JPS6333180Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved snow detector.

Conventional devices of this type emit ultrasonic waves with relatively long wavelengths (frequency of about several tens of kHz) into the air, and measure the height of the snow surface using the ultrasonic waves that reflect back from the snow surface. The presence or absence of snow was detected by measuring it. However, conventional devices of this type have the disadvantage that they may malfunction due to ultrasonic waves (disturbances) generated elsewhere or foreign objects on the ground surface.

The inventor of the present invention focused on the fact that ultrasonic waves with a frequency of several hundred kHz to several MHz are significantly absorbed in the air. In this state, ultrasonic waves are absorbed in the air and there are almost no reflected waves, but when snow accumulates, ultrasonic waves propagate through the snow and the reflected waves become large, so the detection circuit detects the reflected waves. The purpose of the present invention is to provide a snow detector that can prevent malfunctions caused by ultrasonic waves or foreign objects generated elsewhere by determining the presence or absence of a snow detector. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which 1 is a piezoelectric element (transducer) provided with electrodes 2 on both sides, and 3 is an acoustic impedance between the transducer 1 and the snow. 4 is a bucking member made of a material having a large ultrasonic absorption effect and damping effect, 5 is a detection circuit, 6 is snow, 7 is a water drain hole 8 provided on the bottom surface. It is a snow box. Here, the end wall surface 7a of the snow box 7 is used as a reflector to reflect ultrasonic waves, and the thickness of the acoustic matching layer 3 is set to be λ/4 when the wavelength of the ultrasonic waves is λ. selected. Furthermore, in this example,
The transducer 1 is supported by a bucking member 4, but instead of providing such a bucking member 4, acoustic matching layers are provided on both sides of the transducer 1 so that ultrasonic waves are emitted from both sides of the transducer. Alternatively, the transducer 1 may be supported from the side or the bottom. In this case, it is important that the support member supports the transducer 1 so that the ultrasonic waves are not reflected.

Next, the operation of this embodiment configured as above will be explained. First, when there is snow 6 in the snow box 7 as shown in FIG. The waves are converted into ultrasonic waves and emitted into the snow 6 through the acoustic matching layer 3. This ultrasonic wave is efficiently emitted into the snow 6 because of the acoustic matching layer 3. The ultrasonic wave propagates through the snow 6, is reflected by the end wall surface 7a, propagates through the snow 6 again, enters the transducer 1, and is converted into an electrical signal. The presence of snow is detected by the detection circuit 5 detecting this electric signal. Second
The figure shows the state of electrical signals between the electrodes 2. As shown in FIG. 2, the first emitted ultrasonic wave is attenuated and disappears immediately after being generated by the bucking member 4, so that it does not overlap with the reflected wave. In addition, in FIG. 2, t indicates the time from when the ultrasonic wave is emitted until the reflected wave is incident. This time t is the distance between the transducer 1 and the end wall surface 7a, and Letting v be the speed at which the ultrasonic wave propagates, it can be expressed as t=2d/v.

Next, when there is no snow in the snow box 7, the ultrasonic waves generated by the transducer 1 have a short wavelength;
Furthermore, since the acoustic impedance of air is much smaller than that of snow, this ultrasonic wave does not propagate efficiently through the air, and therefore almost no reflected waves are incident.

In this embodiment, only one acoustic matching layer 3 is provided, but if multiple acoustic matching layers 3 are provided to form a multilayer matching layer, ultrasonic waves can be emitted more efficiently into the snow 6. can do.

As described above, the present invention has an advantage not found in the prior art in that it is possible to accurately detect the presence or absence of snow without causing malfunctions due to ultrasonic waves or foreign objects generated elsewhere.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is a diagram showing the state of ultrasonic waves emitted from or incident on the transducer. 1...transducer, 2...electrode, 3...
Acoustic matching layer, 4... Bucking member, 5... Detection circuit, 6... Snow, 7... Snow box, 7a... End wall surface, 8... Water drain hole.

Claims (1)

[Claims for Utility Model Registration] An ultrasonic signal generator that generates an electrical signal in a frequency band in which output ultrasonic waves are attenuated more in the air than in snow, and converts this signal into an output ultrasonic wave at the frequency. and a transducer that reconverts input ultrasonic waves into electrical signals; a reflector provided opposite the transducer; and an acoustic matching provided on a surface of the transducer facing the reflector. layer, and a detection circuit that detects the amplitude of the input ultrasonic wave reflected by the reflection plate, and detects the amplitude between the acoustic matching layer and the reflection plate depending on whether the amplitude of the input ultrasonic wave is equal to or higher than a predetermined value. A snowfall detector characterized by determining the presence or absence of snowfall.