JP2000111421A - Pressure detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure detecting apparatus which detects a level of a pressure through contact of an object. SOLUTION: The apparatus includes a piezoelectric transformer 14 comprising a driving part 12 with input electrodes 12a, 12b set to front and rear faces of one end face in a longitudinal direction of a piezoelectric ceramic plate 11 and a power generating part 13 having an output electrode 13a set to the other end face, a pressure calculating means 16 for calculating a pressure applied to the piezoelectric transformer 14, and a signal generating means 15 for applying a predetermined frequency to the driving part 12. A vibration characteristic changing in accordance with a pressure when the driving part 12 is vibrated by the signal generating means 15 and the pressure is applied to the piezoelectric transformer 14 is detected by the power generating part 13. The applied pressure is calculated by the pressure calculating means 16. A level of the pressure can be detected in a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device.

[0002]

2. Description of the Related Art A conventional pressure detector of this type is as follows.

[0003] First, IEEE Transaction on Electron Dev
In ices, vol. ED-26, No. 5, p815 to p817, 1979 (hereinafter referred to as Reference 1), a bimorph-type pressure detector as shown in FIG. 11 was proposed. As shown in the figure, electrodes 1b, 1c and 2 are provided on both sides of piezoelectric films 1a and 2a.
b, two belt-shaped piezoelectric films 1 and 2 provided with 2c are attached to each other, one end of which is supported in a cantilever shape by a support portion 3, and a voltage is applied to the piezoelectric film 1 from a transmitting portion 4 to vibrate; The output by the vibration was taken out from the piezoelectric film 2. With this configuration, when the object 5 comes into contact with the piezoelectric film 2, the contact of the object is detected based on a change in the output signal of the piezoelectric film 2.

[0004]

However, the pressure detecting device of Reference 1 can detect the presence or absence and the contact position of the object 5 on the piezoelectric film 2, but the pressure level due to the contact of the object 5 can be detected. There was a problem that it could not be detected. In addition, the cantilever type structure has a problem that if an object repeatedly comes into contact with the piezoelectric film, settling occurs on the piezoelectric film, thereby lowering detection sensitivity.

In order to further improve the sensitivity and output, it is necessary to increase the oscillation signal from the signal generating means 15 and to modify the output side circuit and the like, which has a very complicated structure.

Further, it is desired to simultaneously detect pressure and vibration in various applications, but there is a problem that the above-mentioned reference cannot meet such a demand.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a driving unit having electrodes provided on the front and back surfaces on one end surface in the longitudinal direction of a piezoelectric ceramic plate, and an electrode on the other end surface. A piezoelectric transformer comprising a power generation unit provided, pressure calculation means for calculating the pressure applied to the piezoelectric transformer,
Signal generating means for applying a predetermined frequency to the driving unit, wherein the driving unit is vibrated by the signal generating means, and the vibration of the piezoelectric transformer changes according to the pressure when pressure is applied to the piezoelectric transformer. The pressure detecting device detects a characteristic by the power generation unit and calculates an applied pressure by the pressure calculation unit based on an output signal of the power generation unit.

According to the present invention, when the pressure is applied to the piezoelectric transformer, the drive unit vibration characteristic of the piezoelectric transformer, which changes according to the pressure, is calculated by the power generation unit.
The pressure level can be detected with a simple configuration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure detecting device according to a first aspect of the present invention comprises a driving section having an input electrode provided on the front and back surfaces on one end face side in the longitudinal direction of a piezoelectric ceramic plate, and an output electrode provided on the other end face. A piezoelectric transformer comprising a power generating unit provided with: a pressure calculating unit for calculating a pressure applied to the piezoelectric transformer; and a signal generating unit for applying a predetermined frequency to the driving unit. Vibrating the drive,
The pressure generating means detects vibration characteristics of the piezoelectric transformer, which change according to the pressure when the pressure is applied to the piezoelectric transformer, and calculates the applied pressure by the pressure calculating means based on an output signal of the power generating unit. It is.

[0010] When a pressure is applied to the piezoelectric transformer, the vibration characteristic of the piezoelectric transformer, which changes according to the pressure, is calculated by the power generation unit, so that the pressure level can be detected with a simple configuration.

According to a second aspect of the present invention, there is provided a pressure detecting device comprising: a driving portion having an input electrode provided on the front and back surfaces on one end face side in a longitudinal direction of a piezoelectric ceramic plate; And a pressure calculating means for calculating a pressure applied to the piezoelectric transformer, and a signal generating means for applying a predetermined frequency to the driving part, wherein the driving part is vibrated by the signal generating means. Then, when a pressure is applied to the piezoelectric transformer, a vibration characteristic of the piezoelectric transformer that changes according to the pressure is detected by the power generation unit, and an applied pressure is calculated by the pressure calculation unit based on an output signal of the power generation unit. In addition, the signal generating means applies the resonance frequency of the piezoelectric transformer.

The sensitivity of the output signal to pressure is
Since the maximum value is obtained at the resonance frequency, the pressure level can be accurately detected.

In the pressure detecting device according to a third aspect of the present invention, the signal generating means can change the amplitude of the generated signal.

Since the amplitude of the output signal increases or decreases in proportion to the amplitude of the signal from the signal generator, the output signal can be selected as needed.

According to a fourth aspect of the present invention, in the pressure detecting device, the electromechanical coupling coefficient of the piezoelectric ceramic is maximized in a direction from the driving section toward the power generation section.

Then, the vibration generated by the vibration generating means becomes maximum in the direction toward the vibration detecting means.
A large detection signal is obtained by the vibration detection means.

According to a fifth aspect of the present invention, there is provided a pressure detecting device comprising: a driving portion having an input electrode provided on the front and back surfaces of one end surface of a piezoelectric ceramic plate in a longitudinal direction; and a power generating portion having an output electrode provided on the other end surface. A plurality of piezoelectric transformers comprising: and a pressure calculating means for calculating the pressure applied to the piezoelectric transformer, and a signal generating means for applying a predetermined frequency to the drive unit, at least one piezoelectric transformer No pressure is applied, an oscillation signal is applied to the drive unit by the signal generation unit, the vibration characteristics of the piezoelectric transformer are detected by the power generation unit, and the vibration characteristics of the piezoelectric transformer to which the pressure is applied and the pressure are applied. The applied pressure is calculated by the pressure calculating means from the vibration characteristics of the piezoelectric transformer which is not used.

Since a piezoelectric transformer to which no pressure is applied can be used as a reference electrode, an output change due to temperature can be corrected, and highly accurate pressure detection can be realized.

According to a sixth aspect of the present invention, there is provided a pressure detecting device comprising: a driving section having an input electrode on one of the longitudinal end faces of a piezoelectric ceramic plate; and a power generating section having an output electrode on the other end face. And a pressure calculating means for calculating a pressure applied to the piezoelectric transformer, and a signal generating means for applying a predetermined frequency to the drive unit. The driving unit is vibrated by the signal generation unit, and when the pressure is applied to the piezoelectric transformer, the vibration characteristic of the piezoelectric transformer, which changes according to the pressure, is detected by the power generation unit, and based on the output signal of the power generation unit. The applied pressure is calculated by the pressure calculating means.

By using a laminated piezoelectric transformer, the step-up ratio can be increased, the sensitivity can be improved, and the drive circuit can have a simpler configuration.

According to a seventh aspect of the present invention, there is provided a piezoelectric transformer for a pressure detecting device, comprising: a driving section having input electrodes provided on the front and back surfaces on one end face side in the longitudinal direction of a piezoelectric ceramic plate; An electrode is provided.

Since a plurality of detection signals can be used, highly reliable pressure detection can be performed, and the magnitude of the output from each electrode can be arbitrarily obtained, so that the output voltage can be selected as necessary. .

The piezoelectric transformer of the pressure detecting device according to claim 8 of the present invention has a structure in which the length of the piezoelectric ceramic in the longitudinal direction is
It is composed of a drive unit provided with input electrodes in one-third two regions on both ends, and a power generation unit provided with output electrodes in the remaining regions.

Since the driving sections are provided at both ends of the piezoelectric ceramic and the output is obtained from the output electrode formed in the power generation section at the center, the step-up ratio can be increased and the sensitivity of pressure detection can be increased. Can be improved.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing the structure of a pressure detecting device according to Embodiment 1 of the present invention. The input electrode 1 is provided on the front and back surfaces of one end surface of the piezoelectric
The piezoelectric transformer 1 comprises a driving unit 12 provided with 2a and 12b and a power generating unit 13 provided with an output electrode 13a on the other end face.
4 are formed. Further, the input electrode 12 of the drive unit 12
The signal generation unit 15 is connected to a and 12b, and the pressure calculation unit 16 is connected to the output electrode 13a of the power generation unit 13. Here, the input electrodes 12a and 12b and the output electrode 13a are formed by printing silver paste or the like, for example, but may be formed by evaporating a metal material such as aluminum.

The driving section 12 has input electrodes 12a and 12a.
b, and the power generation unit 13 is polarized between the output electrode 13a and the input electrodes 12a and 12b. The arrow shown inside the piezoelectric ceramic 11 in the figure indicates the direction of polarization. Next, the operation and operation will be described. First, the drive unit 12 sandwiched between the input electrodes 12a and 12b vibrates according to the oscillation signal generated by the signal generation unit 15. Here, the frequency of the oscillation signal is f1. This vibration propagates to the power generation unit 13, and a piezoelectric electromotive force (detection voltage) is generated according to the vibration. At this time, when the pressure W is applied to at least one of the driving unit 12 and the power generation unit 13 of the piezoelectric transformer 14 as shown in FIG. 1, a piezoelectric electromotive force corresponding to the pressure is generated in the power generation unit 13.

FIG. 2 shows an oscillation signal V0 (frequency f) of the signal generating means 15 when pressure is applied to the piezoelectric transformer 14.
FIG. 2 is a characteristic diagram showing signal waveforms of 1) and the electromotive force V1.
At this time, the piezoelectric electromotive force was detected from the output electrode 13a.
As shown in the figure, when no object is placed on the piezoelectric transformer 14 (t <t1), V1 is output in synchronization with V0. Further, a phase difference L01 occurs due to the propagation of vibration from the drive unit 12 to the power generation unit 13. Next, when a certain object is mounted or when the pressure W is applied due to the surrounding air pressure or the pressure of the liquid, the vibration of the driving unit 12 is hindered by the pressure application, and the amplitude of V1 becomes D0.
It decreases from 1 to D1. Note that the phase also changes from L01 to L1. The applied pressure is calculated by the pressure calculating means 16 based on the change in the vibration characteristic when the pressure is applied.

FIG. 3 shows that the driving means 12 is driven at a constant amplitude (10 V) over a wide range from the signal generating means 15 and a load of 1 kg and 2 kg is applied to the entire surface of the piezoelectric transformer 14 to obtain the power at the power generating section 13. FIG. 4 is a characteristic diagram showing frequency characteristics of the obtained piezoelectric electromotive force (D). At this time, the electrode 13a
A load resistance of 20 kΩ is provided between the input electrode 12b and the input electrode 12b. From this result, the piezoelectric electromotive force obtained by the power generation unit 13 with respect to the applied pressure W is the highest at the resonance frequency and decreases as the voltage deviates from the resonance frequency. Therefore, the signal generating means 1
By setting the output signal of No. 5 near the resonance frequency, the sensitivity can be improved.

Further, as described above, since the vibration of the piezoelectric transformer 14 is suppressed as the applied load increases, the output voltage decreases as the applied load increases as shown in FIG. FIG. 4 shows the relationship between the applied load and the piezoelectric electromotive force near the first resonance frequency of 32 to 33 kHz of the piezoelectric transformer.

As a result, since the piezoelectric electromotive force changes in accordance with the applied pressure, the applied pressure can be calculated by the pressure calculating means 16 from the piezoelectric electromotive force which is the output signal of the power generation unit.

Next, the amplitude V0 (frequency of 32.4 kHz) of the oscillation signal generated by the signal generation means 15 and the amplitude D of the pressure electromotive force detected by the output electrode 13a provided in the power generation unit 13 are shown.
Is shown in FIG. In the figure, an amplitude D01 is an amplitude obtained when no pressure is applied, and an amplitude D1 is an amplitude obtained when a pressure of 1 kg is applied to the piezoelectric transformer 14. As is apparent from FIG. 5, both the amplitudes D01 and D increase substantially in proportion to the amplitude V0 of the oscillation signal. Therefore, the difference (D01-D1) between them also increases almost in proportion to the amplitude V0 of the oscillation signal. The difference (D01-D1) between the two is the difference between the pressure electromotive force when no pressure is applied and the pressure electromotive force when 1 kg is applied under the measurement conditions shown in the figure, and thus corresponds to the apparent sensitivity. This indicates that the apparent sensitivity is proportional to the amplitude V0 of the oscillation signal.

Signal generating means capable of varying the amplitude of an oscillation signal
By using 15, an appropriate apparent sensitivity can be selected according to the application.

When the oscillating signal generated by the signal generating means 15 is applied to the drive unit 12 to vibrate the piezoelectric transformer 14, the ratio of the electric energy applied to the drive unit 12 that is converted into vibration energy is , Electromechanical coupling coefficient. This electromechanical coupling coefficient differs depending on the crystal direction of the piezoelectric ceramic 11.
Therefore, the electromechanical coupling coefficient is changed from the driving unit 12 to the power generation unit 13.
It is desirable to select the direction of the piezoelectric ceramic 11 so that it becomes maximum in the direction toward. This is because the detection voltage generated in the power generation unit 13 can be increased.

(Embodiment 2) FIG. 6 is a sectional view showing the structure of a pressure detecting device according to Embodiment 2 of the present invention. In this embodiment,
It differs from the first embodiment in the following points. That is, a point is that a plurality of the piezoelectric transformers 14 shown in the first embodiment are provided, and no pressure is applied to at least one of the piezoelectric transformers 14a.

Here, the signal generating means 15 applies the same level of oscillating signal to the drive units 12 of the piezoelectric transformers 14 and 14a, and the pressure detecting means 16 is provided. The applied pressure is calculated from the output signal (amplitude D of the pressure electromotive force) detected by the drive unit 13. Here, since no pressure is applied to the piezoelectric transformer 14a, even if pressure is applied to the piezoelectric transformer 14, the output signal does not change from the initial value. Therefore, the piezoelectric transformer 14a can be used as a reference electrode.

That is, as described in the first embodiment, in the pressure detecting device of the present invention, the vibration of the piezoelectric transformer 14 is suppressed as the applied load increases, so that the applied load increases as shown in FIG. As a result, the output voltage decreases. Although the applied pressure is detected using this relationship, the vibration state of the piezoelectric transformer 14 may change due to external influences such as air temperature. FIG. 7 shows applied loads and output signals of the piezoelectric transformer 14 at 25 ° C. and 60 ° C. As a result, 25 ° C
At 60 ° C. and 60 ° C., the tendency of the applied load and the output characteristic of the output signal are almost the same, and the value at 60 ° C. becomes higher by a certain constant value. However, since the difference from the state where no load is applied at 25 ° C. and 60 ° C. is constant regardless of the temperature,
The initial state of the two piezoelectric transformers 14 is made the same, and one of them is configured not to apply pressure, so that the difference between each output signal is obtained. Accurate pressure detection becomes possible.

(Embodiment 3) FIG. 8 is a block diagram of a pressure detecting device according to Embodiment 3 of the present invention. The difference from the first and second embodiments is that the driving unit 1 in which the input electrodes 12a and 12b are provided on the front and back surfaces of one end surface of the piezoelectric ceramic plate 11 in the longitudinal direction.
2 and a power generating unit 13 provided with an output electrode 13a on the other end face.
This is the point that a laminated piezoelectric transformer constituted by stacking piezoelectric ceramics 14 comprising As shown in FIG. 8, in the laminated piezoelectric transformer, the drive units 12 are laminated so that the polarization directions are alternately arranged, and are firmly fixed with a conductive adhesive. In order for the driving unit 12 to drive in parallel with the polarization, the polarization direction and the polarization direction of the arrow are arranged so as to face alternately, and the input electrode 12a of the piezoelectric ceramic 11 and the electrode sandwiched between the piezoelectric ceramics 17 and 18 and the piezoelectric Ceramic 18
Are connected. Similarly, the output electrodes 13a, 19a, and 20a of the stacked power generation unit 13 are short-circuited to the end face electrode 21, and the output is taken out from this end face electrode.

In the above configuration, an input signal is applied by the signal generating means 15 and an output which is a piezoelectric electromotive force is taken out from the end face electrode 19. The multilayer piezoelectric transformer of the present invention and the input / output force coefficient A are represented by the following equation.

[0040]

(Equation 1)

Here, w: width of the piezoelectric transformer, ε: dielectric constant, s: elastic compliance, k: electromechanical coupling coefficient, and n: the number of laminated piezoelectric ceramics.

As is apparent from this (Equation 1), the force coefficient A increases in proportion to the number n of layers, so that about n times the piezoelectric electromotive force without the layers can be obtained.

Therefore, a high pressure electromotive force can be obtained without increasing the amplitude of the signal generating means 15, and the sensitivity of pressure detection is improved.

(Embodiment 4) FIG. 9 is a block diagram of a pressure detecting device according to Embodiment 4 of the present invention. The difference from the first to third embodiments is that a plurality of output electrodes 13a are provided.

The drive unit 12 of the piezoelectric transformer 14 has input electrodes 12 a and 12 b formed on the upper and lower surfaces thereof,
Is divided in its length direction by a plurality of electrodes. In this embodiment, the length direction is divided into the electrodes 13a to 13d. The width of each of the electrodes 13a, 13b, 13c, and 13d is the same, and the spacing between the electrodes is also the same. With the electrode 13b on the ground side, the electrode 13c
Are the first output electrode, the electrode 13d is the second output electrode, and the electrode 13a is the third output electrode.
d, 13a 1/3 times the reference voltage to each output electrode, 2/3
It is possible to obtain an output of double or equal size.

Further, since the magnitude of the output from each electrode can be arbitrarily obtained by variously changing the number of electrodes and the interval between the electrodes, the output voltage can be selected as needed, Because of this, reliability is increased, and more accurate pressure detection is possible.

(Embodiment 5) FIG. 10 is a block diagram of a pressure detecting device according to Embodiment 5 of the present invention. The difference from the first to fourth embodiments is that a piezoelectric transformer is used in which the input electrodes 12
a, a drive unit 12 provided with 12b, 12c and 12d, and a power generation unit 13 provided with an output electrode 13a in the remaining area. Here, the driving unit 12 is a piezoelectric ceramic 11
The power generation unit 13 is polarized in the thickness direction of the piezoelectric ceramic 1.
1 is polarized in the longitudinal direction. Arrows in the figure indicate the polarization direction.

Each of the input electrodes 12a, 12b, 12c,
When an oscillation signal is applied to 12d by the signal generating means 15, the piezoelectric ceramic 11 resonates in the length direction due to the back electromotive force effect. At this time, the transmitted vibration from the drive units 12 at both ends is transmitted to the power generation unit 13 provided at the center, and approximately twice the vibration is given as compared with the case where only one of the drive units 12 is provided. Double. Therefore, the boost ratio is also doubled. From this, the value of the piezoelectric electromotive force obtained by the output electrode 13a when the pressure W is applied also increases,
The sensitivity can be improved.

[0049]

As described above, the pressure detecting device according to the first aspect of the present invention uses the signal generating means for the piezoelectric transformer composed of the driving section in which the input electrode is formed on the piezoelectric ceramic and the power generating section in which the output electrode is formed. Since the vibration characteristics of the piezoelectric transformer, which changes according to the pressure and weight when the pressure and weight are applied by vibrating the drive unit, are calculated by the pressure calculating means, the pressure level can be detected with a simple configuration. There is an effect that can be.

Further, since the pressure detecting device according to the second aspect of the present invention uses the resonance frequency of the piezoelectric transformer, the sensitivity of the output of the power generation unit to the pressure can be maximized, so that the sensitivity is improved.

Further, since the pressure detecting device according to the third aspect of the present invention has the signal generating means capable of changing the amplitude of the signal, the sensitivity of the output of the vibration detecting means with respect to the pressure can be selected according to the application. .

In the pressure detecting device according to claim 4 of the present invention, since the electromechanical coupling coefficient of the piezoelectric ceramic is maximum in the direction from the vibration generating means to the vibration detecting means, a large detection signal is obtained by the vibration detecting means. Can be

In the pressure detecting device according to the fifth aspect of the present invention, since a piezoelectric transformer to which no pressure is applied can be used as a reference electrode, it is possible to correct an output change due to temperature and realize highly accurate pressure detection.

According to a sixth aspect of the present invention, there is provided a pressure detecting device comprising a laminated piezoelectric transformer formed by stacking piezoelectric ceramics comprising a driving section provided with an input electrode and a power generation section provided with an output electrode. Therefore, the boosting ratio can be increased, the sensitivity can be improved, and the driving circuit can have a simpler configuration.

In the pressure detecting device according to the seventh aspect of the present invention, since the piezoelectric transformer has a driving portion provided with an input electrode and the other end surface provided with a plurality of output electrodes, a plurality of detection signals can be used. Since the pressure can be detected with high reliability and the magnitude of the output from each electrode can be arbitrarily obtained, the output voltage can be selected as needed.

In the pressure detecting device according to the eighth aspect of the present invention, since two driving sections are provided in the piezoelectric transformer and input electrodes are formed in each of the driving sections, the step-up ratio is increased and the detection accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pressure detection device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a signal generation unit of the pressure detection device and a piezoelectric electromotive force of a power generation unit.

FIG. 3 is a characteristic diagram showing a relationship between a frequency of a signal generation unit of the pressure detection device and a piezoelectric electromotive force of a power generation unit.

FIG. 4 is a characteristic diagram showing a relationship between a pressure of the pressure detection device and a piezoelectric electromotive force of a power generation unit.

FIG. 5 is a characteristic diagram showing a relationship between a signal amplitude of a signal generation unit of the pressure detection device and a piezoelectric electromotive force of a power generation unit.

FIG. 6 is another configuration diagram of the pressure detection device according to the second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a relationship between the pressure of the pressure detection device and the piezoelectric electromotive force of the power generation unit.

FIG. 8 is a configuration diagram of a pressure detection device according to a third embodiment of the present invention.

FIG. 9 is a configuration diagram of a pressure detection device according to a fourth embodiment of the present invention.

FIG. 10 is a configuration diagram of a pressure detection device according to a fifth embodiment of the present invention.

FIG. 11 is a block diagram of a conventional pressure detecting device.

[Explanation of symbols]

 11, 17, 18 Piezoelectric ceramic 12 Drive unit 12a, 12b Input electrode 17a, 17b Input electrode 18a, 18b Input electrode 13 Power generation unit 13a, 19a, 20a Output electrode 14 Piezoelectric transformer 15 Signal generation unit 16 Pressure calculation unit 21 End surface electrode

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroyuki Ogino 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahiko Ito 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A piezoelectric transformer comprising: a drive section having input electrodes provided on the front and back surfaces of one end face in a longitudinal direction of a piezoelectric ceramic plate; a power generation section having output electrodes provided on the other end face; Pressure calculating means for calculating the applied pressure, and a signal generating means for applying a predetermined frequency to the drive unit, the drive unit is vibrated by the signal generating means,
Pressure detection in which the power generation unit detects vibration characteristics of the piezoelectric transformer that change according to pressure when pressure is applied to the piezoelectric transformer, and calculates an applied pressure by the pressure calculation unit based on an output signal of the power generation unit. apparatus. 2. A piezoelectric transformer comprising: a drive section provided with input electrodes on the front and back surfaces at one end face in the longitudinal direction of a piezoelectric ceramic plate; and a power generation section provided with an output electrode on the other end face; A pressure calculating means for calculating a pressure applied to the piezoelectric transformer; and a signal generating means for applying a predetermined frequency to the driving section. The driving section is vibrated by the signal generating means, and pressure is applied to the piezoelectric transformer. And the vibration characteristic of the piezoelectric transformer, which varies according to the pressure, is detected by the power generation unit, and the applied pressure is calculated by the pressure calculation unit based on the output signal of the power generation unit. Pressure detecting device. 3. The pressure detecting device according to claim 1, wherein the signal generating means can change the amplitude of the generated signal. 4. The pressure detecting device according to claim 1, wherein an electromechanical coupling coefficient of the piezoelectric ceramic is maximum in a direction from the driving section toward the power generation section. 5. A piezoelectric transformer comprising: a plurality of piezoelectric transformers each including a drive section having input electrodes provided on the front and back surfaces of one end face of a piezoelectric ceramic plate in the longitudinal direction, and a power generation section having output electrodes provided on the other end face; Pressure generating means for calculating the pressure applied to the piezoelectric transformer, and signal generating means for applying a predetermined frequency to the drive unit, at least one piezoelectric transformer is configured to apply no pressure, the signal generating means The driving section is vibrated to detect the vibration characteristics of the piezoelectric transformer by the power generation section, and the piezoelectric transformer is obtained from the output signal of the power generation section of the piezoelectric transformer to which pressure is applied and the output signal of the power generation section of the piezoelectric transformer to which no pressure is applied. A pressure detecting device for calculating the applied pressure of the pressure by the pressure calculating means. 6. A laminated structure in which a piezoelectric ceramic comprising a drive section provided with input electrodes on the front and back surfaces of one end face in the longitudinal direction of a piezoelectric ceramic plate and a power generation section provided with output electrodes on the other end face is stacked. Type piezoelectric transformer, pressure calculating means for calculating the pressure applied to the piezoelectric transformer,
Signal generating means for applying a predetermined frequency to the driving section, wherein the driving section is vibrated by the signal generating means, and when pressure is applied to the piezoelectric transformer, the vibration characteristic of the piezoelectric transformer changes according to the pressure. A pressure detecting device for detecting the pressure by the power generation unit and calculating the applied pressure by the pressure calculation means based on the output signal of the power generation unit. 7. The piezoelectric transformer according to claim 1, wherein the piezoelectric transformer has a drive section provided with input electrodes on the front and back surfaces on one end face side in the longitudinal direction of the piezoelectric ceramic plate, and a plurality of output electrodes provided on the other end face. A pressure detecting device according to any one of the preceding claims. 8. A piezoelectric transformer comprises a drive section having input electrodes provided in two thirds on both ends in a longitudinal direction of a piezoelectric ceramic, and a power generation section having output electrodes provided in the remaining area. The pressure detecting device according to any one of claims 1 to 4, wherein: