Heating device, fixing device and image forming apparatus

A heating device comprising:

• an endless belt;
• an opposed rotator configured to contact the endless belt to form a nip between the endless belt and the opposed rotator;
• a heater configured to heat the endless belt,
• the heater including
• a first heat generator group including at least one resistive heat generator,
• a second heat generator group including resistive heat generators outside the first heat generator group at both end portions of the heater in a longitudinal direction of the heater,
• a first electrode coupled to the first heat generator group,
• a second electrode coupled to the first heat generator group and the second heat generator group, and
• a third electrode coupled to the second heat generator group;
• and
• a heat transfer portion disposed on an opposite side of the first electrode with respect to a center position of a heating span of all the resistive heat generators energized in the longitudinal direction of the heater,
• wherein a ratio of a short-side dimension of each of the resistive heat generators to a short-side dimension of the heater is not less than 40%, and
• wherein a short-side direction of each of the heater and the resistive heat generators intersects the longitudinal direction of the heater along a surface of the heater on which the resistive heat generators are disposed.

A heating device comprising:

• an endless belt;
• an opposed rotator configured to contact the endless belt to form a nip between the endless belt and the opposed rotator;
• a heater including a plurality of resistive heat generators configured to heat the endless belt,
• the heater being configured to generate a larger amount of heat on a first side of the heater than a second side of the heater in a longitudinal direction of the heater, the first side being opposite to the second side with respect to a center position of a heating span of all the plurality of resistive heat generators energized in the longitudinal direction of the heater;
• and
• a heat transfer portion disposed on the first side to release heat from the heating span,
• wherein the heater has an overlapping portion in which the plurality of resistive heat generators overlap in a short-side direction of the heater, and
• wherein the short-side direction of the heater and a short-side direction of each of the resistive heat generators intersect the longitudinal direction of the heater along a surface of the heater on which the resistive heat generators are disposed.