JPS58105700A - Piezo-electric type loudspeaker - Google Patents

Abstract

PURPOSE:To reduce the height of the whole body and obtain a thinned piezo- electric type loudspeaker, by installing a joint face having a diameter which is 0.3-0.5 time of the diameter of the armature to the central part of the diaphragm, whose edge is connected with the frame, and by flattening the frequency of the sound pressure by joint the piezo-electric vibrator to the joint surface. CONSTITUTION:A projection 6 is installed on the bottom of a frame 5 made of a synthetic resin, etc., and a discoidal piezo-electric vibrator 7 is coupled with the projection 6. Then, a cone-shaped diaphragm 9 with a joint surface 8 of a diameter which is 0.3-0.5 times of the diameter (d) of the armature 7 is adhered to the upper surface of the armature 7. Furthermore, the edge of the diaphragm 9 is connected with the edge of the frame 5 and the central part of the joint surface 8 of the diaphragm 9 is lifted up so that the face 8 forms a dome-shaped part 10. Thus the piezo-electric loudspeaker of this invention is formed. Then, the frequency of the sound pressure of the speaker is flattened and the speaker is made thinner by reducing the height of the whole body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker using a piezoelectric vibrator.

A conventional piezoelectric speaker has a structure as shown in FIG.

That is, a protrusion 2 is formed on the inner bottom surface of a frame 1 made of synthetic resin or the like.
A piezoelectric vibrator 3 formed into a disk shape by pasting electrodes and metal plates on a piezoelectric ceramic plate is supported on the protrusion 2 by adhesive, etc., and a cone-shaped diaphragm is mounted on the top surface of the piezoelectric vibrator 3. 4
The top of the diaphragm 4 is connected to the frame 1, and the peripheral edge of the diaphragm 4 is connected to the frame 1.
It was bonded to the 0 peripheral portion with adhesive or the like.

The top of the diaphragm 4 has a diameter of 0 with respect to the diameter d of the piezoelectric vibrator 3.
．． It was cut to a size of 2d or less to increase the bonding area.

However, as shown by the broken line in Figure 7, this configuration has the disadvantage that it is not possible to suppress the peak of resonance of the second or higher order, making it impossible to obtain a flat sound pressure frequency characteristic. Even when using only the diaphragm 4, it is not possible to cut off the high range as shown by the broken line in Figure 8, and the diaphragm 4 needs to have a high overall height to reproduce the same high range limit frequency. There were some drawbacks.

The present invention eliminates the above-mentioned conventional drawbacks, and provides a piezoelectric speaker that can obtain flat sound pressure frequency characteristics and reduce the overall height of the speaker at the same high-frequency reproduction limit frequency. The purpose is to

In order to achieve the above object, the present invention is characterized in that a diaphragm having a joint portion with a diameter 0.3 to 0.5 times the diameter of the piezoelectric vibrator is coupled to the piezoelectric vibrator. /゛.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 8 of the drawings.

First, in the embodiment shown in FIG. 2, reference numeral 5 denotes a frame made of synthetic resin or the like, and a protrusion 6 is provided on the inner bottom surface of this frame 6.

A disk-shaped piezoelectric vibrator 7 called a monomorph or bimorph, which is composed of a piezoelectric ceramic plate provided with metal electrode plates and electrodes, is bonded to the protrusion e using a rubber adhesive or the like. The top surface of this piezoelectric vibrator 7 has a piezoelectric vibrator 7
A cone-shaped diaphragm 9 having a joint surface 8 with a diameter of 0.3 to 0.5 d is adhesively bonded to the diameter d of the diaphragm 9.
The zero peripheral edge is connected to the peripheral edge of the frame 6. Note that the inside of the joint surface 8 of the diaphragm 9 is a dome-shaped portion 1o.

Generally, the fundamental resonance frequency fr1 of the piezoelectric vibrator 7 is given by: However, Q is Young's modulus, P is density, JP-A-58-
105700(2)' σ is the Boann ratio, r is the radius of the element, and t is the thickness of the element.

Moreover, the secondary resonance frequency h2 with respect to this fundamental resonance frequency fr+ is given by fr2-3.91fr1.

In the case of this secondary resonance, the piezoelectric vibrator 7
Nodes occur at 0.38 d and 0.88 d.

Therefore, the bonding surface 8 of the diaphragm 9 coupled to the piezoelectric vibrator 7 is set to 0.
．． By setting it in the range of 3 to 0.6 d, the piezoelectric sensor 70
It is possible to suppress the peak of the sound pressure level that occurs during secondary co-photography.

In addition, as another embodiment, as shown in FIG.
The joint surface 8 is defined as a dimension that satisfies 0.3 to Q, sa with respect to the diameter d.

Note that the apex angle α between a completely conical diaphragm and the diaphragm of the present invention is
When configuring a piezoelectric speaker with the same values, as shown in FIGS. .

6.

Further, by adopting the configuration of the present invention, the sound pressure frequency characteristic can be made extremely flat as shown by the solid line in FIG. By suppressing the influence of resonance, it is possible to cut off the high frequency range as shown in FIG.

Since the piezoelectric speaker of the present invention is configured as described above, the sound pressure frequency characteristics can be flattened, the average sound pressure level can be increased, and the overall height can be reduced, allowing for a thinner design. Potash is measurably of great industrial value.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional piezoelectric speaker, Figure 2 is a sectional view of an embodiment of the piezoelectric speaker of the present invention, and Figure 3 is the operation of secondary resonance of the piezoelectric vibrator of the same piezoelectric speaker. 4 is a cross-sectional view showing another embodiment, FIGS. 5 and 6 are cross-sectional views for comparing the total heights of the piezoelectric speaker of the conventional and the present invention, and FIG. 7 is a cross-sectional view of the conventional and present piezoelectric speakers. FIG. 8 is a sound pressure frequency characteristic diagram of the piezoelectric speaker of the invention in a specific frequency band. 6...Frame, 6...Protrusion, 7...
...Piezoelectric vibrator, 8...Joint surface, 9...
...Vibration plate. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 7 Figure 118 → Koba Kyou -1 Kei

Claims (1)

[Claims] A piezoelectric speaker in which a bonding surface 0.3 to 0.5 times the diameter of the piezoelectric diaphragm is provided in the center of a diaphragm whose peripheral portion is connected to a frame, and a piezoelectric vibrator is bonded to this bonding surface.