Fixing device including a pressure rotator setting an exit guide angle and image forming apparatus incorporating same

A fixing device comprising:

• a fixing rotator;
• a pressure rotator configured to press the fixing rotator to form a nip between the fixing rotator and the pressure rotator;
• a pressure plate configured to rotate about a fulcrum to press the pressure rotator;
• a pressing force adjuster configured to adjust a pressing force of the pressure rotator;
• an entrance guide configured to guide a recording medium entering the nip;
• an exit guide configured to guide the recording medium ejected from the nip;
• and
• a guide configured to guide the pressure rotator in a direction inclined from a line connecting a rotation center of the fixing rotator and a rotation center of the pressure rotator toward downstream in a conveyance direction of the recording medium,
• wherein the pressing force adjuster is configured to rotate the pressure plate about the fulcrum to adjust the pressing force and set the pressure plate to any of a plurality of positions in a rotation direction of the pressure plate,
• wherein the plurality of positions includes a maximum pressure position at which the pressure rotator pressed by the pressure plate presses a sheet of plain paper with a maximum pressing force and an envelope position at which the pressure rotator pressed by the pressure plate presses an envelope with a pressing force smaller than the maximum pressing force,
• wherein the pressure rotator at the maximum pressure position sets an exit guide angle between a reference line connecting an entrance of the nip and an exit of the nip and a straight line connecting a center of the nip and a tip of the exit guide to be in a range from 0° to +15°, and
• wherein the pressure rotator at the envelope position sets the exit guide angle to be in range from −10° to +5°, and
• where a positive angle is formed by the reference line and the straight line inclined toward one of the fixing rotator and the pressure rotator, the one having a convex shape in the nip, and a negative angle is formed by reference line and the straight line inclined toward the other of the fixing rotator and the pressure rotator, the other having a concave shape in the nip.