JP2809907B2 - Piezoelectric actuator for inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator for an ink jet head.

[0002]

2. Description of the Related Art A plurality of piezoelectric elements, each having a signal electrode pattern and a ground electrode pattern provided on both surfaces of a piezoelectric body, are arranged in a comb-teeth shape to drive a multi-nozzle of an ink jet head. Piezoelectric actuators are known.

FIG. 6 is a sectional view showing an example of a conventional piezoelectric actuator of this type, and FIG. 7 is a plan view thereof.

[0004] In these figures, reference numeral 10 denotes a rectangular parallelepiped piezoelectric body that generates strain or stress when a voltage is applied. A signal electrode pattern 11 and a ground electrode pattern 12 are provided on the entire surface of both surfaces of the piezoelectric body 10, respectively.
One piezoelectric element is configured. As shown in FIG. 7, the piezoelectric actuator is formed by arranging a plurality of such piezoelectric elements in a comb-tooth shape and fixing the lower side of one end of the piezoelectric elements to the fixing plate 13. A conductive pattern 14a in a cable 14 is connected to the signal electrode pattern 11 of each piezoelectric element by soldering or a conductive adhesive. In addition, the ground electrode patterns 12 of all the piezoelectric elements
Are commonly connected by soldering or a conductive adhesive.

[0005]

FIG. 8 is a view for explaining the displacement of a piezoelectric element when a pulse-like voltage is applied to such a conventional piezoelectric actuator. As is well-known, the piezoelectric lateral effect type piezoelectric element has a signal electrode pattern 1.
When a voltage is applied between the first and ground electrode patterns 12, a displacement A occurs in the longitudinal direction. The ink droplets are ejected by the displacement A in the longitudinal direction.

However, according to the prior art, since the signal electrode pattern 11 and the ground electrode pattern 12 are provided on the entire surface of the piezoelectric body 10, a displacement force is generated in all parts of the piezoelectric body 10. In addition, the lower side of one end portion is fixed base 1
3, there is a vertically asymmetric restraining force. As a result, in addition to the displacement A in the longitudinal direction, a vertical displacement (warpage) B occurs. This vertical displacement B is a factor of generating noise of the ink jet head.

Accordingly, the present invention provides a piezoelectric actuator for an ink jet head which can reduce the generation of noise due to piezo driving.

[0008]

According to the present invention, at least one layer of a piezoelectric body and a fixed body for fixing a part of the piezoelectric body are provided.
And a plurality of piezoelectric elements each having a signal electrode pattern and a ground electrode pattern provided on both surfaces of the piezoelectric element with the piezoelectric element interposed therebetween. Electrode pattern
So that the area of the piezoelectric body sandwiched between
A piezoelectric actuator for an ink jet head having a signal electrode pattern and a ground electrode pattern formed thereon.

[0009]

Function: sandwiched between the signal electrode pattern and the ground electrode pattern
Signal so that the area of the piezoelectric body
An electrode pattern and a ground electrode pattern are formed. Therefore, the displacement force is applied to the signal electrode pattern and contact
It occurs only in the region of the piezoelectric body sandwiched between the ground electrode patterns, and there is almost no vertical displacement (warpage) that causes noise.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a sectional view schematically showing the configuration of the entire ink jet head relating to the piezoelectric actuator of the present invention.

In FIG. 1, reference numeral 20 denotes an ink chamber 21 inside.
Is an ink chamber block in which is formed. An orifice 22 for discharging ink is provided on the front surface of the ink chamber block 20.
The orifice plate 23 provided with is fixed. On the rear surface of the ink chamber block 20, a filter plate 24
The fixing stand 25 is fixed via the.

The tip of the piezoelectric element 26 is inserted into the ink chamber block 20, and the tip of the piezoelectric element 26 forms a part of the inner wall of the ink chamber 21. The rear end portion of the piezoelectric element 26 is fixed to a fixing plate 27 attached to the fixing table 25.

FIG. 1 is a perspective view showing a part of a piezoelectric actuator in the ink jet head shown in FIG. 2 in more detail, FIG. 3 is a sectional view thereof, and FIG. 4 is a plan view of one piezoelectric element of the piezoelectric actuator. FIG.

In these figures, reference numeral 30 denotes a piezoelectric body made of rectangular parallelepiped (PZT) ceramics in which strain or stress is generated by applying a voltage. A ground electrode pattern 31 is provided on the upper surface of the piezoelectric body 30, and a signal electrode pattern 32 is provided on the lower surface. The piezoelectric body 30 is polarized in the thickness direction and is displaced in the length direction by applying a voltage in the thickness direction. An effect type piezoelectric element 26 is formed. The piezoelectric actuator is formed in a comb shape by fixing the rear end portions of the plurality of (the number of nozzles) piezoelectric elements 26 to a fixing plate 27.

The ground electrode pattern 31 is formed only on a part of the upper surface of the piezoelectric body 30, that is, on the upper surface in front of the portion fixed to the fixing plate 27. Also, the signal electrode pattern 3
As shown in FIG. 3, the lower surface 2 (32a) of the piezoelectric body 30 and the rear surface (32
It is formed up to a part (32c) of the upper surface via b). Therefore, the region of the piezoelectric body 30 sandwiched between the ground electrode pattern 31 and the signal electrode pattern 32 is a region in front of the portion fixed to the fixing plate 27. Also, the piezoelectric element 2
6, the ground electrode pattern 31 and the signal electrode pattern 32 appear together.

At the rear end of each ground electrode pattern 31, there is provided a connection projection 31a having a width much smaller than that of the ground electrode pattern 31, and the connection projection 31a is provided with a ground conductor pattern in the cable 33. 33a are commonly connected. A signal conductor 33b is connected to the upper surface 32c of each signal electrode pattern 32, respectively. These ground conductors 33a and signal conductors 33b are conductor patterns provided on a flexible printed circuit board (FPC), and anisotropically formed on the connection projection 31a of the ground electrode pattern 31 and the upper surface 32c of the signal electrode pattern 32. Thermocompression bonding is performed via the conductive film 34. As described above, since the ground electrode pattern 31 and the signal electrode pattern 32 are exposed on the upper surface of the piezoelectric element 26, the cable 33 can be connected by thermo-compression bonding on one side, so that the mounting cost can be reduced.

As described above, the fixing plate 27 of the piezoelectric body 30
Since only the area in front of the portion fixed to is sandwiched between the ground electrode pattern 31 and the signal electrode pattern 32,
A displacement force is generated only in this portion, and almost no displacement force is generated in the portion fixed to the fixed plate 27. Although a slight displacement force is generated in the connecting projection 31a, the portion adjacent in the width direction is immobile, so that the displacement as a whole is very small in the vicinity. Therefore, according to the present embodiment, only the displacement of the piezoelectric element 26 in the longitudinal direction that contributes to the ejection of the ink droplet occurs, and the displacement of the vertical warp hardly occurs. As a result, the noise due to the piezo drive is greatly reduced.

FIG. 5 is a sectional view of a part of a laminated piezoelectric actuator as another embodiment of the present invention.

In FIG. 1, reference numeral 40 denotes a rectangular parallelepiped piezoelectric (PZ) in which a strain or a stress is generated when a voltage is applied.
T) A laminated piezoelectric body made of ceramics. A ground electrode pattern 41 is provided on the upper surface, the lower surface, and the center of the laminated piezoelectric body 40, and the signal electrode pattern 42 is provided between the ground electrode patterns 41 so as to be interposed between the laminated piezoelectric bodies 40. Thus, a laminated piezoelectric element of a piezoelectric lateral effect type which is displaced in a length direction by applying a voltage in a thickness direction is formed.

The ground electrode pattern 41 is formed only on the upper surface, the lower surface, and a part of the central portion of the piezoelectric body 40, and these are three-dimensionally connected via side surfaces. The signal electrode pattern 42 is formed on the inside of the piezoelectric body 40 and on a part of the upper surface and the lower surface, and these are three-dimensionally connected via side surfaces.

The operation and effects of this embodiment are exactly the same as those of the above embodiment.

[0023]

As described above in detail, according to the present invention, at least one layer of the piezoelectric body and a part of the piezoelectric body are formed.
A piezoelectric lateral effect type piezoelectric actuator comprising a plurality of piezoelectric elements each having a fixing portion for fixing, and a signal electrode pattern and a ground electrode pattern provided on both surfaces of the piezoelectric body with the signal electrode pattern interposed therebetween. The area of the piezoelectric body sandwiched between the ground and the ground electrode pattern is ahead of the fixed part.
So that the signal electrode pattern and ground electrode pattern
Since it is formed, noise generation due to piezo drive can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a part of one embodiment of a piezoelectric actuator of the present invention.

FIG. 2 is a cross-sectional view schematically showing a configuration of an ink jet head using the piezoelectric actuator shown in FIG.

FIG. 3 is a sectional view of the piezoelectric actuator shown in FIG. 1;

FIG. 4 is a plan view of one piezoelectric element of the piezoelectric actuator shown in FIG.

FIG. 5 is a partial sectional view of another embodiment of the piezoelectric actuator of the present invention.

FIG. 6 is a sectional view showing an example of a conventional piezoelectric actuator.

FIG. 7 is a plan view showing an example of the piezoelectric actuator of FIG.

FIG. 8 is a diagram for explaining displacement of a piezoelectric element when a pulse-like voltage is applied to a conventional piezoelectric actuator.

[Explanation of symbols]

 26 Piezoelectric element 30, 40 Piezoelectric body 31, 41 Ground electrode pattern 31a Connection projection 32, 42 Signal electrode pattern 33 Cable 33a Ground conductor 33b Signal conductor 34 Anisotropic conductive film

Claims (2)

(57) [Claims] At least one layer of a piezoelectric body, and the piezoelectric body
A fixed portion for fixing a part of the piezoelectric element, a piezoelectric lateral effect type piezoelectric actuator comprising a plurality of piezoelectric elements each having a signal electrode pattern and a ground electrode pattern provided on both sides of the piezoelectric body, The region of the piezoelectric body sandwiched between the signal electrode pattern and the ground electrode pattern is
The signal electrode pattern so as to be forward of the fixing portion
And a ground electrode pattern formed on the piezoelectric actuator. 2. The piezoelectric actuator according to claim 1, wherein at least a part of each of the signal electrode pattern and the ground electrode pattern is provided on one surface of the piezoelectric body.