US20190062093A1 - Sheet conveyance apparatus and image forming apparatus - Google Patents

Sheet conveyance apparatus and image forming apparatus Download PDF

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Publication number
US20190062093A1
US20190062093A1 US16/109,943 US201816109943A US2019062093A1 US 20190062093 A1 US20190062093 A1 US 20190062093A1 US 201816109943 A US201816109943 A US 201816109943A US 2019062093 A1 US2019062093 A1 US 2019062093A1
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United States
Prior art keywords
sheet
conveyance
straight line
conveyance guide
nip
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US16/109,943
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English (en)
Inventor
Hiroshige Inoue
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
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Canon Inc
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Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Assigned to CANON KABUSHIKI KAISHA reassignment CANON KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: INOUE, HIROSHIGE
Publication of US20190062093A1 publication Critical patent/US20190062093A1/en
Abandoned legal-status Critical Current

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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
    • 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
    • B65H9/006—Deskewing sheet by abutting against a stop, i.e. producing a buckling of the sheet the stop being formed by forwarding means in stand-by
    • 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
    • B65H5/06—Feeding articles separated from piles; Feeding articles to machines by rollers or balls, e.g. between rollers
    • B65H5/062—Feeding articles separated from piles; Feeding articles to machines by rollers or balls, e.g. between rollers between rollers or balls
    • 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
    • B65H5/38—Article guides or smoothers, e.g. movable in operation immovable 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
    • B65H2404/00—Parts for transporting or guiding the handled material
    • B65H2404/60—Other elements in face contact with handled material
    • B65H2404/61—Longitudinally-extending strips, tubes, plates, or wires
    • B65H2404/611—Longitudinally-extending strips, tubes, plates, or wires arranged to form a channel
    • B65H2404/6111—Longitudinally-extending strips, tubes, plates, or wires arranged to form a channel and shaped for curvilinear transport path

Definitions

  • the present invention relates to a sheet conveyance apparatus for conveying sheets and an image forming apparatus equipped with the same.
  • a sheet fed from a sheet feeding unit is abutted against a nip of a registration roller pair whose rotation is stopped, to thereby form a loop on the sheet and correct skewing of the sheet.
  • the registration roller pair rotates to convey the sheet to an image forming portion, and an image is formed on the sheet at the image forming portion.
  • Japanese Patent Laid-Open Publication No. 2000-118801 proposes an image forming apparatus in which an amount of loop formed on the sheet is adjusted based on sheet type information.
  • the image forming apparatus controls the registration roller pair to form a greater loop in a normal paper having relatively weak stiffness compared to a sheet having greater stiffness such as envelope, postcard, thick paper and OHP sheet.
  • a sheet conveyance apparatus includes a first rotary member pair comprising a first nip portion and configured to convey a sheet, a second rotary member pair arranged downstream of the first rotary member pair in a sheet conveyance direction, comprising a second nip portion and configured to convey the sheet being conveyed by the first rotary member pair, and a conveyance guide configured to guide the sheet having passed through the first nip portion to the second nip portion, and forming a curved conveyance path, the conveyance guide including a first conveyance guide portion forming a loop space and a second conveyance guide portion arranged downstream of the first conveyance guide portion in the sheet conveyance direction, the conveyance path including the loop space in which a sheet abutted against the second nip portion is capable of forming a loop.
  • the first rotary member pair and the second rotary member pair are arranged adjacently.
  • the second nip portion is positioned upward than the first nip portion in a vertical direction and positioned at a position different from the first nip portion in a horizontal direction.
  • the conveyance guide is arranged on an outer side of the curved conveyance path between the first nip portion and the second nip portion. The sheet conveyed by the first rotary member pair is abutted against the second nip portion so as to correct skewing of the sheet.
  • a common tangent of the first rotary member pair at the first nip portion is referred to as a first straight line
  • a common tangent of the second rotary member pair at the second nip portion is referred to as a second straight line
  • a straight line that passes an intersection of the second straight line and the conveyance guide and has an inclination corresponding to the second conveyance guide portion is referred to as a third straight line
  • the second straight line and the third straight line intersect each other
  • the loop space is arranged upstream of the intersection of the second straight line and the conveyance guide in the sheet conveyance direction
  • a first intersection at which the first straight line and the third straight line intersect is positioned within the loop space
  • a second intersection at which the first straight line and the second straight line intersect is positioned outside the conveyance path.
  • FIG. 1 is an overall schematic view illustrating a printer according to a present embodiment.
  • FIG. 2 is a schematic diagram illustrating a manual sheet feed apparatus and a skewing correction apparatus.
  • FIG. 3 is a control block diagram illustrating a controller.
  • FIG. 4 is a flowchart illustrating a sheet conveyance control.
  • FIG. 5 is a graph showing a positional relationship between respective rollers and the sheet.
  • FIG. 6A is a view illustrating a state in which a leading edge of the sheet is abutted against a nip of a registration roller pair.
  • FIG. 6B is a view illustrating a state in which the sheet has formed a loop.
  • FIG. 6C is a view illustrating a state in which a sheet is conveyed by the registration roller pair and a pre-registration roller pair.
  • FIG. 7A is a view illustrating a state in which a shearing force acting on the sheet escapes.
  • FIG. 7B illustrates a state in which a trailing edge of the sheet has passed through the pre-registration roller pair.
  • FIG. 8A is a view illustrating a conveyance guide according to a first modified example.
  • FIG. 8B is a view illustrating a conveyance guide according to a second modified example.
  • FIG. 9 is a view illustrating a skewing correction apparatus according to a comparative example.
  • FIG. 10 is a view illustrating torsion acting on the sheet.
  • a printer 201 serving as an image forming apparatus is an electro-photographic full-color laser beam printer.
  • the printer 201 includes, as illustrated in FIG. 1 , a printer body 201 A serving as an apparatus body, and a reading unit disposed above the printer body 201 A for reading image data on a document.
  • the printer body 201 A includes an image forming portion 201 B for forming an image on a sheet P, a fixing portion 220 for fixing an image on the sheet P, and so on.
  • a sheet discharge space to which the sheet P is discharged is formed between the reading unit 202 and the printer body 201 A, and a sheet discharge tray 230 supporting the discharged sheets P is arranged in the sheet discharge space.
  • a sheet feeding unit 201 E for feeding sheets P to the image forming portion 201 B is provided on the printer body 201 A.
  • the sheet feeding unit 201 E includes sheet feed cassettes 100 A, 100 B, 100 C and 100 D arranged at a lower portion of the printer body 201 A and storing sheets P in cassettes 103 , and a manual sheet feed apparatus 100 M arranged on a right side portion of the printer body 201 A.
  • Each of the sheet feed cassettes 100 A, 100 B, 100 C and 100 D and the manual sheet feed apparatus 100 M includes a pickup roller 2 for feeding sheets P, and a feed roller 3 and a retard roller 4 for separating the sheet P one by one and conveying the same.
  • the image forming portion 201 B is a so-called four-drum full color image forming portion that includes a laser scanner 210 , four process cartridges 211 , and an intermediate transfer unit 201 C.
  • the process cartridges respectively form toner images of different colors, which are yellow (Y), magenta (M), cyan (C) and black (K).
  • Each process cartridge 211 includes a photosensitive drum 212 , a charger 213 , a developer 214 , a cleaner not shown and so on.
  • a toner cartridge 215 storing toner of respective colors is removably attached to the printer body 201 A at an area above the image forming portion 201 B.
  • the intermediate transfer unit 201 C includes an intermediate transfer belt 216 wound around a drive roller 216 a , a tension roller 216 b and so on, and the intermediate transfer belt 216 is arranged above the four process cartridges 211 .
  • the intermediate transfer belt 216 is arranged to contact the photosensitive drums 212 of the respective process cartridges 211 , and driven to rotate in a counterclockwise direction, that is, direction of arrow Q, by the drive roller 216 a which is driven by a driving unit not shown.
  • the intermediate transfer unit 201 C includes primary transfer rollers 219 that contact an inner circumferential surface of the intermediate transfer belt 216 at positions opposed to respective photosensitive drums 212 , and a primary transfer portion TP 1 is formed as a nip portion between the intermediate transfer belt 216 and the photosensitive drum 212 .
  • the image forming portion 201 B includes a secondary transfer roller 217 that contacts an outer circumference surface of the intermediate transfer belt 216 at a position opposed to the drive roller 216 a .
  • a secondary transfer portion TP 2 is formed as a nip portion between the secondary transfer roller 217 and the intermediate transfer belt 216 where a toner image borne on the intermediate transfer belt 216 is transferred onto a sheet P.
  • an electrostatic latent image is formed on the surface of the photosensitive drum 212 by the laser scanner 210 , and thereafter, toner is supplied from the developer 214 so that toner images of respective colors charged to negative polarity are formed.
  • the toner images are sequentially transferred in multilayers on the intermediate transfer belt 216 at the respective primary transfer portions TP 1 by having transfer bias voltage of positive polarity applied to the primary transfer roller 219 , and a full color toner image is formed on the intermediate transfer belt 216 .
  • the sheet P fed from the sheet feeding unit 201 E is conveyed toward a registration roller pair 15 and skewing of the sheet P is corrected by the registration roller pair 15 .
  • the registration roller pair 15 conveys the sheet P to the secondary transfer portion TP 2 at a matched timing with the transfer timing of the full color toner image formed on the intermediate transfer belt 216 .
  • the toner image borne on the intermediate transfer belt 216 is secondarily transferred to the sheet P at the secondary transfer portion TP 2 by having transfer bias voltage of positive polarity applied to the secondary transfer roller 217 .
  • the sheet P to which the toner image has been transferred is heated and pressed at the fixing portion 220 , and the color image is fixed to the sheet P.
  • the sheet P on which the image has been fixed is discharged by a sheet discharge roller pair 225 to the sheet discharge tray 230 and supported thereon. If it is necessary to form images on both sides of the sheet P, the sheet P having passed the fixing portion 220 is switched back by a reverse conveyance roller pair 222 that is capable of rotating in normal and reverse directions provided in a reverse conveyance portion 201 D. Thereafter, the sheet P is conveyed again to the secondary transfer portion TP 2 through a re-conveyance path R, and an image is formed on the rear side of the sheet P.
  • the pickup roller 2 , the feed roller 3 and the retard roller 4 of the manual sheet feed apparatus 100 M are connected to a sheet feed motor M 1 , and a torque limiter not shown is arranged between the sheet feed motor M 1 and the retard roller 4 .
  • the pickup roller 2 and the feed roller 3 receive drive force from the sheet feed motor M 1 that rotates the rollers in a direction conveying the sheet P toward the skewing correction apparatus 100 R, and the retard roller 4 receives drive force toward an opposite direction from the sheet feed motor M 1 .
  • the sheet feed motor M 1 is driven in a state where the pickup roller 2 contacts the sheet P with a predetermined pressure.
  • the sheet P fed by the pickup roller 2 is conveyed to a separation nip 3 a formed by the feed roller 3 and the retard roller 4 , and the sheet is separated one by one at the separation nip 3 a . That is, if no sheet P or one sheet P enters the separation nip 3 a , the torque limiter rotates idly, and the retard roller 4 rotates following the rotation of the feed roller 3 , conveying the sheet P toward the skewing correction apparatus 100 R.
  • the sheet P separated one by one at the separation nip 3 a is conveyed to a pre-registration roller pair 8 .
  • the pre-registration roller pair 8 serving as a first rotary member pair is connected to a pre-registration motor M 2 , and the pre-registration roller pair 8 is rotated by driving the pre-registration motor M 2 .
  • the sheet P is conveyed toward a conveyance guide 18 by a nip 8 a serving as a first nip portion of the pre-registration roller pair 8 and guided by the conveyance guide 18 to the registration roller pair 15 .
  • a registration sensor 12 is arranged upstream in a sheet conveyance direction of a nip 15 a serving as a second nip portion of the registration roller pair 15 , and the registration sensor 12 detects a leading edge position of the sheet P.
  • the registration roller pair 15 serving as a second rotary member pair is connected to a registration motor M 3 , and in a state where the leading edge of the sheet P reaches the nip 15 a of the registration roller pair 15 , the registration motor M 3 is stopped. Therefore, the leading edge of the sheet P is abutted against the nip 15 a of the registration roller pair 15 in the stopped state. In this state, the sheet P is further conveyed by the pre-registration roller pair 8 , such that the sheet P forms a loop and skewing is corrected.
  • the registration roller pair 15 starts to rotate after being stopped for a predetermined time, and the sheet P is conveyed by the registration roller pair 15 and the pre-registration roller pair 8 toward the secondary transfer portion TP 2 . Since skewing of the sheet P is corrected by the skewing correction apparatus 100 R, the sheet P and the image transferred to the sheet P at the secondary transfer portion TP 2 will not be skewed or laterally dislocated, and a good product can be obtained.
  • a size detection sensor 11 and the registration sensor 12 are connected to an input side of a controller 9 of the printer 201 .
  • the size detection sensor 11 detects the size of the sheet P supported on the manual sheet feed tray 7 or a cassette 103 .
  • the sheet feed motor M 1 , the pre-registration motor M 2 and the registration motor M 3 are connected to an output side of the controller 9 .
  • a timer 13 is connected to the controller 9 .
  • FIG. 4 is a flowchart illustrating conveyance control of the sheet P
  • FIG. 5 is a graph illustrating theoretical positions of a leading edge and a trailing edge of the sheet at the pickup roller 2 , the pre-registration roller pair 8 , the registration sensor 12 , the registration roller pair 15 and the secondary transfer roller 217 .
  • Line A illustrates a theoretical line indicating the tip position of the sheet P
  • line B illustrates a theoretical line indicating a trailing edge position of the sheet P.
  • Lines D, E and F respectively illustrate peripheral drive speeds of the pickup roller 2 , the pre-registration roller pair 8 and the registration roller pair 15 .
  • the theoretical line B illustrating the trailing edge position of the sheet P can be calculated based on the theoretical line A of the tip position of the sheet P and a length L of the sheet P detected by the size detection sensor 11 .
  • the controller 9 detects the size of the fed sheet P by the size detection sensor 11 (step S 1 ). If the size of the sheet P is detected (step S 1 : YES), the controller 9 determines a length L of the sheet P (step S 2 ). The controller 9 drives the sheet feed motor M 1 and the pre-registration motor M 2 (step S 3 ). At this time, the peripheral drive speed of the pickup roller 2 and the pre-registration roller pair 8 are set to a sheet feed speed V 1 .
  • the controller 9 stops the sheet feed motor M 1 and stops the pickup roller 2 .
  • the pickup roller 2 can be separated from the sheet P by a swing arm not shown.
  • an intermediate plate for supporting a sheet can be provided on the manual sheet feed tray 7 , and the intermediate plate can be moved downward.
  • a one-way clutch can be provided to the pickup roller 2 .
  • the controller 9 measures a control time, which is an elapsed time from when drive of the pickup roller 2 has been started, using a timer 13 , and determines whether a leading edge of the sheet P has been detected by the registration sensor 12 within a control time T 1 calculated in advance (step S 4 ). If the leading edge of the sheet P is not detected within the control time T 1 (step S 4 : NO), the controller 9 determines that delay jam has occurred (step S 5 ). If it is determined that delay jam has occurred, the user is notified that jam has occurred by an alarm sound and a display on an operation panel.
  • a control time which is an elapsed time from when drive of the pickup roller 2 has been started, using a timer 13 , and determines whether a leading edge of the sheet P has been detected by the registration sensor 12 within a control time T 1 calculated in advance (step S 4 ). If the leading edge of the sheet P is not detected within the control time T 1 (step S 4 : NO), the controller 9 determines that delay jam has occurred (step S
  • step S 4 If the leading edge of the sheet P is detected within the control time T 1 by the registration sensor 12 (step S 4 : YES), the controller 9 stops the pre-registration motor M 2 at control time T 2 (step S 6 ).
  • the leading edge of the sheet P reaches the nip 8 a of the pre-registration roller pair 8 between control time T 1 and control time T 2 , and the pre-registration motor M 2 is continued to be driven even after the leading edge has reached the nip 8 a , so that the sheet P forms a loop.
  • the controller 9 sets the control time T 2 so that an amount of loop calculated in advance is formed on the sheet P.
  • the controller 9 drives the pre-registration motor M 2 and the registration motor M 3 at control time T 3 (step S 7 ).
  • the pre-registration roller pair 8 and the registration roller pair 15 are rotated at image forming speed V 2 , and the sheet P is conveyed toward the secondary transfer portion TP 2 .
  • the image forming speed V 2 is equal to a rotational speed of the intermediate transfer belt 216 .
  • the pre-registration roller pair 8 does not have to be driven at the same timing as the registration roller pair 15 at control time T 3 , and driving of the pre-registration roller pair 8 can be started at a later timing than the registration roller pair 15 as long as it is started before the loop formed on the sheet P is dissolved. That is, driving of the pre-registration roller pair 8 can be started on or before control time T 4 , which is a time having added time X 1 to control time T 3 , time X 1 being the time when the registration roller pair 15 dissolves the loop formed on the sheet Pin a state where the pre-registration roller pair 8 is stopped.
  • the controller 9 stops the pre-registration motor M 2 at control time T 5 when the trailing edge of the sheet P passes the pre-registration roller pair 8 and stops the rotation of the pre-registration roller pair 8 (step S 8 ). Further, the controller 9 stops the registration motor M 3 at control time T 6 when the trailing edge of the sheet P passes the registration roller pair 15 and stops the rotation of the registration roller pair 15 (step S 9 ). Thereby, conveyance control of the sheet P is completed.
  • control times T 5 and T 6 are not restricted to the times at which the trailing edge of the sheet passes the pre-registration roller pair 8 and the registration roller pair 15 , and the times can be somewhat varied within a range that does not affect the conveyance of the sheet P Further, conveyance control of the sheet P according to the present embodiment illustrates a case where the sheet feed speed V 1 is approximately 300 mm/sec and the image forming speed V 2 is approximately 250 mm/sec, but the sheet feed speed V 1 and the image forming speed V 2 can be varied arbitrarily.
  • the skewing correction apparatus 101 R includes a pre-registration roller pair 8 , a registration roller pair 15 and a conveyance guide 118 provided between the pre-registration roller pair 8 and the registration roller pair 15 .
  • the conveyance guide 118 includes a guide surface 118 a that extends in parallel with a nip line NL 2 , which is a common tangent of the registration roller pair 15 at the nip 15 a , and guides the sheet P to the nip 15 a . Further, the conveyance guide 118 includes a bulged portion 118 c that curves from an upstream end 118 b of the guide surface 118 a in a sheet conveyance direction, and bulges toward a direction away from a nip line NL 1 , which is a common tangent of the pre-registration roller pair 8 at the nip 8 a .
  • the bulged portion 118 c forms a loop space 119 in which the sheet P is capable of forming a loop. Further, a first opposing guide 20 and a second opposing guide 23 are arranged to oppose to the conveyance guide 118 , and a curved conveyance path CP 1 , including the loop space 119 , is formed by the conveyance guide 118 , the first opposing guide 20 and the second opposing guide 23 .
  • the nip line NL 1 and the nip line NL 2 intersect at an intersection 132 on the guide surface 118 a of the conveyance guide 118 . That is, the nip line NL 1 intersects with the guide surface 118 a . Thereby, the sheet P conveyed to a direction parallel to the nip line NL 1 by the pre-registration roller pair 8 contacts the guide surface 118 a of the conveyance guide 118 near the intersection 132 and changes its path to a direction parallel to the nip line NL 2 along the guide surface 118 a .
  • the nip line NL 2 and the guide surface 118 a are illustrated as if a slight gap is formed therebetween, but the gap is merely illustrated for the sake of explanation, and actually, the nip line NL 2 is overlapped with the guide surface 118 a.
  • the sheet P forms a loop within the loop space 119 by the leading edge of the sheet P abutting against the nip 15 a of the registration roller pair 15 , and by contact force of the sheet P and the conveyance guide 118 , sagging of the sheet by gravity can be prevented even if the rigidity of the sheet P is low. Therefore, conveyance force of the pre-registration roller pair 8 is transmitted to the leading edge of the sheet P, and the leading edge of the sheet P is pressed against the nip 15 a , by which skewing is corrected reliably.
  • the sheet P having its leading edge abutted against the nip 15 a of the registration roller pair 15 and forming a loop is illustrated by a broken line
  • the sheet P whose skewing is corrected and conveyed by the registration roller pair 15 and the pre-registration roller pair 8 is illustrated by a solid line.
  • the sheet P illustrated by the broken line is subjected to skew feed control at the nip 15 a at the leading edge side, but the trailing edge side of the sheet P is still skewed, so that torsion is generated in the loop formed between the registration roller pair 15 and the pre-registration roller pair 8 . Therefore, if the sheet P is continued to be conveyed by the registration roller pair 15 and the pre-registration roller pair 8 , shearing force acting on the sheet P is gradually increased.
  • creases PW tend to be formed on the sheet P. Creases PW tend to be formed on a sheet having a long size or having a low rigidity. Further, creases PW are significantly formed in a case where the distance between two sets of rollers for forming a loop on the sheet is set short or in a case where conveyance force of the two sets of rollers is set high.
  • the skewing correction apparatus 100 R includes the pre-registration roller pair 8 , the registration roller pair 15 , and the conveyance guide 18 provided between the pre-registration roller pair 8 and the registration roller pair 15 .
  • the pre-registration roller pair 8 is composed of a pair of rubber rollers, and nip pressure of the pre-registration roller pair 8 is set high so as to convey a sheet having a relatively high grammage, such as thick paper.
  • the conveyance guide 18 has a different shape as the conveyance guide 118 according to the above-described comparative example.
  • the nip 15 a of the registration roller pair 15 is positioned upward than the nip 8 a of the pre-registration roller pair 8 in the vertical direction and at a position that differs from the nip 8 a in the horizontal direction.
  • the conveyance guide 18 is provided on an outer side of a curved conveyance path CP between the nip 8 a and the nip 15 a .
  • the nip line NL 2 serving as a second straight line, which is a common tangent of the registration roller pair 15 at the nip 15 a intersects with a guide surface 18 a serving as a second conveyance guide portion at an intersection 31 .
  • the guide surface 18 a guides the sheet P to the nip 15 a .
  • the intersection 31 is separated by distance h 2 from the nip 15 a in a direction parallel to the nip line NL 2 .
  • the conveyance guide 18 includes a bulged portion 18 c bulging toward a direction away from the nip line NL 1 as a first straight line which is a common tangent of the pre-registration roller pair 8 at the nip 8 a .
  • the bulged portion 18 c serving as a first conveyance guide portion, is formed in a curved shape and formed continuously with an upstream end 18 b , in the sheet conveyance direction, of the guide surface 18 a . It is noted that the bulged portion 18 c is provided so as to intersect with the nip line NL 1 .
  • the guide surface 18 a is a flat surface which is formed linearly and non-parallelly with the nip lines NL 1 and NL 2 between the upstream end 18 b and a downstream end 18 d .
  • the bulged portion 18 c forms a loop space 19 in which the sheet P can form a loop.
  • the first opposing guide 20 and the second opposing guide 23 are arranged to oppose to the conveyance guide 18 , and a conveyance path CP including the loop space 19 is formed by the conveyance guide 18 , the first opposing guide 20 and the second opposing guide 23 .
  • the pre-registration roller pair 8 and the registration roller pair 15 are arranged adjacently in the conveyance path CP.
  • a straight line that passes the intersection 31 and has an inclination corresponding to the guide surface 18 a that is, if a tangent which is tangent to the conveyance guide 18 at the intersection 31 is referred to as a straight line TL 2
  • the straight line TL 2 serving as a third straight line is inclined by minor angle ⁇ 1 with respect to the nip line NL 2 . That is, the nip line NL 2 and the straight line TL 2 intersect.
  • a minor angle is a smaller angle of angles formed by two straight lines, and it is equal to or smaller than 90 degrees.
  • the straight line TL 2 is inclined by minor angle ⁇ 2 , that is greater than minor angle ⁇ 1 , with respect to the nip line NL 1 of the pre-registration roller pair 8 . That is, the minor angle ⁇ 2 formed by the nip line NL 1 serving as the first straight line and the straight line TL 2 is greater than the minor angle ⁇ 1 formed by the nip line NL 2 serving as the second straight line and the straight line TL 2 ( ⁇ 2 > ⁇ 1 ).
  • an inclined surface 19 a downstream of the bulged portion 18 c formed from the upstream end 18 b of the guide surface 18 a extends along the straight line TL 1 , and the straight line TL 2 is inclined by minor angle ⁇ 3 with respect to the straight line TL 1 .
  • the loop space 19 is a space that is sufficiently greater than a pre-registration conveyance space 21 serving as conveyance space between the conveyance guide 18 and the registration roller pair 15 .
  • the nip 8 a and 15 a are positioned on one side with respect to the straight line TL 2 .
  • the minor angle ⁇ 1 to approximately 10°
  • the minor angle ⁇ 2 to approximately 20°
  • the minor angle ⁇ 3 to approximately 15°
  • the distance h 2 to approximately 10 mm
  • the length of the guide surface 18 a to approximately 15 to 20 mm
  • intersection 32 serving as a first intersection between the nip line NL 1 and the straight line TL 2 is separated by a distance h 1 in a direction parallel with the straight line TL 2 from the upstream end 18 b of the guide surface 18 a , and it is positioned within the loop space 19 . That is, the intersection 32 is positioned within the conveyance path CP. Further, the nip line NL 1 intersects with the inclined surface 19 a of the bulged portion 18 c , and an intersection 33 serving as a second intersection in which the nip line NL 1 and the nip line NL 2 intersect is positioned outside the conveyance path CP through which the sheet passes.
  • the sheet P conveyed by the pre-registration roller pair 8 is conveyed to a direction parallel to the nip line NL 1 and contacts the inclined surface 19 a of the bulged portion 18 c , and changes its course along the inclined surface 19 a . Further, the sheet P is transferred from the inclined surface 19 a to the guide surface 18 a , and the sheet P is guided along the guide surface 18 a to a direction parallel to the straight line TL 2 .
  • the leading edge of the sheet conveyed by the pre-registration roller pair 8 is guided to the guide surface 18 a by the inclined surface 19 a of the bulged portion 18 c , and thereafter, guided by the guide surface 18 a to the nip 15 a of the registration roller pair 15 .
  • the leading edge of the sheet P is abutted against the nip 15 a of the registration roller pair 15 and the leading edge of the sheet P faces a direction parallel to the nip line NL 2 .
  • a reaction force F 1 acting on the leading edge of the sheet P from the nip 15 a and a contact force F 2 between the sheet P and the guide surface 18 a are balanced.
  • the guide surface 18 a extends in a direction inclined by angle ⁇ 4 with respect to a gravity direction (refer to FIG. 2 ), contacts the sheet sagged by its own weight, and receives load from the sheet.
  • the sheet P forms a loop that originates from an area close to the intersection 32 .
  • a reaction force F 3 acting on the leading edge of the sheet P from the nip 15 a and a contact force F 4 between the sheet P and the guide surface 18 a are balanced.
  • contact force between the sheet P and the guide surface 18 a of the conveyance guide 18 prevents sagging of the sheet by gravity even if the rigidity of the sheet P is low. Therefore, conveyance force of the pre-registration roller pair 8 can be transmitted to the leading edge of the sheet P, and the leading edge of the sheet P can be pressed against the nip 15 a , by which skewing can be corrected reliably.
  • the nip line NL 2 of the registration roller pair 15 and the guide surface 18 a of the conveyance guide 18 intersect at the intersection 31 . Therefore, in a state where the sheet abuts against the nip 8 a and forms a loop, the contact force of the sheet P and the guide surface 18 a enables to press the leading edge of the sheet against the nip 8 a , and skewing of even a sheet having low rigidity, such as thin paper, can be corrected reliably.
  • the straight line TL 2 and the nip line NL 1 of the pre-registration roller pair 8 intersect at the intersection 32 within the loop space 19 distant from the conveyance guide 18 . Therefore, in a state where the sheet in which a loop is formed is conveyed by the registration roller pair 15 and the pre-registration roller pair 8 , even if the shearing force acting on the sheet is increased, the shearing force can be released to the loop originated from the intersection 32 . Thus, buckling and creasing of the sheet can be prevented.
  • the loop space 19 is sufficiently greater than the pre-registration conveyance space 21 formed between the conveyance guide 18 and the registration roller pair 15 , the loop of the sheet is mainly formed within the loop space 19 , and shearing force can be released reliably within the loop space 19 .
  • the embodiment is configured such that during conveyance of the sheet P, the sheet P is bent in two steps, one originating from the intersection 31 and the other originating from the intersection 32 , so that even if the distance between the registration roller pair 15 and the pre-registration roller pair 8 is narrow, skewing of the sheet can be corrected reliably and creasing can be prevented.
  • the shearing force can be released to the loop space 19 before the sheet is buckled, so that creasing of the sheet can be prevented. Therefore, the present embodiment is capable of corresponding to various media, such as long-size sheet, small-size sheet, thin paper, thick paper and coated paper.
  • the guide surface 18 a of the conveyance guide 18 and the inclined surface 19 a of the bulged portion 18 c are connected in a curved manner at the upstream end 18 b , but instead of the conveyance guide 18 , conveyance guides 128 and 138 may be formed as described below.
  • the conveyance guide 128 composes a contact portion 128 b between the guide surface 18 a and the bulged portion 18 c by a curved line of radius J, so that the guide surface 18 a and the inclined surface 19 a are connected smoothly.
  • the conveyance guide 138 includes a convex portion 138 e that protrudes inward of the conveyance path CP and a concave portion 138 d that protrudes outward of the conveyance path CP, and the inclined surface 19 a is formed continuously from the convex portion 138 e.
  • the pre-registration roller pair 8 and the registration roller pair 15 are both composed of a pair of rollers, but the present embodiment is not restricted thereto, and one or the other of the rollers may be formed of a rotary member such as a belt. Further, the conveyance guides 18 , 128 and 138 may each be composed of a guide member divided into multiple parts.
  • the present invention can be applied to an inkjet image forming apparatus in which inks are ejected from nozzles to form images on sheets.
  • 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.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Registering Or Overturning Sheets (AREA)
  • Feeding Of Articles By Means Other Than Belts Or Rollers (AREA)
US16/109,943 2017-08-30 2018-08-23 Sheet conveyance apparatus and image forming apparatus Abandoned US20190062093A1 (en)

Applications Claiming Priority (2)

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JP2017166166A JP2019043701A (ja) 2017-08-30 2017-08-30 シート搬送装置及び画像形成装置
JP2017-166166 2017-08-30

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US20190062093A1 true US20190062093A1 (en) 2019-02-28

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US16/109,943 Abandoned US20190062093A1 (en) 2017-08-30 2018-08-23 Sheet conveyance apparatus and image forming apparatus

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US (1) US20190062093A1 (pl)
JP (1) JP2019043701A (pl)

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US20220162025A1 (en) * 2020-11-25 2022-05-26 Canon Kabushiki Kaisha Sheet conveyance device and image forming apparatus equipped with sheet conveyance device
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US11905138B2 (en) * 2020-11-25 2024-02-20 Canon Kabushiki Kaisha Sheet conveyance device and image forming apparatus equipped with sheet conveyance device

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