JP2009025274A - Raindrop quantity detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and low-cost raindrop quantity detector for inhibiting an effect due to an external light, such as a sunlight, properly detecting the raindrop quantity attached on a windshield, and preventing a view of a driver from being blocked since a wiper is intermittently controlled, in response to the raindrop quantity. <P>SOLUTION: A light-emitting section 2 consists of a light-emitting element 21, and a light-emitting prism 22. A light-receiving section 3 consists of a light-receiving element 31, and a light-receiving prism 32. The light-emitting section 2 and the light-receiving section 3 are arrayed horizontally (laterally) on the windshield 5 at an upper part within a vehicle so as to prevent the view of the driver from being blocked. The raindrop quantity detector 1 is mounted and has a small longitudinal dimension. In order to reduce the effects due to the external light, a shape of the light-receiving prism 32 is formed at an angle that is less apt to transmit sunlight, the external light is inhibited by causing only the light-receiving element 31 to receive the light emitted from the light-emitting element 21, and an external light correcting light-emitting element 33 is disposed on the surface of the light-receiving prism 32. Accordingly, the effects due to the external light are eliminated in the light-receiving element 32. The quantity of the light irradiated, scattered and attenuated by the raindrops, attached to the windshield 5, can be detected accurately. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention is mounted on the inner surface of a vehicle windshield, accurately detects the amount of raindrops adhering to the outer surface of the windshield without being influenced by external light such as sunlight, controls the wiper intermittent drive, and The present invention relates to a small and lightweight optical raindrop amount detection device having a simple circuit configuration and a shape that does not impede.

As shown in FIG. 1, a conventional optical raindrop amount detection device 7 includes a light emitting unit 2 and a light receiving unit 3, and the light emitting unit 2 uses a light emitting element such as a light emitting diode (LED) and the emitted light beam as a windshield. The light receiving unit receives light from a light receiving prism that collects the emitted light beam passing through the windshield 5 and a photodiode (PD) that receives light from the light receiving prism. It consists of elements. In the detection device, the light emitting unit and the light receiving unit are arranged on the vehicle inner surface of the windshield 5 at regular intervals to form a light guide path 4, and the light guide is formed by raindrops attached to the vehicle outer surface of the windshield 5. The light receiving unit 3 detects the attenuation amount of the light beam generated by light scattering occurring in the light path 4, calculates the amount of attached raindrops from the attenuation amount, and controls the wiper drive on the windshield 5.

The conventional optical raindrop amount detection device 7 is easy to detect raindrops and reduces the influence of extraneous light such as sunlight coming from the front and front of the vehicle. The light emitting part 1 and the light receiving part 2 are arranged at regular intervals in the vertical direction at the vehicle inner side position corresponding to the uppermost part of the range, and the light guide path 3 is formed in the vertical direction. In such a vertical arrangement method, since the shape of the detection device is increased in the vertical direction, there is a disadvantage that obstructs the driver's view.

Further, in the optical raindrop amount detection method, the light emitting element of the light emitting unit 2 is driven by a high-speed rectangular wave time-series voltage as shown in FIG. 3A to emit light as shown in FIG. A rectangular wave time-series light beam collected by the prism is projected onto the fluorocarbon glass 5. In the light receiving unit 3, the light beam attenuated by scattering by the attached raindrops in the light guide path 4 is collected by the light receiving prism and received by the light receiving element, and a rectangular wave time series as shown in FIG. Get the output signal. The amplitude level of the output signal is close to the power supply voltage Vcc in the section f where the light emitting element in FIG. 3A does not emit light and does not receive light, and in the section n in which the light emitting element emits light and receives light, it depends on the amount of light received. A rectangular waveform with a reduced output amplitude level is obtained. Since the attenuation amount of the light beam fluctuates corresponding to the raindrop adhesion amount, the adhesion raindrop amount can be calculated from the fluctuation amount of the output amplitude level. 3C is a circuit configuration for separating an external light receiving signal whose fluctuation is extremely low as compared with the rectangular wave oscillation number of the light receiving element output of FIG. 3C by a filter, detecting the light receiving element output, and calculating an attenuation amount due to the attached raindrops. Therefore, the number of detection circuit elements is increased, the detection circuit cannot be simply configured, and the shape of the detection device is increased.

As shown in FIG. 1, the conventional detection device 7 has a configuration in which the light guide path is formed in the vertical direction of the windshield. Therefore, the vertical size of the detection device 7 is increased, which hinders the driver's view. .
In the present invention, as shown in FIG. 2, the light emitting unit 2 and the light receiving unit 3 are configured to be installed in the lateral direction on the inner surface of the windshield 5 and the light guide path 4 is formed in the lateral direction. Yes. Thereby, the vertical dimension of the detection apparatus 1 can be shortened, and the driver's view is not obstructed. If the light guide path 4 is taken in the lateral direction, the light receiving unit 3 is likely to receive the extraneous light emitted from the front direction on the vehicle and the amount of received light increases. Is required.

The method of the present invention for solving these problems will be described.
(1) In the raindrop amount detecting device described in claim 1, as shown in FIG. 2, the light emitting unit 2 and the light receiving unit 3 are arranged on the vehicle interior side of the windshield 5 which is the uppermost position of the wiper operating range. The light guide paths 4 are formed in the horizontal direction by being adhered and installed facing each other at a constant interval in the horizontal direction. Thereby, the vertical dimension of the raindrop amount detection device 1 can be reduced, and the driver's view is not obstructed.

On the other hand, when the light guide path is formed in the horizontal direction in this way, the amount of the extraneous light received increases, and it is necessary to suppress the extraneous light reception.
(2) The present invention has the structure shown in FIG. 4 as the raindrop amount detection device for preventing extraneous light according to claim 2, and the amount of attached raindrop is obtained by using a prism configuration having a shape as shown in FIG. There is no need to use a filter circuit for separating the detection signal and the external light receiving signal, thereby simplifying the configuration of the detection circuit and reducing the size, weight and cost of the detection device. As shown in FIG. 4, a rectangular wave time-series light beam shown in FIG. 3B is projected onto the windshield 5 from the light emitting element 21 of the light emitting unit 2 through the projection prism 22. In order to increase the number of reflections in the light guide path 3 within the windshield 5 reaching the light receiving unit 3 and to increase the accuracy of raindrop detection, the incident angle of light incident on the windshield 5 is in the range of 45 degrees to 55 degrees. The shape of the projection prism 22 is formed so that

As shown in FIG. 4, the light receiving prism 32 of the light receiving unit 3 is formed with a prism emission angle in the range of 65 degrees to 75 degrees so as to minimize the reception of extraneous light. Install 31. With such a prism configuration, the amount of extraneous light received by the light receiving element 31 can be reduced, and the ratio of the amount of received light from the light emitting unit 2 can be increased. Therefore, the amount of attached raindrops can be reduced without using a separation filter. Detection accuracy can be improved.

(3) For extraneous light that cannot be prevented only by the shape of the light-receiving prism 32, the present invention is a raindrop amount detection device for correcting extraneous light as set forth in claim 3, and the configuration of the correction method shown in FIG. I have to. FIG. 5 shows a prism configuration similar to that of FIG. 4, except that an extraneous light correcting light emitting element 33 is installed on the surface sandwiching the light receiving element 31 and the light receiving prism 32 as shown in FIG. Flood light.

The extraneous light correction operation with this configuration will be described with reference to FIG. When there is no extraneous light, the output of the light receiving element 31 is a rectangular wave time-series signal having no fluctuation as shown in FIG. 6B, but the extraneous light whose illuminance fluctuates as shown in FIG. 6C. As shown in FIG. 6D, the external light reception amount is superimposed on the light beam reception amount and output as a rectangular wave time-series signal with a varying amplitude level. Since the oscillation frequency of the light beam rectangular wave time series is set at a very high speed compared to the illuminance fluctuation of the external light, the external light illuminance fluctuation is shown by a straight line in FIG.

The correction process for canceling the amplitude level fluctuation caused by the extraneous light is performed as follows. 6A, in the section n where the light emitting element 21 does not emit light, the amplitude level of the light receiving element 32 in FIG. 6D is the amount of received extraneous light, so the amplitude level of the light receiving element 32 is adjusted in the section n. The correction light emitting element 33 is driven in the next section f to generate a light beam having the luminous intensity shown in FIG. 6 (e), and is projected onto the light receiving element 31 through the light receiving prism 32. Since the light beam intensity at this time has an intensity inversely proportional to the illuminance of the external light shown in FIG. 6 (c), the output of the light receiving element 33 is the external light as shown in FIG. 6 (f). The rectangular wave time-series signal is corrected so as to cancel the amplitude fluctuation due to light. By such correction processing, a rectangular wave time-series signal in which level fluctuations caused by the extraneous light are eliminated can be obtained, and the amount of attached raindrop can be accurately calculated.

(4) When the correction method cannot correct the detection level variation due to a change in the direction of the external light irradiation on the windshield caused by a change in the vehicle traveling direction, the present invention provides raindrop amount detection according to claim 4. The apparatus is configured as shown in FIG. In FIG. 7, two detection devices, a detection device 11 and a detection device 12, in which the light emitting unit 2 and the light receiving unit 3 of the detection device 1 shown in FIG. The change amount is compared, and the detection device output with the smaller change amount is selected by the switch 6 to suppress the influence of the irradiation direction change of the external light.

According to the present invention, a small, light and inexpensive optical raindrop detection apparatus capable of accurately detecting the amount of attached raindrops without inhibiting the driver's field of view and suppressing the influence of extraneous light with a simple circuit configuration can be obtained.

Examples of the present invention will be described.

The block diagram of FIG. 8 shows the configuration of the optical raindrop amount detection apparatus described in FIG.
All calculation control processing of the detection device 1 is performed by the CPU 11 (calculation processing device LSI) in FIG. 8, and necessary power is supplied from a battery mounted on the vehicle. A control procedure of the detection apparatus 1 will be described with reference to the configuration diagram of FIG. 8 and the flowchart of FIG.
When the detection apparatus 1 is activated and the control is started, the reference value H is set to the maximum value L and 2/3 of the maximum value L in the initial setting. Next, it is determined whether the light emitting element 21 (hereinafter referred to as the LED 21) is in the light emission section n when the drive is ON or in the non-light emission section f when the drive is OFF, and enters the processing of the next corresponding section.

(1) The following processing is performed when the LED 21 enters the section f where light is not emitted. When the output amplitude of the light receiving element 31 (hereinafter referred to as PD31) is converted into a digital value P by an AD converter 35 (hereinafter referred to as ADC35) and is larger than the preset reference value H, the light emitting element 33 (hereinafter referred to as LED33). ) At a driving voltage value V, light is received by the PD 31 via the light receiving prism 32, and P1 is brought close to the standard value H. An average value M1 of the previous amplitude digital value P is calculated and stored in the memory 12 together with the driving voltage value V at this time.

(2) When the LED 21 enters the light emission section n, the following processing is performed.
In this section, it is determined whether or not it is the end time of light emission. If it is not the end time, the following processing is performed. The average value M1 is compared with the reference value H, and when the value is the same as M1, the driving voltage V of the correction LED 33 is held and emitted. In this state, similarly to (1), the output digital value P of the PD 31 is obtained, and an average value M2 thereof is calculated and stored in the memory 12.

When the LED 21 reaches the end of light emission, the average value M2 is compared with the maximum value L. When the average value M2 is smaller than the maximum value L, the maximum value L is set to the same value as the average value M2. Then, the process described in (1) is entered.
When the average value M2 is larger than the maximum value L, it is determined that there is a raindrop, and a wiper wiping operation instruction is transmitted to the wiper driving unit, and the process proceeds to (1).

The present invention provides a method for reliably detecting the amount of attached raindrops without obstructing the driver's field of view, eliminating the influence of extraneous light, and contributing to the realization of a small, lightweight, and inexpensive raindrop detection device that has fewer components. Thus, the wiper intermittent operation switching can be applied to a wiper automatic control device that eliminates the trouble of manual driving by a driver in rainy weather.

Conventional raindrop detection path Raindrop detection path of the present invention Light emission signal and light reception signal waveform diagram Raindrop detection device Detector with extraneous light correction External light correction processing Detection switching device Raindrop detector block diagram Raindrop detection process flow chart

Explanation of symbols

1 Detection device
11 CPU (arithmetic processing unit)
12 Built-in memory part 2 Light emitting part
21 Light Emitting Element (LED)
22 Projection prism
23 Drive circuit 3 Receiver
31 Light receiving element (PD)
32 Light receiving prism
33 Light emitting element for correction (LED)
34 Receiver circuit
35 AD converter
36 Drive circuit 4 Light guide path 5 Windshield 6 Switching

Claims (4)

Wipe wiper wiper on vehicle windshield The light emitting part consisting of light emitting element and projection prism and the light receiving part consisting of light receiving prism and light receiving element are mounted facing each other at regular intervals in the horizontal direction (lateral direction). Then, a light guide path is formed in the windshield in the horizontal direction (lateral direction) between the light emitting unit and the light receiving unit, and the light emitting element is driven with a pulse voltage to emit light and generate a light beam. The light beam is projected onto the windshield through the projection prism having an incident angle that maximizes the number of reflections on the light guide path, and is scattered and attenuated by raindrops attached to the outer surface of the windshield. The driver's field of view of the light beam received by the light receiving element through the light receiving prism, and the amount of raindrops attached to the windshield is calculated by detecting the attenuation amount of the light beam Shortened raindrop amount detecting apparatus of the vertical dimension so as not to interfere. Since it is installed in the horizontal direction, the light receiving element of the light receiving unit is less likely to receive the extraneous light so that accurate detection of the amount of raindrops is not hindered by the extraneous light received by the light receiving element. A prism surface is formed at an angle to suppress the influence of the extraneous light so that the amount of attached raindrop can be accurately detected without using a filter for separating the beam light and the extraneous light attenuated by the attached raindrop. The raindrop amount detection device according to claim 1, which can be made small and inexpensive with a simple circuit configuration. In order to correct the influence of the extraneous light reception that cannot be suppressed only by the light-receiving prism, an extraneous light correction light-emitting element is installed in contact with the light-receiving prism surface opposite to the installation surface of the light-receiving element in the light-receiving unit. The output amplitude value of the light receiving element is detected and stored as the amount of received extraneous light in the section where the light emitting element is not emitting light, and the external intensity is detected according to the stored amount in the next light emitting section of the light emitting element. The light correction light emitting element emits light, and the light receiving element receives the light to correct the output signal according to the amount of received extraneous light, and correct the influence of the extraneous light without using the extraneous light separation filter. The raindrop amount detection device according to claim 2, wherein the signal is generated so that the amount of the attached raindrop can be accurately detected. Two combinations of the light emitting unit and the light receiving unit of the raindrop amount detection device are installed opposite to each other in the right and left direction, and switched to the combination with less influence of the external light corresponding to the irradiation direction of the external light, The raindrop amount detection device according to claim 3, wherein the amount of attached raindrops can be accurately detected by correcting the influence of extraneous light.

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