JPH0435893Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a color copying apparatus that uses a two-component developer with a low resistance carrier and uses a plurality of photosensitive drums.

[Prior Art] In a color copying apparatus using a plurality of photosensitive drums, the amount of toner adhering to each drum is different. Furthermore, when a low-resistance carrier developer is used, the amount of toner adhesion decreases with the number of times of development. In a color copying device that uses multiple photoreceptor drums, the number of times of development differs depending on the position of the developing device, resulting in differences in toner density for each photoreceptor drum, which will make it impossible to maintain color balance. I had to change.

[Purpose] Therefore, the present invention aims to optimize the amount of toner adhering to the photoreceptor drum before transfer in a color copying device that uses multiple photoreceptor drums and performs multiple development using a two-component developer with a low resistance carrier. The purpose is to

[Structure] The present invention provides a multicolor copying apparatus that performs color copying using a plurality of latent image carriers with different number of times of development, in which one of the developing devices provided for each of the plurality of latent image carriers has a number of times of development. Among the plurality of latent image carriers, a developing device using a toner that is less likely to reduce the amount of toner attached to the latent image carrier as the amount of toner adhered to the latent image carrier increases is installed on the latent image carrier that is frequently developed. It is characterized by this.

[Example] Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a multicolor copying apparatus using three photosensitive drums, and FIG. 2 is a graph showing the relationship between the number of times of development and the amount of toner attached.

The developer according to the present invention uses a low resistance carrier (10 ¹⁰ Ω
cm or less) is used.
Development using a low-resistance carrier has the advantage that a wide area can be uniformly copied.

The original placed on the original placing table 2 on the upper surface of the color copying apparatus 1 is placed in an electrophotographic apparatus M having a magenta developing device;
The document advances in the direction in which the electrophotographic apparatus C having a cyan developing device and the electrophotographic apparatus Y having a yellow developing device are lined up, and is sequentially illuminated by the document illumination device 3 in each electrophotographic apparatus. The image of the original document is formed by each exposure lens device 4 on the photoreceptor drum 5m, a magenta latent image, a cyan latent image on the photoreceptor drum 5c, and a yellow latent image on the photoreceptor drum 5Y. On the other hand, the transfer paper 6 is fed by the registration roller 7 at the same timing, and is conveyed on the transfer belt 8 in the opposite direction to the traveling direction of the document, between each photoreceptor drum and the transfer chargers 9Y, 9c, and 9m. Each time the drum passes, the toner image on the drum is sequentially transferred. At that time, each photoreceptor drum 5Y, 5
m and 5c continue to rotate at a constant speed.

That is, after the photoreceptor drum 5Y is developed once, the transfer is immediately transferred onto the transfer paper 6 by the transfer charger 9Y, but the transfer paper 6 is transferred to the photoreceptor drum 5c only after it has been developed twice. Transfer is not performed by the transfer charger 9c, and transfer is performed by the transfer charger 9m only after the photosensitive drum 5m has been developed three times. After the drum rotates three times in this way, all the toner images on the drum surface are transferred to the transfer paper 6, and the transfer paper 6 is conveyed to the fixing device 10, where the transferred toner image is fixed. Therefore, during this time, the photosensitive drum 5Y is 1
After developing twice, the photosensitive drum 5C is cleaned three times, and similarly, the photosensitive drum 5C is cleaned twice after developing twice, and the photosensitive drum 5m is cleaned three times.

Next, conductive carrier TEF with low resistance carrier
FIG. 2 shows a graph showing the toner adhesion amount for each of the three colors according to the number of times of development using a two-component developer using -V. According to the graph, yellow Y is 1
It monotonically decreases from 1st to 3rd development, magenta M remains constant from 1st to 3rd development, cyan C remains at the same level for 1st and 2nd development, and begins to decrease from 3rd development.

In this manner, when development is performed many times using a low-resistance carrier, the amount of toner adhering to each color on the photoreceptor drum decreases with the number of times of development.

In addition, when observing the images, it was found that the reproduction of line drawings worsened as the number of times of development increased, and in particular, as the toner adhesion amount tended to decrease as shown in Fig. 2 Y, the reproducibility of line drawings deteriorated. There is a strong tendency to

Therefore, when the number of times of development is different, such as in the color copying apparatus 1 having three photosensitive drums, there is little tendency for the amount of toner adhesion to decrease with respect to the number of times of development.
By installing the cyan C developer at the twice development position, the cyan C developer at the twice development position, and the yellow Y developer, where the toner adhesion amount decreases the most with respect to the number of times of development, at the once development position, the predetermined toner of each of the three colors can be It is possible to obtain a sufficient amount of adhesion, and also prevent deterioration in the reproducibility of line drawings.

[Effects] According to the present invention, by utilizing the fact that the relationship between the number of times of development on a photoreceptor drum and the amount of toner adhering to the same surface is different for each color toner developer, colors with characteristics suitable for photoreceptor drums that have different number of times of development are created. By installing a toner developing device, it is possible to bring the amount of toner adhesion close to the target value, and it is possible to achieve excellent color balance and improve the reproducibility of solid areas and fine line images.

In addition, the multicolor copying apparatus of the present invention uses multiple photoreceptor drums and develops multiple times, so the copying speed is higher than that of a device with one photoreceptor drum. In addition to having the effects of preventing misalignment and image unevenness and reducing the number of parts, it is also possible to form an image on the entire surface of the transfer paper without the need for a gripper, so it is possible to make small-sized copies of postcards, business cards, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a multicolor copying apparatus using three photosensitive drums, and FIG. 2 is a graph showing the relationship between the number of times of development and the amount of toner adhesion. 1... Color copying device, 5... Photosensitive drum,
M...Magenta developer, c...Cyan developer, Y
...Yellow developer.

Claims (1)

[Scope of utility model registration request] In a multicolor copying apparatus that performs color copying using a plurality of latent image carriers with different number of developing times, among the developing units provided respectively for the plurality of latent image carriers, as the number of developing times increases, the number of latent image carriers increases. A multicolor image forming apparatus, characterized in that a developing device using a toner with a low tendency for the amount of toner adhering to the body to decrease is provided on a latent image carrier that is frequently developed among the plurality of latent image carriers. Copying equipment.