JPH01265178A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To decrease an acoustic wave level of a turn-in acoustic wave to a receiver from a transmitter by providing the transmitter and the receiver so that a distance between a main axis of the transmitter and a main axis of the receiver becomes larger as it is separated from the acoustic center. CONSTITUTION:A transmitter 11 and a receiver 12 are attached to a cased 10 so that a distance between each main axis X1, X2 becomes larger as they are separated from the acoustic center. In the case 10, a printed wiring board 13 is stored, and a processing circuit part is mounted together with the transmitter 11 and the receiver 12. In such a way, since the transmitter 11 and the receiver 12 are provided, an acoustic wave level of a turn-in acoustic wave is decreased, and scarcely exerts an influence on a detection area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic sensor using a transmitter and a receiver each comprising an ultrasonic vibrator.

[Conventional technology 1 Conventionally, upstream M sound waves are sent to the detection area, and when the Ni sound waves are reflected by an object existing in the detection area, the reflected wave is received. An N1 sound wave sensor is provided that detects the presence or absence of a sensing object. This type of ultrasonic sensor is formed by housing a transmitter 11 that transmits ultrasonic waves and a receiver 12 that receives ultrasonic waves in a case 10, as shown in Figure M4. There is.

[The section that the invention is trying to solve Ja! l By the way, in the conventional ultrasonic sensor, the transmitter 11 and the receiver 12 are arranged so that the main axes X, X2 are substantially parallel.
Since the ultrasonic waves were stored in the case 10, as shown in FIG. Ultrasonic waves emitted in a direction approximately 90 degrees with respect to X1 also entered the receiving wave 512. In this way, there is an ultrasonic wave that directly wraps around from the transmitter 11 to the receiver 12, and when the sound wave level of the wraparound sound wave becomes higher than the sound wave level of the reflected sound wave at the target object O, it becomes difficult to distinguish between the two sound waves. . Therefore, the detection area can only be set in a range where the sound wave level of the reflected sound wave is higher than the sound wave level of the wraparound sound wave, and a problem has arisen in that the detection area of the conventional configuration is limited.

On the other hand, increasing the distance between the transmitter 11 and the receiver 12, or increasing the distance between the transmitter 11 and the receiver 12, or
It has been considered to prevent the IF waves from going around by arranging devices such as . (There is one question.

The present invention aims to solve the above-mentioned problems, and provides an ultrasonic sensor that reduces the sound wave level of the wraparound sound waves from the transmitter to the receiver.

[Hands for Solving the Problems Fc11] In order to achieve the above object, the present invention arranges a transmitter and a receiver such that the distance between the main axis of the transmitter and the main axis of the receiver increases as the distance from the acoustic center increases. In other words, they are equipped with containers.

[Effect 1] According to the above configuration, since the front directions of the transmitter and receiver face outward from each other, the angle at which the receiver is viewed from the transmitter becomes larger than 90°, and the wraparound sound waves are The sound wave level is reduced.

[Example] First of all, ultrasonic waves used as transmitters and receivers!
! An example of the directivity of R and the mover is shown in FIG. here,
The half-value angle is approximately 80 degrees, and in the direction of 90 degrees with respect to the principal axis direction, it is approximately -20 dB.

Since ultrasonic transducers generally have such directivity, the response tends to become smaller as the angle from the main axis increases up to around 120° with respect to the main axis.

Using this directivity, as shown in Figure 1, the transmitter 1
Case 1 and receiver 12 are arranged such that the distance between the main wheels X, X, increases as the distance from the acoustic center increases.
It is set to 0.

A printed wiring board 13 is housed in the case 10, and a processing circuit section is mounted together with a wave transmitter 11 and a wave receiver n12. Further, the case 10 is open on the front side of the transmitter 11 and the receiver 12, and a protective net 14 that transmits ultrasonic waves is attached to this opening. Transmitter 11
The main axes X, X2 of the receiver 12 have an inclination of θ with respect to the front direction of the case 30, respectively. ° is set.

Therefore, the angle at which the receiver 12 is viewed from the transmitter 11 is 90°+2θ. °. Here, θ. °=10
If it is °, then θ. Compared to the case where °=0'', the sound wave level of the wrap-around sound wave could be reduced to approximately -10 dB.

By the way, since the transmitter 11 and the receiver 12 are attached facing outward from each other, there is a possibility that the detection area will change compared to when the main axes are parallel to each other, but according to experiments, θ, ” = about 10 degrees, as shown in Fig. 3, the directional characteristics of the transmitter 11 and the directional characteristics of the receiver 12 overlap to a large extent, so the change in the detection area is large enough to cause a problem. Here, in the wS3 figure, the broken line shows the directivity of the transmitter, the dashed line shows the directivity of the receiver, and the solid line shows the directivity of the transmitter and receiver. Therefore, while the sound level of the wrap-around sound waves is significantly reduced, it has almost no effect on the detection area, making it an excellent configuration for preventing the effects of wrap-around sound waves. It becomes something.

[Effects of the Invention] As described above, the present invention arranges the transmitter and the receiver so that the distance between the main axis of the transmitter and the main axis of the receiver increases as the distance from the acoustic center increases. Therefore, the front directions of the transmitter and receiver face outward from each other, and the angle from the transmitter to the receiver is wider than 90° (so that the sound wave level of the wrap-around sound waves is reduced accordingly). It has the advantage of being

[Brief Description of the Drawings] Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is an operation explanatory drawing showing an example of the directivity of the ultrasonic transducer used in the above,
FIG. 3 is an explanatory diagram of the same operation as above, FIG. 4 is a sectional view showing the conventional example, and FIG. 5 is an explanatory diagram of the operation showing the problems of the conventional example. 11... Transmitter, 12... Receiver, X,,X,...
・Main shaft. Agent Patent Attorney Ishi 1) Ai 713 Mountain Road C) No. 11

Claims (1)

[Claims] (1) In an ultrasonic sensor equipped with a transmitter that transmits ultrasonic waves and a receiver that receives ultrasonic waves, the distance between the main axis of the transmitter and the main axis of the receiver is the acoustic center. An ultrasonic sensor comprising a transmitter and a receiver arranged such that the transmitter and receiver become larger as the distance from the transmitter increases.