Heating device, fixing device, and image forming apparatus

A heating device comprising:

• a heater including a base and a plurality of resistive heat generators arranged on the base in an arrangement direction, separated from each other, and forming a heat generation area, the heater having a separation area that includes an entire gap between neighboring ones of the plurality of resistive heat generators in the arrangement direction;
• a rotator;
• and
• a pressure rotator configured to press the rotator, the pressure rotator including a first region and a second region,
• the second region including a position corresponding to the separation area, the second region facing a part of a range of the heater from a center position of the separation area to a center position of the heat generation area, the second region having an outer diameter increasing in a direction from the center position of the heat generation area toward an end of the heat generation area, the second region based on a peripheral separation area of the heater, and
• the first region nearer to a position being on the pressure rotator and facing the center position of the heat generation area than the second region, the first region having an outer diameter increasing at an increasing rate smaller than an increasing rate of the outer diameter of the second region in the direction from the center position of the heat generation area toward the end of the heat generation area, the first region based on a central separation area of the heater;
• wherein the pressure rotator has an inflection point between a position being on the pressure rotator and facing the center position of the separation area and an end of the pressure rotator opposite the second region with respect to the position being on the pressure rotator and facing the center position of the separation area, and
• wherein, in a part of a range from the inflection point to the end of the pressure rotator, an outer diameter of the pressure rotator increases at an increasing rate in a direction from the inflection point to the end of the pressure rotator, the increasing rate in the part being smaller than the increasing rate of the outer diameter of the second region.