JP6919326B2 - Sheet transfer device and image forming device equipped with it - Google Patents

Description

The present invention relates to a sheet transport technique, and more particularly to a sheet spacing (paper-to-paper) adjustment technique.

The sheet transfer device is mounted on a system for processing sheets such as printing paper and originals, and transfers sheets between processing systems in the system. This system includes, for example, an image forming apparatus such as a printer or a copier, a post-processing apparatus (finisher), or an automatic document feeder (ADF), and prints, images, sorts, binds, folds, etc. on a sheet being conveyed. Is processed. In order for these processes to proceed smoothly to the elements in the system to improve productivity, that is, to increase the number of sheets processed per unit time, the sheet transfer device must move the sheets more quickly between the elements in the system. Must be.

As a device for speeding up the movement of the sheet between the elements, for example, an increase in the sheet transfer speed and a sheet transfer interval, that is, a shortening between papers can be mentioned. However, it is difficult to further increase the sheet transport speed. This is because it is necessary to prevent the noise generated by the motor or the like from increasing with this rise, and it is difficult to reduce the cost required for this measure. On the other hand, with regard to shortening between papers, for example, a technique for transporting papers to the vicinity of a processing unit without gaps is already known. Specifically, in the technique disclosed in Patent Documents 1 and 2, when a plurality of sheets are conveyed from the start end of a transfer path such as a paper feed cassette, the space between papers is set to substantially "0". At the moment when the rear end of the preceding sheet reaches a predetermined position, the transport roller on the upstream side stops and prevents the subsequent sheet from advancing until the target paper gap is opened. According to the technique disclosed in Patent Document 3, when a plurality of sheets are continuously fed from the start end of a transport path, the tip of the next sheet is overlapped with the rear end of the preceding sheet. Since the transfer speed of the sheet by the downstream transfer roller is higher than the speed of the sheet that is repeatedly fed in this way, when the tip of the preceding sheet reaches this transfer roller, the speed of the sheet is higher than that of the next sheet. .. Therefore, the rear end of the preceding sheet will soon overtake the tip of the next sheet, and by the time it reaches the downstream transport roller, the difference from the tip will be widened to the target paper space. In the technique disclosed in Patent Document 4, the tip of the next sheet is superposed on the rear edge of each sheet and sent out. When the rear end of the preceding sheet reaches a predetermined position, not only the transport roller on the upstream side stops, but also the tip of the next sheet being transported hits a movable member that blocks a part of the moving space of the sheet. Its progress is hindered. When the preceding sheet separates until the target paper gap is opened, this movable member retracts from the path and allows the next sheet to advance.

As described above, the technology that is already known as a technique for transporting sheets to the vicinity of the processing unit without gaps for the purpose of speeding up the sheet transportation continues to move the preceding sheet near the processing unit. Stops the next sheet or moves the preceding sheet faster than the next sheet. As a result, the space between the sheets is expanded to the target value by the time the preceding sheet reaches the processing unit. Therefore, the shorter the target paper spacing, the shorter the downtime of the next sheet and the smaller the speed difference between the preceding sheet and the next sheet. Therefore, as long as the target paper spacing is sufficiently short, the amount of reduction in transport time by not leaving the paper spacing is an operation for separating the rear end of the preceding sheet from the tip of the next sheet to leave the paper spacing. Well larger than time. That is, it is effective to increase the speed by transporting without leaving a space between papers.

Japanese Unexamined Patent Publication No. 2003-176045 Japanese Unexamined Patent Publication No. 2004-331357 Japanese Unexamined Patent Publication No. 2001-301998 Japanese Unexamined Patent Publication No. 2014-084222

In recent years, image forming devices such as printers and copiers have become widespread in SOHO and general households. Along with this, the image forming apparatus is required to realize further miniaturization at low cost without impairing the high speed of processing. In order to meet this requirement, the sheet transfer device also needs to be further miniaturized and reduced in cost by simplifying the mechanism and simplifying the control while maintaining the transfer speed at a high level.

However, as a device for satisfying this requirement, it is difficult to apply the above-mentioned technique of transporting without leaving a space between papers. In fact, with this technique, it is difficult to align the overlapping lengths between sheets with high accuracy, so it is difficult to reduce the estimation error of the tip position of each sheet. Further, in order to accurately adjust the space between papers near the processing unit, it is necessary to accurately control the timing of starting and braking of the transport roller on the upstream side to accurately position the tip of each sheet. However, since it is difficult to reduce the error in estimating the overlap length, it is necessary to secure a longer stop time for the transport roller, and if the target paper spacing is large to some extent, the transport time can be shortened by not leaving a space between the papers. Is at risk of being offset. It is inevitable that the cost will increase due to the addition of sensors or the complication of the control system in order to improve the accuracy of the positioning control of the tip of each sheet by actually measuring the overlap length with the paper passing sensor. Furthermore, in order to increase the number of sheets processed per unit time, the transport roller must be repeatedly started and stopped accurately. It is difficult to perform such high-precision and high-speed control at low cost.

An object of the present invention is that it is possible to convey at high speed without leaving a space between papers and to secure a target space between papers with high accuracy in front of the destination by a small and easy-to-control mechanism. The purpose is to provide a sheet transfer device.

The sheet transport device according to one aspect of the present invention is a device that continuously transports a plurality of sheets along a predetermined path, and continuously feeds the plurality of sheets to the path and feeds each sheet. A delivery unit that sets the timing so that the tip of the next sheet overlaps the rear end of the sheet that started feeding immediately before, and a movable member installed so that the tip of the sheet fed by the delivery unit abuts on the path. The sending unit sent out the gate that temporarily blocked the progress of the tip of the abutted sheet and allowed the tip to advance when pushed away from the path by the tip, and the sheet that was reached by pushing away the gate. It is equipped with a retractable part that pulls in at a speed higher than the speed. When the first sheet and the second sheet are continuously fed, the delivery unit applies a first transport force to the tip of the first sheet while feeding the preceding portion of the first sheet in which the second sheets do not overlap. It is set stronger than the second transport force applied to the tip of the second sheet while the succeeding portion of the first sheet on which the two sheets overlap is sent out together with the second sheet. When the force received from the tip of the abutted sheet is the first carrying force, the gate is pushed away from the path to allow the tip to advance, and when the force is the second carrying force, the gate stays in the path and stays at the tip of the gate. Block progress.

In this sheet transfer device, the tip of the second sheet may abut against the gate before the rear end of the first sheet separates from the delivery portion.
The path is drawn by the middle part of the sheet where the rear end is sent out by the sending part and the tip is pulled in by the pulling part, while the first locus is drawn by the tip of the sheet which is only sent out by the sending part. It may include a curved portion whose locus is located inside. The gate may be installed at the curved portion so as to be located outside the second locus and to abut the tip of the sheet traveling on the first locus.

The delivery unit contacts the upper surface of the bundle of sheets to be fed, feeds the sheet located on the upper surface, and starts feeding the next sheet before the rear end of the sheet separates from the tip of the next sheet. The first paper feed roller that contacts the upper surface of the sheet fed by the pickup roller and feeds the sheet to the path, and the sheet is fed to the path while contacting the lower surface of the sheet fed by the pickup roller. After the point of contact with the lower surface of the next sheet that is being fed with the tip overlapping the rear end of the sheet, the second paper feed roller that feeds the next sheet to the path with the overlapping state It may be included. The first transfer force is equal to the total transfer force between the pickup roller, the first paper feed roller, and the second paper feed roller, and the second transfer force is the total transfer force of the first paper feed roller. It may be equal to the excluded value.

The pull-in portion may include a pull-in roller that conveys the tip of the sheet reached by pushing the gate away at a higher speed than the delivery portion. Due to the difference in transport speed with respect to the delivery unit, the pull-in roller may have the tip of the second sheet overtaken by the rear end of the first sheet separated from the delivery part before the tip reaches the pull-in roller.
The gate may correct the skew of the sheet by generating a moment at the tip of the abutted sheet about the normal line of the sheet that penetrates the tip while blocking the advance of the tip of the sheet.

The image forming apparatus according to one aspect of the present invention includes the above-mentioned sheet conveying device that conveys a sheet, and an image forming unit that forms an image on the sheet.

In the above-mentioned sheet transport device according to the present invention, the delivery unit feeds the next sheet by superimposing the tip of the next sheet on the rear end of each sheet. When the delivery unit continuously feeds the first sheet and the second sheet, the first transport force applied to the tip of the first sheet while the preceding portion of the first sheet on which the second sheets do not overlap is fed is It is stronger than the second transport force applied to the tip of the second sheet while the subsequent portion of the first sheet on which the second sheet overlaps is sent out together with the second sheet. When the gate is abutted against the tip of the sheet sent out by the delivery unit, the gate temporarily blocks the progress of the tip. If the force received from the tip of this sheet is equal to the first carrying force, the gate is pushed away from the path to allow the tip to advance, and if equal to the second carrying force, the gate stays in the path and advances its tip. Block. As a result, this sheet transporting device can transport paper at high speed without leaving a gap between papers, and can secure a target paper spacing with high accuracy in front of the transport destination with a compact and easy-to-control mechanism. can.

(A) is a perspective view showing the appearance of the image forming apparatus according to the embodiment of the present invention, and (b) is a schematic cross-sectional view of the image forming apparatus along the straight line bb shown by (a). be. (A) is a perspective view showing the appearance of the gate shown by (b) of FIG. 1, and (b) is a cross-sectional view of the gate along the straight line bb shown by (a). It is a schematic diagram of the fixed shaft of the gate and the swing member seen from the normal direction of the plate surface of the paper passing guide. (A) represents a state in which the tip of the sheet fed from the nip between the paper feed rollers reaches the position of the swing member, and (b) is a position where the tip abuts on the claws of all four swing members. Represents the state in which the sheet is rotated to. It is a schematic diagram which shows the state which two sheets are sent out continuously from a paper cassette in chronological order. Indicates the time when the lead roller has passed the nip. FIG. 4 is a schematic view showing a state in which two sheets are continuously fed out from a paper cassette in chronological order following FIG. 4, and in FIG. 4A, the rear end of the first sheet separates from the nip between the paper feed rollers. (B) indicates the time when the trailing end reaches the nip of the pull-in roller.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Appearance of image forming apparatus]
FIG. 1A is a perspective view showing the appearance of the image forming apparatus 100 according to the embodiment of the present invention. The image forming apparatus 100 is a printer. A paper ejection tray 41 is provided on the upper surface of the housing, and a sheet ejected from the paper ejection port 42 opened at the back thereof is accommodated. An operation panel 51 is embedded in front of the output tray 41. At least one paper cassette 11 is attached to the bottom of the printer 100 so that it can be pulled out.

[Internal structure of image forming apparatus]
FIG. 1B is a schematic cross-sectional view of the printer 100 along the straight line bb shown in FIG. 1A. The printer 100 is an electrophotographic color printer, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper discharging unit 40.
First, the feeding unit 10 separates the sheets one by one from the bundle of sheets housed in the paper cassette 11 by using the transport rollers 12P, 12F, 12G, 13 provided in one group for each paper cassette 11. Then, it is sent to the timing roller 14. Next, the feeding unit 10 sends the separated sheet SH1 from the timing roller 14 to the image forming unit 20 in time with the operation of the image forming unit 20. "Sheet" means a thin or thin plate-shaped member, article, or printed matter. The material of the sheet on which the printer 100 can print includes paper or resin. The types of sheets that can be accommodated in the paper cassette 11, that is, the paper types include plain paper, high-quality paper, color paper, and coated paper, and the sizes include standard sizes defined by JIS standards, for example, A3-A7. , B4-B7, business cards, bookmarks, tickets, postcards, envelopes, photos (L version) are included. Furthermore, the posture of the seat can be set to either vertical or horizontal.

The image forming unit 20 is, for example, an intermediate transfer method, in which the photoconductor units 20Y, 20M, 20C, 20K in a tandem arrangement, the intermediate transfer belt 21, the primary transfer rollers 22Y, 22M, 22C, 22K, and the secondary transfer rollers 23 are used. including. The intermediate transfer belt 21 is rotatably hung between the driven pulley 21L and the drive pulley 21R. In the space sandwiched between these pulleys 21L and 21R, four photoconductor units 20Y-20K and four primary transfer rollers 22Y-22K are arranged so as to form a pair, and an intermediate transfer belt is provided. A nip is formed with 21 sandwiched between them. The secondary transfer roller 23 forms a nip with the drive pulley 21R with the intermediate transfer belt 21 sandwiched between them. The sheet SH2 fed from the timing roller 14 is passed through this nip.

In each of the photoconductor units 20Y-20K, the intermediate transfer belt 21 rotates (counterclockwise in (b) of FIG. 1) and the same surface portion is formed by the primary transfer roller 22Y-22K and the photoconductor drum 24Y-24K. When passing through the nip between them, a toner image of one different color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface portion thereof. When the surface portion passes through the four photoconductor units 20Y-20K, toner images of four colors Y, M, C, and K are superimposed on the surface portion to form one color toner image. The sheet SH2 is passed from the timing roller 14 to the nip at the timing when the color toner image passes through the nip between the drive pulley 21R and the secondary transfer roller 23. As a result, the color toner image is transferred from the intermediate transfer belt 21 to the sheet SH2 at the nip.

The fixing unit 30 heat-fixes the toner image on the sheet SH3 sent out from the image-creating unit 20. Specifically, the fixing portion 30 passes the sheet SH3 through the nip between the fixing roller 31 and the pressure roller 32 while rotating them. At this time, the fixing roller 31 applies the heat of the built-in heater to the surface of the sheet SH3, and the pressurizing roller 32 applies pressure to the heated portion of the sheet SH3 and presses it against the fixing roller 31. The toner image is fixed to the surface of the sheet SH3 by the heat from the fixing roller 31 and the pressure from the pressure roller 32. The fixing portion 30 further sends the sheet SH3 to the paper ejection portion 40 by the rotation of the fixing roller 31 and the pressure roller 32.

The paper ejection unit 40 ejects the sheet SH3 on which the toner image is fixed from the paper ejection port 42 to the paper ejection tray 41. Specifically, the paper ejection unit 40 uses the paper ejection roller 43 arranged inside the paper ejection port 42 to move the sheet SH3 that has moved from the upper part of the fixing portion 30 to the paper ejection port 42 to the paper ejection port 42. It is sent out of the paper and placed on the output tray 41.
[Structure of sheet transfer device]
The sheet transfer device mounted on the printer 100 corresponds to the entire mechanism for driving the transfer rollers 12P, 12F, 12G, 13 and 14 provided in the feeding unit 10 and its control system. This sheet transfer device is roughly classified into a delivery unit 12P, 12F, 12G, a gate 60, a pull-in unit 13, and a timing roller 14.

-Sending part-
The delivery unit is a drive mechanism of the pickup roller 12P and a pair of paper feed rollers 12F and 12G, and the entire control system thereof. In particular, when a plurality of sheets are continuously fed from the paper cassette 11 to the transport path, the delivery unit sets the timing at which each sheet is fed so that the tip of the next sheet overlaps with the rear end of the sheet that started feeding immediately before. do. By double-feeding two consecutive sheets in this way, the delivery unit feeds the plurality of sheets from the nip between the paper feed rollers 12F and 12G without leaving a gap between the sheets. Further, when the first sheet and the second sheet are continuously fed, the delivery unit further applies a first transport force applied to the tip of the first sheet while feeding the preceding portion of the first sheet in which the second sheets do not overlap. It is set stronger than the second transport force applied to the tip of the second sheet while the succeeding portion of the first sheet on which the second sheets overlap is sent out together with the second sheet. Details of the setting of the delivery timing and the transport force will be described later.

-Gate-
The gate 60 is a movable member having an ability to return to the original position, and the tip of the sheet SH1 sent out from the nip between the paper feed rollers 12F and 12G is placed on the transport paths extending from each of the paper feed cassettes 11. It is arranged so that it hits. Due to the structure described later, the gate 60 retreats from the transport path when pushed in the transport direction with a force of a certain strength, and returns to the transport path when the force weakens. Therefore, when abutted by the tip of the sheet SH1, the gate 60 temporarily blocks the advance of the tip, and when pushed away from the path by the tip, allows the tip to advance. With such a function, the gate 60 plays a role of assisting the elimination of double feeding by the pull-in portion and the adjustment between papers in addition to the skew correction by the gate resist method. Details of these roles will be described later.

FIG. 2A is a perspective view showing the appearance of the gate 60, and FIG. 2B is a cross-sectional view of the gate 60 along the straight line bb shown in FIG. 2A. As these figures show, the gate 60 includes a paper guide 610, a frame 620, a fixed shaft 630, a swing member 640, a mounting plate 650, and a torsion spring 660.
The paper passing guide 610 is a flat plate member made of metal or hard resin, and partitions the moving space of the sheet SH1 extending from the paper feed rollers 12F and 12G along the transport path from the outside. The plate surface 611 of the paper passing guide 610 extends along the transfer path, and by sliding the sheet SH1 on the plate surface 611, the sheet SH1 is guided to the transfer path.

The frame 620 is an elongated rod-shaped or plate-shaped member, for example, a groove-shaped (cross-section is "U" -shaped) or chevron-shaped (cross-section is "L" -shaped) steel plate, or a hard resin molded product. As shown in FIG. 1B, the frame 620 is arranged outside the paper passing guide 610 with respect to the moving space of the sheet SH1, and the longitudinal direction is the width direction of the sheet SH1 (perpendicular to the transport direction). It is fixed to the chassis of the printer 100 (not shown) in a posture that coincides with the direction of the side of the sheet SH1. One rectangular plate 621 and 622 extend perpendicularly to the longitudinal direction of the frame 620 at each end of the frame 620 in the longitudinal direction, and downstream of the paper passing guide 610 between the rectangular plates 621 and 622. The end 612 is fitted.

The fixed shaft 630 is, for example, an elongated cylindrical or cylindrical member, and both ends in the longitudinal direction are fixed to rectangular plates 621 and 622 of the frame 620 in a posture in which the longitudinal direction coincides with the width direction of the sheet SH1.
The four swinging members 640 are resin molded products of the same shape and size, and are arranged symmetrically with respect to the center in the longitudinal direction on the outer peripheral surface of the fixed shaft 630. Each swing member 640 includes a hook portion 641, a claw portion 642, and a holding portion 643. The hook portion 641 is a “C” -shaped portion in which a part of the annulus is missing, and the outer peripheral surface of the fixed shaft 630 is held by the inner peripheral surface thereof. As a result, the swing member 640 can slide and rotate around the fixed shaft 630. The claw portion 642 is a claw-shaped portion protruding in the radial direction from one end in the circumferential direction of the hook portion 641. It swings with the position retracted from the space. The holding portion 643 is a hook-shaped portion protruding in the radial direction from the outer peripheral surface of the hook portion 641 located on the side opposite to the claw portion 642 with respect to the center of the hook portion 641.

The mounting plate 650 is an elongated rectangular metal plate or a hard resin plate, and is held in a posture parallel to the fixed shaft 630 by the holding portion 643 of the swinging member 640. As a result, the mounting plate 650 keeps the angle around the fixed shaft 630 common among the four swinging members 640. That is, the mounting plate 650 constrains the four rocking members 640 so that they always rotate as one.

The torsion spring 660 is made of metal or hard resin, and one is arranged next to each swing member 640 coaxially with the fixed shaft 630. As shown in FIG. 2B, one end 661 of the torsion spring 660 is fixed to the frame 620, and the other end 662 is fixed to the mounting plate 650. Therefore, when the four swinging members 640 rotate around the fixed shaft 630 as a unit, the torsion spring 660 expands and contracts with the displacement of the mounting plate 650. At this time, the restoring force of the torsion spring 660 acts on the swing member 640 in the direction of returning the angle around the fixed shaft 630 to the initial value. At this initial angle, as shown by solid lines in FIGS. 2 (a) and 2 (b), the claw portion 642 of the rocking member 640 crosses the plate surface 611 of the paper passing guide 610 and enters the moving space of the sheet SH1. Protrude. On the other hand, when the swing member 640 rotates against the restoring force of the torsion spring 660 and the angle around the fixed shaft 630 is changed from the initial value, (a) and (b) in FIG. As shown, the claw portion 642 retracts to the outside of the plate surface 611 of the paper passing guide 610.

When the swing member 640 is located at the angle of the initial value, the claw portion 642 projects into the moving space of the seat SH1 and is therefore abutted by the tip of the seat SH1. At this time, if the force received by the claw portion 642 from the tip of the sheet SH1 is stronger than the restoring force of the torsion spring 660, the swing member 640 rotates and the claw portion 642 moves outward from the plate surface 611 of the paper passing guide 610. It is pushed away and allows the tip of the sheet SH1 to advance. On the other hand, if the force received by the claw portion 642 from the tip of the sheet SH1 is weaker than the restoring force of the torsion spring 660, the angle of the swing member 640 is maintained at the initial value, so that the claw portion 642 stays in the original position. It continues to block the progress of the tip of the sheet SH1.

-Retractor-
The pull-in portion is a drive mechanism of the pull-in roller 13 arranged between the paper feed rollers 12F and 12G and the timing roller 14 on the transport path, and the entire control system thereof. The pull-in portion uses the pull-in roller 13 to push away the claw portion 642 of the gate 60 and pull in the tip of the sheet SH1 that has reached it. In particular, the pull-in portion sets the sheet transfer speed by the pull-in roller 13 to be higher than the value by the paper feed rollers 12F and 12G of the delivery unit. Due to this difference in transfer speed, the rear end of the preceding sheet overtakes the tip of the next sheet before reaching the lead-in roller 13 after releasing the nip between the paper feed rollers 12F and 12G, and further, the lead-in roller 13 By the time you reach, you will be separated from the tip of the next sheet by the target paper. The target paper spacing is designed so that the tip of the next sheet does not collide with the rear edge of the sheet while the timing roller 14 temporarily stops the preceding sheet, as described below.

-Timing roller-
The timing roller 14 allows the sheet to pass through the nip between the drive pulley 21R of the intermediate transfer belt 21 and the secondary transfer roller 23 at an appropriate timing. Specifically, the timing roller 14 first stops each time the sheet SH1 arrives from the paper cassette 11, and temporarily stops the tip of the sheet SH1 at its own nip. After that, the timing roller 14 starts rotating in response to a command from the main control unit of the printer 100, and sends the stopped sheet SH2 to the image forming unit 20. The main control unit is an electronic circuit (not shown) incorporated in the printer 100, and causes various commands to elements 10-40 of the printer 100 by causing a microprocessor such as a CPU / MPU to execute firmware. Send. In particular, the main control unit determines the timing of the start of rotation of the timing roller 14, and the toner image formed on the surface of the intermediate transfer belt 21 by the photoconductor unit 20Y-20K is a nip between the drive pulley 21R and the secondary transfer roller 23. Determined based on the timing of passing through. As a result, the sheet SH2 sent out from the timing roller 14 passes through the nip between the intermediate transfer belt 21R and the secondary transfer roller 23 at the same time as the toner image. As a result, the toner image is correctly transferred to the sheet SH2.

[Skew correction using a gate]
The gate 60 performs skew correction by a gate resist method on the sheet SH1 sent out from the nip between the paper feed rollers 12F and 12G as described below. In this method, unlike the roller resist method, it is not necessary to stop the sheet to form a loop. Therefore, skew correction can be performed on a sheet that is continuously fed from the nip between the paper feed rollers 12F and 12G and that is conveyed without a gap between the sheets.

FIG. 3A is a schematic view of the fixed shaft 630 of the gate 60 and the swinging member 640 as viewed from the normal direction of the plate surface 611 of the paper passing guide 610, and in particular, between the paper feed rollers 12F and 12G. It represents a state in which the tip LDE of the sheet SH1 sent out from the nip has reached the position of the swing member 640. When the sheet SH1 is skewed, its tip LDE abuts on any of the swinging members 640, for example, one outer claw portion 642, before the other three claw portions. _{Due to the reaction force F RE} received from the claw portion 642 by the tip LDE of the sheet SH1, the sheet SH1 has a moment TRE centered on the normal line penetrating the tip LDE (the normal line on the paper surface in FIG. 3A). Occurs. As a result, the sheet SH1 rotates around the normal line penetrating the tip LDE according _{to the reaction force F RE} from the claw portion 642 before pushing away the claw portion 642 with which the tip LDE abuts.

FIG. 3B is a schematic view of the fixed shaft 630 of the gate 60 and the swinging member 640 as viewed from the normal direction of the plate surface 611 of the paper passing guide 610, and in particular, all four swinging members 640. It represents a state in which the sheet SH1 is rotated to a position where the tip LDE abuts on the claw portion 642 of the paper (a position parallel to the left-right direction in the figure). Since the four swinging members 640 are arranged in a direction (horizontal direction in the figure) perpendicular to the transport direction (vertical direction in the figure), the skew is removed from the seat SH1 in the posture shown in the figure. In this state, if the force applied to the claw portion 642 by the tip LDE exceeds the restoring force of the torsion spring 660, the seat SH1 can proceed by pushing away the claw portion 642 in the correct posture in which the skew is removed.

[Elimination of double feed using a gate and adjustment between papers]
The delivery unit superimposes the tip of the next sheet on the rear end of each sheet and sends it out from the nip between the paper feed rollers 12F and 12G. The pull-in unit pulls in the sheets at a speed higher than the speed at which the delivery unit feeds out the sheets, thereby eliminating the double feed between the sheets and further adjusting the space between the sheets to the target value. By temporarily stopping each sheet that abuts against the gate 60, as described below, the gate 60 assists in eliminating double feeding by the pull-in portion and adjusting between papers.

4 and 5 are schematic views showing how two sheets PSH and NSH are continuously sent out from the paper cassette 11 in chronological order. Specifically, FIG. 4A shows the time point when the tip LDE of the first sheet PSH hits the gate 60, and FIG. 4B shows the time point when the tip LDE passes through the nip of the retracting roller 13. FIG. 5A shows the time when the rear end RRE of the first sheet PSH leaves the nip between the paper feed rollers 12F and 12G, and FIG. 5B shows the time when the rear end RRE reaches the nip of the pull-in roller 13. Indicates the time point.

− The tip of the preceding sheet hits the gate: (a) in FIG.
The pickup roller 12P is arranged above the bundle SHT of the sheets housed in the paper feed cassette 11, and is perpendicular to the paper feed direction (right direction in the figure) in the horizontal plane (normal direction of the paper surface in the figure). It's growing. Both ends of the pickup roller 12P in the longitudinal direction are supported by the chassis of the printer 100 (not shown) so as to be rotatable around the central axis and to be raised and lowered in the vertical direction. The delivery unit rotates the pickup roller 12P around the central axis by a motor (not shown), and lowers the pickup roller 12P toward the bundle SHT of the seats. As a result, the pickup roller 12P rotates while pressing the upper surface of the seat bundle SHT downward. Thus, since the first sheet PSH located on the upper surface of the bundle SHT receives a conveying force F _P from the pickup roller 12P, slides relative to the second sheet NSH just below the tip LDE paper feed roller 12F, between 12G Rush into the nip of.

Both the paper feed rollers 12F and 12G are arranged at the start end of the transport path, extend in the horizontal plane in the direction perpendicular to the paper feed direction, and form nips by bringing their outer peripheral surfaces into contact with each other. Both ends of the paper feed rollers 12F and 12G in the longitudinal direction are rotatably supported around the central axis by the chassis of the printer 100 (not shown). The paper feed rollers 12F and 12G are both drive rollers, and the delivery unit applies a rotational force to each of them from a motor (not shown), and around their central axes in opposite directions at the same speed. Rotate.

When the tip LDE of the first sheet PSH delivered by the pickup roller 12P rushes into the nip between the paper feed rollers 12F and 12G, the upper surface of the tip LDE comes into contact with the first paper feed roller 12F located above the paper feed roller 12F, and then. receiving a conveying force F _F, the lower surface is subjected to the conveying force F _G therefrom in contact with the second paper feed roller 12G is positioned on the lower side. Thus the first sheet PSH tip LDE paper feed roller 12F, since you entered the nip between 12G, for the first sheet PSH added to the conveying force F _P of the pick-up roller 12P, feed roller 12F, 12G both conveying force _F F in, F _G acts. The sum of these transport forces F _P + F _F + F _G is the first transport force F _C1 described above. The first conveying force F _C1, tip LDE first sheet PSH is fed feed roller 12F, from the nip between 12G to the transport path. At this time, the elevation angle θ in the delivery direction, that is, the inclination angle of the common tangent plane TPL at the nip of the paper feed rollers 12F and 12G with respect to the horizontal plane is smaller than the elevation angle φ of the plate surface 611 of the paper passing guide 610 (θ <φ). , The tip LDE of the first sheet PSH is pushed up to the gate 60 along the plate surface 611 of the paper passing guide 610.

After that, the tip LDE of the first sheet PSH abuts on the claw portion 642 of the gate 60 before the rear end RRE of the first sheet PSH reaches the position of the pickup roller 12P. At this time, the force received by the claw portion 642 from the tip LDE is equal to _{the first transport force F C1.} Since the sending unit sets the first transport force F _C1 to a value stronger than _{the restoring force F RC} of the torsion spring 660 of the gate 60 _{(F C1} > F _RC ), the swing member 640 is driven by the first transport force F _C1. Rotates to retract the claw portion 642 from the moving space of the sheet SH1. In this way, the tip LDE of the first sheet PSH pushes away the claw portion 642, and is further pushed up to the pull-in roller 13 along the downstream guide 710 adjacent to the downstream side of the gate 60.

− Reaching the pull-in roller by the tip of the preceding sheet: (b) in FIG.
The tip LDE of the first sheet PSH pushes away the claw portion 642 of the gate 60 and then reaches the nip of the retracting roller 13. The lead-in rollers 13 are a pair of transport rollers, are arranged downstream of the gate 60 on the transport path, extend in the horizontal plane in the direction perpendicular to the paper feed direction, and form nips by contacting the outer peripheral surfaces with each other. doing. Both ends of the pull-in roller 13 in the longitudinal direction are rotatably supported around the central axis by the chassis of the printer 100 (not shown). The delivery unit applies a rotational force to one of the pull-in rollers 13 from a motor (not shown) to rotate it around its central axis. At this time, due to the frictional force at the nip, the other end of the pull-in roller 13 is driven to rotate in the opposite direction.

The transport path from the paper feed rollers 12F and 12G to the lead-in roller 13 includes a curved portion. Especially in the curved section, the passing guide 610, the gate 60, and to the locus L _TR drawn by the tip LDE of the first sheet PSH along the downstream guide 710, a nip and the paper feed roller 12F of the drawing roller 13, between 12G The virtual line segment D _LN that connects the nip linearly is located inside. This virtual line segment D _LN is shorter than the _{locus L TR} drawn by the tip LDE of the first sheet PSH _{: D LN} <L _TR . Elevation [psi virtual line D _LN includes a sheet feeding roller 12F, greater than the elevation angle phi plate surface 611 of the sheet passing guide 610 not only elevation theta common tangent plane TPL at the nip of 12G: ψ>φ> θ.

When the tip LDE of the first sheet PSH rushes into the nip of the pull-in roller 13, the intermediate portion INT suspended from the nip of the pull-in roller 13 to the nip between the paper feed rollers 12F and 12G in the first sheet PSH is rearranged. In addition to the end being pushed out from the paper feed rollers 12F and 12G, the tip is pulled into the pull-in roller 13. _{Since the sheet transfer speed V P} by the pull-in roller 13 is higher than the _{value V F} by the paper feed rollers 12 F and 12 G _(VP > V _F ), the length of the intermediate portion INT is the difference V between these transfer speeds per unit time. to reduce by _P -V _F. As a result, the locus L _{IN drawn by the intermediate portion INT is displaced inward from the locus L TR} drawn by the tip LDE to the inside of the curve of the transport path, and the amount of deflection of the intermediate portion INT, that is, the amount of displacement ε from the _{virtual straight line DLN is reduced.} The intermediate portion INT will soon be separated from the claw portion 642 of the gate 60. Thus since below restoring force F _RC of the torsion spring 660 from the first sheet PSH weakened force received by the claw portion 642, the swing member 640 is rotated to the initial angle, the claw portion 642 is returned to the extended position from the retracted position ..

After that, when the pickup roller 12P finishes feeding out the rear end RRE of the first sheet PSH, the pickup roller 12P continues to rotate while pressing the second sheet NSH directly under the first sheet PSH in place of the first sheet PSH. Thus, since the second sheet NSH receives a conveying force F _P from the pickup roller 12P, starts to slide relative to the sheet immediately below. At this time, since the tip LDE of the second sheet NSH is already located in front of the rear end RRE of the first sheet PSH, the tip LDE of the second sheet NSH rushes into the nip between the paper feed rollers 12F and 12G at the rear end RRE. Therefore, the first sheet PSH and the second sheet NSH are delivered from the nip in an overlapping state. In this case, the upper surface of the tip LDE of the second sheet NSH is blocked from direct contact with the first paper feed roller 12F by the first sheet PSH. The coefficient of friction between the sheets is a sheet and the sheet feeding roller 12F, since negligibly low compared to the coefficient of friction between the 12G, the conveying force of the first paper feed roller 12F F _F is substantially all the first sheet PSH Deprived and does not act on the second sheet NSH. That is, in addition to the conveying force F _P of substantially the pickup roller 12P for the second sheet NSH, only act conveying force F _G of the second feed roller 12G. The sum F _P + F _G of these conveying force is a second conveying force F _C2 described above. That is, the second transport force F _C2 is weaker than the first transport force F _{C1 by the transport force F F of} the first paper feed roller 12F: F _C2 = F _C1- F _F <F _C1 .

On the downstream side of the nip between the paper feed rollers 12F and 12G, the tip LDE of the second sheet NSH is a free end, unlike the intermediate part INT of the first sheet PSH whose tip is pulled by the pull-in roller 13. , Proceed along the plate surface 611 of the paper passing guide 610. Therefore, the intermediate portion INT of the first sheet PSH passes above the claw portion 642 of the gate 60 that has returned to the original protruding position, while the tip LED of the second sheet NSH abuts. If this abutment is before reaching the nip between the paper feed rollers 12F and 12G by the rear end RRE of the first sheet PSH, the force received by the claw portion 642 from the tip LDE of the second sheet NSH is the second transport. Equal to force F _C2. Since the sending unit sets the second transport force F _C2 to a value weaker than _{the restoring force F RC} of the torsion spring 660 of the gate 60 _{(F C2} <F _RC ), the swing member depends on the second transport force F _C2. The 640 does not rotate and the claw portion 642 remains in its original protruding position. In this way, the tip LDE of the second sheet NSH is prevented from advancing by the claw portion 642.

-Detachment from the paper feed roller by the rear end of the preceding sheet: (a) in FIG.
When the rear end RRE of the first sheet PSH passes through the nip between the paper feed rollers 12F and 12G and separates from the nip, the double feed between the first sheet PSH and the second sheet NSH is canceled on the upstream side from the nip. .. Accordingly, the upper surface of the remaining portion of the second sheet NSH receives a conveying force F _F therefrom in direct contact with the first feed roller 12F. Thus the second for the sheet NSH pickup roller 12P and the paper feed roller 12F, the sum of the conveying force between both 12G, namely a first conveying force _{F C1 = F P + F F} + F G acts. Along with this, the force received by the claw portion 642 from the tip LDE of the second sheet NSH _{increases from the second transport force F C2} to the first transport force F _C1 , so that the swing member 640 rotates and the claw portion 642 is seated. Evacuate from the moving space of SH1. In this way, the tip LDE of the second sheet NSH pushes away the claw portion 642 and moves forward.

In this way, the gate 60 prevents the front end LDE of the second sheet NSH, which has been brought along with the rear end RRE of the first sheet PSH, from advancing, and the rear end RRE of the first sheet PSH is the paper feed rollers 12F, 12G. The tip LDE of the second sheet NSH is stopped until the nip between them is released. As a result, the overlapping length between the first sheet PSH and the second sheet NSH at the time when the rear end RRE of the first sheet PSH leaves the nip between the paper feed rollers 12F and 12G is the tip of each sheet PSH and NSH. _{Of the locus L TR} drawn by the LDE, the partial length from the nip between the paper feed rollers 12F and 12G to the claw portion 642 of the gate 60 is guaranteed to be _{L OV or less.}

− Reaching the pull-in roller by the trailing edge of the preceding sheet: (b) in FIG.
_{The sheet transfer speed V P} by the pull-in roller 13 is higher than the _{value V F} by the paper feed rollers 12 F and 12 G _{: V P} > V _F. Thus, the rear end RRE paper feed roller 12F of the first sheet PSH, are accelerated leaves the nip between 12G, the conveying speed difference V _P -V _F, second sheet NSH before reaching the retracted roller 13 overtaken tip LDE of, in addition, the time when it reaches the retracted roller 13 are separated by the inter-sheet G _TG target from the tip LDE second sheet NSH.

As described above, the upper limit of the overlap length between the first sheet PSH and the second sheet NSH at the time when the rear end RRE of the first sheet PSH leaves the nip between the paper feed rollers 12F and 12G by the gate 60 is set. The length of the locus drawn by the tip LDE of the first sheet PSH from the nip between the paper feed rollers 12F and 12G to the claw portion 642 of the gate 60 is equal _{to L OV. Therefore, in order to match the paper spacing between the first sheet PSH and the second sheet NSH with the target value G TG} by the time the rear end RRE of the first sheet PSH reaches the lead-in roller 13, the paper feed rollers 12F and 12G are used. The transfer speed V _{F and the transfer speed V P} of the pull-in roller 13 may satisfy the following equation (1):

ここで、給紙ローラー１２Ｆ、１２Ｇ間のニップから引込ローラー１３のニップまでの範囲において第１シートＰＳＨの先端ＬＤＥが描く軌跡Ｌ_TRと後端ＲＲＥが描く軌跡Ｌ_INとの間での長さの違いは無視されている。

Here, the length between the _{locus L TR drawn by the front end LDE of the first sheet PSH and the locus L IN} drawn by the rear end RRE in the range from the nip between the paper feed rollers 12F and 12G to the nip of the lead-in roller 13. The difference is ignored.

[Advantages of Embodiment]
In the sheet transfer device according to the above-described embodiment of the present invention, each time the pickup roller 12P finishes feeding the rear end of each sheet, the next sheet is immediately started to be fed. As a result, the tip of the next sheet is superposed on the rear edge of each sheet and sent out. When the first sheet PSH and the second sheet NSH are continuously fed, as shown in FIG. 4 (a), while the preceding portion of the first sheet PSH in which the second sheet NSH does not overlap is fed, the first sheet PSH and the second sheet NSH are continuously fed. Both the paper feed rollers 12F and 12G come into direct contact with the leading portion together with the pickup roller 12P. On the other hand, when the preceding portion of the second sheet NSH overlaps with the succeeding portion of the first sheet PSH and begins to be sent out, as shown in FIG. 4B, the following portion makes contact with the first paper feed roller 12F. In addition to the pickup roller 12P, only the second paper feed roller 12G comes into direct contact with the second sheet NSH. Therefore, the first transport force F _C1 given to the preceding portion of the first sheet PSH is stronger than _{the second transport force F C2} given to the second sheet NSH overlapping the succeeding portion of the first sheet PSH. When the rear end RRE of the first sheet PSH is separated from the nip between the paper feed rollers 12F and 12G, the first paper feed roller 12F also comes into direct contact with the second sheet NSH as shown by FIG. 5 (a). Therefore, the transport force given to the second sheet NSH increases _{from the second transport force F C2} to the first transport force F _C1. The first transport force F _{C1 is stronger than the restoring force F RC} of the torsion spring 660 of the gate 60, and the second transport force F _C2 is weak: F _C1 > F _RC > F _C2 . Therefore, when the leading portion of the first sheet PSH hits the claw portion 642 of the gate 60, it pushes it away and advances, and the second sheet NSH overlaps with the succeeding portion of the first sheet PSH and is sent out, that is, the first sheet PSH. Until the rear end RRE of the 1-sheet PSH releases the nip between the paper feed rollers 12F and 12G, the progress is blocked by the claw portion 642 of the gate 60. As a result, the overlap length between the first sheet PSH and the second sheet NSH at the time when the rear end RRE of the first sheet PSH leaves the nip between the paper feed rollers 12F and 12G is the tip of each sheet PSH and NSH. _{Of the locus L TR} drawn by the LDE, the partial length from the nip between the paper feed rollers 12F and 12G to the claw portion 642 of the gate 60 is guaranteed to be _{L OV or less.}

_{As described above, the sheet transfer device according to this embodiment guarantees the upper limit L OV} of the overlap length between the sheets at the time when the rear end RRE of the first sheet PSH leaves the nip between the paper feed rollers 12F and 12G, and the gate. The tip LDE of the second sheet NSH is positioned with high accuracy by the claw portion 642 of 60. Therefore, in order to satisfy the above inequality (1), the delivery unit _{keeps the sheet transfer speed V F} by the paper feed rollers 12F and 12G constant, and the lead-in unit keeps the sheet transfer speed V _{P by the lead-in roller 13.} The space between the papers of the first sheet PSH and the second sheet NSH is adjusted to the _{target value G T G with high accuracy only by keeping the speed constant.} In particular, the delivery unit does not need to stop any of the paper feed rollers 12F and 12G. In this way, this sheet transfer device can transfer at high speed without leaving a space between papers and secure a target space between papers with high accuracy in front of the transfer destination by a small and easy-to-control mechanism. can.

Further, the gate 60 performs skew correction by a gate resist method on each sheet SH1 sent out from the nip between the paper feed rollers 12F and 12G. In this method, unlike the roller resist method, it is not necessary to stop the sheet to form a loop. Therefore, skew correction can be reliably executed even for a sheet that is continuously conveyed from the nip between the paper feed rollers 12F and 12G without leaving a gap between the papers. Further, since it is not necessary to secure a space for forming a loop on each sheet on the transfer path, the sheet transfer device can be easily miniaturized.

[Modification example]
(A) The image forming apparatus 100 shown in FIG. 1 is an electrophotographic color printer. The sheet transfer device according to the embodiment of the present invention may also be mounted on a single-function machine such as an electrophotographic monochrome printer, a copier, a facsimile machine, or an inkjet printer, or a multifunction device (MDF). The sheet transfer device according to the embodiment of the present invention can be further mounted on any system such as a finisher and an ADF that targets a sheet.

(B) The swing member 640 of the gate 60 shown in FIG. 2 rotates around the fixed shaft 630 when the force received from the tip of the sheet with which all the claws 642 abuts exceeds the restoring force of the torsion spring 660. By swinging the claw portion 642, the tip of the sheet is allowed to advance. The movable member to be included in the gate is also arranged so as to be abutted against the seat in the moving space of the seat, and when it is abutted against the tip of the seat, it is pushed away by the tip to allow the tip to advance. Any mechanism like this will do. In particular, it is not necessary to abut a plurality of different members against the tip of the sheet. For example, a single plate-shaped member is arranged so as to lie over the entire width of the moving space of the sheet, the inclination of the sheet with respect to the transport direction is variable, and the sheet is pushed down by being abutted against the tip of the sheet. May be good.

(C) The pickup roller 12P shown in FIG. 4 can be raised and lowered in the vertical direction, and by lowering toward a bundle of sheets housed in the paper cassette 11, the upper surface thereof is pressed from above. In addition, the bottom surface of the paper cassette 11 may include a mechanism for pushing up a bundle of sheets placed on the paper feed cassette 11, and the upper surface of the bundle may be pressed against the pickup roller 12P from below by the push-up.

(D) As shown in FIG. 4, the claw portion 642 of the gate 60 is in the middle of the first sheet PSH suspended from the nip of the lead-in roller 13 to the nip between the paper feed rollers 12F and 12G at the curved portion of the transport path. It is located outside the _{locus L IN} drawn by the partial INT. In addition, the transport path from the paper feed roller to the lead-in roller is straight, and a gate may be arranged in the middle. In this case, the claws of the gate can be returned to the original protruding position because the force received while the seat gets over the top is weaker than the restoring force of the torsion spring after being pushed away by the seat that hits it. It suffices if it is designed.

_{In equation (E) (1), the locus L TR drawn by the front end LDE of the first sheet PSH and the locus L IN} drawn by the rear end RRE in the range from the nip between the paper feed rollers 12F and 12G to the nip of the lead-in roller 13. The difference in length between and is ignored. In addition, the difference in length between the two loci, L _TR- L _IN, may be considered. In this case, the right side of the equation (1), i.e., the upper limit of the conveying speed ratio V _F / V _P is increased. Therefore, even if the transport path from the paper feed rollers 12F and 12G to the lead-in roller 13 is relatively short or the target paper spacing is relatively long, the transport speed ratio V _F / V _P should be sufficiently close to “1”. Is possible in principle.

The present invention relates to a sheet transfer technique, in which a gate 60 is provided on a transfer path between the paper feed rollers 12F and 12G and the lead-in roller 13 so that the tip LDEs of the sheets PSH and NSH abut against the claw portion 642 thereof. .. As such, the present invention is clearly industrially applicable.

100 MFP
11 Paper cassette 12P Pickup roller 12F 1st paper feed roller 12G 2nd paper feed roller 13 Pull-in roller 14 Timing roller 60 Gate 610 Paper guide 611 Paper guide plate surface 612 Downstream end of paper guide 620 Frame 630 Fixed shaft 640 Swing member 641 Hook part 642 Claw part 643 Holding part 650 Mounting plate 660 Twist spring 710 Downstream guide PSH 1st sheet NSH 2nd sheet LDE Seat tip RRE Seat rear end INT Seat intermediate

Claims (7)

A sheet transport device that continuously transports a plurality of sheets along a predetermined path.
A delivery unit that continuously sends out the plurality of sheets to the path and sets the timing of sending out each sheet so that the tip of the next sheet overlaps with the rear end of the sheet that started to be sent immediately before.
It is a movable member installed on the path so that the tip of the sheet sent out by the delivery unit abuts, and once blocks the progress of the tip of the abutted sheet, and when it is pushed away from the path by the tip, the tip The gate that allows the progress of
A pull-in unit that pulls in the sheet reached by pushing away the gate at a speed higher than the speed at which the delivery unit sends out the sheet.
With
When the first sheet and the second sheet are continuously fed, the delivery unit gives a first transport to the tip of the first sheet while feeding the preceding portion of the first sheet in which the second sheet does not overlap. The force is set stronger than the second transport force applied to the tip of the second sheet while the succeeding portion of the first sheet on which the second sheet overlaps is sent out together with the second sheet.
When the force received from the tip of the abutting sheet is the first transport force, the gate is pushed away from the path to allow the tip to advance, and when the force is the second transport force, the gate is pushed to the path. A sheet transfer device characterized by staying and hindering the progress of the tip. The sheet transport device according to claim 1, wherein the tip of the second sheet abuts on the gate before the rear end of the first sheet separates from the delivery portion. The route is
A second locus drawn by the middle portion of the sheet whose rear end is sent out by the sending part and whose tip is pulled in by the pulling part with respect to the first locus drawn by the tip of the sheet which is only sent out by the sending part. Including curved parts where the locus is located inside
Claim 1 or claim 2 is characterized in that the gate is located outside the second locus in the curved portion and is installed so that the tip of a sheet traveling on the first locus abuts. The sheet transport device according to. The sending unit
A pickup roller that comes into contact with the upper surface of a bundle of sheets to be fed, feeds out the sheet located on the upper surface, and starts feeding out the next sheet before the rear end of the sheet separates from the tip of the next sheet.
A first paper feed roller that comes into contact with the upper surface of the sheet fed by the pickup roller and feeds the sheet to the path.
While the sheet is in contact with the lower surface of the sheet fed by the pickup roller, the sheet is fed to the path, and after the time when the sheet is brought into contact with the lower surface of the next sheet being fed with the tip overlapping the rear end of the sheet. With the second paper feed roller that sends the next sheet to the path while keeping the overlapped state,
Including
The first transport force is equal to the sum of the transport forces between the pickup roller, the first paper feed roller, and the second paper feed roller.
The sheet transport device according to any one of claims 1 to 3, wherein the second transport force is equal to a value obtained by subtracting the transport force of the first paper feed roller from the total. The pull-in portion includes a pull-in roller that conveys the tip of the sheet reached by pushing away the gate at a speed higher than that of the delivery portion.
Due to the difference in transport speed with respect to the delivery unit, the pull-in roller overtakes the tip of the second sheet at the rear end of the first sheet separated from the delivery part before the tip reaches the pull-in roller. The sheet transporting device according to any one of claims 1 to 4, wherein the sheet transporting device is characterized. The gate is characterized in that while hindering the advancement of the tip of the abutted sheet, a moment about the normal line of the sheet penetrating the tip is generated at the tip to correct the skew of the sheet. The sheet transport device according to any one of items 1 to 5. The sheet transport device according to any one of claims 1 to 6, and the sheet transport device for transporting the sheet.
An image forming unit that forms an image on a sheet conveyed by the sheet conveying device, and an image forming unit.
An image forming apparatus equipped with.

Images