Image forming device with fusion device driven based on surface temperature of fusion roller and pressure application roller

An image forming device, comprising:

• a heat source;
• a freely rotatable fusion member that is heated by the heat source;
• a pressure application member that is biased against the fusion member and that is heated by the fusion member;
• a first temperature detector that is positioned adjacent to the pressure application member and that is configured to detect a surface temperature of the pressure application member;
• a second temperature detector that is positioned adjacent to the heat fusion member and that is configured to detect a surface temperature of the heat fusion member;
• and
• a controller that is configured to determine whether or not the temperature detected by the first temperature detector is greater than a predetermined temperature, to control the heat source by selecting, as a target temperature, one of a preset first set temperature or a second set temperature that is lower than the first set temperature, to set, as the target temperature, the one of the first set temperature and the second set temperature based on an input timing of print data indicating whether print data is inputted within predetermined time elapsed from initiating heating by the heat source, and to commence printing in one of a Low Temperature Low Speed (LTLS) mode and a High Temperature High Speed (HTHS) mode based on the input timing of print data and on a temperature of the heat fusion member that is detected by the second temperature detector.

In an image forming device, a method of selecting between a Low Temperature Low Speed (LTLS) printing mode and a High Temperature High Speed (HTHS) printing mode, comprising:

• initiating a warm-up operation to heat a fusion roller;
• causing the fusion roller to rotate when a temperature of the fusion roller becomes greater than a rotation starting temperature;
• receiving print data;
• determining whether or not a temperature of a pressure application member is greater than a predetermined temperature;
• determining if an amount of elapsed time from the initiating of a warm-up operation is less than or equal to a predetermined value at the time when the print data is received;
• setting, as a target temperature, one of a preset first set temperature or a second set temperature that is lower than the first set temperature, based on the determination of the amount of elapsed time;
• executing printing in the LTLS mode based on the second set temperature when the amount of elapsed time is less than or equal to the predetermined value;
• and
• executing printing in the HTHS mode based on the first set temperature when the amount of elapsed time is greater than the predetermined value.