JP4774965B2 - Curl correction device and image forming apparatus - Google Patents

Description

  The present invention relates to a technique for correcting curl generated on a recording sheet.

In an image forming apparatus using electrophotographic technology, an electrostatic latent image formed on an image carrier is developed with a developer, and a toner image obtained by the development is transferred to a sheet, and then heated for fixing on the sheet. Image formation is performed by fixing a toner image through a roll or the like, and it is widely known that paper is curled when the toner image is fixed.
The direction and strength of curl varies depending on various conditions. For example, there are two directions of curling, and the phenomenon of curling upward is called “upper curl”, and the phenomenon of curling downward is called “down curl”. Whether the curl generated on the paper is an upper curl or a down curl depends on conditions such as the paper quality of the paper and the density of the toner image. As a mechanism for correcting such curl, there are techniques described in Patent Documents 1 and 2.

  In Patent Document 1, a curl correction mechanism for correcting the curl of the paper discharged from the fixing device is provided for each branch path that branches the transport path to the paper discharge port, and for each return transport path for duplex printing. An installed curl correction device is described. The curl correction device switches the branch path according to the curl direction of the paper conveyed to the curl correction mechanism and corrects the curl.

  Further, in Patent Document 2, a curl correcting unit that corrects a curl formed on one side of a sheet and a curl correcting unit formed on the other side are arranged in series in the sheet conveying direction, and each curl is arranged. The correction means describes a curl correction system having an adjustment mechanism for adjusting the amount of curl correction. This curl correction system appropriately corrects the curl of the paper by appropriately adjusting the curl correction amount of each curl correction means by the adjustment mechanism.

Moreover, FIG. 8 is a figure which shows an example of the conventional curl correction apparatus. This curl correction apparatus is configured to correct upper curl and down curl. In FIG. 8, the conveyance path for conveying the storage sheet is the first conveyance path 3 for conveying the storage sheet from the fixing device 1 to the discharge port 2 and the front and back of the storage sheet carried out from the fixing device 1 are reversed. A second conveyance path 6 that conveys to a reversing device 5 from a branch point 4 provided in the middle of the first conveyance path 3 for conveyance to the outlet 2, and the first conveyance for duplex printing on a recording sheet. The recording sheet on which the toner image is transferred to one of the surfaces conveyed to the reversing device 5 through the path 3, the branch point 4 and the second conveying path 6 is reversed by the reversing device 5 to the image forming unit. A third transport path 7 for transporting.
A pair of curl correction mechanisms 8a and 8b are provided in the middle of the first conveyance path 3 from the branch point 4 to the discharge port 2, and a curl correction mechanism 8c is provided in the middle of the third conveyance path 7. A total of three curl correction mechanisms are provided.

Here, the curl correction mechanism 8a is a mechanism for correcting the curl such that one surface of the recording sheet is convex, and the curl correction mechanism 8b is a curl so that the other surface of the recording sheet is convex. It is a mechanism for correcting The curl correction mechanism 8c is for correcting a curl such that the other surface of the recording sheet is convex.
JP 2002-080158 A JP 2002-060110 A

  As described above, the conventional curl correction apparatus needs to include at least three types of curl correction mechanisms, which increases the number of parts and complicates the recording sheet conveyance control.

  The present invention has been devised under such a background, and an object of the present invention is to correct various shapes of curls with fewer curl correction mechanisms than in the past.

An image forming apparatus according to the present invention discharges the recording sheet on which the toner image is fixed by the fixing unit, and a fixing unit that fixes the toner image on the recording sheet on which the toner image is transferred by the image forming unit. and discharge means for said a first conveying path extending from the fixing means to the discharge means, is disposed along the first conveyance path, the fixing to the recording sheet the toner image is fixed by the fixing means A first curling unit that applies a first curl only in a predetermined first direction for correcting the curl formed on the recording sheet by the unit, and the recording sheet on which the toner image is fixed by the fixing unit. Reversing means for reversing the front and back, a branch point provided between the fixing means and the first curling means, a second transport path extending from the branch point to the reversing means, and the first Are arranged along the conveying path, wherein the fixing means to the surface of the recording sheet that the toner image is fixed only in a predetermined first direction to correct the curl formed on the recording sheet by the fixing means the A second curling unit that imparts a second curl, a third conveyance path that extends from the reversing unit to a position where a toner image is transferred by the image forming unit, and a first conveyance that is a conveyance route during single-sided printing. A conveyance control unit configured to convey the recording sheet on which the toner image has been fixed by the fixing unit according to any one of a conveyance route of a route and a second conveyance route and a third conveyance route that is a conveyance route for duplex printing. In the first transport route, the recording sheet having a toner image fixed on the surface thereof by the fixing unit is passed through the first transport path and the first curling unit to the discharge unit. The second transport route is a route for transporting the recording sheet having a toner image fixed on the surface thereof by the fixing unit via the branch point, the second transport path, and the second curling unit. The recording sheet conveyed to the reversing unit and reversed by the reversing unit passes through the second conveying path, the second curling unit, the branch point, and the first curling unit. The third transport route is a route for transporting the discharge sheet to the discharge unit, and the third transport route applies the recording sheet on which the toner image is fixed on the surface by the fixing unit, the second transport path, and the second curling. The recording sheet that has been reversed by the reversing unit is conveyed to the image forming unit via the third conveying path, and a toner image is formed on the back surface by the fixing unit. The recording sheet on which is fixed Is routed to the discharge means via the first transport path and the first curling means, and the first curling means and the second curling means are the transporting means. In the case of the first transport route, the amount of protrusion by the first curling unit is applied to the recording sheet by the fixing unit. The first protrusion amount corresponding to the degree of curl formed is set, and in the case of the second transport route, the protrusion amount by the first curling means and the protrusion amount by the second curling means are The result of subtracting the protrusion amount of the second curl from the result of multiplying the protrusion amount of the first curl by 2 is set so as to correspond to the first protrusion amount, respectively. In the case, the first cartridge The protrusion amount by the tool applying means and the protrusion amount by the second curling means are both set to the first protrusion amount .

With such a configuration, the transport control unit, during one-sided printing, fixing means first curling means recording sheet passing through the fixing by or the second conveyor to curl of the recording sheet into either one of the curling means Can be corrected. On the other hand, the double-sided printing, after the toner image is conveyed with the recording sheet passing through the fixing by said fixing means are transferred to the front Stories second curling hand stage on the surface, through the third conveyance path the recording sheet to transfer the toner image on the rear surface by the image forming means by further from said through fixing by the fixing means, to correct the curl of the first of the recording sheet recording sheet is conveyed to the curling hand stage Can do.

In the curl correction apparatus, an operation unit that receives an input of the transport route, and a storage unit that stores the protrusion amount corresponding to the first curl applying unit and the second curl applying unit for each transport route. The first curl application is read out from the storage unit by reading the projection amounts of the first curl application unit and the second curl application unit according to the transport route received by the operation unit. And a correction amount adjusting means for adjusting the protruding amount of the second curling means .

  In order to achieve the above object, an image forming apparatus employed by the present invention includes any of the curl correction apparatuses described above and an image forming unit that forms an image on the recording sheet. .

Embodiments of the present invention will be described below with reference to the drawings.
A curl correction apparatus according to an embodiment of the present invention will be described with reference to FIG. In FIG. 1, only the conveyance path from the fixing device to the paper discharge port is shown. In the present embodiment, description of the image forming apparatus is omitted.

<1. Configuration of Embodiment>
<1-1. Image forming apparatus>
First, the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating an image forming apparatus. The image forming apparatus 10 is a copying machine that forms and outputs a toner image corresponding to an image to be copied on a recording material such as printing paper or an OHP sheet by an electrophotographic method, and performs image formation and fixing. In addition to a sheet tray and a paper tray for storing a recording material (both not shown), a user interface unit 11 (hereinafter referred to as U / I unit 11), a controller 12, an input / output control unit 13, a storage unit 14, and a later-described A paper feed control unit 15 for driving and controlling the paper feed mechanism 16 and correction amount control units 17a and 17b for driving and controlling the correction amount adjusting mechanisms 306a and 306b.

  In this embodiment, the case where the present invention is applied to an electrophotographic copying machine will be described. However, the present invention may be applied to an electrophotographic facsimile machine or an electrophotographic printer apparatus. In short, the present invention can be applied to any image forming apparatus that forms an image on a recording material by electrophotography.

  The U / I unit 11 has a function of providing a user interface for allowing a user to use the image forming apparatus 10. The U / I unit 11 includes a display unit and an operation unit (both not shown). The display unit is a liquid crystal display, for example, and various screens for prompting the user to use the image forming apparatus 10. Is displayed. On the other hand, an operation part is comprised by operation elements, such as a numeric keypad, and the transparent pressure-sensitive sensor affixed on the display surface of a display part, and comprises what is called a touch panel with a display part. The U / I unit 11 is for allowing the user to input various instructions.

  The controller 12, the input / output control unit 13, the paper feed control unit 15, and the correction amount control units 17a and 17b in FIG. 1 are each configured by a CPU (Central Processing Unit) and a RAM (Random Access Memory).

The controller 12 controls the operation of the input / output control unit 13, the paper feed control unit 15, the correction amount control units 17a and 17b, and the image forming unit (not shown) according to a control program stored in the storage unit 14. is there. Further, the storage unit 14 stores a correction amount setting map 14a used for curl correction control processing described later.
The input / output control unit 13 performs drive control of the U / I unit 11 under the control of the controller 12. More specifically, the input / output control unit 13 displays various screens on the display unit in response to an instruction from the controller 12 and represents data indicating the user's operation content on the operation element and the touch panel (hereinafter, operation content data). ) From the operation unit, the operation content indicated by the operation content data is converted into various instructions for the image forming apparatus 10 and transferred to the controller 12.

The paper feed control unit 15 takes out the sheets placed on the paper tray (not shown) one by one and conveys each of them to an image forming unit (not shown), or the image forming unit generates a toner image. The drive control of the paper feed mechanism 16 for switching the transport path of the formed paper or transporting it to the discharge port 202 is performed.
Here, the paper feed mechanism 16 includes a transport belt for transporting paper, a roller for stretching the transport belt and driving it in a predetermined direction, a motor for rotationally driving the roller, and transported paper. A sorting mechanism that sorts the items at branch points is included. The paper feed control unit 15 performs drive control of the paper feed mechanism 16 by performing drive control of the motor and the sorting mechanism.

  The correction amount control units 17a and 17b are for performing operation control of the correction amount adjustment mechanisms 306a and 306b for adjusting the correction amount of curl in the curl correction mechanisms 301a and 301B described later under the control of the controller 12.

<1-2. Paper transport path>
Next, the paper conveyance path will be described with reference to FIG.
The conveyance path conveys the sheet on which the toner image is formed on one side by the image forming unit from the fixing device 201 to the discharge port 202. From the fixing device 201 corresponding to the final process of the image forming unit to the discharge port 202 is the first conveyance path 101. A first first branch point 102 for distributing the conveyance direction of the paper is provided in the middle of the first conveyance path 101. The second conveyance path 103 is from the first branch point 102 to the reversing device 110, the third conveyance path 104 is from the reversing device 110 to the image forming apparatus, and the distribution between the second conveyance path 103 and the third conveyance path 104 is performed. The portion becomes the second branch point 105.

  The conveyance paths 101, 103, and 104 are formed by a plurality of rollers and chutes. Further, the branch points 102 and 105 are configured to switch the transport direction by turning a louver (not shown) and closing one of the transport paths. Further, the reversing device 110 reverses the front and back of the sheet by switching back the sheet conveyed by the second conveyance path 103.

There are three paper transport routes: straight transport, invert transport, and duplex printing transport.
In the straight conveyance, the sheet on which the toner image is formed is discharged to the discharge port 202 via the first conveyance path 101.

  Invert conveyance is performed on a sheet on which a toner image is formed on the surface of the first conveyance path 101 up to the first branch point 102 → second conveyance path 103 → reversing device 110 → second conveyance path 103 → first branch point 102 and thereafter. The first conveying path 101 is conveyed to the discharge port 202. When the sheet is switched back by the reversing device 110 and reciprocates in the second conveyance path 103, the reversed sheet is conveyed to the discharge port 202.

In duplex printing conveyance, an image is formed on a sheet having a toner image formed on the surface via the first conveyance path 101 to the first branch point 102 → the second conveyance path 103 → the reversing device 110 → the third conveyance path 104. The image forming unit transfers the toner image to the back surface of the transported paper again, and the fixing device 201 fixes the toner image to the back surface of the paper. It is transported to the discharge port 202 via the transport path 101.
The paper transport route is arbitrarily set by the user operating the U / I unit 11.

<1-3. Curl straightening mechanism>
Next, the curl correction mechanism will be described.
The first curl correction mechanism 301 a is provided in the middle of the first conveyance path 101 after the first branch point 102, and the second curl correction mechanism 301 b is provided in the middle of the second conveyance path 103.

  Here, the structure of the curl correction mechanism will be described with reference to FIG. Hereinafter, since the first curl correction mechanism 301a and the second curl correction mechanism 301b have the same configuration, they will be described as the curl correction mechanism 301.

  The curl correction mechanism 301 includes a carry-in roller 302, a small-diameter urging roller 303 made of a hard material, a carry-out roller 304, and a belt 305 provided between the rollers 302 and 304. The urging roller 303 protrudes with a predetermined protrusion amount so as to push in the belt 305 positioned on the tangent line of the rollers 302 and 304. This protrusion amount can be adjusted by a correction amount adjusting mechanism 306 such as a cam (not shown). In addition, a drive motor (none of which is shown) is connected to at least one of the carry-in roller 302 and the carry-out roller 304 via a transmission mechanism, and the rotation of the rotation shaft of the drive motor is caused by the carry-in roller 302. Alternatively, the feeding operation of the paper that is conveyed to the carry-out roller 304 and is sandwiched between the belt 305 and the urging roller 303 is performed.

  The sheet conveyed to the curl correction mechanism 301 is conveyed in the direction of the arrow from the carry-in side roller 302 side, and is sandwiched between the belt 305 at the position of the urging roller 303. At this time, since the sheet passes through the position where the urging roller 303 is pushed into the rollers 302 and 304, the sheet is corrected so as to curl toward the urging roller 303. Further, in the curl correction mechanism 301, the amount of protrusion of the urging roller 303 is adjusted by the correction amount adjustment mechanism 306, so that the correction amount of curl is appropriately adjusted.

  FIG. 4 shows the degree of curling when the amount of protrusion of the biasing roller 303 can be adjusted by the correction amount adjusting mechanism 306, for example, in five steps (1 is weak and 5 is strong). The curl generated on the sheet by passing through 301 is shown. In this case, the degree of curl is represented by “h” as the difference between the edge of the paper without curl and the edge of the paper with curl.

By setting the urging roller 303 to a minimum protrusion amount of “1”, curling occurs where the surface (upper side) of the sheet is concave and the difference between the ends is “h1”. In other words, the paper on which the curl with the difference between the edges where the paper surface is convex is “h1” is passed through the curl correction mechanism 301 set to the protrusion amount of “1”, thereby causing the convexity. Correct the curl. On the other hand, by setting the biasing roller 303 to a maximum protrusion amount of “5”, a curl in which the difference between the end portions where the front surface (upper side) of the sheet is concave is “h5” occurs. Similarly, the curl correction mechanism 301 set to the protruding amount of “5” is passed through the paper on which the curl with a difference of “h5” at the edge portion where the surface of the paper is convex passes through the curl correction mechanism 301. Get no paper. Since curling similarly occurs in the other protrusion amounts “2”, “3”, and “4”, the description thereof is omitted.
As described above, the curl correction mechanism 301 appropriately adjusts the protrusion amount, thereby enabling curl correction according to the degree of curl of the paper.

<1-4. Correction amount setting map in the storage unit>
Next, the correction amount setting map 14a stored in the storage unit 14 will be described.
FIG. 5 shows a specific example of the correction amount setting map 14a. The correction amounts of the curl correction mechanisms 301a and 301b are set by the correction amount adjustment mechanisms 306a and 306b according to the conveyance route. The correction amount setting map 14a exemplifies the setting of the correction amount in the case of a down curl (curl with a convex surface) where the difference between the curl edges generated on the paper is “h5”. This curl depends on conditions such as the material of the paper and the toner image, but in this embodiment, the degree of curl occurring on the paper is known in advance.

The setting in FIG. 5 will be specifically described. In the case of straight conveyance, the protruding amount of the urging roller 303a of the first curl correction mechanism 301a is set to “5”. In the case of invert conveyance, the protrusion amount of the urging roller 303a of the first curl correction mechanism 301a is set to “1”, and the protrusion amount of the urging roller 303b of the second curl correction mechanism 301b is set to “ 3 ”. . In the case of duplex printing conveyance, the protrusion amount of the urging roller 303a of the first curl correction mechanism 301a is set to “5”, and the protrusion amount of the urging roller 303b of the second curl correction mechanism 301b is set to “5”. To do. For the sake of convenience, the correction amount setting map 14a is described as a protrusion amount, but actually, signals transmitted to the correction amount control units 17a and 17b in order to operate the correction amount adjustment mechanisms 306a and 306b according to the above setting. Will be remembered.

<2. Curl correction processing>
Next, the curl correction processing in this embodiment will be described with reference to the flowchart of FIG.
The controller 12 waits for an instruction from the user input by operating the U / I unit 11 (step S1 to step S4). When an instruction to output a sheet on which an image is formed is input from the user (YES in steps S1 and S2), the process proceeds to step S9 and subsequent steps. In addition, when a transport route instruction is input from the user (YES in step S3 and step S4), the process proceeds to step S5 and subsequent steps.

  The controller 12 determines whether or not the processing of the transport route is invert transport (Step S5). If the determination process in step S5 is affirmative (step S5; YES), a signal corresponding to each protrusion amount of the invert conveyance is read from the correction amount setting map 14a and temporarily stored in a memory such as a RAM ( Step S6).

  On the other hand, when the determination process of step S5 is negative (step S5; NO), the controller 12 moves the process to step S7. In step S <b> 7, the controller 12 determines whether or not the transport route processing is duplex printing transport. If the determination process in step S7 is affirmative (step S7; YES), a signal corresponding to each protrusion amount for duplex printing conveyance is read from the correction amount setting map 14a and temporarily stored in the memory (step S8). ).

Further, if the determination process in step S7 is negative (step S7; NO), the controller 12 assumes that the conveyance route setting by the user is set to straight conveyance, and moves the process to step S9. In step S9, the controller 12 reads a signal corresponding to each protrusion amount of the straight transport from the correction amount setting map 14a and temporarily stores it in the memory (step S9). Even when the user inputs an output instruction without setting the transport route, the process proceeds to step S9.
The controller 12 transmits a signal to the correction amount control units 17a and 17b based on the signal corresponding to the read protrusion amount, operates the correction amount adjustment mechanisms 306a and 306b, and biases the roller 303 to a desired protrusion amount. Is set (step S10).

  Further, the controller 12 controls the paper feed mechanism 16 via the paper feed control unit 15 to carry the paper according to the set carry route (step S11).

  Next, the operation of the curl correction mechanism 301 for each conveyance route will be described. FIG. 7 shows the curl state of the paper at each point on the transport path. Point A is a point that is unloaded from the fixing device 201, point B is a point on the second conveyance path 103 after passing through the second curl correction mechanism 301b, point C is downstream of the branch point 102, and point C of the first curl correction mechanism 301a. A point before loading, a point D is a point in the middle of the third conveyance path 104, and a point E is a point from the first curl correction mechanism 301a to the discharge port 202.

  First, in the case of straight conveyance, the protruding amount of the urging roller 303a of the first curl correction mechanism 301a is set to “5”. As a result, the sheet transported on the transport path is transported in the curl with the surface being convex and the difference between the end portions being “h5” at the points A and C, and the first curl correction mechanism 301a detects the end portion of the sheet. Curls with a difference of “h5” are corrected. Note that no paper is conveyed to the second curl correction mechanism 301b, and thus there is no need to adjust the protrusion amount.

Next, in the case of invert conveyance, the protrusion amount of the urging roller 303a of the first curl correction mechanism 301a is set to “1”, and the protrusion amount of the urging roller 303b of the second curl correction mechanism 301b is set to “ 3 ”. To do. Thereby, at point A passing through the first conveyance path 101 up to the branch point 102, the curl having a convex surface and a difference of “h5” is formed on the sheet, but the second curl correction mechanism 301b is used. At the point B after passing once, the end difference is corrected by “h 3 ”. Further, at the point C after being reversed by the reversing device 110 and again passing through the second curl correction mechanism 301b, the difference between the ends is further corrected by “h 3 ”. Then, the degree of curl, the surface paper became difference edge becomes concavely as "h1", the point E passing through the first curl correcting mechanism 301a, the difference in the end portion is corrected by "h1" min The Thus, in the invert conveyance, the second curl correction mechanism 301b is passed twice by being switched back by the reversing device 110 and reciprocating the second conveyance path, and once passing through the first curl correction mechanism 301a. The curl of the edge difference “h5” generated on the paper is corrected.

In addition, in the case of this invert conveyance, the correction amount of the curl correction mechanisms 301a and 301b is set such that the protrusion amount of the urging roller 303a of the first curl correction mechanism 301a is "3" and the urging force of the second curl correction mechanism 301b is set. It is also possible to set the protrusion amount of the roller 303b to “ 4 ”.

  Further, in the case of duplex printing conveyance, the protrusion amount of the urging roller 303a of the first curl correction mechanism 301a is set to “5”, and the protrusion amount of the urging roller 303b of the second curl correction mechanism 301b is set to “5”. To do. As a result, the sheet transported on the transport path is conveyed at the point A at the point B where the surface is convex and the edge difference is “h5” while being curled, and passes through the second curl correction mechanism 301b. A curl in which the difference between the end portions is “h5” is corrected. At the point D of the third transport path 104, the corrected paper is reversed and passes. After that, an image is formed on the back surface of the paper, and the curled paper whose front surface (back surface because it is inverted) is convex and the difference between the end portions is “h5” passes through points A and C, and the first The curl is corrected by the curl correction mechanism 301a, and the paper with the corrected curl is passed through the point E before the discharge port 202.

<3. Effects of the embodiment>
As described above, in the curl correction apparatus according to the present embodiment, the first curl correction mechanism 301 a provided downstream of the first branch point 102 of the first conveyance path 101 and the second curl provided in the middle of the second conveyance path 103. The amount of correction with the correction mechanism 301b can be set as appropriate according to the sheet conveyance route. As a result, the curl generated on the paper can be efficiently corrected for each conveyance route.

  Further, in the curl correction apparatus of the present embodiment, the curl correction can be performed by the two curl correction mechanisms 301a and 301b. Therefore, the number of the curl correction mechanisms required in the prior art can be reduced, and the number of parts can be reduced. This makes it possible to reduce the size of the image forming apparatus.

  Furthermore, since the curl is corrected by passing the second curl correction mechanism 301b twice during the invert conveyance, the output to the drive source in the correction amount adjustment mechanism 306b is corrected only once. Power consumption can be reduced.

<4. Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, A various aspect is possible.

  In the embodiment described above, the first curl correction mechanism 301a and the second curl correction mechanism 301b are described as correcting the convex curl formed on the surface of the paper, but the present invention is not limited to this, and one of the convex curl correction mechanism 301b is convex. The curl with the other concave may be corrected. In this case, the correction amount setting map 14a may be set again.

Further, the correction amount setting map 14a shown in FIG. 5 is an example, and the present invention is not limited to this, and various settings can be made according to the curl generated on the paper.
Furthermore, the degree of curl generated on the sheet is stored in advance using the material of the sheet (recording sheet) and the image density as parameters, and a plurality of correction amount setting maps 14a are prepared in accordance with the degree of curl. Further, it is possible to realize a curl correction device that can correct curl corresponding to image density.
Moreover, the adjustment amount of the correction amount can be adjusted to 5 steps by adjusting the protruding amount of the urging roller 303 to 5 steps. However, the adjustment amount is not limited to 5 steps, but is 2, 3, 4 The correction amount adjusting mechanism 306 may be designed so that the correction amount can be adjusted in steps 6 to 6.

  Furthermore, in the curl correction apparatus according to the above-described embodiment, it has been described that the curl of the paper is corrected when the paper is transported by three routes of straight transport, invert transport, and duplex printing transport. The present invention is not limited to this, and a curl correction apparatus that corrects the curl of the paper by a similar operation may be used for a conveyance path having two conveyance routes of straight conveyance and duplex printing conveyance.

1 is a block diagram illustrating an image forming apparatus in which a curl correction apparatus according to an embodiment of the present invention is used. It is a figure which shows the curl correction apparatus by embodiment. It is a figure which shows the curl correction mechanism by embodiment. It is a figure which shows the correction amount of the curl according to the protrusion amount of the urging | biasing roller in the curl correction mechanism by embodiment. It is a figure which shows the correction amount setting map used for embodiment. It is a flowchart which shows the curl correction process by embodiment. It is a figure which shows the correction state of the curl in each point of the curl correction apparatus by embodiment. It is a figure which shows the curl correction apparatus by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 12 ... Controller, 14 ... Memory | storage part, 14a ... Correction amount setting map, 15 ... Paper feed control part, 16 ... Paper feed mechanism, 17a, 17b ... Correction amount control part, 101 ... 1st conveyance path DESCRIPTION OF SYMBOLS 102 ... 1st branch point 103 ... 2nd conveyance path 104 ... 3rd conveyance path 105 ... 2nd branch point 110 ... Reverse device 201 ... Fixing device 202 ... Discharge port 301a ... 1st curl correction Mechanism 302b ... second curl correction mechanism 302 ... load-in side roller 303 ... biasing roller 304 ... unload-side roller 305 ... belt 306 ... correction amount adjustment mechanism

Claims (3)

Fixing means for fixing the toner image to the recording sheet onto which the toner image has been transferred by the image forming means;
Discharging means for discharging the recording sheet on which the toner image is fixed by the fixing means;
A first conveyance path extending from the fixing unit to the discharge unit;
Only in a predetermined first direction for correcting the curl formed on the recording sheet by the fixing unit with respect to the recording sheet disposed along the first conveyance path and on which the toner image is fixed by the fixing unit. A first curling means for imparting a first curl;
Reversing means for reversing the front and back of the recording sheet on which the toner image is fixed by the fixing means;
A branch point provided between the fixing unit and the first curling unit;
A second transport path extending from the branch point to the reversing means;
Only in a predetermined first direction for correcting the curl formed on the recording sheet by the fixing unit with respect to the recording sheet arranged along the second conveyance path and having the toner image fixed by the fixing unit. A second curling means for imparting a second curl;
A third conveyance path extending from the reversing unit to a position where the toner image is transferred by the image forming unit;
The toner image is fixed by the fixing unit according to any one of a first transport route and a second transport route that are transport routes at the time of single-sided printing and a third transport route that is a transport route at the time of duplex printing. A conveyance control means for conveying the recording sheet,
The first transport route is a route for transporting the recording sheet having a toner image fixed on the surface thereof by the fixing unit to the discharge unit via the first transport path and the first curling unit. Yes,
The second transport route transports the recording sheet having a toner image fixed on the surface thereof by the fixing unit to the reversing unit via the branch point, the second transport path, and the second curling unit. The recording sheet reversed by the reversing unit is conveyed to the discharge unit via the second conveying path, the second curling unit, the branch point, and the first curling unit. Route to
The third transport route transports the recording sheet having a toner image fixed on the surface thereof by the fixing unit to the reversing unit via the branch point, the second transport path, and the second curling unit. The recording sheet reversed by the reversing unit is conveyed to the image forming unit via the third conveyance path, and the recording sheet having the toner image fixed on the back surface by the fixing unit is A route for transporting to the discharge means via one transport path and the first curling means;
The first curl applying unit and the second curl applying unit respectively apply a curling amount of a protrusion determined according to the conveyance route to the recording sheet ,
In the case of the first transport route, the protruding amount by the first curling unit is set to a first protruding amount corresponding to the degree of curl formed on the recording sheet by the fixing unit.
In the case of the second transport route, the amount of protrusion by the first curling means and the amount of protrusion by the second curling means are calculated by multiplying the amount of protrusion of the first curl by two. The result of subtracting the amount of protrusion of the curl of 2 is set so as to correspond to the amount of protrusion of the first,
In the case of the third transport route, the amount of protrusion by the first curling means and the amount of protrusion by the second curling means are both set to the first protrusion amount. Straightening device. Operating means for receiving an input of the transport route;
Storage means for storing the projection amount corresponding to the first curl application unit and the second curl application unit for each conveyance route;
The protrusion amounts of the first curling application means and the second curling application means corresponding to the transport route received by the operation means are read from the storage means, and the first curling application means and the The curl correction apparatus according to claim 1, further comprising: a correction amount adjusting unit that adjusts a protruding amount of the second curl applying unit. The curl correction apparatus according to claim 1 or 2,
An image forming apparatus comprising: an image forming unit that forms an image on the recording sheet.

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