Fixing apparatus and method for electrophotographic apparatus including temperature detecting mechanism for heat roller

A fixing apparatus for an electrophotographic apparatus comprising:

• a heat roller having therein a plurality of heaters with different heating areas respectively and a pressure roller urged against said heat roller, wherein a recording material holding a toner image thereon is sandwiched and carried while being heated and pressurized at a pressing portion between said heat roller and said pressure roller thereby to fix the toner image on a surface of said recording material;
• control means for controlling turning-on and turning-off of said plurality of heaters;
• first temperature detecting means including a temperature detecting element fixed at an end portion of outer periphery of said heat roller and a sensor head disposed so as to be able to oppose to said temperature detecting element;
• second temperature detecting means including a plurality of temperature detecting elements which are provided in correspondence with said respective heating areas of said plurality of heaters, disposed at a constant interval therebetween along an axial direction of said heat roller and supported so as to be spaced from the outer periphery of said heat roller;
• and
• memory means for storing outputs of said second temperature detecting means.

A fixing method for an electrophotographic apparatus including a heat roller having a plurality of heaters with different heating areas respectively;

• a control means for controlling turning-on and turning-off of said plurality of heaters;
• first temperature detecting means formed by a temperature detecting element fixed at an end portion of an outer periphery of said heat roller and a sensor head disposed so as to be able oppose said temperature detecting element;
• second temperature detecting means formed by a plurality of temperature detecting elements which are provided in correspondence with said respective heating areas of said plurality of heaters, disposed at a constant interval therebetween along an axial direction of said heat roller and supported so as to be spaced from the outer periphery of said heat roller;
• and memory means for storing outputs of said second temperature detecting means, said fixing method comprising the steps of:
• an ideal temperature distribution forming step of controlling turning-on and turning-off of said plurality of heaters before performing a printing operation thereby to obtain uniform temperature distribution in said heat roller;
• a measuring step of measuring, by said second temperature detecting means, temperature of surface of said heat roller in a state where the uniform temperature distribution in said heat roller has been obtained by said ideal temperature distribution forming step;
• and
• a storing step for storing measured temperatures obtained by said measuring step in said memory means;
• wherein at a time of performing a printing operation, said plurality of heaters are turned on and off in accordance with data stored in said memory means.