Dry-type developing device for electrophotography.

摘要

A developing roll (2) is composed of a hollow nonmagnetic sleeve (2a) and a permanent magnet (2b) disposed therein and having a plurality of poles, the sleeve (2a) and the permanent magnet (2b) being independently rotatable in the same direction. The hollow nonmagnetic sleeve (2a) is rotatable at a constant speed. The permanent magnet (2b) is rotatable at varying speeds dependent on a signal indicative of a count value from a printing density counter means for supplying a developer (6) from a developer tank (3). The printing density counter means successively counts print data to be developed.