Electrophotography – Cleaning of imaging surface – Fibrous brush
Reexamination Certificate
2000-01-07
2001-07-31
Braun, Fred L (Department: 2852)
Electrophotography
Cleaning of imaging surface
Fibrous brush
C399S349000
Reexamination Certificate
active
06269236
ABSTRACT:
The present invention relates to a brush cleaning device in a copier, a facsimile, a printer or like image forming apparatus of reversed development type and more particularly to a brush-cleaning device in an image forming apparatus of reversed development type which cleaning device suppresses the adhesion of toner to the outer surface of a photosensitive element by fusion and the scraping of the photosensitive element while maintaining a satisfactory cleaning performance.
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENTS
Toner attached to an image (electrostatic latent image) formed on a photosensitive element to develop the image is electrostatically transferred to a transfer material such as paper by a transfer step. However, about several to 20% of the toner attached to the photosensitive element remains on the photosensitive element without being completely be transferred. If the residual toner on the outer surface of the photosensitive element is carried to the next developing step, a charging device cannot sufficiently charge the photosensitive element since a portion of the outer surface of the photosensitive element where the toner remains is blocked by the toner. Accordingly, an image formed next becomes defective. Besides the toner, if paper powder or the like is carried to the next developing step without being cleaned, it may enter the developing device in a developing area to cause an imaging failure, a developing device trouble or other problem.
Accordingly, in conventional image forming apparatuses, a cleaning device is provided to remove the toner and other materials residual on the photosensitive element. A variety of cleaning methods including magnetic brush-cleaning, electrostatic brush-cleaning, brush-cleaning, magnetic roller-cleaning, blade-cleaning have been proposed as cleaning methods. Among these methods, the brush-cleaning and blade-cleaning are generally used in combination since they provide a satisfactory cleaning performance.
However, the use of the brush-cleaning and blade-cleaning in combination causes an image degradation since the outer surface of the photosensitive element is scraped by a cleaning blade held in strong sliding contact with the outer surface of the photosensitive element. Further, a frictional heat is produced in a position where the cleaning blade is in contact with the photosensitive element and fuses the residual toner to adhere to the outer surface of the photosensitive element, thereby causing so-called “black dots” in a final image.
In view of the above problem, an object of the present invention is to provide a cleaning device which suppresses the adhesion of toner to the outer surface of the photosensitive element by fusion and the scraping of the photosensitive element while maintaining a satisfactory cleaning performance.
SUMMARY OF THE INVENTION
In order to accomplish the above object, the invention is directed to a cleaning device for removing toner residual on the outer surface of a photosensitive element after an electrostatic latent image on the outer surface of the photosensitive element is developed with toner into a toner image by the reversed development method and the toner image is transferred to a transfer material, comprising a photosensitive element having a shaft with an axis of rotation and a brush to be held in contact with the outer surface of the photosensitive element to remove the residual toner said brush having a shaft defining an axis of rotation, wherein the resistance value between the shaft of the brush and the shaft of the photosensitive element is in the range of 10
3
to 10
8
&OHgr;cm; the density thereof is in the range of 30,000 to 100,000 bristlesl(inch)
2
; a DC voltage having a polarity opposite from the charging polarity of the toner and being in the range of 100 to 300 V in absolute value is applied to the brush after an AC voltage having a frequency of 100 to 2000 Hz and an interpeak voltage of 400 to 700 V is superimposed thereon; and the brush is rotated in a direction opposite from the rotating direction of the photosensitive element in its portion held in contact with the photosensitive element.
With the above construction, the toner residual on the outer surface of the photosensitive element is removed by the rotation of the brush, and the adhesion of the toner to the outer surface of the photosensitive element by fusion and the scraping of the photosensitive element can be suppressed while a satisfactory cleaning performance is maintained.
Preferably, a biting degree of the brush into the photosensitive element is set in the range of 0.9 to 1.9 mm. With this arrangement, a satisfactory cleaning performance can be maintained and the durability of the brush can be improved.
Preferably, the leading ends of bristles of the brush are rounded. This arrangement suppresses the scraping of the photosensitive element.
These and other objects, features and advantages of the present invention will become apparent upon reading the following detailed description along with accompanying drawings.
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Higo Shinichi
Mori Yukihiro
Braun Fred L
Jordan and Hamburg LLP
Kyocera Mita Corporation
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