JPS62200A - Piezo-electric type microphone - Google Patents

Abstract

PURPOSE:To obtain acoustic resistance free from variance by providing a circuit element for impedance conversion on a printed substrate fixed on the bottom face side of an insulator and forming acoustic resistance by a thin gap formed by the insulator and printed substrate. CONSTITUTION:The flat frequency response characteristic of an acoustic characteristic is obtained by damping resonance characteristic of a metallic diaphragm 1 and a piezo-electric element disk 2 by acoustic resistance of a thin gap 12 formed by the flat part 3b of the insulator 3, a printed board 4 and a part of a tube part 3a and, a hole 13 of the printed board 4 through a hole 10 provided on the flat part 3b of the insulator 3 from a back air chamber 9. As an impedance conversion circuit element 7 is placed outside, the back air chamber 9 can be kept constant, and the thin gap between the insulator 3 and printed substrate 4 can be utilized as acoustic resistance. Accordingly, simplification of the structure and uniform performance of products can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric microphone having an impedance conversion circuit and having a structure in which acoustic resistance can be most effectively varied.

Prior Art FIG. 2 shows the configuration of a conventional piezoelectric microphone. In FIG. 2, 1 is a metal diaphragm, 2 is a piezoelectric element disk, and as shown in FIG. The piezoelectric element portion 16 is adhesively fixed therebetween. 7 is a circuit element for impedance conversion, and 19 is an output terminal for taking out an output from the circuit side of the printed board 4 to the outside. 3 is an insulator that together with the printed circuit board 4 constitutes a back air chamber 9, has a back hole 20 of the printed circuit board 4, and an acoustic resistance material 21, and is fixed as a whole with a case 8 by caulking. .

Next, the operation of the above conventional example will be explained. When the sound thickness P is applied to the metal diaphragm 1 through the sound hole 11, flexural vibration is generated, and a voltage is generated between both metal electrodes 17 of the piezoelectric element disk 2 due to Kerr electric conversion in the radial direction. Electrically, one electrode is connected to the input of the impedance conversion circuit element 7 via the lead wire 18, and the other electrode is connected to the ground via the case 8, and the impedance conversion output is led out to the terminal 19. There is. Acoustically, metal diaphragm 1
and the resonance characteristics of the piezoelectric element disk 2, the back air chamber 9 and the back hole 2.
0. A flat frequency characteristic was obtained by appropriately braking with the acoustic resistance material 21.

Problems to be Solved by the Invention However, since the conventional piezoelectric microphone described above has an impedance conversion circuit element on the back air chamber side,
There were the following problems.

i) It is difficult to obtain uniform acoustic characteristics due to the adverse effect on thinning and volume variation due to the size of the electric circuit element.

11) It is necessary to lead out the terminal from the back air chamber side, which tends to cause air leakage failure (low frequency characteristics cannot be obtained uniformly).

City) Because it is necessary to use acoustic resistance materials such as canvas to dampen leaks from the back hole, uniform high frequency characteristics cannot be obtained.

The present invention solves these conventional problems,
The object of the present invention is to provide an excellent piezoelectric microphone that can obtain uniform sensitivity frequency characteristics.

Means for Solving the Problems In order to achieve the above object, the present invention provides a circuit element for impedance conversion on a printed circuit board fixed to the lower surface of an insulator, and a narrow gap formed between the insulator and the printed circuit board. This is to create acoustic resistance.

Function: Therefore, the back air chamber can be constructed with a constant volume, and a uniform acoustic resistance can be obtained.

Example FIG. 1 shows the configuration of an embodiment of the present invention.

In Figure 1, 1 is a metal diaphragm, 2 is a piezoelectric element disk,
Reference numeral 3 denotes an insulator having a cylindrical portion 3a and an N flat portion 3b, and the spring terminal 5 is caulked and fixed to the flat portion 3b of the insulator 3 together with the printed circuit board 4 with a rivet 6. It is located at the bottom of 3a. The impedance conversion circuit element 7 is constructed on the printed circuit board 4 using a discrete or chip construction method, and the whole is fixed by caulking with a case 8. Next, the operation of the above embodiment will be explained. In the above embodiment, when sound pressure is applied to the metal diaphragm 1, flexural vibration occurs, and a voltage is generated at both electrodes of the piezoelectric element disk 2 due to Kerr electric conversion in the radial direction. One side is led out from the metal diaphragm 1 through the case 8 and onto the printed circuit board 4 from the printed circuit board outer peripheral pattern 14 . The other one is led out to the pattern on the printed circuit board 4 via the spring terminal 5 and the rivet 6, and is input to the impedance conversion circuit element 7 on the printed circuit board 4, so that a converted output is obtained on the printed circuit board 4. in this case,
The acoustic characteristics are determined by adjusting the resonance characteristics of the metal diaphragm 1, piezoelectric element, and disk 2 from the back air chamber 9 to the hole I provided in the flat part 3b of the insulator 3.
A gap 12 formed by the plane part 3b of the insulator 3, the printed circuit board 4, and a part of the cylindrical part 3a through O, and the printed circuit board 4
Damping is performed by the acoustic resistance of the hole 13 to obtain a flat frequency response characteristic.

In this way, according to the above embodiment, since the impedance conversion circuit element 7 is placed outside, the back air chamber 9 can be kept constant and the gap 12 between the insulator 3 and the printed circuit board 4 can be kept constant.
can be used as an acoustic resistance, which has the advantage of simplifying the structure and achieving uniform product performance. Further, according to the above embodiment, since the structure can be simplified and product performance can be expected to be uniform, the number of man-hours can be reduced, resulting in excellent effects of low cost and mass production.

゛Effects of the Invention As is clear from the above embodiments, the present invention is such that the impedance conversion circuit element is configured on the outside of the printed circuit board integrated with the microphone, and the back air chamber is kept constant. It also has the advantage of being able to achieve a constant acoustic resistance. Furthermore, since the acoustic resistance can be constructed from existing parts, the number of parts can be reduced, the structure can be simplified, and there is less variation in product performance, so it can be mass-produced at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a piezoelectric microphone according to an embodiment of the present invention, FIG. 2 is a sectional view of a conventional piezoelectric microphone, and FIG. 3 is a partially enlarged view of FIG. 2. DESCRIPTION OF SYMBOLS 1...Metal diaphragm, 2...Piezoelectric element disk, 3...Insulator, 3a...Cylinder part, 3
b...Flat part, 4...Printed circuit board,
5... Spring terminal, 6... Rivet, 7
...Impedance conversion circuit element, 8...
...Case, 12...Slit.

Claims (1)

[Claims] A piezoelectric bimorph diaphragm is fixed to the upper surface side of the cylindrical part of an insulator having a cylindrical part and a flat part to form a back air chamber, a printed circuit board is fixed to the lower surface side of the cylindrical part of the insulator, and the insulator A piezoelectric microphone comprising: a narrow gap serving as an acoustic resistance; and a circuit element for impedance conversion provided on the narrow gap and the side surface of the half of the printed circuit board.