JPH01234899A - Piezoelectric sounder - Google Patents

Abstract

PURPOSE:To prevent a diaphragm from curving and to stabilize sound pressure frequency characteristics by tapering the peripheral edge part of the diaphragm and arranging it at one end of a resin case so that an opening is covered, and caulking and fixing the peripheral edge part from above and below. CONSTITUTION:The entire peripheral edge part 23a of the diaphragm 23 on the opposite side from the side where a piezoelectric element 22 is stuck is tapered outwardly radially. Further, the resin case 21 has a bottom part 21a and a side wall 21b and a caulking fixation part 25 is formed at the upper end part of the side wall 21. The tapered peripheral edge part 23a of the diaphragm 23 is caulked and fixed with the caulking fixation part 25. The diaphragm is therefore pressed in the thickness direction by the peripheral edge part and fixed and no undesired pressing force which operates on the center part from the outer peripheral surface is generated. Consequently, the diaphragm never curves and the stable sound pressure frequency characteristics are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric sounder such as a piezoelectric buzzer that outputs sound by applying a driving voltage to a piezoelectric element.

Figure 7 is a sectional view of a conventional piezoelectric buzzer. In this piezoelectric buzzer 1, a diaphragm 4 is fixed to one end of a bottomed cylindrical resin case 2 with one end open so that a piezoelectric element 3 faces inside the resin case 2, and a diaphragm 4 is fixed to the bottom of the resin case 2. Metal terminals 5a and 5b are installed, and this metal terminal 5
The tips of a and 5b are configured to resiliently abut against the piezoelectric element 3 and the diaphragm 4. In this piezoelectric buzzer 1, the periphery of the diaphragm 4 is fixed to the resin case 2 by thermal caulking. Specifically, it is caulked using the following method. That is, as shown in FIG. 8, a convex portion 2a is formed on the open end side of the resin case 2, the peripheral edge of the diaphragm 4 is temporarily fixed to the stepped surface of the resin case 2, and then the convex portion 2a is heated. - The diaphragm 4 is thermally deformed by applying pressure, and the peripheral edge of the diaphragm 4 is fixed to the thermally deformed caulking fixing portion 2b shown by the broken line in FIG. Note that the diaphragm 4 is the eighth
As shown in the figure, the thickness is uniform in the radial direction.

By the way, in the piezoelectric buzzer l having the above configuration, due to variations in the dimensions of the resin case 2 and the diaphragm 4, etc., as shown in Fig. 9 (1)
As shown in ~(3), three caulking fixing states occur. In FIG. 9 (1), the peripheral edge of the diaphragm 4 is fixed by the caulking fixing part 2b and the stepped surface of the resin case 2 on the front and back surfaces, and therefore pressure is applied to the diaphragm 4 in its thickness direction. . On the other hand, in the state shown in FIG. 9(2), the front and back surfaces of the diaphragm 4 are fixed by the caulking fixing portion 2b and the step surface of the resin case 2, and therefore pressure is applied in the thickness direction of the diaphragm 4. . Further, the caulking fixing portion 2b wraps around the outer circumferential surface of the diaphragm 4, and therefore, in addition to the pressure in the thickness direction, pressure acts on the diaphragm from the outer circumferential surface toward the center.

In addition, in the state shown in FIG. 9(3), the caulking fixing portion 2b
does not press against the upper surface of the peripheral edge of the diaphragm 4, but wraps around the outer peripheral surface of the diaphragm. Therefore, pressure is applied to the diaphragm 4 from the outer peripheral surface toward the center thereof. Among the three fixed states shown in FIGS. 9(1) to (3), the fixed state shown in FIG. 9(1) in which pressure is applied only in the thickness direction of the diaphragm 4 is ideal; As mentioned above, the conditions shown in Figures 9 (2) and (3) may occur due to product variations during processing;
In the fixed state shown in (3), warpage occurs in the diaphragm 4 as shown in FIG. When such warpage occurs, the resonance frequency increases.

In this way, when the thickness of the diaphragm 4 is uniform, the fixed states shown in FIG. Pressure frequency characteristics become unstable. Furthermore, when the fixed states of FIGS. 9(2) and (3) occur, the resonant frequency increases.

The purpose of the present invention is to solve the above-mentioned technical problems, to prevent warping of the diaphragm, and to stabilize sound pressure frequency characteristics. It is to provide a sounder.

The present invention for "I" includes a diaphragm with a piezoelectric element pasted on one side surface, a resin case for fixing the diaphragm, and a metal case electrically connected to the piezoelectric element and the diaphragm. In a piezoelectric sounder in which a driving voltage is applied to a piezoelectric element through a terminal, the resin case has a bottomed cylindrical shape with one end open, and a caulking fixing part is formed at one end of the resin case. The diaphragm has a peripheral edge thereof tapered toward the outside in the radial direction, and
This diaphragm is characterized in that it is disposed at one end of the resin case to cover the opening, and its tapered peripheral portion is caulked and fixed from above and below by the caulking fixing portion.

According to the above structure, the peripheral edge of the diaphragm is tapered toward the outside in the radial direction, and this tapered peripheral edge is caulked by the caulking fixing part of the resin case. . Therefore, the diaphragm is fixed by being pressed in the thickness direction at its peripheral edge, and no undesirable pressing force is applied from the outer circumferential surface to the center, so that warping does not occur in the diaphragm.

As a result, it is possible to prevent an increase in the resonance frequency and obtain stable sound pressure frequency characteristics.

Figure 1 is a sectional view of a piezoelectric buzzer as an embodiment of the piezoelectric sounder according to the present invention, and Figure 2 is a plan view seen from the arrow A side in Figure 1. 3 is a side view seen from the arrow B side in FIG. 1. This piezoelectric buzzer 20 includes a bottomed cylindrical resin case 21 with one end open, and a resin case 21.
A disk-shaped diaphragm 23 is attached to cover the opening of the resin case 21 and has a disk-shaped piezoelectric element 22 adhered to the surface facing the inside of the resin case 21. and a metal terminal 24b electrically connected to the diaphragm 23 and having elasticity. Vibration plate 23
The peripheral edge 23a of the surface opposite to the side to which the piezoelectric element 22 is attached is formed into a tapered shape that tapers outward in the radial direction over the entire circumference, as shown in the fourth figure. ing. Further, the resin case 21 has a bottom portion 21a and a side wall 21b.
A caulking fixing portion 25 is formed at the upper end of the side wall 21b in FIG. The tapered peripheral portion 23a of the diaphragm 23 is fixed by the caulking fixing portion 25 as shown in the fourth figure. This configuration prevents the diaphragm 23 from warping, as will be described later.
As a result, an increase in frequency can be prevented and stable sound pressure frequency characteristics can be obtained.

Furthermore, a pair of terminal receiving grooves 26 and 27 are formed in the side wall 21b of the resin case 21, and the terminal receiving grooves 26 and 27 are arranged on one diameter line of the bottom portion 21a. . In this terminal receiver, a sound emitting hole 28 is formed by the insertion groove 26 and the diaphragm 23. Further, in the other terminal receiver, a sound emitting hole 29 is formed by the insertion groove 27 and the diaphragm 23.

The metal terminal 24a is bent at about 90 degrees and the free end thereof is pulled out through the terminal receiving groove 26 at the bent portion 5.
0a, and an elastic portion 51a that is continuous with the bent portion 50a and narrower than the bent portion 50a so as to obtain appropriate elasticity. The elastic part 51a includes the diaphragm 23 and the resin case 21.
The tip thereof is in elastic contact with the piezoelectric element 22 within a resonance space 30 defined by the piezoelectric element 22 . The other metal terminal 24b also has the same configuration as the metal terminal 24a, and corresponding parts are shown with subscripts. The elastic portion 51b of the metal terminal 24b is located within the resonance space 30, and its tip is elastically abutted against the diaphragm 23. These metal terminals 24a and 24b are attached to the caulking fixing part 3 of the bottom part 21a.
It is caulked and fixed by 1a and 31b.

In the piezoelectric buzzer 20 having such a configuration, when a driving voltage is applied to the piezoelectric element 22 via the metal terminals 24a and 24b, the diaphragm 23 vibrates in a vibration mode such as a thickness longitudinal vibration mode, and the diaphragm 23 vibrates in a vibration mode such as a thickness longitudinal vibration mode. A sound wave is emitted into the resonant space 30 by the vibration of 23. And within the resonance space 30,
It resonates at a certain resonance frequency, and this resonance sound is sent out to the outside through the sound emitting holes 28 and 29, thus making the buzzer sound.

In addition, the terminal holder has an opening size of 11 (A26.27).
(see FIG. 3) is selected to a value corresponding to a predetermined resonance frequency. Further, the tapered peripheral portion 23a of the diaphragm 23 may have a shape as shown in FIG.

Next, the assembly work of the piezoelectric buzzer 20 having such a configuration will be explained. First, as shown in FIG.
A resin case 21 having an annular convex portion 35 formed on the upper end surface of 1b is prepared. This resin case 21 has grooves 26 and 27 formed in advance for receiving terminal holders. And next, the metal terminal 24a.

24b is fixed to the bottom portion 21a. That is, the metal terminal 24a
, 24b is partially bent by 90 degrees in advance,
Insert the bent portions 50a and 50b into the terminal holder grooves 26 and 27.
and the bent portion 50a.

The caulking fixing parts 31a and 31b are inserted into the mounting holes 32a and 32b (see FIG. 1) formed in the 50b. Thereafter, the caulking fixing parts 31a and 31b are heated and pressurized to caulk. In this way, the metal terminals 24a and 24b are connected to the resin case 21.
It is fixed to the bottom part 21a of the. In this state, the ends of the elastic portions 51a and 51b of the metal terminals 24a and 24b extend toward the opening of the resin case 21.

Next, in this state, the tapered peripheral edge part 23a of the diaphragm 23 is temporarily fixed to the stepped part 60 (see FIGS. 4 and 6) of the resin case 21, with the piezoelectric element 22 facing the bottom part 21a side. . Then, the convex portion 35 of the resin case 21 is heated and pressurized.

As a result, the convex portion 35 is thermally deformed as shown in the fourth figure, and becomes the caulking fixing portion 25 to fix the tapered peripheral portion 23a of the diaphragm 23. At this time, the thermally deformed portion of the convex portion 35 is always received by the upper surface of the tapered peripheral edge portion 23a, so that no pressing force is generated from the outer circumferential surface of the diaphragm 23 toward the center as in the prior art. Therefore, warpage does not occur in the diaphragm 23, thus preventing the resonance frequency from increasing and providing stable sound pressure frequency characteristics. Thus the first
The illustrated piezoelectric buzzer 20 is assembled.

Further, in the above embodiment, the caulking fixing parts 25, 31a, 3
Although 1b is thermally fused, it may be ultrasonic welded and processed in a short time.

Furthermore, although the piezoelectric buzzer has been described in the above embodiments, the present invention can be suitably implemented in other sounding bodies that emit sounds using other piezoelectric elements.

As described above, according to the present invention, the caulking fixing portion only presses the diaphragm from above and below, and no undesirable pressing force is applied to the diaphragm from the outer peripheral surface toward the center. Therefore, warpage does not occur in the diaphragm, and therefore, it is possible to prevent an increase in the resonant frequency, reduce variations in the resonant frequency, and further improve the sound pressure frequency characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a piezoelectric buzzer that is an embodiment of a piezoelectric sounder according to the present invention, FIG. 2 is a plan view seen from the arrow A side in FIG. 1, and FIG. 3 is an arrow B in FIG. 1. A side view as seen from the side, FIG. 4 is an enlarged sectional view of the vicinity of the caulking fixing part 25, FIG. 5 is a sectional view of another embodiment of the tapered peripheral portion 23a, and FIG. 6 is a perspective view of the resin case during assembly. 7 is a cross-sectional view of a conventional piezoelectric buzzer 1, FIG. 8 is a diagram for explaining the method of fixing the resin case 2 and the diaphragm 4, and FIG. 9 is a fixing mode produced by the fixing method shown in FIG. 8. FIG. 10 is a diagram showing the state of the diaphragm due to the fixing mode shown in FIG. 9. 20... Piezoelectric buzzer, 21... Resin case, 21a
...Bottom of the resin case, 21b...Side wall of the resin case, 22...Piezoelectric element, 23...Vibration plate, 23a...
...Tapered peripheral portion, 24a, 24b...metal terminal,
25...Caulking fixing part. Patent Applicant 2 Murata Manufacturing Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Z 3a Figure 6

Claims (1)

[Claims] (1) Equipped with a diaphragm with a piezoelectric element pasted on one side surface and a resin case that fixes the diaphragm, and driven by the piezoelectric element via a metal terminal electrically connected to the piezoelectric element and the diaphragm. In a piezoelectric sounder that applies a voltage, the resin case has a bottomed cylindrical shape with one end open, a caulking fixing part is formed at one end of the resin case, and the diaphragm is attached to the periphery of the resin case. The diaphragm is formed in a tapered shape that tapers outward in the radial direction, and the diaphragm is disposed at one end of the resin case to cover the opening, and the tapered peripheral edge is formed in the caulking fixing part. A piezoelectric sounder characterized by being fixed by caulking from above and below.