JPS609299A - Piezoelectric element - Google Patents

Abstract

PURPOSE:To suppress generation of a warp even in case a piezoelectric element which has a comparatively large diameter and is thin, and also to save an electrode material by forming at least one of electrodes in a stripe shape, in the piezoelectric element provided with the electrode on both faces in the thickness direction of a base body. CONSTITUTION:An electrode 2 and 3 of both faces of a piezoelectric porcelain base body 1 are formed to a striped pattern on which an electrode applied part (a) and a gap (b) to which the electrode is not applied are formed alternately, and an electrode structure which has connected mutually the circumferential edge of the part (a) by a ring-like conductive part (c) is formed. In this way, an interference degree of the electrode 2 and 3 to the base body 1 is reduced, and even in case the base body 1 is made a large diameter and thin, a warp of the element 1, which is caused by a difference of coefficients of thermal expansion of both of them can be suppressed. Also, the electrode is not applied to the part of the gap (b), therefore, the use quantity of silver which is an electrode material can be reduced. Moreover, a necessary electrode material can be reduced. Moreover, a necessary electrode intensity and an electric resistance value can be secured by the part (a).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric element made of barium titanate porcelain, PZT, or the like.

Prior Art This type of piezoelectric element has advantages such as being lightweight by being formed into a thin plate shape, being mass-producible and cost-effective, consuming little power, producing no noise, and having a long lifespan. It has many characteristics and has been used in acoustic transducer elements of electronic buzzers and the like. As shown in FIG. 1, a conventional piezoelectric element has a structure in which silver electrodes 2 and 3 are deposited on the entire surfaces of opposing surfaces of a piezoelectric ceramic body l formed in the shape of a disk. The silver electrodes 2 and 3 are formed to have the same coating thickness by applying a frit-containing silver paste by means such as screen printing and baking.

Disadvantages of the Prior Art As mentioned above, the conventional piezoelectric element has a structure in which the electrodes 2 and 3 are adhered to both sides of the piezoelectric ceramic body 1 so that they have approximately the same thickness, and therefore have the following disadvantages. was there.

(a) For example, the diameter is about 30 to 50 mm and the plate thickness is 10 mm.
When using a thin piezoelectric ceramic body 1 with a relatively large diameter of about ~50 pm, the thickness of the electrodes 2 and 3 is about 10 JLm compared to the thickness of the piezoelectric ceramic body 1 of ~50 pm. The degree of interference between the electrodes 2 and 3 with respect to the piezoelectric ceramic body 1 increases, and due to the difference in the coefficient of thermal expansion α between the two, warpage occurs in the piezoelectric ceramic body 1, making it impossible to obtain a predetermined electrostrictive phenomenon. .

(b) Since the structure is such that the electrodes 2 and 3 are applied to the entire surface of both sides of the piezoelectric ceramic body 1 with approximately the same thickness, the amount of silver used as the electrode forming material increases, resulting in high costs. .

(C) If the coating thickness of electrodes 2 and 3 is reduced, the above-mentioned drawbacks can be alleviated to some extent, but the adhesive strength of the electrodes decreases and reliability decreases. Further, disadvantages such as an increase in the electrical resistance values of the electrodes 2 and 3 also occur.

Purpose of the Invention Therefore, the present invention eliminates the above-mentioned conventional drawbacks, suppresses the occurrence of warping even when using a thin piezoelectric ceramic body with a relatively large diameter, and reduces the amount of electrode material used. An object of the present invention is to provide a piezoelectric element that can guarantee necessary electrode strength and electrical resistance while reducing electrode formation cost.

Structure of the Invention In order to achieve the above object, the present invention is a piezoelectric element in which electrodes are provided on both sides in the thickness direction of the element body, in which at least one of the electrodes is formed in a ring shape.

Embodiment FIG. 2 is a plan view of a piezoelectric element according to the present invention, and FIG.
FIG. 3 is an enlarged sectional view taken along the line Al-A1 in the figure. In the figure, the same reference numerals as in FIG. 1 indicate the same components. In this embodiment, the electrodes 2 and 3 on both sides of the piezoelectric ceramic body 1 are formed into a striped pattern in which electrode-coated parts (a) and gaps (b) where no electrode is coated are alternately formed, and the electrode-coated parts (i.e., ) with a ring-shaped conductive part (c)
This creates an electrode structure in which the electrodes are connected to each other. The conductive part (c) may be formed in the middle part, as shown in FIG. Such an electrode pattern can be easily formed by screen printing or the like.

With the electrode structure as described above, the substantial average thickness of the electrodes 2 or 3 can be reduced to nearly half of the conventional thickness due to the existence of the gap (b). Even when the degree of interference of the piezoelectric ceramic element 3 is reduced and the piezoelectric ceramic element 1 is made larger in diameter and thinner, it is possible to suppress warping of the piezoelectric ceramic element 1 due to the difference in coefficient of thermal expansion between the two. Furthermore, since no electrode is applied to the gap (b), the amount of silver used as an electrode material is halved, resulting in lower costs. Moreover, the electrode application part (a)
This makes it possible to guarantee the necessary electrode strength and electrical resistance value.

In the above embodiment, both electrodes 2 and 3 are formed in a striped pattern, but even if only one of the electrodes is formed in a striped pattern, similar effects can be obtained within the range. can. Further, although the gap (b) is formed as a complete gap without electrode coating, it is also possible to make the electrode coating thickness thinner than the part (a) and form an uneven striped pattern. Furthermore, in addition to the patterns shown in the embodiments, it is possible to take various other forms, such as concentric circles, spirals, or a combination of these patterns.

Effects of the Invention As described above, the present invention is characterized in that, in a piezoelectric element in which electrodes are provided on both sides of the element body in the thickness direction, at least one of the electrodes is formed in a striped shape. Even when using a thin piezoelectric ceramic body with a relatively large diameter, it is possible to suppress the occurrence of warping, reduce the amount of electrode material used, reduce electrode formation costs, and maintain the necessary electrode strength. Accordingly, it is possible to provide a piezoelectric element whose electrical resistance value can be guaranteed.

[Brief explanation of drawings]

Fig. 1 is a front sectional view of a conventional piezoelectric element, Fig. 2 is a plan view of a piezoelectric element according to the present invention, Fig. 3 is an enlarged partial sectional view taken along the Al-Al line in Fig. 2, and Fig. 4 is an inventive one. FIG. 3 is a plan view of another embodiment of the piezoelectric element according to the embodiment. 1... Piezoelectric ceramic body 2.3... Electrode (a) fist...
Electrode application part (b) φ...gap

Claims (2)

[Claims] (1) A piezoelectric element having electrodes provided on both sides in the thickness direction of the element body, wherein at least one of the electrodes is formed in a striped shape. (2) The piezoelectric element according to claim 1, wherein at least one of the electrodes is formed by alternately forming thick parts and thin parts with a coating thickness.