JPH01232900A - Ultrasonic wave transmitter-receiver - Google Patents

Abstract

PURPOSE:To attain the small sized transmitter-receiver and a wide band of directivity by selecting the shape of the closed end face being a part of the diaphragm so that the outer contours in orthogonal axial directions are different from each other. CONSTITUTION:A vibrator 2 made of a piezoelectric material is fixed incorporatedly to the inner side of the closed end face 1a of a case main body 1. A terminal board is mounted to the open end of the case main body 1 to form closed structure. The shape of the closed end face 1a forming the diaphragm is selected so that the outer contours in orthogonal axial directions are different from each other. Moreover, it is advantageous that the shape of the closed end face 1a is made elliptic or a long circular form.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an ultrasonic transducer with a sealed or drip-proof structure for outdoor use, and is particularly suitable for miniaturization and widening of directivity. The present invention relates to a possible ultrasonic transducer.

[Conventional technology]

Conventional 1 For example, as an obstacle detection device for a vehicle.

An ultrasonic wave transmitter emits ultrasonic pulses, an ultrasonic receiver receives reflected waves from objects to be detected or obstacles, and processes this received signal to emit a warning signal. Common. In order to widen the detection range or directivity of the above-mentioned obstacles, various inventions have been proposed so far (for example, Japanese Patent Laid-Open Nos. 57-40665, 57-182666, and 59-154380). reference). On the other hand, in order to make the above-mentioned detection devices smaller or more compact, devices that serve both as a transmitter and a transfer device are also used, and in consideration of outdoor use, sealed or drip-proof types are also used. There are some configurations.

FIG. 4 is a vertical cross-sectional view of a main part showing an example of the conventional ultrasonic transducer described above. In the figure, reference numeral 1 denotes a case, which is made of, for example, an aluminum alloy and has a closed end shaped like a truncated cone, and has an open end at the other end. A vibrator 2 made of a piezoelectric material is integrally fixed inside the closed end of the case 1, and a terminal plate 3 is attached to the open end to form a sealed structure. Terminals 4 are fixed so as to penetrate inside and outside the terminal board 3, and are electrically connected to the vibrator 2 and the case 1 via lead wires 5, respectively.

[Problem to be solved by the invention]

Generally, the directivity of ultrasonic waves is determined by the relationship between the dimensions of the vibration surface of the ultrasonic transducer, that is, the closed end surface 1a, and the wavelength of the ultrasonic waves. If it is small, it is recognized as an ideal point sound source and can generate one spherical wave. Therefore, it is non-directional and can emit ultrasonic waves of equal level in all directions, making it possible to widen the detection range. however.

The wavelength in an ultrasonic detection device is extremely small.

For example, when the frequency is 40 kHz, one wavelength is approximately 8.51. On the other hand, even if the diameter of the closed end surface 1a of an ultrasonic transducer is made as small as possible, it cannot be ignored compared to the above wavelength, and it is difficult to physically manufacture a diameter so small that it can be ignored. It is technically impossible.

Therefore, the detection range or directivity becomes narrow, resulting in a disadvantage that the performance of the detection device is degraded. Note that if the dimensions of the closed end surface 1a are made small in order to expand the directivity, the above-mentioned problem occurs, and at the same time, there is also the problem that the vibration displacement decreases and the sound pressure becomes insufficient.

Note that in back sonar for vehicles, etc., there is a demand for expanding directivity in the horizontal direction or left and right directions rather than in the vertical direction. In this regard, in conventional configurations, the directivity or detection range has a conical shape with respect to the ultrasonic transmission direction and is at the same angle, so there is a problem that it cannot meet the above requirements.

The present invention solves the problems existing in the above conventional techniques,
The object of the present invention is to provide an ultrasonic transducer that can be downsized and have a wide range of directivity.

(Means for solving problems) In order to achieve the above object, there are two aspects of the present invention.

In an ultrasonic transducer having a sealed structure in which a vibrator made of a piezoelectric material is integrally fixed to the inside of the closed end surface of the case body and a terminal plate is attached to the open end of the case, the above-mentioned part forming the diaphragm The shape of the closed end surface is formed so that the outer contour in the orthogonal axial direction has different dimensions. A technical method was adopted.

Note that it is convenient for manufacturing if the closed end surface is formed into an oval or elliptical shape.

[Effect]

With the above configuration, it is possible to expect an effect of expanding the directivity in the direction in which the external contour size is made small without reducing the detection performance or sensitivity.

FIGS. 2(a) and 2(b) are a block diagram showing an example of a detection device when the ultrasonic transducer of the present invention is used as a sensor, and an explanatory diagram schematically showing input and output signals in each circuit. be. In FIGS. 2(a) and 2(b), a sensor 21 is connected so as to be able to emit ultrasonic waves of, for example, 40 kHz via a wave transmitting circuit 22 upon application of a pulse from a reference time pulse generator 23. . Next, on the output side of sensor 21.

Receiving circuit 24. Gate circuit 25. The alarm circuit 26 and the buzzer 27 are connected in this order, and the gate circuit 25 is connected so that the pulses from the reference time pulse generator 23 can be input. Next, 22□, P2. are pulse signals, which are applied from the reference time pulse generator 23 to the wave transmitting circuit 22 and the gate circuit 25, respectively, to control the operating time of the circuits. A high frequency output signal W2□ is output from the wave transmitting circuit 22 in response to the pulse signal P2□, and an ultrasonic signal is transmitted from the sensor 21. Next, w24 is an input signal to the wave receiving circuit 24, into which the outputs from the sensor 21 and the wave transmitting circuit 22 are input.

Note that in the output signal W2□ and the input signal W24.

a and b are a transmitted wave and a reflected wave, respectively. That is, since the sensor 21 functions as a transducer, the transmitted wave a exists not only in the output signal W2□ but also in the input signal W24, and a part of one reflected wave is also output to the transmitting circuit 22. be done. Next, W2. is an output signal of the gate circuit 25, which is output in response to the reflected wave within the time controlled by the pulse signal Pus from the reference time pulse generator 23. As a result, the alarm circuit 26 and buzzer 27 are activated. By setting the pulse signal PZS corresponding to the detection distance in advance as described above, the sensor 21
An alarm can be issued by the reflected ultrasonic waves.

〔Example〕

FIGS. 1(a) and 1(b) are a partially exploded side view and a plan view showing an embodiment of the present invention, respectively, and the same parts are designated by the same reference numerals as in FIG. 4. In both figures, the case 1 is formed to have a wall thickness of 1 mm, but only the closed end surface 1a has a wall thickness of 0.2 mm.
Form to a thickness of . Case 1 has an outer diameter of 30 mm, a length of the cylindrical part and a truncated conical part of 10 mm each, and a closed end surface 1a with a long axis of 20 mm and a short axis of 7 m.
Form into an oval or elliptical shape of m. The vibrator 2 to be fixed inside the closed end surface 1a is made of lead zirconate titanate (PZ
T) to have a diameter of 5 mm and a thickness of 0.3 mm. The ultrasonic transducer with the above configuration is shown in FIG. 2(a).
The directivity was measured by incorporating it into the detection device shown in . As a comparative example, the dimensions of the closed end surface 1a (see Figure 1) are each set to a diameter of 2.
The directivity of the 0 mm and 7 mm circular shapes was also measured.

FIGS. 3(a) and 3(b) are diagrams showing the directivity in the horizontal plane and the vertical plane in the embodiment of the present invention, respectively, -
2 curve A is shown based on the comparative example in which the closed end surface 1a (see FIG. 4) is formed to have a diameter of 20 mm.
In this example, curves B and C each have a closed end surface with a diameter of 20 mm.
and corresponds to a comparative example formed to 7 mm. In this example, the long axis of the closed end surface is arranged vertically.

As is clear from both figures, there is no significant difference in the directivity in the vertical plane among the three, except that curve C shows a small value of sound pressure in a region where the angle is small. However, as shown in FIG. 3(a), there is a difference in directivity in the horizontal plane.

In other words, in the case where the diameter of the closed end face is 20 mm,
As shown by curve B, the sound pressure is high at the front, but at angles of 30 degrees or more, the sound pressure drops rapidly and the detection range is narrow.

On the other hand, in the case where the diameter of the end face is 71 mm, as shown by curve 1 C, although the detection range is relatively wide, the sound pressure is generally small, and the detection performance is significantly reduced. On the other hand, in the case of the embodiment of the present invention, the sound pressure at the front is slightly lower as shown by the second curve.
It can be seen that the overall sound pressure is relatively high, and the detection range is expanded.

In this example, an example in which the shape of the closed end face is formed into an oval or an ellipse is shown, but the shape is not limited to rectangular, rectangular,
Other geometric shapes, such as a cocoon shape, can be used; in short, the outer contours in the orthogonal axial directions may have different dimensions. Further, the cross-sectional shape of the case body can also be selected from other geometric shapes other than the circular shape in this embodiment. Furthermore, the shape in the vicinity of the closed end surface may be a truncated cone shape other than the shape of a single truncated cone, or may be a cylindrical body having the same external dimensions. Note that the material constituting the case body is not limited to aluminum alloy, and other metal materials or non-metal materials can be used. Furthermore, in this example.

Although the ultrasonic transducer is used for an obstacle detection device for a vehicle as an example, the ultrasonic transducer of the present invention is also applicable to anti-theft devices, parking meters, and golf cart collision prevention devices in addition to the above. , it is natural that it can be applied to other uses as well.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
The ultrasonic transducer can be made smaller and have a wider directivity. Therefore, even in a wide range where conventionally a large number of elements must be used, detection can be performed using 11 ultrasonic transducers, making it possible to significantly downsize the detection system or detection device. Further, it is possible to design the length ratio of the closed end surface outer shape depending on the range to be detected or the shape of the contour, which has the effect of maintaining the detection performance or reliability at a high level.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a partially exploded side view and a plan view showing an embodiment of the present invention, respectively, and FIGS. 2(a) and (b) each use the ultrasonic transducer of the present invention as a sensor. A block diagram showing an example of the detection WW in the case of the above and an explanatory diagram schematically showing input/output signals in each circuit, FIGS. 3(a) and (b)
4 is a diagram showing directivity in a horizontal plane and a vertical plane in an embodiment of the present invention, respectively, and FIG. 4 is a longitudinal sectional view of a main part showing an example of a conventional ultrasonic transducer. Case, 1a: closed end surface, 2: vibrator.

Claims (2)

[Claims] (1) In an ultrasonic transducer with a sealed structure in which a vibrator made of a piezoelectric material is integrally fixed to the inside of the closed end surface of the case body and a terminal plate is attached to the open end of the case, the diaphragm is An ultrasonic transducer characterized in that the shape of the closed end face is formed to have different outer contours in orthogonal axial directions. (2) The ultrasonic transducer according to claim 1, wherein the closed end surface has an oval or elliptical shape.