JPH01269546A - Ink-jet head - Google Patents

Abstract

PURPOSE:To eliminate a machining to a beam shape of a vibrator, and to increase head density by forming a piezoelectric transducer to a plane shape formed and unified at a regular interval from a nozzle plate, independently shaping only a driving electrode and separately driving the piezoelectric transducer in response to a plurality of the nozzles. CONSTITUTION:A piezoelectric transducer 29 and a nozzle plate 22 are laminated and fixed to a frame 21 through an elastic sheet 23 in an ink jet head. The nozzle plate 22 is composed of a metal sheet with a plurality of nozzles 26. The piezoelectric transducer 29 is formed to a unified plane shape, driving electrodes 31 are formed independently onto the surface of a piezoelectric element 30, and the piezoelectric transducer can be driven separately in response to each nozzle. The driving electrodes 31 are driven selectively by wirings 32. Accordingly, a vibrator need not be machined to a beam shape by using the piezoelectric transducer having said constitution, the electrodes may be shaped through a normal photolithographic process, and the ink jet head having high accuracy and high density can be formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inkjet recording device such as a printer that flies ink droplets to form an ink image on a medium such as recording paper, and more specifically relates to an inkjet printer head. Regarding.

[Prior Art] A known structure of a conventional inkjet head includes a nozzle plate having a plurality of nozzle openings and a piezoelectric transducer behind the nozzle plate that directly contacts ink. (Showa 60-8953, etc.) In this structure, the vibrator constituting the piezoelectric transducer vibrates as if displaced in a direction approximately perpendicular to the nozzle plate, and the ink flow path between each nozzle communicates over a short distance. Therefore, the ink droplet ejection efficiency and stability are high, and even if foreign matter such as gas or dust gets mixed into the ink, normal operation is possible without being affected by this. The vibrator used is a cantilever-shaped or double-sided beam-shaped vibrator arranged with a small gap maintained between the nozzle plate and the nozzle plate.

[Problem H to be solved by the invention] In the structure of an inkjet head using a cantilever-shaped vibrator or a double-sided beam-shaped vibrator in the above-mentioned prior art, the vibrator is made into a beam-like shape by machining or the like during the manufacturing process. The higher the density of the head, the more difficult it is to manufacture. Not only is it difficult, but there are limits to increasing density.

Furthermore, in the structure of an inkjet head using a cantilever beam vibrator or a double beam vibrator of the prior art described above, it is virtually impossible to form head nozzles in multiple rows.

That is, in the case of a cantilever-beam vibrator, it is best to abut two rows of separately formed vibrators, and in the case of a double-beam vibrator, nozzles cannot be arranged closely.

Increasing the number of heads is very important in increasing the speed of printers, but the structure of the inkjet head using the cantilever beam vibrator or double-end beam vibrator of the above-mentioned conventional technology is In the manufacturing process, the vibrator must be machined into a beam shape, and the processing cost increases almost in proportion to the number of heads.

An object of the present invention is to solve these problems, eliminate the need to process the vibrator into a beam shape, and realize an inkjet head with high head density.

[Means for Solving the Problems] An inkjet head of the present invention includes a nozzle forming member having a plurality of nozzle openings and a piezoelectric transducer, and an inkjet head filled with ink between the nozzle forming member and the piezoelectric transducer. In the head, the piezoelectric transducer has an integrated planar shape, only the driving electrodes are formed independently, and the piezoelectric transducer can be driven independently in correspondence with each nozzle.

[Function] In the above configuration of the present invention, only the drive electrode is formed independently in an integrated planar shape provided at a constant interval from the nozzle plate, and can be driven independently corresponding to each nozzle. The piezoelectric transducer vibrates in a direction perpendicular to the nozzle plate, pushing out nearby ink and causing it to fly as ink droplets.

[Example] Next, the present invention will be specifically described in detail based on Examples.

FIG. 1 is a perspective view of a printer showing an embodiment of the present invention. In the figure, a recording paper 1 is wound around a platen 2 and is pressed by a feed roller 3. The inkjet head 7 is mounted on a carriage 6 that is guided by a guide shaft 4.5 and movable in a direction parallel to the platen axis. The inkjet head 7 has a plurality of nozzles that can independently eject ink droplets, and is scanned in the platen axis direction, selectively ejecting ink droplets from the nozzles to form an ink image on the recording paper 1. The recording paper 1 is conveyed in a sub-scanning direction perpendicular to the scanning direction by rotation of a platen 2 and a feed roller 3, and printing is performed on the recording paper surface.

FIG. 2 shows a cross section of the inkjet head.

A piezoelectric transducer 29 and a nozzle plate 22 are stacked on a frame 21 with an elastic sheet 23 in between, and fixed using fixing screws 24 and 25. The nozzle plate 22 is composed of a thin metal plate having a plurality of nozzles 26. The piezoelectric transducer 29 has a piezoelectric element 30 made of PZT, whose perspective view is shown in FIG.
A patterned electrode layer 31 has a common electrode layer 33 made of a thin layer, a spacer layer made of a thin Ni layer, and a patterned electrode layer 31 made of a thin N1 layer on the other side.
has. The pattern electrodes 31 are separated from each other, and the integrated piezoelectric elements 30 made of planar PZT are independently driven partially into a horn shape.

FIG. 4 shows a cross-sectional conceptual diagram of an integrated piezoelectric transducer used in the present invention, in which an independent pattern electrode 31 and a common electrode 33, which is formed thicker than the pattern electrode, are formed facing each other. . The common electrode 33 has an elastic modulus as high as that of the PZT layer.

Referring again to FIG. 2, the corresponding nozzles 26 are arranged so as to face each other in the vicinity of the vibrator driving section in the vicinity of the pattern electrode with a small gap a interposed therebetween.

Wiring lines 32 are individually connected to the pattern electrodes, and selective voltage application is performed.

Next, the operation will be explained. Ink (not shown) is supplied from the ink reservoir 27 to the vicinity of the nozzle to fill it.

By applying a voltage between the common electrode 33 and the pattern electrode 31, the piezoelectric element contracts due to the piezoelectric effect. On the other hand, since the layer of the common electrode 33 is formed thickly so as to have a high elastic modulus, dimensional changes are restricted, and as a result, the common electrode 33 curves into a bowl shape toward the common electrode side. As a result, ink near the common electrode side with respect to the pattern electrode 31 is ejected from the nozzle.

In the above structure, the piezoelectric transducer 29 has an integrated planar shape as shown in FIG. 3, and drive electrodes 31 are independently formed on the surface of the piezoelectric element 30, and can be driven independently corresponding to each nozzle. It is a piezoelectric transducer. The drive electrode 31 is selectively driven by the wiring 32.

A common electrode 33 is provided on the opposite side of the surface where the drive electrode 31 is located. A hole 34 for a fixing screw and an ink passage 35 are provided when assembling the inkjet head. Furthermore, the piezoelectric transducer 29 has a spacer layer on its outer periphery. Therefore, by attaching the entire piezoelectric transducer with reference to the nozzle plate, the position of the pattern electrode is positioned and regulated with respect to the hole in the nozzle plate. At the same time, unlike a cantilevered vibrator, the four sides of the vibrator are joined to the nozzle plate 22, so the gap size between the nozzle plate 22 and the movable part of the vibrator can be controlled with high precision, which makes manufacturing easy and increases the manufacturing yield. Stable characteristics can be obtained without any physical changes.

In this embodiment, a thin metal plate integrally formed with the piezoelectric element is used as the spacer, but a separate metal plate may be used as a spacer and sandwiched between the nozzle plate and the piezoelectric element and fixed. It is possible.

[Effects of the Invention] As described above, according to the above configuration of the present invention, only the driving electrodes are formed independently in an integrated planar shape,
By using piezoelectric transducers that can be driven independently for each nozzle, the transducer can be made into a beam shape through machining during the manufacturing process, such as cantilever beam vibrators or double beam vibrators. There is no need for processing, and the electrodes can be formed using a normal photolithography process, making it possible to create a high-precision, high-density inkjet head.

At the same time, since the dimensional tolerance of the vibrator can be reduced due to its structure, it is easy to stabilize the characteristics of the inkjet head. In other words, this is the distance W between the piezoelectric transducer and the nozzle.
This is because the accuracy of the distance between the nozzle plate and the vibrator movable part can be increased.

Furthermore, unlike cantilever beam vibrators and double beam vibrators, the length of the vibrator is not required in the longitudinal direction, so it is easy to form nozzles in multiple rows. Can be made very dense.

As described above, the present invention makes it possible to provide an inkjet head that has high precision, high density, and can reduce manufacturing costs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a printer equipped with an inkjet head showing one embodiment of the present invention. FIG. 2 is a sectional view of an inkjet head showing an embodiment of the present invention. FIG. 3 is a perspective view of a piezoelectric transducer used in an inkjet head showing one embodiment of the present invention. FIG. 4 is a cross-sectional conceptual diagram of a piezoelectric transducer used in an inkjet head showing one embodiment of the present invention. 1 Recording paper 2 Platen 3 Feed roller 4 Guide shaft 5 Guide shaft 6 Carriage 7 Inkjet head 21 Frame 22 Nozzle plate 23 Elastic sheet 24 Fixing screw 25 Fixing screw 26 Nozzle 27 Ink reservoir 29 Piezoelectric transducer 30 Piezoelectric element 31 Pattern electrode 32 Wiring 33 Common electrode 34 Hole for fixing screw 35 Ink path Applicant Seiko Epson Co., Ltd. Representative patent attorney Kizobe Suzuki (1 other person) Figure 2

Claims (1)

[Claims] In an inkjet head that has a nozzle forming member having a plurality of nozzle openings and a piezoelectric transducer, and ink is filled between the nozzle forming member and the piezoelectric transducer, the piezoelectric transducer has an integrated planar shape. An inkjet head characterized in that only the drive electrode is formed independently and is a piezoelectric transducer that can be driven independently in correspondence with each nozzle.