JPH09188456A - Transfer paper curl straightening device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a jamming of paper sheet by a method wherein a curl produced at a fixing part is straightened in a process guided to an intermediate stock part and reformed into a straight. SOLUTION: In the middle of a turn-over paper guide 52 to guide a transfer paper to a double surface unit part from a direction switching plate 51 and in a spot of a conveyance roller pair 53, a curl straightening part 521 to straighten the curl of a transfer paper is formed. A curl straightening part 521 is formed in such a manner that a conveyance passage consisting of guide plates 52a and 52b is formed in a bent shape wherein the conveyance passage is bent at an acute angle or with a high curvature (in an arcuate shape or an oblong shape). Even when the transfer paper is bent at an acute angle, the conveyance roller pair 53 is provided in this position to source normal conveyance of a transfer paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention switches between a re-feeding path side having an intermediate tray section on the downstream side of a fixing section for fixing a toner image transferred to a fed transfer sheet and a discharge path side. The present invention relates to an image forming apparatus such as a copying machine or a printer having a conveyance direction switching unit, and more particularly, to an apparatus for correcting curl of transfer paper generated in a fixing unit.

[0002]

2. Description of the Related Art Conventionally, in a copying machine capable of double-sided copying, when copying is performed on both sides of a transfer sheet, when the image is formed on the front side, the transfer sheet is not discharged and the direction switching means is used. , The paper is once stocked in the intermediate tray portion in the main body, and then the paper is re-fed from the intermediate tray portion to perform copying on the back side. In this case, the toner image on the original surface is transferred to the transfer paper at the image forming unit, and then this toner image is subjected to heat treatment for melting the toner and fixing the toner image on the transfer paper surface at the fixing unit including the heat roller and the pressure roller. I am trying.

[0003]

However, it is known that when heat treatment is performed by a heat roller in the fixing section, the transfer paper will be curled toward the pressure roller when the transfer paper has a normal thickness. If the transfer paper is sent to the intermediate tray section through the re-feeding path while being curled, the transfer tray and the stock processing cannot be properly performed in the intermediate tray section or the like, and so-called paper jam may occur. was there. In particular, since a plurality of transfer paper sheets are stacked in a stack in the intermediate tray section, the curled states of the transfer paper sheets are overlapped, and paper jams are likely to occur when the paper is re-fed for back side copying. .

The present invention has been made in view of the above problems, and corrects curl generated in the fixing unit in the process of leading to the intermediate stock unit and straightens the curl to prevent the occurrence of paper jam. It is an object of the present invention to provide a transfer paper curl straightening device.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a re-feeding path side having an intermediate tray section in the middle and a discharge path side are provided on the downstream side of a fixing section for fixing a toner image transferred on a fed transfer sheet. In the image forming apparatus having the conveyance direction switching means for switching to, the conveyance means is provided in the re-feeding path portion between the direction switching means and the intermediate tray portion, and the re-feeding path is provided with the conveyance means. A bent portion is formed at the position in the direction opposite to the curl of the transfer paper formed by the fixing portion.

According to this structure, when the transfer paper guided to the re-conveyance path passes through the bent portion bent in the direction opposite to the curl formed in the fixing portion, the curl is corrected and corrected. To be done. Further, since the conveying means is provided at the position where the bent portion is formed, the transfer paper can smoothly pass through the bent portion without any trouble despite the high resistance of the transfer paper conveyed by the bent portion.

In the invention according to claim 2, the bent portion is
Since the two guide plates, which are opposed to each other at a predetermined interval, are formed in an arc shape, the curl of the transfer paper is corrected by utilizing the arc shape.

[0008]

1 is an overall perspective view showing an embodiment of a copying machine to which a transfer paper curl correcting device according to the present invention is applied, and FIG. 2 is an internal configuration diagram thereof. Copier 1
Copying machine main body 1a and document placing section 1 arranged on the top thereof
The copying machine main body 1a includes an optical mechanism 2, an image forming unit 3 having a photosensitive drum 31, a sheet conveying mechanism 4, a reversing mechanism 5, and a duplex unit unit 6.

The original document placing portion 1b has an original document pressing portion for opening and closing the surface of the contact glass 1c attached to the top opening of the copying machine main body 1a, and is adapted to manually set an original document. As the document placing section 1b,
It is also possible to use an automatic document feeder which is an upper part of the contact glass 1c and carries the stacked originals one by one onto the contact glass 1c, sets them at the exposure position, and carries them out after reading the originals.

The optical mechanism 2 includes a contact glass 1c.
The upper manuscript is the home position H. A first optical system 21 having a light source 211 consisting of a halogen lamp that scans in the forward movement based on P and a reflecting mirror 212, and a plurality of reflections for guiding the document image irradiated by the light source 211 and reflected on the document surface to the image forming section 3. A second optical system 22 having mirrors 221, 222, a lens 23 for forming the original image on the surface of the photosensitive drum 31,
A pair of guide rails 24 that guide the first and second optical systems 21 and 22 in the reciprocating direction (indicated by arrows in FIG. 2), and the first and second optical systems 21 and 22 along the guide rails 24. Each of them is provided with driving means (not shown) for traveling at a predetermined speed. The reflecting mirror 223 guides the original image that has passed through the lens 23 to the exposure position of the photosensitive drum 31.

The light from the light source 211 is emitted toward the document set on the contact glass and reflected by the document surface to obtain a document image. This original image is reflected by the reflecting mirrors 212, 221, and 222, as indicated by the dashed line in the figure.
After passing through the lens 23, it is guided to the exposure position of the photosensitive drum 31 via the reflecting mirror 223.

The image forming section 3 is provided with a photosensitive drum 31 which is rotated at a constant speed in the clockwise direction by a drive means (not shown), and the main charging section 32 is provided around the photosensitive drum 31 from the upstream side in the rotating direction. , Developing unit 33, toner collecting roller unit 34, transfer unit 35, separating unit 36 and cleaning unit 3
7 is provided. The surface of the photosensitive drum 31 is uniformly charged by the main charging unit 32, and then the original image is exposed to form an electrostatic latent image. This electrostatic latent image is made visible by attaching toner at the developing unit 33, and then the transfer unit 3
5 is transferred to the transfer paper. The transfer paper on which the toner image has been transferred is separated from the photosensitive drum 31 by the separation unit 36,
It is guided to the fixing unit 46 described later.

The paper transport mechanism 4 is detachably provided at a lower position of the copying machine main body 1a, and is provided with a plurality of paper feed cassettes C for accommodating transfer papers of a predetermined size in a stacked state. Paper feed rollers 411 and 412 for feeding the transfer paper one by one from the paper, separation roller pairs 421 and 422 for preventing the double feed of the fed paper, conveying roller pairs 431 to 434, and registration rollers for secondary paper feed It comprises a pair 44. Further, in the downstream direction of the photoconductor drum 31, a conveying belt 45 stretched between a pair of rotating rollers 451 and 452, a fixing unit 46, a discharge roller pair 47, and a discharge tray 48 are provided. Transport guide section 40
Is for transporting the sheet fed from the separating roller pair 42 to the discharging roller pair 47, and is composed of plate-shaped members having a required width and arranged to face each other. Bypass tray 4
Reference numeral 9 denotes a sheet on which a transfer sheet of a required size can be manually set. The sheet 9 has a sheet feeding roller 413 and a separating roller pair 423, and joins the conveyance guide section 40 on the downstream side. The fixing unit 46 includes an upper heat roller 461 and a lower pressure roller 462. The heat roller 461 is provided with a heater inside, and the pressure roller 462 is pressed against the heat roller 461 side with a required pressure.

Paper feed cassette C or manual feed tray 4
The transfer paper fed from the paper feeding rollers 411 to 413 from the sheet 9 is fed to the registration roller pair 44 via the respective conveying roller pairs 431 to 434. The transfer sheet conveyed to the registration roller pair 44 is secondarily fed in synchronization with the exposure scanning start timing of the optical mechanism 2, and is transferred to the transfer unit 3.
At 5, the toner image is transferred. The transfer sheet onto which the toner image has been transferred is conveyed to the fixing unit 46 via the conveying belt 45, where the toner image is fixed on the transfer sheet, and then the discharging roller pair 4
After that, the sheet is discharged to the sheet discharge tray 48.

The reversing mechanism 5 is located in the middle of the conveyance guide section 40 between the fixing section 46 and the discharge roller pair 47, and the transfer sheet of the discharge roller pair 47 is moved around the horizontal shaft 511 by an electromagnetic solenoid (not shown). Has a direction switching plate 51 that can be switched between a rotation position for guiding in the direction and a rotation position for guiding in the direction of the double-sided unit section 6 which will be described later. The reverse sheet guide 52, the transport roller pair 53 in the middle of the reverse sheet guide 52, and the carry-out roller pair 54 provided at the downstream end of the reverse sheet guide 52. The transfer paper whose direction is switched to the duplex unit 6 side is conveyed downward along the reversing paper guide 52, and at the curved portion of the reversing paper guide 52 provided with the conveying roller pair 53, the fixing unit 4 is provided.
The curl formed in 6 is guided to the carry-out roller pair 54 in a state where the curl is straightened and returned as straight as possible.

The double-sided unit section 6 is for copying on both sides of a transfer sheet, and is composed of an intermediate tray section 7 having a unit section body 60 and a re-feeding mechanism 8. The intermediate tray unit 7 includes a paper stock plate 71 on which the inverted transfer paper is placed. Above the paper stock plate 72, a paper scraping unit 72, a nip roller 73, a paper guide 74, and its own weight on the paper surface to drop the paper. A rotary plate 75 is provided that rotates together with the transfer. Note that the paper guide 74 is provided only on the front side of the mounting position of the rotary plate 75, is pivotally supported at the upper portion, and is brought into contact with the paper stock plate 71 by its own weight, or inclined rearward with a slight downward biasing force. The transfer paper carried out from the carry-out roller pair 54 is smoothly guided onto the surface of the paper stock plate 71 to prevent stock mistakes due to the leading end of the transfer paper colliding with the rotary plate 75. There is.

Further, the re-feeding mechanism 8 includes the paper stock plate 7
1 and a re-feeding guide portion 81 formed of a plate-like body that is disposed below and facing each other at a predetermined interval,
Re-feeding roller 8 provided slightly forward of the paper stock plate 71 in the re-feeding direction and partially exposed at the upper peripheral surface.
2, a reversing roller 83 in front of it, a pair of rotating rollers 84
Separation belt 8 which is stretched between 1 and 842 and rotates in the direction opposite to the re-feeding direction while being in contact with the peripheral surface of the reversing roller 83.
4 and the re-feeding guide portion 81, the re-feeding roller pairs 851 to 853 are formed at appropriate positions with a required interval. In addition, the rotation roller 84 of the loosening belt 84
1 and the reversing roller 83 face each other at the paper nip position,
A flexible sheet body 86 hangs downward from the unit main body 60, and the lower end thereof is attached in contact with the reversing roller 83.

The double-sided unit section 6 is the main body of the copying machine 1.
It is configured so that it can be pulled out to the front side from a, and a paper feed cassette C is slid from the front side instead of the double-sided unit at this mounting position, and a three-stage structure of the paper feed cassette can also be formed. It is possible. In this case, a portion corresponding to the sheet feeding roller 411 and the separating roller pair 421 may be configured as a feeding unit, and the feeding unit may be loaded prior to the insertion of the sheet feeding cassette C.

From the pair of carry-out rollers 54 to the paper stock plate 71
When the transfer sheet is sent to the upper side, the sheet knocking section 72 rotates to press the rear end side (the front end side at the time of re-feeding) of the transfer sheet from above and forcibly regulate the remaining curl straight. Then, in this state, the nip roller 73 rotates in the sheet re-feeding direction to transfer the transfer sheet to the sheet nip position between the reversing roller 83 and the sheet body 86 to secure the nip state and align the front end. The transfer state of the transfer sheet is monitored by a rotary encoder (not shown) or the like provided on the rotary shaft of the rotary plate 75. In this state, when there is an instruction to start the re-feeding, that is, the back side copying operation, the re-feeding roller 82, the reversing roller 83, and the separating belt 84 start the rotational driving, and the sheet striking unit 71 presses the sheet from above. The lowest transfer paper is sequentially fed one by one, and is fed to a position where it merges with the conveyance guide unit 40 via the re-feed guide unit 81, and after the merge, the pair of conveyance rollers 433 and the pair of registration rollers 44 form a photoconductor. It is guided to the drum 31. The transfer paper on which the toner image is transferred on the back surface is discharged to the paper discharge tray 48 via the discharge roller pair 47.

FIG. 3 is a side sectional view for explaining the structure of the transfer paper curl correction unit. A curl straightening unit 521 that straightens the curl of the transfer paper is formed at a position of the conveyance roller pair 53 in the middle of the reverse paper guide 52 that guides the transfer paper from the direction switching plate 51 to the double-sided unit 6.

The reversal sheet guide 52 is composed of guide plates 52a and 52b which are arranged to face each other at a predetermined interval, and these guide plates 52a and 52b have notches facing each other at a predetermined interval in the width direction. A plurality of rollers are formed so that the opposing rollers forming the conveying roller pair 52 are in pressure contact with each other from these notches. And
The curl correction unit 521 is provided with these guide plates 52a and 52a.
The conveyance path b is formed in a bent shape with an acute angle or a large curvature (arc shape or elliptical shape). Even when the transfer sheet is bent into an acute angle as described above, the transfer roller pair 53 is provided at this position to ensure the normal transfer sheet transfer.

Then, due to the heat treatment for fixing the toner in the fixing section 46, the fixing section 46 is bent downward (curled) toward the pressure roller 462 side.
The curl of the transfer paper is corrected. That is, when the transfer paper is guided to the curl straightening unit 521 of the reverse paper guide 52, the transfer paper passes between the bent guide plates 52a and 52b, so that the transfer paper is generated at the fixing unit 46. A force in a direction opposite to the residual stress inside the transfer paper (the force that curls the transfer paper) acts. As a result, the transfer paper is sent to the double-sided unit 6 in a state where it is returned to the straight state. Therefore, the curl-corrected transfer paper is sent to the intermediate tray 71 of the double-sided unit 6, and the nipping process is suitably performed for the nip operation with respect to the leading end of the paper for re-feeding. In addition, it is possible to prevent a conveyance error such as a paper jam caused by the curl of the transfer paper as much as possible, and improve the reliability of the apparatus.

The pair of conveying rollers 53 is the curl straightening unit 5.
It may be arranged so as to be an intermediate position of the bent shape of 21 in the transport direction, but the present invention is not limited to such a positional relationship.
It may be slightly upstream from the center of the bent shape, whereby the transfer paper can be pressed by the opposing rollers in a state of being bent in the direction opposite to the curl and the conveyance can be secured. Also,
The curl correcting counter roller may be provided separately from the transport roller pair 53. Further, instead of the facing roller, one roller and a conveyor belt along the peripheral surface of the roller may be used.

In the above embodiment, the intermediate tray portion 7 has been described for double-sided copying. However, the present invention is not limited to this, and the intermediate tray portion 7 is capable of transferring the images of two types of originals onto the surface of the transfer paper. The present invention can also be applied to an image forming apparatus provided with 7.

[0025]

According to the first aspect of the present invention, the conveying means is provided in the re-feeding path section between the direction switching means and the intermediate tray section, and the arranging position of the conveying means in the re-feeding path section. In addition, since the curl of the transfer paper formed in the fixing section is formed in the opposite direction to the curl of the transfer paper, the curl of the transfer paper formed in the fixing section can be straightened and Despite the high resistance of the transfer paper, the transfer paper can smoothly pass through the bent portion.

According to the invention of claim 2, the bent portion is
Since the two guide plates arranged facing each other at a predetermined interval are formed in an arc shape, the curl of the transfer paper can be corrected by utilizing this arc shape.

[Brief description of the drawings]

FIG. 1 is an overall perspective view showing an embodiment of a copying machine to which a transfer paper curl straightening device according to the present invention is applied.

FIG. 2 is an internal configuration diagram of FIG.

FIG. 3 is a side sectional view illustrating a structure of a curl correction unit.

[Explanation of symbols]

 1 Copier 1a Copier main body 46 Fixing unit 5 Reversing mechanism 51 Direction switching plate 52 Paper reversing guides 52a and 52b Guide plate 521 Curl straightening unit (bending unit) 53 Conveying roller pair 7 Intermediate stock unit

Claims (2)

[Claims] 1. A conveyance direction switching means for switching between a re-feeding path side having an intermediate tray section and a discharge path side is provided on the downstream side of a fixing section for fixing the toner image transferred onto the fed transfer paper. In the image forming apparatus, the re-feeding path between the direction switching means and the intermediate tray section is provided with a conveying means, and the re-feeding path is formed at the disposing position of the conveying means by the fixing section. A transfer paper curl straightening device for an image forming apparatus, characterized in that a bent portion in a direction opposite to the curl of the transferred transfer paper is formed. 2. The transfer paper for an image forming apparatus according to claim 1, wherein the bent portion is formed by forming two guide plates facing each other at a predetermined interval in an arc shape. Curling device.