Heat fixing apparatus

A heat fixing apparatus for heating and fixing a toner image formed on a recording material onto the recording material, comprising:

• an endless belt;
• a heater that contacts an internal surface of the endless belt, the heater having a first heat generation member, and a second heat generation member whose ratio of a resistance value per unit length at edge portions to the resistance value per unit length at a center portion in a longitudinal direction of the heater is larger than that of the first heat generation member;
• a back-up member configured to form a fixing nip portion that pinches and conveys a recording material through the endless belt together with the heater;
• and
• a pressure change mechanism configured to set a pressure applied to the fixing nip portion to a first pressure and a second pressure lower than the first pressure,
• wherein a heat proportion of the second heat generation member when the temperature of the heater is raised to a fixable temperature with the pressure applied to the fixing nip portion set to the second pressure is zero, or is smaller than a heat proportion of the second heat generation member when the temperature of the heater is raised to a fixable temperature with the pressure applied to the fixing nip portion set to the first pressure;
• wherein power is supplied to the heater while the second pressure is applied to the fixing nip portion.

A heat fixing apparatus for heating and fixing a toner image formed on a recording material onto the recording material, comprising:

• an endless belt;
• a heater configured to heat the endless belt, the heater having a first heat generation member, and a second heat generation member whose ratio of a heat generating amount per unit length at edge portions to the heat generating amount per unit length at a center portion in a longitudinal direction of the heater is larger than that of the first heat generation member;
• a back-up member configured to contact the endless belt to form a fixing nip portion;
• and
• a pressure change mechanism configured to change a pressure applied to the fixing nip portion to a first pressure and a second pressure lower than the first pressure,
• wherein a heat generating amount of the second heat generation member, when power is supplied to the heater under the second pressure applied to the fixing nip portion, is zero, or a heat generating amount of the second heat generation member, when power is supplied to the heater under the second pressure applied to the fixing nip portion, is smaller than a heat generating amount of the second heat generation member when power is supplied to the heater under the first pressure applied to the fixing nip portion.