JP2005082445A - Multilayer piezoelectric transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer piezoelectric transformer capable of preventing the degradation of piezoelectric transformer characteristics by adding Mn to a piezoelectric ceramic of the piezoelectric transformer. <P>SOLUTION: The multilayer piezoelectric transformer is formed by laminating and integrally sintering a plurality of piezoelectric ceramic layers. The transformer has a driving section equipped with a plurality of the piezoelectric ceramic layers polarized in the thickness direction and a plurality of internal electrodes laminated alternately and a pair of external input electrodes connected to the internal electrodes and an electric power generation section equipped with an output electrode and a piezoelectric ceramic polarized in the longitudinal direction. The piezoelectric ceramic layer is represented by the general formula: Pb<SB>a</SB>Zr<SB>x</SB>Ti<SB>y</SB>(Ni<SB>m</SB>Mn<SB>n</SB>Nb<SB>2/3</SB>)<SB>z</SB>O<SB>3</SB>[wherein 0.93≤a≤1.02, 0.32≤x≤0.50, 0.41≤y≤0.54, 0.03≤z≤0.21, 0.24≤m+n≤0.66 (except the case when m or n is 0), and x+y+z=1.00]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated piezoelectric transformer used for an inverter for backlight of a liquid crystal display, an inverter for lighting a fluorescent tube, and the like.

  2. Description of the Related Art Conventionally, in a small electronic device that requires a high voltage, such as a transistor TV or a fluorescent tube lighting inverter, a laminated piezoelectric transformer has been provided as a small power source for generating a high voltage.

  The piezoelectric transformer usually has a rectangular main body. The said main body is provided with the drive part and the electric power generation part installed adjacent to the said drive part in the longitudinal direction.

The power generation section is formed with a piezoelectric body polarized in the longitudinal direction and an output electrode formed on the end face in the longitudinal direction. In the drive unit, the internal electrodes and the piezoelectric ceramic layers are alternately stacked in the thickness direction of the main body, and a pair of external input electrodes connected to the internal electrodes facing each other are formed. ing.

  Such a drive unit has a rectangular laminated piezoelectric body in which piezoelectric ceramic green sheets formed with an internal electrode paste layer applied in the shape of the internal electrode are laminated and bonded together in the thickness direction thereof. It is obtained by firing.

As such a piezoelectric ceramic, for example, (Pb (Ni _1/3 Nb _2/3 ) O ₃ ) x (PbTiO ₃ ) _(yr) added with Mn in order to prevent deterioration of the insulation resistance due to temperature rise. Piezoelectric ceramics characterized by a four-component solid solution composition represented by (PbZrO ₃ ) _z (MnZrO ₃ ) _r (see Patent Document 1), Pb ((Ni _1/3 Nb _1/3 ) _a Ti _b Zr _c ) In the lead zirconate titanate-based composition represented by O ₃ , the insulation resistance is lowered by adding MnCO ₃ so that Mn is contained in an addition amount range of 0.01 to 0.5 [mol%]. Piezoelectric ceramics (see Patent Document 2) and the like characterized by suppressing the above have been proposed.
JP-A-8-91928 JP-A-11-157929

  The piezoelectric ceramic having the above composition has a problem that the Curie temperature is lowered by the addition of Mn and the piezoelectric transformer characteristics are deteriorated.

  Accordingly, an object of the present invention is to provide a multilayer piezoelectric transformer that prevents the deterioration of the piezoelectric transformer characteristics accompanying the decrease in Curie temperature as described above.

In order to achieve the above object, the multilayer piezoelectric transformer of the present invention is a multilayer piezoelectric transformer in which a plurality of piezoelectric ceramic layers are laminated and integrally sintered, and the multilayer piezoelectric transformer is arranged in the thickness direction. A drive unit having a pair of input external electrodes, in which a plurality of polarized piezoelectric ceramic layers and internal electrodes are alternately stacked and connected to the internal electrodes, and a longitudinally polarized piezoelectric ceramic and output electrodes are provided. has a power generating portion provided with the piezoelectric ceramic layers of the general formula: Pb _a Zr _x Ti _y is represented by _{(Ni m Mn n Nb 2/3)} z O 3, a, x, y, m, n and z are 0.93 ≦ a ≦ 1.02, 0.32 ≦ x ≦ 0.50, 0.41 ≦ y ≦ 0.54, 0.03 ≦ z ≦ 0.21, 0.24. ≦ m + n ≦ 0.66 (except when m or n is 0), x + y + z = 1. 00 is satisfied. Furthermore, in the piezoelectric ceramic layer, m and n satisfy 0.46 ≦ m + n ≦ 0.66.

  By using the multilayer piezoelectric transformer of the present invention, a piezoelectric transformer having good piezoelectric transformer characteristics such as maximum boost ratio and maximum efficiency can be obtained.

  Hereinafter, the manufacturing method of the multilayer piezoelectric transformer of the present invention will be described based on examples.

First, powders of Pb ₃ O ₄ , TiO ₂ , ZrO ₂ , NiO, Nb ₂ O ₅ , and MnCO ₃ were prepared as starting materials.

Next, the composition formula: in _{Pb a Zr x Ti y (Ni} m Mn n Nb 2/3) z O 3, were weighed powders of the so that the respective compositions shown in Table 1, wet mixed by a ball mill To obtain a mixed powder.

  Next, this mixed powder was dehydrated and dried, then calcined at a temperature of 820 ° C. for 2 hours and pulverized to obtain a calcined powder. Additives such as a binder and a plasticizer and a solvent were added to the obtained calcined powder and wet-mixed with a ball mill to obtain a slurry. This slurry was molded by a doctor blade method to produce a ceramic green sheet having a thickness of about 100 μm.

  On the obtained ceramic green sheet, a conductive paste having a silver / palladium conductor mainly composed of silver powder is screen-printed so that the internal electrode thickness after firing becomes 1.0 to 3.0 μm. The ceramic green sheet in which the internal electrode paste layer was formed was obtained by applying and drying. Thereafter, the ceramic green sheets were stacked and bonded by hot pressing to obtain a laminated body.

  Next, this laminate was cut to a predetermined size, the binder component was removed in advance at a temperature of about 500 ° C., and further fired at 1000 to 1100 ° C. for 2 hours.

  An external electrode was applied to the laminated fired body by a screen printing method and fired to form an input external electrode and an output electrode, thereby obtaining a laminated piezoelectric transformer.

  Next, in 60 ° C. insulating oil, the input side was polarized in the thickness direction, and the output side was polarized in the length direction. The polarization conditions at this time were a DC electric field of 4.0 kV / mm and an application time of 60 minutes. Thereafter, the film was aged in air at 120 to 200 ° C. for 30 to 60 minutes to obtain a target multilayer piezoelectric transformer as shown in FIGS. Here, FIG. 1 is a perspective view showing a laminated piezoelectric transformer of one embodiment according to the present invention. FIG. 2 is a cross-sectional view taken along line ab of the multilayer piezoelectric transformer shown in FIG. FIG. 3 is a cross-sectional view taken along line cd of the multilayer piezoelectric transformer shown in FIG. 1-3, 11 is a piezoelectric ceramic, 12 is an internal electrode, 13 is an input external electrode, 14 is an output electrode.

  The structure of the produced laminated piezoelectric transformer had a length of 30 mm, a width of 6 mm, a thickness of 1.72 mm, and a distance between electrodes of 240 μm.

  The piezoelectric transformer characteristics of these laminated piezoelectric transformers, specifically, the maximum step-up ratio and the maximum efficiency were obtained by the following methods. The results are shown in Table 1.

  In Table 1, those marked with * are outside the scope of the present invention, and others are within the scope of the present invention.

The maximum step-up ratio and the maximum efficiency were measured using a piezoelectric transformer characteristic measurement system as shown in FIG. Input voltage V _in and the input current I _in, and the output voltage V _out was measured by the power analyzer. The power source used was an AC power source with variable frequency. In FIG. 4, reference numeral 21 denotes an AC power source, and 22 denotes a laminated piezoelectric transformer. The resistors R1 and R2 are 1 kΩ and 100 kΩ, respectively.

The step-up ratio is indicated by the ratio between the input voltage V _in and the output voltage V _out , and the maximum step-up ratio is a value obtained using Equation 1. Incidentally, V _out was used becomes maximum value upon application of a constant voltage V _in at AC power source. The unit of the maximum boost ratio is dB.

The efficiency is indicated by the ratio of the input power and the output power, and the maximum efficiency is a value obtained using Equation 2. Incidentally, V _out was used becomes maximum value upon application of a constant voltage V _in at AC power source. The unit of maximum efficiency is%. cosφ indicates the power factor.
Maximum step-up ratio = 20 × log (V _out ÷ V _in × 101) Equation 1
Maximum efficiency = 101 × (V _out ) ² × 0.001 ÷ (V _in × I _in cos φ) Equation 2
The step-up ratio indicates the basic performance of the transformer, and the higher the step-up ratio, the higher the performance. The efficiency indicates the conversion efficiency of energy transmission from electricity → machine → electricity. The higher the efficiency, the lower the conversion loss with respect to the input power, which means that the power consumption can be reduced.

  From the results in Table 1, when a was less than 0.93 (sample numbers 1 and 7) or exceeded 1.02 (sample numbers 6 and 12), the maximum step-up ratio and the maximum efficiency were lowered. This is because the sinterability deteriorates in the above range.

  As above, when x is less than 0.32 or more than 0.50 (sample numbers 25 and 29), y is less than 0.41 or more than 0.54 (sample numbers 30 and 33), or z is Also in the case of less than 0.03 or exceeding 0.21 (sample numbers 34 and 37), the sinterability deteriorated, so that the maximum boost ratio and the maximum efficiency were lowered.

  In addition, it was confirmed that the maximum step-up ratio and the maximum efficiency were also reduced when m + n was less than 0.24 or more than 0.66 (sample numbers 13, 14, 18-20, and 24).

  On the other hand, when m + n is 0.24 ≦ m + n ≦ 0.66, the maximum efficiency is 94% or more, the maximum step-up ratio is 31 dB or more, and further, 0.46 ≦ m + n ≦ 0.66 is satisfied (sample) Nos. 2-5, 17, 23, 26-28, 31, 32, 35, 36) have a maximum efficiency of 95% and a maximum boost ratio of 32 dB or more.

  As described above, by using the laminated piezoelectric transformer of the present invention, it is possible to provide a piezoelectric transformer having high piezoelectric characteristics, specifically, a maximum step-up ratio and maximum efficiency.

1 is a perspective view showing a multilayer piezoelectric transformer according to an embodiment of the present invention. It is sectional drawing of the ab line | wire of the lamination type piezoelectric transformer shown in FIG. It is sectional drawing of the cd line | wire of the laminated piezoelectric transformer shown in FIG. It is a circuit diagram for measuring the piezoelectric transformer characteristics of the laminated piezoelectric transformer of one embodiment according to the present invention.

Explanation of symbols

10, 22 Multilayer piezoelectric transformer 11 Piezoelectric ceramic 12 Internal electrode 13 Input external electrode 14 Output electrode

Claims (2)

A multilayer piezoelectric transformer in which a plurality of piezoelectric ceramic layers are laminated and integrally sintered,
The laminated piezoelectric transformer includes a driving unit including a plurality of piezoelectric ceramic layers and internal electrodes polarized in the thickness direction, and a pair of input external electrodes connected to the internal electrodes, and a longitudinal direction. A power generation unit including a polarized piezoelectric ceramic and an output electrode;
The piezoelectric ceramic layer have the general formula: represented by _{Pb a Zr x Ti y (Ni} m Mn n Nb 2/3) z O 3, a, x, y, m, n, z is
0.93 ≦ a ≦ 1.02,
0.32 ≦ x ≦ 0.50,
0.41 ≦ y ≦ 0.54,
0.03 ≦ z ≦ 0.21,
0.24 ≦ m + n ≦ 0.66 (except when m or n is 0),
x + y + z = 1.00
A laminated piezoelectric transformer characterized by satisfying In the piezoelectric ceramic layer, m and n are
0.46 ≦ m + n ≦ 0.66,
The multilayer piezoelectric transformer according to claim 1, wherein:

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