JPS5836558B2 - electroacoustic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroacoustic transducer that uses a flat diaphragm made of a piezoelectric polymer material or the like and is capable of obtaining a large amplitude.

Conventional speakers using polymeric piezoelectric materials convert stretching vibration into bending vibration, so when using a flat plate, they have a bimorph structure, or a structure with both ends fixed to give it a curvature. It was.

Therefore, it cannot be used because of its thin shape, and its piezoelectric constant is small and its power as a speaker is weak, so the efficiency of the direct radial type is low, and therefore it cannot be used in practice.

Furthermore, it has various drawbacks, such as not being able to obtain a large amplitude and therefore not being able to be used for low-frequency applications.

The present invention aims to solve the above-mentioned drawbacks in the prior art.The present invention applies a driving force of an audio signal in the sound wave emission direction of a flat diaphragm, and a frequency twice that of the audio signal is applied in a direction perpendicular to this driving force. The device is characterized in that it is configured to apply a driving force to emit sound waves of audio signals.

FIG. 1 is a sectional view of a piezoelectric speaker showing an embodiment of the present invention. In the figure, 1 is a diaphragm, and the diaphragm 1 is made of a polymeric piezoelectric material with metal vapor-deposited on both sides. , a signal voltage E2 having twice the frequency of the audio signal is applied to both sides through lead wires.

Also, 2 is a voice coil bobbin, 3 is a voice coil, and 4 is a voice coil bobbin.
is a yoke of a magnetic circuit, 5 is a sweater pole, 6 is a permanent magnet, and the voice coil 3 has an audio signal voltage E1 of frequency f.
is added.

Note that 7 is a supporting end, which may be made of a rubber material and may be a free end in order to achieve high compliance, or may be fixed to be a fixed end.

Next, the operating principle of the speaker configured as described above will be explained with reference to FIGS. 2 to 4.

Now, considering the support end 7 as a free end, when a signal voltage E2 is applied to the diaphragm 1, a force in the direction of expansion and contraction acts on the diaphragm 1, and when an audio signal voltage E0 is applied to the voice coil 3, the diaphragm A force acts on the diaphragm 1 in a direction that moves the diaphragm 1 in the front-back direction.

Now, if a voltage with a frequency f is added to the audio signal voltage E1 and a voltage with a frequency 2f is added to the signal voltage E2, a schematic diagram of vibration and driving force becomes as shown in FIG. 2.

This schematic diagram will be explained in detail with reference to FIGS. 3 and 4. A"-h in FIGS. 2 and 4 is the audio signal voltage E1, and signal voltage E2 is the audio signal voltage E1 of a"h in FIG. The state of vibration of the diaphragm 1 corresponding to each case is shown when changing in order.

Now, assuming that the diaphragm 1 receives a force in the compression direction when the signal voltage E2 is positive, and receives a force in the extension direction when the signal voltage E2 is negative, the diaphragm 1 responds to changes in the signal voltage as shown in FIG. As shown in Fig. 4, the state changes from a non-stretching state to a compression direction ↑ and an elongation direction ↓.

That is, at the time a, the diaphragm 1 does not expand or contract with the signal voltage E1-E2-0, and at the time b, the diaphragm 1 has the audio signal voltage E1-E2-0.
It starts to bend in the -X direction with the driving force of 1, and at the same time the signal voltage E2
The driving force acts in the compression direction and increases the amplitude.

When C, the audio signal voltage E1 is the highest, and the signal voltage E2-O
Therefore, only the audio signal voltage E1 is applied.

Further, when reaching d, the audio signal voltage E1 decreases and the amplitude begins to decrease, and at the same time, the signal voltage E2 applies stretching force, so that the decrease in the amplitude is accelerated.

Point e indicates the same state as in case a, and thereafter the phase relationship of the signal voltages becomes reverse to that described above, and the diaphragm 1 changes as f, g, and h.

As is clear from the above description, according to the present invention, a signal voltage with a frequency of 2f, which is twice the audio signal, is applied to both sides of the diaphragm, and a driving force of an audio signal with a frequency of f is applied in a direction perpendicular to this. Therefore, the diaphragm can be configured to be flat and the diaphragm can be vibrated to a large extent.

Furthermore, by giving the signal voltage E2 a certain frequency characteristic, there is an advantage that only a certain frequency range can be made stronger.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the speaker according to the present invention, FIG. 2 is a schematic diagram showing the state of vibration of the diaphragm of the speaker according to the present invention, and FIGS. 3 and 4 are schematic diagrams of FIG. 2. It is an explanatory diagram for explaining a figure. 1...Diaphragm, 2...Voice coil bobbin, 3...Voice coil, 4...Yoke, 5...Center pole, 6・・・・・・
Permanent magnet, 7...Support end.

Claims (1)

[Claims] 1 Apply the driving force of the audio signal in the direction of the sound wave emission of the flat diaphragm, and add a driving force of twice the frequency of the audio signal in the direction perpendicular to this driving force so that the sound wave of the audio signal radiates. An electroacoustic transducer characterized by: