DRY-TYPE DEVELOPING DEVICE FOR ELECTROPHOTOGRAPHY

摘要

A developing roll is composed of a hollow nonmagnetic sleeve and a permanent magnet disposed therein and having a plurality of poles, the sleeve and the permanent magnet being independently rotatable in the same direction. The hollow nonmagnetic sleeve is rotatable at a constant speed. The permanent magnet is rotatable at varying speeds dependent on a signal indicative of a count value from a printing density counter means for supplying a developer from a developer tank. The printing density counter means successively counts print data to be developed.