JPH04126256A - Ink jet head - Google Patents

Abstract

PURPOSE:To stabilize ink discharge characteristics and prevent the occurrence of satellites by disposing an insulating film so as to be brought into contact with the movable ends of vibrators, mounting flying members and return springs, which are laminated to one another, at the movable ends of the vibrators via the insulating film, and filling a space between a nozzle forming member and the insulating film with ink. CONSTITUTION:Flying members 12 composed of ferritic grains are usually pressed to the upper ends of vibrators 13 by a spring force of return springs 11 via an insulating film 23, and ink 21 ascends through a gap between a base 19 and a base 22 due to a capillary force and is filled up to nozzle openings 16. When a drive voltage is applied to the vibrators 13, they are retracted in an arrow direction 25 and, when the application of the drive voltage is stopped, the vibrators 13 are restored in an arrow direction 26, and their movable ends 28 impinge against the flying members 12 via the insulating film 23. This results in the flying members 12 and return springs 11 being displaced to approach or impinge against a nozzle forming member 17, and ink droplets 27 are discharged toward a recording medium 1. Accordingly, the amount of ink flowing into the nozzle openings 16 can be controlled and the occurrence of satellites can also be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet head used in printers and the like that ejects ink droplets to form an ink image on a recording medium such as recording paper.

[Conventional technology]

The structure of a conventional inkjet head disclosed in Japanese Patent Publication No. 60-8953, etc. includes a nozzle forming member 101 having a plurality of nozzle openings 100 arranged in the thickness direction of the paper, as shown in FIG. It is equipped with a vibrating body 102 which is placed behind and comes into direct contact with the ink.
A piezoelectric material is used as the vibrating body. In such an inkjet head, the vibrating body 102 vibrates as if displaced in the normal direction of the nozzle forming member 101. Since the ink flow paths between each nozzle opening 100 communicate over a short distance, the ink droplet ejection efficiency and stability are high, and even if foreign substances such as air bubbles and dust get mixed into the ink, they will not be affected by them. It has the characteristic of being able to maintain normal operation.

[Problem to be solved by the invention]

However, in the conventional inkjet head, only a small displacement occurs due to the characteristics of the vibrating body 102, and ink is ejected using this displacement, so that the energy applied to the ink droplet 103 is small. Therefore, in order to obtain predetermined ejection characteristics, it is necessary to precisely set the distance from the nozzle forming member 101 to the vibrating body 102, resulting in problems of low productivity and unstable ink ejection characteristics.

Furthermore, when the ink droplet 103 is ejected, the ink droplet 103
Because the tail of the ink droplet 103 is not spherical and is long,
The problem is that there are many secondary satellites 104.

Furthermore, when conductive ink is ejected, the vibrating body 10
2 is in direct contact with the ink 105, the vibrating body 102
There was a problem in that conductive ink could not be used because leakage occurred between the electrodes and the vibrating body 102 was destroyed as a result.

The purpose of the present invention is to solve the above-mentioned problems with conventional inkjet heads, improve energy efficiency and productivity, stabilize ink ejection characteristics, and suppress the generation of satellites. The purpose is to enable conductive ink to be ejected as well.

[Means to solve the problem]

In order to achieve the above object, an inkjet head of the present invention includes a nozzle forming member having one or more nozzle openings arranged to face a recording medium, and a vibrating body, the vibrating body being movable. An insulating film is arranged so as to touch the end, and the flying object and return spring are stacked and mounted on the movable end of the vibrating body via the insulating film, so that the gap between the nozzle forming member and the insulating film is filled with ink. It is composed.

<Example> The details of the present invention will be explained below based on examples.

FIG. 1 is a perspective view of a printer using an inkjet head according to the present invention. In the figure, numeral 1 denotes a recording medium which is wound around the platen 4 and pressed by a feed roller 2.3. An inkjet head 9 is mounted on a carriage 8 that is guided by a guide shaft 6.7 and movable in a direction 10 parallel to the platen axis. The inkjet head 9 has a plurality of nozzle openings that can be independently controlled to eject ink droplets by applying an external driving voltage, as will be described later. The inkjet head 9 is scanned in the platen axis direction 10, selectively ejects ink droplets from nozzle openings, and forms an ink image on the recording medium 1.
The recording medium 1 is conveyed in a sub-scanning direction 5 perpendicular to the scanning direction by rotation of the platen 4 and feed rollers 2.3, and printing is performed on the recording medium 1.

FIG. 2 is a sectional view showing a first embodiment of the inkjet head according to the present invention, and FIG. 3 is a perspective view of the main parts.

The vibrating body 13, the second base 19, and the third base 22 are laminated and fixed to the first base 14, and an insulator f123 is connected to the top of the end face of the vibrating body 13 on the side facing the nozzle forming member 16. It is joined to the first base 14 and the second base 19. The flying object 12 is mounted on the upper end surface of the vibrating body 13 via the insulating film 23, and the spacer 18 and the return spring 11 are mounted on the end surfaces of the first base 14 and the third base 22.
and the nozzle forming member 17 are stacked and fixed to form the cavity portion 24.゛Cavity part 24 and frame 20
and are fixed to form an inkjet head. The nozzle forming member 17 has a plurality of nozzle entrances 16, and the vibrating bodies 13 are arranged independently so as to face each nozzle opening 16.

These relationships are shown in FIG.

The flying object 12 is normally pressed against the upper end surface of the vibrating body 13 via the insulating film 23 by the spring force of the return spring 11. The ink 21 is supplied from outside the frame 20 and rises through the gap between the second base 19 and the third base 22 due to capillary force to fill the nozzle opening 16.

In this embodiment, a piezoelectric material is used as the material of the vibrating body 13, specifically, lead zirconate titanate (PbTiO3-PZr0
3 system solid solution), ferrite particles were used as the material for the flying object 12, and a polyimide film was used as the material for the insulating film 23.

A driving voltage is applied to the vibrating body 13 through an electrode pattern formed on the flexible substrate 15 and the first base 14.

Next, the ink droplet ejection operation will be explained based on the process diagrams of ink droplet ejection shown in FIGS. 4(a) to 4(f).

(a) shows an initial state in which no operation is performed.

(b) shows that the driving voltage is applied to the vibrating body 13, and the vibrating body 13
shows a state in which it is contracted in the direction of arrow 25.

(C) shows that by returning the drive voltage to the state before application, the contraction of the vibrating body 13 is released and the vibrating body 13 is restored in the direction of the arrow 26, and in the process of the vibrating body 13 returning to its initial state, the movable end 28 of the vibrating body 13 is covered with an insulating film. 23 shows a collision with the aircraft 12.

(d) shows a state in which the flying object 12 and the return spring 11 are displaced in the ink due to the collision with the movable end 28 of the vibrating body 13, and the head of the ink droplet 27 comes out from the nozzle opening 16.

In (e), the flying object 12 and the return spring 11 are further displaced than in (d), approaching or colliding with the nozzle forming member 17, and the ink 21 is prevented from flowing out from the nozzle entrance 16, and the foot of the ink droplet 25 is moved toward the nozzle. A state in which ink droplets 27 are ejected toward the recording medium 1 away from the opening 16 is shown.

(f) shows a process in which the flying object 12 is displaced in the direction of arrow 25 by the spring force of the return spring 11 to return to the initial state (a).

As described above, a driving voltage is selectively applied to the vibrating body 13 to cause it to vibrate, and the operating steps (a) to (f) are repeated, and the ink droplets 27 are selectively ejected from the nozzle openings 16.

In the configuration of the inkjet head according to the present invention,
As explained in the above-mentioned ink droplet ejection operation, the vibrating body 13
The displacement of the movable end 28 of is amplified by the collision with the flying object 12, and the insulation l! Vibrating body 13 is electrically insulated from ink 21 by 23 .

Although the movable end 28 of the vibrating body 13 only undergoes slight displacement due to its characteristics, as shown in FIG. 4(C), the movable end 28 of the vibrating body 13
When the flying object 12 collides with the flying object 12, the flying object 12 and the return spring are displaced several tens of times as much as the displacement of the movable end 28 of the vibrating body 13. This amplified flying object 12 and return spring 11
In order to eject the ink droplets 25 by displacement with the nozzle forming member 17 to obtain the necessary ejection characteristics,
The range of allowable values for the distance 111L (see Figure 3) up to 3 is wide. Therefore, the control limit value during manufacturing can be set large. Moreover, as shown in FIG. 4(e), the flying object 1
2 and return spring 11 approach or collide with the nozzle forming member 17, the amount of ink flowing into the nozzle opening 16 can be controlled, and the generation of satellites, which is inevitable in conventional inkjet heads, can be suppressed.

Further, since the vibrating body 13 is not in direct contact with the ink 21 and is electrically isolated by the insulating film 23, not only insulating ink but also conductive ink can be ejected. Therefore, the inkjet head according to the present invention has an extremely high degree of freedom in design without being restricted by the type of ink.

The constituent materials of this example are not limited to the above,
The vibrating body 13 is made of barium titanate (BatiO: +
) Other piezoelectric materials can also be used, such as barium niobate (LiNbo3), lithium tantalate (LiNbo3), etc. Further, as the insulating film, any material having good ink resistance and electrical insulation, such as Teflon or polyester, may be used.

<Effects of the Invention> According to the present invention, the collision between the vibrating body and the flying body or the extrusion of the vibrating body causes the flying body and the return spring to be displaced by a minute displacement of the vibrating body, and the amplified flying body and return spring are displaced. Since ink droplets are ejected by the displacement of the spring, an inkjet head with high energy efficiency can be provided. Furthermore, since energy efficiency is good, the radius of the vibrating body and return spring and the flying body can be reduced, so that a high-density and compact inkjet head can be obtained. In addition, since ink droplets are ejected by the amplified displacement between the flying object and the return spring, it is possible to increase the control limit for the distance from the nozzle forming member to the vibrating body, which had to be precisely manufactured in conventional structures. . Therefore, a head with high yield and good productivity can be obtained, and good ink droplet ejection characteristics can be obtained. Furthermore, since the displaced flying object and the return spring approach or collide with the nozzle forming member, the amount of ink flowing into the nozzle opening can be controlled and high-quality printing characteristics without satellites can be obtained. Furthermore, since the vibrating body is electrically insulated from the ink by the insulating film, it has the feature that not only insulating ink but also conductive ink can be ejected.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a printer using an inkjet head according to the present invention. FIG. 2 is a sectional view showing an embodiment of an inkjet head according to the present invention. FIG. 3 is a sectional perspective view of a main part of an embodiment of the present invention. FIG. 4 is a process diagram of ink droplet ejection, and FIG. 5 is a diagram showing the structure of a conventional inkjet head.・Recording medium・Platen・Inkjet head・Return spring・Aircraft・Vibrating body・Nozzle opening・Nozzle forming member・Insulating film・Ink droplet/movable end of vibrator Figure 1 (b) (e) (C)! IE4 diagram (f) 101- To the twist shape part ↑J Figure 15

Claims (1)

[Claims] A nozzle forming member having one or more nozzle openings arranged to face a recording medium, and a vibrating body, an insulating film being arranged so as to be in contact with a movable end of the vibrating body,
An inkjet head characterized in that a flying body and a return spring are laminated and mounted on a movable end of a vibrating body via an insulating film, and a space between a nozzle forming member and the insulating film is filled with ink.