Electrophotography – Cleaning of imaging surface – Blade
Reexamination Certificate
2002-03-15
2003-12-23
Royer, William J. (Department: 2852)
Electrophotography
Cleaning of imaging surface
Blade
Reexamination Certificate
active
06668153
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile device, a composite machine, or the like, employing a xerography method or an electrostatic recording method, and a cleaner and a cleaning blade used in the image forming apparatus and, more particularly, an image forming apparatus capable of preventing generation of the defective cleaning when almost spherical toners are employed as the developer and a cleaner and a cleaning blade.
2. Description of Related Art
As the almost spherical toner cleaning method in the prior art, the method of employing the almost spherical toners and the unshaped toners that are mixed at a particular rate (for example, JP-A-Hei.8-62893, JP-A-Hei.8-95286) is proposed. However, in the case of such method, since the almost spherical toners also pass through clearances between the unshaped toners to go to the blade edge portion, the improvement in the defective cleaning of the almost spherical toners is not sufficient.
The inventors of the present invention thought the above defective cleaning could be overcome by using a cleaning blade having a high rebound resilience, and then made the study.
As the result of the study of the inventors of the present invention, it is found that, if the modulus of repulsion elasticity of a cleaning blade made of a urethane rubber is not less than 20% in a low-temperature/low-humidity atmosphere, the above drawback can be improved. In such case, however, if the modulus of repulsion elasticity in the low-temperature/low-humidity atmosphere is set too high, sometimes a broken edge or the turned-up edge of the cleaning blade is generated due to the change in the rubber characteristics, in a high-temperature/high-humidity (28° C., 85% RH) atmosphere.
In order to prevent the broken edge, of the cleaning blade made of a urethane rubber in the above high-temperature/high-humidity atmosphere, the inventors of the present invention have confirmed as the results of the studies, if the blade having the modulus of repulsion elasticity of not less than 20% at 10° C. and not more than 70% at 40° C. is employed, both the defective cleaning in the low-temperature/low-humidity atmosphere and the broken edge of the cleaning blade in the high-temperature/high-humidity atmosphere can be improved. However, in the cleaning blade whose modulus of repulsion elasticity is within the above range, such cleaning blade can merely attain the improvement of the drawback but cannot get to the settlement. Therefore, the inventors of the present invention repeated earnestly the study and the examination confirmed that, since the value of either the 300% modulus or the tear strength of the cleaning blade or both values of them are still low, the above drawback has not been overcome.
Also, if the cleaning blade that is pushed against the image carrying body is used for a long time in the high-temperature and high-humidity atmosphere, such cleaning blade is set permanently (settling). If the cleaning blade is set, the pushing force of the cleaning blade against the image carrying body is lowered. Thus, there is the problem that the defective cleaning is generated. The inventors of the present invention made the studies and the examinations about this problem, and then confirmed that the above problem can be overcome by suppressing the permanent elongation of the cleaning blade.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problem and studies, and has a following content (1) as a subject.
(1) To provide a cleaning blade, a cleaner, and an image forming apparatus capable of preventing sufficiently the defective cleaning of almost spherical toners without fail from the low-temperature and low-humidity atmosphere to the high-temperature and high-humidity atmosphere.
Next, the present invention created to overcome the above subjects will be explained hereunder. In order to facilitate the correspondence to elements of Examples described later, symbols of the elements in the Examples that are given in parenthesis are added to the elements of the present invention. In this case, the reason for explaining the present invention to correlate with the symbols of the Examples described later is to make the understanding of the present invention easy, and not to intend to limit the scope of the present invention to the Examples.
In order to overcome the above subject, a cleaning blade (
3
) according to a first aspect of the invention has a blade top end portion for frictionally contacting with a surface of an image carrying body (PRy to PRk, B) to remove residual toners on the surface when the surface rotating passes through a cleaning area. The cleaning blade (
3
) is made of elastic material. The cleaning blade (
3
) is formed of urethane rubber. A modulus of repulsion elasticity (JIS K6255) of the cleaning blade (
3
) is not less than 20% at 10° C. and not more than 70% at 40° C. A 300% modulus (JIS K6251) of the cleaning blade (
3
) is not less than 200 kgf/cm
2
. A tear strength (JIS K6252 crescent type) of the cleaning blade (
3
) is more than 35 kgf/cm.
In the cleaning blade (
3
) of the present invention, a tension set (JIS K6262) is preferably not more than 2.5% (a second aspect of the invention), more preferably not more than 1.0%, and still more preferably not more than 0.5%.
Normally, if the shape factor SF of the toner used in the image forming apparatus (U) is SF<140, the defective cleaning is ready to occur as the SF (shape factor) value is reduced. Also, in the cleaning blade (
3
) in the prior art, in order to assure the cleaning performance in the low-temperature and low-humidity atmosphere, the pushing force of the cleaning blade (
3
) against the photoreceptors (PRy to PRk, B) must be increased. However, there is the problem that, if the pushing force is increased, the worn amount of the surface layer of the photoreceptors (PRy to PRk, B) is increased and thus the life of the photoreceptors (PRy to PRk, B) is shortened.
However, in the cleaning blade (
3
) of the present invention having the above configuration, since the cleaning blade (
3
) having the modulus of repulsion elasticity (JIS K6255) of 20% at 10° C. and 40% at 40° C. is used, the temperature dependency (variation) is small. In this case, if the cleaning blade (
3
) having the relatively high modulus of repulsion elasticity on the low temperature side is used to improve the cleaning characteristic in the low-temperature and low-humidity atmosphere, the modulus of repulsion elasticity on the high temperature side can be set to the relatively low value. As a result, since the material having the relatively high modulus of repulsion elasticity on the low temperature side can be employed, the cleaning performance can be assured unless the pushing force applied on the low temperature side is enhanced. Also, since the modulus of repulsion elasticity on the high temperature side is suppressed, the burr or the break of the cleaning blade (
3
) caused in the high-temperature and high-humidity atmosphere can be suppressed.
Also, in the present invention, the 300% modulus (JIS K6251) is 230 kgf/cm
2
, and the tear strength (JIS K6252 crescent type) is 35 kgf/cm. In this manner, if the 300% modulus and the tear strength are high, the minute chip of the cleaning blade (
3
) can be suppressed and particularly the cleaning performance at SF<140 can be improved.
In addition, the cleaning blade (
3
) having the tension set (JIS K6262) of 2.5% is employed. Therefore, the reduction (attenuation) in the pushing force against the photoreceptors (PRy to PRk, B) is small even after the cleaning blade (
3
) is left as it is for a long time in the high-temperature and high-humidity atmosphere, and thus the cleaning performance can be assured.
Also, if the material of the cleaning blade (
3
) is selected with regard to the characteristics of the blade materials, as described above, the necessity for increasing the pushing force against the photoreceptors (PRy
Fuchiwaki Takashi
Koide Hiroyuki
Kojima Noriaki
Nakano Yoshinori
Sakanobe Makoto
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Royer William J.
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