Electrophotography – Image formation – Fixing
Reexamination Certificate
2000-05-12
2001-08-07
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Fixing
C399S328000, C399S329000, C430S124300
Reexamination Certificate
active
06272309
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention generally relates to a fixing apparatus for use in an electrophotographic equipment, such as copier, printer, facsimile and the like, to fuse and press an unfixed toner or an unfixed toner image formed on a recording sheet, such as paper and the like, and to fix the toner to the sheet permanently.
2. Prior Art
For a fixing apparatus of electrophotographic equipment, a roller system, so called two rollers system, has been applied, which comprises a fixing roller containing a heating source and a pressing roller pressed against the fixing roller with a particular pressure. In such a roller system, various related patent applications have been filed and this system has been widely used. In recent years, a new fixing system, so called a belt fixing system, has been proposed and has also been offered for practical use as more advanced fixing system than the two rollers system. Specifically, this system comprises a fixing roller containing no heating source, a heating roller containing a heating source, a fixing belt as sort of endless type which is extended from the fixing roller to the heating roller with tension, and a pressing roller adapted to press the fixing roller through the fixing belt.
Whenever any conventional systems having such constructions are used, it is essential to supply a suitable amount of heat to an unfixed toner or toner image supported on a sheet for fusing it, that is, the unfixed toner should be adequately heated and fused. In addition, a particular pressure must also be applied to the unfixed toner, which has been fused, for fixing it on the sheet, that is, the unfixed toner fused should adequately be pressed.
Thus, in any conventional systems, the fixing roller and the pressing are pressed each other with a particular pressure to form a nip portion therebetween and a sheet supporting an unfixed toner is heated and pressed by the nip when the sheet is passed through the nip portion.
However, in any fixing apparatuses of the conventional systems, when the applied pressure at the nip portion (hereinafter, refer to nip pressure) was insufficient, there causes a problem such that a toner image would not be fixed on a sheet, e.g. the toner image would be fallen off from the sheet by touching the image with hand, due to the offset effect under low pressure. Thus the nip pressure is arranged with relatively high value for ensuring to eliminate the offset effect under low pressure. Specifically, the nip pressure is approximately 200 kPa even in a low speed type fixing apparatus, and the pressure should be increased up to approximately 250 k Pa in an intermediate or high-speed type fixing apparatus.
Since the nip pressure is arranged in the relatively high pressure, the pressure acts to a driving unit for transferring a sheet as driving resistance so that the driving unit must be enforced to drive with higher torque. Consequently, a high torque type driving motor, which is expense, must be equipped as a driving source for the driving unit and the transmission mechanism of the driving unit also requires higher quality on durability for the higher transmitted torque in the driving unit. This results in cost overrun.
Further, since the driving unit is driven with high torque, it may be hard to maintain effective lifetime of each components of the driving unit. Thus, it is desired to improve the effective lifetime.
Furthermore, in such conventional fixing apparatus using rollers, since the major diameter and/or the radial thickness of the roller requires to be larger in order to prevent bending of the roller, the size and weight of the apparatus are increased. It is also desired to improve this problem.
SUMMARY OF THE INVENTION
The present invention is developed to solve the aforementioned problems. One primary object of the present invention is to provide a fixing apparatus which can secure a sufficient fixing performance even if a nip pressure is arranged in relatively low value.
Another object of the present invention is to provide a fixing apparatus which can achieve to reduce its cost by lowering a nip pressure to enable to use a low torque type driving source.
Further, still other object of the present invention is to provide a fixing apparatus which can achieve to reduce the size and weight of a driving source and components used in the apparatus by lowering a nip pressure.
Furthermore, yet other object of the present invention is to provide a fixing apparatus which can achieve to extend an effective lifetime of the entire apparatus by lowering a nip pressure to enable to reduce torque in a driving unit of the apparatus.
For solving the aforementioned problem and also achieving the described object, a fixing apparatus according to the present invention comprises: a fixing member having an elastic layer formed on the fixing member at a side to which a sheet surface supporting an unfixed toner is contacted; a pressing member for making the sheet surface supporting the unfixed toner contact to the fixing member with a particular pressure and forming a nip portion between the fixing member and the pressing member; and a heating means heating the fixing member, wherein 0.05≦P·t/E≦0.50 is satisfied, where t (mm) is thickness of the elastic layer, E (Pa) is Young's modulus of the elastic layer and P (Pa) is pressure of the nip portion, as the first feature.
In addition to the first feature, in a preferable embodiment according to the present invention, the Young's modulus E (Pa) of the elastic layer and the pressure P (Pa) of the nip portion may satisfy P/E≦0.50.
In addition to the first feature, in another preferable embodiment according to the present invention, the fixing member may include a fixing roller having the elastic layer on a periphery of the fixing roller, to which the sheet surface supporting the unfixed toner is contacted, and the pressing means includes an endless-like pressing belt contacted to the elastic layer of the fixing roller with a particular nip width. The heating means may include a first heat-generating source for heating the fixing roller. The pressing belt may be wound around plural supporting rollers spaced apart each other in endless manner with positioning the fixing roller between each of the plural supporting rollers and the heating means may further include a second heat-generating source for heating the pressing belt.
In addition to the first feature, in another preferable embodiment according to the present invention, the fixing member may include an endless-like fixing belt having the elastic layer on a periphery of the fixing roller, to which the sheet surface supporting the unfixed toner is contacted, and the pressing means may include an pressing roller contacted to the elastic layer of the fixing belt with a particular nip width. The fixing belt may be wound around plural supporting rollers spaced apart each other in endless manner with positioning the pressing roller between each of the plural supporting rollers and the heating means may include a first heat-generating source for heating the fixing belt. The heating means may further include a second heat-generating source for heating the pressing roller.
In addition to the first feature, in another preferable embodiment according to the present invention, the fixing member may include a releasing layer on a periphery of the elastic layer.
In addition to the first feature, in another preferable embodiment according to the present invention, thickness t of the elastic layer may be arranged in the range from 0.15 (mm) to 2.0 (mm).
In addition to the first feature, in another preferable embodiment according to the present invention, the Young's modulus E may be arranged in the range from 150 (k Pa) to 2400 (k Pa).
In addition to the first feature, in another preferable embodiment according to the present invention, the nip pressure P may be arranged in the range from 25 (k Pa) to 200 (k Pa).
These and other aspect of the present invention are apparent in the following detailed
Hamada Yasuhide
Higashi Yuichiro
Kitazawa Kesaaki
Armstrong Westerman Hattori McLeland & Naughton LLP
Brase Sandra
Nitto Kogyo Co. Ltd.
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