Image forming apparatus enabled to optimize transfer medium slack between transferring and fixing portions

An image forming apparatus comprising:

• an image bearing member for carrying a toner image, said image bearing member being rotatable at a predetermined peripheral speed;
• transfer means which forms with said image bearing member a transfer nip for transferring the toner image from said image bearing member onto a transfer material;
• fixing means for fixing the image transferred from said image bearing member on the transfer material, said fixing means including a fixing rotatable member and a pressing rotatable member which is press-contacted through said fixing rotatable member to form a fixing nip therebetween, the fixing nip being effective to nip and feed the transfer material;
• control means for controlling a peripheral speed of said fixing rotatable member,
• wherein the following is satisfied:
• Pmin>Lmin
• 0<X≦δL/Pmax
• V0:
• the peripheral speed of said image bearing member;
• Vf:
• a feeding speed of said fixing means;
• Lmin:
• a minimum path length between the transfer nip and the fixing nip;
• Lmax:
• a maximum guide path length between the transfer nip and the fixing nip;
• δL=Lmax−Lmin:
• an amount of loop formed between the transfer nip and a fixing nip;
• Pmax:
• a maximum length of the transfer material on which said image forming apparatus is capable of forming the toner image;
• Pmin:
• a minimum length of the transfer material on which said image forming apparatus is capable of forming the toner image;
• X:
• a fluctuation rate of the feeding speed Vf of said fixing means relative to the peripheral speed V0 of said image bearing member during control of the peripheral speed of said control means.