JP2011048003A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet conveyance device and an image forming apparatus, suppressing temperature rise in a paper non-passing part during parallel conveyance of paper, and preventing a photoreceptor drum or the like from being damaged. <P>SOLUTION: A plurality of sheets P1 and P2 fed at a predetermined interval from a plurality of supporting parts arranged at a predetermined interval are inclined in the same direction to be conveyed to a fixing part 11 by a sheet inclining conveyance part including a skew mechanism part 40 and a conveyance part 51. A controller controls inclination of the sheets by the sheet inclining conveyance part so that passing areas of the plurality of sheets P1 and P2 in the fixing part 11 are partially superposed when the plurality of sheets P1 and P2 conveyed in parallel by an upstream side sheet conveyance part pass through the fixing part 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an apparatus that simultaneously conveys a plurality of sheets and forms images on the plurality of sheets simultaneously.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile, an image forming unit having a photosensitive drum (image carrier) on which a toner image is formed, and a toner image transferred onto a sheet A fixing portion for fixing the toner to the sheet. In addition, a sheet conveying device is provided, and the sheet conveying device conveys the sheet fed from the paper feeding cassette to the image forming unit at the time of image formation, and transfers the toner image formed on the photosensitive drum to the sheet. The sheet is conveyed to a fixing unit to fix the toner image on the sheet.

  Such a fixing unit is a heat roller type having a fixing roller heated by a built-in heat source such as a halogen heater and maintained at a predetermined temperature, and a pressure roller having elasticity that presses against the fixing roller. There is. In this heat roller type fixing unit, when the sheet on which the toner image is transferred passes through the pressure nip (fixing nip) between the fixing roller and the pressure roller, the sheet is pressed and heated to thereby form the sheet. The unfixed toner image on the surface is thermally fixed.

  In some conventional image forming apparatuses, two sheets are simultaneously fed to the image forming unit in order to improve the image forming processing capability (throughput) per unit time. This increases the processing capacity per unit time while keeping the image forming process speed constant.

  As such an image forming apparatus, for example, in addition to a feeding unit that feeds a large size sheet such as A3 size, a sheet feeding unit for small sheets such as A4 and B5 is arranged in parallel with respect to the sheet feeding direction. There is something to place in. When an image is formed on a small-sized sheet, two sheets fed from a plurality of paper feeding units are conveyed in parallel to the image forming unit by a sheet conveying device (Patent Document 1). reference).

JP-A-61-192642

  By the way, in the conventional sheet conveying apparatus, when two sheets are conveyed in parallel, it is almost impossible to convey the sheets so that the interval in the width direction perpendicular to the sheet feeding direction is zero and does not overlap. . For this reason, a gap in the width direction is generated between the two sheets. When the two sheets are conveyed in such a state where the gap in the width direction is generated in this way, the central portion in the width direction of the fixing nip is the sheet. Does not pass through and the heat of the fixing roller is not taken away.

  As a result, a non-sheet passing portion temperature rise region occurs at a portion corresponding to the sheet interval in the fixing nip of the fixing portion. Here, when a temperature rising region occurs in the fixing nip as described above, temperature unevenness occurs, and when a large size sheet such as a small size and an A3 size is alternately heated, an image defect occurs when the large size sheet is heated. May occur.

  In order to prevent the occurrence of such a non-sheet passing portion temperature rising area, for example, an individual halogen heater is arranged at the center in the width direction of the fixing nip portion or the light distribution of the halogen heater is adjusted to A configuration in which detection means is provided is conceivable. However, since the light distribution is generally set higher in the widthwise center of the fixing nip where the sheet passes most, adjusting the heater light distribution in the center of the fixing nip may cause temperature unevenness. Image defects may occur.

  Accordingly, the present invention has been made in view of such a current situation, and provides a sheet conveying apparatus and an image forming apparatus capable of suppressing a temperature increase in a non-sheet passing portion during parallel conveyance in a fixing unit. Objective.

  The present invention relates to an image forming apparatus that transfers a toner image onto a sheet at a transfer unit and fixes the transferred toner image onto a sheet at a fixing unit, and supports a plurality of sheets arranged in parallel in the width direction perpendicular to the sheet conveying direction. And a sheet inclined conveying unit that inclines and conveys the plurality of sheets conveyed in parallel from the plurality of sheet support units in the same direction, and the plurality of sheets conveyed in parallel are the fixing unit When the sheet passes through the sheet, the sheet inclined conveying section inclines the sheet so that a plurality of sheet passing regions partially overlap each other.

  As in the present invention, when the sheets conveyed in parallel pass, by controlling the inclination of the sheets so that the passage areas in the downstream sheet conveying portion of the plurality of sheets overlap, non-sheet passing during parallel conveyance It is possible to suppress the temperature rise.

1 is a diagram illustrating a schematic configuration of a copier that is an example of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of a feeding device provided in the copying machine. FIG. 4 is a diagram illustrating a configuration of a conveyance unit provided in a pre-fixing conveyance unit of the sheet conveyance device. FIG. 4 is a diagram for explaining a configuration of a skew feeding mechanism provided in the pre-fixing conveyance unit. FIG. 2 is a control block diagram of the copying machine. The figure explaining operation | movement of the said skew feeding mechanism part. The figure explaining the state of the sheet according to the rotation angle of the conveyance part by the said skew feeding mechanism part. FIG. 10 is a diagram illustrating a configuration of a sheet inclined conveying unit provided in a sheet conveying apparatus according to a second embodiment of the present invention. The figure explaining operation | movement of the said skew feeding mechanism part. The flowchart explaining the sheet | seat inclination control operation | movement of the said skew feeding mechanism part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a copying machine which is an example of an image forming apparatus provided with a sheet conveying apparatus according to a first embodiment of the present invention. In FIG. 1, 24 is a copying machine, and 25 is a copying machine main body (hereinafter referred to as an apparatus main body). The copier 24 includes an image reading unit 25 a provided on the upper portion of the apparatus main body 25, an image forming unit 26 disposed below the image reading unit 25 a, and a feeding device that feeds sheets to the image forming unit 26. 25b, a sheet conveying device 50, and a fixing unit 11.

  In the present embodiment, the sheet conveying device 50 conveys the sheet to the image forming unit 26 and forms an image on the second surface opposite to the sheet on which the image is formed on the first surface by the image forming unit 26. Thus, the sheet is conveyed again to the image forming unit 26. The sheet conveying apparatus 50 includes a reversing path 16 that is a sheet conveying path for conveying the sheet to the image forming unit 26 again.

  Here, the image reading unit 25 a includes an exposure device 202 that moves in the direction of the arrow while irradiating a document (not shown) set on the document glass 201, and a mirror unit 203 that moves integrally with the exposure device 202. Yes. The image reading unit 25a includes a CCD 204 or the like that receives light reflected by the mirror unit 203 after being irradiated by the exposure device 202 and reflected from the document, and is input via a lens (not shown).

  The image forming unit 26 includes a photosensitive drum 101 that is an image carrier, and a developing unit 102 that develops an electrostatic latent image formed on the photosensitive drum with toner to form a toner image on the photosensitive drum. Yes. The image forming unit 26 is in pressure contact with the photoconductive drum 101, a transfer roller 103 that forms a transfer unit 104 that transfers a toner image onto a sheet, and a laser scanner 100 for forming an electrostatic latent image on the photoconductive drum. It has. The fixing unit 11 includes a fixing roller 30 that is heated by a built-in heat source such as a halogen heater and maintained at a predetermined temperature, and a pressure roller 31 having elasticity that presses against the fixing roller 30. The feeding device 25b separates the sheet feeding cassette 1 that stores sheets, the sheet feeding roller 2 that feeds sheets stored in the sheet feeding cassette 1, and the sheets fed by the sheet feeding roller 2 one by one. And a pair of separating rollers 3 and 4.

  Next, an image forming operation in the copying machine 24 having such a configuration will be described.

  When forming an image on a sheet, first, an original is set on the original glass 201, and when the copy button is pressed, the exposure device 202 moves in the direction of the arrow while irradiating the original, and scans the entire surface of the original. Then, the light irradiated on the original from the exposure device 202 is folded back by the mirror unit 203 and then formed on the CCD 204 by the lens. Thereafter, the original read by the CCD 204 is converted into an electrical signal by the image processing unit, and the laser It is transmitted to the scanner 100. Next, laser light corresponding to image information is emitted from the laser scanner 100 to the photosensitive drum 101, and the photosensitive drum 101 is scanned by this laser light, and an electrostatic latent image is formed on the photosensitive drum 101. Thereafter, the electrostatic latent image is developed by the developing device 102 and visualized as a toner image.

  Further, in parallel with such a toner image forming operation, the paper feed roller 2 rotates, and the sheets stored in the paper feed cassette 1 are sent out. Thereafter, the sheet is separated one by one by the separation roller pair 3 and 4, and then the fed sheet is conveyed to the registration unit 21 by the sheet conveyance roller pair 5 and 6 provided in the sheet conveyance device 50. Then, the resist correction is performed.

  Next, the sheet on which the registration correction has been performed by the registration unit 21 is conveyed to a transfer unit 104 including the photosensitive drum 101 and the transfer roller 103. The toner image is transferred by applying a voltage having a polarity opposite to that of the toner image to the transfer roller 103 in the transfer unit 104. The sheet is detected by a sensor (not shown) as it goes to the registration unit 21, and the control unit 25c registers the sheet in accordance with the detection signal from the sensor so as to send the sheet in accordance with the position of the toner image. The unit 21 is driven.

  Next, the sheet onto which the toner image has been transferred is conveyed by the pre-fixing conveyance unit 10 to a fixing nip N formed by the fixing roller 30 and the pressure roller 31 of the fixing unit 11, and the sheet is heated in the fixing nip N. By applying pressure, the toner image is permanently fixed on the sheet. After the toner image is fixed in this way, when an image is formed only on the first surface, the sheet is discharged out of the apparatus by the reversing roller pair 14 and the discharge roller pair 12 that rotate in the forward direction. As a result, the copying machine 24 ends the one-sided copying operation of the sheet.

  On the other hand, when an image is formed on the second side, the sheet on which the image is formed on one side passes through the fixing unit 11 and is then switched back by the reverse roller pair 14 and passes through the reverse path 16. Then, the registration is corrected again by the registration unit 21 and conveyed to the transfer unit 104. Then, an image is formed on the opposite surface by the transfer unit 104, and then the sheet is conveyed and discharged out of the apparatus as in the single-sided copying operation.

  By the way, the sheet feeding cassette 1 stores (supports) large-sized sheets such as A3 size, and arranges and stores sheets of A4 size and the like in the width direction orthogonal to the sheet feeding direction. The first stacking unit 1A and the second stacking unit 1B shown in FIG. The first and second stacking units 1A and 1B, which are the plurality of sheet support units, are arranged side by side in the width direction so that the sheets can be conveyed in parallel at a predetermined interval in the width direction. . In addition, feed rollers 2 that can be controlled independently are provided above the first and second stacking portions 1A and 1B, respectively. Further, in the first and second stacking units 1A and 1B, a sheet size detecting unit 54 shown in FIG. 5 to be described later for detecting the sheet conveying direction length, the sheet width direction length, and the like of the stored sheets. Are provided respectively.

  When the sheets are fed in parallel, the sheets are stacked and stored in the first and second stacking units 1A and 1B, respectively. Each of the first and second stacking units 1A and 1B includes a middle plate (not shown) that can be moved up and down. When the sheet feeding cassette 1 is set in the main body, the middle plate is moved by a lifter motor (not shown). Rises and paper feed is possible. Then, the sheets stacked on the first and second stacking units 1A and 1B are simultaneously fed by the rotation of the sheet feeding roller 2. The two sheets fed at the same time are then separated one by one by the separation roller pair 3 and 4, and the sheet conveying roller pair 5 and 6 are separated by a predetermined interval in the width direction. Then, the skew is corrected by the registration unit 21 and conveyed to the transfer unit 104. Further, the toner images are transferred to the two sheets at the transfer unit 104 thereafter.

  By the way, in the present embodiment, when the two sheets onto which the toner images are transferred are conveyed to the fixing unit 11, a predetermined interval is set by the transfer unit 104 by the pre-fixing conveyance unit 10 provided in the sheet conveyance device 50. The sheets which are provided and conveyed in parallel are inclined in the same direction. Therefore, the pre-fixing conveyance that is provided between the transfer unit 104 that is the upstream sheet conveyance unit and the fixing unit 11 that is the downstream sheet conveyance unit and is a sheet inclined conveyance unit for adjusting the skew angle of the sheet. The unit 10 includes a skew mechanism unit and a transport unit.

  Here, as shown in FIG. 3, the transport unit 51 includes transport drive rollers 51a and 51b driven by a drive mechanism (not shown), and a transport belt 52 suspended by a predetermined tension by the transport drive rollers 51a and 51b. It is configured. As shown in FIG. 4, the skew mechanism unit 40 includes a rotation base 41 and a rotation driving unit 43 that rotates a rotation shaft 42 provided on the bottom surface of the rotation base 41. Here, the rotation base 41 includes a rotation support portion 44 that rotatably supports the end portions of the transport driving rollers 51 a and 52 b, and rotates around the rotation shaft 42 together with the transport portion 51.

  FIG. 5 is a control block diagram of the copying machine 24. The control unit 25 c outputs sheet size information such as the sheet conveyance direction length and the sheet width direction length from the sheet size detection unit 54 provided in the sheet feeding cassette 1 to the skew amount control circuit 20. To do. Then, the skew amount control circuit 20 drives the rotation mechanism unit 40 to the skew mechanism unit 40 based on the sheet size information, and outputs a drive signal for rotating the rotation base 41.

  In the present embodiment, when an image is formed on two sheets, an operation mode for operating the skew feeding mechanism unit 40 by an operation (not shown) is set. When this operation mode is set, the operation mode detection unit 53 detects this, and the control unit 25c passes the skew amount control circuit 20 based on the operation mode detection signal from the operation mode detection unit 53. Then, drive control of the skew mechanism mechanism 40 is performed.

  Here, when a drive signal is output from the skew amount control circuit 20 and the rotation drive unit 43 is driven, the rotation base 41 is moved from the position shown in FIG. 6A to the position shown in FIG. 6B. Rotate like so. That is, based on the drive signal from the skew feeding amount control circuit 20, the rotation base 41 rotates so that the sheet conveyance direction of the conveyance unit 51 is inclined by a predetermined angle θ from the direction orthogonal to the fixing nip N of the fixing unit 11. To do. In other words, the rotation base 41 rotates so that the sheet conveyance direction of the conveyance unit 51 is inclined by a predetermined angle (inclination angle) θ with respect to the width direction of the fixing nip N of the fixing unit 11. As described above, in the present exemplary embodiment, based on the sheet size information from the sheet size detection unit 54, a predetermined angle θ from the direction in which the sheet conveyance direction of the conveyance unit 51 is orthogonal to the fixing nip N of the fixing unit 11. The skew mechanism mechanism 40 is controlled (adjusted) so as to incline only.

  Then, after the skew feeding mechanism unit 40 is controlled to rotate and the conveyance unit 51 is inclined by the predetermined angle θ, the two sheets P1 and P2 conveyed linearly from the transfer unit 104 have a predetermined angle. First, the front side of the conveyance belt 52 contacts the conveyance unit 51 inclined by θ. Thereafter, the sheets P1 and P2 are conveyed to the fixing nip N while being gradually inclined along the guide portion while being pressed against the guide portion (not shown) by the conveyance belt 52.

  In the conveyance process from the transfer unit 104 through the fixing conveyance unit 10 to the fixing nip N, the sheets P1 and P2 receive the following conveyance force and are conveyed to the fixing nip N. First, since the conveyance force of the transfer unit 104 is dominant until the rear ends of the sheets P1 and P2 pass through the nip of the transfer unit 104, the sheets P1 and P2 are not moved in the sheet conveyance direction even if the conveyance unit 51 is inclined. It is conveyed almost in parallel. Thereafter, when the trailing ends of the sheets P1 and P2 pass through the transfer nip, the conveyance force of the pre-fixing conveyance unit 10 becomes dominant. Accordingly, the sheets P1 and P2 are inclined by the predetermined angle θ and enter the fixing nip N of the fixing unit 11 while maintaining the predetermined angle θ by the conveyance belt 52.

  Here, by inclining the sheet conveyance direction of the conveyance unit 51 with respect to the fixing nip N by a predetermined angle θ, when the sheet enters the fixing nip N, the entry region is only the corner portion of the sheet P. . For this reason, the shock received by the fixing nip N by the sheets P1 and P2 is very small compared to the case where the fixing nip N enters the fixing nip N in the conventional sheet leading end region, and the fluctuation of the fixing driving torque at the time of entering is small. Can be reduced. In the present embodiment, after the conveyance unit 51 is inclined, the sheets P1 and P2 are placed on the conveyance belt 52, but after the sheets P1 and P2 are placed on the conveyance belt 52 by a predetermined amount. The conveying unit 51 may be inclined by a predetermined angle θ.

  By the way, if the predetermined angle θ for rotating the transport unit 51 is too small, as shown in FIG. 7A, when two sheets P1 and P2 are transported in parallel with a predetermined interval w in the width direction, A region where the sheet does not pass is generated in the center in the width direction of the fixing nip N. In this case, the temperature rise of the non-sheet passing portion may occur and the surface of the fixing roller 30 may be damaged.

Therefore, in the present embodiment, the control unit 25c and the skew feeding amount control circuit 20 include information on the length l in the sheet conveyance direction from the sheet size detection unit 54, and a predetermined interval w between the two sheets P1 and P2. Based on the above, the predetermined angle θ is calculated so as to satisfy the following expression (1). Then, by calculating the predetermined angle θ so as to satisfy the expression (1), the passage areas (sheet conveyance areas) of the sheets P1 and P2 conveyed in parallel through the fixing nip N are partially overlapped. Become. Thereby, it is possible to suppress the temperature rise of the non-sheet passing portion during parallel conveyance and to prevent the fixing roller 30 from being damaged.
w / l <tan θ (1)

In the case of a sheet having a long length in the sheet conveying direction, if the predetermined angle θ is increased, two sheets P1 and P2 can pass through the fixing nip N as shown in FIG. There is a possibility that the region W protrudes from both ends in the width direction. In this case, based on the sheet conveyance direction length l information of the sheet from the sheet size detection unit 54, the sheet width direction length b information, the sheet interval w, and the sheet passing area W of the fixing nip N. The predetermined angle θ is calculated so as to satisfy the following expression (2). Then, by calculating the predetermined angle θ so as to satisfy the expression (2), it is possible to prevent the two sheets P1 and P2 from protruding.
(2b + w) cos θ + lsin θ <W (2)

  In this way, by controlling the inclination of the sheets so that the passing areas in the fixing nip N when the sheets conveyed in parallel pass through the fixing nip N partially overlap, non-sheet passing during parallel conveyance is performed. It is possible to suppress the temperature rise in the portion and to prevent the fixing roller 30 from being damaged.

  By the way, in the description so far, the sheet inclination conveyance unit (pre-fixing conveyance unit 10) can adjust the inclination angle of the sheet by rotating the conveyance unit 51 by the skew feeding mechanism unit 40. Two sheets However, the present invention is not limited to this. For example, the sheet inclination conveyance unit may be configured to incline the sheet itself.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a diagram illustrating a configuration of a sheet inclined conveying unit provided in the sheet conveying apparatus according to the present embodiment. In FIG. 8, reference numeral 21A denotes a registration mechanism which is a sheet inclination conveyance unit configured to incline the sheet. The registration mechanism 21A includes a first registration mechanism unit 21a and a second registration mechanism unit 21b which incline the sheet. I have. In the present embodiment, the registration mechanism 21A is provided between the transfer unit 104 and the sheet conveying roller pair 5, 6, but may be provided between the fixing unit 11 and the transfer unit 104. good.

  The first registration mechanism 21a includes a first conveying roller 23a configured to be able to contact and separate from the sheet P1, a first correction roller 24a configured to be able to contact and separate from the sheet P1, and a posture of the sheet P1. And a first register 22A that regulates the above. Here, the first conveying roller 23a is for conveying the sheet P1 to the fixing nip N, and the bus axis of the roller shaft is parallel to the fixing nip N of the photosensitive drum 101, the transfer roller 103, and the fixing unit 11. Is arranged. The first correction roller 24a conveys the sheet to the outside in the width direction. Note that the first registration unit 22A includes first and second registration members 22a and 22b that can move to a position that contacts the leading end of the sheet P1 and a retracted position that allows the sheet P1 to pass therethrough. In addition, the first registration unit 22A includes a third registration member 22e that comes into contact with the side edge of the sheet conveyed outward in the width direction by the first correction roller 24a.

  Here, in the present embodiment, the first and second registration members 22a and 22b are movable up and down in the vertical direction to a position where the first registration member 22a and the second registration member 22a and 22b come into contact with the leading end of the sheet P1 It has become. The second registration member 22b is located closer to the transfer unit than the first registration member 22a and is movable in the sheet conveyance direction. Then, by moving the second registration member 22b in the sheet conveyance direction in this way, the angle of the sheet P1 with respect to the sheet conveyance direction is changed when the leading end contacts the first and second registration members 22a and 22b. Can do.

  The second registration mechanism 21b includes a second conveying roller 23b configured to be able to contact with and separate from the sheet P2, a second correction roller 24b configured to be able to contact and separate from the sheet P2, and a posture of the sheet P2. And a second cash register 22B that regulates the above. Here, the second conveying roller 23b is for conveying the sheet P2 to the fixing nip N, and the bus axis of the roller shaft is parallel to the fixing nip N of the photosensitive drum 101, the transfer roller 103, and the fixing unit 11. Has been placed. The second correction roller 24b conveys the sheet outward in the width direction.

  Note that the second registration portion 22B includes fourth and fifth registration members 22c and 22d that are movable to a position that abuts on the leading end of the sheet P2 and a retracted position that allows the sheet P2 to pass therethrough. The second registration unit 22B includes a sixth registration member 22f that contacts the side edge of the sheet conveyed outward in the width direction by the second correction roller 24b. Here, in the present embodiment, the fourth and fifth registration members 22c and 22d are movable up and down to a position where they are brought into contact with the leading end of the sheet P2 and a retreat position where the sheet P2 can be passed. It has become.

  Further, the fifth registration member 22d is positioned closer to the transfer unit than the fourth registration member 22c and is movable in the sheet conveyance direction. Then, by moving the fifth registration member 22d in the sheet conveyance direction in this way, the angle of the sheet P2 with respect to the sheet conveyance direction is changed when the leading end abuts on the fourth and fifth registration members 22c and 22d. Can do.

  Next, the tilt control operation of the sheets P1 and P2 according to the present embodiment will be described with reference to the flowchart shown in FIG. In the registration mechanism 21A configured as described above, when the sheets P1 and P2 are transported by the paper feed roller 2, the sheets P1 and P2 are first transported by the first and second transport rollers 23a and 23b (step 100, Step 200: Hereinafter, the step is denoted as S). Next, the sheets P1 and P2 abut against the first registration member 22a and the fourth registration member 22c. Thereafter, the sheet P1 is rotated by the conveyance force of the first conveyance roller 23a with the contact position with the first registration member 22a as a rotation fulcrum, and abuts against the second registration member 22b. Further, the sheet P2 is rotated by the conveyance force of the second conveyance roller 23b with the contact position with the fourth registration member 22c as a rotation fulcrum, and abuts against the fifth registration member 22d.

  Here, the first registration member 22a, the second registration member 22b, the fourth registration member 22c, and the fifth registration member 22d are arranged at a position that forms a predetermined angle θ in the width direction as shown in FIG. The predetermined angle θ is an angle calculated by the above-described equations (1) and (2), and a passage area (sheet conveyance area) when the sheets P1 and P2 conveyed in parallel pass through the fixing nip N is defined. Some overlap. Therefore, the temperature rise of the non-sheet passing portion during parallel conveyance can be suppressed, the photoconductor drum 101 can be prevented from being damaged, and the two sheets P1 and P2 can be prevented from protruding. As a result, when the leading end abuts against the second registration member 22b and the fifth registration member 22d, the sheets P1 and P2 are inclined at a predetermined angle θ. Next, when the sheet P1 hits the first registration member 22a and the second registration member 22b and the sheet P2 hits the fourth registration member 22c and the fifth registration member 22d (Y in S101, Y in S201), The second transport rollers 23a and 23b are separated (S102, S202). Thus, the first and second transport rollers 23a and 23b are separated from each other, and the nip between the sheets P1 and P2 is opened. At the same time, the first and second correction rollers 24a and 24b nip the sheets P1 and P2. .

  Thus, the sheets P1 and P2 are conveyed by the first and second correction rollers 24a and 24b (S103 and S203), and then conveyed to positions where they abut against the third and sixth registration members 22e and 22f. When the sheets P1 and P2 hit the third and sixth registration members 22e and 22f (Y in S104, Y in S204), the first and second correction rollers 24a and 24b are separated (S105 and S205). Thereby, the tilting operation of the sheets P1 and P2 is completed (S106, S206).

  The first, second, fourth, and fifth registration members 22a, 22b, 22c, and 22d move (lower) at the same time as the first and second correction rollers 24a and 24b are separated (S120). Further, the first and second transport rollers 23a and 23b nip the sheets P1 and P2 again and transport the sheets P1 and P2 to the transfer unit 104 (S121). The conveyance timing of the sheets P1 and P2 is controlled by the control unit 25c described above. Thereafter, the sheets P1 and P2 are conveyed to the transfer unit 104, and the toner image is transferred thereto. Since the sheets P1 and P2 are conveyed while being inclined, the toner image is developed on the photosensitive drum 101 in accordance with the inclination angle θ of the sheet. The sheets P1 and P2 onto which the toner image has been transferred by the transfer unit 104 are fixed at the fixing nip N of the fixing unit 11. At the time of fixing, the temperature rise of the non-sheet passing portion during parallel conveyance can be suppressed, and the photosensitive drum 101 can be prevented from being damaged.

DESCRIPTION OF SYMBOLS 1 ... Paper feed cassette, 1A ... 1st stacking part, 1B ... 2nd stacking part, 10 ... Pre-fixing conveyance part, 11 ... Fixing part, 20 ... Skew amount control circuit, 21A ... Registration mechanism, 21a ... 1st registration Mechanism part, 21b ... second registration mechanism part, 24 ... copier, 25 ... copier body, 25c ... control part, 26 ... image forming part, 30 ... fixing roller, 31 ... pressure roller, 40 ... slanting mechanism part , 43: Rotation drive unit, 50: Sheet conveying device, 51: Conveying unit, 52: Sheet size detecting unit, 53: Operation mode detecting means, 101: Photosensitive drum, 103: Transfer roller, b: Length in width direction of sheet Well,
l: Length of sheet in the sheet conveyance direction, N: Fixing nip, P1, P2 ... Sheet, W: Paper passing area in fixing nip, w: Predetermined interval in the width direction of two sheets, θ: Predetermined angle

Claims (5)

In an image forming apparatus that transfers a toner image onto a sheet at a transfer unit and fixes the transferred toner image onto a sheet at a fixing unit.
A plurality of sheet support portions arranged in parallel in the width direction orthogonal to the sheet conveying direction;
A sheet inclined conveyance section that conveys the plurality of sheets conveyed in parallel from the plurality of sheet support sections in an inclined direction, and
2. The image forming apparatus according to claim 1, wherein when the plurality of sheets conveyed in parallel pass through the fixing unit, the sheet inclined conveyance unit inclines the sheets so that the passage areas of the plurality of sheets partially overlap. The sheet inclined conveying unit is configured to be able to adjust the inclination angle of the sheet,
A control unit for adjusting the inclination angle of the sheet by the sheet inclination conveying unit;
The control unit adjusts the inclination angle of the sheet by the sheet inclined conveying unit so that the plurality of sheets conveyed in parallel do not protrude from both ends in the width direction of the sheet conveying region of the downstream sheet conveying unit. The image forming apparatus according to claim 1.   The control unit controls the inclination of the sheet by the sheet inclined conveying unit based on the length of the sheet in the sheet conveying direction, the length of the sheet in the width direction, and a predetermined interval between the plurality of sheet supporting units. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 1, wherein the sheet inclined conveyance unit is disposed upstream of the transfer unit in a sheet conveyance direction.   The image forming apparatus according to claim 1, wherein the sheet inclined conveyance unit is disposed upstream of the fixing unit in a sheet conveyance direction.

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