JPS62255962A - Curling device for image forming device - Google Patents

Abstract

PURPOSE:To always stably facilitate a second or following transfer and separation by allowing a sheet to pass between the surfaces of a metallic roller and an elastic roller which are brought into contact with each other under pressure before the second or following transfer is started after a first fixing of the sheet. CONSTITUTION:An upper curling roll 21 and a lower curling roll 22 provided below an intermediate tray consist of a rigid body consisting of a metal or the like and a rubber elastic body respectively. Both rolls are brought into contact with each other by pressure, and the roll 21 is rotated in the direction of an arrow H, and the roll 22 is rotated in the direction of an arrow J. The roll 22 consisting of the elastic body is deformed to generate a nip on the pressure contacting surface, and a sheet 1 forcibly curled along the curved face of the nip when passing the nip. Since the sheet 1 is curled in the opposite direction of the curved face of a photosensitive drum 7 before the second transfer and separation process, the sheet is always stably and easily separated from the drum 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a curling device for an image forming apparatus, and more specifically, at least one curling device is applied to the same side or back side of a sheet on which a toner image has been transferred and fixed once. The present invention relates to a curling device in an image forming apparatus such as an electrophotographic apparatus having a function of transferring and fixing a toner image more than once.

(B) Conventional technology Conventionally, in electrophotographic apparatuses that form and fix a two-fold upper toner image on the same sheet, such as automatic double-sided copying and multiplex copying, the transferred sheet is processed using either a heating method or a pressure method. Regardless, when the fixing process is completed, the image shown in Figure 3 (AII
A curl called a curl as shown in B) occurs.

The direction and size of the curl depend on the moisture absorption state of the transferred sheet 1, the toner distribution state on the sheet 1, and the fixing device 2.
It has been confirmed that curling always occurs, although it may vary slightly due to differences in the structure etc. When the first fixing process is completed in this way and the second and subsequent transfers and separations are performed on the curled sheet 1, the sheet 1 that has passed through the transfer guide 3 as shown in FIG. The sheet 1 may end up along the surface of the photosensitive drum 7 on the transfer charger 5 and the separation charger 6 (Fig. 4 (At), or on the contrary, the sheet 1 may become separated from the surface of the photosensitive drum 7. (4th
(Illustrated)).

9 Problems to be Solved by the Invention By the way, in the conventional apparatus described above, when the sheet 1 is about to separate from the photosensitive drum 7 (see FIG.
B)) The sheet 1 is easily separated from the photosensitive drum 7. However, when the sheet 1 is in a state along the photosensitive drum 7 (FIG. 4 CAI), it is extremely difficult to reliably separate the sheet 1 from the photosensitive drum 7, and the conveyance of the sheet 1 becomes difficult due to poor separation of the sheet 1. If this is not done significantly, there is a risk that the current situation will occur frequently.

(b) Means for Solving the Problem The present invention is aimed at solving the above-mentioned problem, and is to transfer the toner image once to the same side or the back side of the sheet onto which the toner image has been transferred and fixed at least once. In the image forming apparatus having the function of transferring and fixing toner images as described above,
After completing the first fixing process and before starting the second transfer process, the sheet is passed between the pressure contact surfaces of a metal roller and an elastic roller. .

) Effect Based on the above configuration, the rate at which the first fixing is completed is set to 2.
Before starting the subsequent transfer process, the sheet passes between the pressurized contact surfaces of a metal roller and an elastic roller, and as a result, the sheet is curled so that it tends to move away from the photosensitive drum, and is always stable. Then, the second and subsequent transfers and separations can be performed.

(F) Embodiment Hereinafter, an embodiment in which the present invention is applied to a curling device for an electrophotographic apparatus having automatic double-sided copying and automatic multiple copying functions will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the curling device for an electrophotographic apparatus has a photosensitive drum 7 with a developing device 9 arranged adjacently around the periphery, and below the photosensitive drum 7 is a transfer charger 5, Separation zone? Eight vessels 6 are arranged adjacent to each other. A fixing device 2 is installed downstream of the separation charger 6 via a sea hts feeding belt 10 . On the other hand, on the upstream side of the photosensitive drum 7, a conveyance roller 11 and a transfer guide 3 that convey the sheet 1 separated and fed from a sheet stacking table (not shown) are installed.

Here, the latent image formed on the photosensitive drum 7 is
The toner image is visualized and a toner image is formed on the photosensitive drum 7. Further, the sheet 1 conveyed via the conveyance roller 11 and the transfer guide 3 is brought into close contact with the surface of the photosensitive drum 7 on which the toner image is formed, and the toner image is transferred by the transfer device 5 . Then, the transferred sheet 1 is
is separated from the photosensitive drum 7, passes through the sheet conveying belt 10, and is fixed by the fixing member N2, thus completing the first copy. A first flapper 12 is disposed downstream of WW2, and when copying has already been completed, the sheet 1 is guided in the direction of arrow A and ejected from the machine. , in the case of multiple copying or double-sided copying, the sheets 1-1 are distributed in the direction of arrow B. A second flapper 13 is disposed downstream of the first flapper 12, and in the case of multiple copying, the sheet 1 is guided in the direction of arrow C by the second flapper 13, and the sheet 1 is guided as it is in the direction of the arrow C, and the intermediate layer 15 is
In the case of double-sided copying, the sheet 1 is guided in the direction indicated by the arrow, reversed on the reversing tray 16, and then sent in the direction indicated by the arrow E and stacked on the intermediate tray 15. In this way, the rate 1 loaded on the intermediate tray 15 is transported by the pickup roller 17 arranged below the tip of the intermediate tray 15, the lower refeed roller 19 rotating in the direction of arrow F, and the lower refeed roller. 19 and a refeeding upper roller 20 rotating in the opposite direction (direction of arrow G), the sheets are separated one by one and sent to curling rollers 21 and 22 disposed downstream. A conveyance guide 23 is provided between the curling rollers 21 and 22 and the conveyance roller 11, and the sheet 1 that has passed through the curling rollers 21 and 22 passes through the conveyance guide 23, the conveyance roller 11, and the transfer guide 3, and then is transferred to the conveyance guide 23, the conveyance roller 11, and the transfer guide 3. Second transcription, separation,
Be led to the establishment process.

In this embodiment, the curling rollers 21 and 22 are in a state in which an upper roller 21 made of a rigid body such as metal and a lower roller 22 made of a rubber elastic body with a rubber hardness of 40 degrees or less are brought into pressure contact. The upper roller 21 is rotated in the direction of arrow H and the lower roller 22 is rotated in the direction of arrow J by the driving force of a motor or the like.

With this configuration, as shown in FIG. 2, the lower roller 22 made of an elastic body is deformed, creating a nip between the pressure contact surfaces. When the sheet 1 passes through this nip, the sheet 1 is forcibly curled along the curved surface of the nip. This curl is the second transfer and separation process,
As shown in FIG. 4 CB+, the elastic roller 22 is positioned on the sheet transfer surface so that the sheet 1 is in the opposite direction to the curved surface of the photosensitive drum 7, that is, in a state where it is about to move away from the photosensitive drum 7. It is arranged so that In this way, before the second transfer and separation process, the sheet 1, which has been given a curved surface in the opposite direction to the curved surface of the photosensitive drum 7, can be easily and stably separated from the photosensitive drum 1. It becomes possible.

In this embodiment, an apparatus that performs the transfer and fixing processes up to two times has been described, but the same effect can be obtained for an apparatus that performs the transfer and fixing processes two or more times.

Since the present embodiment has the above-described configuration, the sheet 1, which has been conveyed through the conveyance roller 11 and the transfer guide 3, is transferred to the surface of the photosensitive drum 7 on which the 1-toner image is formed by the imager 9. They are brought into close contact and the toner image is transferred by the transfer device 5. Then, by the separation charger 6, the transferred sheet)・1
For example, the sheet is separated from the photosensitive drum 7, passes through the sheet conveyance belt 10, and is fixed by the fixing device 2, and the first copying is completed. Next, the sheet 1 is guided in the direction of the arrow B by the first flapper 12, and further guided in the direction of the arrow C by the second flapper 13 in the case of multiple copying, and stacked on the intermediate tray 15 as it is. In the case of double-sided copying, the sheet 1 is guided in the direction of the arrow, reversed on the reversing tray 16, and then sent in the direction of the arrow E and stacked on the intermediate tray 15. The sheets 1 stacked on the intermediate tray 15 in this manner are separated and fed one by one by a pickup roller 17 and refeeding upper and lower rollers 19 and 20, and are conveyed to curling rollers 21 and 22. Curling roller 2
1 and 22 are upper rollers 21 formed of a rigid body made of gold R;
Since the lower rollers 2, 2 formed of a rubber elastic body with a rubber hardness of 406 or less are placed in pressure contact with each other, the lower roller 22 formed of an elastic body is deformed and the pressure is applied between the contact surfaces. A nip is occurring. As the sheet 1 passes through this nip, the rate 1 is forcibly curled along the curved surface of the nip, and this curl is such that the sheet 1 is oriented in the opposite direction to the curved surface of the photosensitive drum 7 It is attached so that it tends to separate from the photosensitive drum 7. The sheet 1 curled in this way is transferred to the conveyance guide 23,
After passing through the conveyance roller 11 and the transfer guide 3, the photosensitive drum 7 is brought into close contact with the surface of the photosensitive drum 7 for the second transfer, and then separated by the separation charger 6, the rate 1 is curled as described above. Since the sheet 1-1 is curled so as to be separated from the photosensitive drum 7 by the rollers 21 and 22, the sheet 1-1 can always be stably separated from the photosensitive drum 7 with ease.

(g) As described in detail, according to the present invention, when a sheet completes the first fixing process and enters the second and subsequent transfer processes, the sheet is pressed by a metal roller and an elastic roller. The sheet is passed between the contact surfaces, and the sheet is curled in such a way that it tends to move away from the photosensitive drum, so although it has a simple structure, it is always stable regardless of the state of the sheet after the second time. Be able to perform the second and subsequent transfers and separations.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view showing an embodiment of a curling device for an electrophotographic device; Fig. 2 is an enlarged explanatory view of the main part of Fig. 1;
Figure (5) is an explanatory diagram of a conventional sheet that is curled upward by a fixing device, Figure 3 (β) is an explanatory diagram of a conventional sheet that is curled downward by a fuser, and Figure 4 (
3) is an explanatory diagram of a conventional sheet having a curl in the direction along the photosensitive drum, and FIG. 1. Sheet, 2. Fixing device, 5. Transfer charger, 6 Separation band Ti device, 7 Photosensitive drum
, 15 - Intermediate tray, 16 - Inversion) - Ray, 21 - Metal roller, 22 Elastic roller.

Claims (1)

[Claims] (1) In an image forming apparatus having a photosensitive drum and having a function of transferring a toner image once with the photosensitive drum and then transferring and fixing the toner image at least once or more on the same side or the back side of the fixed sheet. , a pressure contact surface consisting of a metal roller and an elastic roller is interposed in the conveyance path for conveying the sheet after the first fixing process to the second and subsequent transfer steps, and the elastic roller A curling device for an image forming apparatus, characterized in that the curling device is configured to pass between the pressure contact surfaces so as to be positioned on the transfer surface for the second and subsequent times.