JP2005241669A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which lateral registration can easily be adjusted without preparing for dedicated paper. <P>SOLUTION: The image forming apparatus includes: an image forming part which forms a lateral registration adjustment image onto the surface of paper P conveyed from a paper feed part; a reverse carrying part 37 which inverts back to front the paper P conveyed from the image forming part, and conveys it to the image forming part again; and a control part which controls the image forming part. The reverse carrying part 37 has a jogger fence 73 by which the position of the thus conveyed paper P in a direction perpendicular to the direction of the paper conveyance is aligned with a reference position, and a sensor 40 which detects the lateral registration adjustment image on the paper P aligned with the reference position. The control part calculates an amount of lateral registration from the reference position of the lateral registration adjustment image detected by the sensor 40. Further, the control part exerts control such that the timing of writing images onto the paper P by the image forming part in the direction perpendicular to the direction of the paper conveyance is corrected based upon the amount of lateral registration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus capable of correcting a lateral resist which is a shift in a direction orthogonal to a transfer material conveyance direction.

  In the image forming apparatus, the skew and registration start timing of the transfer material (paper) fed from each paper feed unit are adjusted by the registration rollers, and the skew and vertical registration are corrected. However, due to the error in assembling each sheet feeding unit into the image forming apparatus main body and the variation in skew correction amount, the lateral registration varies from sheet feeding unit to sheet feeding unit. Also, when forming images on both sides of a sheet, the amount of lateral resist may vary between the front and back sides of the sheet due to assembly errors of the reversing conveyance unit that reverses the front and back of the sheet and conveys them to the image forming unit. .

  In order to eliminate such variations in lateral registration, a sheet with a lateral registration mark is conveyed in advance, and the time from the leading edge of the sheet to the lateral registration mark is measured based on a detection signal from the mark detection means. A technique is known in which the amount of lateral resist is obtained from the difference from a preset time and the optical writing timing to the image carrier is corrected (see, for example, Patent Document 1).

JP-A-5-193785 (FIG. 2, pages 2 to 3)

  However, although the invention of Patent Document 1 can correct the lateral resist amount, it has to prepare a dedicated paper on which a lateral resist mark is printed in advance, and the lateral resist cannot be easily corrected. there were.

  In view of such problems, it is an object of the present invention to provide an image forming apparatus capable of easily correcting a lateral registration without preparing dedicated paper.

  In order to solve the above problems, the invention according to claim 1 is characterized in that a lateral registration adjustment image is formed on the surface of the transfer material conveyed from the paper feeding unit by the image forming unit and conveyed to the reverse conveying unit. In the image forming apparatus for reversing the transfer material to the image forming unit after reversing the front and back of the transfer material in the reversing conveyance unit, a sensor that is provided in the reversal conveyance unit and detects the lateral registration adjustment image; The lateral registration amount from the reference position of the lateral registration adjustment image detected by this sensor is obtained, and the image writing timing in the direction perpendicular to the transfer material conveyance direction to the transfer material in the image forming unit is corrected based on the lateral registration amount. An image forming apparatus including a control unit that controls the image forming apparatus.

  According to a second aspect of the present invention, an image forming unit for forming a lateral resist adjustment image on the surface of a transfer material conveyed from a paper feeding unit, and a front and back of a transfer material conveyed from the image forming unit are reversed. A reversing conveyance unit that conveys the image forming unit again and a control unit that controls the image forming unit are provided, and the reversing conveyance unit has a position in a direction perpendicular to the transfer material conveyance direction of the transferred transfer material. A jogger member aligned with a reference position and a sensor for detecting the lateral registration adjustment image in a transfer material aligned with the reference position are provided, and the control unit detects the lateral registration adjustment image detected by the sensor. The lateral registration amount from the reference position is calculated, and based on the lateral registration amount, control is performed so as to correct the image writing timing in the direction perpendicular to the transfer material conveyance direction to the transfer material in the image forming unit. The image forming apparatus according to.

  According to a third aspect of the present invention, in the first or second aspect, the lateral resist adjustment image is formed to be inclined with respect to a reference image line formed perpendicular to the transfer material conveyance direction and the transfer material conveyance direction. The control unit obtains the lateral resist amount by comparing a detection time difference between the reference image line and the detection image line by the sensor with a predetermined value stored in advance in the control unit. Features.

  According to a fourth aspect of the present invention, there is provided the transfer material according to any one of the first to third aspects, wherein a plurality of the sheet feeding units are provided, and the transfer material is conveyed from each sheet feeding unit toward the image forming unit. The lateral registration amount for each paper feeding unit is obtained by the control unit, and the image writing timing for each paper feeding unit is corrected based on the lateral registration amount.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the lateral resist adjustment image is formed on the back surface of the transfer material conveyed again from the reverse conveying unit to the image forming unit. The transfer material is conveyed to the reversal conveyance unit, and the lateral resist amount on the back surface of the transfer material is obtained by the control unit, and the image writing timing on the back surface of the transfer material based on the lateral resist amount. Is corrected.

  The present invention is configured as described above, and the control unit obtains the lateral resist amount from the reference position of the lateral resist adjustment image detected by the sensor, and the transfer material in the image forming unit is based on the lateral resist amount. Since the image writing timing in the direction orthogonal to the transfer material conveyance direction is corrected, it is possible to easily correct the lateral registration without preparing a dedicated sheet.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is a side view illustrating a schematic configuration of the image forming apparatus, FIG. 2 is a side view illustrating a schematic configuration of a reversing conveyance unit, and FIG. 3 is an enlarged perspective view of a main part near a jogger fence of the reversing conveyance unit. FIG. 5 is a functional block diagram of the image forming apparatus, and FIG. 5 is a schematic diagram of an image for adjusting horizontal registration formed on a sheet.

  First, the configuration of a tandem type color copier as an image forming apparatus in this embodiment will be described with reference to FIG. The color copying machine 1 is disposed between the image forming unit 3 positioned substantially at the center of the apparatus main body, the sheet feeding unit 5 positioned below the image forming unit 3, and the sheet feeding unit 5 and the image forming unit 3. The reversal conveying unit 37, the image reading unit 7 positioned above the image forming unit 3, and the control unit 2 (see FIG. 4) are provided. An intermediate transfer belt 9, which is an endless belt having a transfer surface (stretch surface) extending in the horizontal direction, is disposed in the image forming unit 3, and the upper surface of the intermediate transfer belt 9 has a complementary color relationship with the color separation color. Photoconductors 11Y, 11M, 11C, and 11B for forming color images are provided. That is, the photoreceptors 11Y, 11M, 11C, and 11B that can carry toner images of toners of complementary colors (yellow, magenta, cyan, and black) are arranged along the extended surface of the intermediate transfer belt 9 along the intermediate transfer belt 9. Is placed in contact with.

  Each of the photoconductors 11Y, 11M, 11C, and 11B is configured as a drum that rotates in the same direction (counterclockwise direction). Around the photoconductors 11Y, 11M, 11C, and 11B, a charging roller 13 and an optical book are provided. An inset unit 15, a developing unit 17, a primary transfer roller 19, a cleaning unit 21, a static elimination lamp 23 and the like are arranged. The optical writing unit 15 includes an optical writing device corresponding to each of the photoconductors 11Y, 11M, 11C, and 11B in a single frame. In FIG. 1, only the charging roller 13, the developing unit 17, the primary transfer roller 19, the cleaning unit 21, and the charge removal lamp 23 arranged around the photoreceptor 11 </ b> Y are denoted by reference numerals, but the photoreceptors 11 </ b> M, 11 </ b> C, Similar members are also arranged around 11B.

  The intermediate transfer belt 9 is wound around three support rollers 25a, 25b, and 25c, and is rotatable in a rotating direction at positions facing the photoconductors 11Y, 11M, 11C, and 11B. The support rollers 25a and 25b support the extended surface of the intermediate transfer belt 9. The support roller 25 c faces the secondary transfer unit 27 with the intermediate transfer belt 9 interposed therebetween. A belt cleaning unit 29 for cleaning the surface of the intermediate transfer belt 9 is provided at a position facing the support roller 25a with the intermediate transfer belt 9 in between. The primary transfer roller 19 is pressed against the photoreceptors 11Y, 11M, 11C, and 11B via the intermediate transfer belt 9.

  The secondary transfer unit 27 includes a charging drive roller 27 a, a driven roller 27 b, and a transfer belt 27 c that is wound around these and moves in the rotational direction of the intermediate transfer belt 9. The secondary transfer unit 27 is configured to transport the paper P to the entrance of the fixing unit 31. The fixing unit 31 includes an endless fixing belt 31a, two rollers that support the fixing belt 31a, and a pressure roller 31b that is in pressure contact with the fixing belt 31a. The paper P that has passed through the fixing unit 31 is selected as a paper discharge passage 115 directed toward the paper discharge tray 35 or an introduction passage 57 directed toward the reverse conveyance unit 37 by a reverse switching claw 85 provided on the downstream side of the fixing unit 31. Is conveyed. When the paper P is conveyed toward the paper discharge tray 35, the paper P is discharged onto the paper discharge tray 35 by the paper discharge roller pair 45.

  In the paper feeding unit 5, a plurality of paper feeding cassettes 5a, 5a, 5a in which paper P is stacked and stored, and the paper P stored in the paper feeding cassette 5a are separated one by one in order from the top, and fed. A sheet feeding roller 5b, a conveyance roller pair 5c, a registration roller pair 47 provided upstream of the secondary transfer unit 27 in the sheet conveyance direction, and the like are provided. The paper P fed from the paper feed cassette 5a is temporarily stopped by the registration roller pair 47, and after correcting skew and vertical registration, a predetermined position of the front end of the toner image on the intermediate transfer belt 9 and the front end in the transport direction Are transferred to the secondary transfer means 27 by the registration roller pair 47 at a timing when the two coincide with each other. A manual feed tray 49 that can be rotated in the vertical direction is provided on the right side of the apparatus main body. After the paper P stored in the manual feed tray 49 is fed by the paper feed roller 51, it is directed toward the registration roller pair 47. Sent.

  The optical writing unit 15 is provided with an optical writing device (not shown) for each of the photoreceptors 11Y, 11M, 11C, and 11B. In the optical writing device, a laser diode (not shown) that emits writing light, which is laser light carrying image information, and an image stored in advance in the control unit 2 on the surface of the photoconductors 11Y, 11M, 11C, and 11B. A rotating polygon mirror (not shown) or the like for scanning in the horizontal direction is provided in a range corresponding to the width of the paper P at the writing timing.

  The image reading unit 7 includes an automatic document feeder 7a and a scanner 7b having a contact glass (not shown) as a document placement table. The automatic document feeder 7a is configured to invert a document fed on a contact glass, and is configured to be able to read an image on each side of the document.

  2 has a curved introduction passage 57 whose upper end is connected to the paper discharge passage 115 of the color copying machine 1, a switchback passage 59 connected to the introduction passage 57, and this switchback. A refeed path 75 that transports the paper P in the path 59 again toward the image forming unit 3, a reverse paper discharge path 61 that transports the paper P in the switchback path 59 toward the paper discharge tray 35, and the like. ing.

  The introduction passage 57 is formed by a gap between the guide plates 63 and 65 and a gap between the guide plates 67 and 69. The switchback passage 59 is formed by facing a guide plate 71 horizontal to the guide plates 67 and 69 with a predetermined gap therebetween. The horizontal guide plate 71 is provided with a pair of jogger fences 73 as jogger members for aligning the paper P at the reference position. As shown in FIG. 3, the jogger fence 73 is connected to a drive unit 117 including a stepping motor, a gear train, and the like, and is supported so as to be movable in a direction orthogonal to the paper transport direction. Further, the size of the paper P conveyed to the switchback path 59 is determined by a jogger sensor 119 provided in the switchback path 59. When the paper P is transported to the switchback passage 59, the jogger fence 73 sandwiches the paper P at a predetermined timing according to the size of the paper P determined by the jogger sensor 119, and the paper in a direction orthogonal to the paper transport direction. The position of P is configured so as to be aligned with a reference position that serves as a reference when obtaining the lateral registration amount of the sheet P to be described later.

  The refeed passage 75 is formed by arranging guide plates 79 and 81 facing a guide plate 77 disposed below the horizontal guide plate 71 with a predetermined gap therebetween. The end of the refeed path 75 on the guide plate 81 side is connected to the sheet conveyance path of the color copying machine 1 so that the sheet P is conveyed again to the image forming section 3 through the refeed path 75. It is configured. A sensor 40 having a light receiving element and a light emitting element for detecting a lateral registration adjustment image 34 (described later) formed on the surface of the sheet P is provided near the center of the sheet refeed path 75 in the sheet conveyance direction. It is arranged facing the plate 79 direction. The sensor 40 is arranged on the center line in the direction orthogonal to the conveyance direction of the paper P that is aligned with the reference position by the jogger fence 73 and conveyed to the refeed passage 75. That is, the sensor 40 detects the lateral registration adjustment image 34 formed on the paper P conveyed along the refeed path 75 at a constant speed along the center line.

  The reverse paper discharge path 61 is formed by disposing another guide plate 83 facing the back surface of the above-described guide plate 65 with a predetermined gap therebetween, and the upper part thereof is in the vicinity of the paper discharge roller pair 45 of the color copying machine 1. It is open.

  A reversal switching claw 85 is supported on the guide plate 65 forming the inner surface of the introduction passage 57 so as to be rotatable about a support shaft 87. The reverse switching claw 85 guides the paper P discharged from the fixing unit 31 to the introduction passage 57 in the state shown in FIG. 2, and from the fixing unit 31 in the state rotated clockwise from the state shown in FIG. The discharged paper P is guided to the paper discharge tray 35.

  Further, a paper supply / discharge switching claw 89 is rotatably supported around a support shaft 91 at a branch point where the switchback passage 59 branches from one end to the refeed passage 75 and the reverse paper discharge passage 61. Yes. The paper supply / discharge switching claw 89 guides the paper P from the switchback path 59 to the reverse paper discharge path 61 in the state shown in FIG. 2, and in the state rotated counterclockwise from the state shown in FIG. Is led from the switchback passage 59 to the refeed passage 75.

  A reverse roller 95 and a reverse branch plate 97 for conveying the paper P toward the switchback passage 59 are provided below the introduction passage 57. A plurality of reverse rollers 95 are arranged in an axial direction perpendicular to the paper surface in FIG. The reverse branch plate 97 is urged so as to protrude into the gap between the plurality of reverse rollers 95. When the paper P enters between the reversing roller 95 and the reversing branch plate 97, the paper P is pressed against the reversing roller 95 by the urging force of the reversing branch plate 97, thereby generating a conveying force. It is conveyed toward.

  The switchback path 59 includes a reverse drive roller 99 that conveys the paper P toward the refeed path 75 or the reverse discharge path 61, and a pinch roller 101 that is in contact with and separated from the upper outer peripheral surface of the reverse drive roller 99. Is arranged. The pinch roller 101 is rotatably supported by a roller holder 105 that is driven in the vertical direction.

  Further, a conveyance driving roller 107 and a conveyance driven roller 109 are arranged in contact with each other at a branch point between the refeed path 75 and the reverse sheet discharge path 61. In the refeed path 75, a transport driving roller 111 and a transport driven roller 113 are arranged in contact with each other, and the refeed path 75 is configured to transport the paper P at a constant speed. Yes.

  The control unit 2 shown in FIG. 4 includes a CPU, a storage device, and the like (not shown), is disposed at an appropriate position of the color copying machine 1, and is connected to the sensor 40 and the image forming unit 3. When copying the document, the control unit 2 controls the optical writing unit 15 of the image forming unit 3 so that writing light carrying image information is provided at the image writing timing stored in the control unit 2 in advance. An operation of writing to the photoreceptors 11Y, 11M, 11C, and 11B is performed. Further, the control unit 2 obtains the lateral registration amount from the reference position of the lateral registration adjustment image 34 detected by the sensor 40, and the image writing timing on the paper P in the image forming unit 3, that is, the photoconductors 11Y, 11M, The image writing timing of the writing light to 11C and 11B is corrected.

  The lateral registration adjustment image 34 shown in FIGS. 5A and 5B is stored in the control unit 2 in advance, and the optical writing unit 15 is controlled under the control of the control unit 2 in a test mode to be described later. Are written at predetermined positions on the photoconductors 11Y, 11M, 11C, and 11B and transferred to the paper P by the secondary transfer means 27. The lateral registration adjustment image 34 is formed near the center of the rectangular paper P having a length 2a perpendicular to the paper conveyance direction in the direction perpendicular to the paper conveyance direction, and orthogonal to the paper conveyance direction. The reference image line 36 having a length of 2b and the detection image line 38 formed at an angle of 45 ° with respect to the sheet conveyance direction from one end of the reference image line 36 is included. The reference image line 36 and the detection image line 38 are formed at the same position in the direction orthogonal to the paper transport direction. Further, the reference image line 36 is formed on the front side in the paper conveyance direction, and the detection image line 38 is formed on the rear side in the paper conveyance direction.

  The paper P transported from the paper feed cassettes 5 a, 5 a, 5 a of the paper feed unit 5 and the manual transfer tray 49 to the secondary transfer unit 27 of the image forming unit 3 is aligned at a reference position that is aligned by the jogger fence 73 from the beginning. In other words, that is, when the lateral registration amount of the paper P is 0, as shown in FIG. 5A, the lateral registration adjustment image 34 is formed at the center in the direction orthogonal to the paper transport direction of the paper P. The That is, in this case, the center line (one-dot chain line in the figure) of the paper P coincides with the center line (one-dot chain line in the figure) of the horizontal registration adjustment image 34.

  On the other hand, the sheet P transported from the sheet feeding cassettes 5 a, 5 a, 5 a of the sheet feeding unit 5 to the secondary transfer unit 27 of the image forming unit 3 from the sheet feeding cassettes 5 a, 5 a, 5 a is In the case where the direction is shifted by c, that is, when the lateral registration amount of the paper P is c, the lateral registration adjustment image 34 is orthogonal to the paper transport direction of the paper P as shown in FIG. It is formed at a position deviated by c from the center in the direction to be. That is, in this case, the center line of the paper P (two-dot chain line in the figure) and the center line of the horizontal registration adjustment image 34 (one-dot chain line in the figure) are shifted by c.

  In the lateral registration adjustment image 34, if the detection image line 38 is inclined obliquely with respect to the paper conveyance direction, the inclination angle is not limited to 45 °. Further, one end of the detection image line 38 does not need to coincide with one end of the reference image line 36, and the detection image line 38 and the reference image line 36 are detected so that the sensor 40 can detect both the image lines 36 and 38. It suffices if they are formed at the same position in the direction orthogonal to the paper transport direction. Further, the size of the horizontal registration adjustment image 34 may be a size that allows the sensor 40 to detect the horizontal registration adjustment image 34 even if a large lateral registration in the cm order occurs on the paper P.

  Next, a series of operations of the color copying machine 1 will be described with reference to FIGS. The color copying machine 1 has two types of modes: a normal copying mode in which normal document copying is performed and a test mode that is performed when the color copying machine 1 is set.

  In the normal copy mode, the document set on the tray 7c of the automatic document feeder 7a is sent onto the contact glass, read by the scanner 7b, and the image information is transmitted to the optical writing unit 15. The control unit 2 controls the optical writing unit 15 to perform the operation of writing the writing light carrying the image information to the photoconductors 11Y, 11M, 11C, and 11B at the image writing timing stored in the control unit 2 in advance. Then, electrostatic latent images are formed on the photoconductors 11Y, 11M, 11C, and 11B. The photoconductors 11Y, 11M, 11C, and 11B rotate in the direction of the arrow in FIG. 1, and the electrostatic latent image is converted into a toner image by the developing unit 17. A toner image of a different color is developed on each of the photoconductors 11Y, 11M, 11C, and 11B, and is primarily transferred onto the intermediate transfer belt 9 sequentially from the photoconductors 11Y to 11B. On the other hand, the paper P is conveyed from the paper supply unit 5 to the registration roller pair 47 and stops and stands by. The sheet P is conveyed from the registration roller pair 47 in accordance with the timing at which the image primarily transferred onto the intermediate transfer belt 9 is conveyed, and the images on which the respective colors are primarily transferred by the secondary transfer unit 27 are collectively collected. Second transfer is performed on the paper P. The sheet P that has been secondarily transferred is conveyed as it is to the fixing unit 31 by the transfer belt 27 c of the secondary transfer unit 27. The sheet P on which the image is fixed is discharged as it is to the sheet discharge tray 35 or is conveyed to the reverse conveyance unit 37.

  Here, the timing of image writing of the writing light in the optical writing unit 15 to the photoconductors 11Y, 11M, 11C, and 11B will be described in detail. The control unit 2 issues a DETP signal, which is a reference signal for starting scanning, for each horizontal scanning of writing light by the polygon mirror of the optical writing unit 15. After the DETP signal is generated and the delay time t stored in the control unit 2 elapses, the optical writing unit 15 starts horizontal scanning of the writing light to the photoconductors 11Y, 11M, 11C, and 11B. And write image information. As will be described later, the delay time t is corrected by the amount of lateral registration from the reference position of the paper P. That is, the image writing timing of the optical writing unit 15 in the direction orthogonal to the paper transport direction is corrected based on the lateral registration amount of the paper P via the delay time t.

  In the test mode, first, the lateral registration adjustment image 34 stored in the control unit 2 is written from the optical writing unit 15 to predetermined positions of the photoconductors 11Y, 11M, 11C, and 11B. The written lateral registration adjusting image 34 is primarily transferred to the intermediate transfer belt 9 in the same manner as in the normal copying mode, and then is conveyed in the conveying direction on the surface of the sheet conveyed from the paper supply unit 5 via the registration roller pair 47. Secondary transfer is performed near the center of the orthogonal direction. At this time, when the paper P is transported to the image forming unit 3 by being shifted rightward from the reference position by c due to a mechanical assembly error of the paper feed cassette 5a or the like, that is, the lateral registration amount is c. In this case, as shown in FIG. 5B, the lateral registration adjustment image 34 is formed by being shifted from the center line of the paper P by c. Subsequently, the paper P is conveyed to the reverse conveyance unit 37. That is, the reverse switching claw 85 is rotated to the position shown in FIG. 2, and the paper P conveyed from the fixing unit 31 with the lateral registration adjustment image 34 facing upward is switched back from the introduction passage 57 by the reverse roller 95. It is conveyed to the passage 59 and is reversed so that the horizontal registration adjustment image 34 faces downward. When it is confirmed that the rear end of the paper P has passed through the reverse branch plate 97, the jogger fence 73 is driven to sandwich the paper P from both sides, and the position of the paper P in the direction perpendicular to the paper transport direction is used as a reference. Align to position. At this time, since the reverse roller 95 is retracted upward, the jogger operation of the paper P is not hindered. Subsequently, the roller holder 105 is lowered together with the pinch roller 101, and the reverse rotation driving roller 99 and the conveyance driving roller 107 are rotated counterclockwise at the same peripheral speed, thereby refeeding the paper P in the switchback passage 59. It is conveyed toward the passage 75.

  At this time, the paper supply / discharge switching claw 89 is rotated counterclockwise from the position shown in FIG. 2, and the paper P conveyed from the switchback passage 59 has the lateral registration adjustment image 34 facing upward. In this state, the sheet is transported to the refeed path 75 and is transported through the refeed path 75 at a constant speed by the transport drive roller 111 and the transport driven roller 113. In the process of transporting the paper P in the refeed path 75, the lateral registration adjustment image 34 is detected by the sensor 40 disposed on the center line of the paper P. That is, as the paper P is transported, the reference image line 36 present first in the front of the paper transport direction is detected along the center line of the paper P, and then the detected image line 38 present rearward in the paper transport direction. Is detected. Detection information between the reference image line 36 and the detection image line 38 is transmitted to the control unit 2, and is a time difference from the detection of the reference image line 36 to the detection of the detection image line 38 in the control unit 2. Detection time difference is required. This detection time difference is compared with a predetermined value stored in advance in the control unit 2 to obtain the lateral registration amount of the paper P. Here, the predetermined value stored in advance means that, as shown in FIG. 5A, when the lateral registration amount of the paper P is 0, that is, at the reference position where the paper P is aligned by the jogger fence 73 in advance. In a state of being aligned, the reference image line 36 and the detection image line 38 when it is assumed that the lateral registration adjusting image 34 has been formed on the paper P from the paper feeding unit 5 to the secondary transfer unit 27 of the image forming unit 3. It means the difference in detection time. In this case, since the distance between the reference image line 36 and the detected image line 38 along the center line of the paper P is b, if the transport speed of the paper P in the refeed path 75 is v, the predetermined value is b / v.

  When the lateral registration amount in the right direction of the paper P is c, when the paper P is aligned at the reference position by the jogger fence 73, the paper P on which the lateral registration adjustment image 34 is formed is relatively c to the left. Just moved. Therefore, the distance between the reference image line 36 and the detected image line 38 along the center line of the paper P is b + c, and the reference image line 36 and the detected image line detected by the sensor 40 arranged on the center line of the paper P. The detection time difference from 38 is (b + c) / v. Here, since b and v are known, the control unit 2 compares the detection time difference (b + c) / v between the reference image line 36 and the detection image line 38 with a predetermined value b / v, so that the control unit 2 can detect the lateral registration of the paper P. The quantity c can be determined. The control unit 2 corrects the image writing timing in the direction orthogonal to the paper conveyance direction of the writing light in the optical writing unit 15 to the photoconductors 11Y, 11M, 11C, and 11B from the lateral registration amount thus obtained. Thus, an image is always formed at a predetermined position on the paper P in the normal copy mode. That is, the control unit 2 obtains the delay time t from when the DETP signal is issued until the image is actually written to the photoconductors 11Y, 11M, 11C, and 11B according to the lateral registration amount c of the paper P. Remember. Then, in the normal copying mode, image writing is performed on the photoconductors 11Y, 11M, 11C, and 11B using the delay time t. As a result, an image is always formed on the paper P at a predetermined position regardless of the amount of lateral registration.

  The sheet P transported through the refeed path 75 as described above is transported again to the image forming unit 3 through the sheet transport path of the color copying machine 1 and discharged to the sheet discharge tray 35.

  Since the delay time t may be different for each of the plurality of paper feed cassettes 5a, 5a, 5a and the manual feed tray 49 provided in the paper feed unit 5, the control unit 2 causes the paper feed cassettes 5a, 5a, 5a and the manual feed tray 49 are obtained and stored. Specifically, in the test mode, the lateral registration adjustment image 34 is formed on the paper P conveyed from the respective paper feed cassettes 5a, 5a, 5a and the manual feed tray 49, and the paper feed cassette 5a is subjected to the above-described process. , 5a, 5a and the manual feed tray 49 are obtained, and the delay time t for each of the paper feed cassettes 5a, 5a, 5a and the manual feed tray 49 is calculated and stored from the lateral resist quantity.

  Further, when correcting the lateral registration on the back side of the paper, the control unit 2 forms the horizontal registration adjustment image 34 again on the back side of the paper P that has been transported again to the image forming unit 3 through the above-described process. The sheet P is conveyed again to the reverse conveying unit 37, the lateral registration amount on the back surface of the sheet P is obtained according to the same procedure as described above, and the delay time t is obtained from the lateral registration amount and stored. When correcting the lateral registration amount on the back side of the sheet, the sheet P passes through the reverse conveyance unit 37 twice.

  As described above, the color copying machine 1 of this embodiment forms the horizontal registration adjustment image 34 in the image forming unit 3 at a predetermined position on the surface of the paper P conveyed from the paper supply unit 5, and this horizontal registration adjustment Using the image 34, the control unit 2 obtains the lateral registration amount from the reference position of the paper P, and corrects the image writing timing in the direction orthogonal to the paper transport direction to the paper P from the lateral registration amount. The lateral registration of the paper P can be adjusted without preparing a dedicated paper on which a registration mark or the like is formed in advance.

  Further, the lateral registration adjustment image 34 includes a reference image line 36 formed orthogonal to the paper transport direction and a detection image line 38 formed to be inclined with respect to the paper transport direction. The detection time difference from when the line 36 is detected to when the detected image line 38 is detected changes according to the lateral registration amount of the paper P. By comparing this detection time difference with a predetermined value stored in the control unit 2 in advance, the lateral registration amount of the paper P can be obtained, and the image writing timing can be corrected.

  Further, since the lateral registration amount is obtained for each of the paper feed trays 5 a, 5 a, 5 a and the manual feed tray 49 and the image writing timing is corrected, each of the paper feed trays 5 a, 5 a, 5 a and the manual feed tray 49 is corrected. Variation in lateral resist amount can be suppressed. In the color copying machine 1 of this embodiment, the variation in the amount of lateral resist between the paper feed trays 5a, 5a, 5a and the manual feed tray 49 can be suppressed within 1 mm.

  Further, the lateral registration adjustment image 34 is formed on the back surface of the paper P that has been transported to the image forming unit 3 through the refeed passage 75, and is transported to the reverse transporting unit 37 again so that the lateral resist amount on the back surface of the paper P Since the image writing timing is corrected, variation in the lateral resist amount on the front and back surfaces of the paper P can be suppressed. In the color copying machine 1 of this embodiment, the variation in the amount of lateral resist between the front and back surfaces of the paper P is suppressed to within 0.5 mm.

1 is a side view illustrating a schematic configuration of an image forming apparatus. It is a side view which shows schematic structure of a reverse conveyance part. It is a principal part expansion perspective view near the jogger fence of a reverse conveyance part. 2 is a functional block diagram of the image forming apparatus. FIG. 4A and 4B are schematic diagrams of a lateral registration adjustment image formed on a sheet, where FIG. 5A shows a case where the lateral registration amount is 0, and FIG. 5B shows a case where the lateral registration amount is c.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color copier 2 Control part 3 Image formation part 5 Paper feed part 7 Image reading part 9 Intermediate transfer belt 11Y, 11M, 11C, 11B Photoconductor 13 Charging roller 15 Optical writing unit 17 Development unit 19 Primary transfer roller 21 Cleaning Unit 23 Static elimination lamps 25a, 25b, 25c Support roller 27 Secondary transfer means 29 Belt cleaning unit 31 Fixing unit 34 Horizontal registration adjustment image 35 Paper discharge tray 36 Reference image line 37 Reverse conveying section 38 Detected image line 40 Sensor 45 Paper discharge Roller pair 47 Registration roller pair 49 Manual feed tray 51 Paper feed roller 57 Introduction path 59 Switchback path 61 Reverse paper discharge path 63, 65, 67, 69, 71, 77, 79, 81, 83 Guide plate 73 Jogger fence 75 Feeding passage 85 Reverse switching claw 87, 91 Support shaft 89 Feed / discharge switching claw 95 Reverse roller 97 Reverse branch plate 99 Reverse drive roller 101 Pinch roller 105 Roller holder 107, 111 Transport drive roller 109, 113 Transport driven roller 115 Paper discharge path 117 Drive unit 119 Jogger sensor

Claims (5)

An image forming unit forms a lateral resist adjustment image on the surface of the transfer material conveyed from the paper supply unit and conveys it to the reverse conveyance unit. The reverse conveyance unit reverses the front and back of the transfer material, and then transfers the transfer material. In the image forming apparatus transported again to the image forming unit,
A sensor that is provided in the reversal conveyance unit and detects the lateral registration adjustment image, and obtains a lateral registration amount from a reference position of the lateral registration adjustment image detected by the sensor, and based on the lateral registration amount, the image An image forming apparatus comprising: a control unit that controls to correct an image writing timing in a direction orthogonal to a transfer material conveyance direction to the transfer material in the forming unit. An image forming unit that forms a lateral resist adjustment image on the surface of the transfer material conveyed from the paper supply unit, and a reverse conveyance that reverses the front and back of the transfer material conveyed from the image forming unit and conveys the image again to the image forming unit. And a control unit that controls the image forming unit,
The reversal conveyance unit detects the lateral registration adjustment image in a jogger member that aligns the position of the conveyed transfer material in a direction orthogonal to the transfer material conveyance direction with a reference position, and a transfer material aligned with the reference position. And a sensor that
The control unit obtains a lateral registration amount from a reference position of the lateral registration adjustment image detected by the sensor, and based on the lateral registration amount, in a direction orthogonal to the transfer material conveyance direction to the transfer material in the image forming unit. An image forming apparatus that controls to correct an image writing timing. The lateral resist adjustment image includes a reference image line formed orthogonal to the transfer material conveyance direction and a detection image line formed inclined with respect to the transfer material conveyance direction,
3. The image forming apparatus according to claim 1, wherein the control unit obtains the lateral registration amount by comparing a detection time difference between the reference image line and the detection image line by the sensor with a predetermined value stored in advance in the control unit. .   A plurality of the sheet feeding units are provided, and for the transfer material conveyed from each sheet feeding unit toward the image forming unit, a lateral registration amount for each sheet feeding unit is obtained by the control unit, and the lateral registration is obtained. The image forming apparatus according to claim 1, wherein the image writing timing for each sheet feeding unit is corrected based on the amount. Forming the lateral registration adjustment image on the back surface of the transfer material conveyed again from the reverse conveyance unit to the image forming unit, and configured to convey the transfer material to the reverse conveyance unit;
5. The image according to claim 1, wherein the lateral resist amount on the back surface of the transfer material is obtained by the control unit, and the image writing timing on the back surface of the transfer material is corrected based on the lateral resist amount. Forming equipment.

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