JP2000023293A - Ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which can prevent the position variance of a sound absorbing member that is contained in a case main body and also can prevent the variance of reverberant characteristic. SOLUTION: An ultrasonic sensor 10 consists of a case including an almost cylindrical case main body 11 made of an insulating material and a metallic plate 12 serving as a vibrating part which is made of a conductive material and bonded to the body 11, a piezoelectric vibrating element 13 which is bonded to the inner surface of the plate 12 and the input/output members 14a and 14b which are buried into the body 11 and electrically connected to the element 13. The body 11 has a tapered inner circumference surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ultrasonic sensor used as a back sonar or a corner sonar of an automobile.

[0002]

2. Description of the Related Art An ultrasonic sensor performs sensing using ultrasonic waves, intermittently transmits an ultrasonic pulse signal from a piezoelectric vibrating element, and piezoelectrically reflects a reflected wave from an obstacle present in the vicinity. It detects the presence of an obstacle by receiving the vibration element, or measures the distance to the obstacle by calculating the elapsed time from transmitting the ultrasonic pulse signal to receiving it by an external circuit. is there.

[0003] An ultrasonic sensor operating based on such a principle is required to have a characteristic capable of detecting a long distance and reliably extracting a weak reflected wave as an electric signal without being buried in disturbance noise or the like. You. For this purpose, it is necessary to adopt a structure that does not hinder the vibration operation of the vibrating section so that both the transmission output sound pressure and the reception sensitivity characteristics of the ultrasonic sensor can be enhanced. Specifically, for the wiring directly connected to the piezoelectric vibrating element disposed in the vibrating portion, it has been widely and generally used to use a particularly thin and soft wiring.

However, it is extremely difficult to stably connect thin and soft wiring in a small housing of an ultrasonic sensor, which causes an increase in production cost, and has a low reliability of electrical connection and a characteristic of the sensor. Cause instability.

In order to overcome the above problems, the present applicant has disclosed in Japanese Patent Application No. 10-4882 a structure of an ultrasonic sensor capable of obtaining stable electrical connection with good workability without using thin and soft wiring. Has already been proposed. Less than,
An ultrasonic sensor which is not a known technique but has been proposed by the present applicant in Japanese Patent Application No. 10-4882 will be described with reference to FIG.

As shown in the cross-sectional view of FIG. 3, a conventional ultrasonic sensor 110 has a substantially cylindrical case body 111 made of an insulating material and having a step at one opening, and a step of the case body 111. Case body 1 with adhesive
A case made up of a metal plate 112 as a vibrating part to be joined to the piezoelectric vibrating element 1
13, input / output members 114a and 114b, and a sound absorbing material 115 made of felt or the like.

Electrodes (not shown) are formed on the front and back surfaces of the piezoelectric vibrating element 113, respectively, and the electrodes on the back surface are connected to the metal plate 112 by a conductive adhesive or the like. Input / output member made of 42 nickel (iron-42% nickel alloy) etc.
14a and 114b are integrally formed so as to be embedded in the case main body 111. One of the input / output members 114a has one end connected to an electrode formed on the surface of the piezoelectric vibration element 113 and the other input / output member 114a. One end of the output member 114b is electrically connected to an electrode formed on the back surface of the piezoelectric vibration element 113 by being connected to the metal plate 112. The other ends of the input / output members 114a and 114b are led out of the case body 111. Further, the sound absorbing material 115 is disposed in the case main body 111 and plays a role of absorbing a reverberation wave generated when the ultrasonic sensor 110 emits an ultrasonic pulse signal.

[0008]

In a conventional ultrasonic sensor, a reverberation wave remaining in a case of an ultrasonic sensor when an ultrasonic pulse signal is emitted is absorbed, that is, a reverberation characteristic of the ultrasonic sensor is improved. Therefore, a sound absorbing material has been arranged in the case body. On the other hand, in order not to hinder the vibration of the metal plate as the vibrating part when emitting the ultrasonic pulse signal,
A space is required on the inner surface side of the metal plate, that is, around the metal plate on the side where the piezoelectric vibration element is joined. further,
The reverberation characteristics of the ultrasonic sensor change depending on the size of this space, and the characteristics of the ultrasonic sensor change when the size of the space changes. That is, in order to obtain an ultrasonic sensor having good characteristics, it is necessary to keep the arrangement position of the sound absorbing material constant.

However, in the conventional ultrasonic sensor, the case body has a cylindrical shape having the same opening shape in any part. Therefore, it is necessary to insert the sound absorbing material into the case body and fix the sound absorbing material at a desired position. Is a difficult task. For this reason, the position of the sound absorbing material varies for each ultrasonic sensor, and the reverberation characteristics and the like of the ultrasonic sensor vary,
There was a problem that an ultrasonic sensor having certain characteristics could not be supplied.

The ultrasonic sensor of the present invention has been made in view of the above-mentioned problems, and has as its object to solve these problems and to provide an ultrasonic sensor that is characteristically stable without variation in reverberation characteristics. And

[0011]

To achieve the above object, an ultrasonic sensor according to the present invention comprises a substantially cylindrical case body made of an insulating material, and a vibrating part made of a conductive material and joined to the case body. A piezoelectric vibrating element joined to the inner surface of the vibrating portion, and an input / output member embedded in the case body and electrically connected to the piezoelectric vibrating element. An ultrasonic sensor, wherein an inner peripheral surface of the case main body is at least partially tapered.

Thus, the position where the sound absorbing material is fixed in the case body becomes constant. Further, since the sound absorbing material is fixed by being pushed into the case main body, a force for pressing down the case main body is applied, so that reverberation characteristics are improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic sensor according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of the ultrasonic sensor according to the present embodiment. As shown in FIG. 1, the ultrasonic sensor 10 of the present embodiment is made of an insulating material and has a substantially cylindrical case body 11 having a step at one opening, and is fitted to the step of the case body 11. A case made of a metal plate 12 as a vibrating part joined to the case body 11 by an adhesive, a piezoelectric vibrating element 13 joined to the inner surface of the metal plate 12, and input / output members 14a, 14b, And a sound absorbing material 15 made of felt or the like. The insulating material of the case body 11 is an engineering plastic having excellent heat resistance and durability, specifically, polyphenylene sulfide, polyether ether ketone, polyether sulfone, a liquid crystal polymer, or the like. further,
For the metal plate 12 as the vibrating part, aluminum or the like, which is lightweight and has a high elastic modulus, is used. Furthermore, the input / output member 14
As a and 14b, a metal having high rigidity such as 42 nickel, nickel silver, phosphor bronze, or a metal having low rigidity such as copper is used.

Electrodes (not shown) are formed on the front and back surfaces of the piezoelectric vibrating element 13, respectively. The electrodes on the back surface are connected to the inner surface of the metal plate 12 by a conductive adhesive or solder. The input / output members 14a and 14b are integrally formed so as to be embedded in the case body 11, and one of the input / output members 14a and 14b is
a has one end connected to an electrode formed on the surface of the piezoelectric vibration element 13 by a conductive adhesive or the like, and the other input / output member 14b
Is connected to an electrode formed on the back surface of the piezoelectric vibrating element 13 by being connected to the metal plate 12 with a conductive adhesive or the like. The other ends of the input / output members 14a and 14b are led out of the case body 11.

[0015] In an ultrasonic sensor, not only long-distance detection but also short-distance detection may be required. When the ultrasonic sensor measures the distance from the object to be detected,
The ultrasonic pulse signal is transmitted, the reflected wave from the object is converted into an electric signal, and the signal is sent to an external circuit for calculation. Etc., and it is difficult to distinguish the reflected wave. In other words, it is necessary for the ultrasonic sensor to improve the function of converging reverberation remaining in the case body or the like immediately after transmitting the ultrasonic pulse signal, that is, to improve reverberation characteristics.
Case body 11 to improve reverberation characteristics of ultrasonic sensor 10
A sound absorbing material 15 made of felt or the like is arranged in the inside, but since the inner peripheral surface of the case main body 11 in the ultrasonic sensor 10 of the present embodiment is formed in a tapered shape as shown in FIG. 15 is fixed at a desired position in the case main body 11. That is, if the sound absorbing material 15 is inserted and pushed in from the opening opposite to the side where the metal plate 12 of the case main body 11 is joined, the inner peripheral surface of the case main body 11 is tapered. The sound absorbing material 15 stops at a predetermined position. If the size of the sound absorbing material 15 and the shape of the inner peripheral surface of the case main body 11 are accurately formed, the sound absorbing material 15 can be fixed at a fixed position without any difficulty in work, so that the metal plate can be fixed. An ultrasonic sensor can form a space of a certain size around 12
Variations in the reverberation characteristics of the 10 are eliminated. Also sound absorbing material
Since the case 15 is pushed into the case body 11, a force is applied outward from the sound absorbing material 15 to the case body 11. As a result, the vibration remaining in the case body 11 after the emission of the ultrasonic pulse signal is suppressed, so that the reverberation characteristics are not dispersed and the reverberation characteristics are improved.

In the above embodiment, the case body
Although the taper formed on the inner circumferential surface of the case 11 extends over the entire inner circumferential surface of the case body 11, the effects of the present invention can be obtained even if the taper is formed partially, such as three or four portions. Also, as shown in the cross-sectional view of FIG. 2, an insulating resin having elasticity such as silicon rubber, urethane rubber, and foaming resin.
The present invention can also be applied to the ultrasonic sensor 10a in which the case 16 is filled and cured.

[0017]

As described above, according to the present invention, the inner peripheral surface of the case body made of an insulating material in the ultrasonic sensor is tapered. Thereby, the position of the sound absorbing material arranged inside the case main body is fixed, the reverberation characteristics and the like of the ultrasonic sensor do not vary, and the work of arranging the sound absorbing material is simplified. Further, when the sound absorbing material is pushed into the case main body, a force is applied from the inside to the outside of the case main body, so that the reverberation characteristics of the ultrasonic sensor are improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an ultrasonic sensor according to the present invention.

FIG. 2 is a sectional view of another embodiment of the ultrasonic sensor according to the present invention.

FIG. 3 is a sectional view of a conventional ultrasonic sensor.

[Explanation of symbols]

 10, 10a Ultrasonic sensor 11 Case body 12 Metal plate 13 Piezoelectric vibrating element 14a, 14b Input / output member 15 Sound absorbing material 16 Insulating resin

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Junichi Koshino 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (Reference) 5D019 AA26 BB09 EE01 FF01 GG05

Claims (1)

[Claims] 1. A case comprising a substantially cylindrical case body made of an insulating material, a vibrating part made of a conductive material and joined to the case body, and joined to an inner surface of the vibrating part. An ultrasonic sensor comprising: a piezoelectric vibrating element; and an input / output member embedded in the case main body and electrically connected to the piezoelectric vibrating element, wherein the inner peripheral surface of the case main body is at least partially An ultrasonic sensor characterized by having a tapered shape.