JPS61279880A - Image forming device - Google Patents

Abstract

PURPOSE:To correct the curl of a fixing sheet by a simple device by fixing an image on the sheet by a fixing unit, carrying the sheet to the upper part of the fixing unit through a curved carrier and then curving the sheet in the reverse direction to the curved curl. CONSTITUTION:A sheet 1 is carried to a press-contact part between a photosensi tive body 6 and a transferring electric charger 7 and an image is transferred to the sheet. Then, the sheet 1 is carried to the fixing unit to fix the image. The sheet is heated between a metallic roller including a heater 13-3 in it and an elastic roller 13-2 and water is evaporated from the sheet on the heating side, so that the sheet is curved like a projected curl. Then, the sheet is carried to the upper part of the metallic roller 13-1 through the curved carrier 21. The sheet is passed between a paper discharging roller 14 and a paper discharg ing roll 16, curved like a recessed shape by heated air applied from the lower part to correct the curl and carried to a paper discharging tray 15. Since the fixing sheet is carried to the upper part of the fixing unit and heated, the curl can be corrected without forming a specific device.

Description

[Detailed Description of the Invention] [Industrial Field of Application]: 1 The present invention relates to an image forming apparatus, specifically, for example, an electronic device.
．．゛｝I Heat setting of photocopiers, laser beam printers, etc.
This invention relates to an image forming apparatus having a printing device. [・:1.

[Prior art] i.i. Image forming unit 1' equipped with a fixing device using a heating roller: In the apparatus (Fig. 5), an image is fixed by a heating roller 3-1 and a pressure roller 3-2. Paper is common...
.

As shown in Figure 6, the paper is output in a curled state:
'vinegar,, ,
;,% In a commonly used heat fixing device, the inside of the paper is the heat roller 13-1 side and the pressure roller 1 side.
Because the heating temperature is different on the 3-2 side, the degree of evaporation of water on the paper surface is different, and the degree of shrinkage of the paper is also different.
Generally, a metal roller is used as the heat roller, and the pressure roller 13
-2 uses a rubber-like roller, so the pressure roller becomes concave at the part where it comes into contact with the heat roller, as shown in FIG. 4, and the sheet gets curly.

Therefore, conventionally, in order to reduce this paper curl, a seventh
As shown in the figure, immediately after the fixing roller there are a paper ejection roller 14, a paper ejection roller 16, and a paper ejection guide 19 for correcting curls.
However, it was not possible to completely eliminate curls.

Further, in the conventional image forming apparatus, a fan is provided above the fixing device for exhausting heat, resulting in a complicated configuration.

[Purpose of the invention]

The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and it is an object of the present invention to provide an image forming apparatus that is inexpensive and can reliably perform curl control, heat release, etc. with a simple configuration.

[Means for solving problems]

In order to achieve the above object, the image forming apparatus according to the present invention forms an image on a sheet Murakami using a process means for image formation, and heats the sheet material using an image fixing device to transfer the image onto the sheet material. An image forming apparatus that performs fixing includes: a conveyance section that curves and conveys a sheet material above the fixing device; and a conveyance path located downstream of the conveyance path that curves the sheet material in a direction opposite to the curvature. , characterized by having
: [Example] An example of the present invention is shown in FIGS. 1 and 2.

The paper l fed by one revolution of the paper feed roller 2 is temporarily stopped by the registration roller 3, and the unevenness in the advance of the interleaving paper, skew, etc. is corrected in the zero order.

When the registration rollers are turned on, they are transported toward the photoreceptor 6. On the other hand, a latent image is formed on the photoreceptor 6 in response to the signal of the laser beam 5 emitted from the scanner 4, and is developed by the developer 8. The image is then transferred to paper by a transfer process means.

The transferred paper is conveyed to the fixing device 13 through a conveyance guide 30 and a conveyance roller 31, passes through a fixing device entrance guide 13-4, and is sandwiched between a fixing heat roller 13-1 and a pressure roller 13-2. The image is fixed on the paper by the heat generated by the fixing heat roller 13-1 and the pressure generated by being sandwiched between the pressure rollers 13-2.

The paper exiting the fixing device becomes concavely curled, as shown in FIG. 6 above. This is because the water a lost on the side of the heat fixing roller 13-1 is more than the water lost on the side of the pressure roller 13-2, and also that the heat roller 13-1 and the pressure roller 13-2 are different from each other. This is due to the nip.

After fixing, the paper is transferred to this fixing heat roller 13-1 and pressure roller 1.
As a result of the rotation 3-2, the sheet is guided to the fixing device lower discharge guide 18, the fixing device upper discharge guide 17, the lower sheet discharge guide 20, and the upper sheet discharge guide 21, and is carried to the upper part of the fixing device and reversed. At this time, the surface heated and fixed by the fixing heat roller 13-1 faces downward, and the paper becomes convexly curled at this position (
Figure 2).

On the other hand, the heat generated by the fixing heat roller becomes an upward air current C together with the moisture evaporated from the paper, and the slit 2 of the fixing unit upper cover 22
2-1, passes through a hole (not shown) in the paper discharge lower guide 20, and hits the transfer paper (FIG. 2).

Also second. As shown in FIG. 3, a paper ejection roller 14 and a paper ejection roller tS (as shown in FIG. 3, pressed against the roller 14 by a spring 23) are arranged at the top of the fixing device, and the paper is The rotation of the paper ejection roller 14 creates a concave shape along the circumference, so the transfer paper that is exposed to the hot air generated by the fixing device is conveyed in the concave shape created by the paper ejection roller and the paper ejection roller. The curls are corrected and loaded onto the tray 15.

In this embodiment, the paper ejection roller 14 and the paper ejection roller 16 are arranged in the upper part of the fixing device where the hot air hits, and a recess is provided so that the paper path is reversely curled, and the hot air (rising air current) is applied thereto. Although it is configured.

Instead of the paper ejection roller and the paper ejection roller, a paper conveyance guide 30.
40 (FIG. 4), it may be concave (with curvature portions 30a, 40a) so as to form a reverse curl.

Further, the heat of the heat fixing device may be conducted using a guide plate, a roller, or the like.

Curl control also includes completely eliminating curls or causing curls in convenient directions.

〔Effect of the invention〕

As explained above, by providing a paper transport path above the heat fixing device and applying heat to the sheet material, it is possible to correct curls in the sheet material without adding any special equipment. effective.

[Brief explanation of the drawing]

1 is a front view of an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an enlarged perspective view of the main part of FIG. 1, FIG. 3 is a front view of a portion of FIG. 2, and FIG. FIG. 5 is a front view of another embodiment, FIG. 5 is a front view of a conventional example, and FIGS. 6 and 7 are front views illustrating how curling occurs during fixing. 1--paper, 2--paper feed roller, 3-m-registration roller, 4--11 scanner, 6--photosensitive member, 1
3-m constant fixer unit, 13-1--constant heat roller, 13-2--1 pressure roller, 13-3--heater, 14--1 paper discharge roller, 15--1 paper discharge 16--Paper discharge roller, 17--Constant applicator: Paper discharge upper guide, 18-Constant applicator paper discharge lower guide, :゛20--Paper discharge lower guide, 2
1--1 paper discharge upper guide, 22-m constant deposition device upper cover, 23-11 roller pressure spring,
′□ □

Claims (5)

[Claims] (1) In an image forming apparatus in which an image is formed on a sheet material by a process means for image formation, and the image is fixed on the sheet material by heating the sheet material by an image fixing device, above the fixing device. An image forming apparatus comprising: a conveyance section that conveys a sheet material in a curved manner; and a conveyance path located downstream of the conveyance path that causes the sheet material to be curved in a direction opposite to the curvature. (2) The image according to claim (1), wherein the reverse curved conveyance path is formed by one roller and at least two or more rollers or pressing members facing the roller. Forming device. (3) The image forming apparatus according to claim (1), wherein the reversely curved conveyance path is heated by conduction or radiant heat from the fixing device. (4) The image forming apparatus according to claim 2 or 3, wherein the roller is a discharge means for discharging the sheet material to the outside of the apparatus. (5) The image forming apparatus according to claim (1), wherein the reversely curved conveyance path is curl control means.