JP5287396B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that prevents or reduces curling of recording paper.

  In an image forming apparatus such as a printer or a copying machine, toner is attached to an electrostatic latent image formed on a photosensitive drum, and finally transferred to recording paper. The recording paper is provided in the image forming apparatus. The toner is conveyed to the fixing device, and the toner is fixed on the recording paper by melting the toner in the fixing device.

  Generally, in a fixing device provided in an electrophotographic image forming apparatus, a heating roller is disposed toward a surface to which a recording sheet is transferred, and a pressure roller is disposed toward the opposite surface. . The heating roller has a heater inside, and the pressure roller melts the toner on the recording paper by pressure and heating, and fixes the recording paper to the recording paper by pressing the recording paper against the heating roller.

  However, since the heating roller and the pressure roller respectively apply heat and pressure to only one side of the recording paper, the recording paper may curl and the quality may be greatly impaired.

  About this, the following reasons are generally known. The first reason is toner shrinkage. The toner transferred to the recording paper shrinks as it melts, and curls because the amount of shrinkage differs due to differences in the shrinkage of the recording paper between the toner surface and the boundary surface between the toner and the recording paper, heating differences, etc. May occur. In particular, when more toner is transferred over the entire surface, the degree of curling tends to increase.

  The second reason is evaporation of moisture content. The moisture content of the recording paper evaporates due to heating, and in particular, the heated surface side evaporates more. Therefore, a difference in shrinkage occurs between the heated surface and the opposite surface, causing curling. In particular, the curl tends to increase when the humidity of the environment in which the apparatus is installed is high or when the temperature is low. Further, as the thickness of the recording paper increases, the difference in moisture content between the heated surface and the opposite surface becomes more prominent, and the curl may become more serious.

  The third reason is the pressure on the recording paper. For example, when the conveyance path is not a straight line, there is a case where pressure is applied to the recording paper when the conveyance path is advanced and curls. This is due to the conveyance path curvature and the quality of the recording paper.

  For example, the following solutions have been proposed for such problems. For example, Patent Document 1 discloses an invention in which a curl correction roller having a hard surface hardness and a pressure roller having a soft surface hardness are arranged, and pressure is applied in a direction opposite to the curling direction when the recording paper passes through the nip. Is disclosed. However, if the difference in surface hardness is extremely provided, a nip mark of the correction roller may remain on the pressure roller side, which may cause conveyance failure or abnormal noise. When a high curl correction effect is desired by this method, the above problem may occur. Further, when the pressure adjusting mechanism as described above is installed, there is a problem that the cost for the pressure adjusting mechanism is increased.

  Further, Patent Document 2 discloses an invention in which the degree of curling is estimated based on the image density, and based on that, the peripheral speed difference between the heating roller and the pressure roller is changed to apply pressure in a direction opposite to the curling direction. ing. However, it is not preferable to reduce the cost because it is necessary to provide a motor and a clutch exclusively for the difference in peripheral speed between the heating roller and the pressure roller. Further, when the peripheral speed is increased, the stress on the roller is increased, and the durability of the parts may be a problem.

  Patent Document 3 discloses an invention in which a storage tray that temporarily stores recording paper is disposed, and the recording paper that has passed through the fixing device is discharged to the storage tray and gradually cooled. However, there is a problem that it is necessary to install a space in which the storage tray is arranged and the storage tray itself.

  In Patent Document 4, toner is transferred to a recording paper, passed through a fixing unit, then passed through a fixing unit again using a reversing unit, and an image is recorded on the recording paper that has passed the reversing unit at that time. An invention that does not allow transfer is disclosed. However, it is well known that curling is reduced by reversing the recording paper and passing it twice through the fixing device to reduce heat and pressure on both sides of the recording paper. When this means is used for paper, there is a problem in that productivity is greatly impaired because a reversal part is used in spite of single-sided printing.

  Accordingly, the present invention has been made in view of the above problems, and an image forming apparatus capable of preventing curling, reducing, and improving productivity of a recording sheet by determining an optimum conveying order and conveying the recording sheet. The purpose is to provide.

In order to solve the above-described problems, an image forming apparatus according to the present invention includes a first conveying unit that conveys a recording sheet for recording an image based on image data, and a recording sheet that is conveyed by the first conveying unit. An image transfer means for transferring the image to the image, a fixing means for fixing the recording paper to which the image has been transferred by the image transfer means, by heating and pressing, and a recording paper on which the image has been fixed by the fixing means to the discharge section or recording paper A sheet conveying means for controlling whether the sheet is conveyed to a sheet reversing means for reversing the front and back, a second conveying means for conveying the recording paper to a conveyance destination controlled by the conveyance control means, and acquiring and storing image data information And a curl amount estimating means for estimating a curl amount when each image is transferred to a recording sheet based on image data information stored in the data storage means. And Carl amount estimated by the amount estimating means, and the number of the recording sheets that can be held in the second conveying means, by controlling the conveying order as the transport destination can be processed in the shortest time based on, conveyance control means, the recording sheet When the image is transferred to one side of the sheet, the number of recording sheets retained in the sheet reversing unit is less than the number of recording sheets that can be held by the second conveying unit, and the image estimated by the curl amount estimating unit If the curl amount exceeds a certain value, the image transfer means does not transfer the image to the recording paper conveyed by the first conveying means, and the recording paper is transferred to the second conveying means via the fixing means. Is transferred to the paper reversing means, the image is transferred to the recording paper after the paper reversing means is conveyed, and the recording paper is conveyed to the discharge section by the second conveying means via the fixing means. , characterized in that.

  According to the present invention, it is possible to prevent the curling of the recording paper by determining the optimum transport order and transporting the recording paper.

1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a system configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the flowchart of the operation | movement which concerns on embodiment of this invention. It is a figure which shows the operation | movement which concerns on embodiment of this invention. It is a timing chart figure of operation concerning an embodiment of the present invention.

  In order to simplify the description according to the embodiment of the present invention, the following conditions are used. First, the time required for communication with the host computer and the time until image information is transmitted from the host computer and stored in the RAM 23 of the apparatus are not considered. This is a remarkable improvement in the performance of recent communication I / F (LAN local area network, USB universal serial bus, etc.), and the time required for communication is very small compared to the time for printing operation of the device. This is because it must not. For further simplification, the printing operation of the embodiment described later is only one color of black (Bk). In the case of multiple colors, it is considered that there is no particular change because only a toner image for each color is generated. Also, the amount of blank image data is not considered. This is because one of the following is generally true: The image processing unit 27 has a blank page image output mode, and can output a blank page image even if no blank page image is stored in the RAM 23. Alternatively, even if a blank image is generated in the RAM 23, the blank image is a very simple image. Therefore, when image compression is performed, the image size is extremely small and can be virtually ignored.

  FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the AIO cartridge (6Bk, 6M, 6C, 6Y) of each color is arranged along the transfer belt 5 and is called a so-called tandem type. In FIG. 1, the transfer belt 5 rotates counterclockwise, and a plurality of AIO cartridges (electrophotographic process units) 6Bk, 6M, 6C, 6Y are arranged in order from the upstream side in the rotation direction. The plurality of AIO cartridges 6Bk, 6M, 6C, and 6Y have the same internal configuration except that the colors of the toner images to be formed are different. The AIO cartridge 6Bk forms a black image, the AIO cartridge 6M forms a magenta image, the AIO cartridge 6C forms a cyan image, and the AIO cartridge 6Y forms a yellow image.

  In the following description, the AIO cartridge 6Bk will be described in detail. However, since the other AIO cartridges 6M, 6C, and 6Y are the same as the AIO cartridge 6Bk, each component of the image forming units 6M, 6C, and 6Y is described. Is replaced with Bk attached to each component of the image forming apparatus 6Bk, and only the symbols distinguished by M, C, and Y are displayed in the drawing, and the description thereof is omitted.

  The transfer belt 5 is an endless belt wound around a secondary transfer drive roller 7 and a transfer belt tension roller 8 that are rotationally driven. The secondary transfer drive roller 7 is driven to rotate by a drive motor (not shown), and the drive motor, the secondary transfer drive roller 7 and the transfer belt tension roller 8 serve as drive means for moving the transfer belt 5. Function.

  The image forming unit 6Bk includes a photoconductor 9Bk as a photoconductor, a charger 10Bk arranged around the photoconductor 9Bk, an exposure device 11, a developing device 12Bk, a cleaner blade 13Bk, and the like. The exposure unit 11 is configured to irradiate laser beams 14Bk, 14M, 14C, and 14Y that are exposure lights corresponding to image colors formed by the AIO cartridges 6Bk, 6M, 6C, and 6Y.

  At the time of image formation, the outer peripheral surface of the photoconductor 9Bk is uniformly charged by the charger 10Bk in the dark, and then exposed by the laser beam 14Bk corresponding to the black image from the exposure device 11, thereby forming an electrostatic latent image. Is done. The developing device 12Bk visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photoreceptor 9Bk.

  This toner image is transferred onto the transfer belt 5 by the action of the primary transfer roller 15Bk at a position (primary transfer position) where the photoconductor 9Bk and the transfer belt 5 are in contact with each other. By this transfer, an image of black toner is formed on the transfer belt 5. After the transfer of the toner image, the photosensitive member 9Bk waits for the next image formation after the unnecessary toner remaining on the outer peripheral surface is wiped off by the cleaner blade 13Bk.

  As described above, the transfer belt 5 to which the black toner image is transferred by the AIO cartridge 6Bk is conveyed by the transfer belt 5 to the next AIO cartridge 6M. In the AIO cartridge 6M, a magenta toner image is formed on the photoconductor 9M by a process similar to the image forming process in the AIO cartridge 6Bk, and the toner image is superimposed on the black image formed on the transfer belt 5. Transcribed.

  The transfer belt 5 is further conveyed to the next AIO cartridges 6C and 6Y, and a cyan toner image formed on the photoconductor 9C and a yellow toner image formed on the photoconductor 9Y are subjected to the same operation. Then, the image is transferred onto the transfer belt in a superimposed manner. Thus, a full-color image is formed on the transfer belt 5. The transfer belt 5 on which the full-color superimposed image is formed is conveyed to the position of the secondary transfer roller 16.

  In the case of black-and-white printing at the time of image formation, the primary transfer roller 15M, the primary transfer roller C, and the primary transfer roller Y are retracted to positions separated from the photoconductor 9M, photoconductor 9C, and photoconductor 9Y, respectively. The above-described image forming process is performed only for black.

  During the paper transport operation during image formation, the paper 4 stored in the paper feed tray 1 is sequentially sent out by rotating the paper feed roller 2 counterclockwise from the top, and at the registration roller 3 position. stand by. The driving of the registration roller 3 is started at a timing such that the position of the toner image and the paper 4 overlaps on the toner image conveyed by the transfer belt 5 and the secondary transfer roller 16. (Unless otherwise specified, this secondary transfer position is referred to as a transfer portion or a transfer position.) At this time, the registration roller 3 is driven to rotate counterclockwise to feed out the paper 4.

  The paper 4 sent out by the registration roller 3 is transferred to the paper 4 on the transfer belt 5 by the secondary transfer roller 16, and then the toner image is fixed by heat and pressure in the fixing device 20. The paper is discharged to the outside of the image forming apparatus by a paper discharge roller 18 driven to rotate counterclockwise. (Hereafter, this paper discharge operation is called standard paper discharge.)

  When performing duplex printing, the paper discharge roller 18 is driven to rotate clockwise before the paper 4 passes through the paper discharge roller 18, and the paper 4 is discharged to the double-sided conveyance path. (This paper discharge operation is hereinafter referred to as double-sided paper discharge.) The paper 4 conveyed to the double-sided conveyance path is conveyed again to the registration roller 3 via the double-sided roller 19. The sheet 4 that has reached the registration roller 3 is again fed from the registration roller 3, and after the toner image is transferred to the opposite side of the sheet by the secondary transfer roller 16, the toner image is heated by the fixing device 20. It is also possible to discharge the sheet to the outside of the image forming apparatus by a discharge roller 18 fixed by pressure and driven to rotate counterclockwise.

  The fixing roller 21 is provided with a separation claw (not shown). The separation claw enters between the recording paper and the fixing roller, thereby preventing the recording paper from being wound around the fixing roller.

  FIG. 2 is a schematic electrical system diagram of the image forming apparatus of the present embodiment. The CPU 28 is a central processing unit that controls the entire image forming apparatus of the present embodiment. The flash ROM 22 is a rewritable ROM that stores instruction codes executed by the CPU 28. The RAM 23 is a storage device that can temporarily store data and image information necessary for software control.

  The communication control unit 26 can communicate with an external host computer (not shown), and can receive a print request and image data from the host computer and develop them on the RAM 23. Further, the CPU 28 can display an operation instruction to the user on the host computer through the communication control unit 26. The writing control unit 24 can convert the image data developed on the RAM into a writing signal, and transmits the writing signal to the exposure device 11 to generate an electrostatic latent image corresponding to each color image on the photosensitive member. 9 can be created. Further, after the generation of the first color electrostatic latent image (after the generation of the Bk color electrostatic latent image in the configuration shown in FIG. 1), the writing control unit sets the next output image and then waits for an appropriate pause period. It is a mechanism to start image output. The image processing unit 27 can perform image processing such as CMYK separation, image rotation, and compression / decompression on the image developed on the RAM, and can create a blank image (an image in which all pixels are white). You can also. In the present text, the start of generation of the electrostatic latent image of the first color is expressed as assertion of the KFgate signal, and the end of generation of the electrostatic latent image of the first color is expressed as negation of the KFgate signal.

  The motor driver 25 follows the instructions of the CPU 28 for each color photoconductor 9, each color developing device 12, the transfer belt tension roller 8, the secondary transfer drive roller 7, the secondary transfer roller 16, the paper feed roller 2, the double-side roller 19, and the paper discharge roller. Each motor (not shown) connected to 18 can be freely rotated and stopped, and each color photosensitive member 9 and the transfer belt 5 can be freely changed in contact and separation by a cam-shaped mechanism (not shown).

  FIG. 3 is a flowchart showing instructions executed by the CPU 28 according to the embodiment of the present invention.

  Here, the symbols in the figure are defined as follows. D is a constant that means the number of recording sheets that can stay in the double-sided conveyance path + 1. d is a variable indicating the number of recording papers staying in the duplex conveyance path. Q is a queue (FIFO) for queuing images existing on the RAM 23.

  First, various variables and flags are initialized (step S2). Next, it waits for the reception of a print request transmitted from the host computer (step S3). If not received (step S3, NO), the determination is repeated. If it is received (step S3, YES), it is determined whether the following two conditions are satisfied (step S4). One is to receive the next image and determine whether it can be stored in the RAM 23. That is, it is the same value as whether or not the free capacity of the RAM 23 satisfies the information amount for one page of the image. In the present embodiment, it is assumed that the amount of information for one page of the image is known in advance. For example, the host computer may transmit image information without compression. If a compressed image is received from the host computer, it is possible to determine the worst compression rate and determine whether there is more free space in the RAM 23 or query the host computer in advance for the image size. Secondly, it is determined whether or not the recording paper can stay in the duplex conveyance path. That is, it is equivalent to whether d <D is satisfied.

  If the two conditions are satisfied (step S4, YES), an image transfer request is transmitted to the host computer (step S5), and the reply content (image information) of the image transfer request is determined to the host computer (step S6). . If the image cannot be received (step S6, NO), it is determined that the job has ended, and the job end flag is turned ON (step S20). Step S20 is a step executed when there is a reply without the next image in response to the image transfer request to the host computer in step S6.

  If the image can be received (step S6, YES), the image (this is referred to as image n) is received, the image is stored in the RAM 23, and whether the curl is acceptable when the received image is transferred is determined (step S7). To do. If the expected curl amount is acceptable (step S7, YES), the image n is enqueued in the image queue Q. Here, there are various methods for determining the curl amount, and although it depends on the configuration of the apparatus, the image printing rate, temperature, humidity, paper quality, paper length, etc., it is easy to predict under certain conditions through experiments. is there. From experience, it is known that the printing rate of an image has the strongest influence, so that it can be judged sufficiently accurately when image information is received. A method for determining the curl amount is disclosed in, for example, Reference 5. The amount of curl that can be tolerated depends on the configuration of the apparatus and the target print quality. In this embodiment, a certain value is used.

  When the curl amount of the image n is not allowable (step S7, NO), the recording paper to which the image n is transferred is discharged to the double-sided conveyance path so as to pass the fixing device 20 twice. Further, since the number of staying sheets on the duplex conveyance path increases, the variable d is increased by 1 (step S8). At this time, since the image n is transferred to the second surface, the image (output image) transferred to the first surface is set to a blank image (step S9). In the case of an apparatus or configuration having a no-transfer mode, the no-transfer mode may be used. The image n is enqueued in the image queue Q and arranged in the order of output waiting images (step S10). Next, it waits until the Fgate signal changes to negate (step S11). This is a step of waiting until the next image can be output.

  Steps S4 to S12 are a group of steps in which the image transferred from the host computer is stored in the RAM 23 as much as possible and the recording paper is retained in the double-sided conveyance path for the number of images during which the curl amount is not allowed.

  Next, if the two conditions are not satisfied in step 4 (step S4, NO), it is determined whether the image queue Q is empty (step S13). If the image queue Q is empty (step S13, YES), the job is terminated. (Step S22). If it is not empty (step S13, NO), the image is dequeued from the image queue Q, and the dequeued image is set as the image l (step S14).

  It is determined whether or not there is a back flag in image l (step S15). If there is no back flag (NO in step S15), standard paper discharge is performed from the main body paper feed tray, and image l is set as the output image. (Step S16). As shown in step S4 to step S12, since the curl amount is within the allowable value for the image without the back surface flag, it is not necessary for the recording paper to pass through the fixing device 20 twice. On the other hand, if there is a back face flag (step S15, YES), the paper is fed again from the double-sided conveyance path, the standard paper is discharged, and the output image is set to an image 1 rotated 180 degrees (step S17). As shown in steps S4 to S12, an image with a back flag has a curl amount that is greater than or equal to an allowable value, and therefore needs to be transferred to a recording sheet that has already passed through the fixing device 20. Therefore, curling can be reduced by re-feeding the recording paper staying in the double-sided conveyance path and transferring the image to the re-feeded recording paper.

  Next, the process waits until the Fgate signal changes to negate (step S18). This is a step of waiting until the next image can be output. Then, the output image l is deleted (step S19), and the free space of the RAM 23 is increased. Next, the state of the job end flag is determined (step S21). If the job end flag is ON (step S21, YES), steps S13 to S19 are executed. If the job end flag is OFF, the process is repeated from step S4.

  Next, the operation of the apparatus when there is a print request under the following conditions will be described for specific explanation. The print request is for single-sided three-sheet printing. Since only the third page image has a high printing rate, the curl amount is set to an allowable value or more. The number of recording sheets that can stay in the duplex conveyance path is one, and the RAM 23 can store image information of two pages.

  FIG. 4 illustrates the exchange of communication between the image forming apparatus and the host computer and the output image, paper feed, and paper discharge operations of the image forming apparatus when the flowchart of FIG. 3 is executed under the above conditions. is there. As shown in FIG. 4, the third page image is output to the recording paper that has passed through the fixing device 20 twice.

  FIG. 5 is a timing chart of the operation shown in FIG. As shown in the drawing, since the feeding of the first surface (blank image surface) of the recording paper to which the third page is transferred precedes the feeding of the recording paper to which the image of the second page is transferred, The image forming apparatus can feed, transfer, and discharge the recording paper on which the image on the second page is transferred while the recording paper on which the image on the third page is transferred is conveyed on the double-sided conveyance path. It can be seen that the productivity of is improved.

  In addition, according to the above-described embodiment, the curl amount is estimated for each image, and only a specific recording sheet that is estimated to have a curl amount that exceeds a certain amount passes through the double-sided intermediate conveyance path twice. Productivity improves because there is no re-feeding from the road.

  Further, according to the above-described embodiment, by determining the paper feed / discharge order according to the number of sheets that can be held on the double-sided conveyance path, the high-productivity paper discharge / discharge according to the double-sided conveyance path of the apparatus and the length of the recording paper. The paper order can be determined.

  Further, according to the above embodiment, by determining the paper feed / discharge order according to the image information storage capacity, a highly productive paper feed / discharge order can be set according to the image information storage capacity and the amount of image information of the apparatus. Can be determined.

  Further, according to the above-described embodiment, by heating the both sides of the recording paper, the water retention amount on both sides becomes substantially equal, so the curling of the recording paper is reduced.

  Further, according to the above-described embodiment, by applying pressure to both sides of the recording paper, the pressure is applied to the recording paper in the opposite direction during the first conveyance and during the second conveyance, thereby reducing curling. The

  Further, the conveyance control means of the present invention may control the conveyance destination and the conveyance order based on the number of recording sheets that can be held in the second conveyance means.

  The conveyance control unit of the present invention may control the conveyance destination and the conveyance order based on the image data information stored in the data storage unit.

  Further, the conveyance control means of the present invention heats the first surface of the recording paper by the fixing means and then conveys the second surface of the recording paper by the fixing means by conveying it to the paper reversing means by the second conveying means. You may do it.

  The conveyance control unit of the present invention pressurizes the first surface of the recording paper by the fixing unit and then conveys the second surface of the recording sheet to the sheet reversing unit by the second conveying unit and adds the second surface of the recording sheet by the fixing unit. You may make it press.

  The present invention can be applied to applications such as an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Main body paper tray 2 Paper feed roller 3 Registration roller 4 Paper 5 Transfer belt 6Bk, 6M, 6C, 6Y AIO cartridge 7 Secondary transfer drive roller 8 Transfer belt tension roller 9Bk, 9M, 9C, 9Y, Photoconductor 10Bk Charger DESCRIPTION OF SYMBOLS 11 Exposure device 12Bk Developing device 13Bk Cleaner blade 14Bk, 14M, 14C, 14Y Laser light 15M, 15C, 15Y Primary transfer roller 16 Secondary transfer roller 17 TM sensor 18 Paper discharge roller 19 Double-sided roller 20 Fixing device 21 Fixing roller 22 Flash ROM
23 RAM
24 Write Control Unit 25 Motor Driver 26 Communication Control Unit 27 Image Processing Unit 28 CPU

JP-A-6-3900 Japanese Patent No. 4034117 JP 2004-352423 A Japanese Patent Laid-Open No. 4-93970 JP 2003-302798 A

Claims (4)

First conveying means for conveying a recording sheet for recording an image based on image data;
Image transfer means for transferring the image to the recording paper conveyed by the first conveyance means;
Fixing means for fixing the recording paper, on which the image has been transferred by the image transfer means, with heating and pressure;
A conveyance control unit that controls conveyance by determining whether the recording sheet on which the image is fixed by the fixing unit is conveyed to a discharge unit or a sheet reversing unit that reverses the front and back of the recording sheet;
Second transport means for transporting the recording paper to a transport destination controlled by the transport control means;
Data storage means for acquiring and storing the image data information;
A curl amount estimating means for estimating a curl amount when the image is transferred to the recording paper for each image based on the image data information stored in the data storage means;
With
The conveyance control means includes the conveyance destination and the conveyance order that can be processed in the shortest time based on the curl amount estimated by the curl amount estimation means and the number of the recording sheets that can be held in the second conveyance means. Control
When the image is transferred to one side of the recording paper, the conveyance control unit is configured such that the number of the recording papers retained in the paper reversing unit can be held by the second conveying unit. When the curl amount of the image estimated by the curl amount estimation unit exceeds a certain value, the image transfer unit transfers the image onto the recording paper conveyed by the first conveyance unit. The recording paper is conveyed to the paper reversing means by the second conveying means via the fixing means, and the image transferring means is transferred to the recording paper after the paper reversing means is conveyed. The image forming apparatus , wherein the image is transferred, and the recording sheet is conveyed to the discharge unit by the second conveying unit via the fixing unit .   The transport control means includes
  When the curl amount of the image estimated by the curl amount estimation unit does not exceed a certain value, the image transfer unit transfers the image to the recording paper conveyed by the first conveyance unit. The image forming apparatus according to claim 1, wherein the recording sheet is conveyed to the discharge unit by the second conveying unit via the fixing unit.   The transport control means includes
  When the curl amount of the image estimated by the curl amount estimation unit exceeds a certain value, the image transfer unit transfers the image onto the recording paper conveyed by the first conveyance unit. First, the recording paper is conveyed to the paper reversing means by the second conveying means via the fixing means, and the image with the flag is stored in the storage means,
  When the curl amount of the image estimated by the curl amount estimation unit does not exceed a certain value, the image is stored in the storage unit,
  When the flag is given to the image stored in the storage means, the image transfer means transfers the image to the recording paper after the paper reversing means is conveyed, and the recording paper is Transported to the discharge section by the second transport means via the fixing means,
  If the flag is not given to the image stored in the storage means, the image transfer means transfers the image to the recording paper conveyed by the first conveying means, and the recording paper is 3. The image forming apparatus according to claim 2, wherein the second conveying unit conveys the discharge unit to the discharge unit via the fixing unit.   The transport control means includes
  The image transfer means does not transfer the image to the recording paper, or the image transfer means does not transfer the image to the recording paper by the image transfer means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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