JPH10135530A - Piezoelectric transformer - Google Patents

Abstract

(57) [Problem] To easily take out a lead wire by favorably supporting a piezoelectric transformer. SOLUTION: A vibrating body 22 has an end face 22A, 22B in the longitudinal direction of the vibrating body 22, and a fixing portion 3 of a base 34, 36.
8, 40 fixed. When an AC voltage 30 having a resonance frequency of the vibrating body 10 polarized in the FA and FB directions is applied between the electrodes 24 and 26, a longitudinal vibration occurs in the FC direction due to the electromechanical coupling coefficient d31, and the vibrating body 22 in the FD direction.
Expands and contracts. Since these vibrations and expansion and contraction are transmitted to the secondary side, longitudinal vibration occurs in the FE direction on the secondary side, and the vibrating body 22 expands and contracts in the FF direction. Therefore, the direction of expansion and contraction coincides with the direction of polarization, and a voltage 32 is generated by the electromechanical coupling coefficient d33 to be extracted from the electrode 28. Electrodes 24, 26,
All 28 lead wires are taken out from the fixed end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer, and more particularly, to an improvement in a supporting method thereof.

[0002]

2. Description of the Related Art Piezoelectric transformers have a higher energy density than conventional winding transformers, and can be made smaller and thinner. (2) The switching frequency can be increased. (3) No electromagnetic noise. (4) The influence of heat generation is also reduced. There are such advantages, and research is progressing in various fields.

For example, Japanese Unexamined Patent Publication No. Hei 4-167504 discloses a method of laminating piezoelectric ceramic disks.
A piezoelectric ceramic transformer operating at or above kHz is disclosed. IEICE technical report PE92-68 (1993-
02), pp. 25-31, consider an equivalent circuit of a thickness longitudinal vibration type piezoelectric transformer. Technical report PE93-19 (1993-07), P51 ~
No. 55 discloses a piezoelectric transformer converter in which the efficiency of switching of a piezoelectric transformer is improved by a soft switching method. Technical report US95-21, EMD95-17, CPM95-29
(1995-07), pages 9 to 16, disclose a laminated integrated sintering type piezoelectric transformer capable of obtaining a large boost ratio. The technical report US95-22, EMD95-18, CPM95-30 (1993-02), pages 17 to 21 include piezoelectrics for cold-cathode tubes that are driven at twice the power supply voltage using a full-bridge circuit. A transformer is disclosed.

[0004] Incidentally, these piezoelectric transformers are supported at nodes of vibration determined by the vibration mode, that is, at node points having an amplitude of "0" so as not to hinder the mechanical vibration of the vibrating body formed of the piezoelectric material. FIG. 7A shows a Rosen-type piezoelectric transformer, and a plate-shaped vibrating body 10 is provided.
The electrodes 12 and 14 are respectively formed on the upper and lower (or front and back) surfaces on the left side of the figure, and the electrode 16 is formed on the right side end face. The polarization directions of the vibrating body 10 are directions indicated by arrows, respectively, that is, a vertical direction on the left side and a horizontal direction on the right side. The vibration amplitude of the first mode is as shown in FIG. 4B, and the node point is the center PC. Therefore, in order not to hinder the vibration of the vibrating body 10, the vibrating body 10 must be supported only by the center PC. Further, the electrodes 12 to
There is an inconvenience that the lead wire must be taken out from the vibrating part. In particular, extraction from the right electrode 16 must be performed from the position where the amplitude is the largest.

The present invention has been made in view of such a point, and it is an object of the present invention to satisfactorily support a piezoelectric transformer and easily take out a lead wire.

[0006]

In order to achieve the above object, the present invention provides a method of applying a voltage to a primary electrode of a vibrating body having a predetermined polarization to mechanically vibrate the vibrating body. In a piezoelectric transformer for extracting a voltage generated at a secondary electrode, a fixing means for fixing the vibrating body at an end in a longitudinal direction thereof is provided. The fixing means is provided, for example, with means for fixing the vibrating body in contact with at least one of an end face, a ridgeline, and a top of the vibrating body, and dispersing stress at a polarization boundary between the primary side and the secondary side. For example, a laminated structure of sheets having different densities, a scratch or a film is formed on the surface of the vibrating body, or the pore content in the laminated sheet is adjusted. Further, at least one of the fixing means is provided with a drawing means for one electrode, for example, a drawing hole and a drawing conductor. Alternatively, the fixing means is formed of a conductor. According to the main aspect,
The fixing means is also used as the outer case.

[0007] The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0008]

Embodiments of the present invention will be described below in detail with reference to examples. The piezoelectric transformer according to the present invention is suitable for, for example, a lighting power supply of a cold cathode fluorescent lamp used as a backlight light source in a notebook computer.

[0009]

First Embodiment First, a first embodiment will be described with reference to FIGS. FIG. 1 shows a cross section when the present invention is applied to a well-known Rosen type piezoelectric transformer. In the figure, a piezoelectric transformer 20 is configured around a plate-shaped vibrator 22, and electrodes 24 and 26 are formed on the upper and lower surfaces on the left side, respectively. An electrode 28 is formed on the right end surface. The piezoelectric body 22 is polarized in a thickness direction indicated by an arrow FA at a portion between the electrodes 24 and 26, and is polarized in a length direction indicated by an arrow FB at a portion from the electrodes 24 and 26 to the electrode 28.

When used as a step-up transformer, the electrodes 24 and 26 are the primary side, and the electrode 28 is the secondary side. The AC voltage 30 at the resonance frequency of the vibrating body 10 is
6 is applied. Then, a longitudinal vibration occurs in the direction of arrow FC due to the electromechanical coupling coefficient d31, and the vibrating body 22 expands and contracts in the direction of arrow FD. Since these vibrations and expansion and contraction are transmitted to the secondary side, a longitudinal vibration occurs in the direction of arrow FE on the secondary side,
The vibrating body 22 expands and contracts in the direction of arrow FF. Therefore, the direction of expansion and contraction coincides with the direction of polarization, and a voltage 32 is generated by the electromechanical coupling coefficient d33 to be extracted from the electrode 28.

In this embodiment, both ends of the vibrating body 22 are fixed. That is, the end faces 22A, 22B in the longitudinal direction of the vibrating body 22 are fixed by the fixing portions 38, 40 of the fixing bases 34, 36. At this time,
An adhesive may be used. Since the electrode 28 is provided on the end face 22B side, it is fixed by the fixing portion 40 via the electrode 28.

FIG. 2 shows various examples of the fixing portion. First, in the example shown in FIG. 1A, a fixed portion is formed by a spindle-shaped projection 42. In the example shown in FIG. 6B, a fixing portion is formed by a columnar projection 44. Two protrusions 44 are provided in the width direction of the vibrating body 22 (the direction perpendicular to the paper surface of FIG. 1). The example shown in FIG.
A fixed portion is formed by the quadrangular columnar projection 46.
The protrusion 46 is formed along the width direction of the vibrating body 22. In the example shown in FIG. 4D, a fixed portion is formed by a quadrangular prism-shaped projection 48 having a width corresponding to the thickness of the vibrating body 22. That is, the vibrator 22 is fixed in contact with the protrusion 48 over the entire end face.

FIG. 3 shows still another example of the fixing portion. The example of FIG. 2 is an example of a convex fixing portion, while the example of FIG. 3 is an example of a concave fixing portion. The example shown in FIG. 3A shows a prismatic recess 50 along the end shape of the vibrating body 22.
A fixing portion is formed by the above. In the fixed state, the bottom surface 50A of the recess 50 abuts against the end surfaces 22A and 22B of the vibrating body 22 and is fixed, as shown in the cross section in FIG.
Since the electrode 28 is formed on the end face 22B side of the vibrating body 22, an extraction hole 36A is provided on the base 36 side.
The lead wire is drawn out using this. A conductor for extraction may be embedded instead of the hole for extraction,
The entire base 36 may be a conductor. The same applies to other examples of the fixing portion.

Next, in the example shown in FIG. 3 (C), a fixing portion is formed by a columnar recess 52. FIG. 2 described above
3A, the end face 22 of the vibrating body 22
A and 22B are fixed in contact with each other. In the example of FIG. 3C, the vibrator 22 is fixed in contact with the edge of the end of the vibrating body 22. In the fixed state, the peripheral surface of the recess 52 is fixed in contact with the edge of the end face of the vibrating body 22 as shown in the cross section in FIG. If the recess is formed in an arc shape, it can be fixed in contact with the top of the end face of the vibrating body 22.

As shown in the above example, according to this embodiment, the vibrating body is fixed at its end face. Therefore, since the structure is not fixed at the nodes of vibration (node points) as in the above-described background art, it is not necessary to accurately position the support. In addition, since the end surface is supported, the support structure is simple, and the support portion and the outer casing can be used together. FIG. 4 shows an example thereof.
The sides of the outer casing 54 serve as bases 34 and 36. That is, the vibrating body 22 is supported and stored by the outer casing 54.

From the lower part of the outer case 54, the lead terminals 5
6, 58, 59 are protruding, and can be mounted on a substrate or the like as they are (corresponding to a so-called SMD). It is also advantageous in terms of waterproofing. Electrodes 24, 26
Are connected to the lead terminals 56 by the lead wires 24A and 26A.
The electrode 28 is connected to a lead terminal 59 by a lead wire 28A.

As described above, according to the present embodiment, the vibrating body 2
Since both ends are fixed, the lead wires 24A, 26A, 28A can be taken out from this fixed portion.
Further, since the vibrating body 22 vibrates in a state where both ends are fixed,
The amplitude of the vibration can be increased, and the power capacity can be increased. Alternatively, a hole or a window may be formed in a part of the outer casing 54 to perform an adjustment operation such as fine adjustment of the vibration mode.

Next, still another modification will be described with reference to FIG. Each of the drawings has an electrode structure for facilitating polarization, and is similar to the previous embodiment in that both ends of the vibrator are fixedly supported. First, the piezoelectric transformer 60 shown in FIG.
4 and 26 are formed at the left and right centers of the vibrating body 22, and electrodes 62 and 64 are formed at both ends of the vibrating body 22. That is, the electrode 28 in FIG. 1 corresponds to the electrodes 62 and 64 in this embodiment, and the output voltage 32 is obtained from both electrodes. The polarization is performed by applying a DC voltage to the electrodes 24 and 26 and the electrodes 62 and 64, respectively, and the polarization direction is a direction indicated by arrows FB1 and FB2. Even when the vibrating body 22 has the same length (left-right direction), the distance from the electrodes 24 and 26 to the electrodes 62 and 64 is shorter than in the example of FIG. 1, so that the polarization can be easily performed.

In the piezoelectric transformer 66 shown in FIG.
The positions of the electrodes 24 and 26 are the same as in the example of FIG. 1, except that the polarizing electrodes 68 are laminated at appropriate intervals in a portion from the electrodes 24 and 26 to the electrode 28 on the end face, and the extraction electrodes are alternately formed. 70 and 72 are connected. Extraction electrodes 70, 72
By applying a DC voltage in between, the electrode 2 of the vibrating body 22
Polarization of the portion from 4, 26 to the electrode 28 is performed. Since the interval between the polarization electrodes 68 is narrow, polarization can be easily performed.

The piezoelectric transformer 74 shown in FIG. 3C is provided between the electrodes 24 and 26 of the example shown in FIG.
Are laminated at appropriate intervals, and the polarization electrodes 76 are alternately connected to the electrodes 24 and 26 on the side surfaces of the vibrating body 22. According to this example, since the electrode interval in the vibrating body portion between the electrodes 24 and 26 also becomes narrow, polarization can be easily performed on both the input side and the output side. In addition,
The direction of the polarization electrode 76 may be the same as that of the polarization electrode 68. When the input side has a laminated structure, the boost ratio can be increased.

[0021]

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. As described above, according to the first embodiment, the end face of the vibrating body is fixed. However, when the vibrating body vibrates in this state, the stress becomes the largest at the boundary of polarization,
There is a high possibility that the vibrating body will be damaged at this point. The following example is for improving such inconvenience.

First, the example shown in FIG.
Are laminated with sheets of piezoelectric ceramics or the like. At the time of lamination, sheets having different densities, for example, a doctor sheet 82 and an extruded sheet 84 are alternately laminated, pressed and fired to obtain a vibrating body 80. And this vibrating body 8
The electrodes 24, 26, and 28 are formed at 0, respectively. With such a laminated structure, stress at the position PA of the polarization boundary, which is a breakage point, is dispersed, and the reliability is improved.

Next, in the example shown in FIG. 3B, a flaw 86 is intentionally formed at an appropriate position avoiding the position PA of the vibrating body 22 described above. The scratches 86 are formed on at least one of the upper and lower surfaces of the vibrating body 22 (or on both sides). Alternatively, it may be formed over the entire width (perpendicular to the paper surface) of the vibrating body 22 or may be formed partially. Also,
If necessary, it may be formed at a plurality of locations. The depth of the scratch 86 is, for example, about 1 to 100 μm. When such a flaw is formed, the stress concentrates on the flaw 86, and the stress concentration at the position PA is relatively alleviated, so that the vibrator can be prevented from being broken.

Next, the example shown in FIG.
A film 88 is formed on portions of the upper and lower surfaces where the electrodes 24 and 26 are not formed. As the film 88, for example, an organic alkoxide, SiO ₂ , TiO ₂ , Al
₂ O ₃ , ZrO _{2 and the} like are used. Such a coating 88
Is formed, stress is dispersed, and breakage of the vibrating body at the position PA is prevented.

Next, in the example shown in FIG. 2D, the vibrating body 90 has a laminated structure as in the case of FIG. 2A, but the upper and lower sheets 92, 94 have different glass contents. There are more than sheets. By doing so, the sheet 9
The number of pores (holes) formed in 2, 94 is smaller than in the middle sheet. That is, the surface portion of the vibrating body 90 has a smaller number of pores than the inside, for example, 10%.
It has a small structure. The pores in the vibrating body have an effect of relieving the stress at the time of vibration. However, since the pores are small on the surface of the vibrating body, the stress is dispersed as a result.

[0026]

Other Embodiments There are many embodiments of the present invention, and various modifications can be made based on the above disclosure. For example, the following is also included. (1) In the above embodiment, the case where the present invention is applied to a flat-plate type piezoelectric transformer has been described. However, the present invention can be applied to various types of vibrating bodies such as quadrangular prisms. Which one is the primary side (input side) or the secondary side (output side) is set according to the necessity of step-up and step-down. (2) The design and shape of the fixing portion can be variously changed within the scope of fixing at the end face of the vibrating body. Similarly, the shape and arrangement of the electrodes of the vibrating body, and the directions of polarization and vibration may be appropriately set as necessary. (3) Both ends of the vibrator may be fixed so as to move slightly. For example, an elastic material such as silicon rubber is used as the fixing material, or the fixing member is supported by a structure like a speaker. This has the advantage of being less susceptible to external vibrations.

[0027]

As described above, the present invention has the following effects. (1) Since both ends of the vibrating body are fixed, the vibrating body can be easily supported without requiring precision, and the lead wires can be easily taken out. (2) Since the means for dispersing the vibration stress is provided, it is possible to favorably prevent the vibrator from being broken.

[Brief description of the drawings]

FIG. 1 is a sectional view showing Embodiment 1 of the present invention.

FIG. 2 is a perspective view of a main part showing a shape of a fixing part according to the first embodiment.

FIG. 3 is a perspective view and a cross-sectional view of a main part showing another shape of the fixing part of the first embodiment.

FIG. 4 is a sectional view illustrating an example of a case storage state according to the first embodiment.

FIG. 5 is a cross-sectional view illustrating a configuration example of another vibrating body according to the first embodiment.

FIG. 6 is a sectional view showing a main part of a second embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of the configuration and amplitude of a Rosen-type piezoelectric transformer.

[Explanation of symbols]

 20, 60, 66, 74 Piezoelectric transformer 22, 80, 90 Vibrator 24, 26, 28, 62, 64 Electrode 30 AC voltage 32 Output voltage 34, 36 Base 36A Extraction hole 38, 40 Fixing portions 42, 44, 46, 48 Projections 50, 52 Depressions 50A Bottom 54 Enclosure case 56, 58, 59 Lead terminals 68, 76 Polarizing electrodes 70, 72 Extraction electrodes 82, 84, 92 , 94 ... Sheet 86 ... Scratch 88 ... Film FA, FB ... Polarization direction FC, FE ... Vibration direction FD, FF ... Extension / contraction direction

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Daisuke Kaino 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd.

Claims (5)

[Claims] A piezoelectric transformer for applying a voltage to a primary electrode of a vibrating body having a predetermined polarization to mechanically vibrate the vibrating body and taking out a voltage generated at a secondary electrode by the vibration. A piezoelectric transformer comprising fixing means for fixing a vibrating body at its longitudinal end. 2. The piezoelectric transformer according to claim 1, wherein said fixing means fixes the vibrating body in contact with at least one of an end face, a ridge line, and a top of the vibrating body. 3. The piezoelectric transformer according to claim 1, wherein the vibrating body includes means for dispersing a stress at a polarization boundary between the primary side and the secondary side. 4. The piezoelectric transformer according to claim 1, wherein at least one of the fixing means includes a drawing means for one of the electrodes. 5. The fixing device according to claim 1, wherein the fixing means also serves as an outer casing of the vibrating body.
The described piezoelectric transformer.