JPS5840716Y2 - piezoelectric buzzer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric buzzer, and particularly aims to stably obtain a low oscillation frequency in a piezoelectric buzzer having a small diameter.

FIG. 1 shows the configuration of a conventional piezoelectric buzzer.

In the figure, reference numeral 1 denotes a metal cylinder, one end of which is open, from which a plurality of mounting terminals 2 are protruded, and a piezoelectric ceramic plate 3 is affixed to the inner bottom.

This pasted part of the piezoelectric ceramic plate 3 becomes a vibrator, and when an electric signal is applied between the lead wire 4 connected to each electrode 3 a and 3 b of the piezoelectric ceramic plate 3 and the mounting terminal 2, the vibration is generated. The child part vibrates in bending mode to generate sound waves.

FIG. 2 shows a state in which the mounting terminals 2 and lead wires 4 are connected to the printed circuit board 5 and the piezoelectric buzzer is fixed.

In this state, when the electric signal applied to the piezoelectric buzzer is swept from a low frequency to a high frequency, the piezoelectric buzzer has two resonances near the operating frequency, as shown in FIG. 4a.

Nodal circles 6 and 7 indicate these two resonance states,
At this time, one nodal circle 7 does not become a perfect circle due to the influence of the mounting portion of the terminal 2.

The admittance characteristic at this time is shown by dotted line A in FIG.

From this, it can be seen that there are two resonance frequencies 6' and 7'.

Figure 6 shows an oscillation circuit using the piezoelectric buzzer described above, which uses the resonance described above to generate oscillation, but since there are two resonance frequencies as described above, the circuit is turned on. There were drawbacks such as oscillation at a fixed rate each time at one of the two resonances, and the oscillation frequency changing due to some stimulus during oscillation.

Furthermore, the resonant frequency is lower as the diameter and thickness of the vibrator section becomes larger, but the diameter is generally limited by the shape around the mounting part, and there are also limits to thinning. With a diameter of 20 mm, a frequency in the vicinity of 4 to 6 KHz was obtained, and it was difficult to obtain a frequency lower than this.

The present invention eliminates the above-mentioned conventional drawbacks.

One embodiment will be described below with reference to the accompanying drawings.

In the drawings, parts that are the same as those in FIGS. 1 and 2 will be described with the same numbers.

FIG. 3 shows a protrusion 10 protruding from the open end of the metal cylinder 1 in the same direction as the mounting terminal 2, and the tip of the protrusion 10 with the mounting terminal 2 inserted and fixed into the printed circuit board 5 together with the node wire 4. is arranged so as to come into contact with the surface of the printed circuit board 5.

The state of the nodal circle 11 at this time is shown in FIG. 4, and the admittance characteristic is shown by the solid line B in FIG. 5, respectively.

By bringing the protrusion 10 into contact with the printed circuit board 5 in this manner, the resonant part having a nodal circle that is not a perfect circle, which conventionally occurs due to the influence of the mounting part, disappears, and the frequency is also low. at 3KHz
I was able to obtain nearby frequencies.

When such a piezoelectric buzzer is used in the oscillation circuit shown in FIG. 6, stable oscillation and a low oscillation frequency can be obtained.

Note that the position of the protrusion 10 is most effective when it is provided in the middle between the mounting terminals 2, and the closer the protrusion 10 is to the mounting terminal 2, the more the effect decreases, albeit slightly. confirmed.

Further, the protrusion 10 does not need to be newly formed as shown in FIG. 3, and for example, a burr or the like generated at the open end when manufacturing a cylindrical body with one end open may be used as is.

In the above embodiment, a three-terminal piezoelectric buzzer has been described, but similar effects can be obtained even if the present invention is applied to a two-terminal piezoelectric buzzer.

As explained above, according to the present invention, by providing the open end of the metal cylindrical body constituting the piezoelectric buzzer with a protrusion that comes into contact with a mounting body such as a printed circuit board, a stable oscillation operation with a low frequency can be obtained. I can do it.

[Brief explanation of the drawing]

Figures 1a and 1) are cross-sectional views and bottom views of a conventional piezoelectric buzzer.
Fig. 2 is a sectional view of the piezoelectric buzzer shown in Fig. 1 attached to a printed circuit board, Fig. 3 is a sectional view showing how the piezoelectric buzzer is used in an embodiment of the present invention, and Fig. 4 a and l) are A diagram showing a comparison of the nodal circles during vibration of the conventional piezoelectric buzzer and the piezoelectric buzzer of the present invention,
FIG. 5 is a diagram showing a comparison of the admittance characteristics of a conventional piezoelectric buzzer and the present piezoelectric buzzer, and FIG. 6 is a diagram showing an example of an oscillation circuit using a piezoelectric buzzer. 1...Metal cylindrical body, 2...Mounting terminal,
3...Piezoelectric ceramic plate, 4...Lead wire,
5... Printed circuit board, 10... Protrusion.

Claims (1)

[Scope of utility model registration request] (1) A piezoelectric ceramic plate is fixed to the inner bottom of a metal cylindrical body with one end open, and a plurality of mounting terminals are provided protruding from the open end of the metal cylindrical body, and a plurality of mounting terminals are positioned between the mounting terminals. A piezoelectric buzzer (2) comprising a projection provided at the open end of the metal cylindrical body with a projection that comes into contact with the mounting body while the mounting terminal is fixed to the mounting body; a projection is formed approximately in the center between each mounting terminal; A piezoelectric buzzer according to claim 1 of the utility model registration claim.