Patent ID: 6941099

Claim:
A developing device, comprising: a plurality of magnetic sleeves configured to deposit toner onto a photoreceptor, wherein stirred toner and carriers are supported on an upstream-side magnetic sleeve and a downstream-side magnetic sleeve to form respective magnetic brushes of the stirred toner and carriers, the magnetic brushes contacting the photoreceptor to perform a developing process, wherein a developing bias that is a DC bias overlapped with an AC bias is applied to the sleeves, wherein said DC bias applied to said upstream-side sleeve is different from said DC bias applied to said downstream-side sleeve, wherein a polarity of said DC bias of said upstream-side magnetic sleeve and a polarity of said DC bias of said downstream-side magnetic sleeve are the same polarity, and wherein said developing bias that is a DC bias overlapped with an AC bias is 1-3 kHz at 800-1600V for said upstream side magnetic sleeve and 3-6 kHz at 400-800V for said downstream side magnetic sleeve.