Electrophotography – Image formation – Fixing
Reexamination Certificate
2001-04-18
2002-11-12
Beatty, Robert (Department: 2852)
Electrophotography
Image formation
Fixing
C118S060000
Reexamination Certificate
active
06480694
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an oil application roller that forms part of a fixing device used in electrostatic process copying machines, electrophotographic printers, and related machines.
BACKGROUND ART
In a fixing device employed in electrostatic process copying machines, electrophotographic printers, and related machines, sometimes the toner sticks to a thermal fixing roll when transferred toner is fixed onto a sheet of recording paper as a recording medium. To prevent the toner from contaminating the subsequent sheet of recording paper, an oil application roller is employed to apply an extremely small amount of silicone oil or other lubricant oil to the thermal fixing roll, thereby preventing toner from sticking to the thermal fixing roll and a sheet of recording paper from being wound around the thermal fixing roll so that it curls up. Oil application rollers having such functions have already been made available in many varieties. For example,
FIG. 12
shows an oil application roller a that comprises a formed body of a cylindrical shape made of porous ceramics used as an oil retaining member b that stores lubricant oil to be applied, and an oil transfer layer c made of heat-resistant felt and an oil application amount control layer d made of polytetrafluoroethylene (PTFE) porous film that are wound around the surface of the cylindrical formed body and bonded together by using a mixture of an adhesive material and silicone oil.
FIG. 13
shows an oil application roller h that employs a cylindrical formed body of a metallic drilled hollow pipe e, in which a lubricant oil g is stored in an oil retaining tank f thereof and around which the oil transfer layer c and oil application amount control layer d are wound and bonded together. Furthermore, as an improved version of this oil application roller h, (1) an oil application roller is proposed, having a tubular member for allowing thermal expansion of an air layer interposed in the oil retaining tank to be released to the outside and a tube retaining member that retains a tubular member for increasing the amount of lubricant oil stored in the oil retaining tank (refer to Japanese Patent Application Laid-Open Publication HEI 10-20694). In addition, (2) another oil application roller is proposed that is provided with a film between the cylindrical formed body and the outside to allow thermal expansion of the air layer interposed in the cylindrical formed body made of the metallic drilled hollow pipe to be released to the outside as well as to increase the amount of lubricant oil to be stored (refer to Japanese Patent Application Laid-Open Publication HEI 10-10906).
With the oil application roller a shown in
FIG. 12
, however, the amount of lubricant oil that can be used is limited because of oil retaining characteristics of the porous ceramics, and the amount of unused lubricant oil accounts for, in some cases, as much as about 50% of the entire amount of lubricant oil retained. To extend the service life of the oil application roller a, therefore, it becomes necessary to increase its size. Also, while the oil application roller a is being used, an excessive amount of the lubricant oil is sometimes discharged as a result of the air contained in the oil retaining member b made of porous ceramics expanding with increased temperature. With the oil application roller h shown in
FIG. 13
, when an air layer i formed inside the oil retaining tank f expands, it could result in not only an excessive amount of lubricant oil g being discharged, but also the oil transfer layer c and the oil application amount control layer d being separated or destroyed.
In addition, according to the oil application rollers (1) and (2) disclosed in the respective publications, thermal expansion of the air layer can be released and the amount of lubricant oil stored can be increased. Since these oil application rollers are of a structure in which holes are drilled in metallic pipes, however, there are no layers that retain the lubricant oil. If the roller is placed in a vertical position during transportation or storage, therefore, there is a buildup of hydraulic pressure especially in a bottom portion of the roller, causing lubricant oil to leak, which could lead to an unexpected accident. Further, since lubricant oil is supplied through such holes, discharge of an uneven amount of oil tends to occur and, on top of that, it is difficult to control the amount of oil applied. This increases a possibility of toner sticking to the thermal fixing roll and the recording paper being wound around the roller thus curling up. In addition, the oil application roller according to (1) requires a complicated structure for storing a greater amount of lubricant oil, resulting in an increased manufacturing cost.
It is therefore an object of the present invention to provide an oil application roller that controls the amount of lubricant oil to be supplied to the fixing roller so as to ensure application of a uniform amount of lubricant oil, offers a high utilization efficiency of lubricant oil, develops no oil leak during transportation and storage, is built compact and simply structured, yet offering a long service life, and that prevents ill effects from oil leak or thermal expansion.
DISCLOSURE OF THE INVENTION
The present invention is based on the following facts discovered by the inventors through intense study. Namely, if the conventional cylindrical oil retaining member is hollowed out to make, for example, half of the entire volume is hollowed out, the utilization rate of lubricant oil can be improved from the conventional 50% to 75%. If the hollow cylindrical oil retaining member is of porous ceramics made of an inorganic material having micro-diameter voids and pores inside and its permeability resistance falls within a specific range or its porosity falls within a specific range, the hollow portion becomes decompressed and creates a balance with a capillary force after the lubricant oil has been charged. Accordingly, the possibility of oil leak occurring even during transportation or storage is eliminated and the amount of the lubricant oil supplied to the fixing roll can be controlled and a uniform amount of lubricant oil can be supplied during use despite its compact and simple structure. Furthermore, a pressure buffer mechanism may be provided to prevent ill effects that would otherwise be produced when oil or air expands by heat.
According to a first aspect of the present invention, provided is an oil application roller, in which an oil application layer is provided on an outer periphery of an oil retaining member that is made of a porous formed body of a hollow cylindrical shape and lubricant oil retained in the oil retaining member is supplied to a fixing roll. The porous formed body is made of an inorganic material having micro-diameter voids and pores inside, wherein at least a part of the micro-diameter voids communicates with a surface of the porous formed body and the pores, and at least a part of the pores communicates with the surface of the porous formed body through the micro-diameter voids, and offers a permeability resistance of 100 to 6,000 Pa·s/m
2
. Given this configuration, the oil application roller can increase the utilization rate of lubricant oil to about 75% against 50% of the cylindrical oil retaining member. After the lubricant oil has been charged, the hollow portion is decompressed and creates a balance with a capillary force, which eliminates the possibility of oil leak occurring even during transportation or storage and the amount of the lubricant oil supplied to the fixing roll can be controlled and a uniform amount of lubricant oil can be supplied during use despite its compact and simple structure.
According to a second aspect of the present invention, provided is an oil application roller, in which an oil application layer is provided on an outer periphery of an oil retaining member that is made of a porous formed body of a hollow cylindrical shape and lubricant oil retained in the oil retaining member i
Fukase Munehiko
Kimura Kohichi
Kuboyama Takeshi
Ono Masanori
Takagi Tatsuo
Beatty Robert
Nichias Co., Ltd.
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