1. Field of the Invention
The present invention relates to a fixing device and a fixing method for fixing a toner image on a recording sheet.
2. Description of the Related Art
In Japanese Patent Application Publication No. 2005-274948, a fixing device including a heat roller having a heat generation surface for generating heat for heating a recording sheet by heat generated from the heat generation surface, a pressure roller for pressing the recording sheet to the heat generation surface of the heat roller, and a thermostat for stopping heat generation of the heat generation surface when the temperature at the monitoring portion where the peak of the temperature appears exceeds a predetermined threshold value in the second area of the heat generation surface of the heat roller excluding the first area where the recording sheet always makes contact with at time of press-fit by the pressure roller is disclosed.
Further, in Japanese Patent Application Publication No. 2003-43854, an image forming apparatus composed of a fixing device including a first heater arranged in the neighborhood of the central part of fixing rollers in the axial direction, a second heater arranged in the neighborhood of both ends thereof, a first temperature detecting means for detecting the temperature of the first heater having larger power than that of the second heater, and a second temperature detecting means for detecting the temperature of the second heater is disclosed.
To heat the central part and end parts of each recording sheet, separate heaters are used and to detect abnormal temperatures of the respective heaters, at least two thermostats are required. However, due to use of two thermostats, a problem arises that the whole cost of the copier is increased and no inexpensive products can be provided to users.