JP2007156002A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which conveys paper perfectly in a straight direction even if a print size is large when delivering the paper to an image forming part, and performs processing by conveying the paper in the straight direction while forming an image when the paper has such a paper size that its feed length exceeds a set value, thereby suitably forming the image. <P>SOLUTION: The image forming apparatus is equipped with: the image forming part C forming the image on the surface of the paper P, and is equipped with: a cutter 4 cutting the paper P to optional length; a chucker unit 10 receiving the paper P from a paper supply part A for supplying the paper P at a receiving position P1 on a conveying upstream side and delivering the paper P to the image forming part C in a delivering position P2 on a conveying downstream side; a means for setting the feed length of the paper; and a conveying speed setting means. When the feed length of the paper exceeds the set value, the trailing edge of the paper P is cut while forming the image, and the cut trailing edge is conveyed to the delivering position P2 by the chucker unit 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including an image forming unit that forms an image on the surface of an image forming medium.

  Various structures are known as image forming apparatuses that form images on the surface of paper (corresponding to an image forming medium), and typical structures thereof will be described. The paper is accommodated in a state of being wound around a roll in a paper magazine, and the long paper drawn out from the paper magazine is transported along a predetermined transport path and sent to the position of the cutter. When the cutter is cut to a predetermined print size by the cutter, the cut paper is received by the chucker unit (corresponding to the medium transport unit) at the receiving position and then transported to the delivery position.

  When the downstream transport mechanism receives the paper at the delivery position, image formation is performed on the paper surface in the image forming unit. As this image forming unit, for example, a laser engine is used, and a latent image is formed on the paper surface by repeatedly scanning in the main scanning direction laser light light-modulated by image data while conveying the paper in the sub-scanning direction. Form. This paper can create a photographic print by making a latent image visible by performing predetermined development processing in a development processing section.

  In such an image forming apparatus, a method of cutting roll paper into a desired print size has been proposed. Specifically, as shown in FIG. 17, as a device capable of cutting in the direction perpendicular to the running direction of the roll paper, the transfer material 109 that follows the transfer material 109 is held in a state where the leading edge of the transfer material 109 is held by the registration roller 122. Can be obtained by cutting with a cutter 131 and obtaining a paper of a desired print size when it reaches a predetermined length while being temporarily stored in the storage portion 126 (see Patent Document 1).

JP 2003-50488 A

  In conventional image forming apparatuses including the image forming apparatus shown in FIG. 17, when a print having a considerably large print size such as an advertisement print is to be created, the paper is completely straight because of the large conveyance width dimension. It is difficult to convey in the direction. For example, when transported by a roller, it is difficult to accurately finish the outer dimension of the roller along the axial direction, and therefore the paper is transported in a meandering state during transport. When the paper is transferred to the image forming unit in a state where the paper is inclined as described above, the image formed on the paper is also inclined and the image quality is deteriorated.

  Further, in the image forming apparatus, it is necessary that the length in the feeding direction can be changed in order to appropriately cope with various image sizes. In such a case, it is needless to say that even a conventional image forming apparatus can stably supply paper up to a certain length and can form a suitable image. However, it is a problem how to transport paper that exceeds this length, especially when trying to create a print with a very large print size, such as an advertisement print, with a conventional image forming apparatus. It was difficult to do.

  At this time, in order to cope with a large print size, a storage section is set before image formation from the length in the feeding direction, and for the paper size that does not fit in the storage section, the final end is set while forming an image. A method of cutting may be taken. In such a case, the conventional image forming apparatus may be affected by banding (generation of streak-like images), and an apparatus that does not have such an effect has been desired.

  Furthermore, a print having a considerably large print size such as an advertisement print is considerably large as a photographic print and heavy as a total amount of paper. When creating a print with such a long feed length, the influence of banding due to its weight is particularly problematic.

  The present invention has been made in view of the above circumstances, and the problem is that when paper is delivered to the image forming unit, if the paper feed length exceeds a set amount, the paper can be conveyed in a straight direction. At the same time, it is to provide an image forming apparatus capable of forming a suitable image by conveying and processing in a straight direction while forming an image for a paper size in which the paper feeding length exceeds a set amount. .

In order to solve the above problems, an image forming apparatus according to the present invention provides:
An image forming unit for forming an image on the surface of the image forming medium;
An image forming medium is received from a cutting unit that cuts the image forming medium into an arbitrary length and a medium supply unit that supplies the image forming medium at a receiving position on the upstream side of the conveyance. A medium conveying unit that delivers the forming medium, an image forming medium feeding length setting unit, and a conveying speed setting unit,
When the image forming medium feed length exceeds the set amount, the feature is that the rear end of the cut image forming medium is conveyed to the delivery position by the medium conveying unit at a speed different from the conveying speed of the image forming medium. To do.

  With the image forming apparatus having this configuration, the following operations and effects can be obtained. In this image forming apparatus, the medium transport unit receives the image forming medium (paper) at the receiving position on the upstream side of the transport, and transports the image forming medium (paper) to the delivery position on the downstream side of the transport while sandwiching the image forming medium. The medium transport unit moves from the receiving position to the transfer position in a state where the leading end side of the paper is nipped, and transfers the paper to the downstream image forming unit. Since the moving distance of the medium transport unit is set in advance by the print size according to the print size, the image forming medium feed length (paper feed length) is set. And pass the paper to the image forming unit. On the other hand, when the paper feed length such as advertising print exceeds the set amount, the paper is delivered to the image forming unit without cutting the trailing edge of the paper, and it corresponds to the print size during image formation in the image forming unit Cut the trailing edge of the paper so that it reaches the paper feed length. Further, in the image forming apparatus with this configuration, not only the movement of the front end side of the paper but also the cut rear end portion is conveyed to the delivery position while being sandwiched by the medium conveying portion.

  At this time, the paper transport speed is set by the print size and the paper feed length corresponding to the print size, while the rear edge transport speed is set in the same manner as this to transport the entire paper in a straight direction. Is very difficult. Therefore, in the present image forming apparatus, the paper feed length is set by a predetermined amount as in the case of advertisement printing by conveying the rear edge at a speed different from the paper conveyance speed while sandwiching and conveying the rear edge. Even in the case of exceeding, it is possible to convey in a straight direction. Of course, if the paper feed length exceeds the set amount even for the normal print size, the paper is transported in the straight direction by transporting the trailing edge at a speed different from the paper transport speed. And more suitable image formation is possible. Moreover, it becomes possible to arbitrarily form a loop (sagging state) to be described later by carrying at such different speeds.

  As described above, when the paper feed length exceeds the set amount when delivering the paper to the image forming unit, the paper can be conveyed in a straight direction, and the paper feed length exceeds the set amount even longer. Since the size can be conveyed and processed in a straight direction while forming an image, a suitable image forming apparatus can be provided. The term “arbitrary” used herein includes not only the case where the length is determined according to the paper size but also the case where a desired numerical value is input from a terminal connected to the image forming apparatus. In addition, “clamping” includes not only the crimped state but also the state in which the crimping is released and the paper is placed, unless otherwise specified, and so on. In particular, when the sheet is conveyed again to the delivery position after reverse feeding, it is more preferable because the load on the paper can be further reduced by holding the sheet in the pressure released state.

  In the present invention, there is provided a medium clamping mechanism provided in the medium conveying section, which clamps the leading end side of the image forming medium over the entire area in the conveying width direction or substantially the entire area, and conveys the image forming medium from the receiving position to the delivery position. It is preferable that the sheet is fed backward after the conveyance, and the cut rear end portion is nipped with the nipping member of the medium nipping mechanism spaced apart and conveyed again to the delivery position.

  When a print having a considerably large print size such as an advertisement print is to be created, it is difficult to transport the paper in a straight state not only in the width direction but also in the feed direction because the transport width dimension is large. In the image processing apparatus having this configuration, the medium conveyance unit includes a medium clamping mechanism, and conveys the entire area in the conveyance width direction on the leading edge side of the image forming medium in a straight state on the leading edge side of the paper. Can be secured. At the same time, the medium transport unit after transporting the leading end side of the paper from the receiving position to the passing position is reversely fed to the receiving position, and the cut rear end is sandwiched and transported again to the passing position. It is possible to ensure conveyance in a straight state at the rear end. As for the method of clamping the rear end at this time, it is sufficient to hold the rear end so that the rear end does not fall off, and from the relationship with the conveyance speed described above, it is avoided that the upper end side and the rear end are attracted. However, it is preferable to hold the holding member of the medium holding mechanism in the separated state rather than holding in the pressed state. In this way, it is possible to provide a suitable image forming apparatus by transporting the paper in a completely straight direction by ensuring transport in a straight state at both ends of the cut paper.

  In the present invention, a loop forming mechanism for forming a loop of the image forming medium before moving from the receiving position to the transfer position is provided, and the transfer end position is held by holding the rear end portion in a state where the loop is formed by the loop forming mechanism. It is preferable that the medium transport unit transports the head.

  As described above, when the print size is long in the transport direction, it is preferable to sandwich the rear end portion of the paper and transport it again to the delivery position. It is sufficient to hold it to the extent that it does not fall, and it is possible to hold it in a separated state rather than holding it in a crimped state, in order to avoid the upper end side and the rear end portion from being attracted from the relationship with the above-mentioned transport speed preferable. Therefore, when the loop (sagging state) is formed by the loop forming mechanism, the rear end of the paper is held in a separated state and conveyed to the delivery position, so that the distortion generated at that time affects the entire paper. It is possible to relax and prevent an excessive force from acting on the paper, and a suitable image forming apparatus can be provided.

  In the present invention, it is preferable that the speed at which the rear end portion of the image forming medium is conveyed to the transfer position by the medium conveying portion is smaller than the conveying speed of the image forming medium.

  As described above, in the present image forming apparatus, the rear end portion is simultaneously transported when transporting the paper, thereby preventing transmission of impacts, vibrations, and the like in a direction perpendicular to the transport direction of the paper. At this time, in order to further prevent transmission of impact or vibration in the paper transport direction, it is preferable to reduce the influence in the same direction from the rear end. Therefore, by making the conveyance speed of the rear end portion smaller than the conveyance speed of the paper, the conveyance speed of the image forming medium can lead the entire paper in a straight direction. In particular, when the rear end portion is held apart, there is no transmission of impact or vibration from the rear end portion, and the conveyance speed of the image forming medium can lead the entire paper in a straight direction. This makes it possible to form a more suitable image.

  A preferred embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an internal configuration diagram (schematic diagram) showing a main part of the image forming apparatus.

<Configuration of image forming apparatus>
This image forming apparatus includes a digital exposure engine, and has a function of printing and exposing an image on the surface of paper (photosensitive material and corresponding to an image forming medium) based on image data, thereby creating a photographic print. In particular, it has a function of creating a photographic print having an extremely large print size such as an advertisement print. As main functions, a paper supply unit A (corresponding to a medium supply unit), a paper transport unit B (corresponding to a medium transport unit), an image forming unit C, and a switchback unit D are provided.

  The paper supply unit A can detachably mount two paper magazines M, and paper is supplied from the paper magazine M on the selected side. For example, two types of paper having different width dimensions can be prepared. In the paper magazine M, long paper is accommodated in the form of a roll. The paper drawn from the paper magazine M is conveyed to the pre-cutter roller 2 by the advance roller 1. A paper sensor 3 is disposed in the vicinity of the downstream side of the roller 2 before the cutter, and detects that the leading edge of the paper has passed. A cutter (corresponding to a cutting part) 4 cuts the rear end side of the paper so as to have a set print size. Cut the paper after stopping the paper.

  A post-cutter roller 5 and a paper guide 6 are provided on the downstream side of the cutter 4. The conveyed paper is delivered to the chucker unit 10 at the receiving position P1. The chucker unit 10 includes a chucker roller 11 (corresponding to a medium clamping mechanism), receives paper at the upstream receiving position P1, and transfers the paper downstream at the downstream delivery position P2. The chucker roller 11 includes a pair of rollers (corresponding to a sandwiching member, which includes a drive roller and a pressure roller), and sandwiches the leading end side of the paper over the entire width direction or almost the entire area. That is, the paper is transported to the delivery position P2 while the front end side of the paper is held by the chuck roller 11.

  A paper guide 12 is provided together with the chucker roller 11 to smoothly receive the paper from the paper supply unit A. The paper guide 12 is composed of two upper and lower plates, and is guided to the position of the chuck roller 11 without being caught by expanding the insertion opening 12a on the paper receiving side.

  The image forming unit C is provided with a first exposure conveyance roller 20 and a second exposure conveyance roller 21 arranged on the upstream side of the conveyance. A paper guide 22 is also arranged around the exposure transport rollers 20 and 21. When the paper is delivered from the chucker unit 10, the paper is transported at a predetermined speed by the exposure transport rollers 20 and 21, and an image is printed and exposed on the emulsion surface of the paper.

  The image forming unit C includes a laser engine, and repeats the laser light light-modulated based on the image data in the main scanning direction (conveying width direction) while conveying the paper in the sub scanning direction by the exposure conveying rollers 20 and 21. By scanning, images (latent images) are sequentially formed. In FIG. 1, the direction in which the laser beam is irradiated is indicated by an arrow L. In order to control the exposure start timing by the laser light, an exposure start sensor 23 is disposed in the vicinity immediately downstream of the delivery position P2. This sensor is an optical sensor that detects the leading edge of the paper, and the same sensor as the paper sensor 3 described above can be used.

  The switchback portion D is provided with a mechanism for converting the position of the emulsion surface of the paper. In FIG. 1, the emulsion surface of the paper is on the upper surface side, but this is converted so as to be on the arrow N side by changing the arrangement of the conversion roller 30. The conversion roller 30 includes a driving roller 30a and a pressure roller 30b. The conversion roller 30 sandwiches the paper on which the image is printed and exposed to change the direction. Details will be described later. A take-up roller 31 is provided for the same purpose, and this take-up roller 31 functions in the case of paper having a long length in the transport direction, and is in the direction of the arrow (slanting downward) in the figure. It is configured to be movable. Details of the operation of the winding roller 31 will be described later.

  The paper on which the image is formed by the switchback unit D is sequentially sent to the development processing unit 40, the drying processing unit 41, and the paper discharge unit 42, and the photographic print is completed. The paper sensor 32 detects that paper is fed into the development processing unit 40.

  FIG. 2 is a specific configuration diagram of the image forming apparatus schematically shown in FIG. FIG. 3 is a perspective view showing a specific configuration of the chucker unit 10. On both sides of the chucker unit 10 in the transport width direction, belt conveyors 13 for transporting the chucker unit 10 are provided. The chucker unit 10 is supported by a support 14 with respect to the belt conveyor 13. A first motor 15A and a second motor 15B are provided to drive the pair of belt conveyors 13, and are connected to the belt conveyor 13 by a belt 16a and a pulley 16b. Therefore, the chucker unit 10 can be transported by driving the first motor 15A and the second motor 15B. The first and second motors 15A and 15B, the belt 16a, the pulley 16b, the belt conveyor 13 and the like function as a transport mechanism for transporting the chucker roller 11 (medium clamping mechanism) from the receiving position P1 to the delivery position P2. At the same time, the chuck unit 10 has a function of sending back from the delivery position P2 to the reception position P1.

  The chucker roller 11 includes a drive roller 11a and a pressure roller 11b (see FIG. 2), and the pressure roller 11b can be switched between a state in which it is pressure-bonded to the drive roller 11a and a state in which it is separated (pressure-released). When the crimp release motor 17 is driven, the operating shaft 18 is rotated to move the lever 19. In conjunction with the movement of the lever 19, the pressure roller 11b is moved in a releasing direction. The drive motor 50 drives the drive roller by driving it, and can carry the paper held by the chucker roller 11. Further, when the chucker unit 10 is reversely fed from the delivery position P2 to the reception position P1, the state where the crimping is released is prepared so that the paper is transported again without damaging the paper. The guide mechanism 51 can perform a guide when transporting the chucker unit 10.

  Further, as shown in FIG. 2 as a loop forming mechanism, a first loop restricting body 52 and a second loop restricting body 53 are provided on the upstream side and the lower end side in the transport direction. These are rotatably supported by shafts 52a and 53a with respect to the support frame 54, respectively. These loop regulating bodies 52 and 53 regulate the paper loop (sag) so that it is always formed in the downward direction, and are always attached so that the tip portions 52b and 53b are located in the downward direction. It is energized.

  Further, these loop restrictors 52 and 53 are configured to be flipped upward as the chucker unit 10 moves, and when the chucker unit 10 is located at the delivery position P2 as shown in FIG. The second loop regulating body 53 on the downstream side is flipped up by the chucker unit 10 itself and rotated about 90 °. Conversely, when the chucker unit 10 is positioned at the upstream receiving position P1, the first loop restricting body 52 is flipped up by about 90 °. The paper loop formation will be described later.

<Functional block configuration>
Next, main functions relating to the image forming apparatus shown in FIGS. 1 to 3 will be described with reference to the block diagram of FIG.

  The control unit 60 provides a function that controls the entire image forming apparatus. Specifically, the following chucker control unit 61, correction value storage unit 62, magazine detection unit 63, print size setting unit 64, transport amount detection unit 65, image formation control unit 66, cutter control unit 67, magazine control unit 68 And the switchback control unit 69, and further has functions as meandering correction means 60a, conveyance mode setting means 60b, loop forming means 60c, paper feed length setting means 60d, and conveyance speed setting means 60e.

  The chucker control unit 61 performs drive control on the first motor 15 </ b> A, the second motor 15 </ b> B, the pressure release motor 17, and the drive motor 50. As explained earlier, both sides of the chucker unit 10 in the width direction are driven by the first motor 15A and the second motor 15B. Since the motors 15A and 15B can be independently driven and controlled, the meandering of the paper can be corrected by changing the drive amounts of the motors 15A and 15B.

  The correction value storage unit 62 stores correction values for differentiating the drive amounts of the motors 15A and 15B. Since the correction value varies depending on the width dimension, surface quality, manufacturer, etc. of the paper, a test print is created in advance to obtain the correction value for each paper and stored in the correction value storage unit 62.

  The magazine detection unit 63 detects the information of the paper stored in the loaded paper magazine M. For example, by forming a barcode on the paper magazine M and reading it, information on the paper (paper width, surface quality, manufacturer name, etc.) can be obtained.

  The print size setting unit 64 is set with print size data of a photo print to be created. Based on the print size data, control such as paper cutting is performed. Further, the control unit 60 selects a correction value stored in the correction value storage unit 62 based on data from the magazine detection unit 63 and the print size setting unit 64. Based on the selected correction value, the control unit 60 gives a command to the chucker control unit 61 so as to drive the first motor 15A and the second motor 15B, thereby correcting the meandering of the paper. Therefore, the control unit 60 has the function of the meandering correction means 60a.

  The carry amount detection unit 65 has a function of detecting the carry amount of paper. The carry amount can be detected, for example, by counting the number of pulses output from an encoder linked to a motor or roller. Alternatively, it can be detected by counting the number of drive pulses supplied to the motor (stepping motor). Therefore, the correction value stored in the correction value storage unit 62 can also be defined by the number of pulses. When the leading edge of the paper is detected by the optical sensor, the current position of the leading edge of the paper can be calculated by counting the number of pulses from the timing.

  The image forming control unit 66 controls various operations in the image forming unit C. That is, the laser engine 24 and the exposure transport rollers 20 and 21 are controlled. When the leading edge of the paper is detected by the exposure start sensor 23, the image forming timing by the laser engine 24 is controlled. The conveyance amount of the paper from the detection of the leading edge of the paper to the exposure position can be detected by the conveyance amount detection unit 65. In addition, it is possible to control the start of driving of the first and second exposure conveyance rollers 20 and 21 and the timing of releasing the pressure bonding.

  The cutter control unit 67 performs drive control of the cutter 4, the pre-cutter roller 2, and the post-cutter roller 5. By detecting the leading edge of the paper by the paper sensor 3, the paper conveyance amount from the conveyance amount detection unit 65, and the print size data set in the print size setting unit 64, the driving and stop timings of the rollers 2 and 5 are detected. The operation timing of the cutter 4 is controlled.

  The magazine control unit 68 performs drawing of paper from the paper magazine M, selection switching control of the two paper magazines M, and the like.

  The switchback control unit 69 performs drive control of the conversion roller 30 and the take-up roller 31 provided in the switchback unit D. When the length of the paper in the transport direction is less than a predetermined value, the paper is fed into the development processing unit 40 by the conversion roller 30, and when the length of the paper is greater than the predetermined value, the paper is developed by the take-up roller 31. It is sent to the processing unit. The length data in the paper transport direction can be acquired from the data set in the print size setting unit 64.

  Each function shown in FIG. 4 can be constructed by hardware (CPU, memory, control circuit, etc.) and software (control program, etc.).

  The function as the paper feed length setting means 60d is to set the length for transporting the paper necessary for image formation and the position for cutting the paper according to the print size. Is done. The paper feed length can be acquired from the data set in the print size setting unit 64. With a normal print size, even if the print size is large, the paper transport unit B has the function of a paper storage unit, so that image formation can be performed after cutting the paper. However, when a print having a considerably large print size such as an advertisement print is created, the function as a paper storage unit may not be sufficient. In other words, there is a case where the above-mentioned “paper feed length exceeds the set amount”. At this time, it is necessary to cut the rear end portion of the paper even during image formation and transport the cut rear end portion without impact. There is. At this time, the paper feed length setting unit 60d can perform an appropriate operation according to the print size via the conveyance mode setting unit 60b based on the data of the print size setting unit 64.

The function as the transport speed setting means 60e is to set the speed for transporting the paper necessary for image formation and the moving speed of the chucker unit 10 according to the print size, and the transport mode described later is thereby set. . Here, the paper transport speed differs in a specific transport state, for example, when a loop is formed, before the loop (front end side) and after the loop (rear end part), unless otherwise specified. It means the conveyance speed of the entire paper represented by the movement speed on the paper front end side. The transport speed of the paper is the speed of the transport stage by the advance roller 1 and the pre-cutter roller 2, the speed of the transport stage by the post-cutter roller 5, the speed of the transport stage by the chucker unit 10, and the speed of the transport stage by the exposure transport rollers 20 and 21. Determined by.
When controlling the paper conveyance speed, the paper sensor 3 provided in the vicinity of the downstream side of the cutter front roller 2 and the position immediately downstream of the delivery position P2 are arranged based on the output signal from the conveyance amount detection unit 65. An output signal from the exposure start sensor 23 is used as an index.
(1) First, the advance roller 1 is driven and controlled. (2) Next, the pre-cutter roller 2 and post-cutter roller 5 are driven and controlled via the cutter control unit 67, and (3) chucker control. Drive control of the chucker unit 10 (specifically, the first motor 15A and the second motor 15B) via the part 61, and (4) drive control of the exposure transport rollers 20 and 21 via the image formation control part 66, Is set.

In a normal print size, even if the print size is large, the paper transport unit B has the function of a paper storage unit, so that image formation can be performed after cutting the paper. Is the same from the cutter front roller 2 to the exposure transport rollers 20 and 21. Also, when forming a loop, the downstream conveyance speed is lower than the upstream conveyance speed, and vice versa when eliminating the loop.
In particular, when a print having a considerably large print size such as an advertisement print is created, the function as a paper storage unit may not be sufficient. At this time, while the conveyance speed by the exposure conveyance rollers 20 and 21 is kept constant, the conveyance speed of the pre-cutter roller 2 is increased in order to form a loop before the rear end portion of the paper is cut, and after being cut, the chucker By increasing the conveyance speed of the rear end portion cut by the unit 10, it is possible to cut the rear end portion of the paper even during image formation and convey the cut rear end portion without impact. .
In this way, by setting the conveyance speed of the trailing edge by the chucker unit 10 to a conveyance speed different from the paper conveyance speed, the print size is set via the conveyance speed setting means 60e based on the data of the print size setting unit 64. It is possible to perform an appropriate operation according to the above.

<Explanation on meander correction>
When the paper is pulled out from the paper magazine M and conveyed, the paper is guided in a meandering manner due to various factors such as variations in the width direction of the pressure-bonding force of the pressure roller. If an image is formed while the paper is inclined due to the meandering, a photographic print with low image quality is obtained, and this needs to be eliminated. Therefore, by performing meandering correction, it is possible to form an image with the paper in a correct posture.
(1) When the paper is not inclined, the paper can be delivered to the image forming unit C in the same posture if the drive amounts of the left and right motors 15A and 15B are the same.
(2) When the paper is received in an inclined state due to the meandering conveyance of the paper, the meandering correction can be performed by changing the drive amounts of the left and right motors 15A and 15B, and the inclined state can be eliminated. In this case, by setting the drive amount of the left motor 15A to be larger than the drive amount of the right motor 15B, the leftward inclination with respect to the traveling direction can be corrected. The meandering correction may be performed until the chucker unit 10 moves to the delivery position P2.

  The means for performing meandering correction is not limited to this. In order to handle a paper having a long feeding length, a method of correcting the inclination of the entire paper is preferable, and any method can be adopted as long as it is such a method.

<Explanation about loop formation>
The paper conveyed to the image forming unit C can form a clear image when the exposure process or the like is performed in a precise and constant speed moving state. However, when the print size is long in the conveyance direction, it is affected by vibrations and fine movements other than the paper located in the image forming unit C, and banding occurs. Need to eliminate this. In addition, when the paper is sandwiched at two or more places, distortion generated during the conveyance of the paper affects the entire paper. Therefore, when the paper is nipped and transported, the transport speed setting means 60e causes the transport speed of the advance roller 1, the pre-cutter roller 2 or the post-cutter roller 5, or the transport speed of the exposure transport rollers 20, 21 and the conversion roller 30 to be conveyed. By adjusting the above and forming a loop in the paper transport section B, it is possible to prevent such banding and eliminate the influence of distortion. Based on FIG. 5A (a)-FIG. 5B (f), the function of loop formation is demonstrated.

  (1) When the leading end side of the paper P is moved from the receiving position P1 to the delivery position P2, the first loop restricting body 52 that has been flipped up by the chucker unit 10 as shown in FIG. Is separated from the upstream receiving position P1, and the upper surface of the paper P is lightly pressed as shown in FIG. 5A (b). At this time, the paper P forms a loop by setting the moving speed of the chucker unit 10 below the conveying speed of the advance roller 1, the pre-cutter roller 2 or the post-cutter roller 5 by the conveying speed setting means 60e. At the same time, since the paper P has a predetermined rigidity, the first loop restriction body 52 restricts the paper P to the downward loop. In this state, when the chucker unit 10 approaches the delivery position P2, the second loop restricting body 53 is flipped up by the chucker unit 10 as shown in FIG. 5A (c).

  (2) Next, when the chucker unit 10 moves from the delivery position P2 to the reception position P1, the second loop restricting body 53 that has been flipped up by the chucker unit 10 as shown in FIG. When 10 separates from the upstream delivery position P2, the upper surface of the paper P is lightly pressed as shown in FIG. 5A (d). At this time, since the chucker unit 10 releases the nipping of the paper, the paper P is regulated by the second loop regulating body 53 and maintains a state in which a loop is formed in the downward direction. In this state, when the chucker unit 10 approaches the receiving position P1, the first loop restricting body 52 is flipped up by the chucker unit 10 as shown in FIG. 5B (e).

  (3) When the rear end portion of the paper P is moved from the receiving position P1 to the delivery position P2, the paper P is maintained while maintaining a state where the paper forms a loop downward as shown in FIG. 5B (d). The chucker unit 10 holding the end portion moves to the delivery position P2. At this time, the first loop restricting body 52 that has been bounced up by the chucker unit 10 is positioned in the biased downward direction when the chucker unit 10 is separated from the upstream receiving position P1. As the chucker unit 10 approaches the delivery position P2, the second loop restricting body 53 is flipped up by the chucker unit 10 as shown in FIG. When the loop disappears.

<Explanation about each transport mode>
Next, in the image forming apparatus described with reference to FIGS. 1 to 4, an operation until the paper P is received by the paper supply unit A and delivered to the image forming unit C will be described. Here, the transport operation can be divided into four transport modes according to the length of the paper P in the transport direction, and will be described in order. That is, the control unit 60 has the function of the transport mode setting unit 60b, and performs an appropriate operation according to the print size based on the data set in the print size setting unit 64. At this time, if the paper feed length exceeds the set amount, it functions as the paper feed length setting means 60d and cuts the rear end of the paper even during image formation, Transport can be performed. In this operation, control that forms a loop in the paper P may be performed, and the control unit 60 also functions as the loop control means 60c. At this time, after the loop is formed, the function of the conveyance speed setting means 60e is used to control the movement speed of the chucker unit 10 to a movement speed smaller than the paper conveyance speed. To do.

<1. When the paper feed length is 150 mm to 183 mm (first mode)>
The operation in this case will be described with reference to the operation diagram of FIG. 6 and the operation flowchart of FIG. 6A, in order to receive the paper P from the paper supply unit A, the chucker unit 10 stands by at the receiving position P1. At this time, the pressed state of the chucker roller 10 is released. The paper P is pulled out from the paper magazine M and conveyed (S1). FIG. 6A shows the length of the paper P with respect to the position CP of the cutter 4. However, when the length is 150 mm, the tip of the paper P is positioned on the paper guide 12 when the cutter position CP is used as a reference. Although located inside, the length of 183 mm is almost the same as the tip of the paper guide 12. Using the cutter position CP as a reference, the paper P is conveyed by the feed length (corresponding to the print size), and the paper P is stopped (S2).

  Next, the rear end of the paper P is cut by the cutter 4 (S3), and then the paper P is conveyed to a predetermined position by the post-cutting roller 5 (S4). The predetermined position differs depending on the feed length of the paper P, but is a position where the leading end side of the paper P can be securely held by the chucker roller 11. The predetermined position can be determined as appropriate, and can always be the same regardless of the feed length of the paper P.

  When the paper P is transported to the predetermined position, the chucker roller 11 is switched to the press-bonded state (S5). Thereby, since preparations for moving the chucker unit 10 are completed, the belt conveyor 13 is driven to move toward the delivery position P2 (S6). At this time, the paper P is transported in a state where the leading end side is sandwiched. In addition, when the feed length of the paper P is 150 mm, after cutting the paper P, it can be crimped by the chucker roller 11 and the movement of the chucker unit 10 can be started immediately.

  FIG. 6C shows a state where the chucker unit 10 has arrived at the delivery position P2. Further, meandering correction is performed while the paper P is conveyed by the chucker unit 10 (S7). Specifically, the drive amounts of the first motor 15A and the second motor 15B are made different. For example, the first motor 15A and the second motor 15B are started to be driven at the same time, and after stopping the second motor 15B first at the transfer position P2, the first motor 15A is driven extra by the correction value. The inclination of the paper P can be corrected. With this method, meandering correction is performed at the final stage of the transport process by the chucker unit 10.

  When the meandering correction is performed, the chucker unit 10 stops (S8), and the chucker roller 11 is driven to feed out the sandwiched paper P (S9). At the same time, the rotation of the exposure transport rollers 20 and 21 is also started (S10). However, at this stage, the pressure-conveying rollers 20 and 21 are in a released state. When the paper P is sent out, the leading edge of the paper P is detected by the exposure start sensor 23. As a result, it is possible to detect that the paper P has been transported. When it is detected that the paper P has been transported to the position of the first exposure transport roller 20, the first exposure transport roller 20 causes the paper P to be transported. Is crimped (S11). In conjunction with this, the pressure-bonded state of the chucker roller 11 is released (S12).

  When the exposure conveyance roller 20 is in a pressure-bonded state, exposure conveyance is started and image formation is performed (S13, 14). The paper P on which image formation has been performed is sent to the development processing unit 40 via the switchback unit D, where development processing is performed, and a photographic print is completed.

  According to this configuration, when the meandering correction is performed, the entire paper P is inclined while the paper P is held by the chucker roller 11. Further, the paper P is held only on the front end side of the paper P. Therefore, when the meandering correction is performed, the paper P is not subjected to any force other than the clamping force by the chuck roller 11, so that the meandering correction can be performed without any excessive force acting on the paper P. In addition, since the paper P is delivered to the image forming unit C after the meander correction is completed, the paper P is image-formed with a correct posture. In addition, since no excessive force is applied to the paper P during image formation, no banding problem occurs.

<2. When the paper feed length is 183 mm to 409 mm (second mode)>
Next, the case where the paper feed length is 183 mm to 409 mm will be described with reference to the operation diagram of FIG. 8 and the operation flowchart of FIG. 9. The description will focus on the differences from the first mode.

  The paper P is pulled out from the paper magazine M and conveyed (S31), and the paper P passes through the position of the cutter 4 and is conveyed as it is to a predetermined position in the chucker unit 10. Then, the conveyance of the paper P is stopped and the leading end side of the paper P is clamped by the chucker roller 11 (S32). At this time, the rear end position of the paper P to be cut has not reached the position of the cutter 4 (FIG. 8A). Therefore, the movement of the chucker unit 10 is started and the paper P is continuously conveyed. Even after the chucker unit 10 is moving, the post-cut rollers 5 and the like of the paper supply unit A continue to rotate.

  When the rear end position of the paper P to be cut reaches the position of the cutter 4, the chucker unit 10 is stopped, and at the same time, the post-cutting roller 5 is also stopped (S34) (FIG. 8B). At this time, even when the feed length of the paper P is 409 mm, the chucker unit 10 has not reached the delivery position P2. With the chucker unit 10 stopped, the rear end of the paper P is cut (S35). About the position where the chucker unit 10 stops on the way, it becomes a different position for every feeding length of the paper P.

  After cutting the paper P, the chucker unit 10 starts to move again (S36). The rear end of the cut paper P is detached from the post-cut roller 5 (S37). Thereby, as shown in FIG.8 (c), it will be in the state which the paper rear end hangs down by gravity. Thereafter, the meandering correction of the paper P is performed (S38). The steps after S39 are the same as those described in the first mode. Since the paper P hangs down before the paper P is sent to the image forming unit C, the impact at the time of the sag is subtracted before the image formation, and it has no adverse effect on the image formation such as banding. No (FIG. 8 (d)).

  Although FIG. 8C illustrates two cases where the paper P feed length is 183 mm and 409 mm, the paper transport unit B is hung down even when the paper P feed length is 409 mm. It has a space to accommodate the ends.

<3. When the paper feed length is 409 mm to 594 mm (third mode)>
Next, the case where the paper feed length is 409 mm to 594 mm will be described with reference to the operation diagrams of FIGS. 10A and 10B and the operation flowchart of FIG. 11. The description will focus on differences from the first mode and the second mode.

  The steps from S51 to S53 are the same as those in the second mode (FIG. 10A (a)). Then, the chucker unit 10 holding the paper P stops at the upstream side of the delivery position P2 as in the second mode (S54) (FIG. 10A (b)). This stop position can be a fixed position in the third mode. Even after the chucker unit 10 stops, the post-cutting roller 5, the pre-cutting roller 2, the advance roller 1 and the like continue to rotate (S55). Thereby, the loop R is formed so that the paper P may sag downward (S56) (FIG. 10A (c)). Further, the loop R is forcibly formed downward by the action of the first loop restricting body 52. In the paper transport unit B, a space necessary to accommodate the loop R is secured below the transport surface. In addition to forming a loop after the chucker unit 10 is stopped, during the movement of the chucker unit 10, the paper transport speed is higher than the rotation speed of the post-cut roller 5, the pre-cut roller 2, the advance roller 1, and the like. By controlling the moving speed of the chucker unit 10 to be small and forming a loop, it is possible to improve the operation efficiency.

  When the loop R is gradually formed and the rear end of the paper reaches the position of the cutter 4, the post-cutting roller 5 is stopped (S57), and the rear end of the paper is cut (S58). When the post-cutting roller 5 is driven again after the cutting (S59), the rear end of the paper is detached from the post-cutting roller 5 (S60), and the rear end of the paper hangs down due to gravity as shown in FIG. 10B (d). The paper transport unit B has a space for accommodating the trailing end that hangs down even when the feed length of the paper P is 594 mm.

  Next, the movement of the chucker unit 10 is started again, and meandering correction is performed (S61, 62). The steps after S63 are the same as those described in the first mode (FIGS. 10B (e) and (f)). Since the paper P hangs down before the paper P is sent to the image forming unit C, there is no adverse effect such as banding on the image formation.

In addition, the paper P may be transported in a state where the cut end of the paper P is held by the chucker unit 10 instead of hanging down after the cutting.
Specifically, as shown in FIG. 11B (a), after the front end side of the paper P is pressed against the first exposure transport roller 20, the chucker unit 10 is fed back to the receiving position P1, and then the loop Form. At this time, assuming that the transport speed at the paper supply section A is S1, the transport speed at the paper transport section B (moving speed of the chucker unit 10) is S2, and the transport speed at the image forming section C is S3, S1> S3 ( orS3 = 0) and S2 = 0, a predetermined amount of loop is formed, and then the rear end of the paper P is cut. At this time, image formation in the image forming unit C is not performed until a predetermined amount of loop is formed.

  The cut paper P moves the chucker unit 10 in a state where the rear end portion is sandwiched between the chucker units 10 (FIGS. 11B (b) and (c)). At this time, by the function of the conveyance speed setting means 60e, the image forming unit C performs image processing while conveying at the speed S2, and by setting S3> S2, the chuck unit 10 is moved while gradually reducing the loop. Move to delivery position P2. At this time, since approximately S2 / S3 = (length of the paper transport unit B) / (length of the paper P forming the loop) is established, the exposure transport rollers 20 and 21 are driven and controlled, and the chucker unit Ten moving speeds are set. At this time, the chucker unit 10 functions sufficiently by being held in a separated state, and the load on the paper P due to the crimped state can be eliminated.

  Next, the chucker unit 10 is moved to the delivery position P2, and the paper P is conveyed to the image forming unit C (FIG. 11B (d)). At this time, it is also possible to perform meandering correction by stopping on the upstream side of the delivery position P2.

  In this way, by controlling the moving speed S2 of the chucker unit 10 to a moving speed smaller than the conveying speed S3 of the paper P in the image forming unit C and eliminating the loop, it is possible to improve the operation efficiency. Become.

<4. When the paper feed length is 594 mm or more (fourth mode)>
Next, the case where the paper feed length is 594 mm or more will be described with reference to the operation diagrams of FIGS. 12A and 12B and the flowchart of FIG. 13A. Further, based on the operations of FIGS. 5A and 5B described above, the description will focus on the points different from the first mode to the third mode. The fourth mode corresponds to the case where the paper feed length exceeds the set amount, and the paper feed length setting means 60d cuts the rear end portion of the paper even during image formation, and the cut rear end portion. Can be transported. Further, by controlling the moving speed of the chucker unit 10 to a moving speed smaller than the conveying speed of the paper P during image formation by the function of the conveying speed setting means 60e, the paper P can be cut without causing a load or an impact. It is possible to transport the rear end portion.

  The steps from S71 to S73 are the same as those in the second mode (FIG. 12A (a)). Then, the chucker unit 10 holding the paper P stops upstream of the delivery position P2 as in the second mode and the third mode (S74) (FIG. 12A (b)). This stop position can be a fixed position as in the third mode. Then, similarly to the third mode, the post-cutting roller 5 and the like are continuously rotated to form a loop R (S75, 76) (FIG. 12A (c)). By the action of the first loop restricting body 52, the loop R is forcibly formed downward. At this time, it is possible not only to form a loop after the chucker unit 10 stops, but also to form a loop by adjusting the moving speed and the paper transport speed while the chucker unit 10 is moving. Is the same as in the third mode.

  When the predetermined amount of the loop R is formed, the drive system of the paper supply unit A such as the post-cut roller 5 is stopped (S77). Next, the chucker unit 10 is moved to perform meandering correction (S78, 79). That is, the meandering correction is performed after the loop R is formed, and even if the paper P is inclined by the meandering correction, the deformation can be absorbed in the loop R portion. When the meandering correction is performed, the rear end side is not yet cut and is constrained by the post-cutting roller 5 or the like, but since the loop R is formed, an excessive force acts on the entire paper. Can be prevented.

  When the chucker unit 10 reaches the delivery position P2, the chucker unit 10 is stopped (S80) (FIG. 12A (d)). Next, the chuck roller 11 is rotationally driven to send the leading end of the paper P toward the image forming unit C (S81). Simultaneously or almost simultaneously with this operation, the exposure transport roller 20 is also rotated (S82). When the leading edge of the paper reaches the position of the first exposure / conveyance roller 20, the leading edge of the paper is pressure-bonded by the first exposure / conveyance roller 20 (S83). At this time, since the post-cutting roller 5 on the paper rear end side is stopped, the loop R becomes smaller (FIG. 12A (e)). After the paper P is pressure-bonded by the first exposure transport roller 20, the first exposure transport roller 20 is stopped once.

  Next, the chucking state of the chuck roller 11 is released (S84), and the chuck unit 10 is returned from the delivery position P2 to the receiving position P1 (S85) (FIG. 12B (f)). At this time, the paper P is returned while passing between the chuck rollers 11, but since the pressure is released and the loop R is small at this time, a large load acts on the paper P. There is nothing.

  When the chucker unit 10 returns to the receiving position P1, the driving of the post-cut roller 5 and the like of the paper supply unit A is started again (S86). At this time, since the first exposure transport roller 20 is in a stopped state, a loop is formed on the downstream side of the chucker unit 10 (S87) (FIG. 12B (g)). At this time, the chucking of the chucker roller 11 remains released. Further, the loop R is surely formed downward by the action of the second loop restricting body 53.

  When a predetermined amount of loop is formed, rotation of the exposure transport rollers 20 and 21 is started (S88). As a result, image formation on the paper P is started (FIG. 12B (h)). The rotation of the post-cutting roller 5 and the like is continued, and when the rear end of the paper comes to the position of the cutter 4, the rotation of the post-cutting roller 5 is stopped, and the rear end side of the paper P is pressed by the chucker roller 11, The rear end of the paper is cut (S89, 90). While the paper P is being cut, the exposure transport rollers 20 and 21 are rotated, and image formation continues even during the cutting, but the size of the formed loop R gradually decreases. Further, since the loop R is formed, the impact at the time of paper cutting is not transmitted to the image forming unit C. Therefore, even for the paper P having a long length in the transport direction, the problem of image quality deterioration due to the influence of banding or the like does not occur.

  After the paper cut, the chucker unit 10 is moved again toward the image forming unit C (S91). Therefore, the image is formed in the image forming unit C, and is conveyed in a state where the paper trailing end side is supported by the chucker unit 10. At this time, a small loop R is formed on the downstream side of the chucker unit 10 (FIG. 12B (i)). The conveyance speed by the exposure conveyance rollers 20 and 21 and the movement speed of the chucker unit 10 in the image forming unit C can be set to appropriate speeds so as not to be affected by banding. That is, similarly to FIG. 11B in the third mode, by controlling the moving speed S2 of the chucker unit 10 during image formation to a moving speed smaller than the conveying speed S3 of the paper P, a load or an impact on the paper P is generated. It becomes possible to transport the paper P.

  When the chucker unit 10 starts moving and the rear end of the paper is separated from the post-cutting roller 5, the rotation of the post-cutting roller 5 stops. Further, the pressure bonding of the chuck roller 11 is released (S92). At this time, since the load on the paper P can be further reduced with respect to the rear end side of the paper P, a case where the paper P is moved in a state in which the pressure bonding is released will be described. When the chucker unit 10 reaches the delivery position P2 (S93), the chucker unit 10 stops, and the paper P is continuously transported by the exposure transport rollers 20 and 21 to perform image formation (FIG. 12B (j)). . Since the chucker unit 10 moves in a state where the chucker roller 11 is released from the pressure bonding, the chucker unit 10 has a function of supporting the rear end of the paper so that it does not hang down. Therefore, an excessive force does not act on the paper P while the exposure transport rollers 20 and 21 are transported to form an image.

<Operation of switchback unit>
The paper P on which the image has been formed is sent to the development processing unit 40 via the switchback unit D. The operation in the switchback unit D will be described. FIG. 14 shows an operation when the feeding length of the paper P is short. In this case, the paper P is fed out by the conversion roller 30. That is, as shown in FIG. 14A, the pressure-bonded state of the driving roller 30a and the pressure roller 30b is released, and the exposed paper P enters. When entering a predetermined position, the paper P is pressure-bonded as shown in FIG. 14 (b), and is rotated by 90 ° as shown in FIG. 14 (c). Thereby, the emulsion surface N of the paper P is converted as shown. Thereafter, the paper P is conveyed toward the development processing unit 40 by the conversion roller 30.

  When the feeding length of the paper P is longer than a predetermined value, the paper P is wound around the winding roller 31 as shown in FIG. The paper P is wound around the take-up roller 31 by a crimping mechanism (not shown). Further, the winding roller 31 is lowered obliquely downward as shown in FIG. 15B while winding the paper P. In the state of FIG. 15C, the outer peripheral tangent of the paper P wound around the take-up roller 31 just coincides with the transport path toward the development processing unit 40. When the paper is wound up to this state, the paper P is conveyed toward the development processing unit 40 by the conversion roller 30. Thereby, the emulsion surface N of the paper P is converted as shown. By converting the emulsion surface N as shown in the figure, the development processing in the development processing unit 40 can be performed in a correct posture.

<Modification of chucker roller>
Next, a modification of the chucker roller 11 that holds the paper P will be described with reference to FIG. The width of the chucker roller 11 is formed to be slightly larger than the width of the paper P having the maximum width that can be processed, and the diameter dimension thereof is constant in the width direction. The present invention is not limited to this, and may be set to be slightly shorter than the paper width, as shown in FIG. As shown in FIG.16 (b), you may be divided | segmented into the some roller part over the width direction. In this case, the number of divisions can be set arbitrarily. The chucker roller 11 is composed of the driving roller 11a and the pressure roller 11b. However, one or both of the rollers can be configured as described above.

  There are various width dimensions of the paper P. In either case, the paper P is sandwiched over the entire width direction or almost the entire area of the paper P. In this state, the entire paper P is rotated to perform meandering correction. Therefore, an excessive force does not act on the paper P, and it is not necessary to form a ridge.

  FIG. 16C is a diagram showing another embodiment, and a mechanism is provided in which the paper P including the chucker roller 11 can rotate around a predetermined axis X. For example, a dedicated motor for rotation is provided, and the paper P can be rotated by this motor. Thereby, meandering correction can be performed. In this case, the drive amounts of the left and right motors 15A and 15B are set to be the same. When performing meandering correction, the degree of correction can be defined by the amount of rotation by a dedicated motor. Thereby, the movement in the meander correction becomes smooth.

  Further, even when the drive amounts of the left and right motors 15A and 15B are made different, the mechanism can be rotated smoothly by providing a mechanism that can rotate around the axis X.

<Another embodiment>
In the present embodiment, the image forming unit C including a laser engine has been described, and the paper P, which is a photographic photosensitive material, is taken as an example of the image forming medium. However, the present invention is not limited to this. In addition to the laser engine, an appropriate digital exposure engine such as a CRT engine or a PLZT engine can be used. The present invention can also be applied to an image forming apparatus that forms an image by ejecting ink onto a paper surface by an ink jet printer.

Internal configuration diagram (schematic diagram) showing the main parts of the image forming apparatus Internal configuration diagram showing the main parts of the image forming apparatus (specific illustration) The perspective view which shows the structure of a chucker unit Block diagram showing functions of image forming apparatus Diagram explaining loop formation of paper Diagram explaining loop formation of paper Diagram for explaining paper transport operation (first mode) Flowchart explaining paper transport operation (first mode) Diagram for explaining paper transport operation (second mode) Flowchart explaining paper transport operation (second mode) Diagram for explaining paper transport operation (third mode) Diagram for explaining paper transport operation (third mode) Flowchart explaining paper transport operation (third mode) Diagram explaining paper transport speed Diagram for explaining paper transport operation (fourth mode) Diagram for explaining paper transport operation (fourth mode) Flowchart explaining paper transport operation (fourth mode) Diagram explaining the operation of the switchback unit Diagram explaining the operation of the switchback unit The figure explaining the modification of a chucker roller Internal configuration diagram (schematic diagram) showing a conventional image forming apparatus

Explanation of symbols

A Paper supply part B Paper conveyance part C Image formation part D Switchback part M Paper magazine P Paper P1 Reception position P2 Delivery position 4 Cutter 10 Chucker unit 11 Chucker roller 12 Paper guide 13 Belt conveyor 20 First exposure conveyance roller 21 Second Exposure conveyance roller 60 Control unit 60a Meander correction unit 60b Conveyance mode setting unit 60c Loop forming unit 60d Paper feed length setting unit 60e Conveyance speed setting unit 61 Chucker control unit 62 Correction value storage unit 63 Magazine detection unit 64 Print size setting unit

Claims (4)

An image forming apparatus including an image forming unit that forms an image on the surface of an image forming medium,
An image forming medium is received from a cutting unit that cuts the image forming medium into an arbitrary length and a medium supply unit that supplies the image forming medium at a receiving position on the upstream side of the conveyance. A medium conveying unit that delivers the forming medium, an image forming medium feeding length setting unit, and a conveying speed setting unit,
When the image forming medium feed length exceeds the set amount, the feature is that the rear end of the cut image forming medium is conveyed to the delivery position by the medium conveying unit at a speed different from the conveying speed of the image forming medium. Image forming apparatus.   A medium clamping mechanism is provided in the medium conveying section and clamps the leading end side of the image forming medium over the entire region in the conveying width direction or substantially the entire region, conveys the image forming medium from the receiving position to the delivery position, and after conveyance The image forming apparatus according to claim 1, wherein the rear end portion that is reversely fed and clamped is clamped with the clamping member of the medium clamping mechanism spaced apart and conveyed to the delivery position again.   A loop forming mechanism for forming a loop of the image forming medium between the receiving position and the transferring position, and with the loop forming mechanism forming the loop, the medium conveying unit is moved to the transferring position by sandwiching the rear end portion. The image forming apparatus according to claim 1, wherein the image forming apparatus is conveyed.   The image forming apparatus according to claim 1, wherein a speed at which a rear end portion of the image forming medium is transported to a delivery position by a medium transporting section is made smaller than a transport speed of the image forming medium. .

Images