Fixing device and image forming apparatus

An image forming apparatus for forming and fixing a toner image on and to a sheet, comprising:

• an image forming unit for forming a toner image on a sheet;
• and
• a fixing device for fixing the toner image formed by the image forming unit to the sheet, wherein the fixing device includes:
• a fixing roller configured to be heated by a heat source;
• a pressure roller configured to be pressed into contact with the fixing roller;
• a switcher for switching a pressing force between the fixing roller and the pressure roller between a first pressing force and a second pressing force lower than the first pressing force;
• a pressing force detector for detecting the pressing force between the fixing roller and the pressure roller;
• a temperature detector for detecting the temperature of the fixing roller;
• a storage device for storing control data indicating a control temperature for the fixing roller predetermined in accordance with the number of sheets passing the fixing device;
• and
• a controller for controlling the temperature of the fixing roller to the control temperature by controlling the heat source in accordance with a signal sent from the pressing force detector.