JP2000023295A - Ultrasonic wave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make joining work of a metal plate to a case main body easier and to suppress dispersion of characteristics by providing a step part to at least one of opening parts of the case main body of an almost cylindrical shape and consisting of an insulation material and making a side peripheral surface of the step part partially tapered. SOLUTION: A ultrasonic wave sensor consists of an insulation material and is composed of a case which consists of a case body 11 of an almost cylindrical shape and having a step part 20 at one of opening parts and a metal plate 12 as an oscillation part which is fitted and joined to the step part 20 of the case body 11 with an adhesive material, a piezoelectric oscillation element 13 joined to an inner side of the metal plate 12 and input/output members 14a and 14b. A side face of the step part 20 provided at one of the opening parts of the case body 11 is formed into a taper shape, a position of the metal plate 12 is fixed at a specified position by pressing the metal plate 12 into the step part 20, a position in the case of the piezoelectric oscillation element 13 joined to the metal plate 12 becomes fixed and a resonance frequency and sensitivity characteristics are stabilized.

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 is made of an insulating material and has a step portion 1 at one opening.
A case consisting of a substantially cylindrical case body 111 having 20, a metal plate 112 as a vibrating part fitted to the step part 120 of the case body 111 and joined to the case body 111 by an adhesive; It is composed of a piezoelectric vibration element 113 joined to the inner surface of the plate 112, and input / output members 114a and 114b.

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.

[0008]

In a conventional ultrasonic sensor, a metal plate as a vibrating portion has been fitted to a step portion provided with one opening of a case main body and joined by an adhesive or the like. On the other hand, it is difficult to join the piezoelectric vibrating element to the inner surface of the metal plate after the metal plate and the case body are joined. The plate and the case body were joined.

The metal plate and the case body are formed so that the shape of the metal plate and the shape of the step portion provided at one opening of the case body are substantially the same, but the metal plate is attached to the step portion. In order to fit, it is unavoidable to make the shape of the stepped portion larger than the metal plate to some extent from the viewpoint of work. That is, in the step of fitting the metal plate to the case main body or the step of joining them with an adhesive or the like, the position of the metal plate may be shifted within the step provided in one opening of the case main body. It is.

When the position of the metal plate shifts within the step provided in one of the openings of the case body, the position of the piezoelectric vibrating element joined to the metal plate also shifts. If the position of the piezoelectric vibrating element in the case changes even slightly, the positional relationship between the piezoelectric vibrating element and the case body may change.
In the ultrasonic sensor, a change that cannot be ignored in the resonance frequency and the sensitivity characteristic occurs. That is, since it is inevitable that the position of the metal plate is shifted in operation, the conventional ultrasonic sensor has a problem that the characteristics of each ultrasonic sensor vary due to the shift of the position of the metal plate.

The ultrasonic sensor of the present invention has been made in view of the above-described problems, and solves these problems. The ultrasonic sensor has an ultrasonic wave sensor that is easy to join a metal plate and a case body and has little characteristic variation. It is intended to provide a sensor.

[0012]

In order 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 having a step at at least one opening.
A case made of a conductive material, comprising a vibrating part fitted and fixed to the step part, a piezoelectric vibrating element joined to an inner surface of the vibrating part, and a piezoelectric element embedded in the case main body; An ultrasonic sensor including an input / output member electrically connected to a vibration element, wherein a side peripheral surface of the step portion is at least partially tapered.

Accordingly, the position of the vibrating portion does not shift within the step provided in the one opening of the case body.

[0014]

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, an ultrasonic sensor 10 of the present embodiment has a substantially cylindrical case body 11 made of an insulating material and having a step portion 20 in one opening.
And a metal plate as a vibrating part which is fitted to the step part 20 of the case body 11 and is joined to the case body 11 by an adhesive
12, a piezoelectric vibration element 13 joined to the inner surface of the metal plate 12, and input / output members 14a and 14b. 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, the metal plate 12 as the vibrating portion is made of aluminum or the like, which is lightweight and has a high elastic modulus. Furthermore, as the input / output members 14a 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 vibrating element 13 by a conductive adhesive 15 or the like, and the other input / output member 14
One end of b is electrically connected to an electrode formed on the back surface of the piezoelectric vibrating element 13 by being connected to the metal plate 12. The other ends of the input / output members 14a and 14b are led out of the case body 11.

As shown in FIG. 1, in the ultrasonic sensor 10 of the present embodiment, a side peripheral surface of a step portion 20 provided at one opening of the case main body 11 is formed in a tapered shape. If the side peripheral surface of the step portion 20 is tapered, the metal plate 12
By pushing it into 20, the position of the metal plate 12 is fixed at a predetermined position. That is, the tapered shape of the step portion 20 and the metal plate 12
If the shape of the metal plate 12 is accurately formed, the position of the metal plate 12 will not be displaced due to the work in the fitting process of the metal plate 12 to the stepped portion 20 and the joining process thereof. When the position of the metal plate 12 is constant, the position of the piezoelectric vibrating element 13 joined to the metal plate 12 in the case also becomes constant, and the resonance frequency and sensitivity characteristics of the ultrasonic sensor 10 are stabilized. That is, the characteristics do not vary for each ultrasonic sensor, and the productivity is increased. In addition, conventionally, in order to pay attention to the position of the metal plate 12, the fitting process of the metal plate 12 to the step portion 20 and the like is a laborious operation, but by providing the step portion 20 with a taper Even if the process is rough,
Workability such as a process of fitting the metal plate 12 to the step 20 is improved.

In the above embodiment, the case body
Although the taper formed in the step portion 20 provided in one opening of the 11 extends over the entire side peripheral surface of the step portion 20, even if it is partially formed, for example, three or four portions, the taper is formed. The effects of the invention can be obtained.

Further, the ultrasonic sensor may need to detect not only a long distance but also a short distance.
When an ultrasonic sensor measures the distance from an object to be detected, it transmits an ultrasonic pulse signal, converts a reflected wave from the object into an electric signal, and sends the signal to an external circuit for calculation. In the case of a short distance, the vibration at the time of transmission remains in the case body of the ultrasonic sensor and the like, making it difficult to distinguish the reflected wave from 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. Therefore, as shown in the cross-sectional view of FIG. 2, a sound absorbing material 16 made of felt or the like is inserted into the case of the ultrasonic sensor 10a, and an insulating resin 17 having elasticity such as silicon rubber, urethane rubber, or foaming resin is used. The present invention can be applied to the ultrasonic sensor 10a filled and cured in the case.

[0019]

As described above, according to the present invention, a vibrating portion made of a conductive material is fitted to a step portion of a substantially cylindrical case body made of an insulating material and having a step portion at one opening. In the ultrasonic sensor constituting the case in combination, the side peripheral surface of the case body is tapered. As a result, the position of the vibrating portion within the step portion does not shift due to the work in the process of fitting the vibrating portion to the step portion and the process of joining them, and the variation in the position of the vibrating portion for each ultrasonic sensor is prevented. Does not occur. The fact that the position of the vibrating part is constant means that the position of the piezoelectric vibrating element that is joined to the vibrating part in the case is also constant, which causes variations in the resonance frequency and sensitivity characteristics of the ultrasonic sensor. Does not occur. That is, an ultrasonic sensor having no variation in characteristics can be easily manufactured.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of an ultrasonic sensor according to another embodiment of 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 Conductive adhesive 16 Sound absorbing material 17 Insulating resin 20 Step

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Junichi Koshino 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. 5D019 AA26 BB09 BB28 EE01 FF01 HH03

Claims (1)

[Claims] 1. A substantially cylindrical case body made of an insulating material and having a step in at least one opening, and a vibrating part made of a conductive material and fitted and fixed to the step. An ultrasonic sensor comprising: a case; a piezoelectric vibrating element joined to an 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 a side peripheral surface of the step portion is at least partially tapered.