Fixing device and control method used therein

A method for determining a setpoint temperature at which an operational temperature of a fixing device is regulated during sequential processing of multiple print pages, including a current print page and a previous print page immediately preceding the current page, the method comprising:

• controlling power supply to a heater of the fixing device according to readings of a temperature detector of the fixing device, so as to regulate the operational temperature at the setpoint temperature, the setpoint temperature being variable depending on a print page printed on a recording medium, the controlling including,
• adjusting the setpoint temperature for the current print page to a primary temperature determined based on image information of the current print page, when the primary temperate is equal to or higher than the setpoint temperature;
• and
• adjusting the setpoint temperature for the current print page to a secondary temperature higher than the primary temperature when the primary temperature is lower than the setpoint temperature used to print the previous print page.

A fixing device comprising:

• a rotatable fuser member subjected to heating;
• a rotatable pressure member opposite the rotatable fuser member, the rotatable pressure member configured to press against the rotatable fuser member to form a fixing nip there between, a recording medium being conveyed through the fixing nip;
• a heater adjacent to the rotatable fuser member and configured to heat the rotatable fuser member;
• a temperature detector directed to at least one of the rotatable fuser member, the rotatable pressure member, and the heater, the temperature detector being configured to detect an operational temperature of the fixing device;
• and
• a controller connected to the temperature detector and the heater and configured to control power supply to the heater according to readings of the temperature detector, so as to regulate the detected operational temperature at a setpoint temperature that is variable depending on a print page printed on the recording medium, wherein
• during sequential processing of multiple print pages, including a current print page and a previous print page immediately preceding the current print page, the controller controls the power supply by adjusting the setpoint temperature for the current print page to,
• a primary temperature determined based on image information of the current print page when the primary temperature is equal to or higher than the setpoint temperature used to print the previous print page,
• a secondary temperature higher than the primary temperature when the primary temperature is lower than the setpoint temperature used to print the previous print page, and
• the controller is configured to start adjusting the setpoint temperature for the current print page at a switching time relative to a reference time at which the recording medium on which the previous print page is printed exits the fixing nip, the switching time being variable depending on whether the setpoint temperature for the current print page is lower or higher than the setpoint temperature used to print the previous print page.

A fixing device comprising:

• a temperature detector configured to detect an operational temperature of the fixing device;
• and
• a controller connected to the temperature detector and a heater of the fixing device, wherein
• during sequential processing of multiple print pages, including a current print page and a previous print page immediately preceding the current print page, the controller is configured to regulate the detected operational temperature by adjusting the reference temperature to,
• a primary temperature determined based on image information of the current print page when the primary temperature is equal to or higher than a setpoint temperature used to print the previous print page, and
• a secondary temperature higher than the primary temperature when the primary temperature is lower than the setpoint temperature used to print the previous print page.