JP2009282415A - Image forming apparatus and image formation control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy in registration and to reduce the occurrence risk of wrinkling of a printing medium by allowing paper to be sufficiently fed into a registration roller even when correction of a loop in the printing medium is carried out. <P>SOLUTION: Control is carried out so that the whole paper P is fed out to an image process section 10 by rotational drive of a registration roller 43 and a transporting roller 42a. When such an action is carried out during time T3a, the driving of the registration roller 43 is continued and the transporting roller 42a is stopped. When this state is kept for a time period T3b, the whole paper P is fully fed to the image process section 10 by continuing driving of the registration roller 43 while also driving the transporting roller 42a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image formation control program.

In Patent Documents 1 and 2, attention is paid to printing medium bending (also referred to as “loop”) generated by the registration rollers and wrinkles of the printing medium caused by the loop, and techniques for improving these are disclosed. ing.
JP 11-139624 A JP 2004-323170 A

  In an electrophotographic image forming apparatus, a print medium such as a sheet is conveyed from a sheet feeding tray by a conveyance roller along a conveyance path, and skew correction is performed by abutting against a registration roller. The registration roller is driven to rotate according to the timing of image formation by the printer engine, and the print medium is sent to the printer engine.

  When the printing medium is abutted against the registration roller, the printing medium can be bent (loop), which may cause wrinkles or the like on the printing medium.

  Therefore, in order to solve such problems as printing medium loops and wrinkles, the printing medium is conveyed on the conveying path and abutted against the registration roller, and then the registration roller is rotated to crush the loop, and the registration roller starts rotating. After another short time has passed, another print roller on the upstream side of the print medium conveyance from the registration roller on the conveyance path is driven to rotate, whereby the print medium can be sent to the printer engine by driving the conveyance roller and the registration roller. Conceivable.

  However, there are cases where the print medium is intended to abut against the registration roller, but the print medium does not abut against the registration roller due to insufficient loops formed on the print medium. When the registration roller is driven to rotate, there is a problem that paper is not sufficiently inserted into the registration roller, which causes a problem such as a decrease in registration accuracy and generation of wrinkles on the printing medium.

  An object of the present invention is to improve the registration accuracy and reduce the risk of occurrence of wrinkles on the printing medium by ensuring that the paper is sufficiently inserted into the registration roller even if the loop of the printing medium is corrected. is there.

  The invention described in claim 1 is an image forming device that forms an image on a printing medium, a conveyance path that conveys the printing medium to the imaging device, and the imaging device provided on the conveyance path. A first conveying roller that sends the print medium to the image forming device in accordance with the timing of image formation in the image forming apparatus, and the printing medium that is provided on the upstream side of the movement of the printing medium from the first conveying roller on the conveying path. A second transport roller for transporting the medium in the transport path; a first drive means for rotationally driving the first transport roller; a second drive means for rotationally driving the second transport roller; By controlling the first driving means and the second driving means, the first conveying roller and the second conveying roller are driven to start the first conveying when the first time has elapsed. Maintaining the driving of the roller, the second conveying row Is stopped, and when the second time has passed, the operation of starting the driving of the first transport roller and the second transport roller is performed again, whereby the print medium is transferred to the imager. And an image forming apparatus provided with a control unit for sending out.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a time length storage unit that stores the length of the second time for each type of the print medium; Medium type specifying means for specifying the type, and the control means reads the second time length corresponding to the type specified by the medium type detection means from the time length storage means, and reads the read time. The control is performed for the second length of time.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, at least a section from the second transport roller to the second transport roller in the transport path transports the printing medium. The direction is vertical or acute with the vertical.

  According to a fourth aspect of the present invention, the printing is performed in accordance with a timing at which image forming is performed by the image forming device provided on a transport path for transporting the printing medium to the image forming device that performs image forming on the printing medium. A first driving means for rotationally driving a first conveying roller for sending the medium to the image forming device; and the printing medium provided upstream of the movement of the printing medium from the first conveying roller on the conveying path. By controlling the second drive means for rotationally driving the second transport roller that transports the first transport roller and the second transport roller by starting the driving of the first transport roller and the second transport roller. When the time elapses, the driving of the first conveying roller is maintained and the driving of the second conveying roller is stopped, and when the second time elapses, the first conveying roller and the second conveying roller are again driven. Start driving the transport roller By performing the operation, which is the print medium image formation control program readable on a computer to execute a control means for sending to said image forming unit to the computer.

  According to a fifth aspect of the present invention, in the image formation control program according to the fourth aspect, the control unit is configured to perform the second time according to the type specified by the medium type detection unit that specifies the type of the print medium. Is read from the time length storage means storing the length of the second time for each type of the print medium, and the control is performed with the length of the read second time.

  According to the first and fourth aspects of the invention, since the first transport roller and the second transport roller are driven first, the abutment on the first transport roller serving as the registration roller is insufficient. Even so, the printing medium is sufficiently loaded into the first conveying roller. Thereafter, the first transport roller is driven to stop the second transport roller, so that the print medium loop is corrected. Then, the first conveyance roller and the second conveyance roller can be driven again to send the print medium to the image forming device. Therefore, even if the loop of the print medium is corrected, the print medium is sufficiently inserted into the first conveyance roller, thereby improving the resist accuracy and reducing the risk of print medium wrinkles. Can do.

  According to the second and fifth aspects of the present invention, it corresponds to the difference in the degree of the loop formed when abutting against the first conveying roller according to the type of the print medium, and according to the type of the print medium. Since the length of the second time is variable, problems such as print medium loops and wrinkles can be appropriately solved according to the type of print medium.

  According to the third aspect of the present invention, the conveyance path from the second conveyance roller to the first conveyance roller is not horizontal, but forms an acute angle with the vertical or vertical direction. Since the contact with the first conveying roller tends to be insufficient due to the influence of gravity, it is possible to improve the resist accuracy and reduce the risk of occurrence of jams in the printing medium more effectively.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is an electrophotographic image forming apparatus capable of forming a color image by a so-called tandem method.

  The image forming apparatus 1 includes an image forming process unit 10 serving as an image forming device that forms a toner image on a printing medium such as paper by an electrophotographic method, and a control unit 50 that controls the overall operation of the image forming apparatus 1. I have. The image forming apparatus 1 includes, for example, an image processing unit 51 that performs predetermined image processing on image data of a print job received from an external personal computer (PC) 3, the image reading device 4, and the like, and a hard disk device (for example). And an external storage unit 52 realized by a hard disk drive).

  The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (hereinafter, also simply referred to as “image forming unit 11”) arranged in parallel at regular intervals. . The image forming units 11Y, 11M, 11C, and 11K respectively form yellow (Y), magenta (M), cyan (C), and black (K) toner images.

  Since the basic configurations of the image forming units 11Y, 11M, 11C, and 11K are the same, the image forming unit 11K will be described as a representative here. The image forming unit 11K includes a photosensitive drum 12 on which an electrostatic latent image is formed while rotating in the direction of arrow A, a charging roller 13 that uniformly charges the surface of the photosensitive drum 12 with a predetermined potential, and a charging roller 13 And an exposure device 14 that exposes the photosensitive drum 12 charged in accordance with the image data based on the image data. Further, the image forming unit 11K includes a developing device 15 that develops the electrostatic latent image formed on the photosensitive drum 12, and a drum cleaner 16 that cleans the surface of the photosensitive drum 12. Each of the four image forming units 11Y, 11M, 11C, and 11K is configured in substantially the same manner except for the toner stored in the developing unit 15, and each of the image forming units 11 is yellow (Y) and magenta (M). , Cyan (C) and black (K) toner images are formed.

  Further, the image forming process unit 10 intermediates the intermediate transfer belt 20 onto which the respective color toner images formed on the respective photosensitive drums 12 of the respective image forming units 11 are transferred, and the respective color toner images of the respective image forming units 11. Primary transfer rollers 21Y, 21M, 21C, and 21K (hereinafter simply referred to as “primary transfer roller 21”) that sequentially transfer (primary transfer) to the transfer belt 20 are provided. The yellow (Y), magenta (M), cyan (C), and black (K) toner images formed by the image forming units 11 are sequentially superimposed on the intermediate transfer belt 20 by the primary transfer rollers 21. Transcribed. The image forming process unit 10 is secondary-transferred with a secondary transfer roller 26 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 20 onto the paper P at the secondary transfer unit T. And a fixing device 30 for fixing the image on the paper P.

  Such an intermediate transfer belt 20 includes a driving roller 24 that rotationally drives the intermediate transfer belt 20, a backup roller 25 provided at a position opposite to the secondary transfer roller 26, and a tension roller 27 that applies tension to the intermediate transfer belt 20. Are stretched by the stretching roller 28 and the primary transfer rollers 21Y, 21M, 21C, 21K, etc., and circulate in the direction of arrow B.

  In the image forming apparatus 1, the image forming process unit 10 performs a series of image forming operations under the control of the control unit 50. That is, when a color image is formed, the image data of the print job input from the PC 3 or the image reading device 4 is subjected to predetermined image processing by the image processing unit 51, and the image data for each color is converted to each exposure device. 14. For example, in the black (K) color image forming unit 11K, the surface of the photosensitive drum 12 uniformly charged at a predetermined potential by the charging roller 13 is applied to the K color image data from the image processing unit 51 by the exposure device 14. And an electrostatic latent image is formed on the photosensitive drum 12. The formed electrostatic latent image is developed with toner by the developing device 15, and a black (K) toner image is formed on the photosensitive drum 12. Similarly, in the image forming units 11Y, 11M, and 11C, yellow (Y), magenta (M), and cyan (C) toner images are formed. When a monochrome image is formed, a black (K) toner image is formed only by the black (K) image forming unit 11K.

  The image forming apparatus 1 according to the present embodiment includes transport paths R1, R2, R3, R4, and R5 as a paper transport system. The transport path R1 is a transport path for transporting the paper P from the paper storage trays 40A and 40B to the secondary transfer unit T and the fixing device 30, and the transport path R2 is for transporting the paper P transported by the transport path R1. This is a conveyance path for discharging from the paper discharge unit Q. The transport path R3 is a transport path for discharging the paper P transported by the transport path R1 from the paper discharge unit W.

  The conveyance path R4 is a conveyance path used in the case of duplex printing, and is a conveyance path for conveying the paper P reversed in the conveyance path 3 to the conveyance path R1 again. That is, when the paper P is transported from the transport path R4 to the transport path R1, an image is formed on the back surface of the paper P by passing through the secondary transfer portion T and the fixing device 30.

  The transport path R <b> 5 is a transport path for transporting the paper P from the manual paper storage tray 56 to the secondary transfer unit T. Further, the image forming apparatus 1 according to the present embodiment includes a switching unit (switching mechanism, sheet transport direction switching device) 60 that switches the sheet transported on the transport path R1 to the other transport paths R2, R3, and R4. .

  Each color toner image formed by each image forming unit 11 is applied with a predetermined primary transfer bias voltage from a power supply device 61 as a high voltage primary transfer power source on the intermediate transfer belt 20 that circulates and moves in the direction of arrow B. Then, the toner images are sequentially electrostatically transferred by the respective primary transfer rollers 21, and a superimposed toner image is formed on the intermediate transfer belt 2O by superimposing the toner images of the respective colors. The superimposed toner image is conveyed toward the secondary transfer portion T where the secondary transfer roller 26 and the backup roller 25 are arranged as the intermediate transfer belt 20 moves.

  On the other hand, in the image forming apparatus 1, a plurality of sheets P1 and P2 (collectively referred to as “sheets P”) of different sizes or types are stored in the sheet storage trays 40A and 40B, respectively. For example, when the paper P1 is designated by the control unit 50, the paper P1 is taken out from the paper storage unit 40A by the pickup roller 41, and the paper P1 is transported to the position of the registration roller 43 by the transport roller 42. After the skew generated in the transport process is corrected, the skew is transported to the image forming process unit 10 described above. The details of the skew correction described here will be described later. The same applies when the paper P2 is designated by the control unit 50. In the present embodiment, only the paper storage trays 40A and 40B are shown, but a larger number of paper storage trays may be provided.

  The paper P is fed out from the registration roller 43 in accordance with the timing when each color toner image on the intermediate transfer belt 20 is conveyed to the secondary transfer portion T, and the voltage is supplied from the power supply device 61 as a high voltage secondary transfer power source. Is applied to the secondary transfer portion T. Each color toner image is electrostatically transferred (secondary transfer) onto the paper P at once by the action of the transfer electric field formed by the secondary transfer roller 26 and the backup roller 25.

  Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is peeled off from the intermediate transfer belt 20 and conveyed to the fixing device 30. The unfixed toner image on the paper P conveyed to the fixing device 30 is fixed on the paper P by being subjected to fixing processing by heating and pressing by the fixing device 30. Then, the sheet P on which the image is formed is transported from the transport path R1 to the transport path R2, and is discharged from the sheet discharge portion Q of the image forming apparatus 1 by the post-fixing transport roller 44 and the unloading roller 45, thereby forming an image. It is transported to a post-processing device or the like (not shown) connected to the device 1.

  On the other hand, the toner (transfer residual toner) adhering to the intermediate transfer belt 20 after the secondary transfer is removed by the belt cleaner 23 disposed in contact with the intermediate transfer belt 20 to prepare for the next image forming cycle. In this manner, image formation in the image forming apparatus 1 is repeatedly executed for the designated number of sheets.

  FIG. 2 is a block diagram of electrical connection of the control unit 50. The control unit 50 performs various calculations and connects a CPU 61 that centrally controls each unit, an image formation control program 62 executed by the CPU 61 and a ROM 63 that stores various fixed data, and a RAM 64 that is a work area of the CPU 61. Has been. Connected to the control unit 50 are a communication interface (I / F) 65 that communicates with the image forming process unit 10, the image processing unit 51, the external storage unit 52, and the like, and an operation panel 66 on which a user performs various operations. Has been.

  The image forming control program 62 may be stored in the ROM 63 from the beginning. However, after the image forming apparatus 1 is manufactured, it is transmitted from the outside of the image forming apparatus 1 to the image forming apparatus 1 in the form of a carrier wave via a predetermined communication interface. However, the nonvolatile memory or the external storage device 52 that constitutes a part of the ROM 63 may be set up.

  FIG. 3 shows each conveyance roller in the sheet conveyance path to the registration roller 43 that performs skew correction processing for aligning the leading edge of the sheet P before the sheet P conveyed from the sheet feeding cassettes 40A and 40B reaches the image forming process unit 10. It is explanatory drawing demonstrated.

  The registration roller 43 provided on the conveyance path R1 serves as a first roller, and the leading edge of the paper P conveyed on the conveyance path R1 is abutted against the registration roller 43 and skew correction is performed. Then, the sheet P with the leading end abutted against the registration roller 43 is sent to the image forming process unit 10 by driving the registration roller 43 in accordance with the timing of image formation in the image forming process unit 10. The registration roller 43 uses the motor 200a as a drive source, and the driving force is transmitted to the registration roller 43 by turning on the clutch 210a, which is an electromagnetic clutch.

  The uppermost sheet P stored in the paper cassette 40A is taken out by the pickup roller 41a and sent out to the transport path R1 by the transport roller 42b. The pickup roller 41a and the conveyance roller 42b are driven by a motor 200b.

  Similarly, the uppermost sheet P stored in the sheet cassette 40B is taken out by the pickup roller 41b and sent out to the conveyance path R1 by the conveyance roller 42c. The pickup roller 41b and the conveyance roller 42c are driven by a motor 200c.

  Further, the uppermost sheet P stored in the manual sheet storage tray 56 is taken out by the pickup roller 41c, and sent out from the transport path R5 to the transport path R1 by the transport roller 42e. The pickup roller 41c and the conveyance roller 42e are driven by a motor 200d.

  The sheet P sent out to the transport path R1 by the transport rollers 42b, 42c, or 42e reaches the transport roller 42a or 42d that is the second transport roller on the transport path R1. The transport rollers 42a and 42d both use the motor 200a as a drive source, and the driving force is transmitted to the transport rollers 42a and 42d by turning on the clutch 210b, which is an electromagnetic clutch. In response to an instruction from the control unit 50, the clutch 210b is turned on at a timing at which the conveyed paper P does not stagnate. Thus, the conveying roller 42a to which the driving force is transmitted continues to convey the sheet P until the clutch 210b is turned off in accordance with the same instruction from the control unit 50.

  As a result, the leading edge of the paper P reaches the registration roller 43, but at the intermediate position on the conveyance path R <b> 1 between the conveyance rollers 42 a or 42 d and the registration roller 43, A sensor 220 is provided for detecting the presence of. The sensor 220 is turned on when the paper P is detected, and turned off when the paper P is not detected.

  Next, characteristic control processing executed by the control unit 50 will be described.

  FIG. 4 is a timing chart for explaining the control process, and FIGS. 5 and 6 are explanatory views of the state of conveyance of the paper P in the conveyance path R1 for explaining the control. FIG. 7 is a timing chart as a comparative example.

  The leading edge of the paper P conveyed from the paper feed cassettes 40A and 40B or the manual paper storage tray 56 eventually reaches the registration roller 43. At this time, as shown in FIG. 5, the registration roller 43 has the clutch 210a in the OFF state. Therefore, it is not rotationally driven, and therefore the leading edge of the paper P stops in a state where it is nipped by the registration roller 43 as shown in FIG. In this state, the paper P is detected by the sensor 220 (the sensor 220 is turned on). When time T1 elapses after the sheet P is detected by the sensor 220, the clutch 210b that has driven the transport rollers 42a and 42d is disengaged. And that state is maintained until there is another conveyance start instruction from the controller 50.

  At this time, as shown in FIG. 5, it is expected that the leading end pa of the paper P is completely in contact with the registration roller 43, but this is not always the case. The size of the loop 500 of the paper P is determined by the length of the time T1 shown in FIG. 4, but this time T1 needs to be changed depending on the length, paper quality, type, etc. of the paper P. In some cases, the time must be set to an extremely short time. For example, with label paper, if the time T1 is made too long, that is, if the loop 500 is made too large, there is a problem that the seal is peeled off, so the time is set shorter than that for plain paper.

  Next, as shown in FIG. 5, after receiving the conveyance start signal from the controller 50, the clutch 210a is turned on (after the time T1 has passed and further after the time T2 has passed), and the clutch 210b is also turned on almost simultaneously. Control is performed such that the entire sheet P is sent to the image processing unit 10 by rotational driving of the registration roller 43 and the transport roller 42d (when the sheet P is supplied from the sheet cassettes 40A and 40B).

  That is, considering the case where the leading edge Pa of the paper P is not sufficiently abutted as described above, before the entire paper P is sent to the image processing unit 10 in earnest, the registration roller 43 and the transport roller 42d cooperate. The movement ensures that the leading edge Pa of the paper P has reached the registration roller 43 reliably.

  When such an operation is performed for a time T3a, the clutch 210a is maintained in the ON state and the driving of the registration roller 43 is continued, the clutch 210b is turned OFF, and the conveying roller 42a is stopped (FIG. 6). That is, by driving the registration roller 43 and stopping the conveyance roller 42 a located upstream of the registration roller 43 in the conveyance path of the paper P, the loop 500 of the paper P is crushed.

  When this state is performed for time T3b (time T3a and time T3b are combined to be time T3), the clutch 210a is maintained in the ON state and the driving of the registration roller 43 is continued, and the clutch 210b is also turned on. By driving the transport roller 42a as well, the entire sheet P is sent to the image processing unit 10 in earnest.

  By performing such control, even if the paper P is such that the loop 500 cannot be sufficiently formed, the leading edge Pa is sufficiently abutted against the registration roller 43 and the paper P is inserted into the registration roller 43. Therefore, it is possible to reduce the risk of wrinkling of the paper P and occurrence of registration deviation.

  In particular, as shown in the examples of FIGS. 5 and 6, the conveyance direction of the sheet P on the conveyance path R1 between the registration roller 43 and the conveyance roller 42a is vertical or perpendicular and has an acute angle, and the sheet on the conveyance path R1. If the transport direction of P is not horizontal, the leading edge Pa of the paper P tends to be insufficiently abutted against the registration roller 43 due to the action of gravity, and there is a risk of wrinkling of the paper P and registration misalignment. It can be said that the effect of reducing is particularly great.

  In this case, it is desirable that the length of the time T3b is set to an optimum length for crushing the loop 500 according to the type of the paper P. It can be experimentally obtained in advance how much time T3b is appropriate for which type of paper P. As an example, since the label paper tends to have a smaller loop 500, the time T3b seems to be relatively short. Further, since the loop 500 becomes large when the paper P is thin, it seems appropriate to set the time T3b to a relatively long time.

  The ROM 63 of the control unit 50 is provided with a lookup table in which the length of the time T3b is registered according to the type of the paper P. When there is a print job, the control unit 50 sets the paper P used for printing. The type is determined, the length of time T3b registered in the lookup table is read according to the type, the length of time T3b is set to the read time, and the timing chart of FIG. 4 is referred to. The control process described above is performed.

  In order to specify the type of paper P, a specific type of paper P is associated with each of the paper feed cassettes 40A and 40B and registered in the lookup table, and the paper P is supplied from any of the paper feed cassettes. Alternatively, the user may select the type of paper P by operating the operation panel 66.

  By performing such processing, the degree of the loop 500 of the paper P that is formed when it abuts against the registration roller 43 differs depending on the type of the paper P, and the time T3b depends on the type of the paper P. Therefore, problems such as the loop 500 and wrinkles of the paper P can be appropriately solved according to the type of the paper P.

  On the other hand, the timing chart of FIG. 7 as a comparative example of FIG. 4 differs from the control of FIG. 4 described above in the following points. First, the clutch 210a is turned on to start driving the registration roller 43 to crush the loop 500 of the paper P, and after a time T3, the clutch 210b is turned on to start driving the conveying roller 42a. The paper P is sent out to the image forming process unit 10 by the cooperation of the conveying roller 42a. When the driving of the transport roller 42a is started, the transport roller 42a is not temporarily stopped as shown in FIG.

  In the process of the comparative example in FIG. 7 as described above, the loop 500 of the paper P is crushed by the operation during the time T3. However, the paper is loaded into the registration roller 43 during the time T3a of the process in FIG. Therefore, if the leading edge Pa of the paper P is not sufficiently abutted against the registration roller 43, the correction of the loop 500 becomes insufficient, and the registration accuracy is lowered or the paper P is curled. This will cause problems such as occurrence.

1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a block diagram of the electrical connection of a control part. FIG. 5 is an explanatory diagram illustrating each conveyance roller in a sheet conveyance path to a registration roller before a sheet conveyed from a sheet feeding cassette reaches an image forming process unit. It is a timing chart explaining the characteristic control processing performed by a control part. It is explanatory drawing of the mode of conveyance of the paper in a conveyance path explaining the characteristic control processing performed by the control part. It is explanatory drawing of the mode of conveyance of the paper in a conveyance path explaining the characteristic control processing performed by the control part. It is a timing chart used as the comparative example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image forming process part 42a Conveyance roller 43 Registration roller R1 Conveyance path

Claims (5)

An imager for forming an image on a print medium;
A transport path for transporting the print medium to the imager;
A first conveyance roller that is provided on the conveyance path and sends the print medium to the imager in accordance with the timing of image formation by the imager;
A second transport roller provided on the upstream side of the movement of the print medium from the first transport roller on the transport path, and transports the print medium in the transport path;
First driving means for rotationally driving the first transport roller;
Second driving means for rotationally driving the second transport roller;
By controlling the first driving means and the second driving means, the first driving roller and the second conveying roller are driven, and when the first time has elapsed, the first The operation of stopping the driving of the second conveying roller while maintaining the driving of the conveying roller, and starting the driving of the first conveying roller and the second conveying roller again when the second time has passed. Control means for sending the print medium to the imager by
An image forming apparatus. A time length storage means for storing the length of the second time for each type of the print medium;
Medium type specifying means for specifying the type of the print medium;
Further comprising
The control means reads from the time length storage means the length of the second time corresponding to the type specified by the medium type detection means, and performs the control with the read length of the second time. The image forming apparatus according to claim 1.   3. The image formation according to claim 1, wherein at least a section from the second conveyance roller to the second conveyance roller in the conveyance path has a vertical or acute angle with respect to a conveyance direction of the print medium. apparatus.   A print medium that is provided on a conveyance path that conveys the print medium to an image forming device that forms an image on the print medium is sent to the image forming device in accordance with a timing at which image formation is performed by the image forming device. A first driving unit that rotationally drives one conveyance roller; and a second drive unit that is provided upstream of the movement of the print medium from the first conveyance roller on the conveyance path and conveys the print medium through the conveyance path. By controlling the second driving means that rotationally drives the first conveying roller, the first conveying roller and the second conveying roller are started to drive when the first time has elapsed. The operation of stopping the driving of the second conveying roller while maintaining the driving of the conveying roller, and starting the driving of the first conveying roller and the second conveying roller again when the second time has passed. By doing , The print medium an image forming control program readable on a computer to execute a control means for sending to said image forming unit to the computer.   The control means stores the length of the second time corresponding to the type specified by the medium type detection means for specifying the type of the print medium, and stores the length of the second time for each type of the print medium. 5. The image formation control program according to claim 4, wherein the image forming control program is read from the stored time length storage means, and the control is performed for the read second time length.

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