JP2003017772A - Piezoelectric ceramic transformer circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure insulation of a driving section and a power generating section without lowering efficiency of a piezoelectric ceramic transformer in a piezoelectric ceramic transformer circuit. SOLUTION: A rectangular piezoelectric ceramic body 2 of a piezoelectric ceramic transformer 1 is shaped so that its length is made twice and its width a half the elastic wavelength defined by a driving frequency and propagating in the piezoelectric ceramic body 2, and a driving section 11 and a low impedance power generating section 12 are formed by forming electrodes 3 and 4 on square regions 21 and 22 having its side equaling to a half wave length and polarizing the piezoelectric ceramic body 2 in a direction of width so that resonant vibration corresponding to the driving frequency is excited in a direction of length and width in the piezoelectric ceramic body 2. A boundary section 23 between the driving section 11 and the power generating section 12 where no polarization is formed is a loop of the resonant vibration to reduce distortion of the piezoelectric ceramic body 2 contributing no voltage output even with the boundary section 23 formed wide to increase insulation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric ceramic transformer circuit.

[0002]

2. Description of the Related Art Piezoelectric ceramic transformers that utilize the piezoelectric effect of piezoelectric ceramics have been widely used in high voltage power supplies. FIG. 4 shows a general Rosen type piezoelectric ceramic transformer. In the piezoelectric ceramic transformer 9, an input electrode 901 is formed on the upper and lower surfaces of one half of an elongated and flat plate-shaped piezoelectric ceramic body 900 to form a drive section 91.
An output electrode 902 is formed on the end face of the other half to form a power generation unit 92, and the piezoelectric ceramic body 900 is polarized in the thickness direction by the driving unit 91 and in the length direction by the power generation unit 92.

When an AC voltage is applied to the input electrode 901, the piezoelectric ceramic body 900 is replaced with the piezoelectric ceramic body 900.
An elastic wave is generated which propagates in the length direction. Here, if the length of the piezoelectric ceramic body 900 and the frequency of the voltage applied to the input electrode 901 are appropriately selected, the piezoelectric ceramic body 9
00 resonates and oscillates in, for example, a half-wavelength mode, and a voltage transformed to the output electrode 902 of the power generation unit 92 is generated by the piezoelectric effect and is output to the load. The voltage extracted from the power generation unit 92 is due to the piezoelectric effect, and depends on the magnitude of the stress, that is, the strain inside the piezoelectric ceramic body 900 in the power generation unit 92.

The electric power that can be output by the piezoelectric ceramic transformer greatly differs depending on the magnitude of the impedance R of the load. The capacitance of the output part of the piezoelectric ceramic transformer is C
2. When the drive angular frequency of the piezoelectric ceramic transformer is ω, the largest electric power is output to the load satisfying R = 1 / (ωC2). In the case of the Rosen type piezoelectric ceramic transformer of FIG. 4, its value is several tens k to several hundreds kΩ.

Since a cold cathode tube for a liquid crystal backlight becomes a resistor of about 100 kΩ when turned on, it is well matched with a Rosen type piezoelectric ceramic transformer, and a step-up circuit for the cold cathode tube is provided with the piezoelectric ceramic transformer. Piezoelectric ceramic transformer circuits are widely used.

By the way, in recent years, not only those having a high resistance value such as a cold cathode fluorescent lamp but also a DC-DC converter,
Attempts have also been made to apply the piezoelectric ceramic transformer to loads such as fluorescent lamps and metal halide lamps that exhibit low impedance values of several hundred Ω or less. In this case, in the Rosen type piezoelectric ceramic transformer, the impedance value of the output portion is high as described above and a large amount of electric power cannot be output.
As disclosed in Japanese Patent No. 484, there is also proposed a thickness vibration type piezoelectric ceramic transformer in which a drive unit and a power generation unit are laminated.
Although this structure has a small impedance value at the output part, unnecessary vibration is likely to occur, and it is necessary to use a highly anisotropic piezoelectric material for the piezoelectric ceramic body.

On the other hand, like the piezoelectric ceramic transformer 9A shown in FIG. 5, the driving portion 91 is configured to use one half of the length direction of the piezoelectric ceramic body 900A as in the case of the Rosen type. 92A to the piezoelectric ceramic body 9
There is a structure in which electrodes 902A are formed on both surfaces of the piezoelectric ceramic body 900A in the other half of the piezoelectric ceramic body 900A, and the piezoelectric ceramic body 900A is polarized in the thickness direction, similarly to the drive unit 91. In this case, the impedance of the output section becomes small, and matching with a low-impedance load is good.

Further, as in Japanese Patent No. 2666562,
There is a piezoelectric ceramic body in the form of a disk, a circular input electrode is formed on both sides of a central portion of the piezoelectric ceramic body as a drive unit, and an annular output electrode is formed on the outer periphery of the input electrode as a power generation unit. This device is driven in the 3/2 wavelength mode.
Further, FIG. 6 is a modification of the one in Japanese Patent No. 2666562, which is disclosed in Japanese Patent Laid-Open No. 2000-12918. In the piezoelectric ceramic transformer 9B, the piezoelectric ceramic body 900B has a square shape, and an input electrode 901B is formed on the upper and lower surfaces of the central portion thereof to serve as a driving portion 91B. A square-shaped output electrode 902B surrounding the input electrode 901B is formed as a power generation unit 92B. With this, it is possible to make two-dimensional vibration like that of Japanese Patent No. 2666562. In the structure utilizing such two-dimensional vibration, compared with the structure shown in FIG.
The electromechanical coupling coefficient is large, and the output power per unit volume can be increased.

[0009]

By the way, in the square piezoelectric ceramic transformer (FIG. 6) of Japanese Unexamined Patent Publication No. 2000-12918, which utilizes two-dimensional vibration, a half-wavelength mode is applied in any width direction. Although it is made to vibrate, as shown in FIG. 6, the stress profile due to vibration has a maximum value in the central portion of the piezoelectric ceramic body 900B and tends to gradually decrease toward the peripheral portion of the piezoelectric ceramic body 900B. Indicates. Therefore, the piezoelectric ceramic body 90
Relatively large stress is generated also in the electrode non-formation portion, which forms a boundary between the drive portion 91B located in the inner peripheral portion of 0B and the power generation portion 92B located in the outer peripheral portion. For this reason,
If the boundary between the drive unit 91B and the power generation unit 92B where no electrodes are formed is made large in order to insulate the drive unit 91B and the power generation unit 92B, the output cannot be efficiently extracted.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a piezoelectric ceramic transformer that can efficiently take out output power and can easily achieve impedance matching with a low impedance load.

[0011]

According to a first aspect of the present invention, an input electrode is formed on the upper and lower surfaces of a piezoelectric ceramic body having a substantially rectangular flat plate shape and polarized in the thickness direction to form a drive section,
A piezoelectric ceramic transformer that forms an output electrode on the upper and lower surfaces of the piezoelectric ceramic body at a position different from the input electrode and that serves as a power generation unit, and an AC voltage is applied between the input electrodes to the piezoelectric ceramic body. In a piezoelectric ceramic transformer circuit including a power feeding means for exciting resonance vibration, the piezoelectric ceramic body is used as the resonance vibration in the resonance vibration in one width direction of the piezoelectric ceramic body and the width direction of the other side of the piezoelectric ceramic body. And a boundary between the drive unit and the power generation unit is a position that is an antinode of the resonance vibration.

Since the power generation section is composed of the piezoelectric ceramic body polarized in the thickness direction and the output electrodes formed on the upper and lower surfaces thereof, it can be suitably applied to a low impedance load.

Moreover, since the piezoelectric ceramic body is made to resonate not only in one width direction but also in the other width direction, the electromechanical coupling coefficient of the piezoelectric ceramic body is the same as that of the piezoelectric ceramic transformer of FIG. A large electric power can be taken out, which is larger than k31 in the case of vibration in the depth direction.

At the boundary between the drive section and the power generation section, which is the antinode of the resonance vibration, the stress inside the piezoelectric ceramic body is small, and therefore the strain is small. Therefore, it does not substantially contribute to the output to the load, and the efficiency of the piezoelectric ceramic transformer is not impaired even if the distance between the input electrode and the output electrode is widened to some extent. It is possible to ensure both insulation between the drive unit and the power generation unit and the efficiency of the piezoelectric ceramic transformer.

According to a second aspect of the present invention, in the first aspect of the present invention, the piezoelectric ceramic body has a size in one width direction of the piezoelectric ceramic body when a voltage is applied to the input electrode. The electrode has a shape in which the half-wavelength of the elastic wave propagating inside is a natural number multiple of two or more, and the size of the other width direction of the piezoelectric ceramic body is a natural number multiple of the half-wavelength of the elastic wave. Are formed in the width direction of the piezoelectric ceramic body and the width direction of the piezoelectric ceramic body in the area having the half wavelength of the elastic wave.

Each of the regions of the piezoelectric ceramic body has a node at the center and an antinode at both ends, regardless of the resonance vibration in any width direction, so that power can be more efficiently taken out.

According to a third aspect of the present invention, in the second aspect of the present invention, the piezoelectric ceramic body has a structure in which a peripheral edge portion is cut out so that a corner of the region is dropped.

By making the region closer to a circle, unnecessary vibrations other than the resonance vibration corresponding to the frequency of the AC voltage applied between the input electrodes can be suppressed and the power can be taken out more efficiently. it can.

[0019]

(First Embodiment) FIG. 1 shows the configuration of a piezoelectric ceramic transformer circuit according to the present invention. The piezoelectric ceramic transformer circuit is composed of the piezoelectric ceramic transformer 1 and an input circuit 5 which is a power supply unit in the preceding stage, and outputs a voltage transformed by the piezoelectric ceramic transformer 1 to a load 7.

The piezoelectric ceramic transformer 1 has a slender, flat plate-shaped piezoelectric ceramic body 2, and the piezoelectric ceramic body 2 has a piezoelectric ceramic body 2 on one half portion 21 thereof in one width direction (hereinafter, appropriately referred to as a length direction). Input electrodes 3 are formed on the upper and lower surfaces of the body 2 so as to face each other with the piezoelectric ceramic body 2 interposed therebetween.
In the half portion 21 of the piezoelectric ceramic body 2, the input electrode forming portion is polarized in the direction opposite to the input electrode 3, that is, in the thickness direction of the piezoelectric ceramic body 2, and the electric energy input from the input circuit 5 is generated by the inverse piezoelectric effect. The drive unit 11 that converts the mechanical energy of the piezoelectric ceramic body 2 is configured.

On the other hand, on the other half 22 of the piezoelectric ceramic body 2 in the longitudinal direction, output electrodes 4 are formed on the upper and lower surfaces of the piezoelectric ceramic body 2 so as to face each other with the piezoelectric ceramic body 2 interposed therebetween. The output electrode forming portion of the half portion 22 of the piezoelectric ceramic body 2 is polarized in the direction opposite to the output electrode 4, that is, in the thickness direction of the piezoelectric ceramic body 2, and the mechanical energy is converted into electrical energy again by the piezoelectric effect. The power generation unit 12 is configured.

The piezoelectric ceramic body 2 has one widthwise size (hereinafter, appropriately referred to as length) L and the other widthwise size (hereinafter, appropriately referred to as width) W: L: W = 2: It is set as 1. In addition, the electrodes 3 and 4 are in the shape of a square whose one side is smaller than the width W by one side, so that the drive unit 11 and the power generation unit 12 can be insulated from each other.

The input circuit 5 is provided with an AC voltage generator 50 for generating an AC of, for example, several tens of kHz, and the lead wire 5
A voltage is applied between the input electrodes 3 via 1, 52, and the drive unit 11 generates piezoelectric vibration due to the lateral effect. The output frequency of the AC voltage generator 50 is set to a value obtained by dividing the propagation velocity (sonic velocity) v of the elastic wave in the piezoelectric ceramic body 2 by the length L of the piezoelectric ceramic body 2. Then, since the length L corresponds to one wavelength of the elastic wave, the acoustic wave causes the piezoelectric ceramic body 2 to resonate and vibrate in the one-wavelength mode.

Further, L: W = 2: 1, the width W corresponds to a half wavelength of the elastic wave, and in the other width direction of the piezoelectric ceramic body 2 (hereinafter, simply referred to as width direction) ( 1 /
2) Resonant vibration in the wavelength mode occurs.

The piezoelectric ceramic transformer 1 can be manufactured by the green sheet method which is a general manufacturing method of piezoelectric ceramic transformers. The piezoelectric ceramic body 2 is obtained, for example, by cutting a piezoelectric ceramic sheet, which is the material thereof, so that the length is twice the width. The electrodes 3 and 4 are formed by screen printing or the like.

The operation of the present piezoelectric ceramic transformer circuit will be described. When an AC voltage is input to the drive unit 11 of the piezoelectric ceramic transformer 1 from the AC voltage generation unit 50, the piezoelectric ceramic body 2 resonates in one wavelength mode in the length direction and (1/2) wavelength mode in the width direction. To do. In the power generation unit 12, internal stress is generated in the piezoelectric ceramic body 2 due to the resonance vibration. The internal stress accompanies the strain of the piezoelectric ceramic body 2, the dielectric polarization changes according to the amount of the strain, and the mechanical energy is converted into the electrical energy again. A voltage is output to the output electrode 4 according to the magnitude of strain of the piezoelectric ceramic body 2. Since the power generation unit 12 has a structure in which the piezoelectric ceramic body 23 sandwiches the output electrode 4 in the thickness direction, it is well matched with the load 7 having a low impedance.

As described above, the piezoelectric ceramic transformer 1
Vibrates in one wavelength mode in the length direction, and vibrates in (1/2) wavelength mode in the width direction. On the other hand, since the piezoelectric ceramic body 2 has L: W = 2: 1, the driving unit 1
It is possible to think of a square region in which each side is one and the power generation unit 12 is one, and each side is a (1/2) wavelength square region. These are the half portions 21 and 22 (hereinafter, appropriately, the half portion 21). , 22 are called areas 21 and 22). Then, the areas 21 and 22 are
There is a node for the resonant vibration in both the length direction and the width direction, and the resonant vibration in each of the regions 21 and 22 is
Two-dimensional vibration is a combination of both resonance vibrations. Therefore,
The electromechanical coupling coefficient is larger than k31 in the case of resonant vibration only in the length direction of the piezoelectric ceramic body 2, and a large electric power can be taken out.

Further, FIG. 1 shows a piezoelectric ceramic transformer 1
The stress distribution (strain distribution) in is also shown. As described above, since the electrodes 3 and 4 forming portions of the piezoelectric ceramic body 2 serve as nodes, the boundary portion 23 between the driving portion 11 and the power generating portion 12 sandwiched between the input electrode 3 and the output electrode 4 is antinode. Becomes Therefore, the stress becomes large in the drive unit 11 and the power generation unit 12, and becomes the smallest in the boundary portion 23. As a result, the shapes of the electrodes 3 and 4 are made slightly smaller in the lengthwise direction of the piezoelectric ceramic body 2, and the space between the input electrode 3 and the output electrode 4 is widened to insulate the drive unit 11 and the power generation unit 12 from each other. Even if it is sufficient, the efficiency of the piezoelectric ceramic transformer 1 is hardly reduced.

Table 1 shows the measurement results of the characteristics of the specific example (example) of the piezoelectric ceramic transformer circuit of the present invention and the specific example (comparative example) of the conventional piezoelectric ceramic transformer circuit. In the comparative example, the piezoelectric ceramic transformer has the structure shown in FIG. All of the piezoelectric ceramic bodies of the piezoelectric ceramic transformer are PZT (PbZrO3 -PbTiO3).
It is made of 3) type piezoelectric material. Regarding the shape, the present invention has a length of 40 mm, a width of 20 mm and a thickness of 2 mm, and a comparative example has a length of 40 mm, a width of 14 mm and a thickness of 2 mm. The size of one side of the electrode of the present invention and the comparative example is 14 mm
Is a square and is formed by screen-printing Ag paste. After firing the piezoelectric ceramic body after forming the electrodes, it is immersed in insulating oil at 150 ° C. and 2 kV / mm in the thickness direction between the input electrodes and the output electrodes.
The voltage was applied to polarize the piezoelectric ceramic body. After that, lead wires were connected to the electrodes by soldering or the like.

Each of the produced piezoelectric ceramic transformers has a matching impedance as a load.
The amount of power supply was adjusted by connecting a 2 kΩ resistor and outputting 3 W of power. The frequencies of the alternating voltage applied to the piezoelectric ceramic transformer are the same, which is one wavelength mode in the length direction and (1
/ 2) Resonant vibration in the wavelength mode, and in the comparative example, the resonant vibration is in the single wavelength mode only in the length direction.

[0031]

[Table 1]

As is known from Table 1, in the present invention, a large boost ratio was obtained as compared with the comparative example. Further, the temperature rise is suppressed to a low level, and it is recognized that the efficiency is high accordingly.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention. In the present embodiment, the piezoelectric ceramic transformer 1A has a square piezoelectric ceramic body 2A, and the piezoelectric ceramic body 2A is divided into 2 × 2 regions 21a, 21b, 22 in one width direction and the other width direction.
Electrodes 3a, 3b, 4a and 4b are formed on a and 22b on the upper and lower surfaces of the piezoelectric ceramic body 2A, respectively. The electrodes 3a-4b are, for example, square.

The area 21a of the piezoelectric ceramic body 2A.
Reference numeral 22b is an electrode 3 which is opposed to the piezoelectric ceramic body 2A.
It is polarized by applying a DC voltage between a and 4b. The polarization direction is the same between the electrodes 3a to 4b.

Of the electrodes 3a to 4b, two sets of electrodes 3a and 3b, which are diagonally arranged, have lead wires 51A and 5A.
The electrodes 2a and 3b are connected to a common AC voltage generator 50, and serve as input electrodes 3a and 3b that constitute the driving units 11a and 11b. The drive unit 11a and the drive unit 11b are connected in parallel. The load 7 is connected to the two pairs of electrodes 4a, 4b arranged at the other diagonal position by lead wires 61A, 62A, and serve as output electrodes 4a, 4b constituting the power generation units 12a, 12b. Power generation unit 12a and power generation unit 1
It is connected in parallel with 2b. In addition, the lead wire 51
In the connection of A, 52A, 61A and 62A, the input electrode 3
The electrodes a, 3b and the electrodes 4a, 4b for output, which are formed on the same surface of the piezoelectric ceramic body 2A, are electrically connected to each other and are connected to the same pole of the AC voltage generator 50 or the load 7.

The output frequency of the AC voltage generator 50 of the input circuit 5A is obtained by dividing the propagation velocity (sound velocity) of the elastic wave in the piezoelectric ceramic body 2A by the size in the width direction (side length) of the piezoelectric ceramic body 2A. Set to the specified value. Piezoelectric ceramic body 2A
Since is a square, the elastic wave causes the piezoelectric ceramic body 2A to resonate and vibrate in one wavelength mode in any width direction.

Here, the driving portions 11a, 1 which are in diagonal positions
In 1b, an alternating voltage is applied in phase to the input electrodes 3a, 3b, and the piezoelectric ceramic body 2A is polarized in the same direction, so that the vibration generated by the driving portion 11a and the driving portion 11b are generated. Vibration violates each other. Due to this vibration, the output electrode 4a of each power generation unit 12a, 12b
Meanwhile, a voltage is generated between the output electrodes 4b. Here, the power generation units 12a and 12b are in diagonal positions, and the output electrodes 4a and 4b are
The regions 22a, 2 of the piezoelectric ceramic body 2A in which b is formed.
Vibration occurs in the same phase in 2b, and the area 22a and the area 2
Since it is polarized in the same direction as 2b, the power generation unit 12a
And the voltage generated by the power generation unit 12b appear in phase. That is, the output current to the load 7 is the sum of the output currents of the power generation units 12a and 12b.

Also in this embodiment, each drive unit 11a,
11b, and the 2 × 2 regions 21a to 22b of the piezoelectric ceramic body 2A corresponding to the power generation units 12a and 12b resonate so that the central portion is a node and both ends are antinodes in response to vibration in any width direction. Since it vibrates and becomes a two-dimensional resonance vibration, the electromechanical coupling coefficient becomes large and the efficiency is good.

In addition, the electrode-free boundary portion 23a of the piezoelectric ceramic body 2A in which the electrodes 3a to 4b are provided on both sides.
a, 23ab, 23ba, and 23bb are antinodes of vibration, and as is known from the stress distribution in the figure, the stress is extremely small. Therefore, even if it is wide to some extent, the efficiency of the piezoelectric ceramic transformer 1A is not reduced, and the driving portion 11a. , 11b,
It is possible to achieve both sufficient insulation between the power generation units 12a and 12b and high efficiency of the piezoelectric ceramic transformer 1A.

If the vibrations caused by the two drive units 11a and 11b and the output voltages of the two power generation units 12a and 12b are in phase, the input electrodes 3a and 3b and the lead wire 51A,
52A, output electrodes 4a, 4b and lead wire 61
The connection with A and 62A is not limited to the example shown in the figure. For example, one of the forked ends of each of the lead wires 51A and 52A is connected to the input electrodes 3a and 3b formed on the upper surface of the piezoelectric ceramic body 2A, and each of the lead wires 51A and 5A is connected.
By connecting the other end of the bifurcated end of 2A to the input electrodes 3a and 3b formed on the lower surface of the piezoelectric ceramic body 2A, the input electrode 3 of the one drive unit 11a is electrically connected to each other.
The a and the input electrode 3b of the other driving unit 11b are a combination of those formed on the upper surface and the lower surface of the piezoelectric ceramic body 2A. in this case,
The polarization directions of the driving unit 11a and the driving unit 11b are set to be opposite to each other so that the vibrations are mutually intensified. A combination of the output electrode 4a of one power generation portion 12a and the output electrode 4b of the other power generation portion 12b which are electrically connected to each other are formed on the upper surface and the lower surface of the piezoelectric ceramic body 2A. So that In this case, the polarization direction is set so that the output voltage is output to the load 7 in phase.
2a and the power generation unit 12b are set in opposite directions.

Further, in the present embodiment, the two driving units 11 are
a, 11b and two power generation units 12a, 12b, electrodes are formed on the n × n regions of a square piezoelectric ceramic body so that the drive unit and the power generation unit are in a checkered pattern. It may be placed at. In this case, the output frequency of the AC voltage generator of the input circuit that applies a voltage to the input electrode of each drive unit is the propagation speed (sound velocity) of the elastic wave in the piezoelectric ceramic body, and the length of the side of the piezoelectric ceramic body. (2 /
n) Set to the value obtained by dividing by the value obtained by multiplying. In the case of a square piezoelectric ceramic body, the elastic wave causes the piezoelectric ceramic body to resonate in the (n / 2) wavelength mode in any width direction.

Further, the drive unit and the power generation unit do not necessarily have to be arranged in a checkered pattern. For example, in the configuration such as the first embodiment composed of two drive units and two power generation units, the drive units are arranged in the same manner. , The power generation units may be arranged in one width direction. In this case, the connection between the input electrode and the lead wire is made so that the vibration generated due to one driving unit and the vibration generated due to the other driving unit have the same phase in each portion of the piezoelectric ceramic body. And, the polarization direction of the region of the piezoelectric ceramic body for the drive portion where the input electrode is formed is set. For example, when the lead wires are connected so that the input electrodes formed on the same surface of the piezoelectric ceramic body are electrically connected, the polarization directions are opposite to each other. Further, the polarization direction of the region of the piezoelectric ceramic body for the power generation unit where the connection between the output electrode and the lead wire and the output electrode is formed is set so that the output voltage of the power generation unit is output in phase. For example, when the lead wires are connected so that the output electrodes formed on the same surface of the piezoelectric ceramic body are electrically connected, the polarization directions are opposite to each other.

Further, it is not necessary that the number of regions in which the driving portion or the power generating portion is arranged be the same in one width direction of the piezoelectric ceramic body and the other width direction thereof. Size: size of the other width direction =
As a 3: 2 ratio, resonance vibration may be performed in the (3/2) wavelength mode in one width direction and resonance vibration may be performed in the (2/2) wavelength mode in the other width direction. In this case, six drive units and six power generation units can be provided. Further, it is arbitrary whether each region is used as a drive unit or a power generation unit, and the number of drive units and power generation units may not be the same. For example, in the example in which the number of drive units and the number of power generation units are six, the number of drive units can be four and the number of power generation units can be two.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention. The piezoelectric ceramic transformer 1B of the piezoelectric ceramic transformer circuit includes one drive unit 11B and one power generation unit 12B as in the first embodiment. The difference is the shape of the piezoelectric ceramic body 2B. The piezoceramic body 2B has the same L: W = 2: 1 ratio as in the first embodiment, and is divided into two regions 21B and 22 in the length direction.
Electrodes 3 and 4 are formed on B. Piezoelectric ceramic body 2
The angle of B is notched at an angle of 45 °, and the opposite sides on both sides along the length direction, which are the edge portions, have a central portion of 45 degrees.
It is cut out in a V shape of °. These notches 20
1, 202, 203, 204, 205 and 206 are formed at the four corners of the regions 21B and 22B of the piezoelectric ceramic body 2B where the driving unit 11B and the power generation unit 12B are provided, and the regions 21B and 22B are corners. The shape has been dropped.

As a result, the following effects are obtained. Similar to the first embodiment, the piezoelectric ceramic transformer 1B resonates and vibrates in the one-wavelength mode in the length direction and in the (1/2) wavelength mode in the width direction, but the elasticity generated by the voltage application to the drive unit 11B. Some waves travel not only in these two directions but also in an oblique direction sandwiched by these two directions. The elastic wave in such a direction causes unnecessary resonance that is different from the resonance corresponding to the output frequency of the AC voltage generator 50 in the first embodiment, resulting in a loss. In the present embodiment, the regions 21B and 22B of the piezoelectric ceramic body 2B have a shape close to a circle by reducing the corners thereof, and unnecessary resonance different from the resonance corresponding to the output frequency of the AC voltage generator 50 is suppressed. .
Therefore, the electromechanical coupling coefficient is further improved and the loss is reduced.

Also in this embodiment, the piezoelectric ceramic body 2 is used.
B has a minimum stress at the boundary portion 23B between the drive portion 21B and the power generation portion 22B in which the electrode is not formed, so that the boundary portion 23B can be wide.

The feature of the present embodiment that the corners of each region of the piezoelectric ceramic body in which the drive unit or the power generation unit is arranged is reduced can be applied to the second embodiment.

Further, in each of the above embodiments, the shape of the electrode is a square, but the shape is not necessarily limited to this, and it may be a circle, for example.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a piezoelectric ceramic transformer circuit according to a first embodiment of the present invention and a vibration state in the piezoelectric ceramic transformer.

FIG. 2 is a diagram showing a configuration of a piezoelectric ceramic transformer circuit according to a second embodiment of the present invention and a vibration state in the piezoelectric ceramic transformer.

FIG. 3 is a diagram showing a configuration of a piezoelectric ceramic transformer circuit according to a third embodiment of the present invention.

FIG. 4 is a diagram of a piezoelectric ceramic transformer which is a main part of a conventional piezoelectric ceramic transformer circuit of a first example.

FIG. 5 is a diagram of a piezoelectric ceramic transformer that is a main part of a conventional piezoelectric ceramic transformer circuit of a second example.

FIG. 6 is a diagram of a piezoelectric ceramic transformer that is a main part of a conventional piezoelectric ceramic transformer circuit of a third example.

[Explanation of symbols]

1, 1A, 1B Piezoelectric ceramic transformer 11, 11a, 11b, 11B Driving unit 12, 12a, 12b, 12B Power generation unit 2, 2A, 2B Piezoelectric ceramic body 21, 22, 21a, 21b, 22a, 22b, 21
B, 22B areas 23, 23aa, 23ab, 23ba, 23bb, 23
B Boundary portions 201, 202, 203, 204, 205, 206 Notches 3, 3a, 3b Input electrodes 4, 4a, 4b Output electrodes 5, 5A Input circuit (power supply means) 50 AC voltage generation portions 51, 52, 51A, 52A Lead wire 61, 62, 61A, 62A Lead wire 7 Load

Continued front page    (72) Inventor Katsuhide Akimoto             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO

Claims (3)

[Claims] 1. A substantially rectangular flat plate-shaped piezoelectric ceramic body polarized in the thickness direction, wherein electrodes for input are formed on the upper and lower surfaces of the piezoelectric ceramic body to serve as a driving unit, and the piezoelectric ceramic body is provided at a position different from that of the input electrode. Piezoelectric ceramics comprising: a piezoelectric ceramic transformer having an output electrode formed on the upper and lower surfaces thereof as a power generation section; and a power feeding means for applying an AC voltage between the input electrodes to excite resonant vibration in the piezoelectric ceramic body. In the transformer circuit, the piezoelectric ceramic body has a shape in which, as the resonant vibration, resonant vibration in one width direction of the piezoelectric ceramic body and resonant vibration in the other width direction of the piezoelectric ceramic body are generated, and A piezoelectric ceramic transformer circuit, characterized in that a boundary portion between the drive portion and the power generation portion is located at an antinode of the resonance vibration. 2. The piezoelectric ceramic transformer circuit according to claim 1, wherein the size of the piezoelectric ceramic body in one width direction is such that the inside of the piezoelectric ceramic body is formed by applying a voltage to the input electrode. The size is 2 or more natural numbers times the half wavelength of the propagating elastic wave, and the size of the other width direction of the piezoelectric ceramic body is the natural number times the half wavelength of the elastic wave. A piezoelectric ceramic transformer circuit, wherein one piezoelectric ceramic transformer circuit is formed in each of the width direction and the other width direction of the piezoelectric ceramic body in a region having a half wavelength of the elastic wave. 3. The piezoelectric ceramic transformer circuit according to claim 2, wherein a peripheral edge portion of the piezoelectric ceramic body is cut out to reduce a corner of the region.