JP2008239334A - Sheet loading device and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain floating of a sheet and improve a loading property by loading the sheet by reducing curls. <P>SOLUTION: This sheet loading device 31 is furnished with; a tray 13 on which the sheet discharged from a sheet discharging roller pair 16 is loaded and; a pressurizing member 17 to pressurize the sheet on the tray 13. The tray 13 is furnished with a sheet loading surface 13a to curve by directing an intermediate part upward against the sheet discharging direction. The pressurizing member 17 is devised to pressurize a part on the downstream side in the sheet discharging direction of a contact part 13s of a tangent lie L making contact with the sheet loading surface 13a through the sheet discharging roller pair 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet stacking apparatus that stacks sheets by removing the curl of a sheet that is curled in a U-shaped or reverse U-shaped cross section in a direction intersecting the sheet discharge direction, and the sheet stacking apparatus. The present invention relates to an image forming apparatus provided in a main body.

  An image forming apparatus for forming an image on a sheet includes a sheet stacking apparatus having a tray for stacking the image-formed sheets. Examples of the image forming apparatus include a copying machine, a printer, a facsimile, and a complex machine of these. The sheets stacked on the tray are heated (curled) by the fixing device in the apparatus main body of the image forming apparatus to fix the toner image, and may be curved (curled) by heat.

  When the sheets stacked on the tray are curled, the preceding sheet stacked first on the tray is pushed by the subsequent sheet to be discharged next, and the alignment is lost, or the sheet is dropped from the tray. There are things to do. In addition, the succeeding sheet may sink under the preceding sheet and the page order of image formation may be out of order. As described above, in the conventional sheet stacking apparatus, the succeeding sheet may not be stacked on the preceding sheet. Even when loaded, the alignment accuracy was low.

  For this reason, the curled sheets must be flattened and stacked, and such inventions are disclosed in Patent Documents 1 and 2.

  The amount of curl is the sheet type and basis weight (weight per unit load), the direction of the sheet gap, the temperature and humidity when the sheet was stored, the amount of toner that forms an image on the sheet, and the toner image. It depends on the temperature when fixing on the sheet.

  The curl includes a curl in which the front end or the rear end of the sheet in the sheet discharge direction is curved upward, and a cross section in the direction intersecting the sheet discharge direction (cross section in the width direction) is U-shaped or inverted U-shaped. There are curved curls, but it is particularly difficult to flatten the latter curls.

Japanese Patent Laid-Open No. 9-40264 Japanese Patent Laid-Open No. 6-221408

  However, as shown in FIG. 12, the sheet stacking apparatus described in Patent Document 1 presses the sheet P discharged by the sheet discharge roller pair 203 onto a flat tray 202 by a pressing member 201 that can move up and down. Yes. However, the portion Pa where the pressing member 201 is not pressed has a problem of floating, and the subsequent sheet may not be stacked on the preceding sheet depending on the curl amount of the sheet and the number of stacked sheets. Even when loaded, the alignment accuracy was low.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet stacking apparatus in which stacking is improved by suppressing sheet lifting by reducing curling and stacking.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that includes a sheet stacking apparatus with improved sheet stackability and is easy to handle.

  The sheet stacking apparatus of the present invention includes sheet stacking means for stacking the sheets discharged from the sheet discharge section, and pressing means for pressing the sheet against the sheet stacking means. A sheet stacking surface that curves in an upward direction with respect to the discharge direction, and the pressing means is downstream in the sheet discharge direction from a tangential contact portion that passes through the sheet discharge portion and contacts the sheet stacking surface. It is characterized by pressing the part.

  The sheet stacking apparatus of the present invention includes a sheet stacking unit on which discharged sheets are stacked, and a pressing unit that presses the sheet against the sheet stacking unit, and the sheet stacking unit is arranged in the sheet discharge direction. The sheet stacking surface is curved with the middle portion facing upward, and the pressing means presses the downstream portion of the sheet stacking direction from the uppermost position of the sheet stacking surface.

  An image forming apparatus according to the present invention includes: an image forming unit that forms an image on a sheet; and a sheet stacking device on which a sheet on which an image is formed by the image forming unit is stacked. The sheet stacking apparatus is described.

  The sheet stacking apparatus of the present invention stacks sheets on a sheet stacking surface curved upward. For this reason, in the case of a sheet with the leading edge and the trailing edge curled upward, the sheet deforms following the curvature of the sheet stacking surface due to its own weight. It is easy to be solved. Therefore, the sheet stacking apparatus of the present invention can easily remove the curl at the leading end portion and the trailing end portion of the sheet, and can improve the stackability of the sheet.

  In the sheet stacking apparatus of the present invention, the downstream portion in the sheet discharge direction is pressed by the pressing means from the contact portion of the tangent line that passes through the sheet discharge portion and contacts the sheet stacking surface. For this reason, in the case of a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, the sheet is flattened on the downstream side of the contact portion by the pressing means. Along with this, the portion upstream from the contact portion also becomes flat. At this time, the sheet helps to remove the curl while the portion on the upstream side from the contact portion bends downward due to its own weight and becomes flat. Therefore, the sheet stacking apparatus of the present invention can easily flatten a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, and can improve the stackability of the sheet.

  In the sheet stacking apparatus of the present invention, the downstream portion in the sheet discharge direction is pressed from the uppermost position of the sheet stacking surface by the pressing means. For this reason, in the case of a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, the sheet is flattened on the downstream side from the uppermost position by the pressing means. Along with this, the portion upstream from the uppermost position also becomes flat. At this time, the portion of the sheet on the upstream side from the uppermost position is bent downward by its own weight, and helps to remove the curl while being flattened. Therefore, the sheet stacking apparatus of the present invention can easily flatten a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, and can improve the stackability of the sheet.

  Since the image forming apparatus of the present invention includes the sheet stacking apparatus that improves the stackability of sheets, handling of the sheet becomes easy.

  Hereinafter, a sheet stacking apparatus according to an embodiment of the present invention and an image forming apparatus including the sheet stacking apparatus in an apparatus main body will be described with reference to the drawings. Examples of the image forming apparatus include a copying machine, a printer, a facsimile, and a complex machine of these.

(Image forming device)
FIG. 1 is a cross-sectional view of the image forming apparatus according to the embodiment of the present invention along the sheet conveying direction. An image forming apparatus 1 shown in FIG. 1 is a four-color image forming apparatus.

  At the bottom of the apparatus main body 1A of the image forming apparatus 1, a cassette 2 for storing sheets P is detachably provided. The pickup roller 3 feeds the sheets P from the cassette 2 one by one to the registration roller 4. The registration roller 4 stops rotating, receives the leading edge of the sheet in the stopped state, corrects the skew of the sheet, and then rotates to rotate the sheet between the image forming unit 8 and the transfer conveyance belt 7. To send. The photosensitive drums 8Y, 9M, 10C, and 11Bk of the image forming units 8, 9, 10, and 11 serving as image forming units include laser light emitted from the laser scanner unit 30 based on image information transmitted from the outside, Each color toner image is formed by a developing device (not shown). The color of the toner image includes yellow (Y), magenta (M), cyan (C), and black (Bk).

  The transfer / conveying belt 7 is supported by the driving roller 5 and the driven roller 6 and circulates. While the sheet fed between the image forming unit 8 and the transfer conveyance belt 7 is conveyed by the rotation of the photosensitive drums 8Y, 9M, 10C, and 11Bk and the circulation of the transfer conveyance belt 7, four color toner images are formed. Sequentially transferred.

  The fixing device 12 fixes the toner image by heating the sheet on which the four color toner images are transferred. Subsequently, the discharge roller 14 of the discharge roller pair 16 (FIG. 2) and the opposing roller 15 discharge the sheet P to the tray 13 of the sheet stacking device 31 (or 32), and the pressing member 17 presses the sheet against the tray 13. To do.

(Sheet stacker)
FIG. 2 is a cross-sectional view along the sheet discharge direction of the sheet stacking apparatus according to the embodiment of the present invention.

  The sheet stacking device 31 includes a tray 13 as a sheet stacking unit on which sheets discharged from the discharge roller pair 16 serving as a sheet discharge unit are stacked, and a pressing member 17 as a pressing unit that presses the sheet P against the tray 13. It has. The tray 13 includes a sheet stacking surface 13a that is curved with its intermediate portion facing upward with respect to the sheet discharge direction (arrow A direction).

  The pressing member 17 is a member that is supported by the shaft 19 on the fixed member 21 and is tiltable in the contact / separation direction with respect to the sheet stacking surface 13a. The pressing member 17 presses the downstream portion in the sheet discharging direction from the contact portion 13s of the tangent line L that passes through the discharge roller pair 16 and contacts the sheet stacking surface 13a. Note that, depending on the height position of the discharge roller pair 16, the contact portion 13s may not be coincident with the uppermost position 13b of the sheet stacking surface 13a and may be on the downstream side or the upstream side from the uppermost position 13b. In FIG. 2, the contact portion 13s is located upstream of the uppermost position 13b.

  In the sheet stacking apparatus 31, the sheet P discharged by the discharge roller pair 16 is guided to the sheet stacking surface 13 a of the tray 13 and moved downstream in the sheet discharging direction. Then, the leading end portion Pa of the sheet P passes through the contact portion 13s and enters between the leading end portion 17a of the pressing member 17 and the sheet stacking surface 13a. When the rear end portion Pb is discharged from the discharge roller pair 16, the entire sheet is stacked on the sheet stacking surface 13a.

  As described above, the sheet stacking apparatus 31 stacks sheets on the sheet stacking surface 13a curved upward. For this reason, in the case of the sheet P in which the leading end portion Pa and the trailing end portion Pb are curled upward, the sheet is pressed by the pressing member 17 at the leading end portion Pa, and the entire sheet is curved by the own weight. Therefore, curling is eliminated. In the conventional tray 202 (FIG. 12), the sheet stacking surface 202a is flat, and curling is difficult to be eliminated.

  Therefore, the sheet stacking device 31 can easily remove the curl of the leading end portion Pa and the trailing end portion Pb of the sheet P, and can improve the stackability of the sheet.

  Further, in the sheet stacking device 31, the pressing member 17 presses the downstream portion in the sheet discharging direction from the contact portion 13s of the tangent L that passes through the discharge roller pair 16 and contacts the sheet stacking surface 13a. For this reason, in the case of a sheet (FIG. 3A) whose cross section in the width direction is curled in a U-shape, the sheet is flattened by pressing the side end portion Pc against the pressing member 17. At this time, the portion of the sheet on the upstream side from the contact portion 13s bends downward by its own weight, and helps to remove the curl while being flattened. Further, as shown in FIG. 3B, even when the sheet is curled in an inverted U shape, the pressing member 17 similarly presses the intermediate portion Pd in the width direction (arrow B direction) of the sheet. To flatten the sheet.

  Therefore, the sheet stacking device 31 can easily flatten a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, and improve the stackability of the sheet.

  Further, since the sheet stacking device 31 can press the downstream portion of the sheet contact portion 13s with the pressing member 17 below the tangent L, the subsequent sheet can be easily stacked.

  The pressing member 17 presses the sheet against the sheet stacking surface 13a by its own weight, but if it is too heavy, the sheet may not enter between the pressing member 17 and the sheet stacking surface 13a. Further, there is a case where the succeeding sheet cannot enter between the pressing member 17 and the preceding sheet on the sheet stacking surface 13a. Furthermore, when the sheet is a thin sheet such as thin paper, it is difficult to enter under the pressing member 17, which causes a jam.

  Therefore, the pressing member 17 is lifted by a tension spring 20 provided between a portion upstream of the shaft 19 of the pressing member 17 shown in FIG. 2 and the fixing member 21 so that the pressing force for pressing the sheet can be adjusted. Also good. Further, it is lifted to the pressing member 17 by a compression spring 23 interposed between a portion downstream of the shaft 19 of the pressing member shown in FIG. 4 and the fixing member 21 and a torsion coil spring 24 provided on the shaft 19 shown in FIG. A force may be applied to adjust the sheet pressing force of the pressing member.

  Further, when the pressing member 17 is too light to remove the curl of the sheet, as shown in FIG. 7, a tension spring 20 is provided on the downstream side of the shaft 19 so that the sheet pressing force by the pressing member 17 is increased. May be adjustable. Even when the sheet is thick paper and curling is difficult to remove, the structure shown in FIG. 7 can reliably remove the curling of the thick paper.

  That is, the sheet pressing force of the pressing member is such that the subsequent sheets are received between the pressing member and the tray 13 (or the preceding sheet on the tray) by the springs 20, 23, 24 and a weight 25 (FIG. 6) described later. It is set to a pressing force that can remove the curl of the sheet. As a result, the sheets are stacked on the tray 13 without disturbing the alignment or causing jamming.

  When the sheets are stacked on the tray 13 by the operation of the plunger instead of the springs 20, 23, 24 and the weight 25, the pressing member 17 is tilted upward, and after the sheets are stacked, the pressing member is moved downward. You may make it incline and press a sheet | seat.

  Further, as shown in FIG. 8, instead of the pressing member 17, a blower 18 as a pressing unit that presses the sheet against the tray 13 by wind pressure may be used. The blower 18 starts blowing when the sheet reaches the contact portion 13s of the tray 13. If the blower 18 is used, the curl of the sheet can be removed without contacting the sheet, so that the sheet can be reliably stacked on the tray 13 and the sheet is not jammed.

  Further, the pressing member 17 has a width equal to or larger than the width of the sheet. This is so that the cross-section in the width direction of the sheet can cope with any shape such as a U shape or an inverted U shape. However, when the sheet curls only in a U-shape, as shown in FIGS. 9 and 10, both end portions Pc of the sheet are pressed by the tip portions 17Aa and 17Ba of the pair of pressing members 17A and 17B. You may do it. FIG. 9 is a view showing a state when the sheet P is discharged by the discharge roller pair 16, and the pair of pressing members 17A and 17B are opposed to the curled portion Pc of the sheet. FIG. 10 is a diagram illustrating a state in which the sheet is discharged to the tray 13 and the pair of pressing members 17A and 17B press the curled portion Pc of the sheet to flatten the sheet. When the sheet curls only in an inverted U shape, the pressing member may press only the intermediate portion in the width direction.

(Sheet stacking apparatus of other embodiment)
FIG. 11 is a cross-sectional view along the sheet discharge direction of the sheet stacking apparatus according to another embodiment. The same parts as those of the sheet stacking apparatus 31 shown in FIGS.

  The sheet stacking device 32 includes a tray 13 as a sheet stacking unit on which discharged sheets are stacked, and a pressing member 17 as a pressing unit that presses the sheet P against the tray 13. The tray 13 includes a sheet stacking surface 13a that is curved with its intermediate portion facing upward with respect to the sheet discharge direction.

  The pressing member 17 is a member that is supported by the shaft 19 on the fixed member 21 and can tilt in the contact / separation direction with respect to the sheet stacking surface 13a, and is downstream of the uppermost position 13b of the sheet stacking surface 13a in the sheet discharge direction. The portion 13c is pressed. The pressing member has a width equal to or greater than the width of the sheet so that the curl can be removed regardless of whether the sheet is curled in a U shape or an inverted U shape. When curling into the same shape, only the curled portion may be pressed.

  In the sheet stacking device 32, the sheet P discharged by the discharge roller pair 16 is guided to the sheet stacking surface 13 a of the tray 13 and moved downstream in the sheet discharging direction. And the front-end | tip part Pa of the sheet | seat P passes the said highest position 13b, and approachs between the front-end | tip part 17a of the press member 17, and the part 13c downstream from the highest position 13b. When the rear end portion Pb is discharged from the discharge roller pair 16, the entire sheet is stacked on the sheet stacking surface 13a.

  As described above, the sheet stacking apparatus 32 stacks sheets on the sheet stacking surface 13a curved upward. For this reason, in the case of the sheet P in which the leading end portion Pa and the trailing end portion Pb are curled upward, the sheet is pressed by the pressing member 17 at the leading end portion Pa, and the entire sheet is curved by the own weight. Therefore, curling is easily eliminated.

  Therefore, the sheet stacking device 32 can easily remove the curl of the leading end portion Pa and the trailing end portion Pb of the sheet P, and can improve the stackability of the sheet.

  In the sheet stacking device 32, the pressing member 17 presses the portion 13c on the downstream side in the sheet discharge direction from the uppermost position 13b of the sheet stacking surface 13a. For this reason, as shown in FIG. 3A, in the case of the sheet P whose sheet has a U-shaped cross section in the width direction, the sheet is flattened by pressing the side end portion Pc against the pressing member 17. At this time, the portion of the sheet on the upstream side from the uppermost position 13b bends downward by its own weight, and helps to remove the curl while flattening. Further, as shown in FIG. 3B, the pressing member 17 presses the intermediate portion Pd in the width direction of the sheet to make the sheet flat even if the sheet is curled in an inverted U shape. be able to.

  Accordingly, the sheet stacking device 32 can easily flatten a sheet curled in a U-shaped or inverted U-shaped cross section in the width direction, and can improve the stackability of the sheet.

  Although the sheet pressing force of the pressing member 17 is adjusted by the tension spring 20, it can be adjusted by the springs 23, 24, and 20 shown in FIGS. 4, 5, and 7 and the weight 25 shown in FIG. Good. A plunger may be used instead of the springs 20, 23, 24 and the weight 25.

  Further, instead of the pressing member 17, a blower 18 as a pressing unit that presses the sheet against the tray 13 by wind pressure may be used. If the blower 18 is used, the curl of the sheet can be removed without contacting the sheet, so that the sheet can be reliably stacked on the tray 13 and the sheet is not jammed.

  Further, since the image forming apparatus 1 includes the sheet stacking devices 31 and 32 with improved sheet stacking properties, it becomes easy to handle the sheets.

FIG. 3 is a cross-sectional view of the image forming apparatus according to the embodiment of the present invention along the sheet conveying direction. FIG. 3 is a cross-sectional view of the sheet stacking apparatus according to the embodiment of the present invention along the sheet discharge direction. FIG. 3 is a cross-sectional view in the sheet width direction showing a state in which the pressing member of the sheet stacking apparatus in FIG. 2 has removed the curl of the sheet. (A) is the figure which removed the curl of the sheet | seat with which the cross section of the width direction of the sheet | seat curled in the U shape. (B) is the figure which removed the curl of the sheet | seat which the cross section of the width direction of the sheet | seat curled in reverse U shape. FIG. 3 is a diagram for adjusting a sheet pressing force of a pressing member in the sheet stacking apparatus of FIG. 2. FIG. 3 is a diagram for adjusting a sheet pressing force of a pressing member in the sheet stacking apparatus of FIG. 2. FIG. 3 is a diagram for adjusting a sheet pressing force of a pressing member in the sheet stacking apparatus of FIG. 2. FIG. 3 is a diagram for adjusting a sheet pressing force of a pressing member in the sheet stacking apparatus of FIG. 2. In the sheet stacking apparatus of FIG. 2, it is a figure in the case of removing the curl of a sheet with an air blower instead of a pressing member. In the sheet stacking apparatus of FIG. 2, it is a figure at the time of pressing the sheet | seat with which the cross section in the width direction was curled in U shape with a pair of pressing member. FIG. 10 is a diagram illustrating a state in which the curl of the sheet is removed from the state of FIG. 9. It is sectional drawing along the sheet discharge direction of the sheet stacking apparatus in other embodiment of this invention. FIG. 10 is a cross-sectional view of a conventional sheet stacking apparatus along a sheet discharge direction.

Explanation of symbols

P Sheet Pa Front end portion Pb Rear end portion Pc Side end portion Pd Intermediate portion L Tangential line A Sheet discharge direction B Sheet width direction 1 Image forming apparatus 8, 9, 10, 11 Image forming portion (image forming means)
13 Tray (sheet stacking means)
13a Sheet stacking surface 13b Top position 13c Portion downstream from top position 13s Contact section 16 Discharge roller pair (sheet discharge section)
17 Pressing member (pressing means)
17A, 17B pressing member (pressing means)
18 Blower (Pressing means)
20 Tension spring 23 Compression spring 24 Torsion coil spring 25 Weight 31 Sheet stacking device 32 Sheet stacking device

Claims (6)

Sheet stacking means for stacking sheets discharged from the sheet discharge unit;
In a sheet stacking apparatus comprising: a pressing unit that presses a sheet against the sheet stacking unit;
The sheet stacking means includes a sheet stacking surface that curves with the intermediate portion facing upward with respect to the sheet discharge direction,
The pressing means presses a downstream portion of the sheet discharging direction from a contact portion of a tangent line that contacts the sheet stacking surface through the sheet discharging portion;
A sheet stacking apparatus characterized by that. A sheet stacking means for stacking discharged sheets;
In a sheet stacking apparatus comprising: a pressing unit that presses a sheet against the sheet stacking unit;
The sheet stacking means includes a sheet stacking surface that curves with the intermediate portion facing upward with respect to the sheet discharge direction,
The pressing means presses a downstream portion in the sheet discharge direction from the uppermost position of the sheet stacking surface;
A sheet stacking device. The pressing force of the pressing unit is set to a pressing force capable of receiving a subsequent sheet between the preceding sheet stacked on the sheet stacking unit and the pressing unit and removing the curl of the sheet.
The sheet stacking apparatus according to claim 1, wherein the sheet stacking apparatus is a sheet stacking apparatus. The pressing means is a pressing member that can tilt in a contact / separation direction with respect to the sheet stacking surface.
The sheet stacking apparatus according to claim 1, wherein the sheet stacking apparatus is a sheet stacking apparatus. The pressing means is a blower that presses a sheet against the sheet stacking surface by wind pressure.
The sheet stacking apparatus according to claim 1, wherein the sheet stacking apparatus is a sheet stacking apparatus. An image forming means for forming an image on a sheet;
A sheet stacking apparatus on which sheets on which images are formed by the image forming unit are stacked,
The sheet stacking apparatus is the sheet stacking apparatus according to any one of claims 1 to 5,
An image forming apparatus.

Images