JPH0733185Y2 - Ultrasonic detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a wave-transmitting element that transmits an ultrasonic wave, and a reflected wave that the ultrasonic wave transmitted from the wave-transmitting element hits a detection object and is reflected. The present invention relates to an ultrasonic detection device that is separately provided with a wave receiving element and that determines the presence or absence of a detection object and the distance to the detection object.

[Conventional technology]

FIG. 3 is a block diagram of a conventional ultrasonic wave detection device including this type of transmitting element and receiving element.

In FIG. 3, a drive circuit 1 which emits electric vibration of a predetermined frequency f is connected to a wave transmission element 2 having a resonance frequency of a frequency f. The wave receiving element 3 having the frequency f as a resonance frequency is connected to the amplification circuit 4 of the signal processing circuit 20, the output of the amplification circuit 4 is connected to the amplitude modulation circuit 5, and the output of the amplitude modulation circuit 5 is the determination circuit. Connected to 6.

The electric vibration oscillated by the drive circuit 1 is transmitted from the wave transmitting element 2 toward the detection object 7 to be detected, reflected from the detection object 7 and received by the wave receiving element 3 to be converted into electric vibration. After being amplified by the amplifier circuit 4, the amplitude is modulated by the amplitude modulation circuit 5 and input to the determination circuit 6. In the judgment circuit 6,
The presence or absence of the detection object 7 is determined from the received ultrasonic wave, and the distance from the transmission element 2 to the reception element 3 to the detection object 7 is determined.

[Problems to be solved by the device]

Since the ultrasonic wave transmitted from the wave transmitting element 2 is diffused, as shown in FIG. 4, when the electric vibration E is transmitted from the wave transmitting element 2 as the ultrasonic wave, the wave transmitting element 3 is transmitted to the wave receiving element 3. The diffracted wave S ₁ that directly reaches the wave receiving element 3 from ₂ and the reflected wave S ₂ that is reflected by the detection object 7 and reaches the wave receiving element 3 are received, and the diffracted wave S ₁ is received. When it is received by the element 3, the diffracted wave S ₁
The reflected wave S ₂ is used to determine the presence or absence of the detection object 7 and the distance to the detection object 7. Thus time slot times析波S ₁ is incident on the wave receiving element 3 is not to determine the times析波S ₁ as the dead band as the signal, thus detecting the detection object 7 at a distance closer to the transmitting element 2 Has the disadvantage that it is impossible.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the conventional device and to provide an ultrasonic detection device capable of reliably detecting a detection object existing at a short distance.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention provides a wave transmitting element for transmitting an ultrasonic wave, and a wave receiving element for receiving a reflected wave reflected by the ultrasonic wave transmitted from the wave transmitting element entering a detection object. In an ultrasonic detection device having an element arranged in parallel, a reflection surface is provided on the ultrasonic detection device, and the direction of the reflection surface is transmitted from the wave transmission element, and the ultrasonic wave reflected by the reflection surface is received by the reception surface. Set to face the wave element, a value obtained by subtracting the dimension from the transmitting element to the receiving element from the sum of the dimension from the transmitting element to the reflecting surface and the dimension from the reflecting surface to the receiving element. The dimension divided by 2 is 1/4 of the wavelength of the ultrasonic wave or the sum of 1/4 of this wavelength and an integral multiple of 1/2 of this wavelength.

[Action]

In the present invention, when there are a plurality of ultrasonic receiving signals,
Focusing on the occurrence of interference depending on the conditions, a reflection surface that reflects the ultrasonic waves from the wave transmission element is provided in the vicinity of the wave transmission element, and the ultrasonic waves reflected by hitting this reflection surface are received by the wave reception element. In this way, interference is caused between this reflected wave and the diffracted wave, and the diffracted wave is canceled by the reflected wave from the reflecting surface.
By using only the ultrasonic waves reflected by the detection object as the determination signal, it is possible to detect the detection object at a short distance.

〔Example〕

FIG. 1 is a block diagram of an ultrasonic detecting device showing an embodiment of the present invention, and the same parts as the conventional device shown in FIG. 3 are designated by the same reference numerals. In FIG. 1, the drive circuit 1,
Each element circuit such as the wave transmitting element 2, the wave receiving element 3, the amplifying circuit 4, the amplitude modulating circuit 5, the judging circuit 6 and the like is exactly the same as the conventional one, and therefore its explanation is omitted.

The embodiment shown in FIG. 1 is different from the conventional device shown in FIG. 3 in that an ultrasonic wave detecting device 9 is provided with a reflecting surface 8 which reflects the ultrasonic wave transmitted from the wave transmitting element 2. This is a point formed so as to be reflected and incident on the wave receiving element 3. Therefore, the reflecting surface 8 is set so that its direction is transmitted from the transmitting element 2 and the ultrasonic waves reflected by the reflecting surface 8 are directed toward the receiving element 3. Therefore, when the ultrasonic wave transmitted from the wave transmitting element 2 hits the reflecting surface 8 and is reflected, the reflected wave enters the wave receiving element 3. The position of the reflecting surface 8 is obtained by subtracting the dimension from the transmitting element 2 and the receiving element 3 from the sum of the dimension from the transmitting element 2 to the reflecting surface 8 and the dimension from the reflecting surface 8 to the receiving element 3. The value is divided by 2, that is, the dimension L divided by 2 is the sum of 1/4 of the wavelength λ of ultrasonic waves or 1/4 of the wavelength λ and an integral multiple of 1/2 of this wavelength λ. It is a thing.

In this ultrasonic detecting device, as shown in FIG.
When the electric vibration E output from the driving device 1 is transmitted from the wave transmitting element 2 as ultrasonic waves, the diffracted wave S ₁ shown by the solid line and the reflected wave S that is reflected by the detection object 7 and reaches the wave receiving element 3. ₂
In addition, a reflected wave S ₃ overlapping the diffracted wave S ₁ is generated with a phase difference of 180 degrees from the diffracted wave S ₁ as shown by the dotted line. This is because the value obtained by subtracting the dimension between the wave transmitting element 2 and the wave receiving element 3 from the sum of the dimension from the wave transmitting element 2 to the reflecting surface 8 and the dimension from the reflecting surface 8 to the wave receiving element 3 is 2. The dimension divided by is the wavelength λ
This is because the time difference between the diffracted wave S ₁ and the reflected wave S ₃ is a round trip of the dimension L, that is, the phase shifts by 180 degrees. Therefore, the diffraction wave S ₁ interferes with the reflected wave S ₃ and disappears by appropriately selecting the area of the reflecting surface 8 so that the sound volumes of the diffracted wave S ₁ and the reflected wave S ₃ become equal. Therefore, the detection object 7 located at a short distance from the ultrasonic wave detection device 9 can be surely detected without being disturbed by the diffraction wave S ₁ .

In the embodiment shown in FIG. 1, the dimension L of the reflecting surface 8 is
Although it is set to 1/4, this dimension L is not only 1/4 of the wavelength λ but also the wavelength λ
May be the sum of 1/4 of the above and 1/2 of the wavelength λ. This is because the L dimension where interference occurs
This is because the dimensions for 1/2 wavelength have been added. However, if the L dimension is made too long, a difference occurs between the reception time of the diffracted wave S ₁ and the reception time of the reflected wave S ₃ , so that the reflecting surface 8 is a wave transmitting / receiving element of a case accommodating the ultrasonic detecting device. It is convenient to install it on the side.

[Effect of device]

As described above, according to the present invention, a transmitting element that transmits an ultrasonic wave and a receiving element that receives a reflected wave reflected by the ultrasonic wave transmitted from the transmitting element when entering the detection object. In an ultrasonic detection device having a wave element arranged in parallel, the ultrasonic detection device is provided with a reflecting surface, the direction of the reflecting surface is transmitted from the wave transmitting element, and the ultrasonic wave reflected by the reflecting surface is A value obtained by subtracting the dimension from the transmitting element to the receiving element from the sum of the dimension from the transmitting element to the reflecting surface and the dimension from the reflecting surface to the receiving element, which is set to face the receiving element. Is divided by 2 so that the dimension is equal to 1/4 of the wavelength of the ultrasonic wave or 1/4 of this wavelength and an integral multiple of 1/2 of this wavelength. The diffracted wave directly incident on the wave element and the reflected wave from the reflecting surface are interfered with each other so that the diffracted wave is reflected by the reflecting surface. It is possible to eliminate killing,
As a result, there is an effect that the detection object existing in a short distance can be surely detected by eliminating the interference by the diffraction wave. Further, since the reflecting surface can be easily formed by molding etc. by utilizing a part of the case of the ultrasonic detecting device,
It is possible to provide an ultrasonic detection device with high detection accuracy without increasing costs.

[Brief description of drawings]

1 and 2 respectively show an embodiment of the ultrasonic detecting apparatus of the present invention, FIG. 1 is a block diagram thereof, FIG. 2 is a waveform diagram of the main part of FIG. 1, and FIG. 4 and FIG. 4 respectively show an example of a conventional ultrasonic wave detecting device, FIG. 3 is a block diagram thereof, and FIG. 4 is a waveform diagram of a main part of FIG. 2: Wave transmitting element, 3: Wave receiving element, 7: Detection object, 8: Reflecting surface, 9: Ultrasonic wave detection device.

Claims (1)

[Scope of utility model registration request] 1. A wave-transmitting element for transmitting an ultrasonic wave and a wave-receiving element for receiving a reflected wave reflected by the ultrasonic wave transmitted from the wave-transmitting element incident on a detection object are arranged in parallel. In the ultrasonic detecting device, the ultrasonic detecting device is provided with a reflecting surface, the direction of the reflecting surface is transmitted from the wave transmitting element, and the ultrasonic wave reflected by the reflecting surface is directed toward the wave receiving element. Set,
The dimension obtained by subtracting the dimension from the transmitting element to the receiving element from the sum of the dimension from the transmitting element to the reflecting surface and the dimension from the reflecting surface to the receiving element by 2 is the ultrasonic wave. 1/4 of this wavelength or 1/4 of this wavelength and 1 / of this wavelength
An ultrasonic detection device characterized in that the sum is an integer multiple of 2.