the time constant is large, the output of the operational amplifier 7 does not change much, and the oscillation circuit 2 continues to oscillate. Ru.

Further, the output voltage a is input to the amplifier circuit 8, inverted and amplified by the inverting amplifier circuit 9, and outputs an output voltage having a sinusoidal waveform as shown in FIG.

■ This output voltage is input to the negative input terminal of the comparator 11 of the first discrimination circuit 10;
Since it is based on large water droplets, the first reference value vth,
be higher than Therefore, the comparator 11 is
As shown in the figure, the level is inverted from "H" to "L".

This "L" level pulse signal is transmitted to the one-shot circuit 12.
and the ζ output voltage is “L” as shown in figure (E).
``This becomes a level one-shot pulse signal e.

■ L” level one-shot pulse (+ is sign e is NA
The signal is input to the ND gate 13. At this time, the voltage g of the ζ output of the one-shot circuit I7 is “H” as shown in the figure (G).
Since it is at "H" level, the NAND gate 413 becomes conductive, and the output voltage becomes "H" level as shown in the figure (H), and the transistor Tr.

Turn on to operate the wiper drive circuit.

That is, in the case of large water droplets, the wiper is immediately driven by one water droplet.

■ The output voltage shown in FIG.
h2, and the output voltage d of the comparator 15 is inverted from the "H" level to the "L" level as shown in FIG.

Then, the programmable counter 16 counts +1, but the output voltage of the NAND gate 13 shown in Figure (H) is also input to the counter reset circuit 27, and as shown in Figure (I).
The programmable counter 16 is reset because the reset pulse signal i is output to the positive terminal of the programmable counter 16 at the rise of the output voltage as shown in FIG.

Therefore, the output voltage f of the programmable counter 16 is maintained at the "L" level as shown in FIG.

(2) Furthermore, since the reset pulse signal i is also output to the one-shot circuit 17 of the second discrimination circuit 14, the output voltage g of the one-shot circuit 17 maintains the "H level" as shown in FIG.

Since the reset pulse signal i is also output to the one-shot circuit 12 of the first discrimination circuit 10, the one-shot circuit 12
The voltage e of the ζ output returns to the "H" level as shown in Figure (E). As a result, the output voltage of the NAND gate 13 is inverted to "L" level, the transistor T r a is turned off, and the wiper drive is stopped. That is, the wiper is driven only once.

■ When small water droplets adhere to the detection electrode part 1 (1) When the wiper is driven by three small water droplets ■ Normally, the select switch 26 is connected to the contact T3 for detecting three small water droplets. .

(2) At time t2, when one small water droplet adheres to the detection electrode portion l, the capacitance of the capacitors C, , C changes, and the oscillation amplitude of the oscillation circuit 2 is varied.

However, the amount of variation in the oscillation amplitude is small, and the amount of change in the output voltage a of the inverting amplifier circuit 5 is also small. Therefore, the amount of change in the output voltage S of the inverting amplifier circuit 9 of the amplifier circuit 8 is also small.

■ This output voltage is input to the negative input terminal of the comparator 11 of the first discrimination circuit lO, but this output voltage is
Since it is based on small water droplets, the first reference value Vth+
lower than. Therefore, the output voltage C of the comparator 11 is not inverted, and the voltage e of the ζ output of the one-shot circuit 12 is also not inverted.

@ The output voltage of the inverting amplifier circuit 9 is input to the negative input terminal of the comparator 15 of the second discrimination circuit 14, and this output voltage is higher than the second reference value vth.
The output voltage d of No. 5 is inverted from the "H" level to the "L" level as shown in Figure CD).

Then, the programmable counter 16 counts +1, but since the predetermined number of times (3 times) has not been reached, the output voltage f of the programmable counter 16 is not inverted, and the output voltage g of the one-shot circuit 17 is not inverted, so the NAN
The output voltage of the D gate 13 also maintains the L'' level. That is, the wiper drive circuit does not operate.

■ If a second small water droplet adheres to the detection electrode section 1 at time t, the output voltage f of the programmable counter 16 will be at the "H" level L-fpl lJl as shown in Figure (F).
, l 1-Il/, 1/-, , -LIflMj ri/I"l r+ Since the voltage g of the peak ++ maintains the "H" level, the output voltage of the NAND gate 13 is not inverted. That is, the wiper drive The circuit doesn't work.

[Phase] When the third small water droplet adheres to the detection electrode section 1 a predetermined number of times at time t, the output voltage f of the programmable counter 16 is reversed to "L level" as shown in Figure (F). , the voltage g of the ζ output of the one-shot circuit 17
is inverted to "L" level. As a result, the output voltage of the NAND gate 13 becomes "H" level, and the wiper drive circuit operates.

That is, the wiper is driven only when the third small water droplet is attached.

6 The output voltage from the NAND gate 13 is also input to the counter reset circuit 27, and the reset pulse signal i is sent to the programmable counter 1 at the rise of the output voltage.
6, the programmable counter 16 is reset and waits for the next water droplet to arrive. Also,
Since the one-shot circuit 17 is also reset, the wiper drive circuit stops. That is, in this case as well, the wiper is driven only once.

As described above, when the water droplets adhering to the sensing electrode section 1 are large, the wiper is immediately driven, and the sensing electrode section l
If the water droplets adhering to the wiper are small, the wiper is driven only when the number of water droplets adhering reaches a predetermined number of times (three times).

That is, the drive timing of the wiper is automatically advanced or delayed in accordance with changes in the size of water droplets.

(2) When driving the wiper with two small water droplets [phase] When visibility is poor at night or on cloudy days, switch the selector switch Sw so that the select terminal S2 side is turned on. The select switch 26 is kept connected to the contact T for detecting three small water droplets, as in the case (1) above.

When the lighting switch 20 is connected to the headlight contact 23 and the taillight contact 22, the select terminal S2 of the data selector 25 is selected, and the programmable counter 1
6 is set to be output at a count of "2".

The detection of O large grains is the same as in (11) above.

The operations in (11) [phase] to @ are the same for small particle detection.

[Phase] When the second small water droplet adheres to the detection electrode section 1 a predetermined number of times, the output voltage f of the programmable counter 16 is inverted to "L" level, and the NAND gate 13
The output voltage becomes @H'' level and the wiper drive circuit operates.

That is, the wiper is driven by the adhesion of the second small water droplet.

[Phase] The output voltage from the NAND gate 13 is input to the counter reset circuit 27, the programmable counter 16 is reset, and waits for the next water droplet to adhere. Furthermore, since the one-shot circuit 17 is also reset, the wiper drive circuit stops. The wiper can only be driven once.

(3) When the wiper is driven by one small water droplet [phase] If visibility is particularly poor at night or on cloudy days, switch the switch switch Sw.
is switched so that the select terminal 81 side is turned on. The select switch 26 is kept connected to the contact T for detecting three small water droplets, as in the case (1) above.

When the lighting switch 20 is connected to the headlight contact 23 and the taillight contact 22, the select terminal S of the data selector 25 is selected, and the programmable counter 1
6 is set to be output at a count of "1".

■ Large grain detection is the same as (1) above.

The operation for small particle detection is as follows.

◎ When the first small water droplet adheres to the detection electrode section 1 a predetermined number of times, the output voltage r of the programmable counter 16 is reversed to "L" level, and the output voltage r of the NAND gate 13 is reversed to "H" level. As a result, the wiper drive circuit operates.

That is, as in the case of large water droplet adhesion, the wiper is immediately driven by the first small water droplet adhesion.

@ The output voltage from the NAND gate 13 is the power h1/Ill island-1.

The pull counter 16 is reset and waits for the next water droplet to arrive. Also, since the one-shot circuit 17 is also reset,
The wiper drive circuit stops. The wiper can only be driven once.

■When selecting independently of the lighting of the lighting switch 20■ When visibility is poor at night or on cloudy days, connect the select switch 26 to the contact T2 for detecting two small water droplets, and the data selector 25 The select terminal S2 is selected, and the programmable counter 16 is set to output a count of "2".

The operation is the same as (2) in (2) above.

[Phase] When visibility is particularly poor at night or on cloudy days, set the select switch 26 to contact T for detecting one small water droplet.
, select terminal S of the data selector 25
1 is selected, and the programmable counter 16 is set to output a count of "1".

The operation is the same as (3) and 8 above.

According to this embodiment, in addition to the effects of the invention, there are the following advantages.

That is, the integrating circuit 6 integrates and outputs the output of the oscillating circuit 2 over a long period of time, and the oscillating circuit 2
The oscillation gain is held constant based on the integrated output over a long period of time.

Therefore, if there is no water droplet adhesion, such as during a sunny day, the integration circuit 6 will definitely provide an integrated output over a long period of time, and the oscillation gain of the oscillation circuit 2 will be automatically maintained constant.

That is, the mounting position and angle of the detection electrode section 1 need not be affected by the mounting conditions, and the sensitivity of the detection electrode section 1 is always maintained constant.

Furthermore, for the same reason, the sensitivity of the sensing electrode section is always maintained constant regardless of temperature conditions, even without providing a temperature compensation circuit or the like.

<Second Embodiment> FIG. 3 is a circuit diagram of a water droplet detection sensor according to a second embodiment of the present invention.

<Circuit description> The configurations of the water droplet adhesion detection electrode section 1, the oscillation circuit 2, the detection circuit 4, the amplifier circuit 8, and the lighting detection circuit 24 are the same as in the first embodiment, so the same parts are given the same reference numerals. ,
The explanation will be omitted.

Note that in the amplifier circuit 8, the capacitor C6 is omitted, and a resistor R82 is directly connected to the output terminal of the inverting amplifier circuit 5.

The integration circuit 31 has an operational amplifier 7 and a capacitor C for integration, and includes an integration time constant variable circuit 32.

The integral time constant variable circuit 32 includes a resistor R1? in a series circuit of a resistor R11+ and an analog switch 33. are connected in parallel.

The output terminal of the inverting amplifier circuit 5 of the detection circuit 4 is connected to the negative input terminal of the operational amplifier 7 via the variable integral time constant circuit 32, and is also connected to the output terminal of the operational amplifier 7 via the capacitor C1.

A constant voltage power supply circuit 34 is connected to the positive input terminal of the operational amplifier 7 and creates a threshold for the operational amplifier 7.

The output terminal of the operational amplifier 7 is connected to the gate of the FET 3 of the oscillation circuit 2.

That is, the output of the detection circuit 4 is fed back to the oscillation circuit 2 via the integration circuit 31.

The positive input terminal of the inverting amplifier circuit 9 is connected to a constant voltage power supply circuit 34 to create its threshold.

The discrimination circuit 35 includes a comparator 36 and a flip-flop FF.

The positive input terminal of the comparator 36 is connected to the output terminal of the inverting amplifier circuit 9. A series circuit of resistors Rz+ and Rz□ is connected to a DC power supply Vcc, and a connection point thereof is connected to a negative input terminal of a comparator 36 to create a threshold or reference value vth. The output terminal of the comparator 36 is connected to the set input terminal of the flip-flop FF via a circuit consisting of a diode h, D4, a capacitor CIO+C1, and a resistor R17°R111. A similar circuit is also provided at the reset input terminal of the flip-flop FF.The delay circuit 37 includes a capacitor C1□, a resistor R19, and a comparator 38. The capacitor C1ff1 is connected to the output terminal of the inverting amplifier circuit 9 and to the negative input terminal of the comparator 38 via the resistor RI9. The positive input terminal of the comparator 38 is connected to the constant voltage power supply circuit 34 to create its threshold.

The output terminal of the comparator 38 is connected to the reset input terminal of the flip-flop FF, and is also connected to the trigger terminal of the analog switch 33 of the variable integration time constant circuit 32 via a diode D5.

The 6 output terminals of the flip-flop FF of the discrimination circuit 35 are:
Switching transistor T r of wiper drive circuit
connected to the base of a.

Reference numeral 40 denotes a starting circuit that turns on the analog switch 33 when the water droplet detection sensor is powered on to decrease the combined resistance value of the variable integral time constant circuit 32 and thereby decrease the integral time constant.

This starting circuit 40 includes a PN connected to a DC power supply Vcc.
A P-type transistor Tr6, a resistor R2° that grounds the collector of the transistor Tr, and a capacitor CI3,
It has a diode D& etc.

Diode D6 is connected to the trigger terminal of analog switch 33.

The output terminal of the lighting detection circuit 24 having the same configuration as the first embodiment is connected to the connection point of the resistors RZI+R2* via a series circuit of a resistor RZ3 and a diode D.

Resistors R2□, R23, and diode D7 constitute "a reference value variable circuit 41 that reduces the reference value when the discrimination circuit 35 outputs a drive pulse signal to the wiper drive circuit" as referred to in the configuration of the invention. .

Description of Operation> Next, the operation of this second embodiment will be explained based on the time chart of FIG. 4.

(A) to (F) in FIG. 4 indicate the voltages at points A to F of the circuit of FIG. 3, respectively.

■ When the power is turned on, the transistor Tr of the starting circuit 40
, becomes conductive, and the voltage across the resistor R2° is output to the trigger terminal of the analog switch 33 of the variable integral time constant circuit 32, turning the analog switch 33 on. As a result, the combined resistance value of the variable integration time constant circuit 32 decreases, and the integration circuit 31
The integral time constant of becomes smaller.

Therefore, the integral output rises quickly and the on-resistance of the FET 3 becomes constant quickly, so that the time required for the oscillation amplitude of the oscillation circuit 2 to reach a predetermined amplitude is short. That is, the rise characteristics of the oscillation circuit 2 are good.

When the capacitor CI3 is charged and the base voltage of the transistor Tr6 increases, the transistor Tr& is turned off and the analog switch 33 is turned off, so that the resistance value of the variable integration time constant circuit 32 increases. That is, the integral time constant becomes a large value.

- When the power is turned on, the oscillation circuit 2 operates and starts oscillation. The voltage A at the output terminal of the detection circuit 4 maintains a constant oscillation amplitude in the absence of water droplets (period up to time t).

Further, when the power is turned on, the constant voltage power supply circuit 34 is connected to the integrating circuit 31, operates the operational amplifier 7, and outputs the output to the gate of the FET 3.

If the integrated output of the operational amplifier 7 is the result of integrating the output of the oscillation circuit 2 over a long period of time, that is, up to time t, then it is proportional to the average oscillation amplitude of the oscillation circuit 2 during normal operation. Become. This integrated output is applied to the gate of the FET 3, making the on-resistance of the FET 3 proportional to the integrated output and, in turn, to the oscillation amplitude of the oscillation circuit 2.

As a result, the time constant of the oscillation circuit 20 corresponds to the oscillation amplitude of the oscillation circuit 2.

Therefore, as in the first embodiment, the mounting of the sensing electrode section 1 is difficult even when the oscillation amplitude changes due to the initial capacitance of the capacitors c1°C2 depending on conditions and temperature conditions. changes the amplification gain of the transistor Tr, that is, the oscillation gain of the oscillation circuit 2 to absorb changes in the oscillation amplitude, and always maintains a constant oscillation amplitude unless water droplets are attached.

■ If one large water droplet adheres to the sensing electrode section 1 at time tll, the capacitor C+
, C2 changes, and as a result, the oscillation amplitude of the oscillation circuit 2 is varied.

The high frequency output from the oscillation circuit 2 whose oscillation amplitude has been varied is detected, amplified and smoothed by the detection circuit 4, and the output voltage A of the inverting amplifier circuit 5 changes greatly as shown in FIG.

■ The output voltage A from the inverting amplifier circuit 5 is input to the negative input terminal of the operational amplifier 7 of the integrating circuit 31, but since the integration time constant is large, the output of the operational amplifier 7 changes slowly.
Oscillation of the oscillation circuit 2 continues.

Further, the output voltage A is input to the amplifier circuit 8, inverted and amplified by the inverting amplifier circuit 9, and outputs an output voltage B having a waveform as shown in FIG. 3(B).

■ This output voltage B is applied to the comparator 36 of the discrimination circuit 35.
However, this output voltage B is higher than the reference value vth because it is based on large water droplets. Therefore, the output voltage C of the comparator 36 is as shown in (C
), it is inverted from "L" level to "H" level.

This "H" level pulse signal is applied to the flip-flop FF.
is input to the set input terminal of , and the voltage E of d output is shown in the figure (E
), it becomes "H" level.

(2) The "H" level voltage E from the flip-flop FF turns on the transistor Tr4 and operates the wiper drive circuit.

That is, in the case of large water droplets, the wiper is immediately driven by one water droplet.

■ The output voltage B shown in Figure (B) is input to the delay circuit 37, and is delayed by a predetermined delay time T from the output voltage E of the flip-flop FF, and the output voltage of the delay circuit 37 is
) becomes “H” level.

The "H" level output voltage is output to the analog switch 33 of the variable integration time constant circuit 32 via the diode D, turning on the analog switch 33.

When the analog switch 33 is turned on, the integration time constant becomes smaller, as in the case of turning on the power in item (2) above, the rise of the integration output becomes faster, and the oscillation amplitude of the oscillation circuit 2 instantly returns to the predetermined amplitude. .

(2) Furthermore, since the output voltage of the delay circuit 37 is also output to the reset input terminal of the flip-flop FF, the output voltage E of the flip-flop FF is inverted and becomes "L" level, and the transistor Tr.

turns off and stops the wiper drive circuit. That is, the wiper is driven only once.

■ When small water droplets adhere to the detection electrode part 1 (11 When the wiper is driven with three small particles ■) Because it is bright, the lighting switch 20 is not connected to the headlight contact 23. Criteria for the comparator 36 of the discrimination circuit 35 The value vth is held at a high level as an initial value divided by the resistors R11+R2□.

[Phase] At time t1□, when one small water droplet adheres to the detection electrode section 1, the capacitances of the capacitors C+ and Cz change, and the oscillation amplitude of the oscillation circuit 2 is varied.

However, the amount of fluctuation in the oscillation amplitude is small, and the amount of change in the output voltage A of the inverting amplifier circuit 5 is also small. Therefore, the amount of change in the output voltage B of the inverting amplifier circuit 9 of the amplifier circuit 8 is also small.

■ This output voltage B is applied to the comparator 36 of the discrimination circuit 35.
However, this output voltage B is lower than the initial reference value vth because it is based on small water droplets. Therefore, the output voltage C of the comparator 36 is not inverted, and the voltage E of the output of the flip-flop FF is also not inverted. That is, the wiper drive circuit does not operate.

Similarly, the output voltage of the delay circuit 37 is not inverted either.

(2) The output voltage A of the inverting amplifier circuit 5 is input to the negative input terminal of the integrating circuit 31 via only the resistor R17 of the variable integral time constant circuit 32. As a result, the integrated output voltage F is shown in Figure (F).
As the on-resistance of the FET 3 gradually decreases, the oscillation amplitude of the oscillation circuit 2 becomes smaller.

0 Even when a second small water droplet adheres to the detection electrode section 1 at time tl+, the amount of variation in the oscillation amplitude of the oscillation circuit 2 is small, and the output voltage B of the inverting amplifier circuit 9 is lower than the initial reference value vth. . That is, the output voltage C of the comparator 36 is not inverted, and the voltage E of the d output of the flip-flop FF is not inverted, so the wiper drive circuit does not operate.

Similarly, the output voltage of the delay circuit 37 is not inverted either.

In addition, the integrated output voltage F continues to rise slowly, and F
Since the on-resistance of ET3 is gradually reduced, the oscillation amplitude of oscillation circuit 2 is further reduced.

■ When a third small water droplet adheres to the detection electrode section 1 at time t14, the output voltage B of the inverting amplifier circuit 9 becomes higher than the initial reference value vth, and the output voltage C of the comparator 36 becomes "H". Since the output voltage E of the flip-flop FF also becomes "H" level, the wiper drive circuit operates.

That is, the wiper is driven only when the third small water droplet is attached.

■ After a predetermined delay time T from the output voltage E of the flip-flop FF which has reached the "H" level, the output voltage of the delay circuit 37 becomes the "H" level, and the analog switch 3
Turn on 3.

When the analog switch 33 is turned on, the integration time constant becomes smaller, the rise of the integration output becomes faster, and the oscillation circuit 2
The oscillation amplitude instantly returns to the predetermined amplitude, and the next water droplet is awaited.

[Phase] Furthermore, the output voltage E of the delay circuit 37 is also output to the reset input terminal of the flip-flop FF, and the output voltage E is inverted and becomes "L" level, and the transistor T
r, is turned off to stop the wiper drive circuit. That is, the wiper is driven only once.

Note that even if the wiper drive circuit is unexpectedly driven by external vibration, the output of the delay circuit 37 reduces the integration time constant, so that the oscillation amplitude instantly returns to the initial steady amplitude.

(2) When driving the wiper with two small water droplets O When visibility is poor at night or on a cloudy day, connecting the lighting switch 20 to the headlight contact 23 and taillight contact 22 will cause the comparator 36 of the discrimination circuit 35 to A series circuit of a resistor RZ3 and a diode D is connected to the input terminal. Resistance R2□.

The combined resistance value of R23 becomes smaller than the resistance value of resistor R2□, and the reference value Vtho of the comparator 36 becomes lower than the initial reference value vth.

[Phase] Large particle detection is the same as in (1) above.

The operations in (11) [phase] to @ are the same for small particle detection.

[Phase] When the second small water droplet adheres to the detection electrode part 1 a predetermined number of times, the output voltage B of the inverting amplifier circuit 9 becomes higher than the reference value Vtho, and the output voltage C of the comparator 36 becomes "H". Since the output voltage E of the flip-flop FF also becomes the "H" level, the wiper drive circuit operates.

That is, the wiper is driven by the adhesion of the second small water droplet.

[Phase] After a predetermined delay time T from the output voltage E of the flip-flop FF that has reached the “H” level, the delay circuit 3
The output voltage of the switch 7 becomes "H" level, and the analog switch 33 is turned on. The integral time constant becomes smaller, the integral output rises faster, and the oscillation amplitude of the oscillation circuit 2 instantaneously returns to a predetermined amplitude, waiting for the next water droplet to adhere.

On the other hand, the output voltage of the delay circuit 37 is also output to the reset input terminal of the flip-flop FF, and the output voltage E is inverted and becomes "L" level, and the transistor T r
a is turned off and the wiper drive circuit is stopped. That is, the wiper is driven only once.

According to this embodiment, in addition to the effects of the invention, after the wiper is driven, the integration circuit 3
By reducing the integral time constant of 1, the oscillation amplitude of the oscillation circuit 2 can be immediately returned to its initial state, and even if the next water droplet adheres immediately, the expected water drop detection operation can be repeated. There are advantages.

[Brief explanation of the drawing]

Figure 1 shows the circuit diagram of the water drop detection sensor, and Figure 2 shows the voltage of each part of the circuit. The time charts, FIGS. 3 and 4, relate to the second embodiment of the present invention, FIG. 3 is a circuit diagram of a water droplet detection sensor, and FIG. 4 is a time chart regarding voltages at various parts of the circuit. In the figure, numeral 1 is a detection electrode section, 2 is an oscillation circuit, 6.31 is an integration circuit, 14.35 is a discrimination circuit, 24 is a lighting detection circuit, and 25.41 is a reference value variable circuit.

Claims (1)

[Claims] (1) A detection electrode section that detects adhesion of water droplets by a change in capacitance; an oscillation circuit connected to the detection electrode section that varies the oscillation amplitude based on the change in capacitance; and a predetermined control circuit for the detection electrode section. a discrimination circuit that outputs a drive pulse signal to a controlled object when data from the oscillation circuit based on water droplet adhesion a predetermined number of times, three or more times within a time, is equal to or greater than a reference value; a lighting detection circuit for a lighting device; A water droplet detection sensor comprising: a reference value variable circuit that reduces the reference value based on a detection signal of the detection circuit.