Fixing apparatus

摘要

A fixing apparatus includes: two rotatable members, for forming a nip, including a region where an outer diameter is increased from a longitudinal central portion toward a longitudinal end portion; a heater; and a controller for controlling a heat generation distribution of the heater. The controller is capable of controlling the heater so that the heat generation distribution of the heater is such that a heat generation amount at the longitudinal end portion is larger than that at the longitudinal central portion in a period from start of the heater until the recording material reaches the nip. A ratio of the heat generation amount at the longitudinal end portion to that at the longitudinal central portion is larger when a cumulative amount of use of the fixing apparatus is larger than a predetermined amount than when the cumulative amount of use is smaller than the predetermined amount.

主权项

1. A fixing apparatus for fixing a toner image on a recording material by heating the toner image while conveying the recording material in a nip, said fixing apparatus comprising:
a pair of rotatable members configured to form the nip, wherein at least one of said pair of rotatable members has a region where an outer diameter is increased from a longitudinal central portion toward a longitudinal end portion; a heater, having a variable heat generation distribution with respect to a longitudinal direction, configured to heat said pair of rotatable members; a controller configured to control the heat generation distribution of said heater with respect to the longitudinal direction, and a counting portion configured to count the amount of use of said fixing apparatus from a time of a brand-new state thereof to determine the cumulative amount of use of said fixing apparatus, wherein said controller sets a ratio of an amount of heat generation at the longitudinal end portion to that at the longitudinal central portion at a first ratio in a period from the start of electric power supply to said heater until the recording material reaches the nip when the cumulative amount of use is smaller than a predetermined threshold, and sets the ratio at a second ratio larger than the first ratio in the period when the cumulative amount of use is larger than the predetermined threshold.