JPH09300600A - Image-forming device of ink jet system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the difference in the shape of a dot to be formed by transferring an ink head in the forward/backward directions by controlling a means for changing a speed ratio so that the forward speed of the ink head is lower or faster than the backward speed of the ink head, when an image is formed by the ink head which discharges ink both in the forward transfer and the backward transfer. SOLUTION: A color plotter 10 holds a recording paper 12 mounted on a platen 14 between a transport roller 24 and a pinch roller 26 and transports the recording paper 12 by rotating the transport roller 24 with the help of a motor at the time of forming an image. A carriage 18 is caused to move forward/backward at a varying speed, above the recording paper 12, in the arrow B(forward) and C(backward) directions. In addition, ink is discharged, slightly obliquely into a direction in which the carriage 18 proceeds, from an ink discharge aperture, based on an image signal bearing image information sent to the carriage 18 from a control device. Thus, an image is formed on the recording paper 12. In this case, the control device is provided and controls a motor for driving the carriage 18 in such a way that, for example, the backward speed of the carriage 18 is slower than its forward speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet type image forming apparatus for forming an image on a recording sheet by ejecting ink based on image information.

[0002]

2. Description of the Related Art As one of output devices of computers and workstations, there is known an ink jet type image forming apparatus which forms an image on recording paper by discharging ink. This inkjet type image forming apparatus is, for example,
A plurality of ink ejection ports for ejecting ink are formed, and an ink head that reciprocates in a predetermined direction and a conveying member that intermittently conveys the recording paper in a direction (recording paper conveyance direction) orthogonal to the predetermined direction are provided. ing. When forming an image on a recording sheet, for example, the recording sheet being conveyed by the conveying member is temporarily stopped, and the ink head is reciprocated in the above-described predetermined direction, while the image is formed in the image forming area in front of the ink ejection port. A recording fan located on the recording paper is sucked by a suction fan, and ink is ejected from the ink ejection port to form an image for one band (printing, drawing, etc.), and then the recording paper is conveyed by a predetermined length. Then, the operation of forming an image for the next band on a new portion located in the image forming area is repeated.

In such an ink jet type image forming apparatus, there are a type that forms an image by ejecting ink from an ink ejection port when the ink head moves in the forward direction and a backward direction, and There is a type in which an image is formed by ejecting ink from an ink ejection port only when moving in either one of the reverse direction and the backward direction. From the viewpoint of shortening the image forming time, the type that ejects ink in both the forward and backward directions is superior.

[0004]

By the way, normally, an ink having a diameter larger than the diameter of the ink ejection port is about to be ejected from the ink ejection port. Therefore, the shape of the ink ejected from the ink ejection port becomes elongated and the rear portion of the ink may be cut off. Of the ink, the broken rear part is called satellite, while the main part of the ejected ink other than the rear part is called main ink.
Satellites can also occur due to the low viscosity of the ink.

Since the satellite generated in this manner has a difference in weight and ejection speed of the main ink, the main ink and the satellite generally reach (land) the recording paper.
The timing of doing is different from each other. As a result, the landing positions of the main ink and the satellite on the recording paper are different from each other.

Further, in the ink head, generally, for convenience of manufacturing, the ink ejection port is formed so that the ink is ejected at an angle without being ejected perpendicularly to the recording paper. For this reason, when the ink head is moving in the forward direction and when it is moving in the backward direction, the ink is ejected from the ink ejection ports to form an image, and when the ink head is moving in the forward direction. The amount of deviation between the landing position of the main ink and the landing position of the satellite may differ between when ejecting the ink and when ejecting the ink while moving in the backward direction. in this case,
The shape of the dot formed by the ink ejected when moving in the forward direction and the shape of the dot formed by the ink ejected when moving in the backward direction are different from each other,
As a result, there is a problem that the image quality deteriorates.

In view of the above circumstances, the present invention has a shape of a dot formed by ink ejected while moving in the forward direction and a dot formed by ink ejected when moving in the backward direction. It is an object of the present invention to provide an inkjet-type image forming apparatus that improves the image quality by reducing the difference with the shape.

[0008]

The first ink jet type image forming apparatus of the present invention for achieving the above object comprises:
While reciprocating the ink head in which the ink ejection port for ejecting ink is formed in a predetermined direction, the ink is ejected from the ink ejection port on the recording paper located in the image forming area in front of the ink ejection port based on the image information. In an inkjet-type image forming apparatus that discharges ink to form an image, (1) a speed ratio changing unit that changes a ratio between a forward speed at which the ink head moves in the forward direction and a backward speed at which the ink head moves in the backward direction. 2) When the ink is ejected from the ink ejection port to form an image in both the forward movement and the backward movement of the ink head, the backward speed is set to be slower or faster than the forward speed. It is characterized in that it is provided with a first control means for controlling the speed ratio changing means.

Here, in the second ink jet type image forming apparatus of the present invention for achieving the above object, the ink is ejected while reciprocating the ink head having the ink ejection port for ejecting the ink in a predetermined direction. In an inkjet type image forming apparatus that forms an image by ejecting ink from the ink ejection port based on image information on a recording sheet located in an image forming area in front of the ejection port, (3) the image of the recording sheet Distance changing means for changing the distance between the portion located in the formation area and the ink head (4) When the ink is ejected from the ink ejection port in both the forward movement and the backward movement of the ink head to form an image In addition, the distance changing means is provided so that the distance when moving in the backward direction is shorter or longer than the distance when moving in the forward direction. It is characterized in further comprising a second control means for Gosuru.

In order to achieve the above object, the third ink jet image forming apparatus of the present invention is configured to reciprocate an ink head having an ink ejection port for ejecting ink in a predetermined direction while reciprocating the ink. In an inkjet type image forming apparatus that forms an image by ejecting ink from the ink ejection port based on image information on a recording sheet located in an image forming area in front of the ejection port, (5) the ink head is in the forward direction. Speed ratio changing means for changing the ratio between the forward speed moving in the forward direction and the backward speed moving in the backward direction. (6) Changing the distance between the portion of the recording paper located in the image forming area and the ink head. Distance changing means (7) When both the forward and backward movements of the ink head are made to eject ink from the ink ejection ports to form an image, The speed ratio changing means is controlled so that the backward speed is slower or faster than the forward speed, and the distance when moving in the backward direction is shorter or longer than the distance when moving in the forward direction. Thus, a control means for controlling the distance changing means is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an inkjet type image forming apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 shows a color plotter (hereinafter, referred to as a first embodiment of an ink jet type image forming apparatus of the present invention.
It is a perspective view which shows the schematic structure of a plotter.

The plotter 10 includes a platen 14 on which a recording paper 12 conveyed in the direction of arrow A is placed. A large number of suction holes (not shown) are formed in the platen 14, and the recording paper is sucked by a suction fan (not shown). Two guide shafts 16 are provided above the platen 14 in parallel with the platen 14.
A carriage 18 is attached to the guide shaft 16 via a slide bearing (not shown). An ink head 20 having an ink ejection port 20a (see FIG. 4) for ejecting ink is mounted on the carriage 18. The ink ejected from the ink ejection port 20a when the ink head 20 moves in the forward direction is configured to eject at a slight inclination in the traveling direction, as shown in FIG. 4 described later. In front of the ink discharge port 20a,
An image forming area D on which an image is formed is formed. In addition, a waste ink storage unit that stores ink ejected from the ink ejection port 20a for cleaning the ink ejection port 20a or the like is provided at a position apart from the image forming area D on one side of the movable range of the carriage 18. 22 is formed.

The carriage 18 is formed by moving the carriage 18 in the direction of arrow B (an example of the forward direction according to the present invention.
It is fixed to a belt (not shown) for reciprocating in a direction orthogonal to the direction) and an arrow C direction (which is an example of the backward direction in the present invention and is a direction orthogonal to the arrow A direction).
Since this belt is moved in the arrow B direction and the arrow C direction by the carriage driving motor (not shown), the carriage 18 is also moved in the arrow B direction and the arrow C direction.
As the carriage driving motor, a stepping motor (which is an example of the speed ratio changing device referred to in the present invention) that can rotate in the normal and reverse directions and can change the rotation speed in each of the forward and reverse directions is used. By switching the rotation direction of the carriage drive motor, the carriage 1
8, the moving direction of the ink head 20 is switched. Further, by changing the rotation speed of the carriage driving motor, the ink head 20 moves in the direction of arrow B.
The ratio of the forward speed moving in the direction and the backward speed moving in the arrow C direction is changed.

The plotter 10 is provided with a control device (an example of the first control means according to the present invention, not shown) for controlling the carriage driving motor, and the backward speed is higher than the forward speed. The carriage drive motor is controlled by the control device so as to be delayed. Further, as will be described later, this control device sends an image signal carrying image information to the carriage 18, and ink is ejected from the ink ejection port 20a based on this image signal.

In forming an image on the recording paper 12, the recording paper 12 is placed on the platen 14 and the recording paper 1
2 is a conveyance roller 24 having a part of the outer peripheral surface exposed through an opening (not shown) formed in the platen 14 and the recording paper 12.
Both ends of the sheet are sandwiched by the pinch rollers 26 which press from above, and the conveying roller 24 is rotated by a motor (not shown) to convey the sheet. Carriage 1 above recording paper 12
8 is reciprocated by changing the speed in the arrow B direction and the arrow C direction as described above, and ink is ejected based on the image signal carrying image information transmitted to the carriage 18 from the control device (not shown). Ink is ejected from the outlet 20a to form an image on the recording paper 12.

Next, a plotter of a second embodiment of the ink jet type image forming apparatus of the present invention will be described with reference to FIGS. 2 and 3, the same components as those of the plotter of FIG. 1 are designated by the same reference numerals.

FIG. 2 is a schematic diagram showing the ink head when moving in the forward direction, and FIG. 3 is a schematic diagram showing the ink head when moving in the backward direction.

The plotter of the second embodiment is a carriage 1
8, the pinion gear 30 is rotatably fixed, and an ink head holding portion 34 to which a rack 32 is fixed is formed on the carriage 18.

The pinion gear 30 is rotated by a gear stepping motor (not shown) which can rotate in the normal and reverse directions. The pinion gear 30 and the rack 32 mesh with each other, and as the pinion gear 30 rotates, both the ink head 20 and the ink head holding portion 34 are guided by the guide rails 36 and move in the arrow E direction. Therefore, as the pinion gear 30 rotates, the image forming area D of the recording paper 12 is
The distance between the portion 12a located at and the ink head 20 is changed. Here, the pinion gear 30, the rack 32,
Gear stepping motor and ink head holder 3
4 constitutes an example of the distance changing device according to the present invention.

The plotter of the second embodiment is equipped with a control device (an example of the second control means according to the present invention, not shown) for controlling the gear stepping motor, and moves in the backward direction. The stepping motor for gears is controlled by the control device so that the distance at this time is shorter than the distance at which it moves in the forward direction. Further, this control device transmits an image signal carrying image information to the carriage 18, and ink is ejected from the ink ejection port 20a based on this image signal.

Next, the experimental results of forming an image using the plotter 10 of the first embodiment will be described with reference to FIGS. 4 to 7. In these figures, the same components as those of the plotter of FIG. 1 are designated by the same reference numerals.

FIG. 4 is a schematic diagram showing a state in which ink is ejected from the ink ejection port of the ink head moving in the forward direction, and FIG. 5 is an ink of the ink head moving in the backward direction. FIG. 3 is a schematic diagram showing a state where ink is being ejected from an ejection port.

The ink ejected from the ink ejection port 20a of the ink head 20 has its rear portion cut off, and the main ink 4
0 and the satellite 42, and as shown in FIGS. 4 and 5, depending on the reciprocating speed of the ink head, the recording paper 12
The landing positions above may be different from each other.

FIG. 6 shows the difference between the forward and backward ink dot shapes on the recording paper when the reciprocating speed of the ink head is changed.
(C) and (e) are movements in the forward direction, (b), (d),
(F) is the movement in the backward direction, and (a) and (b) are 36
0 mm / sec, (c) and (d) are 560 mm / sec, (e)
And (f) are dot shapes at 705 mm / sec.

The reciprocating speed of the ink head is 360 mm
In the case of / sec, the main ink 40 and the satellite 42 overlap on the recording paper, but the image forming speed becomes slightly slower.
When the reciprocating speed of the ink head is 560 mm / sec,
In the forward direction, the main ink 40 and the satellite 42 overlap each other on the recording paper, but in the backward direction, the landing positions of the both are displaced and the dot shapes are different from each other. When the reciprocating speed of the ink head is 705 mm / sec, the image forming speed is high, but the landing positions of the main ink 40 and the satellite 42 are deviated in both the forward direction and the backward direction, resulting in different dot shapes. .

In FIG. 7, the forward speed is "1 (= 560 mm
/ Sec) ”shows the experimental result when the backward speed is changed. The vertical axis of the figure shows whether or not there is a difference in dot shape during reciprocation on the recording paper, and the horizontal axis shows the ratio of the backward speed to the forward speed.

The ratio of the backward speed to the forward speed is 0.
When it is 85 or less, there is almost no difference in the dot shapes in both the forward direction and the backward direction on the recording paper. In particular, when the above ratio was 0.65 or less, there was no difference in dot shape, and a high quality image was obtained. However, since the image forming speed becomes slower as the above ratio becomes smaller, it is preferable to set the ratio to 0.65 or less and 0.60 or more. In this experiment, when the forward speed was set to 560 mm / sec and the backward speed was set to 0.65 times and 0.60 times the forward speed, an image was formed on A1 size recording paper. , 0.60 times was 5 seconds slower than that of 0.65 times.

Here, in the first embodiment, the difference in dot shape is reduced by making the backward speed slower than the forward speed, but the configuration such as the inclination at the time of ejection from the ink head is changed. It is easy to understand that there is a case where the difference in dot shape can be reduced by increasing the speed in the backward direction without being limited to slowing the speed in the backward direction. .

Next, with reference to FIGS. 2, 3, 8 and 9, experimental results of forming an image using the plotter of the second embodiment will be described. In these figures, FIG.
The same components as those of the plotter of FIG.

As shown in FIGS. 2 and 3, the ink head 2
The ink discharged from the ink discharge port 20a of 0 is cut off at the rear part and divided into the main ink 40 and the satellite 42, and depending on the distance between the portion of the recording paper 12 located in the image forming area D and the ink head 20, The landing positions on the recording paper 12 may differ from each other.

FIG. 8 shows an image forming area D of the recording paper 12.
Shows the difference in the dot shape of the ink on each of the forward direction and the backward direction on the recording paper when the distance between the ink head 20 and the portion located at the position (inter-paper distance) is changed,
(A), (c), (e) are movements in the forward direction, (b),
(D) and (f) are movements in the backward direction, (a) and (b) are 1.0 mm, (c) and (d) are 1.3 mm,
(E) and (f) are dot shapes in the case of 1.6 mm.

When the paper distance is 1.0 mm, the main ink 40 and the satellite 42 overlap each other on the recording paper. When the paper-to-paper distance is 1.3 mm, the main ink 40 and the satellite 42 overlap on the recording paper in the forward direction, but in the backward direction, the landing positions of the both are displaced and the dot shapes are different from each other. When the paper distance is 1.6 mm, the ink head and the recording paper are sufficiently separated from each other, but the landing positions of the main ink 40 and the satellite 42 are different in both the forward direction and the backward direction, and the dot shapes are different from each other. Became.

FIG. 9 shows the experimental results when the paper distance when moving in the forward direction is set to "1 (= 1.3 mm)" and the paper distance when moving in the backward direction is changed. The vertical axis of the figure shows whether there is a difference in dot shape on the recording paper,
The horizontal axis represents the ratio of the sheet-to-sheet distance when moving in the backward direction to the sheet-to-sheet distance when moving in the forward direction.

When the ratio of the backward movement distance to the backward movement distance is 0.90 or less, there is little difference between the forward and backward dot shapes on the recording paper. In particular, when the above ratio was 0.75 or less, there was no difference in dot shape, and a high quality image was obtained. However, when the above ratio becomes smaller, the distance between the sheets in the backward movement becomes shorter, so it is preferable to set the ratio to 0.75 or less and 0.65 or more. Even if a portion of the recording paper on which ink is attached is sucked up by a suction fan, it may float up by about 0.8 mm. Therefore, considering the contact between the ink head and the recording paper, The lower limit value is 0.8 mm.

Here, in the second embodiment, the difference in dot shape is reduced by making the distance between sheets when moving in the backward direction shorter than the distance between sheets when moving in the forward direction. It is easy to change the configuration such as the inclination when ejecting from the ink head, and by doing this, it is not limited to shortening the paper distance when moving in the backward direction, It is understandable that the difference may be reduced in some cases without detailed explanation.

Further, in the above embodiment, the control of the reciprocating speed and the control of the distance between the recording paper and the ink head are separately performed, but they may be controlled at the same time, and in this case, a high quality image is also obtained. can get.

[0038]

As described above, according to the first ink jet type image forming apparatus of the present invention, the ink is ejected from the ink ejection port for both the forward movement and the backward movement of the ink head to form an image. At this time, the speed ratio changing means is controlled by the first control means so that the backward speed becomes slower or faster than the forward speed. Therefore, both the main ink and the satellite land on the forward and backward printing. Since it is possible to reduce the positional deviation and eliminate the difference in ink dot shape, a high quality image can be obtained.

Further, according to the second ink jet type image forming apparatus of the present invention, when the image is formed by ejecting the ink from the ink ejection port in both the forward movement and the backward movement of the ink head. When moving to
The distance changing means is controlled by the second control means so that the distance between the ink head and the portion of the recording paper located in the image forming area is shorter or longer than the distance when moving in the forward direction. And reduces the deviation of the landing positions of both the main ink and satellite when printing in the backward direction,
Since the difference in ink dot shape can be eliminated, a high-quality image can be obtained.

Further, according to the third ink jet type image forming apparatus of the present invention, the control means is used for forming an image by ejecting ink from the ink ejection port in both the forward movement and the backward movement of the ink head. However, while controlling the speed ratio changing means so that the backward speed becomes slower or faster than the forward speed, the ink head and the portion of the recording paper located in the image forming area when moving in the backward direction are Since the distance changing means is controlled so that the distance becomes shorter or longer than the distance when moving in the forward direction, a high quality image can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a color plotter which is an example of an inkjet image forming apparatus of the present invention.

FIG. 2 is a schematic diagram showing an ink head when moving in a forward direction.

FIG. 3 is a schematic diagram showing the ink head when moving in the backward direction.

FIG. 4 is a schematic diagram showing a state in which ink is ejected from an ink ejection port of an ink head moving in the forward direction.

FIG. 5 is a schematic diagram showing a state in which ink is ejected from an ink ejection port of an ink head moving in a backward direction.

FIG. 6 is a schematic diagram showing a difference in dot shape of ink in each of the forward direction and the backward direction on the recording paper when the reciprocating speed of the ink head is changed,
(C) and (e) are movements in the forward direction, (b), (d),
(F) is the return movement, (a) and (b) is 360m
m / sec, (c) and (d) are 560 mm / sec, and (e) and (f) are 705 mm / sec dot shapes.

FIG. 7 is a graph showing an experimental result when the backward speed is changed by setting the forward speed to “1 (= 560 mm / sec)”, and the vertical axis indicates whether there is a difference in dot shape on the recording paper, The horizontal axis represents the ratio of the backward speed to the forward speed.

FIG. 8 is a schematic diagram showing a difference in dot shape of ink in each of the forward direction and the backward direction on the recording paper when the distance between the portion of the recording paper located in the image forming area and the ink head is changed. , (A), (c) and (e) are movements in the forward direction, (b), (d) and (f) are movements in the backward direction, and (a) and (b) are 1.0 mm, (C) and (d) are 1.3 mm, and (e) and (f) are 1.6 mm dot shapes.

FIG. 9 shows the paper distance when moving in the forward direction as “1 (=
Is a graph showing the experimental results when the distance between sheets when moving in the backward direction is changed to 1.3 mm) ", and the vertical axis indicates whether there is a difference in dot shape on the recording paper,
The horizontal axis represents the ratio of the sheet-to-sheet distance when moving in the backward direction to the sheet-to-sheet distance when moving in the forward direction.

[Explanation of symbols]

 10 Plotter 12 Recording Paper 18 Carriage 20 Ink Head 20a Ink Ejection Port 30 Pinion Gear 32 Rack 34 Ink Head Holding Unit 36 Guide Rail D Image Forming Area

Claims (3)

[Claims] 1. While reciprocating an ink head in which an ink ejection port for ejecting ink is formed in a predetermined direction, the recording paper located in an image forming area in front of the ink ejection port is recorded on the basis of image information. In an inkjet type image forming apparatus that forms an image by ejecting ink from an ink ejection port, a speed ratio change that changes a ratio between a forward speed at which the ink head moves in the forward direction and a backward speed at which the ink head moves in the backward direction. Means for ejecting ink from the ink ejection port for both forward and backward movements of the ink head to form an image, so that the backward speed is slower or faster than the forward speed. An inkjet image forming apparatus comprising: a first control unit that controls the speed ratio changing unit. 2. An ink head having an ink ejection port for ejecting ink is reciprocated in a predetermined direction, and the recording paper is positioned on an image forming area in front of the ink ejection port, based on image information. In an inkjet image forming apparatus that forms an image by ejecting ink from an ink ejection port, a distance changing unit that changes a distance between a portion of a recording paper located in the image forming area and the ink head, the ink head In both the forward movement and the backward movement, when ejecting ink from the ink ejection port to form an image, the distance when moving in the backward direction is shorter than the distance when moving in the forward direction or An inkjet image forming apparatus comprising: a second control unit that controls the distance changing unit so as to be long. 3. An ink head having an ink ejection port for ejecting ink is reciprocated in a predetermined direction, and the recording paper is positioned in an image forming area in front of the ink ejection port, based on image information. In an inkjet type image forming apparatus that forms an image by ejecting ink from an ink ejection port, a speed ratio change that changes a ratio between a forward speed at which the ink head moves in the forward direction and a backward speed at which the ink head moves in the backward direction. Means, a distance changing means for changing the distance between the ink head and a portion of the recording paper located in the image forming area, and ink for moving the ink head from both the forward and backward directions. When ejecting an image to form an image, the speed ratio changing unit is controlled so that the backward speed is slower or faster than the forward speed. In addition, the inkjet image, comprising: a control unit that controls the distance changing unit so that the distance when moving in the backward direction is shorter or longer than the distance when moving in the forward direction. Forming equipment.