JPH0368971A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the lowering of image density and color slurring at the time of transfer by actuating a separation means after completing the action of a transfer means. CONSTITUTION:An electrostatic latent image is formed on the photosensitive drum 6 of a color copying machine 1 and developed with the toner of one color among the colors of developing devices 71-74 and the action for transferring the image to a transfer drum 8 is repeated four times. After the toner image of four colors is completely transferred to a paper held by the drum 8, a separation charger 14 is turned on to separate the paper from the drum 8. Then, the paper is conveyed to a fixing device 16 and fixation is performed. Thus, the lowering of the image density and the color slurring caused by simultaneously performing a transfer stage and a separation stage are prevented. It is desirable to make a distance from a transfer position by a transfer charger 13 to the device 16 shorter than the length of the paper and to miniaturize the copying machine 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image forming apparatus having a holding means for holding a transfer material, and relates to, for example, a color copying machine having a transfer drum. It is something.

<Prior Art> A color copying machine having a transfer drum is known (see, for example, Japanese Patent Application Laid-open No. 113481/1981). In this type of color copying machine, a transfer material such as transfer paper, OHP sheet, label paper, postcard, etc. is wrapped around the circumferential surface of a transfer drum, and the image formed on the photoreceptor drum is transferred to the paper. and a separation step of separating the paper onto which the image has been transferred from the transfer drum.

By the way, when making full color copies, cyan,
Three or four transfer steps are performed for each color, magenta and yellow, and in some cases black.
Multiple colors are layered. Then, when the final transfer step is performed, a separation step is simultaneously performed in which the paper is separated from the transfer drum, and the paper separated from the transfer drum is conveyed to the fixing device.

<Problems to be Solved by the Invention> However, in conventional color copying machines, the transfer process and the separation process are performed at the same time.
There were disadvantages such as a decrease in the image quality, and during multicolor copying, the transfer position was shifted, causing color shift, and the color tone changed.

In addition, if the paper is long, even if the leading edge of the paper reaches the fixing device, the trailing edge of the paper may not be completely transferred, and a slight impact may be applied to the leading edge of the paper from the fixing device. This had the disadvantage that it adversely affected transfer.

The present invention was made to eliminate the drawbacks of the prior art, and aims to provide an image forming apparatus with good image quality that does not cause deterioration of image density or color shift during transfer. do.

Means for Solving the Problems This invention provides a holding means for holding a transfer material, a transfer means for transferring an image to the transfer material held by the holding means, and a transfer material to which the image is transferred. An image forming apparatus characterized in that it includes a separating means for separating the transfer means from the holding means, and a control means for operating the separating means after the operation of the transfer means is completed.

Further, the image forming apparatus according to the present invention further includes a fixing means for fixing the image transferred to the transfer material after the transfer material is separated from the holding means, and the image forming apparatus further includes a fixing means for fixing the image transferred to the transfer material after the transfer material is separated from the holding means. The positions are characterized in that they are set at intervals shorter than the length of the transfer material in the moving direction.

Effect> Since the control means operates the separation means after the operation of the transfer means is completed, the transfer step and the separation step are not performed at the same time. Therefore, during the transfer process, there are no adverse effects associated with separating the transfer material.

Furthermore, since the separation step is performed after the transfer step, the distance from the transfer position to the fixing means may be shorter than the length in the transfer sheet moving direction.

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

FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a full-color copying machine according to an embodiment of the present invention.

The full-color copying machine 1 includes a lamp 2 for illuminating the original, and a C for reading the contents of the original illuminated by the lamp 2.
A reading sensor 3 including an OD, a lamp 2 and an optical system moving device 4 consisting of a wire, a pulley, a motor, etc. for scanning the reading sensor 3, an LSU 5 that outputs a laser beam based on a signal given from the reading sensor 3, A photoreceptor drum 6 on which an electrostatic latent image is formed by being exposed to laser light provided from the LSU 5; magenta, cyan, and
Four yellow and black developing devices 71, 72.
7B, 74, a transfer drum 8 as a holder for holding paper, a paper feed conveyance path 12 for conveying paper fed from the paper feed cassette 9 or 10 or manual paper feed port 11 to the transfer drum 8; A transfer charger 13 for transferring the toner image on the photosensitive drum 6 onto the paper held by the transfer drum 8; a separation charger 14 for separating the paper to which the toner image has been transferred from the transfer drum 8; and a separation charger 14 for separating the paper onto which the toner image has been transferred from the transfer drum. It includes a conveyor belt 15 for conveying the printed paper and a fixing device 6 for fixing the toner image on the paper.

Although not shown, the full-color copying machine 1 also includes a drum motor for rotating the photoreceptor drum 6 and the transfer drum 8, and a drum motor for switching between a state in which the transfer drum 8 is in pressure contact with the photoreceptor drum 6 and a state in which it is slightly separated from the photoreceptor drum 6. A transfer drum pressure contact clutch, a transport motor for driving the transport belt 15 and the fixing roller, and a control circuit 20 for controlling the operation of each drive source and component are provided.

The configuration of the full-color copying machine 1 described above is the same as that of a conventional full-color copying machine.

The feature of this embodiment lies in the control contents when the above-mentioned configuration is controlled by the control circuit 2O.

Next, in order to clarify the characteristic control contents, the control operation of a conventional full-color copying machine and the control operation of the full-color copying machine according to this embodiment will be compared and explained.

FIG. 3 is a timing diagram showing control operations of a conventional full-color copying machine. Referring to FIG. 3, in a conventional full-color copying machine, a drum motor is turned on based on a print key press signal, and the photosensitive drum 6 and transfer drum 8 are rotated at a circumferential speed of o. Also, lamp 2
After turning on the optical system, the optical system is moved forward after a fixed time delay, the document is illuminated, its contents are read by the reading sensor 3, and the optical system is moved back. This operation is repeated four times. This is because it is necessary to create electrostatic latent images for each of magenta, cyan, yellow, and black on the photoreceptor drum 6.

Further, the transfer charger 13 is turned on based on a signal from the print key, and turned off after the last transfer is completed. The transfer drum pressure contact clutch is turned on in conjunction with the advancement of the optical system and the turning on of the lamp, and when the electrostatic latent image formed on the surface of the photoreceptor drum 6 is developed in a predetermined color, the toner image is transferred to the paper. The transfer drum 8 is brought into pressure contact with the photosensitive drum 6 so that the transfer can be performed.

The separation charger 14 is turned on for a short time when the print key is turned on, and is turned on almost at the same time as the fourth and final turning on of the transfer drum pressure clutch to perform a separation operation.

In other words, the fourth and final transfer step and separation step are performed simultaneously.

Furthermore, the conveyor motor that drives the conveyor belt 15 moves at a circumferential speed of V+(
Usually v,=V. ) so that it rotates with
Always on during copy operation.

In contrast to the control content of the conventional apparatus, in the full color copying machine 1 according to this embodiment, the separation charger 14 is turned on after the transfer drum pressure clutch is turned on four times. In other words, until the four-color toner image is completely transferred to the paper held by the transfer drum 8, in other words, until the transfer drum 8 rotates one more time after the fourth color toner image is transferred, the separation charger 14 is not turned on.

In this way, the separation process is performed after the transfer process is completely completed. This is a feature of this embodiment.

At the time of the fourth and final transfer process, conventionally the separate charger 1
4 is turned on, the transfer process and separation process are performed together, and 4
The paper to which the colored toner image has been transferred was immediately separated from the transfer drum 8 and conveyed by the conveyor belt 15, but in this embodiment, the separation charger 14 was not turned on during the fourth and final transfer process. The paper is not separated but is held as it is by the transfer drum 8 and rotated once. Then, the separation charger 14 is turned on and the paper is separated from the transfer drum 8.

In this way, it is possible to prevent changes in image density during transfer that would otherwise occur due to simultaneous execution of the transfer step and the separation step.

Furthermore, when transferring a toner image to a sheet of paper whose length is longer than the distance from the transfer position to the fixing device 16, if the leading edge of the sheet reaches the fixing device and the trailing edge of the sheet is still being transferred, A slight impact caused by the leading edge of the paper reaching the fixing device 16 may be transmitted to the trailing edge of the paper, causing transfer misalignment, but such transfer misalignment can be prevented.

Furthermore, since the paper is held by the transfer drum 8 during transfer, the paper does not separate from the transfer drum 8, so that the transfer can be performed reliably and no transfer deviation occurs.

Furthermore, the circumferential speed vl of the conveyor belt 15 can be set to an arbitrary speed. In other words, the paper separated from the transfer drum 8 can be provided to the fixing device 16 relatively quickly, and
After the paper reaches the fixing device 16, the speed can be changed to a relatively slow speed in accordance with the speed of the fixing device 16.

As described above, according to this embodiment, a full-color copying machine without color shift or color change can be obtained as a whole.

Furthermore, the distance from the transfer position by the transfer charger 13 to the fixing device 16 may be shorter than the length of the paper, so by shortening the distance between the transfer drum 8 and the fixing device 16, the full-color copying machine 1 can be Another advantage is that the overall size can be made more compact.

Although the above description has been made using the full-color copying machine 1 as an example, it should be noted that the present invention is generally applicable to image forming apparatuses including a transfer material holding means such as a transfer drum or a transfer belt.

<Effects of the Invention> Since the present invention is configured as described above, it is possible to form a good and clear image in an image forming apparatus having a transfer material holding means.

Furthermore, the hardware configuration of the apparatus itself may be the same as that of conventional apparatuses, and the apparatus can still form good images.

[Brief explanation of drawings]

FIG. 1 is a timing chart for explaining the characteristic operation of an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a full-color copying machine according to an embodiment of the present invention. FIG. 3 is a timing chart showing the operation of a conventional full-color copying machine. In the figure, 1... Full color copying machine, 2... Lamp, 3... Reading sensor, 4... Optical system moving device, 5
... LSU, 6... Photosensitive drum, 71.72.7
3゜74...Developing device, 8...Transfer drum, 13.
...Transfer charger, 14...Separate charger, 16
. . . Fixing device, 20 . . . Control circuit. (2 others)

Claims (1)

[Claims] 1. Holding means for holding the transfer material; The image is transferred to the transfer material held by the holding means. a transcription means for copying; Remove the transfer material with the image transferred from the holding means. separation means for separation; After the operation of the transfer means is completed, the separation means is activated. control means for causing the An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, Furthermore, the transfer material is separated from the holding means. After that, fix the transferred image on the transfer material. including fixing means for Transfer position by transfer means and fixing means The position is longer than the length of the transfer material in the moving direction. It is characterized by being set at short intervals. It is something to do.