JPH0769507A - Curved paper correcting device - Google Patents

Abstract

PURPOSE:To correct paper curving at the time of fixing by forming one of a pair of conveyance guide plates, which guides the non-fixing surface side of paper, out of a plate material with high thermal conductivity, and thermally- linking the plate with a heating roller. CONSTITUTION:A fixer 1 consisting of a heating roller 2 and a pressure roller 3 is provided, and a pair of conveyance guide plates 12, 13 for guiding paper S to be discharged from the fixer 1 is mounted. Of the conveyance guide plates 12, 13, the conveyance guide plate 13 for guiding the non-fixing surface side of paper S is formed out of a metal plate with high thermal conductivity, such as an iron plate, and a part of the plate is secured onto a metal frame 22 of the fixer 1. With this constitution, while moisture contained in the paper S is dried by the heating roller 2 on the fixing surface side of the paper at the time of fixing, and the paper S is curved so as to be wound around the heating roller 2, moisture contained in the paper S is dried after fixing by heat of the conveyance guide plate 13 from the lower side. It is thus possible to correct paper curving in a direction where the paper is wound around the heating roller 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet curving correction device for correcting curving of a sheet that occurs during fixing in an electrophotographic apparatus.

[0002]

2. Description of the Related Art First, FIG. 4 shows a conventional example. Reference numeral 1 is a fixing device. This fixing device 1 includes a heating roller 2 having a built-in heater and a pressure roller 3 pressed against the heating roller 2.
And the peeling claw 4 that contacts the outer periphery of the heating roller 2. A paper discharge tray 5 is arranged above the fixing device 1. Although not shown, a transfer device for transferring the toner image formed on the photoconductor to the paper S is provided on the upstream side of the fixing device 1. Further, a pair of conveyance guide plates 6 and 7 for conveying the sheet S fixed by the fixing device 1 is provided, and a curved paper discharge passage 8 that connects between these conveyance guide plates 6 and 7 and the paper discharge tray 5. Is provided. A discharge roller 9 and a pinch roller 10 are provided in contact with each other at both ends of the curved discharge path 8.

Further, the paper S is provided on the inner surfaces of the transport guide plates 6 and 7.
A plurality of ribs 11 are formed along the width direction of the. FIG. 5 is a vertical sectional side view of the line AA in FIG. 4, in which the transport guide plates 6 and 7 are flat plates, and the ribs 11 have a uniform protruding height.

[0004]

The sheet S on which the toner image on the photoconductor has been transferred by the transfer unit is fixed by the fixing unit 1 and is ejected by the conveyance guide plates 6 and 7 and the curved ejection passage 8. You will be guided to 5. On the other hand, the paper S absorbs moisture contained in the outside air. When the sheet S containing moisture is fixed, the sheet S is dried by the heating roller 2 and is discharged while being curved so as to wind around the heating roller 2.

[0005]

According to the present invention, a fixing device including a heating roller and a pressure roller pressed against the heating roller is provided, and the fixing device is opposed to the fixing roller with a predetermined gap and is discharged from the fixing device. A pair of conveyance guide plates for guiding the sheet is provided, and among these conveyance guide plates, the conveyance guide plate for guiding the non-fixing surface side of the sheet is formed by a plate material having high thermal conductivity, and heat is applied to the heating roller. Linked together.

[0006]

When the fixing is performed, the fixing surface side of the sheet is dried by the heating roller so that the sheet bends toward the heating roller side. However, after fixing, the non-fixing side of the sheet is dried by the conveyance guide plate so that the sheet moves in the opposite direction. Returned to. Therefore, it is possible to correct the curl of the paper at the time of fixing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. The same parts as those in the conventional example described in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be omitted. A pair of conveyance guide plates 12, 1 for guiding the sheet S fixed by the fixing device 1.
3 is provided, and a curved paper discharge passage 14 that connects these conveyance guide plates 12 and 13 and the paper discharge receiver 5 is provided. The curved paper discharge passage 14 is formed by facing a pair of paper discharge guide plates 15 and 16 curved upward in a U shape with a predetermined gap therebetween. In this embodiment, in order to bend the curved paper discharge passage 14 into a U-shape, the paper discharge guide plate 1
Curved surfaces 15a and 16a whose radial centers are located inward (on the side of the fixing device 1) are formed in the lower portions of the reference numerals 5 and 16, flat surfaces 15b and 16b are formed in the middle portions, and inward are formed in the upper portions. Curved surfaces 15c and 16c whose center of radius is located are formed in the. A discharge roller 9 and a pinch roller 10 are provided in contact with each other at both ends of the curved discharge passage 14.

A plurality of ribs 17 and 18 are formed on the opposing surfaces of the transport guide plates 12 and 13 along the transport direction of the sheet S. As shown in FIG. 2, the protruding height of the rib 17 of the upper conveyance guide plate 12 is set to have the lowest central portion and gradually increase toward both sides. The protruding height of the rib 18 of the lower conveyance guide plate 13 is set to be the highest in the central portion and gradually lower toward both sides.
The spherical surfaces connecting the protruding ends of the ribs 17 and 18 are curved paper guide surfaces 19 and 20, respectively.
That is, these paper guide surfaces 19 and 20 are curved so that the pressure roller 3 side is concave with respect to the tangential direction at the contact portion between the heating roller 2 and the pressure roller 3 in the transport direction of the paper S. In addition, the pressure roller side 3 is curved so as to be concave in the width direction of the sheet S. The degree of curvature is 1 to 2 when converted into the difference in protrusion height between the ribs 17 and 18 at the central portion and the ribs 17 and 18 at the outermost portion.
It is specified in mm. The gap between the paper guide surfaces 19 and 20 is set to 1.2 to 2 mm.

Then, a conveyance guide plate 12 for guiding the fixing surface side surface (upper surface) of the sheet S fixed by the fixing device 1.
Is made of heat-resistant synthetic resin. FIG. 3 is a plan view of the conveyance guide plate 12, and as is clear from this figure,
The transport guide plate 12 is formed with a plurality of holes 21 located between the ribs 17. The transport guide plate 13 that guides the surface (lower surface) of the paper S on the non-fixing surface side is formed of a metal plate having a high thermal conductivity such as an iron plate, and a part thereof is a metal frame 22 of the fixing device 1. Held in.

Further, at the end of the curved paper discharge passage 14 on the inlet side of the paper discharge receiver 5, the curved paper discharge passage 14 is curved in a direction opposite to the curved direction of the curved surfaces 15a, 15c, 16a, 16c. Curved surfaces 23 and 24 are formed.

In such a structure, the heating roller 2 is maintained at a temperature of about 180 ° C. The conveyance guide plate 13 having high thermal conductivity is heated by the radiation from the heating roller 2. The frame 22 is also heated by the radiation from the heating roller 2, and the heat is also conducted to the conveyance guide plate 13. Therefore, the transport guide plate 13 is heated to a temperature of about 90 ° C.

At the time of fixing, since the moisture contained in the paper S is dried by the heating roller 2 on the fixing surface side, the paper S is curved so as to wind around the heating roller 2 side. Since the contained moisture is dried from the lower surface by the heat of the transport guide plate 13, the habit of curving in the winding direction of the heating roller 2 is corrected. At this time, due to the heat of the transport guide plate 13, the moisture contained in the paper S is prevented from being absorbed in the upper transport guide plate 1.
Since it escapes from the second hole 21, the warp of the paper S can be corrected more effectively.

Further, since the unused sheets S are generally laminated, the entire surface of the outermost sheet S is exposed to the outside air, while the sheets S laminated inward are exposed to the outside atmosphere. Therefore, the outermost sheet S absorbs the moisture contained in the outside air over the entire surface, but the sheet S laminated on the inner side absorbs the moisture in the peripheral portion, and the moisture is absorbed in the central portion of the sheet S by the capillary phenomenon. Will be absorbed sequentially. That is, the paper S is more likely to be moistened in the peripheral portion than in the central portion. In such a case, at the time of fixing, the peripheral portion of the paper S is particularly likely to be curved toward the heating roller 2 side. That is, the paper S may have a curl not only in the transport direction but also in the width direction.

However, according to this embodiment, the opposing surfaces of the transport guide plates 12 and 13 are tangential to the contact direction between the heating roller 2 and the pressure roller 3 with respect to the transport direction of the sheet S. The paper guide surfaces 19 and 2 are curved so that the pressure roller 3 side is concave and the pressure roller side 3 is also concave in the width direction of the paper S.
Since 0 is formed, in the process of guiding the sheet S separated from the heating roller 2 by the separating claw 4 immediately after fixing by the sheet guide surfaces 19 and 20 while the temperature does not decrease,
The sheet S can be effectively curved in the conveying direction and the sheet width direction in reverse. As a result, it is possible to effectively correct even the curving habit formed around the paper S. By curving the two transport guide plates 12 and 13 that do not have the ribs 17 and 18, the same effect can be obtained even if curved paper guide surfaces are formed on the surfaces facing each other.

In the fixing device 1, the image on the upper surface of the paper S is fixed, and the paper S is reversed by the curved paper discharge passage 14 and stacked on the paper discharge tray 5 in the page order with the printing surface facing down. Here, in the case of high-temperature fixing, even if the curving at the time of fixing is corrected by the heating action of the thermally conductive conveyance guide plate 13 and the curving action of the sheet guide surfaces 19 and 20, the sheet S is not cooled before the temperature decreases. May be bent again because it is reversed by the curved paper discharge passage 14, but by curving its curl in the opposite direction by the curved surfaces 23 and 24, the paper S curved in the curved paper discharge passage 14 may be deformed. The curved surfaces 23 and 24 can be straightened.

[0016]

According to the present invention, a pair of conveyance guide plates are provided which face each other with a predetermined gap therebetween and guide the paper discharged from the fixing device. Of these conveyance guide plates, the non-fixing surface side of the paper is provided. Since the transport guide plate that guides the surface is formed of a plate material with high thermal conductivity and is thermally connected to the heating roller of the fixing device, the fixing surface side of the paper is dried by the heating roller during fixing, so the paper is heated. Although it is curved to the roller side, after fixing, the non-fixing surface side of the paper is dried by the conveyance guide plate, so that the paper is returned in the opposite direction. Therefore, the curl of the paper at the time of fixing can be corrected. Moreover, since the heat-conducting conveyance guide plate can be heated by the heating roller of the fixing device, the structure for correcting the curl of the paper can be simplified.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a BB line portion in FIG.

FIG. 3 is a plan view of an upper conveyance guide plate.

FIG. 4 is a front view showing a conventional example.

5 is a vertical cross-sectional side view taken along the line AA in FIG.

[Explanation of symbols]

 1 fixing device 2 heating roller 3 pressure roller 12, 13 conveyance guide plate

Claims (1)

[Claims] 1. A pair of conveyance guides provided with a fixing device composed of a heating roller and a pressure roller pressed against the heating roller, facing each other with a predetermined gap and guiding the paper discharged from the fixing device. Characterized in that a plate is provided, and a conveyance guide plate for guiding the non-fixing surface side of the paper among these conveyance guide plates is formed of a plate material having high thermal conductivity and thermally connected to the heating roller. Paper curl correction device.