Fixing device and image forming apparatus incorporating

An image forming apparatus comprising:

• an electrophotographic imaging unit to form a toner image on a recording medium;
• and
• a fixing device to fix the toner image in place on the recording medium, the fixing device including:
• an endless fuser belt looped into a generally cylindrical configuration extending in an axial direction thereof for rotation along a circumferential direction thereof;
• a contact member extending in the axial direction inside the loop of the fuser belt;
• a pressure member extending in the axial direction with the fuser belt interposed between the contact member and the pressure member,
• the pressure member being pressed against the contact member through the fuser belt to form a fixing nip through which the recording medium is passed under heat and pressure;
• a heater to heat the fuser belt to a setpoint temperature, the heater including:
• a first heating element to heat the fuser belt at a first position;
• and
• a second heating element to heat the fuser belt at a second position, different from the first position along the axial direction;
• a first thermometer to detect a first temperature of the fuser belt upstream of the first position along the circumferential direction;
• a second thermometer to detect a second temperature of the fuser belt facing the second position;
• and
• a controller connected to the first and second thermometers to control each of the first and second heating elements by adjusting an operational parameter thereof according to the first and second detected temperatures at least where the fuser belt rotates.

A method to control heating in a fixing device,

• the fixing device including:
• an endless fuser belt looped into a generally cylindrical configuration extending in an axial direction thereof for rotation along a circumferential direction thereof;
• a contact member extending in the axial direction inside the loop of the fuser belt;
• a pressure member extending in the axial direction with the fuser belt interposed between the contact member and the pressure member,
• the pressure member being pressed against the contact member through the fuser belt to form a fixing nip through which a recording medium is passed under heat and pressure;
• a heater to heat the fuser belt to a setpoint temperature, the heater including:
• a first heating element to heat the fuser belt at a first position;
• and
• a second heating element to heat the fuser belt at a second position, different from the first position along the axial direction,
• the method comprising the steps of:
• detecting a first temperature of the fuser belt upstream of the first position along the circumferential direction;
• detecting a second temperature of the fuser belt facing the second position;
• and
• controlling each of the first and second heating elements by adjusting an operational parameter thereof according to the first and second detected temperatures at least where the fuser belt rotates.