US20230017154A1 - Sheet conveyance apparatus, image forming apparatus, and image forming system - Google Patents
Sheet conveyance apparatus, image forming apparatus, and image forming system Download PDFInfo
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- US20230017154A1 US20230017154A1 US17/841,869 US202217841869A US2023017154A1 US 20230017154 A1 US20230017154 A1 US 20230017154A1 US 202217841869 A US202217841869 A US 202217841869A US 2023017154 A1 US2023017154 A1 US 2023017154A1
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- edge
- abutment surface
- reference member
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
- B65H7/02—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors
- B65H7/06—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed
- B65H7/08—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed responsive to incorrect front register
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H9/00—Registering, e.g. orientating, articles; Devices therefor
- B65H9/06—Movable stops or gauges, e.g. rising and falling front stops
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H5/00—Feeding articles separated from piles; Feeding articles to machines
- B65H5/36—Article guides or smoothers, e.g. movable in operation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
- B65H7/02—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors
- B65H7/06—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed
- B65H7/10—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed responsive to incorrect side register
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
- B65H7/20—Controlling associated apparatus
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H9/00—Registering, e.g. orientating, articles; Devices therefor
- B65H9/004—Deskewing sheet by abutting against a stop, i.e. producing a buckling of the sheet
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H9/00—Registering, e.g. orientating, articles; Devices therefor
- B65H9/16—Inclined tape, roller, or like article-forwarding side registers
- B65H9/166—Roller
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H2511/00—Dimensions; Position; Numbers; Identification; Occurrences
- B65H2511/20—Location in space
- B65H2511/24—Irregularities, e.g. in orientation or skewness
-
- B65H2511/242—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H2701/00—Handled material; Storage means
- B65H2701/10—Handled articles or webs
- B65H2701/13—Parts concerned of the handled material
- B65H2701/131—Edges
- B65H2701/1315—Edges side edges, i.e. regarded in context of transport
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H2801/00—Application field
- B65H2801/03—Image reproduction devices
- B65H2801/06—Office-type machines, e.g. photocopiers
Definitions
- This disclosure relates to a sheet conveyance apparatus conveying a sheet, and an image forming apparatus and an image forming system provided with same.
- a registration apparatus of an obliquely conveying registration type which conveys a sheet while abutting a side edge of the sheet against a reference member is suggested formed between a reference edge and a non-reference edge adjacent to the reference edge is determined using a side edge of the sheet as the reference edge. Then, based on this angle, an angle of the reference member is adjusted such that the deviation in margins at the reference and nonreference edges becomes even.
- a post-processing apparatus is coupled to an image forming apparatus such as a printer, and the post-processing such as a cutting process and a stapling process is performed in the post-processing apparatus.
- an edge of the sheet is usually used as a processing reference in the post-processing, and, sometimes, there is a case where a reference (side edge) for the image formation and a skew correction in the image forming apparatus does not match the processing reference for the post-processing.
- the post-processing is performed using an edge adjacent to the side edge as the reference in the post-processing apparatus, a positional variation of an image on the sheet after the post-processing occurs. Therefore, especially in a case where a squareness of the sheet is low, there is a risk that the quality of the final deliverables is degraded.
- a sheet conveyance apparatus includes a conveyance guide configured to guide a sheet along a conveyance center line extending in a conveyance direction, a reference member including an abutment surface extending along the conveyance direction, a conveyance unit configured to convey the sheet while abutting a first edge of the sheet against the abutment surface of the reference member, a detection unit configured to detect a first angle formed between the first edge of the sheet and a second edge adjacent to the first edge, a moving unit configured to move the reference member so as to change a second angle formed between the abutment surface and the conveyance center line, and a control unit configured to perform a movement process in which the moving unit moves the reference member such that, when the first angle is referred to as ⁇ , the second angle becomes an absolute value of a difference 90 degrees minus ⁇ .
- FIG. 1 is an overall schematic diagram showing an image forming system relating to this embodiment.
- FIG. 2 A is a plan view showing a skew correction unit.
- FIG. 2 B is a plan view of the skew correction unit showing a state where the sheet is conveyed by an upstream conveyance portion.
- FIG. 3 A is a plan view of the skew correction unit showing a state where a reference member has been pivoted.
- FIG. 3 B is a plan view of the skew correction unit showing a state where the sheet is conveyed by an obliquely conveying portion.
- FIG. 4 B is a plan view of the skew correction unit showing a state where the sheet has been slid by a registration roller pair.
- FIG. 5 is a plan view of the skew correction unit showing a state where the sheet has been further slid by the registration roller pair.
- FIG. 6 A is a diagram showing an example of the sheet and an image position.
- FIG. 6 B is a diagram showing the other example of the sheet and the image position.
- FIG. 6 C is a diagram showing an error in the image position among the sheets.
- FIG. 7 A is a diagram for describing a method for a calculation of an angle of an abutment reference edge.
- FIG. 7 B is a diagram for describing a method for a calculation of an angle of a non-reference edge
- FIG. 8 is a graph indicating a difference in ON timings of pre-registration sensors.
- FIG. 9 A is a diagram for describing the moving velocity of the registration roller pair.
- FIG. 9 B is a diagram for describing the moving velocity of the registration roller pair.
- FIG. 10 is a diagram for describing a method for a calculation of a slide correction amount of the registration roller pair.
- FIG. 11 is a diagram for describing a method for calculations of an angle of the reference member and an edge position correction amount of the sheet in duplex printing.
- FIG. 12 is a control block diagram relating to this embodiment.
- FIG. 13 is a flowchart showing skew correction control.
- an image forming system 1 relating to this embodiment includes an image forming apparatus 100 and a post-processing apparatus 600 coupled to the image forming apparatus 100 .
- the image forming apparatus 100 is a full color laser beam printer of an electrophotographic system and an intermediate transfer tandem system. Further, the image forming apparatus 100 is a print on demand (POD) machine capable of performing printing including but not limited to general office use, and is able to use various kinds of sheets, serving as a recording medium, including paper such as standard paper and an envelope, coated paper, a plastic film such as a sheet for an overhead projector (OHT), and a cloth.
- POD print on demand
- control unit 9 including, for example, an arithmetic unit such as a central processing unit (CPU), a memory such as a random-access memory (RAM), and a memory unit such as a read-only memory (ROM).
- CPU central processing unit
- RAM random-access memory
- ROM read-only memory
- the image forming apparatus 100 includes an image forming unit 513 , a sheet feed unit 100 B, and a conveyance apparatus 100 D.
- the image forming unit 513 includes four process cartridges PY, PM, PC, and PBk forming four colors of toner images of yellow (Y), magenta (M), cyan (C), and black (K), and exposing units 511 Y, 511 M, 511 C, and 511 Bk.
- the four process cartridges PY, PM, PC, and PBk are the same in a configuration except for differences in colors in which images are formed. Accordingly, only the configuration and an image forming process of the process cartridge PY will be described herein, and descriptions of the other process cartridges PM, PC, and PBk will be omitted.
- the process cartridge PY includes a photosensitive drum 508 , a charge roller, not shown, a cleaner 509 , and a developing unit 510 .
- the photosensitive drum 508 is constructed by coating an organic photoconductive layer on an outer circumferential surface of an aluminum cylinder, and rotated by a drive motor, not shown. Further, an intermediate transfer belt 506 rotated by a drive roller 504 in an arrow G direction is disposed in the image forming unit 513 , and wound around a tension roller 505 , the drive roller 504 , and a secondary transfer inner roller 503 .
- Primary transfer rollers 507 Y, 507 M, 507 C, and 507 Bk are disposed inside of the intermediate transfer belt 506 , and a secondary transfer outer roller 56 is disposed outside of the intermediate transfer belt 506 so as to face the secondary transfer inner roller 503 .
- the sheet feed unit 100 B includes a sheet storage portion 51 storing the sheet S, a lift-up unit 52 ascending and descending while stacking the sheet S, and a sheet feed portion 53 feeding the sheet S on the lift-up unit 52 .
- a pneumatic conveyance type pneumatically sucking and conveying the sheet S by separating the sheet into one sheet at a time is employed in this embodiment, it is not limited to this.
- the sheet feed portion 53 it is acceptable to employ a roller conveyance type conveying the sheet by a pickup roller and the like, and an electrostatic attraction type sucking and conveying the sheet by electrostatic force.
- the conveyance apparatus 100 D includes a conveyance unit 54 , a skew correction unit 55 , a pre-fixing conveyance unit 57 , a fixing unit 58 , a branch conveyance unit 59 , a reverse conveyance unit 501 , and a duplex conveyance unit 502 . These units each include a conveyance roller pair for conveying the sheet.
- the fixing unit 58 includes a fixing nip portion 58 a for conveying the sheet by nipping.
- the exposing unit 511 Y irradiates a laser beam corresponding to the image signal on the photosensitive drum 508 of the process cartridge PY.
- a surface of the photosensitive drum 508 has been uniformly charged in a predetermined polarity and voltage beforehand, and an electrostatic latent image is formed on the surface by the laser beam irradiated from the exposing unit 511 Y via a mirror.
- the electrostatic latent image formed on the photosensitive drum 508 is developed by the developing unit 510 , and a toner image of yellow (Y) is formed on the photosensitive drum 508 .
- the exposing units 511 M, 511 C, and 511 Bk irradiate the respective photosensitive drums of the process cartridges PM, PC, and PBk with the laser beam, and toner images of magenta (M), cyan (C), and black (K) are formed on the respective photosensitive drums.
- the toner images of the respective colors formed on the respective photosensitive drums are transferred onto the intermediate transfer belt 506 by the primary transfer rollers 507 Y, 507 M, 507 C, and 507 Bk. Then, by the intermediate transfer belt 506 rotated by the drive roller 504 , a full color toner image is conveyed to a secondary transfer nip T 2 formed by the secondary transfer inner and outer rollers 503 and 56 .
- a toner remained on the photosensitive drum 508 is collected by the cleaner 509 .
- the image forming processes of the respective colors are performed in the timing superimposing the toner image on an upstream toner image primarily transferred onto the intermediate transfer belt 506 .
- the sheet S is fed from the sheet feed unit 100 B, and the sheet S is conveyed to a duplex conveyance path R of the duplex conveyance unit 502 via a conveyance path 91 . Then, the sheet S passes a conveyance path 54 a of the conveyance unit 54 , and is conveyed to the skew correction unit 55 . The skew of the sheet S is corrected by the skew correction unit 55 , and the sheet S is conveyed to the secondary transfer nip T 2 by a registration roller pair 7 in predetermined conveyance timing.
- the full color toner image on the intermediate transfer belt 506 is transferred onto a first surface (front surface) of the sheet S by a secondary transfer bias applied to the secondary transfer outer roller 56 . A remained toner remained on the intermediate transfer belt 506 is collected by a belt cleaner 2 .
- the sheet S onto which the toner image has been transferred is conveyed to the fixing unit 58 by the pre-fixing conveyance unit 57 . Then, the sheet S is guided to the fixing nip portion 58 a of the fixing unit 58 , and, by proving predetermined heat and pressure, the toner is melted and bonded (fixed). With respect to the sheet S passed through the fixing unit 58 , the path selection of selecting a path between the conveyance to the post-processing apparatus 600 and the conveyance to the reverse conveyance unit 501 is performed by the branch conveyance unit 59 .
- the so called facedown conveyance conveying the sheet S such that the sheet S is conveyed to a sheet discharge tray 500 with the sheet S inverted so as to turn the first surface, on which the image has been formed at the secondary transfer nip T 2 , to the underside.
- the sheet S is conveyed from the branch conveyance unit 59 to the post-processing apparatus 600 .
- the sheet S is conveyed to the reverse conveyance unit 501 by the branch conveyance unit 59 .
- the sheet S is switchbacked by the reverse conveyance unit 501 .
- the sheet S which has been switchbacked is conveyed from the reverse conveyance unit 501 to the duplex conveyance unit 502 , and guided to the conveyance unit 54 and the skew correction unit 55 .
- the image is formed on a second surface (back surface) of the sheet S at the secondary transfer nip T 2 , and discharged to the post-processing apparatus 600 .
- the post-processing apparatus 600 is coupled to the image forming apparatus 100 , and includes a conveyance unit 601 , a swing roller 603 , a stapling unit 620 , and a sheet discharge tray 610 .
- the stapling unit 620 includes a process tray 602 for loading the sheet S, a regulation plate 604 for regulating a position of a trailing edge of the sheet S stacked on the process tray 602 , and a stapler 605 for performing a stapling process on the sheet S.
- the post-processing apparatus 600 receives the sheet S from the branch conveyance unit 59 of the image forming apparatus 100 , and conveys the sheet S by the conveyance unit 601 .
- the swing roller 603 is capable of pivoting between upper and lower positions, and positioned in the upper position when the conveyance unit 601 discharges the sheet S to the sheet discharge tray 610 . When the sheet S has been discharged to the process tray 602 , the swing roller 603 pivots from the upper position to the lower position.
- the swing roller 603 discharges the sheet S to the sheet discharge tray 610 as it is.
- the swing roller 603 conveys the sheet S on the process tray 602 toward the regulation plate 604 . Then, since the trailing edge of the sheet S abuts against the regulation plate 604 , a position of the sheet S in a conveyance direction is regulated, and also the skew of the sheet S is corrected.
- the stapler 605 After an alignment process as described above has been performed with respect to a predetermined number of sheets of the sheet S, the stapler 605 performs the stapling process with respect to the predetermined number of sheets of the sheet S. A sheet bundle which has been provided with the stapling process is discharged to the sheet discharge tray 610 by the swing roller 603 .
- the skew correction unit 55 serving as a sheet conveyance apparatus, includes, from upstream toward downstream in the conveyance direction F, an upstream conveyance portion 41 , an obliquely conveying portion 42 , and a slide portion 43 .
- the upstream conveyance portion 41 includes an upstream conveyance guide 11 , conveyance roller pairs 14 a and 14 b, a contact image sensor (CIS) sensor 101 , and pre-registration sensors 102 a and 102 b.
- CIS contact image sensor
- the upstream conveyance guide 11 constructs a conveyance guide portion 45 guiding the sheet S in the conveyance direction F in the skew correction unit 55 .
- the conveyance guide portion 45 forms a conveyance path CP through which the sheet S passes, and a conveyance center line CT 1 of the conveyance path CP, serving as a conveyance path, extends in the conveyance direction F.
- a center standard using the conveyance center line CT 1 as a reference for the conveyance of the sheet S and the image formation in the image forming unit 513 is adopted.
- the conveyance roller pair 14 b is disposed downstream of the conveyance roller pair 14 a in the conveyance direction F, and the CIS sensor 101 is disposed between the conveyance roller pairs 14 a and 14 b in the conveyance direction F. Further, the pre-registration sensors 102 a and 102 b are disposed downstream of the conveyance roller pair 14 b in the conveyance direction F.
- the CIS sensor 101 and the pre-registration sensors 102 a and 102 b construct a detection unit 47 detecting an angle ⁇ , described later. To be noted, in the detection unit 47 , it is acceptable to include part of the control unit 9 for determining the angle ⁇ based on detection results of the respective sensors. Further, the detection unit 47 is not limited to the configuration of this embodiment, and it is acceptable to determine the angle ⁇ by imaging the sheet, for example, by a camera and the like.
- the CIS sensor 101 is disposed so as to be capable of detecting a position of an abutment reference edge Es which is one side of the sheet S in a width direction W orthogonal to the conveyance direction F. In particular, by acquiring the image at fixed time intervals, the CIS sensor 101 is capable of acquiring a positional change of the abutment reference edge Es as a sequential image at the time when the sheet S passes through a detection area of the CIS sensor 101 .
- the pre-registration sensors 102 a and 102 b are disposed in symmetrical positions in the width direction W with respect to the conveyance center line CT 1 .
- the pre-registration sensors 102 a and 102 b each output a signal of Low in a case where the sheet S is absent in a detection position, and output a signal of High in a case where the sheet S is present in the detection position. Therefore, by a switch of the signal from Low to High, it is possible to detect the timing when the sheet S passes through the respective detection positions of the pre-registration sensors 102 a and 102 b.
- the obliquely conveying portion 42 includes the fixed guide 12 and an obliquely conveying unit 26 , and the obliquely conveying unit 26 includes the movable guide 25 , obliquely conveying roller pairs 24 a to 24 c, and a reference member 20 .
- the abutment reference edge Es of the sheet S is abutted against the reference member 20
- the reference member 20 includes an abutment surface 20 a extending along the conveyance direction F.
- the reference member 20 is pivotable around a pivot shaft 21 as a center, and urged toward a cam 22 by an urging spring 23 .
- a position of the reference member 20 in a pivot direction is determined by abutting against the cam 22 , and, since the cam 22 is rotatably driven by an angle adjustment motor 31 , the reference member 20 pivots around the pivot shaft 21 as the center.
- the angle ⁇ serving as a second angle, is an angle formed between the conveyance center line CT 1 and the abutment surface 20 a.
- the angle ⁇ is an angle formed between the conveyance direction F and the abutment surface 20 a.
- Each of the obliquely conveying roller pairs 24 a to 24 c includes a roller pair, and a rotation shaft of at least one side of the roller pair inclines with respect to the width direction W and the conveyance direction F.
- the sheet S is conveyed toward the abutment surface 20 a by the obliquely conveying roller pairs 24 a to 24 c. That is, the obliquely conveying roller pairs 24 a to 24 c, serving as a conveyance unit, conveys the sheet S while abutting the abutment reference edge Es of the sheet S against the abutment surface 20 a of the reference member 20 .
- the sheet S is conveyed in a state where the abutment reference edge Es is in slide contact with the abutment surface 20 a, and a posture of the sheet S follows the abutment surface 20 a.
- the skew of the sheet S is corrected.
- the movable guide 25 , the obliquely conveying roller pairs 24 a to 24 c, and the reference member 20 of the obliquely conveying unit 26 are integrally movable in the width direction W by a slide drive motor 32 . Further, the obliquely conveying unit 26 is movable to a standby position Pw and a retracting position Pe in accordance with a size of the sheet S which is conveyed. In FIGS. 2 A and 2 B , the standby position Pw and the retracting position Pe are indicated by a position of the abutment surface 20 a of the reference member 20 .
- the obliquely conveying unit 26 moves to and waits in the standby position Pw before the sheet S is conveyed.
- the standby position Pw means a position in which an abutting margin Xo is added to an edge position Xp of the sheet S as defined by the center standard.
- the abutting margin Xo is a distance for conveying the sheet S by following the abutment surface 20 a without colliding with an upstream end of the reference member 20 in the conveyance direction F.
- the retracting position Pe is a position in which a retracting distance Xe is added to the standby position Pw, and the retracting distance Xe is a distance for retracting the reference member 20 in the width direction W such that the reference member 20 does not interfere with the conveyance of the sheet S.
- the obliquely conveying unit 26 is positioned in the retracting position Pe when the sheet S is not present in the obliquely conveying portion 42 , and moves to the standby position Pw when the sheet S has entered the obliquely conveying portion 42 , and returns to the retracting position Pe again after the sheet S has been delivered to the registration roller pair 7 .
- the control unit 9 counts a predetermined time from the timing in which the pre-registration sensors 102 a and 102 b have detected a leading edge of the sheet. Then, the control unit 9 controls such that nips of the conveyance roller pairs 14 a and 14 b are released in the timing in which the leading edge of the sheet S reaches the obliquely conveying roller pair 24 a after the predetermined time has passed.
- the slide portion 43 includes the lower conveyance guide 13 , the registration roller pair 7 , a registration drive motor 33 , a registration slide motor 34 , and a pre-registration sensor 103 .
- the registration roller pair 7 serving as a downstream conveyance portion, is disposed downstream of the obliquely conveying roller pairs 24 a to 24 c in the conveyance direction F, and conveys the sheet S in the conveyance direction F.
- the pre-registration sensor 103 is disposed upstream of the registration roller pair 7 in the conveyance direction F, and, similar to the pre-registration sensors 102 a and 102 b, is capable of detecting the timing of the sheet S passing through the detection position.
- the registration roller pair 7 is rotatable by the registration drive motor 33 , and slidable in the width direction W by the registration slide motor 34 . After the sheet S has been delivered from the obliquely conveying roller pairs 24 a to 24 c, so as to align a position of the sheet S with an image forming position, the registration roller pair 7 slides the sheet S in the width direction W in a state nipping the sheet S. A movement amount of the registration roller pair 7 in the width direction W at this time is the sum of the abutting margin Xo and a slide correction amount Xf, described later.
- the control unit 9 releases nips of the obliquely conveying roller pairs 24 a to 24 c based on the timing in which the pre-registration sensor 103 has detected the sheet S. Further, the control unit 9 releases a nip of the registration roller pair 7 based on the timing in which the sheet S has been delivered to the secondary transfer nip T 2 , and returns the registration roller pair 7 to a standby position before a slide movement.
- FIGS. 6 A and 6 B For example, with respect to a sheet A shown in FIG. 6 A and a sheet B shown in FIG. 6 B , the squarenesses and the shapes of the sheets are different from each other. Then, in FIGS. 6 A and 6 B , an image IM is formed on the sheets A and B based on the abutment reference edge Es.
- a reference edge for the conveyance and the image formation in the image forming apparatus 100 is different from a reference edge in the post-processing apparatus 600 . That is, there is a case where, in the image forming apparatus 100 , the image is formed on the sheet based on the abutment reference edge Es, serving as a first edge, and, in the post-processing apparatus 600 , the post-processing is performed based on a non-reference edge En, serving as a second edge, adjacent to the abutment reference edge Es.
- the post-processing apparatus 600 performs a stapling process of the sheet bundle constituted by these sheets. That is, the stapling process of the sheet bundle is performed with reference to the non-reference edge En.
- the reference edge of the sheet S in the stapling process is referred to as a post-processing reference edge.
- the skew correction unit 55 is controlled such that the image is formed in parallel to the non-reference edge En.
- the non-reference edge En adjacent to the abutment reference edge Es is assumed to be a downstream edge in the conveyance direction F of the sheet S, namely the leading edge of sheet S.
- the abutment reference edge Es is an edge extending along the conveyance direction F of the sheet
- the non-reference edge En is an edge extending along the width direction W orthogonal to the conveyance direction F of the sheet.
- the non-reference edge En abuts against the regulation plate 604 , and becomes an alignment reference in the post-processing apparatus 600 .
- a method for detecting the angle ⁇ , serving as a first angle, formed between the abutment reference edge Es and the non-reference edge En of the sheet S will be described.
- a counter-clockwise direction is expressed as a positive direction.
- the respective angles described below are angles of a case where the conveyance center line CT 1 (refer to FIG. 2 A ) is treated as 0 degree, namely angles with respect to the conveyance center line CT 1 (refer to FIG. 2 A ).
- an angle of the abutment reference edge Es of the sheet S is detected by the CIS sensor 101 .
- the CIS sensor 101 detects a position X 1 of the abutment reference edge Es when the time T equals T 1 , and a position X 2 of the abutment reference edge Es when the time T equals T 2 (which is larger than T 1 ).
- conveyance velocity Vs conveyance velocity
- the angle ⁇ s of the abutment reference edge Es is calculated by the following equation.
- an angle of the non-reference edge En of the sheet S is detected by the pre-registration sensors 102 a and 102 b.
- detection timings of the non-reference edge En by the pre-registration sensors 102 a and 102 b are different from each other.
- the angle ⁇ n of the non-reference edge En is calculated by the following equation.
- the non-reference edge En of the sheet S is inclined by the difference ⁇ minus 90 degrees with respect to the width direction W.
- the stapling process is performed in the post-processing apparatus 600 with respect to the non-reference edge En, due to the inclination of the non-reference edge En described above, the image formed on the sheet bundle on which the stapling process has been performed varies.
- FIGS. 9 A and 9 B a calculation method of a moving velocity of the registration roller pair 7 in the width direction W will be described.
- a travelling direction Fs of the sheet S which is being conveyed while abutting against the abutment surface 20 a is inclined by the angle ⁇ from the conveyance direction F.
- the sheet S is delivered from the obliquely conveying roller pairs 24 a to 24 c to the registration roller pair 7 , a difference arises between the conveyance direction F of the sheet S by the registration roller pair 7 and the travelling direction Fs.
- FIG. 9 A shows a case where ⁇ is larger than 0 degree, and the sheet S receives the rotational moment Ms in the counter-clockwise direction from the reference member 20 .
- FIG. 9 B shows a case where ⁇ is less than 0 degree, and the sheet S receives the rotational moment Ms in the clockwise direction by the conveyance force of the obliquely conveying roller pairs 24 a to 24 c. If the sheet S receives the rotational moment Ms as described above, there is a possibility of causing the skew, a wrinkle, and the damage of the sheet S.
- the registration roller pair 7 is controlled so as to receive the sheet S while being moved in the width direction W by the registration slide motor 34 .
- the moving velocity Vr of the registration roller pair 7 at the time of receiving the sheet S is calculated as described below by using the conveying velocity Vs in the conveyance direction F of the sheet S and the angle ⁇ .
- Vr ⁇ Vs ⁇ tan ⁇ Equation (4)
- a direction of the moving velocity Vr as shown by an arrow Fr, from a lower side of a sheet surface of FIGS. 9 A and 9 B toward an upper side is referred to as positive.
- the obliquely conveying roller pairs 24 a to 24 c release the nips.
- the registration roller pair 7 of this embodiment is moved at the velocity Vr in the width direction W (arrow Fr) while conveying the sheet S at the conveying velocity Vs in the conveyance direction F.
- the registration roller pair 7 is able to convey the sheet S in a direction aligned with the travelling direction Fs of the sheet S in the obliquely conveying portion 42 , so that it is possible to receive the sheet S without arising the rotational moment in the sheet S. Therefore, it is possible to reduce the skew, the wrinkle, and the damage of the sheet S.
- a corrected slide amount Xr that is a distance by which the registration roller pair 7 slides the sheet S in the width direction W is an amount in which the slide correction amount Xf is added to the abutting margin Xo described above.
- the slide correction amount Xf corresponds to the deviation in the width direction W arisen from obliquely conveying the sheet by the angle ⁇ with respect to the conveyance direction F in the obliquely conveying portion 42 .
- the slide correction amount Xf is calculated as follows.
- the count time ⁇ Tc is a time from when the pre-registration sensor 103 has detected the leading edge of the sheet S to when the registration roller pair 7 starts the slide movement.
- a so-called switchback method reversing the leading and trailing edges of the sheet S is employed in the case performing the duplex printing, a relative inclination angle between the abutment reference edge Es and the non-reference edge En is inverted. That is, with respect to the angle ⁇ of the reference member 20 , which is equal to the difference 90 degrees minus ⁇ at the time printing on the first surface, the angle ⁇ of the reference member 20 at the time printing on the second surface becomes minus one, multiplied by the difference 90 degrees minus ⁇ .
- the edge position Xp of the sheet S in the width direction W defined by the center standard of the image is different from the first surface.
- An edge position correction amount Xpd that is the difference described above is expressed by the following equation when the length of the sheet S in the conveyance direction F is referred to as L.
- the angle ⁇ of the reference member 20 , and the standby position Pw and the retracting position Pe of the reference member 20 are respectively calculated by the following equations.
- FIG. 12 is a control block related to the control unit 9 of this embodiment.
- the CIS sensor 101 the pre-registration sensors 102 a and 102 b, and the pre-registration sensor 103 are coupled to an input side of the control unit 9 .
- the angle adjustment motor 31 , the slide drive motor 32 , the registration drive motor 33 , and the registration slide motor 34 are coupled to an output side of the control unit 9 .
- a memory 106 is coupled to the control unit 9 . To be noted, it is acceptable to incorporate the memory 106 inside of the control unit 9 , and dispose in any position in the image forming system 1 .
- the control unit 9 detects the angle ⁇ s (refer to FIG. 7 A ) of the abutment reference edge Es and the angle ⁇ n (refer to FIG. 7 B ) of the non-reference edge En by using the CIS sensor 101 and the pre-registration sensors 102 a and 102 b (STEP S 1 ).
- the control unit 9 calculates the angle a formed between the abutment reference edge Es and the non-reference edge En, and an error (rotational angle) ⁇ that is a difference of the angle ⁇ from a right angle (STEPS S 2 and S 3 ). That is, ⁇ equals 90 degrees minus ⁇ .
- control unit 9 controls the slide drive motor 32 such that the obliquely conveying unit 26 is positioned in the standby position Pw (STEP S 4 ). Then, the control unit 9 judges from job input information whether or not the post-processing reference edge matches the abutment reference edge Es (STEP S 5 ).
- the control unit 9 drives the angle adjustment motor 31 such that the angle ⁇ of the reference member 20 becomes equal to ⁇ (STEP S 6 ). That is, when the counter-clockwise direction around the pivot shaft 21 as a center is treated as positive, the angle ⁇ of the reference member 20 becomes 90 degrees minus ⁇ . In other words, the angle ⁇ of the reference member 20 becomes the absolute value of the difference 90 degrees minus ⁇ .
- STEP S 6 is a movement process in which the reference member 20 is moved such that the angle ⁇ becomes the absolute value of the difference 90 degrees minus ⁇ , and STEP S 6 is executed before the sheet S has reached the abutment surface 20 a or in a state where the sheet S is abutted against the abutment surface 20 a.
- the abutment reference edge Es is abutted against the abutment surface 20 a of the reference member 20 by the obliquely conveying roller pairs 24 a to 24 c, so that the sheet S is conveyed by following the abutment surface 20 a.
- the non-reference edge En of the sheet S becomes parallel to the width direction W.
- the non-reference edge En inclines within 5 degrees with respect to the width direction W, it is acceptable to consider that non-reference edge En is parallel to the width direction W.
- the control unit 9 judges whether or not the pre-registration sensor 103 is turned ON, that is, whether or not the sheet S has reached the pre-registration sensor 103 (STEP S 7 ).
- the control unit 9 moves the registration roller pair 7 in the width direction W at the moving velocity Vr shown in the equation (4) above in a state where the registration roller pair 7 nips the sheet S (STEP S 8 ).
- the control unit 9 moves the registration roller pair 7 by the corrected slide amount Xr shown in the equation (6) above in the width direction W (STEP S 9 ). That is, the registration roller pair 7 receives the sheet S while moving in the width direction W at the moving velocity Vr which is the velocity calculated based on the angle ⁇ .
- control unit 9 controls the slide drive motor 32 such that the obliquely conveying unit 26 moves to the retracting position Pe after a predetermined count from the time when the pre-registration sensor 103 is turned ON (STEP S 10 ). Further, the control unit 9 pivots the reference member 20 by the angle adjustment motor 31 such that the angle ⁇ becomes equal to 0 degree (STEP S 11 ). To be noted, it is acceptable to perform STEPS S 10 and S 11 in parallel with or earlier than STEPS S 8 and S 9 .
- control unit 9 judges whether or not the printing on the second surface is necessary (STEP S 12 ). In a case where the printing on the second surface is not necessary (STEP S 12 : NO), that is, in a case of a simplex printing job, the control unit 9 ends the processing.
- control unit 9 calculates a rotational angle ⁇ , the standby position Pw, and the retracting position Pe, which are used when the sheet S on whose first surface the image has been formed returns to the skew correction unit 55 . Then, the control unit 9 stores these in the memory 106 (STEP S 13 ), and returns to STEP S 6 .
- control unit 9 executes STEPS S 6 to S 11 based on the rotational angle ⁇ , the standby position Pw, and the retracting position Pe stored in the memory 106 , since the STEPS S 6 to S 11 at the time of printing on the second surface are similar to the descriptions at the time of printing on the first surface described above, descriptions will be omitted herein. Since, after the STEPS S 6 to S 11 at the time of printing on the second surface were ended, the printing on the second surface has been already completed at STEP S 12 , STEP S 12 becomes NO, and the control unit 9 ends the processing.
- the skew correction control described above is performed on each sheet of the job, and, for example, in a case where the sheet bundle is formed in the post-processing apparatus 600 , the skew correction control is performed on each sheet constituting the sheet bundle. That is, in a case where the post-processing reference edge does not match the abutment reference edge Es, the processing of STEPS S 6 to S 11 is performed on each sheet constituting the sheet bundle.
- the skew correction control of this embodiment includes a first mode including STEPS S 6 to S 11 and a second mode including STEPS S 14 to S 15 .
- the first mode is a mode in which the reference member 20 is moved such that the angle ⁇ becomes 90 degrees minus a before the sheet S has reached the abutment surface 20 a or in a state where the sheet S is abutted against the abutment surface 20 a.
- the second mode is a mode in which the reference member 20 is positioned such that the abutment surface 20 a becomes parallel to the conveyance direction F before the sheet S has reached the abutment surface 20 a or in a state where the sheet S is abutted against the abutment surface 20 a.
- the skew correction control is performed such that the non-reference edge En becomes parallel to the width direction W. Since, in this state, the image is transferred onto the sheet S at the secondary transfer nip T 2 , the position of the image formed on the sheet S does not vary with respect to the non-reference edge En. Therefore, if the post-processing such as the stapling process is performed with reference to the non-reference edge En in the post-processing apparatus 600 , there is not a variation of the image in the sheet bundle, so that it is possible to improve the quality of the deliverables.
- the skew correction unit 55 employs an obliquely conveying registration method, it is possible to improve productivity, and also possible to perform the skew correction on various media such as thin paper and cardboard. Further, since the image forming position in the image forming unit 513 is fixed regardless of the position of the post-processing reference edge, it is possible to improve the productivity.
- the skew correction unit 55 is treated as the sheet conveyance apparatus, it is acceptable to consider the image forming apparatus 100 including the skew correction unit 55 and the image forming unit 513 as the sheet conveyance apparatus. Further, it is acceptable to consider the image forming system 1 including the image forming apparatus 100 and the post-processing apparatus 600 as the sheet conveyance apparatus.
- the non-reference edge En which becomes the post-processing reference edge is assumed to be the downstream edge in the conveyance direction F of the sheet S, namely the leading edge of the sheet S, it is not limited to this.
- a user is able to arbitrarily choose the leading or trailing edge of the sheet for the post-processing reference edge.
- PC personal computer
- it is acceptable to configure such that the leading and trailing edges of the sheet chosen for the post-processing reference edge are automatically switched in the image forming apparatus 100 in accordance with the post-processing reference edge chosen by the post-processing apparatus 600 .
- whether or not the post-processing reference edge matches the abutment reference edge Es is automatically judged from the job input information, it is not limited to this.
- the user chooses whether or not the post-processing reference edge matches the abutment reference edge Es.
- the descriptions are provided by using the image forming apparatus 100 of the electrophotographic system, this disclosure is not limited to this.
- this disclosure is not limited to a printer, but includes a copier, a facsimile, a multifunction machine, and the like.
- Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s).
- computer executable instructions e.g., one or more programs
- a storage medium which may also be referred to more fully as a
- the computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions.
- the computer executable instructions may be provided to the computer, for example, from a network or the storage medium.
- the storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)TM), a flash memory device, a memory card, and the like.
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Abstract
A sheet conveyance apparatus includes a conveyance guide configured to guide a sheet along a conveyance center line extending in a conveyance direction, a reference member including an abutment surface, a conveyance unit configured to convey the sheet while abutting a first edge of the sheet against the abutment surface, a detection unit configured to detect a first angle formed between the first edge of the sheet and a second edge adjacent to the first edge, a moving unit configured to move the reference member so as to change a second angle formed between the abutment surface and the conveyance center line, and a control unit configured to perform a movement process in which the moving unit moves the reference member such that, when the first angle is referred to as α, the second angle becomes an absolute value of a difference 90 degrees minus α.
Description
- This disclosure relates to a sheet conveyance apparatus conveying a sheet, and an image forming apparatus and an image forming system provided with same.
- Hitherto, a registration apparatus of an obliquely conveying registration type which conveys a sheet while abutting a side edge of the sheet against a reference member is suggested formed between a reference edge and a non-reference edge adjacent to the reference edge is determined using a side edge of the sheet as the reference edge. Then, based on this angle, an angle of the reference member is adjusted such that the deviation in margins at the reference and nonreference edges becomes even.
- Recently, sometimes, a post-processing apparatus is coupled to an image forming apparatus such as a printer, and the post-processing such as a cutting process and a stapling process is performed in the post-processing apparatus. At this time, an edge of the sheet is usually used as a processing reference in the post-processing, and, sometimes, there is a case where a reference (side edge) for the image formation and a skew correction in the image forming apparatus does not match the processing reference for the post-processing.
- For example, in a case where, after the skew correction and the image formation have been performed using the side edge as the reference in the registration apparatus described in Japanese Patent Laid-Open No. 2011-98790, the post-processing is performed using an edge adjacent to the side edge as the reference in the post-processing apparatus, a positional variation of an image on the sheet after the post-processing occurs. Therefore, especially in a case where a squareness of the sheet is low, there is a risk that the quality of the final deliverables is degraded.
- According to an aspect of the present invention, a sheet conveyance apparatus includes a conveyance guide configured to guide a sheet along a conveyance center line extending in a conveyance direction, a reference member including an abutment surface extending along the conveyance direction, a conveyance unit configured to convey the sheet while abutting a first edge of the sheet against the abutment surface of the reference member, a detection unit configured to detect a first angle formed between the first edge of the sheet and a second edge adjacent to the first edge, a moving unit configured to move the reference member so as to change a second angle formed between the abutment surface and the conveyance center line, and a control unit configured to perform a movement process in which the moving unit moves the reference member such that, when the first angle is referred to as α, the second angle becomes an absolute value of a
difference 90 degrees minus α. - Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
-
FIG. 1 is an overall schematic diagram showing an image forming system relating to this embodiment. -
FIG. 2A is a plan view showing a skew correction unit. -
FIG. 2B is a plan view of the skew correction unit showing a state where the sheet is conveyed by an upstream conveyance portion. -
FIG. 3A is a plan view of the skew correction unit showing a state where a reference member has been pivoted. -
FIG. 3B is a plan view of the skew correction unit showing a state where the sheet is conveyed by an obliquely conveying portion. -
FIG. 4A is a plan view of the skew correction unit showing a state where the sheet has reached a pre-registration sensor. -
FIG. 4B is a plan view of the skew correction unit showing a state where the sheet has been slid by a registration roller pair. -
FIG. 5 is a plan view of the skew correction unit showing a state where the sheet has been further slid by the registration roller pair. -
FIG. 6A is a diagram showing an example of the sheet and an image position. -
FIG. 6B is a diagram showing the other example of the sheet and the image position. -
FIG. 6C is a diagram showing an error in the image position among the sheets. -
FIG. 7A is a diagram for describing a method for a calculation of an angle of an abutment reference edge. -
FIG. 7B is a diagram for describing a method for a calculation of an angle of a non-reference edge -
FIG. 8 is a graph indicating a difference in ON timings of pre-registration sensors. -
FIG. 9A is a diagram for describing the moving velocity of the registration roller pair. -
FIG. 9B is a diagram for describing the moving velocity of the registration roller pair. -
FIG. 10 is a diagram for describing a method for a calculation of a slide correction amount of the registration roller pair. -
FIG. 11 is a diagram for describing a method for calculations of an angle of the reference member and an edge position correction amount of the sheet in duplex printing. -
FIG. 12 is a control block diagram relating to this embodiment. -
FIG. 13 is a flowchart showing skew correction control. - Hereinafter, details of representative embodiments of this disclosure will be described. To be noted, embodiments described below exemplarily describe this disclosure, and configurations, and sizes, materials, shapes, relative arrangements, the control, and the like of components described below do not limit a scope of this disclosure unless otherwise specifically stated.
- As shown in
FIG. 1 , animage forming system 1 relating to this embodiment includes animage forming apparatus 100 and apost-processing apparatus 600 coupled to theimage forming apparatus 100. Theimage forming apparatus 100 is a full color laser beam printer of an electrophotographic system and an intermediate transfer tandem system. Further, theimage forming apparatus 100 is a print on demand (POD) machine capable of performing printing including but not limited to general office use, and is able to use various kinds of sheets, serving as a recording medium, including paper such as standard paper and an envelope, coated paper, a plastic film such as a sheet for an overhead projector (OHT), and a cloth. The operation of theimage forming apparatus 100 is controlled by acontrol unit 9 including, for example, an arithmetic unit such as a central processing unit (CPU), a memory such as a random-access memory (RAM), and a memory unit such as a read-only memory (ROM). - The
image forming apparatus 100 includes animage forming unit 513, asheet feed unit 100B, and aconveyance apparatus 100D. Theimage forming unit 513 includes four process cartridges PY, PM, PC, and PBk forming four colors of toner images of yellow (Y), magenta (M), cyan (C), and black (K), and exposingunits - The process cartridge PY includes a
photosensitive drum 508, a charge roller, not shown, acleaner 509, and a developingunit 510. Thephotosensitive drum 508 is constructed by coating an organic photoconductive layer on an outer circumferential surface of an aluminum cylinder, and rotated by a drive motor, not shown. Further, anintermediate transfer belt 506 rotated by adrive roller 504 in an arrow G direction is disposed in theimage forming unit 513, and wound around atension roller 505, thedrive roller 504, and a secondary transferinner roller 503.Primary transfer rollers intermediate transfer belt 506, and a secondary transferouter roller 56 is disposed outside of theintermediate transfer belt 506 so as to face the secondary transferinner roller 503. - The
sheet feed unit 100B includes asheet storage portion 51 storing the sheet S, a lift-upunit 52 ascending and descending while stacking the sheet S, and asheet feed portion 53 feeding the sheet S on the lift-upunit 52. While a pneumatic conveyance type pneumatically sucking and conveying the sheet S by separating the sheet into one sheet at a time is employed in this embodiment, it is not limited to this. For example, for thesheet feed portion 53, it is acceptable to employ a roller conveyance type conveying the sheet by a pickup roller and the like, and an electrostatic attraction type sucking and conveying the sheet by electrostatic force. - The
conveyance apparatus 100D includes aconveyance unit 54, askew correction unit 55, apre-fixing conveyance unit 57, a fixingunit 58, abranch conveyance unit 59, areverse conveyance unit 501, and aduplex conveyance unit 502. These units each include a conveyance roller pair for conveying the sheet. The fixingunit 58 includes a fixing nipportion 58 a for conveying the sheet by nipping. - Next, an image forming operation of the
image forming apparatus 100 configured as described above will be described. When an image signal is input to the exposingunit 511Y from a personal computer, not shown, and the like, the exposingunit 511Y irradiates a laser beam corresponding to the image signal on thephotosensitive drum 508 of the process cartridge PY. - At this time, a surface of the
photosensitive drum 508 has been uniformly charged in a predetermined polarity and voltage beforehand, and an electrostatic latent image is formed on the surface by the laser beam irradiated from the exposingunit 511Y via a mirror. The electrostatic latent image formed on thephotosensitive drum 508 is developed by the developingunit 510, and a toner image of yellow (Y) is formed on thephotosensitive drum 508. - Similarly, the exposing
units intermediate transfer belt 506 by theprimary transfer rollers intermediate transfer belt 506 rotated by thedrive roller 504, a full color toner image is conveyed to a secondary transfer nip T2 formed by the secondary transfer inner andouter rollers photosensitive drum 508 is collected by the cleaner 509. To be noted, the image forming processes of the respective colors are performed in the timing superimposing the toner image on an upstream toner image primarily transferred onto theintermediate transfer belt 506. - In parallel with this image forming process, the sheet S is fed from the
sheet feed unit 100B, and the sheet S is conveyed to a duplex conveyance path R of theduplex conveyance unit 502 via aconveyance path 91. Then, the sheet S passes aconveyance path 54 a of theconveyance unit 54, and is conveyed to theskew correction unit 55. The skew of the sheet S is corrected by theskew correction unit 55, and the sheet S is conveyed to the secondary transfer nip T2 by aregistration roller pair 7 in predetermined conveyance timing. The full color toner image on theintermediate transfer belt 506 is transferred onto a first surface (front surface) of the sheet S by a secondary transfer bias applied to the secondary transferouter roller 56. A remained toner remained on theintermediate transfer belt 506 is collected by abelt cleaner 2. - The sheet S onto which the toner image has been transferred is conveyed to the fixing
unit 58 by thepre-fixing conveyance unit 57. Then, the sheet S is guided to the fixing nipportion 58 a of the fixingunit 58, and, by proving predetermined heat and pressure, the toner is melted and bonded (fixed). With respect to the sheet S passed through the fixingunit 58, the path selection of selecting a path between the conveyance to thepost-processing apparatus 600 and the conveyance to thereverse conveyance unit 501 is performed by thebranch conveyance unit 59. To be noted, it is also possible to perform the so called facedown conveyance conveying the sheet S such that the sheet S is conveyed to a sheet discharge tray 500 with the sheet S inverted so as to turn the first surface, on which the image has been formed at the secondary transfer nip T2, to the underside. - In a case where the image is formed on only one side of the sheet S, the sheet S is conveyed from the
branch conveyance unit 59 to thepost-processing apparatus 600. In a case where the images are formed on both sides of the sheet S, the sheet S is conveyed to thereverse conveyance unit 501 by thebranch conveyance unit 59. Then, the sheet S is switchbacked by thereverse conveyance unit 501. The sheet S which has been switchbacked is conveyed from thereverse conveyance unit 501 to theduplex conveyance unit 502, and guided to theconveyance unit 54 and theskew correction unit 55. Thereafter, the image is formed on a second surface (back surface) of the sheet S at the secondary transfer nip T2, and discharged to thepost-processing apparatus 600. - Next, the
post-processing apparatus 600 will be described in detail. Thepost-processing apparatus 600 is coupled to theimage forming apparatus 100, and includes aconveyance unit 601, aswing roller 603, astapling unit 620, and asheet discharge tray 610. Thestapling unit 620 includes aprocess tray 602 for loading the sheet S, aregulation plate 604 for regulating a position of a trailing edge of the sheet S stacked on theprocess tray 602, and astapler 605 for performing a stapling process on the sheet S. - The
post-processing apparatus 600 receives the sheet S from thebranch conveyance unit 59 of theimage forming apparatus 100, and conveys the sheet S by theconveyance unit 601. Theswing roller 603 is capable of pivoting between upper and lower positions, and positioned in the upper position when theconveyance unit 601 discharges the sheet S to thesheet discharge tray 610. When the sheet S has been discharged to theprocess tray 602, theswing roller 603 pivots from the upper position to the lower position. - In a case where the stapling process is not performed on the sheet S, the
swing roller 603 discharges the sheet S to thesheet discharge tray 610 as it is. On the other hand, in a case where the stapling process is performed on the sheet S, theswing roller 603 conveys the sheet S on theprocess tray 602 toward theregulation plate 604. Then, since the trailing edge of the sheet S abuts against theregulation plate 604, a position of the sheet S in a conveyance direction is regulated, and also the skew of the sheet S is corrected. After an alignment process as described above has been performed with respect to a predetermined number of sheets of the sheet S, thestapler 605 performs the stapling process with respect to the predetermined number of sheets of the sheet S. A sheet bundle which has been provided with the stapling process is discharged to thesheet discharge tray 610 by theswing roller 603. - Next, using
FIGS. 2A and 2B , theskew correction unit 55 will be described. As shown inFIGS. 2A and 2B , theskew correction unit 55, serving as a sheet conveyance apparatus, includes, from upstream toward downstream in the conveyance direction F, anupstream conveyance portion 41, an obliquely conveyingportion 42, and aslide portion 43. To be noted, it is acceptable to include thecontrol unit 9 in theskew correction unit 55. Theupstream conveyance portion 41 includes anupstream conveyance guide 11, conveyance roller pairs 14 a and 14 b, a contact image sensor (CIS)sensor 101, andpre-registration sensors - With a fixed
guide 12, described later, alower conveyance guide 13, and amovable guide 25, theupstream conveyance guide 11 constructs aconveyance guide portion 45 guiding the sheet S in the conveyance direction F in theskew correction unit 55. Theconveyance guide portion 45 forms a conveyance path CP through which the sheet S passes, and a conveyance center line CT1 of the conveyance path CP, serving as a conveyance path, extends in the conveyance direction F. In this embodiment, a center standard using the conveyance center line CT1 as a reference for the conveyance of the sheet S and the image formation in theimage forming unit 513 is adopted. - The
conveyance roller pair 14 b is disposed downstream of theconveyance roller pair 14 a in the conveyance direction F, and theCIS sensor 101 is disposed between the conveyance roller pairs 14 a and 14 b in the conveyance direction F. Further, thepre-registration sensors conveyance roller pair 14 b in the conveyance direction F. TheCIS sensor 101 and thepre-registration sensors detection unit 47 detecting an angle α, described later. To be noted, in thedetection unit 47, it is acceptable to include part of thecontrol unit 9 for determining the angle α based on detection results of the respective sensors. Further, thedetection unit 47 is not limited to the configuration of this embodiment, and it is acceptable to determine the angle α by imaging the sheet, for example, by a camera and the like. - The
CIS sensor 101 is disposed so as to be capable of detecting a position of an abutment reference edge Es which is one side of the sheet S in a width direction W orthogonal to the conveyance direction F. In particular, by acquiring the image at fixed time intervals, theCIS sensor 101 is capable of acquiring a positional change of the abutment reference edge Es as a sequential image at the time when the sheet S passes through a detection area of theCIS sensor 101. - The
pre-registration sensors pre-registration sensors pre-registration sensors - The obliquely conveying
portion 42 includes the fixedguide 12 and an obliquely conveyingunit 26, and the obliquely conveyingunit 26 includes themovable guide 25, obliquely conveying roller pairs 24 a to 24 c, and areference member 20. The abutment reference edge Es of the sheet S is abutted against thereference member 20, and thereference member 20 includes anabutment surface 20 a extending along the conveyance direction F. Further, thereference member 20 is pivotable around apivot shaft 21 as a center, and urged toward acam 22 by an urgingspring 23. - A position of the
reference member 20 in a pivot direction is determined by abutting against thecam 22, and, since thecam 22 is rotatably driven by anangle adjustment motor 31, thereference member 20 pivots around thepivot shaft 21 as the center. As described above, by driving theangle adjustment motor 31, serving as a moving unit, it is possible to change an angle β (refer toFIG. 3A ) of thereference member 20. The angle β, serving as a second angle, is an angle formed between the conveyance center line CT1 and theabutment surface 20 a. In other words, the angle β is an angle formed between the conveyance direction F and theabutment surface 20 a. - Each of the obliquely conveying roller pairs 24 a to 24 c includes a roller pair, and a rotation shaft of at least one side of the roller pair inclines with respect to the width direction W and the conveyance direction F. Thereby, the sheet S is conveyed toward the
abutment surface 20 a by the obliquely conveying roller pairs 24 a to 24 c. That is, the obliquely conveying roller pairs 24 a to 24 c, serving as a conveyance unit, conveys the sheet S while abutting the abutment reference edge Es of the sheet S against theabutment surface 20 a of thereference member 20. Thereby, the sheet S is conveyed in a state where the abutment reference edge Es is in slide contact with theabutment surface 20 a, and a posture of the sheet S follows theabutment surface 20 a. Thus, the skew of the sheet S is corrected. - The
movable guide 25, the obliquely conveying roller pairs 24 a to 24 c, and thereference member 20 of the obliquely conveyingunit 26 are integrally movable in the width direction W by aslide drive motor 32. Further, the obliquely conveyingunit 26 is movable to a standby position Pw and a retracting position Pe in accordance with a size of the sheet S which is conveyed. InFIGS. 2A and 2B , the standby position Pw and the retracting position Pe are indicated by a position of theabutment surface 20 a of thereference member 20. - The obliquely conveying
unit 26 moves to and waits in the standby position Pw before the sheet S is conveyed. The standby position Pw means a position in which an abutting margin Xo is added to an edge position Xp of the sheet S as defined by the center standard. The abutting margin Xo is a distance for conveying the sheet S by following theabutment surface 20 a without colliding with an upstream end of thereference member 20 in the conveyance direction F. - Then, having delivered the sheet S to the
registration roller pair 7, the obliquely conveyingunit 26 moves from the standby position Pw to the retracting position Pe. The retracting position Pe is a position in which a retracting distance Xe is added to the standby position Pw, and the retracting distance Xe is a distance for retracting thereference member 20 in the width direction W such that thereference member 20 does not interfere with the conveyance of the sheet S. - As described above, the obliquely conveying
unit 26 is positioned in the retracting position Pe when the sheet S is not present in the obliquely conveyingportion 42, and moves to the standby position Pw when the sheet S has entered the obliquely conveyingportion 42, and returns to the retracting position Pe again after the sheet S has been delivered to theregistration roller pair 7. - To be noted, when the obliquely conveying roller pairs 24 a to 24 c start the skew correction of the sheet S, it is suitable that the conveyance roller pairs 14 a and 14 b do not nip the sheet S. In this embodiment, the
control unit 9 counts a predetermined time from the timing in which thepre-registration sensors control unit 9 controls such that nips of the conveyance roller pairs 14 a and 14 b are released in the timing in which the leading edge of the sheet S reaches the obliquely conveyingroller pair 24 a after the predetermined time has passed. - The
slide portion 43 includes thelower conveyance guide 13, theregistration roller pair 7, aregistration drive motor 33, aregistration slide motor 34, and apre-registration sensor 103. Theregistration roller pair 7, serving as a downstream conveyance portion, is disposed downstream of the obliquely conveying roller pairs 24 a to 24 c in the conveyance direction F, and conveys the sheet S in the conveyance direction F. Thepre-registration sensor 103 is disposed upstream of theregistration roller pair 7 in the conveyance direction F, and, similar to thepre-registration sensors - The
registration roller pair 7 is rotatable by theregistration drive motor 33, and slidable in the width direction W by theregistration slide motor 34. After the sheet S has been delivered from the obliquely conveying roller pairs 24 a to 24 c, so as to align a position of the sheet S with an image forming position, theregistration roller pair 7 slides the sheet S in the width direction W in a state nipping the sheet S. A movement amount of theregistration roller pair 7 in the width direction W at this time is the sum of the abutting margin Xo and a slide correction amount Xf, described later. - To be noted, when the
registration roller pair 7 slides in the width direction W, it is suitable that the obliquely conveying roller pairs 24 a to 24 c do not nip the sheet S. In this embodiment, thecontrol unit 9 releases nips of the obliquely conveying roller pairs 24 a to 24 c based on the timing in which thepre-registration sensor 103 has detected the sheet S. Further, thecontrol unit 9 releases a nip of theregistration roller pair 7 based on the timing in which the sheet S has been delivered to the secondary transfer nip T2, and returns theregistration roller pair 7 to a standby position before a slide movement. - Next, based on
FIGS. 6A to 6C , an error of an image position on the sheet due to a shape of the sheet will be described. Generally, while, in a registration type which uses a certain edge of the sheet as a reference edge, it is assumed that the sheet is cut perpendicularly, actually, there is the sheet whose accuracy of a squareness is bad. This is because, in addition to a cause resulting from the accuracy of a cutter, since fiber orientation varies inside of the sheet, there is an effect of unevenness in a degree of expansion/contraction caused by changes in temperature and humidity, etc. - For example, with respect to a sheet A shown in
FIG. 6A and a sheet B shown inFIG. 6B , the squarenesses and the shapes of the sheets are different from each other. Then, inFIGS. 6A and 6B , an image IM is formed on the sheets A and B based on the abutment reference edge Es. - However, there is a case where a reference edge for the conveyance and the image formation in the
image forming apparatus 100 is different from a reference edge in thepost-processing apparatus 600. That is, there is a case where, in theimage forming apparatus 100, the image is formed on the sheet based on the abutment reference edge Es, serving as a first edge, and, in thepost-processing apparatus 600, the post-processing is performed based on a non-reference edge En, serving as a second edge, adjacent to the abutment reference edge Es. For example, as described above, having aligned the sheets by abutting the non-reference edges En of the respective sheets against theregulation plate 604, thepost-processing apparatus 600 performs a stapling process of the sheet bundle constituted by these sheets. That is, the stapling process of the sheet bundle is performed with reference to the non-reference edge En. Hereinafter, the reference edge of the sheet S in the stapling process is referred to as a post-processing reference edge. - In this case, if the sheets A and B shown in
FIGS. 6A and 6B are mixed in the sheet bundle, as shown inFIG. 6C , the image positions of the respective sheets constituting the sheet bundle vary, and the quality of the final printed deliverables is degraded. Therefore, in this embodiment, in a case where the post-processing (stapling process) is performed in thepost-processing apparatus 600 with reference to the non-reference edge En, theskew correction unit 55 is controlled such that the image is formed in parallel to the non-reference edge En. - To be noted, in the following, the non-reference edge En adjacent to the abutment reference edge Es is assumed to be a downstream edge in the conveyance direction F of the sheet S, namely the leading edge of sheet S. In other words, the abutment reference edge Es is an edge extending along the conveyance direction F of the sheet, and the non-reference edge En is an edge extending along the width direction W orthogonal to the conveyance direction F of the sheet. In this case, having performed the duplex printing on the sheet S, the non-reference edge En abuts against the
regulation plate 604, and becomes an alignment reference in thepost-processing apparatus 600. - Next, using
FIGS. 7A to 8 , a method for detecting the angle α, serving as a first angle, formed between the abutment reference edge Es and the non-reference edge En of the sheet S will be described. To be noted, hereinafter, in a plan view, a counter-clockwise direction is expressed as a positive direction. Further, unless otherwise specifically stated, the respective angles described below are angles of a case where the conveyance center line CT1 (refer toFIG. 2A ) is treated as 0 degree, namely angles with respect to the conveyance center line CT1 (refer toFIG. 2A ). - As shown in
FIG. 7A , an angle of the abutment reference edge Es of the sheet S is detected by theCIS sensor 101. In particular, theCIS sensor 101 detects a position X1 of the abutment reference edge Es when the time T equals T1, and a position X2 of the abutment reference edge Es when the time T equals T2 (which is larger than T1). Then, when conveyance velocity in the conveyance direction F of the sheet S is referred to as conveyance velocity Vs, the angle Θs of the abutment reference edge Es is calculated by the following equation. -
Θs=tan−1{(X1−X2)/(Vs*(T2−T1))} Equation (1) - Next, as shown in
FIG. 7B , an angle of the non-reference edge En of the sheet S is detected by thepre-registration sensors FIG. 8 , detection timings of the non-reference edge En by thepre-registration sensors pre-registration sensors pre-registration sensors -
Θn=tan−1{X102/(Vs*(Tb−Ta))} Equation (2) - By the equations (1) and (2) above, the angle a formed between the abutment reference edge Es and the non-reference edge En is calculated by the following equation.
-
α=Θs+Θn . . . Equation (3) - Now, in a case where a is not equal to 90 degrees, if the skew correction of the sheet S is performed by the
skew correction unit 55 in a state where the angle β of the abutment reference member is kept at 0 degree, the non-reference edge En of the sheet S is inclined by the difference α minus 90 degrees with respect to the width direction W. In a case where the stapling process is performed in thepost-processing apparatus 600 with respect to the non-reference edge En, due to the inclination of the non-reference edge En described above, the image formed on the sheet bundle on which the stapling process has been performed varies. Therefore, by setting beforehand the angle β of thereference member 20 at thedifference 90 degrees minus α, assuming the counter-clockwise direction as positive, it becomes possible to form the image in line with the non-reference edge En, so that it is possible to reduce variations in the respective images in the sheet bundle. - Next, using
FIGS. 9A and 9B , a calculation method of a moving velocity of theregistration roller pair 7 in the width direction W will be described. As shown inFIGS. 9A and 9B , in a case where the angle β is not equal to 0 degree, a travelling direction Fs of the sheet S which is being conveyed while abutting against theabutment surface 20 a is inclined by the angle β from the conveyance direction F. Then, when the sheet S is delivered from the obliquely conveying roller pairs 24 a to 24 c to theregistration roller pair 7, a difference arises between the conveyance direction F of the sheet S by theregistration roller pair 7 and the travelling direction Fs. - When the sheet S is delivered from the obliquely conveying roller pairs 24 a to 24 c to the
registration roller pair 7, even in a case where a variation arises in the conveyance of the sheet S, it is necessary to surely deliver the sheet S. Therefore, it is common to provide a time in which both of the obliquely conveying roller pairs 24 a to 24 c and theregistration roller pair 7 convey the sheet S at the same time. However, if the sheet S is delivered as described above without sliding theregistration roller pair 7, due to the difference between the conveyance direction F of the sheet S and the travelling direction Fs, a rotational moment Ms arises in the sheet S. -
FIG. 9A shows a case where β is larger than 0 degree, and the sheet S receives the rotational moment Ms in the counter-clockwise direction from thereference member 20.FIG. 9B shows a case where β is less than 0 degree, and the sheet S receives the rotational moment Ms in the clockwise direction by the conveyance force of the obliquely conveying roller pairs 24 a to 24 c. If the sheet S receives the rotational moment Ms as described above, there is a possibility of causing the skew, a wrinkle, and the damage of the sheet S. - Therefore, in this embodiment, the
registration roller pair 7 is controlled so as to receive the sheet S while being moved in the width direction W by theregistration slide motor 34. The moving velocity Vr of theregistration roller pair 7 at the time of receiving the sheet S is calculated as described below by using the conveying velocity Vs in the conveyance direction F of the sheet S and the angle β. -
Vr=−Vs·tan β Equation (4) - To be noted, a direction of the moving velocity Vr, as shown by an arrow Fr, from a lower side of a sheet surface of
FIGS. 9A and 9B toward an upper side is referred to as positive. Further, when the delivery of the sheet S to theregistration roller pair 7 has been surely completed, the obliquely conveying roller pairs 24 a to 24 c release the nips. - As described above, the
registration roller pair 7 of this embodiment is moved at the velocity Vr in the width direction W (arrow Fr) while conveying the sheet S at the conveying velocity Vs in the conveyance direction F. Thereby, theregistration roller pair 7 is able to convey the sheet S in a direction aligned with the travelling direction Fs of the sheet S in the obliquely conveyingportion 42, so that it is possible to receive the sheet S without arising the rotational moment in the sheet S. Therefore, it is possible to reduce the skew, the wrinkle, and the damage of the sheet S. - Next, using
FIG. 10 , a calculation method of a slide correction amount of theregistration roller pair 7 will be described. As described above, since a position of the sheet S delivered to theregistration roller pair 7 varies from a position of the image formation in the width direction W, the sheet S is slid by theregistration roller pair 7 in the width direction W. - A corrected slide amount Xr that is a distance by which the
registration roller pair 7 slides the sheet S in the width direction W is an amount in which the slide correction amount Xf is added to the abutting margin Xo described above. The slide correction amount Xf corresponds to the deviation in the width direction W arisen from obliquely conveying the sheet by the angle β with respect to the conveyance direction F in the obliquely conveyingportion 42. - As shown in
FIG. 10 , using a distance y1 between thepivot shaft 21 and thepre-registration sensor 103 in the conveyance direction F, a count time ΔTc, the conveying velocity Vs of the sheet S, and the angle α, the slide correction amount Xf is calculated as follows. To be noted, the count time ΔTc is a time from when thepre-registration sensor 103 has detected the leading edge of the sheet S to when theregistration roller pair 7 starts the slide movement. -
Xf=(y1+Vs·ΔTc)tan β . . . Equation (5) - Further, the corrected slide amount Xr is expressed by the following equation.
-
Xr=Xo+Xf . . . Equation (6) - Next, using
FIG. 11 , calculation methods of an angle of thereference member 20 at the time of the duplex printing and an edge position correction amount Xpd in the width direction W of the sheet S will be described. In a case performing the duplex printing, so as to improve the quality of the deliverables, when the sheet S is inverted and returned, it is necessary to control a positional relationship between a second surface of the sheet S and the image such that positions of the images on first and second surfaces match each other. - Since, in this embodiment, a so-called switchback method reversing the leading and trailing edges of the sheet S is employed in the case performing the duplex printing, a relative inclination angle between the abutment reference edge Es and the non-reference edge En is inverted. That is, with respect to the angle β of the
reference member 20, which is equal to thedifference 90 degrees minus α at the time printing on the first surface, the angle β of thereference member 20 at the time printing on the second surface becomes minus one, multiplied by thedifference 90 degrees minus α. - Further, since the image is formed in a state where the abutment reference edge Es is inclined with respect to the image, at an edge which becomes the leading edge of the second surface (the tailing edge of the first surface), the edge position Xp of the sheet S in the width direction W defined by the center standard of the image is different from the first surface. An edge position correction amount Xpd that is the difference described above is expressed by the following equation when the length of the sheet S in the conveyance direction F is referred to as L.
-
Xpd =L·tan(−(90°−α)) . . . Equation (7) - Therefore, in the skew correction at the time of printing the second surface of the duplex printing, the angle β of the
reference member 20, and the standby position Pw and the retracting position Pe of thereference member 20 are respectively calculated by the following equations. -
β=−(90°−α) . . . Equation (8) -
Pw=Xp+Xpd+Xo. . . Equation (9) -
Pe=Xp+Xpd+Xo+Xe . . . Equation (10) -
FIG. 12 is a control block related to thecontrol unit 9 of this embodiment. As shown inFIG. 12 , theCIS sensor 101, thepre-registration sensors pre-registration sensor 103 are coupled to an input side of thecontrol unit 9. Theangle adjustment motor 31, theslide drive motor 32, theregistration drive motor 33, and theregistration slide motor 34 are coupled to an output side of thecontrol unit 9. Further, amemory 106 is coupled to thecontrol unit 9. To be noted, it is acceptable to incorporate thememory 106 inside of thecontrol unit 9, and dispose in any position in theimage forming system 1. - Next, with reference to
FIGS. 2A to 5 , a skew correction control by theskew correction unit 55 will be described along a flowchart shown inFIG. 13 . As shown inFIGS. 2A, 2B, and 13 , thecontrol unit 9 detects the angle Θs (refer toFIG. 7A ) of the abutment reference edge Es and the angle Θn (refer toFIG. 7B ) of the non-reference edge En by using theCIS sensor 101 and thepre-registration sensors control unit 9 calculates the angle a formed between the abutment reference edge Es and the non-reference edge En, and an error (rotational angle) γ that is a difference of the angle α from a right angle (STEPS S2 and S3). That is, γ equals 90 degrees minus α. - Next, as shown in
FIGS. 2B and 13 , thecontrol unit 9 controls theslide drive motor 32 such that the obliquely conveyingunit 26 is positioned in the standby position Pw (STEP S4). Then, thecontrol unit 9 judges from job input information whether or not the post-processing reference edge matches the abutment reference edge Es (STEP S5). - In a case where the post-processing reference edge matches the abutment reference edge Es (STEP S5: YES), it is not necessary to change the angle of 0 degree of the
reference member 20 as it is, and, also, it is not necessary to retract the obliquely conveyingunit 26 to the retracting position Pe. That is, theabutment surface 20 a of thereference member 20 becomes parallel to the conveyance direction F. Therefore, in a case where thepre-registration sensor 103 is turned ON (STEP S14: YES) due to the passage of the sheet S, thecontrol unit 9 moves theregistration roller pair 7 by the abutting margin Xo in the width direction W after a predetermined count (SPEP S15). Thereby, thecontrol unit 9 ends the processing. - On the other hand, in a case where the post-processing reference edge does not match the abutment reference edge Es (STEP S5: NO), as shown in
FIG. 3 , thecontrol unit 9 drives theangle adjustment motor 31 such that the angle β of thereference member 20 becomes equal to γ (STEP S6). That is, when the counter-clockwise direction around thepivot shaft 21 as a center is treated as positive, the angle β of thereference member 20 becomes 90 degrees minus α. In other words, the angle β of thereference member 20 becomes the absolute value of thedifference 90 degrees minus α. To be noted, STEP S6 is a movement process in which thereference member 20 is moved such that the angle β becomes the absolute value of thedifference 90 degrees minus α, and STEP S6 is executed before the sheet S has reached theabutment surface 20 a or in a state where the sheet S is abutted against theabutment surface 20 a. - Then, as shown in
FIGS. 3B and 4A , the abutment reference edge Es is abutted against theabutment surface 20 a of thereference member 20 by the obliquely conveying roller pairs 24 a to 24 c, so that the sheet S is conveyed by following theabutment surface 20 a. At this time, the non-reference edge En of the sheet S becomes parallel to the width direction W. To be noted, even if the non-reference edge En inclines within 5 degrees with respect to the width direction W, it is acceptable to consider that non-reference edge En is parallel to the width direction W. - Next, as shown in
FIGS. 4B and 5 , thecontrol unit 9 judges whether or not thepre-registration sensor 103 is turned ON, that is, whether or not the sheet S has reached the pre-registration sensor 103 (STEP S7). In a case where thepre-registration sensor 103 is turned ON (STEP S7: YES), thecontrol unit 9 moves theregistration roller pair 7 in the width direction W at the moving velocity Vr shown in the equation (4) above in a state where theregistration roller pair 7 nips the sheet S (STEP S8). Further, thecontrol unit 9 moves theregistration roller pair 7 by the corrected slide amount Xr shown in the equation (6) above in the width direction W (STEP S9). That is, theregistration roller pair 7 receives the sheet S while moving in the width direction W at the moving velocity Vr which is the velocity calculated based on the angle β. - Further, the
control unit 9 controls theslide drive motor 32 such that the obliquely conveyingunit 26 moves to the retracting position Pe after a predetermined count from the time when thepre-registration sensor 103 is turned ON (STEP S10). Further, thecontrol unit 9 pivots thereference member 20 by theangle adjustment motor 31 such that the angle β becomes equal to 0 degree (STEP S11). To be noted, it is acceptable to perform STEPS S10 and S11 in parallel with or earlier than STEPS S8 and S9. - Then, the
control unit 9 judges whether or not the printing on the second surface is necessary (STEP S12). In a case where the printing on the second surface is not necessary (STEP S12: NO), that is, in a case of a simplex printing job, thecontrol unit 9 ends the processing. - In a case of a duplex printing job in which the printing on the second surface is necessary (STEP S12: YES), in accordance with equations (8) to (10), the
control unit 9 calculates a rotational angle γ, the standby position Pw, and the retracting position Pe, which are used when the sheet S on whose first surface the image has been formed returns to theskew correction unit 55. Then, thecontrol unit 9 stores these in the memory 106 (STEP S13), and returns to STEP S6. - While the
control unit 9 executes STEPS S6 to S11 based on the rotational angle γ, the standby position Pw, and the retracting position Pe stored in thememory 106, since the STEPS S6 to S11 at the time of printing on the second surface are similar to the descriptions at the time of printing on the first surface described above, descriptions will be omitted herein. Since, after the STEPS S6 to S11 at the time of printing on the second surface were ended, the printing on the second surface has been already completed at STEP S12, STEP S12 becomes NO, and thecontrol unit 9 ends the processing. - To be noted, the skew correction control described above is performed on each sheet of the job, and, for example, in a case where the sheet bundle is formed in the
post-processing apparatus 600, the skew correction control is performed on each sheet constituting the sheet bundle. That is, in a case where the post-processing reference edge does not match the abutment reference edge Es, the processing of STEPS S6 to S11 is performed on each sheet constituting the sheet bundle. - As described above, the skew correction control of this embodiment includes a first mode including STEPS S6 to S11 and a second mode including STEPS S14 to S15. The first mode is a mode in which the
reference member 20 is moved such that the angle β becomes 90 degrees minus a before the sheet S has reached theabutment surface 20 a or in a state where the sheet S is abutted against theabutment surface 20 a. The second mode is a mode in which thereference member 20 is positioned such that theabutment surface 20 a becomes parallel to the conveyance direction F before the sheet S has reached theabutment surface 20 a or in a state where the sheet S is abutted against theabutment surface 20 a. - As described above, by this embodiment, even in the case where the post-processing reference edge does not match the abutment reference edge Es, the skew correction control is performed such that the non-reference edge En becomes parallel to the width direction W. Since, in this state, the image is transferred onto the sheet S at the secondary transfer nip T2, the position of the image formed on the sheet S does not vary with respect to the non-reference edge En. Therefore, if the post-processing such as the stapling process is performed with reference to the non-reference edge En in the
post-processing apparatus 600, there is not a variation of the image in the sheet bundle, so that it is possible to improve the quality of the deliverables. - Further, since the
skew correction unit 55 employs an obliquely conveying registration method, it is possible to improve productivity, and also possible to perform the skew correction on various media such as thin paper and cardboard. Further, since the image forming position in theimage forming unit 513 is fixed regardless of the position of the post-processing reference edge, it is possible to improve the productivity. - To be noted, while, in this embodiment, the
skew correction unit 55 is treated as the sheet conveyance apparatus, it is acceptable to consider theimage forming apparatus 100 including theskew correction unit 55 and theimage forming unit 513 as the sheet conveyance apparatus. Further, it is acceptable to consider theimage forming system 1 including theimage forming apparatus 100 and thepost-processing apparatus 600 as the sheet conveyance apparatus. - To be noted, while, in this embodiment, the non-reference edge En which becomes the post-processing reference edge is assumed to be the downstream edge in the conveyance direction F of the sheet S, namely the leading edge of the sheet S, it is not limited to this. For example, it is acceptable to treat an upstream edge in the conveyance direction F of the sheet S, namely the trailing edge Er (refer to
FIG. 2A ), serving as a third edge, opposite to the leading edge of the sheet S as the non-reference edge En which becomes the post-processing reference edge. In this case, by disposing thepre-registration sensors - Further, it is acceptable to configure such that a user is able to arbitrarily choose the leading or trailing edge of the sheet for the post-processing reference edge. For example, it is acceptable to configure such that it is possible to choose the leading or trailing edge of the sheet for the post-processing reference edge by an operation panel of the
image forming apparatus 100, an external personal computer (PC), and the like. Further, it is acceptable to configure such that the leading and trailing edges of the sheet chosen for the post-processing reference edge are automatically switched in theimage forming apparatus 100 in accordance with the post-processing reference edge chosen by thepost-processing apparatus 600. - Further, while, in this embodiment, whether or not the post-processing reference edge matches the abutment reference edge Es is automatically judged from the job input information, it is not limited to this. For example, it is acceptable that the user chooses whether or not the post-processing reference edge matches the abutment reference edge Es. Further, even in the case where the post-processing reference edge does not match the abutment reference edge Es, it is acceptable to configure such that, while not performing the control of STEPS S6 to S13 in
FIG. 13 , the control of STEPS S14 and S15 is performed. By turning OFF the rotation control of thereference member 20 as described above, it is possible to suppress a control load, a motor drive load, and an operational sound. - Further, in any of the embodiments described above, the descriptions are provided by using the
image forming apparatus 100 of the electrophotographic system, this disclosure is not limited to this. For example, it is possible to apply this disclosure to an image forming apparatus of an ink jet system which forms the image on the sheet by ejecting a liquid ink through a nozzle. Further, theimage forming apparatus 100 is not limited to a printer, but includes a copier, a facsimile, a multifunction machine, and the like. - Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
- While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
- This application claims the benefit of Japanese Patent Application No.2021-117930, filed Jul. 16, 2021, which is hereby incorporated by reference herein in its entirety.
Claims (10)
1. A sheet conveyance apparatus comprising:
a conveyance guide configured to guide a sheet along a conveyance center line extending in a conveyance direction;
a reference member including an abutment surface extending along the conveyance direction;
a conveyance unit configured to convey the sheet while abutting a first edge of the sheet against the abutment surface of the reference member;
a detection unit configured to detect a first angle formed between the first edge of the sheet and a second edge adjacent to the first edge;
a moving unit configured to move the reference member so as to change a second angle formed between the abutment surface and the conveyance center line; and
a control unit configured to perform a movement process in which the moving unit moves the reference member such that, when the first angle is referred to as α, the second angle becomes an absolute value of a difference 90 degrees minus α.
2. The sheet conveyance apparatus according to claim 1 , wherein the control unit is configured to perform the movement process such that the second edge of the sheet which is being conveyed while abutting against the abutment surface becomes parallel to a width direction orthogonal to the conveyance direction.
3. The sheet conveyance apparatus according to claim 1 , wherein the movement process is performed on each sheet constituting a sheet bundle.
4. The sheet conveyance apparatus according to claim 1 , further comprising a downstream conveyance unit disposed downstream of the conveyance unit in the conveyance direction and configured to convey the sheet in the conveyance direction,
wherein the downstream conveyance unit is configured to receive the sheet while moving in a width direction orthogonal to the conveyance direction at a velocity determined based on the second angle.
5. The sheet conveyance apparatus according to claim 1 , wherein the second edge is a leading edge or a trailing edge, in the conveyance direction, of the sheet.
6. The sheet conveyance apparatus according to claim 1 , wherein the control unit includes a first mode and a second mode, the first mode being a mode in which the movement process is performed before the sheet has reached the abutment surface or in a state where the sheet is abutted against the abutment surface, the second mode being a mode in which the reference member is positioned such that the abutment surface becomes parallel to the conveyance direction before the sheet has reached the abutment surface or in the state where the sheet is abutted against the abutment surface.
7. The sheet conveyance apparatus according to claim 1 , wherein the reference member is configured to pivot.
8. The sheet conveyance apparatus according to claim 1 , wherein the first edge is an edge extending along the conveyance direction of the sheet, and
wherein the second edge is an edge, extending along a width direction orthogonal to the conveyance direction, of the sheet.
9. An image forming apparatus comprising:
a conveyance guide configured to guide a sheet along a conveyance center line extending in a conveyance direction;
a reference member including an abutment surface extending along the conveyance direction;
a conveyance unit configured to convey the sheet while abutting a first edge of the sheet against the abutment surface of the reference member;
a detection unit configured to detect a first angle formed between the first edge of the sheet and a second edge adjacent to the first edge;
a moving unit configured to move the reference member so as to change a second angle formed between the abutment surface and the conveyance center line;
a control unit configured to perform a movement processing by which the moving unit moves the reference member such that, when the first angle is referred to as α, the second angle becomes an absolute value of a difference 90 degrees minus α; and
an image forming unit configured to form an image on the sheet.
10. An image forming system comprising:
the image forming apparatus according to claim 9 ; and
a post processing apparatus including a regulation portion configured to regulate a position of the second edge or a third edge opposite to the second edge of the sheet, the post processing apparatus being configured to perform processing with respect to the sheet on which the image has been formed by the image forming apparatus and whose position has been regulated by the regulation portion.
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Application Number | Priority Date | Filing Date | Title |
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JP2021-117930 | 2021-07-16 | ||
JP2021117930A JP2023013615A (en) | 2021-07-16 | 2021-07-16 | sheet conveying device |
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US20230017154A1 true US20230017154A1 (en) | 2023-01-19 |
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US17/841,869 Pending US20230017154A1 (en) | 2021-07-16 | 2022-06-16 | Sheet conveyance apparatus, image forming apparatus, and image forming system |
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JP (1) | JP2023013615A (en) |
Citations (6)
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US20040188929A1 (en) * | 2003-03-24 | 2004-09-30 | Fuji Xerox Co., Ltd. | Sheet transporting apparatus and sheet processing apparatus using the same |
US20070085265A1 (en) * | 2005-10-14 | 2007-04-19 | Dejong Joannes N M | Duplex registration systems and methods |
US20070232474A1 (en) * | 2006-03-28 | 2007-10-04 | Hiroki Yamamoto | Sheet folding apparatus |
US20120267847A1 (en) * | 2011-04-22 | 2012-10-25 | Canon Kabushiki Kaisha | Image Forming Apparatus |
US20130113158A1 (en) * | 2011-11-07 | 2013-05-09 | Canon Kabushiki Kaisha | Image forming apparatus |
US20230009594A1 (en) * | 2020-10-26 | 2023-01-12 | Highcon Systems Ltd. | Sheet conveying apparatus |
-
2021
- 2021-07-16 JP JP2021117930A patent/JP2023013615A/en active Pending
-
2022
- 2022-06-16 US US17/841,869 patent/US20230017154A1/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040188929A1 (en) * | 2003-03-24 | 2004-09-30 | Fuji Xerox Co., Ltd. | Sheet transporting apparatus and sheet processing apparatus using the same |
US20070085265A1 (en) * | 2005-10-14 | 2007-04-19 | Dejong Joannes N M | Duplex registration systems and methods |
US20070232474A1 (en) * | 2006-03-28 | 2007-10-04 | Hiroki Yamamoto | Sheet folding apparatus |
US20120267847A1 (en) * | 2011-04-22 | 2012-10-25 | Canon Kabushiki Kaisha | Image Forming Apparatus |
US20130113158A1 (en) * | 2011-11-07 | 2013-05-09 | Canon Kabushiki Kaisha | Image forming apparatus |
US20230009594A1 (en) * | 2020-10-26 | 2023-01-12 | Highcon Systems Ltd. | Sheet conveying apparatus |
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