JPH10235908A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure high quality print by making uniform the size of ink droplet being jetted from the ink jet nozzle in nozzle unit of each color. SOLUTION: An ink supply means 210 comprises ink tanks 213 for respective colors located lower than nozzle units 200 for respective colors while spaced apart therefrom and supplies ink in each ink tank 213 to the ink jet nozzle 207 in the nozzle unit 200 of each color. Level difference between the outlet of the ink jet nozzle 207 and the liquid level of ink in the ink tank 213 of each color is selected depending on the characteristics of ink of each color such that the positional energy on the liquid level of ink at the outlet of the ink jet nozzle 207 will be identical for respective colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to multicolor printing while spraying ink from an ink jet nozzle of a nozzle unit for each color onto a print medium held on the outer peripheral surface of a drum rotatable at a constant peripheral speed and rotating with the drum. The present invention relates to an inkjet printer formed so as to be capable of being used.

[0002]

2. Description of the Related Art A nozzle unit for each color is reciprocated over the entire length in a row direction, and printing is performed during each forward movement to print one line, and after one line printing, a printing medium (plain paper, OHP paper, etc.). Compared to a so-called serial type ink-jet printer which feeds M by one line in the column direction and repeats them, printing speed can be drastically increased and continuous printing operation can be performed over a large number of sheets. The present applicant has proposed an ink jet printer capable of achieving a large size reduction (for example, Japanese Patent Application No. 8-296957).

That is, in FIG. 5, a drum 10 is rotatable at a constant peripheral speed about an axis and can hold a print medium M on an outer peripheral surface 11 thereof. This drum 10
The nozzle unit 200 for each color (C, M, Y, B) is disposed in the rotation (Y) direction of the color filter.

[0004] Therefore, an integrated nozzle unit 200 for each color or an integrated nozzle unit 200 for each color in which a plurality of nozzle unit elements are arranged in the row direction (for example, between the ink jet nozzles). Print medium M rotating while moving back and forth by the pitch
In addition, the ink can be ejected from the ink ejection ports of the inkjet nozzles 207 for each color to perform the printing in the row direction, and the printing in the column direction can be performed while utilizing the rotation of the drum 10 during the forward movement of the pitch between the inkjet nozzles. That is,
Since the printing in the row direction and the printing in the column direction can proceed simultaneously, the printing speed can be greatly increased.

[0005] Further, since the nozzle unit 200 for each color and the ink tank (ink cassette) 213 for each color are arranged at a separated position, the nozzle unit 20 for each color is provided.
0 can be lightened, and the reciprocating movement speed in the row direction can be greatly increased. This further promotes higher printing speed, and the capacity of the ink tank (ink cassette) 213 for each color can be greatly increased. Can be continuously printed.

In order to realize these, a medium feeding means 60 and a medium feeding means 90 are provided on one side (right side in FIG. 5) of the drum 10, and a medium is provided on the other side (left side in FIG. 5). Peeling means 140, medium discharging / conveying means 160, and direction switching means 1
90 are provided.

The medium feeding means 60 includes a cassette feeding means 7.
The print medium M can be selectively fed one sheet at a time from either one of the manual feeding means 61 and the manual feeding means 61. Medium supply means 90
Supplies the fed print medium M to the drum 10 at a predetermined timing. The medium peeling means 140 peels the print medium M from the drum 10 after printing, and the medium discharge / transport means 160 discharges and transports the peeled print medium M leftward in FIG. The direction switching unit 190 selectively switches between the discharge tray 192 and the upper discharge tray 193.

Thus, since the feeding, supply, holding, printing, peeling, and discharging and conveying of the printing medium M can be continuously performed, multicolor printing of, for example, 20 sheets or more of A4 size can be performed in one minute.

[0009]

When the size of the ink droplet ejected from the outlet of the ink jet nozzle 207 of the nozzle unit 200 is different for each color in the previously proposed ink jet printer, each color sprayed on the print medium M is different. A difference occurs in the dot diameter of the ink, and the print quality is reduced.

An object of the present invention is to provide an ink jet printer capable of uniformizing the size of ink droplets ejected from an ink jet nozzle outlet of each color nozzle unit and performing high quality printing.

[0011]

SUMMARY OF THE INVENTION The present invention is directed to a method of spraying ink from an ink jet nozzle of a nozzle unit for each color onto a print medium held on an outer peripheral surface of a drum rotatable at a constant peripheral speed and rotating with the drum. An ink jet printer formed so as to be capable of color printing, wherein the ink tank for each color is disposed at a position separated from the nozzle unit for each color and lower than the nozzle unit for each color, and the ink in the ink tank for each color is used for the nozzle unit for each color. Ink supply means capable of supplying ink to the ink jet nozzles of the respective colors, so that the potential energy held by the liquid surface of the ink at the ink jet nozzle outlet of the nozzle unit for each color is the same for each color and the inside of the ink jet nozzle for each color The difference in height from the ink level of each color should be selected according to the characteristics of each color ink. The features.

In this case, the respective color inks in the respective color ink tanks are supplied (supplied) to the ink jet nozzles of the respective color nozzle units by the ink supply means.
Here, since the potential energy held by the ink surface at the ink jet nozzle outlet of each color nozzle unit is the same for each color, the size of the ink droplet ejected from the ink jet nozzle outlet of each color nozzle unit becomes uniform. . Therefore, high quality printing can be achieved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. This inkjet printer is shown in FIG.
As shown in FIG. 4 to FIG. 4, the basic configuration is the same as that of the previously proposed ink jet painter (FIG. 5), but the ink supply unit 210 and the height difference adjusting unit 300 are provided, and the ink jet unit of each color nozzle unit 200 is provided. Nozzle 207
The ink droplets can be ejected from the outlet so as to be uniform for each color.

The components common to those of the previously proposed ink jet printer (FIG. 5) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

The nozzle unit 200 for each color (cyan, magenta, yellow, black) is composed of a plurality (for example, four) of nozzle unit elements 205 arranged in a direction perpendicular to the plane of FIG. 4 (row direction). Each nozzle unit element 205 is provided with a large number (for example, 159) of inkjet nozzles 207. The ink jet system is not limited, but in this embodiment, the spray control element 20 utilizing the shear deformation of the piezoelectric actuator is used.
8 for ink jet.

Each ink jet nozzle 207 of each nozzle unit element 205 is connected to a common ink buffer (pressure chamber) 206 as shown in FIG. Except during the printing operation, each ink jet nozzle 207 is covered with a cap (not shown) to prevent ink drying.

Here, the nozzle units 200 (ink buffer 206) for each color and the ink tank 213 which are arranged separately are connected (communicated) by an ink supply tube 215 and an ink supply tube 217.

When the urging means 216 is activated, the ink supply tube 215 causes the ink tank 213 to operate.
Can be supplied into the ink buffer 206. The ink supply tube 215 is opened by the tube opening / closing means 218 so that the ink buffer 2 is opened.
06 can be supplied with ink from the ink tank 213.

The urging means 216 is of a rotary type having a plurality (four) of pressing rollers 216R disposed at equal intervals on a circular locus, and each pressing roller 216R rotates and moves along a guide 216G. Sometimes, the ink supply tube 215
The ink inside can be supplied by extruding the ink inside to the ink buffer 206 side. Therefore, the phenomenon of oversupply and the return of ink to the ink tank 213 can be eliminated.

Each of the tube opening / closing means 218 is a rotary type having one pressing roller 218, and performs a closing operation by pressing the ink supply tube 217 against the guide 218G and an opening operation by separating the tube.

The ink tank 213 for each color has an upper portion formed so that an ink cassette 211 can be attached and detached via a liquid level stabilizing means 212, and a filter 214 provided at a lower portion. The ink liquid level is kept constant by the liquid level stabilizing means 212.

As shown in FIG. 3, the liquid level fixing means 212 is formed so as to be able to perform a constant operation by detecting a change in the level of the ink liquid in the ink tank 213. That is, when the ink cassette 211 is inserted downward in the figure, the protrusion 213A provided in the ink tank 213 is
The cap 212C is pushed up within the cap guide 212G against the downward urging force of the cap 212C. Then, 2 in the lower part of the cassette
The ink in 11D flows into the ink tank 213 through the inlet 212H of the cap guide 212G and the supply port 211H at the bottom of the cassette.

When the ink level in the ink tank 213 rises and reaches the supply port 211H, the ink flow stops. When the ink level in the ink tank 213 drops below the supply port 211H due to a printing operation or the like, ink flows again. Therefore, the ink liquid level in the ink tank 213 can always be kept constant.

The ink level in each ink tank 213 is disposed at a position lower than the ink level at the outlet (tip) of the ink jet nozzle 207 of the nozzle unit 200 (nozzle unit element 205) for each color. By applying a suction negative pressure to each nozzle 207, it is possible to prevent ink leakage (outflow) from each inkjet nozzle 207.

In the present invention, the nozzle unit 200 for each color is used.
The height difference (h) between each ink jet nozzle 207 outlet and the ink liquid level in each color ink tank 213 such that the potential energy held by the ink surface at the ink jet nozzle 207 outlet is the same for each color. Is selected according to the characteristics of the respective color inks.

Here, the nozzle unit 20 for each color is used.
At the exit of the ink jet nozzle 207, the ink level at the exit of the ink jet nozzle 207 with respect to the position of the ink
× g × h potential energy. Here, ρ is the specific gravity of each color ink, g is the gravitational acceleration, and h is the height difference. In this embodiment, the height difference adjustment operation based on the above selection is performed using the height difference adjustment means 300.

As shown in FIG. 2, the height difference adjusting means 300 includes a spring 301 for elastically supporting the ink tank 213 so as to be vertically movable, guide members (302L, 302R) for vertically guiding the ink tank 213, and ink. Tank 2
And a screw member 303 that presses the ink tank 13 downward against the elastic force of the spring 301. The height of the ink tank 213 is changed to change the ink liquid level in the ink tank 213 and the ink jet nozzle of the nozzle unit 200 for each color. The height difference (h) with respect to the outlet 207 can be adjusted.

More specifically, the screw member 303 is rotatably screwed above the guide member 302L. The ink tank 213 is provided with a window 304 so that the ink level in the tank 213 can be checked.

For example, black (B) ink (specific gravity ρ
= 0.966) and the height difference h is 30.0 mm, the yellow (Y) ink (specific gravity ρ = 0.96
The height difference h in 0) is calculated by the following equation. 0.966 × g × 30.0 = 0.960 × g × h Therefore, h = 30.2 mm. Therefore, the height of the yellow (Y) ink tank 213 is adjusted by using the height difference
Level of ink inside and nozzle unit 2 for yellow (Y)
The height difference (h) between the 00 and the outlet of the inkjet nozzle 207 is 30.2 mm. The height difference (h) with respect to other magenta (M) and cyan (C) can be similarly calculated and adjusted.

In the ink jet printer having such a configuration, each color ink in each color ink tank 213 is supplied (supplied) to the ink jet nozzle 207 of each color nozzle unit 200 by the ink supply means 210. Here, since the potential energy held by the ink surface at the ink jet nozzle 207 outlet of each color nozzle unit 200 is the same for each color, the size of the ink droplet ejected from the ink jet nozzle 207 outlet for each color is reduced. Become uniform. As described above, since the ink spray conditions (meniscus) from the nozzle unit 200 (205) for each color can be made uniform, high quality printing can be stably performed.

[0031]

According to the present invention, the ink tank for each color is disposed at a position separated from the nozzle unit for each color and lower than the nozzle unit for each color, and the ink in the ink tank for each color is ink-jetted by the nozzle unit for each color. Ink supply means capable of supplying ink to the nozzles is provided, and the ink in the ink jet nozzle outlet and the ink in the ink tank for each color is set so that the potential energy held by the ink surface at the ink jet nozzle outlet of each color nozzle unit is the same for each color. Since the height difference from the liquid level is selected according to the characteristics of the respective color inks, it is possible to make the size of the ink droplet ejected from the ink jet nozzle outlet of each color nozzle unit uniform and perform high quality printing.

[Brief description of the drawings]

FIG. 1 is a diagram for describing an embodiment of the present invention.

FIG. 2 is also a diagram for explaining a height difference adjusting means.

FIG. 3 is a view for explaining a liquid level stabilizing unit.

FIG. 4 is a diagram for explaining the overall configuration.

FIG. 5 is a diagram for explaining a previously proposed inkjet printer.

[Explanation of symbols]

 10 Drum 11 Outer peripheral surface 200 Nozzle unit for each color 207 Ink jet nozzle 210 Ink supply means 212 Liquid level stabilization means 213 Ink tank 300 Height difference adjustment means

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Takada 570 Ohito, Oni-cho, Tagata-gun, Shizuoka Prefecture Inside the Tech Ohi Works, Inc.

Claims (1)

[Claims] 1. An inkjet formed on an outer peripheral surface of a drum rotatable at a constant peripheral speed and capable of multicolor printing while spraying ink from an inkjet nozzle of a nozzle unit for each color onto a print medium rotating with the drum. A printer, wherein the ink tank for each color is disposed at a position separated from the nozzle unit for each color and lower than the nozzle unit for each color, and the ink in the ink tank for each color can be supplied to the inkjet nozzle of the nozzle unit for each color. A supply means is provided, and the height of the ink nozzle outlet and the ink level in the ink tank for each color are adjusted so that the potential energy held by the ink surface at the ink jet nozzle outlet of each color nozzle unit is the same for each color. The difference is selected according to the characteristics of each color ink. Topurinta.