JPH087146B2 - Optical raindrop detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical raindrop detecting device that can be used, for example, for driving a wiper blade for wiping a windshield of an automobile when it is raining.

Background Art [0002] Such an optical raindrop detection device detects a change in received light power due to a raindrop passing through an optical path between a light emitting element and a light receiving element, and detects it on a windshield of an automobile. It is configured to wipe off raindrops, rain and snow with a wiper blade.

Problems that can be Solved by the Invention In such a prior art, when snow and mud adhere to the light emitting element and the light receiving element and the light path is blocked, raindrop detection cannot be performed, and accordingly, during rain. In such a case, the wiper blade cannot be used for wiping automatically. It is convenient for the driver to be able to know that such a blocked state of the optical path has occurred while in the passenger compartment of the automobile.

It is an object of the present invention to provide an optical raindrop detection device that can detect that a light path has been interrupted.

Means for Solving the Problems The present invention relates to an optical raindrop detecting device for detecting raindrops passing through an optical path between a light emitting element and a light receiving element, wherein the light receiving level of the light receiving element is constant. And a means for detecting that the light receiving level of the light receiving element has become low based on the output from the light emitting control means, and an output from the detecting means. And a means for driving the wiper at a constant interval when the received light level becomes low, the optical raindrop detection device.

Operation According to the present invention, the light emission control circuit that receives the light receiving level of the light receiving element controls the light emitting element so as to keep the light receiving level at a normal level by energizing the light emitting element. When it is detected that the light path is blocked by snow or mud based on the output, the wiper is driven at regular intervals, so the light emitting element and the light receiving element are operating in the normal raindrop detection state. It is possible to drive the wiper even when the sensor function is stopped due to the inclusion of snow and mud in the optical path between the wiper and the like.

First Embodiment FIG. 1 is a block diagram showing the structure on which the present invention is based. The optical raindrop detection device 1 basically has a detection unit 2 and a processing unit 3. The raindrop detection element 4 includes a light emitting element 5 realized by a light emitting diode and the like, and a light receiving element 6 that receives light from the light emitting element 5 through an optical path. The light emitting element 5 is driven by the modulation drive signal from the drive circuit 7. The output from the light receiving element 6 is amplified by the amplifier circuit 8 and envelope-detected by the detection circuit 9, and the detected output is derived from the line 10. The detection output through the line 10 generates a pulse each time a raindrop passes through the optical path between the light emitting element 5 and the light receiving element 6. The integrating circuit 11 integrates the pulsed detection output from the line 10, and the integrated output is given to the processing circuit 12 in the processing unit 3. When the output of the integrating circuit 11 reaches a predetermined value, the processing circuit 12 drives the wiper motor 13 and resets the integrating circuit 11 to initialize the integrating operation of the integrating circuit 11. Wiper motor 13
Wiper blade to wipe the windshield of a car
Drive 14

The detection output from the detection circuit 9 via the line 10 is given to the light emission control circuit 15. The light emission control circuit 15 has a low-pass filter 16 to which a detection output is given and a differential amplification discrimination circuit 17. The differential amplifier circuit 17 has an operational amplifier 18 to which the output from the low-pass filter 16 is given, a resistor 19, and resistors 20 and 21 for setting a reference voltage. The low-pass filter 16 has a cut-off frequency that cuts off the pulsed detection output when raindrops pass through the optical path and sends a signal of a frequency lower than that.

When the light emitting surface of the light emitting element 5 and the light receiving surface of the light receiving element 6 are contaminated, when the ambient temperature changes, or when there is an assembly error, the output level from the low-pass filter 16 decreases, which causes the line The output level of 22 rises. The drive circuit 7 energizes the light emitting diode 5 with a large electric power when the level of the signal from the line 10 is lowered, whereby the output level from the light receiving element 6 is applied to the resistors 20 and 21 except when raindrops are detected. Therefore, the value is controlled so as to have a value corresponding to the reference voltage thus determined, and a certain decrease in the received light power is corrected.

On the other hand, when snow, mud, etc. are present in the light path, and the light is not constantly applied to the light receiving element due to this, the fluctuation of the received light power as shown in FIG. Beyond the possible range, the signal delivered on line 22 will be at a certain high voltage.

When snow, mud, etc. adhere to the light path and the signal on the line 22 rises as shown in FIG. 3 (1) as described above, the signal is described in the processing unit 3 as follows. As described above, the discrimination is performed at the discrimination level indicated by the line 1, and the buzzer 23 is sounded. The signal from the line 22 is adjusted for each set by resistors 24 and 25, and is applied to one input of the comparator 27 from the line 26. The other input of the comparator 27 is supplied with the discrimination level 1 set by the resistors 28 and 29. A capacitor 30 is connected in parallel to the line 26, and the resistance 2 of the comparator 27 is
The capacitor 31 is connected in parallel to the input terminal to which the discrimination level by 8, 29 is given. The discrimination level set by resistors 28 and 29 is also provided to one input of comparator 32. The output of the comparator 27 is output via line 33 to the comparator 32.
Given to the other input of. A resistor 34 and an operation delay capacitor 35 are connected to the line 33. The comparator 27 outputs a high level signal to the line 33 when the output from the line 26 becomes equal to or higher than the discrimination level 1, as shown in FIG.
Derive to. The signal on line 33 is also discriminated by discrimination level 1. When the level of the line 33 becomes equal to or higher than the discrimination level 1, the comparator 32 derives a low level signal to the line 36 and causes the buzzer 23 to ring, as shown in FIG. 3 (3).

In this way, the level of the detection output derived from the line 10 of the detection circuit 9 becomes a low level for a certain period of time,
Therefore, when the signal derived from the light emission control circuit 15 to the line 22 becomes a certain high voltage exceeding the received light power correction range for a relatively long time, the buzzer 23 is sounded. . In this way, when snow or mud adheres between the light emitting element 5 and the light receiving element 6 and the light path is blocked, the buzzer 23 is sounded and the driver or the like cuts the light path. You can know it indoors.

FIG. 4 is a block diagram showing an embodiment of the present invention. This embodiment is similar to the configuration shown in FIG. 1 to FIG. 3 described above, and corresponding portions are designated by the same reference numerals. It should be noted that the relay switch 71 is connected in series to the wiper motor 13 that drives the wiper blade.
The relay coil 72 that performs the switching operation of 71 is connected in series to the switching transistor 73. Relay switch
The 71 and the relay coil 72 form a relay 74. The relay coil 72 also has another switching transistor.
75 are connected in series. The processing circuit 12 includes a wiper motor 13
When a wiper blade (not shown) is to be driven by this, a high level signal is applied to the base of transistor 75, which causes transistor 75 to conduct. Therefore, the relay coil 72 of the relay 74 is excited, and as a result, electric power is supplied to the motor 13 via the relay switch 71. When the wiper motor 13 is energized, the integration circuit is switched from the switching switch 76 that interlocks with the wiper blade.
A high level signal is given to 11, and the integrating circuit 11 is reset. When the wiper blade returns to the original rest position, the switch 76 gives a low-level signal to the integrating circuit 11, whereby the integrating circuit 11 can perform the integrating operation again.

When both the transistors 73 and 75 are cut off, the relay coil 72 is demagnetized, and the relay switch 71 gives a low level signal to the integrating circuit 11 via the wiper motor 13 and the motor 13 Is dormant.

Thus, when the amount of raindrops passing through the optical path of the detection element 4 is large, the integrating circuit 11 reaches a predetermined integral value in a relatively short time, which causes the processing circuit 12 to conduct with the switch transistor 75. Then, the wiper motor 13 drives the wiper blade. In this way, the drive time interval of the wiper blade by the motor 13 is changed according to the amount of raindrops.

When snow or mud adheres to the light path of the detection element 4 and the light path remains blocked, the light emission control circuit
15 derives a high voltage on the line 22 and is discriminated by the comparator 77. When the discrimination voltage is equal to or higher than the discrimination level, the oscillation circuit 78 is activated, and the driving circuit 79 causes the transistor 73 to turn on the oscillation circuit 78.
ON / OFF at a constant frequency. Therefore, the relay coil 72 of the relay 74 is excited at a constant frequency. As a result, the wiper blade wipes the windshield at a constant cycle regardless of the amount of raindrops. In this way, even if the sensor cannot detect raindrops, the wiper can be operated intermittently at a constant cycle, and the driver in the vehicle compartment also knows that the optical path of the detection element 4 is blocked. You can

Effect As described above, according to the present invention, the light emission control circuit which receives the light receiving level of the light receiving element urges the light emitting element to perform control so that a normal light receiving level is always maintained. When it detects that the light path is blocked by snow, mud, etc. based on the output of the light emission control circuit, the wiper is driven at a constant interval, so it emits light while normal raindrop detection is being performed. It is possible to drive the wiper even when the sensor function is stopped due to the presence of snow, mud, or the like in the optical path between the element and the light receiving element.

Further, according to the present invention, it is not necessary to separately provide means for detecting the inclusion of snow, mud, and the like in the optical path between the light emitting element and the light receiving element by an optical configuration or the like, and to detect raindrops. The light emission control means provided in association with the light emitting element and the light receiving element having the original function of, is used as it is, and snow and mud are intervened in the light path based on the output from the light emission control means. Since it is configured to detect that the light receiving level of the light receiving element has decreased due to the above, the effect that the configuration can be simplified is also achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration on which the present invention is based, FIG. 2 is a diagram showing a relationship between an output of the LPE 16 and a voltage of the line 22, and FIG. 3 shows an operation of the configuration shown in FIG. 4 is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Optical raindrop detection device, 2 ... Detection unit, 3 ... Processing unit, 4 ... Detection element, 5 ... Light emitting element, 6 ... Light receiving element, 7 ... Drive circuit, 8 ... Amplification circuit, 9 ... Detection circuit, 11 ...
Integrator circuit, 12 ... Processing circuit, 13 ... Wiper motor, 14 ... Wiper blade, 15 ... Light emission control circuit, 23 ... Buzzer

Claims (1)

[Claims] 1. An optical raindrop detecting device for detecting raindrops passing through an optical path between a light emitting element and a light receiving element, wherein the light receiving element receives the light receiving level of the light receiving element so that the light receiving level becomes constant. A light emission control means for controlling the electric power of the light emission control means, a means for detecting that the light reception level of the light receiving element has become low based on the output from the light emission control means, and the light reception level in response to the output from the detection means. And a means for driving the wiper at a constant interval when the temperature becomes low, an optical raindrop detecting device.