JP5962557B2 - Image forming system - Google Patents

Description

The present invention relates to an image forming system.

  Patent Document 1 discloses an image provided with a first reversing conveyance unit having a short circulation length and a second reversing conveyance unit having a long circulation length in order to provide a double-sided image forming apparatus with high productivity, high stability, and high reliability. A forming apparatus is disclosed.

JP 2004-347927 A

  An object of the present invention is to suppress a reduction in the quality of an image formed on a sheet as the sheet is conveyed.

According to the first aspect of the present invention, there is provided a toner image forming unit that forms a toner image on a sheet, a fixing unit that fixes the toner image formed by the toner image forming unit on the sheet, and one direction from the fixing unit. And a branching path that is bent from the conveyance path at a position away from the fixing unit by a predetermined distance from the conveyance path through which the sheet on which the toner image is formed by the fixing unit is conveyed. At a position that is longer than the predetermined distance from the fixing unit and the first branch path on which the sheet on which the toner is formed is branched while being bent from the conveying path, and a toner image is formed at the fixing unit. The toner image is fixed by the fixing unit between the second branch path through which the conveyed sheet is conveyed, the branch at the predetermined distance, and the branch at a position longer than the predetermined distance. Paper A cooling unit for retirement, and a receiving unit that receives information about the sheet on which the toner image is fixed by the fixing unit, according to the information concerning the sheets for the accepting unit accepts, the first branch passage and the second branch passage An image forming system comprising: a switching unit that switches between which a sheet is conveyed .

The invention according to claim 2 is connected to the first branch path and the second branch path, and the sheet transported from the first branch path and the second branch path is transported to the fixing unit again. The image forming system according to claim 1, further comprising a re-conveying path.

According to a third aspect of the present invention, there is provided a toner image forming unit that forms a toner image on a sheet, a fixing unit that fixes the toner image formed by the toner image forming unit on the sheet, and one direction from the fixing unit. A first conveyance path through which a sheet on which a toner image is formed by the fixing unit is conveyed, and a sheet branched from the first conveyance path while being bent, and a sheet on which the toner image is formed is conveyed by the fixing unit. the first housing having a first branch passage, and a receiving portion for receiving the sheet conveyed from one end of the first conveying path, extending along said one direction from said one end of said first conveying path, said receiving portion A second conveyance path that conveys the sheet received by the second conveyance path and a second branch path that is branched from the second conveyance path and that conveys the sheet on which the toner image is formed in the fixing unit. housing, the toner image is fixed by the fixing unit Receiving unit that receives the information concerning the sheets to be, and in response to said information concerning the sheets for accepting unit accepts, further comprising a switching unit for switching whether to convey any on paper of the first branch passage and the second branch passage An image forming system is characterized.

According to the first aspect of the present invention, it is possible to suppress the quality of the image formed on the paper from being deteriorated as the paper is transported as compared with the case where this configuration is not provided. In addition, according to the first aspect of the present invention, it is possible to transport the paper according to the form of the paper such as the thickness of the paper.
According to the invention of claim 2, a toner image can be formed a plurality of times on one sheet.

According to the third aspect of the present invention, it is possible to suppress the deterioration of the quality of the image formed on the paper as the paper is transported, as compared with the case where this configuration is not provided .

1 is a diagram illustrating an overall configuration of an image forming system to which the exemplary embodiment is applied. FIG. 6 is a diagram for explaining a route for conveying a sheet. It is a figure which shows the function structure of a comprehensive control part. It is a figure which shows the function structure of a process control part. It is a flowchart which shows the operation | movement which switches the conveyance path | route of a comprehensive control part.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating an overall configuration of a sheet processing system (image forming system) 1 to which the exemplary embodiment is applied.
A sheet processing system 1 illustrated in FIG. 1 is configured to previously form an image forming apparatus 100 that forms a color toner image on a sheet P by, for example, electrophotography, and a sheet P on which a toner image is formed by the image forming apparatus 100. And a sheet processing apparatus 200 that performs a predetermined process.

In the present embodiment, the image forming apparatus 100 that forms an image by an electrophotographic method is illustrated, but the image forming apparatus 100 may be configured by, for example, an ink jet printer.
Further, the paper processing apparatus 200 that cools the paper P is illustrated, but if the paper P on which the image is formed is subjected to a predetermined process, for example, the paper P on which the image is formed is bound and bound. You may make it the structure provided with the binding apparatus which performs a process, and the punching apparatus which performs a punching process.

<Image forming apparatus 100>
An image forming apparatus 100 shown in FIG. 1 has a so-called tandem configuration, and includes a plurality of image forming units 10 (10Y, 10M, 10C, and 10K) that form toner images of respective color components by an electrophotographic method. I have. The image forming apparatus 100 receives image data and print instructions for image formation from, for example, a PC (personal computer, not shown) connected to the image forming apparatus 100 via a network and the like. A total control unit 80 (described later) for controlling the operation of each device and each part constituting the forming apparatus 100 is provided. Further, the image forming apparatus 100 includes a display panel, and is provided with a user interface (UI) 90 that outputs an instruction received from the user to the general control unit 80 and presents information from the general control unit 80 to the user. ing.

  In addition, the image forming apparatus 100 transfers the toner image formed on each image forming unit 10 sequentially (primary transfer) to hold the toner image and the toner image on the intermediate transfer belt 20. And a secondary transfer device 30 that performs batch transfer (secondary transfer) onto the paper P. Here, each of the image forming units 10, the intermediate transfer belt 20, and the secondary transfer device 30 can be regarded as an image forming unit that forms an image on the paper P.

  The image forming apparatus 100 also includes a first paper transport path R1 through which the paper P transported toward the secondary transfer device 30 passes, and a second paper through which the paper P after passing through the secondary transfer device 30 passes. A first reverse conveyance path R5 branched from the second paper conveyance path R3 on the downstream side of the conveyance path R3 and the fixing device 50 (described later), and branched from the first reverse conveyance path R5 and connected to the first paper conveyance path R1. From the first re-transport path (re-transport path) R7, the third paper transport path R9 branched from the first reverse transport path R5 and connected to the second paper transport path R3, and the end face on the paper processing apparatus 200 side A fourth transport path R10 that extends and is connected to the first re-transport path R7 is provided.

In addition, the first paper transport path R1, the second paper transport path R3, the first reverse transport path R5, the first re-transport path R7, the third paper transport path R9, and the fourth transport path R10 include the paper P A plurality of transport rolls 48 are provided for transporting.
An opening 102 is formed in the housing (first housing) 101 of the image forming apparatus 100. Here, the paper P transported along the second paper transport path R <b> 3 is discharged to the outside of the housing 101 through the opening 102. A positioning hole 103 (described later) is formed on the end surface of the housing 101 where the opening 102 is formed (the surface facing the paper processing apparatus 200).

  Further, the image forming apparatus 100 is provided with a first paper supply device 410, a second paper supply device 420, and a third paper supply device 430 that supply the paper P to the first paper transport path R1. The first paper supply device 410 to the third paper supply device 430 are configured in the same manner, and each of the first paper supply device 410 to the third paper supply device 430 has a paper storage unit 41 that stores the paper P. A take-out roll 42 for taking out and transporting the paper P stored in the paper storage unit 41 is provided.

  Further, a fixing device (fixing unit) 50 for fixing the image secondarily transferred onto the paper P by the secondary transfer device 30 to the paper P is provided on the second paper transport path R3. The fixing device 50 is provided with a heating belt 50A that is heated by a built-in heater (not shown) and a pressing roll 50B that presses the heating belt 50A. Then, when the paper P passes through the nip portion N where the heating belt 50A and the pressing roll 50B press each other, the paper P is pressurized and heated so that the image on the paper P is fixed to the paper P. Is done.

  Further, between the secondary transfer device 30 and the fixing device 50, a transport device 51 that transports the paper P that has passed through the secondary transfer device 30 to the fixing device 50 is provided. Here, the transport device 51 includes a belt 51A that moves around, and transports the paper P by placing the paper P on the belt 51A.

  Further, a curl correction device 52 that corrects the bending (curl) of the paper P on which the image is fixed by the fixing device 50 is provided on the second paper transport path R3. Here, the curl correcting device 52 has two pairs of rolls including a rigid roll 52A and an elastic roll 52B that drives the paper P while pressing the rigid roll 52A on the second paper transport path R3. The positions of the rigid roll 52A and the elastic roll 52B that are provided across the second paper transport path R3 with respect to the second paper transport path R3 are arranged so that one set is opposite to the other set.

  Each of the image forming units (toner image forming units) 10 includes a photosensitive drum 11 that is rotatably mounted. Further, around the photosensitive drum 11, a charging device 12 that charges the photosensitive drum 11, an exposure device 13 that exposes the photosensitive drum 11 to write an electrostatic latent image, and an electrostatic latent image on the photosensitive drum 11 Is provided with a developing device 14 that visualizes the toner with a toner. Further, a primary transfer device 15 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 20 and a drum cleaning device 16 that removes residual toner on the photosensitive drum 11 are provided.

  The intermediate transfer belt 20 is provided so as to be stretched over the three roll members 21 to 23. Of these three roll members 21 to 23, the roll member 22 drives the intermediate transfer belt 20. The roll member 23 is disposed opposite to the secondary transfer roll 31 with the intermediate transfer belt 20 interposed therebetween, and the secondary transfer device 30 is configured by the secondary transfer roll 31 and the roll member 23. A belt cleaning device 24 for removing residual toner on the intermediate transfer belt 20 is provided at a position facing the roll member 21 across the intermediate transfer belt 20.

  In the image forming apparatus 100 of the present embodiment, the paper P on which an image is formed on one side is turned back by the first reverse conveyance path R5 as necessary. Then, the sheet P that has been turned over and whose front end and rear end in the transport direction are switched is transported to the third paper transport path R9 or the first re-transport path R7.

Here, the paper P transported from the first reverse transport path R5 to the third paper transport path R9 is transported on the third paper transport path R9 and the second paper transport path R3 with the front and back being reversed, and the image The forming apparatus 100 is discharged out of the apparatus.
On the other hand, the paper P transported from the first reverse transport path R5 to the first re-transport path R7 is transported again to the secondary transfer device 30 via the first paper transport path R1. As a result, an image is formed on the other side of the sheet P with the front and back sides reversed by the secondary transfer device 30. That is, images are formed on both sides of the paper P. The first reverse conveyance path R5 can be regarded as a switchback path or a duplex printing path.

<Paper Processing Device 200>
The image forming apparatus 100 can form an image on the sheet P alone, but in the present embodiment, a sheet processing apparatus configured as a separate body (so-called option) with respect to the image forming apparatus 100. 200 is connected. Here, as an example, the connection of a sheet processing apparatus 200 as illustrated is described, but other apparatuses for processing the sheet P can also be connected to the image forming apparatus 100.

  First, the sheet processing apparatus 200 cools each color toner image fixed on the sheet P by the fixing device 50 of the image forming apparatus 100 and promotes fixing of each color toner image on the sheet P (processing unit). , Cooling unit) 71, an inline sensor 73 for optically detecting density defects, image defects, image position defects, etc. of the toner image fixed on the paper P, and operations of each device and each part constituting the paper processing apparatus 200 And a processing control unit 180 (described later) for controlling the process.

Further, the paper processing apparatus 200 includes a fifth paper transport path R11 through which the paper P discharged and transported from the image forming apparatus 100 passes, and a fifth branch from the fifth paper transport path R11 downstream of the inline sensor 73. A second reversing conveyance path R13, a second reconveying path R15 branched from the second reversing conveying path R13 and connected to the fourth conveying path R10 of the image forming apparatus 100, and a fifth sheet branched from the second reversing conveying path R13. A sixth paper transport path R17 connected to the transport path R11 is provided.
A plurality of transport rolls 48 for transporting the paper P are provided in the fifth paper transport path R11, the second reverse transport path R13, the second re-transport path R15, and the sixth paper transport path R17. The transport roll 48 provided on the upstream side of the fifth paper transport path R11 can be regarded as a receiving unit.

An opening 202 is formed in the housing (second housing) 201 of the sheet processing apparatus 200. Here, the paper P transported along the fifth paper transport path R11 is discharged to the outside of the housing 201 through the opening 202.
In addition, a positioning pin 203 that protrudes toward the outside of the housing 201 is provided at a position corresponding to the opening 102 of the image forming apparatus 100 on the surface of the housing 201 that faces the image forming apparatus 100. When the paper processing apparatus 200 is connected to the image forming apparatus 100, the position of the paper processing apparatus 200 with respect to the image forming apparatus 100 is determined by inserting the positioning pins 203 into the positioning holes 103.

Here, the cooling device 71 receives air from conveyance belts 71A and 71B that convey while sandwiching the upper and lower surfaces of the paper P on the fifth paper conveyance path R11, and a fan (not shown) provided outside. A heat sink 71C composed of a plurality of fins for cooling the conveyor belts 71A and 71B, and a plurality of stretching rolls that rotate and move the conveyor belts 71A and 71B, respectively.
The heat sink 71C contacts the inner peripheral surface of the transport belt 71A and absorbs heat from the transport belt 71A. As a result, the paper P heated by the fixing device 50 is cooled, and the toner on the surface of the paper P is solidified while maintaining smoothness.

The in-line sensor 73 includes a light source 73A configured by an incandescent lamp or a white light emitting diode, and a light receiving element 73B configured by a CCD (Charge Coupled Device) or the like.
Here, the light receiving element 73B receives the light emitted from the light source 73A and reflected by the paper P on the fifth paper transport path R11. Based on the intensity of the received light, a signal is output to the general control unit 80 of the image forming apparatus 100. The comprehensive control unit 80 corrects the image formed in the image forming unit 10 based on the signal from the inline sensor 73. For example, the intensity of light irradiated by the exposure device 13 and the position of image formation are corrected based on the signal from the inline sensor 73.

In the sheet processing apparatus 200 of the present embodiment, the sheet P on which an image is formed on one side is turned back by the second reverse conveyance path R13 as necessary. Then, the sheet P that has been turned over and whose front end and rear end in the transport direction are switched is transported to the sixth paper transport path R17 or the second re-transport path R15.
Here, the paper P transported from the second reverse transport path R13 to the sixth paper transport path R17 is transported on the sixth paper transport path R17 and the fifth paper transport path R11 in a state where the front and back sides are reversed. It is discharged out of the processing apparatus 200.

  On the other hand, the sheet P conveyed from the second reversal conveyance path R13 to the second reconveyance path R15 is in a state where the front and back are reversed, the fourth conveyance path R10, the first reconveyance path R7, and The sheet is conveyed again to the secondary transfer device 30 via the first sheet conveyance path R1. As a result, an image is formed on the other side of the sheet P with the front and back sides reversed by the secondary transfer device 30. That is, images are formed on both sides of the paper P. The second reverse conveyance path R13 can be regarded as a switchback path or a duplex printing path.

<Reverse transport path>
Next, with reference to FIG. 2, the path for transporting the paper P, more specifically, the arrangement of the first reverse transport path R5 and the second reverse transport path R13 will be described. FIG. 2 is a diagram for explaining a path for conveying the paper P.

First, the second sheet conveyance path (conveyance path, first conveyance path) R3 extends along the direction connecting the fixing device 50 and the opening 102 (along one direction). At the first branch point S1 where the first reverse conveyance path (first branch path) R5 branches from the second sheet conveyance path R3, the conveyance destination of the sheet P conveyed on the second sheet conveyance path R3 is the first. A first switching gate G1 for switching (setting) one of the two-sheet conveyance path R3 and the first reverse conveyance path R5 is provided. The first branch point S1 can be regarded as a branch for traveling from the second paper transport path R3 to the first reverse transport path R5.
Further, the first reverse conveyance path R5 branched from the second paper conveyance path R3 via the first branch point S1 has a first curved portion C1 that curves in a direction away from the second paper conveyance path R3. In the illustrated example, the second paper transport path R3 and the first reverse transport path R5 are in a positional relationship that intersects.

Further, the fifth paper transport path R (transport path, second transport path) 11 extends from the portion facing the one end of the second paper transport path R3 toward the opening 202 (along one direction). At the second branch point S2 where the second reversal transport path (second branch path) R13 branches from the fifth paper transport path R11, the transport destination of the paper P transported on the fifth paper transport path R11 is the first destination. A second switching gate G2 is provided for switching to one of the five sheet transport path R11 and the second reverse transport path R13. The second branch point S2 can be regarded as a branch for traveling from the fifth paper transport path R11 to the second reverse transport path R13.
Further, the second reverse conveyance path R13 branched from the fifth paper conveyance path R11 via the second branch point S2 has a second curved portion C2 that curves in a direction away from the fifth paper conveyance path R11. The fifth paper transport path R11 and the second reverse transport path R13 are in a crossing positional relationship.

  Here, as shown in FIG. 2, the first branch point S1 where the first reverse conveyance path R5 branches from the second sheet conveyance path R3 is a nip portion N of the fixing device 50 along the second sheet conveyance path R3. Distance L1 from On the other hand, the second branch point S2 where the second reverse conveyance path R13 branches from the fifth paper conveyance path R11 is from the nip portion N of the fixing device 50 along the second paper conveyance path R3 and the fifth paper conveyance path R11. The distance is L2 (> distance L1).

  Further, the second curved portion C2 of the second reverse conveyance path R13 is formed so as to be looser (having a larger radius of curvature than the first curved portion C1) than the first curved portion C1 of the first reverse conveyance path R5. Has been. Note that the second paper transport path R3 and the fifth paper transport path R11 may be formed to be curved, but the curvature of the first curving portion C1 and the second reverse transport path R13 of the first reverse transport path R5. It is formed so as to be looser than the second curved portion C2 (the curvature radius is large).

  Note that the sheet processing system 1 according to the present exemplary embodiment includes two reversal transport paths, a first reverse transport path R5 provided in the image forming apparatus 100 and a second reverse transport path R13 provided in the paper processing apparatus 200. Yes. Although details will be described later, the paper processing system 1 in the present embodiment can switch between the first reverse conveyance path R5 and the second reverse conveyance path R13 according to the thickness of the paper P or the like.

<General control unit 80>
Next, the general control unit 80 will be described with reference to FIG. FIG. 3 is a diagram illustrating a functional configuration of the general control unit 80.
The general control unit (reception unit, switching unit) 80 includes, for example, a processor that functions by program control, a nonvolatile memory that stores a program that controls the processor, and a volatile memory that is used for data processing by the processor. Realized.

  The general control unit 80 includes a transmission / reception control unit 81 for exchanging data with the processing control unit 180, a processing device information acquisition unit 82 and a processing device information storage unit 83 for holding information of the processing control unit 180, A processing instruction unit 84 for instructing processing to be executed by the sheet processing apparatus 200 and a job control unit 85 for controlling the operation of each device constituting the image forming apparatus 100 are provided.

The transmission / reception control unit 81 is connected to the processing control unit 180 via a predetermined physical interface, and exchanges data with the processing control unit 180 according to a predetermined communication protocol.
The processing device information acquisition unit 82 receives information regarding the paper processing device 200 acquired from the processing control unit 180 via the transmission / reception control unit 81 and stores the information in the processing device information storage unit 83. The information received here is information regarding identification information and functions of the sheet processing apparatus 200. Further, the processing device information acquisition unit 82 transmits an acquisition request for information regarding the paper processing device 200 to the processing control unit 180 of the paper processing device 200 at a predetermined timing.
The processing device information storage unit 83 is realized by, for example, a RAM (Random Access Memory), and holds information received by the processing device information acquisition unit 82.

The processing instruction unit 84 instructs the paper processing apparatus 200 to request information necessary for controlling the image forming apparatus 100. Further, based on the information stored in the processing device information storage unit 83, it is possible to instruct the processing control unit 180 to perform processing to be executed by the paper processing device 200 as necessary.
The job control unit 85 controls operations in normal image formation, but performs control according to the processing to be executed according to the information stored in the processing device information storage unit 83 and the contents of the processing instruction unit 84. It can be carried out.

<Processing control unit 180>
Next, the processing control unit 180 will be described with reference to FIG. FIG. 4 is a diagram illustrating a functional configuration of the processing control unit 180.
The processing control unit 180 is realized by, for example, a processor that functions by program control, a nonvolatile memory that stores a program that controls the processor, and a volatile memory that is used for data processing by the processor.

  The processing control unit 180 is an information for providing the transmission / reception control unit 181 for exchanging data with the general control unit 80 and information regarding the functions of the sheet processing apparatus 200 to the general control unit 80 of the image forming apparatus 100. A holding unit 182 and an information providing unit 183 are provided.

The transmission / reception control unit 181 is connected to the general control unit 80 via a predetermined physical interface, and exchanges data with the general control unit 80 according to a predetermined communication protocol.
The information holding unit 182 holds identification information (ID) of the paper processing apparatus 200 and information about what function the paper processing apparatus 200 has.
The information providing unit 183 acquires the identification information and function information of the sheet processing apparatus 200 from the information holding unit 182 in response to the information acquisition request received from the general control unit 80 via the transmission / reception control unit 181. It returns to the control unit 80.

  The general control unit 80 and the processing control unit 180 configured as described above establish communication between the general control unit 80 and the processing control unit 180, for example, when the paper processing system 1 is powered on. Then, when the comprehensive control unit 80 receives the identification information from the processing control unit 180, the comprehensive control unit 80 can recognize that the sheet processing apparatus 200 is connected to the image forming apparatus 100.

  Here, it has been described that the general control unit 80 recognizes that the sheet processing apparatus 200 is connected by receiving identification information from the processing control unit 180. However, for example, when the sheet processing apparatus 200 is connected, In addition, it is of course possible to accept designation by the user for identification of the sheet processing apparatus 200 via the UI 90 or the like. Of course, the sheet processing apparatus 200 may not be provided with the processing control unit 180, and the general control unit 80 may be configured to control the entire sheet processing system 1.

<Operation of Paper Processing System 1>
Next, an image forming operation of the sheet processing system 1 in the present embodiment will be described with reference to FIGS. 1 and 2. In the paper processing system 1 in the present embodiment, single-sided printing and double-sided printing are performed on the paper P.
First, single-sided printing will be described.
When image data formed by a PC (not shown) or the like is received by the general control unit 80, the general control unit 80 performs image processing on the image data. The image data that has undergone image processing is output to the exposure device 13. The exposure device 13 that has acquired the image data selectively exposes the photosensitive drum 11 charged by the charging device 12 to form an electrostatic latent image on the photosensitive drum 11. The electrostatic latent image formed on the photosensitive drum 11 is developed by the developing device 14 as, for example, a black (K) toner image.

On the other hand, the take-out roll 42 rotates in accordance with the image formation timing, and the paper P is supplied from the paper storage unit 41 to the first paper transport path R1. The sheet P is conveyed to the secondary transfer device 30 in accordance with the rotation timing of the photosensitive drum 11. Then, in the secondary transfer device 30, the toner image formed on the photosensitive drum 11 is transferred onto the paper P.
Thereafter, the sheet P on which the toner image is transferred is subjected to a fixing process by the fixing device 50 while being conveyed on the second sheet conveyance path R3. The curl correcting device 52 corrects the bending of the paper P on the paper P on which the fixed image is formed. Thereafter, the paper P that has passed through the curl correction device 52 is guided to the discharge roll 53 on the second paper transport path R3 by the first switching gate G1, and is discharged from the opening 102 provided in the housing 101.

  The paper P discharged from the opening 102 of the image forming apparatus 100 is cooled by the cooling device 71 while being transported on the fifth paper transport path R11 of the paper processing device 200, and the inline sensor 73 detects the toner image. Is called. Then, the paper P is discharged from the opening 202 of the housing 201 while being transported on the fifth paper transport path R11 by the second switching gate G2, and is stacked on a paper stacking unit (not shown).

  In addition, after image formation is performed in the image forming unit 10 and the toner image on the photosensitive drum 11 is transferred to the paper P, residual toner may adhere to the photosensitive drum 11 in some cases. The residual toner on the photosensitive drum 11 is removed by the drum cleaning device 16. Similarly, residual toner on the intermediate transfer belt 20 is removed by the belt cleaning device 24.

As described above, in the present embodiment, the sheet P conveyed on the second sheet conveyance path R3 and the fifth sheet conveyance path R11 passes through the fixing device 50, the curl correction device 52, and the cooling device 71. Pass in this order.
Here, the toner used for image formation on the paper P has a thermoplastic property. In the present embodiment, immediately after the toner (fixed image) is heated in the fixing device 50, the curl correction device 52 is passed, so that the temperature of the toner is high and the curling of the paper P can be easily deformed. Correct. Thus, unlike the present embodiment, the cooling device 71 is arranged on the upstream side of the curl correction device 52 in the conveyance direction of the paper P, and compared with the case where the paper P is cooled by the cooling device 71 and the curl is corrected. Thus, correction can be performed more effectively.

Further, in the present embodiment, the paper P whose curl has been corrected is cooled while being sandwiched between the conveying belts 71A and 71B of the cooling device 71. As a result, it is possible to suppress the occurrence of curling of the paper P again as the paper P once curled by the curl correcting device 52 is cooled.
In addition, by cooling the paper P by the cooling device 71, the toner of the paper P stacked in the paper stacking unit overlaps without being cooled to a predetermined temperature or less, and the paper P is prevented from sticking to each other.

Next, the operation in double-sided printing will be described.
In double-sided printing according to the present embodiment, the path for transporting the paper P is switched according to the thickness of the paper P on which an image is formed.
First, in the case of thin paper, the paper P on which the fixed image is formed on one surface of the paper P by the above-described process and has passed through the curl correction device 52 is transferred to the first reverse conveyance path R5 by the first switching gate G1. It is guided. Then, the paper P cut back by the first reverse conveyance path R5 is conveyed again to the secondary transfer device 30 via the first re-conveyance path R7 and the first paper conveyance path R1.

  Then, the paper P on which the toner image is formed on the other side passes through the secondary transfer device 30 and the curl correction device 52 again. Thereafter, the sheet P is guided to the discharge roll 53 by the first switching gate G1, and is discharged from the opening 102. The paper P discharged from the opening 102 of the image forming apparatus 100 is cooled by the cooling device 71 on the fifth paper transport path R11 of the paper processing device 200, and a toner image is detected by the inline sensor 73. The paper P is transported on the fifth paper transport path R11 by the second switching gate G2, and then discharged from the opening 202 and stacked on a paper stacking unit (not shown).

  Next, in the case of thick paper, the paper P having a fixed image formed on one side of the paper P through the above-described process and having passed through the curl correction device 52 is different from the case of thin paper by the first switching gate G1. Then, it is guided to the discharge roll 53 and discharged from the opening 102. The paper P discharged from the opening 102 is cooled by the cooling device 71 on the fifth paper transport path R11 of the paper processing device 200, and a toner image is detected by the inline sensor 73. Then, the sheet P is guided to the second reverse conveyance path R13 by the second switching gate G2. Thereafter, the paper P turned back by the second reverse conveyance path R13 is secondarily transferred again via the second re-conveyance path R15, the fourth conveyance path R10, the first re-conveyance path R7, and the first paper conveyance path R1. It is conveyed to the device 30.

  Then, the fixed image is formed on the other surface, and the paper P that has passed the curl correction device 52 again is guided to the discharge roll 53 by the first switching gate G1, and is discharged from the opening 102. The paper P discharged from the opening 102 is cooled by the cooling device 71 on the fifth paper transport path R11 of the paper processing device 200, and a toner image is detected by the inline sensor 73. Thereafter, after being transported on the fifth paper transport path R11 by the second switching gate G2, it is discharged from the opening 202 and stacked on a paper stacking unit (not shown).

Here, in general, when the paper P on which the fixed image is formed has a curved path for transporting the paper P, the paper P and the paper transport path come into contact with each other when passing through this curve. The fixed image may be rubbed, resulting in a decrease in the quality of the fixed image.
In particular, when the toner image is fixed by the fixing device 50 and the temperature of the thermoplastic toner is high, the deterioration of the image quality due to the rubbing of the fixed image can be remarkable.
Further, this deterioration in image quality also depends on the thickness of the paper P. That is, when the thickness of the paper P is increased, the gap formed between the paper P and the path for transporting the paper P is reduced, and as a result, the possibility that the fixed image is rubbed increases. Furthermore, when the paper P becomes thicker and the rigidity of the paper P increases, the fixed image is more strongly rubbed and the image quality tends to deteriorate.

Therefore, in the present embodiment, when using thick paper whose image quality can be further deteriorated, as described above, the second curve is located farther from the nip N of the fixing device 50 than the first curve C1. Pass part C2. More specifically, the sheet P (toner) heated by the fixing device 50 is cooled by increasing the time from passing through the nip portion N of the fixing device 50 to passing through the second curved portion C2. And the deterioration of image quality is suppressed.
In the present embodiment, a cooling device 71 is provided between the first branch point S1 and the second branch point S2, and the cooling device 71 cools the paper P, whereby the second curve. The temperature of the paper P passing through the section C2 can be further lowered, and image quality deterioration can be further suppressed.

In addition, as described above, the second bending portion C2 is looser than the first bending portion C1 (the radius of curvature is larger than that of the first bending portion C1). Therefore, compared with the case where the first bending portion C1 is passed, the pressure at which the paper P is pressed against the transport path is suppressed when the second bending portion C2 is allowed to pass. As a result, deterioration of image quality can be suppressed.
Further, as described above, the image forming apparatus 100 is provided with the first curved portion C1 that is tightly curved, and the sheet processing apparatus 200 is provided with the second curved portion C2 that is loosely curved. Here, as described above, the image forming apparatus 100 can form an image on the sheet P alone, and the sheet processing apparatus 200 is a so-called option connected to the image forming apparatus 100 as necessary. Therefore, considering that the image forming apparatus 100 is used alone, it is preferable to suppress the size of the image forming apparatus 100 by providing the image forming apparatus 100 with the first curved portion C1 having a larger curvature.

<Operation of General Control Unit 80>
Next, an operation in which the general control unit 80 switches the path for conveying the paper P according to the thickness of the paper P on which an image is formed will be described with reference to FIG. FIG. 5 is a flowchart showing an operation of switching the transport path of the general control unit 80.

First, the overall control unit 80 that has received a job via a PC (not shown), UI 90, or the like determines whether or not double-sided printing is performed based on the received job (step 501). If the accepted job is duplex printing (YES in step 501), the overall control unit 80 determines whether or not the paper P on which an image is to be formed is a thick paper (step 502). If the paper P is a thick paper (YES in step 502), the overall control unit 80 controls to transport the paper P to the second reverse transport path R13. Specifically, the operations of the first switching gate G1 and the second switching gate G2 are controlled, and after the image is formed on one surface of the paper P, the paper P is transported to the second reverse transport path R13.
On the other hand, when the received job is not double-sided printing (single-sided printing, NO in step 501) and not thick paper (thin paper, NO in step 502), the general control unit 80 conveys the paper P to the first reverse conveyance path R5. Control as follows.

  Note that whether or not the paper P is thick paper is switched according to the basis weight of the paper P in the received job, for example. More specifically, when the basis weight of the paper P is larger than a predetermined numerical value (for example, 200 gsm), the paper is determined to be thick paper. When the basic weight of the paper P is equal to or smaller than the predetermined numerical value, it is not thick paper, that is, thin paper. Is determined.

  In FIG. 5, switching of the reverse conveyance path is described based on whether or not the paper P is a thick paper. However, the information is not limited to the thickness of the paper P as long as it is information relating to an image forming job. For example, in addition to the thickness of the paper P, the reverse transport path may be switched according to the type of the paper P, the length of the paper P in the transport direction, the image density, the image quality priority / output speed priority, and the like.

Here, as the switching of the reverse conveyance path depending on the type of the paper P, for example, in the case of coated paper, since it takes time to dissipate the paper P, the paper P is conveyed to the second reverse conveyance path R13 and the plain paper is changed. In this case, control is performed so that the paper P is transported to the first reverse transport path R5.
In addition, as the switching of the reverse conveyance path depending on the length in the conveyance direction of the paper P, for example, when the length in the conveyance direction is longer than a predetermined length, the friction with the conveyance path becomes larger. When the paper P is transported to the reverse transport path R13 and the length is equal to or shorter than a predetermined length, control is performed so as to transport the paper P to the first reverse transport path R5.

Further, as the switching of the reverse conveyance path depending on the image density, when the image density is higher than a predetermined value, the amount of toner is large and it takes time to dissipate, so the paper P is put on the second reverse conveyance path R13. When the image density is less than or equal to a predetermined value, the sheet P is controlled to be conveyed to the first reverse conveyance path R5.
Further, as the switching of the reverse conveyance path by either the image quality priority or the output speed priority, for example, via the UI 90, designation by the user regarding which of the image quality or the output speed is to be prioritized is accepted. If this designation is image quality priority, the paper P is transported to the second reverse transport path R13. If the output speed is prioritized, the paper P is transported to the first reverse transport path R5 where the transport distance of the paper P is shorter. Control to transport.

  In the above description, it has been described that, based on the job received by the integrated control unit 80, it is determined which of the first reverse conveyance path R5 and the second reverse conveyance path R13 is used. However, it is of course possible to accept designation from the user as to which of the first reverse transfer route R5 and the second reverse transfer route R13 is used as the reverse transfer route via the UI 90 or the PC (not shown).

  In the illustrated example, the first reverse conveyance path R5 that branches from the second paper conveyance path R3 via the first branch point S1 and the fifth branch from the fifth paper conveyance path R11 via the second branch point S2. Each of the second reverse conveyance paths R13 has been described. However, it is not always necessary to perform the reverse conveyance as long as the route branches from the second paper conveyance path R3 and the fifth paper conveyance path R11 continuous with the second paper conveyance path R3. For example, the sheet P may of course be transported only in one direction on two path paths that are branched from the transport path.

DESCRIPTION OF SYMBOLS 1 ... Paper processing system, 50 ... Fixing device, 71 ... Cooling device, 80 ... General control part, 100 ... Image forming apparatus, 180 ... Processing control part, 200 ... Paper processing apparatus, G1 ... 1st switching gate, G2 ... 1st 2 switching gates, R1... First paper transport path, R3... Second paper transport path, R5... First reverse transport path, R7... First retransport path, R11. Route, R15 ... second re-transport route, S1 ... first branch point, S2 ... second branch point

Claims (3)

A toner image forming unit that forms a toner image on paper;
A fixing unit for fixing the toner image formed by the toner image forming unit to a sheet;
A conveyance path that extends in one direction from the fixing unit and that conveys a sheet on which a toner image is formed in the fixing unit;
A first branch path that branches while being bent from the conveyance path at a position away from the fixing section by a predetermined distance, and on which a sheet on which a toner image is formed is conveyed by the fixing section;
A second branch path that is branched from the conveyance path at a position that is longer than the predetermined distance from the fixing unit and that is fed with a sheet on which a toner image is formed in the fixing unit;
A cooling unit that cools the sheet on which the toner image is fixed by the fixing unit between the branch of the predetermined distance and the branch of a position that is longer than the predetermined distance ;
A receiving unit that receives information about paper on which the toner image is fixed by the fixing unit;
An image forming system comprising: a switching unit that switches a sheet to be conveyed to either the first branch path or the second branch path according to information on the sheet received by the reception unit. system.   A re-conveying path is connected to the first branch path and the second branch path, and a sheet conveyed from the first branch path and the second branch path is conveyed to the fixing unit again. The image forming system according to claim 1. A toner image forming unit that forms a toner image on paper;
A fixing unit for fixing the toner image formed by the toner image forming unit to a sheet;
A first conveyance path extending in one direction from the fixing unit and carrying a sheet on which a toner image is formed in the fixing unit;
A first housing having a first branch path that branches from the first transport path while being bent and transports a sheet on which a toner image is formed by the fixing unit ;
A receiving unit for receiving paper conveyed from one end of the first conveying path;
A second conveyance path that extends along the one direction from the one end of the first conveyance path and that conveys the sheet received by the receiving unit;
A second casing having a second branch path that branches while being bent from the second transport path and that transports a sheet on which a toner image is formed in the fixing unit ;
A receiving unit that receives information about a sheet on which a toner image is fixed by the fixing unit; and
An image forming system comprising: a switching unit that switches a sheet to be conveyed to either the first branch path or the second branch path according to information about the sheet received by the reception unit. .

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