JPH10308544A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer which allows stable support, connection of a lead wire to a portion generating no vibration, selection of a driving frequency, and driving at a low voltage by reducing the input impedance. SOLUTION: A vibrator 10 made of piezoelectric ceramics or the like has a support 11 and vibrating arms 12a, 12b, 13. When a driving voltage is supplied to input side electrodes 14, 14, the vibrating arms 12a, 12b on both lateral sides and the vibrating arm 13 at the center generate balanced vibration, and a generated voltage is outputted from an output side electrode 15. Since the support 11 is a portion generating no vibration, it can be supported easily. Also, when a lead wire is connected to the support 11, no stress acts on the connection part. Thus, problems such as disconnection can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer using a piezoelectric vibrator, and more particularly to a thin piezoelectric transformer which can be easily supported.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view showing a conventional piezoelectric transformer. In this piezoelectric transformer, an input portion 2 of a flat plate type vibrator 1 formed of a piezoelectric material is polarized in a thickness direction, and input electrodes 3 are provided on both front and back surfaces. The drive voltage applied to the input electrode 3 excites longitudinal vibration in the transverse effect mode. In the power generation unit 4, an output-side electrode 5 is provided on an end face, and a voltage transformed according to impedance is extracted from the output-side electrode 5 by an electromechanical coupling coefficient in a longitudinal effect mode.

[0003]

However, the conventional piezoelectric transformer shown in FIG. 8 has the following problems. (1) Since the entire vibrator 1 has a structure that generates longitudinal vibration, stable support is difficult. (2) Since the input impedance is high, a high driving voltage is required to generate longitudinal vibration, and low-voltage driving cannot be performed. (3) Since the output-side electrode 5 is formed in a portion where the amplitude of the longitudinal vibration is large, the stress acting on the lead wire connected to the output-side electrode 5 is large, and disconnection or the like is likely to occur. (4) Since the drive frequency is uniquely determined by the shape and dimensions of the vibrator 1, there is no selectivity in the drive frequency.

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to stably support and connect a lead wire to a portion where vibration does not occur. It is an object of the present invention to provide a piezoelectric transformer capable of driving at a low voltage with a low impedance.

[0005]

SUMMARY OF THE INVENTION The present invention provides an input-side vibrating arm and an output-side vibrating arm extending in parallel from a support formed of a piezoelectric material, and an input-side vibrating arm formed on the input-side vibrating arm. An electrode, an AC drive power supply unit that applies an AC drive voltage to the input side electrode to vibrate the respective vibrating arms, and an output side that is formed on the output side vibrating arm and extracts a generated voltage that is transformed according to impedance. And an electrode.

For example, the AC drive voltage applied to the input side electrode excites the input side vibrating arm to longitudinal vibration that expands and contracts in the direction in which the arm extends in the transverse effect mode, thereby causing the output side vibrating arm to likewise move. A vertical vibration is generated, and the voltage generated by the vertical vibration of the vibrating arm on the output side is extracted from the output side electrode,

Alternatively, the AC drive voltage applied to the input-side electrode excites the input-side vibrating arm to longitudinal vibration that expands and contracts in the direction in which the arm extends in the transverse effect mode. And a bending vibration, and a voltage generated by the longitudinal vibration of the vibrating arm on the output side is extracted from the output side electrode.

It is also possible to adopt a configuration in which the output impedance of the vibrating arm on the output side is higher than the input impedance of the vibrating arm on the input side, and a boosted voltage is output from the output side electrode.

Alternatively, it is possible to increase the area of the output-side electrode to obtain a large current output from the output-side electrode.

Further, the input side electrode and the output side electrode may extend to the support, and a connection portion between each of the electrodes and the lead wire may be formed in the support.

The piezoelectric transformer of the present invention is a two-leg tuning fork type or a three-leg tuning fork type or a four-leg or more tuning fork type in which a support, a vibrating arm on the input side and a vibrating arm on the output side are integrally formed by a piezoelectric material. Can be configured as

The tuning fork type piezoelectric transformer having two or more legs is
Since large vibrations directly related to input and output do not occur in the portion of the support, the support can be supported, and the support fixing structure can be simplified. In particular, in a tripod tuning fork type, if the vibrating arms on both sides are vibrated in the same phase and the center vibrating arm is vibrated in the opposite phase to the vibrating arms on both sides, a well-balanced vibration is possible as a whole, and the support is rigid. It becomes possible to support.

Therefore, if the input side electrode and the output side electrode are extended on the support and the lead wire is connected to each electrode at the support, vibration and stress act on the portion where the lead wire is connected. No longer occurs, or its size is reduced even if it acts. Therefore, poor connection or disconnection of the lead wire is less likely to occur.

In this piezoelectric transformer, for example, the vibrating arm on the input side and the vibrating arm on the output side are expanded and contracted in the vertical direction at the same phase, or expanded and contracted in the vertical direction with different vibrations. Vibration coupled with vibration can be generated. In each of the vibration modes, since the driving frequencies are different from each other, the piezoelectric transformer can be driven at a plurality of frequencies, and the driving frequency can have selectivity.

[0015] In addition, in the coupled oscillation, since the input impedance is reduced, low-voltage driving can be performed.

[0016]

FIG. 1A is a plan view showing a piezoelectric transformer of the present invention, FIG. 1B is a rear view thereof, and FIG.
FIG. 3A is an end view taken in the direction of the arrow II, FIGS. 3A and 3B are explanatory diagrams of the vibration mode, and FIG. 4 is an equivalent circuit diagram. The vibrating body 10 of the piezoelectric transformer shown in FIG. 1 is entirely formed of a piezoelectric material such as piezoelectric ceramic, and a support 11 and the input-side vibrating arms 12a and 12b and the output-side vibrating arm 13 are integrally formed. Is formed. Each vibrating arm 12a, 12b and 1
3 have the same planar shape and dimensions, and extend parallel to each other. As shown in FIG.
In a, 12b, and 13, the dielectric polarization direction is the thickness direction as indicated by the arrow.

As shown in FIG. 1A, on the surface side of the vibrating body 10, input side electrodes 14, 14 having a relatively large area are formed on the input side vibrating arms 12a and 12b. The output electrode 15 having a relatively small area is formed on the vibrator 13. The lands 14 a, 14 a formed integrally with the input electrodes 14, 14 extend to the base end of the support 11. In addition, a land portion 15 a formed integrally with the output side electrode 15 also extends to the base end of the support 11.

As shown in FIG. 1B, on the back side of the vibrating body 10, ground electrodes 16a, 16a are formed on the input side vibrating arms 12a, 12b.
Reference numerals a and 16a have the same area as the input electrodes 14 and 14 and are formed to face the input electrodes 14 and 14.
A ground electrode 16b is formed on the center vibration arm 13 on the output side. The ground electrode 16b has the same area as the output electrode 15 and is formed to face the output electrode 15. Also, the ground electrodes 16a, 16a and 16
b is formed integrally with a conductor pattern, and the lands 16c, 16c formed integrally with the ground electrode are
The support 11 extends to the base end.

As shown in FIG. 2, each of the ground electrodes 16a,
16a and 16b are connected to the ground potential by a lead wire connected to the land 16c. The lead wires extending from the AC drive power supply unit 17 are connected to the land portions 14a, 14a.
And a land portion 15a integrated with the output side electrode 15 is an output portion, and an output voltage Vout is obtained between a lead wire connected to the output portion and a ground potential.

FIG. 4 shows an equivalent circuit of the vibrating body 10. Cd1 is the braking capacity of the input-side vibrating arms 12a and 12b, Cd2 is the braking capacity of the output-side vibrating arm 13, and m1 and s.
1 and r1 are the equivalent mass, equivalent stiffness and equivalent resonance resistance of each of the vibrating arms 12a, 12b and 13. A1
Is the force constant of the input side vibrating arms 12a and 12b, and A2
Is a force constant of the vibrating arm 13 on the output side.

FIGS. 3A and 3B show the vibration mode at the equivalent mass shown in FIG. 4. The AC driving power supply 17 applies a predetermined frequency to each of the input electrodes 14 and 14. When an AC drive voltage is applied, the vibrating arms 12a, 1
In 2b, the longitudinal vibration due to the electromechanical coupling coefficient K31 in the transverse effect mode is excited, the vibrating arms 12a and 12b vibrate in the longitudinal direction, and the vibrating arm 13 on the output side also vibrates in the longitudinal direction. In the vibration mode shown in FIG. 3A, the input side vibrating arms 12a and 12b on both sides and the central output side vibrating arm 13 generate longitudinal vibrations in opposite phases. For example, the vibrating arms 12a and 12 on both sides
When b extends in the longitudinal direction, the central vibrating arm contracts in the vertical direction. In the vibration mode shown in FIG.
Vibrations of the same phase are generated so that 2a, 12a and the central vibrating arm 13 simultaneously extend in the vertical direction and simultaneously contract. At this time, the output side electrode 15 is
And the ground electrode 16b opposed thereto have a small area, the output impedance is increased, and a boosted voltage (Vout) is output between the output electrode 15 and the ground potential. In this case, the vibration frequency of the vibrating body 10 is different between the vibration mode shown in FIG. 3A and the vibration mode shown in FIG.

Since the vibrating body 10 of this piezoelectric transformer is of a tuning fork type, it is possible to support the portion of the supporting body 11, so that the whole vibrator vibrates in the same state as shown in FIG. It is easier to support than it is. Particularly, in the case of a tripod tuning fork type, the vibrating arms 12 on both input sides are used.
a and 12b vibrate in the same phase, and the vibrating arm 13 on the central output side is set to vibrate in the opposite phase to the vibrating arms 12a and 12b. I do. Further, distortion such as torsion and substantial vibration do not occur in the support 11, and the base end of the support 11 can be supported by a rigid body. Similarly, in the two-leg tuning fork type, if the two vibrating arms are set in the mode of vibrating in different phases, the support 11 can be easily supported.

On the other hand, as shown in FIG. 3B, when the vibrating arms 12a, 12b and 13 vibrate in the same phase, elongation vibration also occurs in the support 11, but in this case, the support 11 By setting the entire structure so that a node of vibration is formed at 11, the vibrating body 10
Can be stably supported. Thus, the piezoelectric transformer constituted by the tuning-fork type vibrator can be easily supported, and the supporting structure can be simplified. Since the land portions 14a, 15a, and 16c of the respective electrodes are located at the base end of the support 11, when a lead wire is connected to these land portions, stress acts on the connection portion of the lead wire. Without disconnecting, disconnection or disconnection of the lead wire can be prevented.

FIG. 5 shows a case where the piezoelectric transformer of the present invention is driven in another vibration mode.
(B) is an end view thereof. The vibrating body 10 of this piezoelectric transformer is the same as that shown in FIGS.
The support 11 and the three parallel vibrating arms 12a, 12b and 13 are integrally formed of a piezoelectric material such as a piezoelectric ceramic. In this vibrating body 10, all the vibrating arms 12
a, 12b and the vibrating arm 13 have the same dimensions. In the piezoelectric transformer of FIG. 5, the center vibrating arm 13 is the input side,
The vibrating arms 12a and 12b on both sides are output sides. When the primary stretching vibration α is excited in the longitudinal direction in the central vibrating arm 13, the vibrating arms 12 a and 12 b on both sides have a predetermined frequency,
The longitudinal dimension L and the width dimension D of each vibrating arm are set so as to generate a combined vibration (complex vibration) of the primary stretching vibration (longitudinal vibration) α and the cantilever secondary bending vibration β. .

FIG. 7 shows the vibrating arms 12a, 12b and 13
The relationship between the ratio (D / L) of the length dimension L to the width dimension D (D / L) and the vibration frequency f is shown. fa indicates a change in the frequency of the longitudinal vibration, and fb indicates a change in the frequency of the bending vibration. The frequency of the longitudinal vibration and the frequency of the bending vibration match when D / L is a predetermined value. Therefore, when the dimensional ratio D / L of the vibrating arms 12a and 12b and the vibrating arm 13 is set to be the coupling region in FIG. 7, the vibration in the coupling mode shown in FIG. it can.

The central vibrating arm 13 on the input side is polarized in the thickness direction, and has an input side electrode (drive side electrode) on its surface.
21a has a ground electrode 21b formed on the back surface thereof, and an AC drive voltage is applied to the input side electrode 21a from an AC drive power supply unit 22. The vibrating arms 12a and 12 on both sides serving as output sides
b is polarized in the width direction. Both vibrating arms 12a and 12
b, an earth electrode 23a, 23a is formed on the inner side end face, and an output side electrode (power generation side electrode) 2 is formed on the outer side end.
3b and 23b are formed, and the electrodes 23a and 23b on the output side are formed so as to face each other in the width direction D on the vibrating arms 12a and 12b on both sides. In addition, each output side electrode 2
The output lead wires connected to 3b and 23b are output terminals 24.
And 24.

From the AC drive power supply 22, the input side electrode 21
When an AC drive voltage of a predetermined frequency is applied to a, the central vibrating arm 13 as an input unit excites primary stretching vibration (longitudinal vibration) α with the electromechanical coupling coefficient K31 in the transverse effect mode. When the longitudinal vibration occurs at a predetermined frequency, the vibrating body 10
As a whole, the vibrating arms 12a and 12b on both sides generate primary stretching vibration (longitudinal vibration) α and secondary bending vibration (bending vibration in the plate surface direction) β, and the vibrating arms 12a and 12b The next bending vibration β occurs in a symmetric direction. In the vibrating arms 12a and 12b on both sides on the output side, the polarization direction is the width direction, and the electrodes 23a and 23b having a small area are formed on the side end faces with an interval in the width direction D. As a result, the output terminals 24 and 24 output a boosted voltage by the electromechanical coupling coefficient K33 in the longitudinal effect mode.

FIG. 6 is an equivalent circuit diagram when the vibrating arm generates a combined vibration of the longitudinal vibration and the bending vibration. Cd
1 is the braking capacity of the input-side vibrating arm 13, Cd2 is the braking capacity of the output-side vibrating arms 12a and 12b, m1, s1, r1
Is the equivalent mass, equivalent stiffness, equivalent resonance resistance, m1 ', s1', r1 'of the output side vibrating arms 12a, 12b in the stretching vibration (longitudinal vibration) mode.
Are equivalent mass, equivalent stiffness, and equivalent resonance resistance in the bending vibration mode. Further, n1 and n2 are force coefficients in a stretching vibration (longitudinal vibration) mode and a bending vibration mode. In this vibrating body 10, since the stretching vibration and the bending vibration of the vibrating arm resonate at the same natural frequency, m1 and s1 and m1 'and s1' can be substantially ignored by resonance. Therefore, the impedance on the input side is determined by the equivalent resonance resistances r1 and r1 '. The equivalent resonance resistances r1 and r
Since 1 'is in parallel, the impedance on the input side is low, and driving at a low voltage is possible.

That is, the piezoelectric transformer shown in FIGS. 5A and 5B has a low input impedance and can be driven at a low voltage by using coupled vibration (complex vibration).
In addition, the boost rate is high. Thus, in the piezoelectric transformer using the tuning-fork type vibrator of the present invention, each vibrating arm 12
a, 12b and 13 are modes shown in FIG.
Vibration occurs in the mode shown in FIG. 3B and further in the coupling mode shown in FIG. 5A, but the vibration frequency differs in each mode. Therefore, the use frequency can be selected even with the same structure.

In the case shown in FIGS. 1A and 1B,
Output-side electrode 15 and ground electrode 16b opposed thereto
, The impedance on the output side can be adjusted. If the area of the electrodes 15 and 16b is reduced, the impedance can be increased to increase the boosting rate. If the area of the electrodes 15 and 16b is increased, the impedance can be reduced. As a result, although the boosting rate decreases, a large current output can be obtained. Then, as shown in FIG. 5A, if a combined vibration mode of longitudinal vibration and bending vibration is used, the input impedance can be reduced, and low-voltage driving can be performed.

[0031]

As described above, in the piezoelectric transformer according to the present invention, since the supporting portion can be supported, the supporting structure is simplified. In particular, in the case of a tripod tuning fork type, since a well-balanced operation occurs as a whole, it is possible to rigidly support the support portion. In addition, by connecting the lead wire to the electrode at the portion of the support, the stress acting on the lead wire can be reduced, and connection failure and disconnection hardly occur.

Further, the driving frequency can be selected according to the vibration mode of each vibrating arm, and the input impedance can be lowered and the output impedance can be raised.

[Brief description of the drawings]

1A is a plan view showing a piezoelectric transformer according to a first embodiment of the present invention, FIG. 1B is a rear view thereof,

FIG. 2 is an end view of the piezoelectric transformer according to the first embodiment shown in FIG.

FIGS. 3A and 3B are plan views showing longitudinal vibration modes of respective vibrating arms; FIGS.

FIG. 4 is an equivalent circuit diagram when the piezoelectric transformer shown in FIG. 1 is driven by longitudinal vibration;

5A is a plan view of a piezoelectric transformer according to a second embodiment of the present invention, FIG. 5B is an end view thereof,

FIG. 6 is an equivalent circuit diagram in the case where the piezoelectric transformer shown in FIG. 5 generates coupling vibration;

FIG. 7 is a diagram showing the relationship between the vibration frequency and the dimensional ratio of the length and width of the vibrating arm;

FIG. 8 is a perspective view of a conventional piezoelectric transformer,

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration body 11 Support body 12a, 12b, 13 Vibration arm 14 Input side electrode 14a Land part 15 Output side electrode 15a Land part 16a, 16b Earth electrode 16c Land part 21a Input side electrode 21b, 23a Earth electrode 23b Output side electrode

Claims (5)

[Claims] An input-side vibrating arm and an output-side vibrating arm extending in parallel from a support made of a piezoelectric material; an input-side electrode formed on the input-side vibrating arm; An AC drive power supply unit that applies an AC drive voltage to vibrate each of the vibrating arms, and an output-side electrode formed on the output-side vibrating arm to extract a generated voltage that is transformed according to impedance is provided. A piezoelectric transformer, characterized in that: 2. An AC drive voltage applied to an input-side electrode excites a longitudinal vibration that expands and contracts in a direction in which the arm extends in a lateral effect mode on an input-side vibrating arm, thereby similarly causing an output-side vibrating arm to move. 2. The piezoelectric transformer according to claim 1, wherein a vertical vibration is generated, and a voltage generated by the vertical vibration of the output-side vibrating arm is taken out from the output-side electrode. 3. An AC drive voltage applied to an input-side electrode excites a longitudinal vibration that expands and contracts in a direction in which the arm extends in a lateral effect mode in the vibrating arm on the input side, thereby causing a longitudinal vibration on the vibrating arm on the output side. The piezoelectric transformer according to claim 1, wherein the voltage generated by the longitudinal vibration of the vibrating arm on the output side is extracted from the output-side electrode. 4. The output impedance of the vibrating arm on the output side is higher than the input impedance of the vibrating arm on the input side.
4. The piezoelectric transformer according to claim 1, wherein a boosted voltage is output from the output electrode. 5. The device according to claim 1, wherein the input side electrode and the output side electrode extend to the support, and a connecting portion between each of the electrodes and the lead wire is formed in the support. The described piezoelectric transformer.