JPS60106298A - Ultrasonic ceramic microphone - Google Patents

Abstract

PURPOSE:To improve the pulse responsiveness by using a resonance barrel set into a case to separate the phase of an ultrasonic wave generated within the case and to reduce the acoustic interference. CONSTITUTION:An electromagnetic vibrator is bonded to the inside of a bottom face part 2a of a cylindrical case 2 to use the part 2a as a bimorph vibrator. The part 2a has a truncated cone section. A resonance ring 10 is provided to the inside of the case 2, and a resonance barrel is provided to the inner circumference of the ring 10. This barrel 11 separates the phase of a sound wave generated within the case 2 and reduces the acoustic interference. While a lead wire 7a soldered to the electrode surface of an electromagnetic vibrator is wired through a recess part 10a of the ring 10 via an elastic adhesive 13 along the inner side of the case 2. In such a constitution, the pulse responsiveness can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is mainly applied to detection systems such as parking meters and automobile rear detection devices, and relates to an ultrasonic ceramic microphone that transmits and receives ultrasonic waves. It is something.

Structure of a conventional example and its problems A conventional ultrasonic ceramic microphone of this type will be explained with reference to FIG. First, reference numeral 1 denotes a piezoelectric ceramic vibrator, which is bonded to the inside of the bottom surface 2a of a cylindrical case 2 having a bottom surface 2ai having a truncated conical cross section, and the bottom surface 2a is constructed as a bimorph vibrator. The 03Fi resonance ring is fixed inside the case 2. 4
is a terminal plate which is fixed to the open end of the case 2 via an elastic member 5 and an elastic adhesive, and is formed by sealing the open end of the case 2. 7a and 7b are lead wires, 8a
and 5b (d) A terminal implanted in the terminal plate 4, and a lead wire 7a soldered to the electrode surface of the piezoelectric ceramic vibrator 1 is connected to the terminal 8a.
In addition, the lead wires 7b and 2 terminals 8b connected to the case 2, which are at the same potential as other electrodes, are connected with an elastic adhesive 9. There is a problem in that reverberation occurs due to the interference of the ultrasonic waves, and that the pulse fall time becomes long when transmitting pulse signals. Here, a method for improving pulse response is resonance of the vibrating part. There are ways to lower this. In other words, resonance. is expressed by the following formula.

fO: Resonance frequency 2m: Mass.

Rm: Mechanical resistance, Cm: Mechanical reactance.

Therefore, although the mechanical resistance Rm can be increased, the Q can be lowered by changing the material of the vibrating part or making it thinner to reduce its mass, but this results in a reduction in the range of ultrasonic waves, making it impractical. Therefore, countermeasures can be taken by changing the shapes of the component parts without changing the basic structure of the conventional structure. -! Furthermore, in the secondary i configuration, there was a problem in that reverberation occurred due to the wiring condition of the lead wires and the shape of the resonant ring.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks by elastically absorbing the vibration of the lead wire, separating the phase of the ultrasonic waves generated within the case, and reducing acoustic interference. The purpose of this invention is to provide an ultrasonic ceramic microphone with excellent pulse response.

Structure of the Invention In order to achieve this object, the ultrasonic ceramic microphone of the present invention has a piezoelectric ceramic vibrator bonded to the inside of the bottom of a cylindrical case having a bottom with a truncated conical cross section, and the bottom has bimorph vibration. A resonant ring is provided inside the cylindrical case configured as a child, and a resonant tube is provided in the inner circle of the resonant ring to separate the different phases of the ultrasonic waves inside and outside the nodal circle of the bimorph vibrator. This structure reduces the interference of ultrasonic waves generated within the case.

A lead wire soldered to the electrode surface of the piezoelectric ceramic vibrator is routed along the inside of the cylindrical case via an elastic adhesive, and the lead wire is inserted through a recess provided on the outer periphery of the resonant ring. A terminal plate is elastically fixed to the open end of the cylindrical case via an elastic member, and the other lead wire, which is taken out using the lead wire and the cylindrical case as an electrode, is wired to the terminal plate. It is what it is.

DESCRIPTION OF EMBODIMENTS An ultrasonic ceramic microphone according to an embodiment of the present invention will be described below with reference to FIG. Note that the same members as in the conventional example are given the same numbers. Reference numeral 1 denotes a piezoelectric ceramic vibrator, which is bonded to the inside of the bottom surface 2a of a cylindrical case 2 having a bottom surface 2af having a truncated conical cross section, thereby forming a bimorph vibrator. Reference numeral 10 denotes a resonance ring, which is adhesively fixed inside the case 2.

A resonant cylinder 11 is adhesively fixed to the inner circle of this resonant ring 10. A lead wire 7a is soldered to the electrode surface of the piezoelectric ceramic vibrator 1, and the other end is hermetically fixed to the open end of the case 2 via an elastic member 12 and an elastic adhesive 9.A terminal 8aVc of the terminal plate 4 is formed. It is connected. This lead wire 7a is routed along the inside of the case 2 via an elastic adhesive 13 and through a recess 10a of the resonance ring 1o. 7b is a lead wire connected to the case 2 which has the same potential as the other electrode surface of the piezoelectric ceramic vibrator 1, and the other end is connected to the terminal 7b [connected n
ing. Although the resonant cylinder 111d is made of a resin member, it may be made of metal if it is integrated with the resonant ring 1o. Further, by setting the length to be close to resonance (λ-wavelength), the effect of preventing ultrasonic waves having different phase differences from interfering with each other is enhanced.

Effects of the Invention According to the present invention, ultrasonic waves having different phases that interfere in a complex manner within the case are separated by a resonant cylinder placed inside the case.
In addition, the resonance Q can be lowered by increasing the acoustic resistance (corresponding to Rm) inside the case using the resonant tube.

Figures 3 and 4 compare the sensitivity-frequency characteristics and pulse response of the microphones of the present invention and the conventional example. This design improves pulse response without lowering OL. At the same time, since the structure does not suppress the vibration of the bimorph vibration surface of the case, it is possible to provide an ultrasonic ceramic microphone that is pulse responsive and has a sharp pulse fall without causing a decrease in sensitivity. Furthermore, since the lead wires are wired using an elastic adhesive, the vibration-proofing effect of the lead wires can be enhanced and interference caused by vibrations of the lead wires can be reduced during resonance. By realizing the configuration of the present invention as described above,
This allows the microphone to be used for both transmitting and receiving ultrasonic waves, and is expected to find new applications in the future, including obstacle detection devices.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional ultrasonic ceramic microphone, Fig. 2 is a sectional view of an ultrasonic ceramic microphone according to an embodiment of the present invention, and Fig. 3 shows the sensitivity-frequency characteristics of the inventive product and the conventional product. FIG. 4 is a diagram similarly showing a comparison of pulse responsiveness. DESCRIPTION OF SYMBOLS 1... Piezoelectric ceramic vibrator, 2... Cylindrical case, 4... Terminal plate, 6... Elastic member,
7a, 7b...Leet wire, 10...Resonance ring, 10a, center recess, 11...Resonance cylinder, 12...
...Elastic member, 13...Elastic adhesive. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 3 Figure 4

Claims (1)

[Claims] A piezoelectric ceramic vibrator is bonded to the inside of the bottom of a cylindrical case having a truncated conical bottom in cross section, and a resonant ring is provided inside the cylindrical case in which the bottom is configured as a bimorph vibrator. A resonant cylinder is provided in the inner circle of the resonant ring, and a lead wire soldered and connected to the electrode surface of the piezoelectric ceramic vibrator is wired along the inside of the cylindrical case via an elastic adhesive. The lead wire is taken out from four parts provided around the circumference of the song, a terminal plate is elastically fixed to the open end of the cylindrical case via an elastic member, and the other lead wire is taken out from the lead wire and the cylindrical case as electrodes. An ultrasonic ceramic microphone is formed by wiring the terminal board to the terminal board.