JPH03240280A - Laminated type piezoelectric element - Google Patents

Abstract

PURPOSE:To enhance a junction strength to an external terminal and to improve reliability, assembling properties of an element by forming an outer electrode on the ground side by directly connecting it to a conductive lower block used also as the terminal. CONSTITUTION:In an element body 21 of a piezoelectric element 20, many piezoelectric ceramics 8 are laminated through inner electrodes 9, and blocks 24, 25 of conductive material such as metal, etc., to be coupled to the top and bottom of elastic coupling members 22, 23 for applying prepressure are provided at the upper and lower ends. Outer electrodes 26, 27 to be alternately connected to the electrodes 9 are formed on the periphery of the body 21, the electrode 27 on the ground side is connected directly to the block 25 to be formed, thereby connecting the electrode 9 to the block 25 at the ground side. The block 25 is used also as an external terminal, complication of processing leads is alleviated, and the mechanical strength of a bonded part is enhanced.

Description

[Detailed Description of the Invention] [Summary] With regard to a multilayer piezoelectric element used as an actuator in a printer, a large number of piezoelectric ceramics are laminated with internal electrodes sandwiched between them in order to improve the reliability and ease of assembly of the element. A pair of external electrodes are provided on the circumferential surface of the element body, which has blocks of conductive material at the upper and lower ends connected above and below the elastic connecting member for applying preload, and are connected alternately to each of the internal electrodes. In the multilayer piezoelectric element, the external electrode on the ground side is directly connected to the block.

[Industrial Application Field] The present invention relates to a laminated piezoelectric element used as an actuator for a printer.

Recently, laminated piezoelectric elements are being adopted as actuators for printers. This element has internal electrodes, external electrodes and external terminals for connecting the internal electrodes, and is driven at high voltage and under severe conditions, so high reliability is required.

[Conventional technology]

FIG. 3 is an explanatory diagram of the structure of a print head using a conventional laminated piezoelectric element. The printing element 3 is a heat radiation fin.

The printing element 2 includes a laminated piezoelectric element 4 , connecting members 5 and 6 made of spring material, and an armature 7 . As shown in detail in FIGS. 4 and 5, the piezoelectric element 4 consists of a pair of internal electrodes 9 connected alternately to the circumferential surface of an element body 10 in which a large number of piezoelectric ceramics 8 are laminated with internal electrodes 9 in between. The external electrodes 11 and 12 are provided, and these are covered with an insulating layer 13. 14 is a semi-cylindrical electrical insulating layer made of glass or the like to enable the above-mentioned connection, and external electrode 11.1
2 and an internal electrode 9 that is not connected thereto. The positive external electrode 11 is connected to the anode terminal of a drive circuit (not shown) via a lead wire 15, and the negative external electrode 12 is connected to the grounded base member 1 via a lead wire (external terminal) 16. has been done. The element body 1O of the piezoelectric element 4 is obtained by stacking a plurality of piezoelectric ceramic green sheets each having a metal paste film formed on one surface that will serve as an internal electrode, and then stacking them together at the bottom of a mine. 4a is fixed to the base member 1 by adhesive or the like. The connecting member 5 connects the upper part 4b of the piezoelectric element 4 and the base of the armature 7, and the connecting member 6 parallel to the connecting member 5 connects the support plate 17 attached to the upper part of the base member 1 and the base of the armature 7. Connected. A printing wire 18 is fixed to the tip of the armature 7, which is supported in a cantilevered manner by the connecting members 5 and 6 in this manner. During printing, the piezoelectric element 4 of a predetermined printing element 2 is energized for a predetermined period of time. As a result, the upper portion 4b of the piezoelectric element 4 moves upward and pushes the connecting member 5 upward. As a result, the armature 7 rotates in the direction of the arrow in FIG. 3 due to the bimetal effect of the connecting member 5.degree. 6, and an enlarged displacement is applied to the printing wire 18, so that printing by the printing wire 18 is performed. At the time of completion of printing, the energization to the piezoelectric element 4 is stopped, and the armature 7, which has completed the printing operation, returns to its original position as the piezoelectric element 4 returns.

The piezoelectric element 4 generates heat due to continuous printing, but this heat is transmitted to the cooling fins 3 via the base member 1 and radiated to the outside.

(Problem to be Solved by the Invention) In the conventional laminated piezoelectric element having such a configuration 9 effect, each lead wire 15, 16 is connected to each external electrode 11° 12 by solder 19 as shown in FIG. It is connected.

In this way, each external electrode 11.12 has each lead wire 15.
．． 16 has a structure in which they are joined by solder, which causes a problem in that the strength of this joint is weak. Furthermore, the external electrodes are damaged by the thermal stress caused by soldering, making them more likely to be disconnected or peeled off. Furthermore, since it is connected to the drive circuit through a pair of lead wires, terminal processing is troublesome, making assembly work difficult.

An object of the present invention is to provide a multilayer piezoelectric element that can improve the reliability and ease of assembly of the element.

[Means to solve the problem]

FIG. 1 is an explanatory diagram of the principle of the present invention, and in the figure, 21 is an element body. Note that the same reference numerals are used for members that are common to the conventional one.

The element main body 21 of the laminated piezoelectric element 20 is formed by laminating a large number of piezoelectric ceramics 8 with internal electrodes 9 interposed therebetween, and the upper and lower ends are connected above and below to elastic connecting members 22 and 23 for applying preload. A block 24 and a block 25 made of a conductive material such as metal are provided. On the peripheral surface of the element body 21,
A pair of external electrodes 26.2 alternately connected to each internal electrode 9
7 is formed. The ground side external electrode 27 is formed to be directly connected to the block 25, and thereby each ground side internal electrode 9 is connected to the block 25.

(Function) As described above, in the present invention, the ground side external electrode is directly connected to the block 25 at the lower end of the element body, and the block 25 also serves as an external terminal.

Therefore, the lead I (lead wire 16 in FIG. 4.5) which was conventionally required is no longer necessary, the troublesome lead wire processing is reduced, and the mechanical strength of the joint is improved.

To attach the piezoelectric element, for example, attach block 2 to the base member.
5 with a conductive adhesive, and thereby the external electrode 27 is grounded via the base member.

(Example〕 The invention will now be described in detail with reference to FIG.

FIG. 2 is an explanatory diagram of the main part structure of a print head using the laminated piezoelectric element 20 of this example, in which numeral 31 is an element mounting base and numeral 32 is a printed circuit board. Note that the same reference numerals are used for the same members as in FIG. 1.

A plurality of piezoelectric elements 20 are provided, and each piezoelectric element 20 is fixed to an element mounting base 32 at a predetermined arrangement in the circumferential direction. When fixing each piezoelectric element 20 to the element mounting base 32, the bottom surface of the block 25 of each piezoelectric element 20 is used to adhere it to the element mounting base 31 with a conductive adhesive 33, and the adhesive 33 and the external The electrode 27 is electrically connected to the electrode 27 by a conductive adhesive 34. As a result, the external electrode 27 is connected to the element mounting base 31.
connected to. The element mounting base 31 is connected to a cathode terminal portion of a printed circuit board 32 via a lead wire 35. In addition,
The external electrode 27 may be formed by applying a conductive adhesive. The external electrode 15 on the anode side is connected to the printed circuit board 3
It is connected to the anode terminal of No.2.

Although detailed illustrations of the print head are omitted, a support is provided outside each piezoelectric element 20 in FIG. 2, and the support, the block 24 of the piezoelectric element, and the base of the armature are connected by two connecting members. It consists of Then, as in the past, printing is performed by energizing a predetermined piezoelectric element at a predetermined time. After printing is completed, the piezoelectric element and armature return to their original state, but the elastic connecting member 222
3 helps the piezoelectric element return. The elastic connecting members 22 and 23 also serve to prevent damage to the piezoelectric element by preventing vertical tension from acting on the piezoelectric element.

Note that the external electrode 26 on the anode side is shaped with conductive adhesive,
The lead wire 15 is connected to the external electrode 26 using the same conductive adhesive.
By connecting it to the terminal, you can eliminate the negative effects of soldering.

[Effects of the Invention] As described above, according to the present invention, the ground-side external electrode of the multilayer piezoelectric element is directly connected to the conductive lower block that also serves as an external terminal. It is possible to increase the bonding strength with external terminals without the need for conventional soldering, and it is possible to improve the reliability of the device by 9Mi.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention. Fig. 2 is an explanatory diagram of the main part structure of a print head using a laminated piezoelectric element according to an embodiment of the present invention. Fig. 3 is an illustration of a print head using a conventional laminated piezoelectric element. 4 is a perspective view showing the structure of the piezoelectric element in FIG. 3; FIG. 5 is a detailed view of FIG. 4; in the figure, 8 is a piezoelectric ceramic; 9 is an internal electrode; 20 21 is a laminated piezoelectric element, 21 is an element body, 2223 is an elastic connecting member, 24 and 25 are blocks, and 2627 is an external electrode.

Claims (1)

[Claims] Consisting of a large number of piezoelectric ceramics (8) stacked with internal electrodes (9) in between, elastic connecting members (22,
The element body (
21), in which a pair of external electrodes (26, 27) are provided on the circumferential surface of the external electrode (27) on the ground side, the external electrode (27) being connected alternately to each of the internal electrodes (9); , the block (25
) A multilayer piezoelectric element characterized in that it is formed by being directly connected to.