JPH0779028A - Piezoelectric transformer - Google Patents

Abstract

PURPOSE:To provide a piezoelectric transformer which does not produce a short-circuit failure, etc., with other electronic components, can be manufactured with the small number of manufacturing processes, is suitable for an automatic production and is small in size as a whole and, further, with which a low profile and thin structure can be realized. CONSTITUTION:A piezoelectric ceramic element 1 is subjected to a polarization treatment in the thickness direction. A driving part 1A which has input electrodes on the surface and the rear of the element 1 and a generating part 1B which has an output electrode 13 on the longitudinal end of the element and lead electrodes 14 on the side surfaces of the node region N2 of a vibration are provided in the piezoelectric ceramic element l. The piezoelectric ceramic element 1 is housed in an insulating frame unit 2 which has metal lead terminals 21, 22, 23 and 24 and the respective electrodes provided on the node region of the vibration of the piezoelectric ceramic element 1 to the metal lead terminals electrically and mechanically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer for transforming an AC voltage in electronic equipment and the like.

[0002]

2. Description of the Related Art A piezoelectric transformer (1) has a simpler structure and can be miniaturized as compared with a wire-wound electromagnetic transformer.
(2) With respect to a short circuit accident on the output side, the input resistance automatically increases and there is no risk of burning. (3) A high boost ratio can be obtained. (4) There is no electromagnetic induction. It has advantages such as the above, and in recent years, development toward practical use is progressing.

As shown in FIG. 10, there is a Rosen type piezoelectric transformer as a typical piezoelectric transformer. The piezoelectric ceramic element 8 has a rectangular plate shape, and a half is formed on one side half 8A of the longitudinal main surface of the element. Direction pair of input electrodes 8
1, 82, and the other half 8B has an output electrode 83 formed on its end face. The former is polarized in the thickness direction and the latter is polarized in the longitudinal direction. Generally, a portion where the input electrode is formed in the thickness direction is called a drive portion, and the other half where the output electrode is formed is called a power generation portion. When an AC voltage is applied to this piezoelectric ceramic element with electrodes formed, longitudinal vibration is excited in the thickness direction in the drive section and vibration in the longitudinal direction in the power generation section. The vibration causes strong mechanical vibration having a vibration displacement as shown in FIG. Note that FIG. 12 is a diagram showing the nodal regions N1 and N2 of the vibration as viewed on a plane. As a result, a high AC voltage can be obtained by the piezoelectric effect at the output electrode of the power generation unit. Although the λ mode is shown as the vibration mode, λ /
It is known that resonance also occurs in the 2 mode and the 3 / 2λ mode, and the vibration displacement distribution and the nodal region of the vibration are different depending on these modes. In the case of the λ mode, conventionally, as shown in FIG. 10, this node region is provided with an elastic body 91 such as resin or rubber.
It was supported by 92, and metal wires A, B, and C were bonded to the respective electrodes for electrical input.

[0004]

However, in the above configuration, since the electrical connection is made by the metal wire, when this piezoelectric transformer is mounted on the printed wiring board, the occupied area becomes large as a whole, and the other electronic components are not occupied. Occasionally, a short circuit accident or a wire breakage accident occurred due to contact with parts. Also, in terms of manufacturing the piezoelectric transformer, since the support of the piezoelectric ceramic element or the metal wire is separately connected, there is a problem that the number of manufacturing steps increases and it is difficult to automate the manufacturing. Further, the conventional piezoelectric transformer has a large thickness because the support body is made of an elastic body, and thus it is difficult to reduce the height and the thickness.

The present invention has been made in order to solve the above-mentioned problems, does not cause a short circuit accident with other electronic parts, has a small number of manufacturing steps, is suitable for automation of manufacturing, and can be downsized as a whole. Another object of the present invention is to provide a piezoelectric transformer that can be reduced in height and can be made thin.

[0006]

In order to solve the above-mentioned problems, the piezoelectric transformer according to the present invention has, as shown in claim 1, a driving portion for one half of the main surface of the plate-shaped piezoelectric ceramic element. The other half is used as a power generation unit, the drive unit is polarized in the thickness direction, and input electrodes are formed on both front and back main surfaces, and the power generation unit is polarized in the direction from the input electrode to the end face of the power generation unit and output to this end face. In a piezoelectric transformer having electrodes and supporting vibration nodes, each of the input electrodes is extended to either side of a vibration node region on the input electrode side to form first and second extraction electrodes. A third lead electrode is formed by extending the output electrode to a vibration node region on the output electrode side of at least one side surface, and each lead electrode portion and a support body are electrically and mechanically connected to each other. Is characterized by.

As a specific example of the supporting structure, the second aspect of the invention is set forth in claim 2.
As shown in the section, one half of the main surface of the plate-shaped piezoelectric ceramic element that is driven in a vibration mode of λ mode or more is used as a drive section, and the other half is used as a power generation section. An input electrode is formed on a surface, each of the input electrodes is extended to either side surface of a vibration node region on the input electrode side to form first and second extraction electrodes, and the power generation unit is connected to the input terminal. The electrode is polarized in the direction from the electrode to the end face of the power generation unit, and the output electrode is formed on this end face, and the output electrode is extended to at least one side surface of the vibration node region on the output electrode side to form the third extraction electrode. It is characterized by comprising a piezoelectric ceramic element and an insulating frame body having a space for accommodating the piezoelectric ceramic element and having metal lead terminals penetratingly arranged to electrically and mechanically connect with each of the lead electrodes.
If necessary, cover plates may be provided above and below these insulating frames.

As described in claim 3, in the above support structure, a buffer mechanism may be provided on the metal lead terminal projecting into the insulating frame.

As described in claim 4, a connecting electrode connecting the output electrode and the extraction electrode may be formed on the side surface of the piezoelectric ceramic element.

[0010]

According to the first aspect of the present invention, the extraction electrode is formed by extending the input electrode and the output electrode in one of the node regions on the side surface of the piezoelectric ceramic element, and the extraction electrode and the support are connected to each other. Since they are electrically and mechanically connected, it is possible to obtain a piezoelectric transformer having an extremely simple structure without disturbing the vibration of the piezoelectric ceramic element.

According to the second aspect of the present invention, the piezoelectric ceramic element having the lead electrodes formed by extending the input electrodes and the output electrodes to any one of the side surfaces of the respective vibration node regions is penetrated through the metal lead terminals. It is installed in the arranged insulating frame body, and each lead electrode is electrically and mechanically connected to the metal lead terminal protruding into the frame body, so that the vibration of the piezoelectric ceramic element is not hindered and an extremely thin piezoelectric transformer is used. Obtainable.

According to the third aspect of the invention, since the protruding metal lead terminal in the insulating frame is provided with the buffer mechanism, even if some vibration leakage occurs in the supporting portion, the vibration of the piezoelectric ceramic element is externally transmitted. When the external impact occurs, the impact is alleviated and transmitted to the piezoelectric ceramic element.

According to the fourth aspect of the present invention, since the connecting electrode is formed on the side surface of the piezoelectric ceramic element, the total area of the connecting electrode can be small, and the vibration of the piezoelectric ceramic element is unlikely to be adversely affected.

[0014]

Embodiments of the present invention will be described with reference to the drawings. First Embodiment A first embodiment will be described taking a piezoelectric transformer vibrating in a λ mode as an example. 1 is a perspective view showing a first embodiment, FIG.
1 is a cross-sectional view taken along the line AA of FIG. 1, FIG. 3 is a perspective view showing a piezoelectric ceramic element, and FIG. 4 is a view showing a side electrode forming method.
The piezoelectric ceramic element 1 is cut into a rectangular plate shape. When the piezoelectric ceramic element 1 is divided into the drive portion 1A and the power generation portion 1B with the central portion in the longitudinal direction as a boundary and vibrates in the λ mode, vibration node regions N1 and N2 are formed. The drive portion 1A is polarized in the plate thickness direction, and the input electrodes 11 and 12 made of silver or the like are provided on the front and back main surfaces. From the input electrodes 11 and 12, the extraction electrode 1 is provided on the side surface of the vibration node region N1.
1a and 12a are pulled out. An output electrode 13 is provided at the longitudinal end of the power generation unit 1B, and a lead electrode 13a is provided on the side surface of the vibration node region N2, and is electrically connected to the output electrode 13 by a connecting electrode 14. . By forming the connecting electrode 14 on the side surface in this way, the total area of the connecting electrode can be small, and there is an effect that it is difficult to adversely affect the vibration of the piezoelectric ceramic element.
Further, the extraction electrode on the power generation section side may be provided on both side surfaces, but there may be no problem even on one side depending on the electrode connection configuration with the outside.

The electrode formation or polarization method of such a piezoelectric ceramic element can be performed more efficiently by the following method. ． Although not shown, an input electrode is formed on each of the front and back surfaces of one side of one main surface (driving section group) of a large rectangular plate-shaped ceramic wafer W, and almost the end surface of the other half of the main surface (power generation section group) is formed. An output electrode is formed on the entire surface. These electrodes may be formed by metallization using screen printing. ． The input electrodes on both the front and back sides formed above are short-circuited, and a high DC voltage (for example, 4 k) is applied between these input electrodes and output electrodes.
V / mm ² , 0.5 hours) is applied. As a result, it is polarized in the direction from the input electrode to the output electrode. ． Next, a high DC voltage is applied between the input electrodes under the same conditions as above, whereby the input electrodes are polarized in the thickness direction. The ceramic wafer that has been electrode-formed and polarized as described above is cut at predetermined intervals to obtain a plurality of piezoelectric ceramic elements having a pair of input electrodes and output electrodes. ． As shown in FIG. 4, a vapor deposition mask 5 having a window formed on a side surface of the piezoelectric ceramic element at a position corresponding to a node of vibration.
Are arranged above and below a plurality of polarized piezoelectric ceramic elements, and side electrodes are formed by a vacuum vapor deposition method. Window 51
Reference character a is for forming a side electrode on the input electrode side, and window 52a is for forming a side electrode and a connecting electrode on the output electrode side. The vapor-deposited metal adheres to the side surface of the piezoelectric ceramic element through this window. The windows 51b and 52b are provided in the lower vapor deposition mask. Although FIG. 4 shows an example in which three piezoelectric ceramic elements are arranged in parallel, usually, a large number of piezoelectric ceramic elements are arranged in a matrix to perform a batch process.

A specific example of supporting the piezoelectric ceramic element 1 will be described with reference to FIGS. The insulating frame body 2 is made of an insulating material such as resin, and has a frame portion 2a having an inner dimension larger than the outer dimension of the piezoelectric ceramic element 1, and the frame portion 2a.
Four metal lead terminals 2 which are arranged at a predetermined interval through the metal lead terminal 2
It consists of 1, 22, 23 and 24. These metal lead terminals are arranged at positions corresponding to the extraction electrodes formed on the piezoelectric ceramic element, and have mounting portions 21a and 22a (other mounting portions are not shown) for mounting the piezoelectric ceramic element in the frame. is doing. Such an insulating frame can be easily manufactured by a resin molding technique. Piezoelectric ceramic elements are installed on the mounting portions 21a and 22a in the frame of the insulating frame 2, and the mounting portion and each extraction electrode are bonded with a conductive bonding material (not shown). Then, if necessary, the upper cover plate 3 and the lower cover plate 4 made of resin or the like may be joined to the upper and lower sides of the frame body to perform hermetic sealing.

Second Embodiment The electrode structure of the piezoelectric ceramic element is not limited to the above-mentioned embodiment, and the connecting electrode 15 may be formed on the main surface as shown in the perspective view of FIG. 5, for example. In this case, the connection electrodes can be formed simultaneously with the formation of the input electrodes. The rest of the configuration is the same as that of the first embodiment, and the same applies to the following embodiments. It

Third Embodiment FIG. 6 is a perspective view showing a third embodiment, and FIG. 7 is a BB line in FIG.
FIG. In this embodiment, the extraction electrode 11a of the input electrode 11 on the front surface is extracted to a part of the back surface, and the extraction electrode 12a of the input electrode 12 on the back surface is extracted to a part of the front surface. With this configuration, even when there is little conductive bonding material,
Since the electrodes are drawn out to the respective opposite surfaces, the reliability of the electrical connection with the metal lead terminals is improved.

Fourth Embodiment FIG. 8 is a sectional view of a piezoelectric transformer showing a fourth embodiment. Lead terminals 25, 26 connected to the insulating frame 2
Inner leads 25a and 26a in the inner portion of the frame (other lead terminals are not shown) are bent and formed in the plate thickness direction of the lead terminals to form a buffer mechanism.

Fifth Embodiment A fifth embodiment will be described with reference to FIG. FIG. 9 is an exploded perspective view showing the shape of the inner lead of the metal lead terminal. A metal lead terminal 61 penetratingly arranged in the insulating frame 6;
The inner leads 62, 63, 64 have through holes 61a, 64a (other parts are not shown) formed at the bent portions to form a buffer mechanism. This buffer mechanism
In addition to the through holes, it is also possible to reduce the width of a part of the lead terminal or reduce the thickness thereof. In addition, notches 61b and 64b are provided on the mounting portion of the piezoelectric ceramic element.
(The other portions are not shown) are formed to facilitate the attachment of the conductive bonding material. Further, a notch is also provided on the outer lead side of the metal lead terminal, which facilitates attachment of the conductive bonding material at the time of external connection.

In the above embodiment, the λ mode having two nodal regions is shown as the vibration mode, but a mode having more vibration nodes (for example, 3/2 λ mode) can also be applied.

[0022]

According to the claims of the present invention, the following effects can be obtained. According to the first aspect of the present invention, the extraction electrodes are formed by extending the input electrode and the output electrode to one of the node regions on the side surface of the piezoelectric ceramic element, and the extraction electrodes and the support are electrically connected to each other. Since they are electrically connected, it is possible to obtain a piezoelectric transformer having an extremely simple structure without disturbing the vibration of the piezoelectric ceramic element. Therefore, unlike the conventional case, it is not necessary to make an electrical connection by a metal wire other than mechanical support, the area occupied by the piezoelectric transformer is not increased, and a short-circuit accident or disconnection accident with other electronic parts does not occur. It also contributes to the thinning of the piezoelectric transformer.

According to the second aspect of the present invention, the piezoelectric ceramic element in which each of the input electrodes and the output electrode is extended to any one of the side surfaces of the vibration nodal region to form the extraction electrode is passed through the metal lead terminal. It is installed in the insulating frame that has been placed, and since each lead electrode is electrically and mechanically connected to the metal lead terminal that protrudes into the frame, it does not hinder the vibration of the piezoelectric ceramic element and is extremely thin and occupies a large area. It is possible to obtain a small piezoelectric transformer. Further, it becomes easy to automate the manufacturing.

According to the third aspect of the present invention, since the protruding metal lead terminal in the insulating frame is provided with the shock absorbing mechanism, even if some vibration leakage occurs in the supporting portion, this vibration causes this shock absorbing mechanism. Since it is attenuated by, the electrical characteristics such as frequency do not change depending on the installation configuration of the piezoelectric transformer. On the contrary, even when an external impact occurs, the impact is alleviated and transmitted to the piezoelectric ceramic element, so that the impact resistance is improved.

According to the fourth aspect of the present invention, since the connecting electrode is formed on the side surface of the piezoelectric ceramic element, the distance between the connecting electrodes is short and the total area is small. Less likely to have an adverse effect.

[Brief description of drawings]

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

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view of a piezoelectric ceramic element used in the first embodiment.

FIG. 4 is a plan view showing a method of forming a side surface electrode.

FIG. 5 is a perspective view of a piezoelectric ceramic element showing a second embodiment.

FIG. 6 is a perspective view of a piezoelectric ceramic element showing a third embodiment.

7 is a sectional view taken along line BB of FIG.

FIG. 8 is a sectional view showing a fourth embodiment.

FIG. 9 is an exploded perspective view showing a fifth embodiment.

FIG. 10 is a perspective view showing a conventional example.

FIG. 11 is a diagram showing a vibration mode.

FIG. 12 is a diagram showing a node region of vibration.

[Explanation of symbols]

1, 8 Piezoelectric ceramic element 11, 12, 81, 82 Input electrode 13, 83 Output electrode 11a, 12a, 13a Extraction electrode 14, 15 Connection electrode 2, 6 Insulation frame body 21, 22, 23, 24 61, 62, 63 , 64 Metal lead terminals 3, 4 Cover plate 5 Evaporation mask N1, N2 Vibration node area

Claims (4)

[Claims] 1. A plate-shaped piezoelectric ceramic element having a driving part on one side of the main surface and a power generating part on the other side, and polarizing the driving part in the thickness direction and forming input electrodes on both front and back main surfaces, the power generating part. In a piezoelectric transformer that polarizes in the direction from the input electrode toward the end face of the power generation unit and forms an output electrode on this end face, and supports the nodes of vibration. The first and second extraction electrodes are formed by extending to one of the side surfaces, and the output electrode is formed by extending to a vibration node region on the output electrode side of at least one side surface to form a third extraction electrode. A piezoelectric transformer characterized in that each of the extraction electrode portions and the support are electrically and mechanically connected. 2. A plate-shaped piezoelectric ceramic element that is driven in a vibration mode of a λ mode or higher, one side of which is a driving portion and the other half is a power generating portion, and the driving portion is polarized in the thickness direction, and both front and back main surfaces are polarized. An input electrode is formed on each of the input electrodes, and each of the input electrodes is extended to either side of a vibration node region on the input electrode side to form first and second extraction electrodes. A piezoelectric element that is polarized in a direction from the end surface to the end surface of the power generation unit, forms an output electrode on the end surface, and extends the output electrode to at least one side surface of a node region of vibration on the output electrode side to form a third extraction electrode. A piezoelectric transformer comprising: a ceramic element; and an insulating frame having a space for accommodating the piezoelectric ceramic element and having metal lead terminals penetratingly arranged to electrically and mechanically connect to each of the lead electrodes. 3. The piezoelectric transformer according to claim 2, wherein a shock absorbing mechanism is provided on the metal lead terminal protruding into the insulating frame. 4. The piezoelectric transformer according to claim 1, wherein a connecting electrode connecting the output electrode and the extraction electrode is formed on a side surface of the piezoelectric ceramic element.