Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
2000-08-18
2001-10-23
Grimley, Arthur T. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
C399S050000, C399S051000, C399S055000, C399S066000, C399S067000
Reexamination Certificate
active
06308018
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an image forming apparatus for multi-color printing using the electrophotography and particularly relates to an image forming apparatus capable of image forming in appropriate conditions even if a plurality of developing units are arranged in an arbitrary order.
(2) Description of the Prior Art
Recently, there has been a tendency toward colorization in the field of image forming apparatus such as copiers and the like, and color copiers have widely been put on the market. In such color copiers, four color, namely black, cyan, magenta and yellow developers are used and the multiple number of developing units storing the different color developers are arranged in a certain relationship.
Conventionally, upon the replacement of the developing units for such an image forming apparatus having multiple developing units, the operator should confirm the developer's color being stored in a developing unit and attach the unit to the predetermined developing unit mounting space on the apparatus body. This configuration not only provides the operator with a burden, but also has frequently induced deficiencies and accidents due to erroneous insert or damages to the parts.
In a color image forming apparatus wherein a multiple number of color image developing units each having a different color of toner are arranged in series in the paper conveyance direction, color components of an image are formed by associated color image developing units and superimposed on a sheet of paper as the paper is conveyed. The paper with the toner image formed thereon in a superimposed manner after the passage of the all the color image developing units is made to pass through the heated, heat roller in the fixing unit so that the toner becomes fused by heat from the roller surface, to thereby complete image formation.
The order or position in which the color image developing units are inserted and set in the main body determines the order of transfer and superimposition. That is, the color toner of the color developing unit laid out on the most downstream side in the transfer and superimposition stage will adhere to the topmost layer of the print paper so that it will be most affected by the heat from the heated surface of the heat roller of the fixing unit. Resultantly, the conventional configuration has the following problem. That is, if the order of insertion of the developing units or the order in which the color toners are superimposed is changed, color or hue in the printed image will vary depending upon the order of superimposition of the color toners.
SUMMARY OF THE INVENTION
In order to solve the above problems, it is therefore an object of the present invention to provide a color image forming apparatus which enables image forming under proper conditions even if a multiple number of developing units are set at arbitrary positions upon replacement of the developing units so as to reduce the operator's burden of replacement and improve the operativity, handling performance and safety, enables quick start of the image forming operation to thereby improve the operating efficiency of the whole apparatus, can promote reasonable design by reducing the number of parts of the developing units and image forming apparatus and by common use of identical parts and still can provide stable image quality.
It is another object of the present invention to provide a color image developing device which can minimize deviation of hues in the final multi-color printed image, regardless of the order of arrangement of the developing units.
It is a further object of the present invention to provide a color image developing device which can provide better color image quality even if the color developing units present insufficient developing functions and if it is difficult to make up for the deficiency by regulating the developing bias voltages to control the amounts of adherence of the color toners appropriately.
In order to achieve the above objects, the present invention is configured as follows:
In accordance with the first feature of the present invention, an image forming apparatus includes
a static latent image support,
a charging device for charging the surface of the static latent image support,
an exposing device for forming a static latent image on the static latent image support, and
a plurality of developing units, each developing the formed static latent image with a developer held therein to produce a visual image, wherein the developed images are transferred and superimposed one over another to a recording medium and fixed thereto, and the image forming apparatus further includes:
a developing unit holding portion having as many holders for accommodating the developing units and allowing the developing units to be detachably attached and set in an arbitrary order; and
a controller for regulating the image forming conditions of each developer under which image is formed, depending on the order of development determined by the arrangement in which the developing units are set in the developing unit holding portion and depending on the colors of the developers held in the developing units.
In accordance with the second feature of the present invention, the image forming apparatus having the above first feature is characterized in that the controller arbitrarily sets up the order of development of the plurality of developing units, when the colors of developers are designated.
In accordance with the third feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that, upon the control of the image forming conditions by the controller, the developing bias voltage for each color of developer is set to be higher in the order in which the developers are to be located closer to the top surface, so that the amount of each developer per unit area to be transferred to the recording medium will be equal to the others.
In accordance with the fourth feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that, upon the control of the image forming conditions by the controller, the exposure power of the exposing device for each color of developer is set to be higher in the order in which the developers are to be located closer to the top surface, so that the amount of each developer per unit area to be transferred to the recording medium will be equal to the others.
In accordance with the fifth feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that, upon the control of the image forming conditions by the controller, the exposure time of the exposing device for each color of developer is set to be longer in the order in which the developers are to be located closer to the top surface, so that the amount of each developer per unit area to be transferred to the recording medium will be equal to the others.
In accordance with the sixth feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that the controller controls the image forming conditions in such a manner that, when the developed images are transferred from the static latent image support, the transfer output voltage for the black developer is set to be lower than that for the chromatic color developers.
In accordance with the seventh feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that the controller controls the image forming conditions in such a manner that, when, upon fixing, any low chromatic color developer is located in a layer higher than a high chromatic color developer on the recording medium, the fixing temperature is set to be higher.
In accordance with the eighth feature of the present invention, the image forming apparatus having the above first or second feature is characterized in that the controller controls the image
Inoue Atsushi
Kido Eiichi
Masuda Jitsuo
Morimoto Junji
Sakai Masahiro
Grimley Arthur T.
Sharp Kabushiki Kaisha
Tran Hoan
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