Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2000-01-18
2001-04-03
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C399S167000, C399S299000
Reexamination Certificate
active
06212345
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention belongs to the technical field of image forming apparatus in which an image is formed by conveying a predetermined recording medium along a plurality of image supports arranged in parallel to each other so as to sequentially and superimposingly transfer the developed images on individual image supports to the recording medium. More detailedly, the present invention relates to an image forming apparatus of the so-called tandem type having a plurality of image supports each having a rotational inertial body such as a flywheel or the like at one end of their rotary shafts.
(2) Description of the Prior Art
In general, in conventional image forming apparatus for recording designated image information by performing line-wise scanning such as laser scanning on an image support such as a phtoreceptor, drive irregularity occurs in the driving mechanism for rotating the image support. When an image of lines is recorded, this drive irregularity will cause image unevenness (so-called banding) which is made up of bands in the final image on the recording medium.
In order to solve the above problem, a rotating inertial body such as a flywheel has been provided at one end of the rotary shaft of the image support. That is, in an attempt to reduce the drive irregularity originating from the driving mechanism, a heavy, rotating inertial body has been provided to produce the desired inertia for the rotation of the image support.
On the other hand, in the field of image forming apparatus, there has been a development towards multil-colorization of recorded images. A known typical example of color image forming apparatus is the so-called tandem type having multiple image supports therein. In such a color image forming apparatus, when a developed image of a relatively more visible color on the image support deviates from the correct position due to drive irregularity, color blur occurs in each developed image even if the deviation is slight. Therefore, it is necessary to establish rotational synchronism between individual image supports, so that rotational inertial bodies of an identical type need to be provided for all the multiple, image supports in order to take into account the rotational drive irregularity of the image supports.
Accordingly, in an image forming apparatus having multiple image supports, provision of rotational inertial bodies of an identical type for all the multiple image supports increases the number of assembly parts, hence causing various problems including: lowering of design flexibility, increase in the manufacturing cost, making the apparatus bulky hence the needing of a large space for installation, and increase in the machine weight hence rise in the cost for transportation.
Japanese Patent Application Laid-Open Hei 4 No.147279 has proposed a technique that reliably establishes synchronized rotations of all the image supports in an image forming apparatus of the so-called tandem type while preventing bulkiness of the apparatus. That is, in this configuration, the rotational inertial bodies are made up of an non-circular shape having the same inertia and attached on the rotational shafts of all the image supports to thereby reduce the distance between image supports.
As above, in the tandem type, image forming apparatus of Japanese Patent Application Laid-Open Hei 4 No.147279, the rotational inertial bodies provided on the rotational shafts of all the image supports, have the same, non-circular sectional feature in order to equally increase the inertia of all the image supports, whereby it is possible to reduce the distance between image supports, and hence this configuration contributes to securing reliable synchronized rotations of multiple image supports whilst minimizing the size of the image forming apparatus.
It is true that the technology described above can shorten the distance between image supports and inhibit the bulkiness of the apparatus as a whole, compared to the conventional configuration where circular rotational inertial bodies are arranged in parallel, but it still suffers from unsolved problems of increase in the manufacturing cost and apparatus weight due to increase in the number of assembly parts since the rotational inertial bodies of the same type are needed for all the image supports. Further, this configuration is limited by the complex shape of the rotational inertial bodies and their arrangement and also by the necessity of a control means and the like for exactly controlling the rotational positions of the rotational inertial bodies so as not to interfere with each other. Thus, there are sill unsolved problems such that design flexibility is markedly hindered.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the above prior art problems and it is therefore an object of the present invention to provide an image forming apparatus which is free from various problems such as of the apparatus becoming bulky, the increase in the manufacturing cost, the increase in apparatus' weight and degradation of design flexibility while preventing deviations of images due to drive irregularities of the image supports from being recognized by the user by differentiating the inertial conditions for designated image supports among the multiple image supports from the others.
The present invention has been devised to achieve the above object, and the present invention is configured as follows:
In accordance with the first aspect of the present invention, an image forming apparatus wherein a multiple number of image supports form developer images of different colors so that the developer images of different colors corresponding to the multiple number of image supports are superimposed one over another onto a recording medium to form an image, is characterized in that the inertial condition of a predetermined image support among the multiple number of image supports is made different from that of the other image supports.
In accordance with the second aspect of the present invention, the image forming apparatus having the above first feature is characterized in that the other image supports have identical rotational inertial bodies at their rotary shaft ends while the predetermined image support has no rotational inertial body or a rotational inertial body which is different in diameter or in weight, at the rotary shaft end thereof.
In accordance with the third aspect of the present invention, the image forming apparatus having the above first feature is characterized in that the color of the developer for the image support for which the inertial condition is made different from that of the others is one which is less visible in the final image, among the developers of the specified colors.
In accordance with the fourth aspect of the present invention, the image forming apparatus having the above second feature is characterized in that the color of the developer for the image support for which the inertial condition is made different from that of the others is one which is less visible in the final image, among the developers of the specified colors.
In accordance with the fifth aspect of the present invention, the image forming apparatus having the above first feature is characterized in that the moment of rotation of the rotational inertial bodies of the other image supports is set greater than that of the rotational inertial body of the predetermined image support.
In accordance with the sixth aspect of the present invention, the image forming apparatus having the above third feature is characterized in that the developer that is less visible is of yellow.
In accordance with the seventh aspect of the present invention, the image forming apparatus having the above fourth feature is characterized in that the developer that is less visible is of yellow.
REFERENCES:
patent: 5528341 (1996-06-01), Shishido et al.
patent: 4-147279 (1992-05-01), None
patent: 6-332289 (1994-12-01), None
patent: 8-194354 (1996-07-01), None
Harada Yoshikazu
Manabe Nobuo
Oda Ayumu
Sakagami Hidekazu
Taka Kyosuke
Lee Susan S. Y.
Renner Otto Boisselle & Sklar
Sharp Kabushiki Kaisha
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