JP4309152B2 - Piezoelectric transformer element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transformer element, for example, a piezoelectric transformer element suitable for use in a step-down transformer (down transformer) of an AC / DC converter.
[0002]
[Prior art]
Conventionally, piezoelectric transformer elements having various structures have been proposed as a transforming means. For example, a drive region (primary side region) and a power generation region (secondary side region) in which a plurality of piezoelectric layers and internal electrodes are stacked. And a piezoelectric transformer element having a structure in which a drive region and a power generation region are stacked in the stacking direction of the piezoelectric layer and the internal electrode (the thickness direction of the element) has been proposed (for example, Patent Document 1). reference).
[0003]
In addition, it has a drive region (primary side region) and a power generation region (secondary side region) in which a plurality of piezoelectric layers and internal electrodes are stacked, and the drive region and the power generation region are arranged adjacent to each other in the longitudinal direction of the element. A piezoelectric transformer element having such a structure has been proposed (see, for example, Patent Document 2).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-215011 (FIGS. 3-4)
[Patent Document 2]
Japanese Patent Laid-Open No. 11-4026 (FIG. 1)
[0005]
[Problems to be solved by the invention]
However, in the above conventional example, in the piezoelectric transformer element according to Patent Document 1, a piezoelectric body is also used at the boundary between the primary side region and the secondary side region. For this reason, although DC insulation is sufficiently obtained, the primary side region and the secondary side region are stacked in the stacking direction of the piezoelectric layer and the internal electrode, and the primary side and the secondary side Due to the opposing internal electrode surfaces in the region, the capacitance between the primary side region and the secondary side region is large, and the impedance is small. For this reason, it is not easy to obtain alternating insulation.
[0006]
Moreover, since the piezoelectric transformer element according to Patent Document 2 is a vibration mode that resonates in the length direction of the element, the electrical coupling coefficient is small and the conversion efficiency is low.
[0007]
Accordingly, an object of the present invention is to provide a piezoelectric transformer element that is excellent in AC insulation and conversion efficiency.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a piezoelectric transformer element according to the present invention is characterized by the following configuration.
[0009]
  In order to achieve the above object, a piezoelectric transformer element according to the present invention is characterized by the following configuration.
  That is, a piezoelectric transformer element whose outer shape is a rectangular parallelepiped,
  The piezoelectric transformer elements (1 to 4, 8) are
Of the plurality of outer surfaces forming the outer shape, the outer surface having the largest area is used as a main surface, and at least one pair of primary and secondary regions arranged adjacent to each other by a surface perpendicular to the main surface. Having a partitioned structure;
  The primary side region and the secondary side region are:
A plurality of electrodes and piezoelectric layers formed in parallel to the main surface are alternately stacked in a direction perpendicular to the main surface, and among the plurality of piezoelectric layers, a piezoelectric layer in contact with the electrode through the electrodes Have structures that are polarized in opposite directions and are driven in a contour spreading vibration modeAnd
  The primary side region and the secondary side region further include
  Of the length direction and the width direction of the main surface, one set is adjacently arranged in the length direction, and the ratio between the length and the width of the main surface is 0.50 to 0.80. Range or 1.30 to 1.75.
It is characterized by that. This piezoelectric transformer element corresponds to FIG. 1, FIG. 2, FIG. 7, FIG. 8, and FIG.
  AlsoThe piezoelectric transformer element having another configuration that achieves the same object is a piezoelectric transformer element having a substantially cylindrical outer shape,
  The piezoelectric transformer element (5-7)
Having a structure that is partitioned into at least one or more adjacent primary side regions and secondary side regions by a plane perpendicular to the bottom surface of the substantially cylindrical outer shape;
  The primary side region and the secondary side region are:
Electrodes and piezoelectric layers formed in parallel to the bottom surface are alternately stacked in a direction perpendicular to the bottom surface, and among the plurality of piezoelectric layers, the piezoelectric layers in contact with each other through the electrodes are mutually It has a structure that is polarized in the opposite direction, and is driven in a radially expanded vibration mode.
It is characterized by that. This piezoelectric transformer element corresponds to FIG. 11, FIG. 12, and FIG. 15 exemplified in the embodiments described later.
  And the piezoelectric transformer element of other composition which achieves the above-mentioned object is a piezoelectric transformer element whose outer shape is a substantially cylindrical shape,
  The piezoelectric transformer element (6)
And having a plurality of primary regions and a plurality of secondary regions in a plurality of regions that pass through the center of the bottom surface of the substantially cylindrical outer shape and are partitioned by two or more surfaces perpendicular to the bottom surface. The primary side region and the secondary side region have a structure in which the centers of the bottom surfaces are symmetrical and are adjacently arranged so that two opposing regions are the same type of region,
  The primary side region and the secondary side region are:
Electrodes and piezoelectric layers formed in parallel to the bottom surface are alternately stacked in a direction perpendicular to the bottom surface, and among the plurality of piezoelectric layers, the piezoelectric layers in contact with the electrodes are opposite to each other. It has a structure that is polarized in the direction, and is driven in a radially expanded vibration mode.
It is characterized by that. This piezoelectric transformer element corresponds to FIG. 12 illustrated in an embodiment described later.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the piezoelectric transformer element according to the present invention is a so-called down transformer (step-down transformer) that steps down the input voltage applied to the primary side region (drive region) when taking out the output voltage from the secondary side region (power generation region). The applied embodiment will be described in detail with reference to the drawings.
[0011]
[First Embodiment]
FIG. 1 is a diagram showing the structure of the piezoelectric transformer element 1 according to the first embodiment (in the case of L19.8w14). FIG. 1 (a) is a front view of the piezoelectric transformer element 1, and FIG. 3 is a cross-sectional view of the element 1 along AA ′.
[0012]
First, in the following description, the “main surface” refers to the outer surface having the largest area among the six outer surfaces constituting the piezoelectric transformer element 1 having a rectangular parallelepiped (that is, parallelepiped, rectangular parallelepiped) shape, The external surface shown in FIG. 1 (a) or the external surface facing the external surface is shown, and in the AA ′ sectional view shown in FIG. 1 (b), the external surface corresponding to the two opposing sides on the upper side and the lower side It is.
[0013]
Further, the “end face” is an outer face corresponding to two opposing sides on the left side and the right side of the piezoelectric transformer element 1 shown in FIGS. 1 (a) and 1 (b).
[0014]
The “side surface” is an outer surface corresponding to two opposing sides on the upper and lower sides of the piezoelectric transformer element 1 shown in FIG.
[0015]
The “length direction” represents the horizontal direction of the piezoelectric transformer element 1 having the full length L shown in FIGS. 1 (a) and 1 (b).
[0016]
The “width direction” represents the vertical direction of the piezoelectric transformer element 1 having the full width W shown in FIG.
[0017]
The “thickness direction (height direction)” represents the vertical direction of the piezoelectric transformer element 1 having the thickness (height) H shown in FIG.
[0018]
In the present embodiment, the main surface of the piezoelectric transformer element 1 has dimensions with a total length L of 19.8 mm and a total width W of 14 mm. The dimensions in this case are expressed as L19.8w14 (the same applies to the following description). To express).
[0019]
The piezoelectric transformer element 1 is electrically connected to an input electrode (not shown) for applying an input voltage, and a primary side in which interlayer electrodes 11 and 12 are formed as a plurality of first interlayer electrodes between piezoelectric layers. And a secondary region in which interlayer electrodes 31 and 32 are formed as a plurality of second interlayer electrodes between the piezoelectric material layers and electrically connected to an output electrode (not shown) for extracting an output voltage. Have.
[0020]
That is, in the primary side region and the secondary side region, as shown in FIG. 1B, the outer surface having the largest area among the plurality of outer surfaces forming the outer shape is used as the main surface and is perpendicular to the main surface. Interlayer electrode (11-12 or 31-32) having a structure partitioned into a set of primary side region and secondary side region arranged adjacent to each other by a surface and formed in parallel to the main surface And a plurality of piezoelectric layers are alternately stacked in the direction perpendicular to the main surface (thickness direction).
[0021]
In the present embodiment, a down transformer (a step-down transformer) is described as an example. Therefore, the number of interlayer electrodes 11 and 12 in the primary region is the number of interlayer electrodes 31 and 32 in the secondary region. Fewer. In other words, the interelectrode distance of the interlayer electrode (11-12) in the primary side region is larger than the interelectrode distance of the interlayer electrode (31-32) in the secondary side region.
[0022]
In FIG. 1B, the arrow indicates the polarization direction (hereinafter the same as in each of the drawings showing the structure), the piezoelectric body located between the layers of the primary-side interlayer electrode 11-12, and 2 The piezoelectric bodies positioned between the interlayer electrodes 31-32 on the next side are polarized in the thickness direction, and among the plurality of piezoelectric layers, the piezoelectric layers in contact with each other through one interlayer electrode are mutually connected. Polarized in the opposite direction.
[0023]
In the primary side and secondary side regions of the piezoelectric transformer element 1, a general material can be used for the piezoelectric body and the interlayer electrode. For example, a lead-based lead zirconate titanate or the like is used for the piezoelectric body. A perovskite piezoelectric material can be employed, and Ag, Ag / Pd alloy, or the like can be employed for the interlayer electrode.
[0024]
Note that variations in the layered structure and interlayer connection structure of the interlayer electrodes and the structure of the input and output electrodes that can be employed in the piezoelectric transformer element according to the present embodiment will be described at the end of the present embodiment.
[0025]
2 is a view showing the structure of the piezoelectric transformer element 2 according to the first embodiment (in the case of L9.8w14). FIG. 2A is a front view of the piezoelectric transformer element 2, and FIG. ) Is a cross-sectional view taken along the line BB ′ of the element 1, and is different from the piezoelectric transformer element 1 described above only in the ratio of the length L to the width W, and the structure of the element is the same.
[0026]
Here, the piezoelectric transformer elements 1 and 2 shown in FIG. 1 and FIG. 2 represent the case where the shape dimension is L19.8w14 and the case of L9.8w14, and the optimum results obtained as a result of the applicant's experiment are shown. Before reaching the ratio of the length L and the width W, for convenience of explanation, here, first, the main surface is a square (that is, the length L and the width W). In the case of a piezoelectric transformer element whose main surface is a square, the ratio of the length and width of the element is appropriately set as a means for solving the problem. The process until the determination of the correct value (range) will be described in order.
[0027]
First, the applicant of the present application has proposed that a piezoelectric transformer element having the above structure in which the main surface is a square in the initial research and experiment for realizing a target piezoelectric transformer element capable of achieving both alternating insulation and conversion efficiency. 1 and 2 are driven in a contour spreading vibration mode (preferably a basic mode of the contour spreading vibration mode) having a large electromechanical coupling coefficient (k). There was a case where resonance (spurious resonance) occurred.
[0028]
Therefore, the applicant of the present application prevents sub-resonance from occurring when the piezoelectric transformer element 1 (L ≧ W) and the piezoelectric transformer element 2 (L ≦ W) having the above-described structure are driven in the contour spreading vibration mode. Therefore, an attempt was made to set the ratio of the element length and width to an appropriate value.
[0029]
Next, with reference to the experimental results for the above trial, description will be made on the ratio of the length and width of the element until the determination of an appropriate value (range).
[0030]
FIG. 3 is a diagram showing a step-up ratio-frequency characteristic when the ratio of length to width is changed in the piezoelectric transformer element 1 according to the first embodiment. In the figure, the vertical axis represents the step-up ratio (transformation ratio). : Step-up Ratio), the horizontal axis indicates the frequency (kHz), and the piezoelectric transformer element 1 according to the present embodiment describes a step-down transformer that is a preferred application example of the present invention. In the vertical axis shown in FIG.
[0031]
FIG. 4 is a diagram showing conversion efficiency-frequency characteristics when the ratio of length to width is changed in the piezoelectric transformer element 1 according to the first embodiment. In the figure, the vertical axis represents the vertical axis. Efficiency (%), the horizontal axis indicates frequency (kHz).
[0032]
3 and 4, the correspondence relationship between the characteristic curves I to VI and the element dimensions is as follows:
・ Characteristic curve I: L24.5w14
・ Characteristic curve II: L23.8w14
・ Characteristic curve III: L22.4w14
・ Characteristic curve IV: L21w14
・ Characteristic curve V: L19.8w14
・ Characteristic curve VI: L18.2w14
It is.
[0033]
When a piezoelectric transformer element is employed as a transformer means of an AC / DC converter, it is common to control the step-up ratio of the piezoelectric transformer element during driving in a predetermined frequency range. More specifically, in the frequency characteristic curve of the piezoelectric transformer element including the frequency fm indicating the maximum boost ratio as the peak of the mountain shape, the frequency range includes the frequency fm indicating the maximum boost ratio and the value of the maximum boost ratio. When driving in a frequency range between the frequency fh on the high frequency side, which is approximately ３ on the same characteristic curve, it is necessary to suppress the occurrence of spurious vibrations that are the basis of efficiency reduction.
[0034]
Therefore, when this viewpoint is applied to the experimental results shown in FIGS. 3 and 4 relating to the piezoelectric transformer element 1, the frequency characteristic curve VI (L18) in the frequency characteristic curves (I to VI) shown in FIGS. In the case of .2w14 (1.3: 1)), the conversion efficiency is extremely reduced near the frequency that shows the maximum step-up ratio, the occurrence of spurious vibrations has been confirmed, and the frequency characteristic curve I (L24.5w14) In the case of (1.75: 1)), it can be seen that the conversion efficiency is also extremely reduced in the vicinity of the frequency on the high frequency side, which is approximately 1/3 of the maximum step-up ratio, and the occurrence of spurious vibration has been confirmed. In contrast, the frequency characteristic curve V (in the case of L19.8w14 (1.4: 1)) shows that spurious vibration is not generated.
[0035]
Therefore, from the above viewpoint, by setting the ratio of the length and width of the piezoelectric transformer element 1 in the range of 1.3 to 1.75, a piezoelectric transformer element suitable for an AC / DC converter, for example, can be realized.
[0036]
On the other hand, FIG. 5 is a diagram showing a step-up ratio-frequency characteristic when the ratio of length to width is changed in the piezoelectric transformer element 2 according to the first embodiment. In FIG. Step-up Ratio), the horizontal axis indicates the frequency (kHz), and the piezoelectric transformer element 1 according to this embodiment describes a step-down transformer that is a preferred application example of the present invention. In the vertical axis shown in the figure, the value of the step-up ratio is 1 or less.
[0037]
FIG. 6 is a diagram showing conversion efficiency-frequency characteristics when the ratio of length to width is changed in the piezoelectric transformer element 2 according to the first embodiment. In the figure, the vertical axis represents the vertical axis. Efficiency (%), the horizontal axis indicates frequency (kHz).
[0038]
5 and 6, the correspondence relationship between the characteristic curves I to VIII and the dimensions of the element is
・ Characteristic curve I: L12.2w14
・ Characteristic curve II: L11.2w14
・ Characteristic curve III: L10.5w14
・ Characteristic curve IV: L9.8w14
・ Characteristic curve V: L9.1w14
・ Characteristic curve VI: L8.4w14
・ Characteristic curve VII: L7.7w14
・ Characteristic curve VIII: L7.0w14
It is.
[0039]
When the above viewpoint is applied to the experimental results shown in FIG. 5 and FIG. 6 regarding the piezoelectric transformer element 2, the frequency characteristic curve II (L11) in the frequency characteristic curves (I to VIII) shown in FIG. 5 and FIG. In the case of .2w14 (0.80: 1), the conversion efficiency is extremely reduced near the frequency that shows the maximum step-up ratio, spurious vibration is confirmed, and the frequency characteristic curve VIII (L7.0w14 (0.50)) In the case of 1)), the conversion efficiency is extremely decreased near the high frequency side of the maximum step-up ratio, spurious vibrations are generated, and the conversion efficiency is low as a whole. In contrast, the frequency characteristic curve IV (in the case of L9.8w14 (0.7: 1)) shows that spurious vibrations are not generated.
[0040]
Therefore, from the above viewpoint, by setting the ratio of the length and width of the piezoelectric transformer element 2 in the range of 0.50 to 0.80, a piezoelectric transformer element suitable for an AC / DC converter, for example, can be realized.
[0041]
<Laminated structure of interlayer electrode and interlayer connection structure>
In the present embodiment, the interlayer electrodes 11-12 and 31-32 in the primary and secondary regions of the piezoelectric transformer elements 1 and 2 are laminated in the thickness direction as shown in FIGS. 1B and 2B. And has an interlayer connection structure that is connected every other layer by an interlayer connection conductor (not shown) formed inside or outside the primary side region or the secondary side region.
[0042]
That is, in the secondary region of the piezoelectric transformer elements 1 and 2, the interlayer electrodes 31 and 32 are further layered by at least one set of interlayer connection conductors (not shown) formed inside or outside the secondary region. By being connected every other time, a plurality of interlayer electrodes 31 are connected to one interlayer connection conductor, and a plurality of interlayer electrodes 32 are connected to the other interlayer connection conductor.
[0043]
Further, in the primary region of the piezoelectric transformer elements 1 and 2, the interlayer electrodes 11 and 12 are at least one pair of interlayer connection conductors (not shown), like the interlayer electrodes 31 and 32 on the secondary region side. 1), the interlayer connection structure connected every other layer is adopted. However, in the primary region of the piezoelectric transformer elements 1 and 2 shown in FIGS. 1 and 2, as an example, two interlayer electrodes 11 and one In this case, two interlayer electrodes 11 are connected to one interlayer connection conductor, and one interlayer electrode 12 is connected to the other interlayer connection conductor. It becomes the structure made.
[0044]
<Structure of input electrode and output electrode>
In this embodiment, when the above-described interlayer connection conductor is formed inside the piezoelectric transformer elements 1 and 2, at least an input electrode for applying an input voltage and an output electrode for extracting an output voltage are included. Either one is formed outside the element in a state of being electrically connected to the interlayer connection conductor.
[0045]
When the interlayer connection conductor is formed outside the element in at least one of the primary and secondary regions of the piezoelectric transformer elements 1 and 2, the interlayer connection conductor itself is connected to the input voltage. May be used as an input electrode for applying voltage or an output electrode for extracting output voltage.
[0046]
<Structure of interlayer electrode, conductor for interlayer connection, and external electrode for input / output>
Here, in the above-described embodiment, in order to reduce the overall shape of the element and improve the transformation efficiency, the interlayer electrode 11 and the secondary side that are stacked in the primary region of the piezoelectric transformer elements 1 and 2 are stacked. In the interlayer electrode 31 laminated in a plurality of regions, the structure in which the uppermost and lowermost electrodes are respectively exposed on the upper and lower main surfaces has been described as an example. However, the piezoelectric transformer element according to the present invention is limited to such a structure. In the primary side and secondary side regions, at least one of the uppermost and lowermost interlayer electrodes is embedded in the element and not exposed on the main surface. You can also
[0047]
Further, in the above-described embodiment, the interlayer electrodes 11-12 and 31-32 of each layer have been described by taking an example of a structure that is offset from the end face and side face of the piezoelectric transformer elements 1 and 2 toward the element inner side. Such a piezoelectric transformer element is not limited to such a structure, and satisfies the AC insulation state in which the interlayer electrode 11-12 in the primary side region and the interlayer electrode 31-32 in the secondary side region are required. As long as the structure is physically separated with a gap length, a structure exposed on at least one of the end surface and the side surface of the primary side and the secondary side region may be employed.
[0048]
According to this embodiment described above, a piezoelectric transformer element excellent in AC insulation and conversion efficiency is realized.
[0049]
That is, in the piezoelectric transformer elements 1 and 2 according to this embodiment, since the primary side region and the secondary side region are adjacent to each other in the length direction of the element, the interlayer electrodes 11 and 12 in the primary side region, Since the interlayer electrodes 31 and 32 in the secondary region do not face each other as a surface, the capacitance between the primary region and the secondary region is small (capacitive coupling state can be reduced), Since the impedance increases, AC insulation can be obtained, and excellent conversion efficiency is exhibited by driving in the contour spreading vibration mode.
[0050]
Further, in various electronic devices (for example, an inverter circuit or an AC / DC converter for driving a display device of a mobile phone or an information processing apparatus) in which the piezoelectric transformer element is used as a transformer, the piezoelectric transformer element in the electronic device is used. In general, the demand for the external dimension is often limited by the thickness (that is, the distance between two opposing main surfaces) as compared with the length in the longitudinal direction of the element. With respect to such restrictions, in the piezoelectric transformer elements 1 and 2 according to the present embodiment, the interlayer electrodes 11 and 12 in the primary side region and the interlayer electrodes 31 and 32 in the secondary side region are described in Patent Document 1. Unlike the structure facing in the thickness direction of the element as described above, since the structure is adjacent in the element length (L) direction, the distance between the internal electrodes is within the range allowed by the required external dimensions. By determining (gap length) as appropriate during design (that is, ensuring the maximum separation distance within the required specification range), it is easy to further ensure the above-mentioned AC insulation characteristics. .
[0051]
[Second Embodiment]
Next, a second embodiment according to the present invention will be described. In the following description, the description similar to that of the first embodiment will be omitted, and the description will focus on the characteristic part of the present embodiment.
[0052]
In the present embodiment, a structure of a piezoelectric transformer element capable of suppressing the occurrence of the sub-resonance (spurious resonance) and realizing good conversion efficiency while keeping the main surface shape of the element to be square will be described. .
[0053]
7A and 7B are diagrams showing the structure of the piezoelectric transformer element 3 according to the second embodiment. FIG. 7A is a front view of the piezoelectric transformer element 3, and FIG. 'Cross-sectional view, FIG. 5C is a cross-sectional view along the line DD' of the element 3.
[0054]
As shown in the figure, the piezoelectric transformer element 3 includes two or more outer surfaces having an outer shape, the outer surface having the largest area as a main surface, passing through the center of the main surface and perpendicular to the main surface. In a plurality of regions defined by an even number of surfaces (here, "even number of surfaces" is for convenience of explanation and does not actually exist inside the element) While having a plurality of primary side regions and a plurality of secondary side regions, these two primary side regions and secondary side regions are symmetrical with respect to the center of the main surface, and the two opposing regions are the same type of region. Thus, it has the structure arranged adjacently.
[0055]
In the piezoelectric transformer element 3, each primary region is electrically connected to an input electrode (not shown) for applying an input voltage, and a plurality of first interlayer electrodes are provided between the piezoelectric layers. Electrodes 13 and 14 are formed, and each secondary side region is electrically connected to an output electrode (not shown) for extracting an output voltage, and a plurality of second interlayer electrodes are provided between the piezoelectric layers. Interlayer electrodes 33 and 34 are formed.
[0056]
Here, the laminated structure of the interlayer electrodes and the interlayer connection structure of the piezoelectric transformer element 3 and the structure of the input electrode and the output electrode itself can adopt the same structure as in the first embodiment.
[0057]
The piezoelectric transformer element 3 having the above structure is also driven in the contour spreading vibration mode (preferably the basic mode of the contour spreading vibration mode) in this embodiment. The experimental results regarding the frequency characteristics in this case will be described.
[0058]
FIG. 9 is a diagram showing a step-up ratio-frequency characteristic in the piezoelectric transformer element 3 according to the second embodiment. In the figure, the vertical axis represents the step-up ratio, and the horizontal axis represents the frequency. In the piezoelectric transformer element 3 according to this embodiment, a step-down transformer that is a preferred application example of the present invention has been described. Therefore, on the vertical axis shown in FIG. 1 or less.
[0059]
FIG. 10 is a diagram showing conversion efficiency-frequency characteristics in the piezoelectric transformer element 3 according to the second embodiment. In the figure, the vertical axis represents efficiency (%), and the horizontal axis represents frequency (kHz). ).
[0060]
As can be seen from the frequency characteristic curve I shown in FIGS. 9 and 10, in the piezoelectric transformer element 3 according to the present embodiment, the main surface is square, and the primary region and the secondary region are point-symmetric in the main surface direction. It can be seen that the occurrence of spurious vibrations is suppressed in a wide range from the frequency indicating the maximum boost ratio to the high frequency side.
[0061]
Therefore, the present embodiment also realizes a piezoelectric transformer element excellent in AC insulation and conversion efficiency.
[0062]
That is, in the piezoelectric transformer element 3 according to the present embodiment, since each primary side region and the secondary side region are adjacent to each other in the length direction and the width direction of the element, the interlayer electrodes 13 and 14 in the primary side region. Since the interlayer electrodes 33 and 34 in the secondary region do not face each other as a surface, the capacitance between the primary region and the secondary region is small (capacitive coupling state can be reduced). Since the impedance increases, AC insulation can be obtained, and excellent conversion efficiency is exhibited by driving in the contour spreading vibration mode.
[0063]
In the piezoelectric transformer element 3 (FIG. 7), in the rectangular parallelepiped outer shape, a pair of a primary side region and a secondary side region in two directions of the main surface (the length direction and the width direction in the rectangular parallelepiped shape) ( 2 × 2) Adjacent structures have been described. However, the present invention is not limited to this structure, and the primary side region and the secondary side region are adjacent to each other in at least one of the two directions (for example, 4 × 2). This structure can also be realized by driving in the contour spreading vibration mode.
[0064]
<Modification of Second Embodiment>
Next, a modification of the second embodiment will be described.
[0065]
FIG. 8 is a diagram showing the structure of a piezoelectric transformer element 4 according to a modification of the second embodiment. FIG. 8A is a front view of the piezoelectric transformer element 4, and FIG. EE 'sectional drawing and the figure (c) are FF' sectional views of the element 4 concerned.
[0066]
The main surface shape of the element is also a square in this modification, but the piezoelectric transformer element 4 forms a triangle when viewed from the main surface in four regions defined by two diagonal lines on the main surface. The secondary side region and the secondary side region have a structure in which the two diagonal lines are symmetric with respect to each other so that two opposing regions are the same type of region.
[0067]
In the piezoelectric transformer element 4, each primary region is electrically connected to an input electrode (not shown) for applying an input voltage, and a plurality of first interlayer electrodes are provided between the piezoelectric layers. Electrodes (15-16 or 17-18) are formed, and each secondary region is electrically connected to an output electrode (not shown) for extracting an output voltage, and between the layers of the piezoelectric body. Interlayer electrodes (35-36 or 37-38) are formed as a plurality of second interlayer electrodes, and also in this modified example, it is driven in the contour spreading vibration mode.
[0068]
According to this modified example as well, it is possible to suppress the occurrence of the sub-resonance (spurious resonance) while maintaining the main surface shape of the element to be square, and to realize good conversion efficiency.
[0069]
[Third Embodiment]
Next, a third embodiment according to the present invention will be described.
[0070]
FIG. 11 is a diagram illustrating the structure of the piezoelectric transformer element 5 according to the third embodiment. FIG. 11A is a front view of the piezoelectric transformer element 5, and FIG. 'Cross section.
[0071]
First, in the following description, the “bottom surface” refers to the outer surface shown in FIG. 11A or the outer shape facing the outer surface among the outer surfaces constituting the cylindrical (substantially cylindrical) piezoelectric transformer element 5. In FIG. 11 (b), the GG ′ cross-sectional view showing the surface is an outer surface corresponding to two opposite sides on the upper side and the lower side, and includes a case of a substantially perfect circle with a radius R and a case of an ellipse. .
[0072]
The “thickness direction (height direction)” represents the vertical direction of the piezoelectric transformer element 5 having a thickness (height) H shown in FIG.
[0073]
The piezoelectric transformer element 5 is electrically connected to an input electrode (not shown) for applying an input voltage, and a primary side in which interlayer electrodes 19 and 20 are formed as a plurality of first interlayer electrodes between layers of a piezoelectric body. And a secondary region in which interlayer electrodes 39 and 40 are formed as a plurality of second interlayer electrodes between the piezoelectric material layers and electrically connected to an output electrode (not shown) for extracting an output voltage. Have.
[0074]
That is, in the primary side region and the secondary side region, as shown in FIG. 11 (b), a set of primary side regions arranged adjacent to each other by a surface perpendicular to the bottom surface of the substantially cylindrical outer shape. Interlayer electrodes (19-20 or 39-40) and piezoelectric layers formed in parallel to the bottom surface are alternately stacked in a direction perpendicular to the bottom surface. Has a structured.
[0075]
Also in the present embodiment, a down transformer (step-down transformer) is described as an example, and therefore the number of interlayer electrodes 19 and 20 in the primary region is the number of interlayer electrodes 39 and 40 in the secondary region. Less than the number. In other words, the inter-electrode distance of the interlayer electrode (19-20) in the primary side region is larger than the inter-electrode distance of the interlayer electrode (39-40) in the secondary side region.
[0076]
Further, in FIG. 11B, the polarization directions of the piezoelectric bodies in the respective layers are the same as those in the first embodiment described above, and the laminated structure and interlayer connection structure of the interlayer electrodes of the piezoelectric transformer element 5 and the input electrodes. The output electrode structure itself can adopt the same structure as that of the first embodiment.
[0077]
In the present embodiment, the piezoelectric transformer element 5 having such a structure is driven in a radially expanded vibration mode (preferably a fundamental mode of the radially expanded vibration mode). However, since the piezoelectric transformer element 5 having a set of primary side and secondary side regions obtained by dividing the bottom surface into two parts is driven in a radially expanding vibration mode, a sub-resonance (spurious resonance) may occur. The piezoelectric transformer element 6 having two sets of primary side and secondary side regions will be described together as an example in the case of equally dividing by a multiple of.
[0078]
12 is a diagram showing the structure of the piezoelectric transformer element 6 according to the third embodiment. FIG. 12A is a front view of the piezoelectric transformer element 6, and FIG. FIG. 4C is a cross-sectional view taken along the line II ′ of the element 6.
[0079]
The piezoelectric transformer element 6 shown in the figure passes through the center P of the bottom surface of a substantially cylindrical outer shape, and two or more even numbers of surfaces (here, “even number of surfaces”) perpendicular to the bottom surface are: For convenience of explanation, a plurality of primary regions and a plurality of secondary regions (in this case, two regions) are divided into a plurality of regions divided by the elements that do not actually exist inside the element. The primary side region and the secondary side region have a structure in which the center P of the bottom surface is symmetric and adjacent two regions are arranged so as to be the same type of region.
[0080]
In the piezoelectric transformer element 6, each primary region is electrically connected to an input electrode (not shown) for applying an input voltage, and a plurality of first interlayer electrodes are provided between the piezoelectric layers. Electrodes (21-22 or 23-24) are formed, and each secondary region is electrically connected to an output electrode (not shown) for extracting an output voltage, and between the layers of the piezoelectric body. Interlayer electrodes (41-42 or 43-44) are formed as a plurality of second interlayer electrodes, and are driven in a radially expanded vibration mode (preferably the fundamental mode of the radially expanded vibration mode).
[0081]
FIG. 13 is a diagram showing a step-up ratio-frequency characteristic in the piezoelectric transformer elements 5 and 6 according to the third embodiment. In the figure, the vertical axis represents the step-up ratio, and the horizontal axis. Indicates a frequency (kHz), and the piezoelectric transformer elements 5 and 6 according to the present embodiment are described with reference to a step-down transformer that is a preferred application example of the present invention. The value of the ratio is 1 or less.
[0082]
FIG. 14 is a diagram showing conversion efficiency-frequency characteristics in the piezoelectric transformer elements 5 and 6 according to the third embodiment. In the figure, the vertical axis represents efficiency (%), and the horizontal axis represents frequency. (KHz).
[0083]
As can be seen from the frequency characteristic curve I (in the case of the piezoelectric transformer element 5 shown in FIG. 11) and the frequency characteristic curve II (in the case of the piezoelectric transformer element 6 shown in FIG. 12) shown in FIGS. In addition, when the characteristics of the piezoelectric transformer elements 5 and 6 according to the present embodiment are compared, in the frequency characteristic curve I, the conversion efficiency is extremely reduced near the frequency indicating the maximum step-up ratio, and spurious vibration is generated. However, in the frequency characteristic curve II, it can be seen that the occurrence of spurious vibrations is suppressed by arranging a plurality of primary regions and secondary regions with the center P of the bottom surface symmetrical.
[0084]
Therefore, the present embodiment also realizes a piezoelectric transformer element excellent in AC insulation and conversion efficiency.
[0085]
That is, in the piezoelectric transformer elements 5 and 6 according to the present embodiment, each primary side region and the secondary side region are adjacent to each other in the direction parallel to the bottom surface of the element. −24) and the interlayer electrode (41-44) in the secondary side region do not face each other, the capacitance between the primary side region and the secondary side region is small (capacitive coupling state). Since the impedance is increased, alternating current insulation can be obtained, and excellent conversion efficiency can be achieved by driving in the radially expanded vibration mode.
[0086]
<Modification of Third Embodiment>
The piezoelectric transformer element according to the third embodiment is limited to a structure in which at least one or more primary side regions and secondary side regions are symmetrically adjacent to each other as shown in FIGS. 11 and 12. The structure described in this modification may be used instead.
[0087]
15A and 15B are views showing the structure of a piezoelectric transformer element 7 according to a modification of the third embodiment. FIG. 15A is a front view of the piezoelectric transformer element 7 and FIG. 7 is a sectional view taken along line JJ ′ of FIG.
[0088]
Also in this modification, the bottom shape of the element is a circle having a radius R. However, in the piezoelectric transformer element 7, as shown in FIG. 15, a primary region formed beyond the center P of the bottom surface and a crescent moon shape are formed. The secondary side region is adjacently disposed.
[0089]
In the piezoelectric transformer element 7, the primary side region is electrically connected to an input electrode (not shown) for applying an input voltage, and the interlayer electrode 25 serves as a plurality of first interlayer electrodes between the layers of the piezoelectric body. 26 are formed in the secondary region, and are electrically connected to an output electrode (not shown) for extracting an output voltage, and an interlayer electrode 45 serving as a plurality of second interlayer electrodes between the layers of the piezoelectric body. , 46 are formed, and also in this modified example, it is driven in a radially expanding vibration mode.
[0090]
According to such a modification as well, it is possible to suppress the occurrence of the sub-resonance (spurious resonance) and to realize good conversion efficiency.
[0091]
[Fourth Embodiment]
Next, a description will be given of a fourth embodiment as a modification common to the first to third embodiments described above.
[0092]
In the above-described first to third embodiments and modifications thereof, when the main surface is a quadrangle (first and second embodiments), the primary side and the secondary formed in parallel to the main surface. When the interlayer electrode in the side region is also square and the bottom surface is circular (third embodiment), the interlayer electrodes in the primary and secondary regions formed parallel to the bottom surface are half An example of a structure having a sector shape including a circle has been described. However, the present invention is not limited to such a structural example, and for example, a structure as described in this embodiment can be adopted.
[0093]
16A and 16B are diagrams showing the structure of the piezoelectric transformer element 8 according to the fourth embodiment. FIG. 16A is a front view of the piezoelectric transformer element 8, and FIG. -K 'sectional view and FIG. 6C are LL' sectional views of the element 8.
[0094]
In the piezoelectric transformer element 8 shown in the figure, the shape of the two pairs of primary and secondary region interlayer electrodes in the piezoelectric transformer element 4 (FIG. 8) is not the same as the partitioned shape. The device 6 (FIG. 12) has a structure formed in the shape of interlayer electrodes in the primary and secondary regions that form a sector.
[0095]
Also with the piezoelectric transformer element 8 having such a structure, it is possible to suppress the occurrence of the sub-resonance (spurious resonance) and realize good conversion efficiency.
[0096]
In the above-described embodiments and modifications thereof, the piezoelectric transformer element according to the present invention has been described as an embodiment applied to a down transformer (step-down transformer). However, the present invention is not limited to this.
[0097]
More specifically, the present invention can also be applied to a step-up transformer that boosts the input voltage applied to the primary side region (driving region) when the input voltage is extracted from the secondary side region (power generation region) as an output voltage. In the case of a step-up transformer, the inter-electrode distance of each interlayer electrode in the primary side region may be made shorter than the inter-electrode distance of each interlayer electrode in the secondary side region. That is, in the case of a step-up transformer, in the piezoelectric transformer elements 1 to 8 described as step-down transformers in each of the above-described embodiments, the primary region is used as the secondary region while the secondary region is used as the primary side. The piezoelectric transformer elements 1 to 8 function as a step-up transformer when used as a region (that is, used with the input / output states reversed).
[0098]
Further, in the structure of the piezoelectric transformer element as the step-down transformer or the step-up transformer, in the case of a step-down circuit specification in which the ratio of the output voltage to the input voltage is required to be about 1, the interlayer electrode in the primary side region A case in which the number of stacked layers and the number of stacked interlayer electrodes in the secondary region are the same is also included in the scope of the present invention.
[0099]
【The invention's effect】
According to the present invention described above, it is possible to provide a piezoelectric transformer element excellent in AC insulation and conversion efficiency.
[Brief description of the drawings]
1A and 1B are diagrams showing a structure of a piezoelectric transformer element 1 according to a first embodiment (in the case of L19.8w14), where FIG. 1A is a front view of the piezoelectric transformer element 1, and FIG. 3 is a cross-sectional view of the element 1 along AA ′. FIG.
2A and 2B are diagrams showing the structure of the piezoelectric transformer element 2 according to the first embodiment (in the case of L9.8w14), where FIG. 2A is a front view of the piezoelectric transformer element 2 and FIG. 3 is a sectional view of the element 1 taken along the line BB ′. FIG.
FIG. 3 is a diagram showing a step-up ratio-frequency characteristic when the ratio of length to width is changed in the piezoelectric transformer element 1 according to the first embodiment.
FIG. 4 is a diagram showing conversion efficiency-frequency characteristics when the ratio of length to width is changed in the piezoelectric transformer element 1 according to the first embodiment.
FIG. 5 is a diagram showing a step-up ratio-frequency characteristic when the ratio of length to width is changed in the piezoelectric transformer element 2 according to the first embodiment.
6 is a graph showing conversion efficiency-frequency characteristics when the ratio of length to width is changed in the piezoelectric transformer element 2 according to the first embodiment. FIG.
7A and 7B are diagrams showing a structure of a piezoelectric transformer element 3 according to a second embodiment, in which FIG. 7A is a front view of the piezoelectric transformer element 3 and FIG. 'Cross-sectional view, FIG. 5C is a cross-sectional view along the line DD' of the element 3.
8A and 8B are diagrams showing the structure of a piezoelectric transformer element 4 according to a modification of the second embodiment. FIG. 8A is a front view of the piezoelectric transformer element 4, and FIG. EE 'sectional drawing and the figure (c) are FF' sectional views of the element 4 concerned.
FIG. 9 is a diagram showing a step-up ratio-frequency characteristic in the piezoelectric transformer element 3 according to the second embodiment.
FIG. 10 is a diagram showing conversion efficiency-frequency characteristics in the piezoelectric transformer element 3 according to the second embodiment.
11A and 11B are diagrams showing the structure of a piezoelectric transformer element 5 according to a third embodiment. FIG. 11A is a front view of the piezoelectric transformer element 5, and FIG. 'Cross section.
12A and 12B are diagrams showing the structure of a piezoelectric transformer element 6 according to a third embodiment. FIG. 12A is a front view of the piezoelectric transformer element 6, and FIG. 'Cross-sectional view, FIG. 5C is a cross-sectional view taken along the line II' of the element 6.
FIG. 13 is a diagram showing a step-up ratio-frequency characteristic in piezoelectric transformer elements 5 and 6 according to a third embodiment.
14 is a diagram showing conversion efficiency-frequency characteristics in piezoelectric transformer elements 5 and 6 according to a third embodiment. FIG.
15A and 15B are diagrams showing the structure of a piezoelectric transformer element 7 according to a modification of the third embodiment. FIG. 15A is a front view of the piezoelectric transformer element 7, and FIG. It is JJ 'sectional drawing.
16A and 16B are diagrams showing the structure of a piezoelectric transformer element 8 according to a fourth embodiment. FIG. 16A is a front view of the piezoelectric transformer element 8, and FIG. 16B is a KK of the element 8. 'Cross-sectional view, FIG. 5C is a cross-sectional view of the element 8 taken along the line LL'.
[Explanation of symbols]
1-8: Piezoelectric transformer element,
11-12, 13-14, 15-16, 17-18, 19-20, 21-22, 23-24, 25-26: primary side interlayer electrodes,
31-32, 33-34, 35-36, 37-38, 39-40, 41-42, 43-44, 45-46: secondary side interlayer electrodes,
P: the center point of the main surface of the cylindrical piezoelectric transformer elements 5 to 7,
Q: Center point of main surface of piezoelectric transformer element 8

Claims (3)

A piezoelectric transformer element whose outer shape is a rectangular parallelepiped,
The piezoelectric transformer element is
Of the plurality of outer surfaces forming the outer shape, the outer surface having the largest area is used as a main surface, and at least one pair of primary and secondary regions arranged adjacent to each other by a surface perpendicular to the main surface. Having a partitioned structure;
The primary side region and the secondary side region are:
A plurality of electrodes and piezoelectric layers formed in parallel to the main surface are alternately stacked in a direction perpendicular to the main surface, and among the plurality of piezoelectric layers, a piezoelectric layer in contact with the electrode through the electrodes Have structures that are polarized in opposite directions, driven in a contour spreading vibration mode ,
The primary side region and the secondary side region further include
Of the length direction and the width direction of the main surface, one set is adjacently arranged in the length direction, and the ratio between the length and the width of the main surface is 0.50 to 0.80. A piezoelectric transformer element characterized by being in the range of 1.30 to 1.75 . A piezoelectric transformer element having a substantially cylindrical outer shape,
The piezoelectric transformer element is
A structure that is partitioned into at least one or more adjacent primary side regions and secondary side regions by a plane perpendicular to the bottom surface of the substantially cylindrical outer shape;
The primary side region and the secondary side region are:
Electrodes and piezoelectric layers formed in parallel to the bottom surface are alternately stacked in a direction perpendicular to the bottom surface, and among the plurality of piezoelectric layers, the piezoelectric layers in contact with each other through the electrodes are mutually A piezoelectric transformer element having a structure polarized in the reverse direction and driven in a radially expanding vibration mode. A piezoelectric transformer element having a substantially cylindrical outer shape,
The piezoelectric transformer element is
And having a plurality of primary regions and a plurality of secondary regions in a plurality of regions that pass through the center of the bottom surface of the substantially cylindrical outer shape and are partitioned by two or more surfaces perpendicular to the bottom surface. The primary side region and the secondary side region have a structure in which the centers of the bottom surfaces are symmetrical and are adjacently arranged so that two opposing regions are the same type of region,
The primary side region and the secondary side region are:
Electrodes and piezoelectric layers formed in parallel to the bottom surface are alternately stacked in a direction perpendicular to the bottom surface, and among the plurality of piezoelectric layers, the piezoelectric layers in contact with the electrodes are opposite to each other. A piezoelectric transformer element having a structure polarized in a direction and driven in a radially expanded vibration mode.

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