JP5880317B2 - Image forming apparatus and conveying apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a conveying apparatus.

  As a conventional technique described in the publication, an attitude correction unit that corrects the attitude of a sheet supplied from a sheet supply unit, an image formation unit that forms an image on a sheet whose attitude is corrected by the attitude correction unit, and an image formation unit A reverse conveyance unit that reverses the front and back of the sheet on which the image is formed and conveys the image again to the posture correction unit. The posture correction unit is provided on one side of the paper conveyance path along the paper conveyance direction. And a skew roll provided adjacent to the side guide in the conveyance path, and the sheet is moved to the side guide side by conveying the sheet in an oblique direction with the skew sandwiched between the sheets, There is one that corrects the skew of the paper by abutting the side edge of the paper against the side guide.

JP 2004-59188 A

  An object of the present invention is to suppress the buckling of the recording material in the skew correction of the recording material.

  According to the first aspect of the present invention, there is provided a skew feeding correcting means for correcting the skew feeding of the recording material along with the feeding, and a recording material in which the skew feeding is corrected by the skew feeding correcting means. An image forming unit that forms an image; and a reverse conveying unit that reverses the front and back of the recording material on which the image is formed by the image forming unit and that conveys the recording material with the front and back reversed toward the skew correction unit. When the recording material is supplied to the skew correction means without going through the reversing conveyance means, the pressure for sandwiching the recording material in the skew correction means is set to the first pressure, and the skew correction means In contrast, when the recording material is supplied through the reversing conveyance unit, the image forming apparatus includes a setting unit that sets the pressure to a second pressure smaller than the first pressure.

The invention according to claim 2 further includes a reading unit that reads an image formed on the recording material by the image forming unit, and the setting unit sets the second pressure based on a reading result of the image by the reading unit. The image forming apparatus according to claim 1, wherein the adjustment is performed.
According to a third aspect of the present invention, the setting means decreases both the first pressure and the second pressure as the number of recording materials passing through the skew feeding correction means increases. Item 3. The image forming apparatus according to Item 1 or 2.

  According to the fourth aspect of the present invention, there is provided a skew feeding correcting means for correcting the skew feeding of the recording material along with the feeding, and a recording material whose skew feeding is corrected by the skew feeding correcting means. When an image forming unit that forms an image and a recording material on which no image is formed are supplied to the skew feeding correcting unit, the pressure for sandwiching the recording material in the skew feeding correcting unit is set to a first pressure. An image forming apparatus including setting means for setting the pressure to a second pressure smaller than the first pressure when a recording material on which an image has already been formed is supplied to the skew feeding correction means. is there.

  According to a fifth aspect of the present invention, the skew feeding correcting means is disposed along the conveyance direction of the recording material, the opposing member facing one side edge of the recording material along the conveyance direction, and the first pressure. The image forming apparatus according to claim 4, further comprising a skew roll that sandwiches the recording material with the second pressure and transports the recording material in an oblique direction with respect to the transport direction toward the facing member. Device.

  According to the sixth aspect of the present invention, the recording material is transported with the recording material sandwiched therebetween, and the skew feeding correcting means for correcting the skew feeding of the recording material accompanying the transport, and the recording material on which no image is formed with respect to the skew feeding correcting device. Is set to the first pressure, and the recording material on which an image is already formed is supplied to the skew feeding correcting means. And a setting means for setting the pressure to a second pressure smaller than the first pressure.

According to the first aspect of the present invention, the buckling of the recording material in the skew correction of the recording material can be suppressed as compared with the case where this configuration is not provided.
According to the second aspect of the present invention, the buckling of the recording material in the skew correction is suppressed regardless of the state of the image already formed on the recording material, as compared with the case where the present configuration is not provided. can do.
According to the third aspect of the invention, the buckling of the recording material in the skew correction can be achieved even when the number of recording materials on which image formation is continuously performed is large as compared with the case where this configuration is not provided. Can be suppressed.
According to the fourth aspect of the present invention, the buckling of the recording material in the skew correction of the recording material can be suppressed as compared with the case where this configuration is not provided.
According to the fifth aspect of the present invention, the skew correction can be performed on the recording material with a simpler configuration than when the configuration is not provided.
According to the sixth aspect of the present invention, the buckling of the recording material in the skew correction of the recording material can be suppressed as compared with the case where this configuration is not provided.

1 is a diagram illustrating an example of an overall configuration of an image forming apparatus to which Embodiment 1 is applied. 3 is a diagram for describing an example of a configuration of an attitude correction device according to Embodiment 1. FIG. FIG. 3 is a diagram for explaining a control system of the posture correction apparatus in the first embodiment. FIG. 6 is a diagram for explaining a paper posture correction operation in the posture correction apparatus according to the first embodiment. It is a flowchart for demonstrating the setting procedure of the nip pressure in each skew roll provided in the attitude | position correction apparatus. FIG. 6 is a diagram illustrating a relationship between an image forming mode (single-sided mode and double-sided mode), a surface of a sheet to be image-formed, and a set nip pressure set for each skew roll provided in the posture correction device. . It is a figure for demonstrating the relationship between the 1st skew nip pressure and the 2nd skew nip pressure in double-sided mode. It is a figure for demonstrating an example of the determination method of a 2nd skew nip pressure. It is a figure for demonstrating an example of the determination method of a 1st skew nip pressure and a 2nd skew nip pressure. FIG. 3 is a diagram illustrating an example of an overall configuration of an image forming apparatus to which Embodiment 2 is applied. FIG. 10 is a diagram for explaining an example of a configuration of an attitude correction device in a second embodiment. FIG. 10 is a diagram for describing a skew correction operation in a second skew correction unit of the posture correction apparatus according to the second embodiment. FIG. 10 is a diagram for explaining a method for determining a second skew nip pressure in the second embodiment. FIG. 10 is a diagram for describing a configuration of a second skew feeding correction unit according to the third embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Embodiment 1>
FIG. 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus to which the first exemplary embodiment is applied. Here, FIG. 1 shows a cross-sectional configuration when the image forming apparatus 1 is viewed from the front side.

  The image forming apparatus 1 includes an image forming unit 10 that forms an image, an intermediate transfer belt 20 on which an image formed by the image forming unit 10 is primarily transferred, and an image that is primarily transferred to the intermediate transfer belt 20 on a sheet P. A secondary transfer device 30 for secondary transfer, a paper supply device 40 for supplying the paper P toward the secondary transfer device 30, and a fixing for fixing the image secondarily transferred to the paper P by the secondary transfer device 30 Device 50. The image forming apparatus 1 also includes an attitude correction device 100 that corrects the attitude of the paper P that is conveyed toward the secondary transfer device 30, and an imaging device 60 that captures an image on the paper P that has passed through the fixing device 50. And a reversing conveyance device 70 for reversing the front and back of the paper P that has passed through the part facing the imaging device 60 and for conveying the paper P with the front and back reversed toward the attitude correction device 100. The image forming apparatus 1 includes a control unit 80 that controls the operation of each of the above-described devices, a touch panel, and the like. The image forming apparatus 1 outputs an instruction received from the user to the control unit 80 and sends information from the control unit 80 to the user. A user interface unit (UI) 90 to be presented is further provided. The image forming apparatus 1 according to the present embodiment includes a housing 2 that accommodates each of the above-described apparatuses.

  In this image forming apparatus 1, the first transport path R <b> 1 through which the paper P transported from the paper supply device 40 toward the secondary transfer device 30 passes, and the paper P after passing through the secondary transfer device 30 pass through. Branches from the second transport path R2 on the downstream side of the portion facing the second transport path R2, the fixing device 50, and the imaging device 60, and extends below the second transport path R2 to transfer the paper P to the reverse transport apparatus 70. A third transport path R3 for guiding and a fourth transport path R4 for guiding the paper P that has passed through the reverse transport device 70 to the first transport path R1 are provided. Therefore, the posture correction apparatus 100 is in the first conveyance path R1, the secondary transfer apparatus 30 is at the boundary between the first conveyance path R1 and the second conveyance path R2, and the fixing device 50 and the imaging device 60 are in the second conveyance path. In R2, the reverse conveying device 70 is provided between the third conveying path R3 and the fourth conveying path R4. Further, the downstream end of the second transport path R <b> 2 in the transport direction of the paper P is connected to an opening 3 provided in the housing 2.

  Note that the image forming apparatus 1 according to the present embodiment operates on a so-called “one-sided reference” in which each size of the paper P is transported with reference to one side end in the width direction orthogonal to the transport direction of the paper P. It has become.

  Among these, the image forming unit 10 includes a plurality of image forming units 10Y, 10M, 10C, and 10K that form toner images of respective color components by an electrophotographic method, and these image forming units 10Y, 10M, 10C, and 10K. Are arranged side by side so as to face the intermediate transfer belt 20. Here, the plurality of image forming units 10Y, 10M, 10C, and 10K form yellow, magenta, cyan, and black images, respectively.

  Each of the plurality of image forming units 10Y, 10M, 10C, and 10K includes a photosensitive drum 11 that is rotatably mounted. In each of the image forming units 10Y, 10M, 10C, and 10K, around the photosensitive drum 11, a charging device 12 that charges the photosensitive drum 11 and the photosensitive drum 11 are exposed to write an electrostatic latent image. An exposure device 13 and a developing device 14 that visualizes the electrostatic latent image on the photosensitive drum 11 with a corresponding color toner are provided. Further, in each of the image forming units 10Y, 10M, 10C, and 10K, 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 residual on the photosensitive drum 11 A drum cleaning device 16 for removing toner is provided.

  Next, the intermediate transfer belt 20 is stretched around three roll members 21 to 23 that are rotatably provided. Here, the roll member 22 is used to drive 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.

  Here, in the present embodiment, the image forming unit 10, the intermediate transfer belt 20, and the secondary transfer device 30 have a function as an image forming unit.

  The paper supply device 40 is provided on the first paper supply device 40A for supplying the paper P to the first conveyance path R1, and on the downstream side in the conveyance direction of the paper P relative to the first paper supply device 40A. A second paper supply device 40B for supplying the paper P to the path R1. Here, the first paper supply device 40A and the second paper supply device 40B have a common configuration, and each of the first paper supply device 40A and the second paper supply device 40B is a paper as an example of a recording material. A paper storage unit 41 that stores P and a supply roll 42 that takes out and transports the paper P stored in the paper storage unit 41 are provided.

  The image forming apparatus 1 according to the present embodiment is provided in each of the first transport path R1 to the fourth transport path R4, and includes a plurality of transport rolls 45 that transport the paper P existing in each transport path. The belt transport unit 46 is disposed between the secondary transfer device 30 and the fixing device 50 in the second transport path R2 and stacks and transports the sheets P existing in this region.

  Further, the fixing device 50 includes a heating roll 50A that is heated by a built-in heater (not shown), a pressing roll 50B that is disposed to face the heating roll 50A across the second transport path R2, and presses the heating roll 50A. have.

  The imaging device 60 as an example of a reading unit is provided along the width direction (corresponding to the main scanning direction) of the paper P intersecting the transport direction (corresponding to the sub-scanning direction) of the paper P in the second transport path R2. A line sensor (not shown) is provided, and the image on the paper P passing through the portion facing the imaging device 60 is captured line by line, so that full-color (eg, RGB) imaging data is output. It has become.

  The reversal conveyance device 70 as an example of the reversal conveyance unit includes a reversal conveyance path Rr having one end connected to both the third conveyance path R3 and the fourth conveyance path R4 provided in the image forming apparatus 1, and the reverse conveyance path Rr. There are provided a plurality of reverse conveying rolls 70a for conveying the paper P existing inside. Here, each reverse conveyance roll 70a is provided to be rotatable in the forward and reverse directions, and reverses the traveling direction of the paper P in the reverse conveyance path Rr.

  FIG. 2 is a diagram for explaining an example of the configuration of the posture correction apparatus 100 in the present embodiment. Here, FIG. 2A shows a top view when the posture correction apparatus 100 is viewed from above, and FIG. 2B shows the conveyance direction of the paper P in FIG. 2A. The side view when it sees from the upstream (IIb direction shown to Fig.2 (a)) is shown. Accordingly, in FIG. 2B, the paper P (not shown) is conveyed from the front side in the drawing toward the back side in the drawing.

  The posture correction apparatus 100 as an example of the skew correction unit includes a side guide 101 disposed along the conveyance direction (indicated by an arrow in the drawing) of the paper P on one side of the first conveyance path R1. Are adjacent to the side guide 101 and arranged side by side along the first transport path R1 (three in this example) skew rolls 102, and the sheet P is more than the side guides 101 and the three skew rolls 102. And a resist roll 105 disposed on the downstream side in the transport direction. In addition, each skew roll 102 is disposed below the first transport path R1, and is driven to rotate by receiving a driving force from the outside, and the skew drive roll above the first transport path R1. 103, and a skew driven roll 104 that rotates by receiving a driving force from the skew driving roll 103. The resist roll 105 is composed of a pair of rolls that come into contact with each other.

Here, the side guide 101 as an example of the opposing member has a concave cross section that opens on the first conveyance path R1 side, and a reference parallel to the conveyance direction of the paper P is provided at the bottom inside the depression. A surface 101a is formed.
Further, each skew roll 102 (the skew driving roll 103 and the skew driven roll 104) is disposed to be inclined at a common angle with respect to the transport direction of the paper P so as to guide the paper P to the side guide 101 side. ing. In this embodiment, the skew driving roll 103 and the skew driven roll 104 constituting each skew roll 102 have a structure capable of adjusting the strength of the nip pressure when contacting each other. Yes.

  FIG. 3 is a diagram for explaining a control system of posture correction apparatus 100 shown in FIG. Here, FIG. 3 shows components related to the posture correction apparatus 100 in the control unit 80, and the description of other components (image forming unit 10 and the like) is omitted.

  The control unit 80 displays an image forming mode of a job to be executed next (for example, a single-side mode in which an image is formed only on one side of the paper P and a double-side mode in which an image is formed on both sides of the paper P) from the UI 90. A signal is input, and imaging data obtained by capturing an image fixed on the paper P is input from the imaging device 60.

  On the other hand, the control unit 80 is configured to rotate the skew drive roll 103 in each skew roll 102, and the nip between the skew drive roll 103 and the skew driven roll 104 in each skew roll 102. Control signals are output to the skew roll pressure setting unit 107 for setting the pressure and the registration roll rotation driving unit 108 for rotating the registration roll 105, respectively. In the present embodiment, the control unit 80 and the skew roll pressure setting unit 107 function as a setting unit.

Now, an image forming operation using the image forming apparatus 1 shown in FIG. 1 will be described.
Along with receiving image information from an external device (not shown), the control unit 80 creates exposure data based on the image information and outputs it to each exposure device 13 in the image forming unit 10, and configures the image forming device 1. An operation start control signal is output to each unit.

  For example, in the yellow (Y) image forming unit 10 </ b> Y, the photosensitive drum 11 that is rotationally driven is charged by the charging device 12 and exposed by the exposure device 13 that emits light based on the exposure data supplied from the control unit 80. Is done. As a result, an electrostatic latent image related to the yellow image is formed on the photosensitive drum 11. The electrostatic latent image formed on the photosensitive drum 11 is developed by the developing device 14, and a yellow toner image is formed on the photosensitive drum 11. Similarly, in the other image forming units 10M, 10C, and 10K, magenta (M), cyan (C), and black (K) toner images are formed according to the above-described procedure.

  The toner images formed on the photoconductive drums 11 of the image forming units 10Y, 10M, 10C, and 10K are primarily transferred (transferred) to the intermediate transfer belt 20 that is rotationally driven by the primary transfer devices 15 provided corresponding to the toner images. Electrostatic transfer) and are superimposed on the intermediate transfer belt 20. Then, the superimposed toner image superimposed on the intermediate transfer belt 20 moves toward the secondary transfer position where the secondary transfer device 30 is provided as the intermediate transfer belt 20 rotates. The residual toner remaining on each photosensitive drum 11 after the primary transfer is removed by a drum cleaning device 16 provided in each image forming unit 10Y, 10M, 10C, 10K.

  On the other hand, in the paper supply device 40, the paper P stored in the paper storage portion 41 of the first paper supply device 40 </ b> A (or the second paper supply device 40 </ b> B) is taken out one by one using the supply roll 42. It sends out to 1 conveyance path | route R1. Then, the posture correction device 100 provided in the first transport path R1 corrects the posture (tilt, position, etc.) of the paper P sent from the paper supply device 40, and also superimposes the toner image on the intermediate transfer belt 20. The paper P is sent out toward the secondary transfer position in synchronization with the timing at which the ink reaches the secondary transfer position.

  The superimposed toner image on the intermediate transfer belt 20 is secondarily transferred (electrostatic transfer) to the paper P passing through the secondary transfer position by the secondary transfer device 30. At this time, secondary transfer of the superimposed toner image is performed on the surface (first surface) of the paper P facing the intermediate transfer belt 20.

  Then, the sheet P on which the superimposed toner image is transferred by passing through the secondary transfer position is transported in the second transport path R2 and passes through the fixing device 50. At this time, the first surface, which is the transfer surface of the superimposed toner image on the paper P, is heated by the heating roll 50A, and the paper P is pressed by the heating roll 50A and the pressing roll 50B, thereby overlapping the paper P. The toner image is fixed. Here, in the single-side mode in which an image is formed only on one side of the paper P, the paper P on which the superimposed toner image is fixed is discharged to the outside through the opening 3 from the second transport path R2. Further, residual toner remaining on the intermediate transfer belt 20 after passing through the secondary transfer position is removed by the belt cleaning device 24.

  On the other hand, in the double-side mode in which images are formed on both sides of the paper P, the paper P that has passed through the fixing device 50 enters the third transport path R3 from the second transport path R2, and further the third transport path. From R3, the reversal conveyance device 70 is entered. In the reverse conveyance device 70, the traveling direction of the paper P that has entered the reverse conveyance path Rr from the third conveyance path R3 is reversed, and the paper P is caused to enter the fourth conveyance path R4 from the reverse conveyance path Rr. . As a result, the sheet P discharged from the reverse conveyance device 70 to the fourth conveyance path R4 is in a state in which the front and back are reversed compared to the state before entering the reverse conveyance device 70 from the third conveyance path R3.

  The image forming unit 10 forms toner images of the respective colors according to the above-described procedure. The toner images of the respective colors are transferred to the intermediate transfer belt 20 to form a superimposed toner image, which is a secondary transfer position. Head to.

  On the other hand, the sheet P whose front and back are reversed by the reversing conveyance device 70 enters the first conveyance route R1 again from the fourth conveyance route R4 and reaches the attitude correction device 100 again. Then, the attitude correction device 100 corrects the attitude of the paper P sent from the reverse conveyance device 70, and at the same time the secondary toner position on the intermediate transfer belt 20 reaches the secondary transfer position. The paper P is sent out toward the transfer position.

  The superimposed toner image on the intermediate transfer belt 20 is secondarily transferred (electrostatic transfer) to the paper P passing through the secondary transfer position by the secondary transfer device 30. At this time, secondary transfer of the superimposed toner image is performed on the surface (second surface) of the paper P facing the intermediate transfer belt 20.

  Then, the sheet P on which the superimposed toner image is transferred by passing through the secondary transfer position is transported in the second transport path R2 and passes through the fixing device 50. At this time, the second surface, which is the transfer surface of the superimposed toner image on the paper P, is heated by the heating roll 50A, and the paper P is pressed by the heating roll 50A and the pressing roll 50B, thereby overlapping the paper P. The toner image is fixed. Thereafter, the paper P on which the overlapping toner images are fixed on both sides by passing through the fixing device 50 is discharged to the outside through the opening 3 from the second transport path R2. Further, residual toner remaining on the intermediate transfer belt 20 after passing through the secondary transfer position is removed by a belt cleaning device (not shown). Thereby, in the duplex mode, an image is formed not only on the first side of the paper P but also on the second side.

Next, the posture correction operation of the paper P using the posture correction apparatus 100 in the above-described image forming operation will be described.
FIG. 4 is a diagram for explaining the posture correction operation of the paper P in the posture correction apparatus 100. Here, Fig.4 (a) has shown the top view when the attitude | position correction apparatus 100 is seen from upper direction. 4B is a side view of the posture correction apparatus 100 when the paper P is in a state indicated by a broken line in FIG. 4A when viewed from the upstream side in the transport direction of the paper P in FIG. 4A. The figure is shown. Further, FIG. 4C is a side view of the posture correction apparatus 100 when the paper P is in a state indicated by a solid line in FIG. 4A when viewed from the upstream side in the transport direction of the paper P in FIG. The figure is shown.

  The paper P is in a skewed state in which the left side portion at the front end in the transport direction of the paper P precedes the right side portion by a transport roll 45 (see FIG. 1) provided on the upstream side of the posture correction apparatus 100 in the transport direction of the paper P. Is carried into the posture correction device 100 (see FIGS. 4A and 4B). Then, the paper P carried into the posture correction device 100 in such a skew state is changed in direction so that the skew state is canceled as it is sandwiched between the skew rolls 102 that are rotationally driven. On the other hand, the sheet P is conveyed by the skew roll 102 so that one side end (the side end on the left side in the conveyance direction) of the sheet P is directed to the side guide 101. Thereafter, one side end of the sheet P conveyed while being sandwiched between the skew rolls 102 hits the reference surface 101 a of the side guide 101. In addition, after one side edge of the sheet P hits the reference surface 101 a of the side guide 101, the skew roll 102 applies a conveying force while sliding against the sheet P, and the sheet P is used as the reference of the side guide 101. It moves along the surface 101a (see FIG. 4A and FIG. 4C). Thereby, the skew state of the paper P is corrected.

  Then, the leading end of the sheet P in the conveyance direction hits the nip portion of the resist roll 105 that has stopped rotating, and then the resist roll 105 matches the timing at which the image on the intermediate transfer belt 20 reaches the secondary transfer position. Is started. Accordingly, the sheet P is conveyed toward the secondary transfer position in a state where the skew feeding correction and the arrival timing correction to the secondary transfer position are performed.

Here, in the present embodiment, the posture correction device is used for forming an image on the first surface of the paper P and for forming an image on the second surface of the paper P on which the image is formed on the first surface. The setting of the nip pressure in each skew roll 102 provided in 100 is made different.
FIG. 5 is a flowchart for explaining the procedure for setting the nip pressure in each skew roll 102 provided in the posture correction apparatus 100.

  When the paper P is supplied to the posture correction apparatus 100 (step 101), the control unit 80 determines whether or not the paper P is supplied from the reverse conveyance device 70 (step 102).

  When a negative determination (NO) is made in step 102, that is, when the paper P is supplied from the paper supply unit 40 instead of the reverse conveyance device 70, the control unit 80 sets the skew roll pressure setting. The nip pressure of each skew roll 102 (the skew drive roll 103 and the skew driven roll 104) is set to the first skew nip pressure F1 (an example of the first pressure) via the section 107 (step 103). The process proceeds to step 107 described later.

  On the other hand, when an affirmative determination (YES) is made in step 102, that is, when the paper P is supplied from the reverse conveying device 70, the control unit 80 receives the paper P from the imaging device 60. Image data of the first surface obtained by capturing an image formed on the first surface is acquired (step 104). Next, the control unit 80 calculates a second skew nip pressure F2 (an example of a second pressure) based on the imaging data of the first surface acquired in step 104 (step 105), and the skew roll pressure setting unit. Via 107, the nip pressure of each skew roll 102 (the skew drive roll 103 and the skew driven roll 104) is set to the second skew nip pressure F2 (step 106), and the routine proceeds to step 107.

  Here, in the present embodiment, the control unit 80 calculates the density of the image formed on the first surface from the first imaging data acquired from the imaging device 60, and the higher the obtained image density, the second The second skew nip pressure F2 is calculated so that the skew nip pressure F2 becomes small. Note that the second skew nip pressure F2 set for a certain paper P is smaller than the first skew nip pressure F1 set for the same paper P.

  Then, as the sheet P passes through each skew roll 102 set to the first skew nip pressure F1 or the second skew nip pressure F2, skew correction for the sheet P is performed (step 107). Thereafter, the control unit 80 determines whether or not the next sheet P exists (step 108). If an affirmative determination (YES) is made in step 108, the process returns to step 101 to continue the above-described processing. If a negative determination (NO) is made in step 108, a series of processing is completed.

FIG. 6 shows the image forming mode (single-sided mode, double-sided mode), the surface of the sheet P to be image-formed, and the set nip pressure set for each skew roll 102 provided in the posture correction device 100. It is the figure which showed the relationship.
First, in the single-sided mode, only the first surface of the paper P is an object for image formation, and the set nip pressure for the paper P before forming an image on the first surface is the first skew nip pressure F1.
On the other hand, in the duplex mode, the first surface and the second surface of the paper P are targets for image formation, and the set nip pressure for the paper P before forming an image on the first surface is the first skew nip pressure. The set nip pressure for the sheet P after the image is formed on the first surface and before the image is formed on the second surface is the second skew nip pressure F2 (F2 <F1).

  FIG. 7 is a diagram for explaining the relationship between the first skew nip pressure F1 and the second skew nip pressure F2 in the duplex mode. Here, FIG. 7A illustrates a case where an image having a low density is formed on the first surface of the paper P and then an image is formed on the second surface of the paper P. FIG. An example of forming an image on the second surface of the paper P after forming a high density image on the first surface of the paper P is illustrated. In the following description, the first surface of the paper P is called a paper front surface Pf, and the second surface of the paper P is called a paper back surface Pb.

  In the example shown in FIG. 7A, when the paper P supplied from the paper supply unit 40, that is, the paper P on which no image is formed on both the paper front surface Pf and the paper back surface Pb, first passes through the attitude correction device 100. Each skew roll 102 is set to the first skew nip pressure F1. Then, a low density image is formed (transferred and fixed) on the sheet surface Pf of the sheet P that has been subjected to the skew correction by the skew roll 102 set to the first skew nip pressure F1. Then, when the paper P on which the low density image is formed on the paper front surface Pf and the image is not formed on the paper back surface Pb is reversely transported by the reverse transport device 70 and then passes through the posture correction device 100, Each skew roll 102 is set to a second skew nip pressure F2 that is smaller than the first skew nip pressure F1. Then, an image is formed (transferred and fixed) on the paper back surface Pb of the paper P that has been subjected to the skew correction by the skew roll 102 set to the second skew nip pressure F2.

  In the example shown in FIG. 7B, the paper P supplied from the paper supply unit 40, that is, the paper P on which no image is formed on both the paper front surface Pf and the paper back surface Pb, first passes through the attitude correction device 100. In doing so, each skew roll 102 is set to the first skew nip pressure F1. In addition, the magnitude | size of the 1st skew nip pressure F1 at this time is the same as the example shown to Fig.7 (a). A high-density image is formed (transferred and fixed) on the paper surface Pf of the paper P that has been subjected to the skew correction by the skew roll 102 set to the first skew nip pressure F1. Then, when the paper P on which the high density image is formed on the paper front surface Pf and the image is not formed on the paper back surface Pb is reversely transported by the reverse transport device 70 and then passes through the attitude correction device 100, Each skew roll 102 is set to a second skew nip pressure F2 that is smaller than the first skew nip pressure F1. Then, an image is formed (transferred and fixed) on the paper back surface Pb of the paper P that has been subjected to the skew correction by the skew roll 102 set to the second skew nip pressure F2. In addition, the magnitude | size of the 2nd skew nip pressure F2 at this time becomes smaller than the example shown to Fig.7 (a). This is because the density of the image formed on the paper surface Pf of the paper P is higher in the example shown in FIG. 7B than in the example shown in FIG.

  Here, before the image is formed on the paper surface Pf of the paper P, the nip pressure when passing through the attitude correction device 100 is set to the first skew nip pressure F1, and the paper P on which the image is formed on the paper surface Pf. The second skew nip pressure F2 that is smaller than the first skew nip pressure F1 is set as the nip pressure when passing through the posture correction device 100 before the image is formed on the back surface Pb of the paper. Because of the reason.

  In the posture correction apparatus 100 according to the present embodiment, as described above, each skew roll 102 abuts one side end of the sheet P against the reference surface 101a of the side guide 101 and then each skew roll with respect to the sheet P. By skewing 102, the skew correction is applied to the paper P. In addition, after adopting a configuration in which each skew roll 102 is difficult to slide with respect to the paper P after the one side edge of the paper P is abutted against the reference surface 101 a of the side guide 101 by each skew roll 102, At one side end, a force that strikes the side guide 101 is applied more, and as a result, one side end side of the paper P may be buckled.

  Here, the paper P (the paper P supplied from the paper supply unit 40) on which no image is formed on both the paper front surface Pf and the paper back surface Pb, the image is formed on the paper front surface Pf, and the image is formed on the paper back surface Pb. Is compared with the paper P on which the toner image is not formed (the paper P supplied from the reverse conveying device 70), the latter paper P has the former (image of the toner image) formed on the paper surface Pf. The coefficient of friction is higher than that of the paper P. For this reason, for example, when the first skew nip pressure F1 and the second skew nip pressure F2 are set to the same magnitude, the former paper P can be skew-corrected with slipping, while the latter paper P. The buckling is likely to occur as much as slippage is less likely to occur.

  Therefore, in the present embodiment, the first skew correction for the paper P and the second skew for the paper P are performed by reducing the second skew nip pressure F2 compared to the first skew nip pressure F1. In addition to enabling correction, buckling of the paper P in the second skew correction is suppressed. In the present embodiment, the second skew nip pressure F2 when a low-density image is formed based on imaging data obtained by imaging an image formed on the first surface of the paper P. Also, the second skew nip pressure F2 when a high-density image is formed is set to be smaller. Accordingly, it is possible to suppress the buckling of the paper P in the second skew correction regardless of the content of the image formed on the first surface.

FIG. 8 is a diagram for explaining an example of a method for determining the second skew nip pressure F2 in the present embodiment.
As described above, in the duplex mode of the present embodiment, the second skew nip pressure F2 is set based on the image data of the image formed on the sheet surface Pf of the sheet P. At this time, the second skew nip pressure F2 may be calculated based on imaging data obtained from the entire surface Pf of the paper P. However, since the image formed on the paper surface Pf is not always uniform, in the present embodiment, each skew roll 102 passes through the imaging data obtained from the entire paper surface Pf of the paper P. Image data corresponding to a possible skew roll passage area Ar (in fact, it is present on the back side of the paper back surface Pb shown in FIG. 8 (the paper surface Pf (not shown) and is shown in parentheses in FIG. 8)). Based on the calculation. Thereby, it is possible to further suppress the occurrence of buckling of the paper P in the second skew correction.

  FIG. 9 is a diagram for explaining an example of a method for determining the first skew nip pressure F1 and the second skew nip pressure F2 in the present embodiment. In FIG. 9, the horizontal axis indicates time (elapsed time), and the vertical axis indicates the nip pressure set for each skew roll 102. FIG. 9 illustrates a case where image formation is performed on 15 sheets P (each sheet P is described as (1), (2),..., (15)) in the duplex mode. .

  As described above, in the present embodiment, the nip pressure when passing through the attitude correction device 100 before forming an image on the paper surface Pf of the paper P is set to the first skew nip pressure F1, and the paper surface Pf. The nip pressure when passing through the posture correction device 100 before the image is formed on the paper back surface Pb of the paper P on which the image is formed is set to the second skew nip pressure F2 smaller than the first skew nip pressure F1. It is set. Further, in this example, every time a total of ten image formations on five sheets P is completed, the first skew nip pressure F1 and the second skew nip pressure F2 are sequentially reduced.

When image formation is continuously performed on a plurality of sheets P in the double-sided mode, the sheet P that has passed through the fixing device 50 passes through the attitude correction device 100, so that the heated sheet P is fed to each skew roll 102. Will be in contact with. For this reason, each skew roll 102 is heated by the heat received from the paper P in the duplex mode. As each skew roll 102 is heated, the coefficient of friction of each skew roll 102 becomes higher than that before heating, and the conveying force of the paper P also becomes higher than before heating. As a result, when the first skew nip pressure F1 and the second skew nip pressure F2 are maintained constant regardless of the number of sheets P, each skew roll 102 is formed during image formation on a plurality of sheets P. Therefore, the paper P is strongly abutted against the side guide 101, and there is a concern that the above-described buckling may occur.
On the other hand, by setting as shown in FIG. 9, even if the number of sheets P increases, buckling due to abutment against the side guide 101 does not easily occur on the sheet P.

<Embodiment 2>
FIG. 10 is a diagram illustrating an example of the overall configuration of the image forming apparatus 1 to which the second exemplary embodiment is applied. Here, the basic configuration of the image forming apparatus 1 according to the present embodiment is the same as that described in the first embodiment, but the configurations of the reverse conveyance device 70 and the posture correction device 100 are described in the first embodiment. It is different from what I did. Further, the image forming apparatus 1 according to the present embodiment operates in a so-called “center reference” in which the paper P of each size is transported on the basis of the center position in the width direction orthogonal to the transport direction of the paper P. This is different from the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

First, the configuration of the reverse conveyance device 70 of the present embodiment will be described with reference to FIG.
The reverse conveyance device 70 of the present embodiment is connected to a third conveyance path R3 provided in the image forming apparatus 1, and is connected to a carry-in path Ra through which the paper P is carried from the third conveyance path R3, and to the carry-in path Ra. The paper P that is connected to the reversing path Rb that reverses the front and back of the paper P while transporting the paper P, and the reverse transport path Rb and the fourth transport path R4 provided in the image forming apparatus 1, And a carry-out route Rc for carrying out to the carry route R4. In the reverse conveyance device 70, the carry-out route Rc is arranged so as to overlap the carry-in route Ra when viewed from above, and the reverse route Rb is curved in a U shape on the front side of the carry-in route Ra and the carry-out route Rc. By doing so, it arrange | positions so that the near side of carrying-in path | route Ra and the near side of carrying-out path | route Rc may be connected. The reversing conveyance device 70 includes a carry-in roll 71 that conveys the paper P that has been carried in from the third conveyance path R3 in the carry-in path Ra, and a paper P that has been carried into the carry-in path Ra in the carry-in path Ra. A first reversing roll 72 that conveys toward the reversing path Rb, a second reversing roll 73 that conveys the paper P carried into the reversing path Rb toward the carry-out path Rc, and the reversing path Rb. The third reversing roll 74 that conveys the paper P that has been carried in from within the carry-out path Rc, and the paper P that has been carried into the carry-out path Rc toward the fourth conveyance path R4. And an unloading roll 75. The reverse conveying device 70 according to the present embodiment has a configuration capable of reversing the front and back of the paper P without replacing the front end and the rear end in the transport direction.

  FIG. 11 is a diagram for explaining an example of the configuration of posture correction apparatus 100 in the present embodiment. Here, FIG. 11A shows a top view when the posture correcting device 100 is viewed from above in FIG. 1, and FIG. 3B is a view when the posture correcting device 100 is viewed from the front side in FIG. The side view of is shown. Therefore, in each of FIGS. 11A and 11B, the paper P is conveyed from the left side in the drawing toward the right side in the drawing. In FIG. 11A, the center position in the width direction of the sheet P targeted in the center reference is shown as a reference line C.

  The posture correction apparatus 100 according to the present embodiment is provided on the most upstream side in the transport direction of the paper P, and performs skew feeding of the paper P sent from the paper supply device 40 or the reverse transport device 70 (both see FIG. 10). A first skew correction unit 110 that performs correction, and a skew of the sheet P that is provided adjacent to the first skew correction unit 110 on the downstream side in the transport direction and has been subjected to skew correction by the first skew correction unit 110. A second skew correction unit 120 that further corrects the line; and a second skew correction unit 120 that is adjacent to the downstream side in the transport direction with respect to the second skew correction unit 120 and provided on the most downstream side in the transport direction. A width direction position correction unit 160 that corrects the center position in the width direction of the paper P that has been subjected to the skew correction by the second skew correction unit 120 to match the reference line C is provided. In this posture correction apparatus 100, the first skew correction unit 110 has a function of roughly adjusting the skew amount of the paper P, and the second skew correction unit 120 finely adjusts the skew amount of the paper P. It has a function to adjust.

  Now, each of the first skew correction unit 110, the second skew correction unit 120, and the width direction position correction unit 160 included in the posture correction apparatus 100 will be described in order.

  First, the first skew correction unit 110 includes a left skew correction roll 110L and a right skew correction roll 110R that are arranged side by side in the width direction D2 and each convey the paper P therebetween. Here, the left skew correction roll 110L is disposed on the left side of the reference line C as viewed from the upstream side in the transport direction D1, and the right skew correction roll 110R is located on the reference line C as viewed from the upstream side in the transport direction D1. Located on the right side. The left skew correction roll 110L and the right skew correction roll 110R are each driven to rotate independently.

  Next, the second skew correction unit 120 is disposed on the downstream side in the transport direction as viewed from the first skew correction unit 110, transports the paper P with the paper P interposed therebetween, and feeds the transport roller 130 toward the downstream side. It is arranged on the downstream side in the transport direction as viewed from the roll 130, and moves along the transport direction while holding the front end of the paper P sent from the output roll 130, so that the front end of the paper P is moved downstream. And a guide unit 140 that guides toward the center of the paper, and a downstream side in the transport direction as viewed from the delivery roll 130 and an upstream side in the transport direction relative to the width direction position correction unit 160, and is sent by the feed roll 130 and the guide unit 140. And a receiving roll 150 that receives and transports the sheet P toward the width direction position correction unit 160 by conveying the sheet P.

  Here, the guide unit 140 includes a lower gate that is disposed below the first transport path R1 and that is partly movably disposed at a position that blocks the first transport path R1 and a position that does not block the first transport path R1. . Moreover, the guide part 140 of this Embodiment is arrange | positioned between the sending roll 130 and the receiving roll 150 so that a movement in a reverse direction with respect to a conveyance direction or a conveyance direction is possible. In addition, the delivery roll 130 of this Embodiment is set to a contact state or a non-contact state because the other advances and retreats with respect to one fixed.

  Further, the width direction position correction unit 160 is disposed on the downstream side in the transport direction as viewed from the second skew correction unit 120, transports the paper P with the paper P interposed therebetween, and sends it out to the secondary transfer device 30 (see FIG. 10). A position correction roll 170 is provided. Here, the position correction roll 170 of the present embodiment can be moved in the width direction or in the direction opposite to the width direction as a unit. Note that the receiving roll provided in the guide unit 140 can also move in the width direction or in the direction opposite to the width direction in conjunction with the position correction roll 170.

  In this posture correction apparatus 100, the first skew correction unit 110 (the left skew correction roll 110L and the right skew correction roll 110R) roughly corrects the skew state of the paper P, and then the second skew correction unit 120 ( The skew state of the sheet P is finely adjusted by the sending roll 130, the guide unit 140, and the receiving roll 150), and then the width direction position of the sheet P is adjusted by the width direction position correcting unit 160 (position correcting roll 170) and the receiving roll 150. At the same time, the posture of the paper P is corrected by adjusting the feed timing to the secondary transfer position.

  FIG. 12 is a diagram for explaining a skew correction operation in the second skew correction unit 120 of the posture correction apparatus 100 according to the present embodiment. Here, FIG. 12A is a diagram illustrating a state where the guide unit 140 is disposed at the start position, and FIG. 12B is a diagram illustrating a state where the guide unit 140 is moved from the start position to the goal position.

  The paper P sent from the first skew correction unit 110 (not shown) is conveyed while being sandwiched between the delivery rolls 130, and the front end of the paper hits the lower gate of the guide unit 140 that stops at the start position. The guide unit 140 starts to move along the transport direction after the leading edge of the sheet P hits the lower gate. At this time, the moving speed of the guide unit 140 is set to be slightly lower than the rotational speed of the feeding roll 130 (moving speed of the paper P), and the paper P is looped by the leading edge of the paper hitting the lower gate. Occurs. At this time, the delivery roll 130 applies a conveying force while sliding on the paper P. Then, the leading end of the sheet P is abutted along the lower gate, so that the skew state is corrected at the leading end of the sheet.

  Then, the leading end of the sheet that moves in the transport direction while being regulated by the lower gate reaches the receiving roll 150 that rotates at the same speed as the feed roll 130, and is blocked from the position where the lower gate blocks the first transport path R1. Move to a position that does not (rotate). At this time, the leading edge of the paper P is sandwiched and conveyed by the feed roll 130 while maintaining the state in which the skew is corrected, and the skew state of the paper P is corrected.

  Here, in the second skew feeding correction unit 120 of the present embodiment, the sheet P is abutted against the lower gate of the guide unit 140 in a state where the sheet P is sandwiched by the delivery roll 130, so that the sheet P The skew state is corrected. At that time, the delivery roll 130 slides against the paper P to suppress buckling due to the paper P being strongly abutted against the lower gate. Therefore, when the delivery roll 130 becomes difficult to slide against the paper P, there is a concern that buckling may occur at the front end of the paper P that is abutted against the lower gate.

  Therefore, also in the present embodiment, the nip pressure in the delivery roll 130 is configured to be adjustable, and before the image is formed on the first surface of the paper P and the second of the paper P on which the image is formed on the first surface. The occurrence of such buckling can be suppressed by making the setting of the nip pressure in the delivery roll 130 provided in the posture correction device 100 different before and after the image is formed on the surface. More specifically, before forming an image on the paper surface Pf of the paper P, the nip pressure when passing through the attitude correction device 100 is set to the first skew nip pressure F1, and the image is formed on the paper surface Pf. By setting the nip pressure when passing through the posture correction device 100 before forming an image on the back side Pb of the sheet P, to the second skew nip pressure F2 smaller than the first skew nip pressure F1, It is possible to perform the first skew correction for the paper P and the second skew correction for the paper P, and to suppress the buckling of the paper P in the second skew correction. .

FIG. 13 is a diagram for explaining a method of determining the second skew nip pressure F2 in the present embodiment.
As described in the first embodiment, in the double-sided mode, the second skew nip pressure F2 for the paper P is set based on the image data of the image formed on the paper surface Pf of the paper P. Here, the delivery roll 130 of this embodiment is attached along the width direction of the paper P. Therefore, as shown in FIG. 13, for example, when a sheet P having a high density region, a low density region, and a high density region is sent along the transport direction, an image along the transport direction is displayed. In accordance with the density distribution, the second skew nip pressure is sequentially set to a high pressure, a low pressure, and a high pressure, so that the slipperiness of the paper P by the delivery roll 130 is less likely to change.

<Embodiment 3>
Although the present embodiment is basically the same as the second embodiment, the configuration of the second skew correction unit 120 provided in the posture correction apparatus 100 is different from the second embodiment. In the present embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 14 is a diagram for describing the configuration of the second skew correction unit 120 of the present embodiment.
The second skew correction unit 120 of the present embodiment includes a receiving roll 150 provided on the downstream side in the transport direction as viewed from the sending roll 130 and the receiving roll 150, and a regulating unit 180 provided adjacent to the receiving roll 150. ing.

  Here, the restricting portion 180 is fixed in a relative position with respect to the sending roll 130 and the receiving roll 150, and a part thereof is disposed so as to be movable to a position where the first transport path R1 is blocked and a position where there is no blocking. Has a lower gate.

  In the second skew correction unit 120 of the present embodiment, the leading end of the sheet P conveyed while being sandwiched between the delivery rolls 130 is brought into contact with the lower gate of the regulating unit 180, and the sheet P A loop occurs when the leading edge of the sheet hits the lower gate. At this time, the delivery roll 130 applies a conveying force while sliding on the paper P. Then, the leading end of the sheet P is abutted along the lower gate, so that the skew state is corrected at the leading end of the sheet.

  Then, the lower gate moves (rotates) from a position where the lower transfer path R1 is blocked to a position where the lower gate is not blocked. At this time, the leading edge of the paper P is sandwiched and conveyed by the feed roll 130 while maintaining the state in which the skew is corrected, and the skew state of the paper P is corrected.

  Here, in the second skew feeding correction portion 120 of the present embodiment, the paper P is abutted against the lower gate of the restriction portion 180 in a state where the paper P is sandwiched by the delivery roll 130, so that the paper P The skew state is corrected. At that time, the delivery roll 130 slides against the paper P to suppress buckling due to the paper P being strongly abutted against the lower gate. Therefore, when the delivery roll 130 becomes difficult to slide against the paper P, there is a concern that buckling may occur at the front end of the paper P that is abutted against the lower gate.

  Therefore, also in the present embodiment, the nip pressure in the delivery roll 130 is configured to be adjustable so that an image is formed on the first surface of the paper P and the second of the paper P on which the image is formed on the first surface. The occurrence of such buckling can be suppressed by changing the setting of the nip pressure in the delivery roll 130 provided in the posture correction apparatus 100 depending on whether the image is formed on the surface. More specifically, before forming an image on the paper surface Pf of the paper P, the nip pressure when passing through the attitude correction device 100 is set to the first skew nip pressure F1, and the image is formed on the paper surface Pf. By setting the nip pressure when passing through the posture correction device 100 before forming an image on the back side Pb of the sheet P, to the second skew nip pressure F2 smaller than the first skew nip pressure F1, It is possible to perform the first skew correction for the paper P and the second skew correction for the paper P, and to suppress the buckling of the paper P in the second skew correction. .

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Image forming part, 20 ... Intermediate transfer belt, 30 ... Secondary transfer apparatus, 40 ... Paper supply apparatus, 50 ... Fixing apparatus, 60 ... Imaging apparatus, 70 ... Reverse conveyance apparatus, 80 ... Control , 90 ... User interface unit (UI), 100 ... Attitude correction device, P ... Paper, Pf ... Paper front, Pb ... Paper back, R1 ... First transport path, R2 ... Second transport path, R3 ... Third transport Route, R4 ... Fourth transport route

Claims (6)

A skew correction means for correcting the skew of the recording material as it is conveyed while sandwiching the recording material,
Image forming means for forming an image on a recording material whose skew has been corrected by the skew correction means;
Reversing conveying means for reversing the front and back of the recording material on which an image is formed by the image forming means, and conveying the recording material with the front and back reversed to the skew feeding correcting means,
When the recording material is supplied to the skew correction means without going through the reversing conveyance means, the pressure for sandwiching the recording material in the skew correction means is set to the first pressure, and the skew correction means On the other hand, an image forming apparatus comprising: a setting unit that sets the pressure to a second pressure smaller than the first pressure when the recording material is supplied via the reverse conveying unit. A reading unit that reads an image formed on the recording material by the image forming unit;
The image forming apparatus according to claim 1, wherein the setting unit adjusts the second pressure based on an image reading result by the reading unit.   3. The image forming apparatus according to claim 1, wherein the setting unit decreases both the first pressure and the second pressure as the number of recording materials passing through the skew feeding correction unit increases. apparatus. A skew correction means for correcting the skew of the recording material as it is conveyed while sandwiching the recording material,
Image forming means for forming an image on a recording material whose skew has been corrected by the skew correction means;
When a recording material on which no image is formed is supplied to the skew feeding correction means, the pressure for sandwiching the recording material in the skew feeding correction means is set to the first pressure, and the skew feeding correction means is already set to the skew feeding correction means. An image forming apparatus comprising: a setting unit configured to set the pressure to a second pressure smaller than the first pressure when a recording material on which an image is formed is supplied. The skew correction means includes:
An opposing member that is disposed along the recording material conveyance direction and faces one side edge of the recording material along the conveyance direction;
5. A skew roll that sandwiches the recording material at the first pressure or the second pressure and conveys the recording material in an oblique direction with respect to the conveying direction toward the opposing member. The image forming apparatus described. A skew correction means for correcting the skew of the recording material as it is conveyed while sandwiching the recording material,
When a recording material on which no image is formed is supplied to the skew feeding correction means, the pressure for sandwiching the recording material in the skew feeding correction means is set to the first pressure, and the skew feeding correction means is already set to the skew feeding correction means. And a setting unit that sets the pressure to a second pressure smaller than the first pressure when a recording material on which an image is formed is supplied.

Images