JPS587999A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To obtain a sufficient acoustic pressure level in the low band side of an audio frequency region and make a piezoelectric speaker small-sized, by protruding a part of the elastic material, which is fixed to a frame, from the frame to constitute this part as a free end and attaching a piezoelectric sound producing material, which oscillates in the bending oscillation mode, to the protruded part. CONSTITUTION:A round piezoelectric sound producing material 4 which oscillates in the bending oscillation mode has a bimorph structure where a round piezoelectric porcelain plate 6 with electrodes constituted on both faces is fixed to a round diaphragm 5 consisting of a metallic plate, an insulatig plate, or the like. A ring-shaped elastic material 7 consisting of rubber consists of a comparatively thick main body part 8 and a comparatively thin projecting part 9 and is supported in the main body part 8 by a ring-shaped frame 10, and the projecting part 9 is constituted as a free end. The sound producing material 4 is fixed to the projecting part 9 of the elastic material 7. Thus, a sufficient acoustic pressure level is obtained in the low band side of the audio frequency region to make the speaker small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker that utilizes a piezoelectric sounding body that operates in a bending vibration mode.

Conventionally, piezoelectric speakers, especially piezoelectric ceramic plates, have been used. Recently, various improvements have been made with the aim of improving frequency characteristics, sound pressure level, etc. However, there is a limit to miniaturization, and when considering miniaturization, it is possible to configure a sounding body with a bimorph structure directly attached to the frame without a diaphragm.In this way, a sounding body with a bimorph structure is attached directly to the frame. If

The resonance peak peculiar to the piezoelectric effect of the sounding body is noticeable, making it impossible to obtain flat frequency characteristics, making it unsuitable for use as a speaker.
It did not have a convex structure. Therefore, the present inventors used a sounding body 1 having a disc-shaped bimorph structure as shown in FIG.
A piezoelectric speaker in which the peripheral edge of the sounding body 1 is attached to the frame 3 via the annular elastic body 2 has already been proposed (-1^^).The speaker shown in Fig. Although the peak was suppressed and the flatness of the frequency response was improved, the response to the low frequency signal was suppressed within the range of expansion and contraction of the elastic body 2, and the low frequency characteristics were insufficient. .

The present invention improves the above-mentioned drawbacks of the prior art.
In addition to photographing the area around the sounding body as freely as possible,
By lowering the mechanical Q and reducing the gentle area on the low-frequency side of the low-Q resonance peak to 1/'1, a sufficient sound pressure level can be obtained even on the low-frequency side of the audible frequency range, and The purpose is to propose a piezoelectric speaker that can be miniaturized.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In Figure 2, 4 is a circular piezoelectric sounding body that vibrates in a bending vibration mode. It has a bimorph structure to which a ceramic plate 6 is fixed.If the diaphragm 2 is conductive, the lead wire is connected to one electrode of the piezoelectric ceramic plate 3 and the diaphragm 2. A relatively thick annular body portion 8 made of an annular elastic body.
It is composed of a relatively thin protruding part 9 which protrudes inward from the main body part 8. The elastic body 7 is the main body part 8 of ¥
The protrusion 9 is supported by the annular frame 10 at a portion thereof, and is configured as a free end that allows the protrusion 9 to vibrate relatively freely. The piezoelectric sounding body 4 is attached so that its peripheral edge, which is constituted by the diaphragm 5, is fixed to the protrusion 9 of the elastic body 7. In this embodiment, when a signal is applied to the lead wire, the piezoelectric sounding body 4 vibrates in a state close to peripheral support, and the peripheral edge of the sounding body 4 is fixed to the protrusion 9 of the elastic body 7.

When the sounding body 4, particularly its peripheral portion, vibrates, the degree of freedom of bending in addition to the expansion and contraction of the elastic body 7 is greatly affected, and the responsiveness of the speaker to low frequency signals is greatly improved. In addition, the peripheral edge of the sounding body 4 is supported by the protrusion 9, which is the free end of the elastic body 7, so that the mechanical Q of the sounding body 4 decreases, and due to the gentle resonance peak of the low Q. C The low frequency side is lifted, and the improvement in the low frequency characteristics becomes even more remarkable.Furthermore, since the piezoelectric sounding body 4 is supported by the elastic body 7, it is easy to protrude (^), and the resonance peak is suppressed, and the high ( If vibrations at convex frequencies are also suppressed, an effect of 1 can be obtained.

FIG. 3 shows another embodiment, and the difference from the above embodiment lies in the shape of the elastic body 11 and the method of fixing it.

That is, the elastic body 11 is formed into a thin 10-ring shape,
The outer part 12 is placed on the annular frame 14 and fixed to the frame 14 by caulking the protrusion of the frame 14. Then, the part 13 configured as the inner free end of the elastic body 11 The piezoelectric sounding body 4 is attached (
＾ru. The operation mode and effects of this embodiment are almost the same as those of the above embodiments, so the explanation thereof will be omitted.

As explained above, the present invention supports the piezoelectric sounding body by the free end portion of the elastic body, so that a sufficient sound pressure level can be obtained even at the low end of the audible frequency range, and 1-1 if the characteristics become flat and the size can be reduced
effect can be achieved at the same time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional piezoelectric speaker, FIG. 2 is a cross-sectional view showing an embodiment of a piezoelectric speaker according to the present invention, and FIG.
The figure is a sectional view showing another embodiment. 4...Piezoelectric sounding body, 7.11...Elastic body, 9°13...Protrusion, 10r 14
...Freno. Patent applicant Murata Manufacturing Co., Ltd. Figure 1 Figure 2 Figure 5 Figure 3

Claims (1)

[Claims] A piezoelectric speaker characterized in that a part of an elastic body fixed to a frame is made to protrude from the frame to form a free end, and a piezoelectric sounding body that vibrates in a bending shooting mode is attached to the protrusion.