| 摘要 |
PROBLEM TO BE SOLVED: To improve the transport performance to improve the quality by detecting traveling speed of a transfer transporting belt at a prescribed position, controlling the driving speed based on this detection result, and stabilizing the speed of the belt at every part. SOLUTION: Optical sensors 24a and 24b are respectively arranged at two section parting from the transfer part (a nip part between photosensitive drum and a transfer roller 20) by approximately 20 mm on the upstream side and the downstream side in the traveling direction, and arranged in nearly the center part in the direction orthogonal to the travel of the transfer belt 18. During the transport operation of the belt transport device, the belt transport speeds on the downstream side and the upstream side of the transfer roller 20 are respectively measured for the prescribed time by the optical sensors 14a and 14b. The fluctuation of the belt transport speed is caused by the rotary fluctuation of stepping motors 35 and 36, and the extension and contraction of the transfer belt 18 at the driving time however, the speed fluctuation range is enlarged by the extension and the contraction of the transfer belt 18. A CPU 26 controls the rotary speed of the stepping motors 35 and 36 by detecting the change in this speed fluctuation width. |
