Image forming apparatus

A method of discriminating a residual life span of a first rotatable member of an image fixing apparatus including the first rotatable member and a second rotatable member which form a nip through which a recording material carrying a toner image is passed so that the recording material is heated to fix the toner image on the recording material, said method comprising:

• setting a fixing operation duration coefficient of a first area provided by dividing said first rotatable member into a plurality of areas in a longitudinal direction of said first rotatable member when a size of the recording material is a first size, and a fixing operation duration coefficient of a second area provided at a different position from the first area in a longitudinal direction of said first rotatable member when the size of the recording material is the first size;
• obtaining an operation length of a fixing operation when the size of the recording material is the first size;
• calculating a fixing operation duration count of the first area when the fixing operation is carried out for the recording materials of the first size, in accordance with the fixing operation duration coefficient of the first area when the size of the recording material is the first size, and the operation length of the fixing operation when the size of the recording material is the first size;
• calculating a fixing operation duration count of the second area when the fixing operation is carried out for the recording materials of the first size, in accordance with the fixing operation duration coefficient of the second area when the size of the recording material is the first size, and the operation length of the fixing operation when the size of the recording material is the first size;
• storing, in a memory, the fixing operation duration count of the first area and the fixing operation duration count of the second area when the size of the recording material is the first size;
• setting a fixing operation duration coefficient of the first area when the size of the recording material is a second size, and a fixing operation duration coefficient of the second area when the size of the recording material is the second size;
• obtaining an operation length of the fixing operation when the size of the recording material is the second size;
• calculating a fixing operation duration count when the fixing operation is carried out for the recording materials of the second size, in accordance with the fixing operation duration coefficient of the first area when the size of the recording material is the second size, and the operation length of the fixing operation when the size of the recording material is the second size;
• calculating a fixing operation duration count when the fixing operation is carried out for the recording materials of the second size, in accordance with the fixing operation duration coefficient of the first area when the size of the recording material is the second size, and the operation length of the fixing operation when the size of the recording material is the second size;
• adding the fixing operation duration count of the first area when the size of the recording material is the second size and the fixing operation duration count, stored in the memory, of the first area when the size of the recording material is the first size, and adding the fixing operation duration count of the second area when the size of the recording material is the second size and the fixing operation duration count, stored in the memory, of the second area when the size of the recording material is the first size;
• comparing the added fixing operation duration count of the first area and the added fixing operation duration count of the second area with a reference value relating to the residual life span;
• and
• discriminating an end of the residual life span when the fixing operation duration count of at least one of the first area and the second the area reaches the reference value.