JP2000219387A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and effectively eliminate the curl generated by printing to the first surface of a sheet by providing, on a return passage, a curl correcting means for correcting the curl of the sheet carried on the return passage. SOLUTION: A sheet with a printed first surface fed to a return passage 12 is carried by a pair of carrying rollers 24, guided by a gate member 23, and sent between a guide member 21 and a cylindrical member (rubber roller) 22. The curl generated in the sheet in the process of the first surface printing is corrected by passing the sheet in a carrying passage protruding down to the return passage 12, which is formed by the guide member 21 and the rubber roller 22. The corrected sheet is traveled in the return passage 12 by the rubber roller 22, a pair of carrying rollers 25 and a pair of succeeding carrying rollers to feed the sheet again to a transfer part for the second surface printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus represented by a printer, a copying machine, and the like, and more particularly to an electrophotographic apparatus capable of printing on both sides of a sheet.

[0002]

2. Description of the Related Art The prior art will be described with reference to FIG.

In FIG. 4, reference numerals 1a, 1b, and 1c denote sheet feeding units which store sheets. Reference numeral 2 denotes a photosensitive drum, which starts rotating based on a signal from a controller (not shown). When the photosensitive drum 2 starts rotating, the surface of the photosensitive drum 2 is uniformly charged by the corona charger 3. An electrostatic latent image is formed on the charged photosensitive drum 2 by a scanning beam from the exposure device 4. When the electrostatic latent image reaches the position of the developing device 5, the electrostatic latent image is developed by toner, and is visualized as a toner image on the photosensitive drum 2. The toner image formed by the well-known electrophotographic process is transferred by the transfer unit 6 to the sheet sent from the sheet feeding unit 1a, 1b, or 1c. A fixing device 7 fixes the toner image transferred to the sheet. Reference numeral 8 denotes a flap for controlling the direction of a sheet to be conveyed. Reference numeral 9 denotes a paper discharge tray serving as a paper discharge unit, which stacks and stores sheets on which image formation has been completed.

In the following description, for convenience, the paper feed units 1a, 1b, 1c and the image forming means 2, 3, 4, 5, 6, 7
-The paper transport path 10 that communicates with the paper output tray 9 is referred to as
Call. Reference numeral 11 denotes a draw-in path, which is provided to branch off from the paper feed path 10 on the downstream side in the paper transport direction with respect to the image forming means, and selectively controls the flap 8 to switch the paper fed from the fixing device 7. Pull in. Reference numeral 12 denotes a return path, which branches off from the middle of the pull-in path 11, and is provided so that the terminal end thereof joins the paper feed path 10 on the upstream side in the sheet transport direction with respect to the image forming means.

Therefore, when image recording is performed on both sides of the sheet, the sheet sent from the fixing device 7 is fed to the pull-in path 1.
1 and the drawn sheet is sent to the return path 12, so that the sheet on which single-side recording has been performed is sent again to the image forming means, whereby double-sided image recording is performed.

In FIG. 4, reference numerals 13 and 14 denote a pair of transport rollers provided before and after the flap 8; 15, 16 a pair of transport rollers provided on the retraction path 11 which can be switched between forward and reverse rotation; This flap is used to switch between feeding the paper drawn into the path 11 to the return path 12 or returning the sheet to the paper feed path 10 again and discharging the sheet to the discharge tray 9.

[0007]

By the way, in the case of the electrophotographic apparatus having the layout shown in FIG. 4, the sheet passing through the fixing device 7 is bent by heat and pressure from the fixing device 7 and the path configuration of the sheet conveying path. In many cases, curling occurs. When the paper is sent to the transfer position via the return path 12 in order to perform printing on the back surface of the curled paper, the curl surface (concave surface) of the paper comes into contact with the surface of the photosensitive drum 2, so that the paper is It becomes easy to wind around the photosensitive drum 2.

When the curl is relatively small, the sheet is sent to the conveyor belt 19 side without being wound around the photosensitive drum 2 by the electric force of the peeler 18 provided at the subsequent stage of the transfer unit 6. When it becomes large, it becomes difficult to peel the sheet from the photosensitive drum 2 only by the action of the peeler 18, resulting in a drawback that the paper jam occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic apparatus capable of efficiently and effectively removing curls generated in printing on the first side of a sheet and performing two-sided printing smoothly.

[0010]

The object of the present invention is to provide a paper feeding unit,
An image forming means for recording and forming an image on the conveyed paper and a paper feed path for communicating a paper discharge unit for accommodating the image-recorded paper; and a paper feed path on the downstream side in the paper conveying direction with respect to the image forming means. An electrophotographic apparatus having a branch path provided therein, and a return path branching from the middle of the branch path and having its end joined to the paper feed path on the upstream side in the paper transport direction with respect to the image forming means. In the above, the present invention is achieved by providing the return path with a curl correcting means for correcting the curl of the sheet conveyed on the return path.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 is an overall configuration diagram showing an electrophotographic apparatus of the present invention, FIG. 2 is a side view of a main part of a return path applied to the electrophotographic apparatus of the present invention, and FIG. 3 is applied to the electrophotographic apparatus of the present invention. It is a principal part perspective view of the return path performed. In addition,
In the drawing, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

The configuration of the electrophotographic apparatus shown in FIG. 1 differs from that of FIG. 4 in that the return path 12 is provided with a curl correcting device 20 as a curl correcting means.

As shown in FIGS. 2 and 3, the curl correcting device 20 is provided with a guide member 21 having a concavely curved surface, a predetermined gap with respect to the surface of the guide member 21, and a rotatable member. The gate member 23 includes a cylindrical member 22 made of, for example, a rubber roller. Here, the gate member 23 is rotatably supported on the shaft 23a as a fulcrum, and guides the sheet so as to be fed between the guide member 21 and the cylindrical member 22 (the state shown in FIG. 2). And a second position for guiding the paper to be fed above the cylindrical member 22 (a state where the sheet is turned counterclockwise from the state of FIG. 2 and the upper surface of the gate member 23 is substantially horizontal). It is provided to be switchable.

The cylindrical member 22 is connected to a gear train (not shown) for driving a pair of conveying rollers.
It rotates relatively to the guide member 21.

In FIG. 1, reference numerals 24, 25, and 26 denote conveying roller pairs provided on the return path 12.

Next, a state in which double-sided printing is performed in the electrophotographic apparatus having the above configuration will be described. Paper feeder 1a, 1
The toner image formed on the photosensitive drum 2 is transferred by the transfer unit 6 to the sheet sent from b or 1c to the transfer unit. The sheet is peeled from the surface of the photosensitive drum 2 by the peeler 18, and is transported to the fixing device 7 by the transport belt 19. The fixing device 7 heats and pressurizes the sheet holding the unfixed toner image to fix the toner image on the sheet. Fixing device 7
The paper sent out of the feeding path 1 by the flap 8
1 and is pulled in by the pair of transport rollers 15 and 16 until the rear end of the sheet is sent out from the pair of transport rollers 15. When the trailing edge of the sheet is fed from the pair of transport rollers 15, the position of the flap 17 switches from the position shown by the broken line in FIG. 2 to the position shown by the solid line. When the rotation direction of the conveying roller pair 16 is reversed in a state where the flap 17 has been switched to the solid line position, the above-mentioned paper trailing end becomes the top and the return path 1
It is sent to 2.

The first-side printed sheet sent to the return path 12 is conveyed by a pair of conveying rollers 24 and is guided by a gate member 23 so that the guide member 21 and a cylindrical member (rubber roller) 22 It is sent in between. The curl attached to the sheet in the process of the first side printing is caused by the return path 1 formed by the guide member 21 and the rubber roller 22.
The sheet 2 is corrected by passing through a conveying path projecting downward with respect to 2, and travels in the return path 12 by the rubber roller 22, the conveying roller pair 25 and the conveying roller pair 26, and is sent again to the transfer section for the second surface printing. It is.

[0018]

As described above, according to the present invention, since the return path is provided with the curl correcting means for correcting the curl of the sheet conveyed on the return path, the curl correction means is provided for printing on the first side of the sheet. It is possible to provide an electrophotographic apparatus capable of efficiently and effectively removing a curled sheet and performing two-sided printing smoothly.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an electrophotographic apparatus of the present invention.

FIG. 2 is a side view of a main part of a return path applied to the electrophotographic apparatus of the present invention.

FIG. 3 is a perspective view of a main part of a return path applied to the electrophotographic apparatus of the present invention.

FIG. 4 is an overall configuration diagram showing a conventional electrophotographic apparatus.

[Explanation of symbols]

10: paper feed path, 11: pull-in path, 12: return path, 20 ...
Curl correcting device, 21: guide member, 22: cylindrical member, 23: gate member, 24, 25, 26: transport roller pair.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H028 BA06 BA09 BA16 3F053 EA02 EA05 EB04 EC02 HA03 HB01 HB11 LA02 LA07 LB01

Claims (2)

[Claims] An image forming means for recording and forming an image on a conveyed sheet; and a paper feed path for communicating a paper discharge section for accommodating the image-recorded sheet; A retraction path provided by branching from a paper feed path on the downstream side in the transport direction, and a branch from the middle of the retraction path, and the terminal end is joined to the paper transport path on the upstream side in the paper transport direction with respect to the image forming means. An electrophotographic apparatus having a return path
An electrophotographic apparatus, comprising: a curl correcting unit for correcting curl of a sheet conveyed on the return path. 2. The curl correcting means includes: a guide member having a concavely curved surface; a cylindrical member provided at a predetermined gap with respect to the guide member surface and rotatably provided; A gate member provided to be selectively switchable between a first position for guiding paper to be fed between the cylindrical member and a second position for guiding paper to be fed above the cylindrical member. 2. The electrophotographic apparatus according to claim 1, comprising: