JP2010265111A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct paper curled in the parallel direction to the carrying direction, to substantially planar paper. <P>SOLUTION: A decurler 86 is made to act when a sensor part detects that the paper is curled in the parallel direction to the carrying direction D1. A decurler 81 is made to act when the sensor part detects that the paper is curled in the orthogonal direction to the carrying direction D1. The decurlers 86 and 87 are made to act when the sensor part detects that the paper is curled in the parallel direction to the carrying direction D1 and detects that the paper is curled in the orthogonal direction to the carrying direction D1. Thus, the paper curled in the parallel direction to the carrying direction D1 and the paper curled in the orthogonal direction to the carrying direction D1, are corrected to the substantially planar paper. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus for forming an image on a recording medium by an electrostatic recording method or the like, and more particularly to an image forming apparatus having a function of correcting a curled recording medium after image fixing.

  Conventionally, electrostatic recording systems have been widely used in image forming apparatuses such as copying machines and printers. The latent image formed on the image carrier is developed to form a toner image, the toner image is transferred to a recording medium such as paper using electrostatic force, and then the transferred image is fixed by heat. It is configured.

  In this case, when the image transferred onto the sheet is fixed by the fixing device, the recording medium is warped (hereinafter referred to as “curl”) after being discharged. That is, when an unfixed toner image on a recording medium is heat-fixed by a fixing device composed of a pair of heat rollers or the like, there is a difference between the shrinkage ratio of the recording medium and the shrinkage ratio of the toner when the recording medium is discharged and cooled. This is one cause of paper curling.

  In order to correct the curled paper in a flat shape, Patent Document 1 proposes an image forming apparatus provided with a decurler. The decurler of Patent Document 1 is installed on a conveyance path through which a sheet is conveyed, and includes, for example, a metal hard roller and a soft roller such as a foam sponge. The curled paper is passed through the nip portion between the hard roller and the soft roller, and the curled paper is curved in a direction opposite to the curled direction when passing through the nip portion. Thereby, the paper curled in the direction orthogonal to the transport direction can be corrected to a substantially flat paper.

  Further, Patent Document 2 proposes a curl reduction device that corrects a curled paper into a flat shape. According to Patent Document 2, a roller is pressed against a belt member to form a nip portion, and a curled sheet is passed through the nip portion. This curled paper is bent in a direction opposite to the curled direction when passing through the nip portion. In this way, curling can be corrected using a belt member and a roller.

JP-A-5-341600 JP-A-6-144777

  By the way, the decurler of Patent Document 1 according to the conventional example is installed on a conveyance path through which a sheet is conveyed. For this reason, although the paper curled in the direction orthogonal to the transport direction can be corrected to a substantially flat paper, it is difficult to correct the paper curled in the direction parallel to the transport direction to a substantially flat paper. is there. Further, the position where the curl reducing device of Patent Document 2 is not disclosed is disclosed, and it is difficult to correct a sheet curled in a direction parallel to the transport direction to a substantially flat sheet as in Patent Document 1. .

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can correct a sheet curled in a direction parallel to the conveyance direction into a substantially planar sheet.

  In order to solve the above-described problem, an image forming apparatus according to a first aspect of the present invention is installed in a feeding unit that feeds the paper in a direction substantially perpendicular to a conveyance direction in which the paper is conveyed, and a paper passing path that is sent by the sending unit. A first decurler that corrects the curl of the paper and a sensor unit that detects the curl of the paper, and based on a detection result of the sensor unit, the paper fed by the sending unit is sent to the first decurler It is corrected with a decurler.

  According to the image forming apparatus of the first aspect, the sending section transports the paper and sends the paper in a direction substantially orthogonal to the transport direction. The first decurler installed in the paper path in the direction substantially perpendicular to the transport direction corrects the curl of the paper. The sensor unit detects paper curl. With this configuration, based on the detection result of the sensor unit, the sheet fed in the substantially orthogonal direction by the sending unit is corrected by the first decurler. As a result, the paper curled in the direction parallel to the transport direction can be corrected to a substantially flat paper.

  According to the image forming apparatus of the second aspect, when the sheet is conveyed in the conveyance direction, the nip of the roller for the conveyance direction is nipped to release the nip of the roller for the orthogonal direction. Further, when the sheet is transported in a direction substantially orthogonal to the transport direction, the nip of the roller for the transport direction is released by nipping the roller for the orthogonal direction.

  According to the image forming apparatus of the third aspect of the present invention, the image forming apparatus further includes a second decurler installed in the sheet passing path in the conveyance direction for conveying the sheet, and corrects the curl of the sheet. According to a fourth aspect of the present invention, there is provided a sheet passing path that does not act on both the first and second decurlers and a sheet passing path that does not act on either the first or second decurler.

  According to the image forming apparatus of the fifth aspect, when the sensor unit detects that the sheet is curled in a direction parallel to the transport direction, the first decurler is operated. In addition, when the sensor unit detects that the sheet curls in a direction orthogonal to the transport direction, the second decurler is activated.

  According to the image forming apparatus of the sixth aspect, when it is detected that the paper is curled in a direction parallel to the transport direction and the sensor unit detects that the paper is curled in a direction orthogonal to the transport direction. Activates the first and second decurlers. Further, when the sensor unit does not detect that the paper has been curled, the first and second decurlers are not operated.

  According to the image forming apparatus of the seventh aspect, the first and second decurlers adjust the nip pressure of the nip portion formed by the hard roller and the soft rotating member.

  According to the image forming apparatus of the eighth aspect, the reversing unit having the first U-turn reversing path for feeding the sheet in a direction substantially orthogonal to the transport direction and reversing the front and back of the sheet is provided. The first decurler installed on the first U-turn inversion path corrects the curl of the paper.

  According to the image forming apparatus of the ninth aspect, the reversing unit has the second U-turn reversing path for feeding the paper in the transport direction and for turning the paper upside down. The second decurler installed in the second U-turn inversion path corrects the curl of the paper.

  According to the image forming apparatus of the first aspect, based on the detection result of the sensor unit, the sheet fed by the sending unit in a direction substantially orthogonal to the transport direction is corrected by the first decurler. As a result, the paper curled in the direction parallel to the transport direction can be corrected to a substantially flat paper.

  According to the image forming apparatus of the second aspect, the sheet can be conveyed in the conveyance direction for conveying the sheet and in the orthogonal direction substantially orthogonal to the conveyance direction.

  According to the image forming apparatus of the third aspect, it is possible to correct a sheet curled in a direction orthogonal to the conveyance direction into a substantially planar sheet.

  According to the image forming apparatus of the fourth and fifth aspects, when the paper is not curled, the paper is not corrected, so that the efficiency can be improved. In addition, the first or second decurler can be selected according to the direction in which the paper curls.

  According to the image forming apparatus of the sixth aspect, even a sheet curled in an oblique direction can be corrected to a flat shape. According to the image forming apparatus of the seventh aspect, the curl can be corrected according to the curl strength of the paper. According to the image forming apparatus of the eighth and ninth aspects, the apparatus can be reduced in size by including the reversing unit having the U-turn reversing path.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus 100 according to the present invention. FIG. 2A is a top view illustrating a part of a configuration example of the image forming apparatus 100, and FIG. 2B is a view of FIG. 2 is a perspective view showing a configuration example of a curl correction apparatus 90. FIG. (A) is a diagram illustrating a configuration example of the decurler 81 and the like, and (B) is a diagram illustrating a correction example of the paper S by the decurler 81 and the like. (A) is an example in which the sheet S1 is curled in a direction perpendicular to the transport direction D1, and (B) is an example in which the sheet S1 is curled in a direction parallel to the transport direction D1. This is an example in which the sheet S1 is curled in an oblique direction with respect to the transport direction D1. 3 is a block diagram illustrating a configuration example of a control system of the image forming apparatus 100. FIG. (A) And (B) is a figure which shows the example (1/2) which corrects the orthogonal curl of the paper S1. (A) And (B) is a figure which shows the example (2/2) which corrects the orthogonal curl of the paper S1. (A) And (B) is a figure which shows the example (1/5) which corrects the parallel curl or diagonal curl of the paper S1. (A) And (B) is a figure which shows the example (2/5) which corrects the parallel curl or diagonal curl of the paper S1. (A) And (B) is a figure which shows the example (3/5) which corrects the parallel curl or diagonal curl of the paper S1. (A) And (B) is a figure which shows the example (4/5) which corrects the parallel curl or diagonal curl of the paper S1. (A) And (B) is a figure which shows the example (5/5) which corrects the parallel curl or diagonal curl of the paper S1. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus 200 according to the present invention. FIG. 15A is a top view illustrating a part of a configuration example of the image forming apparatus 200, and FIG. 15B is a view of FIG. 15A viewed from the direction of an arrow P2. 3 is a perspective view illustrating a configuration example of an inverting device 50. FIG. 3 is a perspective view illustrating a configuration example of a housing of the image forming apparatus 200. FIG. 6 is a diagram illustrating an operation example of the reversing device 50. FIG. 2 is a schematic diagram illustrating a configuration example of an image forming apparatus 300. FIG.

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

[Configuration Example of Image Forming Apparatus 100]
The image forming apparatus 100 according to the present invention can correct a sheet curled in a direction parallel to the conveyance direction into a substantially planar sheet by correcting the sheet fed in a direction substantially orthogonal to the conveyance direction with a decurler. It is what you want to do.

  An image forming apparatus 100 shown in FIG. 1 includes an image forming apparatus main body 10 and a document conveying device 12. The document conveying device 12 is attached to the upper part of the image forming apparatus main body 10 and conveys the placed document onto the document table of the image forming apparatus main body 10.

  The image forming apparatus main body 10 includes a paper feeding unit 30, a registration roller 16, a photosensitive drum 14, a fixing device 22, a paper discharge roller 24, and a reverse roller 82. In this example, the configuration of the image reading unit, the image processing unit, and the like are not described because a known technique is employed.

  The paper feed unit 30 includes a plurality of paper feed trays 18 and 19 and paper feed rollers 20 and 21. The paper feed trays 18 and 19 contain sheets of different sizes. The sheets stored in the sheet feeding trays 18 and 19 are carried out from the sheet feeding trays 18 and 19 by the rotation driving of the sheet feeding rollers 20 and 21. The paper carried out from the paper feed trays 18 and 19 is abutted against the registration roller 16 by the rollers 32 and 33 via the transport path R1.

  The registration roller 16 corrects the bending of the leading edge of the paper by forming a loop on the paper conveyed from the paper feed trays 18 and 19 and matches the toner image carried on the photosensitive drum 14. The sheet is conveyed to the transfer position at a predetermined timing.

  The photosensitive drum 14 transfers the toner image onto a sheet conveyed from the registration roller 16. The sheet on which the toner image is transferred is conveyed to the fixing device 22. The fixing device 22 heats and pressurizes the paper on which the toner image is transferred to melt the toner and fix the toner image on the paper to form an image.

  The sheet on which the image is formed by the fixing device 22 is conveyed to the curl correction device 90. The first conveyance unit 84a of the curl correction apparatus 90 is an example of a sending unit, and sends out a sheet in a direction substantially orthogonal to a conveyance direction in which the sheet is conveyed. The transport unit 84a includes transport direction rollers 54 and 55 and orthogonal direction rollers 58 and 59 (see FIG. 2A). The transport direction rollers 54 and 55 transport the paper to the paper discharge path R2 or the reverse path R3.

  A sensor unit 80 is provided in the vicinity of the first transport unit 84a. The sensor unit 80 detects four sides of the paper and outputs a detection signal S80 to the control unit 110 (see FIG. 7). The controller 110 determines whether or not the paper is curled based on the detection signal S80.

  A branch switching member (not shown) for switching the path is provided at a branch portion between the reversing path R3 and the paper discharge path R2. The path switching member is switched to the paper discharge path R2 or the reverse path R3 based on the control of the control unit 110 (see FIG. 7). When the path switching member is switched to the paper discharge path R2, the sheet is conveyed by the rollers 54 and 55 toward the decurler 81 provided on the paper discharge path R2. When the detection signal S80 of the sensor unit 80 indicates that the paper is curled in a direction orthogonal to the transport direction, the decurler 81 corrects the paper curled in the orthogonal direction to a substantially planar paper. The decurler 81 does not correct the paper when the detection signal S80 of the sensor unit 80 does not indicate that the paper has been curled in the orthogonal direction. The paper discharge roller 24 at the rear stage of the decurler 81 discharges the paper to the paper discharge tray 28.

  When the path switching member is switched to the reversing path R3, the sheet conveyed by the rollers 54 and 55 is conveyed to the reversing roller 82 by the roller 34 provided on the reversing path R3. The reversing roller 82 pulls in the paper, temporarily stops the paper, and then sends the paper at an acute angle in the discharge direction (switchback). As a result, the paper is repeated and the front and back sides are reversed, so double-sided printing and reverse paper discharge are possible.

  When performing duplex printing, the sheet reversed by the reversing roller 82 is again abutted against the registration roller 16 via the transport path R1 by the rollers 83a to 83c. In the case of reverse paper discharge, the paper reversed by the reverse roller 82 is conveyed to the paper discharge path R2 by the roller 34 and discharged to the paper discharge tray 28 by the paper discharge roller 24.

  In this example, an example in which the image forming unit is configured by one photosensitive drum 14 is shown. However, when a color image is formed, for Y color, M color, C color, and K color. The image forming unit can also be constituted by a plurality of photosensitive drums and intermediate transfer belts corresponding to the purpose.

[Configuration example of curl correction apparatus 90]
Next, a configuration example of the curl correction apparatus 90 will be described with reference to FIGS. The curl correcting device 90 includes a first transport unit 84 a, a second transport unit 84 b, a first decurler 86, second decurlers 81 and 87, and a sensor unit 80. The curl correction device 90 includes a paper passing path that does not operate both the decurler 86 and the decurlers 81 and 87, and a paper passing path that does not operate either the decurler 86 or the decurlers 81 and 87.

  The first transport unit 84a transports the paper in the transport direction D1 or the orthogonal direction D2. A decurler 81 is installed in the transport direction D1 of the first transport unit 84a. The decurler 81 corrects a sheet curled in a direction orthogonal to the transport direction D1 into a substantially planar sheet.

  A decurler 86 is installed in the sheet passing path in the orthogonal direction D2 of the first transport section 84a, and a second transport section 84b is installed in the subsequent stage of the decurler 86. The decurler 86 receives the sheet conveyed by the conveying unit 84a, and corrects the sheet curled (toy curled) in a direction parallel to the conveying direction D1 into a substantially planar sheet. The second conveyance unit 84b is an example of a sending unit, receives a sheet from the decurler 86, and conveys the sheet in the orthogonal direction D2 and the conveyance direction D1.

  In this example, the first transport unit 84 a includes rollers 55 and 54 and rollers 58 and 59. The pair of rollers 55 includes a driving roller and a driven roller in contact with the driving roller, and nip and nip release are performed by a solenoid (not shown).

  The driving roller is composed of a rotating shaft and a pair of rollers attached to both ends thereof, and the driven roller is composed of a rotating shaft and a pair of rollers attached to both ends thereof. The configuration of the roller 55 described above is the same in the rollers 85a and 85b and the rollers 85c and 85d described later, and will be described in the following description in a simplified manner.

  The rollers 54 and 55 are installed so as to fit within the outer frame of the smallest sized paper among the paper stored in the paper feed trays 18 and 19. Thus, for example, when a minimum size sheet is transported in the transport direction D1, the pair of rollers 54, 54 nips and feeds the sheet, and the pair of rollers 55 feeds the sheet nipped by the rollers 54, 54. , 55 can be nipped and received. Accordingly, a state in which the minimum size paper is niped for a moment can be created by both the front and rear rollers 54 and 55. Therefore, if the paper is larger than the minimum size paper, both the front and rear rollers 54 and 55 are used. With this, you can create a state where the paper is nipped. As a result, any size paper can be reliably conveyed in the conveyance direction D1 by the rollers 54 and 55.

  The rollers 58 and 59 are also installed so as to fit within the outer frame of the smallest size paper among the papers stored in the paper feed trays 18 and 19. As a result, when the minimum size paper is conveyed in the orthogonal direction D2, the paper is nipped by the pair of rollers 58, 58 and sent out, and the paper nipped by the rollers 58, 58 is sent out by the pair of rollers 59, 58. 59 can be received by nip. Accordingly, a state in which the minimum size paper is nipped for a moment can be created by both the front and rear rollers 58 and 59. Therefore, if the paper is larger than the minimum size paper, With this, you can create a state where the paper is nipped. Accordingly, the paper can be conveyed in the orthogonal direction D2 by the rollers 58 and 59 regardless of the size of the paper. Here, the orthogonal direction D2 is a direction orthogonal to the transport direction D1.

  The 2nd conveyance part 84b is comprised similarly to the 1st conveyance part 84a. That is, the second transport unit 84b includes rollers 85a and 85b and rollers 85c and 85d. The rollers 85 a and 85 b are installed so as to fit within the outer frame of the smallest size paper among the papers stored in the paper feed trays 18 and 19. The rollers 85c and 85d are also installed so as to fit within the outer frame of the smallest size paper among the papers stored in the paper feed trays 18 and 19. Thus, the 1st and 2nd conveyance parts 84a and 84b are comprised.

  A decurler 81 is installed in front of the first transport unit 84a. The decurler 81 includes a soft roller 81a and a hard roller 81b. The soft roller 81a is an example of a soft rotating member, and is formed from an elastic foam (for example, foam sponge) having a relatively low hardness. The hard roller 81b is made of metal or the like. For example, in the decurler 81 shown in FIG. 4A, the soft roller 81a is driven by a motor (not shown). The hard roller 81b is coupled to a solenoid 81c, and is pressed against or separated from the soft roller 81a by the solenoid 81c. The soft roller 81a has a foamed sponge 81d.

  As shown in FIG. 4A, when the sheet S is substantially planar, energization of the solenoid 81c is stopped and the movable iron core 88d is extended to separate the hard roller 81b from the soft roller 81a. In this example, one end of a link 88c is attached to the tip of the movable iron core 88d, and a tension spring 88a and a hard roller 81b are attached to the other end of the link 88c. The link 88c is rotatably attached by a pin 88b. With this configuration, when the movable iron core 88d extends or contracts, the hard roller 81b attached to the link 88c moves up and down with the pin 88b as a fulcrum.

  When the sheet S is curled as shown in FIG. 4B, the solenoid 81c is energized to contract the movable iron core 88d, and the hard roller 81b is pressed against the soft roller 81a to form a nip portion. The nip pressure of the nip portion can be adjusted by changing the position of the soft roller 81a according to the strength of the curl. As a result, the curl can be corrected according to the strength of the curl of the paper. The soft roller 81a is driven to rotate. The curled paper S is passed through the nip formed by the hard roller 81b and the soft roller 81a, and the paper S is bent in a direction opposite to the curled direction. As a result, the curled paper can be corrected to a substantially flat paper S by the decurler 81 as shown in FIG. 4B. The paper corrected by the decurler 81 is discharged to the paper discharge tray 28 by the paper discharge roller 24.

  On the other hand, the decurler 86 is installed between the first transport unit 84a and the second transport unit 84b. The decurler 86 has the same configuration as the decurler 81.

  That is, the decurler 86 includes a soft roller 86a and a hard roller 86b. The soft roller 86a is formed from an elastic foam (for example, foamed sponge) having a relatively low hardness. The hard roller 86b is made of metal or the like. For example, in the decurler 86 shown in FIG. 4A, the soft roller 86a is driven by a motor (not shown). The hard roller 86b is pressed against or separated from the soft roller 86a by a solenoid 86c. In the standby state, the decurler 86 extends the movable iron core 88d of the solenoid 86c to separate the hard roller 86b from the soft roller 86a as shown in FIG. 4A.

  As shown in FIG. 4B, the decurler 86 contracts the movable iron core 88d of the solenoid 86c and presses the hard roller 86b against the soft roller 86a to form a nip as shown in FIG. 4B. Further, the soft roller 86a is driven to rotate. The curled paper S is passed through the nip formed by the hard roller 86b and the soft roller 86a, and the paper S is bent in a direction opposite to the curled direction. As a result, the curled paper can be corrected to a substantially flat paper S as shown in FIG. 4B. The paper corrected by the decurler 86 is discharged to the paper discharge tray 28 by the paper discharge roller 85e. The paper discharged by the paper discharge roller 85e and the paper discharged by the paper discharge roller 24 are overlapped and placed on the paper discharge tray 28.

  Further, the decurler 87 is installed in front of the second transport unit 84b. The decurler 87 has the same configuration as the first and decurlers 81 and 86.

  That is, the decurler 87 includes a soft roller 87a and a hard roller 87b, and corrects the curled paper into a substantially flat paper S as shown in FIG. 4B. The paper corrected by the decurler 87 is discharged to the paper discharge tray 28 by the paper discharge roller 85e.

  Next, an example in which the paper curl direction is detected will be described with reference to FIGS. 5A and 5B and FIG. 5A is a planar sheet, and the solid line sheet S1 is a sheet curled in a direction orthogonal to the transport direction D1. The sensor unit 80 illustrated in FIG. 5A includes four sensors 80a to 80d, and is disposed at a position where four sides of the paper S are detected. For example, the sensor 80a is disposed at a position where the leading edge Sa of the paper S is detected, and the sensor 80b is disposed at a position where the trailing edge Sb of the paper S is detected. The sensor 80c is disposed at a position for detecting the right end Sc of the sheet S, and the sensor 80d is disposed at a position for detecting the left end Sd of the sheet S.

  As the sensors 80a to 80d, transmissive photosensors or reflective photosensors are used. The total length L1 of the sheet S1 is calculated based on the outputs of the sensors 80a and 80b. In this example, a vertical reference size La and a horizontal reference size Lb, which are references for each size of the paper S, are stored.

  The vertical reference size La is compared with the total length L1 of the sheet S1 obtained from the outputs of the sensors 80a and 80b. Further, the horizontal reference size Lb is compared with the full width L2 of the sheet S1 obtained from the outputs of the sensors 80c and 80d.

  For example, as shown in FIG. 5A, when the total length L1 of the sheet S1 is shorter than the vertical reference size La and the total width L2 of the sheet S1 is equal to the horizontal reference size Lb (L1 <La, L2 = Lb), the conveyance direction D1 It is determined that the paper is curled in the orthogonal direction. In this case, the sheet S1 is corrected by the decurler 81.

  Further, as shown in FIG. 5B, when the total length L3 of the sheet S1 is equal to the vertical reference size La and the total width L4 of the sheet S1 is shorter than the horizontal reference size Lb (L3 = La, L4 <Lb), the conveyance direction D1 It is determined that the paper is curled in the parallel direction. In this case, the sheet S1 is corrected by the decurler 86.

  Further, as shown in FIG. 6, when the total length L5 of the sheet S1 is shorter than the vertical reference size La and the total width L6 of the sheet S1 is shorter than the horizontal reference size Lb (L3 <La, L4 <Lb), it is inclined. It is determined that the paper is curled. In this case, the sheet S1 is corrected by the decurlers 86 and 87.

  When the total length of the sheet S1 is equal to the vertical reference size La and the total width of the sheet S1 is equal to the horizontal reference size Lb, it is determined that the sheet S1 is not curled and is conveyed by the roller 55. The sheet S1 is not corrected.

[Block Configuration Example of Control System of Image Forming Apparatus 100]
Next, a block configuration example of the control system of the image forming apparatus 100 will be described with reference to FIG. The image forming apparatus 100 illustrated in FIG. 7 includes a control unit 110 that controls the operation of each unit of the image forming apparatus 100.

  The control unit 110 includes a CPU (Central Processing Unit) 112, a ROM (Read Only Memory) 114, and a RAM (Random Access Memory) 116. The ROM 114 stores a program for operating the image forming apparatus 100. The RAM 116 is used as a temporary storage area for programs read from the ROM 114. The CPU 112 reads a program stored in the ROM 114 and executes processing according to the program.

  The control unit 110 is connected to each of the document conveying device 12, the image forming unit 140, the fixing device 22, the display unit 124, and the operation unit 126. Each of the document conveying device 12, the image forming unit 140, and the fixing device 22 performs processing corresponding to each unit described above based on a control signal supplied from the control unit 110.

  The display unit 124 is configured by a display device such as a liquid crystal display or an organic EL (Electro-Luminescence) display, for example, and selects single-sided printing or double-sided printing, or selection of paper feed trays 18 and 19 in which sheets of various sizes are accommodated. The menu screen etc. for performing are displayed. The operation unit 126 includes, for example, a keyboard and a remote controller, and generates an operation signal corresponding to the user's selection and supplies the operation signal to the control unit 110. In this example, a touch panel in which the display unit 124 and the operation unit 126 are integrally formed is used. The touch panel is provided, for example, in the upper part of the image forming apparatus main body 10, detects an input position corresponding to an operation on the display screen, generates an operation signal based on the input position, and supplies the operation signal to the control unit 110.

  The sensor unit 80 detects four sides of the paper and outputs a detection signal S80 to the control unit 110. The controller 110 determines whether or not the paper is curled based on the detection signal S80. For example, as shown in FIGS. 5 and 6, the vertical reference size La and the total length L1 of the sheet S1 obtained from the outputs of the sensors 80a and 80b of the sensor unit 80 are compared, and the horizontal reference size Lb and the sensors 80c and 80d are compared. The curl of the paper is determined by comparing with the full width L2 of the paper S1 obtained from the output. The control unit 110 controls the conveyance units 84a and 84b and the decurlers 81, 86, and 87 based on the determination result.

  Motors 540, 580, 850a, and 850c are connected to control unit 110. The control unit 110 outputs a control signal S540 to the motor 540 to drive the motor 540. The drive shaft of the motor 540 is connected to the rollers 54 and 55 via gears and shafts (not shown). When the motor 540 is driven, the rollers 54 and 55 rotate, and the paper on the transport unit 84a is transported in the transport direction D1.

  The control unit 110 drives the motor 580 by outputting a control signal S580 to the motor 580. The drive shaft of the motor 580 is connected to the rollers 58 and 59 through a gear, a shaft, etc. (not shown). When the motor 580 is driven, the rollers 58 and 59 are rotated, and the paper on the transport unit 84a is transported in the orthogonal direction D2.

  The controller 110 outputs a control signal S850c to the motor 850c to drive the motor 850c. The drive shaft of the motor 850c is connected to the rollers 85c and 85d via gears and shafts (not shown). When the motor 850c is driven, the rollers 85c and 85d rotate to receive the paper conveyed in the orthogonal direction D2 from the conveyance unit 84a.

  The controller 110 outputs a control signal S850a to the motor 850a to drive the motor 850a. The drive shaft of the motor 850a is connected to the rollers 85a and 85b via gears and shafts (not shown). When the motor 850a is driven, the rollers 85a and 85b rotate, and the paper on the transport unit 84b is transported in the transport direction D1.

  Solenoids 81c, 86c, 87c and motors 810a, 860a, 870a are connected to the control unit 110. The control unit 110 outputs a control signal S81c to extend or contract the movable iron core 88d of the solenoid 81c. For example, the control unit 110 energizes the solenoid 81c to contract the movable iron core 88d, and presses the hard roller 81b against the soft roller 81a to form a nip. Further, the control unit 110 stops energization of the solenoid 81c and extends the movable iron core 88d to separate the hard roller 81b from the soft roller 81a.

  The controller 110 outputs a control signal S810a to the motor 810a to drive the motor 810a. The drive shaft of the motor 810a is connected to the soft roller 81a via a gear (not shown). When the motor 810a is driven, the soft roller 81a and the hard roller 81b pressed against the soft roller 81a rotate to nip the curled paper and correct it to a flat surface as shown in FIG. 4B. In this way, the solenoid 81c and the motor 810a of the decurler 81 are controlled. The hard roller 81b is a driven roller, and is pressed against the soft roller 81a to rotate.

  Similarly, the solenoid 86c and the motor 860a of the decurler 86 are controlled. That is, the control unit 110 outputs the control signal S86c to extend or contract the movable iron core 88d of the solenoid 86c, and press or separate the hard roller 86b from the soft roller 86a.

  The controller 110 outputs a control signal S860a to the motor 860a to drive the motor 860a. When the motor 860a is driven, the soft roller 86a and the hard roller 86b pressed against the soft roller 86a rotate to nip the curled paper and correct it to a flat surface as shown in FIG. 4B. In this way, the solenoid 86c and the motor 860a of the decurler 86 are controlled.

  Similarly, the solenoid 87c and the motor 870a of the decurler 87 are controlled. That is, the control unit 110 outputs the control signal S87c to extend or contract the movable iron core 88d of the solenoid 87c, and press or separate the hard roller 87b from the soft roller 87a.

  The controller 110 outputs a control signal S870a to the motor 870a to drive the motor 870a. When the motor 870a is driven, the soft roller 87a and the hard roller 87b pressed against the soft roller 87a rotate to nip the curled paper and correct it to a flat surface as shown in FIG. 4B. In this way, the solenoid 87c and the motor 870a of the decurler 87 are controlled.

[Operation Example of Image Forming Apparatus 100]
<Paper curled in a direction perpendicular to the transport direction D1>
Next, an operation example of the image forming apparatus 100 will be described with reference to FIGS. 8 and 9. In this example, an example in which the sheet S1 is curled in a direction orthogonal to the transport direction D1 will be described. The rollers 54 and 55 of the transport unit 84a shown in FIG. 8A nip the orthogonally curled paper S1 and transport it in the transport direction D1. At this time, as shown in FIG. 8B, the nip of each of the rollers 58 and 59 is released.

  The control unit 110 compares the vertical reference size La shown in FIG. 5A with the total length L1 of the paper S1 obtained from the outputs of the sensors 80a and 80b, and at the same time, obtains the paper obtained from the horizontal reference size Lb and the outputs of the sensors 80c and 80d. The total width L2 of S1 is compared. When the total length L1 of the paper S1 is shorter than the vertical reference size La and the total width L2 of the paper S1 is equal to the horizontal reference size Lb (L1 <La, L2 = Lb), the control unit 110 is orthogonal to the transport direction D1. When the paper is curled, the solenoid 81c of the decurler 81 is energized and the hard roller 81b is pressed against the soft roller 81a to form a nip portion. Further, the control unit 110 drives the motor 810a to rotate the soft roller 81a. As a result, the soft roller 81a and the hard roller 81b of the decurler 81 rotate.

  The roller 55 of the transport unit 84a shown in FIG. 9A feeds the orthogonally curled paper S1 to the nip portion of the decurler 81 and passes it through. The sheet S1 passed through the nip portion of the decurler 81 is bent in a direction opposite to the curled direction. As a result, as shown in FIG. 4B, the orthogonally curled paper can be corrected by the decurler 81 into a substantially flat paper S1. The paper corrected by the decurler 81 is discharged to the paper discharge tray 28 by the paper discharge roller 24.

  The control unit 110 determines that the sheet is not curled when the total length of the sheet is equal to the vertical reference size La and the total width of the sheet is equal to the horizontal reference size, and extends the movable iron core 88d of the solenoid 81c. Thus, the hard roller 81b is separated from the soft roller 81a. In this way, when the paper is substantially flat, the paper is not nipped by the decurler 81.

<Paper curled in a direction parallel to the transport direction D1>
Next, an example in which the sheet S1 is curled in a direction parallel to the transport direction D1 will be described with reference to FIGS. The rollers 54 and 55 of the transport unit 84a shown in FIG. 10A nip the parallel curled paper S1 and transport it in the transport direction D1. At this time, as shown in FIG. 10B, the nip of each of the rollers 58 and 59 is released.

  The control unit 110 compares the vertical reference size La shown in FIG. 5B with the total length L1 of the paper S1 obtained from the outputs of the sensors 80a and 80b, and also obtains the paper obtained from the horizontal reference size Lb and the outputs of the sensors 80c and 80d. The total width L2 of S1 is compared. When the total length L3 of the sheet S1 is equal to the vertical reference size La and the total width L4 of the sheet S1 is shorter than the horizontal reference size Lb (L3 = La, L4 <Lb), the control unit 110 is parallel to the transport direction D1. When the paper is curled, the solenoid 86c of the decurler 86 is energized and the hard roller 86b is pressed against the soft roller 86a to form a nip portion. Further, the control unit 110 drives the motor 860a to rotate the soft roller 86a. As a result, the soft roller 86a and the hard roller 86b of the decurler 86 rotate.

  When the sheet S1 reaches the position shown in FIG. 11A, the control unit 110 stops the motors 540 of the rollers 54 and 55 and drives the motors 580 of the rollers 58 and 59 to convey the sheet S1 in the orthogonal direction D2. At this time, as shown in FIG. 11B, each of the rollers 54 and 55 is released from the nip.

  The roller 59 of the transport unit 84a shown in FIG. 12A feeds the orthogonally curled paper S1 through the nip portion of the decurler 86. The sheet S1 passed through the nip portion of the decurler 86 is bent in a direction opposite to the curled direction. Thereby, as shown in FIG. 4B, the parallel curled paper can be corrected to the substantially flat paper S <b> 1 by the decurler 86. The sheet whose parallel curl has been corrected by the decurler 86 is conveyed in the orthogonal direction D2 by the roller 59 of the conveying unit 84a and the roller 85c of the conveying unit 84b.

  When the sheet S1 reaches the position shown in FIG. 13A, the control unit 110 stops the motor 580 of the rollers 58 and 59 and stops the motor 850c of the rollers 85c and 85d. After that, as shown in FIG. 14A, the control unit 110 drives the motors 850a of the rollers 85a and 85b to transport the paper S1 in the transport direction D1. The paper discharge roller 85e discharges the paper S1 conveyed by the roller 85b to the paper discharge tray 28. At this time, as shown in FIG. 14B, the nip of each of the rollers 85c and 85d is released.

  In this example, the sheet S1 curls only in the direction parallel to the transport direction D1, and does not curl in the direction orthogonal to the transport direction D1, so the decurler 87 is not driven. That is, the movable iron core 88d of the solenoid 87c of the decurler 87 is extended so that the hard roller 87b is separated from the soft roller 87a.

<Paper curled obliquely with respect to transport direction D1>
Next, an example in which the sheet S1 is curled obliquely with respect to the transport direction D1 will be described with reference to FIGS. The rollers 54 and 55 of the transport unit 84a shown in FIG. 10A nip the slanted curled paper S1 and transport it in the transport direction D1.

  The control unit 110 compares the vertical reference size La shown in FIG. 6 with the total length L1 of the paper S1 obtained from the outputs of the sensors 80a and 80b, and the paper obtained from the horizontal reference size Lb and the outputs of the sensors 80c and 80d. The total width L2 of S1 is compared. When the total length L5 of the sheet S1 is shorter than the vertical reference size La and the total width L6 of the sheet S1 is shorter than the horizontal reference size Lb (L3 <La, L4 <Lb), the control unit 110 curls the sheet curled obliquely. And the solenoid 86c of the decurler 86 is energized to press the hard roller 86b against the soft roller 86a to form a nip portion. In addition, the control unit 110 drives the motor 860a to rotate the soft roller 86a. Further, the control unit 110 energizes the solenoid 87c of the decurler 87 and presses the hard roller 87b against the soft roller 87a to form a nip portion. In addition, the control unit 110 drives the motor 870a to rotate the soft roller 87a.

  As described above, the parallel curl of the sheet S1 is corrected by the decurler 86 shown in FIG. 12A. Further, the orthogonal curl of the sheet S1 is corrected by the decurler 87 shown in FIG. 14A.

  As described above, according to the image forming apparatus 100 according to the first embodiment of the present invention, based on the detection result of the sensor unit 80, in addition to the correction of the paper by the decurler 81, the orthogonal direction substantially orthogonal to the transport direction D1. The paper sent to D2 is corrected by the decurler 86. As a result, the paper curled in the direction parallel to the transport direction D1 can be corrected to a substantially flat paper.

[Configuration Example of Image Forming Apparatus 200]
Next, an image forming apparatus 200 as Example 2 will be described. The same components as those of the image forming apparatus 100 described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  An image forming apparatus 200 illustrated in FIG. 15 includes a reversing device 50 that reverses the front and back of a sheet. The inverting device 50 is an example of an inverting unit, and includes a first inverting unit 50A provided in the first stage and a second inverting unit 50B provided in the second stage. The reversing unit 50 </ b> A conveys the paper on which the toner image is fixed by being heated and pressed by the fixing device 22 toward the paper discharge roller 24. The reversing unit 50A reverses the sheet on which the toner image is fixed and conveys the paper to the second-stage reversing unit 50B. The reversing unit 50B conveys the sheet reversed by the reversing unit 50A to the conveyance / reversing roller 82a. In this example, a decurler 81A is installed on the path from the reversing unit 50B to the transport / reversing roller 82a. The decurler 81A corrects a sheet curled in a direction orthogonal to the transport direction D1 into a substantially planar sheet. The transport / reverse roller 82 a switches back the paper and transports it toward the paper discharge roller 25. Further, the transport / reverse roller 82a transports the sheet toward the roller 83a.

  Next, a configuration example of the reversing device 50 will be described with reference to FIGS. 16 and 17. The reversing device 50 reverses the front and back sides of the paper that is pressure-bonded and conveyed by the fixing device 22 without changing the front and rear ends of the paper, and re-feeds the paper to the transfer position of the photosensitive drum 14. The inversion device 50 includes a first inversion unit 50A provided in the first stage, a second inversion part 50B provided in the second stage, a first U-turn inversion path R3u, and a second U-turn inversion path R4u. And. A first decurler 86A is installed on the U-turn inversion path R3u, and a second decurler 81A is installed on the U-turn inversion path R4u.

  The first reversing unit 50A includes rollers 52 and 53 for the conveyance direction and rollers 56 and 57 for the orthogonal direction. The rollers 52 and 53 for the conveyance direction and the rollers 56 and 57 for the orthogonal direction are installed so as to fit within the outer frame of the paper of the smallest size among the papers stored in the paper feed trays 18 and 19.

  The second reversing unit 50B includes rollers 54 and 55 for the conveyance direction and rollers 58 and 59 for the orthogonal direction. The rollers 54 and 55 for the conveyance direction and the rollers 58 and 59 for the orthogonal direction are installed so as to fit within the outer frame of the smallest size paper among the papers stored in the paper feed trays 18 and 19.

  The roller 52 includes a driving roller and a driven roller that is in contact with the driving roller, and the nip and the nip are released by a solenoid (not shown). The driving roller is composed of a rotating shaft and a pair of rollers attached to both ends thereof, and the driven roller is composed of a rotating shaft and a pair of rollers attached to both ends thereof. In addition, since the structure of the roller 52 mentioned above is the same also in the rollers 53-59 mentioned later, it simplifies and demonstrates in the following description.

  The conveyance direction rollers 52 and 53 convey the sheet conveyed from the fixing device 22 in the conveyance direction D1. The orthogonal direction rollers 56 and 57 convey the sheet conveyed by the rollers 52 and 53 in the orthogonal direction D2. The U-turn reversing path R3u makes the paper fed in the orthogonal direction D2 by the rollers 56 and 57 U-turn 180 ° and conveys it to the second reversing unit 50B.

  The U-turn reversing path R3u is provided between the carry-out side of the roller 56 of the first reversing unit 50A and the carry-in side of the roller 58 of the second reversing unit 50B. The U-turn reversing path R3u is constituted by guide plates 62a and 62b made of, for example, a metal member, and is curved in an arc shape. The guide plate 62a installed on the inner side constitutes the first path r1, and the guide plate 62b installed on the outer side constitutes the second path r2. A decurler 86A is installed on the guide plate 62b constituting the second path r2. The paper conveyed to the second path r2 is curled by the decurler 86A, and the paper is reversed and carried into the second-stage roller 58. The sheet conveyed to the first path r1 is conveyed to the second-stage rollers 58, 58 after being reversed without performing the curl correction of the sheet. The first route r1 and the second route r2 are switched by a switching member (not shown).

  The rollers 54 and 55 convey the paper carried by the rollers 58 and 59 in the conveyance direction D1. The U-turn reversing path R4u causes the sheet fed in the transport direction D1 by the rollers 54 and 55 to turn 180 ° U-turn and feeds it in the arrow direction D1a toward the transport / reverse roller 82a.

  The U-turn reversing path R4u is provided between the carry-out side of the roller 55 of the second reversing unit 50B and the receiving side of the transport / reverse roller 82a. The U-turn reversing path R4u is configured by, for example, guide plates 63a and 63b made of a metal member, and is curved in an arc shape. The guide plate 63a installed on the inner side constitutes the first path s1, and the guide plate 63b installed on the outer side constitutes the second path s2. A decurler 81A is installed on the guide plate 63b configuring the second path s2. The paper transported to the second path s2 is curled by the decurler 81A, and the paper is reversed and carried into the transport / reverse roller 82a. The sheet conveyed to the first path s1 is reversed and carried into the conveyance / reversing roller 82a without correcting the curl of the sheet. The first route s1 and the second route s2 are switched by a switching member (not shown).

  Further, the guide plates 62a and 62b constituting the U-turn reversing path R3u are provided on the front side of the image forming apparatus main body 10 as shown in FIGS. 18A and 18B. An opening / closing door 10a that can be opened and closed in the vertical direction is provided on the front surface portion of the image forming apparatus main body 10 corresponding to the U-turn reversing path R3u. Thereby, for example, even when the paper S is jammed in the U-turn reversing path R3u, the jam processing of the U-turn reversing path R3u can be easily performed by opening the door 10a. The U-turn reversing path R3u can be provided on the back side of the image forming apparatus main body 10. Further, the open / close door 10a may be configured to open and close left and right.

[Operation Example of Image Forming Apparatus 200]
<Paper curled in a direction perpendicular to the transport direction D1>
Next, an operation example of the image forming apparatus 200 will be described with reference to FIGS. 17, 19A and 19B. In this example, an example in which the paper is curled in a direction orthogonal to the transport direction D1 will be described. The rollers 52 and 53 shown in FIG. 17 nip the orthogonally curled paper and transport it in the transport direction D1.

  The vertical reference size La shown in FIG. 5A is compared with the total length L1 of the paper S1 obtained from the outputs of the sensors 80a and 80b, and the horizontal reference size Lb and the full width L2 of the paper S1 obtained from the outputs of the sensors 80c and 80d are compared. Compare When the total length L1 of the paper S1 is shorter than the vertical reference size La and the total width L2 of the paper S1 is equal to the horizontal reference size Lb (L1 <La, L2 = Lb), the paper curled in the direction orthogonal to the transport direction D1. It is determined that there is, and the path of the sheet S1 is switched to the path r1 of the U-turn inversion path R3u shown in FIG. 19A by a switching member (not shown). As a result, the sheet S1 is reversed without being routed through the decurler 86A and carried into the second-stage roller 58. The rollers 54 and 55 convey the paper carried by the rollers 58 and 59 to the path s2 of the U-turn reversing path R4u. The paper S1 conveyed to the path s2 is corrected for orthogonal curl by the decurler 81A. For example, the decurler 81A corrects a substantially flat sheet by curving it in the direction opposite to the direction curled through the orthogonally curled sheet at the nip portion between the hard roller and the soft roller.

  The paper whose orthogonal curl has been corrected is reversed and carried to the transport / reverse roller 82a. The transport / reverse roller 82a re-feeds the paper during double-sided printing, and transports the paper toward the paper discharge roller 25 by switching back the paper during single-sided printing. At the time of duplex printing, the sensor unit 80 detects the curl state again, and curl correction is performed based on the detection result.

  If the total length of the sheet is equal to the vertical reference size La and the total width of the sheet is equal to the horizontal reference size, the control system determines that the sheet is not curled and removes the sheet from the decurlers 81A and 86A. Transport.

<Paper curled in a direction parallel to the transport direction D1>
As shown in FIG. 5B, when the total length L3 of the sheet S1 is equal to the vertical reference size La, and the total width L4 of the sheet S1 is shorter than the horizontal reference size Lb (L3 = La, L4 <Lb), it is parallel to the transport direction D1. It is determined that the sheet is curled in the direction to be turned, and the path of the sheet S1 is switched to the path r2 of the U-turn reversing path R3u shown in FIG. As a result, the sheet S1 is conveyed to the path r2, and the parallel curl is corrected by the decurler 86A. For example, the decurler 86A is curved in a direction opposite to the curled direction through a curled paper parallel to the nip portion of the hard roller and the soft roller, and is corrected to a substantially flat paper.

  The paper whose parallel curl has been corrected is reversed and carried to the second-stage roller 58. The rollers 54 and 55 shown in FIG. 19B convey the paper S1 carried by the rollers 58 and 59 to the path s1 of the U-turn reversing path R4u. The sheet S1 transported along the path s1 is reversed and carried into the transport / reversing roller 82a. The transport / reverse roller 82a re-feeds the paper during double-sided printing, and transports the paper toward the paper discharge roller 25 by switching back the paper during single-sided printing. At the time of duplex printing, the sensor unit 80 detects the curl state again, and curl correction is performed based on the detection result.

<Paper curled obliquely with respect to transport direction D1>
As shown in FIG. 6, when the total length L5 of the sheet S1 is shorter than the vertical reference size La and the total width L6 of the sheet S1 is shorter than the horizontal reference size Lb (L3 <La, L4 <Lb), curl in an oblique direction. The sheet S1 is switched to the path r2 of the U-turn reversing path R3u shown in FIG. As a result, the sheet S1 is conveyed to the path r2, and the parallel curl is corrected by the decurler 86A. The paper whose parallel curl has been corrected is reversed and carried to the second-stage roller 58.

  The rollers 54 and 55 shown in FIG. 19B convey the paper S1 carried by the rollers 58 and 59 to the path s2 of the U-turn reversing path R4u. The paper S1 conveyed to the path s2 is corrected for orthogonal curl by the decurler 81A.

  The paper whose orthogonal curl has been corrected is reversed and carried to the transport / reverse roller 82a. The transport / reverse roller 82a re-feeds the paper during double-sided printing, and transports the paper toward the paper discharge roller 25 by switching back the paper during single-sided printing. At the time of duplex printing, the sensor unit 80 detects the curl state again, and curl correction is performed based on the detection result.

[Configuration Example of Image Forming Apparatus 300]
Next, an image forming apparatus 300 as Example 3 will be described. The same components as those of the image forming apparatus 200 described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  An image forming apparatus 300 illustrated in FIG. 20 includes a reversing device 500 that reverses the front and back of a sheet. This inversion device 500 is an example of an inversion unit, and includes a first inversion unit 50A provided in the first stage and a second inversion unit 500B provided in the second stage. In this example, the configuration in which the reversing unit 500B has a U-turn reversing path R5u is different from the reversing device 50 described above.

  The U-turn inversion path R5u has the same configuration as the U-turn inversion path R4u. That is, the U-turn reversing path R5u is provided between the carry-out side of the roller 54 and the receiving side of the roller 83a of the reversing unit 50B. The U-turn reversing path R5u is formed of, for example, a guide plate made of a metal member and is curved in an arc shape. The guide plate installed on the inner side constitutes the first path t1, and the guide plate installed on the outer side constitutes the second path t2. A second decurler 81B is installed on the guide plate that constitutes the second path t2. The sheet conveyed to the second path t2 is curled in the orthogonal direction by the decurler 81B, and the sheet is reversed and carried into the roller 83a. The sheet conveyed to the first path t1 is reversed and carried into the roller 83a without correcting the curl of the sheet.

  Thus, by installing the U-turn reversing path R5u, switchback by the transport / reversing roller 82a becomes unnecessary. That is, when refeeding by double-sided printing is necessary, the sheet is conveyed to the U-turn reversing path R4u, and when refeeding is not necessary, the sheet is conveyed to the U-turn reversing path R5u. As a result, the paper can be stably conveyed and the printing speed can be improved.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. For example, although a hard roller and a soft roller are used for the decurler, the present invention is not limited to this, and a belt-type decurler may be used.

10. Image forming apparatus main body (housing)
14 ... photosensitive drum 16 ... registration rollers 50,500 ... reversing device 50A ... first reversing part 50B ... second reversing parts 52, 53, 54, 55 ... rollers 56, 57, 58, 59 ... roller 80 ... sensor unit 81, 86, 87, 81A, 86B ... decurler 100, 200, 300 ... image forming apparatus 110 ... control unit R3u, R4u , R5u ... U-turn inversion path

Claims (9)

A delivery section that sends out the paper in a direction substantially perpendicular to a conveyance direction for conveying the paper;
A first decurler which is installed in a paper passing path sent out by the sending unit and corrects the curl of the paper;
A sensor unit for detecting the curl of the paper,
An image forming apparatus characterized in that, based on a detection result of the sensor unit, a sheet fed by the sending unit is corrected by the first decurler. The sending section is
A plurality of conveyance direction rollers for nipping and conveying the sheet in the conveyance direction;
A plurality of orthogonal rollers that nip the paper and feed the paper in a direction substantially perpendicular to the transport direction;
When transporting the paper in the transport direction, release the nip of the roller for the orthogonal direction,
2. The image forming apparatus according to claim 1, wherein when the sheet is conveyed in a direction substantially orthogonal to the conveying direction, the nip of the roller for the conveying direction is released.   The image forming apparatus according to claim 1, further comprising a second decurler that is installed in a sheet passing path in a conveyance direction for conveying the sheet and corrects the curl of the sheet.   4. The image according to claim 3, further comprising: a paper passing path that does not act on both the first and second decurlers, and a paper passing path that does not act on either the first or second decurler. 5. Forming equipment. When the sensor unit detects that the paper is curled in a direction parallel to the transport direction, the first decurler is operated,
5. The image forming apparatus according to claim 4, wherein when the sensor unit detects that the sheet is curled in a direction orthogonal to the transport direction, the second decurler acts. When the sensor unit detects that the paper is curled in a direction parallel to the transport direction and detects that the paper is curled in a direction orthogonal to the transport direction, the first and second decurlers Act
5. The image forming apparatus according to claim 4, wherein the first and second decurlers do not act when the sensor unit does not detect that the sheet is curled. 6. The first and second decurlers are:
A hard roller, and a soft rotating member to which the hard roller is pressed,
The image forming apparatus according to claim 1, wherein a nip pressure of a nip portion formed by the hard roller and the soft rotating member is adjusted. A reversing unit having a first U-turn reversing path for feeding the paper in a direction substantially orthogonal to the transport direction and reversing the front and back of the paper;
The first decurler is
The image forming apparatus according to claim 1, wherein the image forming apparatus is installed in the first U-turn reversing path to correct the curl of the paper. The reversing unit has a second U-turn reversing path that feeds the paper in the transport direction and causes the front and back of the paper to face each other.
The second decurler is
The image forming apparatus according to claim 3, wherein the image forming apparatus is installed in the second U-turn inversion path to correct the curl of the sheet.

Images