JPH0992902A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small sized piezoelectric transformer excellent in characteristics at a low cost wherein a piezoelectric plate is isolated from an external part and handling is facilitated by covering the piezoelectric plate with coating resin. SOLUTION: A retaining member 11 having elasticity is fixed on one main surface side of a piezoelectric plate 1 on which input electrodes 2, 2 and an output electrode 3 are formed. The piezoelectric plate 1 is covered with coating resin 13 interposing the retaining member 11 and a cavity 14. External terminals like lead wires 6 and lead terminals which are connected with the input electrodes 2, 2 and the output electrode 3 are retained and fixed with the coating resin 13 and led out to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer used for a backlight inverter of a liquid crystal display, and more particularly to a structure covered with an exterior resin.

[0002]

2. Description of the Related Art As shown in FIG. 7, for example, a piezoelectric transformer of this type has an input electrode 2 on both main surfaces of one side half of a piezoelectric plate 1 made of piezoelectric ceramics on a rectangular flat plate.
2 is formed, the output electrode 3 is formed on the end face in the length direction on the other side, and as shown by the arrow, the part where the input electrodes 2 and 2 on the input side are formed is polarized in the thickness direction, and the output side is formed. The other side, which is, is polarized in the length direction.

Input side wirings 4 and 4 are connected to positions corresponding to the node points of the input electrodes 2 and 2, and output side wiring 5 is connected to the output electrode 3. One input side wiring 4 serves as a common end (ground) for input and output.

Then, an input voltage is applied between the input electrodes 2 and 2 through the input side wiring, and the boosted output voltage generated at the output electrode 3 is taken out through the output side wiring 5 by the action of the piezoelectric effect and the inverse piezoelectric effect. Be done. External terminals such as lead wires and lead terminals are used as the wirings 4 and 5, and are connected to the input electrode 2 and the output electrode 3 by soldering or the like.

This piezoelectric transformer uses a basic (first-order) vibration mode called a λ / 2 mode, and the vibration has zero vibration displacement at 1/2 (λ / 4) in the length direction. It becomes a so-called node point and has maximum displacement at both ends.

Usually, this type of piezoelectric transformer is constructed by using a longitudinal vibration mode of an integral multiple of λ / 2. When a longitudinal vibration mode of a second order or higher is used, each λ / 2 section in the longitudinal direction. A node point is generated in the center of, and both λ /
The maximum displacement occurs at position 2, and the input electrode is formed in a section of λ / 2 from one end in the length direction.

In such a piezoelectric transformer, it is desirable to support the piezoelectric transformer at a position corresponding to the node point where the displacement is minimized so as not to hinder vibration as much as possible, and the electrical connection for input / output is also connected at the node point. Is desirable.

[0008]

As described above, the piezoelectric transformer utilizes the vibration of the entire piezoelectric plate, and the vibration displacement is large. Conventionally, as a packaging method for the piezoelectric transformer, the node is arranged so as to suppress the vibration as much as possible. Although methods such as devising the support at points and storing it in a case are being studied, there are problems in practical application such as cost and size because the supporting method is complicated and the case is used. .

[0009] Therefore, an object of the present invention is to provide a piezoelectric transformer which can easily isolate the piezoelectric plate from the outside without suppressing vibration, and which is small in size and has good characteristics and which is inexpensive. It is in.

[0010]

In order to achieve the above object, the invention according to claim 1 provides a piezoelectric plate having an input electrode and an output electrode, and an input / output connected to the input electrode or the output electrode. An external terminal for use in the piezoelectric plate, the entire surface of the piezoelectric plate is covered with a supporting member having elasticity, the supporting member is covered with an exterior resin, and the external terminal is pulled out from the exterior resin. Is.

According to a second aspect of the present invention, a piezoelectric plate having an input electrode and an output electrode formed thereon and an external input / output terminal connected to the input electrode or the output electrode are provided, and a part of the piezoelectric plate is provided. A supporting member having elasticity is attached, the piezoelectric plate is covered with an exterior resin so as to separate the cavity and the support member, and the external terminals are drawn out from the exterior resin.

The invention according to claim 3 is the piezoelectric transformer according to claim 2, wherein a supporting member having elasticity is attached to a position corresponding to a node point of the piezoelectric plate. .

According to the above construction, the piezoelectric plate, which is the vibrating body, is covered with the elastic support member or the elastic support member with the outer resin separated from the cavity by a cavity, so that the vibration of the piezoelectric plate is not suppressed. It is isolated from the outside and can be manufactured at low cost.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings showing embodiments thereof. In the following drawings, the same reference numerals are given to those described in the related art and the description thereof will be omitted.

The structure of the piezoelectric transformer according to the first embodiment of the present invention is shown in FIGS. FIG. 1 is an external perspective view,
FIG. 2 is a sectional view taken along line XX of FIG.

The piezoelectric transformer of this embodiment has the structure shown in FIGS.
As shown in FIG. 3, lead wires 6 are soldered and connected as external terminals to the input electrodes 2 and 2 and the output electrode 3 of the piezoelectric plate 1, respectively, and the entire surface of the piezoelectric plate 1 is covered with a supporting member 11 having elasticity. The support member 11 is covered with the exterior resin 13, and the lead wire 6 is supported and fixed by the exterior resin 13 and is drawn out to the outside. That is, the piezoelectric plate 1, which is a vibrating body, is housed in the exterior resin 13 via the elastic support member 11. The piezoelectric transformer of this embodiment uses the fundamental vibration mode, and the lead wires 6 connected to the input electrodes 2 and 2 are attached to the piezoelectric plate 1 substantially at the center in the longitudinal direction corresponding to the node points. There is.

The support member 11 is made of a material that does not suppress the vibration of the piezoelectric plate 1, such as a gel-like silicon adhesive or a gel-like epoxy adhesive that maintains a gel state even after curing.

The exterior resin 13 is for isolating the piezoelectric plate 1 from the outside and protecting the piezoelectric plate 1 from impacts and moisture applied from the outside, and is made of a material having a high mechanical strength such as an epoxy resin. ing. Support member 11 and exterior resin 13
Are formed by a method such as dipping.

In this structure, since the piezoelectric plate is covered with the exterior resin and is isolated from the outside, it can be a component that is easy to handle, and the supporting member that covers the piezoelectric plate is made of a material that does not suppress vibration. Since it is used, the suppression of vibration is reduced and the deterioration of the characteristics such as the boost ratio is greatly reduced.

Further, the supporting member and the exterior resin can be formed by a simple method such as dipping, and the material cost and the manufacturing cost thereof can be greatly reduced as compared with, for example, a method of housing in a case and a structure. .

FIG. 3 shows a sectional view of a piezoelectric transformer using the secondary vibration mode according to the second embodiment of the present invention.

In the piezoelectric transformer of the present embodiment, a supporting member 11 having elasticity is adhered to one main surface side of the piezoelectric plate 1 so as to protrude from the four end faces of the piezoelectric plate 1, and the piezoelectric plate 1 has a supporting member 11 and a cavity 14. It is configured to be covered with an exterior resin 13 with a space therebetween. Although not shown, each lead wire 6 is fixed by an exterior resin 13 and drawn out to the outside. That is, the piezoelectric plate 1 is supported and fixed to the exterior resin 13 by the support member 11,
A cavity 14 is formed in a portion between the piezoelectric plate 1 and the exterior resin 13 except the support member 11. Since the secondary vibration mode is used in this embodiment, each lead wire 6 is connected at a position corresponding to a node point which is substantially the center of the input electrodes 2, 2.

As the support member 11, a gel adhesive is used as in the first embodiment, and the piezoelectric plate 1 is mounted on the adhesive applied or flowed in with a certain thickness through the release agent. It is attached to the piezoelectric plate 1 by placing it or coating it on the piezoelectric plate 1 with a dispenser or the like.

As shown in FIG. 4, the cavity 14 is formed by the piezoelectric plate 1.
After the cavity forming agent 12 such as wax is applied to a portion other than the portion where the supporting member 11 is attached and the exterior resin 13 is dipped so as to cover the supporting member 11 and the cavity forming agent 12,
It is formed by baking and curing the exterior resin 13 at a temperature of 100 to 200 ° C. That is, the cavity forming agent 12 is melted and sublimated when the exterior resin 13 is baked and cured, so that the exterior resin 1 is formed.
3 is absorbed and the cavity 14 is formed in the portion where the cavity forming agent 12 was attached.

In this structure, since the cavity is formed in the portion other than the portion where the supporting member 11 is attached, the suppression of vibration is further reduced, and the step-up ratio is larger than that of the structure shown in the first embodiment. Can be obtained.

In each of the above embodiments, a single-plate piezoelectric transformer is shown and described. However, a piezoelectric transformer having a laminated structure in which the input electrodes of each layer are alternately connected at the end faces by using a multilayer piezoelectric plate also has the same structure. Of course you can.

Next, Table 1 shows the measurement results of the boosting ratio in each of the above-mentioned configurations and the free state in which only the piezoelectric plate was placed on the sponge.
And shown in Table 2. Table 1 is a single-plate piezoelectric transformer, Table 2
Shows the step-up ratio in a five-layer piezoelectric transformer, and is the experimental result when the load resistance is 11 MΩ and 100 KΩ in the primary mode and the secondary mode. The support member is formed by using gel silicone rubber having a penetration of about 100.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Tables 1 and 2, even in the case of the gelled silicone rubber / exterior resin in the primary mode in which the boosting ratio is the lowest (the structure of the first embodiment), the reduction in the boosting ratio is 11 dB. , Is at a level that can be used in practice. In the configuration of the second embodiment in which the cavity is formed, the maximum decrease in the boost ratio is 4 dB, and it can be seen that the suppression of vibration is significantly reduced as compared with the configuration of the first embodiment.

Next, FIG. 5 shows a sectional view of a piezoelectric transformer using the secondary vibration mode according to the third embodiment of the present invention.

In the piezoelectric transformer of the present embodiment, the supporting members 11 having elasticity over the entire circumference of the piezoelectric plate 1 are provided at two positions corresponding to the node points in the lengthwise direction of the piezoelectric plate 1. The piezoelectric plate 1 is coated and adhered, and is covered with the exterior resin 13 with the support member 11 and the cavity 14 separated from each other. Although not shown, each lead wire 6 is fixed by an exterior resin 13 and drawn out to the outside. That is, the piezoelectric plate 1 is supported and fixed to the exterior resin 13 by the support member 11 near the node point, and the cavity 14 is formed between the piezoelectric plate 1 and the exterior resin 13 except the support member 11. It has a structure. The cavity 14 is formed by the method described in the second embodiment.

In this structure, the supporting member 11 is provided only at the position corresponding to the node point of the piezoelectric plate 1,
Moreover, since the cavity 14 is increased in number, the suppression of vibration of the piezoelectric plate 1 is further reduced, and a larger boost ratio can be obtained. Further, it is a support at a position corresponding to the node point, and as the support member, not only the gel adhesive but also a low hardness silicon-based or epoxy-based resin adhesive or a ring-shaped low-hardness silicone rubber is used. Can also be used.

In each of the above-mentioned embodiments, the lead wire is used as the input / output external terminal and the output electrode is formed on the end face, but the present invention is not limited to this.

FIG. 6 is an external perspective view of a piezoelectric transformer according to the fourth embodiment of the present invention. This piezoelectric transformer uses a third vibration mode and has a length of 3λ / 2.
Of the input electrode 2 in the section of λ / 2 from one end of the length direction of
2 is formed, and a strip-shaped output electrode 3 is formed over the entire circumference at a position corresponding to a node point of λ / 4 from the other end. As the external terminal, a lead wire 6 and a lead terminal 7 connected to each other is used, and the central portions of the input electrodes 2 and 2, which are the connecting portions of the lead wires 6, and the output electrode 3 forming portion are covered with a supporting member 11 having elasticity. Each lead terminal 7 is fixed by the exterior resin 13 and is pulled out to the outside.

A supporting member may be attached to the piezoelectric plate 1 at a position corresponding to the node point at the center in the length direction. Also, the external terminals may be only lead terminals. In this case, the width on the side connected to the piezoelectric plate should be reduced so that vibrations are not suppressed, or the tip end should be bent to facilitate soldering, etc. Is applied.

In this structure, the external terminals on the output side can also be connected at the node points, and all the support and electrical connections can be made at the positions corresponding to the node points, thus providing more stable support and electrical connection. A connection can be obtained and stable characteristics can be obtained. In addition, the lead terminals are pulled out to allow insertion and mounting on the mounting board.

The structure shown in FIG. 6 can be applied to vibration modes of the second or higher order. Also in the primary vibration mode, the output electrode can be formed in a band shape near the output side end as shown in FIG.

[0039]

As described above, according to the piezoelectric transformer of the present invention, the piezoelectric plate, which is the main body of the piezoelectric transformer, is covered with the outer supporting resin by separating the elastic supporting member or the elastic supporting member from the cavity. Therefore, the component can be easily handled, and the suppression of vibration can be significantly reduced, and good characteristics with little deterioration in characteristics such as step-up ratio can be realized.

Further, the number of parts is small, and the supporting member and the exterior resin can be formed by a simple method such as dipping, and can be manufactured in a small size and at a low cost.

[Brief description of drawings]

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

FIG. 2 is a sectional view taken along line XX of the piezoelectric transformer shown in FIG.

FIG. 3 is a sectional view of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a piezoelectric transformer according to a second embodiment of the present invention before forming a cavity.

FIG. 5 is a sectional view of a piezoelectric transformer according to a third embodiment of the present invention.

FIG. 6 is an external perspective view of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating a basic configuration of a general piezoelectric transformer.

[Explanation of reference numerals] 1 piezoelectric plate 2 input electrode 3 output electrode 6 lead wire 7 lead terminal 11 support member 12 cavity forming agent 13 exterior resin 14 cavity

Claims (3)

[Claims] 1. A piezoelectric plate having an input electrode and an output electrode formed thereon, and an external input / output terminal connected to the input electrode or the output electrode, wherein the entire surface of the piezoelectric plate is covered with an elastic support member. The piezoelectric transformer is characterized in that the support member is covered with an exterior resin, and the external terminals are pulled out from the exterior resin. 2. A support member having a piezoelectric plate on which an input electrode and an output electrode are formed and an external input / output terminal connected to the input electrode or the output electrode, wherein a part of the piezoelectric plate has elasticity. A piezoelectric transformer, wherein the piezoelectric plate is attached, the piezoelectric plate is covered with an exterior resin so as to separate the cavity and the support member, and the external terminals are pulled out from the exterior resin. 3. The piezoelectric transformer according to claim 2, wherein a supporting member having elasticity is attached to a position corresponding to a node point of the piezoelectric plate.