JP2023000035A - image forming device - Google Patents

Abstract

An object of the present invention is to prevent deterioration of print quality.
Inkjet heads 31K, 31C, 31M, 31Y provided with nozzle arrays arranged with nozzles for ejecting ink; , 31Y, the nozzle rows 102 are aligned in the main scanning direction, and the retreating nozzles 103 are provided downstream from the nozzle rows 102 in the sheet conveying direction by the suction conveying unit 3 at a third interval d3.
[Selection drawing] Fig. 5

Description

The present invention relates to an image forming apparatus that forms an image on a print medium.

2. Description of the Related Art A line-type inkjet recording apparatus performs printing by ejecting ink from an inkjet head based on image data onto conveyed paper.

In Patent Document 1, a plurality of ejection holes having a plurality of ejection hole rows extending from a first ejection area to a second ejection area along an oblique direction forming a predetermined angle with respect to a first direction is provided. A liquid ejection head is disclosed.

JP 2020-157659 A

However, in the liquid ejection head of Patent Document 1, the same number of nozzles are evenly assigned to a plurality of rows.

Such an arrangement is used to realize a high-resolution head, but since the nozzles in each row are uniform, the self-jet flow generated by the ejection of each row is uniform across the width of each row. When it interferes with the carrier wind, the carrier wind passing through the self-air current causes turbulence in flight. The position where the turbulence occurs interferes with the uniform self-airflow of the nozzles arranged at uniform intervals, so there is a problem that the image quality deteriorates due to random fluctuations.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that prevents deterioration in print quality.

In order to achieve the above object, the image forming apparatus according to the present invention is characterized by:
a conveying means for conveying paper;
an inkjet head provided with a nozzle row in which nozzles for ejecting ink are arranged;
In the inkjet head, the nozzle rows are aligned in the main scanning direction, and retreating nozzles are provided at a plurality of intervals including an arbitrary one on the downstream side of the paper transport direction from the nozzle rows. There is a thing.

According to the characteristics of the image forming apparatus according to the present invention, deterioration of print quality can be prevented.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention; FIG. (a) is a diagram showing nozzle arrays of an inkjet head according to the prior art for comparison, and (b) is a diagram showing disturbances in droplet flight when ink is ejected from the nozzle arrays in (a). It is an explanatory view explained. For comparison, it is a perspective view illustrating disturbance of ink droplet flight according to the prior art. FIG. 10 is a perspective view for explaining variations in dots formed after landing of ink droplets in a conventional technique, for comparison. (a) is a diagram showing nozzle rows of an inkjet head of an inkjet printing apparatus according to an embodiment of the present invention, and (b) is a view of droplets when ink is ejected from the nozzle rows in (a). It is an explanatory view explaining a state.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent reference numerals are attached to the same or equivalent parts and components throughout each drawing. However, it should be noted that the drawings are schematic and differ from reality. In addition, there are portions with different dimensional relationships and ratios between the drawings.

Further, the embodiments shown below are examples of apparatuses and the like for embodying the technical idea of the present invention. not specific to The technical idea of this invention can be modified in various ways within the scope of claims.

(Configuration of inkjet printer 1)
An embodiment of an inkjet printing apparatus 1 to which an image forming apparatus according to the present invention is applied will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of an inkjet printer 1 according to an embodiment of the present invention.

In the following description, the front side of FIG. 1 where the user is positioned is the left direction, and the back side of the paper is the right direction. Also, in FIG. 1, the up and down direction is defined as the up and down direction as viewed from the user. Further, the path indicated by the dashed line in FIG. 1 is the transport path R along which the paper PA, which is the print medium, is transported. The transport direction of the sheet of paper PA is defined as the front-rear direction. Upstream in the following description means forward direction and downstream means backward direction.

As shown in FIG. 1 , the inkjet printing apparatus 1 includes a paper feeding section 2 , a suction transport section 3 , a printing section 4 and a paper discharging section 6 .

The paper feed unit 2 feeds paper PA, which is a print medium. The paper feed unit 2 includes a paper feed table 11 , paper feed rollers 12 , and registration rollers 13 .

Sheets of paper PA used for printing are stacked on the paper feed tray 11 .

The paper feed rollers 12 pick up the paper sheets PA stacked on the paper feed table 11 one by one and convey them toward the registration rollers 13 . The paper feed roller 12 is arranged above the paper feed table 11 . The paper feed roller 12 is rotationally driven by a motor (not shown).

The registration rollers 13 temporarily stop the paper PA conveyed by the paper feed rollers 12 and then convey it toward the suction conveying section 3 . The registration rollers 13 are arranged downstream of the paper feed rollers 12 . The registration rollers 13 are rotationally driven by a motor (not shown).

The suction transport unit 3 transports the paper PA transported from the registration rollers 13 toward the printing unit 4 and the paper discharge unit 6 . The suction conveying section 3 includes a conveying belt 21 , a drive roller 22 , driven rollers 23 to 25 , a belt drive motor 26 , a platen plate 27 and a suction fan 28 .

The conveying belt 21 is an annular endless belt stretched over a driving roller 22 and driven rollers 23-25. The conveying belt 21 is formed with air intake holes, which are through holes for sucking and holding the sheet of paper PA, at predetermined intervals along the conveying direction of the conveying belt 21 . The conveying belt 21 sucks and holds the sheet of paper PA on the conveying belt 21 by means of negative pressure (adsorption force) generated in the suction holes by driving the suction fan 28 .

The conveying belt 21 rotates clockwise in FIG. As a result, the conveying belt 21 conveys the sheet of paper PA to the right by endlessly moving.

The driving roller 22 and the driven rollers 23 to 25 are over which the conveying belt 21 is stretched. The driving roller 22 is rotationally driven by a belt driving motor 26 to rotate the conveying belt 21 . The driven rollers 23 to 25 are driven by the driving roller 22 via the conveying belt 21 . The driven roller 23 has substantially the same height as the drive roller 22 and is spaced apart from the drive roller 22 in the left-right direction by a predetermined distance. The driven rollers 24 and 25 are arranged below the driving roller 22 and the driven roller 23 at substantially the same height, separated from each other by a predetermined distance in the horizontal direction.

A belt drive motor 26 rotates the drive roller 22 .

The platen template 27 is arranged below the conveying belt 21 between the driving roller 22 and the driven roller 23 and supports the lower surface of the conveying belt 21 so as to be slidable.

The suction fan 28 is arranged below the platen plate 27 to generate a downward airflow.

The printing unit 4 prints on the paper PA conveyed by the suction conveying unit 3 . The printing unit 4 is provided above the suction transport unit 3 . The printing unit 4 is fixed inside a housing (not shown) of the inkjet printer 1 . The printing unit 4 includes black (K), cyan (C), magenta (M) and yellow (Y) inkjet heads 31K, 31C, 31M and 31Y and a head holder 32 .

The inkjet heads 31K, 31C, 31M, and 31Y have a plurality of nozzles in their lower portions, and print by ejecting ink from the nozzles onto the paper PA conveyed while being sucked by the suction conveying section 3 . The nozzles form a linearly arranged nozzle row as described later.

The head holder 32 holds the inkjet head 31 above the suction/conveyance unit 3 . The head holder 32 is formed in a hollow, substantially rectangular parallelepiped shape.

The paper PA printed by the printing unit 4 is discharged to the paper discharge unit 6 .

FIG. 2(a) is a diagram showing nozzle rows of an inkjet head according to the prior art for comparison, and FIG. FIG. 10 is an explanatory diagram illustrating disturbance of flight of droplets;

As shown in FIG. 2A, nozzle rows 101 of the conventional inkjet head are arranged at first nozzle positions with a predetermined first interval d1 so as to form a straight line in the horizontal direction (main scanning direction). there is

In the nozzle row 101 shown in FIG. 2(a), as shown in FIG. 2(b), when ink is ejected from the nozzle row 101, the flight of ink droplets is disturbed.

Specifically, although ink is ejected from each nozzle to generate a downward self-airflow, the nozzle row 101 shown in FIG. is generated uniformly across the width direction (horizontal direction).

Further, a transport wind is generated in the rearward direction due to the transport of the paper.

When the self-air current interferes with the carrier wind, the carrier wind passing through the self-air current disturbs the flight of the ink droplets.

In the example shown in FIG. 2B, the ink droplets ejected from the nozzles N101 and N102 are disturbed in flight by the carrier air F11 that pushes aside the uniform self-air current and passes through. It fluctuates within the range of W11.

Similarly, for the nozzles N103 and N104, the jetted ink droplets are disturbed in flight by the carrier wind F12 passing through the self-air current, and the landing position fluctuates within the range of the width W12.

3 and 4 are perspective views for explaining the disturbance of ink droplet flight according to the prior art for comparison.

As shown in FIG. 3, each nozzle of the nozzle row 101 discharges ink to generate a downward self-air current, and the paper is conveyed to generate a backward transport wind F. As shown in FIG. At this time, the carrier air F pushes away the own air current S and flows.

At this time, the flight is disturbed, and the landing positions of the ink droplets fluctuate at random, resulting in unevenness in the landing.

Furthermore, macroscopically, as shown in FIG. 4, the self-airflow S is formed like a uniform curtain by ink ejection. The carrier wind F randomly pushes away areas that are relatively weak with respect to the surroundings of the self-airflow S so that this curtain trails. Therefore, the landing positions formed under the self-airflow S fluctuate randomly.

In this way, the position to be pushed away moves at random, so that the printed matter has fluctuating densities.

FIG. 5(a) is a diagram showing nozzle rows of the inkjet head of the inkjet printing apparatus 1 according to the embodiment of the present invention, and FIG. 5(b) shows ink ejected from the nozzle rows of FIG. 5(a). FIG. 10 is an explanatory diagram for explaining the state of a droplet when it is dropped.

As shown in FIG. 5A, the nozzle row 102 of the inkjet head according to the embodiment of the present invention is arranged at the first nozzle position by a predetermined first interval d1 so as to form a straight line in the left-right direction (main scanning direction). , or a second interval d2 longer than the first interval d1. A gap area formed by the second gap d2 is called a slit 102s.

Nozzles (hereinafter referred to as retreating nozzles) are provided at the second nozzle positions located behind the slits 102s, and the nozzle row 103 is provided by the retreating nozzles. That is, the inkjet head has the nozzle rows 102 aligned in the main scanning direction, and the nozzles of the nozzle rows 102 are replaced with the nozzles of the nozzle rows 102 downstream of the nozzle rows 102 in the paper transport direction at a predetermined third interval d3. Nozzles 103 are provided at a predetermined third spacing d3.

Since the nozzle row 102 shown in FIG. 5(a) is provided with the slit 102s, the swinging of the portion where the carrier wind F pushes away the self-airflow S is suppressed.

In other words, the slit 102s provides a relatively weak portion in the self-airflow S to suppress the fluctuation of the position where the self-airflow is pushed away due to interference with the carrier wind F. It is possible to suppress the random variation of the position where the flight is disturbed by F. As a result, it is possible to prevent random fluctuations of the positions where the ink droplets land, and as a result, it is possible to prevent deterioration of the image quality.

In addition, since the nozzle row 103 composed of retreating nozzles is provided at the second nozzle position behind the slit 102s of the nozzle row 102, a non-ejection region is formed by the slit 102s and white streaks are formed in the printed image. can be prevented.

As a result, deterioration in print quality can be prevented.

(Appendix)
This application discloses the following inventions.

(Appendix 1)
a conveying means for conveying paper;
an inkjet head provided with a nozzle row in which nozzles for ejecting ink are arranged;
The inkjet head has a plurality of nozzle rows aligned in the main scanning direction, and a plurality of retreating nozzles in place of the nozzles downstream of the nozzle rows in the paper transport direction by the transport means. An image forming apparatus characterized by being provided at an interval of .

As a result, the variation range of the position where the self-airflow interferes with the carrier wind can be suppressed, so that the carrier wind passing through the self-airflow S can be prevented from disturbing the flight. Therefore, it is possible to suppress the fluctuation of the position where the ink droplets land, and as a result, it is possible to prevent the deterioration of the image quality. In addition, since the retreating nozzle is provided, it is possible to prevent the formation of a non-ejection region and the formation of a white streak on the printed image.

As a result, deterioration in print quality can be prevented.

1 Inkjet printing device 2 Paper feed unit 3 Suction transport unit 4 Print unit 6 Paper discharge unit 11 Paper feed table 12 Paper feed roller 13 Registration roller 21 Conveyor belt 26 Belt drive motor 28 Suction fan 31 (31C, 31K, 31M, 31Y) Inkjet head 32 Head holder 101, 102, 103 Nozzle row 102s Slit

Claims (1)

a conveying means for conveying paper;
an inkjet head provided with a nozzle row in which nozzles for ejecting ink are arranged;
In the inkjet head, the nozzle rows are aligned in the main scanning direction, and retreating nozzles are provided at a plurality of intervals including an arbitrary one on the downstream side of the paper transport direction from the nozzle rows. An image forming apparatus characterized by:

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