JPH01294044A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain an ink jet head having high energy efficiency, by constituting the title head so that the ink present in the gap between a nozzle forming member and a cantilevered beam like vibrator is not brought into contact with the vicinal part of the fixed end of the cantilevered beam like vibrator. CONSTITUTION:The ink present in the gap between a nozzle plate 22 and a cantilevered beam like vibrator 52 is prevented from the contact with the vicinal part of the fixed end of the vibrator 52. As a result, the resistance and inertia added in the same minute gap (a) when the vibrator 52 is displaced in the ink corresponding to an electric signal become small as compared with such a case that the gap between the vibrator 52 and the nozzle plate 22 is entirely filled with ink. Therefore, the vibrator 52 can reach the final displacement while performs damping vibration having a long time constant and the max. value of ink emitting pressure is largely taken and the time reaching the max. emitting pressure can be shortened. Therefore, an ink jet head excellent in energy efficiency can be realized.

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 particularly relates to an inkjet printer head. .

[Conventional technology]

The structure of the conventional inkjet head was developed in 1986.
A structure such as No. 953, which has a nozzle plate with multiple nozzle openings and a piezoelectric transducer in direct contact with the ink behind the nozzle plate, is known, and has a high ink droplet ejection efficiency and stability, and eliminates air bubbles, dust, etc. in the ink. It has the characteristic that even if foreign matter gets mixed in, normal operation is possible without being affected by this. 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.

[Problem to be solved by the invention]

In the structure of the conventional inkjet head described above, there is a small gap between the nozzle plate and the movable part of the vibrator facing it, which adds large resistance and inertia when the vibrator is displaced in ink in response to an electrical signal. The final displacement is reached in an over-damped or nearly over-damped state. Therefore, compared to the case where the final displacement is reached while performing damped oscillation with a long time constant, the maximum value of the ink ejection pressure is smaller, and the time required to reach the maximum ejection pressure is longer, resulting in lower energy efficiency. had.

An object of the present invention is to solve these problems and provide an inkjet head with high energy efficiency.

[Means to solve the problem]

An inkjet head according to the present invention includes a nozzle forming member having at least one or more nozzle openings, and at least one cantilever-like vibrator facing the nozzle forming member and having one end as a free end and the other end as a supported end. and a piezoelectric transducer consisting of a piezoelectric transducer, and the ink existing in the gap between the nozzle forming member and the cantilevered vibrator does not come into contact with a portion near the fixed end of the cantilevered vibrator. shall be.

[Effect]

In the above configuration of the present invention, when the vibrator is deformed and displaced to eject ink, the resistance and inertia of the ink near the fixed end of the cantilever vibrator are not added. The resistance and inertia of the ink between the oscillators become smaller, and the damping time constant of the vibrator becomes longer.

〔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, a recording paper 10 is wound around a platen 11 and is pressed by feed rollers 12 and 13. The inkjet head 16 is mounted on a carriage 15 that is guided by guide shafts 14 and 17 and movable in a direction parallel to the platen axis. The inkjet head 16 has at least one or more nozzles that can independently control the ejection of ink droplets, and is scanned in the shift platen axis direction to eject ink droplets from the nozzles to form an ink image on the recording paper 10.

The recording paper 10 is conveyed in the sub-scanning direction perpendicular to the scanning direction by rotation of the platen 11 and feed rollers 12 and 13, and printing is performed on the recording paper surface.

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

A piezoelectric transducer 2 is installed between the frame 20 and the subframe 21.
4 are laminated with an elastic sheet 25 interposed therebetween and fixed using fixing screws 28. The nozzle plate 22, which is a nozzle forming member, is made of a thin metal plate having a plurality of nozzles 23.
The nozzle plate is fixed between the frame 20 and the subframe 21 using fixing screws 29 such that the upper end portion of the nozzle plate facing the nozzle plate 2 is between the free end and fixed end of the vibrator 52.

FIG. 3 shows a perspective view of the piezoelectric transducer 24. Piezoelectric transducer 2
4 is a plurality of vibrators 52 separated by notches 56;
and a fixed portion 58.

The piezoelectric element 30 made of PZT has a common electrode 53 made of a single layer of Au on one side, a spacer 51 made of a thin layer of Ni on the fixed portion 58, and a signal electrode 54 made of a thin layer of Nl on the other side.

Again in FIG. 2, the vibrators 52 are arranged so as to face their corresponding nozzles 23 with a small gap a in the vicinity of their free ends. Wirings 27 are individually connected to the signal electrodes 54, and selective voltage application is performed.

Next, the operation will be explained using FIG. 2. First, ink is supplied from the ink reservoir 26 through the ink supply path 31 to the vicinity of the nozzle, and is filled up to the upper end of the nozzle plate 22 by capillary force. The polarization direction of the piezoelectric element 30 is arranged so that when a voltage is applied between the common electrode 53 and the signal electrode 54, the piezoelectric element 30 contracts in a direction perpendicular to the electric field. - force signal ii [5
Since the Ni thin layer No. 4 has a high elastic modulus, dimensional changes are restricted, and a bending moment is generated as if the Ni thin layer is bent toward the common electrode 53 side. As a result, the free end of the vibrator 52 is deformed and displaced in the direction of the nozzle plate, causing nearby ink to be ejected from the nozzle 23.

It goes without saying that a heater should be installed in this case.

If the structure is such that ink is not filled near the fixed end of the cantilevered vibrator, the resistance and inertia added near the fixed end of the vibrator when the cantilevered vibrator is displaced in the ink will be reduced. Therefore, the resistance and inertia added in the same minute gap a become smaller than when the space between the cantilever vibrator and the nozzle plate is completely filled with ink.

Further, in this embodiment, the cantilever-like vibrator 52 is connected to the spacer 51.
Since the spacers 51 are laminated with each other interposed therebetween, the gap a near the nozzle is determined by the thickness of the spacer 51. As a result, if the thickness of the spacer 51 is set so that the gap a near the nozzle has an optimum value, good ink ejection characteristics can be obtained.

In this embodiment, a thin metal plate integrally formed with the piezoelectric element is used as the spacer, but it is also possible to use a separate thin metal plate as a spacer and to sandwich and fix it between the nozzle plate and the piezoelectric element. .

FIG. 4 is a sectional view of an inkjet head in another embodiment. The nozzle plate 22 is hollowed out only in a portion facing the vicinity of the fixed end of the cantilever vibrator 52.
2, the piezoelectric transducer 24, and the elastic sheet 25 are fixed between the frame 20 and the subframe 21 using fixing screws 28 and 29.

This makes it possible to arrange the nozzle plate to accurately set the gap a between the nozzle 23 and the cantilever vibrator 52.

〔Effect of the invention〕

As described above, according to the above configuration of the present invention, when the vibrator is displaced in ink in response to an electric signal, compared to the case where the space between the cantilever vibrator and the nozzle plate is completely filled with ink, The resistance and inertia added in the same minute gap a become smaller, and the vibrator is able to reach its final displacement while performing damped vibration with a long time constant, allowing the maximum value of the ink ejection pressure to be large and the maximum ejection pressure to be achieved. Since the time required to reach 1 is also shortened, it is possible to realize an inkjet head using a cantilever vibrator with excellent energy efficiency. Furthermore, since the gap between the vibrator and the vibrator facing the nozzle can be arbitrarily set in order to optimize the characteristics, an inkjet head with excellent ink ejection characteristics can be realized.

Another important effect of the present invention is that when the cantilever-like vibrator is displaced in ink, the resistance and inertia added near the fixed end of the vibrator are eliminated, so that when the minute gap a changes, As a result, the amount of change in resistance and inertia added in the microgap a of the vibrator is reduced, and fluctuations in the ink ejection characteristics due to changes in the microgap a are suppressed to a small level.
This also has the effect that the margin of the minute gap a can be increased, making it easier to assemble the head.

[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 sectional view of an inkjet head in another embodiment of the present invention. 16 Inkjet head 22 Nozzle plate 23 Nozzle 24 Piezoelectric transducer 30 Piezoelectric element 51 Spacer 52 Vibrator 53 Common electrode 54 Signal electrode and above Applicant Seiko Epson Co., Ltd. agent Patent attorney Kizobe Suzuki and one other person 16: Isoczinit Herad 22 :Nostal ratio Figure 3 Figure 4

Claims (1)

[Claims] A piezoelectric transducer comprising a nozzle forming member having at least one nozzle opening, and at least one cantilever vibrator facing the nozzle forming member and having one end as a free end and the other end as a supported end. An inkjet head comprising: an inkjet head comprising: ink existing in a gap between the nozzle forming member and the cantilever vibrator does not come into contact with a portion near a fixed end of the cantilever vibrator.