JPS61159670A - Color copying machine - Google Patents

Abstract

PURPOSE:To eliminate an image shift due to load variation during return operation by allowing an original platen to start returning after a transfer process. CONSTITUTION:A color copying machine has the 1st - the 3rd transfer stations C, M, and Y, which are provided with photosensitive drums 5c, 5m, and 5y. Transfer paper 12 is conveyed by a transfer belt 11 in the opposite direction of the copy conveying direction of the original platen 2. Further, the returning operation of the original platen 2 which is performed after the exposure of the final-stage photosensitive drum 5y is carried out after the completion of final transfer end of a color-separated image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color copying machine that obtains color copies by transferring one-color separated images multiple times using a plurality of photosensitive drums.

Conventionally, in color copying machines equipped with multiple photoreceptor drums, after forming a color-separated original toner image on each photoreceptor drum, each photoreceptor drum is rotated in the opposite direction, and the transfer paper is sent to the document platen. The color-separated toner images are sequentially transferred onto the transfer paper by conveying them in the same direction with a transfer belt, thereby obtaining a color copy. In addition, jitter occurs due to load fluctuations during the stop and return of the document table during the transfer process.
Image misalignment may occur.

Therefore, the present invention is based on the viewpoint that if the return of the document table is started after the transfer by the final stage photoreceptor in the transfer process is completed, the load fluctuation at the time of return will have no relation to the image transfer. , which attempts to solve the problem of image misregistration that is a problem with color copying machines.

1. The present invention leaves the document table that has completed the exposure process as it is without inverting it until the end of the transfer process, and starts the return movement of the document table after the transfer process is completed, thereby reducing load fluctuations at the time of return. The present invention is intended to eliminate the occurrence of image misalignment due to the above-mentioned images, and the present invention will be described in accordance with an embodiment using a color copying machine equipped with a transfer station using three-color photosensitive drums of cyan, magenta, and yellow as shown in the drawings.

FIG. 1 is a cross-sectional view showing the schematic configuration of a color copying machine according to the present invention, which includes a document illuminating device, an exposure lens device, a photosensitive drum, a main charger, a developing device, a pre-transfer charger, a transfer charger, a quenching lamp, and more. 1. For example, each device develops cyan.

Three electrophotographic devices that perform magenta development and yellow development are installed in series, and originals placed on the top of the copying machine @ and @ stand are sequentially sent to each electrophotographic device, where they are exposed and developed into three colors. A color-separated image is formed on each photoreceptor drum, and the toner image on each photoreceptor drum is transferred onto a transfer belt from a direction opposite to the direction in which the document table is fed for exposure. The color separation image is transferred from each photoreceptor drum to paper in reverse order.

Therefore, each electrophotographic device is transferred to the first transfer station (cyan) C according to the exposure order of the original placed on the original placing table.
1, a second transfer station (magenta) M, and a third transfer station (yellow) Y.

In FIG. 1, a document table 2 is illuminated on the top surface of a color copying machine 1 while being moved from left to right, and color-separated images are formed on each photoreceptor drum at each transfer station. The document mounting table 2 is designed to return to the initial position in preparation for the next process.

The first transfer station C has an original (red light) illumination device 3.
．． exposure lens device 4, photosensitive drum 5c, main charger 6,
It is composed of a developing device device i7c, a pre-transfer charger (which may be optically neutralized) 8, a transfer charger 9c, and a quenching lamp 10, and exposes the image from the 1M draft to red light to form a cyan toner image on the photoreceptor drum 5C. The cyan image is transferred onto a transfer paper 12 that is transferred by a transfer belt (Mylar 100μ) 11 (to be described later), and the quenching lamp IO performs photostatic discharge in front of the charger, and the main charger 6 again transfers the cyan image to the photoreceptor drum. 5c is charged and the same operation can be repeated. However, until the toner image on the photoreceptor drum is transferred, unnecessary chargers and the like are not operated.

The second transfer stage J-M performs the same work as the first transfer station C, but here.

A magenta toner image is transferred to the photoreceptor drum SlI with green exposure.
The third transfer station Y performs blue exposure to form a yellow toner image on the photoreceptor drum 5y.

Each photoreceptor drum has the same diameter and is configured to be driven by the main motor 13 via a gear, and the interval between each photoreceptor drum is half the drum circumference length (πD/2).
Transfer chargers 9c, 9m, and 9y are provided on the lower surface of each photoreceptor drum, facing each photoreceptor drum via a transfer belt 11 that commonly contacts each photoreceptor drum. It is being

This transfer belt 11 is configured to transport the transfer paper in the opposite direction to the direction of transport for exposure of the original document mounting table 2, and supports rollers 14 and 15 are arranged so as to contact each photoreceptor drum.
The support roll 14 on one side is driven by a retiming belt 16 from the main motor 13, and is charged by a transfer belt charging device 17 provided on the outside of this support roll (rubber roll) 14. The transfer paper 12 sent from the transfer paper tray 18 via the registration roll 19 is electrostatically attracted and sent to the photoreceptor drum of each station, and after the toner image of each color is transferred to the transfer paper by the transfer charger, the support roll The transfer paper is separated and transferred to the fixing bag W120 side by the curvature separation action of the (separation roll) 15.

Note that the registration roll 19 is driven by the timing belt 16 in the same manner as the support roll 14.

Further, the transfer belt 11 is provided with auxiliary support rolls 21 and 22 to prevent the transfer belt from bending downward.
Further, the transfer belt facing the photoreceptor drum 5c of the first transfer station C is not connected to the photoreceptor drum 5c except when necessary.
The support roll 15 is movable downward together with the transfer charger 9c by an arm rod 24 that is swingable about a support shaft 23 so as not to come into contact with the transfer charger 9c. Similarly, the second
The transfer belt 11 is also lowered to a position where it does not come into contact with the photosensitive drum 5I11 in the transfer station M by the downward displacement of the auxiliary support roll 22. Note that the reference numeral 25 is a static eliminator for the transfer belt, and the reference numeral 26 is a cleaning device.

Next, the operation of the color copying machine according to the present invention will be explained.

The original on the original placing table 2 is transferred from the first transfer station to the second transfer station. The transfer belt 11 is transferred to the third transfer station, returns to its original position, and repeats the same operation again. Initially, the transfer belt 11 is in a position where it does not come into contact with the photoreceptor drum of the first transfer station, Ii! Rod 24. Auxiliary support roll 2
In the first transfer station C, after a cyan toner image corresponding to the photoreceptor drum 5c &'-document is formed by the gutter image device 7c, the pre-transfer charger, transfer charger, The photosensitive drum 5c continues to rotate with the quenching lamp and main charger inactive. Similarly, second transfer station M
, a magenta toner image is formed on the photoreceptor drum 5a+, and it continues to rotate while holding the image on the surface, but the transfer belt 11 is separated from the photoreceptor drum 5m due to the downward displacement of the auxiliary support roll 22. be.

Next, when the leading edge of the document reaches the third transfer station Y, the transfer paper is supplied to the transfer belt 11 from the registration roll 19 provided at a distance of half the drum length from the photoreceptor drum 5y. The belt 11 is a charged bag [
The transfer paper is moved with the electrostatic adsorption force exerted by the transfer paper 17, and the yellow toner image formed on the photosensitive drum 5y is transferred to a proper position on the transfer paper by the transfer charger 9y.

Immediately before reaching the second transfer station M, the auxiliary support roll 22 rises and brings the transfer paper transferred by the transfer belt into contact with the photoreceptor drum 5+w at the same time. The magenta image is superimposed on the yellow image and transferred.

Similarly, the transfer paper sent to the third transfer station C is
As the arm rod 24 rises, the transfer charger 9C and the support roll 15 are displaced upward and come into contact with the photosensitive drum 5c of the first transfer station C, and the cyan image is further superimposed and transferred by the action of the transfer charger 9c, completing the color transfer. . Thereafter, the transfer paper 12 is curvature separated by the support roll 15, and then transferred to the fixing device! 20, where it is fixed and color copying is completed.

As understood from the above description, the cyan toner image on the photosensitive drum 5c of the first transfer station C is transferred to the transfer paper in the third rotation after exposure and development, that is, after three times of development. Further, the magenta toner image on the photosensitive drum 5 of the second transfer station M is transferred to the transfer paper after being developed twice.

Only the yellow toner image on the photosensitive drum 5y of the third transfer station Y is immediately transferred to the transfer paper.

In addition, at each transfer station, after transfer.

Cleaning is performed in the developing section by switching the bias. Furthermore, although development is performed several times at the first transfer station and the second transfer station, the development conditions may be set appropriately.

Similarly, cleaning will be performed several times at the third transfer station and the second transfer station.

Further, for a photosensitive drum that continues to rotate on which toner images have been adhered multiple times, a shutter 27 is provided at the exposed portion to prevent it from being re-exposed and is kept closed except when necessary.

As explained above, in this embodiment, when the leading edge of the transfer paper is sent to the lower end of the photosensitive drum 5y of the third transfer station Y, the leading edge of the document toner image comes to the corresponding position, and at that point, The center of the document is at the exposure position, and when the end of the document leaves the exposure position, the center of the toner image of the document is at the transfer position.

Therefore, the document table passes the final exposure position and stops.

If an attempt is made to reverse and return to the initial copy start position, this will necessarily occur during a period in which transfer is being performed.

However, since the return operation of the original table is naturally accompanied by load fluctuations, when the superimposed transfer of one color separated toner image is performed,
Image misalignment occurs.

In the present invention, it is only necessary for the document placing table to reach the start position before the start signal generation timing for the next copy. By performing the return operation of the document mounting table after the final transfer is completed, load fluctuations that occur in the drive system during transfer can be eliminated, and the return operation is performed after the transfer, where the load fluctuations at the time of return are completely unrelated to image transfer. Therefore, if the return speed is set within a range in which the document placing table reaches the start position before the start signal generation timing for the next copy, there will be no problem in the performance of the copying machine.

As described above, according to the present invention, the timing for starting the return of the original placing table is set after the final transfer is completed, and the original placing table is returned at a speed within the range where it returns to the starting position by the time preparation for the next copy is completed. Therefore, it is possible to eliminate the occurrence of transfer image shift due to load fluctuations during return during transfer in the conventional apparatus.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the schematic structure of a color copying machine according to the present invention. l...Color copying machine, 2...Original (, lli loading stand. 3...Original illumination device, 4...Exposure lens device, 5
...Photosensitive drum, 6...Main charger. 7...Developing device, 9...Transfer charger, 1
1... Transfer belt, 12... Transfer paper. 13... Main motor, 14.15... Support roll, 16... Timing belt, 17... Charging device, 19 Registration roll, 20... Fixing device. 21, 22... Auxiliary support roll, 23... Support shaft, 2
4... Arm rod, 25... Belt static eliminator. 26... Cleaning device, 27... Exposure section shutter C... First transfer station (cyan). M...Second transfer station (magenta), Y...
Third is the photo station (yellow).

Claims (1)

[Claims] In a color copying machine equipped with a plurality of photoconductor drums, the document table is configured so that a transfer sheet is transferred by a transfer belt in a direction opposite to the direction in which copying is carried on the document table, and the document table is used after exposure of the final stage photoconductor drum. A color copying machine characterized in that a backward movement operation is started after the final transfer of a color separation image is completed.