JP5420425B2 - Piezoelectric transformer - Google Patents

Description

  The present invention relates to a piezoelectric transformer that obtains a desired output voltage using mechanical vibration of a piezoelectric body.

  This type of piezoelectric transformer is used for a high-voltage power source such as an inverter for a backlight of a liquid crystal display. A piezoelectric transformer can generate a high voltage output from a relatively low voltage input. Specifically, the piezoelectric transformer contains a piezoelectric body (piezoelectric vibrator) in its case, and this piezoelectric body has a function of converting electrical energy into mechanical energy. That is, a primary electrode and a secondary electrode are formed on the piezoelectric body, and when an input voltage is applied to the primary electrode, the piezoelectric body generates mechanical vibration (resonance phenomenon), thereby causing the secondary electrode to A desired output voltage can be obtained in a transformed state.

Conventionally, when processing a piezoelectric transformer into the form of a mounted component, a method of absorbing mechanical vibration of a piezoelectric body by accommodating the piezoelectric body in a case body and supporting the piezoelectric body with an elastic body or the like inside is generally used. Is. For example, as a prior art in which a piezoelectric body is accommodated in a case body, a metal foil (metal film) is integrally formed on the surface of a soft elastic body, and the electrodes and terminals of the piezoelectric body are electrically connected by the metal foil, A structure that supports electrical connection with a soft elastic body is known (for example, see Japanese Patent Application Laid-Open No. 2006-49671: Patent Document 1).
JP 2006-49671 A

  However, when an extremely thin metal foil (metal film) formed on the surface of a soft elastic body as in the prior art is used as a conductor, the conductor is structurally fragile and has a long-term durability. I have anxiety.

  In addition, since the elastic modulus (Young's modulus) of the material is greatly different between the metal foil and the soft elastic body, even if the soft elastic body can sufficiently follow the vibration of the piezoelectric body with high elasticity, The metal foil integrally formed on the surface can hardly follow the vibration. In this case, the metal foil may be broken or peeled off on the surface of the soft elastic body, so that there is a problem that it is difficult to withstand long-term use.

  Furthermore, since the prior art integrally molds different materials “soft elastic body” and “metal” (plating treatment, sputtering, etc.), the molding requires a complicated processing technique. There is also a problem that processing costs increase.

  For this reason, in the technical field of piezoelectric transformers, one problem is that it can withstand long-term use and can be manufactured at a relatively low cost.

  The piezoelectric transformer of the present invention, a piezoelectric body having an electrode formed on the outer surface, a case body having a housing portion for housing the piezoelectric body, a terminal provided at the case body, at least a part of which is exposed in the housing portion, An elastic body installed in a compressed state between the electrodes and terminals of the piezoelectric body in the housing portion, and housed in the housing portion together with the elastic body in a state along at least two outer surfaces facing the compression direction of the elastic body Thus, a conductive member is provided that is crimped to the electrode and the terminal, respectively, and electrically connects the electrode and the terminal.

  According to the present invention, since the piezoelectric body is supported by the elastic body in the case body (housing portion), the mechanical vibration of the piezoelectric body can be absorbed by the elastic body. Furthermore, the elastic body not only supports the piezoelectric body, but also has a function of guiding the conductive member along the outer surface thereof, and causing the conductive member to be crimped to the electrode and the terminal of the piezoelectric body so as to conduct each other. .

  In this case, since the conductive member does not need to be integrally formed on the surface of the elastic body, the durability of the conductive member itself can be increased by appropriately selecting the material and dimensions as a single component. In addition, since the conductive member is firmly pressed against both the electrode and the terminal of the piezoelectric body by the repulsive force (repulsive force against compression) of the elastic body, even if the piezoelectric body vibrates, the elastic body and the electrode or terminal The conductive member does not fall out of the gap. Therefore, the piezoelectric transformer of the present invention can sufficiently withstand long-term use.

  In addition, according to the present invention, it is not necessary to integrally mold different materials such as an elastic body and a conductive member (for example, rubber and metal). Cost can be kept low.

  That is, it is preferable that the conductive member is separate from the elastic body and can be deformed alone. For example, if the conductive member is a highly flexible metal wire, gold thread wire, metal plate, etc., the conductive member may be freely deformed along the outer surface of the elastic body during assembly of the piezoelectric transformer. it can. And when accommodating a piezoelectric body in a case body (accommodating part), an electroconductive member is accommodated in a case body together by press-fitting an elastic body between the electrode and a terminal. At this time, since the elastic body is compressed between the electrode and the terminal, the conductive member can be strongly pressed against the electrode or the terminal by the repulsive force.

  As described above, according to the structure adopted by the present invention, the assembly work of the piezoelectric transformer becomes easy, which is suitable for complete automation using an automatic machine when producing the piezoelectric transformer. Therefore, the present invention has an industrial advantage that a product can be provided in a larger amount and at a lower cost.

  Moreover, it is preferable that an elastic body has a holding part holding a conductive member in order to prevent the conductive member from falling off at least two outer surfaces. If the elastic body has a holding portion, the conductive member can be held for a long time without using an adhesive or the like. Therefore, the durability and reliability of the piezoelectric transformer can be made more reliable.

  The piezoelectric transformer of the present invention has a simple structure, is easy to assemble, and can greatly contribute to a reduction in manufacturing cost.

FIG. 1 is an exploded perspective view showing a piezoelectric transformer according to an embodiment as components. 2 is a horizontal sectional view showing the piezoelectric transformer in a completed state (a sectional view taken along line II-II in FIG. 1). FIG. 3 is a partial cross-sectional view showing an enlarged installation site of the elastic block, FIG. 4 is a plan view showing the elastic block of the first example alone, FIG. 5 is a front view showing the elastic block of the first example alone; FIG. 6 is a front view of the elastic block of the second example, and FIG. 7 is a longitudinal sectional view of the elastic block of the second example.

Explanation of symbols

100 Piezoelectric transformer 102 Piezoelectric ceramics (piezoelectric material)
104 Resin case
104c, 104d, 104e, 104f Concave portion 105 Housing portion 106 Primary electrode (electrode)
108 Secondary electrode (electrode)
110, 112, 114 Terminal 116, 120 Elastic body block (elastic body)
117 Conductive wire (conductive member)

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a piezoelectric transformer 100 according to an embodiment in an exploded manner. FIG. 2 is a horizontal cross-sectional view (cross-sectional view taken along the line II-II in FIG. 1) showing the piezoelectric transformer 100 in a completed state. The piezoelectric transformer 100 of one embodiment is used for a high voltage power source such as an inverter for a backlight of a liquid crystal display, and can generate a high voltage output from a relatively low voltage input.

[Piezoelectric body]
As shown in FIG. 1, the piezoelectric transformer 100 mainly includes a piezoelectric ceramic (piezoelectric body) 102 and a resin case (case body) 104. The piezoelectric ceramic 102 is accommodated in a case 104, and an accommodating portion 105 for the piezoelectric ceramic 102 is formed in the case 104. When the piezoelectric transformer 100 is mounted on a circuit board (not shown), the upward direction in FIG. 1 corresponds to the bottom surface side of the resin case 104. That is, the piezoelectric transformer 100 is mounted with the bottom surface side of the resin case 104 facing the mounting surface of a circuit board (not shown).

  The piezoelectric ceramic 102 of the present embodiment is obtained by polarizing a piezoelectric vibrator such as lead zirconate titanate ceramic (PZT). The shape of the piezoelectric ceramic 102 is not particularly limited, but here, as an example, a substantially rectangular parallelepiped shape (flat plate shape) can be given.

〔electrode〕
Of the outer surfaces of the piezoelectric ceramic 102, primary electrodes 106 are respectively formed on both surfaces that are paired in the thickness direction. Although only one side is shown in FIG. 1, a similar primary electrode 106 is formed on the opposite side surface (see FIG. 2). In addition, a secondary electrode 108 is formed on one end of the outer surface of the piezoelectric ceramic 102 in the longitudinal direction. In the present embodiment, the secondary-side electrode 108 is formed only on one surface (one surface shown in FIG. 1) paired in the thickness direction of the piezoelectric ceramic 102.

  The primary electrode 106 and the secondary electrode 108 are formed on the outer surface of the piezoelectric ceramic 102 by screen printing using, for example, a metal paste. When viewed in the width direction of the piezoelectric ceramic 102, that is, in the direction substantially orthogonal to the longitudinal direction and the thickness direction described above, the lengths of the electrodes 106 and 108 are slightly shorter than the width of the piezoelectric ceramic 102. The primary electrode 106 has a length of about half of the total length (longitudinal direction) of the piezoelectric ceramic 102.

[Case body]
The resin case 104 has a case body 104b whose bottom surface is opened. Further, the resin case 104 has an inner wall 104a extending from the bottom surface side toward the upper surface side (located downward in FIG. 1). The resin case 104 has an accommodating portion 105 formed inside the inner wall 104a.

  Although not shown in the drawing, the opening of the resin case 104 is only on the bottom surface side, and the top surface thereof is closed. Further, these inner walls 104 a are slightly longer than the entire length of the piezoelectric ceramic 102. For this reason, the piezoelectric ceramics 102 can be accommodated in the case main body 104b, that is, in the accommodating portion 105, in a vertically placed posture (a state where the side end surface around the waist is set upside down).

  The resin case 104 is provided with recesses 104c, 104d, 104e, 104f at four locations in the case main body 104b. These four recesses 104c to 104f are formed so as to scrape (depress) the resin of the case body 104b with a certain width from the inner wall 104a toward the outside of the body 104b.

  Of the recesses 104c to 104f, the two recesses 104c and 104d are disposed on the primary electrode 106 side, and these are in a positional relationship facing each other with the piezoelectric ceramic 102 interposed therebetween in the main body 104b. The concave portions 104c and 104d have the same (symmetric) shape.

  The recesses 104c and 104d are formed at a node of mechanical vibration generated in the longitudinal direction of the piezoelectric ceramic 102 (position where the theoretical amplitude becomes zero). More specifically, the recesses 104c and 104d are provided at a position away from the front end portion in the longitudinal direction by λ / 4 with respect to the entire length (λ) of the piezoelectric ceramic 102.

  This is because the piezoelectric ceramic 102 of the present embodiment is driven by the voltage of its natural resonance frequency (λ wavelength), and the vibration nodes at that time are respectively from the front end portion and the rear end portion in the longitudinal direction. It is at a position separated by λ / 4. Here, the end where the primary electrode 106 is formed is referred to as “front” in the longitudinal direction, and the end where the secondary electrode 108 is formed is referred to as “rear”. At the same time, although it is smaller than the mechanical vibration generated in the longitudinal direction, mechanical vibration is also generated in the width direction and the thickness direction described above. The vibration node in the width direction is at a substantially central position between the upper end portion and the lower end portion, and the vibration node in the thickness direction is also at a substantially central position between the tip portion and the end portion. is there.

  On the other hand, the recesses 104e and 104f arranged close to the secondary electrode 108 are also in a positional relationship facing each other with the piezoelectric ceramic 102 interposed therebetween. Of these, the concave portion 104e located on the near side as viewed in FIG. 1 has a larger shape than the concave portion 104f located on the far side.

(Terminal)
The resin case 104 is provided with a total of three terminals 110, 112, and 114. Among these, the two terminals 110 and 112 are respectively disposed in the resin case 104 so as to face the primary electrode 106. On the other hand, the remaining terminals 114 are disposed in the resin case 104 so as to face the secondary electrode 108. The three terminals 110, 112, and 114 are inserted into the case main body 104 b from the upper surface side to the bottom surface side of the case 104. At this time, the side surfaces of the terminals 110, 112, and 114 are partially exposed in the corresponding recesses 104c, 104d, and 104e, and the tips of the terminals protrude from the bottom surface side.

  As shown in FIG. 2, on the inner wall 104a, the piezoelectric ceramic is located at a position (λ / 4 mechanical vibration node in the longitudinal direction) away from the rear end portion in the longitudinal direction of the piezoelectric ceramic 102 by λ / 4. Protruding ribs 104t for guiding 102 from both sides are formed. Then, for example, the piezoelectric ceramic 102 is bonded to the resin case 104 via the silicone adhesive 124 by filling the main body 104b with the silicone adhesive 124 so as to cover the rib 104t.

[Elastic body]
Thus, in the state where the piezoelectric ceramic 102 is accommodated in the case main body 104b, the elastic body block 116 is installed in each of the two recesses 104c and 104d that make a pair. In addition, another elastic body block 120 is installed in the recess 104e. An insulating rubber 122 is installed in the other concave portion 104f. The piezoelectric ceramic 102 is accommodated in the resin case 104 in a state of being floated from the upper surface side. At this time, the piezoelectric ceramic 102 is held by being sandwiched between the two elastic body blocks 116 and between the elastic body block 120 and the other insulating rubber 122. The elastic body blocks 116 and 120 are also made of an insulating rubber material (for example, silicone rubber) that is not particularly conductive.

  Each elastic body block 116 is disposed between the primary electrode 106 of the piezoelectric ceramic 102 and the terminals 110 and 112 in the resin case 104. In other words, one side end surface of the elastic body block 116 is in contact with the primary electrode 106, and the other side end surface is in contact with the terminal 110 or the terminal 112. At this time, the elastic body block 116 is fitted into the corresponding concave portions 104c and 104d, and is compressed (press-fitted) between the primary electrode 106 and the terminals 110 and 112.

  The elastic body block 120 is disposed between the secondary electrode 108 of the piezoelectric ceramic 102 and the terminal 114 in the resin case 104. Here, similarly, one side end face of the elastic body block 120 is in contact with the secondary electrode 108 and the other side end face is in contact with the terminal 114. At this time, the elastic body block 120 is fitted into the corresponding recess 104e and is compressed (press-fitted) between the secondary electrode 108 and the terminal 114.

  Thus, in this embodiment, since the elastic body block 120 is compressed between the secondary side electrode 108 and the terminal 114, the balance in the resin case 104 is considered and it is opposite to the secondary side electrode 108. It is preferable to arrange the insulating rubber 122 also on the side surface. That is, the insulating rubber 122 contributes to sandwiching the piezoelectric ceramic 102 between the elastic body block 120 in the case 104 and absorbing the mechanical vibration. Therefore, the insulating rubber 122 is also compressed (pressed) between the outer surface of the piezoelectric ceramic 102 and the inner wall 104a (recessed portion 104f) in the resin case 104.

[Conductive member]
A conductive wire 117 is wound around each of the elastic body blocks 116 and 120 along the outer surface. That is, the conductive wires 117 are separate from the elastic blocks 116 and 120, and are each a material (for example, a metal wire, a gold thread wire, etc.) that can be flexibly deformed individually. In the present embodiment, a wire-like one is taken as an example in the figure, but the conductive wire 117 may be a plate-like conductive member.

  FIG. 3 is a partial cross-sectional view showing an enlarged installation site of the elastic body blocks 116 and 120. Hereinafter, FIG. 3 will be added to FIGS. 1 and 2, and the electrical connection between the primary side electrode 106 and the secondary side electrode 108 and the terminals 110, 112, and 114 will be described.

[Connection between primary electrode and terminal]
First, the elastic body block 116 is U-shaped along two outer surfaces facing the primary electrode 106 and the terminals 110 and 112, and a lower outer surface (that is, a lower surface) positioned between the two outer surfaces. A conductive wire 117 is wound around the shape. When the elastic body block 116 is press-fitted in this state, the conductive wire 117 is applied to the primary electrode 106 and the terminals 110 and 112 by the repulsive force against the compression of the elastic body block 116 as shown in FIGS. Each is crimped. Thereby, in the resin case 104, the electrical connection of the two primary side electrodes 106 and each terminal 110,112 is implement | achieved.

[Connection between secondary electrode and terminal]
Next, the elastic body block 120 is U-shaped along the two outer surfaces facing the secondary electrode 108 and the terminal 114, and the lower outer surface (lower surface) located between the two outer surfaces. A conductive wire 117 is wound around the wire. When the elastic body block 120 is press-fitted in this state, the conductive wire 117 is applied to the secondary electrode 108 and the terminal 114 by the repulsive force against the compression of the elastic body block 120 as shown in FIGS. Each is crimped. Thereby, in the resin case 104, the electrical connection between the secondary electrode 108 and the terminal 114 is realized.

  Although the conductive wire 117 is shown in FIG. 1 with a surplus length, it is desirable that, for example, the surplus portion protruding from the resin case 104 is cut off after being pressed into the resin case 104. Thereby, it is possible to prevent an electrical connection with an irrelevant part when mounting on the circuit board.

  As described above, in the present embodiment, the primary electrode 106, the terminals 110 and 112, and the secondary electrode 108 using the conductive wire 117 by pressure bonding using the elastic force (repulsive force) of the elastic blocks 116 and 120. And the terminal 114 can be securely connected to each other. Even when the piezoelectric ceramics 102 vibrate mechanically when the piezoelectric transformer 100 is used, the conductive wire 117 is held by the strong pressure bonding, and therefore, durability can be exhibited over a long period of time.

[Holding part]
In addition to the above, in the present embodiment, it is possible to prevent the conductive wires 117 from falling off with respect to the elastic body blocks 116 and 120, and to more reliably hold them. Hereinafter, some examples will be described.

[First example]
4 is a plan view showing the elastic blocks 116 and 120 of the first example alone, and FIG. 5 is a front view thereof.

  As shown in FIGS. 4 and 5, the elastic body blocks 116 and 120 are formed with holding grooves 116a and 120a on the outer surfaces (both end surfaces and the lower surface) around which the conductive wire 117 is wound as described above. These holding grooves 116a and 120a have, for example, a semicircular cross section and are formed in a single line with an equal width.

  The holding grooves 116a and 120a reliably hold the conductive wire 117 in the recess, prevent the conductive wire 117 from being displaced in the press-fitted state of the elastic body blocks 116 and 120, and reliably prevent the drop. Can do. Thereby, the reliability as the piezoelectric transformer 100 can be improved, and durability over a long period of time can be improved.

[Second example]
Next, FIG. 6 is a front view of the elastic body blocks 116 and 120 of the second example, and FIG. 7 corresponds to a longitudinal sectional view (cross section VII-VII in FIG. 6).

  The front view shown in FIG. 6 is a view of the elastic body blocks 116 and 120 in the compression direction within the resin case 104. In the second example, holding holes 116b and 120b are formed through the elastic body blocks 116 and 120 in the compression direction. Further, the elastic body blocks 116 and 120 are formed with cut portions 116c and 120c that extend from the side surfaces to the holding holes 116b and 120b over the entire length of the holding holes 116b and 120b.

  Therefore, the conductive wire 117 can be easily inserted into the holding holes 116b and 120b through the side cut portions 116c and 120c. In this case, even if the conductive wire 117 is a highly flexible material, it can be easily inserted into the holding holes 116b and 120b, so that the workability can be improved accordingly.

  As shown in FIG. 7, even when the conductive wire 117 is inserted through the holding holes 116b and 120b, the conductive wire 117 is positioned along the both end surfaces as viewed in the compression direction. 117 can be securely crimped to the primary side electrode 106 and the terminals 110 and 112, or the secondary side electrode 108 and the terminal 114.

  Further, when the elastic blocks 116 and 120 are press-fitted into the resin case 104, if the conductive wires 117 are inserted into the holding holes 116b and 120b in advance, the positions of the conductive wires 117 may be shifted during the press-fitting operation. There is no. Thereby, each conductive wire 117 can be reliably crimped | bonded to the primary side electrode 106 and the terminals 110 and 112 or the secondary side electrode 108 and the terminal 114. FIG.

  As described above, in the present embodiment, since the elastic body blocks 116 and 120 and the conductive wire 117 are separate bodies, complicated processing such as integrally molding different materials is not required. Further, when the piezoelectric transformer 100 is assembled, it is only necessary to press-fit into the resin case 104 with the conductive wires 117 along the outer surfaces of the elastic body blocks 116 and 120. Therefore, workability is improved and automation is supported. Easy. Therefore, it is possible to reduce material processing costs and assembly costs, and to supply piezoelectric transformer products to the market in large quantities and at low cost.

  The present invention can be implemented with various modifications without being limited to the above-described embodiment. For example, in the first example shown in FIGS. 4 and 5, the holding grooves 116a and 120a are formed on the lower surface in addition to the both side surfaces of the elastic body blocks 116 and 120, but the holding grooves 116a and 120a are only on both side surfaces. It may be formed in only one of both side surfaces. Further, the cross-sectional shape, width dimension, length, and the like of the holding grooves 116a and 120a are particularly arbitrary, and may be appropriately modified in accordance with the shape of the conductive wire 117 or the like used.

  Further, in the second example shown in FIGS. 6 and 7, only one holding hole 116b, 120b is formed in the center of the elastic body block 116, 120, but the position and number of the holding holes 116b, 120b are particularly limited. There are no restrictions and it can be changed to any number and number.

  In the embodiment, the elastic body blocks 116 and 120 are arranged by forming the recesses 104c, 104d, and 104e in the resin case 104. However, the recesses 104c, 104d, and 104e do not have to be provided.

  In addition, the form of each member shown with illustration is a preferable example, and it goes without saying that these can be appropriately modified.

Claims (2)

A piezoelectric body having electrodes formed on the outer surface;
A case body having a housing portion for housing the piezoelectric body;
A terminal provided in the case body, at least a part of which is exposed in the housing portion;
An elastic body installed in a compressed state between the electrode of the piezoelectric body and the terminal in the housing portion;
The elastic body is housed in the housing portion together with the elastic body in a state along at least two outer surfaces facing the compression direction, so that the electrode and the terminal are bonded to each other. and a conductive member for conducting the,
The conductive member is
A piezoelectric transformer, which is separate from the elastic body and can be deformed alone. The piezoelectric transformer according to claim 1,
The elastic body is
A piezoelectric transformer comprising: a holding portion for holding the conductive member so as to prevent the conductive member from falling off from at least the two outer surfaces.

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