JPH02123070A - Sheet material discharge device - Google Patents

Abstract

PURPOSE:To prevent a wrinkle or the like from being left in a sheet material moderately corrected by curving an inverse conveying route itself by constituting the inverse conveying route so as to form not only an inverting curved part for inverting the sheet material but also a correcting curved part flexing reversely to the inverting curved part for correcting a curl of the sheet material. CONSTITUTION:An inverse conveying path forms not only an inverting curved part C but also a correcting curved part B. Thus in this correcting curved part B, a sheet material S is corrected in its curl. As the result, a wrinkle and/or a roller track can be eliminated to be left in the sheet material S.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a laser beam printer, an electrophotographic copying machine, etc. that performs processing such as forming an image on a sheet material such as printing paper, copy paper, printing paper, etc.; The present invention relates to a sheet material discharging device that discharges sheet material in an image forming apparatus such as a printing machine.

(Prior Art) Conventionally, image forming apparatuses such as laser beam printers, electrophotographic copying machines, and printing machines have a method of forming an image on a sheet material such as print paper, copy paper, or printing paper to form one image. A sheet material discharging device for discharging the sheet material to the outside after processing is incorporated therein.

The sheet material discharging device requires not only a mechanism for discharging the sheet material with the image-formed surface (hereinafter referred to as the "image surface") facing upward, but also a mechanism for discharging the sheet material with the image surface facing downward. Note that if you eject the image side up (hereinafter referred to as face-up), it has the advantage of allowing you to immediately check the image condition, but on the other hand, the order of the pages on the sheet material may be reversed. There is an image forming apparatus that also includes a mechanism for inverting the material and ejecting the material with the image surface facing downward (hereinafter referred to as "face down").

In the following, a laser beam printer will be used as an example of image forming apparatus 1, and the conventional technology of image forming apparatus and sheet material discharging apparatus will be described in Section 7.
This will be explained in detail using figures.

In FIG. 7, l is a machine box of a laser beam printer, 2 is a process cartridge detachably installed in the machine box 1, and inside the cartridge z is a photosensitive drum 3 as an image carrier and a photosensitive drum 3 arranged around it. Known process equipment such as a charger, a developer, a cleaner 6, and the like are built-in. Reference numeral 7 denotes a scanner unit that emits and scans a laser beam, and the photosensitive drum 3 uniformly charged by the charger 4 is irradiated with the laser beam emitted from the unit 7 via a mirror 8 to print a desired mark. (Image) A latent image corresponding to the information is formed, and the latent image is developed by the developing device 5.

Reference numeral 9 denotes a cassette for storing sheet materials S such as transfer paper, and the sheet materials S are fed out one by one from 9 by a feeding roller IO, and are transferred to the photosensitive drum 3 by a registration roller 11.
The sheet material S is conveyed toward the drum 3 in synchronization with the rotation of the drum.

Reference numeral 12 denotes a transfer charger that transfers the developed image formed on the photosensitive drum 3 by the developer 5 onto a sheet material;
The sheet material S on which the image has been transferred is guided to a fixing device 14 by a conveying roller 13.

The fixing device 14 includes a fixing roller 15 having a heater 15a inside, and a pressure roller 16 that contacts the fixing roller 15 with a constant pressure.
The surface is made of an elastic member such as rubber.

17a-17b are discharge rollers that discharge the sheet material S that has passed through the fixing device 14 and the fixing process has been completed out of the machine;
18a1118b is a tray on which the sheet material S discharged by the discharge rollers 17a-17b is loaded;
0 is a guide member that guides the sheet material S that has passed through the fixing device 14 to discharge rollers 17a and 17b, and 21 is a flapper that selectively guides the discharge direction of the sheet material.

In this example, when the flapper 21 is at the solid line position in FIG. 7, the sheet material S is discharged face-up onto the tray 18a via the discharge roller 17a, and the flapper
1 is at the chain line position in the figure, the sheet material S is reversed via the discharge roller 17a1117b (hereinafter, the conveyance path in which this reversal is performed will be referred to as the reverse conveyance path).
It is ejected face down onto b.

In the configuration described, when a print start command is input from a computer, image reader, etc. (not shown), the printer starts printing (image forming) operation, and the sheet material S in the cassette 9 is transferred to the feed roller 10 and the registration roller. The paper is supplied and conveyed by 11, printed by a known electrophotographic process, and guided to a fixing device 14. The sheet material S guided to the fixing device 14 receives heat from the fixing roller 15 and
．． The developed image on the sheet material is fixed by a pressure of 16 degrees.

In this fixing process, heat and pressure are applied to the sheet material S, so that water contained in the sheet material evaporates, causing the sheet material to curl. In particular, when discharging sheet materials face-down, a large curl is created at the reversing curved part of the reversing conveyance path to reverse the sheet material, and stiff sheet materials such as postcards are even more curled. Therefore, a curl removing roller 22 is provided which comes into contact with the discharge roller 17b, and the curl of the sheet material is corrected by squeezing the sheet material between both rollers.

(Problem to be Solved by the Invention) However, if the sheet material is squeezed too strongly with the curl removal roller, wrinkled re-rolled paper may remain on the sheet material, damaging the image surface, and vice versa. If the squeezing force is weak, there is a problem in that curls of stiff sheet materials such as postcards cannot be corrected.

This invention has been made in view of one or more problems, and an object of the present invention is to provide a sheet material discharging device capable of correcting curls without leaving many wrinkles or roller marks even in the case of a strong sheet material.

(Means for Solving the Problems) The present invention includes a fixing device for fixing an image transferred onto a sheet material to the sheet material, and a sheet material after the fixing step is reversed from the fixing device and discharged from the fixing device. In a sheet material discharging device having a reversing conveyance path leading to a sheet material, the reversing conveyance path includes not only a reversing curved section for performing the reversal of the sheet material but also the reversing curved section for correcting curls of the sheet material. This sheet material discharging device is configured to also form a correction curved portion that bends in the opposite direction.

(Function) Since the reversing conveyance path forms not only one reversing curved portion but also a straightening curved portion, the curl of the sheet material is corrected in this straightening curve.

Conventionally, the above-mentioned problem has arisen because the sheet material is locally squeezed and straightened by a curl removal roller that comes into contact with the discharge roller. In this invention, by forming a portion of the reversing conveyance path into a gently curved portion for correction, it is possible to prevent the wrinkles and roller marks of the above-mentioned problem from remaining.

(Example) Hereinafter, the present invention will be described in detail using the drawings. FIG. 1 shows a first embodiment of the present invention, and is a sectional view of a laser beam printer similar to FIG. 7 of the conventional example, and FIG. 2 is an enlarged view of the fixing device and reversal conveyance path in FIG. 1. It is a diagram.

Incidentally, members having the same functions as those in FIG. 7 are designated by the same reference numerals and will not be described again.

As shown in FIG. 2, the sheet material S that has passed through the fixing device 14
is the direction opposite to the reversal direction of the sheet material S, that is, the sheet is placed on the pressure roller 16 side with respect to the tangential direction of both rollers 15 and 16 (direction of dotted line A in the figure) at the contact point between the fixing roller 15 and the pressure roller 16. A guide member 19 is arranged to protrude so that the material is conveyed and curled toward the pressure roller 16.

As a result, the two reversal conveyance paths form a curved portion B for correction. Here, the required amount of curl formed on the pressure roller 16 side by the protrusion of the guide member 19 is determined by the shape of the reversing curved portion C. That is, in this embodiment, as shown in FIG. 2, the sheet material S that has passed through the fixing device 14 is conveyed by the guide members 19 and 20 along the reverse conveyance path shown by the dashed line in the figure. The middle point P in Figure 0, which has a reversing curved portion C along an arc with radius R = 25, is a point on the guide member 19 that determines the conveyance direction of the sheet material S after passing through the fixing device 14. can be,
This point P is located at a distance from the tangent line to the pressure roller 16 side. The size of this L depends on the paper type and the environment, but in this example, when L = 2 to 5, the sheet material passed the 0 point P, which was effective in curl correction. is conveyed to the reversing curved portion C by a discharge roller L7a located downstream of point P.

According to the above configuration, the sheet material S after passing through the fixing device 14 and completing the fixing process is curled in advance by the straightening curved portion B on the side opposite to the printing surface (pressure roller 16 side), but is reversed. At the curved portion C, the paper is now curved toward the printing surface, so that the curl that has conventionally occurred is corrected and the paper is discharged.

(Other Embodiments) In the above embodiments, the correction curved portion B of the reversing conveyance path is
Although it is formed by the protrusion of the guide member 19, in other embodiments it is also possible to form it by the protrusion of the discharge roller. That is, FIG. 3 shows the second embodiment, and is an enlarged view similar to FIG.
The configuration is the same as that of the first embodiment except that point a is located upstream from point P and protrudes toward the conveyance trajectory of the sheet material, thereby increasing the curvature of correction curve B. In this case, the curl correction effect will be even greater. Further, as shown in the second embodiment, a discharge roller 17 essential for conveying the sheet material
The position a can be arbitrarily set not only on the downstream side but also on the upstream side of the point on the guide member that determines the conveyance method of the sheet material after passing through the fixing device, taking into consideration the configuration of the 4 m machine, etc.

FIG. 4 shows a third embodiment, which is an enlarged view similar to FIG. 2, and has the same configuration as the first embodiment except that the discharge roller 23 contacts and follows the discharge roller 17a It is. In this way, by providing the discharge rollers 23, it is possible to supplement the conveyance force that tends to be insufficient in the reverse conveyance path without providing a new drive source.

In the first embodiment, the correction curved portion B of the reversing conveyance path is formed by the guide member 19, but in other embodiments, it may be formed by the protrusion of the ejection roller, i.e., as shown in FIG. 2 shows a fourth embodiment, and is a diagram similar to FIG.
The configuration is the same as that of the first embodiment except that it is located not on the top but on the newly provided discharge roller 17c.

Further, as shown in the second embodiment, a discharge roller may be used instead of the guide member that determines the conveyance direction of the sheet material after the completion of the five fixing steps. It can supplement the conveying force during the route.

In the above embodiments, the reversing conveyance path curves upward from the fixing device, but in other embodiments, it may curve downward, i.e., as shown in FIG. 1 shows a PfII5 embodiment, which is a cross-sectional view of a laser beam printer similar to that shown in FIG. be done. In this embodiment as well, the guide member 19 protrudes to form a straightening curved portion, so that the sheet material that has passed through the fixing device 14 is directed in the opposite direction to the reversal direction, that is, at the contact point between the fixing roller 15 and the pressure roller 16. Both rollers 15.16
It is conveyed to the fixing roller 15 side with respect to the tangential direction, and the printed surface side is precurled. Thereafter, the sheet material is curved at the reverse curved portion in the direction opposite to the printing surface, so that the conventional curl is corrected and the sheet material is discharged.

In the above embodiments, the curved portion for correction was formed by the guide member 19, the discharge roller 17a, the discharge roller 17c, etc., but in other embodiments, other elements constituting the reversing conveyance path, such as the conveyance belt It is also possible to form the straightening curved portion using a conveyor chain or a conveyor chain. In such a case as well, the conveyor belt or the conveyor chain protrudes toward the conveyance locus of the sheet material to form a straightening curved section that bends in the opposite direction to the reversing curved section.

It should be noted that, although each of the above embodiments applies a laser beam printer, the present invention can also be applied to an electrophotographic copying machine, a printing machine, or other sheet material output equipment.

(Effects of the Invention) As described above, according to the present invention, when the sheet material is reversed and discharged after the fixing process is completed.

The sheet material is bent in the opposite direction to the curling direction created by the reversing curved section of the reversing conveyance path in advance at the straightening curved section, and is then conveyed to the reversing curved section, so that as a result, the curl of the sheet material is corrected. is discharged.

Therefore, the curvature of the reversing conveyance path itself is gently corrected, there is no need to install a curl removal roller or the like in the discharge section as in the conventional case, and there is no fear of leaving wrinkles or roller marks on the sheet material.

[Brief explanation of the drawing]

1 is a cross-sectional view of a laser beam printer which is an image forming apparatus equipped with a first embodiment of the sheet material discharging device of the present invention; FIG. 2 is an enlarged view of the vicinity of the sheet material discharging device in FIG. 1;
FIG. 3 shows the second embodiment and corresponds to FIG. 2, FIG. 4 shows the third embodiment and corresponds to FIG. 2, and FIG. 5 shows the fourth embodiment. FIG. 6 shows the fifth embodiment and corresponds to FIG. 1, and FIG. 7 shows a conventional image forming system equipped with a discharge sheet material. 1 is a cross-sectional view of a laser beam printer that is an apparatus. Explanation of symbols l...Machine box 2...Process cartridge 3...Photosensitive drum 4...Charger 5...Developer 6...Cleaner 7...Scanner unit 8...Mirror 9. ...Cassette S... Sheet material lO... Roller 11... Registration roller 12... Transfer charger 13... Conveyance roller 14.
...Fuser 15...Fixing roller tSa...
Heater 16... Pressure rollers 17a, 17b.-
・Discharge port-ra 18a, 18b-) Ray 19.20...Guide member 21...Flapper 22...Curl removing roller 23...Discharge roller

Claims (1)

[Scope of Claims] A fixing device for fixing the image transferred on the sheet material to the sheet material, and a reversing conveyance path that reverses the sheet material after the fixing step from the fixing device and guides it to a discharge section. In the sheet material discharging device, the reversing conveyance path includes not only a reversing curved portion for reversing the sheet material, but also a rectifying portion that bends in the opposite direction to the reversing curved portion to correct curls of the sheet material. A sheet material discharge device configured to also form a curved portion.