JP2000124519A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive a reduction in the thickness of the external shape of a product, the simplification of a packaged case, a reduction in the cost of the product which is accompanied by this simplification, and a reduction in the production cost, by a method wherein the formation of the element electrodes of a piezoelectric element board is performed on the end surface (longitudinal side surface) only on one side of the end surfaces in the widthwise direction of the board, and the electrical connection of the packaged case with the element electrodes is made on the longitudinal side surface on one side of the longitudinal side surfaces of the board. SOLUTION: A piezoelectric transformer is formed into a constitution, wherein a piezoelectric element board 30 is provided within a packaged case 40 provided with metal plate terminals 51, 52 and 53, which are used as input/output terminals, and in the case where the board 30 is supported by an oscillation nodal part, elastic members 61, 62, 63 and 64 are made to interpose between both end surfaces in the widthwise direction of the board 30 and the inner wall surfaces of the case 40 to pinch the board 30 between the elastic members, element electrodes 31, 32 and 33 are provided on the end surface on one side of the end surfaces in the widthwise direction of the board 30, and ones to make contact with at least the element electrodes out of the above elastic members are connected electrically with the terminals 51, 52 and 53 as the members 61 and 62.

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 a piezoelectric element used for a high-voltage power supply of a cold cathode tube, a copying machine, an air purifier, and the like. It relates to a piezoelectric transformer.

[0002]

2. Description of the Related Art Conventionally, as this kind of piezoelectric transformer, there is a piezoelectric transformer described in Japanese Patent Application Laid-Open Nos. 5-21858 and 6-334234.

FIG. 9 shows a prior art example 1 showing the most basic arrangement of element electrodes of a Rosen type piezoelectric transformer, wherein 1 is a piezoelectric element plate, 2 is a driving electrode formed on the front and back surfaces of the piezoelectric element plate,
Reference numeral 3 denotes a power generation electrode (or an electrode connected to the power generation electrode), and a thin lead wire 4 is soldered to each electrode to apply a high-frequency drive voltage between the drive electrodes 2 and to generate power output from one side of the power generation electrode 3. Between the drive electrodes.

In the prior art 2 of FIG. 10, element electrodes 5 connected to drive electrodes (not shown) of the piezoelectric element plate 1 are formed on both end surfaces in the width direction of the piezoelectric element plate 1 and are connected to power generation electrodes. 6 is formed on one end surface of the piezoelectric element plate 1 in the longitudinal direction, and the application of the high-frequency drive voltage and the extraction of the power generation output are performed by thin lead wires 7 soldered to each electrode.

9 and 10, the supporting structure of the piezoelectric element plate is not shown. However, since the piezoelectric element plate is accompanied by mechanical vibration, the piezoelectric element plate usually has the structure shown in FIGS. 11 (A) and 11 (B). As shown in the plan view and the front view, the elastic members support the vibration nodes at a distance of 1/4 of the total length L from both ends. Note that FIG.
The displacement of the medium vibration is indicated by a dotted line.

Japanese Patent Laid-Open No. 10-79992 proposes a structure in which a conductive rubber is used for electrodes on the piezoelectric element plate side, and this case is shown in FIG.
In this figure, a piezoelectric element plate 10 is supported and housed in a case 20 via rubber elastic bodies 21, 22 and 23, and rubber elastic bodies 21 and 23 in contact with the drive electrode 11 and the power generation electrode 12 are made of conductive rubber. Through which the conductive portion 2
4, 25.

As described above, since the piezoelectric transformer involves mechanical vibration, the piezoelectric element must be supported by some structure. In a conventional Rosen-type piezoelectric transformer, the piezoelectric transformer has to support the vibrating nodes of the piezoelectric element. A wide variety of support structures have been proposed.

[0008]

By the way, in the conventional example 1,
In the configuration in which the lead wire of No. 2 is connected to the device electrode by soldering, resonance occurs in the lead wire due to mechanical vibration, and problems such as beat sound and disconnection due to vibration, and peeling of the soldered portion have occurred.

In order to solve the problem of the use of the lead wire, a conventional example 3 using conductive rubber has been proposed, which has a structure in which the piezoelectric element plate is held at upper and lower (or left and right) nodes of the piezoelectric element plate. However, in order to form an element electrode, two upper and lower (or left and right) forming steps are required, which has caused a cost increase. In addition, since the structure is such that conductive rubber is brought into contact with the drive electrodes on the front and back surfaces of the piezoelectric element plate to conduct electricity, it is disadvantageous in reducing the thickness of the piezoelectric transformer.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and the device electrodes of the piezoelectric element plate are formed only on one side (long side surface) in the width direction end surface, and the electrical connection with the device electrodes is made by the piezoelectric element. An object of the present invention is to provide a piezoelectric transformer that can be formed on one longitudinal side surface of a plate to reduce the thickness of a product outer shape, simplify an outer case, and thereby reduce costs and manufacturing costs.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0012]

In order to achieve the above object, a piezoelectric transformer according to the present invention has a piezoelectric element plate provided in an outer case provided with input / output terminals, and the piezoelectric element plate is supported by a vibrating node. In the configuration described above, the piezoelectric element plate is sandwiched by interposing an elastic member between both end surfaces (longitudinal side surfaces) in the width direction of the piezoelectric element plate and the inner wall surface of the outer case, and one of the width directions of the piezoelectric element plate is provided. An element electrode is provided on an end face, and at least one of the elastic members that contacts the element electrode is electrically connected to the input / output terminal as a conductive elastic member.

In the piezoelectric transformer, the input / output terminal has an extension along the inner wall surface of the outer case, and the other surface of the conductive elastic member, one surface of which is in contact with the element electrode, is connected to the extension. It is good to make contact with.

A cover body is mounted on the upper part of the outer case, and the piezoelectric element plate is formed by a lower elastic body provided on the inner bottom surface of the outer case and an upper elastic body provided on the ceiling surface of the cover body. May be supported. Alternatively, the piezoelectric element plate may be bonded and supported on the inner bottom surface of the outer case via a lower elastic body.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the piezoelectric transformer according to the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view of a first embodiment of the present invention, FIG. 2 is a plan view, and FIG. 3 is a front sectional view of the Rosen-type piezoelectric transformer. As shown in these figures, the piezoelectric transformer comprises a piezoelectric element plate 30, an insulating outer case 40, and metal plate terminals 51, 52, 5 as input / output terminals.
3, elastic members 61, 62, 63, 64, lower elastic body 65
And a holding member (cover body) 70. However, in this example, an elastic adhesive, such as a rubber-based adhesive, that maintains elasticity after curing is used as the lower elastic body 65.

The piezoelectric element plate 30 has a rectangular thin plate shape, and driving-side element electrodes 31 and 32 and a power-generating element electrode 33 for external connection are formed on one end face (long side face) 30a in the width direction. I have. The piezoelectric element plate 30 has, for example, a laminated structure. As shown in FIG. 4, a driving electrode 35 connected to the driving element electrode 31 in the first layer and a power generation electrode 36 connected to the power generation element electrode 33 are driven in the second layer. Side element electrode 32
Are formed, and a power generating electrode 38 connected to the power generating element electrode 33 is formed. Therefore, the piezoelectric element plate 30 applies a high-frequency drive voltage between the drive-side element electrodes 31 and 32 to vibrate the piezoelectric element plate 30 and output voltage between the power-generation-side element electrode 33 and one of the drive-side element electrodes. Can be taken out.

The insulating outer case 40 is a molded product of an insulating resin or the like, and has ribs (protrusions) 41a for positioning a lower elastic body 65 for supporting (holding) the piezoelectric element plate 30 on the lower side on the inner bottom surface. , 41b, 41c, 41d are integrally formed, and a rib (protrusion) 42 for positioning one of the elastic members 63, 64 is integrally formed on the inner side surface. The ribs 41a, 41b, 41d are metal plate terminals 5.
Positioning of 1, 52 and 53 is also performed. Further, for positioning and fixing the metal plate terminals 51, 52, 53, positioning holes 54 of the metal plate terminals 51, 52, 53 are provided.
Are formed respectively.
Metal plate terminals 51, 52,
A slit hole 44 is formed in order to make the tip of 53 project from the case. Further, a locking projection 45 for locking the holding member 70 is formed on the outer surface of the outer case 40. The ribs 41a, 41
When the lower elastic body 65 is formed of a rubber-based adhesive or the like, b, 41c, and 41d support the bottom surface of the piezoelectric element plate 30 with vibration nodes and also function as an adhesive reservoir.

A metal plate terminal 51 as the input / output terminal,
52 and 53 have alignment holes 54, respectively, and have integrally extended portions 51a, 52a and 53a bent along the inner wall surface (inner side surface) of the outer case 40, respectively.

The pressing member 70 has a U-shaped cross section and is placed over the upward opening of the outer case 40 from above, and is a molded product of the same insulating resin as the outer case 40. A locking hole (or concave portion) 71 that fits into the locking convex portion 45 is formed.

Of the elastic members 61, 62, 63, 64, the elastic members 61, 6 on the side in contact with the driving-side element electrodes 31, 32 and the power generation-side element electrode 33 of the piezoelectric element plate 30.
Reference numeral 2 denotes a conductive elastic member such as a conductive rubber. Further, as shown in FIG. 5, the conductive elastic member 61 is in contact with the drive-side element electrodes 31 and 32 arranged with a narrow gap G therebetween. 6
1a has conductivity in the thickness direction (arrow T) in FIG.
It is made of a material having no conductivity in a plane direction perpendicular to the arrow T (for example, a structure in which a large number of fine copper wires are arranged in an elastic rubber in a thickness direction).

Assembling of each part is performed, for example, in the following procedure.
First, the tip portions of the metal plate terminals 51, 52, 53 project outward from the respective slit holes 44 of the outer case 40, and the positioning holes 54 are fitted into the case-side projections 43 as shown in FIG.
The projection 43 is fixed by deforming the upper portion by heat staking. Further, between the ribs 41a and 41b and the rib 41
The lower elastic body 65 is arranged between c and 41d. Here, as the lower elastic body 65, an elastic adhesive that retains elasticity after curing such as a rubber adhesive is applied between predetermined ribs,
After the curing, the piezoelectric element plate 30 is elastically held.

Then, the piezoelectric element plate 30 is attached to the outer case 4.
0 and elastically held by an elastic adhesive as a lower elastic body 65, and elastic members 61, 62, 63, 64 between both end surfaces in the width direction of the piezoelectric element plate 30 and the inner wall surface of the outer case.
Are interposed to sandwich the piezoelectric element plate 30.

The support at the bottom surface by the lower elastic body 65 of the piezoelectric element plate 30 and the support (sandwich) at both end surfaces in the width direction by the elastic members 61, 62, 63 and 64 are performed as described with reference to FIG. When the total length of the plate 30 is L, L
This is performed at the node of the vibration which is located at a position closer to the center by / 4. Ideally, the nodes of the vibration should be supported linearly, but practically, they are held with a certain width, which hinders the vibration and causes a reduction in efficiency. Therefore, from the viewpoint of efficiency, it is necessary to improve the positional accuracy for supporting the nodes of vibration when the piezoelectric element plate 30 is held and fixed, and to reduce the width of the holding and fixing. For example, in the case of a piezoelectric element plate having a length of 32 mm, it is known from experiments that the width that can be held without affecting the efficiency is about 2 mm on both sides from the center of the node. The shorter the length, the narrower the width. In view of this point, each elastic member 6
It can be said that it is desirable that the widths of the lower elastic body 65 along the longitudinal direction of the piezoelectric element plate 30 be L × (2/32) × 2 or less. However, the conductive elastic member 61 is formed of a pair of drive element electrodes 31 and 32 separated by a gap G.
In some cases, the condition of L × (2/32) × 2 or less may not be satisfied due to the need for common contact with the members. However, it is preferable to narrow the gap G and the width of the conductive elastic member 61 in terms of characteristics.

The piezoelectric element plate 30 and the elastic members 61 and 6
After assembling the 2, 63 and 64 into the outer case 40, the holding member 70 is fitted from above the outer case 40. That is, the piezoelectric transformer is completed by fitting the locking hole (or concave portion) 71 on the pressing member 70 side to the locking convex portion 45 and fixing the pressing member 70.

FIG. 6 is a graph showing the relationship between the driving frequency and the efficiency in the first embodiment. The solid line in the first embodiment, the dotted line is thin without the piezoelectric element plate 30 in the case. The figure shows a case where a lead wire is soldered and placed on a sponge for measurement (a state close to an ideal where the piezoelectric element plate 30 can freely vibrate). In the case of the present embodiment, it can be seen that there is no difference in efficiency as compared with the case where the case is not used.

FIG. 7 is a graph showing the relationship between the drive frequency and the load current according to the first embodiment. The solid line in the first embodiment indicates a case where the piezoelectric element plate 30 is not placed in the case. The figure shows a case where a thin lead wire is soldered and placed on a sponge for measurement. In the case of the present embodiment, it can be seen that there is no difference in the frequency characteristics of the load current as compared with the case where the case is not included.

From the measurement results of FIGS. 6 and 7, the support structure of the piezoelectric element plate 30 of the first embodiment is
It does not hinder the mechanical vibration of the sample and does not cause deterioration of the characteristics.

According to the first embodiment, the following effects can be obtained.

(1) The drive element electrodes 31, 32 and the power generation element electrode 33 formed on the piezoelectric element plate 30 for external connection are only one end face (long side surface) 30a in the width direction of the piezoelectric element plate 30. The electrode manufacturing process can be simplified, and the cost can be reduced.

(2) The elastic members 61, 62, 63, between the both end surfaces in the width direction of the piezoelectric element plate 30 and the inner wall surface of the outer case 40.
Although the piezoelectric element plate 30 is sandwiched between the nodes of the vibration with the interposition of 64, only two elastic members 61 and 62 abutting on the element electrodes 31, 32 and 33 on the longitudinal side face are made of conductive rubber or the like. What is necessary is just to use a conductive elastic member, and also in this respect, cost reduction can be achieved.

(3) By using an elastic adhesive such as a rubber-based adhesive as the lower elastic body 65 for elastically supporting the piezoelectric element plate 30 on the lower side, the upper support becomes unnecessary and the piezoelectric element plate 3
The thickness can be reduced as compared with a structure in which 0 is sandwiched between elastic members from above and below.

(4) Metal plate terminal 5 as input / output terminal
1, 52, and 53 have extensions 51a, 52a, and 53a along the inner wall surface of the outer case 40, so they are directly connected to the conductive elastic members 61 and 62, and do not require electric wiring and have a simple structure. It has become.

The extension portions 51a, 52a, 53a of the metal plate terminals 51, 52, 53 are directly connected to the drive-side element electrodes 31,
Although it is conceivable to solder to the element electrode 32 and the power generation side element electrode 33, the portion to be soldered is extremely narrow, and short circuit accidents easily occur (especially, the drive side element electrodes 31, 32).
In addition, since the displacement of the piezoelectric element plate 30 also occurs at the end face in the width direction, if the metal plate terminals 51, 52, 53 have a practical thickness, for example, about 0.2 to 0.3 mm, a vibration load is generated, and the efficiency is increased. There is a problem that causes a decrease in Therefore, the present embodiment is superior.

An elastic rubber having a required shape is used in advance as the lower elastic body 65 and an adhesive is used in combination with the lower elastic body 6.
5, the lower surface of the lower elastic body 65 may be bonded to the bottom surface of the piezoelectric element plate 30.

FIG. 8 shows a second embodiment of the present invention.
In this case, a holding member 70 as a cover body is attached (fitted or the like) to the upper part of the outer case 40, and the lower elastic body 65 provided on the inner bottom surface of the outer case and the upper side provided on the ceiling surface of the holding member 70. The piezoelectric element plate 30 is supported (sandwiched) by the elastic body 66. In this case, the adhesive may not be used together. Other configurations, operations and effects are the same as those of the above-described first embodiment.

In the first or second embodiment, it is actually troublesome to mount the elastic members 61, 62, 63, and 64 at the time of assembling whether or not they are conductive.
All the elastic members 61, 62, 63, 64 may be constituted by conductive elastic members.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0039]

As described above, according to the piezoelectric transformer of the present invention, the piezoelectric element plate is sandwiched with the elastic member interposed between both end surfaces in the width direction of the piezoelectric element plate and the inner wall surface of the outer case. An element electrode is provided on one end face in the width direction of the piezoelectric element plate, and at least one of the elastic members that is in contact with the element electrode is electrically connected to an input / output terminal as a conductive elastic member. Each element electrode formed on the piezoelectric element plate for external connection may be formed only on one end face (longitudinal side face) in the width direction of the piezoelectric element plate,
The manufacturing process can be simplified, and the cost can be reduced.
Further, it is easier to reduce the thickness as compared with the case where the element electrodes are provided on the front and back surfaces of the piezoelectric element plate.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the same.

FIG. 3 is a front sectional view of the same.

FIG. 4 is an explanatory diagram showing an example of the internal electrode configuration of a piezoelectric element plate.

FIG. 5 is a diagram showing a driving element electrode according to the first embodiment;
It is a perspective view explaining the positional relationship with the extension part of a conductive elastic member and a metal plate terminal.

FIG. 6 is a frequency characteristic diagram of the efficiency of the piezoelectric transformer according to the first embodiment.

FIG. 7 is a frequency characteristic diagram of a load current of the piezoelectric transformer according to the first embodiment.

FIG. 8 is a front sectional view showing a second embodiment of the present invention.

FIG. 9 is a perspective view showing a first conventional example of a piezoelectric transformer.

FIG. 10 is a perspective view showing a second conventional example of a piezoelectric transformer.

FIG. 11 is an explanatory diagram showing displacement of vibration of the piezoelectric element plate and positions of nodes.

FIG. 12 is a front sectional view showing a third conventional example of the piezoelectric transformer.

[Explanation of symbols]

 1, 10, 30 Piezoelectric element plate 2, 11 Drive electrode 3, 12 Power generation electrode 5, 6, 31, 32, 33 Element electrode 20, 40 Case 41a, 41b, 41c, 41d, 42 Rib 44 Slit hole 45 Locking Convex portions 51, 52, 53 Metal plate terminals 61, 62, 63, 64 Elastic member 65 Lower elastic member 66 Upper elastic member 70 Holding member

Claims (4)

[Claims] 1. A piezoelectric transformer in which a piezoelectric element plate is provided in an outer case provided with input / output terminals, and the piezoelectric element plate is supported by a vibrating node, wherein both end faces in the width direction of the piezoelectric element plate and the outer case are provided. Sandwiching the piezoelectric element plate by interposing an elastic member between inner wall surfaces,
An element electrode is provided on one end face in the width direction of the piezoelectric element plate, and at least one of the elastic members that comes into contact with the element electrode is electrically connected to the input / output terminal as a conductive elastic member. Piezo transformer. 2. The input / output terminal has an extension along an inner wall surface of the outer case, and the other surface of the conductive elastic member having one surface in contact with the element electrode is in contact with the extension. The piezoelectric transformer according to claim 1, wherein 3. A piezoelectric element comprising a cover body attached to an upper portion of the outer case, and a lower elastic body provided on an inner bottom surface of the outer case and an upper elastic body provided on a ceiling surface of the cover body. 3. The piezoelectric transformer according to claim 1, wherein said piezoelectric transformer supports a plate. 4. The piezoelectric transformer according to claim 1, wherein the piezoelectric element plate is adhered and supported on the inner bottom surface of the outer case via a lower elastic body.