JP2004035196A - Paper sheet carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the productivity of image formation by making the interval between the paper sheets carried short. <P>SOLUTION: A paper sheet carrying device is provided with a pair of first rolls 31 for carrying a paper sheet toward a transferring section 4, a pair of second rolls 32 arranged in the carrying passages provided between a pair of the first rolls 31 and the transferring device 4, an axial direction moving means for axially moving a pair of the second rolls 32, and a nip control means for controlling the contact state of a pair of the second rolls 32. In the nip control means, the contact state of a pair of the second rolls 32 is held as it is until the displacement of a paper sheet in the direction perpendicular to the paper sheet carrying direction is corrected by the axial direction moving means before a paper sheets reaches a pair of the second rolls 32 and is released after correcting the displacement of the paper sheet in the direction perpendicular to the paper sheet carrying direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet conveying device provided with a mechanism for correcting a sheet conveyance deviation when conveying a sheet to a transfer member.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, a sheet for transferring an image is conveyed in the apparatus and sent to a transfer member. In transporting the paper, a predetermined transport path is advanced while sandwiching the paper between a pair of rolls.
[0003]
Here, as means for correcting the positional deviation of the paper being transported in the direction perpendicular to the transport direction, there is a means capable of moving the roll pair in the axial direction (direction perpendicular to the transport direction). For example, there is known an apparatus that enables the registration roll pair to move in the axial direction, detects a shift in the transport position of the sheet conveyed to the registration roll pair, and corrects the shift by moving the registration roll pair in the axial direction. JP-A-63-185758, JP-A-1-294141, JP-A-1-294142, and the like.
[0004]
[Problems to be solved by the invention]
However, after correcting the sheet transport position deviation due to the axial movement of the registration roll pair, it is necessary to return the registration roll pair to the home position in preparation for the next paper deviation correction. In this case, the paper transport interval must be set for the time, which causes a decrease in productivity in image formation.
[0005]
For example, in order to enhance the performance of correcting the paper transport position deviation, the amount of movement of the registration roll pair in the axial direction must be set large, but on the other hand, the time required to return to the home position becomes long, and The space between the sheet and the next sheet must be large. Therefore, in order to improve one or both of the deviation correction performance and the productivity, it is necessary to increase the paper conveyance speed and the axial movement speed of the registration roll pair. This causes problems such as a decrease in durability.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve such a problem. That is, the present invention provides a first roll pair that transports a sheet in the direction of a transfer member, a second roll pair provided on a transport path between the first roll pair and the transfer member, The paper transport device includes an axial moving unit that moves the roll pair along the axial direction, and a nip control unit that controls a contact state between the rolls in the second roll pair. Before reaching the second pair of rolls, the contact state of the second pair of rolls is maintained until the displacement in the direction perpendicular to the sheet conveyance direction is corrected by the axial moving means. After the deviation is corrected, the contact state of the second roll pair is released.
[0007]
According to this aspect of the invention, while the paper is being conveyed by the second roll pair, the deviation in the direction perpendicular to the paper conveyance direction is corrected by the axial moving means, and then the rolls of the second roll pair are moved together. Since the contact state has been released, the second pair of rolls can be immediately returned to the home position after correcting the positional deviation of the sheet.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an image forming apparatus to which the sheet transport device of the present embodiment is applied. The image forming apparatus includes a paper feed unit 1 that feeds the stored paper, a transport unit 2 that transports the fed paper, and a registration unit that transports the transported paper to the transfer unit 4 in synchronization with the image. 3, a transfer unit 4 for transferring an image to a sheet, a fixing unit 5 for fixing an image to a sheet, a discharge unit 6 for discharging a sheet after fixing, a reversing unit 7 for reversing the fixed sheet, and transporting the reversed sheet. A double-sided conveyance unit 8 is provided.
[0009]
The paper feed unit 1 includes a plurality of cassettes each capable of storing paper of various sizes, and discharges paper of a designated size from the cassette and sends it to the transport unit 2. The transport unit 2 transports the sheet sent from the cassette along a predetermined path by rotation of a roll pair.
[0010]
The registration unit 3 is a unit that corrects the positional deviation of the sheet sent from the transport unit 2 and sends the sheet to the transfer unit 4 at an accurate position. The transfer unit 4 transfers the toner image to one surface of the sheet whose position has been corrected by the registration unit 3. The fixing section 5 is a section for applying a predetermined heat to the toner image transferred to the sheet to fix the image on the sheet.
[0011]
The discharge unit 6 is a part that discharges a sheet on which an image is formed to a discharge tray. The reversing section 7 is a section for reversing the front and back of the sheet when forming an image on both sides of the sheet. The sheet is fed to the registration section 3 in a state where the sheet is reversed by passing through the two-sided conveying section 8. . The inverted sheet is discharged from the discharge unit 6 through the registration unit 3, the transfer unit 4, and the fixing unit 5 as described above.
[0012]
FIG. 2 is an enlarged view mainly showing the resist portion. The registration unit is provided with a first roll pair 31 and a second roll pair 32, and the operation of these roll pairs corrects the positional deviation of the sheet.
[0013]
A transfer member 41 of the transfer unit 4 is disposed downstream of the second roll pair 32 in the sheet transport direction, and the transfer member 41 can transport the sheet by itself. Further, near the downstream side of the first roll pair 31 in the sheet conveyance direction and near the transfer member 41, detection members S1 and S2 for detecting a sheet are arranged.
[0014]
To correct the positional deviation of the sheet by the registration unit 3, the first roll pair 31 conveys the sheet with the first roll pair 31 while the rotation of the second roll pair 32 is stopped. A loop is formed on the sheet between the pair of rolls 32, and then the rotation of the second pair of rolls 32 is started. As a result, the sheet is conveyed while having a loop, and the slant feeding deviation of the sheet can be corrected by the tension of the loop.
[0015]
In addition, in order to correct the deviation in the direction perpendicular to the sheet conveying direction (the axial direction of the roll pair), the second roll pair 32 is moved in the axial direction. FIG. 3 is a perspective view illustrating a roll pair moving unit that moves the second roll pair in the axial direction.
[0016]
The second roll pair 32 is engaged by an engagement member K in the axial direction. A rack L is attached to one of the rolls, and the rack L and the moving motor M are connected by a gear. The rack L moves in the axial direction by the forward / reverse rotation of the moving motor M, and the second roll pair 32 moves in the axial direction following the rack L.
[0017]
A detection member S3 is provided at the home position in the axial direction, so that the home position of the second roll pair 32 can be detected. Further, a sheet misalignment detection sensor S4 is arranged near the second pair of rolls. Therefore, when the sheet is conveyed and is being applied to the sheet misalignment detection sensor S4, the second roll pair 32 is moved in the axial direction until the sheet is disengaged from the sheet misalignment detection sensor S4. On the other hand, if the sheet is not conveyed by the sheet misalignment detection sensor S4 when the sheet is conveyed, the second roll pair 32 is moved in the axial direction until the sheet misaligns with the sheet misalignment detection sensor S4.
[0018]
FIG. 4 is a perspective view illustrating nip control means provided on the second roll pair. The nip control means includes a solenoid 310 and a link member 320, and the link member 320 is engaged with the second roll pair 32 on the driven roll 32b side. The link member 320 is rotated by the operation of the solenoid 310, and the claw T interlocked with the link member 320 moves the axis of the driven roll 32b in the vertical direction to make contact with and separate from the drive roll 32a. Thus, the contact state (nip) between the rolls in the second roll pair 32 can be controlled.
[0019]
In the above description, the mechanism for moving the second roll pair 32 in the axial direction shown in FIG. 3 and the nip control means for the second roll pair 32 shown in FIG. 4 are described separately. It is assumed that both the moving mechanism and the nip control means are provided in the second roll pair 32 in the paper transport apparatus of (1).
[0020]
FIG. 5 is a block diagram of a configuration for controlling the second roll pair. In the second roll pair, the nip is controlled by the controller 100 sending a signal to the solenoid 310 based on a signal from the sensors SS. Further, the motors MM are controlled by the control unit 100 via the motor control unit 110.
[0021]
Next, a procedure for conveying a sheet in the sheet conveying apparatus of the present embodiment will be described. FIG. 6 is a flowchart illustrating the transport procedure. In the following description, reference numerals not shown in FIG. 6 refer to FIGS. 1 to 5.
[0022]
First, sheet feeding is started, and the sheet is transported from the cassette to the registration unit 3 via the transport unit 2 (step S1). The registration unit 3 corrects the skew of the sheet, starts the conveyance of the image in synchronization with the sheet (step S2), and then starts correcting the deviation of the sheet in the main scanning direction (the direction perpendicular to the conveyance direction). I do.
[0023]
That is, if the detection signal of the paper misalignment detection sensor S4 provided near the second roll pair 32 indicates that there is no paper, the paper is shifted in the direction of the paper misalignment detection sensor S4, and if there is paper, the paper misalignment detection sensor is moved in the opposite direction. The second roll pair 32 is moved in the axial direction until the detection signal in S4 changes, and deviation correction is performed (steps S3 to S7).
[0024]
After completion of the deviation correction, the motor for moving the second roll pair 32 in the axial direction is stopped (step S8), and if the sheet is detected by the detection member S2 near the transfer member 41 (step S9), the nip control means (solenoid) The nip releasing operation of the second roll pair 32 is performed by the link member 310 and the link member 320) (Step S10). After the end of the nip release operation, the movement of the second roll pair 32 to the home position is started (step S11).
[0025]
In this way, by releasing the nip and moving to the home position before the sheet passes through the second roll pair 32, it is not necessary to move to the home position at the interval with the next sheet, It is possible to minimize the interval between sheets that are continuously fed.
[0026]
In the above example, the nip of the second pair of rolls 32 is released when the sheet enters the transfer member 4 on the downstream side. It is also conceivable that the sheet may shift during conveyance by the transfer member 4 due to the repulsive force of the sheet corrected for the shift in the feed or main scanning direction.
[0027]
To cope with this, the nip of the second pair of rolls 32 may be released when the sheet enters the downstream transfer member 4 and the sheet passes through the first pair of rolls 31 on the upstream side. Good. In this case, the passage of the sheet is detected by the detection member S1 provided near the first roll pair 31, and the nip of the second roll pair 32 may be released at this timing.
[0028]
The example in which the second roller pair 32 movable in the axial direction is arranged on the registration unit 3 has been described above, but may be provided on a transport roll other than the registration unit 3. Also in this case, it is necessary to provide a transport member capable of transporting the sheet on the downstream side. In addition, although an example in which the detection signals of the various detection members are used as the trigger for releasing the nip has been described, the control may be performed by counting the time from the start of conveyance by the second pair of rolls 32 using a timer. The use of timer timing has the advantage that it is not necessary to provide detection members at various places.
[0029]
【The invention's effect】
As described above, the present invention has the following effects. That is, after correcting the sheet transport position deviation by moving the roll pair in the axial direction, the nip of the roll pair is released before the paper passes, so that the roll pair can be returned to the home position before the paper passes. It is possible to set the interval between the sheet and the next sheet to a minimum. As a result, productivity can be improved without increasing the paper conveyance speed or the rotation speed of the roll pair, and it is possible to suppress an increase in operation noise of roll rotation, an increase in power consumption, and a decrease in durability of the roll pair. Become.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an image forming apparatus to which a sheet conveying device according to an embodiment is applied.
FIG. 2 is an enlarged view mainly showing a resist unit.
FIG. 3 is a perspective view illustrating roll pair moving means for moving a second roll pair in the axial direction.
FIG. 4 is a perspective view illustrating a nip control unit provided in a second roll pair.
FIG. 5 is a block diagram of a configuration for controlling a second roll pair.
FIG. 6 is a flowchart illustrating a transport procedure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... paper feed part, 2 ... conveyance part, 3 ... registration part, 4 ... transfer part, 5 ... fixing part, 6 ... discharge part, 7 ... reversal part, 8 ... double-sided conveyance part, 31 ... 1st roll pair 32: second roll pair, 41: transfer member

Claims (2)

A first pair of rolls for conveying the sheet in the direction of the transfer member;
A second roll pair provided on a transport path between the first roll pair and the transfer member;
Axial moving means for moving the second roll pair along the axial direction;
Nip control means for controlling a contact state between the rolls in the second roll pair,
The nip control unit controls the contact state of the second roll pair from before the paper reaches the second roll pair until the axial movement unit corrects a shift in a direction perpendicular to the transport direction of the paper. A sheet transport device, wherein the contact state of the second pair of rolls is released after correcting the deviation in a direction perpendicular to the transport direction of the sheet. The nip control unit is configured to correct a shift in a direction perpendicular to the sheet conveyance direction, and to contact the second roll pair after the rear end of the sheet in the conveyance direction has passed through the first roll pair. 2. The sheet conveying device according to claim 1, wherein the state is released.

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