JP5250249B2 - Piezoelectric transformer - Google Patents

Description

  The present invention relates to a piezoelectric transformer used in a power supply circuit of electronic equipment, for example.

  Conventionally, when the ambient temperature of piezoelectric ceramics used in piezoelectric transformers changes, the so-called pyroelectric effect works, and electric charges are generated in the direction opposite to the polarization direction between the primary side electrodes, or discharge is likely to occur. The problem is known. As a countermeasure against this pyroelectricity, a prior art is known in which an impedance having a magnitude equal to or larger than the impedance value between the drive unit electrodes is connected in parallel between the primary terminals of the piezoelectric transformer (for example, see Patent Document 1).

Conventionally, in order to improve the reliability with respect to a rapid temperature change of a thinned piezoelectric element, there is also known a prior art for short-circuiting between input electrodes (primary electrodes) of a piezoelectric element with a conductive paste (for example, (See Patent Document 2). In this prior art, when the device characteristics are improved by making the piezoelectric element thin, the heat resistance (pyroelectric durability) of the piezoelectric element is reduced accordingly. Short-circuit with paste.
Japanese Unexamined Patent Publication No. 2000-307166 (FIG. 3) Japanese Patent Laid-Open No. 11-330578 (FIG. 8)

  The technique of the prior art (Patent Document 1) listed first pays attention to the change in ambient temperature when the piezoelectric transformer is driven, and takes measures against the pyroelectric effect generated at that time. That is, the pyroelectric countermeasure impedance (resistance) is connected between the primary electrodes in a state of being incorporated in a circuit on the substrate separately from the piezoelectric transformer.

  However, the pyroelectric effect does not occur only when the piezoelectric transformer is driven. That is, when the piezoelectric transformer is mounted on the circuit board by reflow or flow technology, a pyroelectric effect is generated in the piezoelectric body by heat during soldering. In this regard, the countermeasure of the prior art (Patent Document 1) is not useful unless the piezoelectric transformer is already mounted on the circuit board, and does not serve as a countermeasure for pyroelectricity in the soldering process.

  On the other hand, in the technique of the prior art (Patent Document 2) listed later, when packaging a piezoelectric element as a mounting part in a resin case or the like, a conductive paste is applied to the piezoelectric element in advance and cured (or dried). It takes time and effort to ensure that it is firmly established. Furthermore, it is necessary to package the piezoelectric element after testing reliable conduction by the conductive paste, and there is a problem that the manufacturing process is complicated accordingly.

  Accordingly, the present invention is intended to provide a piezoelectric transformer that can take effective pyroelectric countermeasures in the process of mounting the piezoelectric transformer and can simplify the manufacturing process.

The piezoelectric transformer of the present invention includes a piezoelectric body in which primary electrodes having different polarities are formed in at least two places, a case body that accommodates the piezoelectric body, and two primary side electrodes of the piezoelectric body provided in the case body. At least two primary terminals connected to each other, and a conductive member connecting the two primary terminals to each other , the two primary terminals projecting from the case body, and the conductive member is This is a structure in which the base end positions of the portions where the two primary terminals protrude from the case body are connected.

  For this reason, in this invention, the aptitude as a mounting component is covered by employ | adopting the structure which accommodated the piezoelectric material in the case body. Also, the terminal (primary side terminal) provided on the case body bears connection with a wiring pattern or the like when mounted on a circuit board or the like, and at least two primary side electrodes of the piezoelectric body are respectively primary side terminals. It is connected to the circuit board via. Note that the case body may be provided with a secondary side terminal in addition to the primary side terminal.

  In addition, the piezoelectric transformer of the present invention solves the above problem by connecting two primary terminals to each other by a conductive member, instead of providing any conductor directly on the piezoelectric body. That is, by connecting the primary side terminals with a conductive member, even if a pyroelectric effect occurs in the piezoelectric body due to a temperature change at the time of mounting, for example, the polarity of the piezoelectric body through the primary side terminal and the conductive member Since the primary electrodes at two different locations are electrically connected to each other, the generated charge can be immediately extinguished (or the charge itself does not accumulate). As a result, it is possible to reliably prevent polarization deterioration due to the pyroelectric effect during mounting, discharge to the periphery of the circuit, and the like.

  Further, since the conductive member only needs to be crimped to the primary side terminal, no special work process (for example, thermosetting or drying) is required. Furthermore, if a conductive member connects primary side terminals, there will be no restriction | limiting in particular in a form. Therefore, the degree of freedom in design and manufacturing can be increased accordingly. In addition, it is not necessary to attach the conductive member directly to the piezoelectric body during the manufacturing process of the piezoelectric transformer, and the conductive member can be accommodated at any timing during the accommodation before the piezoelectric body is accommodated in the case body. Since it may be attached, the manufacturing process is not restricted or inadvertently complicated.

  In addition, when the two primary side terminals protrude and extend from the case body, it is desirable that the conductive member is in a form of connecting the base end positions of the portions where the two primary side terminals protrude from the case body.

  With such a configuration, it becomes easy to use a portion (tip portion) other than the base end position of the primary side terminal when mounted on the circuit board, and the usefulness as a mounting component can be improved accordingly.

  Further, the conductive member may be held in a state where the two primary terminals are inserted. In this case, it is not necessary to connect the primary side terminals after fixing the conductive member to the case body or the piezoelectric body, and the primary side terminals are directly held while holding the conductive member simply by inserting the primary side terminals. Can be connected, so that the installation work becomes easier.

  In the present invention, the conductive member only needs to have an impedance characteristic higher than the input impedance of the piezoelectric body. Thereby, when the piezoelectric transformer is driven, the conductive member is not subjected to a substantial partial pressure, and the performance as the piezoelectric transformer can be sufficiently exhibited.

  The piezoelectric transformer of the present invention can suppress the pyroelectric phenomenon of the piezoelectric body due to a temperature change during mounting, and does not deteriorate the characteristics of the piezoelectric transformer due to the pyroelectric effect. In addition, the manufacturing process of the piezoelectric transformer is not inadvertently complicated, which can contribute to the improvement of productivity.

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

  FIG. 1 is a perspective view showing a piezoelectric transformer 10 according to an embodiment in an exploded manner. The piezoelectric transformer 10 has a structure in which, for example, a plate-like piezoelectric ceramic 12 is housed in a resin case body 14 and assembled, and mounted on a circuit board (not shown), for example, with the orientation shown in FIG. It is. Here, although the form of insertion mounting is assumed, the piezoelectric transformer 10 may be surface mounted.

  Primary electrodes 12 a are formed at two locations on the outer surface of the piezoelectric ceramic 12. Although only one place is shown in FIG. 1, the primary electrode 12a is also formed on the surface opposite to the illustrated outer surface, and these have different polarities. The piezoelectric ceramic 12 has a secondary electrode 12b formed at the end opposite to the primary electrode 12a in the longitudinal direction. When the piezoelectric ceramic 12 is viewed in the longitudinal direction, the portion where the primary electrode 12a is formed functions as a drive unit. Moreover, the part in which the primary side electrode 12a is not formed functions as a power generation part.

  The case body 14 has an outer shape larger than that of the piezoelectric ceramic 12, and a concave accommodating portion 14b is formed therein. In the state shown in FIG. 1 (upside down state), the case body 14 has an open upper surface, and the accommodating portion 14 b extends from the opening toward the inside of the case body 14. The accommodating portion 14b has a shape that is slightly larger than the piezoelectric ceramic 12, and therefore, the piezoelectric ceramic 12 is accommodated in the accommodating portion 14b so as to be inserted from the opening in a posture in which the piezoelectric ceramic 12 is stood up as shown in the drawing. be able to.

  The case body 14 is integrally formed with projecting portions 14a on both side surfaces thereof, and the projecting portions 14a project from the side surfaces of the case body 14 to the side with a certain thickness. A primary terminal 18 is inserted through each protrusion 14a. Each protrusion 14a is formed with an insertion hole (not shown) for the primary terminal 18, and this insertion hole extends through the inside of each protrusion 14a in the vertical direction. These two primary terminals 18 protrude upward from the upper surface of the case body 14 in the state shown in FIG.

  The case body 14 is provided with a secondary terminal 20 at one end opposite to the primary terminal 18 when viewed in the longitudinal direction. The secondary terminal 20 also protrudes upward from the upper surface of the case body 14 in the state shown in FIG. The primary side terminal 18 and the secondary side terminal 20 are both conductive and solid rods (so-called lead pins).

  One end of a conductive wire 16 (for example, a gold thread wire) is soldered to each of the two primary side electrodes 12a of the piezoelectric ceramic 12 at a substantially central position. One end of a conductive wire 16 (also a gold thread wire) is soldered to the secondary electrode 12b. Then, with the piezoelectric ceramic 12 housed in the case body 14, the other end of each conductive wire 16 is soldered in a state of being entangled with the primary side terminal 18 or the secondary side terminal 20. Yes. As a result, the two primary side electrodes 12 a are connected to the primary side terminal 18, and the secondary side electrode 12 b is connected to the secondary side terminal 20.

  The piezoelectric ceramic 12 is bonded and held by, for example, a silicone adhesive (not shown) or the like in a state of being stored in the case body 14 (in the storage portion 14b). The case body 14 has, for example, two recesses 14c formed at the edge of the opening adjacent to the pair of protrusions 14a on both sides, and is filled (or coated) with silicone adhesive at the positions of these recesses 14c. It has become. The silicone adhesive adheres and holds the piezoelectric ceramic 12 to the case body 14 and exhibits moderate elasticity even after fixing (drying). For this reason, the piezoelectric ceramic 12 can freely vibrate inside the case body 14 during driving, and the vibration is absorbed by the elasticity of the silicone adhesive.

  The piezoelectric transformer 10 is configured such that two primary terminals 18 are connected to each other by a conductive member 24 in a completed state. The conductive member 24 is, for example, a conductor such as a conductive rubber sheet or a resistance resin, and the electrical characteristics of the conductive member 24 are higher than the input impedance of the piezoelectric ceramic 12 (for example, several MΩ to several GΩ at the maximum). If it is.

  In the present embodiment, the conductive member 24 is a rectangular sheet-like conductor, and two through holes 24 a are formed in advance in the conductive member 24 at positions corresponding to the two primary terminals 18. For this reason, the electroconductive member 24 can be easily attached only by inserting the primary side terminal 18 in the two insertion holes 24a. Further, at this time, the conductive member 24 is firmly pressed against the primary side terminal 18 at the inner edge of the insertion hole 24a, so that electrical conduction can be ensured.

  FIG. 2 is a perspective view showing an assembled state of the piezoelectric transformer 10. As described above, the piezoelectric ceramic 12 is accommodated in the case body 14 (accommodating portion 14b), and this is adhered with a silicone adhesive, and the conductive wires 16 are respectively entangled with the corresponding primary side terminals 18 and secondary side terminals 20, respectively. Solder in a brazed state. In this embodiment, the primary side terminal 18 can be inserted and attached to the conductive member 24 thereafter. Since the conductive member 24 is simply inserted through the primary side terminal 18 and thereafter is held by frictional force, the assembly is completed without using any adhesive or the like. If the arrangement of the conductive member 24 does not hinder the insertion of the piezoelectric ceramic 12, the piezoelectric ceramic 12 may be inserted into the case body 14 after the conductive member 24 is attached. These may be performed in parallel.

  The piezoelectric transformer 10 shown in FIG. 2 can be mounted on a circuit board (not shown) with the top and bottom inverted as described above. At this time, since the conductive member 24 has a thin sheet shape, the conductive member 24 does not become an obstacle particularly when the piezoelectric transformer 10 is mounted, and the mounting operation can be easily performed. In the example shown in FIGS. 1 and 2, the conductive member 24 protrudes laterally from the case body 14, but the conductive member 24 is reduced in size as a whole and within the range of the mounting area including the protruding portion 14 a. You may make it fit.

  When the piezoelectric transformer 10 of this embodiment passes a solder flow tank or a reflow device, for example, even if a pyroelectric effect occurs in the piezoelectric ceramic 12 due to the temperature change, the primary terminals 18 are electrically conductive. Since they are connected by the member 24, the charges cancel each other between the primary electrodes 12a having different polarities, and the charges can be immediately lost (or no charges are accumulated). Therefore, an excessive charge is not applied to other electronic components on the circuit board, and no discharge occurs around the piezoelectric transformer 10, so that the quality of the product can be continuously guaranteed even after the completion of the mounting operation. .

  The present invention can be implemented with various modifications without being limited to the above-described embodiments. For example, the shape of the piezoelectric ceramic 12 is not limited to the illustrated shape, and may be other shapes. Further, the shape of the case body 14 can be appropriately modified in accordance with the outer shape of the piezoelectric ceramic 12.

  In the embodiment, an example in which the insertion hole 24a is formed in advance in the conductive member 24 is described, but it is not necessary to provide the insertion hole 24a in particular. In this case, the primary side terminal 18 can be inserted into the conductive member 24 so as to be pierced and firmly bonded to each other. Further, the size and shape of the conductive member 24 are merely examples, and the form can be appropriately modified.

  When the primary side terminal 18 protrudes to the opposite side of the case body 14 (downward in FIGS. 1 and 2), the conductive member 24 may be attached to the opposite side of the primary side terminal 18.

  In addition, the structure given with illustration in the embodiment is only a preferable example, 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 the perspective view which decomposed | disassembled and showed the piezoelectric transformer of one Embodiment to the component. It is a perspective view which shows the assembly state of the piezoelectric transformer of one Embodiment.

Explanation of symbols

10 Piezoelectric transformer 12 Piezoelectric ceramics (piezoelectric material)
12a Primary side electrode 14 Case body 18 Primary side terminal 20 Secondary side terminal 24 Conductive member

Claims (3)

A piezoelectric body in which primary electrodes having different polarities are formed in at least two locations;
A case body for housing the piezoelectric body;
At least two primary-side terminals provided on the case body and respectively connected to two primary-side electrodes of the piezoelectric body;
A conductive member connecting the two primary side terminals to each other ;
The two primary terminals extend from the case body, and
2. The piezoelectric transformer according to claim 1, wherein the conductive member connects base positions of portions where the two primary side terminals protrude from the case body . The piezoelectric transformer according to claim 1 ,
The conductive member is
A piezoelectric transformer, wherein the piezoelectric transformer is held in a state where the two primary terminals are inserted. The piezoelectric transformer according to claim 1 or 2 ,
The piezoelectric transformer, wherein the conductive member has an impedance characteristic higher than an input impedance of the piezoelectric body.

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