JPH024516A - Ink jet head - Google Patents

Abstract

PURPOSE:To enhance the accuracy of the size of a gap between a cantileverlike vibrator and a nozzle by reducing a pressing distance of a nozzle forming mem ber shorter than a static displacing distance at the time of application of a voltage to the free end of a piezoelectric converter to decrease the irregularity in the warpage of the free end of the vibrator. CONSTITUTION:The free end of a vibrator 52 is disposed at a position (c) in a state that a nozzle plate 22 is removed to be free at the time of application of no voltage, displaced to a position (a) at the time of application of a voltage, and its static displacement distance is (d). On the other hand, when the plate 22 is attached, the free end of the vibrator 52 is corrected, and it is displaced at a displacing distance (e). The irregularity of the warpage of the vibrator 52 is corrected by pressing the plate 22 into contact therewith to meet the high accuracy of the free end of the vibration. Accordingly, the sizes of the gaps between the vibrator 52 and nozzles 23 are accurately uniform. Therefore, the irregularity in the nozzles is substantially eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording device that flies ink droplets to form an ink image on a medium such as recording paper.
More specifically, it relates to an inkjet printer head.

[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. has. As the piezoelectric transducer, a cantilever-shaped vibrator or a double-sided beam-shaped vibrator is used. This inner cantilever vibrator has advantages such as low bending rigidity, high electromechanical conversion efficiency, and the ability to obtain the necessary displacement of the movable part of the vibrator with small stress. Further, the gap between the vibrator and the nozzle plate is configured to maintain a small gap because it affects the ink droplet ejection characteristics.

[Problem to be solved by the invention]

In the structure of the inkjet head using the conventional cantilever vibrator described above, the size of the gap between the vibrator and the nozzle has a great influence on the inkjet characteristics. It is necessary to control the gap dimensions in microns. However, as a practical matter, it is difficult to achieve such highly accurate dimensions at a practical level due to the limit of suppressing variations in warpage at the free end of a cantilevered vibrator, so some variation in characteristics is acceptable. However, this was dealt with by lowering the specifications of the head accordingly.

An object of the present invention is to solve these problems and realize an inkjet head with excellent performance in which various characteristics such as ink droplet ejection speed, ejection mode, and ejection amount are uniform among each nozzle.

[Means to solve the problem]

The inkjet head of the present invention includes a nozzle forming member having at least one or more nozzle openings, and is arranged to face the nozzle openings in a one-to-one manner, and can be driven independently with one end being a free end and the other end being a fixed end. In an inkjet head having a piezoelectric transducer, the space between the nozzle forming member and the piezoelectric transducer is filled with ink, the position of the free end of the piezoelectric transducer when a voltage is applied and when no voltage is applied. Each of the positions corresponds to the pressure on the nozzle forming member.
It is determined by the can liquid state and the non-contact state, and is characterized in that the amount of pressure is smaller than the amount of static displacement when voltage is applied at the free end of the piezoelectric transducer.

[Effect]

According to the above configuration of the present invention, variations in the warpage of the free end of the cantilever vibrator are corrected by pressing with the nozzle forming member, so the dimension of the gap between the vibrator and the nozzle is ensured with high precision. be done.

〔Example〕

Next, the present invention will be explained based on examples.

FIG. 1 is a perspective view for explaining an embodiment of a recording apparatus equipped with an inkjet head according to the present invention. The recording medium 1 is wound around the platen 4 by the pressure of the feed roller 2.3, and is conveyed in the direction of the arrow 5 as recording progresses. An inkjet head 9 having a plurality of nozzles that can independently control the ejection of ink droplets is mounted on a carriage 8 that is guided by a guide shaft 6°7 and movable in a direction parallel to the axis of the platen 4. The recording medium 1 is scanned in 10 directions, and ink droplets are selectively ejected from each nozzle to form an ink image on the recording medium 1.

FIGS. 2(a) and 2(b) are cross-sectional views of an inkjet head according to the present invention and diagrams for explaining how the warpage of the vibrator is corrected. Frame 20 and subframe 2
1, a nozzle plate 22 composed of a thin metal plate having a plurality of nozzles 23, a piezoelectric transducer 24, and an elastic sheet 25.
are stacked and fixed using fixing screws 28 and 29. An ink reservoir 26 is formed in the subframe 21, and ink (not shown) is supplied to the vicinity of the nozzle to fill it.

A drive signal is supplied to the piezoelectric transducer 24 through wiring 27 .

FIG. 3 is a perspective view for explaining the configuration of the piezoelectric transducer 24. FIG. Piezoelectric transducer 24 is comprised of a plurality of vibrators 52 and a fixed portion 58 separated by notches 56 . On one side of the piezoelectric element 30 made of PZT, A u 7
It has a signal electrode 54 made of 0.07 layer, and a common electrode 53 made of a thin Ni layer and a spacer 51 on the other side.

The principle of ejecting ink droplets will be explained using FIG. 2 again.

The free end of the vibrator 52 is placed facing the nozzle 23 while being pressed against and in contact with the nozzle plate 22 . Common electrode 53 and signal electrode 5 of piezoelectric transducer 24 in which vibrator 52 is formed
4, when a voltage is applied, the piezoelectric element 3
0 is contracted.

On the other hand, since the Ni thin layer of the common electrode 53 has a high elastic modulus, dimensional changes are restricted, and as a result, a bending moment is generated and the vibrator 52 is deformed so as to bend toward the signal electrode 54 side. Therefore, by applying a voltage during standby and selectively releasing the voltage, the free end of the vibrator 52 is deformed and displaced in the direction of the nozzle plate 22, causing nearby ink to be ejected from the nozzle 23.

Next, the manner in which warpage of the vibrator is corrected will be explained using FIG. 2(b). The free end of the vibrator 52 is at a position C in a free state with the nozzle plate 22 removed when no voltage is applied, and when a voltage is applied, it is displaced to a degree position a, and its static displacement amount is d. On the other hand, when the nozzle plate 22 is attached, the free end of the vibrator 52 is corrected to the position b, and the amount of displacement is e.
It is. Furthermore, even if the vibrator 52 is corrected in advance by the nozzle plate, the amount of displacement of the vibrator 52 when a voltage is applied is determined based on the position C of the signal electrode 52 when the free end of the vibrator is free when no voltage is applied. Since it has been confirmed that the free end of the vibrator 52 is displaced toward the nozzle plate 22, the free end of the vibrator 52 presses and comes into contact with the nozzle plate 22, based on the static displacement id when the voltage is applied when the free end of the vibrator 52 is free. The value obtained by subtracting the displacement e that has been deformed in advance is the actual displacement f of the vibrator 52.
become.

This means that the maximum amount of pressure applied to the nozzle plate by the free end of the vibrator, that is, the maximum value for correcting the variation in warpage at the free end of the vibrator, is the static displacement d when voltage is applied to the vibrator. This indicates that unless it is below, the vibrator displacement required for ink ejection cannot be obtained.

In the above structure, variations in the warpage of the vibrator 52 are corrected by pressing and contacting the nozzle plate 22, and the free ends of the vibrator are aligned with high precision, so that the gap between the vibrator 52 and the nozzle 23 is The dimensions can also be aligned with high precision, making it possible to realize an inkjet head with almost no variation in characteristics between each nozzle.

Note that in the above embodiment, the free end of the vibrator is pressed and in contact with the nozzle plate when no voltage is applied. There is no restriction on the relationship between the contact and non-contact states, and in the present invention, a configuration in which the free end of the vibrator is pressed and in contact with the nozzle plate when voltage is applied is also possible. is obvious from the gist of the invention.

〔Effect of the invention〕

As described above, according to the above configuration of the present invention, variations in the free end of the vibrator are corrected by suppressing and abutting the free end of the vibrator with the nozzle plate, so that variations in warpage of the vibrator are The gap between the vibrator and the nozzle is ensured with high precision, and by utilizing the initial stress of the vibrator that is generated when the vibrator is pressed against and in contact with the nozzle plate, the ejection speed of ink droplets can be increased. It is possible to provide an inkjet head with excellent performance in which all the nozzles have uniform characteristics such as appearance and ejection amount.

Infusiella nozzle plate Piezoelectric element common electrode head nozzle vibrator signal electrode that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Kizobe Suzuki and 1 other person

[Brief explanation of the drawing]

FIG. 1 is a perspective view for explaining an embodiment of a recording apparatus equipped with an inkjet head according to the present invention. FIGS. 2(a) and 2(b) are cross-sectional views of the inkjet head according to the present invention, and diagrams for explaining how the warpage of the vibrator is corrected. FIG. 3 is a perspective view of a piezoelectric transducer of an inkjet head according to the present invention. 1 Recording medium Figure 1 22! Nomata 11-Saka Diagram 2

Claims (1)

[Scope of Claims] A nozzle forming member having at least one or more nozzle openings, arranged to face the nozzle openings one-to-one, and capable of being driven independently with one end being a free end and the other end being a fixed end. In an inkjet head having a piezoelectric transducer, in which ink is filled between the nozzle forming member and the piezoelectric transducer, the position of the free end of the piezoelectric transducer when a voltage is applied and the position when no voltage is applied. each of which presses and presses the nozzle forming member.
An inkjet head characterized in that the pressing amount is determined by a contact state and a non-contact state, and is smaller than a static displacement amount when a voltage is applied to the free end of the piezoelectric transducer.