JP2010024036A - Paper feeder, image forming apparatus, and image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-capacity paper feeder capable of supplying paper free from bend or fold line, an image forming apparatus having high print quality and high productivity, and an image forming system with high print quality and high productivity including the high-capacity paper feeder and the image forming apparatus for forming image. <P>SOLUTION: The paper feeder includes: a first roller pair for carrying paper; a second roller pair for carrying paper in the lower course of the pair of first rollers; a first driving means which drives the first and second roller pairs; a first clutch which turns ON/OFF of the driving force from the first driving means to the first roller pair; a second clutch which turns ON/OFF of the driving force to the second roller pair; a control means which controls the first clutch and the second clutch; a second driving means which is controlled by the control means to drive the first roller pair; and a power transmitting member which transmits the driving force from the second driving means to the first roller pair only in one direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a registration unit that corrects paper bending and adjusts a paper conveyance interval.
The present invention relates to a paper supply apparatus having the registration means, an image forming apparatus having the registration means, and an image forming system having the paper supply apparatus and an image forming apparatus for forming images.

  2. Description of the Related Art Image forming apparatuses such as copying machines and printers are provided with a paper feed cassette that stacks and feeds a plurality of sheets for image formation.

  In addition, high quality prints are required for image-formed prints, and the print position displacement dimension in the width direction with respect to the length direction dimension of the sheet is conventionally within 1% (for example, approximately 4 mm for A3). However, in recent years, customer demands for print quality have become stricter and improvements are desired.

  Also, in order to respond to a large number of print orders from customers, a large-capacity paper feeding device that feeds a large amount of paper continuously to the image forming apparatus, or an image formation in which the image forming apparatus and the large-capacity paper feeding device are connected. Although a system is required, the above-mentioned required quality is particularly severe in a commercial image forming system equipped with such a large-capacity paper feeding device, and the print positional deviation dimension is 0.25%. High quality has been demanded.

  The print position misalignment is caused by skew during conveyance of the sheet, and this skew is corrected by the registration portion of the transfer portion of the image forming apparatus.

  However, there is a possibility that the above-described strict printing tilt tolerance cannot be achieved only by the resist portion of the transfer portion of the image forming apparatus depending on the state of the paper.

  For this purpose, in addition to the transfer unit of the image forming apparatus, an image forming apparatus provided with a pre-registration unit that adjusts the sheet interval length (feed timing) in advance upstream and corrects the skew caused by the skew of the sheet. Is known (for example, see Patent Document 1).

  In general, it is known that stepping motors cause step-out and stop when the acceleration / deceleration is larger than the acceleration / deceleration that can cope with a predetermined load.

For this reason, as in the image forming apparatus described in Patent Document 1, it is not possible to drive a roller with a stepping motor for driving a paper conveyance roller that needs to be accelerated and decelerated. And drive the paper transport roller via the electromagnetic clutch,
By turning on / off the electromagnetic clutch, the paper transport roller is suddenly accelerated and decelerated (intermittently driven).
JP 2001-39585 A

In a conventional image forming apparatus, a pre-registration unit is configured by a registration roller, a loop roller that is positioned on the downstream side of the registration roller, and a motor that drives these loop rollers.
An electromagnetic clutch is connected to each of the registration roller and the loop roller, etc., and the rotational force of the motor is transmitted / cut off by ON / OFF of the clutch to generate a predetermined loop between the sheets, and the leading edge of the sheet is pushed against the registration roller. By applying this, paper feed timing adjustment and paper skew correction are performed.

However, at the time of registration, when the registration roller and the loop roller are stopped with the clutch disengaged, the roller side connected to the output side of the clutch is disconnected and becomes free. Will continue to rotate slightly,
If the loop amount formed on the upstream side of the registration roller is not constant and the loop amount is small, the leading edge of the downstream side of the paper cannot be brought into contact with the registration roller, and the skew correction of the paper, that is, the correction of the bending can be performed. In addition, when the loop amount becomes too large, there is a possibility that the paper is cramped in the loop forming space.

  If the correction of the bending becomes impossible, the sheet is inclined with respect to the toner image on the toner image carrier during transfer, and the print image is inclined with respect to the sheet and the print quality is deteriorated. there were.

  Such bending of the paper is particularly noticeable when double-sided printing is performed, and the print positions of the front surface and the back surface may be shifted by, for example, 4 mm each, for a total of 8 mm.

  Further, when the buckling occurs, there is a problem that the paper is creased and the quality of the output product is remarkably lowered.

The present invention has been made in view of such problems, and by making the loop formed in the upstream portion of the registration roller constant,
A paper supply apparatus having registration means capable of supplying paper to a predetermined interval and position without bending of the paper or paper, and an image having the registration means and having high print quality and high productivity It is an object of the present invention to provide an image forming system having a forming apparatus, the paper supply apparatus, and an image forming apparatus for forming an image, and having high print quality and high productivity.

  The above object is achieved by the following means.

1. A paper stacking unit for loading paper,
A first roller pair for transporting the paper delivered from the paper stacking unit;
A second roller pair that is positioned downstream of the first roller pair in the paper conveyance direction and conveys the paper;
First driving means for rotationally driving the first roller pair and the second roller pair;
A first clutch that is positioned between the first driving means and the first roller pair to turn on / off the rotational driving force from the first driving means to the first roller pair;
A second clutch located between the first driving means and the second roller pair, and for turning on / off the rotational driving force from the first driving means to the second roller pair;
Control means for controlling the first clutch and the second clutch;
Second driving means controlled by the control means to rotationally drive the first roller pair;
A power transmission member that is located between the second driving means and the first roller pair and transmits a rotational driving force from the second driving means to the first roller pair in only one direction;
A paper supply device comprising:

2. The first driving means is a continuously rotating motor,
The first clutch and the second clutch are electromagnetic clutches capable of turning on / off transmission of rotational driving force,
The second driving means is a motor capable of controlling a rotation amount,
The power transmission member is a mechanical one-way clutch,
2. The control unit according to item 1, wherein the control unit turns off the first clutch when the second driving unit rotationally drives the first roller pair via the power transmission member. Paper feeder.

3. A paper storage section for storing paper;
A separating and conveying unit for separating and conveying the sheets one by one from the sheet accommodating unit;
A first roller pair for transporting the paper separated by the separation transport unit;
A second roller pair that is positioned downstream of the first roller pair in the paper conveyance direction and conveys the paper;
First driving means for rotationally driving the first roller pair and the second roller pair;
A first clutch that is positioned between the first driving means and the first roller pair to turn on / off the rotational driving force from the first driving means to the first roller pair;
A second clutch located between the first driving means and the second roller pair, and for turning on / off the rotational driving force from the first driving means to the second roller pair;
Control means for controlling the first clutch and the second clutch;
Second driving means controlled by the control means to rotationally drive the first roller pair;
A power transmission member that is located between the second driving means and the first roller pair and transmits a rotational driving force from the second driving means to the first roller pair in only one direction;
An image forming apparatus comprising:

4). The first driving means is a continuously rotating motor,
The first clutch and the second clutch are electromagnetic clutches capable of turning on / off transmission of rotational driving force,
The second driving means is a motor capable of controlling a rotation amount,
The power transmission member is a mechanical one-way clutch,
4. The image forming apparatus according to claim 3, wherein the control unit turns off the first clutch when the second driving unit rotationally drives the first roller pair.

  5. 3. An image forming system comprising: the paper supply apparatus according to 1 or 2; and an image forming apparatus that forms an image on a paper supplied from the paper supply apparatus.

  According to the above invention, there is no paper bending or crease, and there is a paper supply device having a registration means capable of supplying paper at a predetermined interval and position, and the registration means, and high print quality and high productivity. It is possible to provide an image forming system having a high print quality and high productivity, including the image forming apparatus having the image forming apparatus, the paper supply apparatus, and the image forming apparatus for forming an image.

  Hereinafter, the registration unit that corrects the skew of the sheet and adjusts the conveyance interval of the sheet, which is the point of the present invention, will be described by taking an image forming system including an image forming apparatus and a large-capacity sheet feeding apparatus having the registration unit as an example. To do.

To explain the wording, in the following explanation,
Upstream refers to the direction in which the paper is transported, and downstream refers to the direction in which the paper is transported.

  The width refers to the side perpendicular to the paper transport direction, and the length refers to the side parallel to the paper transport direction.

  A loop refers to a slack of paper that occurs in a certain part.

  The skew indicates that the sheet is conveyed obliquely with respect to the conveyance direction, and the bending indicates a state where the sheet is not perpendicular to the conveyance direction.

  FIG. 1 is a diagram illustrating an example of an image forming system including an image forming apparatus and a large-capacity paper feeding apparatus.

  First, a configuration of an image forming system including an image forming apparatus and a large-capacity paper feeding apparatus will be described with reference to FIG.

  The image forming apparatus A is referred to as a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer member 6, a paper feeding device 20, a fixing device 30, and the like. have.

  On the upper part of the image forming apparatus A, an original image reading apparatus B is installed.

  The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure unit of the document image reading apparatus B, and the reflected light corresponding to the document image is read into the line image sensor.

  The analog signal of the original image photoelectrically converted by the line image sensor is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then exposure means 3Y, 3M, Input to 3C and 3K.

  The image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 5Y disposed around a photosensitive drum 1Y as an image carrier.

  The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 5M.

  An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image carrier, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 5C.

  The image forming unit 10K that forms a black (K) image includes a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 5K.

  The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit.

  Developing devices 4Y, 4M, 4C, and 4K visualize latent images with a two-component developer composed of a small particle size toner of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. To do.

  The intermediate transfer member 6 can carry a toner image, is wound around a plurality of rollers, and is rotatably supported.

  The toner images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred (primary transfer) by the primary transfer units 7Y, 7M, 7C, and 7K onto the rotating intermediate transfer body 6 to obtain a color image. Is synthesized.

  The sheet S accommodated in the sheet feeding cassette 21A of the sheet feeding device 20 is picked up by the sheet feeding means 22A, passes through the transport rollers 23, 24, 25, the loop roller 26, the registration roller 27, etc., and enters the transfer region p. Be transported.

  The transfer area p is a portion where the transfer roller 9 and the intermediate transfer body 6 are opposed to each other, and the color image carried on the intermediate transfer body 6 is transferred (secondary transfer) to the paper S.

  The sheet S on which the color image is transferred is heated and pressed by the heating roller 30A and the pressure roller 30B in the fixing device 30.

  As a result, the toner image on the paper S is fixed and fixed on the paper S, and is sandwiched between the paper discharge rollers 28 and placed on the paper discharge tray 29 outside the apparatus.

  The intermediate transfer member 6 separates the curvature of the sheet S after transferring the color image, and the cleaning unit 8 removes the toner remaining on the intermediate transfer member 6.

  In the case of reversely discharging the fixed sheet S, the sheet S passes through the lower conveyance path of the branch plate 28A disposed between the fixing device 30 and the sheet discharge roller 28, and the lower conveyance path. After being transported to r1, it is transported in the reverse direction, passes through the transport path r2 on the left side of the branch plate 28A, and is discharged out of the apparatus by the paper discharge roller 28.

  When printing on both sides of the sheet S, after fixing the image formed on the first surface of the sheet S, the sheet S is introduced into the transport path r1 and further into the transport path r3, and then transported in the reverse direction to transport the path r4. Transport to.

  Then, the paper whose front and back are reversed is conveyed to the transfer region p through the loop roller 26, the registration roller 27, and the like.

  Then, the color image is transferred to the second surface which is the back surface of the first surface, subjected to heat fixing processing by the fixing device 30, and discharged outside the device by the paper discharge roller 28.

  The image forming apparatus A is provided with a manual sheet feeding device C.

  The paper S accommodated in the manual paper feed tray 21B of the manual paper feed device C is fed by the paper feed means 22B, sent to the transfer region p through the transport roller 25, the loop roller 26, and the registration roller 27, An image is formed in the same manner as described above.

  The image forming apparatus A described above is an image forming apparatus that forms a color image, but may be an image forming apparatus that forms a monochrome image.

  On the upstream side of the image forming apparatus A, a paper feeding device for feeding paper, for example, a large capacity paper feeding device LT for feeding a large amount (for example, 1000 sheets or more) of paper is connected.

  The large-capacity paper feeding device LT has a main body 40 that stores the paper S, and a lid 50 that is configured to be openable and closable with respect to the main body 40 when the paper S is stored.

  The main body 40 includes a paper stacking unit 41 for stacking the paper S, a feed roller 42 for picking up the paper S, a separation roller 43 for separating the paper S one by one, and adjusting the paper interval length in advance (feed timing). A pre-registration unit 60 that performs adjustment) and prevents the sheet from being bent.

  The lid 50 is provided with a plurality of rear end guides 70 (71 to 77) for regulating the rear end of the paper according to a plurality of sizes.

  The pre-registration unit 60 includes a loop roller 61 that forms a loop (broken line) on the paper S in the transport path r11, a pre-registration roller 62 that adjusts the paper interval length (paper feed timing adjustment) and corrects the skew of the paper, and the transport path. and a first sheet sensor 63 that detects the sheet S transported by r11.

  The conveyance path r11 is located between the loop roller 61 and the pre-registration roller 62, and is a conveyance path for the paper S that forms a loop.

  The paper stacking unit 41 is driven by a motor (not shown) and can move up and down.

When the lid 50 is opened, the paper stacking portion 41 is moved downward by a motor (not shown) so that the paper can be easily stacked.
When the sheet S is stacked and the lid 50 is closed, the sheet stacking unit 41 is moved upward by the motor, and stops at a position where the feeding roller 42 can easily pick up the uppermost sheet.

  The discharge port 44 of the large-capacity sheet feeding device LT and the receiving port 1 of the image forming apparatus A are disposed at positions facing each other, so that the paper S can be delivered.

  The large-capacity paper feeder LT can store paper of different sizes.

  The downstream front end portion of the sheet S abuts on a fixing member in the main body 40, and the upstream rear end portion is regulated by rear end guides 70 (71 to 77) corresponding to a plurality of sizes.

  Further, in the width direction of the paper S, side guides (not shown) that restrict both side ends of the paper S are provided in the main body 40. When one side guide is moved, the other side guide is interlocked. The center position does not change even if the paper moves in the reverse direction and has a different width.

  This side guide may be a well-known or conventional one.

An outline of the operation of the large capacity sheet feeding device LT will be described.
The image forming apparatus A outputs a paper feed instruction signal instructing the supply of the paper S to the large capacity paper feeding device LT.

  When the large-capacity sheet feeding device LT receives the sheet feeding instruction signal, the feeding roller 42 that presses against the sheet S positioned on the uppermost surface is rotated to pick up the sheet, and the separating roller pair 43 separates the sheet into individual sheets. .

  Then, the separated paper S is conveyed by the loop roller 61 and abuts against the pre-registration roller 62, and stops in a state where a loop is formed at the downstream end portion of the paper.

  The pre-registration roller 62 corrects the skew of the sheet by this loop, and discharges the sheet S toward the receiving port 1 of the image forming apparatus A with a predetermined interval between the preceding and succeeding sheets.

  FIG. 2 is a conceptual diagram of power transmission of the drive system from the pre-registration unit 60 of the large-capacity sheet feeding device LT to the registration rollers 27 of the image forming apparatus A.

  First, the large capacity sheet feeder LT will be described. The loop roller 61 is driven by the DC motor M1 via the first clutch CL1 and the first drive system G1, and the stepping motor M3 via the one-way clutch CL7. The state driven by is controlled to be switchable.

  The pre-registration roller 62 is driven by a DC motor M1 via a second clutch CL2 and a first drive system G1.

  The first drive system G1 only needs to be a drive system that can transmit a rotational force, and a belt, a gear, or the like can be used.

  The DC motor M1 is always rotating during the paper feeding operation of the large capacity paper feeding device LT.

The one-way clutch CL7 can transmit a rotational force in only one direction, and a mechanical one-way clutch that is normally used that is free for the other rotational force can be used.
The rotational force can be transmitted only when the loop roller 61 is driven by the stepping motor M3 in the direction of the arrow (the direction in which the paper is conveyed).

  Further, the first clutch CL1, the second clutch CL2, and the stepping motor M3 are controlled by a control unit C1 that controls the large-capacity paper feeding device LT.

  The first clutch CL1 and the second clutch CL2 are clutches capable of turning on / off the transmission of rotational force, and for example, an electromagnetic clutch can be suitably used.

  Further, the stepping motor M3 may be any motor that can precisely control the amount of rotation. For example, a stepping motor that can be used in an open loop can be suitably used.

  The communication unit T1 is controlled by the control unit C1, communicates with the communication unit T2 of the image reading apparatus B, and receives a paper feed instruction signal and the like.

  Here, in order to clarify the invention, some conventional control will be described.

Conventionally, the drive system for the loop roller 61 is only the first clutch CL1, the first drive system G1, and the DC motor M1,
The loop roller 61 is driven only by the DC motor M1 via the first clutch CL1 and the first drive system G1, and is not driven by the stepping motor M3.

  For this reason, when the first clutch CL1 is turned OFF, the conveyance distance of the paper S by the loop roller 61 varies due to the inertia of the loop roller 61 connected to the output shaft of the first clutch CL1, and the conveyance path r11. It was difficult to secure a precise loop amount in

  For this reason, as described in (Problem to be Solved by the Invention), for example, when the loop amount is extremely small, adjustment of the sheet interval length (feed timing) by the pre-registration roller 62 and correction of the skew of the sheet are performed. There was a problem that it was impossible.

  Next, the image forming apparatus A will be described.

The transport roller 24 is driven by a DC motor M2 via a third clutch CL3 and a second drive system G2,
The transport roller 25 is driven by a DC motor M2 via a fourth clutch CL4 and a second drive system G2,
The loop roller 26 is driven by the DC motor M2 via the fifth clutch CL5 and the sixth clutch CL6 and the second drive system G2,
The registration roller 27 is driven by a DC motor M2 via a sixth clutch CL6 and a second drive system G2.

  The clutch CL6 is a clutch that drives the loop roller 26 and the registration roller 27. Unlike the other clutches CL1 to CL5, the driving speed input via the clutch CL6 is a gear that conveys the sheet at the same speed as the toner image. The ratio is set. When the clutch CL6 is ON, the loop roller 26 and the registration roller 27 are driven at the same rotation speed and the same rotation amount.

  The loop roller 26 includes an encoder (not shown) (for example, a sensor for detecting blades) for measuring the amount of rotation of the loop roller 26 (that is, the transport distance of the paper transported by the loop roller 26). )] Is attached.

  The second drive system G2 may be any drive system that can transmit a rotational force, and a belt, a gear, or the like can be used.

  The DC motor M2 is always rotating while the image forming apparatus A is powered on.

  The third clutch CL3, the fourth clutch CL4, the fifth clutch CL5, and the sixth clutch CL6 are clutches capable of turning on / off the transmission of rotational force, and for example, an electromagnetic clutch is preferably used. The image forming apparatus A is controlled by a control unit C2 that controls the image forming apparatus A.

  Further, the communication unit T2 is controlled by the control unit C2, and communicates with the communication unit T1 of the large-capacity sheet feeding device LT to transmit a sheet feeding instruction signal and the like.

  As described above, as the paper driving source, the DC motor M1 drives the loop roller 61 and the pre-registration roller 62, and the DC motor M2 drives the conveyance rollers 23, 24, and 25, the loop roller 26, and the registration roller 27. The drive area by one motor may be made smaller by using more motors (for example, one motor for two rollers), and in this case, it becomes possible to carry a sheet that can withstand a higher speed or a higher load.

  FIG. 3 is an explanatory diagram illustrating a sheet conveyance state from the pre-registration unit 60 of the large-capacity sheet feeding device LT to the registration roller 27 of the image forming apparatus A.

  The vertical axis represents the distance from the exit of the paper stacking section 41 of the large capacity paper feeder LT toward the downstream side. The loop roller 61, the pre-registration roller 62, the loop roller 26, the registration roller 27, and the paper to be conveyed are shown. The schematic arrangement positions of the first paper sensor 63, the second paper sensor 64, the third paper sensor 65, and the fourth paper sensor 66 to be detected are shown.

  The horizontal axis shows the passage of time.

X indicates the first sheet, Y indicates the second sheet, Z indicates the third sheet,
A solid line a indicates the locus of the upstream rear end of the first sheet X.

  The solid line b indicates the locus of the downstream end of the second sheet Y, and the solid line c indicates the locus of the upstream rear end of the second sheet Y.

  The solid line d indicates the locus of the downstream leading edge of the third sheet Z, and the solid line e indicates the locus of the upstream trailing edge of the third sheet Z.

  The solid line f indicates the locus of the downstream leading edge of the fourth sheet, and the solid line g indicates the locus of the upstream trailing edge of the fourth sheet.

  Therefore, a portion where the solid lines a to g are inclined toward the upper right means that the sheet S is being conveyed, and a lying portion means that the sheet S is stopped, and the inclination thereof. Indicates the sheet conveyance speed (the steeper slope has a higher speed).

  For example, the portion where the solid lines b and c are inclined toward the upper right means that the second sheet S is being conveyed, and the portion where the solid lines b and c lie is the second sheet This means that the sheet S is stopped.

In addition, although the solid lines c, e, and g, which are the trajectories of the upstream rear end of the sheet, have stopped, the solid lines b, d, and f, which are the trajectories of the downstream end of the same sheet, have an upwardly convex Δ shape. The portions b1, d1, and f1 that are used mean that a pre-registration roller 62 and a loop roller 61 form a loop at the downstream end,
The upwardly convex Δ-shaped portions b2, d2, and f2 mean that a loop is formed in the transport path r11 at the downstream end by the registration roller 27 and the loop roller 26.

For example, it means that a loop is formed on the second sheet S by the pre-registration roller 62 and the loop roller 61 in the upwardly convex Δ-shaped portion b1.
The upwardly convex Δ-shaped portion b2 means that the registration roller 27 and the loop roller 26 form a loop of the second sheet S in the transport path r11.

  In the drawing, the downstream end of the sheet is shown as protruding from the pre-registration roller 62 (registration roller 27), but this is for ease of understanding. In fact, the downstream end is the pre-registration roller. 62 (registration roller 27) but a loop is formed between the pre-registration roller 62 (registration roller 27) and the loop roller 61 (loop roller 26).

  Hereinafter, the second sheet Y is taken as an example, and the conveyance thereof will be described in detail, but other sheets are also conveyed in the same manner.

  In the following description, since the ON / OFF of which clutch or the like conveys the sheet differs depending on the sheet size, at least the one that must be turned on / off is described.

1) Region H
The second sheet Y is fed from the sheet stacking unit 41 by the feed roller 42.

  Then, the second sheet Y is conveyed by the loop roller 61 via the one-way clutch CL7 by the stepping motor M3, and stops after forming a loop at the downstream end.

  In the storage means (not shown), the rotation amount of the loop roller 61 corresponding to the loop conveyance distance, which is a distance obtained by adding the necessary loop amount to the distance l1 from the paper sensor 63 to the pre-registration roller 62, that is, the loop The number of drive pulses of the stepping motor M3 (number of loop transport drive pulses) corresponding to the transport distance is stored.

  Here, the necessary loop amount refers to the amount of paper that can be reliably brought into contact with the pre-registration roller 62 with a margin at the downstream end of the paper in the conveyance path r11.

  The control means C1 reads out the number of loop transport driving pulses, drives the stepping motor M3 by the number of loop transport driving pulses from the time point when the downstream end of the second sheet Y is detected by the paper sensor 63, and the loop roller 61 Is slowly decelerated and stopped so as not to lead by inertia.

  As a result, the downstream end of the second sheet Y abuts against the pre-registration roller 62, and the remaining sheet corresponding to the “required loop amount” forms a loop between the loop roller 61 and the pre-registration roller 62. Sag and form a loop.

  At this time, the first clutch CL1 is OFF, and the one-way clutch CL7 is latched by the driving of the stepping motor M3, and the loop roller 61 can be rotated by the stepping motor M3.

2) Region I
The second sheet Y continues to be stopped by turning off the first clutch CL1 and stopping the stepping motor M3 for a predetermined time.

  The stepping motor M3 maintains the stopped state by the holding torque at the time of stopping while the leading edge of the second sheet Y is in contact with the pre-registration roller 62 with certainty. This holding torque prevents the loop roller 61 from rotating in reverse due to the rigidity (return force) of the paper on which the loop is formed.

  This makes it possible to secure and maintain a necessary loop (convex portion b1) between the loop roller 61 and the pre-registration roller 62 (conveying path r11).

3) Region J
When the second sheet sensor 64 detects the rear end of the first sheet X (change from ON to OFF), the first clutch CL1, the second clutch CL2, etc. are turned on, the loop roller 61, The rotation of the pre-registration roller 62 and the like is started, and conveyance of the stopped second sheet Y is started.

  Thereafter, the second sheet Y is transferred to the image forming apparatus A, and the third clutch CL3 is turned ON, so that the inside of the image forming apparatus A can be conveyed by the conveying roller 24.

  Then, after the second sheet Y passes through the sheet sensor 64 and is conveyed for a predetermined distance, all the sheets Y that are transporting the sheet Y are avoided in order to avoid collision with the rear end of the first sheet X. The roller clutch is turned off, and the paper is stopped and waited.

  In the first sheet X, after the area J, the sixth clutch CL6 and the like for driving the registration roller 27 and the loop roller 26 to be connected are turned on in synchronization with the toner image carried on the intermediate transfer member 6. As a result, the first sheet X is conveyed in the loop forming unit r12 while maintaining the loop, further conveyed to the fixing device 30, and further discharged to the discharge tray 29.

4) Region K
The second sheet Y continues to stop until the third sheet sensor 65 detects the rear end of the conveyed first sheet X (change from ON to OFF).

5) Region L
The first sheet CL1, the second clutch CL2, the third clutch CL3, and the like are turned on, and the rotation of the loop roller 61, the pre-registration roller 62, the conveyance roller 24, and the like is started and stopped. The conveyance of the first sheet Y is started.

  After that, when the leading edge of the second sheet Y reaches the third sheet sensor 65, all the rollers for transporting the second sheet are in order to avoid collision with the rear end of the first sheet X again. Turn off the clutch and wait for it to stop.

  When the first sheet sensor 63 detects the passage of the upstream end of the second sheet Y, the loop roller 61 is driven by the motor M3 (one-way clutch CL7) in preparation for transporting the third sheet Z. ).

6) Region M
The second sheet Y continues to stop,
When the fourth paper sensor 66 detects the upstream rear end of the first sheet X being conveyed (change from ON to OFF),
The second sheet that has been stopped by turning on the third clutch CL3, the fourth clutch CL4, the fifth clutch CL5, etc., and starting the rotation of the carry roller 24, the carry roller 25, the loop roller 26, etc. The conveyance of the paper Y of the eye is started.

7) Region N (H)
The second sheet Y is started to be transported,
The loop is formed by the loop roller 26, and the rotation amount of the loop roller 26 can be measured, for example, by counting the number of pulses detected by the impeller blades attached to the loop roller 26.

  In the storage means (not shown), the rotation amount of the loop roller 26 corresponding to the second loop conveyance distance, which is a distance obtained by adding the necessary loop amount to the distance from the fourth paper sensor 66 to the registration roller 27, that is, Stored is the number of pulses (second loop conveyance driving pulse number) detected for the blades of the impeller corresponding to the second loop conveyance distance.

  The fourth sheet sensor 66 detects the downstream end of the second sheet Y of the second sheet Y started to be conveyed when the fifth clutch CL5 and the like are turned on.

  The control unit C1 detects the fourth clutch upstream of the fifth clutch CL5 based on the detection signal (change from OFF to ON) of the fourth sheet sensor 66 that detects the downstream end of the second sheet Y. By turning off CL4 and the like, the conveying roller 25 and the like are made free, and the rotation amount of the loop roller 26 is measured.

The control means C1 reads the second loop conveyance drive pulse number,
The fifth clutch CL5 and the like are kept on until the rotation amount of the loop roller 26, for example, the count value of the pulse that detects the blade of the impeller coincides with the second loop conveyance drive pulse number, and the loop roller 26 continues to turn on. Transport the second sheet Y,
If they match, the fifth clutch CL5 and the like are turned off, and the conveyance of the second sheet Y is stopped.

  At this time, the downstream end of the second sheet Y being conveyed hits the resist roller 27 that is stopped, and the length of the sheet corresponding to the “required loop amount” described above is equal to the loop roller 26 and the resist. A loop is formed between the rollers 27, and a loop (convex portion b2) is formed.

  In addition, at least before the loop formation in the region N, the conveyance connected to the output shaft of the fourth clutch CL4 is turned off by turning off the fourth clutch CL4 and the like upstream from the fifth clutch CL5 as described above. By making the roller 25 and the like free and increasing the load on the upstream side of the loop roller 26, over-rotation due to the inertia of the transport roller and the like is prevented, and the loop formation by the loop roller 26 is ensured.

  The area N corresponds to the above-described area H, and the third sheet Z is sent out from the paper stacking section 41 by the feed roller 42 as in the area H.

  Then, the third sheet Z is conveyed by the loop roller 61 via the one-way clutch CL7 by the stepping motor M3.

7) After the region N The region I ′ corresponds to the region I, the region J ′ corresponds to the region J, and the region K ′ corresponds to the region K.

  Then, the region H (N) to the region M are sequentially repeated.

  FIG. 4 is an explanatory diagram of an image forming apparatus D having a pre-resist part.

  The image forming apparatus D having the pre-registration unit 60 ′ has a configuration other than the pre-registration unit 60 ′ provided between the paper feeding device 20 that is a paper storage unit that stores paper and the transport roller 24 that transports the paper. Since the configuration and operation are the same as those of the image forming apparatus A described with reference to FIG. 1, descriptions other than the pre-registration unit 60 ′ are omitted.

The pre-registration unit 60 ′ includes a loop roller 61 ′ corresponding to the loop roller 61, a pre-registration roller 62 ′ corresponding to the pre-registration roller 62, a conveyance path r11 ′ corresponding to the conveyance path r11, and a first paper sensor. A first sheet sensor 63 ′ corresponding to 63;
A first clutch CL1 '(not shown) corresponding to the first clutch CL1, a second clutch CL2' (not shown) corresponding to the second clutch CL2, and a first drive system G1 corresponding to the first drive system G1. 1 drive system G1 ′ (not shown), a DC motor M1 ′ (not shown) corresponding to the DC motor M1, and a one-way clutch CL7 ′ (not shown) corresponding to the one-way clutch CL7.

  The first clutch CL1 ', the second clutch CL2', and the stepping motor M3 'are controlled by a control unit that controls the image forming apparatus D.

  The first clutch CL1 ′, the second clutch CL2 ′, and the stepping motor M3 ′ are the same as the first clutch CL1, the second clutch CL2, and the stepping motor M3 described with reference to FIG. By performing the control, it is possible to perform the same operation as that of the region H in FIG.

  As described above, when the pre-registration unit 60 is provided in the image forming apparatus, the conveyance state of the sheet from the sheet feeding device 20 is very bad (slanting, etc.), and it is not possible to sufficiently correct the bending or the like with only the transfer unit. However, it is possible to reliably correct the bend in the transfer section by performing the bend correction in advance upstream of the transfer section.

  As explained above, in the pre-registration mechanism that corrects paper skew in the middle of the paper transport path, the loop amount during loop formation is precisely controlled by using a stepping motor to drive the loop roller. In addition to the stepping motor and the driving by the clutch, the formed loop is consumed during the transportation even when the paper is frequently driven and stopped in the transportation path. This makes it possible to perform more accurate bend correction.

1 is a diagram illustrating an example of an image forming system including an image forming apparatus and a large-capacity paper feeding apparatus. 3 is a conceptual diagram of power transmission of a drive system from a pre-registration unit 60 of a large capacity sheet feeding device LT to a registration roller 27 of an image forming apparatus A. FIG. FIG. 6 is an explanatory diagram illustrating a sheet conveyance state from a pre-registration unit 60 of the large-capacity sheet feeding device LT to a registration roller 27 of the image forming apparatus A. 2 is an explanatory diagram of an image forming apparatus D having a pre-registration unit 60. FIG.

Explanation of symbols

2627
26 Loop Roller 27 Registration Roller 60 Pre-Registration Unit 61 Loop Roller 62 Pre-Registration Roller 63 First Paper Sensor A Image Forming Apparatus C1 Control Unit CL1 First Clutch CL2 Second Clutch CL3 Third Clutch CL4 Fourth Clutch CL5 Fifth clutch CL6 Sixth clutch CL7 One-way clutch G1 First drive system G2 Second drive system LT Large-capacity paper feeder M1 DC motor M2 DC motor M3 Stepping motor p Transfer region r11 Transport path S Paper

Claims (5)

A paper stacking unit for loading paper,
A first roller pair for transporting the paper delivered from the paper stacking unit;
A second roller pair that is positioned downstream of the first roller pair in the paper conveyance direction and conveys the paper;
First driving means for rotationally driving the first roller pair and the second roller pair;
A first clutch that is positioned between the first driving means and the first roller pair to turn on / off the rotational driving force from the first driving means to the first roller pair;
A second clutch located between the first driving means and the second roller pair, and for turning on / off the rotational driving force from the first driving means to the second roller pair;
Control means for controlling the first clutch and the second clutch;
Second driving means controlled by the control means to rotationally drive the first roller pair;
A power transmission member that is located between the second driving means and the first roller pair and transmits a rotational driving force from the second driving means to the first roller pair in only one direction;
A paper supply device comprising: The first driving means is a continuously rotating motor,
The first clutch and the second clutch are electromagnetic clutches capable of turning on / off transmission of rotational driving force,
The second driving means is a motor capable of controlling a rotation amount,
The power transmission member is a mechanical one-way clutch,
2. The control unit according to claim 1, wherein the control unit turns off the first clutch when the second driving unit rotationally drives the first roller pair via the power transmission member. Paper feeder. A paper storage section for storing paper;
A separating and conveying unit for separating and conveying the sheets one by one from the sheet accommodating unit;
A first roller pair for transporting the paper separated by the separation transport unit;
A second roller pair that is positioned downstream of the first roller pair in the paper conveyance direction and conveys the paper;
First driving means for rotationally driving the first roller pair and the second roller pair;
A first clutch that is positioned between the first driving means and the first roller pair to turn on / off the rotational driving force from the first driving means to the first roller pair;
A second clutch located between the first driving means and the second roller pair, and for turning on / off the rotational driving force from the first driving means to the second roller pair;
Control means for controlling the first clutch and the second clutch;
Second driving means controlled by the control means to rotationally drive the first roller pair;
A power transmission member that is located between the second driving means and the first roller pair and transmits a rotational driving force from the second driving means to the first roller pair in only one direction;
An image forming apparatus comprising: The first driving means is a continuously rotating motor,
The first clutch and the second clutch are electromagnetic clutches capable of turning on / off transmission of rotational driving force,
The second driving means is a motor capable of controlling a rotation amount,
The power transmission member is a mechanical one-way clutch,
4. The image forming apparatus according to claim 3, wherein the control unit turns off the first clutch when the second driving unit rotationally drives the first roller pair. 5. An image forming system comprising: the paper supply device according to claim 1; and an image forming device that forms an image on a paper supplied from the paper supply device.

Images