JP2976340B2 - Multilayer piezoelectric element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A multi-layer piezoelectric element used as a printer actuator is intended to improve the reliability and assemblability of the element. A pair of external electrodes alternately connected to the internal electrodes are provided on the peripheral surface of the element body having upper and lower blocks of a conductive material connected to the upper and lower sides of the elastic connecting member for applying a preload. In the laminated piezoelectric element configured as above, the external electrode on the ground side is directly connected to the block.

[Industrial applications]

The present invention relates to a laminated piezoelectric element used as an actuator of a printer.

Recently, a laminated piezoelectric element has been adopted as an actuator of a printer. This element has an internal electrode, an external electrode and an external terminal for connecting the internal electrode,
Since it is driven under high voltage and severe conditions, high reliability is required.

[Conventional technology]

FIG. 3 is an explanatory view of the structure of a print head using a conventional laminated piezoelectric element. In the drawing, reference numeral 1 denotes a substantially cylindrical base member, and 2 denotes a plurality of print elements held in a predetermined arrangement on the base member 1. Numerals 3 are heat radiation fins.

The printing element 2 includes a laminated piezoelectric element 4, connecting members 5 and 6 made of a spring material, and an armature 7. As shown in detail in FIGS. 4 and 5, the piezoelectric element 4 has an element body 10 in which a large number of piezoelectric ceramics 8 are laminated with an internal electrode 9 interposed therebetween.
A pair of external electrodes 11 and 12 alternately connected to the internal electrodes 9 are provided on the peripheral surface of the semiconductor device, and these are covered with an insulating layer 13. Reference numeral 14 denotes a semi-cylindrical electric insulating layer made of glass or the like for enabling the above connection, and is formed between the external electrodes 11 and 12 and the internal electrode 9 not connected thereto. The positive external electrode 11 is connected to an anode terminal of a drive circuit (not shown) via a lead 15, and the negative external electrode 12 is connected to the grounded base member 1 via a lead (external terminal) 16. Have been. The element body 10 of the piezoelectric element 4 is formed by laminating a plurality of piezoelectric ceramic green sheets having a metal paste film serving as an internal electrode formed on one surface thereof,
This is obtained by firing together, and the base 4a is fixed to the base member 1 by bonding 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. The printing wire 18 is fixed to the end of the armature 7 supported in a cantilever manner by the connecting members 5 and 6 as described above. When printing, the piezoelectric element 4 of the predetermined printing element 2 is energized for a predetermined time. Thereby, the upper part 4b of the piezoelectric element 4 moves upward and pushes up 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 members 5 and 6,
The print wire 18 is provided with an enlarged displacement,
Is performed. When the printing is completed, the power supply to the piezoelectric element 4 is stopped, and the armature 7 that has completed the printing operation returns to the original position with the return of the piezoelectric element 4.

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

[Problems to be solved by the invention]

In the conventional multilayer piezoelectric element having such a configuration and operation, each of the leads 15 and 16 is connected to the solder 1 as shown in FIG.
9 are connected to the external electrodes 11 and 12, respectively.

As described above, since the lead wires 15 and 16 are joined to the external electrodes 11 and 12 by soldering, the joints are weak in strength, which is problematic. Further, the external electrode is damaged by thermal stress due to soldering, and disconnection and peeling are likely to occur. Further, since the terminal is connected to the drive circuit via a pair of lead wires, the terminal processing is troublesome and the assembling work is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated piezoelectric element that can improve the reliability and assemblability of the element.

[Means for solving the problem]

FIG. 1 is a view for explaining the principle of the present invention, in which 21 is an element body. The same reference numerals are used for members common to the related art.

The element body 21 of the laminated piezoelectric element 20 is formed by laminating a large number of piezoelectric ceramics 8 with the internal electrode 9 interposed therebetween, and is connected to upper and lower ends of elastic connecting members 22 and 23 for applying a preload. A block 24 and a block 25 of a conductive material such as a metal are provided. On the peripheral surface of the element body 21, each internal electrode 9
And a pair of external electrodes 26 and 27 alternately connected. One end of the ground-side external electrode 27 made of one metal plate of the pair of external electrodes is extended to the side surface of the ground-side block 25, and this extended portion is connected to the side surface of the block 25.

(Operation)

As described above, in the present invention, the ground-side external electrode is formed by directly connecting 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 wire (lead wire 16 in FIGS. 4 and 5) which has been required conventionally becomes unnecessary, and the trouble of the lead wire processing is reduced, and the mechanical strength of the joint is improved.

For mounting the piezoelectric element, for example, block on the base member
This is performed by fixing 25 with a conductive adhesive, whereby the external electrode 27 is grounded via the base member.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

FIG. 2 is an explanatory view of a main part structure of a print head using the laminated piezoelectric element 20 of this embodiment. In FIG. 2, reference numeral 31 denotes an element mounting base, and 32 denotes a printed board. The same members as those in FIG. 1 are denoted by the same reference numerals.

A plurality of piezoelectric elements 20 are provided, and
32 is fixed in a predetermined arrangement in the circumferential direction. When fixing each piezoelectric element 20 to the element mount 32,
The bottom surface of the block 20 and the element mounting base 31 are adhered and fixed by a conductive adhesive 33, and are electrically connected.
In addition, the ground-side external electrode 27 of the metal plate is extended to the side surface of the ground-side conductive block 25, and the extended portion of the external electrode 27 of the metal plate is connected to the side surface of the conductive block 25. In this case, since the extended portion of the external electrode 27 and the block 25 can be connected with a relatively large area, it is possible to relatively firmly fix and reduce the electric resistance. The sign
Reference numeral 34 denotes a conductive adhesive for connection between the external electrode 27 and the block 25. The element mounting base 31 is connected to the cathode terminal (ground terminal) of the printed circuit board 32 via the lead wire 35, and the external electrode 26 on the non-ground side is connected to the anode terminal (non-ground terminal) of the printed circuit board 32. Section).

Thus, the ground-side external electrode 27 of the metal plate connected to every other internal electrode 9 of the piezoelectric ceramics 8 is directly connected to the ground-side conductive block 25 by an extension thereof.

Although a detailed illustration of the print head is omitted, a support is provided outside each piezoelectric element 20 in FIG. 2, and the support and the block 24 of the piezoelectric element and the base of the armature are connected by two connecting members. It is composed. Then, as in the conventional case, printing is performed by energizing a predetermined piezoelectric element at a predetermined time. Although the piezoelectric element and the armature that have completed the printing return to their original states, the elastic connecting members 22 and 23 assist the return of the piezoelectric element. In addition, the elastic connecting members 22 and 2
3 serves to prevent breakage of the piezoelectric element by preventing the vertical tension from acting on the piezoelectric element.

In addition, it is also possible to connect each part using a conductive adhesive.

〔The invention's effect〕

As described above, the present invention provides each of the internal electrodes 9.
Conductive blocks 24 and 25 are arranged on the upper and lower ends of the piezoelectric ceramics 8 laminated through the intermediary of the piezoelectric ceramics 8. Provide a pair of external electrodes 26 and 27 on the ground side and the non-ground side connected to every other one, and extend one end of the external electrode 27 on the metal ground side to the side surface of the block 25 at the lower end. Is connected to the side surface of the block 25, so that the ground-side external electrode 27 of the metal plate and the conductive ground-side block 25 can be directly connected over a relatively large area. Compared to a conventional example in which a lead wire is connected to the electrode 27 by soldering, there are advantages in that assembling is easy and mechanical and electrical reliability can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle of the present invention, FIG. 2 is an explanatory view of a main part structure of a print head using a laminated piezoelectric element according to an embodiment of the present invention, and FIG. 3 is a drawing using a conventional laminated piezoelectric element. FIG. 4 is a perspective view showing the structure of the piezoelectric element of FIG. 3, FIG. 5 is a detailed view of FIG. 4, wherein 8 is a piezoelectric ceramic, 9 is an internal electrode, 20 Denotes a laminated piezoelectric element, 21 denotes an element body, 22 and 23 denote elastic connecting members, 24 and 25 denote blocks, and 26 and 27 denote external electrodes.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-219972 (JP, A) JP-A-59-193078 (JP, A) JP-A-1-135512 (JP, U) JP-A-69-1 27356 (JP, U) Shokai Sho 55-68365 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 41/08

Claims (1)

(57) [Claims] An electrically conductive block (24, 25) is disposed at an upper end and a lower end where a large number of piezoelectric ceramics (8) are laminated via an internal electrode (9), and a space between the blocks for applying a preload is provided. On the peripheral surface of the element body (21) connected by the elastic connecting members (22, 23), a pair of external electrodes (2
6, 27), one end of the ground-side external electrode (27) of the metal plate is extended to the side surface of the block (25) at the lower end, and the extended portion is connected to the block (25). A multilayer piezoelectric element having a configuration connected to the side surface of (1).