JPS5992699A - Piezoelectric diaphragm for buzzer - Google Patents

Abstract

PURPOSE:To obtain a small-sized buzzer which sounds at a low frequency by sticking a piezoelectric magnetic plate to the flat surface part of a thin plate of elastic material, such as metal, which is sectioned in a U-shape and has plural notches at a bent part. CONSTITUTION:The plural notches 13 are made in the outer circumferential part 12 of the metallic plate 11 and is bent to obtain a U sectioned shape. The piezoelectric magnetic plate 5 is stuck to the top plane of the metallic plate 11 and a main electrode 6 and a feedback electrode 7 are provided. Lead wires 8- 10 are attached to the electrodes 6 and 7 and metallic plate 11 and connected to an oscillation circuit which is not shown in a figure. Consequently, the oscillation sound of low frequency is obtained even when the size is reduced, and the length of the bent part 12 is controlled to adjust the musical scale of the oscillation sound.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a piezoelectric diaphragm for a buzzer in which a piezoelectric ceramic plate is attached to a thin elastic plate such as a metal plate, and in particular, it is used to support the vibration nodes of the piezoelectric diaphragm. This relates to a piezoelectric diaphragm used in a piezoelectric buzzer.

Conventional configuration and its problems A piezoelectric buzzer with a structure that supports the nodes of a diaphragm has a piezoelectric diaphragm configured as a three-terminal structure with a return electrode, and a tube of vibration at the resonant wave number of the piezoelectric diaphragm. Support the inside to obtain sharp resonance characteristics.

2.7 The so-called self-oscillation type is widely used, which generates sound near the resonant frequency of the piezoelectric diaphragm by constructing a self-oscillation circuit using its resonance characteristics. A cross-sectional view of an example of a conventional piezoelectric buzzer of this type is shown in FIG. This conventional piezoelectric buzzer has a ring-shaped piezoelectric vibrator mounting part 3 that protrudes from the case 2 of the piezoelectric sounding body, at which the cylindrical part of the vibration at the resonance frequency when the piezoelectric diaphragm 1 is allowed to freely vibrate.
The structure is such that it is supported by adhesive, etc. A typical example of the piezoelectric diaphragm 1 used here is the one whose plan view is shown in FIG. 2, and has a structure in which a piezoelectric ceramic plate 5 is integrated with a conductive elastic flat plate 4 such as a metal plate. , a piezoelectric ceramic plate 60 surface vCt/i, a main electrode 6 and a return electrode 7 are provided, and the electrode provided on the back surface is electrically connected to the metal plate 4. For example, lead wires 8, 9, and 10 are connected to the main electrode 6, return electrode 7, and metal plate 4 as means for connecting to an oscillation circuit. As an example of a self-excited oscillation circuit that drives this piezoelectric buzzer, the one shown in FIG. 3 is often used.

31° - This type of piezoelectric buzzer has a simple drive circuit and high sound pressure, so it is often used for various alarm sounds, but as the devices used have become smaller, piezoelectric buzzers have also become smaller. There is a strong demand for a system with a relatively low sounding frequency. However, in order to miniaturize the piezoelectric buzzer, the diameter of the piezoelectric diaphragm must be reduced, which is a condition that contradicts the reduction in the sound frequency, so it is possible to simultaneously reduce the size of the piezoelectric buzzer and lower the sound frequency. It is a big challenge to do so.

In order to lower the resonant frequency without increasing the diameter of the piezoelectric diaphragm, there is a method of making the piezoelectric diaphragm thinner, but this method also has its limits and is insufficient. Furthermore, if the outer periphery of the piezoelectric diaphragm is supported, the resonant frequency will be lowered, but the Q during co-photography will be lowered, making it unsuitable for self-excited oscillation.

Purpose of the Invention The present invention eliminates these conventional drawbacks and realizes a piezoelectric buzzer that is small and has a relatively low sounding frequency. The purpose is to reduce the

Structure of the Invention In order to achieve this object, the piezoelectric diaphragm according to the present invention is made by bending the outer periphery of the flat disk to make it into a tray shape with a U-shaped cross section. , is characterized by providing a notch in the bent portion, and has a configuration in which a piezoelectric ceramic plate is attached to a flat disk portion of this metal plate.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 4, the same parts as in FIG. 2 of the conventional example are indicated by the same symbols.

In FIG. 4, reference numeral 11 is a metal plate whose outer periphery is bent at right angles, and a notch 13 is formed in the bent part 12.
is provided.

A piezoelectric ceramic plate 5 is attached to the upper surface of the metal plate 11, and a main electrode 6 and a return electrode 7 are provided on the piezoelectric ceramic plate 5. Further, lead wires 8, 9, and 10 are connected to each electrode and the metal plate.

Self-excited oscillation 61-- which incorporates this piezoelectric diaphragm into the case
An embodiment of the jib buzzer is shown in cross-section in FIG.

In FIG. 5, the same parts as in FIG. 1 of the conventional example are indicated by the same symbols.

As is clear from FIG. 5, the bent portion 12 of the piezoelectric diaphragm 5
is bent in the direction of entering the inside of the case 2.

Effects of the Invention By bending the outer periphery of the metal plate of the piezoelectric diaphragm into a U-shape and making cuts in the bent portion to divide the bent portion as in the present invention, the bent portion can also vibrate freely. The same effect as increasing the apparent diameter of the main diaphragm can be obtained without increasing the actual diameter of the diaphragm, and the resonant frequency of the piezoelectric diaphragm of the present invention can be adjusted by stretching the bent portion of the outer periphery. The resonant frequency drops to almost the same as when it is made into a flat plate. Since the resonant frequency of the piezoelectric diaphragm is inversely proportional to the square of the diameter, its effect is very large. Therefore, even if the diameter of the diaphragm is the same, the resonant frequency can be changed by changing the length of the bent part, and the resonant frequency can also be changed by 6 / -7 by changing the width of the cut in the bent part (width of the bent part). I can do it. Therefore, the degree of freedom in designing piezoelectric diaphragms with the same diameter is greatly increased. Furthermore, since the bent portion is divided into many parts and can freely vibrate, the bent portion does not suppress vibration and reduce the Q of the piezoelectric diaphragm, making it ideal for self-excited oscillation. Furthermore, when this piezoelectric diaphragm is incorporated into a case, the bent portion of the metal plate enters into what was previously a dead space within the case, making it possible to reduce only the sounding frequency without increasing the size of the piezoelectric buzzer. As described above, the present invention is very useful for downsizing and lowering the frequency of piezoelectric buzzers.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional self-oscillation type piezoelectric buzzer with node support, Fig. 2 is a plan view showing an example of a piezoelectric diaphragm used in the piezoelectric buzzer of Fig. 1, and Fig. 3 is A circuit diagram showing an example of an oscillation circuit that drives a self-oscillation type piezoelectric buzzer, FIGS. FIG. 7 is a cross-sectional side view of a self-oscillation type piezoelectric buzzer using a diaphragm of 71-mm. 5...Piezoelectric diaphragm, 12...Bend portion, 13...Notch.

Claims (1)

[Claims] It has a thin elastic plate made of metal, etc., which has a U-shaped cross section and is divided into a plurality of pieces by making a plurality of cuts on the outer side, and a piezoelectric ceramic plate is attached to the flat part of the elastic thin plate. A piezoelectric diaphragm for FI buzzer made by pasting.