Terminal Device For Piezoelectric Ceramic Transformer

Abstract

A terminal device for a piezoelectric ceramic transformer of the plate-type consists of a rectangular ring made of rubber-elastic high-molecular material has two metallic members. The metallic members are mounted at opposite portions of the ring so as to contact respective input electrodes of the transformer when the terminal device is attached to the input section of the transformer. Input leads for the transformer will be connected to the respective metallic members serving as interconnection between the input electrodes and input leads. A terminal device for the output of the ceramic transformer is attached around the output section of the transformer so that the output can be taken out from any point of the output section.

Description

BACKGROUND OF THE INVENTION

This invention relates to a terminal device for a piezoelectric ceramic transformer and more particularly, to such a device which serves also as a support for the ceramic transformer.

In general, the piezoelectric ceramic transformer known in the art will be made by plating silver paste to form input electrodes on opposite surfaces in one-half portion of a plate-type ceramic and an output electrode on an end face in the other half portion, and by effecting polarization of the ceramic through application of a DC voltage in the thicknesswise direction to the input half section or the one-half portion and in the lengthwise direction to the output half section or the other half portion.

To operate the so constructed ceramic transformer, hitherto a system has been employed in which relatively bold wires are used as input leads and soldered directly to the input electrodes. The input section was supported by those bold wires and the output section was supported by a mica plate and the like.

In such conventional systems, there exist such disadvantages that, since the lead wires are soldered to the electrodes, the stripping off of the wires from the silver electrodes tends to occur due to vibration to thereby result in a fatal trouble or incomplete electrical connection, and the operating life of such a support may also be shortened.

Further, the soldering method has the defect that resonance frequency would deviate or output voltage decrease unless the soldering be done at a very due point or node point and with a proper amount of solder.

Therefore, it is an object of the present invention to provide a novel terminal device for a piezoelectric ceramic transformer.

It is another object of the present invention to provide a terminal device for the input electrodes of the ceramic transformer which serves also as a support thereof.

It is a related object of the present invention to provide an output terminal device for the ceramic transformer.

It is another related object of the present invention to provide a method of manufacturing and mounting a support to the ceramic transformer.

SUMMARY OF THE INVENTION

The present invention resides in a terminal device used for a piezoelectric ceramic transformer of the plate type which consists of a rectangular ring made of rubber-elastic high-molecular material such as neoprene.

According to the first feature of the present invention, the rectangular ring is provided with two metallic rectangular cylinders at opposite portions of the ring so that the cylinders contact the respective input electrodes of the transformer when the ring is attached to the transformer. In the second feature and aforesaid rectangular cylinders are replaced by metallic solid elements of the same dimension as that of the ring. In the third feature the aforesaid rectangular cylinders are replaced by members each of which consists of two discs and a tube connecting the discs at the ends of the tube and is secured to that portions of the ring so that one metallic disc faces and abuts against one input electrode, the other disc is on the external surface of the ring opposite to the one disc, and the tube is embedded in the ring material and connects at its both ends with the two discs.

The present invention resides further in a terminal device for the output of the ceramic transformer which is an electrically conductive and elastic rectangular ring and is attached around the output section of the transformer. By the use of this novel device the output of the transformer can be taken out from any points of the output section besides from the usual output end face.

The present invention provides further a method of manufacturing a support of the ceramic transformer and of mounting the same thereto which comprises the steps of setting a ceramic body in a metallic mold for molding supporting rings and injecting molten rubber material into the mold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a piezoelectric ceramic transformer with conventional supports and electrical connection;

FIG. 2 is a schematic view showing vibration modes of the ceramic transformer;

FIG. 3 is a perspective view of the first embodiment of the terminal device according to the present invention attached to the ceramic transformer;

FIG. 4 is a front view of the first embodiment shown in FIG. 3;

FIG. 5 is a partial side view of the first embodiment shown in FIG. 3;

FIG. 6 is a front view of the second embodiment in accordance with the present invention;

FIG. 7 is a perspective view of the third embodiment according to the present invention attached to the ceramic transformer;

FIG. 8 is a cross-sectional view of the third embodiment shown in FIG. 7;

FIG. 9 is a perspective view of a metal member included in the third embodiment shown in FIG. 7;

FIG. 10 is a cross-sectional view of a modification of the third embodiment shown in FIG. 7;

FIG. 11 is a cross-sectional view of another modification of the third embodiment shown in FIG. 7;

FIG. 12 is a graph showing an output voltage characteristic along the length of the ceramic transformer;

FIG. 13 is a perspective view of an embodiment of the output terminal device according to the present invention attached to the ceramic transformer; and

FIG. 14 is a perspective view of the ceramic transformer with attached thereto two supports manufactured in accordance with the present invention .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, in order to facilitate understanding of the present invention and of the superiority of the present invention over the prior art, reference will be taken to FIGS. 1 and 2 showing a conventional system and vibration state of a ceramic transformer.

A piezoelectric ceramic transformer (it will be abbreviated as "PCT") shown in FIG. 1 will be made by plating silver paste to provide input electrodes 1 and 2 on opposite surfaces in the left half portion, as viewed in FIG. 1, of a plate-type ceramic 3 and an output electrode 4 on an end face in the right half portion of the ceramic body 3, and by performing polarization of the ceramic through application of a DC voltage in the thicknesswise direction shown by arrow d.sub.1 to an input section or to the left half portion between points L.sub.0 and L.sub.1 and in the lengthwise direction shown by arrow d.sub.2 to an output section or to the right half portion between points L.sub.1 and L.sub.2 of the ceramic body 3.

So constructed piezoelectric ceramic transformer will generate a high AC output voltage across the output electrode 4 and one input electrode 1 or 2 in response to application of an AC voltage across the input electrodes from an AC source OSC through lead wires 5 and 5'. In case of the circuit connection shown in FIG. 1, the generated AC voltage is transferred in the form of a DC voltage to a load R.sub.L through a lead wire 8 and an output circuitry consisting of two diodes D.sub.1 and D.sub.2 forming a voltage doubler rectifier.

In operation, the piezoelectric ceramic transformer will preferably be driven into a fundamental mode longitudinal vibration or into a second higher harmonic mode longitudinal vibration. FIG. 2 shows schematically the magnitude of displacement in the longitudinal vibration where curve a illustrates the magnitude of displacement in the fundamental mode vibration and curve b illustrates that in the second higher harmonic mode vibration, the arrow depicted in this drawing indicating the direction of displacement. Small zones 7, 7' and 7" where the displacement is substantially null represent nodes of vibration in the fundamental or second higher harmonic mode vibration.

The ceramic transformer of the above structure will generate voltages higher than 10 kv. with application of a voltage of some 10 volts to the input section, so it is utilizable as a fly-back transformer for televisions, a high-voltage source for electronic copying machines and the like.

However, because the ceramic transformer vibrates intensively at frequency of 20 to 60 kHz. it is important to pay attention to mounting means for the ceramic body as well as to electrical connecting means for the input.

Hitherto the system has been employed in which, as shown in FIG. 1, relatively bold wires are used for the input lead wires 5 and 5' and they are soldered directly to the input electrodes 1 and 2. Through these bold wires 5 and 5' the input power is applied to the transformer and by the same the input section is supported. Further, to sustain and fix the transformer within a vacuum tube, for example, a mica plate 6 would be mounted to the output section.

In such a system, there exist the disadvantages such that, since the lead wires in the input section are soldered to the input electrodes, the stripping off of the lead wires from the silver electrodes tends to occur due to vibration to thereby result in a fatal trouble or incomplete electrical connection, and the operating life of such supporting means may also be shortened. Further, the soldering method of lead wires has the defect that the resonance frequency could deviate or the output voltage decrease unless the soldering be done at a due point or node point and with a proper amount of solder.

The present invention aims to overcome the foregoing drawbacks of the prior art, and will be explained hereinafter with reference to FIGS. 3 through 14.

FIG. 3 shows the first embodiment T.sub.1 of the input terminal device according to the present invention attached to the input section of the conventional piezoelectric ceramic transformer PCT.

Two rectangular rings 9 and 10 are made of rubber-elastic high-molecular material such as neoprene and both function as supports for the transformer PCT. The ring 10 has rectangular cylinders 11 and 11' made of conductive material or of metal plates, as shown in FIGS. 4 and 5, which are attached to opposite portions of the ring 10 so that, when the ring 10 is mounted around the input section, one cylinder 11 contacts the upper input electrode 1 and the other cylinder 11' contacts the lower input electrode 2, as viewed in FIG. 3. Thus, the two rectangular cylinders 11 and 11' can interconnect the input electrodes and the corresponding external input lead wires (5 and 5' shown in FIG. 1).

As shown exaggeratedly in FIG. 4, the rectangular conductive cylinders 11 and 11' are urged toward the ceramic body 3 by the elasticity of the body part of the ring 10 passing therethrough, so that the cylinders come into intimate contact with the input electrodes 1 and 2 plated on the opposite surfaces of the ceramic body 3, thus, complete electrical connection will result therebetween.

As a result of using the foregoing input terminal device T.sub.1, flexible thin wires can be used as the input lead wires 5 and 5' and can be connected to the rectangular conductive cylinders 11 and 11' by a conventional manner or soldering.

This input terminal device T.sub.1 can be modified so as to have more complete contacting and gripping properties by making the inner dimension of the ring 10 slightly smaller than the peripheral dimension of the ceramic body 3, or, as to prevent the ring 10 from dispositioning due to vibration of the working transformer from a proper location by forming gridlike slits on the inner contact surfaces of the cylinders 11 and 11'.

In the state shown in FIG. 3, the rectangular elastic ring 9 supports the output section of the transformer, so that connection of the output lead wire 8 (FIG. 1) with the output electrode 4 can be done in a conventional manner or through soldering.

FIG. 6 shows in cross section the second embodiment T.sub.2 of the input terminal device according to the present invention attached to the ceramic body 3. The appearance of this device T.sub.2 will be substantially the same as the view of the first embodiment T.sub.1 shown in FIG. 3.

As seen from FIG. 6, this terminal device T.sub.2 consists of two U-shaped side portions 10a and 10a' made of plastic or rubber and two metal portions 12 and 12' made of copper, for example, and is made in the form of a continuous rectangular ring like the ring 10 of the first embodiment shown in FIG. 4.

Thus, the second embodiment T.sub.2 will yield substantially the same advantages as that of the structure shown in FIGS. 3 through 5, and thin wires can be soldered to the solid metal portions 12 and 12'. Further, because the portions 12 and 12' are solid, their self-heating owing to input current will be reduced substantially.

FIGS. 7, 8 and 9 show the third embodiment T.sub.3 of the terminal device according to the present invention.

In this embodiment T.sub.3, the rectangular ring 10 made of material like that of the first and second embodiments has at its opposite portions two metallic contact members 21 and 21'. As shown in FIGS. 8 and 9, each of the contact members consists of two metal discs formed with a small central hole and a short metal tube connecting the two discs at its ends.

In the completed form, as shown in FIG. 8, the short tube is embedded in the ring material, and the two discs are leveled with the opposite surfaces (or outer and inner surfaces) of the ring 10 and connected at their center with the embedded tube. One disc inside the ring will contact the corresponding input electrode 1 or 2 and the other outer disc will be connected to one input lead wire.

Similarly to the first and second embodiments, the conductive members 21 and 21' of this device T.sub.3 are urged toward the input electrodes by the elastic rectangular ring 10, thus, the perfect electrical connection between the contact members and the input electrodes is achieved. The modifications in the first embodiment with respect to the rectangular ring 10 will also be applied to this third embodiment.

FIG. 10 shows one modification of the third embodiment shown in FIGS. 7 through 9.

In FIG. 10, the inner disc contacting the input electrode is enlarged in area. That is, the inner surface portion 22, 22' of the ring 10 including the inner disc is coated with metallic material. This coating may be prepared by mixing, for example, carbon powder with the ring material of that portion and by vulcanizing the same so that the inner surface portion is changed into conductive.

Thus, the structure shown in FIG. 10 will result in a good electrical conduction of the contact member with the input electrode.

FIG. 11 shows another modification of the third embodiment shown in FIGS. 7 through 9.

In FIG. 11, the effective area of the other disc is enlarged in order to strengthen the urging force of the outer disc against the inner disc contacting the input electrode. This urging force will be transferred to the inner disc through the ring material interposed therebetween, or whereby the elastic ring will cause the inner disc to come into more intimate contact with the corresponding input electrode.

This enlargement of the effective area of the outer disc will be achieved by securing a larger metal plate 23, 23' to the outer disc, or by attaching a bold lead 23, 23' wire to the outer disc so as to run along the outer surface of the rectangular ring 10.

As will be apparent from the foregoing description with respect to the first, second and third embodiments and their modified structures illustrated in FIGS. 3 through 11, the input terminal devices according to the present invention includes the elastic rectangular ring and two metallic contact members urged by the elastic ring as to come into intimate contact with the respective input electrodes of the ceramic transformer, thus, the input lead wire can be connected directly to a portion of the member remote from the other portion contacting the input electrode, or there is no need of soldering the input lead directly to the input electrode.

Therefore, the present input terminal device does not cause stripping off and wearing down of the silver input electrodes under vibration, and there rises no disposition or shifting of the supporting position by the use of the elastic ring.

In the prior art, the output of the piezoelectric ceramic transformer was taken out from the output electrode 4 located at the end face of the transformer as shown in FIG. 1. However, the ceramic transformer has generally the output voltage distribution characteristic shown diagrammatically in FIG. 12. That is, the magnitude of the generated voltage is substantially constant on the surface between points L.sub.0 and L.sub.1 or in the input section, and increases as measurement is effected from point L.sub.1 to point L.sub.2, then it takes the maximum value at the end point L.sub.2 or the output end of the conventional system.

Therefore, the present invention proposes the provision of possibility for drawing out the output from any points on the surface of the output section other than the output end, by the use of an electrically conductive ring made of high-molecular material which hardly suppresses vibration of the ceramic body.

FIG. 13 shows one embodiment of the output taking-out system according to the present invention. A ring body 20 made of high-molecular material and having electrical conductivity is mounted around the output section of the transformer at any appropriate point between points L.sub.1 and L.sub.2. The output will be transferred to a load R.sub.L ' through a lead wire 5b connected to a portion of the conductive ring body 20. This ring body 20 is elastic, so it does not suppress vibration really, thus, the voltage generation characteristic deteriorates little. Further, the present system does not require the process of attaching an electrode to the output section surface by a conductive adhesive, for example, so that taking-out of the output is very easily achieved with reliable output lead connection.

As was explained with reference to FIG. 2, the piezoelectric ceramic transformer has one or more nodes of vibration depending upon the vibration mode.

In general, if the transformer is not supported at its node points of vibration or at areas within .+-.0.5 mm. from the node point, any supporting means tend to damp the vibration or may displace from the initial set point due to vibration whereby the voltage step-up characteristic deteriorates.

In this connection, the present invention provides a novel method of manufacturing a support for the ceramic transformer and, at the same time, of mounting the same to the node point.

FIG. 14 shows in perspective the ceramic transformer PCT with the completed supports 30 and 30' manufactured and mounted in accordance with the present invention.

First, the conventional piezoelectric ceramic transformer is prepared having the input electrodes 1 and 2 and the output electrodes 4 formed by plating silver paste on appropriate surface portions of the ceramic body 3. Then, this transformer is set in a metallic mold (not shown) for molding supports 30, 30', and molten rubberlike material is poured into the mold. While applying pressure the molten material is cooled, whereby the support rings 30, 30' are formed and secured around desired node areas of the ceramic body. In the above operation, because the positions where recesses for molding supports are formed correspond exactly to the node points, there is no need of operation to adjust the positions of the formed supports 30 and 30'.

In the present invention, rubberlike material is used as material of the support, that can be molded at relatively low temperatures (about 150.degree. C.), so that deterioration in characteristic of the ceramic transformer due to temperature rise during a support forming operation can be avoided, and there appears no lowering of voltage step-up ratio and power efficiency of the transformer through a support forming the manufacturing 8c installing operation. high-molecular

Further, because the support is assuredly secured at the node point around the ceramic body while cooling, it does not disposition or displace even if a mechanical shock is subjected thereto. It will also be apparent that the manufacturing and mounting processes are very simple and the present method is very effective on the property of the ceramic transformer and the manufacturing cost thereof.

Claims

What is claimed is:

1. A terminal device for a piezoelectric ceramic transformer comprising a rectangular ring (10) made of rubber-elastic high-molecular material the inner peripheral dimension of which corresponds substantially to the outer peripheral dimension of the transformer, said ring having attached thereto at its opposite portions two rectangular cylinders (11, 11') made of metal so that when said ring is mounted around an input section of the transformer said metal cylinders contact respective input electrodes of the transformer, wherein said ring urges said metal cylinders so as to make them intimately contact the respective input electrodes.

2. A terminal device for a piezoelectric ceramic transformer as specified in claim 1 wherein said ring is made of neoprene.

3. A terminal device for a piezoelectric ceramic transformer as specified in claim 1 wherein the inner peripheral dimension of said ring is made slightly smaller than the outer peripheral dimension of the transformer.

4. A terminal device for a piezoelectric ceramic transformer as specified in claim 1 wherein gridlike slits are formed on the surface portions of said metal cylinders, whereby they come into stable contact with the input electrodes of the transformer.

5. A terminal device for a piezoelectric ceramic transformer consisting of two generally U-shaped portions (10a, 10a') and two metal portions (12, 12') and forming a continuous rectangular ring, the inner peripheral dimension of said ring corresponding substantially to the outer peripheral dimension of the transformer, wherein said metal portions are coupled to said generally U-shaped portions such that, when said ring is mounted around an input section of the transformer, said metal portions come into contact with respective input electrodes of the transformer, said generally U-shaped portions being made of rubberlike elastic high-molecular material.

6. A terminal device for a piezoelectric ceramic transformer as specified in claim 5 wherein the inner peripheral dimension of said ring is made slightly smaller than the outer peripheral dimension of the transformer.

7. A terminal device for a piezoelectric ceramic transformer as specified in claim 5 wherein gridlike slits are formed on the surface portions of said metal portions which come into stable contact with the input electrode of the transformer.

8. A terminal device for a piezoelectric ceramic transformer comprising a rectangular ring (10) made of rubberlike high-molecular material the inner peripheral dimension of which corresponds substantially to the outer peripheral dimension of the transformer, said ring having secured thereto at its opposite portions two metal contact members (21, 21'), each of said contact members consisting of two discs and a short tube connecting at its ends said two discs, wherein said tube is embedded in said ring, and said two discs are positioned on opposite surface portions of said ring and connected at their centers to said embedded tube so that, when said ring is mounted around an input section of said transformer, the inner discs of said respective contact members come into contact with the respective input electrodes of the transformer, whereby input lead wires can be connected to the outer discs of said metal contact members.

9. A terminal device for a piezoelectric ceramic transformer as specified in claim 8 wherein the inner discs of said contact members are enlarged respectively in effective contact area.

10. A terminal device for a piezoelectric ceramic transformer as specified in claim 8 wherein the outer discs of said contact members are enlarged respectively in effective area so as to strengthen urging force effecting on the inner discs.

11. A terminal device for a piezoelectric ceramic transformer as specified in claim 8 wherein the inner peripheral dimension of said ring is made slightly smaller than the outer peripheral dimension of the transformer.

12. A terminal device for a piezoelectric ceramic transformer as specified in claim 8 wherein gridlike slits are formed on the surface portions of the inner metal discs of said respective contact members.

13. A method of taking out an output of a piezoelectric ceramic transformer from any desired surface points of an output section of the transformer comprising the step of providing a rectangular ring made of electrically conductive high-molecular material on any desired surface point of the output section of the transformer, wherein output lead wires are led from said rectangular ring and one of the input electrodes of the transformer.