Image forming apparatus that effectively charges a latent image carrier

A charging device for applying a voltage to a latent image carrier of an image forming apparatus, the charging device comprising:

• a brush roller including a cylindrical shaft, and a brush having an oblique brush amount and a plurality of flat brush hairs on an outer circumference surface of the cylindrical shaft, wherein the brush roller is disposed with respect to a surface of the latent image carrier in such a manner that the brush roller is abutted with a suitable brush contact amount, and configured to uniformly charge the surface of the latent image carrier during a charging process;
• a voltage applying mechanism configured to apply a charging voltage to the brush roller;
• and
• a driving mechanism configured to rotationally drive the brush roller at a predetermined rotation number so as to satisfy a relationship Z>150−50A, where Z is a value of a rotation number (rpm) of the brush roller, and A is the oblique brush amount (mm),
• wherein the latent image carrier is rotated in a first direction and the brush roller is rotated in a second direction different from the first direction so that during rotation, the area of the brush roller abutted with the surface of the latent image carrier moves in a same movement direction as a movement direction of the surface of the latent image carrier,
• wherein the brush roller has an outside diameter of 12 mm or less.

A method of applying a voltage with a brush roller to a latent image carrier of an image forming apparatus, the method comprising:

• disposing a brush roller including a cylindrical shaft and a brush having an oblique brush amount in such a manner that the brush roller is abutted with a suitable brush contact amount to uniformly charge the surface of the latent image carrier during charging;
• applying a charging voltage to the brush roller;
• and
• rotationally driving the brush roller at a predetermined rotation number so as to satisfy a relationship Z>150−50A, where Z is a value of a rotation number (rpm) of the brush roller, and A is a value of the oblique brush amount (mm),
• wherein the latent image carrier is rotated in a first direction and the brush roller is rotated in a second direction different from the first direction so that during rotation, the area of the brush roller abutted with the surface of the latent image carrier moves in a same movement direction as a movement direction of the surface of the latent image carrier,
• wherein the brush roller has an outside diameter of 12 mm or less.