JPH0456877A - Color image forming device - Google Patents

Abstract

PURPOSE:To carry out superposing of color toner to a same latent image at low torque and low cost by providing a second image forming mode carrying out the processes of electrification, image exposure, and developing, and then the procedure of only developing for every rotation of an image carrier. CONSTITUTION:The second image forming mode carrying out the processes of electrification, image exposure, and developing, and then the procedure of only developing for every rotation of an image carrier is provided. Therefore, toner images are sequentially superposed and the toner image of full color is synthesized on a photosensitive body drum 1 by a developing device 4 to 7 by a fourth rotation of the photosensitive body drum 1. Thus, each developing device 4 to 7 are operated at each individual timing, and since operation is carried out by changing over of a drive force system making a large driving of torque unnecessary, and because bias power source can also be changed over, the construction and facility are simplified.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a color image forming apparatus that forms a color toner image by superimposing a plurality of toner images of different colors on an image carrier using an electrophotographic method. .

[Background of the invention]

There are many ways to obtain color images using electrophotography.
device has been proposed. For example, Japanese Patent Publication No. 61100770
As disclosed in the publication, a latent image is formed and developed on a photosensitive drum, which is an image carrier, according to the number of separated colors of the original image, and is transferred onto a transfer drum each time it is developed. There is a method of forming a multicolor image and then transferring it onto recording paper to obtain a color copy. In addition to the photoreceptor drum, the device using this method is large enough to transfer one image onto its circumferential surface; it is necessary to provide a transfer drum, and the device becomes large and has a complicated structure. is unavoidable.

For example, as disclosed in Japanese Patent Laid-Open No. 61-149972, a latent image is formed and developed on a photoreceptor drum according to the number of separated colors of the original image, and is transferred onto a transfer material each time it is developed. This is a method of obtaining multicolor copies. With this method, it is difficult to overlap multicolor images with high precision, and it is impossible to obtain high-quality color copies.

Another method is to repeatedly form a latent image on a photoreceptor drum according to the number of separated colors of an original image and develop it with color toner, and then overlap the color toner images on the photoreceptor drum and then transfer the images to obtain a color image. The basic process of forming a multicolor image is disclosed in Japanese Patent Application Laid-open No. 60-75850 and No. 60-7 by the present applicant.
No. 6766, No. 60-95456, No. 60-9545
No. 8, No. 60-158475, etc.

In order to form a multicolor image in which a color image is obtained by such superimposition, a plurality of developing devices containing different colored toners are arranged around the periphery of the photoreceptor drum. The photosensitive drum is rotated multiple times to develop the latent image on the photosensitive drum to obtain a color image.

[Purpose of the invention]

The applicant has specifically proposed a color image forming apparatus that repeatedly develops a latent image on a photoreceptor drum with color toner, superimposes the color toner images on the photoreceptor drum, and then transfers the images to obtain a color image. The proposal was made in Japanese Patent Publication No. 18977/1983.

The gist of this is that there is an image forming mode in which a plurality of colored toners of different colors are sequentially deposited on the same latent image on an image carrier, and a plurality of colored toners of different colors are deposited on different latent images. This is a proposal for a color image forming apparatus having an image forming mode in which images are attached to each image.

In such a color image forming apparatus, full-color monochrome or multi-color images are formed in the same device, so the device can be configured to be small and low-cost, and synchronization control during operation is easy. It has the excellent feature of being accurate.

Furthermore, monochrome printing has the advantage that high-speed printing is possible and that image positional deviation does not occur.

However, in the image forming mode proposed above, colored toners of different colors are superimposed on the same latent image by simultaneously operating a developing device containing the toners, and the position of the image is This printer has the advantage of being able to print quickly and without misalignment, but on the other hand (1) multiple developers operate at the same time, which increases the driving torque required for the developers.

(2) Since development is performed simultaneously by a plurality of developing units, separate power supplies are required for the developing bias applied to the developing sleeves of both developing units.

It had the following drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image forming apparatus that can superimpose colored toners on the same latent image with low torque and low cost.

[Structure of the invention]

The above object is to provide a color image forming apparatus in which a charging means, an image exposure means, and a plurality of developing means are disposed on the peripheral edge of an image carrier, a latent image is formed on the image carrier, and this latent image is developed with toner. , a first image forming mode in which the steps of charging, image exposure, and development are repeated each time the image carrier rotates; and a first image forming mode in which the steps of charging, image exposure, and development, and only the development step are performed each time the image carrier rotates. This is achieved by a color image forming apparatus characterized in that it has a second image forming mode.

〔Example〕

An embodiment of the color image forming apparatus of the present invention will be explained with reference to FIGS. 1 to 4.

FIG. 1 shows an outline of the structure of the apparatus, and its image forming section is composed of the following Proyas equipment.

(2) is a photosensitive drum whose outer peripheral surface is an image carrier; 2 is a charging means, that is, a charger; 3 is a laser layering system unit that is an image exposure means; A charge is applied to the surface by a charger 2, and then the laser layering system unit 3 receives a color signal from the separate pickup device, and the light image of the document is exposed and scanned, thereby forming a document image corresponding to a specific color. Forms an electrostatic latent image. 4 to 7 are developing means, that is, yellow (Y), magenta (M
), cyan (C), and black (BK) color toners, and the corresponding electrostatic latent images are reversely developed to form toner images.

Therefore, by superimposing the toner images developed by the respective developing devices described above, a full color or specified monocolor toner image can be formed.

Each developing device has the same structure and function.
The details will be explained using the developing device 4 shown in FIG.

In the figure, 401 is a housing, 402 is a developing sleeve, 403 is a magnet roller, and 404 is a rigid and magnetic rod-shaped body (cylindrical rod) 405 that regulates the amount of developer.
is a holder that holds the cylindrical rod 404, and 406 is the cylindrical rod 4.
04 and the developing sleeve 402, the cylindrical rod 404 is a spring member that enables the developer to be conveyed, and the cylindrical rod 404 is pressed against the developing sleeve 402 with a constant load without any developer present. 407 and 408 are first and second stirring members, 409 is a supply roller, 410 is a scraper, 4
11 is a stirring partition plate. Further, 412 is a toner replenishing section, 413 is a toner replenishing rotor, 414 is a sponge roller, and 415 is a handle. The toner in the toner supply section 412 is supplied to the developer stirring section by a rotating toner supply rotor 413 and a sponge roller 414.

The toner supplied to the stirring section is sufficiently stirred and mixed with the carrier by a first stirring member 407 that rotates in the direction of the arrow and a second stirring member 408 that rotates in the opposite direction so as to overlap each other, resulting in positive development. It is sent as a agent to the developing sleeve 402 via a supply roller 409.

The first stirring member 407 and the second stirring member 408 are screw-shaped members with a left-handed helical angle that rotate in mutually opposite arrow directions, and are conveyed to the back side by the thrust of the second stirring member 408. The toner and carrier are transported to the front side of the drawing by the thrust of the first stirring member 407, passing over the stirring partition plate 411 whose upper edge is sloped low toward the back of the drawing, and the toner and carrier are conveyed to the front of the drawing by the thrust of the first stirring member 407. A homogeneous developer is triboelectrically charged by the mixing action of the developer and the carrier, and is deposited in a layer on the circumferential surface of the developing sleeve 402 by a sponge-like supply roller 409 rotating in the direction of the arrow.

In this embodiment, a fixed magnet roller 403 and a developing sleeve 40 rotating in the direction of the arrow (clockwise) on the outside of the magnet roller 403 are fixed.
This developer layer, which forms a thin layer attached to the two circumferential surfaces, develops the latent image on the photoreceptor drum L rotating in the direction of the arrow in the development area E without contacting it at a distance, thereby forming a toner image. It was configured as follows.

During this non-contact development, a developing bias containing an AC component is applied to the developing sleeve 402 from a power source (not shown),
On the image forming sleeve 402, only the toner in the developer is selectively transferred and adhered to the surface of the latent image.

The developer that has consumed toner components has a high carrier ratio, is transported by the developing sleeve 402, is peeled off and collected by the scraper 410, and is mixed again with the developer that has a high toner ratio.

Further, 8 is a transfer device, 9 is a separator, and the photosensitive drum l
The above-mentioned toner image is transferred onto a recording paper by a transfer device 8, and the transferred recording paper is further transferred to a separator 9.
Separate and continue rotating.

On the other hand, the photosensitive drum 1 from which the recording paper has been separated by the cleaning device IO is cleaned by removing residual toner thereon by slidingly contacting the photosensitive drum 1 with the blade A of the cleaning device IO.

These equipment, together with the charging, image exposing and developing means described above, are arranged at the periphery of the photoreceptor drum 1, facing the image carrier surface on the outer periphery.

The image forming apparatus of the present invention has a first image forming mode in which a full-color toner image is obtained by superimposing all of the toner images of the four colors developed by the respective developing devices on the latent image of each color. , a second method for obtaining a monochrome image by superimposing two toner images of two colors developed by the two specified developing devices for the same latent image; It has two image forming modes.

First, the process of full-color image copying in the first image forming mode will be explained with reference to the time chart shown in FIG.

When the copy button is pressed, the photosensitive drum 1 starts rotating at a speed of 3 seconds per rotation, and at the same time, the charger 2 starts charging the image carrier.

During the first rotation, the photoreceptor drum 1 receives image exposure of an original light image corresponding to yellow (Y) by the laser layering system unit 3, and the latent image formed thereby is AC and DC.
A yellow (Y) toner image is obtained by reversal development by the developing device 4 to which a bias voltage of 1 is applied in a superimposed manner.

Photosensitive drum l carrying a yellow (Y) toner image
In the second rotation, the image exposure of the original light image corresponding to magenta (M) is superimposed, and the latent image is reversely developed by the developing device 5 to which AC and DC bias voltages are applied in a superimposed manner, resulting in magenta (M). toner image or yellow toner image.

Similarly, in the third and fourth rotations of the photoreceptor drum l, the developing units 6 and 7 are used to produce cyan (C).
) and (BK) are sequentially superimposed to form a full-color toner image on the photoreceptor drum l.

Note that a high DC bias is applied to the developing sleeve during non-development in order to prevent the toner from flying back from the photoreceptor to the developing sleeve, but instead of this, a 70-ting state may be applied.

This full-color toner image is transferred to the paper feed section 11 shown in FIG.
The toner image is transferred onto the recording paper fed by the transfer device 8, and the recording paper, on which the toner image has been transferred, is separated from the photoreceptor drum l and then conveyed via the conveyor belt 12 to the fixing device 13, where the toner is fused and the toner image is transferred. is ejected to the outside of the device as a copy.

Next, the process of monochrome image copying in the second image forming mode will be explained with reference to the time chart shown in FIG.

The mode selection is done by switching the button on the operation panel.
When the image forming mode is selected, the monocolor type is further specified, but in this example, yellow (Y) and cyan (C) toner images are superimposed on the same latent image. A case will be described in which a green (G) toner image obtained by performing alignment is specified.

As in the case of the first image forming mode, when the copy button is pressed, rotation of the photoreceptor drum l and charging of the image carrier by the charger 2 are started, but charging is stopped when charging for the image size is completed. Ru.

During the first rotation of the photosensitive drum 1, an optical image of the document is exposed to laser light, and the latent image formed thereby is reversely developed by a developing device 4 to which AC and DC bias voltages are applied in a superimposed manner. This is used as a yellow (Y) toner image.

Photosensitive drum l carrying a yellow (Y) toner image
In the second rotation, there is no charging or image exposure, and A
A developing device 6 to which C and DC bias voltages are applied in a superimposed manner
A cyan (C) toner image that is subjected to reversal development is superimposed on the yellow (Y) toner image, thereby synthesizing a green (G) toner image.

In the image forming mode described above, the developing devices 5 and 7 are not operated, so that a monochrome toner image is formed by two rotations of the photosensitive drum 1 and one operation each of charging and image exposure.

The monochrome toner image formed in this way is transferred onto recording paper using the same process as the full-color toner image described above, and the transferred recording paper fixes the toner image and is then processed as a monochrome copy. It is discharged to the outside.

Therefore, not only in the first image forming mode but also in the second image forming mode, each developing device is operated at individual timings, so operation is performed by switching the drive power system, and a large drive torque is not required. Since the bias power source can also be used selectively, the structure and equipment are significantly simplified.

In the second image forming mode, the second developing device takes a long time and the potential of the photoreceptor decreases. Therefore, (1) the charging potential is set higher in advance than in the first image forming mode. (i
) During the second development, it is desirable to set the DC bias for development to be lower than that during the first development to prevent fogging in non-image areas, taking into account the potential drop of the photoreceptor.

[Effects of the Invention] The present invention makes it possible to freely select and form full-color monochrome or multi-color images using the same easily equipped image forming apparatus, and as a result, it is compact and low cost. However, a color image forming apparatus that can be used for a variety of purposes has now been provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus of the present invention, FIG. 2 is a cross-sectional view of a developing device included in the apparatus, FIG. 3 is a time chart showing a full-color image forming process by the apparatus, and FIG. is a time chart showing a monochrome image forming process by the apparatus. ■...Photosensitive drum 2...Charger 3...
・Laser layering system unit 4.5.6.7...Developer 8...Transfer device 9...Separator

Claims (1)

[Scope of Claims] A color image forming method in which a charging means, an image exposing means, and a plurality of developing means are arranged on the peripheral edge of an image carrier, a latent image is formed on the image carrier, and this latent image is developed with toner. In the apparatus, a first image forming mode in which the steps of charging, image exposure, and development are repeated each time the image carrier rotates; A color image forming apparatus characterized by having a second image forming mode performed every rotation.