JP3082976B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and an electrophotographic printer, and more particularly, to an image forming apparatus having double-sided or multiple functions.

[0002]

2. Description of the Related Art In recent years, multifunctional image forming apparatuses have been developed,
Those with double-sided or multiplex functions are widely used.

For example, when an image is formed on both sides of one sheet, an image is first formed on one side of the sheet, and the designated number is stored in an intermediate tray in the image forming apparatus.

[0004] The sheets stored in the intermediate tray are separated one by one and re-fed, and an image is formed on the back surface of the sheets.

[0005]

However, at the time of re-feeding, the image may be rubbed and the sheet edge may be stained.

Particularly, in the case of a configuration in which sheets are re-fed in order from the bottom sheet stored in the intermediate tray, sheets can be re-fed before storage of a specified number of sheets is completed, so that the speed is increased. However, since the sheet is fed from the bottom sheet, the sheet bundle on the fed sheet always enters the separation unit and is separated, and the fed sheet is moved upward by the separation unit Z. The sheet is rubbed and conveyed (FIG. 8). For this reason, in the case of the double-sided mode, since the sheet stored in the intermediate tray has the image forming surface on the upper surface, the toner 52 forming the image of the sheet 51 fed by the sheet re-feeding unit is in the range of 52 a ( The upper sheet 53 is rubbed and conveyed by a shaded portion).
4 occurs.

When a release liquid is applied to the fixing roller to prevent offset, the friction coefficient between the sheets is small because the release liquid is absorbed by the sheets.

However, as shown in FIG. 9, the width A of supplying oil to the fixing roller 61 by the oil supply means 62 is equal to or larger than the width of the maximum sheet S that can be passed through the image forming apparatus. Will increase.

[0009]

According to the present invention, there is provided an image forming means for forming an unfixed image on a recording material, and a recording material carrying the unfixed image formed by the image forming means. A fixing rotator for contacting the surface opposite to the surface carrying the unfixed image and fixing the unfixed image on the recording material; and a recording material on which the unfixed image is fixed by the fixing rotator. A storage unit for storing a recording material for forming an image again, a separating rotator separating the recording material stored in the storage unit one by one, and an application unit for applying a release agent to the fixing rotator In the image forming apparatus having the above, the coating unit is substantially equal to the width of the separation rotating body whose coating width is smaller than the fixing area, and is located at the position of the fixing rotating body corresponding to the position of the separation rotating body in the width direction. Characterized by applying a release agent A.

[0010]

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention.

The image forming apparatus of the present embodiment is capable of a duplex mode for forming images on both sides of a recording material sheet and a multiplex mode for forming images on one side a plurality of times.

Reference numeral 1 denotes an image forming apparatus main body. In the case of double-sided copying, an image forming unit 3 forms an image on a sheet fed by a sheet feeding unit 2 by a known electrophotographic method. After being heated and pressurized and fixed by the fixing device 4, the toner is conveyed to the intermediate tray 6 with the flapper 5 facing upward, and is stacked. Then, the sheets stacked on the intermediate tray are separated and conveyed one by one in order from the bottom by the sheet re-feeding unit 7, and the image forming unit 3 forms an image on the back surface of the sheet.

FIGS. 2 and 3 are sectional views of the sheet re-feeding means 7 for re-feeding sheets from the intermediate tray, and FIG. 4 is a side view of the same.

The re-feeding means 7 comprises a transport roller 21, a feed roller 22, and a separation roller 23. The transport roller 21 has a function of feeding the lowermost sheet stacked on the intermediate tray 6 and feeding the sheet to the pair of separation rollers 22 and 23. The separation roller 23 is a pressing means (not shown),
Pressurizes the paper feed roller 22 with the separation roller shaft 24.
Is driven in a direction to return the sheet via a torque limiter 26 with the driving unit. Torque limiter 26
Is a magnetic body 26 that connects the torque limiter shaft 25 and the body 26a.
b, the torque applied to the trunk 26a is less than a predetermined value T, the trunk 26a and the torque limiter shaft 25 rotate together, and the torque is reduced to a predetermined value T.
Is exceeded, the body 26a rotates independently with respect to the torque limiter shaft 25.
Is connected to the body 26a of the torque limiter 26 by a coupling 27. Here, the paper feed roller 22
The coefficient of friction between the surface of the separation roller 23 and the sheet is μ1, the coefficient of friction between the sheets is μ2, the radius of the sheet feeding roller 22 and the separation roller 23 is R, and a sheet bundle existing on the sheet to be fed. Μ1> μ2, T / μ1
If F and T are determined so that / R + μ2 / μ1 <F <T / μ2 / R-2, when one sheet enters the separation unit, the separation roller rotates in the sheet conveyance direction (FIG. 2). When two sheets are inserted, the second sheet can be returned by rotating the separation roller in the driving direction, thereby preventing double feeding of the sheets (FIG. 3).

FIG. 5 is an enlarged sectional view of the fixing device 4, and FIG. 6 is a side view of the same.

The fixing device 4 includes a fixing nip 18 formed by an upper fixing roller 11 and a lower fixing roller 12 having a heater H therein.
To form

The recording material sheet conveyed with the unfixed toner image on the side of the upper fixing roller is heated and pressurized and fixed when the recording material sheet is nipped and conveyed by the fixing nip 18.

An oil holding container 14 is attached to the fixing bottom plate 13 and contains a release oil 17 made of silicone oil. An oil-applied felt 15 immersed in oil is attached to the oil holding container 14 by a felt mounting plate 19, and is in contact with the lower fixing roller 12 by a leaf spring 16.

FIG. 7 shows the relationship between the width of the oil-applied felt 15 and the width of the paper feed / separation roller.

As shown in this figure, the oil application width is smaller than the maximum paper passing area A which is a fixing area.
The separation rollers 22 and 23 are provided so as to be substantially equal to the width X.

For this reason, the oil applied to the lower fixing roller 12 by the oil application felt 15 is applied to the sheet passing through the fixing nip 18, and the paper is fed and separated by the separation rollers 22 and 2.
With a width X of 3, the coefficient of friction between sheets is reduced.

The release liquid is applied to the sheet by a heating and high-temperature fixing rotating body in a heated state.

For this reason, since the release liquid has a low viscosity due to heat, a high-viscosity release liquid with little volatilization can be used.

Incidentally, the image forming means of the present invention is not limited to the above-described electrophotographic method, but may employ an electrostatic recording method or other methods.

[0025]

As described above, according to the present invention, it is possible to prevent the recording material from being stained due to re-feeding in the double-sided or multiple image forming mode with a small consumption of the release liquid.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a sheet re-feeding unit.

FIG. 3 is a sectional view of a sheet re-feeding unit.

FIG. 4 is a side view of the sheet re-feeding unit.

FIG. 5 is a sectional view of the fixing device.

FIG. 6 is a side view of the fixing device.

FIG. 7 is a diagram illustrating a relationship between a coating area of a release liquid and a separation rotating body.

FIG. 8 is a view for explaining contamination of a recording material.

FIG. 9 is a perspective view of an example of a fixing device including a release liquid applying unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 4 Fixing device 11 Fixing upper roller 12 Fixing lower roller 14 Oil holding container 15 Oil application felt

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/20

Claims (2)

(57) [Claims] 1. An image forming means for forming an unfixed image on a recording material, and a surface of the recording material carrying the unfixed image formed by the image forming means opposite to a surface carrying the unfixed image. A fixing rotator for fixing an unfixed image on a recording material by contacting the recording material, and a storage unit for storing the recording material for forming an image again on the recording material on which the unfixed image is fixed by the fixing rotator. An image forming apparatus comprising: a separating rotator configured to separate recording materials stored in the storage unit one by one; and an application unit configured to apply a release agent to the fixing rotator. An image forming apparatus, wherein a release agent is applied to a position of the fixing rotator having a width substantially equal to a width of the separation rotator smaller than a fixing area and corresponding to a position of the separation rotator in the width direction. . 2. The image forming apparatus according to claim 1, wherein a recording material is stacked on the storage section with an image surface facing upward, and the separation rotating member is sequentially separated from a lower recording material.