JPH05104715A - Piezoelectric actuator for ink jet head - Google Patents

Abstract

PURPOSE:To reduce generation of noise to be generated by piezo-driving of a piezoelectric actuator. CONSTITUTION:A piezoelectric actuator comprises at least a piezoelectric body 30 with one layer, and a plurality of piezoelectric devices 26. Each device 26 has a signal electrode pattern 32 and an earth electrode pattern 31 provided on both faces of the piezoelectric body 30 pinching the piezoelectric body 30. At least one of the signal electrode pattern 32 and the earth electrode pattern 31 is provided on only a face area of a part corresponding to an area where displacement force is to be generated.

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 sides of a piezoelectric body, are arranged in a comb shape, and each of the multi-nozzles of an inkjet head is driven. 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.

In these drawings, reference numeral 10 denotes a rectangular parallelepiped piezoelectric body which is distorted or stressed by applying a voltage. A signal electrode pattern 11 and a ground electrode pattern 12 are provided on the entire surfaces of both surfaces of the piezoelectric body 10.
Two piezoelectric elements are configured. As shown in FIG. 7, the piezoelectric actuator is formed by arranging a plurality of such piezoelectric elements in a comb shape and fixing the lower side of one end portion of the piezoelectric elements to the fixing plate 13. The conductive pattern 14a in the 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 conductive fixing plates 13
Are commonly connected by soldering or a conductive adhesive.

[0005]

FIG. 8 is a diagram for explaining the displacement of the piezoelectric element when a pulsed 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 1 and the ground electrode pattern 12, a displacement A occurs in the longitudinal direction. 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, displacement force is generated in all parts of the piezoelectric body 10. Moreover, the lower side of one end is the fixed base 1
Since it is fixed to 3, there is a vertically asymmetrical restraining force, and as a result, vertical displacement (warpage) B occurs in addition to displacement A in the longitudinal direction. The vertical displacement B becomes a cause of noise of the inkjet head.

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

[0008]

According to the present invention, a plurality of piezoelectric elements each having at least one layer of piezoelectric material and a signal electrode pattern and a ground electrode pattern provided on both surfaces of the piezoelectric material with the piezoelectric material interposed therebetween. Provided is a piezoelectric actuator for an inkjet head, wherein at least one of a signal electrode pattern and a ground electrode pattern is provided only in a partial surface region corresponding to a region where a displacement force is to be generated. To be done.

[0009]

The signal electrode pattern or the ground electrode pattern, or both the signal electrode pattern and the ground electrode pattern are not provided on the entire surface of the piezoelectric body, but a partial surface area corresponding to the area where the displacement force should be generated. It is provided only in. Therefore, the displacement force is generated only in a portion corresponding to a part of the surface area, and vertical displacement (warpage), which is a source of noise generation, hardly occurs.

[0010]

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

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

In the figure, 20 is an ink chamber 21 inside.
Is an ink chamber block in which is formed. An orifice 22 for ejecting ink is provided on the front surface of the ink chamber block 20.
The orifice plate 23 having the is fixed. A filter plate 24 is provided on the rear surface of the ink chamber block 20.
The fixed base 25 is fixed via the.

The tip portion of the piezoelectric element 26 is inserted into the ink chamber block 20, and the tip surface of the piezoelectric element 26 constitutes a part of the inner wall of the ink chamber 21. The rear end portion of the piezoelectric element 26 is fixed to a fixed plate 27 attached to the fixed base 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. It is a figure.

In these figures, reference numeral 30 denotes a piezoelectric body made of rectangular parallelepiped piezoelectric (PZT) ceramics in which strain or stress is generated when a voltage is applied. 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 thereof, whereby 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 a plurality of such piezoelectric elements (of the number of nozzles) 26 to the 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 clearly shown in FIG. 3, reference numeral 2 denotes the entire lower surface (32a) of the piezoelectric body 30 and the rear surface (32a) of the three-dimensional wiring.
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. In addition, the piezoelectric element 2
Both the ground electrode pattern 31 and the signal electrode pattern 32 will appear on the upper surface of 6.

At the rear end of each ground electrode pattern 31, there is provided a connection protrusion 31a having a width much narrower than that of the ground electrode pattern 31. The connection protrusion 31a has a ground conductor pattern in the cable 33. 33a are commonly connected. A signal conductor 33b is connected to the upper surface portion 32c of each signal electrode pattern 32. These ground conductors 33a and signal conductors 33b are conductor patterns provided on a flexible printed circuit board (FPC), and the connecting projections 31a of the ground electrode patterns 31 and the upper surface 32c of the signal electrode patterns 32 are anisotropic. 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 thermocompression-bonded on one side, and thus the mounting cost can be reduced.

As described above, the fixing plate 27 of the piezoelectric body 30
Since only the region in front of the portion fixed to is sandwiched between the ground electrode pattern 31 and the signal electrode pattern 32,
The displacement force is generated only in this portion, and the displacement force is hardly generated in the portion fixed to the fixing plate 27. Although some displacement force is generated in the connecting protrusion 31a, the adjacent portion in the width direction is immovable, and therefore the displacement as a whole is very small in this vicinity. Therefore, according to the present embodiment, only the displacement in the longitudinal direction of the piezoelectric element 26 that contributes to the ejection of the ink droplets occurs, and the displacement in the vertical warpage hardly occurs. As a result, noise due to 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 the figure, reference numeral 40 is a rectangular parallelepiped piezoelectric (PZ) in which strain or stress is generated when a voltage is applied.
T) A laminated piezoelectric body made of ceramics. The ground electrode pattern 41 is provided on the upper surface, the lower surface, and the central portion of the laminated piezoelectric body 40, and the signal electrode pattern 42 is provided between the ground electrode patterns 41 so as to be polarized in the thickness direction. Thus, a piezoelectric lateral effect type laminated piezoelectric element that is displaced in the length direction by applying a voltage in the 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 the side surface. Further, the signal electrode pattern 42 is formed inside the piezoelectric body 40 and a part of the upper surface and the lower surface, and these are three-dimensionally connected via the side surface.

The operation and effect of this embodiment are exactly the same as those of the above-mentioned embodiment.

[0023]

As described in detail above, according to the present invention, a plurality of piezoelectric bodies each having at least one layer of piezoelectric material and a signal electrode pattern and a ground electrode pattern provided on both sides of the piezoelectric material are sandwiched therebetween. A piezoelectric actuator including the piezoelectric element according to claim 1, wherein at least one of the signal electrode pattern and the ground electrode pattern is provided only in a partial surface area corresponding to an area in which a displacement force is to be generated. Noise generation can be reduced.

[Brief description of drawings]

FIG. 1 is a partial perspective view of an embodiment of a piezoelectric actuator of the present invention.

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

3 is a cross-sectional view of the piezoelectric actuator shown in FIG.

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

FIG. 5 is a partial cross-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 pulsed voltage is applied to a conventional piezoelectric actuator.

[Explanation of symbols]

 26 Piezoelectric element 30, 40 Piezoelectric body 31, 41 Grounding electrode pattern 31a Connecting protrusion 32, 42 Signal electrode pattern 33 Cable 33a Grounding conductor 33b Signaling conductor 34 Anisotropic conductive film

Claims (2)

[Claims] 1. A piezoelectric actuator comprising a plurality of piezoelectric elements each having at least one layer of a piezoelectric body, and a signal electrode pattern and a ground electrode pattern provided on both surfaces of the piezoelectric body with the piezoelectric body sandwiched therebetween. A piezoelectric actuator for an inkjet head, wherein at least one of a signal electrode pattern and a ground electrode pattern is provided only in a partial surface region corresponding to a region where a displacement force is to be generated. 2. The piezoelectric actuator according to claim 1, wherein at least a part of the signal electrode pattern and the ground electrode pattern is provided on one surface of the piezoelectric body.