JPS5825678Y2 - Nejishimeranjiyuubangatashindoushi - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a screw-fastened Langevin type vibrator used in ultrasonic cleaners, various ultrasonic processing machines, and the like.

In general, a screw-fastened Langevin type vibrator has a pair of piezoelectric elements 1, 1 and 2 facing each other with a terminal plate 3 in between, as shown in FIG.
2 is sandwiched between the front plate 4 and the backing plate 5, and the piezoelectric element and the inner surfaces of the backing plate are inserted from the center of the inner end surface of the front plate 4 to project into the counterbore 5a on the outer end surface of the backing plate 5. A piezoelectric element is formed between the front plate 4 and the backing plate 5 by screwing a normal hexagonal nut 7 arranged in the counterbore together with a washer 8 onto the provided central bolt shaft 6 and abutting against the counterbore surface 5a. 1.
In this case, the compressive stress applied to the piezoelectric element by tightening the hexagonal nut is large in the inner part near the center bolt, and almost unaffected to the outer part, as shown in Figure C. Because the piezoelectric element is uniform, the vibration is unstable, the efficiency is poor, and the prestress on the outer part of the piezoelectric element is not sufficient, so the piezoelectric element becomes easily damaged when driven with high power for a long period of time or when used in a high temperature atmosphere. It had the disadvantage of being damaged.

On the other hand, as shown in FIG. 2, a plate-shaped tightening nut 7' having the same diameter as the backing plate and having an annular protrusion 7a' on the lower surface that abuts against the outer periphery of the outer end of the backing plate is used to tighten the front plate. A Langevin type vibrator in which piezoelectric elements 1 and 2 are fastened and fixed between 4 and a backing plate 5 is also known, but in this case, the compressive stress distribution applied to the piezoelectric elements is opposite to that in FIG. It has the same defects as the vibrator shown in FIG. 1, with unevenness being larger in the inner part and smaller in the inner part.

This invention solves the above-mentioned conventional drawbacks by making it possible to fasten the piezoelectric element between the front plate and the backing plate under uniform compressive stress. explain.

In the figure, reference numerals 11 and 12 denote a pair of annular piezoelectric elements manufactured from lead zirconate titanate porcelain, which are opposed to each other with the same polar surfaces on the inside, with the same annular terminal plate 13 interposed therebetween.

14 is a metal front plate that is in contact with the outer end surface of one of the piezoelectric elements 12; 15 is a metal backing plate that is also in contact with the outer end surface of the other piezoelectric element 11; and 16 is the center of the inner end surface of the front plate 14. A central bolt shaft is vertically installed so as to pass through the piezoelectric elements 11, 12, the terminal plate 13, and the inner surfaces 11a, 12a, 13a, and 15a of the backing plate 15 and protrude above the backing plate 15. Although it is provided integrally with 14, it can also be provided separately using a stud bolt.

Reference numeral 17 denotes a plate-shaped nut having approximately the same diameter as the backing plate and having an annular protrusion 17a on the lower surface that is screwed into the upper end threaded portion 16a of the central bolt shaft 16 and abuts against the outer circumference of the outer end surface of the backing plate 15. The configuration up to this point is the same as that shown in FIG.
By carving a male screw 16b screwed into the female screw 15b in the center of the body of the central bolt shaft 16 that passes through the inner surface 15a, when the backing plate 15 is tightened, the inner part of the piezoelectric element is sufficiently The structure is such that a compressive stress is applied thereto.

According to the present invention having the above configuration, the compressive stress in the outer portion of the piezoelectric element is reduced by tightening the plate-shaped nut, which has an annular projection on the lower surface that has approximately the same diameter as the backing plate and abuts on the outer periphery of the outer end surface of the backing plate. Furthermore, by tightening the backing plate, the compressive stress in the inner part of the piezoelectric element can be increased, and uniform compressive stress can be applied to the piezoelectric element as a whole as shown in FIG. 3C.
Various conventional drawbacks due to non-uniform compressive stress on the piezoelectric element can be overcome.

Furthermore, according to the present invention, since the plate nut and the backing plate exhibit the same loosening effect as a double nut, the piezoelectric element,
There is no loosening between the contact surfaces of the front plate and backing plate, and stable mechanical contact is maintained at all times. This, in combination with the above-mentioned uniformity of compressive stress, further improves performance and durability. There is a potential effect.

[Brief explanation of drawings]

Figures 1 and 2 show a conventional example of a screw-fastened Langevin type vibrator, and Figure 3 shows an example of the present invention. The figure is a distribution curve of compressive stress applied to the surface of the piezoelectric element during tightening. The same numbers in Figures 1 and 2 indicate the same parts. 11.12...Piezoelectric element, lla, 12a...
...Inner surface, 14...Front plate, 15...
...Backing board, 15 a...Inner surface thereof, 15
b...Female thread, 16...Center bolt, 16a...Outer threaded portion, 16b...
Body neck part, 17...Plate nut, 17 a...
...Annular process.

Claims (1)

[Scope of utility model registration request] A piezoelectric element is sandwiched between the front plate and the backing plate, and a central bolt shaft is vertically installed so as to pass through the piezoelectric element and the inner surfaces of the backing plate from the front plate and protrude above the backing plate, and the backing plate. A piezoelectric element is fastened by a plate-shaped nut having an annular projection on the lower surface that has approximately the same diameter as the outer end surface of the backing plate and contacts the outer periphery of the outer end surface of the backing plate. A screw-tight Langevin type vibrator, characterized in that male screws that are screwed into the female screws are formed in the center of the body of the vibrator, and the compressive stress in the inner part of the piezoelectric element is increased by tightening the backing plate.