JP2005247463A - Paper feed control method for image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a paper conveying route without causing large size of an image formation device and to perform paper feed without generating printing failure even when paper is continuously fed. <P>SOLUTION: Before a leading end of paper arrives at an image formation recording part 22, rotation/non-rotation control of a separation roller 17 is performed such that a curved part (loop) of the paper formed between the separation roller 17 and a pair of resist rollers 21 becomes zero. Thereby, the paper conveying rout is shortened without causing large size of the image formation device and even when the paper is continuously fed, the paper feed can be performed without generating printing failure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to feeding of printing paper or the like in an image forming apparatus such as a laser printer, an ink jet printer, or a facsimile.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer, a sheet of paper stacked on a paper tray, a paper feed cassette, a paper stacker, or the like is picked up one by one from the top or bottom one by one and fed to an image recording unit A device is provided. This is disclosed in, for example, Japanese Patent Application Laid-Open No. 07-69464 and Japanese Patent Application Laid-Open No. 08-245006.

  Hereinafter, a sheet feeding device and a control method thereof in a conventional image forming apparatus, which is a tandem color laser printer as a representative example, will be described.

  FIG. 5 is a functional block diagram showing the paper feed control unit of the image forming apparatus according to the embodiment of the present invention.

  In FIG. 5, the paper feeding unit 100 of the conventional image forming apparatus feeds paper in contact with the top of the paper stacking plate 15 that stacks and stores the paper P in the paper feeding cassette 13 and the stacked paper P. The pickup roller 16 and the pickup roller 16 for picking up the uppermost sheet from the sheet P picked up by the pickup roller 16 cooperate with the separation roller 17 and the separation roller 17 for feeding only the uppermost sheet to the image recording unit. Is provided with a separation pad 18, a pickup roller 16, and a drive motor 19 that rotationally drives the separation roller 17 through the separation pad 18.

  A one-way clutch 17a is incorporated in the separation roller 17, and is configured to rotate only in one direction (the direction in which the paper P is fed) and to intermittently transmit the drive from the drive motor 19. On the downstream side of the separation roller 17 in the sheet conveyance direction, a registration sensor 20 that detects the leading edge of the sheet P and a registration roller pair 21 that conveys the sheet P to the image recording unit in synchronization with the image forming operation are provided. On the further downstream side of the registration roller pair 21, a second transfer unit 22 is provided as an image recording unit for transferring an image onto the paper P. The paper P is transferred between the second transfer unit 22 and the second transfer roller 12. By sandwiching, the color toner image formed on the intermediate transfer belt 7 is transferred onto the paper P and the image is recorded. The paper P to which the image has been transferred is fixed at the second transfer unit 22 and is carried out of the apparatus.

  Next, paper feed control in the paper feed unit 100 will be described with reference to FIGS. 6 and 7 as well.

  FIG. 6 is a timing chart showing feed control on the first sheet of the conventional image forming apparatus, and FIG. 7 is also a timing chart of the sheet P2.

In FIG. 6, the feeding of the first sheet is started at the start of the printing operation. Here, the sheet stacking plate 15 is set so that the sheet feeding operation of one sheet is completed in one rotation cycle of a stacking plate cam (not shown), and moves up and down in accordance with one rotation cycle of the stacking plate cam. When the sheet stacking plate 15 rises and the uppermost sheet P1 of the stacked sheets comes into contact with the pickup roller 16, the drive motor 19 starts to drive, and at the same time, the pickup roller 16 rotates. The driving force of the drive motor 19 is transmitted to the separation roller 17 via the pickup roller 19 and the one-way clutch 17a, and the separation roller 17 also starts to rotate. Along with this, only the uppermost sheet of the stacked sheets P1 is separated by the separation roller 17 and fed into the image forming apparatus main body. When the leading edge of the fed paper P1 is detected by the registration sensor 20, the drive motor 19 stops driving. As a result, drive transmission to the separation roller 17 is interrupted. Since the separation roller 17 is driven and transmitted via the one-way clutch 17a, the separation roller 17 can rotate around the paper P1 when it is conveyed.

  The drive motor 19 resumes driving after the elapse of a predetermined time (T3) from the start of the sheet feeding operation of the stacking plate cam, and rotates the separation roller 17. The time T3 is set to a time during which a curve (loop) can be formed between the separation roller 17 and the registration roller pair 21 to eliminate problems such as skew associated with the conveyance of the paper P1. The rotation of the separation roller 17 causes a load on the sheet P1 to be conveyed, but the conveyance of the sheet P1 is restricted between the separation roller 17 and the pair of registration rollers 21 because the leading edge of the sheet is restricted by the pair of registration rollers 21. A curved portion (loop) is formed, and the skew of the paper P1 is corrected.

  Next, the registration roller pair 21 starts to rotate. Further, as the stacking plate 15 is lowered, the separation roller 17 stops driving. Along with this, the paper P1 is conveyed only by the registration roller pair 21 (the separation roller 17 is in a rotating state), and the curved portion (loop) of the paper P1 formed between the separation roller 17 and the registration roller pair 21 is gradually eliminated. To do. When the curvature becomes zero, a back tension due to a frictional force between the sheet P1 and the separation pad 18 acts on the sheet P1. Due to the back tension action, the behavior of the paper P1 becomes unstable (the transport is temporarily stopped / slips), but the first paper feed has a sufficient time from the start of the paper feed and the transport distance. The behavioral instability is eliminated before the leading edge of the paper P1 reaches the second transfer portion 22.

The second and subsequent sheets are fed in the same steps as the first sheet.
Japanese Patent Application Laid-Open No. 07-69464 Japanese Patent Laid-Open No. 08-245006

  However, for the second and subsequent sheets of paper P2, the leading edge of the sheet is already positioned between or near the separation roller 17 and the separation pad 18 by the first sheet feeding operation. Therefore, as shown in FIG. 7, the leading edge of the sheet P <b> 2 arrives in a shorter time than the leading edge of the first sheet reaches the registration sensor 20. For this reason, the time during which the separation roller 17 is stopped becomes longer than that of the first sheet. That is, after the registration roller pair 21 starts to rotate, the separation roller 17 is driven to rotate for a longer time from the first sheet until one cycle of the stacking plate cam is completed. For this reason, the leading edge of the paper P <b> 2 reaches the second transfer unit 22 at a stage where the curved portion (loop) is not eliminated.

  Thereafter, when the curved portion becomes zero, the back tension due to the frictional force with the separation pad 18 acts on the paper P2, and the behavior of the paper P2 becomes unstable. For this reason, the conveyance of the paper P2 is temporarily affected, and problems occur in the image recording and the toner image transfer in the second transfer unit 22. Specifically, white streaks occur in the image. It was also a cause of poor printing.

  Such a problem can be solved to some extent by increasing the interval between the second transfer portion 22 and the registration roller pair 21, but increasing the interval between the second transfer portion 22 and the registration roller pair 21. This leads to an increase in the size of the image forming apparatus and is contrary to the market needs for downsizing the image forming apparatus.

Therefore, the present invention shortens the paper conveyance path without causing an increase in the size of the image forming apparatus,
It is an object of the present invention to provide a technique capable of feeding paper without causing defective printing even when feeding continuously.

  In order to solve this problem, the paper feed control method of the image forming apparatus according to the present invention detects the leading edge of the paper fed by the paper feeding means and separated and fed one by one by the paper separating means. And a paper feeding control method in an image forming apparatus that synchronizes the paper transport and the printing operation of the image recording unit by temporarily interrupting the paper transport by the registration means and driving the paper separating means. The paper feeding operation is started, and then the driving of the paper separating means is stopped when the paper leading edge detecting means detects the leading edge of the paper, and then the paper separating means is turned on after the first predetermined time has elapsed from the start of driving of the paper separating means. Then, the registration unit is driven with the leading edge of the sheet held therebetween, and then the sheet separation unit is stopped again after a second predetermined time has elapsed since the registration unit was driven. The first predetermined time is set to a time during which a sheet can be curved from the start of driving of the paper separating unit to the start of driving of the registration unit, and the second predetermined time is from the driving of the registration unit. Before the leading edge of the paper reaches the image recording section, the time is set so that the curve of the formed paper can be eliminated.

  According to the present invention, a special distinction is made in the sheet feeding control for the first sheet and the second and subsequent sheets even in the case of continuous sheet feeding while shortening the sheet conveyance path without causing an increase in the size of the image forming apparatus. There is an effective effect that paper can be fed while ensuring good print quality without performing separate control and without causing poor printing.

  In addition, the curving can be more reliably eliminated by setting the driving speed for driving the sheet separating unit again and again to be lower than the driving speed of the registration unit.

  In addition, the unstable behavior of the sheet is eliminated before the leading edge of the second and subsequent sheets reaches the image recording unit.

  According to the first aspect of the present invention, the leading end of the sheet fed by the sheet feeding unit and separated and fed one by one by the sheet separating unit is detected by the sheet leading end detection unit, and the sheet is detected by the registration unit. Is a paper feed control method in an image forming apparatus that temporarily interrupts the transport of the paper and synchronizes the paper transport and the printing operation of the image recording unit, and starts the paper feed operation by driving the paper separating means, Next, when the paper leading edge detecting means detects the paper leading edge, the driving of the paper separating means is stopped, and then the paper separating means is driven again after a first predetermined time from the start of driving of the paper separating means, Next, the registration unit is driven with the leading end of the sheet held therebetween, and then the sheet separation unit is stopped again after a second predetermined time has elapsed since the registration unit was driven. The first predetermined time is set to a time during which a curve can be formed on the sheet from the start of driving of the sheet separating unit to the start of driving of the registration unit, and the second predetermined time is The sheet feeding control method of the image forming apparatus is set to a time during which the curvature of the formed paper can be eliminated before the leading edge of the paper reaches the image recording unit from the driving of the registration means. Since the time from the start of driving to the stop of driving of the sheet separating means is set to a time that can eliminate the curvature formed before the leading edge of the sheet reaches the image recording section, the leading edge of the second and subsequent sheets Has the effect of eliminating the unstable behavior of the paper before it reaches the image recording section.

Hereinafter, the best mode for carrying out the present invention will be described more specifically with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, process cartridges 2, 3, 4, and 4 for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) in the main body of the image forming apparatus 1. 5 is provided, and exposure units 6a, 6b, 6c, and 6d are provided corresponding to the process cartridges 2 to 5, respectively. The process cartridges 2 to 5 are supplied from photosensitive drums (photosensitive members) 2a, 3a, 4a, and 5a that form electrostatic latent images on the peripheral surfaces thereof by irradiation with laser beams from the exposure units 6a to 6d, and toner tanks. The developing roller (developing means) 2b, 3b, 4b, 5b and the surfaces of the photosensitive drums 2a to 5a are electrostatically attached to the photosensitive drums 2a to 5a to visualize the electrostatic latent images as toner images. Prior to the formation of the latent image, charging rollers 2c to 5c arranged in contact with the surfaces of the photosensitive drums 2a to 5a are provided in order to be charged to a uniform potential.

  Below the process cartridges 2 to 5, an endless intermediate transfer belt (intermediate transfer belt) on which the color toner images visualized on the photosensitive drums 2a, 3a, 4a, and 5a are superimposed and transferred to form a color toner image. A transfer member 7 is disposed so as to be able to travel in the direction of the arrow. In the intermediate transfer belt 7, a driving roller 8, a tension roller 9, four first transfer rollers 10a, 10b, 10c, 10d, and a driven roller 11 are arranged in a loop.

  A paper feed cassette 13 that stores paper (recording medium) P is provided at the lower part of the apparatus. Then, the paper P is sent out one by one from the paper feed cassette 13 to the paper transport path by the paper feeding means. Details of this will be described later.

  A second transfer roller 12 for transferring a color image on the intermediate transfer belt 7 onto the paper P by contacting the outer peripheral surface of the intermediate transfer belt 7 over a predetermined amount at the position of the driven roller 11 on the paper conveyance path, on the paper P A fixing device 14 for fixing the color image transferred to the paper P is disposed.

  In the image forming apparatus having such a configuration, yellow, magenta, cyan, and black toner images are attached to the surface of the intermediate transfer belt 7 by the photosensitive drums 2a to 5a of the process cartridges 2 to 5, thereby forming a color image. . The toner color image is transferred onto the paper P taken out from the paper feed cassette 13 by the nip force between the driven roller 11 and the second transfer roller 12. Then, the paper P is supplied to the fixing device 14 to fix the toner image, and then discharged.

  Next, a configuration from the paper feeding unit to the image recording unit will be described with reference to FIG. Here, FIG. 2 is a schematic diagram showing a paper feed unit of the image forming apparatus according to the embodiment of the present invention.

In FIG. 2, the paper feeding unit is picked up by a paper stacking plate 15 for stacking and storing paper P, a pickup roller 16 for feeding paper in contact with the top of the stacked paper P, and a pickup roller 16. A separation roller 17 for feeding only the topmost sheet from the sheet P to the image recording unit, and a separation pad for feeding only the top sheet P to the image recording unit in cooperation with the separation roller 17 18, a pickup roller 16 and a drive motor 19 that rotationally drives the separation roller 17 through the pickup roller 16 are provided. A one-way clutch 17a is incorporated in the separation roller 17, and is configured to rotate only in one direction (the direction in which the paper P is fed) and to intermittently transmit the drive from the drive motor 19. Here, when the friction coefficient K1 between the paper P and the separation roller 17, the friction coefficient between the papers is K2, and the friction coefficient between the paper P and the separation pad 18 is K3, the relations of K1> K2 and K3> K2 are set. Has been.

  Further, on the downstream side of the separation roller 17 in the sheet conveyance direction, the registration sensor 20 that detects the leading edge of the sheet P and the image recording unit synchronize with the image forming situation so that an image is recorded at a predetermined position on the sheet P. Then, the conveyance of the paper P is temporarily stopped, and in synchronization with the image forming operation, a registration roller pair 21 that conveys the paper P to the image recording unit, and a second image recording unit that transfers the image onto the paper P. A transfer unit 22 is provided. The second transfer unit 22 records the image by transferring the color toner image formed on the intermediate transfer belt 7 onto the paper P by sandwiching the paper P between the second transfer roller 12 and the intermediate transfer belt 7. To do. The paper P to which the image has been transferred is fixed by a fixing unit (not shown) and is carried out of the apparatus.

  Next, the paper feed control of the image forming apparatus 1 according to the present embodiment will be described with reference to FIGS. FIG. 3 is a functional block diagram showing the paper feed control unit of the image forming apparatus according to the embodiment of the present invention. The sheet feed control unit of the image forming apparatus 1 includes a drive motor control unit 23 that controls the drive of the drive motor 19, a registration roller drive unit 24 that drives the registration roller pair 21, and a registration roller that controls the drive of the registration roller drive unit 24. The driving control unit 28 and the image forming control unit 26 that controls the image forming operation of the image forming apparatus 1 are configured.

  Next, the paper feed control flow will be described with reference to FIG. Note that the sheet feeding control flow for the first sheet is the same as that for the second and subsequent sheets, and there is no particular problem as in the conventional example. explain.

  FIG. 4 is a timing chart showing sheet feeding control of the image forming apparatus according to the embodiment of the present invention.

  The sheet stacking plate 15 is set so that the sheet feeding operation of one sheet is completed in one rotation cycle of a loading plate cam (not shown), and moves up and down in one rotation cycle of the stacking plate cam.

  As the first sheet is fed, the leading edge of the second and subsequent sheets is already positioned between or near the separation roller 17 and the separation pad 18, and as shown in FIG. The leading edge of the sheet reaches the registration sensor 20 in a shorter time than the leading edge of the first sheet reaches the registration sensor 20. For this reason, the time during which the separation roller 17 is stopped becomes longer than that of the first sheet.

  The sheet stacking plate 15 is raised, the uppermost sheet P2 of the stacked sheets is brought into contact with the pickup roller 16, and the drive motor 19 starts to be driven by the drive motor control unit 23, so that the pickup roller 16 is rotationally driven. . The driving force of the drive motor 19 is transmitted to the separation roller 17 via the pickup roller 19 and the one-way clutch 17a, and the separation roller 17 also starts to rotate. Only the uppermost stacked paper P2 is separated by the separation roller 17 and is fed into the image forming apparatus 1 main body.

  When the leading edge of the fed paper P <b> 2 is detected by the registration sensor 20, the drive motor control unit 23 stops driving the drive motor 19. As a result, drive transmission to the separation roller 17 is interrupted. Since the separation roller 17 is driven and transmitted via the one-way clutch 17a, the separation roller 17 can rotate around the paper P2 when it is conveyed.

  The drive motor control unit 23 resumes driving the drive motor 19 and rotates the separation roller 17 again after the first predetermined time (T1) has elapsed from the start of driving of the separation roller 17. The time T1 is set to a time during which a curve (loop) can be formed between the separation roller 17 and the registration roller pair 21 to eliminate problems such as skew associated with the conveyance of the paper P2.

  When the rotation of the separation roller 17 is resumed, the paper P2 is loaded in the direction of the registration roller pair 21, but the conveyance of the leading edge of the paper P2 is restricted by the registration roller pair 21, so the separation roller 17 and the registration roller 21 Between the pair of rollers 21, a curved portion (loop) is rapidly formed on the paper P2, and the skew of the paper P2 is corrected (FIG. 4 (1)).

  Next, in a state where the rotation of the separation roller 17 is continued, the image forming control unit 26 causes the registration roller drive control unit 28 to start driving the registration roller driving unit 24, and the registration roller pair 21 starts rotating. At this time, the separation roller 17 grips the rear portion of the sheet P2 and conveys it in the direction of the registration roller pair 21, and the registration roller pair 21 also grasps and conveys the front portion of the sheet P2, so that FIG. ), A curved portion (loop) is formed on the paper P2 at a slower speed than in the case of FIG. 4 (2).

  Here, after the second predetermined time (T2), the driving of the registration roller pair 21 is started, the leading end of the sheet is securely held between the registration roller pair 21, and the driving of the separation roller 17 is stopped again. Is set to a time that can secure a time that can be eliminated before the leading edge of the paper reaches the image recording portion.

  After the second predetermined time (T2) has elapsed since the registration roller pair 21 started to rotate, the driving of the separation roller 17 is stopped. At this time, the separation roller 17 is stopped (holding state or free state) while holding the rear part of the sheet P2, and the registration roller pair 21 continues to convey the sheet P2 from the front part. Therefore, the curvature of the paper P2 is quickly eliminated (FIG. 4 (3)).

  When the curved portion (loop) becomes zero (resolved), back tension is applied to the paper P2 due to the frictional force (pulling) between the registration roller pair 21 and the separation pad 18. Due to this action, the behavior of the paper P2 becomes unstable (the conveyance is temporarily stopped / slips), but the behavior of the paper P2 is unstable before the leading edge of the paper P2 reaches the second transfer portion 22. There is no problem because it is solved.

  After the curved portion (loop) of the paper P2 is eliminated, the drive motor control unit 23 starts driving the drive motor 19 again. As a result, the driving of the separation roller 17 starts again. At this time, since the separation roller 17 and the registration roller pair 21 are both driven, the sheet P2 is conveyed without resistance.

  In this case, the separation roller 17 may be driven at a lower speed than the driving speed of the registration roller pair 21. By doing so, the sheet P2 can be conveyed while maintaining an appropriate tension.

  One rotation cycle of the stacking plate cam is terminated and the sheet feeding operation for one sheet is completed.

  As described above, in this exemplary embodiment, the time (T2) from the start of rotation of the registration roller pair 21 to the stop of driving of the separation roller 17 is the curve formed before the leading edge of the sheet reaches the image recording unit. Since the time was set to be able to solve the problem, it was possible to secure good print quality without causing printing failure for the second and subsequent sheets.

  In the present embodiment, the form applied to an image forming apparatus that forms a color image has been described. However, the present invention is not limited to this, and image recording is also performed in an image forming apparatus that forms a monochrome image or an inkjet image forming apparatus. It is also possible to apply the paper feed control method of the present invention by making the part an ink jet recording part.

  The present invention reduces the paper conveyance path without increasing the size of the image forming apparatus, and makes a special distinction and separate control in the first and second and subsequent sheet feeding control even when continuously feeding sheets. This is an invention that enables paper feeding while ensuring good print quality without causing printing defects, and is suitable for the field of paper transport technology of image forming apparatuses.

1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a paper feeding unit of an image forming apparatus according to an embodiment of the present invention. 1 is a functional block diagram showing a paper feed control unit of an image forming apparatus according to an embodiment of the present invention. 1 is a timing chart showing sheet feeding control of an image forming apparatus according to an embodiment of the present invention. 1 is a functional block diagram showing a paper feed control unit of an image forming apparatus according to an embodiment of the present invention. Timing chart showing sheet feeding control for the first sheet of a conventional image forming apparatus Timing chart showing sheet feeding control for second and subsequent sheets of conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 7 Intermediate transfer belt 16 Pickup roller 17 Separation roller 18 Separation pad 19 Drive motor 20 Registration sensor 21 Registration roller pair 22 2nd transfer part

Claims (3)

The leading end of the sheet fed by the sheet feeding unit and separated and fed one by one by the sheet separating unit is detected by the sheet leading end detection unit, and the sheet conveyance is temporarily interrupted by the registration unit. A paper feed control method in an image forming apparatus that synchronizes with a printing operation of an image recording unit,
Driving the paper separating means to start the paper feeding operation,
Next, when the paper leading edge detecting means detects the paper leading edge, the driving of the paper separating means is stopped,
Next, after the first predetermined time has elapsed from the start of driving of the paper separating means, the paper separating means is driven again,
Next, the registration means is driven while holding the leading edge of the paper,
Next, after the second predetermined time has elapsed since the registration unit driving, the sheet separation unit is stopped again,
Next, the paper separating means is driven again,
The first predetermined time is set to a time during which a curve can be formed on a sheet from the start of driving of the sheet separating unit to the start of driving of the registration unit,
The second predetermined time is set to a time during which the curve of the formed paper can be eliminated before the leading edge of the paper reaches the image recording unit from the previous resist manual drive. The paper feed control method of the device. 2. The sheet feeding control method for an image forming apparatus according to claim 1, wherein a driving speed for driving the sheet separating unit again is lower than a driving speed of the registration unit. Paper feeding means for feeding in contact with the paper loaded and stored in the paper feeding unit, paper separation means for separating and feeding paper one by one from the paper fed by the paper feeding means, and separation feeding An image forming apparatus having a sheet leading edge detecting means for detecting the leading edge of the sheet and a registering means for temporarily interrupting the sheet conveyance to synchronize the sheet conveyance and the printing operation of the image recording section. And
Means for starting a paper feeding operation by driving the paper separating means;
Means for stopping driving of the paper separating means when the paper leading edge detecting means detects the paper leading edge;
Means for driving the paper separation means again after a first predetermined time has elapsed since the start of driving of the paper separation means;
Means for driving the registration means while pinching the leading edge of the paper;
Means for stopping the paper separation means again after a second predetermined time has elapsed since the registration means driving;
Means for driving the paper separating means again and again,
The first predetermined time is set to a time during which a curve can be formed on a sheet from the start of driving of the sheet separating unit to the start of driving of the registration unit.
The second predetermined time is set to a time during which the curve of the formed paper can be eliminated before the leading edge of the paper reaches the image recording unit from the previous resist manual drive. apparatus.

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