Image forming apparatus and heating device comprising plural pressing devices configured to generate different pressing forces

A heating device comprising:

• a rotator;
• an opposed rotator configured to contact the rotator to form a nip;
• a heater configured to heat the rotator,
• the heater including:
• a first heat generator group including at least one resistive heat generator;
• a second heat generator group including at least two resistive heat generators outside the first heat generator group at both end sides of the heater in a longitudinal direction of the heater;
• a plurality of conductors;
• a first electrode coupled to the first heat generator group via at least one of the conductors;
• a second electrode coupled to the first heat generator group and the second heat generator group via at least one of the conductors;
• and
• a third electrode coupled to the second heat generator group via at least one of the conductors;
• and
• a plurality of pressing devices arranged in the longitudinal direction of the heater and each configured to press at least one of the rotator and the opposed rotator and cause the rotator and the opposed rotator to press each other,
• the pressing devices including:
• a first pressing device disposed on a first portion corresponding to the first electrode;
• and
• a second pressing device disposed on a second portion that is different from the first portion in the longitudinal direction of the heater,
• the first pressing device being configured to generate a larger pressing force than the second pressing device when both of the first heat generator group and the second heat generator group are energized and generate a smaller pressing force than the second pressing device when the first heat generator group is energized and the second heat generator group is not energized.

A heating device comprising:

• a rotator;
• an opposed rotator configured to contact the rotator to form a nip;
• a heater configured to heat the rotator;
• a plurality of temperature detectors facing the rotator and including:
• a first temperature detector facing the rotator and disposed corresponding to one side of the heater in a longitudinal direction of the heater;
• and
• a second temperature detector facing the rotator and disposed corresponding to the other side of the heater in the longitudinal direction of the heater;
• and
• a plurality of pressing devices arranged in the longitudinal direction of the heater and each configured to press at least one of the rotator and the opposed rotator and cause the rotator and the opposed rotator to press each other,
• the pressing devices including:
• a first pressing device disposed corresponding the first temperature detector;
• and
• a second pressing device disposed corresponding to the second temperature detector,
• wherein the first pressing device is configured to press the at least one of the rotator and the opposed rotator with a smaller pressing force than the second pressing device when a temperature detected by the first temperature detector is higher than a temperature detected by the second temperature detector and a temperature difference between the temperature detected by the first temperature detector and the temperature detected by the second temperature detector is equal to or larger than a predetermined value, and
• wherein the second pressing device is configured to press the at least one of the rotator and the opposed rotator with a smaller pressing force than the first pressing device when the temperature detected by the second temperature detector is higher than the temperature detected by the first temperature detector and the temperature difference between the temperature detected by the first temperature detector and the temperature detected by the second temperature detector is equal to or larger than the predetermined value.