JPH09127071A - Waterdrop detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a waterdrop detection apparatus which can be applied to plates other than a transparent plate and which is hardly affected by a disturbance by comparing a reception intensity inside a prescribed time width with a reference value, and outputting the detection result. SOLUTION: When a waterdrop D exists on the propagation route of ultrasonic surface waves oscillated from an ultrasonic element 12, the surface waves are reflected by the waterdrop D, and they are returned to the element 12 so as to be received. When the waterdrop D is stuck within a detection range, a waterdrop echo DE which is reflected by the waterdrop D, is abserved in addition to an edge echo TE. The size of the waterdrop D, i.e., whether the stuck waterdrop is approximately a waterdrop in the size of a fog or approximately a waterdrop in the size of a raindrop, is judged by a computing and control circuit. In addition, gates which are used to monitor respective voltages are set so as to correspond to respective observation positions, and the level of the waterdrop echo DE and that of the edge echo TE are monitored by the respective gates. Then, the reference value of every gate is set, a reception intensity detected by every gate is compared with the level, and the size of the waterdrop D is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water drop detecting device for detecting water drops and cloudiness attached to a surface to be detected by utilizing ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, various types of water drop detecting devices using optical means as shown in FIG. 8 have been proposed. For example, in the water droplet detection device disclosed in Japanese Patent Laid-Open No. 59-44641, as shown in FIG. 8, the light emitting element 1 and the light receiving element 2 are arranged on the surface of the transparent plate 3 opposite to the surface to be detected 4. The light emitted from the light receiving element 1 is totally reflected inside the transparent plate 3 and is incident on the light receiving element 2 when no water droplets are attached to the detected surface 4. When water droplets adhere to the surface to be detected 4, the reflection of light from the light emitting element 1 changes at the water droplet adhered portion, the amount of light incident on the light receiving element 2 decreases, and the light receiving level decreases. Adhesion of water droplets can be detected from this decrease in the light receiving level.

[0003]

However, since this type of water drop detection device is of an optical type, it can be applied only to a transparent plate, is greatly affected by disturbance (ambient light), and has a small detection area. There were problems such as strict adjustment of the optical axis.

In consideration of the above circumstances, the present invention can be applied to other than a transparent plate, is not easily affected by disturbances such as ambient light, has a wide detection area, and does not require strict position adjustment when mounting. An object of the present invention is to provide a water drop detection device having a simple structure.

[0005]

According to a first aspect of the present invention, there is provided a water drop detecting device for detecting a water drop adhering to a surface to be detected, the device being mounted on the surface to be detected. Ultrasonic wave transmitting / receiving means for transmitting an ultrasonic surface wave propagating through and receiving a reflected wave thereof, monitoring the time from the transmission of the ultrasonic surface wave to the reception and the reception intensity of the reflected wave, and An arithmetic circuit for comparing the reception intensity within the time width with a reference value and outputting a detection result.

The water drop detecting device of the invention of claim 2 is a device for detecting water drops adhering to the surface to be detected, which is attached to the back surface of the surface to be detected and transmits an ultrasonic plate wave. An ultrasonic wave transmitting / receiving means for receiving a reflected wave, and monitoring the time from the transmission of the ultrasonic plate wave to the reception and the reception intensity of the reflected wave,
And an arithmetic circuit that compares the reception intensity within a predetermined time width with a reference value and outputs a detection result.

According to a third aspect of the present invention, in the water drop detecting apparatus according to the first or second aspect, a plurality of the predetermined time widths are provided at time intervals, and a reference value is set for each time width. Is characterized by.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. The water droplet detection apparatus of the first embodiment detects a water droplet adhering to the surface of a material by using a reflected wave (hereinafter referred to as an echo) of a surface wave which is one mode of a propagation mode of ultrasonic waves. As shown in FIG. 1, this water drop detecting device includes an ultrasonic element 12 which is an ultrasonic wave transmitting / receiving means attached to a surface 11 to be detected of a material 10, and an ultrasonic element 12.
Connected to the transmission / reception circuit 13 for switching the transmission mode and the reception mode of the ultrasonic element 12 at predetermined intervals, and measuring the time from transmission to reception and comparing the reception wave intensity with a reference value and outputting the calculation result. Arithmetic control circuit 14 for
The calculation control circuit 14 is composed of a raindrop removing device 15 which operates in response to a control signal generated when water droplets are detected.

Here, the ultrasonic surface wave is an ultrasonic wave that propagates in the vicinity of the surface of the surface 11 to be detected (a portion from the surface to a height corresponding to the amplitude of the ultrasonic wave), and the acoustic matching of the ultrasonic element 12 is performed. It can be generated by adjusting and arranging the layer so that the refraction angle with respect to the detected surface 11 becomes 90 degrees. It is known that the incident / reflecting mode of ultrasonic waves between different kinds of media follows Snell's law, and the refractive index is such that ultrasonic waves incident on one medium at an incident angle travel to the other medium. It is defined as the approach angle at time. According to the law, the refraction angle changes depending on the propagation angle of the ultrasonic wave in the medium in addition to the incident angle of the ultrasonic wave, and the propagation speed changes depending on the material forming the medium. It is necessary to set the incident angle in consideration of the combination of media. For example, the ultrasonic element 12 is integrally provided with a waveguide section (not shown) for guiding ultrasonic waves to the surface 11 to be detected, and this waveguide section is generally used as an ultrasonic transmission material. Acrylic resin,
When the detected surface 11 is a window glass of an automobile,
In order to obtain the refraction angle of 90 degrees necessary for generating the surface wave, it is advisable that the ultrasonic wave be incident on the surface 11 to be detected at an angle of about 60 degrees.

In the water drop detecting device configured as described above, when the water drop D exists on the propagation path of the ultrasonic surface wave oscillated from the ultrasonic element 12, as shown in FIG. It is reflected by D, returns to the ultrasonic element 12, and is received. In the figure, N is a pulsed transmission wave, and is observed after the generation of the transmission wave N and after the echo DE has passed a time corresponding to the attachment position of the water droplet D (distance from the ultrasonic element 12).

By the way, when the water drop detecting device is applied to a surface 11 to be detected having a finite size, such as a rearview mirror or a window glass of an automobile, as shown in FIG. It is reflected by the end surface T and returns to the ultrasonic element 12. Therefore, the detection range P of the water droplet detection device is an area (hatched portion in the figure) obtained by multiplying the width W of the wave transmitting surface of the ultrasonic element 12 by the distance L to the end T. When the water droplet D does not exist in the detection range P, the ultrasonic surface wave oscillated from the ultrasonic element 12 is always reflected by the end surface T of the detected surface 11 and returns to the ultrasonic element 12. Since the detected surface 11 is finite, the end surface echo TE (see FIG. 4), which is a reflected wave, is observed at a constant position on the time axis and with a constant intensity.

However, in the case where the water droplet D adheres within the detection range P, as shown in FIG.
In addition to E, the water drop echo DE reflected by the water drop D is observed. At this time, since the intensity of the ultrasonic surface wave oscillated from the ultrasonic element 12 is constant, the reception intensity of the end surface echo TE is lower than that when there is no water droplet D. Since this amount of decrease is proportional to the size and amount of the water droplet D, the size and amount of water droplet D can also be estimated from the amount of decrease in the reception intensity of the water droplet echo DE or the reception intensity of the end face echo TE. That is, as shown in FIG. 4, when the water droplet D has a small diameter ((a) in the figure), the reception intensity of the water droplet echo DE is low, and when the water droplet D has a large diameter ((b) in the figure). , The reception intensity of the water drop echo DE increases, and the reception intensity of the end face echo TE decreases. However, the position of the end surface echo TE on the time axis does not change.

The calculation process for determining the size of the water droplet D, that is, whether the water droplet D is cloudy or rainy is attached will be described in detail below. This arithmetic processing is performed in the arithmetic control circuit 14. The position on the time axis at which the end surface echo TE is observed is defined by the shape and dimensions of the detected surface 11, and is observed at a fixed position. Also,
The water drop echo DE is also observed within the detection range P, that is, between the end surface echo TE and the transmitted wave N on the time axis. Therefore,
As shown in FIG. 5, a gate for monitoring the voltage is set corresponding to each position, and the level (reception intensity) of the water drop echo DE and the end surface echo TE is monitored at each gate. Here, the gate of the detection range P is set to GA
TE1 and the gate of the end face T are GATE2. Then, the reference value of each gate (threshold for distinguishing between Hi and Lo)
Is set and the level is compared with the reception intensity detected at each gate, so that the size of the water droplet D can be detected. For example, as shown in FIG. 6, when the reference value of GATE1 is G1 and the reference value of GATE2 is G2, when there is no water droplet D in the detection range P, the water droplet echo DE is not observed and only the end surface echo TE is observed. GATE1 is Lo from the comparison with G1 and GATE2 is Hi from the comparison with G2.
Becomes Further, when the water droplet D is in the detection range P, the water droplet echo DE and the end surface echo TE reflected by the end surface T without hitting the water droplet D are observed, and GATE1 and GATE are obtained.
2 becomes Hi, the control signal is output from the arithmetic and control circuit 14 to the raindrop removing device 15 (see FIG. 1), and the raindrop removing device 15 operates.

Here, the waveform observed in GATE 1 varies depending on the size of the water droplet D and the adhered state. That is, when the water droplets D have a relatively large diameter and are scattered, relatively large peaks exceeding G1 are observed at a distance of the number of water droplets attached in the detection range P (in the figure). , Center column). Further, since the time axis corresponds to the distance from the ultrasonic element 12, the attachment position of the water droplet D can also be detected from this time axis. In addition, when a large number of minute water droplets M are distributed and attached like cloudy weather or fog, innumerable water droplet echoes DE having a level lower than G1 are observed and end face echo TE is hardly observed. GATE1, GATE2
Both become Lo. Here, GATE2 becomes Lo,
The transmitted wave is repeatedly attenuated by countless water droplets D, and the end surface T
Because it cannot reach to. Therefore, G1
As for the level of, the reception intensity by the water droplet M such as cloudy or fog is experimentally obtained, and is set to a level higher than that, and G2 is set.
Is preferably set to be lower than the reception intensity of the water droplet M such as cloudy weather or fog. Although the levels of G1 and G2 are different in FIG. 6, they may be at the same level if the above relationship is satisfied.

As described above, by monitoring the levels of GATE1 and GATE2, it is possible to detect not only the presence or absence of the water droplet D but also the size and the adhesion state of the water droplet D, and the raindrop removing device 15 is controlled more finely. be able to. This is because, for example, in an automobile, various raindrop removing devices 15 are detected depending on the state of water drops, such as automatically detecting the rainfall and automatically activating the wiper, detecting the cloudiness of the window and automatically activating the heater. It is possible to automatically switch and operate.

In the above embodiment, the case where the ultrasonic surface wave is used for detection has been described. However, when the material 10 is a thin plate material such as glass or a mirror, other propagation of the ultrasonic wave is used instead of the ultrasonic surface wave. Similar water drop detection is possible using the mode "ultrasonic wave". When ultrasonic waves are incident on the thin material 10, as shown in FIG. 7, in addition to ultrasonic waves propagating on the element mounting surface of the material 10, ultrasonic waves propagating on the back surface of the mounting surface are generated. The ultrasonic wave that propagates on both the front and back surfaces of the material 10 is called an ultrasonic plate wave. The water droplet detection principle of the second embodiment using this ultrasonic plate wave is the same as the detection principle in the above-mentioned water droplet detection device using an ultrasonic surface wave, and detects an echo due to a water droplet. When this ultrasonic plate wave is used, the ultrasonic element 12 is attached to the surface 11 to be detected.
Since it can be disposed on the back surface of the vehicle, it can be disposed, for example, inside the housing of the door mirror of the automobile or on the side of the window glass in the passenger compartment, which is advantageous in terms of freedom of installation and prevention of damage to the device.

[0017]

As described above, according to the water drop detecting device of the present invention, the water drops are detected by using the ultrasonic surface wave or the plate wave. Therefore, regardless of whether the material is a transparent body or not. Instead, it is possible to detect water drops. Moreover, it is also possible to detect the size and the adhered state of the water droplets, and the optimum control of the raindrop removal device can be automatically realized. Further, when the ultrasonic plate wave is used, the ultrasonic element can be arranged on the back surface of the surface to be detected, which is advantageous in terms of freedom of installation and prevention of damage to the device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a detection principle of the first embodiment.

FIG. 3 is an explanatory diagram of a detection range according to the first embodiment.

FIG. 4 is an explanatory diagram showing a difference in observed waveform depending on the size of water droplets in the first embodiment.

FIG. 5 is an explanatory diagram of the principle of detecting the size of water droplets in the first embodiment.

FIG. 6 is a diagram showing a relationship between a water droplet adhesion state and an observed waveform in the first embodiment.

FIG. 7 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a conventional water drop detection device.

[Explanation of symbols]

 11 Detected Surface 12 Ultrasonic Element 14 Calculation Control Circuit 15 Rain Drop Removal Device D Water Drop DE Water Drop Echo TE Edge Echo

Claims (3)

[Claims] 1. An apparatus for detecting water droplets adhering to a surface to be detected, which is mounted on the surface to be detected, transmits an ultrasonic surface wave propagating on the surface to be detected, and reflects it. An ultrasonic wave transmitting / receiving unit for receiving a wave, monitoring the time from the transmission of the ultrasonic surface wave to the reception and the reception intensity of the reflected wave, and comparing the reception intensity within a predetermined time width with a reference value to calculate. A water droplet detection device comprising: an arithmetic circuit that outputs a result. 2. A device for detecting water droplets adhering to a surface to be detected, which is attached to the back surface of the surface to be detected, transmits and receives an ultrasonic plate wave, and receives the reflected wave. Means, and an arithmetic circuit for monitoring the time from the transmission of the ultrasonic plate wave to the reception and the reception intensity of the reflected wave, and comparing the reception intensity within a predetermined time width with a reference value and outputting a calculation result. A water drop detection device comprising: 3. The water droplet detection device according to claim 1, wherein a plurality of the predetermined time widths are set at time intervals, and a reference value is set for each time width.