Fixing device, image forming apparatus incorporating same, and method for heating fixing rotary body

摘要

A fixing device includes an induction heater constructed of an exciting coil, a first pair of degaussing coils, and a second pair of degaussing coils. A controller turns off the exciting coil while the controller turns on one of the first pair of degaussing coils and the second pair of degaussing coils and at the same time turns off the other one of the first pair of degaussing coils and the second pair of degaussing coils, and then turns on the exciting coil for an extra time period corresponding to reserved power not supplied to the exciting coil while the exciting coil is turned off.

主权项

1. A fixing device comprising:
a fixing rotary body rotatable in a predetermined direction of rotation; an induction heater disposed opposite the fixing rotary body to heat the fixing rotary body; and a controller operatively connected to the induction heater, the induction heater including:
an exciting coil to generate a magnetic flux toward the fixing rotary body;a first pair of degaussing coils disposed opposite lateral ends of the exciting coil in an axial direction of the fixing rotary body to offset the magnetic flux generated by the exciting coil, each degaussing coil of the first pair having a first width in the axial direction of the fixing rotary body;a second pair of degaussing coils disposed opposite the lateral ends of the exciting coil in the axial direction of the fixing rotary body to offset the magnetic flux generated by the exciting coil, each degaussing coil of the second pair having a second width in the axial direction of the fixing rotary body greater than the first width of each degaussing coil of the first pair;an exciting coil switch connected to the exciting coil and a power supply to connect and disconnect the exciting coil to and from the power supply to turn on and off the exciting coil;a first degaussing coil switch connected to the first pair of degaussing coils to turn on and off the first pair of degaussing coils; anda second degaussing coil switch connected to the second pair of degaussing coils to turn on and off the second pair of degaussing coils,wherein the controller causes the exciting coil switch to turn off the exciting coil for a given time after the controller starts turning on one of the first degaussing coil switch and the second degaussing coil switch and at the same time turns off the other one of the first degaussing coil switch and the second degaussing coil switch, and then causes the exciting coil switch to turn on the exciting coil for an extra time period corresponding to the given time when the exciting coil is turned off.