Developing device and magnetic roller for the same

Application Number: 00107936
Application Date: 2000.05.24
Publication Number: 1274873
Publication Date: 2000.11.29
Priority Information: 1999/5/24 JP 143256/99
International: G03G15/10
Applicant(s) Name: Ricoh Co. Ltd.
Inventor(s) Name: Imamura Katashi;Koizuke Kyota;Ishiguro Kenichi
Patent Agency Code: 72002
Patent Agent: huang jianfeng
Abstract There are provided a developing device which prevents a biased distribution of a developer caused by an axial magnetic force of the magnet roller, and which can form an image uniform in the axial direction; and a magnet roller for a developing device which is used in the above developing device and is limited in axial magnetic force. The developing device includes a rotatable sleeve which carries a developer on the surface thereof, a fixed magnet roller which is provided within the sleeve and has a plurality magnetic poles, and a doctor blade which controls the amount of developer carried on the sleeve. The developing deviceis constructed so that among the plurality of magnetic poles of the magnet roller, the ratio of the axial magnetic flux density to the radial magnetic flux density of a magnetic pole opposing the doctor blade is 2.5% or below in a central portion in axial direction.