JP3397302B2 - Multilayer piezoelectric ceramic transformer and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric ceramic transformer, and more particularly to a step-down type AC-DC converter piezoelectric ceramic transformer for high efficiency and large power transmission.

[0002]

2. Description of the Related Art Japanese Laid-Open Patent Publication No. 10-79535 discloses a laminated piezoelectric transformer. This publication describes a rectangular laminated piezoelectric transformer that operates in a longitudinal longitudinal vibration mode laminated in the thickness direction by using the piezoelectric lateral effect, and a disk-type laminated piezoelectric transformer that operates in a radial expansion vibration mode.

One embodiment of the piezoelectric transformer of this publication is shown in FIG.
Shown in. This piezoelectric transformer has an input section near the upper and lower main surfaces and an output section in the center. The volume of the input portion occupies two-thirds of the total piezoelectric transformer, and the volume of the output portion is only one-third. Therefore, since the volume of the output portion is smaller than the volume of the input portion, the effective electromechanical coupling coefficient on the output side is reduced, and the output power for the same vibration amplitude is reduced. In addition, the external electrodes 103A and 103G and the internal electrodes 103B and 103
Since C, 103D, 103E, and 103F serve as the entire surface of the main surface electrode, there is a disadvantage that the step-down ratio (the ratio of the output voltage to the input voltage) cannot be freely obtained. 101A to 101F are piezoelectric ceramic layers.

FIG. 19 shows an embodiment of another piezoelectric transformer of this publication. This piezoelectric transformer has the same volume in the input portion as that in the output portion, and this also has the drawback that the output power for the same vibration amplitude becomes small. In addition, the external electrodes 103A and 103E and the internal electrode 1
Since 03B, 103C and 103D are full-scale electrodes, there is a drawback that the step-down ratio cannot be freely obtained. 101A to 101D are piezoelectric ceramic layers.

FIG. 20 shows another embodiment of this publication. FIG. 20 discloses a piezoelectric transformer that utilizes the radial expansion vibration mode of a disk. In FIG. 20, 107
A is an external electrode of the input section, 107B is a ground electrode, 107C
Indicates an external electrode of the output section. 105A and 105B are piezoelectric ceramic layers. This laminated piezoelectric transformer also has a drawback that the output power for the same vibration amplitude is small because the volumes of the input portion and the output portion are substantially the same. Further, arrows in FIGS. 18, 19 and 20 indicate polarization directions.

[0006] These laminated piezoelectric transformers are piezoelectric transformers having a three-terminal structure in which there is no insulating portion between the input and output, and do not have a four-terminal structure. Since the electrodes are almost entirely electrode-shaped, it is necessary to take special measures during polarization, for example, to insulate adjacent electrodes by attaching glass or the like by a method such as electrophoresis.
Further, there is a drawback that no countermeasure is taken against external electromagnetic noise such as lightning surge.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above,
The conventional laminated piezoelectric transformer has a three-terminal structure, and since the internal electrodes cover the entire main surface, the degree of freedom in design is low, and a special device is required for polarization.
It could not be manufactured at low cost. In addition, AC-
When mounted on a DC converter, no lightning surge countermeasure was taken. Furthermore, since the volume of the output portion is as small as one half or less of the total volume of the piezoelectric transformer, there are disadvantages that the electromechanical coupling coefficient of the output portion is small and the output power for the same vibration amplitude is small.

The present invention has been made in view of the above-mentioned circumstances, and realizes a laminated piezoelectric ceramic transformer which operates in the contour expansion mode or the basic diameter expansion vibration mode having the largest electromechanical coupling coefficient due to the piezoelectric lateral effect. It is an object.

[0009]

In order to achieve the above object, the present invention provides a laminated piezoelectric ceramic transformer and a method for manufacturing the same as shown in (1) to (12) below.

(1) In the multilayer piezoelectric ceramic transformer operating in the lateral effect contour spreading mode in which the external shape is square and the input side internal electrode and the output side internal electrode are formed parallel to the main surface, The volume is 60% or more of the volume of the entire piezoelectric ceramic transformer, the shape of the input-side and output-side internal electrodes is circular, and the area of the internal electrodes is the total area of the main surface of the multilayer piezoelectric ceramic transformer. 5
A piezoelectric ceramic transformer characterized by being set to 0% or more.

(2) In a laminated piezoelectric ceramic transformer operating in a piezoelectric lateral effect widening vibration mode in which the external shape is a disk shape and the input side internal electrode and the output side internal electrode are formed parallel to the main surface. , The volume of the output part should be 60% or more of the volume of all piezoelectric ceramic transformer, and
The central portion of the direction is included in the output portion, the shape of the internal electrode is circular, and the area of the input side and output side internal electrodes is 50% of the total area of the main surface of the multilayer piezoelectric ceramic transformer. A piezoelectric ceramic transformer characterized by the above.

(3) The multilayer piezoelectric ceramic transformer of (1), wherein the area of the output side internal electrode is equal to or larger than the area of the input side internal electrode.

(4) The multilayer piezoelectric ceramic transformer according to (2), characterized in that the area of the output side internal electrode is equal to or larger than the area of the input side internal electrode.

(5) The input-side internal electrodes are arranged symmetrically in the thickness direction near the outer surface of the laminated piezoelectric ceramic transformer, and the output-side internal electrode is arranged in the central portion in the thickness direction.
The laminated piezoelectric ceramic transformer according to (1), characterized in that an insulating layer is provided between the input side internal electrode layer and the output side internal electrode layer.

(6) The input side internal electrodes are symmetrically arranged in the thickness direction near the outer surface of the laminated piezoelectric ceramic transformer, and the output side internal electrode is arranged in the thickness direction central portion.
The laminated piezoelectric ceramic transformer according to (2), characterized in that an insulating layer is provided between the input side internal electrode layer and the output side internal electrode layer.

(7) The input side electrode is provided from one surface of the main surface of the laminated piezoelectric ceramic transformer to the central portion in the thickness direction, and the output side electrode is provided from the other surface of the main surface to the central portion in the thickness direction, The laminated piezoelectric transformer according to (1), characterized in that an insulating layer is provided between the electrode and the output-side electrode.

(8) The input side electrode is provided from one surface of the main surface of the laminated piezoelectric ceramic transformer to the central portion in the thickness direction, and the output side electrode is provided from the other surface of the main surface to the central portion in the thickness direction. The laminated piezoelectric transformer according to (2), characterized in that an insulating layer is provided between the electrode and the output side electrode.

(9) The laminated piezoelectric ceramic transformer according to (1), (3), (5) or (7), characterized in that a shield electrode is provided in the central portion on the input side and the output side.

(10) A shielding electrode is provided in the central portion of the input side and the output side (2), (4), (6).
Alternatively, the laminated piezoelectric ceramic transformer of (8).

(11) The laminated piezoelectric ceramic transformer according to (1) or (2), characterized in that the internal electrodes are made of Ag / Pd.

(12) In the method for manufacturing a laminated piezoelectric ceramic transformer according to (1) or (2), a green sheet is produced by a doctor blade method, laminated, pressure-bonded and sintered, and then an input terminal is formed. , A method of manufacturing a laminated piezoelectric transformer, characterized in that a high DC voltage is applied to each of the output terminals to perform polarization.

The laminated piezoelectric transformer according to the first aspect of the present invention is a piezoelectric ceramic transformer whose main surface is a square shape or a disk shape, and adjacent piezoelectric ceramic layers polarized in the thickness direction are opposite to each other. It is polarized. The contour lines of the electric flux density distribution (corresponding to the charge distribution) of the contour broadening vibration mode or the diameter broadening vibration mode at the time of resonance of these piezoelectric transformers are both circular, and the portion with the largest electric flux density is Analyze that the central part has the largest area and the area is the smallest if it is close to the surface, and for a piezoelectric transformer of the same volume,
Regarding the output part, its internal electrode is circular, and in order to maximize the effective electromechanical coupling coefficient of the output part that is directly related to the output power, it is provided in the center part in the thickness direction of the piezoelectric transformer, and its volume is the total volume of the piezoelectric transformer. Of 60% or more. Then, by setting the circular electrode to the maximum area (diameter) capable of reliably performing the polarization treatment, it is possible to obtain a piezoelectric transformer having a high power density and capable of highly efficient voltage conversion.

In the laminated piezoelectric transformer according to the second aspect of the present invention, the input portion is provided on one of the main surfaces and the output portion is provided on the other of the principal surfaces, and the structure of the laminated piezoelectric transformer according to the first aspect. Is a simplified piezoelectric transformer, and an insulating layer is naturally inserted between the input section and the output section. Since the volume of the output portion occupies 60% or more of the entire piezoelectric transformer, the output portion includes the middle portion in the thickness direction where the electric flux density is maximum, so that the piezoelectric transformer having a large power density can be realized.

When the laminated piezoelectric transformer according to the third aspect of the present invention is used for an AC-DC converter, the original input voltage is AC100V or AC2.
40V, the output voltage from the piezoelectric transformer is about 15V to 20V in the case of the bridge rectifier circuit, and about 50V is necessary in the case of the current doubler rectifier circuit. In this case, the voltage of DC16V should be used for the frequency control of the piezoelectric transformer. Can be achieved by Therefore, the AC voltage applied between the electrodes of the piezoelectric transformer input is the AC voltage of the output
Several times larger than the voltage. Therefore, it is necessary to make the electrode interval of the input portion of the piezoelectric transformer larger than the electrode interval of the piezoelectric transformer output portion. Therefore, when performing polarization of the piezoelectric transformer, it is necessary to set the polarization voltage of the input part to a value considerably larger than that of the output part. To avoid discharge during polarization, is the area of the electrode of the input part equal to that of the output part? Or it needs to be smaller than that.

When the laminated piezoelectric transformer according to the fourth aspect of the present invention is used as an AC-DC converter,
Since the capacitance between the input part and the output part is as large as several nF,
When a lightning surge occurs, the varistor alone has a drawback that electromagnetic noise due to the lightning surge is transmitted through from the input unit to the output unit. As a measure against this, a shield electrode is provided from the input part to the output part, and this shield electrode allows electromagnetic noise to escape to the ground side so that electromagnetic noise does not go through from the input part to the output part. is there.

The laminated piezoelectric transformer according to the fifth aspect of the present invention is doped with Mn and Sb, which has a high sintering temperature of 1100 ° C. or less, for example, a large coupling coefficient of lateral effect and excellent high power characteristics. Manufactured by a doctor blade method (tape casting method) similar to the ceramic capacitor manufacturing method, using a PZT-based piezoelectric ceramic material, printing an Ag / Pd conductive paste that can be used for internal electrodes at a sintering temperature of 1100 ° C or less on a green sheet Then
The present invention provides a manufacturing method that can be mass-produced at low cost.

In the laminated piezoelectric ceramic transformer using the contour spreading vibration of the square plate and the radial spreading fundamental vibration of the disk according to the present invention, the volume of the piezoelectrically active portion of the output portion is 60 times the total volume of the piezoelectric transformer. %, And the effective electromechanical coupling coefficient on the output side is made larger than that on the input side to increase the output power of the piezoelectric transformer.

From the electric flux density distribution of the piezoelectric transformer,
By making the area of the output electrode equal to or larger than the area of the input electrode, the value of the effective electromechanical coupling coefficient on the output side is further increased, and the output power of the piezoelectric transformer is increased.

In order to completely suppress the spurious vibration of the piezoelectric transformer due to bending vibration, the input side internal electrodes are arranged symmetrically in the thickness direction near the outer surface of the laminated piezoelectric transformer, while the output side electrode is thickened. It is located in the central part of the direction. In a piezoelectric transformer in which the input side electrode and the output side electrode are asymmetrically arranged in the thickness direction and only one insulating layer is provided between the input part and the output part, spurious vibration of the piezoelectric transformer due to bending vibration cannot be suppressed. It is not possible, but by experimentally determining the resonance frequency of the contour expansion vibration mode of the square plate used, the diameter expansion basic mode of the disk and the bending vibration mode that becomes spurious vibration, the outer shape of the piezoelectric transformer is set to an appropriate dimensional ratio. Can be separated from each other. In the piezoelectric transformer having such a configuration, it is possible to sufficiently bring out the performance of the piezoelectric transformer if the resonance frequencies of the vibration mode to be used and the bending vibration mode that becomes spurious are sufficiently separated.

The weak point of the piezoelectric transformer according to the present invention is that the capacitance between the input and output is large, and when electromagnetic noise such as lightning surge occurs, this noise easily reaches the output portion directly from the input portion of the piezoelectric transformer. However, this problem can be easily solved by inserting the shield electrode between the input portion and the output portion of the piezoelectric transformer.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Some concrete examples of the laminated piezoelectric ceramic transformer according to the present invention and calculation results and experimental results for each example will be described below.

[0032]

First Embodiment As a first embodiment of the present invention, FIG.
A piezoelectric transformer having the structure shown in FIG. 1 and operating in the contour spreading vibration mode will be described. In FIG. 1, (a) is a plan view of a piezoelectric transformer according to the present invention, (b) is a sectional view taken along the center line aa ′, and (c) is a sectional view taken along the center line bb ′. Show. Compared with the area of the internal electrode of the output part,
The area of the internal electrodes of the input section is set small. The external dimensions of this piezoelectric transformer are a square having a length of 14 mm and a width of 6 mm. The piezoelectric material is a PZT-based piezoelectric ceramic (NEPEC-
No. 8, manufactured by TOKIN Co., Ltd.), and the internal electrodes were made of Ab / Pd by the tape casting method. The sintering temperature is 1075 ° C.

In the figure, 11 is an input internal electrode, and 12
Is the output internal electrode, and the diameter of the input internal electrode is 1
The diameter of the output part internal electrode is 1.5 mm and 12.5 mm. Further, the interval of the internal electrodes of the input section is set to be larger than the interval of the internal electrodes on the output side because the DC voltage obtained by rectifying AC100V by the bridge rectifier circuit is driven by the current resonance circuit including the half-bridge switching circuit and the series inductor. . In addition, the polarization treatment is performed on the external electrodes 13 and 13 '.
And 14, 14 'by applying a DC voltage. The reason why the internal electrode shape is circular and the area of the electrode is 0.5 or more with respect to the area of the main surface of the piezoelectric transformer is as follows.

FIG. 2 shows a side view of a square piezoelectric vibrator 15 having a side length of 14 mm and a thickness of 6 mm. The polarization is made uniform in the thickness direction by applying a DC voltage to the external electrodes 16 and 16 '. A finite element method (F
EM). In FIG. 2, the arrow indicates the polarization direction. Dotted lines cc 'and gg' in FIG. 2 indicate surface electrode portions. Further, ee 'indicates the central portion in the thickness direction of this vibrator. dd ′ and ff ′ represent a quarter portion (1.5 mm) of the thickness of the vibrator from the surface electrode.

FIG. 3 shows dotted lines cc 'and g- shown in FIG.
g'surface electrode portion electric flux density distribution, FIG. 4 shows the dotted line d-d 'and ff' portions shown in FIG. 2, and FIG. 5 shows the dotted line e-e also shown in FIG. 'Shows the electric flux density distribution of the part. As can be seen from the electric flux density distributions shown in FIGS. 3 to 5, the area of the shaded area with the highest electric flux density increases toward the central portion in the thickness direction, and the shapes of these contour lines are You can see that it is circular. Therefore, it is understood that by making the shape of the internal electrode circular, it is possible to excite the piezoelectric transformer and generate electric power most effectively.

FIG. 6 shows an example of the piezoelectric vibrator shown in FIG.
Effective electromechanical coupling coefficient k_effAnd the electrode area S
You The vertical axis is the effective electricity when the entire main surface is covered with electrodes.
Mechanical coupling coefficient k_{eff, 0}Is standardized in. The horizontal axis is the main surface
Area S₀Is standardized in. As is clear from FIG.
To S / S₀From 0.8 to 0.9, k_eff/ K_{ef
f, 0}Takes the maximum value, S / S₀When is 0.5, k_eff/ K
_{eff, 0}Is slightly higher than 0.9, and S / S₀But
Rapidly k when 0.5 or less_eff/ K_{eff, 0}Becomes smaller
I understand.

In the square plate-shaped contour spread mode piezoelectric transformer shown in FIG. 1, in order to increase the electromechanical coupling coefficient on the output side and supply the maximum electric power to the load side for a predetermined vibration amplitude, The volume of the output section is 60% or more of the volume of the piezoelectric transformer. For this reason, the value of the effective electromechanical coupling coefficient on the input side is 25%, while the value of the effective electromechanical coupling coefficient on the output side is as high as 42%. The resonance frequency of this piezoelectric ceramic transformer is 1
It was 35 kHz.

The high power characteristics of the piezoelectric transformer shown in FIG. 1 are shown in FIG. This piezoelectric transformer is designed on the assumption of a current doubler system in which the output impedance of the piezoelectric transformer can be set high in the rectifier circuit. The output power of 30 W shows a temperature rise of 30 ° C. and an efficiency of 96%. Therefore, the power density reaches 25.5 W / cc, and the value of this power density is astonishing as about 5 times that of the electromagnetic transformer. On the other hand, in the piezoelectric transformer in which the output section is provided near both main surfaces of the piezoelectric transformer and the input section is provided in the central portion in the thickness direction, the output power is 1 at the same external dimension at a temperature rise of 30 ° C.
It was as low as 8W. The piezoelectric transformer is connected to a current doubler rectifier, and the piezoelectric transformer is subjected to current resonance drive by a half bridge drive circuit and an inductor connected in series with the piezoelectric transformer.
It was possible to obtain a high AC-DC converter efficiency close to%.

[0039]

Second Embodiment However, in the piezoelectric ceramic transformer according to the present invention shown in FIG. 1, when a lightning surge occurs, the capacitance between the input and output of the piezoelectric ceramic transformer is several n.
Since it is large as F, the varistor may not be able to absorb it sufficiently. Therefore, as a second embodiment, a shield electrode is provided between the input portion and the output portion of the piezoelectric ceramic transformer according to the present invention shown in FIG. 1, the lead is taken out from the shield electrode, and the earth portion of the AC-DC converter is provided. By connecting to, when electromagnetic noise such as lightning surge occurs, the electromagnetic noise can be completely released to the ground portion. FIG. 8 shows the piezoelectric transformer of the second embodiment. FIG. 8 shows FIG.
6 is a cross-sectional view taken along the alternate long and short dash line bb 'in FIG. 4, in which the electromagnetic noise generated on the primary side (input side) is passed to the secondary side (output side) by inserting the shield electrode 17 between the input and the output. It is possible to completely block the path that causes it. It goes without saying that the performance of this piezoelectric transformer is no different from that of the piezoelectric transformer shown in FIG.

[0040]

Example 3 P doped with an organic binder and Mn and Sb
A mud-like high-viscosity liquid mixed with ZT-based piezoelectric ceramics (NEPEC-8, manufactured by Tokin) was made, and a green sheet with a thickness of about 100 μm was created by the doctor blade method. Ag / Pd internal parts were formed where necessary. The electrode paste was printed. After that, stack these green sheets,
It was pressed and sintered at a temperature of 1100 ° C. using an electric furnace.
FIG. 9 shows a laminated sintered body of piezoelectric ceramic transformers. 9, (a) is a plan view of the piezoelectric transformer according to the present embodiment, (b) is a sectional view taken along the center line aa ′ in the plan view of the piezoelectric transformer shown in (a), and (c) is The center line b in the plan view of the piezoelectric transformer shown in FIG.
A sectional view at -b 'is shown.

In FIG. 9, the input part and the output part of the piezoelectric transformer have an asymmetric structure in the thickness direction, and a high DC voltage is applied using the input side terminal electrodes 13 and 13 'and the output side terminal electrodes 14 and 14'. Polarization treatment is performed to impart piezoelectricity.
In the piezoelectric transformer shown in FIG. 9, since the internal electrode configuration is asymmetric with respect to the thickness direction, the bending vibration mode of the square plate is excited in addition to the contour spreading vibration used. However, the spurious vibration based on the bending vibration mode of this square plate is set far enough from the resonance frequency of the contour spreading vibration to be used by setting the outer wall dimension ratio of the piezoelectric transformer to an appropriate value, and the influence of the spurious vibration is reduced. It can be made so small that it can be ignored. Further, the piezoelectric transformer having the internal electrodes having an asymmetrical structure in the thickness direction shown in FIG. 9 has a portion between the input portion and the output portion as compared with the piezoelectric transformer having the internal electrodes symmetrical in the thickness direction shown in FIG. The capacitance value can be reduced, and the influence of external electromagnetic noise can be reduced.

On the other hand, when the piezoelectric transformer is operating in the contour widening vibration mode, the central portion in the thickness direction of the piezoelectric transformer can store the maximum charge, but the effective electromechanical coupling coefficient of the piezoelectric transformer is increased. In order to raise it, it is necessary to provide an output side electrode in the central portion in the thickness direction. In the case of the piezoelectric transformer of this embodiment, the volume of the output portion can be set to 60% or more of the volume of the entire piezoelectric transformer, so that this problem can be easily achieved.

In FIG. 9, the length of one side is 14 mm, the height is 6 mm, the volume of the output part is 70% of the volume of the piezoelectric transformer, the diameter of the electrode of the input part is 11.5 mm, and the electrode of the output part is 12.5 mm. A piezoelectric transformer according to this example was prototyped. As a result, an effective electromechanical coupling coefficient value of 0.23 at the input portion and an effective electromechanical coupling coefficient value of 0.44 at the output portion were obtained. FIG. 10 shows the relationship between the output power of this piezoelectric transformer and the efficiency and temperature rise. At an output power of 30 W, the efficiency was 97% and the temperature rise was 25 ° C. Also. 27W power density at a temperature rise of 30 ° C
/ Cc, which is about 5 times the value of the electromagnetic type transformer, and is extremely large. In this piezoelectric transformer, the flexural vibration mode that is a spurious is located sufficiently away from the resonance frequency (135 kHz) of the contour spreading vibration mode of the piezoelectric transformer, so that the spurious has no adverse effect on the piezoelectric transformer.

Next, FIG. 11 is a sectional view of a piezoelectric transformer having a structure in which a shield electrode 17 is provided between the input side and the output side of the present piezoelectric transformer, based on FIG. 9C. As is apparent from FIG. 11, it is possible to completely prevent the electromagnetic noise generated on the input side from being transmitted to the output side by the shield electrode 17.

[0045]

[Fourth Embodiment] As a fourth embodiment of the present invention, a disk-shaped piezoelectric ceramic transformer which operates in a radial expansion vibration mode will be described. In order to explain the operation of the piezoelectric transformer according to the present invention, a disk-shaped piezoelectric ceramic vibrator having electrodes on the entire main surface as shown in FIG. 12 will be described. FIG. 12 shows a side view of the disk-shaped piezoelectric ceramic vibrator. In FIG. 12, 18 is a disk-shaped piezoelectric ceramic oscillator, 19 and 19 'are external electrodes, and the arrows in the figure indicate the polarization directions uniformly polarized in the thickness direction.

The electric flux density distributions when the disk-shaped piezoelectric ceramic oscillator is driven in the radial expansion fundamental mode (vibration mode which uniformly spreads in the radial direction) are shown in FIGS. 13, 14 and 15.
Shown in. FIG. 13 shows principal planes pp ′ and t− of the vibrator 18.
The electric flux density distribution of t'part is shown. FIG. 14 shows principal planes p-p 'and t-t' of the oscillator 18 and a central portion r in the oscillator thickness direction.
The electric flux density distribution in the middle part qq 'and ss' part of -r' is shown. FIG. 15 shows the electric flux density distribution in the r-r 'part. Comparing FIG. 13, FIG. 14, and FIG. 15, it can be seen that the closer to the central portion in the thickness direction, the larger the area where the electric flux density becomes maximum. That is, by providing the electrode area of the output portion as large as possible in the portion close to r-r ', and making this portion the output portion. It is considered possible to realize a piezoelectric transformer having high power density and high power transmission efficiency.

FIG. 16 shows a fourth embodiment of the piezoelectric transformer according to the present invention, which operates in the fundamental mode of expanding the diameter of a disk.
Shown in. FIG. 16A is a plan view of a disk-shaped piezoelectric transformer,
16B is a sectional view taken along the center line aa 'in FIG. 16A, and FIG. 16C is a sectional view taken along the center line bb' in FIG. 16A. In FIG.
Reference numeral 10 is a piezoelectric transformer according to the present invention, 11 is an internal electrode of an input portion, 12 is an internal electrode of an output portion, 13 and 13 '.
Is an external electrode of the input part, and 14 and 14 'are external electrodes of the output part. The internal electrodes 11 and 12 are provided symmetrically in the thickness direction like the piezoelectric transformer operating in the contour spreading vibration mode shown in FIG. Has been. As a result, the piezoelectric transformer can completely suppress spurious vibrations due to the bending vibration mode.

The disk-shaped piezoelectric transformer shown in FIG. 16 has one more processing step (for example, outer peripheral polishing) as compared with the square-plate piezoelectric transformer shown in FIG. 1, but has an effective electromechanical coupling coefficient. Has the advantage of being high, which means that a piezoelectric transformer with high power density can be realized. Further, in the disk-shaped piezoelectric transformer shown in FIG. 16, the electrode area of the output section is set larger than that of the input section in order to increase the power density of the transformer. When the electrode area of the input section is 50% or less of the electrode area of the main surface of the piezoelectric transformer, the value of the effective electromechanical coupling coefficient of the input section rapidly decreases, so it is set to 50% or more.

As an example of the piezoelectric transformer of this structure,
A disk-shaped piezoelectric transformer having a diameter of 14 mm and a height of 6 mm will be described. The input side internal electrode has a diameter of 11 mm, and the output side internal electrode has a diameter of 12.5 mm. This piezoelectric transformer was polarized by applying high DC voltage to the input side external electrodes 13 and 13 'and the output side external electrodes 14 and 14', respectively. This piezoelectric transformer has an efficiency of 9 when the output power is 20W.
8%, power density is 36W / c at 30 ℃ temperature rise
c was shown.

[0050]

[Embodiment 5] FIG. 17 shows an embodiment of a piezoelectric ceramic transformer according to the present invention, which operates in a basic diameter expansion vibration mode having another structure. The internal electrode structure of the piezoelectric ceramic transformer shown in FIG. 17 is asymmetric in the thickness direction, like the piezoelectric ceramic transformer shown in FIG. For this reason, spurious vibration modes due to the flexural vibration mode of the disk appear, but with the dimensional ratio of the piezoelectric transformer set to an appropriate value, the resonance frequency of spurious vibrations will not be affected at all from the resonance frequency of the radial expansion fundamental vibration mode used. Need to keep away. In this embodiment, in order to raise the effective coupling coefficient on the input side to a necessary and sufficient level, the area of the input side electrode must be 50% or more of the main surface of the piezoelectric transformer.

The size of the prototype piezoelectric ceramic transformer was 14 mm in diameter, and the diameter of the electrode of the input section was 10.5 mm.
The diameter of the electrode of the output part was 12.5 mm. This piezoelectric transformer was manufactured by the same method as the doctor blade method described in the third embodiment. In this piezoelectric transformer, the effective electromechanical coupling coefficient of the input part is 0.24, and the electromechanical coupling coefficient of the output part is 51% because the volume of the output part occupies 65% of the volume of the piezoelectric transformer. It shows a high value. As a result of measuring the performance of this piezoelectric transformer, the efficiency when output power was 20 W was as high as 97.5%, and the power density at a temperature rise of 30 ° C. was 37 W / cc.

However, in the piezoelectric ceramic transformer according to the present invention, in the piezoelectric transformers described in the fourth and fifth embodiments, the capacitance value between the input and the output is several n.
There is a weakness that it is about F and is easily affected by electromagnetic noise generated on the input side. As a countermeasure against this, by providing a shield electrode 17 as shown in FIGS. 8 and 11 between the input portion and the output portion of the piezoelectric transformer, the problem can be easily solved without impairing the performance of the piezoelectric transformer.

[0053]

As described in detail above, according to the present invention,
By realizing a laminated piezoelectric ceramic transformer that operates in the contour spreading mode or the basic diameter spreading vibration mode with the largest electromechanical coupling coefficient due to the piezoelectric lateral effect, it is suitable for small size and large power transmission, and at the input section. It is possible to provide a piezoelectric transformer that can avoid transmitting the generated electromagnetic noise to the output section.

[Brief description of drawings]

FIG. 1 (a) is a top view of a laminated piezoelectric ceramic transformer showing a first embodiment according to the present invention, FIG. 1 (b).
FIG. 1A is a sectional view taken along the line aa ′ in FIG. 1A, and FIG. 1C is a sectional view taken along the line bb ′ in FIG.

FIG. 2 is a side view of a square piezoelectric ceramic vibrator.

FIG. 3 is an electric flux density distribution diagram of dotted line cc ′ and gg ′ surface electrode portions shown in FIG. 2.

FIG. 4 is a distribution diagram of electric flux densities on the dotted line d-d ′ and f-f ′ plane portions shown in FIG. 2.

5 is an electric flux density distribution chart of a dotted line ee ′ portion shown in FIG.

6 is a graph showing the relationship between the effective electromechanical coupling coefficient k _eff and the electrode area S in the piezoelectric vibrator shown in FIG.

FIG. 7 is an efficiency vs. output power and temperature rise Δt in the laminated piezoelectric ceramic transformer according to the first embodiment of the present invention.
FIG.

FIG. 8 is a side sectional view of a laminated piezoelectric ceramic transformer showing a second embodiment of the present invention.

FIG. 9 (a) is a top view of a laminated piezoelectric ceramic transformer showing a third embodiment according to the present invention, and FIG. 9 (b).
9A is a cross-sectional view taken along the plane aa ′ in FIG. 9A, and FIG. 9C is a cross-sectional view taken along the plane bb ′ in FIG. 9A.

FIG. 10 is an efficiency vs. output power and a temperature rise Δ in the multilayer piezoelectric ceramic transformer according to the third embodiment of the present invention.
It is a figure which shows t.

FIG. 11 is a cross-sectional view of a piezoelectric transformer having a structure in which a shield electrode is provided between the input side and the output side in the multilayer piezoelectric ceramic transformer according to the third embodiment of the present invention.

FIG. 12 is a side view of a disk-shaped piezoelectric ceramic vibrator.

13 is an electric flux density distribution diagram of dotted line pp 'and tt' surface electrode portions shown in FIG.

FIG. 14 is an electric flux density distribution diagram of dotted line qq ′ and ss ′ plane portions shown in FIG.

15 is an electric flux density distribution diagram of a dotted line r-r 'part shown in FIG.

FIG. 16 (a) is a top view of a multilayer piezoelectric ceramic transformer operating in a disk radial expansion basic mode according to a fourth embodiment of the present invention, and FIG. 16 (b) is (a).
FIG. 16C is a sectional view taken along the line aa ′ in FIG.
It is sectional drawing of b'side.

FIG. 17 (a) is a top view showing another example of the structure of the multilayer piezoelectric ceramic transformer operating in the basic mode of the disk diameter expansion according to the fifth embodiment of the present invention, FIG.
7 (b) is a sectional view taken along the line aa 'in FIG. 17 (a), and FIG. 17 (c).
(A) is a cross-sectional view taken along the line bb 'of FIG.

FIG. 18 is a configuration diagram of a piezoelectric transformer showing a conventional technique of a laminated piezoelectric transformer.

FIG. 19 is another configuration diagram of a piezoelectric transformer showing a conventional technique of a laminated piezoelectric transformer.

FIG. 20 is a configuration diagram of a piezoelectric transformer showing a conventional technique of a laminated piezoelectric transformer that utilizes a disk spreading vibration mode.

[Explanation of symbols]

10 Multilayer piezoelectric ceramic transformer 11 Input part internal electrode 12 Output internal electrode 13,13 'Input section external electrode terminal 14 'output part external electrode terminal 15 Square piezoelectric ceramic vibrator 16, 16 'External electrode terminal 17 Shield electrode 18 Disc-shaped piezoelectric ceramic vibrator 19, 19 'External electrode terminal 101,105 Piezoelectric ceramic plate 103,107 electrodes

Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 41/107 H01L 41/22

Claims (12)

(57) [Claims] 1. A multilayer piezoelectric ceramic transformer operating in a lateral effect contour spreading mode, wherein an external shape is a square shape, and an input side internal electrode and an output side internal electrode are formed in parallel with a main surface. Is 60% or more of the volume of the entire piezoelectric ceramic transformer, the shape of the input-side and output-side internal electrodes is circular, and the area of the internal electrodes is 50% of the total area of the main surface of the multilayer piezoelectric ceramic transformer. Piezoelectric ceramic transformer characterized by being set to at least%. 2. A multilayer piezoelectric ceramic transformer operating in a piezoelectric lateral effect widening vibration mode, the external shape of which is a disk, and the input side internal electrode and the output side internal electrode are formed parallel to the main surface, The volume of the output part should be 60% or more of the volume of the whole piezoelectric ceramic transformer, and the thickness
The output center portion is included in the output portion, the shape of the internal electrode is circular, and the area of the input side and output side internal electrodes is 50% of the total area of the main surface of the multilayer piezoelectric ceramic transformer.
Piezoelectric ceramic transformer characterized by being set to at least%. 3. The laminated piezoelectric ceramic transformer according to claim 1, wherein the area of the output side internal electrode is equal to or larger than the area of the input side internal electrode. 4. The laminated piezoelectric ceramic transformer according to claim 2, wherein the area of the output side internal electrode is equal to or larger than the area of the input side internal electrode. 5. The input-side internal electrodes are arranged symmetrically in the thickness direction near the outer surface of the multi-layer piezoelectric ceramic transformer, and the output-side internal electrode is arranged in the central portion in the thickness direction. The multilayer piezoelectric ceramic transformer according to claim 1, wherein an insulating layer is provided between the internal electrode layers. 6. The input-side internal electrodes are arranged symmetrically in the thickness direction near the outer surface of the multi-layer piezoelectric ceramic transformer, and the output-side internal electrode is arranged in the central portion in the thickness direction. The multilayer piezoelectric ceramic transformer according to claim 2, wherein an insulating layer is provided between the internal electrode layers. 7. An input side electrode is provided from one surface of a main surface of a multilayer piezoelectric ceramic transformer to a central portion in the thickness direction, and an output side electrode is provided from the other surface of the main surface to a central portion in the thickness direction. The laminated piezoelectric transformer according to claim 1, wherein an insulating layer is provided between the electrode and the output side electrode. 8. An input side electrode is provided from one surface of a main surface of a multilayer piezoelectric ceramic transformer to a central portion in the thickness direction, and an output side electrode is provided from the other surface of the main surface to a central portion in the thickness direction. The laminated piezoelectric transformer according to claim 2, wherein an insulating layer is provided between the electrode and the output side electrode. 9. The laminated piezoelectric ceramic transformer according to claim 1, wherein a shield electrode is provided in the central portion on the input side and the output side. 10. The laminated piezoelectric ceramic transformer according to claim 2, wherein a shield electrode is provided at a central portion on the input side and the output side. 11. The laminated piezoelectric ceramic transformer according to claim 1, wherein the internal electrodes are made of Ag / Pd. 12. The method for manufacturing a laminated piezoelectric ceramic transformer according to claim 1, wherein a green sheet is produced by a doctor blade method, laminated, pressure-bonded and sintered, and then an input terminal, A method for manufacturing a laminated piezoelectric transformer, characterized in that a high DC voltage is applied to each of the output terminals and polarization is performed.