Electrophotographic copier and charging means used therefor

An electrophotographic copier, equipped with a conductive roller or a conductive brush as a charging device of a contact type for effecting an electrophotographic copying process, characterized in that

• said charging device comprises:
• an aggregation of conductive fiber formed like a brush;
• vibrating means to vibrate said aggregation of conductive fiber;
• and a comb-like vibration regulating member held through across an entire part of said aggregation of conductive fiber, and
• when an image bearing medium is to be charged by bringing said brush-like charging member into contact therewith, said aggregation of conductive fiber is vibrated by said vibrating means while regulated by said comb-like vibration regulating member, in a state in which said aggregation of conductive fiber is kept in contact with said image bearing medium, wherein said charging member is vibrated in a direction substantially perpendicular to the rotational direction of said image bearing medium.

An electrophotographic copier, equipped with a conductive roller or a conductive brush as a charging device of a contact type for effecting an electrophotographic copying process, wherein an image bearing medium is charged by bringing a charging device into contact therewith, and a developer of the same polarity with the charging potential of said image bearing medium is used, being characterized in that,

• said charging device comprising:
• a conductive, cylindrical substrate having on its surface a plurality of through-holes through which cold or hot air can be passed;
• and conductive fiber formed like a brush and planted conductively on the surface of said substrate, and
• said electrophotographic copier further comprising a closed container having an air-exhausting means and enclosing said charging device.

An electrophotographic copier, equipped with a conductive roller or a conductive brush as a charging device of a contact type for effecting an electrophotographic copying process, wherein an image bearing medium is charged by bringing a charging device into contact therewith, and a developer of the same polarity with the charging potential of said image bearing medium is used, being characterized in that,

• said charging device comprising:
• a conductive, cylindrical substrate having on its surface a plurality of through-holes through which cold or hot air can be passed;
• and conductive fiber formed like a brush and planted conductively on the surface of said substrate, wherein an air stream is introduced from a heating means of a fixing unit of said electrophotographic copier, and
• said electrophotographic copier further comprising a closed container having an air-exhausting means and enclosing said charging device.

An electrophotographic copier, equipped with a conductive roller or a conductive brush as a charging device of a contact type for effecting an electrophotographic copying process,

• comprising a photoconductor drum and a charging device of a roll-shaped body with conductive fiber or an aggregation thereof planted thereon,
• wherein a photoconductive layer on said photoconductor drum is charged by bringing said charging device into contact therewith while said photoconductor drum and said roll-shaped body are individually rotated with a voltage impressed therebetween, being characterized in that
• planting intervals between fibers and a ratio of a peripheral velocity of rotation of said photoconductor to that of said roll-shaped are limited so that, a product, d1.times.d2.times.(Vp/Vr) is smaller than the average size of developer particles used in the electrophotographic process,
• where d1 is a planting interval between fibers in the rotational direction of said roll-shaped body with said conductive fiber of an aggregation planted thereon;
• d2 is an interval between fibers in the axial direction of said roll-shaped body;
• Vr and Vp are peripheral velocities of rotation, respectively, of said roll-shaped body forming said charging device and said photoconductor drum, and therefore, (Vp/Vr) indicates a ratio of peripheral velocity of rotation.

An electrophotographic copier, equipped with a conductive roller or a conductive brush as a charging device of a contact type for effecting an electrophotographic copying process, comprising:

• a charging roller having conductive fiber covered on a surface thereof;
• a dirt preventing member disposed in alignment with a longitudinal direction of said charging roller so as to be shifted between a uniformly contacting position with said charging roller and a spaced position therefrom;
• and
• means for bringing said dirt preventing member into uniform contact with the conductive fiber on the charging roller surface when said charging device is in operation and in contact with a photoconductor so as to clean the surface of the conductive fiber on said charging roller, and for retracting the dirt preventing member from the charging roller when said charging device is out of operation.