JP2000198573A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actually feed a recording medium by a predetermined distance regardless of a thickness of the recording medium by controlling a feeding means to make a distance between a plurality of line segments drawn on the recording medium by a printing means, agree with the predetermined distance on the basis of the distance between the line segments. SOLUTION: In determining the pressing force on a feeding roller, the recording paper 30 is fed with the pressing force A of the feeding roller, and then a printing pattern 32a is drawn on a recording paper sheet 30 to measure a distance (a). Then the recording paper sheet 30 is fed with the pressing force B of the feeding roller, and then a printing pattern 32b is drawn on the recording paper 30 to measure a distance (b). Then the recording paper sheet 30 is fed with the pressure force C of the feeding roller, and a printing pattern 32c is drawn on the recording paper sheet 30 by a printing means to measure a distance (c). The pressure force (pressure force B in this case) capable of providing the distance (distance (b) in this case) closest to the predetermined distance is determined among the measured distances (a), (b) and (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for forming an image on a recording medium conveyed in a predetermined direction.

[0002]

2. Description of the Related Art As one of output devices of a computer or a workstation, an electrophotographic image forming apparatus for forming an image on a recording medium using a developer, and an ink jet for forming an image by discharging ink onto the recording medium. 2. Description of the Related Art A conventional image forming apparatus is known.

Among these image forming apparatuses, for example, an ink jet type image forming apparatus includes a print head having a plurality of ink discharge ports for discharging ink, a carriage on which the print head is mounted and which reciprocates in a predetermined scanning direction. ,
A direction perpendicular to this scanning direction (the recording paper transport direction,
Recording paper (an example of a recording medium) on the sub-scanning direction)
And a plurality of pairs of conveying rollers for intermittently conveying the sheet.

When an image is formed on a recording sheet, the recording sheet being conveyed by a plurality of pairs of conveying rollers is temporarily stopped,
While the carriage is reciprocating in the above-described predetermined direction, the ink for one band is ejected from the ink ejection port according to the control of the print head to the portion of the recording paper located in the image forming area where the image is formed. Is formed (printed), and thereafter, the operation of conveying the recording paper by a predetermined length and forming an image for the next band on the surface newly located in the image forming area is repeated.

When an image is formed on a recording sheet as described above,
The operation of conveying the recording paper by a predetermined length to form an image is repeated. However, the recording paper cannot be conveyed by the above-mentioned predetermined length due to abrasion of the conveyance rollers for conveying the recording paper, a difference in the thickness of the recording paper, slippage due to generated paper dust, and the like. The transport amount may become uneven and unstable. If the transport amount of the recording paper becomes uneven, the recording paper cannot be transported exactly by the width of one band (print width). As a result, unevenness occurs in an area in the sub-scanning direction of the print area, or a gap occurs between adjacent print areas. When this gap occurs, for example, when a solid black is printed (ink is ejected to the entire surface), no printing is performed in the gap, and this portion becomes a white line, and the printing quality is extremely deteriorated. In order to prevent this deterioration in print quality,
2. Description of the Related Art There is known a technique for controlling a rotation speed and the like of a conveying roller according to a thickness of a recording sheet.

[0006]

However, this technique has a problem that if the slippage caused by paper dust causes unevenness in the recording paper conveyance amount, the unevenness cannot be eliminated. In order to eliminate the unevenness of the recording paper conveyance amount due to the slip, it is necessary to improve a mechanical structure that does not adversely affect the conveyance of the recording paper even if paper dust is generated.
However, even with such an improvement, the recording paper transport amount may be uneven due to the difference in the thickness of the recording paper.

The present invention has been made in view of the above circumstances, and provides an image forming apparatus that can convey a recording sheet a predetermined distance even if there is a difference in the thickness of a recording medium or paper dust is generated. With the goal.

[0008]

According to an aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording medium conveyed in a predetermined direction. Conveying means for conveying the medium; (2) printing means for drawing on a recording medium a plurality of line segments extending in an intersecting direction intersecting the predetermined direction and arranged in parallel with the intersecting direction; and (3) the printing means. Measuring means for measuring the distance between a plurality of line segments drawn on the recording medium by (4)
And control means for controlling the transport means such that the distance becomes a predetermined distance based on the distance measured by the measurement means.

Here, (5) the transporting means has a pair of rollers for transporting the recording medium in the predetermined direction while nipping the recording medium. May be used to control the pressing force for holding the sheet.

(7) The control means may be capable of continuously controlling the pressing force. further,
(8) The printing means draws a plurality of line segments extending in a direction orthogonal to the predetermined direction on a recording medium within a predetermined time, and (9) the measuring means records the line segments within the predetermined time. Of the plurality of line segments drawn on the medium, the distance between the first line segment and the last line segment may be measured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of a color plotter (hereinafter, referred to as a plotter) which is an example of an image forming apparatus using an ink jet system.

The plotter 1 is fixed to an upper part of a stand 2 with casters 2a. The plotter 1 includes an operation unit 3 for operating the plotter 1. Various switches and the like provided on the operation unit 3 indicate a paper type, online / offline, commands, and the like. The recording paper inserted into the recording paper insertion slot 4 from the direction of arrow A is conveyed into the plotter 1 based on an instruction from the operation unit 3, where a color image is printed and discharged.

Referring to FIG. 2, the recording paper transport path and the printing (image forming) process will be described.

FIG. 2 is a perspective view showing a path from insertion to ejection of the recording sheet by cutting out the plotter of FIG.

The plotter 1 can print on a sheet of recording paper inserted from the recording paper insertion slot 4 and on a recording paper (roll paper 6) wound in a roll. Here, the transport path of the sheet-shaped recording paper inserted from the recording paper insertion slot 4 will be described, but the transport path of the roll paper 6 is also the same.

The recording paper (for example, large-sized cut paper) is arranged on the cover 7 of the roll paper 6 and inserted into the recording paper insertion slot 4 from the direction of arrow A. The inserted recording paper passes between the cover 7 and the upper guide 8 and is rotatably fixed to the paper transport roller 10a and the upper transport roller support plate 11 rotatably fixed to the lower transport roller support plate 9. The paper is transported above the printing plate 14 while being sandwiched between both the paper transport rollers 10 b and the drive roller 12. The recording paper that has passed above the printing plate 14 is thereafter discharged by being sandwiched between a discharge roller 20 and a spur 22 located above the discharge roller 20. The spur 22 is a spur plate 21
It is fixed rotatably.

The plotter 1 is provided with a carriage 16 which reciprocates in a direction indicated by an arrow B (an example of an intersecting direction in the present invention and an orthogonal direction). The carriage 16 includes a head holder 18. The head holder 18 includes a plurality of print heads (printing means according to the present invention) containing respective color inks (for example, cyan, magenta, yellow, and black inks). 19) is mounted. The carriage 16 is fixed to a belt 17 hung on a drive motor (not shown), and the belt 17 reciprocates in the direction of arrow B by forward and reverse rotation of the drive motor. When the belt 17 reciprocates in the arrow B direction, the carriage 16 is also guided by the guide rail 18 and reciprocates in the arrow B direction.

The recording paper inserted from the recording paper insertion slot 4 is intermittently conveyed in the direction of arrow A.
0b or in the direction of arrow A ′ while being nipped by the drive roller 12 (an example of a predetermined direction according to the present invention;
In the opposite direction). To form an image on the recording paper, the recording paper is temporarily stopped, and while the carriage 16 is reciprocated in the direction of arrow B, the print head 19 is placed on a portion of the recording paper located in the image forming area.
The ink is ejected based on the image information input to the printer. Thereafter, the recording paper is conveyed by a predetermined length, and an image for the next band is formed on a new portion located in the image forming area. This operation is repeated over the entire length of the recording paper. This allows
A color image is formed on the recording paper. The recording paper on which the color image is formed is discharged along the discharge guide 23 while being sandwiched between the discharge roller 20 and the spur 22.

Referring to FIG. 3, an experiment on which the present invention is based will be described.

FIG. 3 is a graph showing the results of an experiment on which the present invention is based.

In this experiment, three types of recording paper A,
Using B and C, the relationship between the pressing force of a pair of conveying rollers for conveying these three types of recording papers A, B and C and the paper thickness was examined. The pair of transport rollers here will be described later with reference to FIGS. The thickness of the recording paper A is 0.09 mm
The thickness of the recording paper B is 0.15 mm, and the thickness of the recording paper C is 0.06 mm. The vertical axis of the graph in FIG. 3 represents the vertical magnification, and A, B, and C in the graph represent the recording papers A, B, and C described above. The vertical magnification is a percentage of the difference between the actual distance that the recording paper has been conveyed and a predetermined distance. Therefore, the closer the vertical magnification is to 0, the closer the actual distance the recording paper has been conveyed to the predetermined distance. The vertical magnification shown on the left side of each of the recording papers A, B, and C is obtained when the pressure of the pair of transport rollers is an initial set value, and the vertical magnification shown on the right is the pressure of the pair of transport rollers. Is 1.5 times the initial set value.

In the recording paper A, the actual transport distance tends to be shorter than a predetermined distance due to slippage caused by paper dust attached to the surface. With such recording paper,
When the sliding pressure was reduced by increasing the pressing force of the transport roller, the longitudinal magnification was reduced, and the actual transport distance approached a predetermined distance.

The recording paper B has a relatively large thickness, and the actual transport distance of such a recording paper tends to be longer than a predetermined distance. In this case, when the pressing force of the transport roller was increased, the longitudinal magnification was reduced, and the actual transport distance approached a predetermined distance.

The recording paper C has a relatively small thickness, and the actual transport distance of such a recording paper tends to be shorter than a predetermined distance. In this case, when the pressing force of the transport roller was increased, the longitudinal magnification was increased, and the actual transport distance was away from a predetermined distance.

As a result of examination based on the above experimental results,
Depending on the paper thickness and surface condition (presence or amount of paper dust) of the recording paper,
It became clear that there was a difference in the actual distance that the recording paper was transported. In order to make the actual transport distance a predetermined distance, it has been found that it is necessary to change the pressure of the transport roller that transports the recording paper while nipping it, and the present invention has been accomplished. It is considered that a pressure roller that can change the pressing force in a wider range can correspond to various types of recording paper.

With reference to FIGS. 4 to 6, a description will be given of a transport roller capable of changing the pressing force.

FIG. 4 is an explanatory diagram showing a print pattern printed to make the actual distance that the recording paper has been conveyed approach a predetermined distance. FIG. 5 is a plan view schematically showing a transport roller capable of changing the pressing force, and FIG.
FIG.

In order to make the actual distance that the recording paper has been conveyed approach a predetermined distance, as shown in FIG. 4, a print pattern 3 is printed on the recording paper 30 before forming an image.
Form 2 The print pattern 32 is formed in an orthogonal direction (arrow B) perpendicular to the transport direction of the recording paper 30 (arrow A ′ direction).
Direction) and includes a plurality of line segments 34a to 34g arranged in parallel to the orthogonal direction. This print pattern 32
It is drawn within a predetermined time by the print head 19 (see FIG. 2).

Further, as shown in FIG.
Is mounted with an optical sensor 36 that reads a plurality of line segments 34a to 34g. The optical sensor 36 can read, for example, only the first drawn line segment 34a and the last drawn line segment 34g among the plurality of line segments 34a to 34g. The optical sensor 36 has two line segments 34a,
The distance X between the two line segments 34a and 34g is calculated by an arithmetic unit (not shown) based on the timing at which the distance X is read, whereby the distance X at which the distance X is measured is calculated as
This is the actual distance that the recording paper 30 has been transported. The arithmetic unit and the optical sensor 36 constitute an example of a measuring unit according to the present invention. The optical sensor 36 may be mounted on another component different from the carriage 16, or the optical sensor 36
May be independently arranged.

The distance X measured as described above is sent to a controller (one example of control means according to the present invention, not shown). This controller controls a motor 42 incorporated in the transport roller unit 40 to rotate or stop by a predetermined number of revolutions. Transport roller unit 4
0 indicates that the recording paper is conveyed by a predetermined distance based on the measured distance X.

The transport roller unit 40 is provided with about four pairs of transport rollers 44 for transporting the recording paper in a direction perpendicular to the paper surface of FIG. 5 (the direction of arrow A ′ in FIG. 6). The pair of transport rollers 44 includes a sub-scanning roller 48 and a pressure roller 46. The sub-scanning roller 48 is fixed to a rotating shaft 50 connected to a pressure transport motor (not shown), and rotates with the rotation of the rotating shaft 50. The rotating shaft 50 is rotatably fixed to a main body side plate 52 of the plotter 1 (see FIG. 2) via a bearing 54. The pressure roller 46 is rotatably held by a pressure roller holding member 56 formed in parallel with the rotation shaft 50.

Of the pressing roller holding members 56, the pressing rollers 4
One end of a coil spring 58 is fixed to each of the opposite ends opposite to the portion where 6 is held. The other end of the coil spring 58 is fixed to the bottom of the “U” -shaped push-up member 60. The height of the push-up member 60 (the depth of the concave portion in which the coil spring 58 is accommodated) is longer than the length of the coil spring 58 when no load is applied. Therefore, as described below,
When the pressure roller holding member 56 is pushed upward (in the direction of arrow E) by the lifting member 60, the pressure roller 46 is separated from the sub-scanning roller 48.

The lifting member 60 is fixed to a movable plate 62 extending in parallel with the rotating shaft 50. The movable plate 62 has an arrow E
It is movably fixed to the main body side plate 52 in the direction and the opposite direction (vertical direction). A rack 64 extending in the up-down direction is arranged at the center of the movable plate 62 in the longitudinal direction. A pinion 66 meshes with the rack 64, and the pinion 66 is fixed to a rotation shaft of the motor 42. The motor 42 is fixed to the movable plate 62. Therefore, the pinion 66 depends on the rotation speed of the motor 42.
Rotates, and the movable plate 62 moves in the vertical direction with this rotation.

When the movable plate 62 moves upward (in the direction of arrow E), the tensile force of the coil spring 58 is relaxed, so that the force with which the pressing roller 46 is pressed against the sub-scanning roller 48 is reduced, and the pressing force of the transport roller 44 is reduced. I do. On the other hand, when the movable plate 62 moves downward (the direction opposite to the direction of the arrow E), the tensile force of the coil spring 58 increases, so that the force with which the pressing roller 46 is pressed against the sub-scanning roller 48 increases, and Pressing force increases. A motor reference position center 68 for determining a reference position of the motor 42 is fixed below the movable plate 62. An “L” -shaped reference positioning member 70 extending downward is fixed to the center of the movable plate 62 in the longitudinal direction. The position where the reference positioning member 70 turns on the motor reference position center 68 is the reference position of the motor 42. If the movable plate 62 can be moved continuously, the pressing force of the transport roller 44 can be changed continuously.

An example of a procedure for determining the pressing force of the transport roller 44 will be described with reference to FIGS.

FIG. 7 is an explanatory diagram showing a procedure for determining the pressing force of the transport roller, and FIG. 8 is a flowchart showing a procedure for determining the pressing force of the transport roller.

To determine the pressing force of the transport roller 44 (see FIG. 5), first, as shown in FIG. The print pattern 32a is drawn on the paper 30, and the distance a is measured. Next, the recording paper 30 is conveyed with the pressing force of the conveying roller 44 set to the pressing force B, a print pattern 32b is drawn on the recording paper 30, and the distance b is measured. Next, the recording paper 30 is conveyed with the pressing force of the conveying roller 44 set to the pressing force C, the print pattern 32c is drawn on the recording paper 30, and the distance c is measured. The distance closest to the predetermined distance among the distances a, b, and c thus measured (here, the distance b)
Is set to the pressing force at this time (pressing force B in this case).

A general example of the above procedure will be described with reference to a flowchart.

In determining the pressing force of the transport roller 44 (see FIG. 5), first, as shown in FIG. 8, the actual distance that the recording paper has been transported by changing the pressing force of the transport roller 44 is measured. The number of times (Θ) is determined (S801). Next, the recording paper 30 is transported with the pressing force of the transport roller 44 set to F (i) (S802), and a print pattern for n bands is drawn on the print area E (i) of the recording paper 30 (S803). In order to measure the actual distance that the recording paper has been conveyed, the distance (interval X (i)) of this print pattern is measured (S804). The measured value X (i) is read (S805), and it is determined whether or not the distance has been measured a predetermined number of times (Θ) (S80).
6). If the measurement has not been performed a predetermined number of times (Θ),
Returning to S802 (S807), the measurement is repeated while changing the pressing force of the transport roller 44. When it is determined that the distance has been measured a predetermined number of times (Θ), the measured value X (i)
The pressing force at the time when it is closest to a predetermined distance is F
(I) is set (S808). Thus, even if the thickness of the recording paper changes or paper dust is generated, the actual distance over which the recording paper is conveyed can be made substantially the same as the predetermined distance.

Referring to FIG. 9 and FIG.
Another example of the procedure for determining the pressing force will be described.

FIG. 9 is an explanatory diagram showing a procedure for determining the pressing force of the transport roller, and FIG. 10 is a flowchart showing a procedure for determining the pressing force of the transport roller.

In order to determine the pressing force of the transport roller 44 (see FIG. 5), first, as shown in FIG. The print pattern 32a is drawn on the paper 30, and the distance a is measured. Next, the recording paper 30 is conveyed with the pressing force of the conveying roller 44 set to the pressing force B, a print pattern 32b is drawn on the recording paper 30, and the distance b is measured. Next, the recording paper 30 is conveyed with the pressing force of the conveying roller 44 set to the pressing force C, the print pattern 32c is drawn on the recording paper 30, and the distance c is measured. The distance closest to the predetermined distance among the distances a, b, and c thus measured (here, the distance b)
The above-mentioned measurement is repeated again with a plurality of pressing forces between the pressing force B of the second distance and the pressing force C of the second closest distance (here, the distance c). In this way, the pressure is set to the pressure at the distance closest to the predetermined distance.

A general example of the above procedure will be described with reference to a flowchart.

In determining the pressing force of the conveying roller 44 (see FIG. 5), first, as shown in FIG. 10, the actual distance of the recording paper being conveyed by changing the pressing force of the conveying roller 44 is measured. The number of times (Θ) is determined (S101). Next, the recording paper 30 is transported with the pressing force of the transport roller 44 set to F (i) (S102), and n is added to the print area E (i) of the recording paper 30.
A print pattern for the band is drawn (S103). In order to measure the actual distance that the recording paper has been conveyed, the distance (interval X (i)) of this print pattern is measured (S104).
The measured value X (i) is read (S105), and it is determined whether or not the distance has been measured a predetermined number of times (Θ) (S10).
6). If the measurement has not been performed a predetermined number of times (Θ),
Returning to S802 (S107), the measurement is repeated while changing the pressing force of the transport roller 44. When it is determined that the distance has been measured a predetermined number of times (Θ), the measured value X (i)
A plurality of (m) pressures between the pressure when the distance is closest to the predetermined distance and the pressure when the distance is second is set (S108). Thereafter, it is determined whether or not the distance of the print pattern has been measured at all the set pressures (S109). If it is determined that the distance of the print pattern has not been measured for all of the plurality of pressing forces, the process proceeds to S101.
And the operation for distance measurement is repeated (S11).
0). When it is determined that the distance of the print pattern has been measured with all of the plurality of pressing forces, the pressing force when the distance closest to the predetermined distance is determined from the measured values X (i) by F
(I) is set (S111). Thus, even if the thickness of the recording paper changes or paper dust is generated, the actual distance over which the recording paper is conveyed can be more reliably made substantially the same as the predetermined distance.

[0046]

As described above, in the image forming apparatus of the present invention, the distance between a plurality of lines drawn by the printing means is measured by the measuring means. The distance measured in this way is the actual distance that the recording medium has been transported. The transporting means is controlled by the control means so that the actual distance becomes a predetermined distance. As a result, even if there is a difference in the thickness of the recording medium or paper dust is generated, the distance over which the recording medium is actually conveyed can be set to a predetermined distance.

Here, the transport means has a pair of rollers for transporting the recording medium in the predetermined direction while nipping the recording medium, and the control means controls the pressing force for nipping the recording medium by the pair of rollers. In the case of controlling, by controlling the pressing force of the pair of rollers, the distance in which the recording medium is actually conveyed can be set to a predetermined distance, so that a simple configuration is required.

In the case where the control means can continuously control the pressing force, the control means can control the pressing force continuously, so that the conveyance amount of the recording medium can be more finely controlled.

Further, the printing means draws a plurality of line segments extending in a direction orthogonal to the predetermined direction on a recording medium within a predetermined time, and the measuring means prints the recording medium within the predetermined time. In the case of measuring the distance between the first drawn line segment and the last drawn line segment among multiple line segments drawn in, draw a line segment extending in the orthogonal direction and draw the line segment Therefore, the distance in the transport direction (predetermined direction) of the recording medium is measured. Therefore, the distance by which the recording medium is actually conveyed can be more accurately set to the predetermined distance. Further, since the distance between the first and last line segments drawn within a predetermined time is measured, it is possible to quickly and accurately control the distance over which the recording medium is actually conveyed to a predetermined distance.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a plotter that is an example of an image forming apparatus using an inkjet method.

FIG. 2 is a perspective view showing a path from insertion to ejection of a recording sheet by cutting out the plotter of FIG. 1;

FIG. 3 is a graph showing the results of an experiment on which the present invention is based.

FIG. 4 is an explanatory diagram showing a print pattern printed to make the actual distance that the recording paper has been conveyed approach a predetermined distance.

FIG. 5 is a plan view schematically showing a transport roller capable of changing a pressing force.

FIG. 6 is a view as seen from the direction of the arrow DD in FIG. 5;

FIG. 7 is an explanatory diagram illustrating an example of a procedure for determining a pressing force of a transport roller.

FIG. 8 is a flowchart illustrating an example of a procedure for determining a pressing force of a transport roller.

FIG. 9 is an explanatory diagram showing another example of a procedure for determining a pressing force of a transport roller.

FIG. 10 is a flowchart illustrating another example of a procedure for determining a pressing force of a transport roller.

[Explanation of symbols]

 Reference Signs List 1 plotter 19 print head 30 recording paper 32 print pattern 34a to 34g line segment 36 optical sensor 40 transport roller unit 44 pair of transport rollers 46 pressure roller 48 sub-scanning roller 56 pressure roller holding member 58 coil spring 60 push-up member 62 movable Plate 64 Rack 66 Pinion

Claims (4)

[Claims] 1. An image forming apparatus for forming an image on a recording medium conveyed in a predetermined direction, comprising: conveying means for conveying the recording medium in the predetermined direction; Printing means for drawing a plurality of line segments arranged in parallel on a recording medium, measuring means for measuring the distance between the plurality of line segments drawn on the recording medium by the printing means, and measurement by the measuring means. Based on the distance, this distance
An image forming apparatus comprising: a control unit configured to control the transport unit so as to be a predetermined distance. 2. The method according to claim 1, wherein the conveying unit includes a pair of rollers that convey the recording medium in the predetermined direction while nipping the recording medium, and the control unit controls a pressing force of the pair of rollers nipping the recording medium. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein the control unit is capable of continuously controlling the pressing force. 4. The printing means draws a plurality of line segments extending in a direction orthogonal to the predetermined direction on a recording medium within a predetermined time, and the measuring means prints the recording medium within the predetermined time. The distance between the first drawn line segment and the last drawn line segment among a plurality of line segments drawn in (1) is measured. Image forming apparatus.