JP2013060241A - Paper sheet discharge device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper sheet discharge device that prevents a stacking failure caused by the reminder of a paper sheet rear end or the like without an increase of a size of a paper ejection stack part and using a particular drive source or a drive mechanism for the prevention of the stacking failure by a simple structure.SOLUTION: The device includes a paper ejection roller 11 and a paper ejection driven roller 12 which constitute a paper ejection roller pair. The device further includes first and second paper pressing members 14 and 15 of which the base ends are supported coaxially with the roller 11 on a top side of the paper sheet P and which are formed of forks. The second paper pressing member 15 is positioned on a paper ejection roller pair side rather than the first paper pressing member 14, and a swing radius thereof is reduced more than the first paper pressing member 14. When the second paper pressing member comes into contact with the paper sheet, a relation is set so that the first pressing member 14 is in non-contact with the paper sheet.

Description

  The present invention relates to a sheet discharge device and an image forming apparatus, and more particularly to a sheet discharge mechanism to a discharge stack unit.

  In an image forming apparatus using an electrophotographic method in a copying machine, a facsimile machine, a printer, a printing machine, etc., an unfixed image made of unfixed toner transferred and carried on a sheet as a recording medium is fixed. Then, copy and print output.

The sheet on which the toner is fixed is nipped and conveyed by a sheet discharge roller to a sheet stack unit provided in a sheet discharge unit of the apparatus, and is discharged.
The sheet may be curled in the direction perpendicular to the discharge direction, that is, in the state where both ends in the width direction of the sheet are warped upward due to the influence of thermal stress and ambient temperature during fixing before discharge.
For this reason, when a plurality of sheets are stacked on the sheet stack, the succeeding sheet whose bending rigidity in the ejection direction is strengthened by the curl is advanced by pushing the trailing edge of the previously ejected sheet. There may be a phenomenon of page misalignment that goes under the paper and changes the stacking order.

Further, as shown in FIG. 6, when the paper Pa discharged to the paper stack unit C is nipped and conveyed by the pair of paper discharge rollers A and B and the leading end moves toward the paper stacking unit C, the leading end in the discharging direction is the paper stack. When the surface of the part C is contacted, there may be a phenomenon that the rear end is left behind by the pair of paper discharge rollers A and B due to frictional resistance on the surface of the stack part C.
When this phenomenon occurs, as shown in FIG. 6B, the leading edge of the subsequent sheet Pb pushes and moves the trailing edge of the preceding sheet Pa, and the alignment state of the leading edge changes, or the trailing sheet Pa follows the trailing sheet Pa. The paper Pb may sink and cause page misalignment.
Such a paper discharge trouble becomes a cause of hindering smooth discharge of continuous paper.

  Therefore, conventionally, in order to reduce the influence of the curl generated on the paper, a pressing member having a habit of being pushed up by hitting the discharged paper is provided in the vicinity of the paper discharge roller, opposite to the curl of the discharged paper. There has been proposed a configuration in which curling is corrected by applying a load on the side by the weight of the pressing member to suppress the occurrence of page misalignment due to curling (for example, Patent Document 1).

  In the configuration disclosed in the above patent document, since the pressing member always acts on the discharged paper, when the curl of the paper is corrected, the bending rigidity of the paper itself is lowered. For this reason, when the frictional force when traveling on the paper stack is received by the conveying force of the paper discharge roller, the paper is easily bent, and as a result, the progress on the stack is prevented and the trailing edge remains on the paper discharge roller. There is a risk that stacking defects may occur, such as folding, and the rear end not being smoothly removed from the paper discharge roller.

FIG. 7 is a view showing a curl correction mechanism disclosed in the above-mentioned patent document.
In FIG. 7, of the pair of paper discharge rollers A and B, the roller A positioned on the upper surface side of the sheet is supported so as to be swingable on the same axis, and the end holding member D in a state where the tip can swing downward by its own weight. Is provided.

  When the sheet is not discharged, the pressing member D has its swing end positioned below the common tangent L at the discharge roller pair A and B due to its own weight (FIG. 7A). Is nipped and conveyed by the pair of paper discharge rollers A and B, the rocking end moves upward from the common tangent by being pushed and moved by the leading edge of the paper (the state indicated by the solid line in FIG. 7B).

  When the discharge of the sheet is continued and the trailing end of the sheet exits the pair of discharge rollers A and B, the trailing end of the sheet is pressed by utilizing the fact that the pressing member D moves downward by its own weight (FIG. 7C). In the state indicated by the arrow in FIG. 7, the rear end of the sheet is prevented from remaining at the nipping position of the discharge roller pair A, B by reaching the sheet stack C from the nipping position of the discharge roller pair A, B (FIG. 7). (C)).

However, since the pressing member D is a member having a swinging radius, the swinging end of the pressing member D has a certain distance from the swinging fulcrum, and this distance is the position of the swinging fulcrum. On the other hand, the sheet is pushed down at a position distant from the rotation axis A) (state indicated by reference symbol P ′ in FIG. 7D).
For this reason, when a thin sheet having relatively low bending rigidity is discharged, the sheet P discharged from the discharge roller pair A, B by the pressing member D as shown by a solid line in FIG. The sheet stack C is pressed against the surface of the sheet stack C, and the movement of the leading end side is hindered by the frictional resistance received from the stack surface.

  As a result, the rear portion where the leading edge of the sheet is fed from the paper discharge roller pair A and B is likely to bulge toward the stack surface due to the frictional resistance that the leading edge receives from the stack surface, and the trailing edge is difficult to be discharged along the common tangent line. In other words, the so-called trailing edge residue is likely to occur, which causes a discharge failure when the subsequent sheet is discharged.

  SUMMARY OF THE INVENTION In view of the above-described problems in the conventional paper discharge device, the object of the present invention is to make the remaining of the rear end of the paper without using a drive source or a drive mechanism for preventing the enlargement of the discharge stack portion and special stack failure with a simple configuration. It is an object of the present invention to provide a sheet discharge apparatus and an image forming apparatus having a configuration capable of preventing stack defects caused by the above.

  In order to achieve this object, the present invention is a paper discharge device that discharges paper by nipping and conveying it with a pair of paper discharge rollers in which a paper discharge roller and a paper discharge driven roller are brought into contact with the paper stack portion. The base end of the pair of paper discharge rollers is coaxially supported with the paper discharge roller located on the upper surface side of the sheet, and the swing end is below the common tangent at the position where the rollers face each other due to its own weight. A first sheet pressing member that can be lowered toward the first sheet, and a base end that is coaxial with the first sheet pressing member, and is bifurcated together with the first sheet pressing member when viewed from the shaft end. A second paper pressing member formed on the common tangent line with a swing end positioned upstream of the first paper pressing member in the paper discharge direction. Than the first sheet pressing member. The paper is characterized in that the first paper pressing member is set to be in non-contact with the paper when the swinging radius is set and the second paper pressing member is in contact with the paper. In the discharge device.

  According to the present invention, the swinging radius is smaller than that of the first paper pressing member located upstream of the paper discharge direction and downstream of the paper discharge direction, and the first paper presser is in contact with the paper. By providing the second sheet pressing member in which the member is set in a non-contact relationship with the sheet, the sheet discharged along the common tangent line of the sheet discharge roller pair is in the vicinity of the nipping and conveying position of the sheet discharge roller pair. To contact the second sheet pressing member.

  Thereby, unlike the case of contacting the first paper pressing member having a larger swing radius than that of the second paper pressing member, the action of the leading edge of the discharged paper directed to the paper stack can be reduced. Therefore, it is possible to reduce the resistance that the front end of the paper receives from the paper stack and to prevent the rear end of the paper from remaining at the nipping and conveying position.

It is a figure explaining the Example of the image forming apparatus concerning embodiment of this invention. FIG. 2 is a diagram illustrating a main part of a sheet discharge device used in the image forming apparatus illustrated in FIG. 1. It is a figure explaining the principal part of the other example concerning a paper discharge apparatus. It is a figure explaining the principal part of the other example which concerns on a paper discharge apparatus. It is a figure explaining the principal part of another example which concerns on a paper discharge apparatus. FIG. 6 is a diagram for explaining a paper discharge state in the paper discharge device. It is a figure explaining the structure and effect | action of the prior art example in a paper discharge apparatus.

Hereinafter, embodiments for carrying out the present invention will be described with reference to illustrated embodiments.
FIG. 1 is a diagram showing an image forming apparatus in which a paper discharge device is used. An image forming apparatus 100 shown in FIG. 1 is a tandem-type full-color printer (hereinafter referred to as a printer for convenience) in which a plurality of photosensitive members are juxtaposed. is there. The image forming apparatus according to the present invention is not limited to the above-described printer, but includes a copying machine, a facsimile machine, a printing machine, or a multifunction machine having these functions.

  In the printer 100 shown in FIG. 1, an image forming unit is provided substantially in the center in the vertical direction inside the apparatus main body, and the image forming unit includes a plurality of photoconductors 1, 2, 3, 4 juxtaposed in the horizontal direction and these. A transfer device 5 having a transfer belt 5A having a stretched surface facing the photoconductor below the photoconductors 1, 2, 3, and 4 is provided.

The photoconductors 1, 2, 3, and 4 are components of the image forming unit. The image forming unit is equipped with a charging device, a developing device, a cleaning device, and the like (not shown).
A writing device 6 for forming a latent image on the photosensitive member is disposed above the photosensitive member.

A paper feeding device 7 is provided below the image forming unit in the apparatus main body.
The paper feeding device 7 is provided with a cassette 7A containing paper P, a feed roller 7B for feeding the paper P, and a friction pad 7C for preventing double feeding of paper.

  The sheet P fed out from the sheet feeding cassette 7A of the sheet feeding device 7 is subjected to the secondary transfer after the registration timing is set by the registration roller pair 8 in the process of being conveyed toward the sheet stack unit 100A located at the upper part of the apparatus main body. By being conveyed toward the apparatus 9, the image carried on the transfer belt 5 </ b> A of the transfer apparatus 5 is transferred.

  The paper P to which the image has been transferred by the secondary transfer device 9 is subjected to image fixing by the fixing device 10 and then a paper discharge device using a paper discharge roller pair constituted by a paper discharge roller 11 and a paper discharge driven roller 12. 13 is discharged to the paper stack 100A.

  In the present embodiment, the fixing device 10 uses a heat roller fixing system including a fixing roller 10A having a built-in heat source and a pressure roller 10B that is in contact with the fixing roller 10B and forms a conveyance nip. As a fixing device system, a belt fixing system using a fixing belt heated at a position different from the fixing roller can be used.

  FIG. 2 is a diagram showing a main configuration of the paper discharge device 13. In FIG. 2, the paper discharge device 13 has a base end coaxially supported by the paper discharge roller 11 located on the upper surface side of the paper, and a swing end. Are provided with first and second paper pressing members 14 and 15 that can swing toward the common tangent line L at the position where the rollers face each other due to their own weight.

  The first and second paper pressing members 14 and 15 are swing members whose base ends are supported by the rotation shaft 11A of the paper discharge roller 11 located on the upper surface side of the paper.

  As shown in FIG. 2A, the first sheet pressing member 14 has a swing radius in which the swing end is lowered downward from the common tangent line L of the rollers by its own weight.

The second paper pressing member 15 has a swing end positioned on the upstream side of the first paper pressing member 14 in the paper discharge direction, so that the first paper pressing member 15 is viewed from the shaft end of the rotation shaft 11A. A forked shape is formed together with the sheet pressing member 14.
The second paper pressing member 15 has a swing radius smaller than that of the first paper pressing member 14, and preferably has a length at which the swing end is positioned slightly below the common tangent line L.

  The second paper pressing member 15 has a shorter swing radius than the first paper pressing member 14 and is positioned upstream of the first paper pressing member 14 in the discharge direction. 11 and the paper discharge driven roller 12, it swings in the nipping and conveying position of the paper, that is, in the vicinity of the nip portion.

  On the other hand, since the first paper pressing member 14 has a larger swing radius than the second paper pressing member 15, the first paper pressing member 14 is applied to the paper at a position where the feeding amount of the paper fed out from the nip portion becomes large. Can touch.

  As described above, the first and second paper pressing members 14 and 15 are in different positions in contact with the paper, so that when the second paper pressing member 15 comes into contact with the paper, the second paper is changed depending on the paper. In association with the lifting of the pressing member, a relationship is established in which the first sheet pressing member 14 is placed in a non-contact state with the swing end positioned above the common tangent line L.

  Further, as shown in FIG. 2C, the second paper pressing member 15 has a minimum width (reference S in FIG. 2C) in the paper width direction corresponding to the direction perpendicular to the paper transport direction. Is provided).

Since the present embodiment is configured as described above, the sheet P that is nipped and conveyed in the nip portion where the paper discharge roller 11 and the paper discharge driven roller 12 are in contact with each other, as shown in FIG. Immediately after passing, the second paper pressing member 15 is brought into contact with the second paper pressing member 15 and pushed up in a direction away from the common tangent line L.
At this time, the first sheet pressing member 14 is separated from the sheet and is in a non-contact state.

  The paper P in contact with the second paper pressing member 15 is directed toward the paper stack portion 100A at the position where the paper P is fed from the nip portion, but the feeding amount from the nip portion is relatively small. Since the contact is made in a state where there is little sagging deformation with the portion as the base end, in other words, in a state where it moves along the common tangent line L, the phenomenon of bending downwardly concave along the moving direction is suppressed.

This prevents the leading edge of the paper from biting into the paper stack surface when bent downwardly in the direction of movement, reducing the frictional resistance when contacting the paper stack surface, The sheet can move smoothly in the range up to the rear end.
As a result, the situation in which the succeeding sheet pushes and moves the trailing edge of the sheet remaining in the nip portion is eliminated, and the occurrence of a malfunction such as page misalignment in which the succeeding sheet enters under the preceding sheet is prevented.

  On the other hand, when the rear end of the sheet exits the nip portion formed by the paper discharge roller 11 and the paper discharge driven roller 12 during the movement process of the paper P, the second paper pressing member 15 slightly swings the common tangent line L due to its own weight. When it is swung toward a position exceeding the first position, the first sheet pressing member 14 is swung in a direction in contact with the sheet P, and the sheet rear end side is guided to the sheet stack 100A side.

Next, another example of the paper discharge device will be described with reference to FIG.
The configuration shown in FIG. 3 is characterized in that a configuration in which a part of the sheet is curved to increase the bending rigidity is provided in the discharge roller pair.
In FIG. 3, the discharge driven roller 12 located on the lower surface side of the sheet is provided with a bending rigidity reinforcing portion 12 </ b> A at a peripheral edge portion on one end side in the axial direction in a cross section along the axial direction.

  As shown in FIG. 3C, the bending rigidity reinforcing portion 12A is a portion that can form a curved portion such as an upward convex shape, a downward convex shape, or a wave shape in the width direction of the paper P. In the configuration shown in FIG. The peripheral edge of one end in the axial direction of the paper discharge driven roller 12 is a tapered surface (see FIG. 3B) whose diameter increases toward the end in the axial direction.

  The paper discharge driven roller 12 is axially oriented so that the bending rigidity reinforcing portion 12A is positioned on the outer side in the width direction of the paper P, and the base end is supported by the rotation shaft 11A of the paper discharge roller 11. As shown in FIGS. 3A and 3C, the second sheet pressing member 15 is positioned in the vicinity of the bending rigidity reinforcing portion 12A.

In the configuration as described above, a part of the paper P in the width direction of the paper P sandwiched between the paper discharge roller 11 and the paper discharge driven roller 12 faces the bending rigidity reinforcing portion 12A of the paper discharge driven roller 12. Thereby, the curved part along the form is formed.
When the curved portion is formed in a part in the width direction as described above, the buckling strength along the sheet conveyance direction can be increased.

  For the paper whose buckling strength in the transport direction is increased, the second paper pressing member 15 is brought into contact with the paper in the vicinity of the nip portion of the paper discharge roller pair as in the case shown in FIG. Pushed up by the paper.

Since the second sheet pressing member 15 that contacts the sheet is in contact with the sheet at a position close to the nip portion, the second sheet pressing member 15 may move without significantly deforming the curved portion formed on the sheet by the bending rigidity reinforcing section 12A. it can.
As a result, the sheet can move substantially along the common tangent line L without curving downward in the transport direction, and the resistance when the leading end contacts the sheet stack 100A is also reduced.

Next, a modified example of the bending rigidity reinforcing portion shown in FIG. 3 will be described with reference to FIG.
In FIG. 4, as the bending rigidity reinforcing portion (indicated by reference numeral 12A ′ for convenience), a plurality of concave and convex portions provided along the circumferential direction on one axial end side of the paper discharge driven roller 12 are used. In the vicinity of the paper discharge driven roller 12 provided with the bending rigidity enhancing portion 12A ′ having such a configuration, the second sheet pressing member 15 is disposed adjacent to the bending rigidity enhancing portion 12A ′.

  In the configuration as described above, the second paper pressing member 15 has its swing end positioned below the common tangent line L due to its own weight, so that when the paper is fed out from the nip portion of the paper discharge roller pair, FIG. Similarly to the case shown in FIG. 3, the paper P can be moved without impairing the buckling rigidity in the transport direction.

  In addition, since the second sheet pressing member 15 has its swinging end positioned below the common tangent line L due to its own weight, the trailing end of the sheet P is positioned as shown in FIG. It can be guided between the convex portions of the bending rigidity reinforcing portion 12A ′ of the true paper discharge driven roller 12, in other words, into the concave portion located between the convex portions.

  As a result, the paper P can be abutted against the convex portion of the bending rigidity reinforcing portion 12A ′, and thus the paper P is fed out in a state where the rear end is kicked with the rotation of the paper discharge driven roller 12, and is fed to the nip portion. It will be surely prevented from remaining.

Next, a modification of the configuration of the second sheet pressing member 15 will be described with reference to FIG.
In FIG. 5, a rotatable roller 16 is provided at the rocking end of the second sheet pressing member 15.
In such a configuration, it is possible to reduce the sliding resistance during the movement of the paper P and smooth discharge.

DESCRIPTION OF SYMBOLS 11 Paper discharge roller 11A Rotating shaft 12 Paper discharge driven roller 12A, 12A 'Bending rigidity reinforcement part 13 Paper discharge apparatus 14 1st paper press member 15 2nd paper discharge apparatus 16 Roll 100 Printer L Common tangent line P, Pa, Pb Paper S Minimum paper width

JP 2010-6599 A

Claims (6)

A paper discharge device that discharges paper by nipping and conveying it by a pair of paper discharge rollers in contact with a paper discharge roller and a paper discharge driven roller toward a paper stack portion,
Of the pair of paper discharge rollers, the base end is supported coaxially with the paper discharge roller located on the upper surface side of the paper, and the swinging end is directed downward from a common tangent at a position where the rollers face each other by its own weight. A first sheet pressing member that can be lowered;
A second sheet pressing member having a proximal end coaxially with the first sheet pressing member and bifurcated with the first sheet pressing member in a state viewed from the shaft end;
The second paper pressing member is smaller than the first paper pressing member with respect to the common tangent by positioning a swing end upstream of the first paper pressing member in the paper discharge direction. The paper discharge is characterized in that when the swing radius is set and the second paper pressing member is in contact with the paper, the first paper pressing member is set in a non-contact relationship with the paper. apparatus.   2. One of the first and second paper pressing members is provided within a minimum width in a width direction corresponding to a direction perpendicular to the paper discharge direction. Paper ejector.   Of the pair of paper discharge rollers, the paper discharge driven roller facing the lower surface of the paper has an upward convexity capable of forming a curved portion in a part in the width direction of the paper in a cross section along the axial direction. 2. A paper sheet bending rigidity reinforcing portion comprising a curved, downward convex or wavy curved forming portion is provided, and the second paper pressing member is disposed in the vicinity of the curved forming portion. Or the paper discharge apparatus of 2.   4. The sheet bending follower roller is provided with a sheet bending rigidity reinforcing portion including a plurality of concave and convex portions along a circumferential direction of the discharge driven roller. Paper ejector.   5. The sheet discharge device according to claim 1, wherein a rotatable roller is provided at a swing end of the second sheet pressing member.   An image forming apparatus using the paper discharge device according to claim 1.

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