JP2758678B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a PPC copying machine or an information device using a PPC copying machine process, and more particularly to a peripheral speed control of a fixing roller thereof.

<Prior art> Generally, a copying machine performs electrostatic transfer by a transfer device,
The transfer paper is transported to the fixing device by a transport device (suction belt), and the toner image transferred to the transfer paper by the rollers of the fixing device is fixed.

At this time, in the conventional fixing device, the fixing roller is rotated in synchronization with the photosensitive member, but the peripheral speed is always kept constant.

<Problem to be solved by the invention> If the transfer paper is longer than a certain length,
Until the leading edge of the transfer paper enters the fixing roller of the fixing device during the transfer by the transfer device and the transfer paper passes on the transfer device,
There is a section where the image is transferred while being conveyed by the fixing roller.

At this time, in the conventional fixing device, the peripheral speed of the fixing roller is kept constant without adjusting the transfer paper conveyance speed of the fixing roller at the time of electrostatic transfer, so that when the transfer paper enters the fixing roller, The transfer speed of the transfer paper becomes slow, the image is reduced, and the transfer paper shift occurs, and the image quality deteriorates.

If the distance between the fixing roller and the transfer device is longer than the maximum size (length) of the transfer paper, the above phenomenon does not occur. However, due to a reduction in the size of the copying machine and other restrictions on the layout of each image forming apparatus, In many cases, this condition cannot be satisfied.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an image forming apparatus capable of preventing a transfer deviation caused by the influence of a fixing roller and improving image quality by changing a peripheral speed of the fixing roller.

<Means for Solving the Problems> An image forming apparatus for achieving the above object of the present invention employs a photoconductor (P) on a transfer paper (P) by a transfer device as shown in FIGS. 1 and 2, for example. 3) The transfer of the toner image is performed, the transfer paper is conveyed to a fixing device, and the toner image transferred to the transfer paper by the fixing rollers (21, 22) of the fixing device is fixed. An image forming apparatus in which the interval of the transfer paper is set shorter than the length of the transfer paper, wherein a detector (23) arranged close to the paper discharge side of the fixing roller (21, 22) to detect the position of the transfer paper; Until the leading edge of the transfer paper is detected by the detector, the peripheral speed of the fixing roller is drive-controlled faster than the peripheral speed of the photoconductor, and from the time when the leading edge of the transfer paper is detected by the detector. Until the trailing edge of the transfer paper is detected, the peripheral speed of the fixing roller is Drive control is performed slower than the peripheral speed of the photoconductor, and after the rear end of the transfer paper passes through the fixing roller and is detected by the detector, the peripheral speed of the fixing roller is set to be lower than the peripheral speed of the photoconductor. Control device with fast drive control (24)
And characterized in that:

<Operation> In the means for solving the above problems, the transfer roller on which the toner image on the photoconductor 3 is transferred is fixed by the fixing rollers 21 and 22.

At this time, the position detector 23 detects the position of the transfer paper,
An output signal is output to the control device 24.

Then, the control device 24 controls the driving of the peripheral speed of the fixing rollers 21 and 22 at a speed higher than the peripheral speed of the photoconductor 3 until the detector 23 detects the leading end of the transfer sheet P without detecting the transfer sheet P. Therefore, the fixing rollers 21 and 22 are moved at a high speed until the leading end of the transfer sheet onto which the toner image has been transferred by the transfer device passes between the fixing rollers 21 and 22 and is detected by the detector 23 on the discharge side. Being driven. As a result, the leading edge of the transfer paper is fixed to the fixing rollers 21 and 2
When the sheet 2 enters (enters) 2, it can hit the fixing roller and prevent the occurrence of transfer deviation such as image shrinkage caused by a reduction in the conveying speed.

Thereafter, when the leading end of the transfer paper passes through the fixing rollers 21 and 22 and is detected by the detector 23, the control device 24
Controls the peripheral speed of the fixing rollers 21 and 22 so as to be lower than the peripheral speed of the photoconductor 3.

Accordingly, it is possible to prevent elongation of an image caused by pulling of the transfer paper due to a difference in peripheral speed between the fixing rollers 21 and 22 and the photoconductor 3, and to prevent deterioration in image quality due to occurrence of transfer deviation.

This speed state is maintained until the rear end of the transfer paper completely passes through the fixing rollers 21 and 22 and is detected by the detector 23. Therefore, the state of the fixing process is stabilized without changing the fixing state during the fixing process of the transfer sheet.

Then, the rear end of the transfer paper P passes through the fixing rollers 21 and 22, and this is detected by the detector 23.
The drive speed of the peripheral speed of 1,22 is controlled faster than the peripheral speed of the photoconductor 3,
It is in a state of waiting for the next transfer paper P to be sent to the fixing roller.

<Embodiment> An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a functional block diagram of a control device of a fixing device showing one embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a paper passing position of a transfer sheet and a peripheral speed ratio of a fixing roller, and FIG. FIG. 2 is an overall configuration diagram of the copying machine.

Generally, as shown in FIG. 3, a copying machine includes an exposure optical system 2 for exposing a document on a document table 1, a photoreceptor 3 for forming an electrostatic latent image on the surface by reflected light from the optical system 2, and The photoconductor 3
A developing device 4 for visualizing the electrostatic latent image, a transfer device 5 for transferring the toner image on the photoreceptor 3 visualized by the transfer machine, and fixing the transferred toner image to transfer paper. Device 6;
A paper feeding device 7 for feeding the transfer paper to the photoreceptor 3 and a transport device 8 for transporting the transfer paper from the transfer device 5 to the fixing device 6
And a paper discharging device 9 for discharging the transfer paper from the fixing device 6
It is composed of

In the drawing, reference numeral 8a denotes a suction belt of the conveying device 8, 10a.
Is a first mirror motor that drives the mirrors 1a, 1b, 1c of the optical system 2, 11 is a second mirror motor that drives the mirrors 1d, 1e of the optical system 2, and 12 is a lens that drives the lens unit 1f of the optical system 2. A motor, 13 is a charging device, 14 is a blank lamp, 15 is a static eliminator, 16 is a cleaning device, 17 is a main motor, and 18 is a cleaner.

Then, the fixing device of this embodiment is, as shown in FIGS.
An upper fixing roller 21 for heating the transfer paper is provided in the fixing device body 20.
And a lower fixing roller 22 for pressing the transfer paper, and the fixing roller
A position detector 23 disposed close to the paper ejection side of the transfer rollers 21 and 22 for detecting the position of the transfer machine; and a control for controlling the peripheral speed of the fixing rollers 21 and 22 based on an output signal from the position detector 23. Device 24
And

As shown in FIGS. 2 and 3, the upper fixing roller 21 is supported rotatably clockwise in the fixing device main body 20, and a heater lamp 25 for heating the upper fixing roller 21 is provided therein. I have. A peeling claw 26 for removing the toner attached to the fixing roller 21 is provided below the upper fixing roller 21 on the sheet discharge side.
Are arranged in close proximity.

The lower fixing roller 22 is supported by the fixing device main body 20 so as to press against the upper fixing roller 21 and rotate counterclockwise following the upper fixing roller 21. Then, the lower fixing roller 22
A release claw 27 for removing the toner attached to the lower fixing roller 22 is disposed close to the upper part of the paper discharge side.

As shown in FIG. 2, the position detector 23 includes a light emitting element 23a and a light receiving element 23b. The light emitting element 23a and the light receiving element 23b
When the sheet reaches the conveyance start position of the fixing rollers 21 and 22 from the entry start position of the fixing rollers 21 and 22, it is disposed to face a position where the detection optical path of the position detector 23 is blocked.

The control device 24 is a general one-chip microcomputer having a data RAM and a program CPU, and performs control according to a program stored in advance in the ROM. Then, as shown in FIG.
Position determining means 28 for determining whether or not the transfer paper is at the fixing position based on the output signal from the position detector 23, and when the determination result by the position determining means 28 is the non-fixing position (when the leading end of the transfer paper is (Until they enter the fixing rollers 21 and 22 and when the rear end of the transfer sheet comes out of the fixing rollers 21 and 22)
The first peripheral speed control means 29 for controlling the peripheral speed of the fixing rollers 21 and 22 faster than the peripheral speed of the photoconductor 3 and the position discriminating means 28 determine that the leading end of the transfer paper starts conveying the fixing rollers 21 and 22. A second peripheral speed control means for controlling the peripheral speeds of the fixing rollers 21 and 22 to be lower than the peripheral speed of the photoconductor 3 when it is determined that the peripheral position has been reached;
30 and has.

In addition, the driving of the fixing rollers 21 and 22 can be variably controlled by a DC motor or the like separately from the driving of the photoconductor 3 or the like, or a transmission device is provided between other driving systems, and the driving of the fixing rollers 21 and 22 is performed. The peripheral speed can be variably controlled.

In the above configuration, when the transfer paper is fed to the photoconductor 3 by the paper feeding device 7, the electrostatic latent image on the photoconductor 3 is visualized on the transfer paper by the developing device 4. Then, the visualized toner image on the photoconductor 3 on the transfer paper is transferred by the transfer device 5, and the fixing device 6 is transferred by the suction belt 8 a of the transport device 8.
Transported to Thereafter, the transferred toner image is heated and pressed by the fixing rollers 21 and 22 of the fixing device 6 and is fixed on the transfer paper.

At this time, the position detector 23 detects the position of the transfer paper,
An output signal is output to the control device 24.

Then, the position determining means 28 in the control device 24 determines that the transfer sheet is in the non-fixing position (until the leading end of the transfer sheet enters the fixing rollers 21 and 22) based on the output signal from the position detector 23. Then, a signal is output to the first peripheral speed control means 29.
Then, the first peripheral speed control unit 29 controls the peripheral speed of the fixing rollers 21 and 22 based on the output signal from the position determination unit 28 to be several percent to several tens percent faster than the peripheral speed of the photosensitive member 3 ( (See FIG. 2).

As a result, when the transfer paper enters the fixing rollers 21 and 22, it is possible to prevent the transfer speed of the transfer paper from being momentarily reduced, so that transfer deviation due to image shrinkage can be prevented.

By the way, if the peripheral speed of the fixing rollers 21 and 22 is maintained as described above, the transfer paper is stretched due to the difference in speed between the conveying speed of the fixing rollers 21 and 22 and the peripheral speed of the photoconductor 3, and
Transfer deviation occurs.

However, when the position determination unit 28 determines that the leading end of the transfer sheet has reached the transport start position of the fixing rollers 21 and 22 based on the output signal from the position detector 23, the second peripheral speed control unit 30 Output a signal. Then, the second peripheral speed control means
The control unit 30 controls the peripheral speed of the fixing rollers 21 and 22 based on the output signal from the position determining unit 28 to be several percent lower than the peripheral speed of the photoconductor 3.

Here, the reason why the peripheral speed of the fixing rollers 21 and 22 is not the same as the peripheral speed of the photoconductor 3 is that the peripheral speed of the fixing rollers 21 and 22 and the peripheral speed of the photoconductor 3 are different.
When the peripheral speeds of the transfer rollers are the same, the transfer paper expanded by the high-speed rotation of the fixing rollers 21 and 22 at the time of entering the fixing rollers 21 and 22 is conveyed by the fixing rollers 21 and 22 in an expanded state, and an image is formed. This is because the image is transferred and fixed while being stretched, and the image quality is reduced.

Thereby, the first peripheral speed control unit 29 and the second peripheral speed control unit
The speed difference between the peripheral speeds caused by the operation of the transfer roller 30 is absorbed as the deflection between the photosensitive member 3 of the transfer paper and the fixing rollers 21 and 22, so that the image difference due to the speed difference between the peripheral speeds of the fixing rollers 21 and 22 and the photosensitive member 3 is obtained. Elongation can be prevented, and transfer misregistration can be prevented.

Thereafter, when the position determining unit 28 determines again that the transfer sheet is in the non-fixed position (when the rear end of the transfer sheet has come out of the fixing rollers 21 and 22) based on the output signal of the position detector 23,
A signal is output to the first peripheral speed control means 29 again. Then, the first peripheral speed control unit 29 controls the peripheral speed of the fixing rollers 21 and 22 to be higher than the peripheral speed of the photoconductor 3 again based on the output signal from the position determination unit 28.

The timing at which the first peripheral speed control means 29 is operated again may be any time after the transfer of the transfer paper is completed. It is desirable that the switching be performed after the section has left the fixing rollers 21 and 22.

As described above, the position detector 23 is provided in the vicinity of the fixing rollers 21 and 22, and the control device 24 is provided with the fixing rollers 21 and 22 at the time of non-fixing.
First peripheral speed control means 29 for controlling the peripheral speed of the photoconductor 3 faster than the peripheral speed of the photoconductor 3, and the peripheral speed of the fixing rollers 21 and 22 based on the transfer paper tip passage signal from the position detector 23. And a second peripheral speed control means 30 for controlling the peripheral speed of the fixing rollers 21 and 22 to be lower than the peripheral speed of
And at the time of fixing, the speed is lower than the peripheral speed of the photoconductor 3, so that the transfer paper transport speed of the fixing rollers 21 and 22 can be adjusted.

Therefore, it is possible to prevent the occurrence of transfer deviation due to the influence of the fixing rollers 21 and 22, and to improve the image quality.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention.

<Effects of the Invention> As described above, according to the image forming apparatus of the present invention, even when the transfer paper reaches the fixing device and is fixed while the transfer to the transfer paper is being performed, the fixing roller The shift of the toner image on the transfer paper caused when the leading edge of the transfer paper enters the transfer paper can be prevented, and the transfer shift due to the influence of the fixing roller can be prevented even during the fixing process. further,
Until the rear end of the transfer sheet passes through the fixing roller, the speed is not changed and the fixing state does not change halfway, so that the image quality during fixing does not deteriorate. These can be achieved by providing a detector close to the paper discharge side of the fixing roller, and one detector is sufficient.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a control device of a fixing device showing an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a paper passing position of a transfer sheet and a peripheral speed ratio of a fixing roller, and FIG. FIG. 2 is an overall configuration diagram of the machine. 3 photoconductors, 21 and 22 fixing rollers, 23 position detectors, 24 control devices, 28 position determination means, 29 first peripheral speed control means, 30 second circulation Speed control means.

Continuation of front page (56) References JP-A-64-44475 (JP, A) JP-A-60-80885 (JP, A) JP-A-62-161182 (JP, A) JP-A-62-161157 (JP) JP-A-1-248171 (JP, A) JP-A-2-132482 (JP, A) JP-A-64-44474 (JP, A)

Claims (1)

(57) [Claims] A transfer device for transferring the toner image of the photoreceptor onto the transfer paper; conveying the transfer paper to a fixing device; fixing the toner image transferred to the transfer paper by a fixing roller of the fixing device; In an image forming apparatus in which a distance between a transfer device and a fixing roller is set to be shorter than a length of a transfer sheet, a detector that is disposed close to a discharge side of the fixing roller and detects a position of the transfer sheet; The driving speed of the peripheral speed of the fixing roller is controlled to be faster than the peripheral speed of the photoconductor until the leading edge of the transfer paper is detected by the detector. Until the trailing edge of the paper is detected, the peripheral speed of the fixing roller is drive-controlled to be lower than the peripheral speed of the photoconductor,
A control device that drives and controls the peripheral speed of the fixing roller faster than the peripheral speed of the photoconductor after the trailing end of the transfer paper passes through the fixing roller and is detected by the detector. An image forming apparatus characterized in that: