JP2003098775A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus improved so that recording material can be stably carried when it rushes in a fixing means. SOLUTION: This image forming apparatus having a carrying stage where the recording material is carried in a state where the trailing edge of the precedent recording material and the leading edge of the following recording material are overlapped is provided with a reversing means for reversing the positional relation of the overlapped part of the recording material between an electrophotographic sensitive drum and the fixing means.

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 for forming an image on a recording material.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, recording materials are conveyed so as to overlap each other even a little (hereinafter, referred to as double feeding).
It was not a configuration that allowed the state.

Therefore, in a conventional sheet feeding device, a configuration as shown in FIG. 7 has been adopted as a configuration in which double feeding is unlikely to occur. When continuous feeding is performed in such a sheet feeding device, the electromagnetic clutch 213 is carried out at a certain timing immediately before the sheet feeding roller 205 conveys the recording material and the rear end thereof passes through the nip between the sheet feeding roller 205 and the retard roller 204.
Is turned off, the drive input of the paper feed roller shaft is cut off, and thereafter, a roller pair (hereinafter referred to as a pull-out roller) immediately downstream of the nip between the paper feed roller 205 and the retard roller 204 2
Many of them controlled to pull out at 06.

As described above, since the image forming apparatus is configured not to accept the sheet feeding in the double feeding state, the sheet feeding apparatus connected to the image forming apparatus is suitable as the sheet feeding apparatus which does not cause the double feeding. It was developed to provide the necessary conditions.

By the way, in order to meet the recent demand for higher speed, not only the recording material conveyance speed increases, but also the distance between recording materials conveyed one by one (feeding interval ) Tends to become smaller.

However, the sheet feeding device waits until the pulling-out roller has completely pulled out the preceding recording material, and then controls the sheet feeding roller shaft to be connected again. There was a limit to it.

Therefore, there is a sheet feeding device that controls the rotation stop timing of the sheet feeding drive shaft during the continuous sheet feeding operation to feed the preceding recording material and the next (subsequent) recording material in a desired amount in a superimposed manner. Proposed.

[0008]

In the image forming apparatus connected by the paper feeding device, for example, the leading end of the succeeding recording material is provided immediately upstream of the fixing means for fixing the toner transferred to the recording material. There may be a positional relationship in which the upper surface of the trailing edge of the preceding recording material overlaps. When the recording material tries to enter the fixing under such a situation, the rushing position of the leading edge of the succeeding paper, which overlaps with it, becomes unstable due to a change in the geometrical shape such as waviness of the preceding paper, and when the fixing means rushes in. It is assumed that there is a possibility of catching and conveying defects.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of realizing stable conveyance of a recording material when the fixing unit enters. .

[0010]

In order to achieve the above object, the present invention provides an image forming apparatus having a conveying process in which a trailing edge of a preceding recording material and a trailing edge of a succeeding recording material are conveyed in an overlapping state. A reversing unit for reversing the positional relationship of the recording material overlapping portion is provided between the electrophotographic photosensitive drum and the fixing unit.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, an electrophotographic copying machine as one form of the image forming apparatus according to the present invention will be described with reference to FIG.

FIG. 8 is a cross-sectional view of the electrophotographic copying machine. In FIG. 8, reference numeral 100 denotes the main body of the electrophotographic copying machine (hereinafter referred to as the apparatus main body), and the original document is placed on the original platen glass 102. ing. Then, an optical image corresponding to the image information is formed on the electrophotographic photosensitive drum 104 by the plurality of mirrors M and lenses Ln of the optical unit 103.

Reference numeral 105 denotes a cassette, which is suitable for the recording material (hereinafter referred to as "paper") P loaded in these cassettes 105, based on the information input by the user from the operation unit or the paper size of the original. Paper 105
Select from the paper size information in. Here, the recording material is not limited to a paper sheet, and an OHP sheet or the like can be appropriately selected.

Then, one sheet P conveyed by the sheet feeding / separating apparatus 105A is conveyed to the registration roller 110 via the conveying section 109, and the timing of rotation of the photosensitive drum 104 and scanning of the optical section 103. And carry in synchronization. Incidentally, 111 and 112 are a transfer charger and a separation charger. Here, the transfer charger 111 transfers the toner image formed on the photosensitive drum 104 onto the paper P. Then, the separation charger 112 separates the paper P on which the toner image is transferred from the photoconductor drum 104.

After that, the sheet P conveyed by the conveying section 113 is subjected to fixing of the toner image on the sheet by heat and pressure in the fixing device 114, and then in the case of one-sided copying, the sheet P is ejected from the inner sheet ejection roller 123. After passing through the paper reversing unit 115, the paper is discharged to the paper discharge tray 117 by the paper discharge rollers 116. In the case of double-sided copying, the flapper 11
Under the control of No. 8, the sheet is temporarily conveyed to the reverse path 120 via the re-feeding conveyance path 119. Here, the trailing edge of the sheet P passes through the re-feeding conveyance path 119, and the reversing roller 122 is reversely rotated at the timing when it is still nipped by the reversing roller 122, so that the sheet P is conveyed again into the apparatus. After that, the paper P is passed through the double-sided path 121 and the registration roller 11
After being conveyed to 0, the sheet is discharged to the sheet discharge tray 117 by following the same route as in the case of single-sided copying.

Next, the details around the fixing device will be described with reference to FIG.

In FIG. 1, the recording material P conveyed by the conveying section 113 is fixed to a pair of fixing rollers 114a and 114b via a fixing inlet guide 124 provided on the downstream side of the conveying section.
It is pinched and conveyed. Further, in the fixing separation claw 127 which is in contact with the fixing roller 114 a, the leading end of the recording material P is the fixing roller pair 11.
After passing through 4a and 114b, the recording material P is fixed on the fixing roller 11
This is to prevent the separation failure caused by winding around 4a.

The recording material P separated from the pair of fixing rollers 114a and 114b is nipped and conveyed by the inner paper discharge roller 123,
It is discharged to the outside of the apparatus main body or conveyed again into the apparatus.

The fixing entrance guide 124 is the center of rotation 12.
I have 8. The rotating cam 125 provided below the fixing entrance guide 124 contacts the lower surface of the fixing entrance guide 124, and is rotationally driven by a drive unit (not shown) at a predetermined timing in synchronization with a signal generated from the main body apparatus. Further, a guide spring 126 is provided, and the fixing inlet guide 124 is rotated at a predetermined timing in association with the rotation of the rotating cam 125.

As shown in FIG. 2, assuming that there are recording materials Pa and Pb passing through the conveying section 113, the trailing end portion of the preceding recording material Pa (hereinafter referred to as preceding paper) and the succeeding recording material Pb ( Hereinafter, referred to as a succeeding sheet) The overlapped portion K with the leading end portion
And the leading end of the succeeding paper Pb overlaps the upper surface of the trailing end of the preceding paper Pa.

Here, the rotating cam 125 is rotationally driven as shown in FIG. 3 in conjunction with a signal generated from the main body device at a predetermined timing. As the rotating cam 125 rotates,
The lower surface of the fixing entrance guide 124 is pushed up to rotate around the rotation center 128, and the upper surface of the fixing entrance guide 124 further rotated pushes up the preceding paper Pa. Therefore, the trailing edge of the preceding paper Pa is pulled out from the overlapping portion K and moves above the succeeding paper Pb.

Thereafter, the rotating cam 125 is further driven to rotate (illustrated in FIG. 4), and the fixing inlet guide 124 is rotated by the guide spring 126 and pulled back downward. Therefore, the trailing edge of the preceding paper Pa is inverted and overlaps with the upper surface of the leading edge of the following paper Pb, and is thrust and conveyed to the fixing roller pair 114a and 114b while holding the overlapping portion.
For this reason, the leading end of the recording material P entering the fixing device 114 always maintains a stable position, and the fixing roller 114 during the entering.
It is possible to prevent a defective conveyance due to being caught in a.

FIG. 5 shows details of the nip portion between the pair of fixing rollers 114a and 114b.

The trailing edge of the preceding paper Pa and the leading edge of the following paper Pb shown in FIG. 5 are sandwiched between the fixing roller pairs 114a and 114b. Here, one end of the preceding paper Pa is similarly sandwiched by the inner paper discharge roller 123. Therefore,
The leading edge of the succeeding sheet Pb is sandwiched between the nip portion of the fixing roller pair 114a and 114b and the nip portion of the inner sheet discharging roller 123 without wrapping around the fixing roller 114a.
It becomes possible to separate from the fixing roller pair 114a, 114b along the lower surface of the.

As described above, by providing a mechanism capable of appropriately selecting the positional relationship of the overlapping portions of the recording materials P when the recording material P collides with the fixing device 114, the recording material P is pulled when the recording material P enters the fixing device 114. It is possible to reliably prevent a defective conveyance.

Further, according to the separation of the recording material P in the nip portion of the pair of fixing rollers 114a and 114b, the fixing separation claw used in the conventional example is, for example, as shown in FIG. It is also possible to first separate only the recording material conveyed to the fixing device, and thereafter, as shown in FIGS. 2 to 4, move the separation claws, which are in contact with the fixing roller, away from the fixing roller. . Therefore, it is possible to realize the reduction in the life of the fixing roller due to the friction of the fixing separation claw, which has been a problem in the past.

[0028]

As is apparent from the above description, according to the present invention, there is provided an image forming apparatus having a conveying process in which a trailing edge of a preceding recording material and a leading edge of a succeeding recording material are conveyed in an overlapping state. Since the reversing means for reversing the positional relationship of the recording material overlapping portion is provided between the electrophotographic photosensitive drum and the fixing means, it is possible to realize stable conveyance of the recording material when the fixing means enters. Is obtained.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a fixing device portion of the image forming apparatus according to the present invention.

FIG. 3 is a sectional view of a fixing device portion of the image forming apparatus according to the present invention.

FIG. 4 is a sectional view of a fixing device portion of the image forming apparatus according to the present invention.

FIG. 5 is a sectional view of a fixing unit portion of the image forming apparatus according to the present invention.

FIG. 6 is a sectional view of a fixing device portion of the image forming apparatus according to the present invention.

FIG. 7 is a perspective view of a sheet feeding unit of a conventional image forming apparatus.

FIG. 8 is an image forming apparatus (electrophotographic copying machine) according to the present invention.
FIG.

[Explanation of symbols]

100 device body 102 Platen glass 103 Optics 104 photoconductor drum 105 cassettes 105A separation device 110 Registration roller 111 Transfer charger 112 Separation charger 113 Transport section 114 fixer 115 Paper output reversing unit 116 paper ejection roller 117 Output tray 118 flapper 119 Re-feeding conveyance path 120 inversion paths 121 double-sided pass 122 Reverse roller 124 Fixing entrance guide P recording material

Claims (3)

[Claims] 1. An image forming apparatus having a conveyance process in which a trailing edge of a preceding recording material and a leading edge of a succeeding recording material are conveyed in an overlapping state, and the recording material overlaps between an electrophotographic photosensitive drum and a fixing unit. An image forming apparatus comprising an inverting means for inverting the positional relationship of the parts. 2. The image forming apparatus according to claim 1, wherein the reversing unit includes a fixing inlet guide provided on the upstream side of the fixing unit, and a rotating hand sink for rotating the fixing inlet guide. apparatus. 3. The fixing entrance guide starts rotating when a trailing edge of the recording material reaches a position upstream of the fixing entrance guide by a predetermined distance, and before the leading edge of the recording material reaches the fixing entrance guide. The image forming apparatus according to claim 2, wherein the image forming apparatus is controlled to return to the original position.