Patent ID: 8594523

Claim:
An image forming apparatus comprising: a heat source; a heating member configured to be heated by the heat source to fix a developer image on a recording sheet, wherein the heating member is configured to rotate; a temperature sensor disposed apart from the heating member to detect a temperature of the heating member; and a controller including a memory which stores a first linear function having a first slope, a second linear function having a second slope smaller than the first slope of the first linear function, a third function having a third slope smaller than the second slope of the second linear function, and a fourth linear function having a fourth slope smaller than the third slope of the third linear function, wherein the controller is configured to: control the heat source based upon a temperature determined mathematically by application of the first linear function to the temperature detected by the temperature sensor during a warm-up mode in which continuous increase in temperature of the heating member takes place; control the heat source based upon a temperature determined mathematically by application of the second linear function to the temperature detected by the temperature sensor during a first fixing mode in which the heating member is maintained at a predetermined fixing temperature and in which the heating member rotates at a first rotational speed; control the heat source based upon a temperature determined mathematically by application of the third linear function to the temperature detected by the temperature sensor during a ready mode in which the heating member is maintained at a ready temperature that is lower than the fixing temperature; and control the heat source based upon a temperature determined mathematically by application of the fourth linear function to the temperature detected by the temperature sensor during a second fixing mode in which the heating member is maintained at a predetermined fixing temperature and in which the heating member rotates at a second rotational speed, wherein the second rotational speed is faster than the first rotational speed.