JPH10175338A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable retention of a print medium on a rotating drum without causing a positional slippage and thereby to enable stable execution of printing of high quality. SOLUTION: This printer is so formed that a print medium M can be retained on the outer peripheral surface 11 of a rotatable drum 10 by using a medium retaining means and that printing can be made on the retained print medium M in rotation by jetting ink thereto, while occurrence of a difference in the density of ink, oozing and others is prevented, and also the medium retaining means is so formed that it comprises a plurality of suction holes 12 piercing through the outer peripheral surface 11 of the drum 10 and a means for bringing about negative pressure fully which puts the inside of the drum 10 under negative pressure and that it enables execution of suction and retention by the negative pressure. Besides, it is made to have a constitution wherein a porous sheet-like member 41 having a large number of air flow pores 42 being much smaller than each suction hole 12 is fitted on the outer peripheral surface 11 of the drum 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer capable of holding a print medium on an outer peripheral surface of a rotatable drum by using a medium holding means and spraying ink on the held print medium while rotating. About.

[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, M can be fed one line in the column direction and repeated, so that the printing speed can be greatly increased and continuous printing operation can be performed on a large number of sheets. The present applicant has proposed an ink-jet printer capable of achieving a great reduction in size (for example, Japanese Patent Application No. 8-296959).

That is, in FIG. 4, a drum 10 is rotatable at a constant peripheral speed and can hold a print medium M on an outer peripheral surface 11 thereof. Rotation of this drum 10 (Y)
The nozzle unit for each color (200C, 200M,
200Y, 200B).

Accordingly, the nozzle units for the respective colors (200C, 20C) are integrated over the entire length in the row direction (perpendicular to the paper surface).
0M, 200Y, 200B) or an integrated nozzle unit for each color (200C, 200M, 200Y, 200B) in which a plurality of nozzle unit elements are arranged in the row direction, while being reciprocated by the pitch between the inkjet nozzles, for example. Ink is sprayed from the inkjet nozzles 207 for each color onto the print medium M to print in the row direction, and the drum 1 is moved during the forward movement of the pitch between the inkjet nozzles.
Printing in the column direction can be performed while utilizing the rotation of 0.
That is, since the line-direction printing and the column-direction printing can proceed simultaneously, the printing speed can be greatly increased.

In addition, a nozzle unit for each color (200C
Etc.) and the respective color ink tanks (not shown) are disposed at separate positions, so that the nozzle unit 200 for each color is provided.
In addition, the point that the reciprocating movement speed in the row direction can be significantly increased further promotes higher printing speed, and the capacity of the ink tank for each color can be greatly increased.
This means that zero or more continuous printing operations can be performed.

In order to realize these, one side (right side in the figure) of the drum 10 is provided with a feeding means 60 and a medium feeding means 90.
The other (left) side is provided with a medium peeling unit 140, a discharging and conveying unit 160, and a direction switching unit 190. Further, a medium holding means 20 capable of holding the printing medium M by negative pressure suction is provided on the drum 10 and its periphery. In some cases, the charge holding unit is provided as an auxiliary unit.

The feeding means 60 can selectively feed the printing medium M one by one from one of the cassette feeding means 71 and the manual feeding means 61. The medium supply means 90 feeds the fed print medium M to the drum 1 at a predetermined timing.
Feed to the 0 side.

As shown in FIGS. 4 and 5, the medium holding means 20 has a number of suction holes 12 penetrating radially in and out of the drum 10, and a negative pressure establishing means 31 capable of generating a negative pressure in the drum 10. The print medium M is formed so as to be able to be sucked and held on the outer peripheral surface 11 of the drum.

The charge adsorption and holding as auxiliary means is performed by the charging means 51. The charging means 51 charges the print medium M with a positive charge and uses the charge attraction generated between the print medium M and the grounded drum 10 to transfer the print medium M to the drum outer peripheral surface 11.
Hold by suction. The replenishment charging means 55 replenishes the amount of the decrease in the charge attraction force accompanying the execution of printing. After the printing, the charge removing means 55 adds a charge opposite to that of the charging means 51 to remove the charge for adsorption.

The medium peeling means 140 peels the print medium M from the drum 10 after printing, and the discharge transport means 160 discharges and transports the peeled print medium M leftward in FIG. The direction changing means 190 selectively switches between the discharge tray 192 and the upper discharge tray 193.

In this manner, 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.

[0012]

By the way, in the above-mentioned proposed printer, an A4-size print medium M per minute is used.
When 20 or more are printed, the drum 10 is rotated at a high speed of 800 mm / sec or more at a peripheral speed of, for example, 130 mm. Such a drum 10
In order to realize high-speed rotation of the print medium M, the force (negative pressure suction force) of the medium holding means 20 for sucking the print medium M through each suction hole 12 is considerably increased so that the print medium M It is necessary to hold firmly so that it does not shift.

Here, when the negative pressure suction force increases, as shown in FIG. 6, a portion (M1) of the print medium M facing each suction hole 12 is dented, and printing may be disturbed. Further, since the printing medium portion (M1) is more strongly sucked than other portions, the ink sprayed on the portion (M1) penetrates deeper into the inside, and a difference in ink density or bleeding occurs. There is a possibility that.

An object of the present invention is to provide an ink jet printer capable of achieving high quality printing by holding a printing medium on a rotating drum without displacing while preventing the occurrence of a difference in ink density or bleeding. Is to do.

[0015]

SUMMARY OF THE INVENTION According to the present invention, a print medium can be held on the outer peripheral surface of a rotatable drum by using a medium holding means, and printing can be performed by spraying ink onto the held print medium while rotating. The medium holding means is formed so as to be capable of holding a negative pressure by suction, the medium holding means including a plurality of suction holes penetrating the outer peripheral surface of the drum into and out of the drum and negative pressure establishing means for making the inside of the drum a negative pressure. And a porous sheet-like member having a large number of air flow holes which are much smaller than the suction holes.

In this invention, the printing medium is suctioned at a negative pressure through each suction hole provided in the drum, and is suction-held on the outer peripheral surface of the drum. Here, since the porous sheet member is interposed between the printing medium and the drum, the air suction flow relating to the negative pressure suction is dispersed by the large number of air flow holes of the porous sheet member.

Therefore, the negative pressure suction force acting on the print medium is averaged while preventing the occurrence of the ink density difference and the bleeding, etc., so that the print medium portion facing each suction hole is dented or the ink density difference or the like is reduced. The occurrence of bleeding or the like is prevented.

Accordingly, high quality printing can be achieved by holding the printing medium on the rotating drum without displacing it.

[0019]

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. 3, a medium holding means 20 capable of holding a print medium M by negative pressure suction is provided, and a perforated sheet member 41 is attached to the outer peripheral surface 11 of the drum 10 so that a negative pressure suction force acting on the print medium M is provided. Is configured to be able to be averaged.

The ink jet printer of FIG.
Has the same structure as that of the prior proposal (Japanese Patent Application No. 8-296959).

As shown in FIGS. 2 and 3, the medium holding means 20 has a plurality of suction holes 12 penetrating the drum outer peripheral surface 11 in and out, and a negative pressure establishing means 31 for making the inside of the drum 10 a negative pressure.
By generating a negative pressure in the internal space 16 of the drum 10, the printing medium M can be suction-held by negative pressure through each suction hole 12.

The negative pressure establishing means 31 includes a corresponding suction port 34 corresponding to the suction port 14 on the drum 10 side and a corresponding suction port 3
4 and a suction fan 32 that sucks air to establish a negative pressure in the drum internal space 16 through a duct 35.

The suction port 14 is a side end plate (end face) of the drum 10.
15R, the corresponding suction port 34 corresponds to the suction port 14 and is fixed to the bracket 5R in the main body case 1. Drum 10 (15R) and negative pressure establishing means 30
(5R) means that it approaches in the drum axis direction but does not contact. The side end plate (end surface) 15L is a blind plate. In addition,
In FIG. 2, 10S is a rotation axis of the drum 10.

As shown in FIG. 1, the porous sheet member 41 has a number of air flow holes 42 which are much smaller than the suction holes 12 formed in the drum 10, and It is installed so as to cover.

In this embodiment, the porous sheet member 41
Is a charge accelerating member (for example, a thin woven fabric of 6-6 nylon)
Is formed from. Thereby, the porous sheet member 4
1 serves to assist the charge of the print medium M by the charging means 51 and the like.
The charge adsorption holding force at the time of mounting 0 and during printing can be more stably secured.

Next, the operation of this embodiment will be described. To print, the drum 10 is rotated in a predetermined direction (Y direction). Next, the negative pressure establishing means 31 is driven to generate a negative pressure in the internal space 16 of the drum 10. Then, the print medium M supplied at a predetermined timing from the medium supply means 90 is suctioned at a negative pressure through the suction holes 12 and is suction-held on the drum outer peripheral surface 11.

Here, between the print medium M and the outer peripheral surface 11 of the drum, as shown in FIG.
1 is interposed, so that the air suction flow relating to negative pressure suction is dispersed by the large number of air flow holes 42 of the member 41.

Therefore, the negative pressure suction force acting on the printing medium M is averaged, and the printing medium portion (M1) facing each suction hole 12 is dented, and a difference in ink density or bleeding occurs in the portion (M1). Is prevented.

Further, since the porous sheet-like member 41 is rich in chargeability, the power for holding and absorbing the electric charge during printing can be more stably secured, and the printing medium M can be firmly fixed without displacing the print medium M. It can be held on the drum outer peripheral surface 11.

According to this embodiment, the medium holding means 20 capable of holding the printing medium M by negative pressure suction while preventing the occurrence of a difference in ink density and bleeding is provided. Since the sheet-shaped member 41 is attached, the printing medium M can be held on the rotating drum 10 without being displaced, and high quality printing can be achieved.

Further, since the porous sheet-like member 41 is formed of the charge accelerating member, the printing medium suction holding force is enhanced, and the printing medium M can be firmly held on the drum outer peripheral surface 11.

[0032]

According to the present invention, since the medium holding means capable of holding the printing medium by negative pressure suction is provided and the porous sheet member is attached to the outer peripheral surface of the drum, the negative pressure suction force acting on the printing medium is reduced. Can be averaged. Therefore,
It is possible to prevent the printing medium portion facing each suction hole from being dented, or from causing a difference in ink density or bleeding. As a result, it is possible to achieve high-quality printing by holding the print medium on the rotating drum without displacing the print medium while preventing the occurrence of a difference in ink density or bleeding.

[Brief description of the drawings]

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

FIG. 2 is a side sectional view for explaining a medium holding means and a porous sheet member.

FIG. 3 is a diagram for explaining the overall configuration.

FIG. 4 is a diagram for explaining a previously proposed inkjet printer.

FIG. 5 is a view for explaining a medium holding unit.

FIG. 6 is a view for explaining a suction holding state of a print medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Drum 11 Outer peripheral surface 12 Suction hole 20 Medium holding means 31 Negative pressure establishing means 41 Porous sheet member 42 Air flow hole 51 Charging means 53 Replenishment charging means 55 Charge removing means

Claims (1)

[Claims] An image forming apparatus includes: a medium holding unit configured to hold a print medium on an outer peripheral surface of a rotatable drum and spraying the held print medium with ink to form a printable medium; It includes a plurality of suction holes penetrating the outer peripheral surface of the drum in and out and negative pressure establishing means for negative pressure inside the drum. An ink jet printer comprising a perforated sheet member having a number of much smaller air flow holes.