JPH1111804A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the paper jam on a conveying path, and to prevent the dislocation of an image of a second face on an image bearing part, by straightening the curl of the transfer paper by changing the curling direction of the transfer paper. SOLUTION: An automatic turnover retransport device (ADU) 80 comprises a curl straightening means 61 for changing a curling direction of a transfer paper. A curl straightening means 610 is formed by rotatably supporting a driving shaft 612, a driven shaft 614 and a guide shaft 617 on a main body of the automatic turnover retransport device 80. When an image is transferred onto a second face of the transfer paper, the curls (a), (b) are generated in the same directions on a circulation turnover paper supply path C, and a curl (c) is generated in the same direction by the turnover of the transfer paper by the automatic turnover retransport device 80. After this turnover, the transfer paper is passed through between a rubber belt 615 and the guide shaft 617 in the curl straightening means 610, whereby the curling direction of the transfer paper is changed to be a curl (d).

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 capable of forming images on first and second surfaces of a transfer sheet.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a copying machine, a transfer sheet is conveyed to an image carrier, an image is formed by transferring the image on a first surface, and the image transferred on the transfer sheet is fixed and re-conveyed. In some cases, the image is reversed on the road and an image is formed again on the second surface of the transfer paper by the image carrying unit.

[0003]

In such an image forming apparatus, an image is formed on one first surface of a transfer sheet and then fixed by applying heat, and then inverted to reverse the second surface of the transfer sheet. Therefore, the transfer path of the transfer sheet circulates and bends in the same direction, and the curl generated by the transfer increases.

Further, the transfer sheet is easily bent by the influence of heat, and the curl generated by the transfer of the transfer sheet is increased, which may cause a paper jam in the transfer path or an image shift.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an image forming apparatus capable of correcting a curl of a transfer sheet to reduce a paper jam in a transport path and preventing an image shift. It is intended to provide.

[0006]

In order to solve the above-mentioned problems and to achieve the object, the invention according to claim 1 is directed to a method of "transferring a transfer paper to an image carrier and transferring an image to a first surface. An image forming apparatus that forms, transfers the image transferred to the transfer paper, reverses the image on the re-transport path after fixing, and forms an image on the second surface of the transfer sheet again by the image bearing unit. An image forming apparatus comprising: a curl correcting unit that changes a curl direction of the transfer sheet. By changing the curl direction of the transfer paper, it is possible to correct the curl of the transfer paper, reduce paper jams in the transport path, and prevent image deviation of the second surface in the image carrying unit. be able to.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the curl correcting means is arranged so as to change the curl direction after the transfer sheet is reversed. If the curl direction is changed after reversing the transfer paper, the curl of the transfer paper is likely to occur in the re-conveyance path because the curl direction is easily changed. Can be efficiently corrected.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the curl correcting unit is provided in a reversing unit for reversing the transfer sheet. ], And the curl correcting means can be easily mounted, and the maintenance and inspection of the curl correcting means can be performed together with the reversing section.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: a cooling means for cooling the transfer sheet in the re-conveying path; and a curling correcting means arranged to change a curl direction after cooling by the cooling means. Claims 1 to 3
The image forming apparatus according to any one of the above. The curl of the transfer paper after the correction is stabilized by changing the curl direction after cooling the transfer paper and performing the correction.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below in detail with reference to the drawings. 1 is a configuration diagram of the image forming apparatus, FIG. 2 is a diagram illustrating a transfer paper transport system, FIG. 3 is a plan view of the reversing unit, FIG. 4 is a plan view of the reversing unit showing a state where the guide plate is opened, and FIG. Is a sectional view showing the configuration of the curl correcting means, and FIG. 6 is a perspective view showing the configuration of the curl correcting means.

In this embodiment, a copying machine is shown as the image forming apparatus 1. The image forming apparatus 1 includes an automatic document feeder 2. The automatic document feeder 2 includes a document tray 3, a feed roller 4, a takeout table 5, and the like. The document set on the document tray 3 is automatically driven one by one by the driving of the feeding roller 4.
Then, the document whose image has been read is sent out onto the take-out table 5.

Further, the image forming apparatus 1 is provided with an image information reading section 20 for reading image information of a fed document. The image information reading unit 20 includes a light source 21 and a mirror 2
2 to 24, a lens 25 and a CCD 26 are provided. The light source 21 and the mirrors 22 to 24 are reciprocally arranged below the document placing glass 10 so that the light source 21 irradiates the document on the document placing glass 10. I do. The reflected light is mirror 22
Through an optical system consisting of a lens 25 and a CCD 26
Is read optically. Position detection sensors S1 and S2 for reciprocating the light source 21 are arranged below both ends of the document placing glass 10, and the position detection sensors S
When 1, S2 detects the light source 21, the light source 21 is moved in the opposite direction. The CCD 26 is controlled by the control unit 30 and stores the read image signal in the image storage unit 27.

The image forming apparatus 1 includes an image carrying unit 40, a fixing unit 50, a paper feeding unit 60, a registration control unit 70, and an automatic reversing and re-conveying unit (ADU) 80 as a reversing unit.
Further, a transfer conveyance path A for conveying the transfer paper to the image carrier 40, a discharge path B for discharging the transfer paper on which the image is formed out of the apparatus, and an automatic reversal of the transfer paper on which the image is formed by the image carrier 40 A circulation reversing sheet feeding path C for circulating to the re-conveying unit (ADU) 80, an automatic reversing re-conveying unit (ADU) 8
And a return path D from 0.

A photosensitive drum 41 as an image bearing member is disposed in the image bearing section 40, and the photosensitive drum 41 is uniformly charged by a charging electrode 42, and the image information writing section 43 performs image information writing. Is irradiated on the peripheral surface of the photosensitive drum 41 to form an electrostatic latent image. Image information writing unit 43
Is configured to write the image information stored in the image storage unit 27 by laser on the peripheral surface of the photosensitive drum 41.

The electrostatic latent image is developed by a developing unit 44 to form a toner image. The transfer paper is sent to the transfer unit 45 in synchronization with the rotation of the photosensitive drum 41, and the toner image is transferred. Thereafter, the transfer paper is separated from the photosensitive drum 41, and is conveyed to the fixing unit 50 in the next step via the conveyance belt 300. A cleaning unit 46 is provided around the photosensitive drum 41.
The surface of the photoconductive drum 41 after the transfer is cleaned and charged again by the charging electrode 42 for the next image formation.

The fixing section 50 has a pair of rollers 51 and 52, and fixes the toner image on the transfer paper heated and pressed by the transfer paper. Switching gate 10 arranged after fixing unit 50
By 0, the transfer path of the transfer sheet is switched between the discharge side and the re-conveyance side. Switching of the switching gate 100 is performed at a timing from the start of the registration roller 71.

The paper feed section 60 includes a plurality of paper feed step sections 61 and 6.
2 are provided, and in this embodiment, they are arranged at the upper stage and the lower stage. The upper paper feed stage 61 and the lower paper feed stage 62 include:
Trays 63 and 64 for storing transfer papers are arranged. Paper feed rollers 65 and 66 are arranged on the upper surface of the transfer paper of the upper paper feed step 61 and the lower paper feed step 62, respectively, and intermittently feed the transfer paper. Each paper feed roller 65, 6
6, a double feed prevention roller pair 67, 68 is disposed in front of
The transfer paper is transported to the transport path A one by one. Transport path A
Is provided with a transport roller pair 101.

The automatic inversion re-transport unit (ADU) 80 includes:
Loading roller pair 81, reversing roller pair 82, transport roller pair 2
02, 203, 204, 205 and sensors S3, S4
S5, S6, and S7 are provided. The transfer paper sent from the reversing paper feed path C is carried in by the forward rotation of the carry-in roller pair 81 and the reverse roller pair 82, and the reverse of the reverse roller pair 82 and the driving of the transport roller pairs 202, 203, 204, 205. To return to the transport path D. In this way, the non-stat type is adopted, and the conventional stacking method, in which single-sided copied transfer paper is temporarily stacked, is not stacked. Since no loss of target occurs, the productivity is improved, and the transfer paper can be always gripped by the roller, so that it is possible to prevent the occurrence of a jam or the like due to the curl of the transfer paper, which is easily generated by the fixing unit 50. . In the circulation reversing sheet feeding path C, a pair of conveying rollers 200 and 201 are arranged.

The registration control unit 70 includes a registration roller pair 71 and a sensor S8. The registration roller pair 71 is driven by a motor 73. The transferred transfer paper abuts against a pair of registration rollers 71, aligns the image on the image carrier with the transfer paper, and forcibly forms a spool to correct the skew of the transfer paper. Supply so as to eliminate.

In the image forming apparatus 1, a re-conveying path E is formed so as to surround a sheet feeding section 60 for sending a transfer sheet to the image carrying section 40. The re-conveying path E has a circulation reversing sheet feeding path C and a return conveying path D. In the re-conveying path E, an automatic reversing re-conveying device (AD
U) 80 are provided.

A pair of guide plates 5 for guiding the transfer paper are provided at the entrance 80a of the automatic reversing and re-conveying unit (ADU) 80.
00, 501 are arranged to face each other, and the transfer paper moves between the pair of guide plates 500, 501. Further, a switching member 502 is provided at the entrance 80a of the automatic reversing and re-transporting unit (ADU) 80. When the transfer sheet is conveyed from the circulation reversing sheet feeding path C to the automatic reversing and re-conveying device (ADU) 80, the switching member 502 opens the introduction passage 503 to enable the conveyance. When the transfer sheet is inverted from the automatic reversing and re-conveying unit (ADU) 80 and sent out to the return conveyance path D, the introduction path 503 is closed and the transfer sheet can be sent out from the output path 504.

A pair of guide plates 50 for guiding the transfer paper
0 and 501 are formed with air outlets 500a and 501a. The air outlets 500a and 501a are formed longer in the transfer direction of the transfer paper.

An automatic inversion re-transport unit (ADU) 80
Is provided with a blower fan 510 that blows air to the transfer paper, and can blow air in the direction of the blower ports 500a and 501a. The air outlets 500a and 501a and the air blowing fan 510 constitute the cooling means X.

When the transfer paper is transported between the pair of guide plates 500, 501, the transfer paper can be directly cooled from the air vents 500a, 501a of the guide plates 500, 501, and the cooling efficiency is high. At this time, the guide plates 500, 50
The first air outlets 500a and 501a function as air outlets after the first sheet of transfer paper has passed until the second sheet comes. Since the blower fan 510 drives the transfer paper to blow air, the cooling performance is improved. Further, the transfer paper can be cooled twice before and after the reversal by cooling the transfer paper by the automatic reversing and re-conveying device (ADU) 80 which is the reversing unit.

Further, the re-conveying path E is formed so as to surround a sheet feeding section 60 for sending the transfer sheet to the image carrying section 40, and a cooling means X is disposed below the sheet feeding section 60, X
Is located away from the fixing unit 50, the transfer paper can be efficiently cooled without the influence of heat from the fixing and without lowering the fixing temperature.

The automatic inversion re-transport unit (ADU) 80 includes:
After reversing the transfer paper, guide plates 600 and 601 are arranged,
Further, a curl correcting means 61 for changing the curl direction of the transfer paper
0 is provided.

The curl correcting means 610 includes a rubber roller 61.
1 and a driven shaft 614 having a roller 613. A rubber belt 615 is stretched between the rubber rollers 611 and 613. Guide plate 60
At 0, a guide body 616 is provided. Drive shaft 61
2. The driven shaft 614 and the guide shaft 617 are rotatably supported by the main body of the automatic reversing and re-conveying device (ADU) 80.

The guide plate 600 has an upper roller 202 on the pair of conveying rollers 202, 203, 204 and 205.
a, 203a, 204a, and 205a are rotatably provided, and a guide roller 620 is further rotatably provided. The guide plate 600 is provided to be openable and closable with the support shaft 621 as a fulcrum with respect to the guide plate 601.
0 is opened and closed by a handle 622.

The guide shaft 617 pushes the rubber belt 615 to urge it in the approaching direction, and the guide shaft 617 is rotatable by the rubber belt 615. With the guide plate 600 assembled, the guide body 616 transfers the transfer paper to the rubber belt 6.
15 can be guided between the guide shaft 617 and the transfer paper, and the curl direction of the transfer paper can be changed by passing between the rubber belt 615 and the guide shaft 617.

As described above, when an image is transferred to the second surface of the transfer sheet, curls a and b are generated in the same direction in the reversing sheet feeding path C as shown in FIG.
Due to the reversal of the transfer paper at DU) 80, the curl c occurs in the same direction. By providing the curl correcting means 610 after the reversal, the transfer paper can be transferred to the rubber belt 615 and the guide shaft 61.
7, the transfer paper can be changed in curl direction to be curled d.

By correcting the curl of the transfer paper, paper jams in the transport path can be reduced, and furthermore, the image deviation of the second surface in the image carrier can be prevented.

Further, the curl correcting means 610 is arranged so as to change the curl direction after the transfer sheet is inverted. Since a large curl in the direction a is formed before the transfer sheet is inverted, the curl direction is changed after the transfer sheet is inverted. If it is changed, the curl of the transfer paper can be efficiently corrected.

An automatic reversing and re-conveying unit (ADU) 80 which is a reversing unit for reversing the transfer paper by using the curl correcting means 610.
, The curl correcting means 610 can be easily attached, and the jam correction and maintenance inspection of the curl correcting means 610 can be performed together with the reversing section.

Further, a cooling means X for cooling the transfer paper is provided in the re-conveying path, and the curl correcting means 610 is arranged so as to change the curl direction after cooling by the cooling means X.
After the transfer paper is cooled, the curl direction is changed to correct the transfer paper, so that the transfer paper after the correction is stabilized.

[0035]

As described above, according to the first aspect of the present invention, the curl of the transfer paper can be corrected by changing the curl direction of the transfer paper, and the paper jam in the transport path can be reduced. It is possible to prevent an image shift on the second surface in the image carrier.

According to the second aspect of the present invention, the curl of the transfer paper is increased before the reversal of the transfer paper. Therefore, if the curl direction is changed after the reversal of the transfer paper, the curl of the transfer paper can be efficiently corrected.

According to the third aspect of the present invention, the curl correcting means can be easily mounted, and the jam correction and maintenance and inspection of the curl correcting means can be performed together with the reversing section.

According to the fourth aspect of the present invention, the curl direction of the transfer sheet after the correction is stabilized by changing the curl direction after cooling the transfer sheet.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming apparatus.

FIG. 2 is a diagram illustrating a transfer paper transport system.

FIG. 3 is a plan view of a reversing unit.

FIG. 4 is a plan view of a reversing unit showing a state where a guide plate is opened.

FIG. 5 is a cross-sectional view illustrating a configuration of a curl correcting unit.

FIG. 6 is a perspective view illustrating a configuration of a curl correcting unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 30 control means 40 image carrier 80 automatic reversing re-transport unit (ADU) 610 curl correcting means E re-transport path

Claims (4)

[Claims] An image transfer unit configured to transfer a transfer sheet to an image holding unit and transfer an image on a first surface of the transfer unit to form an image on the first surface; An image forming apparatus for forming an image on a second surface of a transfer sheet according to claim 1, further comprising a curl correcting means for changing a curl direction of the transfer sheet in the re-conveying path. 2. An image forming apparatus according to claim 1, wherein said curl correcting means is arranged so as to change the curl direction after the transfer sheet is reversed. 3. The image forming apparatus according to claim 1, wherein the curl correcting unit is provided in a reversing unit for reversing the transfer sheet. 4. The apparatus according to claim 1, further comprising cooling means for cooling the transfer paper in the re-conveying path, wherein the curl correcting means is arranged to change the curl direction after cooling by the cooling means. Item 4. The image forming apparatus according to any one of Items 3.