JP3194234B2 - Piezoelectric ceramic rectangular plate, method of manufacturing the same, piezoelectric transformer using the piezoelectric ceramic, and oscillation circuit using the piezoelectric transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer utilizing mechanical vibration of a piezoelectric vibrator, particularly to a DC high voltage power supply used in an electronic copying machine or an electrostatic air cleaner.
The present invention relates to a piezoelectric transformer whose reliability is improved by extracting an input / output terminal from a node of a vibration and at the same time, a driving circuit is simplified, a manufacturing method thereof, and an oscillation circuit using the piezoelectric transformer.

[0002]

2. Description of the Related Art FIG. 4 is a perspective view schematically showing the structure of a conventional piezoelectric transformer. In FIG. 4, electrodes 2 and 3 are formed on a piezoelectric ceramic rectangular plate 1 at approximately half the length thereof in the thickness direction. Electrodes 2 and 3 are formed on the end face opposite to the portion where these electrodes 2 and 3 are formed. 4 are formed. In this piezoelectric transformer, portions of the electrodes 2 and 3 are polarized in the thickness direction, and portions between the electrode 4 and the electrodes 2 and 3 are polarized in the length direction of the piezoelectric ceramic rectangular plate 1.

FIGS. 5A and 5B are explanatory diagrams of the operation principle of the piezoelectric transformer. FIG. 5A is a sectional view of a piezoelectric ceramic rectangular plate, and FIG. FIG. 5C shows a displacement distribution in the case of vibrating in the resonance mode, and FIG. 5C shows a strain distribution at that time. FIG.
In FIG. 5A, when the electrode 3 is used as a ground terminal and a voltage having a frequency equal to the resonance frequency of the one-wavelength resonance mode of the longitudinal vibration of the piezoelectric ceramic rectangular plate is applied to the electrode 2, the rectangular plate becomes as shown in FIGS. Vibrates as shown in c). At this time, a voltage is generated between the electrode 3 and the end face electrode 4 by a piezoelectric effect. Here, the input voltage applied to the electrode 2 and the output voltage generated at the end face electrode 4 will be described. The distance between the electrode 2 and the electrode 3 is sufficiently smaller than the distance between the electrode 3 and the end face electrode 4. , 3 are sufficiently larger than the area of the end face electrode 4, the capacitance on the input side is a sufficiently large value compared to the capacitance on the output side. Therefore, when a low voltage is applied to the input side to excite the vibrator, a voltage of approximately the same magnitude as that required to generate the same magnitude of vibration when the voltage is applied to the output side is applied to the output terminal. appear.
That is, a voltage several tens times the input voltage can be easily generated at the output terminal.

[0004]

However, in such a conventional piezoelectric transformer, it is necessary to support the vibrator at a node of the vibration in order to support the vibrator without affecting the vibration. On the other hand, as described above, since the output terminal needs to be taken out from the end face having the largest vibration amplitude,
There are drawbacks such as changes in the oscillator characteristics due to the weight of the lead wire, and breakage of the lead wire take-out part due to vibration, which leads to deterioration in characteristics and reliability. Special processes were required, such as using a material having little effect on vibration and forming an electrode having high adhesion to piezoelectric ceramics as an end face electrode.

FIG. 6 shows an example of an oscillation circuit using a conventional piezoelectric transformer. In response to a voltage applied to the vibrator 1 by a driving transformer 5, a magnitude of a current flowing through the vibrator 1 is determined by a feedback transformer 6. Thus, self-oscillation is enabled at the frequency at which the current is maximized in addition to the base of the amplification transistor 7, that is, the resonance frequency of the piezoelectric vibrator.

FIG. 7 shows another example of an oscillation circuit using a conventional piezoelectric transformer. The magnitude of the current flowing through the vibrator 1 for the piezoelectric transformer is detected by a resistor 8, and an amplifying transistor is provided via a phase shift circuit 9. In addition to the 10, and 10 'bases,
Self-excited oscillation is enabled at the frequency at which the current is maximized, that is, at the resonance frequency of the piezoelectric vibrator.

In the conventional oscillator circuit using a piezoelectric transformer shown in FIGS. 6 and 7, a driving transformer is used or a feedback transformer is required, so that the driving circuit included in the oscillator circuit is complicated. Had the disadvantage of becoming

The technical object of the present invention is to eliminate the above-mentioned drawbacks of the conventional piezoelectric transformer, to provide a method for manufacturing a piezoelectric transformer having a simple structure, high reliability and a simple driving circuit, and to use the piezoelectric transformer. It is to provide an oscillation circuit that has been used.

[0009]

According to the present invention, a length,
One end face in the length direction, having thickness and depth
From the first to third portions having substantially the same size as each other.
A first and a second facing each other in the thickness direction.
A ceramic rectangular plate having a main surface;
On the first and second major surfaces of the first portion of the rectangular plate
In addition, each formed in opposition to each other in the thickness direction
First and second electrodes, the second part and the third part
On the first and second main surfaces at the boundary with
Opposing each other in the thickness direction and extending in the depth direction.
Third and fourth strip-shaped electrodes formed so as to extend;
The first and the third central portions in the longitudinal center position
2 on the main surface of each, facing each other in the thickness direction,
A fifth strip-shaped member extending in the depth direction;
And a sixth electrode, wherein the third electrode and the fourth electrode
Are electrically connected to each other, and the fifth electrode
The electrode and the sixth electrode are electrically connected to each other.
Between the first electrode and the second electrode.
Pressure is applied, the thickness
The second electrode and the third electrode are polarized.
And between the third electrode and the fifth electrode
When a high DC voltage is applied, the
It is characterized by the opposite polarization in the vertical direction
Is obtained. In addition,
According to the description, first to third portions having a length, a thickness and a depth and having substantially the same size from one end face in the length direction and facing each other in the thickness direction. A ceramic rectangular plate having first and second main surfaces is prepared, and is opposed to each other in the thickness direction on the first and second main surfaces of the first portion of the ceramic rectangular plate. Forming first and second electrodes on the first and second main surfaces at a boundary between the second portion and the third portion, respectively, in a thickness direction. And forming strip-shaped third and fourth electrodes extending in the depth direction, on the first and second main surfaces at the longitudinal central position of the third portion, respectively, in the thickness direction. Fifth and sixth strip-shaped electrodes facing each other and extending in the depth direction are formed. , The third electrode and a fourth electrode electrically connected to one another, the said fifth electrode 6
Are electrically connected to each other, a high DC voltage is applied between the first electrode and the second electrode, and polarization in the thickness direction is applied between the first electrode and the second electrode. Electrodes and the third
A DC high voltage is applied to and between the third electrode and the fifth electrode of the electrodes, the piezoelectric ceramic rectangular having a step of applying a reverse polarization to each other in the longitudinal direction between them A method of manufacturing a plate is obtained.

A piezoelectric transformer using a piezoelectric ceramic rectangular plate manufactured by this manufacturing method, wherein the piezoelectric ceramic rectangular plate vibrates in a three-half wavelength resonance mode of longitudinal vibration. A piezoelectric transformer in which the input terminal and the output terminal are mounted at the positions of the nodes of vibration is obtained.

An oscillation circuit using the piezoelectric transformer, further comprising an amplifier circuit for driving the piezoelectric transformer and a phase shift circuit for performing a phase shift, wherein an output from the feedback terminal is output to the phase shift circuit. And the output from the phase shift circuit is input to the amplifier circuit, and the output of the amplifier circuit is supplied to the input terminal as an input signal to oscillate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view schematically showing the structure of a piezoelectric vibrator 1 'used in a piezoelectric transformer according to one embodiment of the present invention. An electrode 23 is formed on substantially the entire surface of one side of a length of the piezoelectric ceramic rectangular plate 21 from one end surface of the piezoelectric ceramic rectangular plate 21.
, An electrode 22 and an island-shaped partial electrode 24 are formed. The electrode 22 is a land-like electrode formed by separating island-like partial electrodes. The partial electrode 24 is preferably formed as far as possible from an end face serving as a node of vibration to one sixth of the length of the rectangular plate. Two thirds of the length of the rectangular plate from the same end face
And the strip electrodes 25, 25 'and 26, 26' opposed to each other in the thickness direction are formed at the position of. After the strip electrodes 25, 25 'and 26, 26' are electrically connected to each other, polarization in the thickness direction is applied to the electrode 23, the electrode 22, and the partial electrode 24, and a portion between the electrode 23 and the strip electrode 25 is formed. And the strip electrode 25 and the strip electrode 2
The portions between 6 are polarized in opposite directions to each other in the length direction of the rectangular plate.

Further, the steps of the method of manufacturing the piezoelectric ceramic rectangular plate 21 of the present invention will be listed and described in detail.
First, a first portion having a length, a thickness, and a depth, having first to third portions substantially equal to each other from one end face in the length direction and facing each other in the thickness direction.
And a ceramic rectangular plate having a second main surface is prepared. First and second electrodes 22 and 23 are formed on the first and second main surfaces of the first portion of the ceramic rectangular plate so as to face each other in the thickness direction. On the first and second main surfaces at the boundary between the second portion and the third portion, third and third strip-shaped third and third strips are provided to face each other in the thickness direction and extend in the depth direction, respectively. Four electrodes 25 and 25 ' are formed. The third
The strip-shaped fifth and sixth electrodes 26 and 26 respectively opposing each other in the thickness direction and extending in the depth direction are provided on the first and second main surfaces at the center positions in the length direction of the portion.
And 26 ' . The third electrode 25 and the fourth electrode 25 ' are electrically connected to each other, and the fifth electrode 25'
The 26 sixth electrode 26 'and Ru electrically connected to <br/> each other. A high DC voltage is applied between the first electrode 22 and the second electrode 23 to polarize them in the thickness direction. A DC high voltage is applied between the fifth electrode 26 and between the third electrode 25 of the said second electrode 23 the third electrode 25, the length between them Polarization is performed in opposite directions.

Through such steps, a piezoelectric ceramic rectangular plate is obtained.

The piezoelectric transformer using the piezoelectric ceramic rectangular plate manufactured by this manufacturing method is a vibration node in a case where the piezoelectric ceramic rectangular plate is vibrating in a three-wavelength resonance mode of longitudinal vibration. Input terminal 22a in position
And an output terminal 26a. The second electrode is an earth electrode 23, and an earth terminal 23a is attached to the center of the earth electrode 23 in the longitudinal direction. The input terminal 22 is attached to the center of the first electrode in the longitudinal direction. And the output terminal 26a is attached to the fifth electrode. The first electrode has a first partial electrode occupying a relatively small area at a center position in a longitudinal direction thereof, and the remaining portion of the first electrode is insulated from the first partial electrode. , The input terminal is attached to the second partial electrode, the first partial electrode is a feedback electrode 24, and a feedback terminal 24a is attached to the feedback electrode 24. Have been.

FIG. 2 is an explanatory view of the operation principle of the piezoelectric transformer of the present invention. FIG.
1 is a cross-sectional view, and FIG.
Fig. 6 (c) shows a displacement distribution when vibrating in the three-half wavelength resonance mode of the longitudinal vibration, and Fig. 6 (c) shows a strain distribution at that time. In FIG. 2, when the electrode 23 is used as a ground terminal, and a voltage having a frequency equal to the resonance frequency of the three-half wavelength resonance mode of the longitudinal vibration of the piezoelectric ceramic rectangular plate is applied to the electrode 22, the rectangular plate becomes as shown in FIG. And vibrate as shown in FIG. At this time, when the electrode 23 is used as a ground terminal according to the same principle as that described with reference to FIG.
6 produces a high output voltage.

In FIG. 2, the strip electrodes 25, 25 'are floating electrodes when used as a piezoelectric transformer, and may be removed.

In the piezoelectric transformer of the present invention, FIG.
As shown in (b), since the input / output terminals including the partial electrode acting as the feedback electrode are taken out from the position of the node of the vibration, not only the influence on the vibration characteristics of the piezoelectric transformer is small, but also the terminal connection portion is provided. Does not vibrate, so that the terminal does not come off and the reliability is greatly improved.

FIG. 3 is a circuit diagram of one embodiment of an oscillation circuit using the piezoelectric transformer of the present invention. In FIG. 3, the output voltage of the amplifier circuit 27 is connected to the input electrode 22 of the vibrator 1 ', and the electrode 23 is connected to the ground. On the other hand, the partial electrode 24 is connected to the input terminal of the amplifier circuit 27. The output voltage of the partial electrode 24 is input to a phase shift circuit 30 composed of a capacitor and a resistor in order to perform a phase shift, and the output voltage at the resonance frequency of the vibrator 21 is adjusted by adjusting the impedance of the detection-side terminal 30a. The phase can be substantially 180 ° with respect to the input voltage. Therefore, by using the inverting amplifier circuit 27a as the amplifier circuit 27, a self-excited oscillation circuit that oscillates at the resonance frequency can be configured.

[0020]

As described above, according to the present invention, the input / output terminal and the feedback terminal are formed after forming the partial electrode separated from the continental electrode at the position of the node of the vibration. It is possible to obtain a highly reliable piezoelectric transformer with less wire breakage. Further, by using a partial electrode formed alongside the input electrode as a feedback electrode and using this output voltage as the input of the amplifier circuit, a self-excited oscillation circuit can be easily configured, so that the effect is very practical. Big.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a structure of a piezoelectric vibrator used for a piezoelectric transformer of the present invention.

FIG. 2 is an explanatory diagram of the operation principle of the piezoelectric transformer of the present invention.

FIG. 3 is a diagram of an oscillation circuit including a drive circuit used for a piezoelectric transformer according to one embodiment of the present invention.

FIG. 4 is a perspective view schematically showing the structure of a conventional piezoelectric transformer.

FIG. 5 is a diagram illustrating the operation of a conventional piezoelectric transformer.

FIG. 6 is an example of an oscillation circuit using a conventional piezoelectric transformer.

FIG. 7 is another example of an oscillation circuit using a conventional piezoelectric transformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 1 'Transducer for piezoelectric transformer 2, 22 Input electrode 3, 23 Earth electrode 4 End face electrode (output electrode) 5 Driving transformer 6 Feedback transformer 7, 10 Amplification transistor 8 Current detection resistor 9 Phase shift circuit 21 Piezoelectric ceramic rectangular plate 22a Input terminal 23a Ground terminal 24 Partial electrode (return electrode) 24a Return terminal 25, 25 ', 26, 26' Strip electrode (electrode for polarization,
Output electrode) 26a Output terminal 30 Phase shift circuit 30a Detection side terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03H 3/00-3/04 H01L 41/00-41/26

Claims (7)

(57) [Claims] 1. The method of claim 1 , wherein the length, the thickness, and the depth are the same.
From one end face in the vertical direction
It has first to third portions, and is opposed to each other in the thickness direction.
Ceramic rectangular plate having first and second main surfaces
And the first and second portions of the first portion of the ceramic rectangular plate.
And on the second principal surface, respectively, in the thickness direction
A first electrode and a second electrode formed at a boundary between the second portion and the third portion.
On the first and second principal surfaces, respectively, in the thickness direction
Opposing and formed to extend in the depth direction
Strip-shaped third and fourth electrodes, and the first and second electrodes at the longitudinal center position of the third portion.
2 on the main surface of each, facing each other in the thickness direction,
A fifth strip-shaped member extending in the depth direction;
And a sixth electrode, wherein the third electrode and the fourth electrode are electrically connected to each other.
Are continued, mutually electrically contact the said sixth electrode and the fifth electrode
It is continued, high DC voltage between the first electrode and the second electrode
The thickness polarization between them by being applied
Is provided between the second electrode and the third electrode and the third electrode.
DC high voltage is applied between the first electrode and the fifth electrode.
By turning them opposite each other longitudinally
Piezoelectric ceramic characterized by being polarized
Rectangular plate. 2. A first, second, and third portion having a length, a thickness, and a depth and having substantially the same size from one end face in the length direction, and facing each other in the thickness direction. A ceramic rectangular plate having first and second main surfaces is prepared. On the first and second main surfaces of the first portion of the ceramic rectangular plate, the ceramic rectangular plates oppose each other in the thickness direction. Forming first and second electrodes, respectively, on the first and second main surfaces at the boundary between the second part and the third part, facing each other in the thickness direction; And forming strip-shaped third and fourth electrodes extending in the depth direction, and forming the strip-shaped third and fourth electrodes on the first and second main surfaces at the longitudinal center position of the third portion, respectively, in the thickness direction. Belt-shaped fifth and sixth electrodes facing each other and extending in the depth direction are formed. The third electrode and the fourth electrode are electrically connected to each other, the fifth electrode and the sixth electrode are electrically connected to each other, and the first electrode and the fourth electrode are connected to each other. by applying a high DC voltage between the second electrode is subjected to polarization in the thickness direction therebetween, between the third electrode and the second electrode and the third
Applying a DC high voltage between the first electrode and the fifth electrode to apply polarizations in opposite directions in the longitudinal direction therebetween. 3. A piezoelectric transformer using pressure conductive ceramic rectangular plate according to claim 1, wherein the piezoelectric ceramic rectangular plate is half the length direction vibration 3
A piezoelectric transformer in which an input terminal and an output terminal are attached at positions of nodes of vibration when vibrating in the wavelength resonance mode. 4. The method according to claim 1, wherein the second electrode is a ground electrode,
Ground terminals are mounted in the longitudinal direction center position of the ground electrode, wherein the input terminals are mounted in the axial center location of the first electrode, wherein said output terminal is attached to said fifth electrode Item 3. The piezoelectric transformer according to Item 3 . 5. The first electrode includes a first partial electrode occupying a relatively small area at a central position in a longitudinal direction thereof, and the first partial electrode being insulated from the first partial electrode. A second partial electrode forming the remainder of the electrode, wherein the input terminal is attached to the second partial electrode, the first partial electrode is a return electrode, and the return electrode has a return terminal. 5. The piezoelectric transformer according to claim 4 , wherein said piezoelectric transformer is mounted. 6. An oscillation circuit using the piezoelectric transformer according to claim 5 , further comprising an amplifier circuit for driving the piezoelectric transformer and a phase shift circuit for performing a phase shift, and an output from the feedback terminal. Is input to the phase shift circuit, an output from the phase shift circuit is input to the amplifier circuit, and an output of the amplifier circuit is supplied to the input terminal as an input signal to oscillate. . 7. The oscillation circuit according to claim 6 , wherein the input signal supplied to the input terminal of the piezoelectric transformer has a frequency equal to a mechanical resonance frequency in the resonance mode.