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DESCRIPTION JPH08116595

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DESCRIPTION JPH08116595
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric transformer utilizing the piezoelectric effect of a piezoelectric body.
[0002]
2. Description of the Related Art A piezoelectric transformer using a piezoelectric material such
as lead zirconate titanate (PZT) is already well known. FIG. 1 is a perspective view showing an
example of a piezoelectric transformer using a piezoelectric body. In the figure, 1 is a
piezoelectric body of length L and width T, 2a to 2c are electrodes, 3a to 3d are lead wires, 4 is a
lead The primary side terminal 5 is a secondary side terminal.
[0003]
Next, the operation will be described. By applying a voltage (V1) having a unique frequency (f0)
determined by the length (L) of the piezoelectric body 1 to the primary side terminal 4, the
piezoelectric body 1 is mechanically vibrated, and this vibration is generated by the piezoelectric
effect. In the piezoelectric body 1, it is converted again to a power of a predetermined voltage,
and a voltage (V2) is generated at the secondary side terminal 5 through the electrode 2c. At this
time, the voltage (V2) generated at the secondary side terminal 5 is determined by the following
equation (1). V2 = α · (L / T) · V 1 (1: (α: proportional constant) Therefore, if you want to
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increase the voltage (V2) while maintaining the desired performance, the length (L) of the
piezoelectric body 1 You need to extend it.
[0004]
Further, even if it is not necessary to increase the voltage (V 2) in particular, in order to maintain
the predetermined performance, the length (L) of the piezoelectric body 1 is increased to some
extent except that the piezoelectric effect of the piezoelectric body 1 is enhanced. You need to
keep it long. Further, the inherent frequency (f0) of the piezoelectric body 1 is determined by f0
= 2v0 / L (2) (v0: the speed of sound propagating through the piezoelectric material), but it is
used for the conventional piezoelectric body 1 In the case of a piezoelectric material, the sound
velocity (v0) is fast, and in order to obtain a desired frequency (f0), it is generally necessary to
increase the length (L) of the piezoelectric body.
[0005]
As described above, since it is necessary to make the length (L) of the conventional piezoelectric
transformer relatively long due to the material of the piezoelectric body, it is possible to
miniaturize the device. There was a problem that it was difficult.
[0006]
The present invention has been made to solve the above problems, and the size of the device can
be reduced by relatively shortening the length (L) of the piezoelectric body while obtaining
performance equivalent to that of the conventional piezoelectric transformer. The aim is to
provide a possible piezoelectric transformer.
[0007]
SUMMARY OF THE INVENTION A piezoelectric transformer according to the present invention is
characterized by using a piezoelectric body made of a porous piezoelectric material in which a
large number of pores are formed.
A plurality of piezoelectric members made of a porous piezoelectric material in which a large
number of pores are formed are stacked with a plurality of lead-out electrodes interposed
therebetween to form a multistage transformer.
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Furthermore, it is characterized in that the lengths of the plurality of stacked piezoelectric
members are made different from each other.
[0008]
The piezoelectric body made of a porous piezoelectric material has a high piezoelectric effect,
and the speed of sound propagating through the piezoelectric body becomes slow. Therefore,
even if the length (L) of the piezoelectric body is shortened, equivalent performance can be
obtained.
[0009]
Embodiments of the present invention will be described below with reference to the drawings.
The device configuration in the embodiment of the present invention is the same as the
configuration shown in FIG. 1 except that the piezoelectric body 1 is different from that of the
conventional device, and the operation is also the same.
[0010]
Next, the piezoelectric body 1 in the present invention will be described. As the piezoelectric
body 1 in the present invention, a porous piezoelectric material in which a large number of pores
are formed is used. FIG. 2 is a figure which shows an example of the manufacturing method of
the porous piezoelectric material used for a present Example, and in the figure, S1-S3 show each
step, respectively. In step S1, for example, a powder of lead zirconate titanate (PZT) having an
average particle diameter of 1.2 μm and a methacrylic resin powder (for example, a polymer of
polymethyl methacrylate) having an average particle diameter of 30 μm are mixed at an
appropriate ratio. The mixing ratio determines the ratio of pores to the total volume of the
manufactured porous piezoelectric material (hereinafter referred to as the porosity), and as
described later, the piezoelectric effect and the velocity of sound propagating through the
material are also determined. It will be decided. In the next step S2, as in the conventional
production of the piezoelectric body, molding and firing are performed, and in the next step S3,
an electric field of about 1 kV / mm is applied to polarize it to obtain a porous piezoelectric
material.
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[0011]
FIG. 3 is a diagram showing the relationship between the porosity and the piezoelectric effect,
and as shown in the figure, by making it porous, the piezoelectric effect necessarily increases,
and the piezoelectric effect depends on the porosity. I understand that. Therefore, by making it
porous, it is possible to configure a high-performance piezoelectric transformer with piezoelectric
bodies of the same size. FIG. 4 is a diagram showing the relationship between the porosity and
the speed of sound (v0) propagating through the material, and as shown in the figure, the speed
of sound (v0) propagating through the material is porous when it is made porous. It can be seen
that as the rate increases, it becomes slower. Therefore, from the above-mentioned formulas (1)
and (2), a piezoelectric transformer of high voltage and a desired working frequency can be
obtained by the smaller-sized piezoelectric body 1 by making it porous.
[0012]
Next, a method of manufacturing a piezoelectric transformer will be described. The porous
piezoelectric material that has been fired in step S2 of FIG. 2 is processed into a rectangular
shape as shown in FIG. 1, and silver paste is printed at a predetermined position and baked to
form electrodes 2a to 2c. The lead wires 3a to 3d are connected to form the primary side
terminal 4 and the secondary side terminal 5 and polarization is performed by applying an
electric field of 1 kV / mm between the respective terminals.
[0013]
FIG. 5 is a view for explaining another embodiment of the present invention, in which a plurality
of the piezoelectric bodies 1 made of the above-mentioned porous piezoelectric material are
stacked with a plurality of extraction electrodes interposed therebetween to constitute a
multistage transformer. An example is shown. By configuring such a multistage transformer,
different voltages can be generated from the output terminals 5a, 5b,. The lengths L1, L2,... Of
the piezoelectric bodies 1 may be the same or different.
[0014]
As described above, according to the piezoelectric transformer of the present invention,
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downsizing of the device and high performance can be achieved by using a piezoelectric body
made of a porous piezoelectric material in which a large number of pores are formed. Has the
effect of being able to
[0015]
Brief description of the drawings
[0016]
1 is a perspective view showing a configuration example of a piezoelectric transformer.
[0017]
2 is a diagram showing an example of a method of manufacturing a porous piezoelectric material
used in the present invention.
[0018]
3 is a diagram showing the relationship between the porosity of the porous piezoelectric material
and the piezoelectric effect.
[0019]
4 is a diagram showing the relationship between the porosity of the porous piezoelectric material
and the speed of sound propagating through the material.
[0020]
5 is a diagram for explaining another embodiment of the present invention.
[0021]
Explanation of sign
[0022]
DESCRIPTION OF SYMBOLS 1 piezoelectric material 2a-2e electrode 3a-3d Lead wire 4 Primary
side terminal 5, 5a, 5b, 5c Secondary side terminal
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