Fixing device selectively operable in color or black/white coping mode

Claim 1

A fixing device for a dry process copier selectively operable in a black-and-white copy mode which uses a black toner, and a full-color copy mode which transfers color-separated images one upon another to a paper sheet, comprising: a first fixing roller comprising a rigid roller and having a heat source in said first fixing roller; a second fixing roller coated with an elastic layer and having a heat source in said second fixing roller, said second fixing roller being pressed against said first fixing roller to rotate, in a pressing portion, in a same direction and at a same linear speed as said first pressing roller; a pressing roller coated with an elastic layer and pressed against said first fixing roller to rotate, in a pressing portion, in a same direction and at a same linear speed as said first fixing roller; guide means movable between a first position for guiding a paper sheet fed from an image transfer station to a first nipping section which is defined between said first fixing roller and said pressing roller such that an image surface of said paper sheet contacts said first fixing roller, and a second position for guiding said paper sheet to a second nipping section defined between said first fixing roller and said second fixing roller such that said image surface contacts said second fixing roller; drive means for selectively rotating said first fixing roller in opposite directions; and control means for controlling said first fixing roller and said drive means such that in the full-color copy mode said guide means assumes the second position and said first fixing roller is rotated in a direction for transporting the paper sheet in a predetermined direction in said second nipping section while, in a black-and-white copy mode, said guide means assumes the first position and said first fixing roller is rotated in a direction for transporting said paper sheet in said predetermined direction in said first nipping section.