| 摘要 |
PROBLEM TO BE SOLVED: To provide a color image forming device capable of obtaining a excellent image being free from a drum ghost, even though time constant of an intermediate transfer body falls, and capable of always performing a notice of a residual life for the intermediate transfer body at the optimum time regardless of the use environment, the use mode, or the like. SOLUTION: This device allowed to set a charge imparting roller 16 provided with a constant voltage power source 22, with respect to an intermediate transfer belt 5, to successively apply a voltage 2 times to the same section on the intermediate transfer belt 5, during 2 rotation periods of the intermediate transfer belt 5, to detect the respective current values flowing to the intermediate transfer belt 5 at this time by current detecting means 24, to assume the time constant (τ) of the intermediate transfer belt 5 by a CPU 20, in accordance with the respectively detected current value, to set/control respective primary transfer biases for the 1st color, 2nd color, 3rd color and 4th color applying to the primary transfer roller 8a based thereon, as shown by the next formulas, Vt10=100, Vt20=500+100×(1-12/11), Vt30=550+300×(1-12/11), Vt40=600+500×(1-12/11), (V). |
