Image forming apparatus and image heating apparatus
Provided is an image heating apparatus including: a heater having a plurality of heating elements arranged in a direction orthogonal to a conveying direction of the recording material; and a control portion that controls electric power to be supplied to the plurality of heating elements and is capable of individually controlling the plurality of heating elements, the image heating apparatus heating an image formed on the recording material with heat by the heater, wherein the control portion sets a heating condition when controlling each of the plurality of heating elements, according to the thermal history of a heating region heated by one heating element and the thermal history of a heating region heated by a heating element adjacent to the one heating element.
1. An image heating apparatus that heats an image formed on a recording material, the image heating apparatus comprising:
a tubular film arranged to contact the recording material, the tubular film including a base layer made of heat-resistant resin or metal, a rubber layer provided on an outer side of the base layer, and a releasing layer provided on a surface of the tubular film and made of heat-resistant resin;
a heater provided in an inner space of the tubular film, the heater having a plurality of heating elements arranged in a direction orthogonal to a conveying direction of the recording material;
a roller contacting an outer surface of the tubular film and configured to form a nip portion for conveying the recording material in cooperation with the heater via the tubular film, the roller includes a rubber layer;
a plurality of temperature detecting elements corresponding to the plurality of heating elements configured to detect a temperature of each of the plurality of heating elements; and
a control portion configured to control electric power to be supplied to the plurality of heating elements, the control portion being capable of individually controlling electric power to be supplied to the plurality of heating elements so that each of the plurality of temperature detecting elements is maintained at a target temperature,
wherein
the control portion sets target temperatures corresponding to the plurality of heating elements when controlling each of the plurality of heating elements, according to a first thermal history of a first heating region heated by a first heating element among the plurality of heating elements, a second thermal history of a second heating region heated by a second heating element adjacent to the first heating element, and a density of the image formed on the recording material,
the first thermal history of the first heating region heated by the first heating element and the second thermal history of the second heating region heated by the second heating element are variable according to a heat storage amount of the rubber layer of the film and a heat storage amount of the rubber layer of the roller,
the control portion calculates a first heat storage amount in the first heating region according to a distance from a front end to a rear end of a first image on a first recording material heated by the first heating region, and calculates a second heat storage amount in the second heating region according to a distance from a front end to a rear end of a second image on the first recording material heated by the second heating region, and
when a second recording material is conveyed to the nip portion after the first recording material, the control portion sets the target temperature of the first heating element according to the first heat storage amount and the second heat storage amount.