JPH022005A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain an ink jet head having stable characteristics and high manufacturing yield by constituting a piezoelectric converter of a beam-shape vibrator which is constituted by laminating a control layer changing in length on a base layer to bond both of them at a plurality of places. CONSTITUTION:Each of piezoelectric converters 22 is constituted by a vibrator formed by bonding a piezoelectric element chip 42 constituting a shrinkage controllable control layer, wherein an electrode layer 41 is applied to the single surface of a piezoelectric element 40, to a base layer 43 at two points 44, 45 by laser beam welding and the vibrators are arranged so as to be opposed to the respective corresponding nozzles 27 in the vicinity of the leading end parts thereof through a fine gap (a). After ink is supplied to the region close to the nozzles from an ink reservoir 29 to fill the same, voltage is applied between the base layer 43 and the pattern electrode 41 of each vibrator. Whereupon the piezoelectric element chip 42 is contracted to generate warpage in the base layer and the leading end of each of the vibrators is displaced in the direction increasing the gap with the nozzle. When the application of voltage to the desired vibrator is stopped in this state, the piezoelectric element chip returns to the original state to emit the ink in the vicinity of the leading end of the vibrator from the nozzle 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet head used in an inkjet type recording apparatus such as a printer that flies ink droplets to form an ink image on a medium such as recording paper.

[Conventional technology]

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 is in direct contact with ink. (Japanese Patent Publication No. 60-8953, etc.) This structure has high ink droplet ejection efficiency and stability, and even if foreign matter such as air bubbles or dust gets mixed into the ink, normal operation is possible without being affected by this. . As the vibrator, a cantilever beam vibrator or a double beam vibrator is used. Further, since the gap between the vibrator and the nozzle plate affects the ink droplet ejection characteristics, the structure is such that a minute gap is maintained.

The beam-shaped vibrator is constituted by a piezoelectric transducer having a two-layer structure (bimorph structure) in which a metal layer and a piezoelectric material layer are bonded over the entire surface.

[Problem to be solved by the invention]

In the structure of the conventional inkjet head described above, the vibrator may warp due to variations in conditions during the bonding process between the metal layer and the piezoelectric material layer, and the dimensions of the gap between the vibrator and the nozzle forming member may vary, resulting in stable characteristics. Furthermore, the manufacturing yield was low. Particularly in the case of a cantilever-like vibrator, it is difficult to manage the above-mentioned gap size.

An object of the present invention is to solve these problems and realize an inkjet head using a beam-shaped vibrator with stable characteristics and high manufacturing yield.

[Means to solve the problem]

An inkjet head of the present invention includes a nozzle forming member having a plurality of nozzle openings and a piezoelectric transducer, and in the inkjet head in which ink is filled between the nozzle forming member and the piezoelectric transducer, the piezoelectric transducer is a beam-shaped vibrator, and the beam-shaped vibrator is characterized by being constructed by laminating a control layer of varying length on a base layer and joining the two at a plurality of locations.

[Effect]

In the above configuration of the present invention, warping is less likely to occur due to the rigidity of the base layer of the vibrator, and since the control layer is joined at at least two points, the cavity at the tip of the vibrator can be secured with high precision without being affected by the warpage that the control layer has in advance. .

〔Example〕

Next, the present invention will be explained based on examples. FIG. 1 is a perspective view of a printer showing an embodiment of the present invention. In the figure, recording paper 10 is wound around a platen 11 and driven by feed roller shafts 12 and 13. Guide shaft 14.1
The inkjet head 16 is mounted on a carriage 15 that is guided by a carriage 7 and movable in a direction parallel to the platen axis. The inkjet bed 16 has a plurality of nozzles that can independently control the ejection of ink droplets, and is scanned in the platen axis direction to selectively eject ink droplets from the nozzles to form an ink image on the recording paper 10. The recording paper 10 is conveyed in a sub-scanning direction perpendicular to the scanning direction by rotation of a platen 11 and a feed roller, and printing is performed on the surface of the recording paper.

FIG. 2 shows a cross-sectional view of the inkjet head.

A piezoelectric transducer 22 is laminated on a frame 21 via a nozzle plate 23 and an elastic sheet 24, and fixed using fixing screws 25 and 26. The nozzle plate 23 is composed of a thin metal plate having a plurality of nozzles 27. FIG. 3 shows a perspective view of the piezoelectric transducer 22. Au on one side of the piezoelectric element 40 made of PZT.
A piezoelectric element chip 42 constituting a control layer capable of controlling shrinkage on which an electrode layer 41 made of a thin layer is applied is attached to a base layer 4 made of a Ni plate.
3 and two points 44.45 by optical beam blast contact to form a vibrator. The base layer 43 is cut into a plurality of comb-like branches, and piezoelectric element chips are joined to each branch to form a piezoelectric transducer 22 having a large number of vibrators. The electrode layer 41 is connected to a corresponding pattern on the substrate 46 by bonding. On the other hand, since the base layer 43 is an integral metal plate and is conductive, it is wired to maintain a common potential for each vibrator. These are mounted opposite to the nozzle plate via spacers 47. Again in FIG. 2, the piezoelectric transducers are arranged so that the corresponding nozzles 27 face each other with a small gap a in the vicinity of the tip of the vibrator. Wiring lines 28 are individually connected to the patterns, and selective voltage application is performed.

Next, the operation will be explained. Ink (not shown) is supplied from the ink reservoir 29 to the vicinity of the nozzle to fill it.

By applying a voltage between the base layer 43 and the patterned electrode 41, the piezoelectric element chip 42 contracts due to the piezoelectric effect.

In order to maintain the original dimensions of the base layer 43, the base layer is warped and the tip thereof is displaced in a direction that increases the gap with the nozzle. By stopping the voltage application to the desired vibrator in this state, the vibrator returns to its original state due to the elasticity of the base layer.

As a result, ink near the tip of the vibrator is ejected from the nozzle 23.

Next, another embodiment is shown in FIG. In this embodiment, a vibrator is constructed by bonding piezoelectric element chips 52 at two points 54 and 55 to branches 51 formed on a base layer 53 made of Ni, as in the previous embodiment. This example differs from the previous example in that the area around the junction points 54 and 55 of the branches is open. As the bent state of the vibrator is shown in FIG. 5, since the base layer is bent at the portion separated by the opening, no bending deformation occurs in the piezoelectric element chip. Since piezoelectric elements are generally fragile, the above structure reduces stress caused by deformation and improves durability. Also, in this example, point 56
Since it is configured to branch and extend from two directions so as to indicate the position facing the nozzle, it is possible to form nozzles at high density and mount the vibrator while maintaining the width necessary to ensure mechanical properties.

A third embodiment is shown in FIG. The figure shows the operating state of the vibrator. In the vibrator of this embodiment, a base N61 in which piezoelectric element chips 62 are joined at two points is supported at both ends, and a nozzle is arranged opposite the maximum amplitude point. In this structure, one end of the vibrator is positioned by the stopper 63, so that a gap with the nozzle can be secured with higher precision than in the previous embodiment.

In the above embodiment, the piezoelectric element chip is joined to the base layer at two points by welding, but the piezoelectric element chip can also be joined using rivet-like pins.

〔Effect of the invention〕

As described above, according to the above structure of the present invention, unlike the conventional structure, a bimorph type piezoelectric transducer is not used, so that bending due to the process of bonding different layers across the entire surface is less likely to occur. Furthermore, since the piezoelectric element chip is joined to the base layer at two points, even a piezoelectric element chip that has been deformed in advance can be fixed without causing any bending in the base layer. Therefore, since the base layer does not warp, the gap between the nozzle plate and the nozzle plate can be maintained with high accuracy, and an inkjet head with stable characteristics and high manufacturing yield can be realized. Furthermore, in the conventional structure, the piezoelectric element is fragile, so there are restrictions on processing methods, and it was impossible to manufacture the vibrator in any shape other than a relatively simple shape.However, in the structure of the present invention, since the base layer is a metal plate, press processing, Since even complicated shapes can be formed by etching, etc., the vibrator can be made into an optimal shape from the viewpoint of ensuring ink ejection characteristics, high-density packaging, etc., and has the effect of realizing a high-performance inkjet head. Furthermore, since the piezoelectric element is small in size, there are fewer restrictions on processing methods, so it has the advantage that it can be manufactured at a low cost.

[Brief explanation of the drawing]

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 of an inkjet head showing one embodiment of the present invention. FIG. 4 is a perspective view of a piezoelectric transducer of an inkjet head showing another embodiment of the present invention. FIG. 5 is a diagram showing the operating state of the piezoelectric transducer of the present invention. FIG. 6 is a diagram showing the operating state of a piezoelectric transducer according to another embodiment of the present invention. 16 Inkjet head 23 Nozzle plate 27 Nozzle 40 Piezoelectric element 42.52.62 Piezoelectric element chip 22 Vibrator 4353.61 Base layer 4445.54.55 Above the joint 10, 16, 'ink 5; 71-head Figure 1: 40 pages: 41: piezoelectric collection: 42: piezoelectric collection: 43:

Claims (1)

Scope of Claims: A nozzle forming member having at least one or more nozzle openings, and a piezoelectric transducer arranged opposite to the nozzle opening and capable of being driven independently, the nozzle forming member and the piezoelectric transducer In the inkjet head, the piezoelectric transducer is composed of a beam-like vibrator, and the vibrator is constructed by laminating a control layer capable of controlling contraction on a base layer and bonding the two at a plurality of points. An inkjet head characterized by: