JPS6129299A - Piezoelectric transducer - Google Patents

Abstract

PURPOSE:To reduce the number of parts and to shorten hours required for assembly work by obtaining a resistance for braking by means of a thin fluid layer formed by a recessed part provided at the bottom of an insulator and a printed circuit board. CONSTITUTION:A piezoelectric element 22 is coupled to a metallic plate 21 to constitution a diaphragm. A thin fluid layer 33 consists of a shallow recessed part 34 provided at the bottom of an insulator 23 and a printed circuit board 26. The resistance of the thin fluid layer 33 acts as a resonance brake resistance, and this resistance value is decided by the thickness and length of the thin fluid layer 33. Accordingly, the resistance value can be set arbitrarily in accordance with the shapes of the insulator 23 and the printed circuit board 26, both of which form the thin fluid layer 33. As the resistance for braking is decided in accordance with the shapes of the insulator and printed circuit board, a stable resistance value can be obtained. Further an acoustic resistance material is made unnecessary to reduce the cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric transducer used, for example, in a telephone handset.

Conventional configuration and its problems FIG. 1 shows a conventional piezoelectric transducer.

The configuration of this conventional example will be explained below with reference to FIG. 1. In FIG. 1, 1 is a metal plate, and 2 is a piezoelectric element, which is joined to the metal plate 1 to constitute a diaphragm. 3 is an insulator, 4 is a spacer ring.

5 is a case, and 6 is an acoustic resistance material. 7゛ is the lead wire,
8 and 9 are terminals for electrical signals. 1o is the front air chamber, 11
12 is a back air chamber, 12 is a rear sound hole, and 13 is a front sound hole.

Next, the operation of the above conventional example will be explained. FIG. 2 shows an equivalent circuit when the above conventional telephone receiver is operated. In FIG. 2, ro, mo, -S.

is the resistance 2 equivalent mass of the diaphragm, stiffness + sl is the stiffness 7 of the back air chamber 11, 2 ml is the equivalent mass of the rear sound hole 12, R1 is the resistance of the acoustic resistance material 6, Sn is the stiffness of the front air chamber 10, 1 mn is the front The equivalent mass of the sound hole 13, Sc, is
This is the stiffness of the measuring coupler when this piezoelectric transducer is operated as a telephone receiver.

P is the output sound pressure, S is the area of the diaphragm, and F is the driving force generated by the supplied electric signal.

In this equivalent circuit, the resistance R7 of the acoustic resistance material 6 is set to an appropriate value to obtain flat characteristics. However, the resistance value of the acoustic resistance material 6 varies widely, and this variation directly manifests itself as variation in characteristics.

Furthermore, in order to stably bond the resistive material 6 to the insulator 3 during assembly, special equipment and a lot of work time are required.

OBJECT OF THE INVENTION The present invention eliminates the problems of the above-mentioned conventional example.
The purpose is to easily stabilize the characteristics, reduce the number of parts, and shorten the working time.

Structure of the Invention In order to achieve the above-mentioned object, the present invention has a structure in which a thin fluid layer formed of an insulator and a printed circuit board can be used as an acoustic resistance for braking, thereby obtaining a stable resistance value and It is easy to assemble.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 21 is a metal plate, and 22 is a piezoelectric element, which is joined to the metal plate 21 and forms a diaphragm 7. Reference numeral 23 is an insulator, and together with a spacer ring 24, the metal plate 21 is supported and fixed at the open end thereof. 25 is a case, and 26 is a printed circuit board, which is provided at the bottom of the insulator 23.

27 is a lead wire, and 28 is a terminal for electrical signals.

29 is a front air chamber, 30 is a back air chamber, 31 is a rear sound hole provided on the bottom surface of the insulator 23, 32 is a sound hole provided on the printed circuit board 26, and a sound hole 33 is a shallow recess provided on the bottom surface of the insulator 23. This is a thin fluid layer formed by the section 34 and the printed circuit board 26.

Next, the operation of the above embodiment will be explained. FIG. 4 shows an equivalent circuit when the above embodiment is operated as a telephone receiver. In Figure 4, s r O+ rrl Or SO
is the resistance 2 equivalent mass and stiffness of the diaphragm, S1 is the stiffness of the back air chamber 30, ml is the equal image mass p of the back sound hole 31, r2 is the resistance of the thin fluid layer 33, and m2 is the equal image mass of the thin fluid layer 33. 2m3 is the equal image volume of the sound hole 32 of the printed circuit board 26, and Sn is the stiffness of the front air chamber 29.

mn is the equal image mass of the front sound hole 35, and Sc is this example.
This is the stiffness of the measuring coupler when I is operated as a receiver. P is the output sound pressure, S is the area of the diaphragm, and F is the driving force generated by the supplied electric signal.

In this equivalent circuit, the resistance r2 of the thin fluid layer 33 acts as a resistance for resonance damping. This r2 is a value determined by the thickness and length of the thin fluid layer 33. Therefore, the value of the resistance r2 can be arbitrarily set depending on the shape of the insulator 23 forming the thin fluid layer 33 and the printed circuit board 26.

In this example, since the value of the braking resistor is determined by the shape of the insulator and printed circuit board, a stable resistance value can be obtained, and cost reduction can be achieved since no acoustic resistance material is required. There is an advantage.

Effects of the Invention In the present invention, acoustic resistance for braking is obtained by a thin fluid layer formed by a recess provided on the bottom of an insulator and a printed circuit board, so a stable resistance value can be obtained and the number of parts can be reduced. This makes it possible to reduce the number of parts and the assembly work time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional piezoelectric transducer, FIG. 2 is an equivalent circuit diagram of a conventional piezoelectric transducer, and FIG. 3 is a sectional view of a piezoelectric transducer according to an embodiment of the present invention. FIG. 4 is an equivalent circuit diagram of the piezoelectric transducer in the above embodiment. 21... Metal plate, 22... Piezoelectric element, 23... Insulator, 26... Printed circuit board, 33... Thin fluid layer.

Claims (1)

[Claims] a diaphragm formed by bonding a piezoelectric element to a metal plate; an insulator supporting the diaphragm at an open end and having a recessed part and a rear sound hole provided on the bottom surface thereof; A piezoelectric transducer comprising a substrate provided on the bottom surface of a piezoelectric transducer, the recess and the substrate forming a fluid layer.