DEVELOPING DEVICE

PURPOSE:To obtain a device which has a simple and inexpensive mechanism and has high reliability and easily copes with physical properties of a developer, by generating a rotary magnetic field practically by the phase difference among AC voltages applied to plural windings arranged in a developing roll. CONSTITUTION:A conductive and non-magnetic developing roll 5 involving a 6-pole fixed core 4 where windings 3 are wound around iron cores 2 and a toner 6 are provided in a developing device enclosure 1. The toner 6 is carried onto the roll 5, and the AC voltage of a single phase is converted to three-phase voltages and they are applied to the windings 3 of the fixed core 4, and a continuous rotary magnetic field is generated on the surface of the roll 5 by the phase difference. The toner 6 is carried onto the roll 5 by this rotary magnetic field as if a normal permanent magnet roll were rotated in the roll 5. The amplitude and the frequency of the applied AC voltage are changed to easily change the attraction of the toner and the carrying speed.