Electrophotography – Image formation – Fixing
Reexamination Certificate
2002-06-17
2003-12-23
Braun, Fred L. (Department: 2852)
Electrophotography
Image formation
Fixing
Reexamination Certificate
active
06668150
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an oil application roller for applying release oil to a fixing roller of a fixing device for use in monochrome printers, color printers, copying machines, facsimile machines, etc. The present invention also relates to a seal ring for use in the oil application roller and a fixing device using the oil application roller.
BACKGROUND ART
Color toner for use in image forming apparatuses, such as copying machines, printers, and the like, for forming full-color images through an electrophotographic image forming process needs to have an excellent light transmittance when fixed on recording materials. Accordingly, heretofore, color toner based on a binder resin, which can melt quickly and has a low melt viscosity, has been used, and a method of fixing this color toner by a fixing device equipped with a silicone-rubber based heating roller as a fixing roller has been employed.
However, since the above-mentioned fixing device employs the fixing roller whose surface is formed of silicone rubber and the color toner based on a binder resin, which can melt quickly and has a low melt viscosity, “hot offset”, a phenomenon in which melted color toner adheres to the surface of the fixing roller, is liable to occur. Therefore, to prevent the hot offset, a considerable amount of a release agent, e.g., silicone oil having a great affinity for silicone rubber and being relatively inexpensive, is applied to the surface of the fixing roller.
Also, in recent years, a release component is added to the toner itself to prevent the hot offset. In this case, however, application of the release agent is still necessary, although the amount of the release agent may be small.
Conventionally, oil application rollers in various roll shapes have been proposed as a member for applying oil to the members involved in a fixing operation or the like. One example is the oil application roller disclosed in JP 1(1989)-60144B. The oil application roller includes a pipe with a number of pores on its outer periphery, release oil held in the central portion of the pipe, and heat-resistant felt made of Nomex or the like wound around the outer periphery of the pipe. JP 61(1986)-104469U discloses an oil application roller in which heat-resistant felt is wound around a member covered with a porous material such as paper to control the amount of oil exuding from the felt and to diffuse the oil in the axial direction of the oil application roller so as to attain the uniform application of the oil throughout a fixing roller. JP 5(1993)-123623A discloses an oil application roller in which silicone rubber sponge or the like is provided as an intermediate layer so as to impart elasticity to the oil application roller. Further, JP 61(1986)-104469U discloses an oil application roller in which a heat-resistant porous material other than heat-resistant felt is used.
However, in these conventional oil application rollers, controlling the amount of oil applied to the fixing roller is difficult since the oil exuding from the felt or porous material provided on the surface of the oil application roller is applied directly to the fixing roller to migrate thereto. On this account, as an oil application roller capable of controlling the amount of oil applied to the fixing roller, there has been proposed an oil application roller in which a heat-resistant microporous film layer (oil permeation control layer) is provided on the surface of felt or a porous material, thereby controlling the amount of oil passing through the layer (JP 61(1986)-183679A). Further, as an oil application roller capable of applying a smaller amount of oil uniformly and with high accuracy, there has been proposed an oil application roller in which, in place of the microporous film, a composite film obtained by filling the pores in a microporous film with a mixture of silicone rubber and oil is used as an oil permeation control layer (JP 62(1987)-178992A).
However, in these conventional oil application rollers, the amount of oil supplied to the oil permeation control layer needs to be kept constant so that the oil permeation control layer can control the amount of oil passing therethrough stably. In addition, in order to attain a stable oil application over a long time period, these oil application rollers desirably include an oil holder with a two-layer structure including an oil supply layer and an oil diffusion layer.
In this case, a difference in osmotic pressure is required between the two layers so that oil can move. In addition, the porosity (the ratio of the volume of pores to the total volume) of the oil supply layer is required to be higher than that of the oil diffusion layer. Also, for an extended service life of the oil application rollers, the porosity of the oil supply layer is required to be high. However, an increase in the porosity of the oil supply layer results in a decrease in its oil holding power, thereby causing a problem that an oil leak is liable to occur. Moreover, if an oil tank is used instead of the oil supply layer, the risk of the oil leak further increases.
Furthermore, when release oil comes into contact with the microporous film or composite film used as an oil permeation control layer, the pores in the microporous film are closed by the release oil. As a result, if large volumes of gas are generated abruptly, smooth permeation of the gas becomes difficult. If the gas is forced to pass through the pores, a pressure of several millions of Pa is required, for example. For this reason, if the pore diameter of the microporous film is made smaller to decrease the amount of oil passing through the film, the higher pressure is required. Moreover, when the composite film as described above is used as an oil permeation control layer, it is difficult to allow the gas to pass though the film without breaking the film.
Furthermore, vapor pressure is created by the moisture absorbed in the oil and the porous material at the time of heating and cooling the members involved in a fixing operation. In addition, pressure also is created by the thermal expansion of air in the oil application roller. As a result, the oil permeation control layer is subjected to an excessive pressure. This may cause the oil to spout out, thereby increasing the amount of the oil applied initially. Further, in some cases, the oil permeation control layer may be broken or swollen like a balloon.
In order to prevent the above troubles, providing a vent hole, which allows the pressure inside the oil application roller to be released, in a seal ring provided at each end face of the oil application roller has been proposed (JP 11(1999)-219059A).
However, the conventional oil application roller provided with a vent hole suffers the following problem. If the user detaches the oil application roller from the fixing device and leaves the roller in the state where the rotation axis thereof runs vertically during use, the oil will be unevenly distributed in the roller due to gravity. This causes the oil to leak from the lower part of the roller through the vent hole to stain documents and the like.
Also, when the user detaches the oil application roller from the fixing device and leaves the roller in the state where the rotation axis thereof runs vertically after use, the problem of an oil leak still occurs.
Further, when the fixing device is heated, the internal pressure inside the roller increases to generate water vapor. As a result, the oil held in the oil application roller is extruded though the vent holes of the seal rings, thereby causing an oil escape from the oil application roller. The interior of the fixing device is stained if the oil escape occurs in the fixing device. In addition, the service life of the oil application roller is shortened since the wasteful oil is discharged from the roller and accelerates oil consumption.
DISCLOSURE OF INVENTION
The present invention has been made to overcome the above-mentioned problems in the prior art. It is an object of the present invention to provide an oil application roller capabl
Kitano Takumi
Nakayama Yoshihiro
Sima Michihiro
Tajima Noriyuki
Toyoda Akinori
Braun Fred L.
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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