JP2595728Y2 - Rain detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rain detection device for detecting rain by detecting the presence of raindrops, and is used, for example, in a vehicle to automatically operate a wiper during rain. The present invention relates to a rain detection device.

[0002]

2. Description of the Related Art Conventionally, as an automatic wiper device using the above-described rain detection device, for example, Japanese Utility Model Application Laid-Open No. 63-696 has been proposed.
No. 61 was disclosed.

That is, FIG. 4A shows the structure of a raindrop sensing unit of the rain detection device described in the above publication, and the raindrop sensing unit 100 shown in the figure includes an infrared light emitting diode 101 and a windshield. 102, and a phototransistor 103. The phototransistor 103 receives infrared light emitted from the infrared light emitting diode 101, incident on the windshield 102, and reflected on the outer surface 102a of the windshield 102. The phototransistor 103 performs an output according to the amount of received light.

When raindrops D adhere to the outer surface 102a of the windshield 102, the windshield 102
The infrared light incident on the inside is divided into an infrared ray incident on the raindrop D and an infrared ray reflected on the windshield 102 at a boundary surface between the windshield 102 and the raindrop D.
Infrared rays incident on the outside, further on the outer surface of the raindrop D,
It is divided into infrared rays incident on the air and infrared rays reflected on the raindrop D. The infrared light reflected during the raindrop D reduces the amount of light by partially reflecting at the boundary surface between the windshield 102 and the raindrop D and the inner surface 102b of the windshield 102, and then enters the air as indicated by the broken line in the drawing. Incident. At this time, the windshield 102 and the raindrop D
The amount of infrared light reflected from the windshield 102 at the interface between the phototransistor 102 and the raindrop D is smaller than that before the raindrop D is attached due to the density difference between the air and the raindrop D. Therefore, the output of the phototransistor 103 is reduced due to the attachment of the raindrop D.

[0005] As shown in FIG. 4 (b), the raindrop sensing unit 100 having such a configuration includes a filter 110 and an amplifier 11.
1, waveform shaping circuit 112 and A / D converter 113
Via the CPU 114a, the ROM 114b and the RA
M114c is connected to a one-chip microcomputer 114 having a built-in M114c.
The output from the photo transistor 103 immediately after the wiper blade (not shown) wipes the raindrops on the windshield 102 by the initial operation of the wiper device 115 from the RAM 1 of the one-chip microcomputer 114.
When the value becomes smaller than the value obtained by subtracting the value set by the variable resistor (not shown) from the reference data value stored in the memory 14c, a wiper drive signal is output from the one-chip microcomputer 114 to the wiper device 115, The wiper blade makes one reciprocation based on this.

[0006]

However, in the above-mentioned conventional automatic wiper device, as described above, when the output from the phototransistor 103 falls below the reference value immediately after wiping by the initial operation by a set value or more, The blade is operated, and the amount of infrared light emitted from the infrared light emitting diode 101 is always constant.
It is necessary to adjust the sensitivity (initial setting) in accordance with the transmittance and reflectivity of infrared rays which are different from one another for each case. There is a problem that the amount of received light is not stable and the detection sensitivity of raindrops varies, and solving such a problem has been a problem in this type of rain detection device.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional rain detection device, and can stabilize the amount of light received by the light receiving means, and particularly without adjusting the sensitivity of the windshield. It is an object of the present invention to provide a rain detection device capable of detecting raindrops attached to a transparent body such as the one with high responsiveness and high sensitivity.

[0008]

SUMMARY OF THE INVENTION A rain detecting device according to the present invention comprises: a light emitting means for emitting light (not limited to visible light); a transparent body for reflecting a part of the light from the light emitting means;
A light receiving unit that receives light from the light emitting unit reflected by the transparent body and outputs an output according to a received light amount; a first capacitor connected to the light receiving unit and averaging an output from the light receiving unit; Connected to the first capacitor,
Inverting amplification means for inverting and amplifying the output from the capacitor,
Connected to the first capacitor via the inverting amplification means,
A second determining a voltage applied to the light-emitting means from a light-emitting power source in accordance with the inverted and amplified output of the first capacitor;
And a comparator configured to compare an output of the first capacitor and an output of the second capacitor, which is inverted and amplified by the inverting amplifier, and output a signal based on the comparison result. As a preferred embodiment, an intermittent means for intermittently switching the output of the second capacitor in accordance with an oscillator is provided between the second capacitor and the light emitting power supply, Such a configuration of the apparatus is used as a means for solving the above-described conventional problem.

[0009]

[Operation of the present invention] In the rain detector according to the present invention,
Noise is removed by averaging the output from the light receiving means by the first capacitor connected to the light receiving means, and the second capacitor connected to the first capacitor via the inverting amplifying means is inverted and amplified by the first capacitor. The voltage of the light emitting means is determined according to the output from the capacitor. That is, when the output from the light receiving means decreases, the voltage applied to the light emitting means is increased to increase the amount of light emitted by the light emitting means so that the output from the light receiving means is always constant. Since the feedback control is performed so that the amount of received light is always constant, the transmittance or reflectance of the light changes due to the change in the material of the transparent body that reflects the light from the light emitting means to the light receiving means or the contamination. Even so, there is no change in the amount of light received by the light receiving means, and the need for sensitivity adjustment is eliminated.

The output of the first capacitor, which has been inverted and amplified, and the output delayed by the second capacitor are compared by the comparing means to detect a change in the rate of change of the amount of light. The detection of raindrops attached to the surface of the body is performed with high responsiveness and high sensitivity.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a rain detection device according to an embodiment of the present invention. In this embodiment, the rain detection device is connected to a wiper device of an automobile to detect raindrops. This is an example in which the wiper is automatically operated intermittently.

The rain detecting device 1 shown in FIG. 1 receives an infrared ray from a light emitting diode 3 reflected by an infrared light emitting diode 3 as a light emitting means and a windshield 4 used as a transparent body in this embodiment. A raindrop detector 2 provided with an infrared photodiode 5 as a light receiving means for performing output in accordance with the amount; and an amplifier connected to the infrared photodiode 5 of the raindrop detector 2 to amplify an output from the photodiode 5. A circuit 6 and a first capacitor 7 connected to the infrared photodiode 5 via the amplifier circuit 6 and averaging the amplified output from the photodiode 5
And an inverting amplifier circuit (inverting amplifier means) connected to the first capacitor 7 for inverting and amplifying the output from the first capacitor 7; The second capacitor 9 determines a voltage to be applied to the infrared light emitting diode 3 of the raindrop sensing unit 2 via the light emitting power supply 10 in accordance with the output of the first capacitor 7 and the first capacitor 7 inverted and amplified by the inverting amplifier circuit 8. The output of the second capacitor 9 is compared with the output of the second capacitor 9.
A comparison circuit 11 (comparing means) for outputting a wiper driving signal to the wiper device W when the output of the first capacitor 7 that has been inverted and amplified is larger than the output of the first capacitor 7 is provided. In the example, an intermittent circuit 12 (intermittent means) is connected between the second capacitor 9 and the light-emitting power supply 10, and the output from the second capacitor 9 is intermittent based on a pulse of a predetermined frequency from the oscillator 13. As a result, a pulse voltage is applied from the light emitting power source 10 to the infrared light emitting diode 3 to cause the light emitting diode 3 to blink at a high speed, thereby distinguishing light from the infrared light emitting diode 3 from disturbance light such as sunlight. It is supposed to.

As shown in FIG. 2, the raindrop sensing unit 2 comprises:
The infrared light emitting diode 3 and the infrared photodiode 5 are provided in the vehicle interior immediately below the windshield 4,
In this embodiment, a convex lens 3a is provided between the infrared light emitting diode 3 and the windshield 4, so that the infrared light from the infrared light emitting diode 3 is collected.

As shown in FIG. 2, the infrared light emitting diode 3 and the infrared photodiode 5 emit infrared light emitted from the infrared light emitting diode 3 and reflected on the outer surface 4a of the windshield 4 while being converged by the convex lens 3a. The light enters the room and the infrared photodiode 5
Is arranged so as to be condensed at a central portion of the front glass 4, and the output from the photodiode 5 is maximized in this state where no raindrops adhere to the outer surface 4a of the windshield 4.

The output from the infrared photodiode 5 is amplified by the amplifier circuit 6 shown in FIG. 1, averaged by the first capacitor 7, and then inverted and amplified by the inverting amplifier circuit 8, and is output from the inverting amplifier circuit 8. Is input to the comparison circuit 11 and the second capacitor 9 and is compared with the output from the second capacitor 9 in which the delay has occurred.
In the state where no raindrops are attached, there is no change in the output from the photodiode 5 and there is no difference between the output value from the inverting amplifier circuit 8 and the output value from the second capacitor 9. There is no signal output.

In this state, when the raindrop D adheres to the outer surface 4a of the windshield 4, as shown in FIG. 3, the amount of infrared rays incident on the raindrop D at the boundary between the windshield 4 and the raindrop D increases, At the boundary surface, the amount of infrared rays reflected on the windshield 4 and entering the vehicle interior decreases, and the output from the infrared photodiode 5 decreases. When the output from the infrared photodiode 5 decreases, the output from the first capacitor 7 decreases, and the output from the inverting amplifier circuit 8 obtained by inverting the output increases. Therefore, the output value of the inverting amplifier circuit 8 becomes Since the output value is larger than the delayed output value from the second capacitor 9, the wiper drive signal is output from the comparison circuit 11, and based on this, the wiper device W operates and the wiper blade makes one reciprocation.

When the output of the second capacitor 9 increases, the voltage applied from the light-emitting power supply 10 to the infrared light-emitting diode 3 increases.
And the amount of infrared light emitted from the infrared photodiode 5 returns to the same level as before the attachment of the raindrop D. At this time, the output from the infrared photodiode 5 increases, and a difference occurs between the output value from the inverting amplifier circuit 8 and the output value from the second capacitor 9. Therefore, the wiper drive signal is not output from the comparison circuit 11.

In this embodiment, an example is shown in which the rain detection device is connected to a wiper device of an automobile, and the windshield of the automobile is used as a transparent body that receives raindrops and reflects light. It can also be placed on a car roof or hood using a separate glass or acrylic plate. Further, the rain detection device can be used not only for an automatic wiper device of an automobile but also for automatically closing a skylight of a house or a greenhouse at the time of rain, for example.

[0020]

As described above, the rain detecting device according to the present invention is connected to the first capacitor through the above configuration, particularly, the inverting amplifier, and emits light according to the output of the inverted and amplified first capacitor. Means for comparing the output of the first capacitor, which has been inverted and amplified, with the output of the second capacitor, and generating a signal based on the comparison result. Since the light emission of the light-emitting means is controlled so that the light reception of the light-receiving means is always constant, the sensitivity can be adjusted even if the material of the transparent body such as the windshield is changed or the transparent body becomes dirty. Is not necessary, and the first capacitor and the second
Since the change in the rate of change in the amount of light is detected by the condenser, an excellent effect of being able to detect raindrops attached to the surface of the transparent body with high responsiveness and high sensitivity is provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a rain detection device according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing a structure and an optical path of a raindrop sensing unit of the rain detection device shown in FIG.

FIG. 3 is a schematic explanatory view showing an optical path when raindrops adhere to the raindrop sensing unit shown in FIG. 2;

FIG. 4A is a schematic explanatory view showing a structure and an optical path of a raindrop sensing unit in a conventional rain detection device. (B) It is a block diagram showing the composition of the conventional rain detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rain detection device 3 Infrared light emitting diode (light emitting means) 4 Window glass (transparent body) 5 Infrared photodiode (light receiving means) 7 First capacitor 8 Inverting amplifier circuit (inverting amplifier means) 9 Second capacitor 10 Light emitting power supply 11 Comparison Circuit (comparison means) 12 Intermittent circuit (intermittent means) 13 Oscillator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/00-21/01 G01N 21/17-21/61

Claims (2)

(57) [Scope of request for utility model registration] A light emitting unit that emits light; a transparent body that reflects a part of the light from the light emitting unit; and a light receiving unit that receives light from the light emitting unit reflected by the transparent body and outputs an output according to a received light amount. And a first capacitor connected to the light receiving means and averaging the output from the light receiving means; and an inverting amplifying means connected to the first capacitor and inverting and amplifying the output from the first capacitor. Connected to the first capacitor via the inverting amplification means,
A second determining a voltage applied to the light-emitting means from a light-emitting power source in accordance with the inverted and amplified output of the first capacitor;
A capacitor, and comparing means for comparing the output of the first capacitor and the output of the second capacitor inverted and amplified by the inverting amplifying means, and outputting a signal based on the comparison result. Detection device. 2. The rain detection device according to claim 1, further comprising an intermittent means for intermittently switching the output of the second capacitor according to an oscillator, between the second capacitor and the light emitting power supply.