JPH05110368A - Manufacture of piezoelectric ceramics rectangular plate, piezoelectric transformer using the manufactured piezoelectric ceramics rectangular plate and oscillation circuit using the piezoelectric transformer - Google Patents

Abstract

PURPOSE:To obtain the piezoelectric transformer with high reliability and simple structure and the oscillation circuit with simple circuit configuration employing the piezoelectric transformer. CONSTITUTION:The piezoelectric transformer consists of a piezoelectric ceramic rectangular plate whose length in the lengthwise direction is 2/3 wavelength and electrodes formed thereon. The input electrode 22 covers the part of almost 1/3 from one end and has a partial electrode 24. A ground electrode 23 is placed to a face opposite to the input electrode 22. Output electrodes 26, 26' are formed to a position by 1/6 wavelength from the other end of the rectangular plate and polarization electrodes 25, 25' are formed to a position by 1/6 wavelength from the output electrodes. The electrodes 26, 26' and 25, 25' are connected respectively. A DC high voltage is applied to the electrodes 22, 23 to polarize the plate in the broadwise direction. Furthermore, a high DC voltage is applied between the electrodes 25 and 26 to polarize reversely the plate in the lengthwise direction. The oscillation circuit employing the piezoelectric transformer amplifies partial power from the electrode 24 via a phase shift circuit and feeds back it to the input electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric high-voltage power source used in electronic copying machines, electrostatic air cleaners, etc., and more particularly to a piezoelectric transformer utilizing mechanical vibration of a piezoelectric vibrator,
The present invention relates to a piezoelectric transformer in which reliability is improved by taking out an input / output terminal from a node of vibration and a drive 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, the piezoelectric ceramic rectangular plate 1 is provided with electrodes 2 and 3 facing each other in the thickness direction in approximately half the lengthwise direction, and electrodes 2 and 3 facing each other in the thickness direction are formed on the end face opposite to the part where the electrodes 2 and 3 are formed. 4 are formed. In this piezoelectric transformer, the electrodes 2 and 3 are polarized in the thickness direction, and the portion between the electrode 4 and the electrodes 2 and 3 is polarized in the length direction of the piezoelectric ceramic rectangular plate 1.

FIG. 5 is an explanatory view of the operation principle of this piezoelectric transformer. FIG. 5 (a) is a sectional view of a piezoelectric ceramic rectangular plate, and FIG. 5 (b) is one wavelength of longitudinal vibration of the piezoelectric ceramic rectangular plate. It is a displacement distribution when vibrating in the resonance mode, and FIG. 5C shows a strain distribution at that time. Figure 5
In FIG. 5B, when a voltage having a frequency equal to the resonance frequency of the one-wavelength resonance mode of longitudinal vibration of the piezoelectric ceramic rectangular plate is applied to the electrode 2 in FIG. It vibrates as shown in c). At this time, a voltage is generated between the electrode 3 and the end surface electrode 4 by the piezoelectric effect. Here, the input voltage applied to the electrode 2 and the output voltage generated at the end surface electrode 4 will be described. The facing distance between the electrodes 2 and 3 is sufficiently smaller than the distance between the electrode 3 and the end surface electrode 4. , 3 is sufficiently larger than the area of the end face electrode 4, the electrostatic capacitance on the input side is sufficiently larger than the electrostatic capacitance on the output side. Therefore, when a low voltage is applied to the input side to excite the vibrator, a voltage approximately equal to the voltage required to generate the same magnitude of vibration when a voltage is applied to the output side is applied to the output terminal. Occur.
That is, the output terminal can easily generate a voltage which is several tens of times the input voltage.

[0004]

However, in such a conventional piezoelectric transformer, in order to support the vibrator so as not to affect the vibration, it is necessary to support it at the vibration node. On the other hand, as mentioned above, the output terminal must be taken out from the end face with the largest vibration amplitude.
There are drawbacks such as changes in oscillator characteristics due to the weight of the lead wire and disconnection of the lead wire lead-out section due to vibration, which leads to deterioration of characteristics and reliability. A special process such as using a material having a small influence on vibration or forming an electrode having high adhesion to the piezoelectric ceramics as an end face electrode has been required.

FIG. 6 is an example of an oscillation circuit using a conventional piezoelectric transformer. The magnitude of the current flowing through the vibrator 1 with respect to the voltage applied to the vibrator 1 by the driving transformer 5 is determined by the feedback transformer 6. In addition to the base of the amplifying transistor 7, the self-excited oscillation is possible at the frequency at which the current is maximized, that is, the resonance frequency of the piezoelectric vibrator.

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

Since the conventional oscillator circuit using the piezoelectric transformer shown in FIGS. 6 and 7 requires a drive transformer and a feedback transformer, the drive circuit included in this oscillator circuit is complicated. There was a drawback that

The technical problem of the present invention is to eliminate the above-mentioned drawbacks of the conventional piezoelectric transformer and to use a method and a method for manufacturing a piezoelectric transformer having a simple structure and high reliability and a simple drive circuit. It is to provide the oscillation circuit that was used.

[0009]

According to the invention, the length,
First and second main parts having a thickness and a depth, having first to third portions 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 a surface is prepared, and first and second electrodes facing each other in the thickness direction are provided on the first and second main surfaces of the first portion of the ceramic rectangular plate, respectively. And on the first and second main surfaces at the boundary between the second portion and the third portion, the strip-shaped strips facing each other in the thickness direction and extending in the depth direction. Forming third and fourth electrodes, the third electrode
Band-shaped fifth and sixth electrodes facing each other in the thickness direction and extending in the depth direction are formed on the first and second main surfaces at the center position in the length direction of the portion of, respectively, 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 second electrode are electrically connected to each other. A direct current high voltage is applied between the second electrode and the third electrode, and polarization in the thickness direction is performed between them, and between the second electrode and the third electrode and between the third electrode and the fifth electrode. A method of manufacturing a piezoelectric ceramic rectangular plate having a step of applying a direct current high voltage between them and polarizing them in opposite directions in the longitudinal direction 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-wavelength resonance mode of longitudinal vibration. A piezoelectric transformer is obtained in which an input terminal and an output terminal are attached at the positions of vibration nodes.

Further, an oscillation circuit using this piezoelectric transformer is provided with 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 output by 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 as an input signal to the input terminal to oscillate.

[0012]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing a schematic structure of a piezoelectric vibrator 1'used in a piezoelectric transformer according to an embodiment of the present invention. The electrode 23 is formed on substantially the entire one surface of one area of the piezoelectric ceramic rectangular plate from one end surface of the piezoelectric ceramic rectangular plate 21 to one third.
And an electrode 22 and an island-shaped partial electrode 24 are formed facing each other. The electrode 22 is a land-shaped electrode formed by separating island-shaped partial electrodes. It is preferable that the partial electrode 24 is formed at a position ⅙ of the length of the rectangular plate from the end face which becomes a node of vibration as much as possible. Two-thirds of the length of the rectangular plate from the same end face
And strip-shaped electrodes 25, 25 'and 26, 26' facing each other in the thickness direction are formed at positions 5 and 6/6, respectively. After electrically connecting the strip electrodes 25, 25 ′ and 26, 26 ′, respectively, the electrode 23, the electrode 22 and the partial electrode 24 are polarized in the thickness direction to form a portion between the electrode 23 and the strip electrode 25. 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 for manufacturing a piezoelectric ceramic rectangular plate of the present invention will be listed and described in detail. First, a first to 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 a first portion facing each other in the thickness direction. A ceramic rectangular plate having a second main surface is prepared. First and second electrodes 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. The first and second portions at the boundary between the second portion and the third portion
Band-shaped third and fourth electrodes facing each other in the thickness direction and extending in the depth direction are formed on the main surface of the. Strip-shaped fifth and sixth electrodes facing each other in the thickness direction and extending in the depth direction are respectively provided on the first and second main surfaces at the center position in the length direction of the third portion. Form. The third electrode and the fourth electrode are electrically connected to each other, and the fifth electrode and the sixth electrode are electrically connected to each other. A direct current high voltage is applied between the first electrode and the second electrode to polarize them in the thickness direction. A high direct current voltage is applied between the second electrode and the third electrode and between the third electrode and the fifth electrode to polarize them in opposite directions in the longitudinal direction. Apply.

A piezoelectric ceramic rectangular plate is obtained through these steps.

The piezoelectric transformer using the piezoelectric ceramic rectangular plate manufactured by this manufacturing method has a node of vibration when the piezoelectric ceramic rectangular plate vibrates in a three-wavelength resonance mode of longitudinal vibration. Input terminal 22a at position
And the output terminal 26a is attached. The second electrode is a ground electrode 23, a ground terminal 23a is attached to the center position of the ground electrode 23 in the longitudinal direction, and the input terminal 22 is attached to the center position of the first electrode in the longitudinal direction. 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 the longitudinal direction, and the remaining part of the first electrode in a state of being insulated from the first partial electrode. And a second partial electrode forming a feedback electrode 24, the input terminal is attached to the second partial electrode, the first partial electrode is a return electrode 24, and the return terminal 24a is attached to the return electrode 24. Has been.

FIG. 2 is an explanatory view of the operating principle of the piezoelectric transformer of the present invention, and FIG. 2 (a) is a piezoelectric ceramic rectangular plate 2
2 is a sectional view of the piezoelectric ceramic rectangular plate 21.
Is the displacement distribution in the case of vibrating in the ½ wavelength resonance mode of the longitudinal vibration, and FIG. 6C shows the 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 ⅔ wavelength resonance mode of the longitudinal vibration of the piezoelectric ceramic rectangular plate is applied to the electrode 22, the rectangular plate is formed as shown in FIG. And vibrate as shown in (c). At this time, when the electrode 23 is used as a ground terminal according to the same principle as described with reference to FIG.
6 produces a high output voltage.

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

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

FIG. 3 is a circuit diagram of an 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 to perform a phase shift, and by adjusting the impedance of the detection side terminal 30a, at the resonance frequency of the oscillator 21. The phase can be approximately 180 ° with respect to the input voltage. Therefore, by using the inverting amplifier circuit 27a as the amplifier circuit 27, it is possible to configure a self-excited oscillation circuit that oscillates at the resonance frequency.

[0020]

As described above, according to the present invention, since the input / output terminal and the feedback terminal are formed after the partial electrode separated from the continental electrode is formed at the position of the vibration node, the lead due to the vibration is generated. It is possible to obtain a highly reliable piezoelectric transformer with few wire breaks. Furthermore, by using a partial electrode formed side by side with the input electrode as the 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 its effect is very practical. Is very large.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of the structure of a piezoelectric vibrator used in a piezoelectric transformer of the present invention.

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

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

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

FIG. 5 is an operation explanatory view 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]

1,1 'Piezoelectric transformer vibrator 2,22 Input electrode 3,23 Earth electrode 4 End face electrode (output electrode) 5 Driving transformer 6 Feedback transformer 7,10 Amplifying transistor 8 Current detection resistor 9 Phase shift circuit 21 piezoelectric ceramic rectangular plate 22a input terminal 23a earth terminal 24 partial electrode (return electrode) 24a return terminal 25, 25 ', 26, 26' strip electrode (polarizing electrode,
Output electrode) 26a Output terminal 30 Phase shift circuit 30a Detection side terminal

Claims (6)

[Claims] 1. A first to a 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. Prepared ceramic rectangular plate having the first and second main surfaces, and facing each other in the thickness direction on the first and second main surfaces of the first portion of the ceramic rectangular plate, respectively. Forming first and second electrodes on the first and second main surfaces at the boundary between the second portion and the third portion, respectively, facing each other in the thickness direction, And forming strip-shaped third and fourth electrodes extending in the depth direction, on the first and second main surfaces at the center position in the length direction of the third portion, respectively in the thickness direction. Form strip-shaped fifth and sixth electrodes facing each other and extending in the depth direction. 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, the first electrode and the A direct current high voltage is applied between the second electrode and the second electrode to polarize them in the thickness direction, and between the second electrode and the third electrode and between the third electrode and the third electrode. 5. A method for manufacturing a piezoelectric ceramic rectangular plate, comprising a step of applying a direct current high voltage between the electrode and the electrode of No. 5 and performing polarization between them in opposite directions in the longitudinal direction. 2. A piezoelectric transformer using a piezoelectric ceramic rectangular plate manufactured by the manufacturing method according to claim 1, wherein the piezoelectric ceramic rectangular plate is ⅔ of longitudinal vibration.
A piezoelectric transformer in which an input terminal and an output terminal are attached at the vibration nodes when vibrating in the wavelength resonance mode. 3. The second electrode is a ground electrode,
A ground terminal is attached to a center position in the length direction of the ground electrode, the input terminal is attached to a center position in the length direction of the first electrode, and the output terminal is attached to the fifth electrode. Item 2. The piezoelectric transformer according to item 2. 4. The first electrode comprises a first partial electrode occupying a relatively small area at a center position in the longitudinal direction, and the first partial electrode in a state of being insulated from the first partial electrode. A second partial electrode forming the remaining part of the electrode, said input terminal being attached to said second partial electrode, said first partial electrode being a return electrode, said return electrode being connected to said return terminal The piezoelectric transformer according to claim 3, wherein the piezoelectric transformer is attached. 5. An oscillation circuit using the piezoelectric transformer according to claim 4, comprising an amplifier circuit for driving the piezoelectric transformer and a phase shift circuit for performing phase transition, and an output from the feedback terminal. Is input to the phase shift circuit, the output from the phase shift circuit is input to the amplifier circuit, and the output of the amplifier circuit is supplied as an input signal to the input terminal to oscillate. .. 6. The oscillator circuit according to claim 5, wherein the input signal supplied to the input terminal of the piezoelectric transformer has a frequency equal to a mechanical resonance frequency of the resonance mode.