Fixing apparatus having temperature controller which controls temperature according to width size and number of recording sheets

An image forming apparatus comprising:

• image forming means for forming an unfixed image on a recording material;
• a pair of fixing rotating members forming a nip, at least one of said pair of fixing rotating members being heated by a heating source, said pair of fixing rotating members fixing an unfixed image onto a first recording material and a second recording material which are fed through said nip, said second recording material having a width different from said first recording material;
• a temperature detecting element for detecting a surface temperature of at least one of said pair of fixing rotating members, wherein said temperature detecting element is positioned outside both the passing region of said first and second recording materials and is spaced farther away from a side edge of said second recording material than from a side edge of said first recording material;
• control means for controlling electricity to said heating source so as to maintain the surface temperature detected by said temperature detecting means at a predetermined temperature;
• wherein said predetermined temperature for said second recording material is higher than the predetermined temperature for said first recording material.

An image forming apparatus comprising:

• image forming means for forming an unfixed image on a recording material;
• a pair of fixing rotating members forming a nip, at least one of said pair of fixing rotating members being heated by a heating source, a first recording material having a first size and a second recording material having a second size being feedable through said nip to allow an unfixed image to be fixed thereon;
• a temperature detecting element for detecting a surface temperature of at least one of said pair of fixing rotating members, wherein said temperature detecting element is provided at a position within the passing region of said first recording material and outside the passing region of said second recording material;
• control means for controlling electricity to said heating source so as to maintain the surface temperature detected by said temperature detecting element at a predetermined temperature;
• wherein said predetermined temperature for said second recording material is higher than the predetermined temperature for said first recording material.

An image forming apparatus comprising:

• image forming means for forming an unfixed image on a recording material;
• a pair of fixing rotating members for fixing the unfixed image onto a recording material carried through a nip formed by said pair of fixing rotating members, wherein at least one of said pair of fixing rotating members is heated by a heating source;
• a temperature detecting element for detecting a surface temperature of at least one of said pair of fixing rotating members, said temperature detecting element being provided outside a passing region of a recording material having the largest width;
• control means for controlling electricity to said heating source so as to maintain the surface temperature detected by said temperature detecting element at a predetermined temperature;
• counting means for counting each completed fixing operation;
• and
• accumulating means for accumulating the total number of counted completed fixing operations;
• wherein said control means raises said predetermined temperature when the accumulated total number of said accumulating means reaches a predetermined value;
• and
• wherein, when the recording material is continuously fed through the nip of said pair of fixing rotating members, a difference between a temperature of a surface region of the fixing rotating member detected by the temperature detecting element and a temperature of the passing region of the recording material increases.