Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-01-20
2001-02-06
Grimley, Arthur T. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S302000, C399S308000, C399S357000
Reexamination Certificate
active
06185391
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, in particular, one employing an indirect transfer method.
This application is based on Patent Application No. Hei 11-15870 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In the transfer and fixing section of conventional image forming apparatuses, it has been difficult to select a material suitable for the surface layer of the primary or first transfer roller because ozone deterioration of a silicone roller may occur, or a portion of the roller where no cross-linking process was performed may gradually run off.
More specifically, the transfer of a toner image is performed using the difference between the critical surface tension values of the surface layer of the belt-like photosensitive body and the surface layer of the primary transfer roller. Therefore, it is necessary that the critical surface tension of the surface of the primary transfer roller is always higher than that of the belt-like photosensitive body. Simultaneously, in order to easily detach the paper subjected to a secondary transfer and fixing process, it is necessary to keep the adhesive power between the surface of the primary transfer roller and the toner image lower than the adhesive power between the paper and the toner image. Therefore, the upper limit of the critical surface tension of the surface of the primary transfer roller must be strictly defined. It has been difficult to satisfy such a requirement by selecting a suitable material.
SUMMARY OF THE INVENTION
In consideration of the above circumstances, an object of the present invention is to provide an image forming apparatus having a mechanism for scraping away a deteriorated layer of the transfer roller by using a polishing roller and a cleaning roller.
Therefore, the present invention provides an image forming apparatus comprising:
a belt-like photosensitive body;
a backup roller which contacts the belt-like photosensitive body and moves the belt-like photosensitive body according to the rotation of the backup roller;
a transfer roller for transferring a toner image formed on the belt-like photosensitive body moved by the backup roller;
a fixing roller for further transferring and fixing the toner image, which was transferred by the transfer roller, to a paper;
an isolating plate for detaching the paper, on which the toner image was fixed by the fixing roller, from the fixing roller;
a first cleaning roller for absorbing and removing a toner element remaining on the transfer roller;
a polishing roller for scraping away a deteriorated layer on the surface of the transfer roller;
a second cleaning roller for removing polishing dust remaining on the surface of the transfer roller which was polished by the polishing roller;
a brush roller for brushing off polishing dust remaining on the surface of the polishing roller; and
a cleaner case for containing the polishing dust removed by the first and second cleaning rollers.
Typically, the surface layers of the primary transfer roller and the belt-like photosensitive body have different critical surface tension values by controlling the cross-linking temperature.
The transfer roller may have a metallic core on which a silicone rubber is deposited by using the injection molding method or the extruding method, and the surface of the transfer roller may be polished after a thermal cross-linking process.
Preferably, the silicone rubber is a high temperature cross-linking (HTV) type subjected to a hydrophobic process.
The base of the fixing roller may be a metallic hollow cylinder, and a surface layer having low surface tension, formed using polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), or a mixture of the PTFE and PFA, may be deposited on the surface of the fixing roller.
The base of the isolating plate may be metal or heat resistant plastic, and a surface layer having low surface tension, formed using polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), or a mixture of the PTFE and PFA, may be deposited on the surface of the isolating plate.
The base of the first cleaning roller may be a metallic hollow cylinder on which an adhesive layer using an acrylic adhesive is formed, or which is coated using a toner material.
The polishing roller may be formed using a grindstone for a metallic material, or may be made of porous ceramics.
The base of the second cleaning roller may be a metallic hollow cylinder on which an adhesive layer using an acrylic adhesive is formed, or which is coated using a toner material.
The brush roller may be made by spirally winding a resin fiber around a metallic or resin shaft.
According to the present invention, a mechanism for scraping away a deteriorated layer of a primary transfer roller is provided, so that the deteriorated layer can be removed. Therefore, a suitable critical surface tension of the surface of the primary transfer roller, necessary for the primary and secondary transfer processes, can be maintained.
In addition, another cleaning roller is provided, which works after the polishing process; thus, the efficiency for removing the ink element remaining on the surface of the primary transfer roller can be improved.
REFERENCES:
patent: 5742873 (1998-04-01), Kubo et al.
patent: 6-222688 (1994-08-01), None
patent: 7-209894 (1995-08-01), None
Grimley Arthur T.
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Tran Hoan
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