JP2853243B2 - Paper transport device in image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper transport device in an image forming apparatus such as an electronic copying machine or a printer. More particularly, the present invention relates to a sheet conveying device for feeding a sheet separated from a photoconductor to a fixing unit.

[Conventional technology]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electronic copying machine or a printer, a toner image developed on a photoreceptor is transferred onto a copy sheet, and the transferred image is fixed on the sheet by a fixing unit. For this purpose, there is provided a transporting means for feeding the transferred paper peeled off by a peeling means such as a peeling claw provided adjacent to the photoreceptor to the fixing means. The conveying means includes a belt for receiving and sending the paper, and a vacuum suction means disposed below the belt. The paper peeled from the photoreceptor is attracted to the belt by the vacuum suction means and To the fixing means.

By the way, image forming apparatuses such as copiers and printers are increasingly required to perform double-sided copying and multiple copying in accordance with their multifunctionality. In order to achieve such a function, it is necessary to return the copy sheet on which the toner image has been transferred and fixed to the transfer position again to perform transfer, peeling and fixing. But,
In many cases, the sheet on which the toner image has been fixed is curled in many cases, and the leading end of the sheet is curved upward, which hinders feeding to the fixing unit. The paper sent to the fixing means
If the unfixed toner image is on the top surface, it cannot be pressed down from above and if the paper is conveyed with the curl at the tip, feeding to the fixing unit will fail and paper jams will occur. Become. Paper jams due to this curl are particularly likely to occur when the paper is highly water-containing.

To address these paper jam issues,
Although the vacuum suction force of the sheet conveying means is increased to reliably attract the leading edge of the sheet to the conveyance belt, increasing the suction force increases power consumption. The problem is that it cannot be applied.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem that a paper jam occurs due to curling of a sheet in a conventional sheet conveying apparatus for an image forming apparatus. In particular, it is an object of the present invention to provide a paper transporting apparatus that can transport a curled paper to a fixing unit without causing a paper jam and that does not require increasing the suction force of a vacuum suction unit.

[Means for solving the problem]

In order to solve the above-mentioned problem, in the present invention, a guide member is provided above the sheet conveying means between the photoreceptor and the fixing means. The guide member extends along the conveying surface of the sheet conveying means, and is disposed such that an end on the upstream side in the sheet conveying direction overlaps the peeling means in a vertical direction above the peeling means. Further, the guide member is disposed parallel to the transport surface of the sheet transport means or inclined downward toward the downstream side in the transport direction.

In a preferred aspect of the present invention, the guide member includes a star wheel having a radial projection on the periphery at an end on the downstream side in the sheet transport direction. In another aspect of the invention, the downstream end of the guide member is a line connecting the tip of a lower chute provided between the downstream end of the sheet conveying means and the fixing means and the nip entrance of the fixing means. It is arranged so that it may be located above the extension of.

[Action]

In the present invention, since the guide member extending along the sheet conveying surface is provided above the sheet conveying means, even if the leading end of the conveyed sheet is curled, the leading end of the sheet is directed in the conveying direction by the guide member. Is sent to the fixing means.
In the configuration of the present invention, since the guide member is disposed such that the upstream end is located above the peeling means and overlaps the peeling means in the up-down direction, the paper peeled from the photoreceptor by the peeling means is provided. Even if the tip is curled, the tip does not enter the gap between the peeling means and the guide member to cause a jam.

If the downstream end of the guide member is too close to the conveying surface of the sheet conveying means, the contact between the end of the guide member and the upper surface of the sheet is too strong. An unfixed toner image is formed on the upper surface of the copy sheet. If the tip of the guide member makes strong contact with the upper surface of the sheet, the toner image is damaged. In a preferred aspect of the present invention, since the star wheel is provided at the tip of the guide member, the problem that the toner image on the upper surface of the sheet fed to the fixing unit is rubbed and damaged by the tip of the guide member is solved. If the star wheel is not provided at the tip of the guide member, the extension of the line connecting the tip of the lower chute provided between the downstream end of the sheet conveying means and the fixing means and the nip entrance of the fixing means is provided. If it is located, this problem can be solved.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a copying machine. The copying machine includes a drum-shaped photoconductor 1, which is rotated in the direction of arrow A. Exposure and development are performed on the photoreceptor 1 by a method known in the art of electronic copying to form a toner image. At the transfer position, the copy sheet 3 is fed in the direction indicated by the arrow B and brought into contact with the photoconductor 1. A transfer corona discharge device C is provided at the transfer position. On the downstream side of the transfer position as viewed in the rotation direction of the photoconductor 1, a peeling unit including a peeling claw 2 is provided. The exfoliation claw 2 comes into contact with the peripheral surface of the photoreceptor 1 at its tip, and exfoliates the paper 3 on the photoreceptor 1 from the surface of the photoreceptor 1.

A transport unit 4 for transporting the sheet 3 separated from the photoconductor 1 to a fixing unit 5 including a pair of fixing rolls 6 and 7
Is provided. The transporting means 4 includes a plurality of parallel endless belts 4a as shown in FIG. 2, and these belts 4a are stretched between a pair of rolls 4b. The upper surface of the belt 4a becomes the paper transport surface 4c. A vacuum suction box 4d is provided below the upper surface of the belt 4a of the conveying means 4. This vacuum suction box
4d has a number of small holes 4e on the upper surface as shown in FIG. 2,
The suction force acts on the paper 3 on the belt 4a through the small holes 3e. A lower chute 9 and an upper chute 10 for guiding the leading end of the sheet 3 from the conveying means 4 to the fixing means 5 are arranged between the downstream end of the sheet conveying means 4 and the fixing means 5.

In the embodiment of the present invention shown in the drawings, a guide member 8 is provided above the transport means 4. One end of the guide member 8 is supported by a fixed portion of the copying machine above the peeling claw 2 by a shaft 11 so as to be vertically swingable. The guide member 8 extends substantially along the sheet conveying surface 4c formed by the belt 4a of the conveying means 4. In the present embodiment, the guide member 8 is inclined downward by an angle θ with respect to the paper transport surface 4c as viewed in the paper transport direction. This inclination angle θ is set to 0 ° to 10 °.
In order to set the guide member 8 at the inclination angle θ, the guide member 8 is formed with an extension 8a at the upstream end, and the extension of the guide member 8 is set at the set inclination angle θ at the fixed portion of the copying machine. Department
A stopper 8b engaging with 8a is formed.

The end of the guide member 8 on the upstream side in the paper transport direction is located above the peeling claw 2 and is arranged to overlap the peeling claw 2 in the vertical direction. At the downstream end of the guide member 8, a star wheel 12 having a number of small protrusions around the periphery is rotatably attached.

In operation, the paper 3 peeled from the photoconductor 1 is
As shown in FIG. 1, the sheet is received on a sheet conveying surface 4c formed by a belt 4a of the conveying means 4. Even when the leading end of the sheet 3 is curled as shown in FIG. 1, the leading end comes into contact with the lower edge of the guide member 8 and is turned in the transport direction, so that the leading edge may be bent. The toner is sent to the fixing unit 5 without causing any problem. It is important to set the inclination angle θ of the guide member 8 to 0 ° to 10 ° in order to prevent bending of the leading end of the sheet and rubbing of the image formed on the upper surface of the sheet. If the inclination angle θ of the guide member 8 is larger than 10 °, the leading end of the sheet is wound in a U-shape as shown in FIG. 3 and is bent. Further, when the guide member 8 is inclined upward with respect to the sheet conveying surface 4c, the sheet 3 is not only at the leading end but also at the leading end.
As shown in FIG.
, Causing damage such as rubbing of the toner image on the upper surface of the sheet. In FIG. 1, the inclination angle θ is shown as an angle between a line passing through the axis of the shaft 11 and parallel to the sheet conveying surface 4c and the upper surface of the guide member 8. If the angle between them is substantially negligible as in the case of the illustrated guide member, even if this angle is displayed as the inclination angle of the guide member 8, the guide member 8 is an actual guide surface. There is no particular hindrance in defining the angle of inclination of the lower surface.

The paper 3 is thus fixed by the conveying means 4 to the fixing means 5.
However, since the guide member 8 is inclined downward as described above, the upper surface of the sheet 3 is moved to the tip of the guide member 8 in the process of transferring the sheet 3 from the conveying means 4 to the chutes 9 and 10. There is a risk of contact. In the present embodiment, the above-described star wheel 12 is provided to prevent the toner image on the upper surface of the paper from being damaged due to contact between the leading end of the guide member 8 and the upper surface of the paper. Since the star wheel 12 has a large number of small protrusions on the peripheral surface, the star wheel 12 contacts the upper surface of the sheet at a small point, and does not damage an unfixed toner image on the sheet.

In FIG. 1, when the relationship between the extension of the line D connecting the nip 5a between the rolls 6 and 7 of the fixing means 5 and the upper surface 9a at the downstream end of the lower chute 9 and the tip of the guide member 8 is considered, If the guide member 8 is arranged so that the downstream end of the member 8 is located above the line D, the upper surface of the sheet 3 is located behind the leading end of the sheet 3 even in the case of stiff paper. Can be prevented from contacting the tip. That is, the nip between the rolls 6 and 7 of the fixing unit 5
After being bitten by the nip 5a, the sheet is supported by the nip 5a and the upper surface 9a of the downstream end of the lower chute 9, but in the case of a stiff sheet, the nip 5a and the lower chute 9 The upward force applied to the sheet by the upper surface 9a of the downstream end portion overcomes the suction force from the vacuum suction box 4d acting on the sheet conveying surface 4c, causing a phenomenon that the subsequent portion of the sheet is lifted from the sheet conveying surface 4c. . As a result, the upper surface of the succeeding portion of the sheet comes into contact with the leading end of the guide member 8 and rubs. Normally, in order to prevent this rubbing, a star wheel 12 as shown in the figure is provided and acts so as to push the upper surface of the sheet away from the leading end of the guide member 8.

However, if the position of the guide member 8 is set as described above, there is no possibility that the upper surface of the rear portion of the sheet 3 comes into contact with the front end of the guide member 8. Therefore, if the arrangement of the guide members 8 is set as described above, it is not always necessary to provide the star wheel 12.

〔effect〕

As described above, according to the present invention, in an image forming apparatus such as an electronic copying machine or a printer, a conveying device that conveys a sheet having an unfixed toner image peeled off from a photoreceptor to a fixing unit is provided. Since the guide member is provided so as to be positioned above the sheet, the sheet can be conveyed to the fixing unit without causing a bend or the like at the leading end even if the leading end of the sheet has a curl or the like. Particularly in the present invention,
Since the end of the guide member on the upstream side in the sheet conveying direction is disposed above the peeling means and overlaps with the peeling means in the up-down direction, the leading end of the paper immediately after being peeled off from the photoreceptor is formed with the guide member. There is no possibility that jamming occurs due to being caught in the gap between the separating means. Further, since the guide member is inclined downward in the conveyance direction in the range of 0 ° to 10 ° with respect to the conveyance surface of the conveyance means, the leading edge of the paper may be bent or the unfixed toner image on the upper surface of the paper may be damaged. And the sheet is reliably conveyed to the fixing means even when the leading end of the sheet is curled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a transfer device of a copying machine showing one embodiment of the present invention, FIG. 2 is a plan view of the transfer device of FIG. 1, and FIG. FIG. 4 is a partial sectional view showing a problem that occurs when the angle is too large, and FIG. 4 is a partial sectional view showing a problem that occurs when the inclination of the guide member is upward. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Peeling claw, 3 ... Paper, 4 ... Conveying means, 5 ... Fixing means, 8 ... Guide member, 12 ... Star wheel.

Claims (4)

(57) [Claims] A sheet conveying device for an image forming apparatus provided with a sheet conveying means for feeding, to a fixing means, a copy sheet onto which a toner image is transferred on a photoreceptor and peeled off from the photoreceptor by a peeling means; , A paper guide member extending along the transport surface of the paper transport means is provided above the paper transport means, and the paper guide member has an end on the upstream side in the paper transport direction that is peeled above the peeling means. A sheet conveying device in the image forming apparatus, wherein the guide member is disposed so as to vertically overlap with the means, and the guide member is disposed parallel to the conveying surface or inclined downward toward the downstream side in the conveying direction. . 2. The sheet conveying device according to claim 1, wherein the guide member includes a star wheel having a radial projection on a periphery at a downstream end in a sheet conveying direction. 3. The sheet conveying device according to claim 1, wherein the downward inclination angle of the guide member is not larger than 10 °. 4. The sheet conveying apparatus according to claim 1, wherein an upper chute and a lower chute for guiding a leading end of the sheet to the fixing means are provided between the downstream end of the sheet conveying means and the fixing means. And a downstream end of the guide member is disposed above an extension of a line connecting a tip of the lower chute and a nip entrance of the fixing unit.