JP4381368B2 - Image forming apparatus - Google Patents

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, 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 completely straight direction because the transport width dimension is large. 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. Thus, meandering correction means for correcting the meandering of the paper is disclosed in the following patent document.

JP 2001-146345 A JP 2000-272774 A

  Patent Document 1 relates to a printing apparatus that records and forms a toner image on an image forming medium (recording material), and discloses a technique for performing meandering correction accompanying paper contraction due to a temperature change. That is, the image forming medium is conveyed by a heating roller and a pressure roller for transferring an image onto the image forming medium by a transfer belt, and meandering correction means is incorporated in the nipping and conveying roller on the downstream side. Specifically, the pressing roller of the nipping and conveying roller is divided into a plurality of parts in the width direction, and the pressure portion of each of the divided rollers can be changed. As a result, the meandering image forming medium is returned to the normal conveyance state.

  However, this Patent Document 1 discloses a technique for correcting meandering of an image forming medium after image formation, and does not perform meandering correction of an image forming medium sent to an image forming unit as in the present invention. . In addition, meandering correction is to change the pressure distribution in the width direction while the image forming medium is conveyed by the nipping and conveying roller. Therefore, in the case of an image forming medium having a large width such as an advertisement print, an unreasonable force acts. May cause drought.

  In Patent Document 2, in a transport mechanism for transporting an image forming medium (paper), a pair of left and right transport rollers are arranged such that their axes are V-shaped with their valleys facing each other in the transport direction of the image forming medium. Automatically corrects meandering that occurs during transport. This meandering correction means also corrects meandering while nipping and transporting the image forming medium. Since the transport rollers are arranged in a V shape, in the case of a wide image forming medium such as an advertisement print. Unreasonable force may act to generate wrinkles.

  The present invention has been made in view of the above circumstances, and the problem is that when the image forming medium is transferred to the image forming unit, it can be transferred in a meandering correction form, and the print size is large. Another object of the present invention is to provide an image forming apparatus that performs meandering correction so that an excessive force does not act.

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;
A medium conveying unit that receives the image forming medium from a medium supply unit that supplies the image forming medium at a receiving position on the upstream side of the conveyance, and delivers the image forming medium to the image forming unit at a conveying position on the downstream side of the conveyance;
A medium clamping mechanism that is provided in the medium conveying section and clamps the leading side of the image forming medium over the entire area in the conveying width direction or substantially the entire area;
A pair of transport mechanisms that are provided on both sides in the width direction of the medium transport unit and transport the medium clamping mechanism from a receiving position to a delivery position;
While the medium clamping mechanism moves from the receiving position to the delivery position, the meandering of the image forming medium is corrected by changing the conveyance amount of the pair of conveyance mechanisms while the image forming medium is clamped by the medium clamping mechanism. Meandering correction means.

  The operation and effect of the image forming apparatus having this configuration will be described. In the image forming apparatus, when the medium transport unit receives the image forming medium at the receiving position on the upstream side of the transport, the medium transport unit transports the image forming medium to the transfer position on the downstream side of the transport. The medium conveyance unit includes a medium clamping mechanism, and clamps the entire or almost entire area in the conveyance width direction on the leading side of the image forming medium. The medium transport unit moves from the receiving position to the transfer position while sandwiching the image forming medium, and transfers the image forming medium to the downstream image forming unit. The meandering correction means performs meandering correction in a state where the image forming medium is held by the medium holding mechanism. The meandering correction is performed before moving from the receiving position to the delivery position. Therefore, since the image forming medium is delivered to the image forming unit in a meandering-corrected form, high quality image formation can be performed. Further, when the meandering correction is performed, the leading end of the image forming medium is sandwiched along the width direction by the medium sandwiching mechanism, so that the meandering correction without excessive force is possible. As a result, when the image forming medium is transferred to the image forming unit, it can be transferred in a meandering-corrected form, and the image forming is performed such that excessive force does not act even if the print size is large. An apparatus can be provided.

  In the present invention, a loop forming means for forming a loop of the image forming medium before moving from the receiving position to the delivery position is provided. After the loop is formed by the loop forming means, the meander correction by the meander correcting means is performed. It is preferable.

  When the print size becomes longer in the transport direction, a loop (sagging state) of the image forming medium is formed in order to prevent the trailing edge cutting timing and the vibration during the cutting from affecting the image formation. When the meandering correction of the image forming medium is performed by forming a loop, the distortion that occurs at that time is alleviated from affecting the entire image forming medium, preventing excessive force from acting on the image forming medium. can do. Therefore, meandering correction can be performed without difficulty by performing meandering correction after forming a loop.

  In the present invention, the medium transport unit includes a pair of transport mechanisms for transporting the medium clamping mechanism from a receiving position to a delivery position on both sides in the width direction, and the meandering correction unit includes the pair of transport mechanisms. It is preferable to perform meandering correction by varying the transport amount.

  According to this configuration, the pair of transport mechanisms are provided on both sides in the width direction of the medium holding mechanism, and the inclined state is corrected by changing the transport amounts, and the meandering correction is performed. Since correction is performed so that the leading side of the image forming medium is entirely tilted while the leading side of the image forming medium is sandwiched, meandering correction can be performed without applying excessive force to the image forming medium. . Further, by changing the setting of the carry amount according to the type and size of the image forming medium, it is possible to perform an appropriate meandering correction corresponding to the print size.

  In the present invention, it is preferable to provide a mechanism for allowing the medium clamping mechanism to rotate around a predetermined axis perpendicular to the conveyance surface.

  By configuring the medium clamping mechanism to be rotatable, it is possible to correct the inclination of the image forming medium without applying an excessive force when performing meandering correction.

  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 pre-cutter roller 2, and detects that the top of the paper is loaded. The cutter 4 cuts the rear end side of the paper so as to obtain the 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 (a driving roller and a pressure roller), and sandwiches the front side of the paper over the entire region in the width direction or almost the entire region. That is, the paper is transported to the delivery position P2 while the leading side of the paper is held by the chucker 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 beam, 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 top 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 by the conversion roller 30 so as to be on the arrow N side. 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. .

  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. The guide mechanism 51 can perform a guide when transporting the chucker unit 10.

  Further, as shown in FIG. 2, 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 as shown in FIG. 2, when the chucker unit 10 is located at the delivery position P2, 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. 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.

  FIG. 5 is a diagram showing a state when the meander correction is performed. FIG. 5A shows a state in which the paper is not inclined. In this case, if the drive amounts of the left and right motors 15A and 15B are the same, the paper P is put on the image forming unit C in the same posture. Can be handed over. Further, as shown in FIG. 5B, when the paper P is received in a state of being inclined by θ due to the meandering conveyance of the paper P, the meandering correction is performed by changing the drive amounts of the left and right motors 15A and 15B. An inclined state can be eliminated. In this case, the inclination of the angle θ can be corrected by setting the drive amount of the left motor 15A to be larger than the drive amount of the right motor 15B. FIG. 5C shows a state in which the meandering is corrected, and it is only necessary that the meandering correction is performed before the chucker unit 10 moves to the delivery position P2.

  When the paper P is pulled out from the paper magazine M and conveyed, the paper P is conveyed in a meandering state due to various factors such as variations in the width direction of the pressure-bonding force of the pressure-bonding rollers, although guided on both sides in the width direction. If an image is formed while the paper P 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 as described above, it is possible to form an image with the paper in a correct posture.

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

  The magazine detection unit 63 detects information on the paper P 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 the paper P. 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 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 top of the paper P 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 P from the detection of the top of the paper P to the position to be exposed 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 P 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 rollers 2 and 5 are driven and stopped. The timing, the operation timing of the cutter 4 and the like are controlled.

  The magazine control unit 68 performs pulling out of the paper P 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 transport direction of the paper P is less than a predetermined value, the paper P is sent to the development processing unit 40 by the conversion roller 30, and when the length of the paper P is equal to or longer than the predetermined value, the take-up roller 31 Paper P is sent to the development processing unit. The length data in the transport direction of the paper P 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.).

<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. In this operation, a control for forming a loop on the paper P may be performed, and the control unit 60 also functions as the loop forming unit 60c.

<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). 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 top of the paper P is the top of 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 varies depending on the feed length of the paper P, but is a position where the leading 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, as described in FIG. 5, 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 beginning 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 leading 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 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 diagram of FIG. 10 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 the steps in the second mode (FIG. 10A). Then, the chucker unit 10 holding the paper P stops at the upstream side from the delivery position P2 as in the second mode (S54) (FIG. 10B). 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. 10C). 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.

  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). After the cutting, when the post-cutting roller 5 is driven again (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. 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. 10E and 10F). 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.

<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. The description will focus on the differences from the first mode to the third mode.

  The steps from S71 to S73 are the same as the steps in the second mode (FIG. 12A). 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. 12B). This stop position can be a fixed position as in the third mode. Then, similarly to the third mode, the post-cutting rollers 5 and the like are continuously rotated to form a loop R (S75, 76) (FIG. 12C). By the action of the first loop restricting body 52, the loop R is forcibly formed downward.

  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. 12 (d)). Next, the chucker roller 11 is rotationally driven to send the leading edge 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. 12E). 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 chucker roller 11 is released (S84), and the chucker unit 10 is returned from the delivery position P2 to the receiving position P1 (S85). 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 / conveyance roller 20 is in a stopped state, a loop is formed on the downstream side of the chucker unit 10 (S87) (FIG. 12 (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. 12H). 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. 12 (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.

  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). 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, and image formation is performed. 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 crimped and rotated 90 ° as shown in FIG. 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 the figure 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 modified example of the chucker roller 11 that holds the paper P will be described with reference to FIG. As shown in FIG. 5, 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. 16B, it may be divided into a plurality of roller portions over the width direction. In this case, the number of divisions can be set arbitrarily. The chucker roller 11 includes a drive roller 11a and a pressure roller 11b, but 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.

  Although the means for performing meandering correction has been described in the present embodiment, the present invention 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.

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 paper meandering correction 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 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

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 61 Chuck control unit 62 Correction value storage unit 63 Magazine detection unit 64 Print size setting unit

Claims (2)

An image forming apparatus including an image forming unit that forms an image on the surface of an image forming medium,
A medium conveying unit that receives the image forming medium from a medium supply unit that supplies the image forming medium at a receiving position on the upstream side of the conveyance, and delivers the image forming medium to the image forming unit at a conveying position on the downstream side of the conveyance;
A medium clamping mechanism that is provided in the medium conveying section and clamps the leading side of the image forming medium over the entire area in the conveying width direction or substantially the entire area;
A pair of transport mechanisms that are provided on both sides in the width direction of the medium transport unit and transport the medium clamping mechanism from a receiving position to a delivery position;
While the medium clamping mechanism moves from the receiving position to the delivery position, the meandering of the image forming medium is corrected by changing the conveyance amount of the pair of conveyance mechanisms while the image forming medium is clamped by the medium clamping mechanism. An image forming apparatus comprising a meandering correction unit.   It comprises loop forming means for forming a loop of the image forming medium before moving from the receiving position to the delivery position, and after the loop is formed by the loop forming means, meander correction by the meander correcting means is performed. The image forming apparatus according to claim 1.

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