Image forming apparatus and control method for driving the same

A control method of driving an image forming apparatus, the method comprising:

• moving a transfer belt supported by a driven roller and a driving roller to travel in a predetermined direction;
• forming a first predetermined color image on the transfer belt by using a first image bearing body in contact with the transfer belt;
• engaging the transfer belt with a second image bearing body by changing a traveling track of the transfer roller without causing a change in the length of the transfer belt between the first image bearing body and the driving roller;
• and
• transferring a second predetermined color image onto the transfer belt by using the second image bearing body.

An image forming apparatus, comprising:

• a first image bearing body and a second image bearing body positioned to form predetermined images;
• a transfer belt traveling in a predetermined direction to transfer images onto a printing medium, wherein the images are selectively formed on the first image bearing body and the second image bearing body and transferred and superposed onto the transfer belt;
• and
• a belt length adjusting unit to control a traveling distance of the transfer belt by changing a traveling track of the transfer belt to compensate for a change in the traveling track of the transfer belt.

A control method of driving an image forming apparatus, the method comprising:

• moving a transfer belt to travel in a predetermined direction;
• forming a first image on the transfer belt by using a first image bearing body in contact with the transfer belt;
• controlling a traveling distance of the transfer belt going via the first image bearing body and a second image bearing body to be constant by changing a traveling track of the transfer belt around the second image bearing body so as to compensate for a change in the traveling track of the transfer belt;
• and
• transferring a second predetermined color image onto the transfer belt by using the second image bearing body.