JP4016621B2 - Transport device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transport apparatus that transports a sheet-like transport target such as paper. More specifically, for example, it is used in an image forming apparatus such as a copying machine or a printing apparatus (printer), stops the rotation of the downstream conveyance unit, functions as an abutting member, and conveys the paper in the upstream conveyance unit. The present invention also relates to a transport device having a mechanism for correcting paper distortion by abutting the paper against a downstream transport unit.
[0002]
[Prior art]
In image forming apparatuses such as copying machines and printing apparatuses, for example, a toner image is formed by charging, exposing, and developing the photosensitive member, and a sheet is formed on the photosensitive drum on which the toner image is formed. A toner image is transferred onto the sheet by supplying a sheet of paper or a document (hereinafter also referred to simply as a sheet), and an image is formed on the sheet by heating and pressing the sheet onto which the toner image has been transferred. In this process, the sheet is disposed on the sheet conveyance path and is conveyed by a pair of rolls that nipping and conveying the sheet.
[0003]
By the way, when the sheet is conveyed by the roll pair in this way, for example, only one of the various types of rolls is disposed obliquely with respect to the sheet conveyance path, or only one of the various types of rolls is not uniform. Even if it is formed with a different roll diameter, the sheet is transported by the roll in a direction deviated from the original transport direction, that is, the direction along the transport path of the sheet. In this case, the sheet is conveyed in a state where the posture of the sheet is deviated from the conveying direction. Such a conveyance state of the sheet is called oblique feeding (skew, skew distortion). For example, if the sheet is supplied to the transfer position while being obliquely fed, the toner image is transferred obliquely with respect to the sheet, and the image formed on the sheet is formed obliquely shifted.
[0004]
In order to solve this problem, a pair of registration rolls (registration resists) functioning as an abutting member on the upstream side of the sheet conveyance path from the transfer position and serving as a downstream conveyance unit that sandwiches (grips) and conveys the sheet. Roll) and a pair of pre-registration rolls (pre-registration roll pairs) as an upstream-side conveyance unit that sandwiches and conveys the sheet on the upstream side of the sheet conveyance path from the registration roll. Many conveying apparatuses having a mechanism that corrects skew distortion by abutting one side of a sheet tip against a member (registration roll) have been proposed (for example, Japanese Utility Model Laid-Open No. 58-158049 and Japanese Patent Laid-Open No. 10-181934).
[0005]
[Problems to be solved by the invention]
Here, for example, a thick sheet such as thick paper may pierce the roller element when the skewed sheet leading edge enters the roller nip (contact portion) of the rotation-stopped registration roll pair that functions as an abutting member. In this case, one side of the sheet front end does not uniformly contact the registration roll pair, and thus skew distortion cannot be corrected sufficiently.
[0006]
Also, in order to increase productivity when processing a large number of sheets at once, it is necessary to reduce the interval of waiting for the conveyance of the previous sheet and the next sheet. Since the registration roll pair must be uniformly contacted, the next sheet must not be fed to the registration roll pair until the rotation of the registration roll pair is stopped after the previous sheet is conveyed. In other words, when considering variations in the roller stop time, variations in the sheet feed amount, or variations in the skew feeding amount, the leading edge of the next sheet is not aligned with the registration roll unless a certain interval is provided in consideration of the safety factor. It will rush into the roller nip before stopping. When the sheet enters the roller nip, the sheet is sandwiched between the roller nips, so that skew distortion cannot be corrected. In addition, if the sheet is conveyed downstream in that state, the registration accuracy may be deteriorated.
[0007]
The present invention has been made in view of the above circumstances, and even when a sheet is caught in a contact portion of a downstream conveyance unit or pierced into a roll element, skew correction can be reliably realized. An object is to provide a transport device.
[0008]
[Means for Solving the Problems]
That is, a transport apparatus according to the present invention includes an upstream transport unit that is disposed on the upstream side of a transport path and transports a sheet-shaped transported body between a pair of rotating bodies, and a transport path. A downstream transport unit disposed downstream of the upper upstream transport unit and sandwiching the transported body transported by the upstream transport unit between a pair of rotating bodies and transporting further downstream; A transport device that forwardly drives the upstream transport section to transport the transported body and abuts the transported body against the downstream transport section to correct skew distortion of the transported body, A control unit that corrects skew distortion by driving the downstream conveyance unit in reverse rotation at a timing near the end of the body reaching the downstream conveyance unit, and then releasing the reverse rotation driving of the downstream conveyance unit after a predetermined time has elapsed. Prepared.
For example , System The control unit has a contact state detection unit that detects whether one side that is the tip of the transported body is in contact with the downstream transport unit substantially uniformly, and first stops the rotation of the downstream transport unit. On the condition that the transported body is transported to the downstream transport unit side by the upstream transport unit, and then the contact state detection unit detects that one side of the transported body is not substantially in contact with the downstream side. The side transport unit is driven in reverse.
[0009]
Here, “the timing in the vicinity of the leading end of the transported body reaching the downstream transport unit” is not limited to the point in time when the leading end of the transported body reaches the downstream transport unit, and the leading end points to the downstream transport unit. It means to include the time when the fixed amount has passed and the time when the tip almost reaches the downstream side transport unit (for example, immediately before). In short, if it is an appropriate timing in the vicinity where the tip of the transported body hits the downstream side transport unit Good.
[0010]
[Action]
In the transport apparatus of the present invention, the control unit reverses the downstream transport unit at an appropriate timing before and after the leading end of the transported body hits the downstream transport unit, and then reverses the downstream transport unit after a predetermined time has elapsed. By canceling, the skew distortion is corrected. On this occasion This The downstream conveyance unit is driven in reverse rotation on the condition that the contact state detection unit detects that one side of the transported body does not contact substantially uniformly. In other words, one side of the transported body is applied substantially uniformly. The downstream conveyance unit is driven in reverse until the contact state detection unit detects that the contact has occurred.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a diagram illustrating an outline of the overall configuration of an embodiment of an image forming apparatus including a conveyance unit which is an example of a conveyance apparatus according to the present invention. This image forming apparatus supplies a sheet to an image forming unit 100 that transfers a toner image onto a sheet (paper medium) that is an example of a sheet-like transported body and a transfer position that transfers the toner image onto the sheet. A conveyance unit 200 is included. The image forming unit 100 provided in the image forming apparatus includes a photosensitive drum 1 that is rotatably arranged, a charging corotron 2 that charges the photosensitive drum 1 to a uniform potential, and a photosensitive drum 1 that has been charged. The toner is transferred to the sheet P supplied to the transfer position between the exposure unit 3 that exposes the image according to the image information, the developing unit 4 that supplies the toner to the exposed photosensitive drum 1, and the photosensitive drum 1. The transfer corotron 5 is provided. Further, the image forming unit 100 includes a neutralizing corotron 6 that neutralizes the sheet P and the photosensitive drum 1 after the transfer, a cleaning member 7 that removes dirt such as residual toner from the photosensitive drum 1 after the neutralization, and a sheet more than the transfer position. A heating roll pair 8 having a heating roll 8a and a pressing roll 8b that heat and press the paper P that is pressed against each other at a fixing position downstream in the transport direction of P and passes through the fixing position. With this configuration, the image forming apparatus forms an electrostatic latent image on the photosensitive drum 1 with the charging corotron 2 and the exposure device 3, and develops the electrostatic latent image with the developing device 4 to form a toner image. The toner image is transferred to the paper P supplied to the transfer position by the transfer corotron 5, the paper P is peeled off from the photosensitive drum 1 by the static elimination corotron 6, and the paper P on which the toner image has been transferred is further heated and pressurized. The toner image is melted and fixed on the paper P by being sandwiched and conveyed by the roll 8b, whereby an image is formed on the paper P. The cleaning member 7 cleans the photosensitive drum 1 after transfer.
[0013]
The conveyance unit 200 provided in the image forming apparatus includes three sheet trays 9 that store a plurality of sheets P, a discharge tray 10 that stores sheets P after image formation, and various types of sheets that regulate the conveyance direction of the sheets P. A paper guide 11. The various paper guides 11 draw in the paper supply path L1 from each paper tray 9 to the transfer position, the paper discharge path L2 from the fixing position to the discharge tray 10, and the paper P on the discharge path L2, and the front and back sides thereof. An inversion path L3 for the sheet to be supplied to the supply path after being inverted is set.
[0014]
The transport unit 200 includes three pickup rolls 12 that carry out the paper P from each paper tray, and a pair of friction rolls 13 that feed the paper P carried out from the paper tray 9 one by one to the supply path L1. , A pair of registration rolls 14 for supplying the paper P from the supply path L1 to the transfer position, and a pair of pre-discharge rolls 15 for supplying the fixed paper P to the carry-out path L2. The transport unit 200 also includes a pair of discharge rolls 16 that discharges the paper P from the carry-out path L2 to the discharge tray 10, a pair of pull-in rolls 17 that draws the paper P that passes through the carry-out path L2 into the reverse path L3, A pair of reversing rolls 18 disposed in the reversing path L3 and reversing the transport direction of the paper P, and a plurality of pairs of transporting rolls disposed on the supply path L1 or the reversing path L3 and transporting the paper P. 19 and a pair of transport rolls 20 that are disposed between the registration roll pair 14 and the transport roll pair 19 and that supply the paper P fed from the transport roll pair 19 to the transport roll pair 14.
[0015]
The rolls other than the reversing roll pair 18 are in pressure contact with each other in pairs (pairs) in a direction in which the rotation axis is perpendicular to the conveyance direction of the paper P, and the pressure contact portion is positioned on the conveyance path of the paper P. In this state, the paper P supplied to the press contact position is conveyed while being held in a state of rotating in one direction, thereby conveying the paper P to the downstream side of the conveyance path. The reverse roll pair 18 is different from the other rolls only in that the reverse roll 18 operates to draw the paper P into the press contact portion and then reversely rotate to send the paper P back in the carrying-in direction.
[0016]
In the transport unit 200 having such a configuration, the paper P stored in the paper tray 9 is supplied to the supply path L1 one by one by the pickup roll 12 and the friction roll pair 13 and supplied by the plurality of transport roll pairs 19 and 20. It moves in the path L1, is supplied to the transfer position by the registration roll pair 14, is supplied to the carry-out path L2 by the pre-discharge roll pair 15, and is discharged to the discharge tray 10 by the discharge roll pair 16, thereby being conveyed to the discharge tray 10. Is done. Further, the transport unit 200 pulls the paper P on the carry-out path L2 into the reversing path L3 with a pair of pulling rolls 17, reverses the transport direction of the paper P with the reversing roll pair 18, and a plurality of transport roll pairs 19, By re-supplying the paper P to the supply path L1 at 20, the paper P is turned over and supplied again to the transfer position and the fixing position.
[0017]
When an image is formed on one side of the paper P in the image forming apparatus configured as described above, the paper P discharged from the paper tray 9 is supplied to the transfer position via the supply path L1, and is photosensitive at the transfer position. The toner image is transferred from the body drum 1, the toner image is fixed at the fixing position, and is further discharged to the discharge tray 10 via the discharge path L2, thereby forming an image on one side thereof. When images are formed on both sides of the paper P, after the images are formed on one side of the paper P, the paper P is turned over again through the discharge path L2, the reversing path L3, and the supply path L1, and transferred again. The toner image is transferred from the photosensitive drum 1 at the transfer position, the toner image is fixed at the fixing position, and further discharged to the discharge tray 10 via the discharge path L2, thereby forming images on both sides. Is done.
[0018]
FIG. 2 is a diagram illustrating details of the transport unit 200. The conveyance unit 200 uses the registration roll pair 14 disposed on the conveyance path of the paper P as a downstream conveyance unit so that the posture of the paper P is corrected to be aligned in the conveyance direction and then supplied to the transfer position. A pair of transport rolls 20 (hereinafter referred to as a pre-registration roll pair) disposed on the upstream side of the transport path of the paper P is provided as an upstream transport unit. One of the registration roll pairs 14 positioned inside the conveyance path is called a driving registration roll 14a, one positioned outside the conveyance path is called a driven registration roll 14b, and one of the pre-registration roll pairs 20 positioned inside the conveyance path is a drive pre-registration roll. 20a, the one located outside the conveyance path is called a driven pre-registration roll 20b. The roll members of the registration roll pair 14 and the pre-registration roll pair 20 may be composed of a plurality of narrow roll elements each divided in the rotation axis direction. The paper transport path between these two roll pairs 14 and 20 is set in an arc shape.
[0019]
The conveyance unit 200 is disposed opposite to the first rotation shaft 21 disposed in parallel with the drive registration roll 14a on the inner side of the conveyance path and the sheet conveyance path on the upstream side of the registration roll pair 14, and the presence or absence of the sheet P is determined. And a resist sensor 25 for optical detection. Further, the transport unit 200 includes a second rotating shaft 26 disposed in parallel to the registration roll 14a outside the transport path, an electromagnetic solenoid 27 disposed outside the transport path, and linearly moves the movable iron piece 27a by electromagnetic force. One end of the sheet guide 11 is fixed to the rotary shaft 26 and has an engaging portion 28a that engages with the movable iron piece 27a, and becomes a part of the sheet guide 11 outside the conveyance path between the registration roll pair 14 and the pre-registration roll pair 20. And a movable guide 28. When the paper P is carried in from the pre-registration roll pair 20, the rotation of the registration roll pair 14 is stopped, and the movable guide 28 is set in a posture along the transport path.
[0020]
FIG. 3 is a block diagram illustrating a schematic configuration of the control system 300 of the transport unit 200. The control system 300 operates the drive motor 36 for driving the pre-registration roll, the drive motor 76 for various other roll members such as the registration roll pair 14, the operation of the registration roll pair 14, the pre-registration roll pair 20, or the electromagnetic solenoid 27 for moving the movable guide. A transfer system control unit 40 for controlling the image, an image system control unit 41 for forming a toner image on the photosensitive drum 1 and further transferring and fixing the toner image on the sheet P, and a sheet detection signal of the registration sensor 25 are input. A main control unit 42 that synchronously controls these two control units 40 and 41 is provided. When the image forming apparatus is activated, first, a paper carry-out signal is sent from the main control unit 42 to the conveyance system control unit 40, and the conveyance system control unit 40 responds accordingly to the contact portion of the registration roll pair 14. The paper P is conveyed until the leading edge of the paper P comes into contact with the paper P.
[0021]
Next, at a timing after the detection signal of the sheet P is input from the registration sensor 25 (corresponding to a sheet sensor 400 to be described later) to the main control unit 42, the image control unit 41 and the transport system are transferred from the main control unit 42. An image formation start signal is sent to the control unit 40, and in response to this, the image system control unit 41 forms a toner image on the photosensitive drum 1, while the transport system control unit 40 moves from the registration roll pair 14 to the transfer position. The paper P is supplied, the toner image is transferred onto the paper P, the toner image is fixed on the paper P, and the paper P is discharged to the discharge tray 10. In such a series of operations, after the image formation start signal is input, the conveyance system control unit 40 moves the movable guide 28 or stops the rotation of the registration roll pair 14 to use the registration roll pair 14 as an abutting member. The rotation of the registration roll pair 14 and the pre-registration roll pair 20 is controlled so that the posture of the paper P is corrected (skew correction) by holding the leading edge of the paper P at the contact portion (pressure contact portion, roller nip). Or
[0022]
FIG. 4 is a diagram showing a first embodiment of an arrangement relationship between the registration roll pair 14 that functions as a bumping member and the pre-registration roll pair 20 as an upstream-side conveyance unit, which are main components of the conveyance unit 200. The transport unit 200 has a mechanism for rotating the pre-registration roll pair 20. That is, first, the drive motor 36 in which the driven gear 34 is fitted and fixed to one end of the roll shaft 20c of the drive pre-registration roll 20a and the drive gear 35 is fixed on the main frame 31 (not shown) in the vicinity of the pre-registration roll pair 20 is provided. It is arranged. Each roll element of the pre-registration roll pair 20 may be configured to be movable in the axial direction. Further, the transport unit 200 has a mechanism for rotating the registration roll pair 14. Specifically, first, a driven gear 74 is fitted and fixed to one end of the roll shaft 14c of the drive registration roll 14a, and a drive motor 76 having a drive gear 75 fixed on the main frame 31 (not shown) in the vicinity of the registration roll pair 14 is disposed. Has been. The conveyance unit 200 further includes a sheet sensor 400 (corresponding to the registration sensor 25 in FIG. 2) that detects the leading edge of the sheet P on the upstream side of the conveyance path in the vicinity of the registration roll pair 14.
[0023]
Hereinafter, an operation of correcting the posture of the paper P (correcting skew distortion) and discharging the paper P by stopping the rotation of the registration roller pair 14 and functioning as an abutting member in this configuration will be described.
[0024]
FIG. 5 is a diagram for explaining a first example of the drive control method of the registration roll pair 14 and the pre-registration roll pair 20 by the transport system control unit 40. FIG. 5 (A) is a timing chart in the present embodiment, and FIG. B) is a timing chart of a conventional example to which the present invention is not applied, and FIGS. 5C to 5G are views showing the position of the paper P at a predetermined time. Each time point in the timing chart is a time point T0 when the paper sensor 400 detects the leading edge of the paper, a time point T1 when the current supply for normal rotation (forward current supply) to the drive motor 76 for the registration roll pair 14 is stopped, and a pre-registration roll. The time T2 when the forward rotation current supply to the drive motor 36 for the pair 20 is stopped and the time T3 when the forward rotation of the registration roll pair 14 is stopped. Further, when the reverse rotation current supply (reverse current supply) to the drive motor 76 for the registration roll pair 14 is started, at the time T5 when the forward rotation of the pre-registration roll pair 20 is stopped, to the drive motor 76 for the registration roll pair 14. The time T6 when the reverse current supply is stopped and the time T7 when the reverse rotation of the registration roll pair 14 is stopped. Further, at the time T8 when the forward rotation current supply is started to the drive motors 36 and 76 for the roll pairs 14 and 20, the time T9 when the roll pairs 14 and 20 reach the steady rotational speed, the paper sensor 400 detects the trailing edge of the paper. The detected time T10 is the time T11 when the leading edge of the paper P hits the registration roll pair 14.
[0025]
After time T8 when the forward rotation current supply to the drive motors 36 and 76 is started, the paper P is discharged toward the photosensitive drum 1 by rotating forwardly while synchronizing the rotation of the roll pairs 14 and 20. From the time T10 when the sheet sensor 400 detects the trailing edge of the sheet to the time T0 when the leading edge of the sheet is detected is the conveyance waiting time T22 of the previous sheet and the next sheet. Further, the paper P is bent between the registration roll pair 14 and the pre-registration roll pair 20 from time T11 when the leading edge of the paper P hits the registration roll pair 14 to time T5 when the normal rotation of the pre-registration roll pair 20 is stopped. This is the original period for forming and correcting skew distortion. On the other hand, since the registration roll pair 14 is reversed in the present embodiment, the reversal period T24 is substantially incorporated into the period for correcting skew distortion (loop formation period). The interval from time T10 when the paper sensor 400 detects the trailing edge of the paper to time T11 when the leading edge of the paper P hits the registration roll pair 14 is detected by the paper sensor 400 in the immediate vicinity of the registration roll pair 14. By doing so, it can be substantially zero (“0”).
[0026]
First, the transport system controller 40 drives the drive motor 36 for the pre-registration roll pair 20 to drive the pre-registration roll pair 20 in the normal direction so that the paper P is transported to the registration roll pair 14 side. Next, after a predetermined time has elapsed after the paper sensor 400 provided in the vicinity of the registration roll pair 14 detects the position of the leading edge of the paper (T0), the current supply to the drive motor 76 for the registration roll pair 14 is stopped (T1 to T1). T3) The normal rotation drive of the registration roll pair 14 is stopped, and the registration roll pair 14 is caused to function as a contact member. Next, the transport system control unit 40 stops the forward rotation driving of the pre-registration roll pair 20 after a predetermined time has elapsed after the paper sensor 400 detects the position of the leading edge of the paper (T2 to T5). Accordingly, the pre-registration roll pair 20 conveys the paper P toward the registration roll pair 14 that is shifting to the rotation stop state.
[0027]
Further, the transport system control unit 40 detects an appropriate time point after a predetermined time has elapsed after the paper sensor 400 detects the front end of the paper (T0), that is, before and after the front end of the paper hits the registration roll pair 14 as an example of the downstream side transport unit. At (T4), a reverse current is supplied to the drive motor 76 for the registration roll pair 14 to drive the registration roll pair 14 in the reverse direction. Further, after a predetermined time has elapsed (T6), the reverse current to the drive motor 76 for the registration roll pair 14 is stopped and the reverse rotation driving of the registration roll pair 14 is released (in this example, stopped) (T6 to T7). That is, the conveyance system control unit 40 reverses the registration roll pair 14 by a predetermined amount, and then corrects the skew. As a result, the paper P carried by the pre-registration roll pair 20 is conveyed in the direction of the registration roll pair 14 (FIG. 5C), and one side (front edge) of the leading edge of the paper P is transferred to the registration roll pair 14 in a substantially stopped state. Are uniformly abutted (FIG. 5D), and further conveyed by the pre-registration roll pair 20, the paper P is bent between the pre-registration roll pair 20 and the registration roll pair 14, and a skew distortion is corrected. (FIG. 5E). The loop amount can be controlled by controlling the time (T5) from the timing (T0) when the paper sensor 400 detects the leading edge of the paper P until the rotational driving of the pre-registration roll pair 20 is stopped.
[0028]
Next, the transport system control unit 40 waits for a predetermined time after the normal rotation of the pre-registration roll pair 20 stops (T5) (or the reverse rotation of the registration roll pair 14 stops (T7)), and then the registration roll pair 14 and the pre-registration roll pair 20 Are synchronously driven to start transporting the paper P (T8), and the paper P is discharged toward the photosensitive drum 1. At this time, after the skew correction is completed, the registration roll pair 14 and the pre-registration roll pair 20 are activated in accordance with the image writing timing to synchronize the leading edge of the sheet with the image. Thereafter, the same processing as described above is repeated for the next sheet.
[0029]
Here, when the leading end of the sheet enters the contact portion of the registration roll pair 14 before the registration roll pair 14 stops normal rotation, the vicinity of the leading end of the sheet P is sandwiched between the registration roll pair 14 as shown in FIG. However, as described above, in the present embodiment, since the registration roll pair 14 is once reversed for a predetermined time (predetermined amount), the state in which the paper P is returned in the direction opposite to the conveyance direction and released is released. Therefore, one side of the leading edge of the sheet comes into contact with the registration roll pair 14 reliably and uniformly (FIG. 5E). For example, when a strong sheet such as thick paper is skewed and enters the roller nip of the registration roll pair 14, the vicinity of the leading edge of the paper P may pierce the roller element as shown in FIG. However, in this case as well, the registration roll pair 14 is once reversed for a predetermined time, so that the stabbed state (indented state) is released, and one side of the sheet leading edge is reliably and evenly in contact with the registration roll pair 14. (FIG. 5E). In this way, by controlling the normal rotation, stop, and reverse rotation of the registration roll pair 14 at the above timing, even if the paper P is caught between the registration roll pair 14 or pierced by the roll element, the skew correction is reliably realized. (The skew correction capability is improved), and the alignment accuracy of the read image is improved.
[0030]
Further, since the pinched state can be released by reversing the sheet, as long as the trailing edge of the front sheet passes through the registration roll pair 14 (for example, after time T10), the sheet does not wait for the registration roll pair 14 to completely stop. P can also be abutted against the registration roll pair 14. For example, as shown in FIG. 5B, in the prior art, even if there is a sensor detection variation or a conveyance speed variation, the leading edge of the sheet P is surely moved after time T3 when the normal rotation of the registration roll pair 14 is stopped. In order to detect (T0), it is necessary to take a sufficiently long conveyance waiting time T32 in anticipation of the safety factor, but in the above embodiment, as shown in FIG. The leading edge of the paper P may be detected before the time T3 when the rolling stops, and the conveyance waiting time T22 can be set short. Therefore, although the reverse rotation time T24 for reversing the registration roll pair 14 increases, it is possible to satisfy T22 + T24 <T32 (conventional conveyance waiting time). That is, the entire processing time (one cycle) T20 for one sheet P can be made shorter than the conventional (T30) by narrowing the interval of waiting for transporting the previous sheet and the next sheet to an unprecedented level. High productivity can be achieved.
[0031]
As described above, according to the above-described embodiment, when the paper P, which is an example of the transported body, is continuously transported, the leading edge of the paper reaches the registration roll pair 14 which is an example of the downstream transport unit (T11). At a nearby timing (T4 in the above example), the registration roll pair 14 is reversed by a certain amount for each sheet P, and after a predetermined time has elapsed (T7 in the above example), the reverse rotation of the registration roll pair 14 is released to correct skew distortion. Thus, even when the paper P is caught or bitten, the entire processing time can be shortened while ensuring skew correction.
[0032]
Further, for example, in the feeding device described in Japanese Patent Laid-Open No. 2000-128400 (referred to as Conventional Example 1), when skew correction is performed, the leading end of the sheet is the contact portion of the conveyance roller corresponding to the registration roll pair 14 for all sheets. After passing, it is necessary to stop the feeding roller corresponding to the pre-registration roll pair 20 and to reverse the transport roller to form a loop. The amount of reverse rotation for this loop formation is relatively large, so the time loss increases. . On the other hand, the transport unit 200 of the above embodiment normally corrects skew by stopping the rotation of the registration roll pair 14 and transporting the paper P to the registration roll pair 14 side by the pre-registration roll pair 20 to form a loop. The registration roll pair 14 is reversed by a predetermined amount for the purpose of releasing pinching and biting, and the predetermined amount is smaller than the amount of reversal for loop formation in Conventional Example 1, so that time loss is small.
[0033]
FIG. 6 is a diagram for explaining another example of the driving timing of the registration roll pair 14 and the pre-registration roll pair 20 by the transport system control unit 40. In the first example, the reverse rotation of the registration roll pair 14 is started immediately before the time T5 when the pre-registration roll pair 20 is stopped, that is, while the pre-registration roll pair 20 is moving to the stop state (during slowdown). As shown in FIG. 6A, the reverse rotation of the registration roll pair 14 may be started after the normal rotation of the pre-registration roll pair 20 is completely stopped. Further, the reverse rotation of the registration roll pair 14 may be started while the pre-registration roll pair 20 is being driven to rotate forward, that is, while the state where the paper P, which is an example of the transported body, is transported to the registration roll pair 14 side is maintained. In this case, skew correction is performed by bending the sheet P between the pre-registration roll pair 20 that is rotating forward and the registration roll pair 14 that is rotating backward to form a loop. In this case, the reversal period T24 of the registration roll pair 14 falls within the loop creation period, that is, the skew correction period. Further, in this case, for example, as shown in FIG. 6B, the forward rotation current to the registration roll pair 14 is switched to the reverse rotation current at a time T0 when the paper sensor 400 detects the leading edge of the paper P, so that it can be directly performed in a short time. That is, it is possible to shift from normal rotation to reverse rotation without substantially stopping. Further, for example, as shown in FIG. 6C, the entire processing time can be further shortened by shortening the stop periods T5 to T8 of the pre-registration roll pair 20.
[0034]
FIG. 7 is a diagram showing a second embodiment of the arrangement relationship between the registration roll pair 14, the pre-registration roll pair 20, and peripheral members. The difference from the first embodiment is that a nipping state detection unit is provided that detects whether or not the vicinity of the leading end of the sheet P, which is an example of a transported body, is nipped by a registration roll pair 14, which is an example of a downstream transport unit. That is, a plurality of sheet sensors 402 for detecting the leading edge of the sheet P are provided on the downstream side of the conveyance path near the registration roll pair 14. Each paper sensor 402 functions as a clamping state detection unit 412. The paper sensor 402 may be a sensor that detects the presence or absence of the paper P without contact with the paper P, such as a reflective or transmissive optical sensor, or detects the presence or absence of the paper P by contacting the paper P. You may do. For example, the sandwiching state detection unit 412 can be configured by a light source such as an LED as an optical sensor and a photodiode, a phototransistor, or a photocoupler that is a light receiving unit.
[0035]
Each paper sensor 402 is arranged in pairs for each size of the paper P so as to detect the vicinity of both edges in the width direction of the paper P. In the figure, the pair relationship is indicated by a dotted line. The output signal of each paper sensor 402 is sent to the transport system control unit 40. Since the paper sensor 402 is disposed further downstream in the vicinity of the registration roll pair 14 and on the downstream side of the conveyance path, the paper sensor 402 detects the paper P when the leading end of the paper P is applied to the registration roll pair 14 and skew correction is attempted. Whether or not the paper P is sandwiched between the registration roll pair 14 can be detected on the basis of whether or not it has been done. For example, when the paper sensor 402 detects the paper P during the original skew correction period after the time T11 when the paper P hits the registration roll pair 14 (this state is referred to as a pinching signal), the paper P is pinched by the registration roll pair 14. Indicates that Therefore, the transport system control unit 40 first stops the rotation of the registration roll pair 14 for skew correction and causes the registration roll pair 14 to function as an abutting member, and transports the paper P to the registration roll pair 14 side by the pre-registration roll pair 20. . Thereafter, the registration roll pair 14 is reversed by a certain amount on condition that any one of the sheet sensors 402 outputs a clamping signal, that is, the sheet P is sandwiched between the registration roll pair 14. On the other hand, when no nipping signal is output from any of the sheet sensors 402, skew correction is performed as usual without reversing the registration roll pair 14.
[0036]
That is, in the first embodiment, the registration roll pair 14 is always reversed by a predetermined amount for each sheet, whereas in the second embodiment, the sheet P is sandwiched between the registration roll pair 14 using a sensor. Only in this state, the registration roll pair 14 is reversed by a predetermined amount. However, also in the second embodiment, when the sheet P is sandwiched between the registration roll pair 14, it is possible to reliably detect that and to make sure that one side of the leading edge of the sheet comes into contact with the registration roll pair 14. As in the first embodiment, even when the paper P is sandwiched between the registration roll pair 14, the skew correction can be reliably realized. In addition, since the reverse rotation is performed only when it is pinched, for example, even when the reverse rotation period is set at the timing shown in FIG. 5A of the first embodiment, when the reverse rotation is not necessary and the reverse rotation is not necessary. By shortening the stop periods T5 to T8 of the registration roll pair 20, the entire processing time can be shortened. Moreover, since it is not reversed when it is not pinched (when reverse rotation is unnecessary), power consumption does not increase more than necessary.
[0037]
Note that, at the control timing of the second embodiment, the registration roll pair 14 is reversed only once at a predetermined fixed amount. Therefore, depending on the setting of the predetermined amount, the pinching state may not be released when the passing amount is large. There is. On the other hand, in the arrangement configuration of the second embodiment, for example, the nipping signal from any of the sheet sensors 402 is detected until it is detected that the nipping state has been released and one side of the sheet P has contacted the registration roll pair 14 substantially uniformly. Can be repeatedly reversed (including continuing the reverse rotation state; the same shall apply hereinafter). Thereby, even in the arrangement configuration of the second embodiment, the pinched state can be reliably released regardless of the passing amount.
[0038]
In the second embodiment, the paper sensors 402 are arranged so that two pairs are provided for each size of the paper P so as to detect the vicinity of both end edges in the width direction of the paper P. For example, The sandwiched state detection unit 412 may be configured by arranging a long CCD line sensor so that its longitudinal direction is along the width direction. In this case, one line sensor having a length sufficient to detect the vicinity of the side edge of the paper P having the maximum width may be used, or the vicinity of the side edge of the paper P having the minimum width to the maximum width in the vicinity of both ends. Two line sensors that are slightly shorter as long as they are detected may be used.
[0039]
FIG. 8 is a diagram showing a third embodiment of the arrangement relationship between the registration roll pair 14, the pre-registration roll pair 20, and peripheral members. The first embodiment is provided with a passage amount detection unit that detects a passage amount that is an amount in which the vicinity of the leading end of the sheet P that is an example of a transported body passes through a registration roll pair 14 that is an example of a downstream side transport unit. And different. That is, a plurality of long sheet sensors 404 for detecting the leading edge of the sheet P are provided on the downstream side of the conveyance path in the vicinity of the registration roll pair 14 so that the longitudinal direction thereof is along the conveyance direction. Each paper sensor 404 has a plurality of detection elements in the longitudinal direction (that is, in the transport direction), and the leading edge position of the paper P, that is, the paper, based on which detection element detects the paper P. The passage amount of P from the registration roll pair 14 can be shown. In this way, each paper sensor 404 functions as the passage amount detection unit 414. The paper sensor 404 may detect the presence or absence of the paper P without contacting the paper P as in the second embodiment, or detect the presence or absence of the paper P by contacting the paper P. There may be.
[0040]
Each sheet sensor 404 is arranged in pairs near each edge of the sheet P in the width direction so as to detect the passing amount of the sheet P from the registration roll pair 14 for each size of the sheet P. The In the figure, the pair relationship is indicated by a dotted line. A passage amount signal indicating the leading edge position of the paper P detected by each paper sensor 404 is sent to the transport system control unit 40. A memory (not shown) of the transport system control unit 40 stores a table in which the value of the passage amount signal output from the paper sensor 404 and the amount of reverse rotation of the registration roll pair 14 are associated with each other. Since the sheet sensor 404 provided with a plurality of detection elements in the longitudinal direction is disposed further downstream in the conveyance path near the registration roll pair 14, the skew correction is attempted by applying the leading edge of the sheet P to the registration roll pair 14. When this is done, it is possible to detect not only whether or not the sheet P is sandwiched but also the amount of passage of the sheet P from the registration roll pair 14. Therefore, the transport system control unit 40 first stops the rotation of the registration roll pair 14 for skew correction and causes the registration roll pair 14 to function as an abutting member, and transports the paper P to the registration roll pair 14 side by the pre-registration roll pair 20. . Thereafter, the reversal amount of the registration roll pair 14 corresponding to the passage amount signal from the paper sensor 404 is determined based on the table, and the registration roll pair 14 is reversed by the determined reversal amount. On the other hand, when no passing amount signal is output from any of the sheet sensors 404, skew correction is performed as usual without reversing the registration roll pair 14.
[0041]
That is, the third embodiment is common to the second embodiment in that the registration roll pair 14 is reversed only when the paper P is sandwiched between the registration roll pair 14. On the other hand, the third embodiment is different from the second embodiment in which the rotation is reversed by a predetermined amount in that the rotation is reversed by an amount corresponding to the passage amount. As a result, in the second embodiment, depending on the setting of the predetermined amount, there is a possibility that the sandwiched state cannot be released when the passage amount is large, whereas in the third embodiment, a sufficiently long sheet sensor 404 and By doing so, the state can be reliably canceled regardless of the passing amount.
[0042]
In the control timing of the third embodiment, the registration roll pair 14 is reversed by the amount corresponding to the passage amount, but the number of reverse rotations is one, so the correspondence between the passage amount and the amount of reverse rotation is inappropriate. If the paper P is not returned in the opposite direction due to a case or slip, there is a possibility that the sandwiched state cannot be released. On the other hand, in the arrangement configuration of the third embodiment, the amount of passage from any of the sheet sensors 404 is detected until it is detected that the sandwiched state is released and one side of the sheet P comes into contact with the registration roll pair 14 substantially uniformly. Until the signal is not output, the reversal of the pair of registration rolls 14 can be repeated many times with an amount associated in advance. As a result, even in the arrangement configuration of the third embodiment, even if the paper P is not returned in the reverse direction due to slipping or the like, the sandwiched state can be reliably released.
[0043]
In the third embodiment, two papers are paired for each size of the paper P so that the passing amount of the paper P from the registration roll pair 14 is detected in the vicinity of both edges in the width direction of the paper P. Although the long paper sensor 404 is disposed, for example, a plurality of sensors similar to those of the first embodiment are disposed in the transport direction, and one long shape is substantially formed by the plurality of sensors. The sensor may be configured to function as the passage amount detection unit 414.
[0044]
Further, for example, a rectangular CCD area sensor may be provided. In this case, one area sensor having a width sufficient to detect the vicinity of the side edge of the paper P having the maximum width may be used, or the vicinity of the side edge of the paper P having the minimum width to the maximum width in the vicinity of both ends. The passage amount detection unit 414 may be configured using two area sensors having a slightly narrow width corresponding to the amount to be detected.
[0045]
FIG. 9 is a view showing a fourth embodiment of the positional relationship between the registration roll pair 14, the pre-registration roll pair 20, and peripheral members. The first point is that a contact state detection unit that detects whether or not the vicinity of the leading end of the sheet P, which is an example of the transported body, is in contact with the registration roll pair 14 which is an example of the downstream transport unit substantially uniformly. Different from one embodiment. That is, a paper sensor 406 for detecting the leading edge of the paper P is provided on the upstream side of the conveyance path in the vicinity of the registration roll pair 14. The sheet sensor 406 functions as the contact state detection unit 416. The paper sensor 406 may detect the presence or absence of the paper P without contacting the paper P as in the second embodiment, or detect the presence or absence of the paper P by contacting the paper P. There may be. The paper sensor 400 of the first embodiment is removed, and the leading edge of the paper P is detected based on the output signal of the paper sensor 406.
[0046]
The paper sensor 406 is disposed so as to detect the leading edge of the paper P in the vicinity of the upstream pole of the registration roll pair 14 at a substantially central portion in the width direction of the paper P. The output signal of the paper sensor 406 is sent to the transport system control unit 40. Since the paper sensor 406 is disposed in the vicinity of the upstream side of the conveyance path in the vicinity of the registration roll pair 14, the paper sensor 406 is used when the paper sensor 406 attempts to correct the skew by applying the leading edge of the paper P to the registration roll pair 14. It is possible to detect whether or not the paper P is in contact with the registration roll pair 14 substantially uniformly based on whether or not this is detected. For example, when the paper sensor 406 detects the paper P during the original skew correction period after the time T11 when the paper P hits the registration roll pair 14 (this state is referred to as a uniform contact signal), the paper P is registered with the registration roll pair 14. It shows that it is contacting substantially uniformly. On the other hand, when the paper sensor 406 does not detect the paper P, it indicates that the paper P is not uniformly in contact with the registration roll pair 14 because, for example, the vicinity of the front end of the paper P is stuck into the roller element. Therefore, the transport system control unit 40 first stops the rotation of the registration roll pair 14 for skew correction and causes the registration roll pair 14 to function as an abutting member, and transports the paper P to the registration roll pair 14 side by the pre-registration roll pair 20. . Thereafter, on the condition that the sheet sensor 406 does not output a uniform contact signal, that is, the sheet P does not contact the registration roll pair 14 uniformly, the registration roll pair 14 is reversed by a certain amount. On the other hand, when the uniform contact signal is not output from the paper sensor 406, skew correction is performed as usual without reversing the registration roll pair 14.
[0047]
That is, in the first embodiment, the registration roll pair 14 is always reversed once for each sheet, whereas in the fourth embodiment, the sheet P is not uniformly in contact with the registration roll pair 14. Only occasionally, the registration roll pair 14 is once reversed by a predetermined amount. However, also in the fourth embodiment, when the paper P pierces the registration roll pair 14, the state can be reliably released so that one side of the leading end of the sheet can be reliably brought into contact with the registration roll pair 14. Similar to the embodiment, even if the paper P may pierce the registration roll pair 14, the skew correction can be surely realized.
[0048]
In the fourth embodiment, the sheet sensor 406 is disposed so as to detect the leading end of the sheet P in the vicinity of the registration roller pair 14 in the substantially central portion of the sheet P in the width direction. In order to detect the vicinity of both end edges in the width direction, point sensors are arranged so that two pairs of each size of the paper P are paired, or short CCD line sensors are arranged in the width direction. The contact state detection unit 416 may be configured. In the former case, when at least two of the pair both detect the leading edge of the paper P, the paper P uniformly contacts the registration roll pair 14, and when either or both does not detect the leading edge of the paper P, the paper It can be determined that P does not contact the registration roll pair 14 uniformly. In the latter case, when all the pixels of the CCD line sensor detect the leading edge of the paper P, the paper P uniformly contacts the registration roll pair 14, and when any pixel does not detect the leading edge of the paper P, the paper It can be determined that P does not contact the registration roll pair 14 uniformly.
[0049]
Further, at the control timing of the fourth embodiment, the registration roll pair 14 is reversed only once by a predetermined fixed amount. However, the registration roll pair 14 is long in order to detect the unreachable amount of the paper P from the registration roll pair 14. These sensors may be arranged so that the longitudinal direction thereof is along the conveying direction (only the center part in the width direction may be the end part on both sides), and the registration roll pair 14 may be reversed by an amount corresponding to the unreachable amount. Good.
[0050]
Further, if the registration roll pair 14 is reversed only once according to a predetermined fixed amount or an unreached amount, depending on the setting of the predetermined amount, there is a possibility that the state cannot be canceled when the biting is intense. On the other hand, in the arrangement configuration of the fourth embodiment, a predetermined constant amount or an unreachable amount is detected until it is detected that the biting state is released and one side of the paper P abuts the registration roll pair 14 substantially uniformly. The reversal of the pair of registration rolls 14 can be repeated many times with the corresponding amount. Thereby, even in the arrangement configuration of the fourth embodiment, the state can be reliably released regardless of the biting state. In this case, in order to avoid bending (buckling) of the leading end of the sheet, an example of the upstream side conveyance unit is detected until it is detected that the biting state is completely released and the sheet P is in contact with the registration roll pair 14 substantially uniformly. It is preferable that the rotation of the pre-registration roll pair 20 is stopped.
[0051]
As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment, and the forms added with such changes or improvements are also included in the technical scope of the present invention. Moreover, said embodiment does not limit the invention concerning a claim, and all the combinations of the characteristics demonstrated in embodiment are not necessarily essential for the solution means of invention.
[0052]
For example, any one of the second and third embodiments may be combined with the fourth embodiment, and the registration roll pair 14 may be reversed only in each state in both the sandwiched state and the biting state. Further, for example, in the second and third embodiments, when the reverse rotation of the registration roll pair 14 is repeated until the sandwiched state is released, the sandwiching state detection unit that detects whether or not the sandwiched state is detected using the paper sensor 402. 412 and the paper sensor 404 are used to detect whether or not the pinching state has been released by the passage amount detection unit 414 that detects the passage amount. The contact state detection unit 416 of the fourth embodiment is used. Also good. In this case, sensors for detecting the vicinity of both edges in the width direction of the paper P are arranged, and the pair of sensors at both ends detect both the front ends of the paper P, that is, the paper P is uniformly contacted with the registration roll pair 14. It is preferable that the reversal of the pair of registration rolls 14 is repeated until the value is indicated.
[0053]
Further, for example, in the above-described embodiment, after the registration roll pair 14 is reversed, the rotation of the registration roll pair 14 and the pre-registration roll pair 20 is once stopped, and after a predetermined time has elapsed, the registration roll pair 14 and the pre-registration roll pair 20 are driven synchronously. The conveyance of the sheet P is started and the sheet P is discharged toward the photosensitive drum 1, but without waiting for the reverse rotation of the registration roll pair 14 to stop completely, the registration roll pair 14 and the pre-registration roll pair 20 Synchronous driving (forward rotation) may be started. In this case, skew correction is performed by bending the sheet P between the pre-registration roll pair 20 in the rotation stopped state and the registration roll pair 14 in the rotation stop state to form a loop.
[0054]
In the above embodiment, the transported body is transported to the downstream transport section side by the upstream transport section, and the transported body is bent on the downstream side of the transport path of the upstream transport section to form a loop, thereby forming the loop of the transported body. The configuration for correcting the skew distortion is not limited to this, but the configuration may be such that the skew distortion is corrected by pressing (striking) the transport target to the downstream side transport unit without forming a loop. . Note that a configuration in which a loop is formed and skew distortion is corrected as in the above embodiment can realize highly accurate skew correction.
[0055]
Furthermore, in the above description, paper (paper medium) has been described as an example of a transported body. However, the transported body is not limited to this, and any material such as a plastic film may be used as long as it is a sheet. Good.
[0056]
Further, in the above description, the transfer portion transport device used in the image forming apparatus has been described as an example. However, the transport device of the present invention is not limited to this, for example, an automatic document feeder for image reading (Auto Document Feeder). : ADF) and the like. Further, the present invention is not limited to an image forming apparatus such as a copying machine or a printing apparatus, and may be used for other apparatuses.
[0057]
【The invention's effect】
As described above, according to the present invention, at the time of skew correction, the downstream side transport unit is once reversely driven, so that the transported body is sandwiched between the contact parts of the downstream side transport unit or stuck into the roll element. Even if this happens, the skew correction can be reliably realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the overall configuration of an embodiment of an image forming apparatus provided with a conveying device according to the present invention.
FIG. 2 is a diagram illustrating details of a transport unit.
FIG. 3 is a block diagram illustrating a schematic configuration of a control system of a sheet conveying unit.
FIG. 4 is a diagram illustrating a first embodiment of an arrangement relationship between a registration roll pair, a pre-registration roll pair, and peripheral members, which are main components of a transport unit.
FIG. 5 is a diagram illustrating a first example of a driving control method of a registration roll pair and a pre-registration roll pair by a transport system control unit.
FIG. 6 is a diagram for explaining another example of driving timing of a registration roll pair and a pre-registration roll pair by a transport system control unit.
FIG. 7 is a diagram showing a second embodiment of an arrangement relationship between a registration roll pair, a pre-registration roll pair, and peripheral members.
FIG. 8 is a diagram showing a third embodiment of the positional relationship between a registration roll pair, a pre-registration roll pair, and peripheral members.
FIG. 9 is a diagram showing a fourth embodiment of the arrangement relationship between a registration roll pair, a pre-registration roll pair, and peripheral members.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 14 ... Registration roll pair, 20 ... Pre-registration roll pair, 40 ... Conveyance system control part, 66 ... Drive motor, 100 ... Image formation part, 200 ... Conveyance part, 412 ... Holding state detection part, 414 ... Passing Amount detection unit, 416 ... contact state detection unit

Claims (4)

More than the upstream transport unit disposed on the upstream side of the transport path and transporting the sheet-like transported body sandwiched between a pair of rotating bodies, and the upstream transport unit on the transport path A downstream transport unit disposed on the downstream side and sandwiching the transported body transported by the upstream transport unit between a pair of rotating bodies and transporting further downstream; the upstream side A transport device that forwardly drives a transport unit to transport the transported body and abuts the transported body against the downstream transport unit, thereby correcting skew distortion of the transported body;
The skew is obtained by driving the downstream transport unit in reverse at a timing near the end of the transported body reaching the downstream transport unit, and then canceling the reverse drive of the downstream transport unit after a predetermined time has elapsed. A controller that corrects distortion; and the controller includes a contact state detector that detects whether one side, which is a tip of the transported body, is in contact with the downstream transport unit substantially uniformly. First, the rotation of the downstream transport unit is stopped and the transported body is transported to the downstream transport unit side by the upstream transport unit, and then the contact state detection unit detects that one side of the transported body is The transport device characterized in that the downstream transport unit is driven in reverse rotation on the condition that it is detected that the contact is not substantially uniform. The said control part reversely drives the said downstream conveyance part, maintaining the state which conveyed the said to-be-conveyed body to the said downstream conveyance part side by the said upstream conveyance part. Transport device. The control unit repeats reverse driving of the downstream transport unit based on a detection result of the detection unit until one side of the transported body comes into contact with the downstream transport unit substantially uniformly. The conveying apparatus according to claim 1 or 2 . By forming the flexed the conveyance object in the conveying path downstream of the object to be transferred is transported to the lower stream side transport side the upstream conveying section loop by the upstream transport unit, the object to be transported The skew device of a body is correct | amended. The conveying apparatus in any one of Claim 1 to 3 characterized by the above-mentioned.

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