JPS6115383A - Cylindrical piezoelectric ceramic element - Google Patents

Abstract

PURPOSE:To adjust the inner diameter of the titled element varied by wearing on the basis of voltage values by a method wherein internal electrode layers exposed to the end surface of the element produced by integral lamination of many plates are alternately covered with insulators, and external electrodes are provided from above them. CONSTITUTION:The internal electrodes 5 are buried in layer form inside a thin plate ceramic cylindrical element 6, and then exposed to the element end surface. The internal electrode layers 5 are alternately covered with insulators 7 and coated with external electrodes 8 and 9 from above them; therefore, the layers 5 are electrically connected to each other in parallel. The ceramic 6, being under polarization in the thickness direction, expands in the thickness direction and therefore contracts in the diameter direction in proportion to the following voltage when a voltage is impressed between the external electrodes 8 and 9 in order to promoto the polarization.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cylindrical piezoelectric ceramic element used for clamping objects, etc.

(Prior Art) A conventional cylindrical element using a piezoelectric material utilizes strain caused by an electric field applied to the piezoelectric material, and the configuration of one type thereof is shown in FIG.

Electrodes are coated with silver on the inner and outer surfaces of the cylindrical element shown in Figure 1, and when an electric field is applied inside the element through these electrodes, contraction occurs in the radial direction, causing the inside of the cylindrical element to shrink. This clamps the inserted cylindrical shaft. Si is a switch. Another type is the hollow laminated piezoelectric element shown in FIG. FIG. 2 is a schematic cross-sectional view. Referring to FIG. 2, the hollow laminated piezoelectric element has a large number of inner St electrode layers embedded in a ceramic layer in a layered manner and exposed at the end faces of the element. This exposed internal electrode layer is covered with another layer (this is covered with insulator 2,
Since the external electrodes 3.4 are applied from above, the internal electrode layers are electrically connected in parallel to each other. In addition, since these elements are polarized in the thickness direction, when a voltage is applied between the outer St poles, they expand in the thickness direction in proportion to the magnitude of the voltage, and therefore the diameter This clamps a cylindrical shaft inserted into a hollow space.

(Problems with the Prior Art) Of the two types of cylindrical elements having the configurations described above, the inner and outer surfaces of the cylindrical element are coated with silver coach ink.
A problem with devices having internal electrodes deposited on them is the technical limitation in increasing the amount of elongation of the piezoelectric material. Since the expansion and contraction rate of piezoelectric materials is approximately proportional to the electric field strength, a large voltage is required to increase the thickness of the ceramic element and increase the amount of expansion and contraction. Therefore, the dimensions of the T cylindrical element shown in FIG.
It is determined by taking into consideration mechanical strength, ease of obtaining uniform engagement between the cylindrical element and the shaft, etc.

As a guideline, a ceramic element with an inner diameter of 11cm and a wall thickness of 1m has a voltage of 2 to 3μ by applying a voltage of about 600V.
The change in inner diameter is obtained. In other words, in Figure 1, when a voltage of about 600 V is applied to the ceramic element,
This results in a reduction in the radial direction and restrains the shaft. In that case, since the reduction is only 2 to 3μ, the tolerance range for variations in the size of the ceramic element and the shaft is small.
Manufacturing techniques such as processing and assembly to obtain uniform engagement between the ceramic element and the shaft are close to their limits. −
10, by further increasing the voltage applied to the ceramic element,
Increasing the amount of expansion and contraction is undesirable from the standpoint of circuit safety and operation of the clamp element at higher speeds. That is, in order to operate the clamp element at higher speed, switch 8. is required to operate at high speed,
A transistor is used. Increasing the voltage applied to ceramic elements requires the development of transistors that operate isometrically at high voltages and high speeds.

Figures 3(a) and 3(a) show the structure of an alloy junction transistor for power use, in which the current areas of the emitter and collector are made as large as possible so that the current density does not become excessive. As the switching speed increases, current flows only near the electrode surface due to the skin effect, so it is necessary to further increase the surface area of the electrode. Therefore, the higher the speed and higher breakdown voltage of a transistor, the larger the surface area of the semiconductor and electrode, and the lower the yield and the higher the cost compared to a transistor with a lower breakdown voltage. 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 the problem of delay and balance of each transistor. For the reasons stated above, the cylindrical element of the type shown in Figure 1 is preferable when the shaft must be clamped with a large force due to its large wall thickness, or when the clamping element is to be moved at high speed. do not have.

- The hollow laminated piezoelectric element shown in FIG. 2 eliminates all the drawbacks of the cylindrical element shown in FIG. 1 described above. In other words, by applying a voltage in parallel to a thin plate-shaped element with integrated electrodes on the front and back surfaces in the thickness direction, the electric field strength is increased and the overall strain is extracted. It is possible for distortion to occur.

Moreover, a hollow one-layer type piezoelectric element can be easily obtained.

In other words, Institute of Electronics and Communication Engineers Research Report Vol. 83
, Ji, 18 (US83-8), p. 55, the small piezoelectric ceramic element utilizes the manufacturing technology of multilayer ceramic capacitors to integrate piezoelectric ceramic plates into one layer without using adhesives. In addition to having a large degree of freedom, this is an epoch-making multilayer piezoelectric element that overcomes all the drawbacks of conventional manufacturing techniques. Conventional manufacturing techniques use adhesives to laminate thin plates, resulting in poor productivity. The cost is high. Furthermore, since the adhesive layer is present, it is impossible to obtain pure and uniform strain as an element, and the device has drawbacks such as a lack of reliability such as life span.

Therefore, the hollow laminated piezoelectric element shown in FIG. 2 can be obtained by processing the hollow wall area.
When used as a clamp element, the internal electrodes are likely to be short-circuited, and if short-circuited, the function as a clamp element cannot be satisfied. That is, the ceramic part and the internal electrode part of the clamp element that come into contact with the shaft are worn out every time the clamp element clamps the shaft, and the worn metal of the internal electrode short-circuits adjacent internal electrodes. If a short circuit occurs between the internal electrodes, part or all of the internal electrodes will be damaged, making it impossible to fulfill the required function as a clamp element.

Therefore, a method of attaching an insulator to the internal electrode portion or both the internal electrode portion and the ceramic portion constituting the hollow void is effective in eliminating the above drawback. However, the technology for attaching an insulator to the internal electrode part or both the internal electrode part and the ceramic part that constitutes the hollow void is different from the manufacturing technology for obtaining the groundbreaking multilayer piezoelectric element described above. However, it has the disadvantage that it cannot take full advantage of the advantages of low cost and high productivity. That is, first, it is necessary to uniformly adhere the insulator to the void portion ζ. If the insulator is not evenly attached, uneven force will be applied to the insulator during clamping, which may cause the insulator to peel off from the laminated piezoelectric element, or if it does not separate, promote local wear of the insulator. As a result, the life of the clamp element will be shortened due to short circuits between the internal electrodes or failure to apply uniform force to the shaft.

Therefore, in principle, the more uniform the insulating material is, the better it is, as well as the stronger the adhesion force and resistance to abrasion. This is different from the technique in which every other electrode layer is covered with an insulator 2.

For the reasons mentioned above, the technology of attaching an insulator to the hollow voids is different from the manufacturing technology for obtaining innovative multilayer piezoelectric elements, and cannot take full advantage of the advantages of low cost and high productivity. It has its drawbacks.

(Object of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks, to provide a lamp element that can be driven efficiently at low voltage, can be adjusted by voltage value even if the inner diameter of the element changes due to wear, and has high productivity and low cost. It provides:

(Structure of the Invention) The present invention provides a cylindrical piezoelectric ceramic element in which cylindrical piezoelectric ceramic parts and cylindrical internal electrode parts are alternately stacked together, and each internal part exposed at both ends of the element. An insulator is coated on one of both ends of the electrode and every other layer on both ends ζ of the element, and furthermore, external electrodes are formed on both ends of the element to be connected to the internal electrodes every other layer. This is a cylindrical piezoelectric ceramic element characterized by:

(Example) The present invention will be explained below based on an example of implementation.

FIG. 4 is a schematic cross-sectional view of a cylindrical piezoelectric ceramic element according to the present invention. In FIG. 4, reference numeral 5 denotes an internal electrode layer which is embedded in a layered manner inside the thin ceramic cylindrical element 6 and exposed at the end face of the element.

This exposed internal electrode layer is covered with an insulator 7 every other layer, and external electrodes 8 and 9 are applied from above, so that each internal electrode layer is electrically connected in parallel to each other. It turns out. Since the ceramic portion 6 is polarized in the direction indicated by the arrow l in FIG. 4 in its thickness direction, when a voltage is applied between the external electrodes to further promote polarization, the magnitude of the voltage changes. It stretches in the thickness direction and therefore stiffens in the radial direction in proportion to. The inner diameter of the concentric laminated piezoelectric ceramic cylindrical element of this embodiment is 14 m, the outer diameter of the lunar fin is 14 m, the thickness of the thin plate ceramic cylindrical element 6 is 100 μm, the height is 13 m, and the thickness of the electrode 8.9 is 50 μm. be. This concentric laminated piezoelectric ceramic cylindrical element can change the inner diameter by 2 to 3μ by applying a voltage of about 60V, and the voltage required for the conventional clamp element of the type shown in FIG. Equivalent clamping function was obtained with , and in case of wear, the required clamping function was obtained by adjusting the voltage value corresponding to the amount of wear.

A method for manufacturing the present cylindrical piezoelectric ceramic element will be described. The fifth material is made of a tin-lead alloy with a melting point of 150°C.
A cylindrical jig 11 shown in Figure (a) is prepared.

The entire circumferential surface of the tin-lead alloy is wrapped with platinum foil 12 so that the outer diameter is uniform and the required inner diameter of the piezoelectric ceramic element is 11 m. In this case, the length of the cylindrical jig 11 is longer than the height 13 of the required concentric laminated piezoelectric ceramic cylindrical element 2
0 easily selected. Further, the length of the platinum foil in the vertical direction is longer than the length of the cylindrical jig 11.

Next, the wall thickness 100 was created using the slip casting method.
A dark green sheet 13 with a width of 13 μm is wrapped around the circumference of the platinum foil. In this case, a rolled gun. In this way, the green sheet is evenly wrapped around the surface of the platinum foil. An internal electrode 14 having a thickness of 3 μm is provided thereon by a transfer method. The above-described operation of wrapping the green notebook and providing the internal electrodes is repeated 30 times alternately. The element 15 shown in FIG. 5(b) formed by the method described above includes:
A pressure of about 0.25 ton/d is applied using a pressurizer 16, and the pieces are thermocompressed for 30 minutes at a temperature of 110° C. to be integrated. After that, the pressurizer 16 is removed and the 1000
Fired at a temperature of T culm. The cylindrical jig 11 made of tin-lead alloy melts during firing and can be removed. The exposed inner electrode layer of the thus obtained concentrically laminated cylindrical element is covered with an insulator as previously explained using the fourth voice, and the outer electrode is covered from above. Thus, the cylindrical piezoelectric ceramic element of the present invention is obtained. As mentioned above, manufacturing of the present cylindrical piezoelectric ceramic element can be carried out using the previously described manufacturing technology for multilayer ceramic capacitors by simply preparing a cylindrical jig and a pressurizer for crimping the thin ceramic cylindrical element and internal electrodes. By applying this method, it can be integrated without using adhesives, resulting in good productivity and low cost.

(Detailed Description of the Invention) As explained above, the piezoelectric ceramic element of the present invention is an element in which electrodes are formed on the front and back surfaces of a thin plate-like cylindrical element in the thickness direction, and a number of these plates are laminated and integrated. Since the internal electrode layer exposed on the end face is covered every other layer with an insulator and the external electrode is placed on top of this, 1) a high amount of strain can be efficiently produced, which occurs when applied to a clamp element. There is a degree of freedom in the range of strain utilization, and therefore low voltage driving is possible.

2) Easily mass-produced because it is a one-piece firing type laminated element.

It has high reliability and other effects, as well as its economical and dual functions.
The credibility ripple effect is enormous.

[Brief explanation of the drawing]

, FIG. 1 is an explanatory diagram of a conventional cylindrical clamp element, and FIG.
1a is a schematic diagram of a conventional hollow laminated clamp element;
4 is a schematic diagram of a cylindrical piezoelectric ceramic element showing an embodiment of the present invention, and FIG. 5 is an explanatory diagram of a method of manufacturing the same element. ■・・・Internal electrode layer, 2・・・Insulator,
3, 4.7.8...External electrode, 5...
・Internal electrode layer. 6... Thin plate-like cylindrical ceramic element, lO...
... Cylindrical gap, 11 ... Cylindrical jig, 1
2... Platinum foil, 13... Clean sheet, 14... Internal electrode, 15... Piezoelectric ceramic element, 16... Pressure M, 30...
...Emitter, 31...Collector, 32...
...Base, 33...Semiconductor 1, □, 11 Iso, 7. of. Kabuto Figure 1 Figure 2 @ Figure 3 Figure 4

Claims (1)

[Claims] A cylindrical piezoelectric ceramic element in which cylindrical piezoelectric ceramic portions and cylindrical internal electrode portions are integrally laminated alternately, one of both ends of each internal electrode being exposed at both ends of the element, and A cylindrical piezoelectric ceramic element characterized in that both ends of the element are coated with an insulator every other layer, and external electrodes are formed on both ends of the element.