JPS5835000B2 - piezoelectric speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker using two pieces of flexible piezoelectric film as a bimorph diaphragm. The bimorph diaphragm is indirectly supported and fixed, and the bimorph diaphragm is made to expand and contract in the direction of its waveform, and the bimorph diaphragm formed into a waveform moves the bimorph diaphragm unit from its end to the inflection point or at each inflection point. The present invention relates to a speaker in which adjacent bimorph diaphragm units expand and contract in a waveform-shaped direction in response to an input signal, and air is sucked in and out from behind the bimorph diaphragm.

Conventionally, piezoelectric speakers that use this type of piezoelectric film as a bimorph as a diaphragm include those in which the bimorph diaphragm is stretched directly on a plane or in a curved manner, or in which it is formed into a continuous semicircle and stretched. However, in both cases, the air was simply vibrated directly in the direction of the expansion and contraction motion of the bimorph diaphragm, and as a result, the basic characteristics of the speaker, such as sound pressure level and directivity characteristics, were very poor.

This invention was made by focusing on these conventional drawbacks, and provides a piezoelectric speaker using a completely new method using a piezoelectric film in a bimorph configuration.The main purpose of this invention is to use a piezoelectric film with flexibility to A bimorph diaphragm is created with a bimorph configuration, and the effective length of the bimorph diaphragm is effectively extended structurally, and electricity is generated in a completely new way without simply vibrating the air in the direction of the expansion and contraction motion of the bimorph diaphragm. An object of the present invention is to provide a piezoelectric speaker that performs mechanical conversion.

Another object of the present invention is to provide a piezoelectric speaker that is easy to manufacture and has excellent basic speaker characteristics such as sound pressure level and directional characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to figures showing one embodiment to which the present invention is applied.

1, 2, and 3 are a sectional view, a front view, and a partially enlarged sectional view of a piezoelectric speaker showing an embodiment of the present invention.

In these figures, IA and IB are piezoelectric films made of a polymeric material such as polyvinylidene fluoride PVDF, which have been variously processed so that the entire surface exhibits piezoelectricity in the same direction, and these two piezoelectric films IA and IB are The bimorph diaphragm 1 is constructed by laminating them together taking into account the polarization direction that determines the direction of piezoelectricity.

This bimorph diaphragm 1 is provided with electrodes la and lb formed by conductive metal layers on both sides by vapor deposition or the like, and its cross section is curved into a waveform of at least one cycle with a predetermined curvature.

In addition, the bimorph diaphragm 1 formed into a waveform forms bimorph diaphragm units 1-11, 12, 13, etc. in sections from its inflection point to each inflection point. .

Note that the piezoelectric film IA constituting the bimorph diaphragm 1,
In this embodiment, the polarization direction of IB is directed one direction outward from the center of the bimorph diaphragm 1 which is laminated together, as shown in FIG. 3, which is an enlarged view of section P in FIG. 1. This is the direction of the arrow in the figure (Figure 3).

Edges 2 support both ends of the bimorph diaphragm 1, and are made of an elastic material designed to elastically support the bimorph diaphragm 1, and are formed in a corrugated shape like the bimorph diaphragm 1.

Reference numeral 3 denotes a support member that directly holds the edge 2 or the bimorph diaphragm 1; in the case of the embodiment, the bimorph diaphragm 1 is indirectly held via the edge 2.

This support member 3 is a member such as the base or frame of this piezoelectric speaker, and is an immovable member that does not directly vibrate by the bimorph diaphragm 1.

Electrode 1a of bimorph diaphragm 1 configured in this way,
Input signal E to 1b.

To explain the operation when E is applied, first, an input signal E is applied to the electrode 1a of one piezoelectric film constituting the bimorph diaphragm 1.

When a positive voltage of E is applied, the piezoelectric film 1A receives the input signal E in its polarization direction.

Since a positive voltage of E is applied, the entire piezoelectric film 1B contracts, and the input signal E is applied to the piezoelectric film 1B in the opposite direction to its polarization direction.

Since a positive voltage of is applied via the piezoelectric film 1A,
Stretch overall.

Therefore the piezoelectric film IA. The bimorph diaphragm 1 made of 1B and formed into a wave shape breaks its initial curvature waveform shape and becomes individual bimorph diaphragm units 11, 13, (
(hereinafter referred to as odd numbered figures)...... is expanded at each inflection point of the waveform as a boundary, and the individual bimorph diaphragm units t-12, 14 (hereinafter referred to as even numbered figures) are expanded at each inflection point of the waveform.・・・・・・
... is compressed as a whole at each inflection point of the waveform, and is displaced as shown by the dotted line A in Fig. 1, and as a result, as shown by the white arrow in Fig. 1, the bimorph diaphragm Unit IL
13, .
14, . . . discharge air in the same way.

On the other hand, an input signal E is input to the electrode 1b of the piezoelectric film 1B constituting the bimorph diaphragm 1.

When a positive voltage is applied, the piezoelectric film receives an input signal E in the opposite direction to its polarization direction.

Since the positive voltage of is applied via the piezoelectric film 1B,
Since the positive voltage of the input signal Eo is applied to the piezoelectric film 1B in its polarization direction, the piezoelectric film 1B contracts as a whole.

Therefore, the bimorph diaphragm 1 formed into a waveform made of piezoelectric films IA and IB loses its initial waveform shape with curvature, and the individual bimorph diaphragms HL13, . . .
. . . is compressed as a whole at each inflection point of the waveform, and each bimorph diaphragm unit 12, 14
, . . . is expanded as a whole at each inflection point of the waveform, and is displaced as shown by the dotted line B in Figure 1, and as a result, as shown by the black arrow in Figure 1. As shown, the bimorph diaphragm units 11, 13, . . . exhaust the air on the side curved in the waveform, and the bimorph diaphragm units 12, 14, . ... inhales air in the same way.

Therefore, this bimorph frequency 1 electrode 1a.

1b is a positive and negative alternating current input signal E.

By applying , each bimorph diaphragm unit NL13,・
. . . and bimorph diaphragm unit 12,
14, . . . are input signals E with each inflection point as a boundary.

Due to the positive and negative voltages of produce.

In this embodiment, the bimorph diaphragm 1 is formed into a wave shape and each inflection point is arranged in a straight line, but the geometric arrangement of each inflection point may be curved or circular as necessary. You may force it to form a superior shape.

Further, both ends of the bimorph diaphragm 1 are supported and fixed to support members 3, 3 via edges 2, 2 formed into waveforms of different sizes with respect to the cross-sectional waveform of the bimorph diaphragm 1. 2.2 is provided as needed and is not essential to this invention.

As explained above, the present invention uses a bimorph diaphragm made by laminating two flexible piezoelectric films exhibiting piezoelectricity in a single direction so that their polarization directions are opposite to each other for one or more cycles. Since the bimorph diaphragm is formed into a wave shape and its both ends are supported and fixed, and an input signal voltage is applied between the electrodes formed on the front and back surfaces of this bimorph diaphragm, there is When one side expands in the direction of wave propagation, the other side contracts, vibrating.
Air vibration can be applied without causing any overall expansion or contraction, and when the piezoelectric film on the front side of each diaphragm unit expands, the piezoelectric film on the back side contracts.
On the other hand, when the piezoelectric film on the front side contracts, the piezoelectric film on the back side can act to expand, and therefore the change in curvature in each unit increases synergistically.
Large air vibrations can be caused without expanding or contracting the entire diaphragm, and the diaphragm as a whole does not vibrate in the front-rear direction, making it possible to construct a thin speaker.

[Brief explanation of the drawing]

The figures are all related to the present invention; FIG. 1 is a sectional view thereof, FIG. 2 is a front view thereof, and FIG. 3 is an enlarged view of the bimorph diaphragm shown in FIG. 1. 1...Bimorph diaphragm, IA, IB...
...Piezoelectric film, la, lb...electrode, 2.
...Edge, 3...Support member, Eo...
...Input signal, 11, 12°13, ...
・・・・・・Bimorph diaphragm unit.

Claims (1)

[Claims] 1 Two flexible piezoelectric films exhibiting piezoelectricity in a single direction are pasted together so that their polarization directions are opposite to each other to form a bimorph structure, and at least one cycle or more is applied at predetermined intervals in the cross section. The bimorph diaphragm is equipped with a bimorph diaphragm curved into a corrugated shape and a support member that supports and fixes both ends of the bimorph diaphragm, and an input signal voltage is applied between electrodes formed on the front and back surfaces of the bimorph diaphragm. A piezoelectric speaker characterized by: