JPH04247474A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the color contamination of a color developing tank and to improve the quality of an image by oppositely arranging a black developing tank and the color developing tanks by interposing a photosensitive drum and preventing the splashing area of black toner from reaching the color developing tanks. CONSTITUTION:In a developing device provided with the color developing tanks Y, M and C of yellow, magenta and cyan and the black developing tank B of black, the tanks Y, M and C are arranged by being opposed to the tank B so as to interpose the photosensitive body 10. By arranging them in such a way, the splashing toner is intercepted by the body 10 even when the toner is splashed from the tank B. Besides, since an isolating distance between the tank B and the tanks Y, M and C can be set large, the color contamination caused by the toner splashed from the tank B is not generated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to yellow, magenta,
The present invention relates to a developing device having a cyan color developer tank and a black color developer tank.

0002

2. Description of the Related Art FIG. 3 shows a conventional example of a full-color copying machine equipped with this type of developing device. Developer tank Y, magenta developer tank M, cyan developer tank C
and black developer tank B are arranged adjacently in this order. In color copying, the optical system 2 scans the document on the platen glass three times, and each time the light reflected from the document passes through a color separation filter and is exposed to a slit onto the photosensitive belt 1, it produces yellow, magenta, and cyan colors. An electrostatic latent image is formed in a complementary color to the toner. Each time an electrostatic latent image is formed, a yellow developer tank Y, a magenta developer tank M,
Yellow toner, magenta toner, and cyan toner are individually supplied in this order from the cyan developer tank C, and images are superimposed on the transfer belt 3 that is pressed against the photosensitive belt 1.

When the image overlapping is completed, the copy paper is conveyed from the paper feed cassette 4 to the position of the transfer roller 5, where the toner image is transferred to the copy paper. The copy paper that has completed the transfer process is fixed by a fixing device, and then discharged outside the machine.

[0004] Only black toner is used for black and white copying.

[0005]

By the way, according to the developing device having the above structure, since the respective developer tanks are arranged adjacent to each other, toner scattering from the black developer tank B causes the color developer tank Y to
. Incidentally, the area indicated by P in FIG. 3 is the color contamination range.

[0006] When such color contamination occurs, color reproducibility during color copying deteriorates, resulting in an overall black and cloudy image, which impairs image quality.

SUMMARY OF THE INVENTION The present invention has been made to solve these drawbacks of the prior art, and aims to provide a developing device that can reliably prevent color contamination and improve image quality during color copying.

[0008]

[Means for Solving the Problems] The developing device of the present invention has color developing tanks for yellow, magenta, and cyan, and a black developing tank for black. The above object is achieved by arranging it opposite to the tank.

[0009]

[Function] If each developer tank is arranged as described above, even if toner scatters from the black developer tank, the scattered toner will be blocked by the photoreceptor. Since the separation distance from the color developer tank can be set large, color contamination due to toner scattering from the black developer tank does not occur.

0010

[Examples] Examples of the present invention will be described below.

As shown in FIG. 1, the rotation range of the photosensitive drum 10, which can now rotate in the direction of arrow B, includes a charger 11, an inter-image eraser 12, a developing device 13, a transfer belt 14, a cleaning blade 15, and Static elimination lamp 16
are arranged in this order. The developing device 13 includes a yellow developer tank Y, a magenta developer tank M, a cyan developer tank C, and a black developer tank B, and each developer tank stores toner of the same color. The color developer tanks Y, M, and C are arranged opposite to the black developer tank B with the photoreceptor drum 10 in between.

In the above configuration, color copying is performed by the following operating procedure. Once the surface of the photoreceptor drum 10 is uniformly charged by the charger 11, a first scan is performed by a scanner (not shown), and the reflected light from the document is passed through a color separation filter (not shown) to the charger 11 and the inter-image eraser 12. The surface of the photoreceptor drum located between the two is exposed to slit light, and a blue electrostatic latent image is formed in the exposed area. Next, the inter-image eraser 12 erases the portion of the electrostatic latent image corresponding to the non-image area, and yellow toner is supplied from the yellow developer tank Y to the electrostatic latent image in the image area that is not erased, forming a toner image of the same color. be done.

Next, the toner image moves around in the direction of arrow C, and a portion of the toner image is transferred onto a transfer belt 14 that is pressed against the surface of the photosensitive drum 10. At this time, some toner that does not contribute to transfer remains on the surface of the photoreceptor drum 10;
A cleaning blade 15 scrapes off this residual toner. Next, the static elimination lamp 16 eliminates the residual charge on the surface of the photoreceptor drum.

After completing the above steps, the charger 1
1 uniformly charges the surface of the photoreceptor drum again, and the light reflected from the document obtained by the second scan is exposed to the slit, forming a green electrostatic latent image. Thereafter, the non-image area is similarly erased by the inter-image eraser 12, and magenta toner is supplied from the magenta developer tank M to the electrostatic latent image to form a toner image of the same color. Then, this toner image is transferred to the transfer belt 14 and image overlapping is performed. Thereafter, when the same process as described above is performed, the charging charger 11 uniformly charges the surface of the photoreceptor drum again, and cyan toner is supplied from the cyan developer tank C to the photoreceptor drum 10 in the same manner to form a toner image of the same color. is formed. Then, this toner image is transferred to the transfer belt 14, and final image overlapping is performed. Thereafter, the superimposed toner images on the transfer belt 14 are transferred to copy paper, fixed, and then discharged outside the machine.

On the other hand, black-and-white copying is performed by supplying black toner from a black developer tank B to the electrostatic latent image on the photosensitive drum 10, and transferring this toner image onto copy paper via the transfer belt 14.

When each developer tank is arranged as shown in FIG.
For the reasons described below, the color developing tanks Y, M, and C are not contaminated by the black toner scattered from the black developing tank B. That is, FIG. 2 shows a state in which the black toner is scattered. By arranging the color developing tanks Y, M, and C to face the black developing tank B with the photosensitive drum 10 in between, the scattered toner is removed by the photosensitive drum 10. Since the separation distance between the color developer tanks Y, M, and C and the black developer tank B can be increased, the black toner scattering area shown by symbol P in FIG. 2 is located at the position of the color developer tanks Y, M, and C. Because you will never reach it.

In the above embodiment, the present invention is applied to a full-color copying machine equipped with a photosensitive drum, but it can be similarly applied to a full-color copying machine equipped with a photosensitive belt.

[0018]

According to the present invention, even if toner scatters from the black developer tank, the scattered toner is blocked by the photoreceptor, and since the photoreceptor is placed between the black developer tank and the color developer tank, the black developer tank and the color developer tank are separated. Since you can set a large separation distance from
Color contamination due to toner scattering from the black developer tank does not occur. Therefore, the image quality can be significantly improved without adversely affecting color reproducibility during color copying.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a developing device of the present invention together with a photosensitive drum.

FIG. 2 is a drawing showing a state in which black toner is scattered from a black developer tank.

FIG. 3 is a drawing showing a conventional example.

[Explanation of symbols]

10 Photoreceptor drum 13 Developing device Y Yellow developer tank M Magenta developer tank C Cyan developer tank B Black developer tank

Claims (1)

[Claims] 1. A developing device having color developer tanks for yellow, magenta, and cyan and a black developer tank for black, wherein the color developer tank is arranged opposite to the black developer tank with a photoreceptor sandwiched therebetween.