JP5576015B2 - Piezoelectric transformer - Google Patents

Description

  The present invention relates to a piezoelectric transformer having a structure in which piezoelectric ceramics and internal electrodes are alternately stacked.

As a prior art relating to this type of piezoelectric transformer, a piezoelectric transformer of a type in which piezoelectric ceramics and internal electrodes are laminated and each internal electrode is connected by an external electrode provided outside is known (for example, see Patent Document 1). ). In this prior art, the end portion of the internal electrode is exposed to the outer surface of the laminate and connected to the external electrode, but the inner end portion of the internal electrode is positioned so as not to be exposed from the external electrode. When a high voltage is applied, the electric field is prevented from concentrating on the inner end, and discharge is prevented from occurring from the inner end. As a result, desired polarization can be performed to improve the productivity of the piezoelectric transformer and also improve the reliability of the product.
JP 2006-156732 A (page 3, FIGS. 1 and 2)

  When this type of piezoelectric transformer is operated, for example, a desired electric circuit (driving circuit for a cold cathode tube for a backlight of a liquid crystal display, etc.) in a state where wiring is soldered to each external electrode on the primary side and the secondary side Connect. Then, an input voltage is applied to the primary-side external electrode, and electric power transformed using the mechanical vibration of the piezoelectric ceramic is taken out from the secondary-side external electrode and used in an electric circuit.

  However, in general, when a piezoelectric ceramic laminate is placed at a high temperature in the firing process or a high electric field is applied in the polarization process, the internal electrode exposed to the outer surface and the external electrode are in direct contact with each other. In this case, the metal component may move, and a phenomenon such as corrosion (Kirkendoll phenomenon) may occur. When such a phenomenon occurs, the soldering strength at the external electrode tends to decrease.

  Accordingly, the present invention intends to provide a technique for preventing a decrease in soldering strength with respect to an external electrode in a laminated type piezoelectric transformer.

  The present invention is a piezoelectric transformer in which piezoelectric ceramics and internal electrodes are alternately stacked to form a laminated body, and external electrodes are formed on the outer surface of the laminated body. In particular, in the present invention, the above-mentioned problems are solved by the internal electrode being not in contact with the external electrode without being exposed to the outer surface of the laminate, and being electrically connected to the external electrode through the polarization treatment of the piezoelectric ceramic. .

  As described above, in the present invention, the internal electrode and the external electrode are not brought into direct contact with each other, and the electrical connection is made while maintaining no contact on the structure. In other words, since the piezoelectric ceramic itself is a high dielectric, even if the internal electrode and the external electrode are not in direct contact, the electrical connection can be realized with respect to alternating current by performing the polarization treatment. Is possible. Thereby, the corrosion which arises in an external electrode (or internal electrode) can be prevented, and the fall of the soldering strength can be prevented reliably.

  Moreover, this invention may have the following independent structures. That is, the piezoelectric transformer according to the present invention includes a laminate formed by alternately stacking piezoelectric ceramics and internal electrodes, an external electrode formed on the outer surface along the stacking direction of the laminate, and an inside of the laminate. And a conducting portion that is secured between each internal electrode and the external electrode and electrically connects the internal electrode and the external electrode in a non-contact state through a polarization process of the piezoelectric ceramic.

  According to said structure, a conduction | electrical_connection part intervenes between an internal electrode and an external electrode inside a laminated body, and the direct contact with an internal electrode and an external electrode is prevented by this conduction | electrical_connection part. However, since the conducting portion is composed of a piezoelectric ceramic body, the internal electrode and the external electrode can be electrically connected with respect to alternating current through the polarization process. Thereby, the corrosion which arises in an external electrode (or internal electrode) can be prevented, and the fall of the soldering strength can be prevented reliably.

  The internal electrode and the external electrode are preferably used as secondary electrodes for outputting a voltage generated by piezoelectric ceramics. In this case, it is possible to adjust the capacity according to the load characteristics by forming the internal electrode on the secondary side, and the soldering strength of the external electrode on the secondary side that is higher than the primary side. For example, even when the piezoelectric transformer is operated by soldering the wiring to the secondary-side external electrode, the reliability as a product can be ensured for a long period of time.

  According to the present invention, direct contact between the internal electrode and the external electrode can be avoided, the occurrence of corrosion can be eliminated, and the soldering strength of the external electrode can be kept high. Thereby, the reliability and durability as a product can be greatly improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a perspective view showing a piezoelectric transformer 100 according to an embodiment. The piezoelectric transformer 100 includes a drive unit 100a on the primary side and a power generation unit 100b on the secondary side. The drive unit 100a and the power generation unit 100b are each configured by stacking a plurality of sheet-like piezoelectric ceramics 102. A film-like primary internal electrode 104 and secondary internal electrode 106 are provided between the piezoelectric ceramics 102. Among these, the primary side internal electrode 104 is arrange | positioned in the drive part 100a, and the secondary side internal electrode 106 is arrange | positioned in the one end part in the electric power generation part 100b. When viewed in the thickness direction of the piezoelectric transformer 100, the piezoelectric ceramics 102 and the internal electrodes 104 and 106 overlap each other, whereby a laminate 101 is formed.

  In the laminated body 101, a primary side external electrode 108 and a secondary side external electrode 110 are formed. Among these, the primary side external electrode 108 is provided on the outer end surface of the drive unit 100a, and the secondary side external electrode 110 is provided on the outer end surface of the power generation unit 100b. In FIG. 1, only the primary external electrode 108 on the near side is shown, but the primary external electrode 108 is also formed in a pair on the outer end surface on the heel side (not shown).

  FIG. 2 is a horizontal cross-sectional view (II-II cross section in FIG. 1) showing the individual (one by one) piezoelectric ceramics 102 constituting the laminated body 101. In the laminated body 101, the piezoelectric ceramics 102 respectively shown by (A) and (B) in FIG.

  The primary side internal electrodes 104 are alternately arranged in the width direction (direction orthogonal to the longitudinal direction) of the piezoelectric ceramics 102, and each primary side internal electrode 104 is exposed on one outer end face in the width direction. doing. Accordingly, each primary side internal electrode 104 is connected in direct contact with one of the pair of primary side external electrodes 108 on both sides in the width direction.

  The secondary side internal electrode 106 is formed at one end in the longitudinal direction on the surface of the piezoelectric ceramic 102. In particular, in the present embodiment, the secondary-side internal electrode 106 is not exposed to the outside from one end of the piezoelectric ceramic 102 (the outer end surface of the multilayer body 101), and the secondary-side internal electrode 106 is in the longitudinal direction of the piezoelectric ceramic 102. A gap (reference symbol C in the figure) is ensured between the first external electrode 110 and the secondary external electrode 110. Therefore, the secondary internal electrode 106 is not in contact with the secondary external electrode 110 due to its structure.

  3 is a longitudinal sectional view (III-III section in FIG. 1) of the secondary side portion of the piezoelectric transformer 100. FIG. The gap C is structurally configured so that the secondary side internal electrode 106 and the secondary side external electrode 110 are not in contact with each other, but the gap C is composed of an element body of the piezoelectric ceramic 102. , Itself has a high dielectric constant. Therefore, when the plurality of piezoelectric ceramics 102, the primary side internal electrodes 104, and the secondary side internal electrodes 106 are alternately stacked to form the laminated body 101, and the polarization process is performed, the gap C has a secondary side with respect to the alternating current. Since the electrical connection between the internal electrode 106 and the secondary external electrode 110 is performed, the gap C is configured as a conduction portion.

  Thus, in the first embodiment, since the secondary side internal electrode 106 and the secondary side external electrode 110 are configured in a non-contact state, even if the laminate 101 is fired or polarized, Corrosion does not occur in the secondary side internal electrode 106 and the secondary side external electrode 110. Therefore, when soldering a wiring or the like to the secondary side external electrode 110 (symbol S in the figure), it is possible to ensure the high soldering strength.

[Second Embodiment]
FIG. 4 is a diagram illustrating a second embodiment of the piezoelectric transformer 100. The second embodiment differs from the first embodiment in that the secondary-side internal electrode 106 is not rectangular but is U-shaped (C-shaped). Other configurations can be the same as those in the first embodiment.

  Also in the second embodiment, since the secondary side internal electrode 106 and the secondary side external electrode 110 are configured in a non-contact state, even if the laminate 101 is fired or polarized, the secondary side Corrosion does not occur in the side internal electrode 106 and the secondary side external electrode 110. Furthermore, in the second embodiment, since each secondary internal electrode 106 has a shape recessed inward, the amount of metal paste used is reduced in the recessed portion, so that the manufacturing cost of the entire product is reduced. Has the advantage of being kept low.

  The present invention can be implemented with various modifications without being limited to the above-described embodiments. For example, the shape of the secondary side internal electrode 106 is not limited to that exemplified in each embodiment, and various shapes can be appropriately employed.

  In addition, the structure shown with illustration in each embodiment is a preferable example to the last, and it can be said that the present invention can be suitably implemented even if various elements are added to the basic structure or a part thereof is replaced. Not too long.

It is a perspective view which shows the piezoelectric transformer of one Embodiment. It is a horizontal sectional view (II-II section in Drawing 1) showing each piezoelectric ceramic. It is a longitudinal cross-sectional view (III-III cross section in FIG. 1) in the secondary side part of a piezoelectric transformer. It is the figure which showed 2nd Embodiment of the piezoelectric transformer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Piezoelectric transformer 101 Laminated body 102 Piezoelectric ceramics 104 Primary side internal electrode 106 Secondary side internal electrode 108 Primary side external electrode 110 Secondary side external electrode C Crevice (conduction part)

Claims (3)

In a piezoelectric transformer in which piezoelectric ceramics and internal electrodes are alternately stacked to form a laminate, and external electrodes are formed on the outer surface of the laminate,
The piezoelectric transformer, wherein the internal electrode is not in contact with the external electrode without being exposed to the outer surface of the multilayer body, and is electrically connected to the external electrode with respect to alternating current in the multilayer body. A laminate formed by alternately stacking piezoelectric ceramics and internal electrodes;
External electrodes formed on the outer surface along the overlapping direction of the laminate,
A conduction part secured between the internal electrode and the external electrode in the laminated body, and electrically connecting the internal electrode and the external electrode with respect to alternating current in a non-contact state in the laminated body. And a piezoelectric transformer. The piezoelectric transformer according to claim 1 or 2,
The piezoelectric transformer, wherein the internal electrode and the external electrode are used as a secondary electrode for outputting a voltage generated by the piezoelectric ceramic.

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