JPH09214012A - Piezoelectric transformer and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve conversion efficiency of electro-mechanical energy and facilitate matching with load resistance by connecting a plurality of internal electrodes with a common external electrode at first and second side surfaces on alternate electrodes so as to form counter electrodes. SOLUTION: In a piezoelectric transformer using a resonance mode in the length direction of a piezoelectric ceramic rectangular plate 11 a plurality of internal electrodes 12 are provided at a substantially half part of the rectangular plate 11 in the length direction of the same perpendicularly to the length direction. The internal electrodes 12 are connected with a common external electrodes 13 at first and second side surfaces on alternate electrodes so as to form counter electrodes. A remaining half part of the rectangular plate 11 in the length direction includes an end surface electrode or a plurality of internal electrodes 14. The internal electrodes 14 are connected with a common external electrode 15 at first and second side surfaces on alternate electrodes so as to form counter electrodes. Hereby, there is useable a piezoelectric longitudinal effect in the length direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer using piezoelectric ceramics, and in particular, electrodes for polarization and input / output are formed inside and on the surface of a rectangular plate of piezoelectric ceramics, and the electrodes are arranged in the longitudinal direction of the rectangular plate. The present invention relates to a piezoelectric transformer that utilizes resonance.

[0002]

2. Description of the Related Art With the spread of battery-powered portable devices such as mobile phones and notebook personal computers, a battery such as a dry battery is used as an input power source, 3V IC drive, 6V motor drive, 12V backlight lighting, etc. For electronic components driven by a voltage different from the input power supply voltage,
DC / DC converters are often used. Currently, electromagnetic transformers are used for these DC / DC converters as transformers, but due to demands such as reduction of generated electromagnetic noise, low power consumption, high efficiency, and small and low profile of equipment, electromagnetic transformers are being used. In place of the above, the practical application of piezoelectric transformers is being studied.

FIG. 3 is a schematic perspective view of the structure of a piezoelectric vibrator used in a conventional Rosen type λ mode piezoelectric transformer. In FIG. 3, the piezoelectric ceramic rectangular plate 3
1, an input surface electrode 32 is formed at a position approximately half of the length of the input part 1 so as to face the thickness direction. Further, an output surface electrode 33 is formed on the end face in the length direction on the side opposite to the portion where the input surface electrode 32 is formed on the piezoelectric ceramic rectangular plate 31. Piezoelectric ceramic rectangular plate 31
Indicates that the portion of the input surface electrode 32 is polarized in the thickness direction of the rectangular plate as indicated by the arrow, and the portion between the output surface electrodes 33 is aligned in the length direction of the piezoelectric ceramic rectangular plate as indicated by the arrow. It is polarized.

Further, as the piezoelectric transformer, it is necessary to support it at a vibration nodal point which has less influence on the vibration of the ceramic rectangular plate and take out the input / output electrodes at the nodal point. 41, 41
Indicates a node of vibration in the λ mode. 4A and 4B are explanatory views of the operation principle of a λ-mode resonance drive piezoelectric transformer using the piezoelectric vibrator of FIG. 3, FIG. 4A is a cross-sectional view of a piezoelectric ceramic rectangular plate, and FIG. 4B is a piezoelectric ceramic. FIG. 4C is a displacement distribution when the rectangular plate is vibrating in the one-wavelength resonance mode of longitudinal vibration, and FIG. 4C shows the strain distribution at that time. When a voltage having a frequency equal to the resonance frequency of the one-wavelength resonance mode in the length direction of the piezoelectric ceramic rectangular plate is applied to the electrode 32 in FIG. 4 (a), the rectangular plate becomes as shown in FIGS. 4 (b) and 4 (c). Vibrate to. At this time, a voltage is generated between the electrodes 32 and 33 due to the piezoelectric vertical effect. Here, the input voltage applied to the electrode 32 and the output voltage generated between the electrodes 33 will be described. The interval between the counter electrodes of the electrode 32 is sufficiently smaller than the interval between the electrodes 32 and 33, and the area of the electrode 32 is the area of the electrode 33. Since it is sufficiently larger than the area, the capacitance on the input side becomes a value sufficiently larger than the capacitance on the output side. Therefore, when a low voltage is applied to the input side to vibrate the vibrator, the ratio of the input side electrode spacing to the output side and the spacing between the input side electrode and the output side electrode, and the capacitance ratio of the input and output sides are A large proportional voltage is generated.

[0005]

In the piezoelectric transformer described in FIG. 3, the input surface electrode 32 is polarized in the thickness direction of the rectangular plate and vibrates the resonance in the length direction. The direction and the electric field direction on the input side are orthogonal to each other, and the so-called piezoelectric lateral effect is used. In the input part of the piezoelectric transformer, the rate at which electrical input energy is converted into mechanical vibration energy is approximately proportional to the electromechanical coupling coefficient of the piezoelectric lateral effect. Here, the piezoelectric effect includes the above-described piezoelectric transverse effect and the piezoelectric longitudinal effect in which the vibration direction and the electric field direction are the same. In ordinary isotropic ceramics, the magnitude of the electromechanical coupling coefficient of the piezoelectric longitudinal effect is the piezoelectric transverse effect. It is about twice the electromechanical coupling coefficient of the effect. Therefore, in the piezoelectric transformer using the piezoelectric lateral effect on the input side shown in FIG. 3, the rate of exchanging the electric input energy with the energy of mechanical vibration is only about half that in the case of the piezoelectric longitudinal effect. There is.

Also, since the output side of the piezoelectric transformer shown in FIG. 3 uses the piezoelectric longitudinal effect, it is sufficient as a piezoelectric effect for converting the energy of mechanical vibration into electrical output energy, but The impedance matching with the load resistance is important for the output resistance, and when the matching is good, the energy of mechanical vibration can be efficiently converted into electrical output energy. The output resistance of the piezoelectric transformer is determined by the product of the reciprocal of the resonance angular frequency and the reciprocal of the braking capacity of the output section. In the piezoelectric transformer shown in FIG. 3, the output resistance depends only on the external dimensions of the rectangular plate, and the load resistance is When there is a change, impedance matching cannot be obtained, and the output efficiency decreases.

Therefore, an object of the present invention is to provide a piezoelectric transformer having a structure in which a piezoelectric longitudinal effect is used for an input portion and an output portion to enhance the conversion efficiency of electromechanical energy, and a matching with a load resistance can be easily achieved, and the manufacturing thereof. To provide a method.

[0008]

According to the present invention, in a piezoelectric transformer utilizing the longitudinal resonance mode of a piezoelectric ceramic rectangular plate, the longitudinal direction is provided at approximately half the length of the rectangular plate. Has a plurality of internal electrodes orthogonal to each other, and the internal electrodes are connected to a common external electrode on each of the first side surface and the second side surface so as to be a counter electrode, and the length of the rectangular plate The other half of the direction is orthogonal to the length direction,
A piezoelectric transformer having a structure in which an end face electrode or a plurality of internal electrodes are provided, and the internal electrodes are alternately connected to common external electrodes on the first side surface and the second side surface so as to be opposed electrodes, respectively. can get.

Further, there is an end face electrode or a plurality of internal electrodes which are orthogonal to the lengthwise direction, and the internal electrodes are arranged in a single layer so as to be opposed electrodes, and the external electrodes common to the first side surface and the second side surface, respectively. And a first member connected to each other and an end face electrode or a plurality of internal electrodes that are orthogonal to the lengthwise direction, and the internal electrodes are placed one by one on the first side surface and the second side surface so as to be opposed electrodes, respectively. A method for manufacturing a piezoelectric transformer is obtained, which is characterized in that a second member connected to a common external electrode is fixed to each end face in the longitudinal direction.

Further, according to the present invention, in the piezoelectric transformer utilizing the resonance mode in the lengthwise direction of the piezoelectric ceramic rectangular plate, the thickness of the piezoelectric transformer input portion is formed in approximately half the lengthwise direction of the rectangular plate. It has a plurality of internal electrodes orthogonal to the direction, and the internal electrodes are connected to a common external electrode on each of the first side surface and the second side surface so as to be a counter electrode and connected to a common external electrode. The remaining half portion in the vertical direction has a plurality of internal electrodes as a piezoelectric transformer output portion that are orthogonal to the thickness direction, and the internal electrodes are arranged in a single layer so that the internal electrodes are opposite electrodes and the first side surface and the second side electrode. A piezoelectric transformer having a structure in which each side is connected to a common external electrode is obtained.

Further, according to the present invention, in the piezoelectric transformer utilizing the resonance mode in the lengthwise direction of the piezoelectric ceramic rectangular plate, the thickness of the piezoelectric transformer as an input portion is formed in approximately half the lengthwise direction of the rectangular plate. It has a plurality of internal electrodes orthogonal to the direction, and the internal electrodes are connected to a common external electrode on each of the first side surface and the second side surface so as to be a counter electrode and connected to a common external electrode. The remaining half portion in the vertical direction has a plurality of internal electrodes that are orthogonal to the length direction as a piezoelectric transformer output portion, and the internal electrodes are arranged in a single layer so that the internal electrodes are opposite electrodes and the first side surface and the second side surface. A piezoelectric transformer having a structure in which each side is connected to a common external electrode is obtained.

[0012]

In a piezoelectric transformer using the length resonance mode of a rectangular plate, a structure in which a plurality of opposing internal electrodes are laminated in a direction orthogonal to the thickness direction of the rectangular plate in order to reduce the input voltage is a structure of Japanese Patent Application No. 6-242. -280590 and the like have already been presented. However, in this structure, since the electric field direction of the input voltage and the vibration direction are orthogonal to each other, the piezoelectric lateral effect is used on the input side. In addition, a piezoelectric transformer having a structure in which a piezoelectric vertical effect is used in the input section and an input voltage is lowered is disclosed in Japanese Patent Application No.
9377. However, the piezoelectric transformer of this structure utilizes the resonance mode in the thickness direction of the piezoelectric plate, and since the input part is composed of a plurality of opposed internal electrodes that are orthogonal to the thickness direction, The fundamental structure is different from the present invention which uses resonance and is constituted by a plurality of opposed internal electrodes which are orthogonal to the length direction. As in the structure of the present invention, an end face electrode or a plurality of internal electrodes are provided in a substantially half portion of the rectangular plate in the lengthwise direction at right angles to the lengthwise direction. On the other hand, the piezoelectric vertical effect can be utilized in the length direction by connecting the common external electrodes to the first side surface and the second side surface.

A laminated piezoelectric actuator has already been commercialized as a laminated vibrator utilizing the piezoelectric longitudinal effect. However, the actuator is generally used with a DC voltage or an AC voltage with a non-resonant frequency, and uses mechanical energy of displacement or stress generated by an applied voltage. The usage mode of vibration is completely different from that of a piezoelectric transformer that converts energy into mechanical energy of vibration and then into electrical energy. Further, here, in order to improve the impedance matching with the load resistance in the above-mentioned piezoelectric transformer, the output resistance of the piezoelectric transformer is determined by the product of the reciprocal of the resonance angular frequency and the reciprocal of the braking capacitance of the output section, and the resonance angular frequency vibrates. Since the length depends on the length of the child, it is necessary to change the damping capacitance and the resonance angular frequency when the load resistance changes to achieve impedance matching. That is, the length of the vibrator is an important factor for impedance matching, but the limit of the length of the commercially available laminated piezoelectric actuator is about 20 mm, and the impedance matching range is narrow. Therefore, as in the manufacturing method of the present invention, two members having opposing internal electrodes are fixed to each other at their end faces in the longitudinal direction so as to utilize the piezoelectric longitudinal effect, thereby obtaining selectivity in the length dimension and resonance. Adjusting the angular frequency facilitates impedance matching.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail in the section of Examples with reference to the drawings.

[0015]

EXAMPLES Four examples of the present invention will be sequentially described below.

(Embodiment 1) Dimensions having a plurality of internal electrodes orthogonal to the length direction of a rectangular plate 40 mm long and 10 m wide
A PZT-based piezoelectric ceramics laminate having a thickness of 2.0 mm and a thickness of 2.0 mm was experimentally manufactured. In the half part of the rectangular plate which is the input part, the silver-palladium internal electrodes connected to the common external electrode on the side surface every other layer are arranged at intervals of 200 μm in the thickness of the ceramic layer.
0 layers are stacked, and the remaining half of the rectangular plate that is the output section is
Four layers of internal electrodes of silver-palladium, which are connected to a common external electrode on the side surface of every other layer, were laminated at intervals of a ceramic layer thickness of 0.5 mm.

FIG. 1 is an external perspective view of a prototype piezoelectric transformer.
It was shown to. Reference numeral 11 is a piezoelectric ceramic rectangular plate, 12 is an internal electrode on the input side of the piezoelectric transformer, 13 is an external electrode on the side surface on the input side, 14 is an internal electrode on the output side of the piezoelectric transformer, and 15 is an external electrode on the side surface on the output side. Show.

By utilizing the one-wavelength resonance mode of the trial-produced piezoelectric transformer, one quarter of the length from the end face of the rectangular plate in the longitudinal direction is used.
mm position, input voltage 10V, load resistance 10
The piezoelectric transformer characteristic at 0 kΩ was measured. Table 1 below compares the measurement results with the conventional structure shown in FIG.
It was shown to.

[0019]

[Table 1]

From Table 1, it is clear that the piezoelectric transformer of Example 1 of the present invention has a boosting ratio similar to that of the conventional structure, but is excellent in efficiency and heat generation.

(Embodiment 2) Dimensions having a plurality of internal electrodes orthogonal to the length direction of a rectangular plate Length 20 mm, width 10 m
A PZT-based piezoelectric ceramics laminate having a thickness of 2.0 mm and a thickness of 2.0 mm was experimentally manufactured. The piezoelectric ceramic laminate serving as the input part was laminated every 100 layers, and 100 layers of silver-palladium internal electrodes connected to common external electrodes on the side surfaces were laminated at intervals of 200 μm in thickness of the ceramic layers. The piezoelectric ceramic laminate serving as the output portion has a plurality of internal electrodes that are orthogonal to the thickness direction of the rectangular plate, and the silver-palladium internal electrodes connected to the common external electrode on the side surface every other layer have a ceramic layer thickness of 0. Four layers were laminated at intervals of 0.5 mm. These piezoelectric ceramics laminates are fixed at the end face with a width of 10 mm and a thickness of 2.0 mm with an epoxy adhesive, and have a length of 40 mm, a width of 10 mm and a thickness of 2.0.
mm trial production of a piezoelectric transformer.

FIG. 2 is a perspective view showing the appearance of a prototype piezoelectric transformer.
It was shown to. Reference numeral 21 is a piezoelectric ceramic rectangular plate, 22 is an internal electrode on the input side of the piezoelectric transformer, 23 is an external electrode on the side surface on the input side, 24 is an internal electrode on the output side of the piezoelectric transformer, 25 is an external electrode on the side surface on the output side, 26 Indicates the bonded portion at the center of the rectangular plate.

FIG. 2 is a perspective view showing the appearance of a prototype piezoelectric transformer.
It was shown to. Using the one-wavelength resonance mode of the prototype piezoelectric transformer, a quarter of 10m from the end face in the length direction of the rectangular plate
Supporting position m, input voltage 10V, load resistance 50k
The piezoelectric transformer characteristic when Ω was measured. The bonded portion of the central portion of the piezoelectric transformer corresponds to the antinode of vibration, and the vibration amplitude is maximum to prevent damage when the piezoelectric transformer is driven, but stress is at the minimum position. The measurement results are shown in Table 2 below in comparison with the conventional structure having the same dimensions as shown in FIG.

[0024]

[Table 2]

From Table 2, it is apparent that the piezoelectric transformer manufactured by the manufacturing method of Embodiment 2 of the present invention has a step-up ratio comparable to that of the conventional structure, but is excellent in efficiency and heat generation.

(Embodiment 3) A PZT piezoelectric ceramic rectangular plate having a plurality of internal electrodes orthogonal to the thickness direction, and having a dimension of 40 mm, a width of 10 mm, and a thickness of 1.5 mm was manufactured as a prototype. The half portion of the rectangular plate which is the input portion is laminated every other layer with 15 layers of silver-palladium internal electrodes which are connected to the common external electrode at the side surfaces at a ceramic layer thickness of 100 μm, and the rectangular portion which is the output portion of the rectangular plate. In the other half, every other layer, ten internal electrodes of silver-palladium, which are connected to a common external electrode on the side surface, were laminated at a ceramic layer thickness of 150 μm.

FIG. 1 is an external perspective view of a prototype piezoelectric transformer.
It was shown to.

The optimum load resistance value calculated from the resonance frequency of the prototype piezoelectric transformer and the braking capacity on the output side is shown in Table 3 below.
It was shown to. Also, by utilizing the one-wavelength resonance mode of the prototype piezoelectric transformer, a position of a quarter of 10 mm from the end face in the length direction of the rectangular plate is supported, and an input voltage of 3 V and a load resistance of 5
The piezoelectric transformer characteristic at 0Ω was measured. The measurement results are shown in Table 3 below in comparison with the conventional structure having the same dimensions as shown in FIG.

[0029]

[Table 3]

(Embodiment 4) Dimensional length 50 having a plurality of internal electrodes orthogonal to the length direction of a PZT-based piezoelectric ceramic rectangular plate and a plurality of internal electrodes orthogonal to the thickness direction of the rectangular plate.
A piezoelectric transformer having a size of 15 mm, a width of 15 mm, and a thickness of 2 mm was prototyped. In almost half of the length direction of the piezoelectric ceramics laminate serving as the input part, silver-palladium internal electrodes connected to the common external electrodes at the side surfaces are placed every other layer and the thickness of the ceramic layer is 2
120 layers were laminated at intervals of 00 μm. In the remaining half of the piezoelectric ceramics laminate in the length direction, which is the output part, 10 layers of silver-palladium internal electrodes, which are connected to the common external electrodes on the side surfaces every other layer, were laminated at a ceramic layer thickness of 200 μm. An external perspective view of the prototype piezoelectric transformer is shown in FIG. Table 3 shows the optimum load resistance value calculated from the resonance frequency of the prototype piezoelectric transformer and the braking capacitance on the output side. In addition, the one-wavelength resonance mode of the prototype piezoelectric transformer was used to support the position of a quarter of 10 mm from the end face in the length direction of the rectangular plate, and the piezoelectric transformer characteristics when the input voltage was 10 V and the load resistance was 10 Ω. Was measured. Table 3 shows the measurement results.

From Table 3, the piezoelectric transformers of Examples 3 and 4 of the present invention have a step-up ratio of 4-5 times and an input voltage of 1.5-3.
The input voltage of a battery of about V can be boosted to about 6 to 15 V, and the impedance matching is good, so that a high efficiency of 90% or more is achieved. Impedance matching cannot be obtained with the conventional structure, and DCD
It is clear that the characteristics as the transformer for the C converter cannot be obtained.

[0032]

As is apparent from the above description, according to the present invention, there is provided a piezoelectric transformer having a step-up ratio comparable to that of the prior art, but excellent in efficiency and heat generation, and a manufacturing method thereof. You can Further, according to the present invention, it is possible to provide an excellent piezoelectric transformer having a step-up ratio several times that of the conventional technique and an efficiency of 90% or more.

[Brief description of drawings]

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

FIG. 2 is a perspective view of a piezoelectric transformer according to examples 2 and 4 of the present invention.

FIG. 3 is a schematic perspective view of a conventional one-wavelength resonance mode piezoelectric transformer.

FIG. 4 shows the piezoelectric ceramic rectangular plate of FIG. 3, (a) is a cross-sectional view, (b) is a displacement distribution when the piezoelectric ceramic rectangular plate is vibrating in a longitudinal one-wavelength resonance mode, (c) Is the strain distribution at that time.

[Explanation of symbols]

 11 piezoelectric ceramic rectangular plate 12 internal electrode on the input side 13 external electrode on the side surface on the input side 14 internal electrode on the output side 15 external electrode on the side surface on the output side 21 piezoelectric ceramic rectangular plate 22 internal electrode on the input side 23 side surface on the input side External electrode 24 Internal electrode on the output side 25 External electrode on the side surface on the output side 26 Adhesive part at the center of the rectangular plate 31 Piezoelectric ceramic rectangular plate 32 Input surface electrode 33 Output surface electrode 41 Vibration node

Claims (4)

[Claims] 1. A piezoelectric transformer using a resonance mode in a length direction of a piezoelectric ceramic rectangular plate, wherein a plurality of internal electrodes are provided at approximately half of the length direction of the rectangular plate in a direction orthogonal to the length direction. The internal electrodes are connected to the common external electrodes on the first side surface and the second side surface in alternate layers so as to be opposed electrodes, and the remaining half of the rectangular plate in the longitudinal direction is in the longitudinal direction. Characterized by having an end face electrode or a plurality of internal electrodes orthogonal to, and alternately connecting the internal electrodes to a common external electrode on the first side surface and the second side surface so as to be opposite electrodes. And a piezoelectric transformer. 2. An external electrode having an end face electrode or a plurality of internal electrodes which are orthogonal to the lengthwise direction, wherein the internal electrodes are placed in one layer so as to be opposed electrodes and are common to the first side surface and the second side surface, respectively. And a first member connected to each other and an end face electrode or a plurality of internal electrodes that are orthogonal to the lengthwise direction, and the internal electrodes are placed one by one on the first side surface and the second side surface so as to be opposed electrodes, respectively. 2. The method for manufacturing a piezoelectric transformer according to claim 1, further comprising a method of fixing a second member connected to a common external electrode at each end face in the length direction. 3. A piezoelectric transformer utilizing a resonance mode in the length direction of a piezoelectric ceramic rectangular plate, wherein a piezoelectric transformer input portion is orthogonal to the thickness direction at approximately half of the rectangular plate in the length direction. A plurality of internal electrodes are provided, and the internal electrodes are arranged in a single layer so as to be opposed electrodes and the first side surface and the second electrode.
Connected to a common external electrode on each side surface, and the remaining half of the rectangular plate in the length direction has a plurality of internal electrodes that are orthogonal to the thickness direction as piezoelectric transformer output parts, and the internal electrodes are The first side surface and the second
A piezoelectric transformer characterized by a structure in which each side is connected to a common external electrode. 4. A piezoelectric transformer utilizing a resonance mode in a length direction of a piezoelectric ceramic rectangular plate, wherein a piezoelectric transformer input section is orthogonal to the thickness direction at a substantially half portion of the rectangular plate in the length direction, A plurality of internal electrodes are provided, and the internal electrodes are arranged in a single layer so as to be opposed electrodes and the first side surface and the second electrode.
Connected to a common external electrode on each side, and the other half of the rectangular plate in the longitudinal direction has a plurality of internal electrodes that are orthogonal to the piezoelectric transformer output portion in the longitudinal direction. The first side surface and the second
A piezoelectric transformer characterized by a structure in which each side is connected to a common external electrode.