JPH0430022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrophotographic copying machine that performs copying by performing multiple transfers of different colors onto a single sheet of paper.

Prior Art A conventional color electrophotographic copying machine is constructed as shown in FIG.

That is, a platen glass 1 is installed on the top of the copying machine, and an original 2 placed on the platen glass 1 is irradiated in a slit shape with an exposure lamp 3.
The light diffusely reflected by mirror 4, lenses 5 and 3
The image is projected onto an exposure area 8 of a drum-shaped photoreceptor 7 through a filter 6 selected from one of the types of primary color filters.

Further, around the drum-shaped photoreceptor 7, three types of developing units 11a, 11b,
11c, a charger 12, a transfer drum 13, a cleaner 14, and a charger 10 are arranged in this order.
The paper 16 in the cassette tray 15 is transferred to the paper feeder 17.
The paper 16 is sent to the transfer drum 13 by the gripper of the drum 13, and the leading edge of the paper 16 is gripped by the gripper of the drum 13. A complementary color of a certain color is exposed onto the drum-shaped photoreceptor 7, and the complementary color is developed by the developing device 11a corresponding to the complementary color. The toner is developed and transferred to the paper 16 in the transfer area 9, and then complementary colors of other colors are sequentially repeated twice and exposed.
The three types of complementary color toners are transferred and layered on the surface of the paper 16.

Furthermore, the paper 16 that was being held by the gripper
The leading edge of the paper 16 is removed from the gripper after three transfers, and the paper 16 is transferred to the transfer drum 1 by the switching claw 18.
3 and sent to a plain heater type fixing device 20 by a conveyor belt 19.
The toner image is fixed by a printer and then discharged by a discharge roll 21.

In a conventional color electrophotographic copying machine that performs multiple copies while holding the paper 16 on the transfer drum 13, the toner image transferred to the paper 16 remains unfixed and is transferred to the transfer drum along with the paper 16. 13, therefore, when rotating at high speed or when the rotation speed changes, the toner image is likely to be disturbed, affecting the copied image, and the toner may separate from the paper and contaminate the inside of the copying machine. .

For this reason, the rotation speed is a constant rotation below a predetermined speed, and as a result, unlike single-color electrophotographic copying machines that do not use a transfer drum, the copying speed cannot be changed according to the document size, and color transfer is performed multiple times. In copying, this has been a major obstacle in improving copying speed.

Purpose of the Invention The present invention relates to an improvement of a color electrophotographic copying machine that overcomes the above-mentioned difficulties.The purpose of the present invention is to fix each transfer without using a transfer drum, and to circulate the copying machine while fixing each transfer. By doing so, it is possible to provide a color electrophotographic copying machine at a low cost that does not cause disturbance of transferred toner images even when the circulation transport speed of paper is increased or changed.

Structure of the Invention The present invention provides a color electrophotographic copying machine that performs copying by performing multiple transfers on one sheet of paper.
a circulating paper feeding means for peeling off the photosensitive member and the transfer paper from the transfer area of the photosensitive member and circulating the same to the photosensitive body transfer area again; a fixing means interposed in the circulating paper feeding means; The circulating paper feeding means includes a paper ejection switching means disposed downstream of the fixing means, and a timing paper feeding means for supplying the transfer paper to the transfer area at a timing just before the transfer area, and The paper transport means is a color electrophotographic copying machine that transports the transfer paper that has passed through the fixing means to the timing paper transport means at a higher speed than the speed at which it passes through the transfer area. Since the transfer speed of the paper after fixing is increased, the cycle time required for copying can be shortened.

Embodiment An embodiment of the present invention illustrated in FIG. 2 will be described below.

In the embodiment shown in FIG. 2, except for the transfer section and fixing section of the conventional copying machine shown in FIG.
Other parts such as an exposure system, a charging system, and a developing system are formed in the same manner as each part of the conventional copying machine.

Further, a transfer charger 22 and a peeling charger 23 are arranged opposite to the transfer area 9 of the drum-shaped photoreceptor 7, and a transport roll 25 and a guide 26 are arranged so that the transfer area 9 becomes a part of the circulation path. A circulating paper feeder 24 is formed, and the paper 16 is circulated and fed clockwise within the circulating paper feeder 24 in response to the drum-shaped photoreceptor 7 which is rotationally driven in the counterclockwise direction. It's becoming like that.

Further, in the circulation paper feeder 24, a heating roll type fixing device 27 is installed downstream of the transfer area 9 and adjacent to the transfer area 9, and the paper 16 is supplied from the cassette tray 15 toward the fixing device 27. A paper feeding device 17 is arranged so that the paper feed device 17 is arranged so that the paper feeding device 17 is

Furthermore, within the circulation paper feeder 24, a switching branch guide 28 is arranged downstream of the heating roll type fixing device 27, and when the switching branch guide 28 is switched downward as shown in FIG. The paper 16 fixed by the fixing device 27 is circulated in the circulating paper feeder 24, and when the switching branch guide 28 is switched upward, the paper 16 is ejected to the paper ejection tray 29 via the ejection roll 21. It's summery.

In the circulation paper feeder 24, the conveyance speed of the conveyance roll 25 on the downstream side of the switching branch guide 28 is set higher than the circumferential speed of the drum-shaped photoreceptor 7.

Further, a register roll 30 corresponding to timing sheet feeding means is disposed upstream of the guide 26.

Since the embodiment shown in FIG. 2 is constructed as described above, the paper 16 in the cassette tray 15
The heated roll type fixing device 27 is fed by the paper feeder 17 in synchronization with the scanning of the exposure systems 3, 4, 5, and 6.
After being dried and shrunk in the fixing device 27, it passes through the circulation feeder 24 and is transferred to the register roll 30.
The leading edge of the paper 16 is sent to the transfer area 9 by the register roll 30 at the same time as the leading edge of the toner image of the document 2 formed on the drum-shaped photoreceptor 7 reaches the transfer area 9. A toner image of a predetermined complementary color is transferred onto the paper 16 by the transfer charger 22, the paper 16 is peeled off from the drum-shaped photoreceptor 7 by the peeling charger 23, and the toner image is fixed on the paper 16 by the fixing device 27. be done.

Next, the filter 6 is switched to a filter of another primary color, and the developing device 11b of a complementary color corresponding to the same primary color is operated, and a document toner image of the complementary color is formed on the circumferential surface of the drum-shaped photoreceptor 7.
2 on the first original toner image transferred and fixed on top.
After the th complementary color original toner image is superimposed and transferred, it is fixed again by the fixing device 27, and after repeating such exposure, development, transfer and fixing three times, the switching branch guide 28 is switched upward. The paper is discharged onto the paper discharge tray 29.

In this case, the paper 16 that has passed through the fixing device 27 is
Since the transfer paper is rapidly sent to the transfer area 9 by the high-speed conveyance roll 25 located downstream of the switching branch guide 28, the transfer paper is moved at a backward scanning speed that is higher than the forward scanning speed during exposure scanning of the original 2. 16 can be circulated to perform copying within a short time.

For example, if the diameter of the transfer drum 13 is selected so that A3 size paper can be copied using the conventional copying machine shown in FIG.
The scanning cycle for A3 size paper is the _a1 curve in Figure 5-a (in Figure 5, the horizontal axis is time and the vertical axis is distance), and the transfer cycle for the same size paper is a in Figure 5-a. ₂ curves (the part that overlaps with the a ₁ curve is a solid line, the rest is a dotted line). And the scanning cycle for A4 size paper, which is √2/2 times the A3 size, is 5-a.
b ₁ curve in the figure, and its cycle time is reduced by a factor of √2/2, but the transfer cycle is reduced by 1 transfer drum.
Since the diameter of the document 3 remains unchanged, it is the same as in the case of A3 size copying, and therefore the copying cycle remains constant regardless of the size of the document.

Further, in the embodiment shown in FIG. 2, the scanning cycle for A3 size and A4 size paper is 5-b.
As shown by the a ₁ and b ₁ curves in the figure, there is no difference from the conventional one. In the transfer cycle for A3 size paper, the speed of the paper is constant until the time point D1 when the trailing edge of the A3 size paper passes through the fixing device ₂₇ after passing through the reciprocating switching point _C1 of the scanning cycle.
After this time point _D1 , the paper is transported at a high speed as shown by line _E1 , and the paper is transferred in time with the restart of the scanning cycle.
However, if the paper (same document) size is reduced to A4, one scan of an A4 size document passes through ₂ points C, ₂ points D, and ₂ lines E in Figure 5-b. When the transfer is completed, the paper can be transferred at the same time, and there is no waiting time until the transfer is completed, and the copy cycle time is shortened by the reduction in the size of the original and the paper. In this way, by increasing the transport speed of the paper after transfer, the cycle time required for copying can be shortened, and in response to such speed changes, the toner image transferred to the paper is fixed each time it is transferred, so the image may be distorted. I won't let you.

Furthermore, the toner image transferred to the paper is fixed and circulated, so the circulation paper feeder 2 for conveying the paper
4, a conveyance roll 25 can be used, and the structure can be simplified and costs can be reduced.

Furthermore, since the paper 16 is heated and shrunk before transfer, color shift due to shrinkage of the paper 16 can be prevented, and high-quality color copies can be obtained.

In the circulating paper feeder 24 of the embodiment shown in FIG. 2, the paper 16 was transported only by the transport rolls 25, but as shown in FIG. may be interposed,
In such an embodiment, unreasonable tension is not generated in the paper 61 due to a speed difference during conveyance.

In addition, as shown in FIG.
An insulating elastic belt 32 is used instead of paper 1.
The paper 16 may be attracted to the belt 32 and conveyed by the electrostatic force between the paper 16 and the belt 32.

By providing the above-described high-speed paper feeding means, it is possible to freely correspond to the size of the transfer paper, and it is possible to use a transfer paper of a larger size than that using a transfer drum.

Effects of the Invention The present invention provides a color electrophotographic copying machine that performs copying by performing multiple transfers on one sheet of paper.
A circulating paper feeding means is provided for peeling off the transfer paper from the transfer area of the photoreceptor and circulating it again to the photoreceptor transfer area, and a fixing means is interposed in the circulation paper feeding means. A developed toner image of a certain color can be transferred and fixed onto paper, and a high-quality image can be maintained without disturbing the toner image even when the paper transport speed changes.

Further, since the transferred toner image is fixed each time it is transferred, a normal conveyance roll can be used as the circulating paper conveyance means, and the cost can be reduced with a simple structure.

Further, in the present invention, since the paper ejection switching means is disposed downstream of the fixing means in the circulating paper feeding means, by operating the paper ejection switching means, the paper on which the required color copying has been completed is transferred to the circulating paper feeding means. It can be discharged by means.

As described above, in the present invention, since the paper that has been fixed in the circulating paper feeding means is circulated to a predetermined transfer area at high speed, completely independent of the moving speed of the photoreceptor, it is possible to In order to shorten the time required to scan a document, the circulating paper feeder 2 is
It is possible to shorten the time required for one circulation of the paper in the four sheets, and to greatly improve the copying speed.

In addition, since high-speed paper feeding is performed on the transfer paper after fixing, the paper feeding means such as a conveyance roll can be freely configured, the structure can be made smaller and simpler, and costs can be reduced. It is possible to use a larger size transfer paper than the one used.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of a conventional color electrophotographic copying machine, FIG. 2 is a schematic side view illustrating an embodiment of a color electrophotographic copying machine according to the present invention, and FIGS. 3 and 4 are different from each other. FIG. 5 is a schematic side view of the main part of the embodiment, and is an explanatory view showing the difference in function and effect between the conventional one and the present invention. 1...Platen glass, 2...Original, 3...Exposure lamp, 4...Mirror, 5...Lens, 6...Filter,
7... Drum-shaped photoreceptor, 8... Exposure area, 9... Transfer area,
10... Charger, 11... Developer, 12... Charger, 1
4...Cleaner, 15...Cassette tray, 16...
Paper, 17...Paper feeding device, 21...Ejection roll, 22
... Transfer charger, 23... Peeling charger, 24... Circulating paper feeder, 25... Conveyance roll, 26... Guide, 27...
Heating roll type fixing device, 28...Switching branch guide, 2
9... Paper output tray, 30... Register roll, 31
...Vacuum type conveyance means, 32...Insulating elastic belt.

Claims (1)

[Claims] 1. In a color electrophotographic copying machine that performs copying by performing multiple transfers on one sheet of paper, one photoreceptor and transfer paper are separated from the transfer area of the photoreceptor and circulated again to the transfer area of the photoreceptor. and a fixing means interposed in the circulating paper feeding means.
The circulating paper feeding means includes a paper ejection switching means disposed downstream of the fixing means, and a timing paper feeding means for supplying the transfer paper to the transfer area at a timing just before the transfer area, and A color electrophotographic copying machine characterized in that a paper transport means transports the transfer paper that has passed through the fixing means to a timing paper transport means at a higher speed than the speed at which the paper passes through the transfer area.