Image forming apparatus

An image forming apparatus comprising:

• an image forming station for forming an unfixed image on a recording material;
• a fixing portion for fixing an unfixed image formed on the recording material thereon, said fixing portion including an endless belt, a heater contacted to an inner surface of said endless belt, a back-up member forming a fixing nip for nipping and feeding the recording material together with said heater through said endless belt, said heater including a first heat generating element and a second heat generating element provided at a position downstream of said first heat generating element with respect to a feeding direction of the recording material;
• and
• an electric power control portion for controlling electric power supplied to said first heat generating element and said second heat generating element in accordance with a temperature of the fixing portion;
• wherein said electric power control portion supplies the electric power to said first heat generating element and said second heat generating element so that a feeding speed V1 of the recording material at the fixing nip, a distance A between said first heat generating element and said second heat generating element, a ratio Pin (%) of total electric power supplied to said first heat generating element and said second heat generating element set in accordance with the temperature of said fixing portion relative to maximum total electric power supplyable to said first heat generating element and said second heat generating element, a ratio E203(t) (%) of electric power supplied to said first heat generating element at timing t relative to the maximum total electric power, and a ratio E204(t) (%) of electric power supplied to said second heat generating element at timing t relative to the maximum total electric power, satisfy the following equation,
• E
• 203
• ⁡
• (
• t
• )
• +
• E
• 204
• ⁡
• (
• t
• +
• A
• V
• ⁢
• ⁢
• 1
• )
• ≅
• Pin
• ⁢
• .