JP2001166064A - Raindrop sensing device using light - Google Patents

Abstract

(57) [Summary] [Problem] Even if the frequency on the light emitting side changes due to the characteristics of the vehicle, etc., external light can be cut off according to the frequency on the light emitting side without changing the internal circuit, and it can respond to raindrops accurately. To obtain a raindrop sensing device using light capable of detecting only a signal component to be changed. SOLUTION: A light emitting element 22a, 22b of a raindrop sensor is driven by a pulse signal from an oscillating section 21 to be received by light receiving elements 23a, 23b, and an external light quantity signal generating section 25 sets the received light signal as a raindrop signal. The voltage of the external light component is extracted from the raindrop signal and held by synchronizing the inverted signal of the pulse signal of the oscillation unit with the raindrop signal. Then, the raindrop amount signal extraction unit 26 obtains the voltage difference between the voltage of the external light component and the raindrop signal received by the light receiving element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raindrop sensing device using light, and more particularly to a true light receiving signal by completely removing an external light component when a raindrop sensor for detecting raindrops by pulse light is provided outside. The present invention relates to a raindrop sensing device using light for extracting only a component (raindrop amount).

[0002]

2. Description of the Related Art In recent years, an optical raindrop sensor has been used for intermittently operating a wiper of an automobile.

For example, in a wiper driving apparatus disclosed in Japanese Patent Application Laid-Open No. 4-38609 shown in FIG. 8, a pulse light from a light emitting element 2 is pulse-modulated by an oscillator 1 and received by a light receiving element 4.

[0004] The bandpass filter 5 passes only the modulated wave from the light receiving signal from the light receiving element 4, and inputs the modulated wave to the detector 7 via the amplifier 6, and the detector 7 performs envelope detection.

The envelope-detected raindrop signal is input to a bandpass filter 8 which removes ripples due to pulse modulation.

The band pass filter 8 is an active filter, and obtains an output whose level is inverted.

[0007] The raindrop signal from the detector 7 is simultaneously input to a low-pass filter 9.
The level of the raindrop signal is averaged by the comparator 10, and the average is compared by the comparator 10 with the reference value L <b> 2 for detecting a decrease in sensitivity.

[0008] The comparison result from the comparator 10 and the output from the bandpass filter 8 are input to an integrator 11 (comprising a switch S3, a resistor R, and an integrator 12).

That is, the comparison result of the comparator 10
By allowing the route of cc → R → integrator 12 to be selected, if the sensor sensitivity is normal, the output of the band-pass filter 8 is directly input to the integrator 12 to perform wiper control in proportion to the amount of raindrops. I have.

[0010]

However, the conventional wiper driving device emits a pulse using a light emitting element to cut off external light, and after receiving the pulse with a light receiving element, the band pass filter 5 applies a pulse. An output whose ripple due to modulation is removed or whose level is inverted by the band-pass filter 8 and smoothed by the band-pass filter 9 is obtained.

For this reason, if the frequency of the pulse signal from the light emitting element is changed by changing the frequency of the output signal of the oscillator 1 on the light emitting side, external light cannot be cut unless all bandpass filters are changed. There was a problem that.

If the frequency of the pulse signal from the light emitting element is changed by changing the frequency of the output signal of the oscillator 1 on the light emitting side, all band pass filters must be changed each time to cut off the external light. There is a problem that the cost must be increased because it must be avoided.

The present invention has been made in order to solve the above-mentioned problems. Even if the frequency of the light emitting side changes due to the characteristics of the vehicle or the like, the external circuit can be changed according to the frequency of the light emitting side without changing the internal circuit. An object of the present invention is to provide a raindrop sensing device using light that can cut light and accurately detect only a signal component corresponding to a raindrop.

[0014]

A raindrop sensing device using light according to the present invention comprises a raindrop sensor provided with a light-emitting element and a light-receiving element opposed to each other so as to be capable of optically detecting raindrops. The oscillator emits a pulse signal corresponding to the pulse signal from the light emitting element by transmitting a pulse signal of a predetermined period to the light emitting element, and corresponds to the oscillating unit for transmitting an inverted signal of the pulse signal, and the pulse light of the light receiving element of the raindrop sensor. In the received light signal,
Synchronizing the inverted signal of the pulse signal from the oscillating unit to extract the L level of the light receiving signal, and generating an external light quantity signal generating unit for holding this L level voltage as an external light component received by the light receiving element; A raindrop signal that extracts the difference between the voltage of the light receiving signal corresponding to the pulsed light of the light receiving element of the sensor and the voltage of the external light component held by the external light quantity signal generating unit as the true raindrop voltage received by the light receiving element The gist of the present invention is that an extraction unit is provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic structural view of a raindrop detecting device using light according to the present invention. Raindrop sensing device 2 shown in FIG.
0 causes a pulse signal of a predetermined frequency from the oscillating unit 21 to be transmitted to the light emitting unit 22 (the light emitting elements 22a and 22b), and the LED light corresponding to the pulse signal from the light emitting unit 22 is transmitted to the light receiving unit 23 (the light receiving elements 23a and 23b). At 23b), light is received. The light receiving section 23 and the light emitting section 22 (collectively referred to as a raindrop sensor)
When this device is used for sensing raindrops for driving a wiper of a vehicle, it is attached to the rear side of the rearview mirror of the windshield.

The light receiving signal from the light receiving unit 23 is input as a raindrop signal (including an external light amount and a raindrop amount) to an amplifying unit 24, which amplifies and amplifies the signal. To send to.

The oscillating section 21 is constituted by a flip-flop or the like, and sends a positive logic output as a modulated pulse signal to the light emitting section 22 and sends it to an analog switch SWB described later.

The oscillating section 21 sends an inverted signal of the pulse signal to the external light quantity signal generating section 25.

The external light quantity signal generating section 25 receives the inverted signal of the pulse signal from the oscillating section 21 and the raindrop signal from the amplifying section 24, and converts the component of the raindrop signal synchronized with the inverted pulse signal into the external light quantity signal ( Pulse), and the external light quantity signal accompanying this extraction is stored at a predetermined DC level.

The raindrop amount signal extraction unit 26 extracts a difference between the raindrop signal from the amplification unit 24 and the DC level external light amount signal obtained by the external light signal generation unit 25 as a true raindrop amount signal.

The output of the raindrop amount signal extraction unit 26 is connected to an analog switch SWB which is opened and closed by a pulse signal from the oscillation unit 21.
Is connected to a smoothing unit 27.

The output of the smoothing unit 27 is connected to an analog switch SWC that opens and closes according to an on / off signal from a switch unit 28.

Further, an on / off signal from the switch unit 28 and a DC level external light amount signal generated by the external light signal generating unit 25 are input. When the external light amount signal is equal to or higher than a predetermined level, the circuit is closed. Switch SW of switch section 28
An analog switch SWD is provided to invalidate the pressing signal even when 1 is pressed.

Further, the output of the analog switch SWC is connected to a pull-up resistor Ro connected to the Vcc power supply.
Is provided.

(Details of Each Unit) The amplification unit 24 includes a light receiving unit 23
And a resistor R1 having one connected to the anode of each of the light receiving elements 23a and 23b and the other connected to ground.
And a resistor R2 connected to the plus input of the amplifier APM1, a resistor R3 connected to the ground and connected to the minus input of the amplifier AMP1, and feedback resistors R4 and VR1 of the amplifier AMP1. The received light signal from the section 23 is sent out as an amplified raindrop signal e to the external light quantity signal generation section 25 and the raindrop quantity signal extraction section 26.

The external light intensity signal generation unit 25 generates an inverted pulse signal a for driving the light emitting unit 22 from the oscillation unit 21.
Is delayed by one pulse and shaped by the resistors R5 and R6, the diode D1, and the capacitor C1 and the signal is sent to the analog switch SWA as an external light extraction signal.

The analog switch SWA receives as input a raindrop signal from the amplifier 24 and an on / off control terminal for an external light extraction signal.

That is, only the external light signal obtained when the emission of light from the light emitting section 22 is stopped is converted to the analog switch S
It is extracted under the control of WA.

The external light signal is charged in the capacitor C2 to obtain a DC level external light quantity signal.

The raindrop amount signal extraction unit 26 converts the raindrop signal e from the amplification unit 24 into an amplifier AMP2 via resistors R8 and R9.
To the plus input of. The feedback resistor R10 is connected to the minus input.

One terminal of the resistor R7 is connected to the negative input, and the other terminal is connected to the capacitor C2, the output of the analog switch SWA of the external light intensity signal generator 25, and the resistors R11 and R12.

The smoothing section 27 has an analog switch SWB. The anode of the diode D2 is connected to the analog switch SWB.
Connected to WB output. Further, the cathode of the diode D2 is connected to a smoothing circuit including a capacitor C3 and a resistor R13.

Further, the switch unit 28 includes a switch SW
1 and a resistor R14 and a capacitor C5 are connected in series.
One of the switches SW1 is connected to the power supply Vcc, and the other of the capacitor C5 is connected to the ground.

The raindrop sensing device 20 using the light configured as described above will be described with reference to the timing charts of FIGS.

(Operation when it is not raining) For example,
As shown in FIG. 2, when a pulse signal a is output from the oscillation unit 21, a light emission pulse c corresponding to the pulse signal is emitted from the light emission unit 22.

At this time, an inverted signal obtained by inverting the pulse signal a from the oscillation unit 21 is output from the resistance R of the external light amount signal generation unit 25.
5, R6, the capacitor C1, and the diode D1 are input to the control terminal of the analog switch SWA as the external light extraction signal f.

The light emitting pulse c from the light emitting section 22 is received by the light receiving section 23. External light is received along with this light reception.

Therefore, as shown in FIG. 2, a light receiving signal d is obtained by superimposing the actual light receiving signal Pi on the external light Qi.

The light receiving signal d is amplified by the amplifying unit 24, and becomes an amplified light receiving signal Pih (Qih in which external light is also amplified).

The above-mentioned external light extraction signal f (H level)
Is input, the analog switch SWA is turned on.

That is, since the external light extraction signal f is synchronized with the pulse signal a of the oscillation section 21, only the external light level Qih is sequentially extracted from the amplified light receiving signal e.

Each time the external light level Qih is obtained, the capacitor C2 is charged. When the external light extraction signal f is L
Since the SWA is opened each time the level becomes high, a discharge current flows from the capacitor C2 via the resistors R11 and R12. Therefore, as shown in FIG. 2, the output of the SWA becomes a DC level due to the discharge voltage Cpi of the capacitor C2 and the external light level Qih. That is, a DC level voltage corresponding to the external light amount can be obtained.

The external light quantity signal g is used as the raindrop quantity signal extraction unit 26.
Operating amplifier (APM2, R7, R8, R9, R10)
To enter.

That is, as shown in FIG. 2, the difference (PHi = Pih-Cpi) between the amplified light receiving signal e (Pih, Qih) from the amplifying unit 24 and the external light amount signal g is obtained as shown in FIG. The signal h from which such external light components are completely removed is obtained.

As shown in FIG. 3, the pulse signal a of the oscillating unit 21 is sent out as a SWB control signal.
For this reason, the signal h (PHi) of only the true light receiving signal component extracted by the raindrop amount signal extracting unit 26 synchronized with the light emission pulse c (H level) becomes the output of the SWB.

Then, the signal h (PHi ') caused by the voltage drop of the diode D2 of the smoothing section 27 is smoothed by the capacitor C3 and the resistor R13. That is, the DC level signal k (PHi ″) including only the true light receiving signal component is transmitted to the analog switch SWC.

At this time, the switch SW of the switch unit 28
If 1 is in the OFF state, the output of the SWC is at the Vcc level as shown in FIG. 3 since the SWC is in the open circuit state.

The reason why the pull-up resistor Rp is provided is that the input circuit of the wiper control unit 30 forms a comparator composed of resistors R15, R16, VR2, an amplifier AMP3 and the like as shown in FIG. When the voltage of the raindrop amount signal is lower than the value (it is determined that it has rained), the transistor Q1 is turned on by the output of the comparator. Is operated to drive the wiper motor M to operate the wiper 33.

On the other hand, since the switch SW1 of the switch section 28 is manually turned on and off, it is turned on even in fine weather.

When the switch SW1 is turned on in this fine weather, the output of the switch SWC rises to the H level by the pull-up resistor RD as shown in FIG. When the output of the switch unit 28 rises slowly due to the charging of the capacitor C5, the output level of the smoothing unit 27 becomes Phi.

(Operation when it rains) Next, the operation when it rains will be described. As shown in FIG. 2, when rain (W) falls, the amount of light received by the light receiving unit 23 is attenuated. This light receiving signal d is referred to as a raindrop signal d (Pp). Amplifier 24
In FIG. 2, the external light level is Qph and the raindrop level is Pph in FIG.

At this time, an external light extraction signal f based on the inverted signal b of the pulse signal a is sent to the SWA from the oscillation unit 21 to the external light signal generation unit 25, and is closed and opened in synchronization with the external light extraction signal f. are doing.

Therefore, as shown in FIG. 2, every time the external light level Qph is obtained, the capacitor C2 is charged. Each time the external light extraction signal f becomes L level, SWA
Is opened, the discharge current flows from the capacitor C2 to the resistor R1.
1. Flow through R12.

This capacitor C2, resistors R11 and R12
Are collectively called an external light amount holding circuit.

For this reason, as shown in FIG. 2, the output of the SWA is determined by the discharge voltage Cph of the capacitor C2 and the external light level Qp.
h and the DC level. That is, it is possible to obtain a DC-level voltage corresponding to the amount of external light during rain.

The external light quantity signal g is used as the raindrop quantity signal extraction unit 26.
Operating amplifier (APM2, R7, R8, R9, R10)
To enter.

That is, as shown in FIG. 2, the difference (PPH = Pph-Cph) between the amplified light receiving signal e (Pph, Qph) from the amplifying unit 24 and the external light amount signal g during rain is obtained. As shown in FIG. 2, it is possible to obtain a signal h from which external light components during rain have been completely removed.

On the other hand, when it rains, the switch SW1 of the switch unit 28 is turned on as shown in FIG. As a result, Vcc is charged in the capacitor C5, and the wiper-on signal m which rises slowly is transmitted.

At this time, the resistance R of the external light amount signal
11, the external light level g (Cp
h, Qph) decrease during rain, so the SWD is open. For this reason, as shown in FIG. 3, the wiper-on signal m maintains the H level to close (turn on) the SWC.

That is, the pull-up resistor Rp and the smoothing unit 2
7, the Vcc becomes a negligible potential due to the resistor R13. As shown in FIG. 3, a DC level signal k (Pph ″: lower than when the switch SW1 is turned off), which is a raindrop amount signal during rain, is provided in the subsequent wiper control unit. 30.

For this reason, the wiper 33 is driven according to the DC level signal k (Pph ″) that is the true raindrop amount signal. Therefore, accurate control is performed according to the amount of raindrops.

That is, since the external light component is extracted from the raindrop signal received by the light receiving element in synchronization with the inversion signal of the pulse signal from the light emitting section for driving the light emitting element, the pulse signal of the oscillation section 21 is extracted for some reason. Even if the period of the pulsed light from the light emitting elements 22a and 22b is changed by changing the frequency, the circuit does not need to be changed at all and the amount of raindrops with high accuracy can be extracted.

The description of the switch unit 28, the smoothing unit 27 and the SWD will be supplemented. When the switch SW1 is turned on during rain, as shown in FIG. 6, the output of the switch SWC rises to the H level by the pull-up resistor RD as in the case of fine weather. When the output of the switch unit 28 rises slowly due to the charging of the capacitor C5, the smoothing unit 2
7, the output level Pph.

On the other hand, the SWD detects the potential of the external light level g. However, strong external light may enter even during rain. When such strong external light enters, the amplitude of the pulse of the output waveform of the light receiving element is broken, and the output of the raindrop amount signal extraction unit 26, that is, the amplitude of (h) in FIG. May be broken and the wiper may operate. The SWD prevents this malfunction.

The cause of the collapse of the amplitude of the output waveform of the light receiving element is that the power supply uses 5 V as shown in FIG. For this reason, if there is strong light, the external light level Qi does not increase by 5 V or more, and the amplitude decreases.

When the external light level g (potential of C2) becomes the potential at which the SWD is turned on (the voltage immediately before the external light is very strong and the amplitude is collapsed), the output of the SWD is connected to GND. SWC is turned off. Therefore, 5 V of the pull-up resistor RD is transmitted to the wiper control unit without transmitting the output of the smoothing unit 27.

Then, when the external light becomes weak, the SWD is turned off again and the SWC is turned on, so that the output of the smoothing unit 27 is transmitted to the wiper control unit. In other words, the SWD is hardly turned on during rain. That is, malfunction is not caused by sunlight when it is not raining.

Although the above embodiment has been described as a raindrop sensing device used for a wiper, it may be used as a sensing device that detects only a true amount of received light when external light inevitably enters.

[0069]

As described above, according to the present invention, the light emitting element of the raindrop sensor is driven by the pulse signal from the oscillating section and received by the light receiving element, and the received light signal is used as a raindrop signal. The voltage of the external light component is extracted from the raindrop signal and held by synchronizing the inverted signal of the pulse signal of the oscillator, and the voltage difference between the voltage of the external light component and the raindrop signal received by the light receiving element is obtained.

For this reason, even if the amount of raindrops is sensed by pulsed light, the effect is obtained that only the true amount of raindrops can be easily extracted.

Since the external light component is extracted from the raindrop signal received by the light receiving element in synchronization with the inversion signal of the pulse signal from the light emitting section for driving the light emitting element, the pulse signal of the oscillation section is extracted for some reason. Even if the frequency is changed and the period of the pulse light from the light emitting element is changed, there is an effect that there is no need to change the circuit. For this reason, cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a raindrop sensing device according to the present embodiment.

FIG. 2 is a timing chart illustrating the operation of the raindrop sensing device according to the present embodiment.

FIG. 3 is a timing chart illustrating the operation of the raindrop sensing device according to the present embodiment.

FIG. 4 is a schematic configuration diagram of a wiper control unit using the raindrop sensing device of the present embodiment.

FIG. 5 is a waveform diagram illustrating an output of a switch unit and an analog switch SWC in fine weather.

FIG. 6 is a waveform diagram illustrating an output of a switch unit and an analog switch SWC during rainy weather.

FIG. 7 is an output waveform diagram of a photodiode due to strong sunlight.

FIG. 8 is a schematic configuration diagram of a conventional wiper driving device.

[Explanation of Symbols] 21 oscillating unit 22 light emitting unit 23 light receiving unit 24 amplifying unit 25 external light amount signal generating unit 26 raindrop amount signal extracting unit 27 smoothing unit

Claims (5)

[Claims] 1. A raindrop sensor provided with a light-emitting element and a light-receiving element opposed to each other so as to optically detect raindrops. An oscillating unit that emits a pulse light corresponding to the pulse signal and transmits an inverted signal of the pulse signal, and a light receiving signal corresponding to the pulse light of the light receiving element of the raindrop sensor, the pulse from the oscillating unit. Synchronizing the inverted signal of the signal, extracting the L level of the light receiving signal, and holding an L level voltage as an external light component received by the light receiving element; The difference between the voltage of the light receiving signal corresponding to the pulsed light of the light receiving element and the voltage of the external light component held by the external light amount signal generation unit is defined as the true raindrop voltage received by the light receiving element. A raindrop detecting device using light, comprising: 2. The external light quantity signal generation unit receives the light reception signal, and gates the light reception signal from an output terminal when the inverted signal from the oscillation unit is at an H level. A resistor is connected in series, a capacitor is connected in parallel to this series circuit, and an external light amount holding circuit in which one of the capacitor and the series circuit is connected to an output terminal of the gate means and an input of the raindrop amount signal extraction unit. The raindrop sensing device using light according to claim 1, wherein: 3. An amplification unit for amplifying a light receiving signal from the light receiving element by a predetermined factor and sending the amplified signal to the external light amount signal generating unit and the raindrop amount signal extracting unit. Raindrop sensing device using the light of the sky. 4. A smoothing unit which receives a raindrop amount signal from the raindrop amount signal extraction and a pulse signal from the oscillating unit, and uses the pulse signal to smooth the raindrop amount signal. A raindrop sensing device using light according to claim 1, 2 or 3. 5. When the raindrop amount signal from the smoothing unit is used for wiper control when the voltage of the raindrop amount signal is lower than a reference voltage, the wiper operation is performed until the switch is pressed down. The output of the unit is set to the reference voltage or more, and when the switch is pressed, when the raindrop amount signal is equal to or less than the divided voltage value of the series circuit of the external light amount holding circuit (less than the reference value), the switch is pressed. 5. The raindrop sensing device using light according to claim 1, further comprising: means for transmitting the raindrop amount signal to a subsequent wiper control unit as being effective.