JPS60209285A - Piezoelectric vibration generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a piezoelectric vibration generator, and more particularly, to a piezoelectric vibration generator using a piezoelectric element that enables localized vibration soaping with high accuracy. Regarding.

(Prior Art) When considering all the characteristics of so-called objects such as material parts, devices, and systems, their vibration characteristics are one of the essential performances. In the case of materials and parts, all kinds of applications are considered, and in the case of devices and systems, in addition to the vibration characteristics of the component parts, the vibration characteristics from the perspective of the aggregate are important.

When examining the vibration characteristics of an object as described above, it is often possible to find out whether there is a problem with condensed matter theory or simieracity through a so-called theoretical study based on empirical theory, but if there are uncertain elements, it is necessary to use experimental studies. This will require consideration.

As a vibration generator, a vibration generator whose mechanical strength can be varied from low frequency to high frequency has been developed and used for commercial purposes. Using these vibrators to elucidate what kind of distortion occurs when an uneven sword is applied to a glass or adhesive surface, for example, will help improve the properties of glass and adhesives and expand their applications. It is indispensable. As these characteristics become clearer, the experimental conditions usually become stricter. The severity is different from the severity that occurs when vibration resistance tests are performed using actual airplanes or automobiles, for example, when the power is relatively large. In other words, it is necessary to apply a vibration with a smaller amplitude and higher frequency to a part of the glass surface or adhesive surface, and it is also necessary to be able to detect the distortion in that case. As means for detecting minute distortions, optical interference or holography can be used to detect them with high precision. As a vibration generation source, one that utilizes the magnetostrictive phenomenon of a magnetic material and one that utilizes the piezoelectric phenomenon of a piezoelectric material are being considered.

(Problems with conventional technology) The magnetostriction phenomenon described above occurs when a magnetic field is applied to a magnetic material.
This is a phenomenon in which the magnetic material expands in proportion to the magnitude of the magnetic field and the dimensions of the magnetic material, and expands and contracts as the magnetic field turns on and off. -The electrostrictive phenomenon is a phenomenon in which when an electric field is applied to a piezoelectric material, the piezoelectric material stretches in proportion to the magnitude of the electric field and the dimensions of the electrostrictive material.

A driver circuit for producing the same strain using a magnetic material and a piezoelectric material of the same size is easier to obtain using a piezoelectric material.

Also, when the on/off interval is shortened.

In other words, piezoelectric materials have much better frequency followability. The main reason for this is the eddy current product of the magnetic material. For the above reasons, piezoelectric materials are regarded as promising materials for the vibration generation sources mentioned in the prior art section. As shown in FIG. 1, a conventional piezoelectric vibration generator includes a piezoelectric element 1 provided on an electrode 11, a power source E that applies voltage to the piezoelectric element 1, and a switch 81 that controls the electric field.

A problem in developing a vibration generator using this piezoelectric material is the technical restriction in increasing the amount of expansion and contraction of the piezoelectric material. Since the expansion/contraction rate of a piezoelectric material is approximately proportional to the electric field intensity, if the thickness of the piezoelectric element shown in FIG. 1 is increased to increase the amount of expansion/contraction, a large applied voltage is required. Approximate value of applied voltage and amount of elongation f? In other words, when a voltage of about 600 V is applied to a ceramic element with a thickness of 1 mm, the amount of expansion and contraction is about 1 μm. On the other hand, increasing the voltage applied to the ceramic element to increase the amount of expansion and contraction is not preferable in order to operate the fine movement device at higher speed. That is, as can be seen from the explanation of the piezoelectric phenomenon described above.

To expand and contract the piezoelectric element to a high distance, use switch S in Figure 1.
1 is required to operate at high speed, and a transistor is used as this high-speed switch. Increasing the voltage applied to the ceramic element equivalently means that it is necessary to develop a transistor that operates at high voltage and high speed.

FIGS. 2(a) and 2(b) show the structure of an alloy junction transistor for power use suitable as a switch 81 operating at high speed, with an emitter 3. The current area of the collector 5 is made as large as possible so that the current density does not become excessive. Note that 4 is the base. The faster the switching speed, the better.

Due to the skin effect, current only flows near the electrode surface, so two people needed to devise ways to increase the surface area of the electrode. Therefore, the higher the speed and the higher the voltage resistance, the larger the surface area of the semiconductor and electrodes, and the lower the yield and the higher the cost compared to the transistors with lower voltage resistance. There is also a method of dividing and switching a high voltage using a plurality of low-voltage transistors, but this requires adjustment time to solve all the problems of delay and balance of each transistor.

For the reasons mentioned above, increasing the voltage applied to the ceramic element to increase the amount of expansion and contraction is important in terms of both the switching transistor used and the miniaturization of the device. Undesirable for driving
This is a major obstacle in reducing the cost of piezoelectric vibration generators.

- In order to achieve high distortion generation by applying low voltage and driving, electrodes are set on the front and back surfaces of the thin plate element in the thickness direction, and voltages are applied in parallel to the integrated element by stacking a large number of these. Therefore, a laminated piezoelectric element has been developed that increases the electric field strength per layer and achieves high strain as a whole, but since each thin piece cannot be made very thin, a high driving voltage is still required. Since adhesive is used to laminate all the thin plates, productivity is low and costs are high.

Furthermore, since the adhesive layer is present, it is not possible to obtain uniform strain as in a pure piezoelectric element. It lacks the reliability of Kotobuki et al. Further, due to the large size, etc., it was not fully satisfactory as an element for electronic parts.

However, recently, small-sized piezoelectric ceramic elements have been developed,
59. It was announced in May 1982. This ultra-small piezoelectric ceramic element is made by laminating and integrating piezoelectric ceramic plates without using an adhesive, and has been able to solve many of the above problems.

(Object of the Invention) The object of the present invention is to eliminate the drawbacks of conventional piezoelectric vibration generators using piezoelectric elements, and to provide a piezoelectric vibration generator that can be driven at low voltage and generate high distortion at high speed. It is about providing.

(Structure of the Invention) The piezoelectric vibration generator of the present invention includes a laminated piezoelectric element exhibiting an inverse piezoelectric effect, and an electric field applied to the laminated layer within the piezoelectric element in order to cause the piezoelectric element to expand and contract in the axial direction. , an electric field applying means for changing the electric field strength, and a housing for storing and fixing the laminated piezoelectric element.

the magnitude of the electric field applied to the laminated piezoelectric element;

It is constructed by controlling the amount of displacement and the cycle of expansion and contraction of the laminated piezoelectric element by controlling the connection and disconnection of the electric field.

(Embodiment 5A) Hereinafter, an embodiment of the present invention will be described with reference to one drawing.

FIG. 3 is a partial plan cross-sectional view of an embodiment of the present invention.

FIG. 4 is a sectional view of essential parts of a laminated piezoelectric element used in the device of the present invention. Referring to FIG. 4, the laminated piezoelectric element 10 has a large number of internal electrode layers 25 embedded inside the cell is7 in a layered manner and exposed at the end faces of the element. These exposed internal electrode layers are covered every other layer with an insulator 26, and external electrodes 27 and 28 are applied from above, so that the internal electrode layers are electrically connected in parallel to each other. It turns out. - Since these elements are polarized in the thickness direction, when a voltage is applied between the external electrodes.

It expands in the thickness direction in proportion to the magnitude of the applied voltage. The laminated piezoelectric element has a diameter of 39 mm and the length of the laminated body is 5 f3
mm, and the electrode spacing is preferably 50 μm.

When the applied voltage is 100 V, the voltage of the element alone is 108μ.
Stretch m. Although the laminated piezoelectric element is provided with a gap 7 of 5 mm φ x 20 mm for fitting into the housing 6, it does not affect the amount of expansion and contraction of the laminated piezoelectric element. The bottom surface of the laminated piezoelectric element is fixed to the housing 6 using adhesive 8, and the nearly hemispherical ceramic element 9 is connected to the top surface using adhesive 8. Power supply 11 and switch 12 are computer controlled.

As explained above, according to the one-piece embodiment, it is superior in mass production and reliability because it uses a monolithically fired laminated piezoelectric element that does not use any adhesive.
The equivalent thickness of the thin film can also be set to 50 m. In addition, since the internal electrodes are insulated at the end face of every other layer and external electrodes are attached, a voltage of 600V was conventionally required to be applied to a 1mm thick element, but with the above structure, a voltage can be applied in parallel to the portion corresponding to each thin plate. Therefore, it can be driven at 100v. Further, since each thin plate is formed thinly, it is possible to increase the applied voltage of the unit 9 to increase the amount of expansion and contraction. Therefore, the difficulty of using high-voltage, high-speed transistors required as switches is eliminated.

In addition, since the laminated piezoelectric element is fixed with a gap provided at the lower center of the element and fixed with adhesive, it is possible to securely fix the element.

Furthermore, since a nearly hemispherical ceramic element is fixed to the upper surface with an adhesive, good contact with the object to be contacted can be achieved.

For the above reasons, the device and drive circuit can be made non-oxidizing and compact.

(Effects of the Invention) As explained above, according to the present invention, by using a laminated piezoelectric element as the drive source of the vibration generator, (1) low voltage driving is possible.

(Mass production and reliability are high because it is a multi-layered element of 4-integrated firing type.

(3) For the above reasons, it is possible to make the device and drive circuit smaller and more compact.

The economic, functional, and reliability ripple effects are enormous.

[Brief explanation of the drawing]

FIG. 3 is a partial plan sectional view of an embodiment of the present invention, and FIG. 4 is a sectional view of essential parts of a laminated wall piezoelectric element. 1...piezoelectric element, la...electrode, 2...
·····semiconductor. 3...Emitter, 4...Pace, 5.
...Collector, 6...Housing, 7.
...Void, 8...Adhesive. 9... Ceramic, 10... Laminated piezoelectric element. 11... Variable power supply, 12... Switch, 25... Internal electrode layer, 26... Insulator, 27, 28... Electric Early 1 @ (kui rod 2 times)

Claims (1)

[Claims] A laminated piezoelectric element exhibiting an inverse piezoelectric effect, a means for applying an electric field within the laminated piezoelectric element to cause the laminated piezoelectric element to expand and contract in the axial direction, and a means for changing the intensity of the electric field. An electric field applying means, a housing for storing and fixing the laminated piezoelectric element, and '! 1-A, the laminated layer is configured to control the magnitude of the electric field applied to the piezoelectric element and the connection/disconnection of the cough electric field.