JP2000006477A - Image-printing apparatus and image printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a color shift phenomenon by changing a pinch pressure in accordance with an image print process to make a movement amount of a print paper equal when the paper is printed and when the paper is returned. SOLUTION: This image-printing apparatus essentially consists of a printing head 10, a feed roller 12 and a pinch roller 14. The printing head 10 prints images to a print paper 16 by every constant print lines. The feed roller 12 is driven to rotate by a stepping motor 18. The pinch roller 14 holds the print paper 16 together with the feed roller 12 thereby supporting the paper. When printed, the print paper 16 is supported in a state while caught between the feed roller 12 and the pinch roller 14. In the constitution, a catch force of the feed roller 12 and pinch roller 14 for catching the print paper 16 is made variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing head which performs printing in a fixed printing line unit, and relatively moves a printing paper in a direction orthogonal to a printing line to thereby form a two-dimensional image. The present invention relates to an image printing apparatus for printing.

[0002]

2. Description of the Related Art In a printer apparatus for printing a color image, a printing head which prints in a predetermined line unit is caused to reciprocate a printing paper relatively in a direction perpendicular to a printing line direction, and thereby a Y (yellow) printing is performed. ), M (magenta)
And monochromatic images such as C (cyan) are sequentially superimposed at the same position. Therefore, a paper feed mechanism for moving the printing paper with respect to the print head is provided. Conventionally, as a paper feed mechanism for printers and copiers, a print paper is sandwiched between a pinch roller and a feed roller, and the feed roller is rotated to drive the print paper and send it to the print head. A configuration in which the relative movement is performed is widely used.

[0003]

However, in the above-described conventional paper feed mechanism, the relative amount of movement between the print head and the print paper is unstable, and each monochromatic image to be printed is printed on the print paper. Position shifts. as a result,
A so-called color shift phenomenon in which the color of the edge (edge) of the image looks blurred appears on the printing paper. Hereinafter, a description will be given of factors that cause the relative movement amount between the print head and the printing paper to be unstable.

Generally, in this type of paper feed mechanism, a pinch roller is pressed against a feed roller to generate a gripping force between the feed roller and the printing paper. Further, a large number of minute projections are provided on the surface of the feed roller. These projections cut into the printing paper pressed by the pinch roller, thereby increasing the gripping force.

The pinch roller and the feed roller are both cylindrical in shape, and are arranged in a state where the directions in which the cylindrical surfaces extend, that is, the directions in which the rotating shafts extend, match. Therefore, geometrically, there is line contact between the two rollers. However, an elastic material such as rubber or urethane is often used for the pinch roller,
At the pressing portions of both, the pinch roller itself slightly deforms. Therefore, surface contact having a certain width is performed instead of line contact.

In such a paper feed mechanism, it has been experimentally confirmed that when the pinch pressure, which is the amount of force pressing the pinch roller against the feed roller, changes, the grip force on the printing paper changes. It is presumed that this is because the degree of biting of the fine protrusions provided on the surface of the feed roller into the printing paper and the degree of deformation of the pinch roller differ according to the change in the pinch pressure.

Next, referring to FIG. 5, an image printing process of a printer for printing a color image in the above-described method will be described. FIG. 5 is a flowchart showing a conventional image printing process.

First, in S1 of FIG. 5, a print sheet is sandwiched between a pinch roller and a feed roller at a predetermined pinch pressure. Next, in S2 of FIG. 5, the feed roller is rotationally driven to move the printing paper to a predetermined printing start position. Subsequently, in S3 of FIG. 5, a monochrome image is printed by the print head while the print paper is moved by the feed roller. The paper feed speed by the feed roller at that time is represented by symbol A.

Next, in S4 of FIG. 5, the control unit of the printer determines whether or not printing of all colors has been completed. And if you have not finished printing all colors,
Proceeding to S5 in FIG. 5, the feed roller is rotated in the opposite direction to that during printing, and the printing paper is returned to the printing start position described above. The paper feed speed by the feed roller at that time is represented by symbol B.
Then, the process proceeds to S3 in FIG. 5 again, and another single-color image is printed. On the other hand, when printing of all colors is completed, FIG.
In step S6, the printing paper is discharged by the feed roller.

In the image printing process described above, the paper feed speed A and the paper feed speed B are generally different. Normally, the paper feed speed B is set higher than the paper feed speed A in order to print the next color quickly. In this way, the printing time is often reduced.

During printing, the print head is brought into direct contact with the printing paper, or the printing head is pressed against the printing paper via an ink ribbon. Therefore, the load required for the feed roller to feed the printing paper is determined during printing (FIG. 5).
5 is different between the load a) in S3 and the paper return (load b in S5 in FIG. 5).

On the other hand, it has been confirmed that when the load and the feeding speed required for feeding the printing paper are different, a difference occurs in the feeding amount of the printing paper even if the rotation amount of the feed roller is the same. Therefore, it is considered that the printing start position is shifted during printing of each color, and a color shift phenomenon occurs.

Therefore, conventionally, the pinch pressure is changed in accordance with the image printing process so that the amount of movement of the printing paper is equal between the time of printing and the time of paper return, thereby preventing the occurrence of the color shift phenomenon. The advent of a device was desired.

[0014]

Therefore, according to the image printing apparatus of the present invention, there is provided a print head for printing an image on printing paper in a fixed print line unit, a feed roller rotated by a motor, and the feed roller. And a pinch roller for sandwiching and supporting the print paper, and by rotating the feed roller, the print paper is moved relative to the print head in a direction orthogonal to the line extending direction of the print line, In an image printing apparatus for printing a two-dimensional image composed of a plurality of pixels on a printing paper surface, the amount of force for sandwiching the printing paper between a feed roller and a pinch roller is made variable.

According to such a configuration, the amount of force for pinching the printing paper, that is, the pinch pressure can be changed, so that the amount of force of the printing paper is appropriately set so that the amount of movement of the printing paper is equal between printing and returning. can do. Therefore, the occurrence of the color shift phenomenon is prevented.

Further, in the image printing apparatus according to the present invention,
Preferably, in each of the steps of printing an image, the above-mentioned amount of power may be changeable.

For example, when the image printing step includes a printing step of moving the printing paper and performing printing, and a paper feeding step of simply moving the printing paper without performing the printing, the printing step and the paper feeding step are performed. It is preferable that the above-mentioned abilities have different values.

According to this configuration, the amount of force can be appropriately set so that the amount of movement of the printing paper is equal between the time of printing (printing process) and the time of paper return (paper feeding process). The occurrence is prevented.

It is preferable that the amount of force is changed according to the material, thickness and shape of the printing paper.

With this configuration, it is possible to prevent a color shift phenomenon from occurring due to a difference in printing paper.

Further, in the image printing apparatus according to the present invention,
Preferably, a pinch spring for generating a force, a first bracket rotatably provided around a rotation center axis, and a second bracket provided rotatably about the rotation center axis and sandwiching the pinch spring together with the first bracket. , A pinch cam for controlling an angle between the first and second brackets.

As described above, the pinch spring for generating the force is provided between the first and second brackets. For example, a pinch roller is supported by a first bracket, and the first bracket is coupled to a second bracket via a pinch spring. Therefore, the pinch roller is pressed against the feed roller by the amount of force generated by the pinch spring. The amount of force generated by the pinch spring changes according to the included angle between the first and second brackets. First and second
The angle between the brackets is controlled by a pinch cam. Therefore, the pinch cam can control the amount of force for pinching the printing paper between the pinch roller and the feed roller, and as a result, the occurrence of the color shift phenomenon can be prevented.

In the image printing apparatus according to the present invention,
Preferably, the pinch cam is provided on a cam shaft provided with a head cam for controlling a relative position between the print head and the printing paper.

With such a configuration, the number of parts is reduced and control is facilitated.

According to the image printing method of the present invention,
A print head that prints an image on printing paper in fixed print line units, a feed roller that is rotationally driven by a motor,
A method for controlling an image printing apparatus including a pinch roller for sandwiching and supporting a printing paper together with the feed roller, wherein the rotation of the feed roller causes the printing paper to be rotated in a direction orthogonal to a line extending direction of the printing line. Relative to the print head, and printing a two-dimensional image composed of a plurality of pixels on a printing paper,
(A) a step of pinching the printing paper with a predetermined force by a pinch roller and a feed roller; (b) a step of driving the feed roller to rotate and moving the printing paper to a predetermined printing start position; Changing to a constant value Pa;
(D) While moving the printing paper by the feed roller,
A step of printing a single-color image by the print head; (e) a step of determining whether or not printing of all colors has been completed; and (f) when printing of all colors has not been completed, the force amount is Pa. Changing the feed roller to the different value Pb, rotating the feed roller in the opposite direction to the printing, and returning the printing paper to the printing start position;
(G) when printing of all colors is completed, a step of discharging printing paper by a feed roller.

As described above, since the amount of force for sandwiching the printing paper is changed in accordance with the image printing process, the amount of movement of the printing paper can be made equal between printing and returning the paper. Therefore, the occurrence of the color shift phenomenon can be prevented.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the configuration, size, and positional relationship so that the present invention can be understood. The conditions and materials such as numerical values described below are merely examples. Therefore, the present invention is not limited to this embodiment.

Referring to FIG. 1, the configuration of the image printing apparatus according to this embodiment will be described. FIG. 1 is a perspective view illustrating a main configuration of the image printing apparatus according to the embodiment. In this embodiment, a thermal sublimation printer will be described as an example of an image printing apparatus.

The image printing apparatus according to this embodiment includes a print head 10, a feed roller 12, a pinch roller 14,
And is mainly provided. The print head 10 prints an image on the printing paper 16 in a fixed printing line unit. In this configuration example, the print head 10 is configured as a thermal head. The print surface of the print head 10 is provided with a heat line in which a plurality of heaters are arranged. This heat line is pressed against printing paper via an ink film during printing. In this state, heat is generated by a heat line to sublimate the ink in the ink film, and the sublimated ink permeates the printing paper. In this way, printing of a single-color image is performed. Change the ink film to change the color. Here, the direction in which the print lines extend is the direction in which the heat lines are arranged, and is the so-called main scanning direction (the direction indicated by arrow a in FIG. 1).

The above-mentioned feed roller 12 and pinch roller 14 are both cylindrical members. The extending directions of the rotating shafts 12a and 14a that rotatably support the rollers 12 and 14, respectively, are arranged so as to match the above-described main scanning direction. Feed roller 12
Are driven to rotate by a stepping motor 18. The rotational force generated by the stepping motor 18 is transmitted to the feed roller 12 via the motor-side pulley 20, the belt 22, and the roller-side pulley 24 in order. The pinch roller 14 sandwiches the printing paper 16 together with the feed roller 12 and supports the printing paper 16.

At the time of printing, the printing paper 16 is supported while being sandwiched between the cylindrical surfaces of both the feed roller 12 and the pinch roller 14. At the time of printing, the print head 10 applies the ink film 2 to the printing paper 16.
6 is pressed. On the other hand, a platen roller 28 is provided on the side of the printing paper 16 opposite to the print head 10. The platen roller 28 is a cylindrical member, and an axis extending direction of a rotation shaft 28a that rotatably supports the roller 28 coincides with the main scanning direction. During printing, the print head 10 is pressed against the platen roller 28. Printing paper 16 and ink film 26
Are sandwiched between the print head 10 and the platen roller 28 in a state where they overlap each other. When the feed roller 12 is driven to rotate, the printing paper 16 moves relatively to the print head 10 in a direction orthogonal to the line extending direction of the printing line, that is, in the sub-scanning direction.
As a result, a two-dimensional image composed of a plurality of pixels is printed on the printing paper 16.

The image printing apparatus according to this embodiment is characterized by a feed roller 12 and a pinch roller 14.
And that the force for pinching the printing paper 16 is made variable.
In order to realize this configuration, a pinch spring 30, a first bracket 32, a second bracket 34, and a pinch cam 3
6 and so on. Thus, a configuration is obtained in which the position of the rotation shaft 14a of the pinch roller 14 can be relatively moved with respect to the feed roller 12.

The above-described pinch spring 30 is a spring that generates an amount of force for pinching the printing paper 16, that is, a so-called pinch pressure. The first bracket 32 is provided rotatably around a fixed rotation center shaft 38 and is a member that supports the rotation shaft 14 a of the pinch roller 14. One end of the first bracket 32 is attached to the rotation center shaft 38, and the other end of the first bracket 32 is attached to the rotation shaft 14 a of the pinch roller 14. The axial direction of the rotation center axis 38 coincides with the main scanning direction. Accordingly, the rotation axis 14a of the pinch roller 14 can rotate around the rotation center axis 38, and the distance between the feed roller 12 and the pinch roller 14 can be changed.

The second bracket 34 is provided so as to be rotatable around a rotation center axis 38, and the first bracket 32
In addition, the pinch spring 30 is sandwiched. Similarly to the first bracket 32, one end of the second bracket 34 is attached to the rotation center shaft 38. On the other hand, one end of the pinch spring 30 is attached to one end of the second bracket 34 on the side close to the rotation shaft 14a of the pinch roller 14.
The other end of the pinch spring 30 is connected to one end of the first bracket 32 on the side where the rotating shaft 14a is attached.
Therefore, the pinch spring 30 is provided in a state of being sandwiched between the first bracket 32 and the second bracket 34. That is, by changing the angle between the first bracket 32 and the second bracket 34, the elastic force generated by the pinch spring 30 changes. For example, when the pinch angle is reduced, the pinch spring 30 contracts, the elastic energy stored in the pinch spring 30 increases, and the elastic force generated by the pinch spring 30 increases.

In this configuration example, the first bracket 32 is provided at a position relatively close to the pinch roller 14 with respect to the second bracket 34. Therefore, by pressing the second bracket 34 toward the first bracket 32, the pinch spring 30 contracts. As a result, the pressing force with which the pinch roller 14 is pressed against the feed roller 12 increases, and the pinch roller 14 and the feed roller 12
With this, the amount of force for pinching the printing paper 16, that is, the pinch pressure increases.

On the other hand, the pinch angle between the first bracket 32 and the second bracket 34 is controlled by a pinch cam 36. The pinch cam 36 is provided in a state where the cam surface is in contact with the surface of the second bracket 34 opposite to the side where the pinch spring 30 is provided. Also, this pinch cam 3
Reference numeral 6 is attached to a cam shaft 40 whose axial direction coincides with the main scanning direction. By rotating the camshaft 40,
Since the cam radius corresponding to the distance between the cam shaft 40 and the second bracket 34 changes, the second bracket 34 and the first
The included angle with the bracket 32 changes. Therefore, with the rotation of the camshaft 40, the amount of force that pinches the printing paper 16 between the pinch roller 14 and the feed roller 12 changes. Thus, the pinch angle between the second bracket 34 and the first bracket 32 is controlled by the shape and the rotation angle of the pinch cam 36, and as a result, the pinch pressure is controlled.

In this configuration example, two sets of the configuration of the pinch spring 30, the first bracket 32, the second bracket 34, and the pinch cam 36 described above are provided. Each set is provided at each end of the pinch roller 14.

In this configuration example, the head cam 42 for controlling the relative position between the print head 10 and the print paper 16 is
The pinch cam 36 is attached to a cam shaft 40 to which the pinch cam 36 is attached. This head cam 42 is used during printing.
When the print head 10 is the printing paper 16, that is, the platen roller 2
8 is provided so as to be pressed. Further, a press-contact plate 44 rotatable around the rotation center axis 38 is provided between the print head 10 and the cam shaft 40. The head cam 42 holds the camshaft 4 in contact with the pressure contact plate 44.
0 is attached.

A press spring 46 is provided between the press plate 44 and the print head 10. Therefore, when the camshaft 40 is rotated, the pressure plate 44 is
Is pressed, the distance between the camshaft 40 and the press contact plate 44 changes. With this change in the distance, the elastic force generated by the press contact spring 46 changes, causing the print head 10 to be pressed against the platen roller 28 or
Is operated to be separated from the platen roller 28.

Therefore, the head cam 42 and the pinch cam 36
Is appropriately provided, the above-described control of the pinch pressure is performed in accordance with the printing process. In addition, as the cam shaft 40 is shared by the pinch cam 36 and the head cam 42, the number of components is reduced, and there is an advantage that control of the printing operation and control of the pinch pressure are facilitated.

Next, the operation of the image printing apparatus will be described with reference to FIGS. FIG. 2 is a side view showing a configuration of a main part at the time of printing. FIG. 3 is a side view showing a configuration of a main part at the time of paper return (paper feed).

First, the operation at the time of printing will be described with reference to FIG. As shown in FIG. 2, at the time of printing, the cam radius of the head cam 42 is a rotation angle at which the cam radius becomes the maximum,
The pressure plate 44 is moved by the head cam 42 to the platen roller 28.
Side. Accordingly, the press spring 46 provided between the press plate 44 and the print head 10 is reduced, and the print head 10 is pressed against the platen roller 28 by the elastic force generated by the press spring 46.

At this time, the cam radius of the pinch cam 36 becomes the maximum value ra, and the second bracket 34 is pressed by the pinch cam 36 toward the first bracket 32. Accordingly, the pinch spring 30 provided between the second bracket 34 and the first bracket 32 contracts, and the first bracket 32 is pressed toward the feed roller 12 by the elastic force generated by the pinch spring 30. Therefore, the pinch roller 1 in which the rotation shaft 14a is supported by the first bracket 32
4 is pressed against the feed roller 12. Thus, in this configuration example, the pinch pressure is set to the maximum value Pa during printing. This pinch pressure Pa
Can be appropriately set by designing the shape and size of the pinch cam 36.

As described above, during printing, the printing paper 16 is sandwiched by the pinch pressure Pa, and the printing paper 16 is fed at the speed A. At this time, the load a required to send the printing paper 16 is:
It acts in a direction along the paper surface of the printing paper 16 and acts in a direction opposite to the direction in which the printing paper 16 is fed.

As shown in FIG. 2, the ink film 26 is moved together with the printing paper 16 in the same direction and at the same speed. Both end portions of the ink film 26 are wound around the first bobbin 48 and the second bobbin 50, respectively. At the time of this printing, the first bobbin 48
Is the winding bobbin, and the second bobbin 50 is the supply bobbin.

Next, the operation of returning the paper will be described with reference to FIG. As shown in FIG. 3, when returning the paper, the cam radius of the head cam 42 is set to a rotation angle that is smaller than that during printing.
4 is weakened toward the platen roller 28 side. Accordingly, the press contact spring 46 provided between the press contact plate 44 and the print head 10 extends more than during printing, and as a result, the print head 10 is separated from the platen roller 28 by the press contact spring 46.

Further, at this time, the cam radius of the pinch cam 36 becomes a radius rb smaller than ra, and the force of pressing the second bracket 34 toward the first bracket 32 is reduced. Therefore, the pinch spring 30 provided between the second bracket 34 and the first bracket 32 extends more than during printing. Therefore, the pinch roller 14 is
Is weaker than during printing. In this configuration example, when the paper is returned, the value of the pinch pressure is configured to be a value Pb smaller than Pa.
The magnitude of the pinch pressure Pb can be appropriately set by designing the shape and size of the pinch cam 36.

As described above, when returning the paper, the printing paper 16 is sandwiched by the pinch pressure Pb, and the printing paper 16 is fed at a speed B higher than the speed A. Since the feed roller 12 is rotated in the direction opposite to the direction during printing, the printing paper 16 is sent in the direction opposite to the direction during printing. At this time, the load b required to feed the printing paper 16 acts in a direction along the plane of the printing paper 16 and acts in a direction opposite to the direction in which the printing paper 16 is sent.

As shown in FIG. 3, the ink film 26 does not move when returning the paper.

Next, an image printing process performed by the image printing apparatus according to this embodiment will be described with reference to FIG. FIG.
5 is a flowchart illustrating an image printing process according to the embodiment. Hereinafter, description will be made sequentially according to the steps (a) to (g).

First, in S1 of FIG. 4, (a) the printing paper 16 is sandwiched between the pinch roller 14 and the feed roller 12 with a predetermined force. That is, the printing paper 16 is fed into the printing apparatus, the camshaft 40 is rotated by a predetermined angle, and the pinch cam 36 controls the pinch angle between the first bracket 32 and the second bracket 34.

Next, in S2 of FIG. 4, (b) the feed roller 12 is driven to rotate, and the printing paper 16 is sent to a predetermined printing start position. Subsequently, in S3 of FIG. 4, (c) the amount of force for pinching the printing paper 16 by the pinch roller 14 and the feed roller 12 is changed to the above-mentioned constant pinch pressure value Pa. That is, the cam radius of the pinch cam 36 is ra
The camshaft 40 is rotated to an angle as follows. As shown in FIG. 2, at this time, the print head 10 is pressed against the printing paper 16 via the ink film 26. Then, in S4 of FIG. 4, the print head 10 prints a monochrome image on the printing paper 16 while the printing paper 16 is moved at the speed A by the feed roller 12 (d).

At S5 in FIG. 4, it is determined whether or not (e) printing of all colors is completed. Such a determination is performed by, for example, a control unit that controls the image printing apparatus. Then, when it is determined by the control unit that printing of all colors has not been completed, in S6 of FIG. 4, the power is changed to another value Pb different from Pa. That is, the cam shaft 40 is rotated to an angle at which the cam radius of the pinch cam 36 becomes rb. As shown in FIG. 3, at this time, the print head 10 is separated from the platen roller 28. Then, FIG.
In S7, the feed roller 12 is rotated in the direction opposite to the direction at the time of printing, and the printing paper 16 is returned to the printing start position at the speed B. Then, after changing the ink film to another color, the process returns to S3 in FIG. 4, and the printing process shown in S3 to S5 in FIG. 4 is performed again.

On the other hand, when the control unit determines that printing of all colors has been completed, in step S8 of FIG. 4, (g)
The printing paper 16 is discharged by the feed roller 12.

As described above, according to the image printing apparatus of this embodiment, the pinch pressure can be controlled by the shape and the rotation angle of the pinch cam 36. Therefore, even if the paper feeding load or the paper feeding speed fluctuates between printing and paper returning, the pinch pressure can be changed, so that the amount of paper movement can be made equal regardless of the printing process. it can. Therefore,
The occurrence of the color shift phenomenon can be prevented.

Further, the head cam 42 and the pinch cam 36
Are mounted on the common camshaft 40, so that the number of parts is reduced and control becomes easy.

Further, there may be a case where a difference occurs in the paper feed amount due to a difference in the material, thickness, shape, and the like of the printing paper. In order to control the pinch pressure according to the type of printing paper, the shape of the pinch cam 36 should be a cam shape that can obtain a larger number of pinch pressures according to the rotation angle of the cam shaft 40. It is suitable.

[0058]

According to the image printing apparatus of the present invention, since the force for pinching the printing paper between the feed roller and the pinch roller is made variable, the force for pinching the printing paper, that is, the pinch pressure can be changed. Therefore, the amount of force can be appropriately set so that the amount of movement of the printing paper is equal between the time of printing and the time of paper return, and the occurrence of a color shift phenomenon is prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image printing apparatus according to an embodiment.

FIG. 2 is a diagram illustrating a configuration of an image printing apparatus during printing.

FIG. 3 is a diagram illustrating a configuration of the image printing apparatus when returning paper.

FIG. 4 is a diagram illustrating an image printing process according to the embodiment.

FIG. 5 is a diagram showing a conventional image printing process.

[Explanation of symbols]

 10: print head 12: feed roller 12a: rotating shaft 14: pinch roller 14a: rotating shaft 16: printing paper 18: stepping motor 20: motor side pulley 22: belt 24: roller side pulley 26: ink film 28: platen roller 28a: Rotating shaft 30: Pinch spring 32: First bracket 34: Second bracket 36: Pinch cam 38: Rotation center axis 40: Cam shaft 42: Head cam 44: Press-contact plate 46: Press-contact spring 48: First bobbin 50: Second bobbin

Claims (7)

[Claims] 1. A print head that prints an image on printing paper in a fixed printing line unit, a feed roller that is driven to rotate by a motor, and a pinch roller that sandwiches and supports the printing paper together with the feed roller. By rotating the feed roller, a printing paper is moved relative to the print head in a direction orthogonal to a line extending direction of the printing line, and a two-dimensional image formed by a plurality of pixels is formed. The image printing apparatus for printing on the printing paper surface, wherein an amount of force for sandwiching the printing paper between the feed roller and the pinch roller is made variable. 2. The image printing apparatus according to claim 1, wherein the amount of force can be changed in each step of printing an image. 3. The image printing apparatus according to claim 2, wherein the image printing step includes a printing step of performing printing while moving the printing paper, and a paper feeding step of simply moving the printing paper without performing printing. Wherein the force has a different value between the printing step and the paper feeding step. 4. The image printing apparatus according to claim 1, wherein the amount of force is changed according to the material, thickness, and shape of the printing paper. 5. The image printing apparatus according to claim 1, wherein the pinch spring generates the force, a first bracket rotatably provided around a rotation center axis, and rotatable about the rotation center axis. And the first
An image printing apparatus, comprising: a second bracket for sandwiching the pinch spring together with a bracket; and a pinch cam for controlling a sandwich angle between the first and second brackets. 6. The image printing apparatus according to claim 5, wherein the pinch cam is provided on a cam shaft provided with a head cam for controlling a relative position between the print head and printing paper. Image printing device. 7. An image printing apparatus comprising: a printing head for printing an image on printing paper in a fixed printing line unit; a feed roller rotationally driven by a motor; and a pinch roller for sandwiching and supporting the printing paper together with the feed roller. A method for controlling an apparatus, comprising: rotating a feed roller relative to the print head in a direction perpendicular to a line extending direction of the print line by rotationally driving the feed roller; In printing the constituted two-dimensional image on the printing paper, (a) by the pinch roller and the feed roller,
(B) rotating the feed roller to move the printing paper to a predetermined printing start position, and (c) changing the power to a constant value Pa. (D) printing a single color image by the print head while moving the printing paper by the feed roller; (e) determining whether printing of all colors has been completed; and (f). If printing of all colors has not been completed, the amount of force is changed to another value Pb different from the above Pa, and the feed roller is rotated in the opposite direction to that during printing so that printing paper is moved to the printing start position. And (g) discharging printing paper by the feed roller when printing of all colors is completed.