Patent ID: 6829450
Filing Date: 2004-12-07
Classification: G03G

Abstract:
In a bias applying device configured to form, at each of image transfer positions where a plurality of image carriers and an image transfer belt moving in contact with surfaces of said plurality of image carriers, an electric field for transferring a toner image formed on a respective image carrier to a transfer medium applying a bias to said image transfer belt,said bias applying device comprising: a plurality of bias sources each for applying the bias to said image transfer belt at a respective image transfer position; a plurality of high-potential power supplies each being connected to one of said plurality of bias sources for applying a bias, of a DC component and a particular AC component superposed on said DC component, to respective bias sources; a plurality of sensors each being connected to one of said plurality of bias sources for sensing the AC component of the bias of respective bias sources; and a central processing unit configured to control said plurality of high-tension power supplies and said plurality of sensors; a bias applying method for said bias applying device comprising the steps of: detecting an AC component of a second high-tension power supply, which is detected at an output of a first high-tension power supply; determining an AC resistance between said first high-tension power supply and said second high-tension power supply on the basis of an absolute value of the AC component detected; estimating a leak current of a DC component by referencing a table listing a correlation between AC resistances and DC resistances and prepared beforehand; and adding the leak current to a set DC value assigned to said first high-tension power supply to thereby correct the bias.