JPS6115382A - Clamp element - 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 Field of the Invention The present invention relates to a laminated piezoelectric ceramic clamping element used for clamping objects.

(Prior Art) A conventional clamp element using a piezoelectric body utilizes strain caused by an electric field applied to the piezoelectric body, 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 i1, and when an electric field is applied inside the element through these electrodes, contraction occurs in the radial direction and the element is inserted into the cylindrical element. This clamps a shaft having a cylindrical shape. Sl 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 internal pole layers 1 embedded in a ceramic layer in a layered manner and exposed at the end surfaces of the element. This exposed internal electrode layer is covered every other layer with an insulator 2, and then exposed from above. Since the fiS poles 3 and 4 are deposited, the internal electrode layers are electrically connected in parallel to each other. In addition, since these elements are polarized in the lateral direction, when a voltage is applied between the external electrodes, they expand in the thickness direction in proportion to the magnitude of the voltage, and therefore extend in the radial direction. This clamps a cylindrical shaft inserted into the hollow.

(Problems with the prior art) Of the two types of cylindrical elements with the above-mentioned configuration, the type in which the inner and outer surfaces of the cylindrical element are coated with silver and the internal electrodes are coated is used. The problem is the technical constraints in increasing the amount of expansion and contraction of piezoelectric materials. Since the expansion/contraction rate of piezoelectric materials is approximately proportional to the electric field strength, increasing the thickness of the ceramic element and increasing the amount of expansion requires a large pressure. Therefore, the first
The dimensions of the cylindrical element shown in the figure are determined by taking into account the applied voltage mentioned above, mechanical strength, ease of obtaining uniform engagement between the cylindrical element and the shaft, etc.

As a guideline, a voltage of about 600 V is applied to a ceramic element with an inner diameter of 11 m and a wall thickness of 1 mm, thereby obtaining a change in the inner diameter of 2 to 3 μm. That is, when a voltage of about 600 V is applied to the ceramic element 2 in FIG. 1, it contracts in the radial direction and restrains the shaft. In that case, since the size is reduced by only 2 to 3μ, the tolerance for variations in the size of the ceramic element and shaft is small, and manufacturing technology such as processing and assembly to obtain uniform engagement between the ceramic element and shaft is close to its limit. be. Ten thousand,
By further increasing the voltage applied to each ceramic element, the elongation
Increasing the amount of j is undesirable from the viewpoint of circuit safety and operation of the clamp element at higher speed. That is, in order to operate the clamp element at a higher speed, the switch S1 needs to operate at a higher speed, and a transistor is used. Increasing the voltage applied to ceramic elements requires the development of transistors that operate isometrically at high voltages and at high speeds. Figures 3(a) and 3(b) show the structure of an alloy junction transistor for power use.
The current area of the emitter and collector is made as large as possible to prevent the current density from becoming excessive. As the switching speed becomes faster, 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 faster and higher the voltage resistance of the transistor ζ, 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 voltage resistance. There is also a method of dividing and switching a high voltage using a plurality of low voltage transistors 4-m, which requires adjustment time to solve problems of delay and balance of each transistor.

For the reasons stated above, the cylindrical element shown in Figure 1 is not preferred when the wall thickness is large and the shaft must be clamped with a large force, or when the clamping element is operated at high speed. .

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 an element that integrates electrodes on the front and back surfaces of a thin plate element in the thickness direction, the electric field strength is increased and the overall strain is extracted. It is possible to generate high distortion.

83-8) The electronic communication piezoelectric ceramic element published in No. 55 uses the manufacturing technology of multilayer ceramic capacitors to integrate the piezoelectric ceramic layers without using adhesives, so it has a high degree of freedom in shape. Moreover, it is an epoch-making multilayer piezoelectric element that overcomes all the shortcomings of conventional manufacturing techniques. In the conventional manufacturing technology, productivity is poor because adhesive is used to bond the thin plate. The cost is high. Due to the presence of an adhesive layer in the process, pure and uniform strain cannot be obtained as an element, and the device has drawbacks such as a lack of reliability such as a long life.

Therefore, the hollow laminated piezoelectric element shown in FIG. 2 can be obtained by forming hollow voids in a sintered laminated piezoelectric element. However, the disadvantage of the medium 7F-shaped piezoelectric element is that when used as a clamp element, the internal πL pole is easily short-circuited, and if short-circuited (A), the function as a clamp element cannot be satisfied. Short-circuit between the ceramic, rib and internal electrode parts that contact the shirt I of the clamp element.If the internal electrodes are short-circuited, part or all of the internal electrodes will be damaged. It becomes impossible to satisfy the required function as a clamp element.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks and provide a clamp element that can be efficiently driven at a low voltage.

(Structure of the Invention) That is, the present invention is an element in which thin ceramic plates and internal electrodes are alternately layered, and the end portions of each internal electrode layer exposed on the side surface of the element are made of an insulator every other layer. , an external electrode is formed from above the side surface of the element, a cylindrical cavity is provided inside the element, and an insulator is formed on the wall surface of the cylindrical cavity. This is a clamp element that

(Example) Next, an example of the ζζ tree invention will be described with reference to the drawings. FIG. 4 is a schematic cross-sectional view of a clamping element according to the invention. In FIG. 4, reference numeral 3 denotes an internal electrode layer, which is embedded in the ceramic 6 in a layered manner and is exposed on the electronic side. This exposed interior.

Every other electrode layer is covered with insulator 2, and from above 5 is 8
The i02 insulator is attached to both the single end face of the internal electrode portion constituting the hollow cavity and the ceramic portion 6. Attachment was carried out using the reduced pressure OVD method using 500% SiH4 and N.
The reaction was carried out at ℃. Furthermore, since the ceramic portion 6 is polarized in its thickness direction, when a voltage is applied between the external electrodes, the magnitude of the voltage is proportional to ζ.
It stretches in the thickness direction and therefore contracts in the radial direction. The insulator 5 is also interlocked with the ceramic part 6. The inner diameter of the hollow laminated piezoelectric element of this example is 11 mm, the thickness of the ceramic element 6 is 1 mm, the interval between electrodes is 50 μm, and the thickness of electrodes 3 and 4 is 50 μm.
The thickness of the insulator 5 is 50 μm. This hollow laminated piezoelectric element can change the inner diameter by 2 to 3μ by applying a voltage of about 100μ, and can achieve the same change at a voltage lower than that required for the conventional clamping element of the type shown in Figure 1. Clamp function was obtained. In addition, as a result of comparing the life test of the type of clamp element shown in Fig. 2 of the same size, the life is 100%.
It has doubled in size.

In this embodiment, the internal electrode ilX constituting the hollow cavity is
Although an insulator is attached to both the electrode portion and the ceramic portion, it goes without saying that the same effect can be obtained by attaching an insulator to the internal electrode portion.

(Detailed Description of the Invention) As explained above, the present invention has a structure in which an insulator is attached to the internal electrode portion or both the internal electrode portion and the ceramic portion that constitute the hollow cavity of the hollow laminated piezoelectric element. Since a high amount of strain can be efficiently produced, there is a wide range of utilization of the generated strain when applied to a clamp element, and low-voltage driving is therefore possible.

2) One-piece firing type (because it is a laminar element, it is less mass-producible and reliable.

3) Since the insulator is attached with 4=J, the worn metal forming the internal mold (lliii) short-circuits the adjacent internal phase electrodes, allowing for a long life.

The economic, opportunity, and credibility ripple effects are enormous.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional cylindrical clamp element, Shikoku; Figure 2 is a schematic diagram of a conventional hollow YN Paris clamp; The figure is a schematic diagram of a clamp element showing an embodiment of the present invention. ■・・・・・・Nonelectrode layer, 2.5・・・Insulator, 3.4・・・External electrode, 6・・・・・・
Ceramic, 30...Emitsuto, 31.
°°...=Rukugu, 32...Base

Claims (1)

[Claims] It is an element in which a plurality of thin ceramic plates and internal electrodes are alternately laminated, and the ends of each internal electrode layer exposed on the side of the element are covered with an insulator every other layer, and external electrodes are placed on the side of the element from above. What is claimed is: 1. A clamp element characterized in that a cylindrical cavity is formed inside the element, and an insulator is formed on a wall surface of the cylindrical cavity.