| 摘要 |
PROBLEM TO BE SOLVED: To prevent a flaw at the end part of a belt or the nonlinear shape thereof from appearing on a recording sheet by forming an image based on an imaginary belt end signal. SOLUTION: A belt end detector 2 detects the end part of a light shield and the end part of a photosensitive belt. A ramp signal is generated with reference to detection of the end part of the light shield and delivered to a comparator 7. The comparator 7 compares the output from an integrator 6 with the ramp signal and generates an imaginary belt end signal which is fed back to a phase comparator 4 and subjected to phase comparison with a belt end signal from the belt end detector 2. A charge pump 5 performs charge/ discharge processing based on the phase difference signal and delivers a marking signal detected by a belt seam marking detector 8 to a charge pump gain switch 9 in order to control the charge/discharge current to increase at a belt seam part. A voltage varied through charge/discharge processing is outputted after being integrated by an integrator 6. An image forming section 2000 forms an image based on the imaginary belt end signal. |
