JP2000150980A - Piezoelectric transformer, drive method and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer which is small in size and high in step-up ratio and reliability, a drive method and the manufacturing method thereof. SOLUTION: A piezoelectric transformer carries out a voltage conversion through mechanical vibrations, where the piezoelectric transformer is composed of a low impedance part 111 formed of one or more piezoelectric layers 14 and a high impedance part 112 formed of one or more piezoelectric layers 15, and the piezoelectric layers 14 and 15 of the impedance parts 111 and 112 are set parallel with each other in the direction of polarization. As a result, voltage conversion can be carried out, taking advantage of the vibrations of longitudinal effect (k33).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer used in various power supply circuits for generating a high voltage, and more particularly to a small-sized piezoelectric transformer for an inverter requiring a high step-up ratio, a driving method and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 25 shows the structure of a Rosen type piezoelectric transformer which is one of the conventional piezoelectric transformers. This piezoelectric transformer has advantages such as miniaturization, non-combustibility, and no generation of noise due to electromagnetic induction as compared with an electromagnetic transformer. The piezoelectric transformer includes a low impedance section 231 and a high impedance section 232. The low impedance section 231 is an input section when used for boosting. The low impedance portion 231 is polarized in the thickness direction, and the electrodes 233U and 233D are arranged on the main surface in the thickness direction. On the other hand, the high impedance section 232 is an output section when used for boosting. High impedance part 2
Reference numeral 32 is polarized in the length direction, and an electrode 234 is arranged on an end face in the length direction.

In this piezoelectric transformer, when a voltage corresponding to the resonance frequency of the mechanical vibration on the output side is applied to the electrodes 233U and 233D of the input section, the electrical energy is converted into mechanical energy by the (reverse) piezoelectric effect, and the energy is converted. Longitudinal vibration in the vertical direction is excited. The energy ratio at this time is the electromechanical coupling coefficient k31. When the driving frequency is near the resonance frequency of the primary mode or the secondary mode of the longitudinal vibration in the longitudinal direction, large mechanical vibration also occurs in the output unit 232. In the output unit 232, mechanical energy is converted into electric energy by a piezoelectric effect, and a voltage is generated. The energy ratio in this case is the electromechanical coupling coefficient k33. At this time, the polarization direction of the output section 232 is the length direction, and the length is larger than the thickness, so that a high voltage can be easily obtained from the electrode 234.

The step-up characteristic of this piezoelectric transformer is expressed by the following equation. Vo / Vin ∝ k31 · k33 · Qm · L2 / L1 Here, k31 represents an electromechanical coupling coefficient for a lateral effect, and k33 represents an electromechanical coupling coefficient for a longitudinal effect. further,
L1 is the thickness of the substrate of the piezoelectric layer 235 in the low impedance portion,
L2 represents the size of the piezoelectric layer 237 in the high impedance portion in the length direction of the substrate. Further, Qm is the value of each piezoelectric layer 235, 23
7 represents the mechanical quality factor of the substrate No. 7.

[0005]

In the above-mentioned conventional Rosen type piezoelectric transformer, in the low impedance portion, the vibration of the transverse effect (k31) in which the polarization direction and the vibration direction are orthogonal to each other, and in the high impedance portion, the polarization direction is changed. And electrical energy and mechanical energy are converted using the vibration of the longitudinal effect (k33) in which the vibration direction is parallel to Therefore, the polarization directions of the input section and the output section are different by 90 °. Generally, when the polarization directions cross each other, the lattice constant of the crystal has anisotropy. Therefore, if the polarization directions of the input part and the output part of the piezoelectric transformer differ by 90 ° as described above, stress is applied to the joint part,
Causes a decrease in strength. For this reason, there was a problem that reliability was lowered.

The present invention has been made to solve the above problems, and an object of the present invention is to realize a small-sized piezoelectric transformer having a high step-up ratio, a highly reliable piezoelectric transformer, and a driving method thereof. And a manufacturing method.

[0007]

In order to solve the above-mentioned problems, a piezoelectric transformer according to the present invention comprises a low-impedance section for converting an input voltage into mechanical vibration, and a low-impedance section connected to the low-impedance section. This is a piezoelectric transformer including a high-impedance section that converts mechanical vibration of the section into a predetermined output voltage, and performs voltage conversion using only vibration due to the longitudinal effect (k33) of the vibrator in each impedance section. To this end, in the piezoelectric transformer, the low impedance portion includes at least one vibrator formed to be polarized and having a piezoelectric effect, and the vibrator for applying the input voltage in a polarization direction of the vibrator. An input electrode connected thereto, wherein the high impedance portion is at least one vibrator formed to be polarized and having a piezoelectric effect;
An output electrode connected to the vibrator to take out the output voltage generated in the polarization direction of the vibrator, and further comprising: The low impedance section is connected to the high impedance section.

The low-impedance portion is composed of a plurality of vibrators integrally formed so that the polarization directions are opposite between adjacent vibrators, and an internal portion connected to the input electrode between the vibrators. It may have electrodes. The high impedance portion includes a plurality of vibrators integrally formed so that the polarization directions are opposite between adjacent vibrators, and an internal electrode connected to the output electrode between the vibrators. May be provided.

In the piezoelectric transformer, the low impedance portion and the vibrator of the high impedance portion may be formed using materials having different dielectric constants.

In the above-mentioned piezoelectric transformer, the low impedance portion and the high impedance portion may be integrally connected in a length direction, a thickness direction or a width direction of the piezoelectric transformer.

Further, in the piezoelectric transformer, the high impedance section is divided into first and second output impedance sections, and the low impedance section is divided between the first output impedance section and the second output impedance section. It may be connected in between.

In the piezoelectric transformer, an insulating layer may be provided between the low impedance section and the high impedance section.

A method for driving a piezoelectric transformer according to the present invention is as follows.
The above-described piezoelectric transformer is provided with a longitudinal longitudinal vibration mode in which a resonance frequency of a longitudinal longitudinal vibration primary mode in which one wavelength is equal to half the length of the piezoelectric transformer or a longitudinal mode in which one wavelength is equal to the length of the piezoelectric transformer. Drive at the resonance frequency of the next mode.

A first method for manufacturing a piezoelectric transformer according to the present invention includes the steps of: providing a green sheet made of a material exhibiting a piezoelectric effect;
A green sheet having an internal electrode printed in a predetermined shape is laminated and pressed in a predetermined order to form a laminate of a low impedance portion and a high impedance portion, and then the laminate is fired and cut into a predetermined shape. A step of forming an external electrode at an end of the cut laminate, and a step of applying a voltage to the external electrode to polarize the low impedance portion and the high impedance portion.

According to a second method of manufacturing a piezoelectric transformer according to the present invention, a green sheet made of a material exhibiting a piezoelectric effect is provided;
A green sheet having internal electrodes printed in a predetermined shape is laminated and pressed in a predetermined order to form a laminate, the laminate is fired, the fired laminate is cut into a predetermined shape, and the cut laminate is cut. Forming a low impedance portion by forming an external electrode at the end of the material; sintering a material exhibiting a piezoelectric effect; forming an external electrode at the end of the sintered material to form a high impedance portion; Joining the low impedance section and the high impedance section via an insulating layer, and applying a voltage to the external electrode to polarize the low impedance section and the high impedance section.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a piezoelectric transformer according to the present invention will be described with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a perspective view of a piezoelectric transformer according to a first embodiment. As shown in FIG. 1, the piezoelectric transformer has a low impedance section 111 as an input section and a high impedance section 112 as an output section. The low impedance section 111 has eight piezoelectric layers 14 and internal electrodes 17 provided between the piezoelectric layers 14.
The high impedance section 112 is
It is composed of one piezoelectric layer 15 having the same thickness as one. Each piezoelectric layer of the low-impedance portion 111 and the high-impedance portion 112 is polarized in the length direction (in the drawings, the symbols “←” and “→” indicate the polarization direction. The same applies to the following embodiments. I do.) At this time, the piezoelectric layers of the low impedance section 111 are formed so as to be polarized in opposite directions to the adjacent piezoelectric layers. Each piezoelectric layer is formed by laminating materials having a piezoelectric effect, and performs electric-mechanical energy conversion. That is, when a high-frequency voltage is applied to the piezoelectric layer, the piezoelectric layer operates as a vibrator that vibrates at a predetermined resonance frequency.

Further, as shown in FIG. 1, the piezoelectric transformer includes electrodes 13U and 13D provided on the main surface in the thickness direction of the low impedance portion 111 and a high impedance portion 11D.
2 and an output electrode 16 provided on an end face in the length direction of the second. The internal electrode 17 is alternately connected to one of the upper electrode 13U and the lower electrode 13D so that a voltage is applied in a direction opposite to the adjacent piezoelectric layer in each piezoelectric layer of the low impedance section 111. You. External connection terminals 13x, 13y, 16x for applying a voltage are connected to the electrodes 13U, 13D, 16 respectively.

In the piezoelectric transformer configured as described above,
The input voltage of the predetermined frequency is applied to the external connection terminals 13x, 13y
Through the electrodes 13U, 13 of the low impedance section 111
D. At this time, the low impedance section 111
Then, a longitudinal vibration is generated by the piezoelectric effect, and a vibration is generated in the high impedance section 112 by the vibration of the low impedance section 111. In the high impedance section 112, this vibration is converted into electric energy, and a voltage is induced on the electrode 16. The voltage induced at the electrode 16 is applied to the external connection terminal 1
It is taken out as an output voltage via 6x.

The piezoelectric transformer includes a low impedance section 111 as an input section and a high impedance section 1 as an output section.
The input voltage is transformed by the impedance conversion between the input voltage and the input voltage, that is, the capacitance ratio. A low impedance section 111;
The capacitance ratio with the high impedance portion 112 changes according to the ratio of the number of piezoelectric layers in each impedance portion. Therefore, the step-up ratio or the step-down ratio of the piezoelectric transformer can be changed by changing the number of piezoelectric layers in each impedance section.

FIG. 2 is a diagram showing a lumped constant approximation equivalent circuit near the resonance frequency of the piezoelectric transformer of this embodiment.
In FIG. 2, the equivalent circuits have the capacities Cd1 and Cd2, the equivalent mass m, the equivalent compliance on the input side and the output side, respectively.
C, including equivalent mechanical resistance Rm. The input-side force coefficient A1 and the output-side force coefficient A2 that determine the step-up ratio of the piezoelectric transformer are proportional to the capacities Cd1 and Cd2, respectively. Binding capacity Cd1,
Cd2 is the low impedance part (input part) 1 of the piezoelectric transformer
11 and the high-impedance section (output section) 112 respectively. FIG.
In the piezoelectric transformer shown in FIG.
1 and the high impedance portion 112
Form a capacitor. At this time, the length of the piezoelectric layer of the high impedance portion 112 is longer than that of each piezoelectric layer of the low impedance portion 111, and the thickness is the same. In the low impedance section 111, the capacitors formed by the respective piezoelectric layers are connected in parallel.
Therefore, the capacity of the low impedance section 111 is larger than the capacity of the high impedance section 112, and the force coefficient A1 is larger than the force coefficient A2. Therefore, in FIG. 2, the voltage is boosted by two equivalent ideal transformers. Also, since the piezoelectric transformer includes a series resonance circuit composed of the equivalent mass m and the equivalent compliance C, the output voltage becomes a value larger than the transformation ratio of the transformer, particularly when the value of the load resistance is large. ).

FIGS. 3A to 3C show the operating characteristics of the piezoelectric transformer according to the present embodiment as a function of the load resistance Ro.
These relationships are obtained based on Mason's equivalent circuit model. As shown in FIG. 3A, in the piezoelectric transformer of the present embodiment, the resonance frequency changes stepwise around a load resistance value of about 100 kΩ. FIG. 3B shows the step-up / step-down characteristics of the piezoelectric transformer. FIG. 3C shows a change in efficiency of the piezoelectric transformer. As shown in this figure, the maximum efficiency is exhibited near the load resistance value of 10 kΩ, and the efficiency decreases as the distance from the load resistance increases.

In the piezoelectric transformer of the present embodiment, the low impedance section 111 and the high impedance section 112
Since the piezoelectric layers are formed such that the polarization directions of the piezoelectric layers are parallel to each other, no stress is applied to the joint between the low-impedance section 111 and the high-impedance section 112, and the strength does not decrease. Further, since the electromechanical energy conversion is performed using the longitudinal effect (k33) in both the low impedance section and the high impedance section, a high boost ratio can be realized.

Next, a method for manufacturing the piezoelectric transformer of the present embodiment will be described. First, a green sheet is prepared.
That is, a PZT-based piezoelectric ceramic powder as a piezoelectric material is dispersed in a solvent together with an organic binder to form a slurry,
The slurry is dried to produce a green sheet having a thickness of 40 μm. Thereafter, the green sheet is cut into a predetermined shape required for laminating and pressing by a hot press machine. Next, a green sheet serving as an internal electrode layer is prepared by printing a Pt paste including platinum (Pt), a binder, and an organic solvent on the above-described green sheet by a screen printing method. This Pt paste portion corresponds to the internal electrode 17 portion.

Thereafter, the green sheets are laminated in a predetermined combination to produce a piezoelectric layer. FIG. 4 is a diagram showing the steps from the step of laminating the green sheets to the step of producing the piezoelectric layer. FIG. 4A shows a green sheet 61 produced by the above method and a green sheet 62 on which a Pt paste 63 is printed by a screen printing method. At this time, as shown in FIG. 4A, in the green sheet 62, the Pt paste 63 is not printed on the entire upper surface of the green sheet 62, but is formed in a band shape at one end in the width direction of the green sheet 62. Print to leave blank space. That is, the green sheet 62
Is provided with a region on which no electrode is formed.

After the green sheets are produced, as shown in FIG. 4A, these green sheets 61 and 62 are stacked in accordance with a predetermined combination, and then laminated and pressed by a hot press machine. As shown in FIG.
5 is formed. Here, on the green sheet 62 on which the Pt paste 63 is printed, as shown in FIG. 4A, the green sheets 62 are laminated such that the areas where the electrodes are not formed are alternately opposite. Thus, the completed internal electrode layers alternately reach the main surface in the thickness direction.
The green laminate 65 is heat-treated at 650 ° C. in the air to remove the binder. Then, after firing at 1200 ° C. for 2 hours, the piezoelectric layer 14 of the low impedance portion 111 including the internal electrode 17 and the high impedance portion 1 are cut by a dicing saw into a predetermined shape as shown in FIG.
Twelve piezoelectric layers 15 are integrally formed.

Thereafter, external electrodes 13U and 13D are provided on the end faces (end faces perpendicular to the thickness direction) of the piezoelectric layer 14,
An external electrode 15 is attached to the end face
Baking. Then, a DC voltage of 3 kV / mm is impressed between the terminals of the electrodes 13U, 13D, and 16 to simultaneously polarize the piezoelectric layers 14 and 15 of the low impedance portion 111 and the high impedance portion 112, respectively.

Here, the piezoelectric layer is formed using a PZT-based piezoelectric material and platinum. However, the piezoelectric layer may be formed using a piezoelectric material having piezoelectricity and an electrode material that can be integrally fired therewith. Can also. Green laminate 6
After firing and polarization treatment, the piezoelectric transformer may be cut into a predetermined shape by a dicing saw and an external electrode may be baked on an end face to produce a piezoelectric transformer.

In the above method, the length of the low impedance portion is 19 mm, the number of piezoelectric layers is 7, and the length of the high impedance portion is 19 mm, the number of piezoelectric layers is 1, the overall length is 38 mm, and the width is 38 mm. A piezoelectric transformer having a thickness of 7 mm and a thickness of 1 mm was manufactured. The resonance frequency of the longitudinal secondary mode in the longitudinal direction of the piezoelectric transformer thus manufactured was measured as 76 kHz from the frequency characteristics of admittance. When a load resistance of 100 kΩ was connected to the output portion (between the connection terminal 16x and the connection terminal 13y) of this piezoelectric transformer, an output of 210V was obtained for an input voltage of 30V, and the output power at this time was 0.3V. It was 5W.

Next, a method of driving the piezoelectric transformer will be described. FIG. 5 is a diagram showing the distribution of the displacement and stress of the rod-shaped vibrator in the longitudinal longitudinal secondary mode in which one wavelength is equal to the length of the rod-shaped vibrator. As shown in the drawing, a node of vibration exists inside the rod-shaped vibrator 41 by one quarter from both ends. Therefore, when the entire piezoelectric transformer is made to correspond to one rod-shaped vibrator 41, when driving the piezoelectric transformer in the longitudinal longitudinal vibration secondary mode, if the length of the piezoelectric transformer is L, the low impedance portion 11
It can be seen that it is preferable to arrange the one external connection terminal 13x, 13y at a position of L / 4 from one end face in the length direction of the piezoelectric transformer. That is, the external connection terminal 13 is located at this position.
x, 13y, and driving the piezoelectric transformer at the resonance frequency of the longitudinal longitudinal secondary mode in the longitudinal direction, the external connection terminals 13x, 13
y does not affect the vibration. Therefore, the external connection terminal 1
The loss of vibration energy due to the connection of 3x and 13y is eliminated.

FIG. 6 is a diagram showing the distribution of the displacement and stress of the rod-shaped vibrator in the longitudinal longitudinal primary mode in which the half wavelength of the vibration is equal to the length of the rod-shaped vibrator. As shown in FIG. 6, in this case, a vibration node exists at the center of the rod-shaped vibrator 41. Therefore, the external connection terminals 13x, 13
y is located at the center of the piezoelectric transformer in the longitudinal direction,
It may be driven in the longitudinal longitudinal primary mode. By driving the piezoelectric transformer in the longitudinal vibration primary mode, the drive frequency can be lower than in the case of the longitudinal vibration secondary mode if the shape of the piezoelectric transformer is the same as in the case of the longitudinal vibration secondary mode. If the driving frequency is the same, the size of the piezoelectric transformer can be further reduced. When the piezoelectric transformer is driven in the longitudinal longitudinal primary mode in the longitudinal direction, the low impedance section 111 is lengthened and the high impedance section 112 is driven.
, The longitudinal vibration secondary mode can be suppressed, and the boost ratio can be further increased.

FIG. 7 shows another example of the present embodiment in which the piezoelectric layer of the high impedance portion 112 in the piezoelectric transformer shown in FIG. 1 has a laminated structure.

In FIG. 7, high impedance section 112
Is composed of three piezoelectric layers whose polarization directions are opposite to each other. The polarization direction of each piezoelectric layer of the high impedance portion 112 is formed so as to be parallel to the polarization direction of the low impedance portion 111, and the polarization directions of adjacent piezoelectric layers are opposite to each other.

In the piezoelectric transformer shown in FIG. 7, the lower electrode 13D of the low impedance portion 111 extends to the high impedance portion 112 side. In the high impedance portion 112, an external electrode 71 is provided on the main surface facing the electrode 13D. Is provided. Internal electrodes 17 are provided between the piezoelectric layers of the high impedance section 112, and these internal electrodes are alternately connected to the external electrodes 71 or the external electrodes 13D. The electrode 71 is connected to an external connection terminal 71x for extracting an output voltage.

As described above, the low impedance section 111 and the high impedance section 112 are constituted by a plurality of piezoelectric layers,
By adjusting the number of these piezoelectric layers, a desired step-up ratio can be obtained, and matching with a load can be achieved. In this case, by arranging the external connection terminal 71x of the high impedance portion 112 at a position of L / 4 from the end in the length direction, it is possible to eliminate the influence of the external connection terminal 71x on vibration.

In this embodiment, the piezoelectric materials used for the low impedance section 111 and the high impedance section 112 are the same, but different types of piezoelectric material are used for the low impedance section 111 and the high impedance section 112, respectively. Can also be used. For example, a high step-up ratio can be obtained by using a lead titanate-based piezoelectric material for one of the low impedance section 111 and the high impedance section 112 and using a lead zircon titanate-based piezoelectric material having a large dielectric constant for the other. The same applies to the embodiments described later.

(Embodiment 2) FIG. 8 is a perspective view of a piezoelectric transformer according to Embodiment 2. FIG. In the piezoelectric transformer of the present embodiment, the insulating layer 81 is provided between the low impedance section 111 and the high impedance section 112 in the piezoelectric transformer shown in FIG. The piezoelectric transformer has an electrode 16b on an end face of the high impedance portion 112 facing the electrode 16 for extracting an output voltage. An external connection terminal 16y is connected to the electrode 16b. In this embodiment, the number of laminated piezoelectric layers of the low impedance section 111 of the piezoelectric transformer is seven.

In the piezoelectric transformer configured as described above,
Electrodes 13U, 13 via external connection terminals 13x, 13y
A high-frequency voltage is input to D. When this high-frequency voltage is input, longitudinal vibration occurs in the low impedance section 111 due to the piezoelectric effect, and the high impedance section 11
2 generates vibration. In the high impedance section 112,
This vibration is converted into electric energy, and a voltage is induced between the electrode 16 and the electrode 16b. Electrode 16 and electrode 16
b is applied to the external connection terminals 16x, 16x
It is taken out as an output voltage via y.

As described above, in the piezoelectric transformer of the present embodiment, the input section and the output section of the piezoelectric transformer can be electrically separated by insulating the low impedance section 111 and the high impedance section 112.

Hereinafter, a method for manufacturing the piezoelectric transformer of this embodiment will be described with reference to FIG. First, a green sheet to be a piezoelectric layer or an electrode layer is manufactured in the same procedure as that described in the first embodiment.

After the production of the green sheet, as shown in FIG. 9A, the green sheet 6 serving as a piezoelectric layer or an electrode layer is formed.
After laminating 1, 62 according to a predetermined combination, they are laminated and bonded by a hot press machine to form an integral green laminate shown in FIG. 9B. The green laminate is heat-treated at 650 ° C. in air to remove the binder. Then, after firing the green laminate at 1200 ° C. for 2 hours, the green laminate is cut into a predetermined shape by a dicing saw to form a low impedance portion 1.
7 is produced.

Also, a PZT-based piezoelectric ceramic powder as a piezoelectric material is fired at 1200 ° C. for 2 hours so as to have a predetermined shape to produce a piezoelectric layer having a high impedance portion (FIG. 9C). Cut into a predetermined shape, and electrodes are added to the end faces to form a high impedance portion 15.
Is prepared.

After that, as shown in FIG. 9D, the low impedance portion 17 and the high impedance portion 15 are press-bonded via the insulator 97 and fired. Then, FIG.
An external electrode is baked on a predetermined end face of the piezoelectric layer of the piezoelectric transformer shown in the above, and a DC voltage of 6 kV / mm is imprinted between the electrode terminals.
The high impedance section 15 and the low impedance section 17 are simultaneously polarized.

The following piezoelectric transformer was manufactured by the above method. That is, a piezoelectric transformer having a length of 19 mm in the low impedance part 111 and 21 piezoelectric layers, a length of 19 mm in the high impedance part 112, one piezoelectric layer, and a total length of 38 mm for the piezoelectric transformer was manufactured. An unpolarized piezoelectric layer was formed as the insulating layer 81 at a boundary between the low impedance section 111 and the high impedance section 112 with a thickness of 0.3 mm. The width and thickness of the piezoelectric transformer were 7 mm and 1 mm, respectively. The resonance frequency of the longitudinal vibration secondary mode in the length direction of the piezoelectric transformer was measured to be 77 kHz from the frequency characteristics of admittance. When a load resistance of 100 kΩ is connected to the output section (between the electrode 16 and the electrode 16b) of this piezoelectric transformer, an output of 580 V is obtained for an input voltage of 30 V, and the output power at this time is 3.2.
W.

In this embodiment, similarly to the first embodiment, in the piezoelectric transformer having the length L, the external connection terminals 13x and 13y of the low impedance portion 111 are positioned at L / 4 from the longitudinal end face of the piezoelectric transformer. , And the piezoelectric transformer is driven at the resonance frequency of the longitudinal longitudinal secondary mode in the longitudinal direction. Thereby, the influence of the low impedance section 111 on the vibration of the external connection terminals 13x and 13y can be removed.

Further, the piezoelectric transformer of this embodiment may be driven in a longitudinal longitudinal primary mode, which is a vibration mode in which the length of the piezoelectric transformer in the longitudinal direction is equal to a half wavelength.
In this case, if the shape of the piezoelectric transformer is the same, the drive frequency can be lower than in the case of the secondary mode of longitudinal vibration, and if the drive frequency is the same, the piezoelectric transformer can be made smaller than in the case of the secondary mode of longitudinal vibration. . In this case, by increasing the length of the low impedance section 111 and shortening the length of the high impedance section 112, the longitudinal vibration secondary mode can be suppressed, and the boost ratio can be increased. Also, at this time, the external connection terminals 103x, 103
y is arranged at a position of L / 4 from the end in the longitudinal direction so that the external connection terminals 103x and 103y do not adversely affect the vibration.

FIG. 10 shows another example of the present embodiment in which the high-impedance portion 112 has a laminated structure in the piezoelectric transformer shown in FIG. As described above, the piezoelectric transformer includes a plurality of piezoelectric layers, the internal electrode 104, the external electrodes 102,
03, a desired boost ratio can be obtained,
In addition, matching with the load can be obtained.

Third Embodiment FIG. 11 is a perspective view of a piezoelectric transformer according to a third embodiment. In the piezoelectric transformer according to the first or second embodiment, the low impedance portion 111 and the high impedance portion 11 having a polarization direction in the length direction are provided.
2 were connected in the longitudinal direction to form a piezoelectric transformer. On the other hand, the piezoelectric transformer of the present embodiment is configured by connecting a low impedance section 111 and a high impedance section 112 having a polarization direction in the length direction in the thickness direction.

As shown in FIG. 11, the piezoelectric transformer includes a low impedance section 111 and its low impedance section 1.
12 high impedance section 112 connected in the thickness direction
And The piezoelectric transformer has electrodes 116R and 116L on its end surface perpendicular to the longitudinal direction, and a low impedance portion 1
Electrodes 115a and 115b are provided on end faces perpendicular to the width direction of No. 11. Here, the electrode 115b and the electrodes 116L, 116
R is electrically connected. Further, the piezoelectric transformer has an external electrode 114 on a main surface of the high impedance portion 112 opposite to a boundary surface with the low impedance portion 111. The low impedance section 111 has eight piezoelectric layers and seven internal electrodes 17. Further, the electrode 11
5a and 115b are connected to external connection terminals 115x and 1 respectively.
The electrode 114 is connected to the external connection terminal 114x.

The low impedance section 111 and the high impedance section 112 are polarized in the length direction. Each piezoelectric layer of the low-impedance portion 111 is polarized so as to be opposite to each other between adjacent piezoelectric layers, and the internal electrodes 17 are alternately connected to one of the electrodes 115a and 115b.

The input voltage to the piezoelectric transformer configured as described above is applied to the electrodes 115a and 115b via the external connection terminals 115x and 115y. At this time,
The electrode 115a (external connection terminal 115x) is on the reference potential side. When an input voltage is applied, the low impedance portion 111 of the piezoelectric transformer vibrates in the length direction, and accordingly, the high impedance portion 112 vibrates in the length direction. In the high impedance section 112, the vibration energy is converted into electric energy, and an output voltage is extracted from the electrodes 115a and 114 via the external connection terminals 115x and 114x.

Hereinafter, a method for manufacturing the piezoelectric transformer of this embodiment will be described with reference to FIG. First, a green sheet to be a piezoelectric layer or an electrode layer is prepared in the same manner as described above. The Pt paste is printed on the green sheet serving as the electrode layer by a screen printing method. In the case of the present embodiment, the Pt paste 63 is separated from the green sheet 61 by a predetermined length as shown in FIG. Printed in a band. At this time, one end of the band-shaped Pt paste 63 is formed so as to reach only one end in the width direction on the green sheet 61.

Next, as shown in FIG. 12A, the green sheets 67 are stacked in accordance with a predetermined combination, and then laminated and bonded by a hot press, thereby forming an integrated green laminate shown in FIG. 12B. To form At this time, as shown in FIG. 12A, the green sheet 67 is
Are stacked in such a manner that the portions where the band-shaped portions do not reach the ends are alternately oriented in opposite directions. After that, the green laminate was
The binder is removed by heat treatment in air at 0 ° C. Thereafter, after baking at 1200 ° C. for 2 hours, the resultant is cut into a predetermined shape by a dicing saw, and a low impedance portion 14 and a high impedance portion 15 are integrally formed as shown in FIG.

Thereafter, as shown in FIG. 12D, electrodes 114, 115a, 115b, 1
16L and 116R are baked and 6kV is applied between their electrodes.
/ mm DC voltage, and the low impedance part 111,
Polarization is performed simultaneously in each of the high impedance portions 112.

In the above method, the low impedance section 111
A piezoelectric transformer having a length of 19 mm, a number of piezoelectric layers of 11, a length of 19 mm in the high impedance portion, a number of piezoelectric layers of 1, a total thickness of 3 mm, and a total width of 7 mm was produced. The resonance frequency of the longitudinal vibration primary mode in the length direction of this piezoelectric transformer is 75 kHz from the frequency characteristics of admittance.
It was measured. A load resistance of 100 kΩ is applied to the output portion (electrode 114 and electrode 116L or 116L).
R), an output of 300 V is obtained for an input voltage of 30 V, and the output power at this time is 0.9 W
Met.

The piezoelectric transformer according to the present embodiment is connected to an external connection terminal at the center position in the longitudinal direction, and is driven at the resonance frequency of the longitudinal longitudinal primary mode in the longitudinal direction. That is, the external connection terminals 115x, 115y, 114x of the low impedance section 111 and the high impedance section 112 are arranged at the center of the length of the piezoelectric transformer in the longitudinal direction, and the piezoelectric transformer is operated at the resonance frequency of the longitudinal vibration primary mode in the longitudinal direction. If driven, the influence of the vibration of the external connection terminals 115x, 115y, 114x can be reduced in the low impedance portion and the high impedance portion.

Further, the piezoelectric transformer of this embodiment may be vibrated in the secondary mode of longitudinal vibration. In this case, as described above, the external connection terminals 115x and 115y are connected to the position of L / 4 from the longitudinal end of the low impedance portion 111 in the length L piezoelectric transformer.

Further, in the present embodiment, the thickness of the piezoelectric layer in the low impedance section 111 and the thickness of the piezoelectric layer in the high impedance section 112 are the same, but the thickness may be changed respectively. That is, by changing the thickness of the piezoelectric layer, the capacitance impedance thereof can be changed, and thus, a piezoelectric transformer can be designed that is adapted to the load.

FIG. 13 shows another example of the present embodiment in which the piezoelectric layer of the high impedance section 112 in the piezoelectric transformer shown in FIG. 11 has a laminated structure. FIG. 14 is a perspective view of the piezoelectric transformer shown in FIG.

High impedance section 112 of piezoelectric transformer
Is composed of four piezoelectric layers. Like the low impedance section 111, these piezoelectric layers are polarized in the length direction such that the polarization directions of the adjacent piezoelectric layers are opposite. Internal electrodes 17a, 17b, 17c are provided between the piezoelectric layers of the high impedance section 112, and these internal electrodes 17a are alternately connected to the external electrodes 115b or 121. The electrodes 115b and 116
b, 116R and 116L are electrically connected.

As described above, the low impedance section 111 and the high impedance section 112 are constituted by a plurality of piezoelectric layers,
By adjusting the number of these piezoelectric layers, a desired step-up ratio can be obtained, and matching with a load can be achieved.

(Fourth Embodiment) FIG. 15 is a perspective view of a piezoelectric transformer according to a fourth embodiment. The piezoelectric transformer according to the present embodiment is configured by connecting a low impedance section 111 as an input section and a high impedance section 112 as an output section having the same thickness as the low impedance section 111 in the thickness direction. An insulating layer 135 is provided between the impedance section 111 and the high impedance section 112. The low-impedance portion 111 is composed of a plurality of piezoelectric layers that are polarized in the length direction and the polarization directions of the adjacent layers are opposite to each other.

In the low impedance portion 111, external electrodes 133 and 134 are provided on the main surfaces in the thickness direction, respectively.
Are connected, and an internal electrode 17 alternately connected to one of the electrodes is provided between the electrodes. In the high impedance section 112, external electrodes 132R and 132L are connected to the respective main surfaces in the length direction.

In the piezoelectric transformer configured as described above,
An input voltage is applied between the electrodes 133 and 134, and an output voltage is extracted from the electrodes 132R and 132L.

In the above configuration, the low impedance section 111
A piezoelectric transformer having a length of 20 mm, a number of piezoelectric layers of 11, a high impedance section 112, a length of 20 mm, a number of piezoelectric layers of 1, a total thickness of 3 mm, and a width of 7 mm was produced.
The resonance frequency of the first mode of longitudinal vibration in the longitudinal direction of the piezoelectric transformer was measured to be 80 kHz from frequency characteristics of admittance. When a load resistance of 100 kΩ was connected to the output section of this piezoelectric transformer, the input voltage was 25 V for an input voltage of 30 V.
An output of 0 V was obtained, and the output power at this time was 0.6 W.

The piezoelectric transformer of the present embodiment is driven at the resonance frequency of the longitudinal longitudinal primary mode in the longitudinal direction. At this time,
The external connection terminal is connected to a central position in the length direction of the piezoelectric transformer. Further, the piezoelectric transformer may be driven at the resonance frequency of the longitudinal longitudinal secondary mode in the longitudinal direction. At this time, assuming that the length of the piezoelectric transformer is L, the external connection terminal is connected to a position at a length of L / 4 from the end face in the longitudinal direction of the piezoelectric transformer.

Further, in this embodiment, the low impedance portion and the high impedance portion have the same thickness. However, if the thicknesses are changed, a piezoelectric transformer suitable for the load can be obtained.

FIG. 16 shows another example of the present embodiment when the high impedance section 112 is composed of a plurality of piezoelectric layers in the piezoelectric transformer shown in FIG.

The high-impedance section 112 is connected to the external electrode 1
41 and an electrode 142, and an internal electrode 143 inside. Internal electrodes 143 are provided between the piezoelectric layers, and the internal electrodes 143 are alternately connected to the external electrodes 141 or the external electrodes 142.

In FIG. 16, the high impedance section 1
Reference numeral 12 includes three piezoelectric layers. High impedance section 11
Each of the piezoelectric layers 2 is polarized in the longitudinal direction such that the polarization direction of the adjacent piezoelectric layer is opposite to that of the low impedance section 111.

As described above, the low impedance section 111 and the high impedance section 112 are constituted by a plurality of piezoelectric layers,
By adjusting the number of these piezoelectric layers, a desired step-up ratio can be obtained, and matching with a load can be achieved.

(Fifth Embodiment) FIG. 17 is a perspective view of a piezoelectric transformer according to a fifth embodiment. In the piezoelectric transformer according to the fourth embodiment, in the high impedance section 112, the output voltage electrodes 132L and 132R are connected to the high impedance section 1
12 is connected to the end face perpendicular to the length direction, but in the piezoelectric transformer of the present embodiment, the electrodes 151L, 151 are provided on the main surface side opposite to the connection surface with the low impedance portion 111.
R is provided.

Based on such a configuration, the low impedance section 111 has a length of 19 mm and the number of piezoelectric layers is 15, and the high impedance section 112 has a length of 19 mm, the number of piezoelectric layers is 1, the total thickness is 3 mm, and the width is 3 mm. Was made 5 mm. The resonance frequency of the longitudinal mode in the longitudinal direction of the piezoelectric transformer in the longitudinal direction was measured to be 76 kHz from the frequency characteristics of admittance. 100kΩ to this piezoelectric transformer
Was connected to the electrodes 151L and 151R, an output voltage of 300 V was obtained for an input voltage of 20 V, and the output power at this time was 0.9 W.

The piezoelectric transformer of the present embodiment is driven at the resonance frequency of the longitudinal longitudinal primary mode in the longitudinal direction. At this time,
An external connection terminal (not shown) of the low impedance portion is connected to a center position in the length direction of the piezoelectric transformer. Further, the piezoelectric transformer may be driven at the resonance frequency of the longitudinal longitudinal secondary mode in the longitudinal direction. At this time, the external connection terminal of the low impedance portion is connected to a position having a length of 1/4 in the length direction of the piezoelectric transformer.

Further, also in the present embodiment, a desired step-up ratio can be obtained by changing the thickness of each of the low impedance section 111 and the high impedance section 112 and matching the load with the load.

(Sixth Embodiment) FIG. 18 is a perspective view of a piezoelectric transformer according to a sixth embodiment. FIG. 19 is a top view of the piezoelectric transformer according to the present embodiment.

In the piezoelectric transformer of this embodiment, the high impedance section 112 is connected to the low impedance section 111 in the width direction as shown in FIG. The low impedance section 111 is composed of a plurality of piezoelectric layers whose polarization directions are opposite to each other.

Further, the low impedance section 111 and the high impedance section 112 are connected via an insulating layer 168. The polarization directions of the piezoelectric layers of the low impedance section 111 and the high impedance section 112 are both parallel to the length direction. The low impedance section 111 and the high impedance section 112 have the same thickness.

Based on the above configuration, the low impedance portion 111 has a width of 2.5 mm and the number of piezoelectric layers is 11, and the high impedance portion has a width of 2.5 mm, the number of piezoelectric layers is 1, and the total thickness is 1.3 mm. A piezoelectric transformer having a total length of 28 mm was manufactured. The resonance frequency of the longitudinal vibration secondary mode in the length direction of the piezoelectric transformer was measured to be 130 kHz from the frequency characteristics of admittance. This piezoelectric transformer has 1
When a load resistance of 00 kΩ was connected to the output section, an output of 370 V was obtained for an input voltage of 40 V, and the output power at this time was 1.4 W.

The piezoelectric transformer of the present embodiment is driven at the resonance frequency of the longitudinal longitudinal secondary mode in the longitudinal direction. At this time,
External connection terminal of low impedance section 111 (not shown)
Is connected to a position 1/4 of the length from the longitudinal end face of the piezoelectric transformer. Further, the piezoelectric transformer may be driven at the resonance frequency of the longitudinal longitudinal primary mode in the longitudinal direction. At this time, the external connection terminal of the low impedance section 111 is connected to a position which is １ ／ the length from the longitudinal end face of the piezoelectric transformer.

In the present embodiment, the low impedance section 11
1 and the high-impedance portion 112 have the same width, but if the width is changed, matching with the load can be achieved.

FIG. 20 shows another example of the present embodiment in which the high impedance section 112 in FIG. 18 is constituted by a plurality of piezoelectric layers. FIG. 21 is a top view of the piezoelectric transformer shown in FIG. As shown in FIGS. 20 and 21, the high impedance section 112 is composed of three piezoelectric layers. Like the low impedance section 111, each piezoelectric layer of the high impedance section 112 is polarized in the length direction such that the polarization directions of the adjacent piezoelectric layers are opposite to each other. Internal electrodes 184 are provided between the piezoelectric layers, and these internal electrodes 184 are alternately connected to external electrodes 181L or 181R.

(Seventh Embodiment) FIG. 22 is a perspective view of a piezoelectric transformer according to a seventh embodiment. The piezoelectric transformer according to the present embodiment has one low impedance section 201 as an input section.
And two high impedance sections 202L as output sections,
202R. At this time, the low impedance section 2
01, a high-impedance section 202
L and 202R are arranged.

The piezoelectric transformer is connected to the low impedance section 20.
1 has electrodes 204U and 204D on the upper and lower main surfaces in the thickness direction, and has an internal electrode 209 between the electrodes 204U and 204D. The connection and polarization direction between the internal electrode 209 and the electrodes 204U and 204D in the low impedance section 201 are the same as those described in the above-described embodiment. The electrode 204U has an external connection terminal 204x
However, the external connection terminal 204y is connected to the electrode 204D. The electrode 203L has an external connection terminal 203x and the electrode 2
An external connection terminal 203y is connected to 03R. Further, the piezoelectric transformer includes a high impedance section 202L,
02R has electrodes 203L and 203R on its end face not connected to the low impedance section 201, respectively.

The polarization directions of the piezoelectric layers of the high impedance portions 202L and 202R are respectively parallel to the polarization directions of the low impedance portion 201. The polarization direction in the high impedance section 202L is opposite to the polarization direction in the high impedance section 202R.

In the piezoelectric transformer configured as described above, an input voltage of a predetermined frequency is applied to the external connection terminal 204x,
The electrode 20 of the low impedance section 201 through the electrode 204y
4U, applied to 204D. At this time, the electrode 204U
Is the electrode on the reference potential side. When an input voltage is applied, a longitudinal vibration in the length direction occurs in the low impedance section 201 due to a piezoelectric effect. Due to the longitudinal vibration of the low impedance section 201, vibration occurs in the high impedance sections 202L and 202R, and this vibration is converted into electric energy. This electric energy is supplied to the electrode 204U and the electrode 20U.
3L or from the electrode 204U and the electrode 203R as an output voltage via the external connection terminals 203x and 203y.

As described above, by arranging the high impedance portions 202L and 202R at both ends of the low impedance portion 201, when driven in the longitudinal longitudinal primary mode, longitudinal mode resonance can be eliminated. At this time, the external connection terminals 204x and 204y are arranged at the center position in the length direction of the low impedance portion 201 in order to eliminate the influence on the vibration.

Based on the above configuration, the low impedance portion 201 has a length of 10 mm, the number of piezoelectric layers is 11, and the high impedance portions 202L and 202R have a length of 5 mm.
The number of piezoelectric layers is 1, the total thickness is 1.2 mm, and the width is 5 mm
Was produced. The resonance frequency of the longitudinal mode in the longitudinal direction of the piezoelectric transformer was measured to be 86 kHz from the frequency characteristics of admittance. When a load resistance of 100 kΩ was connected to each output section of this piezoelectric transformer, an output of 600 V was obtained for an input voltage of 30 V, and the output power at this time was 3.5 W.

In this embodiment, the high impedance portions 202L and 202R are connected to both ends of the low impedance portion 201 in the longitudinal direction.
The same applies to the case of connecting to both ends in the thickness direction or width direction of No. 01.

(Eighth Embodiment) FIG. 23 is a perspective view of a piezoelectric transformer according to an eighth embodiment. The difference from the piezoelectric transformer of the seventh embodiment is that the polarization direction of the high impedance portion 202L is the same as the polarization direction of the high impedance portion 202R.

With this configuration, the electrode 203L connected to the end of the high impedance portion 202L is
Electrode 20 connected to end of high impedance section 202R
The output voltage can be extracted from each of the 3Rs, and a high boosting ratio can be obtained. Further, the input electrode and the output electrode can be electrically separated. Further, it can be driven as a 1-input / 2-output piezoelectric transformer.

In the above configuration, the low impedance section 201
A piezoelectric transformer having a length of 10 mm, a number of piezoelectric layers of 11, a length of 5 mm in the high impedance portions 202L and 202R, a number of piezoelectric layers of 1, and a total thickness of 1.2 mm and a width of 5 mm was produced. . The resonance frequency of the longitudinal mode in the longitudinal direction of the piezoelectric transformer was measured to be 86 kHz from the frequency characteristics of admittance. When a load resistance of 100 kΩ was connected to each output section of the piezoelectric transformer, an output of 700 V was obtained for an input voltage of 40 V, and the output power at this time was 4.5 W.

Further, the piezoelectric transformer is driven at the resonance frequency of the longitudinal longitudinal primary mode in the longitudinal direction. At this time, the external connection terminals 204x and 204y of the low impedance section 201 are arranged at the center position in the length direction of the piezoelectric transformer. Thereby, in the low impedance section 201, the external connection terminals 204x and 204y do not adversely affect the vibration, and the longitudinal vibration secondary mode in the length direction can be suppressed.

Ninth Embodiment FIG. 24 is a perspective view showing a piezoelectric transformer according to a ninth embodiment. The piezoelectric transformer shown in this figure is different from the piezoelectric transformer of the seventh embodiment (FIG. 22) in that insulating layers 223L and 223 are provided between low impedance section 201 and high impedance sections 202L and 202R.
3R is provided.

The low impedance section 201 is constituted by alternately stacking six piezoelectric layers and seven internal electrodes 209. At this time, the polarization direction of the piezoelectric layer is opposite between adjacent piezoelectric layers. External electrodes 204U and 204D are connected to the main surface in the thickness direction of the low impedance portion 201, and external connection terminals 204x and 204D are connected to the external electrodes 204U and 204D.
204y are respectively connected. External electrode 204U, 2
The internal electrodes 209 are alternately connected to 04D.

The high-impedance portion 202L is
An electrode 224L is provided on the end face in contact with 3L.
An electrode 203L is provided on the end face opposite to the end face to which 24L is connected.
Having. The high-impedance portion 202R includes an insulating layer 223.
An electrode 224R is provided on the end face in contact with R, and the electrode 22
An electrode 203R is provided on an end face opposite to the end face to which 4R is connected. Here, the polarization direction of the low impedance section 201 is parallel to the polarization directions of the high impedance sections 202L and 202R. External connection terminals 204x and 204y are connected to the electrodes 204U and 204D, respectively. The electrodes 203L and 203R have external connection terminals 203 respectively.
x and 203y are connected.

As described above, the low impedance section 201
And the high impedance portions 202L and 202R are connected to the insulating layer 2
By connecting via 23L and 223R, input and output can be electrically separated.

In this case, the input voltage is applied to the electrodes 204U and 204D via the external connection terminals 204x and 204y, and the output voltage is applied to the electrodes 203L and 224L or between the electrodes 203R and 224R.
It is taken out via 04x, 203x and 203y.

In the above configuration, the low impedance section 201
A piezoelectric transformer having a length of 10 mm, a number of piezoelectric layers of 40, a length of 5 mm in the high impedance portions 202L and 202R, a number of piezoelectric layers of 1, a total thickness of 1.2 mm, and a width of 5 mm was produced. The resonance frequency of the longitudinal mode in the longitudinal direction of the piezoelectric transformer was measured to be 86 kHz from the frequency characteristics of admittance. This piezoelectric transformer has 10
A load resistance of 0 kΩ is applied to each output electrode 203L,
When connected to 224L or 203R, 224R,
An output of 450 V was obtained with respect to the input voltage of 20 V, and the output power at this time was 2.0 W.

Further, the piezoelectric transformer of the present embodiment is driven at the resonance frequency of the longitudinal vibration primary mode in the longitudinal direction. At this time, the external connection terminal 204 of the low impedance unit 201
x and 204y are arranged at the center position in the length direction of the piezoelectric transformer. Accordingly, in the low impedance section 201, the external connection terminals 204x and 204y do not adversely affect the vibration, and the longitudinal longitudinal secondary mode in the longitudinal direction can be suppressed.

[0101]

According to the present invention, there are provided a low impedance portion comprising at least one vibrator having a piezoelectric effect and a high impedance portion comprising at least one vibrator having a piezoelectric effect. Provided is a piezoelectric transformer in which a piezoelectric layer is formed so that polarization directions are parallel. In this piezoelectric transformer, electromechanical energy conversion is performed in both the low impedance section and the high impedance section using the longitudinal effect (k33). This suppresses the stress applied to the joint between the low-impedance portion and the high-impedance portion, so that a reduction in strength can be prevented, and a high boost ratio can be realized. Therefore, it is possible to realize a piezoelectric transformer having high reliability, small size and capable of generating a high voltage.

[Brief description of the drawings]

FIG. 1 is a perspective view of a piezoelectric transformer according to a first embodiment of the present invention.

FIG. 2 is a lumped constant equivalent circuit diagram of the piezoelectric transformer according to the first embodiment.

FIG. 3 is a diagram illustrating various characteristics of the piezoelectric transformer according to the first embodiment with respect to additional resistance.

FIG. 4 is a diagram illustrating a method for manufacturing the piezoelectric transformer according to the first embodiment.

FIG. 5 is a diagram showing a displacement distribution and a stress distribution of a rod-shaped vibrator in a longitudinal longitudinal vibration secondary mode.

FIG. 6 is a diagram showing a displacement distribution and a stress distribution of a rod-shaped vibrator in a longitudinal longitudinal primary mode in a longitudinal direction.

FIG. 7 is a perspective view of another example of the piezoelectric transformer according to the first embodiment.

FIG. 8 is a perspective view of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating a method for manufacturing the piezoelectric transformer according to the second embodiment.

FIG. 10 is a perspective view of another example of the piezoelectric transformer according to the second embodiment.

FIG. 11 is a perspective view of a piezoelectric transformer according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a method for manufacturing the piezoelectric transformer according to the third embodiment.

FIG. 13 is a perspective view of another example of the piezoelectric transformer according to the third embodiment.

FIG. 14 is a perspective view of the piezoelectric transformer having the structure shown in FIG.

FIG. 15 is a perspective view of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 16 is a perspective view of another example of the piezoelectric transformer according to the fourth embodiment.

FIG. 17 is a perspective view of a piezoelectric transformer according to a fifth embodiment of the present invention.

FIG. 18 is a perspective view of a piezoelectric transformer according to a sixth embodiment of the present invention.

FIG. 19 is a plan view of the piezoelectric transformer according to the sixth embodiment as viewed from above.

FIG. 20 is a perspective view of another example of the piezoelectric transformer according to the sixth embodiment.

21 is a plan view of the piezoelectric transformer of FIG. 20 as viewed from above.

FIG. 22 is a perspective view of a piezoelectric transformer according to a seventh embodiment of the present invention.

FIG. 23 is a perspective view of a piezoelectric transformer according to an eighth embodiment of the present invention.

FIG. 24 is a perspective view of a piezoelectric transformer according to a ninth embodiment of the present invention.

FIG. 25 is a perspective view of a Rosen-type piezoelectric transformer as an example of a conventional piezoelectric transformer.

[Explanation of symbols]

111, 201 Low impedance section 112, 202L, 202R High impedance section 13U, 13D, 16, 115a, 102, 114, 1
15a, 115b, 116L, 116R, 132L, 1
32R, 133, 134, 141, 142, 151L,
151R, 161, 162, 163L, 163R, 18
1L, 181R, 203L, 203R, 204U, 20
4D, 221U, 221D, 224L, 224R, 22
5L, 225R External electrode 14, 15, 208 Piezoelectric layer 17, 104, 184, 209 Internal electrode 81 Insulating layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Asahi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Kawa ▲ Osamu Osamu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. A piezoelectric device comprising: a low-impedance section for converting an input voltage into mechanical vibration; and a high-impedance section connected to the low-impedance section for converting mechanical vibration of the low-impedance section into a predetermined output voltage. In the transformer, the low-impedance portion is formed by being polarized and has at least one vibrator having a piezoelectric effect, and an input electrode connected to the vibrator to apply the input voltage in a polarization direction of the vibrator. The high impedance portion is formed by polarization, and is connected to the at least one vibrator having a piezoelectric effect and the vibrator to take out the output voltage generated in the polarization direction of the vibrator. An output electrode, and the low impedance section and the high impedance section so that the polarization directions of the oscillators of the impedance sections are parallel. A piezoelectric transformer characterized by connecting. 2. The low-impedance section includes a plurality of vibrators integrally formed so that the polarization directions are opposite between adjacent vibrators, and is connected to the input electrode between the vibrators. 2. The piezoelectric transformer according to claim 1, further comprising an internal electrode. 3. The high impedance section includes a plurality of vibrators integrally formed so that the polarization directions are opposite between adjacent vibrators, and is connected to the output electrode between the vibrators. 2. The piezoelectric transformer according to claim 1, further comprising an internal electrode. 4. The piezoelectric element according to claim 1, wherein the vibrators in the low impedance portion and the high impedance portion are formed using materials having different dielectric constants. Trance. 5. The piezoelectric device according to claim 1, wherein the low impedance portion and the high impedance portion are integrally connected in a length direction of the piezoelectric transformer. Trance. 6. The piezoelectric transformer according to claim 1, wherein the low impedance section and the high impedance section are integrally connected in a thickness direction of the piezoelectric transformer. . 7. The piezoelectric transformer according to claim 1, wherein the low impedance section and the high impedance section are integrally connected in a width direction of the piezoelectric transformer. . 8. The piezoelectric transformer according to claim 5, wherein an insulating layer is provided between the low impedance section and the high impedance section. 9. The driving method of a piezoelectric transformer according to claim 1, wherein a longitudinal direction vibration in which one wavelength is equal to の of a length of the piezoelectric transformer. A method for driving a piezoelectric transformer, comprising: driving the piezoelectric transformer at a resonance frequency in a primary mode. 10. The method according to claim 1, wherein:
The method of driving a piezoelectric transformer according to any one of claims 1 to 3, wherein the piezoelectric transformer is driven at a resonance frequency of a longitudinal longitudinal vibration secondary mode in which one wavelength is equal to the length of the piezoelectric transformer. Drive method. 11. The high impedance section comprises first and second output impedance sections, and the low impedance section is connected between the first output impedance section and the second output impedance section. The piezoelectric transformer according to any one of claims 1 to 4, wherein: 12. The low impedance section and the first impedance section.
The piezoelectric transformer according to claim 11, wherein an insulating layer is provided between the piezoelectric transformer and the second output impedance section. 13. The method for driving a piezoelectric transformer according to claim 11, wherein a resonance in a longitudinal longitudinal vibration primary mode in which one wavelength is equal to １ ／ of the length of the piezoelectric transformer. A method for driving a piezoelectric transformer, comprising driving the piezoelectric transformer at a frequency. 14. A green sheet made of a material exhibiting a piezoelectric effect and a green sheet on which internal electrodes are printed in a predetermined shape are laminated in a predetermined order and pressed to form a laminate of a low impedance portion and a high impedance portion. Then, firing each of the laminates and cutting them into a predetermined shape; forming external electrodes at the ends of the cut laminates; applying a voltage to the external electrodes to reduce the impedance And a step of polarizing the high impedance portion. 15. A laminate is prepared by laminating a green sheet made of a material exhibiting a piezoelectric effect and a green sheet having an internal electrode printed in a predetermined shape in a predetermined order, and firing the laminate, Cutting the fired laminate into a predetermined shape, forming an external electrode at an end of the cut laminate to produce a low impedance portion, sintering a material exhibiting a piezoelectric effect, and sintering the end of the material. Forming an external electrode on the portion to form a high impedance portion; joining the low impedance portion and the high impedance portion via an insulating layer; applying a voltage to the external electrode, And a step of polarizing the high impedance portion.