JPH01267255A - Curl correcting device - Google Patents

Abstract

PURPOSE:To prevent generation of poor quality image by forming the contact part of a curl correcting part with a sheet from a low friction member. CONSTITUTION:The central part of a sheet is curling convex upward with its leading and trailing edges facing down. The sheet is pinched and transported by a roller couple 8 and transported on a curved path P under guidance of guides 14, 15 and a curl correcting part 16. When the leading edge is pinched by another roller couple 11, the sheet is transported in tensioned condition between the roller couples 11, 8 because the transport speed of the roller couple 11 is greater than that of the roller couple 8, and it travels while in contact with the curl correcting part 16 and is squeezed in the direction opposite to the curling. Thus the curl is corrected. In this curl correcting part 16, a low friction layer 18 is formed on the surface of a shaft 17, so that the friction coefficient with the sheet moving in slide contact therewith is small, and there is no risk of stripping the toner fixed onto the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a curl correction device for correcting curls that occur on a sheet after toner has settled in an image forming apparatus such as a copying machine. .

(Prior Art) Generally, in an image forming apparatus that uses an electrophotographic copying process, toner transferred from an electrostatic latent image carrier to a sheet is heated and melted to be fixed on the sheet. has a tendency to curl on either the front or back side under the influence of heat from the fixing device.

Curling causes stacking failure or jamming when sheets are ejected onto a paper ejection tray. In addition, in an image forming apparatus equipped with an editing function such as double-sided copying or composite copying, which forms an image on one side of the sort and then forms the image again on the remaining side or the same, A shift occurs in the second image, resulting in poor image quality.

Therefore, conventionally, as a device for straightening curls,
There is one proposed in Japanese Patent No. 0-50547.

This curl correction device is arranged between a pair of fixing rollers and a pair of paper ejection rollers that discharge a sheet fed out from the pair of fixing rollers, and the sheet is fed out from the pair of fixing rollers with respect to a line connecting the nip position of both roller pairs. A bending path protruding in the opposite direction to the curl direction of the sheet is provided, and the sheet being conveyed under tension between the main fixing roller pair and the paper ejection roller pair is squeezed and straightened from the opposite direction to the curl direction. It's Shino.

(Problem to be solved by the invention) However, the curl direction of sorting depends on the nature of the sheet (
For example, the direction of curl of a sheet discharged from an image forming apparatus is not always constant because it is determined by various factors such as basis weight), fixing temperature, and conveyance speed.

For this reason, in the curl correction device, the toner correction section may come into pressure contact with the surface of the sheet onto which the toner has been transferred, and depending on the bending angle of the curl correction section, the toner is scraped and the image is disturbed, resulting in poor image quality. This had the problem of inviting defects.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and therefore,
An explanation will be given with reference to the attached drawings showing one embodiment. A sheet on which toner is heated and fixed is transferred between two roller pairs (8) and (t).
1) is used to transport the sheet in a tensioned state, and a curl correction unit (16) is brought into pressure contact with the sheet being transported in the tensioned state, thereby straightening the sheet while bending it in the opposite direction to the curl direction. In the apparatus, the contact part of the curl correction part (16) with the sort is made of a low friction material, such as Teflon.

(Example) The present invention will be described below with reference to the accompanying drawings.

1 and 2 show a curl straightening device and a fixing device according to the present invention, in which (1) is a curl straightening device, (20) is a curl straightening device, and (20) is a curl straightening device.
is the fixing device.

As shown in Figure 1, the housing (2) of the curl straightening device (1) roughly consists of a cover (3) and a lower cover (4).
Opening guide portions (6) and (7) are formed on the upstream and downstream side walls in the sorting and conveyance direction, respectively.

Inside the housing (2) there is an open [ ] guide part (6).
, (7), roller pairs (8) and (l I) each consisting of a pair of parallel rollers that press against each other are arranged.

The roller pair (8) is composed of rollers (9) and (10), and the roller pair (11) is composed of rollers (12) and (13).
The roller pair (11) or the roller pair (
8) Set the conveyance speed fast from the upstream.

Guides (14) and (15) are disposed between the two roller pairs (8) and (lI), and a downwardly bent curved line extending from the roller pairs (8) to (11) is disposed between the two roller pairs (8) and (11). Curved route (P
) is formed, and the upper guide (14) has a substantially central portion expanded upward to form a housing portion (14a), in which a curl correction portion (16) is disposed.

This curl correction part (16) is made of Teflon or the like and is attached around a conductive shaft (17) rotatably provided on the side walls (5), (5) on the back side of the housing (2). Friction layer (
18), so as shown in Figure 2, the shaft (1
7) is in contact with a pair of electric hGs (19), (19) at both ends thereof.

In the fixing device (20), opening guide portions (22) and (2) are provided on the upstream and downstream side walls of the housing (21), respectively.
3) is formed. Moreover, roller pairs (24) and (29) are arranged in the housing (21) at the sides of the opening guide parts (22) and (23), respectively.

The roller pair (24) is a pair of parallel rollers (25,).

(28), both of which are pressed against each other and rotated in the direction of the arrow by driving means (not shown), and the upper roller (26) has a built-in heater (26) as a heating means. , a temperature detection sensor (
27) is the contact.

Another pair of rollers (29) is a pair of parallel rollers (
30) and (31), which are pressed against each other and rotated in the direction of the arrow by respective driving means (not shown).

Guide plates (32) and (33) are provided between these roller pairs (24) and (29).

The operations of the curl correction device (1) and fixing device (20) having the above configuration will be explained.

The sheet with a white toner image on its upper surface is conveyed from the left side in FIG. 1 along the dotted line, and is fed into the housing (21) of the fixing device (20) through the open log gate section (22), where it is connected to the roller pair. When the toner is held and conveyed at (24), the toner is melted and fixed by the heat of the heater (26).

When conveyed between the roller pair (24), heat applied from the heater (26) also causes the roller (25
) and (27), the sheet curls with its leading and trailing ends facing upward or downward, respectively.

The direction in which the sheet curls varies depending on the type of sheet, etc., but in this embodiment, the sheet is curled with its leading and trailing ends facing downward and its central portion convex upward.

Next, the sheet is conveyed to the right along the dotted line while being guided by the guide plates (32) and (33), and is conveyed to the right by the roller pair (29).
) through the opening guide part (23) to the fixing device (20).
is discharged from.

Subsequently, the sheet is conveyed into the housing (2) via the opening guide part (6), conveyed between the roller pairs (8), and fed out between the guides (14) and (15).
The paper is conveyed along the curved path (P) while being guided by the guides (+4), (15) and the curl correction section (16).

When the tip is clamped by the roller pair (11), the conveying speed of the roller pair (2) is greater than that of the roller pair (8), so the roller pair (11) (8), the sheet is conveyed under tension, and the sheet under tension is conveyed between roller pairs (8) and (11).
The curl correction part (I9) moves between the curl correction parts (I9) and is squeezed in a direction opposite to the curl direction, thereby correcting the curl.

In addition, when the tensile force exceeds a predetermined value, the roller (13)
This prevents damage to the seat due to slipping between the seat and the seat.

In addition, in the curl correction section (16), the surface of the shaft (I7) is coated with a low-friction layer (18), so the coefficient of friction with the sheet moving while sliding thereon is small, and the surface of the shaft (I7) is coated with a low friction layer (18). There is no need to scrape off the existing toner.

Furthermore, the shaft (I
A current is applied to 7) through the electrode plates (19), (19), which generate heat and transfer the heat to the sheet, thereby further enhancing the curl correction effect.

In the above embodiment, a case where a curled sheet is corrected with the leading edge and trailing edge of the sheet pointing downward is shown, but depending on the type of sheet, the conditions of the fixing device (20), etc., curling may occur in the opposite direction. In this case, an upwardly curved inflection path is formed between the roller pairs (8) to (11), and the curl correction section (16) is brought into contact with the lower surface of the sheet.

Further, in the embodiment described above, the conveying speed of the roller pair (8) and (11) is fixed, but it may be possible to adjust these speeds.

(Effects of the Invention) As is clear from the above description, the curl straightening device according to the present invention straightens the curl by squeezing the sheet conveyed under tension between two sets of rollers in the curl straightening section. In this method, a low friction layer is formed on the surface of the contact portion of the curl correction portion with the sheet, so that the sheet passes through this layer with little resistance.

Therefore, even if the curl correction section comes into contact with the toner-adhering surface of the sheet, the toner is not disturbed by the curl correction section, and a beautiful image can be obtained.

[Brief explanation of the drawing]

1.2 shows a curl straightening device and a fixing device, FIG. 1 is a sectional view, and FIG. 2 is a perspective view. l... Curl correction device, 2... Housing,
5... Side wall, 8, 11... Roller pair, 9
．． 10, 12.13... Roller, 14, 1.4... Guide, 16... Curl correction part, 17... Shaft, 18... Low friction layer, I9... Electrode plate, 20 ...Fixing device. Patent applicant Minolta Camera Co., Ltd. agent Patent attorney Maeda Ao and one other person

Claims (1)

[Claims] (1) The sheet on which the toner has been heated and fixed is conveyed in a tensioned state using two pairs of rollers, and a curl correction unit is brought into pressure contact with the sheet being conveyed in the tensioned state, so that the sheet is aligned in the curl direction. A curl straightening device that corrects curling while bending in the opposite direction, characterized in that a contact portion of the curl straightening portion that contacts the sheet is formed of a low-friction member.