JP2001260336A - Imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging method in which print speed is increased by printing a plurality of sheets of recording media of small size simultaneously in an arrangement employing a low density line head. SOLUTION: In a method for forming an image by repeating the operation of holding a recording medium 4 on a horizontal plane 18a, traveling a print head 14 in the main scanning direction on the horizontal plane 18a with respect to the recording medium 4 and feeding the recording medium 4 in the sub- scanning direction orthogonal to the main scanning direction, printing is performed simultaneously on a plurality of recording media 4 held on the horizontal plane 18a when the recording media 4 (e.g. postcards) are smaller, in size, than the horizontal plane 18a. The print head 14 is an ink jet head provided with a plurality of ink ejection openings across the entire width of recording area in the sub-scanning direction on the recording medium 4 having a smaller size than the horizontal plane 18a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for forming an image by moving a print head relative to a recording medium.

[0002]

BACKGROUND OF THE INVENTION At present, the present inventors are studying a method for performing high-speed printing in an ink jet printer.
Ideally, a line-type print head having nozzles arranged in a line in the direction perpendicular to the paper feed direction at the same density as the image resolution to be printed, and covering at least the print width of the print area of the recording medium It is conceivable that an image is formed by a single paper feed by using. However, in practice, arranging a large number of nozzles in a line at a high density has many technical problems. Therefore, a low density (for example, a nozzle density (print density) of 12 dpi for an image resolution of 720 dpi) is required.
It is conceivable that a recording medium placed on a flat surface is shifted a plurality of times (six times in the above example) by one or several pixels in the sub-scanning direction by using a line type head of 0 dpi), and main scanning is performed each time. .

An object of the present invention is to provide an image forming method for increasing the printing speed by simultaneously printing a plurality of small-sized recording media in a configuration using such a low-density line type head.

[0004]

SUMMARY OF THE INVENTION To achieve the above object, an image forming method according to the present invention comprises holding a recording medium on a substantially flat surface, and moving a print head on the flat surface with respect to the recording medium in the main scanning direction. In an image forming method of forming an image by repeating scanning and paper feeding of a recording medium in a sub-scanning direction orthogonal to the main scanning direction, when printing a recording medium having a size smaller than the flat surface, The printing is performed while simultaneously holding a plurality of the recording media. The print head is an ink jet head having a plurality of ink ejection ports over the entire width of a recording area in the sub-scanning direction of a recording medium smaller than a flat surface.

[0005]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, an inkjet printer is shown as an image forming apparatus,
An image forming method according to the present invention is a form in which a print head scans a recording medium in a main scanning direction, and a recording medium is fed at a predetermined pitch in a sub-scanning direction orthogonal to the main scanning direction to further perform main scanning Can be applied to all the image forming apparatuses.

(First Embodiment) FIG. 1 is a schematic view of an ink jet printer using an image forming method according to the present invention. The printer 1 has a housing 2, and a plurality of storage units 6 each storing various papers (A3 sheet, A4 sheet, postcard, etc.) 4 are arranged in the housing 2. The uppermost sheet of the sheets 4 stacked in each storage section 6 is in contact with the paper feed roller 8 disposed above the storage section 6, and is sent out of the storage section 6 by the rotation of the paper feed roller 8. ing. In addition, the accommodating section 6 and the paper feed roller 8
Will be described in more detail later.

Each of the paper feed rollers 8 with respect to the paper feeding direction
A separating roller pair 9 and a plurality of conveying roller pairs 10 are sequentially arranged on the downstream side of the printer 1. The rotation of these rollers 9 and 10 causes the paper 4 to move along the paper guide 11 along the image forming unit 1.
2 is transported.

A timing roller pair 14 is provided in the vicinity of the image forming section 12, and rotates in the direction shown in FIG.

The image forming section 12 has a line type print head 14 having a plurality of nozzles (not shown) arranged at predetermined intervals in parallel with the sheet conveying direction, and a sheet conveying mechanism 16. Is ejected from the nozzles and adheres to the sheet 4 conveyed by the sheet conveying mechanism 16 to the portion facing the print head 14. The paper transport mechanism 16 includes an endless belt 18 having at least a portion facing the print head 14 forming a horizontal plane (flat surface) 18 a, and a roller 2 for suspending and driving the belt 18.
0A, 20B, and 20C, and a back plate 22 provided to maintain the horizontal surface 18a of the belt 18 so that the interval between the paper 4 conveyed on the belt 18 and the print head 14 is substantially constant. Have. Rollers 20A, 20
One of B and 20C is used for paper conveyance (feeding of the paper 4 to the area facing the print head 14 and discharging of the paper 4 from the area), and paper feeding for sub-scanning. (Hereinafter, any one of the rollers 20A, 20B, and 20C is referred to as a driving roller 20). ). In the present embodiment, the sub-scanning direction is set to the same direction as the paper transport direction, but may be opposite to the paper transport direction.

FIG. 2 is a top view of the image forming unit 12.
Referring to (a) and (b), the print head 14
It has about 1000 nozzles at a pitch of 20 dpi in a line parallel to the paper transport direction.
When the sheet is conveyed such that the short side direction is parallel to the sheet conveying direction, the printing width (the entire width of the recording area) in the short side direction of the A4 sheet is covered. The size of the horizontal plane 18a is
The setting is such that the entire A4 sheet can be set.

The print head 14 is reciprocated in a main scanning direction orthogonal to the paper direction by a scanning mechanism (not shown).

Returning again to FIG. 1, above the roller 20A located at the right end of the belt horizontal surface 18a with respect to FIG.
A paper pressing roller 24 is provided near the belt 18.
The rotation direction 26 of the endless belt 18 (this is
8a is the same as the paper transport direction and the sub-scanning direction. The charging roller 28 is provided on the upstream side of the paper pressing roller 24 with respect to (2) so as to be in contact with the belt 18.
A predetermined voltage (for example, −1000 V) is applied to the charging roller 28 by a power supply (not shown), whereby the belt 18 is charged, and the paper 4 is pressed by the paper pressing roller 24 to receive the charged belt 18. To be electrostatically attracted. In this way, the print head 14
The spacing between the paper 4 conveyed downward with respect to FIG. 1 and the print head 14 can be kept substantially constant. The belt 18 is preferably made of a material having a resistance of about 10 ⁸ to 10 ¹⁰ Ωcm.

The electrostatic attraction between the belt 18 and the paper 4 may be further increased by applying an appropriate voltage to the paper pressing roller 24 in addition to charging the charging roller 28. The charging voltage of the belt 18 may be positive. Further, the charging roller 2 is used as a member for charging the belt 18.
In addition to 8, a charger such as a corotron or a scorotron may be used. When using a charged charger,
Several kV is required as an applied voltage.

As means for holding the sheet 4 on the belt 18, an air suction system may be adopted instead of the above-mentioned electrostatic system. More specifically, the air suction method refers to a belt 18
The rear plate 22 is made of a gas-permeable member (mesh or porous member), and the paper 4 is sucked from below the rear plate 22 with a fan or the like with respect to FIG.
Is transported in a state where the belt 18 is sucked and held on the belt 18.

In order to separate the paper 4 having passed the print head 14 together with the belt 18 from the belt 18 and discharge the paper 4 to the paper discharge tray 30, the paper 4 is separated close to the roller 20B located at the left end of the horizontal surface 18a of the belt 18. A claw 32 is provided.

FIG. 3A is a top view of an A4 sheet storage section 6 among various paper 4 storage sections. In the accommodation section 6,
A section surrounded by the regulating plate 34 is formed, and the A4 sheet is stacked on the section such that the short side direction of the A4 sheet is parallel to the sheet feeding direction.
One or more (six in the figure) paper feed rollers 8 are rotatably supported by a pair of frames 36 and are drivingly connected to a motor (not shown) for the A4 sheets stacked in the section. The uppermost sheet of the A4 sheets stacked in the section is fed out by being fixed to the shaft 38.

FIG. 3B is a top view of the postcard storage section 6 of the storage section for the various types of paper 4. Two sections surrounded by the regulating plate 34 'are formed in the storage section 6, and postcards are stacked in each section such that the long side direction of the postcard is parallel to the sheet feeding direction. The postcards stacked in each section are sent out by an independent sending mechanism. That is, one or more (three in the figure) paper feed rollers 8 are fixedly mounted on a shaft 38 'rotatably supported by a pair of frames 36' for postcards stacked in each section. And each shaft 38 'is drivingly connected to a separate motor (not shown) so that postcards loaded in one section can be sent out independently of postcards loaded in another section. It is like that.

The operation of the printer 1 having the above configuration is described below.
The case of a postcard will be described with reference to FIGS. 1, 2 (b), 3 (b) and 4. In FIGS. 1 and 3B, the postcards stored in the storage section 6 are simultaneously sent out from the uppermost side where the paper feed roller 8 contacts by rotating the two shafts 38 'in synchronization. . At this time, the sheet under the uppermost sheet may be sent out due to friction. However, sheets other than the uppermost sheet are separated from the uppermost sheet by the counterclockwise rotation of the lower separating roller 9 (FIG. 1), and the supply from here on is prohibited. Then, the separating roller pair 9
Are passed to the image forming unit 12 via the plurality of transport roller pairs 10, the timing roller pair 14, and the paper pressing roller 24. (If only one postcard is to be printed, In 3 (b), one postcard is sent out by rotating only one of the two shafts 38 '). Subsequently, by rotating the driving roller 20 in the counterclockwise direction in FIG. 1 and rotating the belt 18 in the direction of the arrow 22, the postcard reaches the position facing the print head 14 as shown in FIG. Moving.

FIG. 4 shows a print head 14 having nozzles arranged at a pitch of 120 dpi (in this figure, four nozzles 40 are simplified, and small circles indicate ink dots formed on a postcard). Using 720 dpi resolution
This shows a method of printing a solid image. First,
In FIG. 2B, the print head 14 waiting on the upper side
Is moved downward along the main scanning direction, and one line is printed by each nozzle 40 (FIG. 4A). Subsequently, by rotating the drive roller 20 in the counterclockwise direction in FIG. 1, the belt 18 and the two postcards move by one pixel in the direction of the arrow 22 (the sub-scanning direction in FIG. 2B). . Then, the print head 14 arranged on the lower side is moved upward along the main scanning direction, and the second row is printed by the nozzles 40 (FIG. 4B). In this way, one postcard is set in the sub-scanning direction.
A solid image is created by further repeating the main scanning shifted by pixels [FIG. 4 (c)].

Returning to FIG. 1, the two postcards on which the images are formed are conveyed to the discharge tray 30 by rotating the driving roller 20 in the counterclockwise direction and rotating the belt 18 in the direction of the arrow 22. Is done.

If the horizontal plane 18a on which the entire A4 sheet can be set at a time is used as in this embodiment, a postcard can be used up to four horizontal planes 18a as shown in FIG.
It is possible to print while simultaneously holding the print data. Further, as shown in FIG. 5B, printing can be performed in a state where sheets 4 of different sizes are simultaneously held on the horizontal surface 18a.

The above description relates to one embodiment of the present invention, and the present invention can be variously modified. For example,
In the above embodiment, the main scanning is performed by moving the print head 14 side, and the sub-scanning is performed by moving the paper 4 side. However, both the main scanning and the sub-scanning may be performed by moving the print head 14 side. In both the sub-scan and the sub-scan, the paper 4 may be moved. Further, the paper transport direction (the direction of paper feeding to the area facing the print head 14 or the direction of paper ejection from the area) need not be parallel to the sub-scanning direction, and these directions are, for example, orthogonal to each other. May be.

Even when a serial type head is used as the print head 14 instead of the line type,
Compared with the printing speed using the conventional serial type head,
The printing speed of a size smaller than the flat surface can be increased.

[0024]

According to the image forming method of the present invention, printing can be performed on a recording medium having a size smaller than the flat surface while a plurality of recording media are simultaneously held on the flat surface. Can be raised.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a line-type inkjet printer using an image forming method according to the present invention.

FIG. 2A is a top view of the image creating unit when an A4 sheet is arranged on a horizontal plane of the image creating unit. (B) Top view of the image creation unit when two postcards are arranged on the horizontal plane of the image creation unit.

FIG. 3A is a top view of an A4 sheet storage unit.
(B) A top view of the postcard storage unit.

FIG. 4 is a simplified diagram showing an image creation process using a line type print head.

FIG. 5A is a top view of the image creating unit when four postcards are arranged on a horizontal plane of the image creating unit. FIG. 4B is a top view of the image creating unit when sheets of different sizes are arranged on a horizontal plane of the image creating unit.

[Explanation of symbols]

1: inkjet printer, 4: paper, 6: paper storage unit, 8: paper feed roller, 14: line type print head,
18: belt, 18a: horizontal surface (flat surface), 20
(20A, 20B, 20C): belt drive roller, 3
4: regulating plate, 36: frame, 38: shaft of paper feed roller.

Claims (2)

[Claims] 1. A recording medium is held on a substantially flat surface,
An image forming method of forming an image by scanning a print head on a recording medium in the main scanning direction on the flat surface and repeatedly feeding a recording medium in a sub-scanning direction orthogonal to the main scanning direction. An image forming method comprising: when printing a recording medium having a size smaller than a flat surface, performing printing while simultaneously holding a plurality of the recording media on the flat surface. 2. The image forming method according to claim 1, wherein the print head is an inkjet head having a plurality of ink ejection ports over the entire width of a recording area in a sub-scanning direction of a recording medium smaller than the flat surface. .