Fixing device having temperature control means

An image forming device comprising:

• a rotatable fixing roll arranged on a paper discharge side of a photosensitive body;
• a heating means for heating said fixing roll;
• a temperature detection means for detecting the surface temperature of said fixing roll;
• a temperature control means for controlling the fixing roll surface to maintain a predetermined temperature by supplying a predetermined electric power to said heating means based on a detection signal from said temperature detection means;
• wherein the temperature of said fixing roll during continuous image forming is detected by said temperature detection means, and said temperature control means controls an electric Power quantity supplied to said heating means by increasing or decreasing a half-wave unit cycle number of a commercial power source in order to reduce the temperature difference between a predetermined reference temperature and said detected temperature;
• and
• wherein the temperature control means corrects the reference electric power quantity at the time to start the image forming based on the detected commercial power source.

An image forming device comprising:

• a rotatable fixing roll arranged on a paper discharge side of a photosensitive body;
• a heating means for heating said fixing roll;
• a temperature detection means for detecting the surface temperature of said fixing roll;
• a temperature control means for controlling the fixing roll surface to maintain a predetermined temperature by supplying a predetermined power to said heating means based on a detection signal from said temperature detection means;
• and
• wherein said temperature control means comprises a first temperature control means operating during image forming, and a second temperature control means operating during standby, said first temperature control means and said second temperature control means detecting said fixing roll temperature by said temperature detection means, controlling an electric power quantity supplied to said heating means by increasing or decreasing a half-wave unit cycle number of a commercial power source in order to reduce a temperature difference between a predetermined reference temperature and said detected temperature, and said second temperature control means further controlling the power supply to said heating means having a predetermined hysteresis width with respect to said reference temperature.

An image forming device comprising:

• a rotatable fixing roll arranged on a paper discharge side of a photosensitive body;
• a heating means for heating said fixing roll;
• a temperature detection means for detecting the surface temperature of said fixing roll;
• a temperature control means for controlling the fixing roll surface to maintain a predetermined temperature by supplying a predetermined electric power to said heating means based on a detection signal from said temperature detection means;
• wherein the temperature of said fixing roll during continuous image forming is detected by said temperature detection means, and said temperature control means controls an electric power quantity supplied to said heating means by increasing or decreasing a half-wave unit cycle number of a commercial power source in order to reduce the temperature difference between a predetermined reference temperature and said detected temperature;
• and
• wherein the electric power quantity supplied at the final copying operation for each of the copying paper is stored, and said stored electric power quantity is utilized as the reference electric power at the start of the next copying operation.

An image forming device comprising:

• a rotatable fixing roll arranged on a paper discharge side of a photosensitive body;
• a heating means for heating said fixing roll;
• a temperature detection means for detecting the surface temperature of said fixing roll;
• a temperature control means for controlling the fixing roll surface to maintain a predetermined temperature by supplying a predetermined electric power to said heating means based on a detection signal from said temperature detection means;
• wherein the temperature of said fixing roll during continuous image forming is detected by said temperature detection means, and said temperature control means controls an electric power quantity supplied to said heating means by increasing or decreasing a half-wave unit cycle number of a commercial power source in order to reduce the temperature difference between a predetermined reference temperature and said detected temperature;
• and
• wherein in the control for switching the reference temperature corresponding to the image forming number of sheets from the start of the image forming operation, the difference in electric power quantity supplied to the heating means at each reference temperature is stored and said difference in electric power quantity is subtracted from the presently supplied power to the heating means when switching said reference temperature.