JPH02273242A - Ink jet head - Google Patents

Abstract

PURPOSE:To enhance frequency response without loss of ink discharging speed and amount hy composing the thickness of a piezoelectric element for composing a pressure generating member to be thinner toward the end. CONSTITUTION:A pressure generator 13 is composed of a laminated material of a piezoelectric element 12 and a metal plate 11, and ink 19 is filled in a space surrounded by a nozzle plate 15 and a casing 18. When a voltage 16 is applied to the member 13, the member 13 is displaced to the side of an arrow 22, and an ink droplet 20 is discharged from a nozzle 14. When the voltage 16 is continuously applied, the member 13 is laterally vibrated at a beam to continuously discharge the droplet 20 from the nozzle 14. In this case, since the element 12 of the end 21 of the beamlike member 13 is deleted to reduce its inertial moment, the intrinsic vibration period of the member 13 is shortened to shorten an ink discharging interval time, thereby enhancing its frequency response.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus such as a printer that forms an ink image on a medium such as a recording paper by flying ink droplets, and more particularly to an inkjet printer head.

[Conventional technology]

A piezoelectric transducer consisting of a nozzle forming substrate having a plurality of nozzles, a pressure generating member arranged one-to-one facing each nozzle, and a gap between the piezoelectric transducer and the nozzle forming substrate and a gap between the piezoelectric transducer and the nozzle forming substrate. Japanese Patent Publication No. 8953/1983 discloses an on-demand inkjet head that includes ink that fills the periphery of the head and that displaces a piezoelectric transducer using an applied voltage to eject ink from a nozzle. An inkjet head with this structure has high ink ejection efficiency and ejection stability because the piezoelectric transducer is displaced almost perpendicularly to the nozzle forming substrate and the ink flow path of the nozzle meniscus is short. It has the advantage that even if foreign matter such as air bubbles or dust gets mixed in, normal operation is possible without being affected by this. Furthermore, since the pressure generating member has a cantilevered or double-sided beam structure, the electromechanical conversion efficiency is high and the required pressure generating member displacement can be obtained with a low voltage.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, it has been found that the natural vibration period and maximum vibration displacement amount of the pressure generating member affect the characteristics such as the frequency response, ejection speed, and ejection amount of the ink droplet. It is extremely difficult to satisfy all the characteristics by making the dimensions specific, and specifications were determined by trade-offs between each characteristic. In other words, in order to shorten the time between ink ejections and increase frequency response, it is necessary to increase the elasticity of the pressure generating member and shorten the natural vibration period, but this reduces the maximum vibration displacement of the pressure generating member. However, this method has problems in that it reduces the ink ejection speed and ejection amount and makes it difficult to determine the dimensions of the pressure generating member.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide an inkjet head that has excellent frequency response as well as sufficient ink ejection speed and amount.

[Means for Solving the Problems] An inkjet head of the present invention includes a nozzle forming substrate having a plurality of nozzles, and a pressure generating substrate disposed one-to-one facing each of the nozzles and immersed in ink. a member, the pressure generating member is displaced by an applied voltage,
The inkjet head increases the pressure of ink existing in a gap with the nozzle forming substrate and ejects it from the nozzle, characterized in that the thickness of the pressure generating member in a direction perpendicular to the nozzle forming substrate is not uniform.

[Effect]

According to the effects of the present invention, since the thickness of the pressure generating member in the direction perpendicular to the nozzle forming substrate is not uniform, the moment of inertia can be reduced without substantially reducing the elasticity of the pressure generating member. The vibration natural period becomes shorter without reducing the maximum vibration displacement amount.

〔Example〕

The details of the present invention will be explained below using examples with reference to the drawings.

FIG. 1 is a perspective view of a printer equipped with an inkjet head according to the present invention, in which a recording medium 1 is wound around a platen 4 by pressure from feed rollers 2 and 3, and is conveyed in the direction of an arrow 5 as recording progresses. Ru. Guide shafts 6, 7
An inkjet head 9 having a plurality of nozzles is mounted on a carriage 8 that is guided by a carriage 8 and movable in a direction parallel to the axis of the platen 4, and as it moves in the direction of an arrow 10, ink droplets are ejected from each nozzle. The ink is ejected to form an ink image on a recording medium.

FIG. 2 is a sectional view of an inkjet head showing an embodiment of the present invention. The spacer 1 is arranged so that each tip of the plurality of pressure generating members 13 is arranged at a position corresponding to the plurality of nozzles 14 arranged in a row on the nozzle plate 15 with an appropriate gap.
It is attached to the nozzle plate 15 via 7. The pressure generating member 13 is made of a laminated material of a piezoelectric element 12 and a metal plate 11.

A space surrounded by the nozzle plate 15 and the casing 18 is filled with ink 19. Pressure generating member 1
When an applied voltage 16 is applied to 3, the pressure generating member 13 is displaced to the arrow 22 side, and an ink droplet 20 is ejected from the nozzle 14. By continuously applying the applied voltage 16, the pressure generating member 13 causes the beam to vibrate transversely and directs the ink droplet 20 to the nozzle 14.
However, at this time, the beam-shaped pressure generating member 13
Since the piezoelectric element 12 at the tip portion 21 is removed and the moment of inertia is reduced, the natural vibration period of the pressure generating member 13 is shortened, the ink ejection interval time can be shortened, and the frequency response is increased. Since the piezoelectric element 12 that has been removed is only at the tip, when the pressure generating member 13 is deformed with equal moments, the displacement of the tip is hardly affected and the ink ejection speed and ejection amount hardly change.

FIG. 3 is a sectional view of an inkjet head showing an embodiment of the present invention. In FIG. 3, components common to those in FIG. 2 are given the same numbering.

In this embodiment, since the piezoelectric element 12 of the pressure generating member 13 is thicker than the embodiment shown in FIG. 2, the elasticity of the pressure generating member 13 as a beam is increased, making it possible to shorten the natural vibration period. It is possible.

FIG. 4 is a sectional view of an inkjet head showing an embodiment of the present invention. In FIG. 4, components common to those in FIG. 2 are given the same numbering.

In this embodiment, the thickness of the piezoelectric element 12 of the pressure generating member 13 is thick at the root of the pressure generating member 13 and becomes thinner toward the tip, so that the elasticity of the pressure generating member 13 is ensured at the thick portion of the root. , since the tip is thin, the moment of inertia is minimized. Therefore, the natural vibration period of the pressure generating member 13 can be made shorter.

FIG. 5 is a sectional view of an inkjet head showing an embodiment of the present invention. Components in FIG. 5 that are common to those in FIG. 2 are given the same numbering.

In this embodiment, the thickness of the piezoelectric element 12 of the pressure generating member 13 is thick at the root of the pressure generating member 13, thinner toward the tip, and concentrated near the root of the pressure generating member 13, as shown in FIG. The moment of inertia can be further reduced compared to the embodiment described above. Therefore, the natural vibration period of the pressure generating member 13 can be made shorter. This makes it possible to shorten the time between ejecting ink droplets and improve frequency response. Furthermore, since the piezoelectric element 12 is concentrated near the root of the pressure generating member 13, the bending moment is concentrated at the root, and the maximum vibration displacement can be sufficiently achieved. Therefore, both the ink ejection speed and the ejection amount can be ensured.

〔Effect of the invention〕

As described above, the inkjet head of the present invention is configured such that the thickness of the piezoelectric element constituting the pressure generating member is thinner at the tip. Moment of inertia decreases. On the other hand, since the elasticity hardly changes, the natural vibration period can be shortened without impairing the maximum vibration displacement. Therefore, the effect of increasing the frequency response can be obtained without impairing the ink ejection speed and ejection amount. In this way, the present invention can provide an inkjet head that simultaneously improves the characteristics such as the ejection speed, ejection amount, and frequency response of ink droplets. By installing an inkjet head with such excellent performance, it becomes possible to realize a high-performance recording device. Further, according to the present invention, since the piezoelectric element at the tip of the pressure generating member is eliminated, the piezoelectric element constituting the pressure generating member can be eliminated to the minimum necessary, and costs can be reduced.

In this embodiment, a cantilever-shaped pressure generating member is used as the pressure generating member, but a similar configuration is possible with a double-sided beam-shaped pressure generating member. Also, regarding the nozzle, although the shape is horn-shaped in this embodiment, this does not impose any restrictions on the nozzle shape, and it is within the scope of the present invention that the nozzle may have any shape. It is clear from the gist of

[Brief explanation of drawings]

FIG. 1 is a perspective view of a printer equipped with an inkjet head showing one embodiment of the present invention. FIG. 2, FIG. 3, FIG. 4, and FIG. 5 are cross-sectional views of an inkjet head according to the present invention. 1: Recording medium 9: Inkjet head 11: Metal plate 12 Two piezoelectric elements 13: Pressure generating member 14. ' Nozzle 15: Nozzle forming plate 16, Applied voltage 17: Spacer 19, Ink 18, Two casings 20, ' More than ink droplets Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki and one other person Figure 3 Figure 2 4R

Claims (1)

[Claims] A nozzle forming substrate having a plurality of nozzles, and a pressure generating member disposed one-to-one facing each of the nozzles and immersed in ink, the pressure generating member being displaced by an applied voltage, An inkjet head that increases the pressure of ink existing in a gap with the nozzle forming substrate and ejects it from the nozzle, wherein the thickness of the pressure generating member in a direction perpendicular to the nozzle forming substrate is not uniform. .