JP4764081B2 - Sheet conveying apparatus, image forming apparatus, and image reading apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus, an image forming apparatus, and an image reading apparatus, and more particularly to a configuration for correcting skew feeding of a sheet such as a recording sheet or a document conveyed to an image forming unit or an image reading unit.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and image reading apparatuses are provided with a sheet conveying device that conveys a sheet such as a recording sheet or a document to the image forming unit or the image reading unit. The sheet conveying apparatus includes a skew correction unit that corrects the skew of the sheet in order to adjust the posture and position of the sheet before being conveyed to the image forming unit and the image reading unit.

  Further, in recent image forming apparatuses, it is possible to shorten the separation distance between conveyed sheets by digitization. However, when the separation distance between the sheets is shortened in this way, the processing speed increases, and accordingly, it is necessary to correct the skew that occurs when the sheet is conveyed in a short time.

  Here, as a conventional skew correction unit, for example, there is a method of correcting skew by abutting the leading end of a sheet against a nip portion of a stopped roller pair. Since it is difficult to handle when the separation distance is short, a so-called active registration method that corrects skew while conveying a sheet has recently been adopted (see Patent Document 1).

  FIG. 8 shows the configuration of a conventional skew correction unit employing such an active registration system. In FIG. 8, 101a and 101b are upstream of the sheet conveyance direction of the photosensitive drum 100 serving as image forming means. The two sensors are arranged at a predetermined interval in a direction substantially orthogonal to the sheet conveying direction indicated by the arrows (hereinafter referred to as the width direction).

  Reference numerals 103a and 103b denote registration roller pairs. The registration roller pairs 103a and 103b are arranged in the width direction and coaxially at predetermined intervals, and are independently driven by motors 102a and 102b, respectively. It is like that.

  Here, in the skew feeding correction portion having such a configuration, when the leading edge of the sheet P conveyed from the downstream crosses the sensors 101a and 101b, a signal indicating that the sheet has crossed is output from the sensors 101a and 101b. .

  A control unit (not shown) detects the amount of conveyance of the sheet P by the pair of registration rollers 103a and 103b independently driven and controlled by the motors 102a and 102b based on signals from the sensors 101a and 101b. The control is performed according to the amount, and the skew of the sheet P is corrected by such control.

  The control of the conveyance amount of the sheet P by the registration roller pair 103a, 103b is performed, for example, in order to correct the sheet P skewed in the state shown by the broken line in FIG. 8, the registration roller pair 103b on one side (advanced side). The conveyance speed of the registration roller pair 103a on the other side (delayed side) is made slower than the conveyance speed of the registration roller pair 103a on the other side (delayed side). In this control, the speed is higher than the conveying speed of the roller pair 103b. Then, by controlling the conveyance amount based on the sheet conveyance speed of the sheet P, the skew of the sheet P is corrected as indicated by the solid line in FIG.

Japanese Patent Laid-Open No. 2001-058741

  However, in the conventional sheet conveying apparatus provided with such a skew correction unit, in order to change the conveyance amount of the sheet P by the registration roller pair 103a and 103b, the driving control of the registration roller pair 103a and 103b is performed. It is necessary that the conveyance amount of the sheet P accurately corresponds to the number of rotations. For this reason, it is required that the clamping force of the sheet P is secured to some extent in the registration roller pairs 103a and 103b.

Further in recent years in a variety of user needs due development of colorization, the basis weight of the sheet P is necessary to convey the same pair of registration rollers 103a, 103b from 50 g / ^{m 2} approximately thin paper to 300 g / ^{m 2} or more cardboard There is a need to set the pinching force higher than before in order to accurately convey thick paper having a large inertial force.

  However, when the clamping force is set to be high in this way, when the skew correction of the sheet P having a large skew amount is performed in a short time, a conveyance speed difference is given at the front in the width direction as shown in FIG. The sheet P sandwiched and conveyed by the registration roller pairs 103a and 103b may be distorted toward the center in the width direction of the sheet P. This is caused by a large amount of feeding of one registration roller 103a and a small amount of feeding of the other registration roller 103b, and is caused by a difference in the amount of feeding, and particularly a sheet having low bending rigidity such as thin paper is remarkably generated.

  Here, in the case where the sheet P tends to have a low bending stiffness, such as thin paper, when such a distortion occurs, the stress that caused the distortion is not released after the skew correction, and therefore the sheet is wavy. Or there was a problem that wrinkles occurred and the sheet was damaged.

  On the other hand, when the sheet P is a thick paper having a high bending rigidity, the stress toward the center portion is to be released to the outside. It was a hindrance to accurate skew correction.

  Accordingly, the present invention has been made in view of such a current situation, and can prevent damage to the sheet during the skew feeding correction operation, and can perform high-precision skew feeding correction and image formation. An object of the present invention is to provide an apparatus and an image reading apparatus.

The present invention provides, in a sheet conveying apparatus for conveying a sheet, a sheet detecting unit for detecting a skew amount of a conveyed sheet, and a predetermined interval in a direction perpendicular to the sheet conveying direction, each independently. A pair of skew feeding correcting means for feeding the sheet and correcting the skew feeding of the sheet by controlling the sheet feeding amount according to the skew feeding amount of the sheet detected by the sheet detecting means; A moving unit that moves at least one of the correcting units in a direction orthogonal to the sheet conveying direction; a calculating unit that calculates in advance a distortion amount of the sheet generated during the skew correcting operation by the skew correcting unit; and the moving unit. control to and control means for performing control to move at least one of the skew correcting unit, wherein, during the skew correcting operation by the skew correcting unit, wherein Based on the calculation result of the calculation means, controlling said moving means to move at least one of the skew correction means of the skew correcting means in a state of clamping the sheet in the direction in which the spacing spread to other skew correction means The sheet distortion generated during the skew correction operation is eliminated .

  As in the present invention, during the skew correction operation by the pair of skew correction means, at least one of the pair of skew correction means in a state where the sheet is sandwiched is moved in a direction in which the distance from the other skew correction means increases. The distortion in the direction perpendicular to the sheet conveying direction generated in the sheet is eliminated during the skew correction operation. As a result, damage to the sheet during the skew correction operation can be prevented, and skew correction with high accuracy can be performed.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of an image forming apparatus provided with a sheet conveying apparatus according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 100 denotes an image forming apparatus, and 101 denotes an image forming apparatus main body. An image reading unit 102 for reading image information of a document is arranged on the upper part of the image forming apparatus main body 101. Here, the image reading unit 102 includes a document platen 1 made of a transparent glass plate that is fixedly provided, and a document that presses and fixes a document placed at a predetermined position on the document platen 1 with the image surface facing downward. A pressure plate 1a and an optical reading system 2 provided on the lower side of the document table 1 for optically reading the document are provided. When reading an original image, the original image is read by moving (scanning) the optical reading system 2 in the left-right direction at a predetermined speed.

  Further, an image forming unit 103 that forms an image on the sheet P according to the image information data acquired by the image reading unit 102 is provided below the image reading unit 102. The image forming unit 103 includes a photosensitive drum 5, a developing device 6 that forms a toner image on the surface of the photosensitive drum 5, a transfer roller 13 that transfers the toner image formed on the surface of the photosensitive drum 5, and the like. ing.

  Further, a sheet feeding device 104 including cassettes 7a and 7b on which sheets P made of paper, synthetic resin, and the like are stacked and stored, and pickup rollers 8a and 8b, and the like is provided at the lower portion of the image forming apparatus main body 101. Yes. Between the sheet feeding device 104 and the image forming unit 103, a sheet conveying device 105 including a conveying roller 11 and a skew feeding correcting unit 12 is provided.

  The sheet P fed from the sheet feeding device 104 is guided to the skew feeding correction unit 12 by the transport roller 11. Reference numeral 24 denotes a manual sheet feeding unit. A sheet from the manual sheet feeding unit is guided to the skew feeding correction unit 12 by the conveyance rollers 25 and 11.

  In the image forming apparatus 100 having such a configuration, when an image is formed, a document image is first read by the image reading unit 102, and then a signal is sent to a laser oscillator by a controller (not shown) to generate image information. In response, a laser beam is emitted. Next, the laser beam is reflected by the rotating polygon mirror 3, further reflected by the reflecting mirror 4, and then folded back, so that the surface of the photosensitive drum 5 whose surface is uniformly charged is irradiated.

  As a result, an electrostatic image is formed on the surface of the photosensitive drum 5, and the toner image is then formed on the surface of the photosensitive drum 5 by developing the electrostatic image with the developing device 6. Is done.

  On the other hand, the sheets P stored in the cassettes 7a and 7b are selectively fed out by the pick-up rollers 8a and 8b, and then separated one by one by a separation unit constituted by the feed rollers 9a and 9b and the retard rollers 10a and 10b. Sent. Thereafter, the sheet is guided to the skew feeding correction unit 12 by the conveying roller pair 11.

  The skew correction unit 12 corrects the skew while the sheet P is conveyed as will be described later. Thereafter, the sheet P is configured by the photosensitive drum 5 and the transfer roller 13 at a timing in accordance with the rotation of the photosensitive drum 5. Sent to the transfer section. A toner image previously formed on the photosensitive drum 5 is transferred to the transfer portion.

  Further, after the toner image is transferred in this way, the sheet P is guided to the fixing device 15 by the conveyance belt 14. In the fixing device 15, the toner image is permanently fixed on the sheet P by being heated and pressed when being nipped and conveyed by the fixing roller 15 a and the pressure roller 15 b.

  Thereafter, the sheet P discharged from the fixing device 15 is nipped and conveyed by the discharge roller pair 19 so that the image surface faces upward on the discharge tray 22 by appropriately switching the flappers 16a and 16b when face-up discharge. To be discharged. Further, when face-down paper discharge is performed, the discharge roller pair 19 is reversed at a predetermined timing, and the discharge roller pairs 20 and 21 are discharged onto the discharge tray 23 with the image surface facing downward.

  Further, when forming images on both sides of the sheet P, the sheet P discharged from the fixing device 15 is guided to the double-sided path 17 by switching the flappers 16a and 16b as appropriate, and then the front and back surfaces are reversed. It is conveyed to the skew feeding correction unit 12 by the roller pair 18. Thereafter, it is discharged out of the machine through the same process as that on one side.

  Further, the sheet P set on the manual feed tray 24 is fed by the feeding roller 25 and conveyed to the skew feeding correction unit 12 by the conveying roller pair 11. Then, the skew correction is corrected by the skew correction unit 12 and is sent to a transfer unit constituted by the photosensitive drum 5 and the transfer roller 13 at a timing in accordance with the rotation of the photosensitive drum 5 to form a toner image. Thereafter, the image is fixed and discharged outside the apparatus.

  FIG. 2 is a perspective view of the skew feeding correction unit 12, and in FIG. 2, 12a and 12b are a pair of registration rollers. A plurality of registration roller pairs 12a and 12b, which are two skew correction units in the present embodiment for correcting the skew that occurs when the sheet P is fed, are skewed while transporting the sheet P. This is a so-called active registration method for correcting rows.

  Here, the registration roller pairs 12a and 12b correct the skew of the sheet by controlling the respective sheet conveyance amounts according to the skew amount of the sheet detected by a sheet sensor described later. The registration roller pairs 12a and 12b are fixed to rotational drive shafts 26 and 27 arranged coaxially in the width direction substantially orthogonal to the arrow a direction in FIG. Each of the registration rollers 28 and 29 is a rotating body disposed at a predetermined distance from each other, and the rollers 30 and 31 are driven rotating bodies that are driven to rotate in pressure contact with the registration rollers 28 and 29, respectively. Has been.

  Reference numerals 32 and 33 denote motors as driving means for the registration rollers 28 and 29, and the registration rollers 28 and 29 are independently rotated by the motors 32 and 33, respectively. The motors 32 and 33 are driven and controlled by a control device 70 as control means shown in FIG.

  By the way, in this embodiment, the rotation drive shafts 26 and 27 to which the registration roller pairs 12a and 12b are fixed can be moved in the axial direction (width direction) by moving means 38 and 39 having a worm gear (not shown), for example. It is configured. The moving means 38 and 39 are controlled by the controller 70 so that the registration roller pair 12a and 12b can be moved. For example, from the position (initial position) indicated by the solid line where the separation distance in the width direction of the nip portion between the registration rollers 28 and 29 and the rollers 30 and 31 is L1, the separation distance in the width direction of the nip portion is a broken line L2. It can be moved to any position between the positions shown.

  Reference numerals 34 and 35 denote sheet sensors that serve as two (a plurality of) sheet detecting means disposed in the width direction at predetermined intervals on the downstream side of the registration roller pair 12a and 12b in the sheet conveying direction. Based on the outputs from the sheet sensors 34 and 35, the control device 70 detects the skew amount of the sheet P. The separation distance in the sheet width direction of the sheet sensors 34 and 35 is M1.

  Here, the sheet sensors 34 and 35 include light emitting elements 34a and 35a such as LEDs (light emitting diodes) disposed on the lower surface side of the sheet P to be conveyed, and light receiving elements 34b disposed on the upper surface side of the sheet P. 35b.

  A slit plate 37 having a slit 37a having a predetermined width is disposed above the light emitting elements 34a and 35a on the lower surface side of the conveyed sheet P. Light emitted from the light emitting elements 34a and 35a passes through the slits 37a of the slit plate 37, and is detected by the light receiving elements 34b and 35b. And the position of the edge part of the sheet | seat P is accurately detectable by interposing such a slit 37a.

  In such a skew correction unit 12, when the sheet P enters the registration roller pair 12a and 12b and the leading end of the sheet blocks the optical path between the light emitting elements 34a and 35a and the light receiving elements 34b and 35b, the sheet sensor 34 and 35 are each turned OFF at a predetermined timing. Then, the skew amount of the sheet P is measured based on the time difference.

  FIG. 4 shows an example of a detection signal when the skewed sheet P is detected by the sheet sensors 34 and 35. In FIG. 4, first, the sheet sensor 34 detects the leading edge of the sheet P and is turned OFF, and after the T1 time, the sheet sensor 35 detects the leading edge of the sheet P and is turned OFF.

  The detection signals detected by the sheet sensors 34 and 35 in this way are input to the skew amount calculation unit 71 of the control device 70 shown in FIG. 3, and the skew amount calculation unit 71 detects the sheet from the time difference of the detection signals. The skew amount of P is calculated. Further, based on the calculated skew amount, the control amount calculator 72 calculates the sheet conveyance amount by the registration rollers 28 and 29 necessary for correcting the skew of the sheet P. Based on this, the control device 70 controls the motors 32 and 33 to control the rotational speeds of the registration rollers 28 and 29.

  For example, the registration roller pair 12a, 12b is set to a position (initial position) where the distance in the width direction of the nip portion between the registration rollers 28, 29 and the rollers 30, 31 shown by the solid line in FIG. To do. At this time, when the correction conveyance distance Ls of the sheet P corresponding to the skew amount of the sheet P shown in FIG. 5 is obtained using the sheet sensors 34 and 35, the correction necessary for correcting the skew of the sheet P is obtained. The conveyance distance Ls is obtained by the following equation (1).

  T1 is a time difference when the sheet sensors 34 and 35 detect the leading edge of the sheet P, M1 is a separation distance in the width direction of the sheet sensors 34 and 35, and L1 is each of the registration rollers 28 and 29 and the rollers 30 and 31. The separation distance in the width direction of the nip portion, V is the conveyance speed of the sheet P.

    Ls = L1 (T1V / M1) (1)

  That is, in this case, for example, by the correction conveyance distance Ls, the rotation speed of the motor 33 on the side where the sheet P has advanced is temporarily reduced and then returned to the original rotation speed to change the conveyance amount of the sheet P left and right. Thus, the skew of the sheet P can be corrected.

  By the way, as described above, when the skew amount of the sheet P is large, if the skew correction of the sheet P having a large skew amount is performed in a short time, the sheet P is transported by the registration roller pair 12a and 12b. Nipped and conveyed. As a result, the sheet P is distorted toward the center in the width direction of the sheet (see FIG. 9).

  Next, the amount of skew in the state where the nip positions of the registration rollers 28 and 29 and the rollers 30 and 31 of the registration roller pairs 12a and 12b are at the position shown by the solid line in FIG. 2 (the separation distance L1 in the width direction of the nip portion). A method for obtaining the distortion amount at the center of the sheet P according to the above will be described. In this embodiment, such a calculation of the distortion amount is performed by the control amount calculation unit 72 which is a calculation means.

  As described above, the corrected conveyance distance Ls of the sheet P is obtained by the above equation (1). At this time, the input skew angle θ shown in FIG. 5 is simply expressed by the following equation (2). The

    tan θ = Ls / L1 (2)

  Further, the sheet P is pushed in the center direction by relatively shifting the conveyance amount by the skew correction operation within the range of the separation distance L1 in the width direction of the nip portion between the registration rollers 28 and 29 and the rollers 30 and 31. Assuming that the rare distortion amount is S, the distortion amount S is expressed by the following equation (3).

    S / Ls = tan (θ / 2) (3)

  Here, when the formula (2) is modified, the following formula (4) is obtained.

tan θ = tan (θ / 2 + θ / 2)
= {Tan (θ / 2) + tan (θ / 2)} / {1-tan (θ / 2) × tan (θ / 2)} = Ls / L1 (4)

  Substituting equation (3) into equation (4) yields equation (5) below.

    {S / Ls + S / Ls} / {1-S / Ls × S / Ls} = Ls / L1 (5)

  Therefore, the strain amount S into which the sheet P is pushed in the center direction can be expressed by the following equation (6).

S = (L1 ² + Ls ² ) ^1/2 −L1 (6)

  Here, in this embodiment, as described above, the registration roller pair 12a and 12b can be moved in the width direction. Then, by making the registration roller pair 12a and 12b move in the width direction during the skew correction operation as shown in FIG. 6, the distortion amount generated during the skew correction operation is released in the width direction. be able to.

  That is, after the registration roller pair 12a, 12b starts to relatively shift the conveyance amount by the skew correction operation, the correction conveyance distance Ls of the sheet P corresponding to the skew amount is moved to complete the skew correction. The registration roller pair 12a and 12b are controlled to move. In this way, the skew correction operation is performed by controlling the registration roller pair 12a and 12b to move outward in the width direction, which is the direction in which the gap between the nip portions increases, by an amount substantially corresponding to the strain amount S. Can be prevented from being distorted.

  For example, the width direction separation distance L1 of the nip portions of the registration roller pairs 12a and 12b is 250 mm, the width direction separation distance M1 of the sheet sensors 34 and 35 is 200 mm, and the conveyance speed V of the sheet P is 300 mm / s. Here, when the sheet P is conveyed at an oblique angle θ of 10 ° under this condition, the detection time difference T1 between the sheet sensors 34 and 35 is 117.6 ms, and the sheet P correction conveyance distance Ls at the nip portion. Is 44.1 mm. The distortion amount S generated by the skew correction operation at this time is 3.9 mm.

  Assuming that the skew correction control method is such that one of the registration roller pairs 12a and 12b is stopped and the other is conveyed with the conveyance speed V = 300 mm / s, the nip portion is separated in the sheet width direction. The correction time at the distance L1 = 250 mm is 147 ms. Therefore, the control device 70 controls the moving units 38 and 39 so as to move the registration roller pairs 12a and 12b 3.9 mm outward in the width direction within 147 ms from the start of the skew feeding correction operation.

  As such a movement control method, if one of the registration roller pairs 12a and 12b is stopped and only the other is moved, the movement amount is set to 3.9 mm, and the movement speed is set to about 30 mm / s. It is possible to move within the skew correction end time. Alternatively, even when both the registration roller pairs 12a and 12b are moved at the same time, and each movement amount is set to about 2 mm and the movement speed is set to about 15 mm / s, the registration roller can move within the skew correction end time. it can.

  In this manner, during the skew correction operation by the registration roller pair 12a and 12b, at least one of the pair of registration roller pairs 12a and 12b in a state where the sheet P is sandwiched is moved in the direction in which the interval is increased.

  As a result, the distortion generated in the sheet P due to the skew feeding correction operation can be eliminated during the skew feeding correction operation, and the occurrence of damage to the sheet P during the skew feeding correction operation, particularly the occurrence of undulations and wrinkles with respect to the thin paper conveyance. Can be prevented. Further, with respect to thick paper, the twisting force is transmitted to the nip portion, and it is possible to prevent the skew correction ability from being lowered due to slipping, and it is possible to perform skew correction with high accuracy.

  By the way, in the present embodiment, the control device 70 repeatedly performs the distortion elimination operation associated with the skew feeding correction operation. At this time, the control is performed so that at least the distance between the nip portions of the registration roller pairs 12a and 12b in the width direction reaches the outside of the operating range so that the nip portion interval returns to the original interval L1. That is, by the time when L1 reaches the broken line portion L2 in FIG. 2, the moving means 38 and 39 are controlled so that the pair of registration rollers 12a and 12b is returned to the position where the interval between the nip portions becomes the original interval L1. is doing.

  Note that the control device 70 returns the registration roller pair 12a and 12b to the initial position in this manner when the sheet P is not being sandwiched, for example, between sheets or between jobs. By returning the registration roller pairs 12a and 12b to their original positions in this way, distortion generated in the sheet P by the skew correction operation can be continuously eliminated during the skew correction operation.

  It should be noted that the amount of movement by the moving means 38 and 39 does not necessarily have to be moved by an amount corresponding to the amount of distortion obtained by calculation based on the rigidity of the sheet P or the friction coefficient between the sheet P and the registration rollers 28 and 29. May set the amount of movement as appropriate.

  Further, the configuration and control method of the moving means 38 and 39 are not limited to the present embodiment. Calculation means for calculating the amount of distortion in the center direction of the width generated by the skew correction operation, and movement means 38 and 39 for moving the registration roller nip portion substantially in the width direction in order to release the distortion toward the center direction. It only has to. In addition, if the movement timing is from the start to the end of the skew correction operation, the same effect can be obtained.

  In the present embodiment, the control device 70 controls the sheet conveyance amount of the registration roller pairs 12a and 12b and controls to move at least one of the registration roller pairs 12a and 12b. However, these two controls may be performed by two control means.

  Next, a second embodiment of the present invention will be described.

  FIG. 7 is a cross-sectional view illustrating a configuration of a scanner which is an example of an image reading apparatus including the sheet conveying apparatus according to the present embodiment.

  In FIG. 7, reference numeral 50 denotes a scanner. The scanner 50 moves a document D with respect to a fixed optical reading system to read an image recorded on the document D, a so-called flow-reading automatic document feeder A, and a lower part of the automatic document feeder A. And an image reading optical system B serving as image reading means.

  In the automatic document feeder A, the document D stacked on the document tray 41 is fed out by the pickup roller 42. Thereafter, the sheet is separated and fed one by one by the separation roller pair 43, and is then conveyed by the conveyance roller pair 44 to the image reading unit 45 where the image can be read by the image reading optical system B.

  Here, in the present embodiment, the registration rollers configured in substantially the same manner as the registration roller pairs 12a and 12b having the configuration shown in FIG. 2 described above on the upstream side and the downstream side of the image reading unit 45 in the document conveyance direction. A pair 46 is arranged. Further, a registration roller pair 47 provided on the opposite side across the image reading unit 45 is disposed.

  The registration roller pair 46 corrects the skew of the document D conveyed from the upstream side in the document conveyance direction of the image forming unit 45, and the document conveyed by the registration roller pair 47 from the downstream side in the document conveyance direction of the image reading unit 45. The skew of D is corrected. Then, the corrected document is conveyed to the image reading unit 45.

  Next, a document image reading operation of the scanner 50 configured as described above will be described.

  For example, when reading an image on one side of the document D, the document D is placed and set on the document tray 41 with the image surface facing upward, and the document D is fed out by the pickup roller 42 and then separated into a pair of separation rollers. 43 separate and feed one by one. Thereafter, the document D is guided to the registration roller pair 46 by the conveyance roller pair 44 and the flapper 57.

  The registration roller pair 46 corrects the skew of the document D and conveys it to the image reading unit 45 so that the document image is read by the image reading optical system B disposed below the image reading unit 45. To do. After the original image is read in this way, the original D is guided in the direction of arrow b by the registration roller pair 47, the transport roller pair 48, and the flapper 49, and the original surface is directed downward on the discharge tray 51 by the discharge roller pair 50. To discharge.

  Further, when reading the document images on both sides of the document D, the document D is conveyed as described above, and the document image on the first surface that is facing upward on the document tray 41 is read by the image reading unit 45. Thereafter, the resist roller pair 47, the transport roller pair 48, and the flapper 49 are guided in the direction of arrow c.

  Thereafter, the document D is reversed by the conveyance roller pair 52 and guided to the registration roller pair 47, and conveyed to the image reading unit 45 while correcting skew by the registration roller pair 47, and the second image reading optical system B performs the second reading. Read the original image on the front side. After the image is read in this way, the document D is guided in the direction of the arrow d by the registration roller pair 46 and the flapper 57, and then further guided in the direction of the arrow b by the conveyance roller pair 53 and discharged by the discharge roller pair 50. The paper is discharged on the tray 51 with the second surface facing upward.

  When reading a document image such as a thick document D or an extremely thin document D that is difficult to be conveyed by the automatic document feeder A, the document D is placed on the manual feed tray 54 with the document surface facing downward. And is conveyed in the direction of arrow e by the pair of feeding rollers 55 and the pair of conveying rollers 56. Then, after the document D is transported by the transport roller pair 52, it is transported to the image reading unit 45 while correcting skew by the registration roller pair 47, and the document image is read by the image scanning optical system B.

  After reading the original image in this way, the original D is guided by the registration roller pair 46 and the flapper 57 and conveyed in the direction of the arrow f, and the original roller surface is placed on the discharge tray 59 by the discharge roller pair 58. Discharge.

  By the way, also in this embodiment, the registration roller pairs 46 and 47 convey the registration rollers 28 and 29 according to the skew amount detected by the sheet sensors 34 and 35, as in the first embodiment described above. By controlling the speed, skew correction of the document D is performed.

  Further, the same movement means as in the first embodiment is used to move the registration roller pair 46, 47 in the direction in which the interval between the registration rollers is widened. I'm trying to eliminate it inside. Since this is the same as the first embodiment, a detailed description is omitted. As a result, damage to the sheet during the skew correction operation can be prevented, and skew correction with high accuracy can be performed.

1 is a cross-sectional view of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. FIG. 3 is a perspective view illustrating a configuration of a skew feeding correction unit provided in the sheet conveying apparatus. The control block diagram of the said skew correction part. FIG. 4 is a diagram illustrating a detection signal when a sheet of a sheet sensor provided in the sheet conveying apparatus is detected. The figure explaining the distortion amount to the sheet | seat center part which arises when correcting a skew by the said skew correction part. The figure explaining the distortion elimination operation | movement in the said skew feeding correction part. FIG. 5 is a cross-sectional view illustrating a configuration of a scanner that is an example of an image reading apparatus including a sheet conveying device according to a second embodiment of the invention. The figure which shows the structure of the conventional skew feeding correction | amendment part. The figure which shows the distortion which arises when correcting skew by the conventional skew correction part.

Explanation of symbols

12a, 12b Registration roller pair 28, 29 Registration roller 30, 31 Roller 32, 33 Motor 34, 35 Sheet sensor 38, 39 Moving means 45 Image reading unit 46, 47 Registration roller pair 50 Scanner 70 Controller 71 Skew amount calculation unit 72 Control Amount Calculation Unit 100 Image Forming Apparatus 102 Image Reading Unit 103 Image Forming Unit P Sheet

Claims (4)

In a sheet conveying apparatus that conveys a sheet,
Sheet detecting means for detecting the skew amount of the conveyed sheet;
By being provided at predetermined intervals in a direction orthogonal to the sheet conveying direction, each sheet is independently conveyed, and each sheet conveying amount is controlled according to the skew amount of the sheet detected by the sheet detecting means A pair of skew correction means for correcting the skew of the sheet;
Moving means for moving at least one of the skew feeding correcting means in a direction perpendicular to the sheet conveying direction;
Arithmetic means for calculating in advance the amount of sheet distortion that occurs during the skew correction operation by the skew correction means;
Control means for controlling the moving means to move at least one of the skew feeding correcting means;
With
The control means determines at least one skew correction means of the skew correction means in a state where the sheet is sandwiched based on the calculation result of the calculation means during the skew correction operation by the skew correction means. A sheet conveying apparatus characterized by controlling the moving means so as to move in a direction in which an interval between the skew correcting means and the skew correcting means is increased, thereby eliminating sheet distortion caused during the skew correcting operation . In a sheet conveying apparatus that conveys a sheet,
Sheet detecting means for detecting the skew amount of the conveyed sheet;
By being provided at predetermined intervals in a direction orthogonal to the sheet conveying direction, each sheet is independently conveyed, and each sheet conveying amount is controlled according to the skew amount of the sheet detected by the sheet detecting means A pair of skew correction means for correcting the skew of the sheet;
Moving means for moving at least one of the skew feeding correcting means in a direction perpendicular to the sheet conveying direction;
With
The control means determines at least one skew correction means of the skew correction means in a state where the sheet is sandwiched based on the calculation result of the calculation means during the skew correction operation by the skew correction means. The moving means is controlled so as to move in the direction in which the interval with the skew correction means is expanded to eliminate sheet distortion caused during the skew correction operation, and at least the skew correction means moved during the skew correction operation. one of, in a state that does not nip the sheet, the moving means initial skew correction means, characterized and to Resid over preparative conveying device to return so that the spacing of the. 3. An image forming apparatus comprising: an image forming unit; and the sheet conveying device according to claim 1 or 2 that conveys a sheet to the image forming unit. Image reading apparatus characterized by comprising an image reading unit for reading an image of a sheet, a sheet conveying apparatus according to claim 1 or 2, wherein conveying the original as a sheet to the image reading unit.

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