JPH02277644A - Ink jet head - Google Patents

Abstract

PURPOSE:To improve the response property of frequency and, to obtain sufficient discharge speed and sufficient discharge amount of ink by a method wherein a width in a direction parallel to a nozzle forming substrate of a pressure generating component is so constructed not to be uniform. CONSTITUTION:When applicable voltage 16 is impressed to a pressure generating component 13, the pressure generating component is displaced to the arrow 22 side, and an ink drop 20 is discharged from a nozzle 14. When a shape of a section A-A of the pressure generating component 13 is taken as a T character form likely to have a thick root part and a thin top part, since inertia moment around the root of the pressure generating component 13 is decreased and resilience as a beam is improved, natural oscillating frequency of the pressure generating component 13 is shortened. Therefore, ink discharge interval time can be decreased, and response property in frequency is increased. Since the pressure generating component 13 is deformed by equal moment, when a maximum value of applicable voltage 16 is constant, displacement at a top of the pressure generating component 13 is constant irrespective of a shape of the pressure generating component 13 at the section A-A, and the discharge speed and discharge amount of the ink are hardly varied.

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. 60-8953 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, with the above-mentioned conventional technology, it has been found that the natural vibration period and maximum vibration displacement of the pressure generating member affect various characteristics such as the frequency response, ejection speed, and ejection amount of the ink droplet, but the width is uniform. It is extremely difficult to satisfy all the characteristics of a pressure generating member with a beam structure by making the pressure generating member a specific size, 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. As a result, the maximum vibration displacement of the pressure generating member becomes smaller, and the ink ejection speed and
This has the problem of reducing the discharge amount and making 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 to solve the problem]

The inkjet head of the present invention includes a nozzle forming substrate having a plurality of nozzles, and a pressure generating member disposed one-to-one opposed to each of the nozzles and immersed in ink. Displacing the pressure generating member,
In the inkjet head that increases the pressure of ink existing in a gap with the nozzle forming substrate and ejects it from the nozzle, the width of the pressure generating member in a direction parallel to the nozzle forming substrate is not uniform.

[Effect]

According to the effect of the present invention, since the width of the pressure generating member in the direction parallel to the nozzle forming substrate is not uniform, the elasticity of the pressure generating member can be increased and the moment of inertia can be reduced. 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 shaft 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 plurality of pressure generating members 13 are attached to the nozzle plate 15 via spacers 17 so that the respective tips of the plurality of pressure generating members 13 are arranged at positions corresponding to the plurality of nozzles 14 arranged in a row on the nozzle plate 15 while maintaining gaps. . The nozzle exit diameter R is configured to be 100 μm or less, and the gap is configured to be 50 μm or less. The pressure generating member 13 is made of a laminated material of a piezoelectric element 12 and a metal plate 11, and its length is 5.
mm or less. Nozzle plate 15 and casing 18
The space surrounded by is filled with ink 19. When the applied voltage 16 is applied to the pressure generating member 13, the pressure generating member 13 is displaced in the direction of the arrow 22, and an ink droplet 20 is ejected from the nozzle 14. By continuously applying the applied voltage 16, the pressure generating member 13' becomes a beam. The ink droplet 20 continues to be ejected from the nozzle 14 with horizontal vibration. Pressure generating member 13
If the shape of the cross section A-A is made into a T-shape so that the base part is thick and the tip part is thin (Fig. 3), the pressure generating member 1
Since the moment of inertia around the base of the pressure generating member 3 is reduced and the elasticity of the beam is improved, the natural vibration period of the pressure generating member 13 is shortened. Therefore, the ink ejection interval time can be shortened and the frequency response can be improved. Since the pressure generating member 13 deforms with equal moments, if the maximum value of the applied voltage 16 is constant, the displacement of the tip of the pressure generating member 13 is constant regardless of the shape of the pressure generating member 13 in the cross section A-A. The ink ejection speed and ejection amount hardly change.

FIG. 4 is another example of the cross section AA of the pressure generating member 13 showing the embodiment of the present invention. In this embodiment, the pressure generating member 13
Since the cross-sectional shape is trapezoidal, the elasticity of the pressure generating member 13 as a beam is ensured at the wide part at the base, and the moment of inertia is reduced by the tapered tip. Therefore, the natural vibration period of the beam vibration of the pressure generating member 13 can be shortened, the ink ejection amount time is shortened, and the frequency response is improved. Further, the cross-sectional shape of the pressure generating member 13 is trapezoidal, and the end portions are not discontinuous like the figure 7 shape, but are formed by straight lines, which is advantageous when manufacturing the pressure generating member 13 by dicing or the like.

〔Effect of the invention〕

As described above, since the inkjet head of the present invention is configured such that the width of the pressure generating member is narrower at the tip, the moment of inertia of the pressure generating member is smaller than that of a pressure generating member having a uniform width. Decrease. On the other hand, by making the root portion of the pressure generating member thicker, the elasticity of the beam member can be increased, so that the natural vibration period becomes shorter. Further, since the pressure generating member deforms with equal moments due to the applied voltage, the width of the pressure generating member has no relation to 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 in which the characteristics such as the ejection speed, ejection amount, and frequency response of ink droplets are improved at the same time. By installing an inkjet head with such excellent performance, it becomes possible to realize a high-performance recording device.

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 example, 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 is a sectional view of an inkjet head according to the present invention. 3 and 4 are cross-sectional views taken along the cross-section A-A shown in FIG. 2. 1 Recording medium 9 Inkjet head 11 Metal plate 12 Piezoelectric element 13 Pressure generating member 14 Nozzle 15 Nozzle forming plate 16 Applied voltage 17 Spacer 18
Casing 19 Ink 20 Ink drops Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki and one other person Figure 1 13, ゛Pressure to life relief Figure 3 73゛Pressure arm support 1 lower 47

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 width of the pressure generating member in a direction parallel to the nozzle forming substrate is not uniform. head.