JPH11204851A - Piezoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transducer which is easily changed in output-side damping capacity, even if a load resistor is 1 kΩ or below and excellent in impedance matching to a load resistor. SOLUTION: A piezoelectric transducer is equipped with a surface electrode 12b and inner electrodes 12a which are formed on the upper half of a ceramic rectangular plate as electrode layers overlapping a ceramic layer 21, so as to excite the ceramic rectangular plate in the lengthwise direction taking advantage of its piezoelectric effect and a first, and a second outer electrode, 13a and 13b, electrically connected to the electrode 12b and the inner electrodes 12a. The piezoelectric transducer is equipped with a belt-like electrodes 14a and 14b which are laminated on the lower half of the ceramic rectangular plate through the intermediary of a ceramic layer 11 being arranged in the above lengthwise direction, extending in the widthwise direction of the rectangular plate, and being exposed on both the sides of the ceramic plate so as to extract an electric power from the rectangular plate taking advantage of a piezoelectric vertical effect; and outer electrode groups 16a and 16b which are connected in the lengthwise direction on one side or the vertical direction on the other side, so as to enable the electrodes 14a and 14b to confront each other in the lengthwise 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, a piezoelectric ceramic rectangular plate and internal electrodes are laminated in the thickness direction of the rectangular plate, and resonance in the longitudinal direction of the rectangular plate is used. The present invention relates to a piezoelectric transformer.

[0002]

2. Description of the Related Art In recent years, with the spread of notebook personal computers and portable video cameras, liquid crystal units have become widespread as image display systems, and inverters are frequently used for turning on a liquid crystal backlight. This inverter uses an electromagnetic transformer for generating high voltage. However, due to demands for reduction of generated electromagnetic noise, low power consumption, high efficiency, and compact and low-profile equipment, the use of electromagnetic transformers Instead, practical use of piezoelectric transformers using piezoelectric materials is progressing. The power transfer of the piezoelectric transformer is bidirectional,
It is also possible to input a high voltage and step down to obtain a low voltage. DC / DC converters using piezoelectric transformers and AC
Research on adapters has been done.

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, a piezoelectric vibrator 30 includes a piezoelectric ceramic rectangular plate 31 and a piezoelectric ceramic rectangular plate 31.
The electrodes 32 and 33 facing each other in the thickness direction are formed in approximately half of the length direction. The other half of the piezoelectric ceramic rectangular plate 31 opposite to the portion where the electrodes 32 and 33 are formed is provided with an electrode 34 on its longitudinal end face.
Are formed. As shown by an arrow 35, the portions of the electrodes 32 and 33 of the piezoelectric ceramic rectangular plate 31 are polarized in the thickness direction of the piezoelectric ceramic rectangular plate 31,
Alternatively, a portion between the electrode 33 and the electrode 34 is polarized in the longitudinal direction of the piezoelectric ceramic rectangular plate 31 as indicated by an arrow 36.

In this conventional piezoelectric transformer, the electrodes 3
When a voltage near the resonance frequency of the piezoelectric ceramic rectangular plate 31 is applied between the piezoelectric ceramic rectangular plate 31 and the piezoelectric ceramic rectangular plate 31, the piezoelectric ceramic rectangular plate 31 is excited by the lateral piezoelectric effect. A voltage is generated between the electrode 34 and the electrode 34 formed by the piezoelectric longitudinal effect. Here, the input voltage applied to the electrodes 32 and 33 and the output voltage generated at the electrode 34 will be described. The distance between the opposing electrodes of the electrodes 32 and 33 is sufficiently smaller than the distance between the electrodes 33 and 34.
Since the area of the electrodes 32 and 33 is sufficiently larger than the area of the electrode 34, the capacitance on the input side is a value sufficiently larger than the capacitance on the output side. Therefore, when a vibrator is excited by applying a low voltage to the input side, the input side electrode 3
A large voltage is generated which is proportional to the ratio of the interval between the electrodes 2 and 33 and the interval between the output electrodes 33 and 34 and inversely proportional to the ratio of the respective capacitances on the input and output sides.

On the other hand, due to the bidirectional nature of the piezoelectric transformer, when a high voltage is applied to the electrode 34 to excite the vibrator,
In 2, 33, a low voltage is obtained.

[0006]

As described above, various types of piezoelectric transformers utilizing resonance in the longitudinal direction of a piezoelectric ceramic rectangular plate based on a Rosen type piezoelectric transformer have been proposed and put into practical use. However, each structure is a structure in which the length direction of the piezoelectric ceramic rectangular plate is divided into an input unit and an output unit according to the mode of vibration. Therefore,
When a length vibration is excited on the piezoelectric ceramic rectangular plate, the ratio of the total length of the piezoelectric ceramic rectangular plate to the length of the input portion is 2/3 for the Rosen type and 1/2 for the 1.5 wavelength mode.
Since the length of the excitation portion is smaller than the length of actual vibration, there is a problem that the apparent electromechanical coupling coefficient becomes smaller and the excitation efficiency is reduced.

In order to efficiently convert mechanical vibration energy into electrical energy at the output section, it is important to match the impedance between the load resistance and the output section.

Here, since the resistance of the liquid crystal backlight is, for example, about 100 kΩ, the braking capacitance value of the output part of the piezoelectric transformer for impedance matching is about several tens pF, and the longitudinal direction of the piezoelectric ceramic rectangular plate is A configuration is possible by forming electrodes on both end surfaces.

However, in the case of DC / DC converters and AC adapters, the load resistance is several tens of ohms, so the braking capacity of the output part of the piezoelectric transformer for impedance matching is several tens nF. A structure using the piezoelectric longitudinal effect is used, and therefore, it is necessary to polarize the output section in the length direction.

In order to realize such a large braking capacity, it is necessary that the output section also has a laminated structure of internal electrodes.

Therefore, a technical problem of the present invention is that even when the load resistance is 1 kΩ or less, the output-side braking capacity of the piezoelectric transformer can be easily changed, and the piezoelectric transformer having a structure that is well matched with the load resistance. To provide a transformer.

[0012]

According to the present invention, there is provided a piezoelectric transformer utilizing a longitudinal vibration mode of a ceramic rectangular plate in which a plurality of ceramic layers and electrode layers are alternately stacked in a thickness direction. The ceramic rectangular plate is provided with a thickness of the ceramic rectangular plate as the electrode layer in approximately half of the thickness direction to excite the ceramic rectangular plate in the length direction by utilizing the piezoelectric transverse effect of the ceramic rectangular plate. A surface electrode and a plurality of internal electrodes formed so as to overlap with the ceramic layer so as to intersect in a vertical direction, and first and second external electrodes electrically connected to the surface electrode and the internal electrode. The ceramic rectangular plate has a remaining portion in the thickness direction, and the length of the ceramic rectangular plate is set so as to extract electric power from the ceramic rectangular plate vibrating in the length direction by using a piezoelectric longitudinal effect. And a plurality of strip-shaped electrodes that extend in the width direction of the ceramic rectangular plate and are stacked via the ceramic layer so as to be exposed on both sides in the length direction of the ceramic rectangular plate. And a plurality of external electrode groups connected in the thickness direction of the ceramic rectangular plate on one side or the other side in the length direction so as to become the counter electrode in the height direction. Can be

Further, according to the present invention, in a piezoelectric transformer utilizing a longitudinal vibration mode of a ceramic rectangular plate in which a plurality of ceramic layers and electrode layers are alternately stacked, the ceramic rectangular plate has a thickness direction. In almost half of
In order to excite the rectangular plate in the length direction by utilizing a piezoelectric transverse effect, a plurality of surface electrodes and a plurality of surface electrodes are formed as the electrode layers so as to overlap with the ceramic layer so as to intersect with the thickness direction of the ceramic rectangular plate. And the first and second external electrodes electrically connected to the surface electrode and the internal electrode, and the ceramic rectangular plate is vibrated in the length direction in the remaining portion in the thickness direction. In order to extract electric power from the rectangular plate using the piezoelectric longitudinal effect, the ceramic rectangular plate extends in a direction intersecting the longitudinal direction of the rectangular plate, and is arranged side by side in the longitudinal direction and alternately in the longitudinal direction. A plurality of interdigital electrodes connected via connection electrodes on both sides of the ceramic rectangular plate and stacked via the ceramic layer, and third connection electrodes respectively connecting the connection electrodes exposed on both side surfaces of the rectangular plate; And the fourth outside A piezoelectric transformer is obtained which is characterized by having an electrode.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a perspective view showing a schematic structure of a piezoelectric vibrator used in the piezoelectric transformer according to the embodiment. As shown in FIG.
A piezoelectric vibrator 10 used for a piezoelectric transformer integrally includes an input unit 1 and an output unit 2 formed in an upper half of a ceramic rectangular plate. The input section 1 includes an internal electrode 12a and a surface electrode 12 which are laminated so as to be alternately exposed on both sides in the longitudinal direction via a ceramic layer 11 made of piezoelectric ceramic.
b and first and second external electrodes 13a, 13b, which are long in the thickness direction and connect the exposed ends of the internal electrode 12a and the surface electrode 12b exposed on both sides in the length direction of the stacked body, respectively. It is comprised including.

The output section 2 is provided on a ceramic layer 15 made of piezoelectric ceramic, and extends on one surface of the ceramic layer 15 in the width direction of the ceramic layer and at predetermined intervals in the length direction. Strip electrodes 14a, 14
b are alternately stacked, and an external electrode group that connects one side surface of the strip-shaped electrode 14a and the other side surface of the strip-shaped electrode 14b that are respectively exposed on both sides at the same position in the length direction in the thickness direction. 16a and 16b are provided.

The first and second external electrodes of the piezoelectric vibrator 10 are used as input terminals, and the external electrode group 16a and the external electrode group 16
If b is an output terminal, a piezoelectric transformer having an input terminal and an output terminal is constructed.

In the piezoelectric transformer according to the first embodiment of the present invention having such a configuration, the length and width of the input portion 1 are substantially equal to those of the ceramic rectangular plate in order to excite the longitudinal vibration of the ceramic rectangular plate. It is possible to excite mechanical vibration with high efficiency compared to the conventional example in which the input portion obtained by dividing the length direction is excited by using the piezoelectric transverse effect.

The efficiency of the piezoelectric transformer depends on the impedance matching between the output section 2 and the load. In the piezoelectric transformer according to the first embodiment of the present invention, the output section 2 uses the piezoelectric longitudinal effect and has a length. In this structure, a plurality of strip electrodes are arranged in the direction, and the output unit 2 is divided in the length direction.

Therefore, it is possible to adjust the value of the output side braking capacity for obtaining impedance matching.

Further, in the piezoelectric vibrator 10, if a low dielectric constant paraelectric ceramic portion is provided between the input portion 1 and the output portion 2 to ensure a dielectric strength, the polarization axis may be disturbed or the input during polarization may be disturbed. This prevents a short circuit between the outputs and improves the performance of the piezoelectric transformer.

Next, a specific method for manufacturing the piezoelectric transformer according to the first embodiment of the present invention will be described with reference to FIG. 1 again.

As shown in FIG. 1, a PbTiO ₃ —PbZrO ₃ based material was used
The piezoelectric transformer 10 having a thickness of 5 mm, a width of 5 mm, and a thickness of 1.2 mm was prototyped. The thickness of each of the piezoelectric ceramic layers 11 and 15 of the ceramic rectangular plates as the input / output units 1 and 2 is 0.6 m.
m.

The input section 1 is composed of six layers of the internal electrode 12a and the surface electrode 12b on the surface at an interval of 0.1 mm so as to form a plane perpendicular to the thickness direction of the ceramic rectangular plate. First and second external electrodes 13a and 13b, which are connected so that the electrode 12b serves as a counter electrode, are formed on the side surfaces of the rectangular plate at a position 5.5 mm from one end of the rectangular plate.

The output section 2 includes a ceramic layer 15 in which 60 strip electrodes 14a and 14b each having a width of 0.1 mm and penetrating in the width direction perpendicular to the length direction are arranged in parallel at predetermined intervals of 0.25 mm. It was formed by laminating six layers at intervals of 0.1 mm in the thickness direction of the rectangular plate. These strip-shaped electrodes were arranged in the thickness direction as one row so as to be the counter electrode one by one in the length direction, and external electrodes 16a and 16b were formed alternately on different side faces in every other row and connected.

The polarization is performed at a temperature of 150 ° C., a voltage of 100 V applied to the input unit 1 for 15 minutes, and a voltage of 200 V applied to the output unit 2.
V-15 minutes each. A piezoelectric vibrator 10 of a piezoelectric transformer having the appearance as shown in FIG. 1 was obtained.

Using a one-wavelength resonance mode for the piezoelectric vibrator 10, the piezoelectric transformer characteristics were measured when the input voltage was 100 Vpp and the load resistance was 50Ω. Sample 1
The results are shown in Table 1 below. Also, for comparison, the measurement results of the conventional Rosen-structured piezoelectric vibrator (comparative sample) shown in FIG.

(Second Embodiment) FIG. 2A is a perspective view showing a schematic configuration of a piezoelectric vibrator used in a piezoelectric transformer according to a second embodiment of the present invention. Also, FIG.
(B) is a horizontal sectional view of the output unit 4 of the piezoelectric vibrator.
As shown in FIG. 2A, the piezoelectric vibrator 20 integrally includes an input unit 3 and an output unit 4 formed in the upper half of a ceramic rectangular plate.

The input unit 3 includes an internal electrode 22a and a surface electrode 22b which are alternately exposed on both sides in the longitudinal direction via a ceramic layer 21 made of piezoelectric ceramic.
First and second long sides in the thickness direction that connect the exposed ends of the internal electrode 22a and the surface electrode 22b exposed on both sides in the length direction of the stacked body are formed so as to face the side faces. External electrodes 23a and 23b.

The output unit 2 includes a ceramic layer 21 made of piezoelectric ceramic, interdigital electrodes 26a and 26b,
The ceramic layers 21 and the interdigital electrodes 26a, 26b are alternately laminated, and the exposed 26a, 26b on both sides are
Third and fourth external electrodes 27 connected in the thickness direction, respectively
a, 27b.

As best shown in FIG. 2B, the interdigital electrodes 26a and 26b are formed on one surface of the ceramic layer 21 so as to extend in the width direction of the ceramic layer, and to have predetermined shapes in the length direction. Strip electrodes 24 arranged side by side at intervals of
a, 24b and connecting electrodes 25a, 25b alternately connecting one ends of the strip electrodes 24a, 24b, each of the connecting electrodes 25a, 25b having one side on either side of the rectangular plate. It is exposed to.

If the first and second external electrodes 23a and 23b of the piezoelectric vibrator 20 having such a configuration are used as input terminals and the third and fourth external electrodes 27a and 27b are used as output terminals, the piezoelectric transformer becomes Be composed.

In the piezoelectric transformer according to the second embodiment of the present invention, as in the first embodiment, the length and width of the input section 3 are required to excite the longitudinal vibration of the ceramic rectangular plate. Is approximately equal to the length and width of the rectangular plate, and it is possible to excite mechanical vibration with higher efficiency than to excite the input section divided in the length direction by the conventional technique using the piezoelectric lateral effect.

It is important for the efficiency of the piezoelectric transformer that the impedance matching between the output unit 4 and the load is important. In the piezoelectric transformer according to the second embodiment of the present invention, the output unit 3 is used.
Using the piezoelectric longitudinal effect for the strip electrodes (electrode fingers) 2 in the length direction
A structure in which a plurality of interdigital electrodes 26a and 26b formed so that 4a and 24b are arranged alternately is arranged, and the output unit 4 is divided in the length direction. Therefore, it is possible to adjust the value of the output side braking capacity for obtaining impedance matching.

Further, if the piezoelectric vibrator 20 is provided with a paraelectric ceramic part having a low dielectric constant between the input part 3 and the output part 4 so as to ensure a dielectric strength, the polarization axis may be disturbed and the input / output during polarization may be disturbed. It is also possible to prevent short-circuiting and improve the performance of the piezoelectric transformer.

Next, a specific method of manufacturing the piezoelectric transformer according to the second embodiment of the present invention will be described with reference to FIG. 2 again.

As shown in FIGS. 2A and 2B, a piezoelectric transformer 20 having a length of 22 mm, a width of 5 mm, and a thickness of 1.2 mm was manufactured on a trial basis using a PbTiO ₃ -PbZrO ₃ material as piezoelectric ceramics. The thickness of the piezoelectric ceramic layer 21 of the rectangular plate as the input / output units 3 and 4 is 0.6 m each.
m.

The input unit 3 has six internal electrodes 22a perpendicular to the thickness direction of the rectangular plate (electrodes exposed on the surface among these electrodes are called surface electrodes 22b), and six layers are laminated at intervals of 0.1 mm. First and second external electrodes 23a, 2a connected such that the internal electrode 22a and the surface electrode 22b become counter electrodes.
3b was formed on the side surface of the rectangular plate centered on a position 5.5 mm from one end of the rectangular plate.

The output unit 4 is a band-shaped electrode 24a, 2 having a width of 0.1 mm and a length of 4 mm, which extends perpendicularly to the length direction.
4b, the interdigital electrodes 26a, 26b
6 so that 4a and 24b are each spaced by 0.25 mm.
Zero ceramic layers 21 are arranged in a rectangular plate in the thickness direction.
Six layers were laminated at 1 mm intervals. Cross finger electrodes 26a, 26b
Is the third on the side so that it becomes a counter electrode one by one in the length direction.
And the fourth external electrodes 27a and 27b were formed and connected. The polarization of this laminate is performed at a temperature of 1500 ° C., the input section 3 is applied with an applied voltage of 100 V for 15 minutes, and the output section 4 is applied.
, The applied voltage was 200 V for 15 minutes. FIG. 2A shows a prototyped piezoelectric s vibrator 20.
1 shows the appearance. Using this piezoelectric vibrator 20, 1
Using the wavelength resonance mode, the piezoelectric transformer characteristics were measured when the input voltage was 100 Vpp and the load resistance was 50Ω. The measurement results are shown in Table 1 below as Sample 2. Table 1 also shows the same size of the Rosen structure according to the prior art shown in FIG.

[0040]

[Table 1]

As shown in Table 1, the samples 1 and 2 of the piezoelectric transformer according to the first and second embodiments of the present invention have a boost ratio of 4 to 5 times and an input voltage of about 1.5 to 3 V. Input voltage can be boosted to about 6 to 15 V and impedance matching is good.
% Of high efficiency has been achieved.

On the other hand, it is apparent that in the conventional structure, impedance matching cannot be obtained, and characteristics as a DC / DC converter transformer cannot be obtained.

[0043]

As described above, according to the present invention, it is possible to provide a piezoelectric transformer having a structure with a voltage step-up ratio several times higher and an efficiency as high as 90% or more.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a piezoelectric vibrator used for a piezoelectric transformer according to a first embodiment of the present invention.

FIG. 2A is a perspective view illustrating a schematic configuration of a piezoelectric vibrator used for a piezoelectric transformer according to a second embodiment of the present invention. (B) is a horizontal sectional view showing the output unit of (a).

FIG. 3 is a perspective view showing a schematic configuration of a piezoelectric vibrator of a conventional piezoelectric transformer.

[Explanation of symbols]

 1,3 input unit 2,4 output unit 10,20,30 piezoelectric vibrator 11,15,21 ceramic layer 12a, 22a electrode layer (internal electrode) 12b, 22b electrode layer (surface electrode) 13a, 23a first external Electrodes 13b, 23b Second external electrodes 14a, 14b, 24a, 24b Strip electrodes 16a, 16b External electrode groups 25a, 25b Connection electrodes 26a, 26b Interdigital electrodes 27a Third external electrodes 27b Fourth external electrodes 32, 33 , 34 Electrode 35, 36 Arrow indicating polarization direction

Claims (2)

[Claims] 1. A piezoelectric transformer utilizing a longitudinal vibration mode of a ceramic rectangular plate in which a plurality of ceramic layers and electrode layers are alternately stacked in the thickness direction, wherein the ceramic rectangular plate is substantially in the thickness direction. In one half portion, the ceramic layer is used as the electrode layer so as to intersect the thickness direction of the ceramic rectangular plate in order to excite the ceramic rectangular plate in the longitudinal direction by utilizing the piezoelectric transverse effect of the ceramic rectangular plate. A surface electrode and a plurality of internal electrodes formed so as to overlap with each other, and first and second external electrodes electrically connected to the surface electrode and the internal electrode. In order to extract power from the ceramic rectangular plate vibrating in the longitudinal direction by utilizing the piezoelectric longitudinal effect, A plurality of strip-shaped electrodes extending in the width direction of the shape plate and laminated on the ceramic layer via the ceramic layer so as to be exposed on both sides in the length direction of the ceramic rectangular plate; And a plurality of external electrode groups connected in the thickness direction of the ceramic rectangular plate on one side or the other side in the length direction. 2. A piezoelectric transformer using a longitudinal vibration mode of a ceramic rectangular plate in which a plurality of ceramic layers and electrode layers are alternately stacked, wherein the ceramic rectangular plate is provided in a portion substantially half in the thickness direction. A surface electrode formed so as to overlap the ceramic layer so as to intersect the thickness direction of the ceramic rectangular plate as the electrode layer in order to excite the rectangular plate in the length direction by utilizing a piezoelectric transverse effect; The ceramic rectangular plate has a plurality of internal electrodes, and first and second external electrodes electrically connected to the surface electrode and the internal electrode. In order to take out electric power from the vibrating rectangular plate by utilizing the piezoelectric longitudinal effect, the ceramic rectangular plate extends in a direction intersecting the length direction of the ceramic rectangular plate, and is arranged side by side in the length direction and alternately in the length direction. The ceramic A plurality of interdigital electrodes connected via connection electrodes on both sides of the rectangular plate and stacked via the ceramic layer, and third and fourth connection electrodes respectively connecting the connection electrodes exposed on both side surfaces of the rectangular plate. A piezoelectric transformer having a fourth external electrode.