JPH09252149A - Piezoelectric transformer - Google Patents

Abstract

(57) [PROBLEMS] To provide a highly reliable piezoelectric transformer having no breakage of output lead wires, no insulation breakdown. A piezoelectric transformer that vibrates in an nth-order resonance mode in a length direction of a piezoelectric ceramic rectangular plate 11,
On the upper and lower surfaces or side surfaces of the piezoelectric ceramic rectangular plate 11,
An insulating layer 36 made of a material having a permittivity sufficiently lower than that of piezoelectric ceramics such as borosilicate glass is formed, a conductive portion 37 is formed on the insulating layer 36, and vibration of the conductive portion 37 is suppressed. Piezoelectric transformer with output leads attached to the nodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator machine used in a high-voltage DC / DC converter used for charging a toner of a copying machine, a DC / AC inverter used in a liquid crystal backlight inverter, and the like. The present invention relates to a piezoelectric transformer that utilizes vibration, and particularly to a structure of the piezoelectric transformer.

[0002]

2. Description of the Related Art In a DC / DC converter, a DC / AC inverter, etc., when the frequency becomes high, problems such as generation of noise occur. Therefore, the vibration mode of the piezoelectric transformer used for them is a vibration mode having a relatively low frequency. Is 0.5
λ, λ, 1.5λ, 2λ, etc. are common.

FIG. 4 shows that the piezoelectric ceramic rectangular plate vibrates in a one-wavelength resonance mode in the longitudinal direction, and a vibration node exists at a position ¼ from both end faces in the longitudinal direction of the piezoelectric ceramic rectangular plate. It is a perspective view showing an example of the structure of the piezoelectric transformer which does.

In FIG. 4, a piezoelectric ceramic rectangular plate 1
A pair of drive electrodes 42 facing each other in the thickness direction is formed in a region approximately one-half of the length of the piezoelectric ceramic rectangular plate 11 from one end face of the piezoelectric ceramic rectangular plate 11, and the other end face of the piezoelectric ceramic rectangular plate 11 is formed. An output electrode 43 is formed on the.

Further, the piezoelectric ceramic rectangular plate 11 is polarized in the thickness direction by using the drive electrode pair 42 in a region of approximately ½ of the length direction, and the drive electrode is polarized in the remaining ½ region. It is polarized in the longitudinal direction by using the pair 42 and the output electrode 43. The polarization direction P is indicated by an arrow.

FIG. 5 is an explanatory diagram of the operating principle of the piezoelectric transformer. FIG. 5A is a front view of a piezoelectric transformer rectangular plate,
5B is a diagram showing a displacement distribution when the piezoelectric transformer is vibrating in a one-wavelength resonance mode of longitudinal vibration, FIG.
(C) is a diagram showing a strain distribution at that time.

In FIG. 5A, one of the drive electrode pairs 52 is used as a GND terminal, and 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 11 is applied to the drive electrode pair 52. Then, the piezoelectric ceramic rectangular plate 11 vibrates as shown in FIGS. 5B and 5C, and the GN of the output electrode 53 and the driving electrode pair 52 is vibrated.
A high voltage is generated between the D terminals by the piezoelectric effect.

Further, as shown in FIG. 5 (b), when the piezoelectric ceramic rectangular plate 11 is vibrating in the one-wavelength resonance mode of longitudinal vibration, the piezoelectric ceramic rectangular plate 11 is cut from both end faces thereof. 4 of the length of the plate 11
It is possible to support the piezoelectric transformer at any position on a straight line which is horizontal to the end face of the piezoelectric ceramic rectangular plate 11 passing through the nodes 54 and 55 of the vibration of one-half.

FIG. 6 is a perspective view showing an outline of an example of taking out an output lead wire of a conventional piezoelectric transformer. As shown in FIG. 6, the output lead wire 68 is taken out from the output electrode 63 formed on the end surface of the piezoelectric ceramic rectangular plate 11.

[0010]

However, the output electrode 63
Since the end surface of the piezoelectric ceramic rectangular plate 11 on which is formed is an antinode of vibration, it is a portion where vibration is extremely large. Therefore, there is a problem such as disconnection of the output lead wire.

Further, as shown in FIG. 7, the output electrode 73 is generally taken out from the end face of the piezoelectric ceramic rectangular plate 11 to the vibration node 75 through the conductive portion 77. When the conductive portion 77 is formed without forming it, an electric field is concentrated between the drive electrode pair 72 and the conductive portion 77, which causes a problem that the piezoelectric transformer causes dielectric breakdown during driving or polarization.

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional piezoelectric transformer and to provide a highly reliable piezoelectric transformer having no disconnection of lead wires and no dielectric breakdown.

[0013]

According to the present invention, in a piezoelectric transformer vibrating in the nth resonance mode in the length direction of a piezoelectric ceramic rectangular plate, a borosilicate-based material is formed on the upper and lower surfaces or side surfaces of the piezoelectric ceramic rectangular plate. An insulating layer made of a material such as glass having a dielectric constant sufficiently lower than that of the piezoelectric ceramic is formed, a conductive portion is formed on the insulating layer, and an input / output lead wire is provided at a vibration node on the conductive portion. A piezoelectric transformer characterized by being attached can be obtained.

Further, according to the present invention, the output electrode is formed up to the node of vibration on the surface of the piezoelectric ceramic rectangular plate on the insulating layer formed of a material having a dielectric constant ε sufficiently lower than that of the piezoelectric ceramic. By forming a conductive part for drawing out and attaching the output lead wire to the part corresponding to the vibration node on the conductive part, it is possible to take out the output voltage from the vibration node and disconnect the output lead wire. In addition to being able to prevent the electric field distribution at the output part during driving and polarization in the length direction of the piezoelectric ceramic rectangular plate, it is possible to avoid electric field concentration between the drive electrode pair and the conductive part. It is possible to prevent dielectric breakdown of the piezoelectric transformer at the time of polarization.

[0015]

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

FIG. 1 is a perspective view showing an example of the structure of the piezoelectric transformer of the present invention. In FIG. 1, an insulating layer 16 made of a material having a dielectric constant ε sufficiently lower than that of the piezoelectric ceramic is formed on the side surface of the piezoelectric ceramic rectangular plate 11.
A conductive part 17 for drawing out the output electrode 13 to the vibration node 15 is formed on the insulating layer 16 by using a thick silver film method or the like, and an output lead is provided at a part corresponding to the vibration node on the conductive part 17. A wire 18 is attached to take out the output voltage.

With this, the output lead wire 18 can be attached at the node of vibration, so that the disconnection of the output lead wire 18 due to the vibration of the piezoelectric ceramic rectangular plate 11 can be prevented.

Here, the portion where the insulating layer is formed does not necessarily have to be the side surface of the piezoelectric ceramic rectangular plate. or,
The conductive portion formed on the insulating layer may be formed of a thin film such as a sputter. Further, as the material used for the insulating layer, it is preferable to use, for example, a material having a dielectric constant ε of about 10, which is sufficiently lower than that of piezoelectric ceramics (dielectric constant ε = 1000).

FIG. 2 shows an equivalent model of the piezoelectric transformer and the output portion of the piezoelectric transformer when the insulating layer and the conductive portion are formed. FIG. 3 is a diagram showing an electric field distribution of the piezoelectric transformer according to the embodiment of the present invention. FIG. 3A is a diagram showing that the electric field E of the piezoelectric transformer of the present invention is concentrated on the drive electrode pair and the conductive portion. FIG. 3B is a diagram showing that the electric field E of the piezoelectric transformer of the present invention is uniformly distributed without being concentrated in the drive electrode pair and the conductive portion. In FIG. 2, C1 is the capacitance between the drive electrode pair 22 and the output electrode 23, and C1 is
2 is the capacitance between the drive electrode pair 22 and the insulating layer 26, and C3 is the capacitance of the insulating layer 26.

In FIG. 2, the dielectric constant ε of the insulating layer 26 is
When it is the same as the piezoelectric ceramics (when there is no insulating layer), only C2 and C1 <C2 are satisfied.
As shown in (a), the electric field E is concentrated on C2, that is, between the drive electrode pair 32 and the conductive portion 37. Therefore, there is a risk that the piezoelectric transformer may cause dielectric breakdown during driving or polarization.

On the other hand, in FIG. 2, when the dielectric constant ε of the insulating layer 26 is sufficiently low, C3 becomes very small, and the portion represented by C3, that is, the insulating layer 26 is in an insulating state. Therefore, the electric field is not applied to C2 and C3,
As shown in FIG. 3B, the electric field distribution in the output portion during driving or polarization is calculated in the longitudinal direction of the piezoelectric ceramic rectangular plate 11 (driving electrode pair 32−output electrode 33).
Evenly). In this way, the lead layer lead-out position can be freely designed if the insulating layer 26 is formed in consideration of the dielectric constant ε and the film thickness so that the capacitance of the portion C3 does not become large, and the electrode area is not made excessive. can do.

Therefore, it is possible to avoid the electric field concentration between the drive electrode pair 32 and the conductive portion 37 as shown in FIG. 3A, and to prevent the dielectric breakdown of the piezoelectric transformer during driving or polarization. .

[0023]

As described above, according to the present invention, it is possible to provide a highly reliable piezoelectric transformer having no breakage of lead wires, no dielectric breakdown.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a structure of a piezoelectric transformer according to an embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent model of a piezoelectric transformer and an output unit of the piezoelectric transformer according to an embodiment of the present invention. FIG. 2A is a plan view of the piezoelectric transformer. FIG. 2B is a diagram showing an equivalent model of the output part of the piezoelectric transformer.

FIG. 3 is a diagram showing an electric field distribution of a piezoelectric transformer according to an example of the present invention. FIG. 3A is a diagram showing that the electric field E of the piezoelectric transformer of the present invention is concentrated on the drive electrode pair and the conductive portion.
FIG. 3B is a diagram showing that the electric field E of the piezoelectric transformer of the present invention is uniformly distributed without being concentrated in the drive electrode pair and the conductive portion.

FIG. 4 is a perspective view showing a configuration of a conventional piezoelectric transformer.

FIG. 5 is an explanatory diagram of an operation principle of a conventional piezoelectric transformer. FIG.
(A) is a front view of the conventional piezoelectric transformer. FIG. 5B is a diagram showing a displacement distribution of a conventional piezoelectric transformer. FIG. 5C is a diagram showing a strain distribution of a conventional piezoelectric transformer.

FIG. 6 is a perspective view showing an outline of an example of mounting an output lead wire of a conventional piezoelectric transformer.

FIG. 7 is a perspective view showing an example of an output lead wire of a conventional piezoelectric transformer.

[Explanation of symbols]

11 Piezoelectric ceramic rectangular plate 12, 22, 32, 42, 52, 62, 72 Drive electrode pair 13, 23, 33, 43, 53, 63, 73 Output electrode 14, 15, 54, 55, 74, 75 Vibration node 16, 26, 36 Insulating layer 17, 27, 37, 77 Conductive part 18, 28, 38, 68, 78 Output lead wire P Polarization direction

Claims (1)

[Claims] 1. An n in the longitudinal direction of a piezoelectric ceramic rectangular plate.
In a piezoelectric transformer vibrating in a second resonance mode, an insulating layer made of a material having a dielectric constant lower than that of the piezoelectric ceramic is formed on the upper and lower surfaces or side surfaces of the piezoelectric ceramic rectangular plate, and a conductive portion is formed on the insulating layer. Then, a piezoelectric transformer characterized in that an input / output lead wire is attached to a vibration node on the conductive portion.