JPS6327372A - Image former - Google Patents

Abstract

PURPOSE:To prevent a jam or the like due to a drop in separability of a sheet from a sensitizer from occurring, by altering the corrective quantity according to multi-copying and duplex copying, in case of an image former provided with a device for remedying a curvature on the sheet. CONSTITUTION:A pair of curl corrective rollers 38 are constituted of a rigid roller 39a consisting of a nonelastic material of resin or metal or the like, and an elastic roller 39b consisting of an elastic material of silicone sponge rubber or urethane or the like. This rigid body 39a is supported free of rotation by a side plate (unillustrated herein). And, this elastic roller 39b is rotatably supported by a bearing member 40, and this member 40 is designed so as to press the elastic roller 39b to the rigid roller 39a by actuation of a cam 41. In addition, this cam 41 is connected to a motor 42 serving as a power source. And, this motor 42 detects duplex-multi-copying mode setting signal 43 and it is connected to a control circuit 45 controlling this motor 42.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer. The present invention relates to a forming device.

(b) Conventional technology Conventionally, when performing multiple copying or double-sided copying with an image forming apparatus, such as a copying machine, the amount of charge in the post charger, transfer charger, and separation charger is varied while maintaining a balance. An image is formed on the sheet, and the image-formed sheet is fixed in a fixing device. Furthermore, the copied sheet is again introduced into the image forming section via the sheet re-conveying path, and multiple copies or double-sided copies are performed.

(/→ Problem to be solved by the invention However, since the sheet passing through the fixing device of the copying machine is heated and pressurized by the fixing device to perform fixing, upward warping occurs at the leading edge of the sheet. This often results in a curled sheet.
Then, when the curled sheet is again introduced into the image forming section via the sheet re-feeding path in order to perform multiple copying, the curled sheet is warped upward, causing the image forming section to pass through the image forming section. It tends to wrap around the photoreceptor, and the separation of the sheet from the photoreceptor is significantly reduced.

For this reason, the sheet is not separated from the photoreceptor and hits the cleaner of the image forming section, which may damage the photoreceptor or the rubber blade of the cleaner or cause a jam.

Therefore, in order to correct the warpage of the sheet, there is a device in which a curl correction means is placed in the ejection roller part of the fuser, but the amount of curl of the sheet differs depending on the difference in copy area between multiple copying and double-sided copying. The correcting means could not properly correct multiple copies and double-sided copies, and curled sheets were still introduced into the image forming section. Furthermore, since the amount of curl differs between multiple copying and double-sided copying, it is troublesome to change and set the amount of charge of the post charger, transfer charger, and separation charger while maintaining a balance.

(B) Means for Solving the Problems The present invention aims to solve the above-mentioned problems by arranging a curl correction means for the transfer sheet in the re-conveyance path, and in which the curl correction means is This method is characterized in that the amount of correction is changed between multiple image formation and double-sided image formation.

Based on the above structure, when the first transferred sheet is conveyed to the curl correction means through the re-conveyance path, the sheet is strongly straightened by the curl correction means in the case of multiple copying, and also double-sided copying is performed. In the case of , it is slightly corrected and conveyed to a pair of registration rollers. Then, the sheet is conveyed to the image forming section by a pair of registration rollers and is copied a second time.

(F) Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the copying machine 1 is equipped with a document table 2 on which a document M is placed, a light source 3, a lens system 5, and a cassette 6 on which sheets S are placed. An upper photoreceptor 7 is provided. Furthermore, a primary charger 9, a developing device 10, a post charger 11, and a cleaning mechanism 12 are arranged near the periphery of the photoconductor 7, and a transfer charger N15 and a separation charger 16 are arranged at the tip of the conveyance device 13. It is set up. Further, a paper feed roller 17 is disposed in the cassette 6 portion, and is guided to a pair of registration rollers 20 via a path 19. Further, a fixing device 21 is provided at the rear end portion of the conveyance device 13.
A flapper 22 and a discharge tray 23 are provided downstream of the fixing device 21.

The sheets are branched and selected by the flapper 22 to form a sheet re-conveyance path 25, and the re-conveyance path 25 is provided with a pair of conveyance rollers 26, 27, a flapper 29, and an intermediate tray 30. In addition, the flapper 31 branches and
A double-sided copying path 31 is selected and a pair of conveying rollers 32 and 33 are arranged on the path 31. Further, on the downstream side of the intermediate tray 30, a pair of paper feed rollers 35, a pair of transport rollers 36 and 37, and a pair of curl correcting rollers 39 are arranged.

As shown in detail in FIG. 2, the curl correction roller pair 39 includes a rigid roller 39a made of a non-elastic material such as resin or metal, and an elastic roller 39b made of an elastic material such as silicone sponge rubber or urethane. The rigid roller 39a is rotatably supported by a side plate (not shown). Further, the elastic roller 39b is rotatably supported by a bearing member 40.
0 is configured to press the elastic roller 39b against the rigid roller 39a by the operation of the cam 41.

Further, the cam 41 is connected to a motor 42 serving as a power source, and the motor 42 is connected to a control circuit 45 that detects a duplex multiple copying mode setting signal 43 and controls the motor 42.

Since this embodiment has the above-described configuration, when the light source 3 moves, the original M placed on the original platen 2 is irradiated with the light R3, and the reflected light passes through the lens system 5 and is charged to the primary charger in advance. 9 forms an electrostatic latent image on the uniformly charged surface of the photoreceptor 7. Then, as the photoreceptor 7 rotates in the direction of the arrow, the electrostatic latent image is formed at the developing device 10 position. Form a toner image. On the other hand, the sheets S loaded in the cassette 6
is fed by the paper feed roller 17 through the path 19 to the registration roller 20, aligned with the toner image on the surface of the photoreceptor by the registration roller 20, and further transferred to the toner image at the transfer charging mold 15. is transferred to the sheet surface.

Further, the sheet S carrying the toner image is charged by a separation charger 16.
The image is separated from the photoreceptor 7 by the conveyance device 13, and is sent to the fixing device 21, where it is fixed by the fixing device N21. At this time, the sheet S is heated and pressurized by the fixing device 21, and becomes a curled sheet S having an upward warp at the leading edge of the sheet.

When the double-sided copy mode is selected, the sheet S fixed by the fixing device 21 is guided by the flapper 22 and guided to the sheet re-conveying path 25. Furthermore, the sheet S is conveyed to the double-sided copying path 31 by the rotation of the pair of conveying rollers 26 and 27 and the guidance of the flapper 29, and is then held and conveyed by the pair of conveying rollers 32 and 33 and stacked on the intermediate tray 30.

Then, when a copy signal for the other side is transmitted from the copying machine main body, the paper feed roller pair 35 is rotated, and further, with the paper feed roller pair 35 biting the curled sheet S, the sheet S side The curled sheet S is moved in a direction perpendicular to the sheet conveyance direction until the end is detected by an optical sensor (not shown), and the lateral position of the curled sheet S with respect to the manufacturing conveyance direction is adjusted. Furthermore,
The sheet S is held and conveyed by a pair of conveyance rollers 36 and 37 and conveyed to a pair of curl correction rollers 39. The curl of the sheet S is slightly corrected by the pair of correction rollers 39, and then conveyed to a pair of registration rollers 20. Furthermore, the sheet S is conveyed by a pair of registration rollers 20, and a toner image is transferred to the back surface (the non-copied surface) of the sheet by the photoreceptor 7, transfer charger 15, etc., as described above. that time,
Since the back surface of the sheet S, which is curved upward, is in contact with the photoreceptor 7, the sheet S can be easily separated from the photoreceptor 7. After the sheet S is fixed by the fixing device 21, the sheet with copies on both sides is discharged to the discharge tray 23.

In addition, when the multiple copying mode is selected, the flapper 22 is switched to the sheet re-conveyance path #25 side, and the fixing M2
The copied sheet S fixed in step 1 is guided by a flapper 22 and led to a sheet re-conveying path 25. Then, the sheet S is pinched and transported by a pair of transport rollers 26 and 27, guided by a flapper 29, and stacked on an intermediate tray 30, its lateral position is adjusted by a pair of paper feed rollers 35, and then the pair of transport rollers 36 , 37 to the curl correction roller 39. At this time, the double-sided multiple copying mode setting signal 43
The remoter 42 rotates and operates the cam 41 in response to a command from the control circuit 45 that detects this. Further, the cam 41 moves the bearing member 40 toward the rigid roller 39a and moves the bearing member 40 toward the elastic roller 39b.
The amount of curl correction can be changed by pressing the sheet S against the rigid roller 39a and changing the amount of pressure applied to the sheet S at this time. Then, the sheet S is held between the pair of curl correction rollers 39 to correct its warp, and the corrected sheet S
is conveyed to the registration roller pair 20.

Further, the sheet S is conveyed by a pair of registration rollers 20, and a second image is superimposed and copied on the surface of the sheet S that has been copied once. At this time, since the sheet S whose warp has been corrected comes into contact with the photoreceptor 7, the sheet S can be easily separated from the photoreceptor 7. Furthermore, after the sheet S that has been copied multiple times is fixed in the fixing device 21, it is discharged to the discharge tray 23.

As another embodiment, as shown in FIG.
and a curl correction roller pair 39 that operates only during multiple copying.
d can also be arranged in series. At this time, the correction roller pair 39dl is rotated by a motor 42 which is rotated by a command from a control circuit 45 that detects a double-sided multiple copy mode setting signal 43.
The curl of the sheet S is corrected by operating the cam 41' to press the elastic roller 39b' against the rigid roller 39a'. The amount of curl correction is determined by the rigid roller 3.
It is adjusted by the pressure nip width between 9a' and elastic roller 39b'.

Furthermore, in this embodiment, the curl correction means has one path, but as shown in FIG. The same effect can be obtained even if the curl correction means is configured by a multiple copying path 47 in which the roller pair 39f is arranged.

At this time, the path 46 and the path 47 are branched and guided by a flapper 50 whose driving means is a solenoid 49 that is activated by a command from a control circuit 45 that detects the double-sided multiple copy mode setting signal 43'.

The amount of curl correction is adjusted by changing the diameter of the rigid roller 39a'.

(G) As described in detail, according to the present invention, in the case of multiple copying,
Since the curl of a curled sheet is strongly corrected by the curl correcting means, the separation of the sheet from an image bearing member such as a photoreceptor can be maintained in a good condition equivalent to double-sided copying, and jams caused by bumping can be prevented. You can reduce that. In addition, since we were able to make the curls of double-sided copying and multiple copying equal in the direction away from the image carrier such as the photoreceptor before retransferring, the amount of charge in the post charger, transfer charger, and separation charger was reduced. Since the same amount can be set for double-sided copying and multiple copying, the complexity of changing the charge amount of the post charger, transfer charger, and separation charger can be eliminated.

On the other hand, if the sheet straightening means is composed of an elastic roller and a rigid roller, the amount of sheet straightening (or, the amount of pressure applied to the sheet by the elastic roller and the rigid roller, the pressure nip width, and the diameter of the rigid roller can be adjusted) It is possible.

Furthermore, if a curl correction device with a weak correction force and a curl correction device with a strong correction force that operates only during multiple copying are arranged in series, the sheet will be corrected in two stages, so that the sheet will not be unreasonably curled. Straighten curls without applying force.

If the sheet straightening means is used for double-sided copying and multiple copying in separate paths, the sheet straightening means can be kept operating with a constant straightening force, and the control device can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an image forming apparatus according to the present invention, and FIG.
FIG. 3 is a side view showing the sheet straightening means, and FIGS. 3 and 4 are side views showing sheet straightening means of other embodiments. 7.9, 10, 11.12 Image forming section, 21...
Fixing unit (fixer), 2s...Sheet re-conveying path, 39, 39c, 39d, 39e. 39f - sheet correction means, 39a, 39a'
. 39a'-rigid roller, 39b, 39b'-elastic roller.

Claims (2)

[Claims] (1) In an image forming apparatus that feeds a transfer sheet to an image forming section through a re-conveyance path to form multiple images or double-sided images, the transfer sheet is provided with curl correction means on the re-conveyance path. 1. An image forming apparatus characterized in that the curl correcting means changes the amount of correction during multiple image formation and during double-sided image formation. (2) The image forming apparatus according to claim 1, wherein the curl correction means includes an elastic roller and a rigid roller.