JP2596629B2 - Inkjet recording head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ink jet recording head.

2. Description of the Related Art Printers are widely used as output devices for electronic devices such as word processors and personal computers.
One of the heads of this printer is an ink jet recording head.

FIG. 10 is an exploded perspective view of this type of conventional ink jet recording head.

As shown in the figure, a vibration plate 12 is mounted on a piezoelectric actuator unit 11, and a cover plate 13 is mounted on the vibration plate 12 to constitute an ink jet recording head.

Ink supplied from an ink supply hole 14 provided in the cover plate 13 is jetted from nozzles 15a to 15d integrated with an ink chamber provided on the front surface of the cover plate 13, and printed on paper.

 FIG. 11 shows a front view of the conventional example of FIG.

As shown in the figure, when a signal voltage is applied to both electrodes 17 of the laminated piezoelectric body 16a of the piezoelectric actuator unit 11, the piezoelectric actuator unit 11 is displaced in the laminating direction (the direction of the arrow α in the figure) by the piezoelectric longitudinal displacement effect, and the diaphragm 12 is displaced. Press. When the vibration plate 12 is pressed, the ink chamber 18a of the cover plate 13 is compressed, and the ink is ejected from the nozzle, so that printing is performed on paper or the like.

[Problem to be Solved by the Invention] According to such a configuration, in order to displace the laminated piezoelectric body 16a in the arrow α direction and effectively press the ink chamber 18a via the diaphragm 12, the diaphragm 12 must be The laminated piezoelectric body 16b as a supporting portion for supporting is required. As a result, the laminated piezoelectric body 1
The pitch x between the nozzle communicating with the ink chamber 18a corresponding to 6a and the nozzle communicating with the ink chamber 18b corresponding to the laminated piezoelectric body 16c is inevitably large, making it difficult to increase the density of the nozzles.

Accordingly, it is an object of the present invention to provide a high density nozzle ink jet recording head.

[Means for Solving the Problems] According to the present invention, there is provided an ink jet recording head including a plurality of nozzles and a plurality of ink chambers respectively communicating with the nozzles. A plurality of piezoelectric actuators arranged between two plates to form opposing side walls of the ink chamber, a nozzle plate having a plurality of nozzles, and a plurality of spacers provided between the piezoelectric actuators to face the nozzles Each voltage actuator is configured by alternately stacking a plurality of piezoelectric bodies and a plurality of electrodes in the same direction as the arrangement direction, and connecting every other electrode. This is achieved by an inkjet recording head, which utilizes a piezoelectric longitudinal displacement effect that expands in a stacked direction when a signal voltage is applied. It is.

[Operation] When a signal voltage is applied to each piezoelectric actuator configured by laminating a plurality of piezoelectric bodies in the same direction as the arranged direction, both piezoelectric actuators expand on both lamination surfaces. As a result, the ink chamber formed by each piezoelectric actuator is compressed, and ink is ejected from a nozzle communicating with the ink chamber.

EXAMPLES Hereinafter, the ink jet recording head according to the present invention will be described in more detail with reference to examples.

FIG. 1 is an exploded perspective view of an ink jet recording head as one embodiment of the present invention.

In the figure, a plurality of piezoelectric actuators 22 are mounted on a plate 21. The grooves on the plate 21 formed by the piezoelectric actuators 22 are separated from each other by a plurality of spacers 23. A cover plate 24 is mounted on the piezoelectric actuator 22 and the spacer 23. The nozzle plate 25 is attached to the front surface of the plate 21, the piezoelectric actuators 22, and the cover plate 24 to form an ink jet recording head as shown in FIG.

FIG. 2 is a perspective view of the ink jet recording head shown in FIG. 1 after assembly.

In the drawing, the ink supplied from the ink supply port 26 is stored in an ink reservoir provided inside the ink cover 24 and in each ink chamber between the piezoelectric actuators. When the piezoelectric actuator 22 operates, the ink stored in the ink chamber is ejected from a plurality of nozzles 29 provided on the nozzle plate 25 to perform printing.

In FIG. 1, a piezoelectric actuator 22 is a kind of a laminated piezoelectric element formed by laminating a plurality of piezoelectric bodies and conductive layers. The piezoelectric actuator 22 is mounted on the plate 21 so that the lamination surface and the plate 21 are perpendicular to each other.
Attached to. Here, the lamination surfaces are both surfaces perpendicular to the lamination direction of the piezoelectric actuator 22. Further, an assembly of the piezoelectric actuators 22 is referred to as a piezoelectric actuator unit.

The plurality of piezoelectric actuators 22 on the plate 21 are mounted at predetermined intervals in parallel with each other, and form a plurality of grooves between the respective piezoelectric actuators 22. At the base of the piezoelectric actuator 22, the piezoelectric actuator 22
A spacer 23 having the same height as that of the groove and having the same width as the groove is attached so as to cover a part of the groove.

A cover plate 24 is bonded on the piezoelectric actuator 22 and the spacer 23 so as to cover them. The plate 21, the piezoelectric actuator 22, the spacer 23, and the cover plate 24 form a plurality of ink chambers 28 (eight in the figure).

The plate 21, the cover plate 24, and the nozzle plate 25 are formed, for example, by performing photo-etching on photosensitive glass, but may be formed using a ceramic, metal plate, plastic, or the like.

Each ink chamber 28 is provided with an ink supply port 26 provided in the cover plate 24 and an ink reservoir 27 communicating with the ink supply port 26.
Is in communication with The ink chamber 28 further includes a nozzle plate
The plurality of nozzles 29 (eight in the figure) provided in the nozzle 25 communicate with each other.

Although the number of nozzles 29 is eight in the drawing, it may be increased or decreased with the number of ink chambers 28.

Two electrodes, a signal electrode 30a and a common electrode 30b, are provided on both side surfaces of the piezoelectric actuator 22, and are respectively connected to external driving circuits (not shown).

When a signal voltage is applied from the drive circuit, the piezoelectric actuator 22 is displaced in the direction of the laminated surface by the piezoelectric longitudinal displacement effect. The ink jet recording head of the present invention utilizes this piezoelectric longitudinal displacement effect.

Here, the piezoelectric longitudinal displacement effect will be described with reference to the explanatory diagram of FIG.

In the figure, a plurality of piezoelectric bodies and electrodes are alternately laminated. A plurality of electrodes are commonly connected to every other one. One of the electrodes is connected to the anode terminal of the power supply, and the other electrode is connected to the cathode terminal of the power supply. When a voltage is applied to each of these terminals, or Are polarized as shown by, and displace in the direction perpendicular to the electrode surface as shown by arrows D ₁ and D ₂ . This phenomenon is the piezoelectric longitudinal displacement effect.

On the other hand, there is a bimorph effect as a phenomenon similar to the piezoelectric longitudinal displacement effect.

FIG. 4 is an explanatory diagram for explaining this bimorph effect.

In the figure, two piezoelectric elements having a thickness T / 2 are polarized in the direction of the thickness T / 2 as shown respectively. When one end (the lower end in the figure) of this joined body is fixed and a voltage is applied between the electrode provided on the joining surface of the piezoelectric element and the electrodes provided on both outer surfaces, the piezoelectric body on the right side in the figure becomes an arrow D ₃ displaced in the direction, the left piezoelectric member is displaced in the arrow D ₄ direction. However, 2
Like the piezoelectric element occurs resiliently deformed free end for being joined, it will deflect the arrow D ₅ direction as a whole. Such a phenomenon is the bimorph effect, which is clearly different from the above-described piezoelectric longitudinal displacement effect.

Next, a method of manufacturing the piezoelectric actuator 22 will be described with reference to the process explanatory view of FIG.

In FIG. 3A, a green sheet 31 (thickness t (for example, 50 μm), width L, width W) made of a piezoelectric ceramic material powder as a piezoelectric material, an organic binder, a plasticizer, or the like.
And the conductor layers 32a and 32b are alternately laminated to each other until the thickness of the piezoelectric actuator 22 is reached. In addition,
PZT (lead zircon titanate) is preferably used as the piezoelectric ceramic material.

Each of the conductor layers 32a and 32b has a width W and a width slightly shorter than L. These conductor layers 32a and 32b are stacked so as to be adjacent to each other in the horizontal direction (L direction in the figure). At this time, the right end of the conductor layer 32a is located at the right end of the green sheet 31, and the left end of the conductor layer 32b is located at the green sheet 31.
Are stacked so as to be located at the left end of the.

The laminate 33 of the green sheet 31 and the conductor layers 32a and 32b is cured by firing. At this time, the conductor layer 32a is exposed on the right side surface of the laminate 33, and the conductor layer 32b is exposed on the left side surface of the laminate 33 (FIG. 2B).

The laminate 33 is sliced with a width 1 (for example, 500 μm) perpendicular to the lamination surface by a cutting device such as a dicing saw. The sliced laminate is subjected to electroless plating on the right side surface and the right side surface in the figure. The conductor layers 32a are commonly connected to each other by electroless plating, and the conductor layers 32b are also commonly connected to each other to form the piezoelectric actuator 22 (FIG. 3C). At this time, a coating may be applied to a portion that becomes a part of the inner wall of the ink chamber.

As another manufacturing method, the green sheet and the conductive layer are laminated until the width becomes equal to the width Wa of the ink jet recording head, and the fired laminated body is sliced perpendicularly to the lamination surface. The sliced laminate is joined to the plate 21 and a plurality of grooves 34 (for example, 500 μm in width and 5 μm in thickness) are
00 μm) to form the piezoelectric actuator 22 (see the perspective view of the piezoelectric actuator unit in FIG. 6).

Further, a piezoelectric actuator unit may be configured such that an organic sheet made of an organic compound is previously laminated on a portion to be a groove when the green sheets 31 are laminated, and the portion becomes a groove when baked.

The conductor layer 32a connected to the external drive circuit is connected to the signal electrode 3
0a, and the conductor layer 32b is a common electrode 30b (for example, a GND (ground) electrode).

Next, the operation of such an ink jet recording head will be described with reference to FIG. 7 and FIG.

FIG. 7 is an explanatory diagram for explaining the operation when the ink jet recording head is viewed from above.

In the figure, when a signal voltage Va is applied to a signal electrode of a piezoelectric actuator 22a and a common electrode from a driving circuit (not shown), a piezoelectric actuator
22a is displaced in the vertical arrows D ₆ and D ₇ direction to the laminated surface of the piezoelectric body. Similarly displaced in vertical arrow D ₈ and D ₉ direction in the laminated surface of the well piezoelectric piezoelectric actuator 22b when the signal voltage Vb is applied to the common electrode to the signal electrode and the piezoelectric actuator 22b by a piezoelectric longitudinal displacement effect. That is, the piezoelectric actuators 22a and 22b expand as shown in the figure.

This allows the piezoelectric actuators 22a and 22b and the spacer
23 and the ink chamber 28a, which forms a part of the wall surface, contracts as shown by the broken line in the figure. As a result, a compression pressure is generated in the ink chamber 28a, and the ink inside the ink chamber 28a is ejected from the nozzle 29a communicating with the ink chamber 28a.

FIG. 8 is an explanatory diagram for explaining the operation when the inkjet recording head is viewed from the front.

In the figure, a part of the inner wall of the ink chamber 28a is formed by the plate 21, the cover plate 24, and the piezoelectric actuators 22a and 22b.

When the piezoelectric actuators 22a and 22b operate, they expand as indicated by broken lines in the figure, and the ink chamber 28a contracts. Thus, the ink inside the ink chamber 28a is ejected from the nozzle 29a.

However, when the piezoelectric actuator 22a is operated, for example, both side surfaces of the piezoelectric actuator 22a expand, so that the adjacent ink chambers 28b and 28c also contract at the same time. Therefore, the ink cannot be ejected from the nozzles by independently contracting the adjacent ink chambers.

Therefore, it is necessary to operate the piezoelectric actuator 22 every third one. However, such inconvenience can be avoided by providing a dummy chamber in which ink is not inserted every other chamber.

FIG. 9 is an exploded perspective view of another embodiment of the present invention.

As shown in the figure, the piezoelectric actuator 22 is mounted on the substrate 35 together with the plate 21. Piezoelectric actuator 22
The ink path 36 is mounted on the top. A nozzle plate 37 is attached to the front surfaces of the substrate 35, the plate 21, the piezoelectric actuator 22, and the ink path 36 to form an ink jet recording head.

A drive circuit 38 and a wiring pattern 39 connected to the drive circuit 38 are formed on a substrate 35 of the inkjet recording head. On the other hand, each piezoelectric actuator 22
A wiring pattern (not shown) connected to these electrodes is provided. The wiring patterns are respectively connected by means such as screen printing of a conductive adhesive.

An ink supply port 40 is provided in the ink path 36,
Each piezoelectric actuator 22 communicates with a plurality of ink chambers in which a part of the inner wall is formed.

The nozzle plate 37 is provided with a plurality of nozzles 41, each of which communicates with the ink chamber.

Ink supply port of such an ink jet recording head
The ink supplied from 40 is stored in each ink chamber, and is ejected from the nozzle 41 when the piezoelectric actuator 22 operates.

Further, in the present invention, since the arrangement direction of each piezoelectric actuator 22 is configured to be the same direction as the lamination direction of the piezoelectric bodies, the displacement amount can be sufficiently increased by the lamination direction displacement, and the ink Injection efficiency can be improved.

Further, the laminated piezoelectric body as the conventional supporting portion can be omitted, and the thickness of the green sheet, the number of laminations, and the width of the dummy ink chamber used for firing during the formation of the piezoelectric actuator are appropriately selected (dummy ink chamber). (The piezoelectric actuator forming the inner wall of the nozzle is narrowed to the extent that it does not come into contact when it expands.) This enables high integration of nozzles (narrowing of nozzle pitch) and low voltage driving at 30 V or less (conventionally). Requires a high voltage of 100V or more).

[Effects of the Invention] As described above in detail, according to the present invention, there is provided an ink jet recording head including a plurality of nozzles and a plurality of ink chambers respectively communicating with the nozzles. A plate, a plurality of piezoelectric actuators arranged between the two plates to form opposing side walls of each ink chamber, a nozzle plate having a plurality of nozzles, and a nozzle plate provided between the piezoelectric actuators to face each nozzle. Each piezoelectric actuator is formed by alternately stacking a plurality of piezoelectric bodies and a plurality of electrodes in the same direction as the arrangement direction, and connecting every other electrode. The piezoelectric actuator uses a piezoelectric longitudinal displacement effect that expands in the stacking direction when a signal voltage is applied. Can be increased sufficiently to improve the ink ejection efficiency, and can be driven at a low voltage. In addition, since each piezoelectric actuator itself forms the side wall of the ink chamber, it is possible to increase the nozzle pitch.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an ink jet recording head as one embodiment of the present invention, FIG. 2 is a perspective view of the ink jet recording head shown in FIG. 1 after assembly, and FIG. FIG. 4 is an explanatory diagram for explaining the bimorph effect, FIG. 5 is a process explanatory diagram, FIG. 6 is a perspective view of a piezoelectric actuator unit, and FIGS. 7 and 8 are operations of the same embodiment. FIG. 9 is an exploded perspective view of another embodiment of the present invention, FIG. 10 and FIG.
The figure shows a conventional example of an ink jet recording head. 21 ... plate, 22 ... piezoelectric actuator, 23 ... spacer, 24 ... cover plate, 25 ... nozzle plate, 26 ... ink supply port, 27 ... ink reservoir, 28 ...
Ink chamber, 29 ... Nozzle, 30a ... Signal electrode, 30b ... Common electrode.

Claims (1)

(57) [Claims] An ink jet recording head comprising a plurality of nozzles and a plurality of ink chambers respectively communicating with the nozzles, wherein the plurality of ink chambers include upper and lower plates,
A plurality of piezoelectric actuators arranged between the two plates to form opposing side walls of each ink chamber, a nozzle plate having the plurality of nozzles, and a nozzle plate provided between the piezoelectric actuators so as to face each nozzle. Each of the piezoelectric actuators is alternately stacked with a plurality of piezoelectric bodies and a plurality of electrodes in the same direction as the arrangement direction, and is connected to every other electrode. An ink jet recording head, comprising: a piezoelectric vertical displacement effect that expands in a stacking direction when a signal voltage is applied.