(54) DEVELOPING APPARATUS FEATURING MULTIPLE MAGNETIC ROLLERS FOR DEVELOPING A LATENT IMAGE MULTIPLE TIMES
(75) Inventors: Kazukiyo Akashi, Kashiwa (JP);
Tomoyuki Sakamaki, Toride (JP)
(73) Assignee: Canon Kabushiki Kaisha, Tokyo (JP)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 260 days.
(21) Appl.No.: 11/499,731
(22) Filed: Aug. 7, 2006
(65) Prior Publication Data
US 2007/0053724 Al Mar. 8, 2007
(30) Foreign Application Priority Data
Sep. 7,2005 (JP) 2005-259967
(51) Int. CI.
(52) U.S. CI 399/277; 399/267; 399/269;
399/119; 399/275; 399/279
(58) Field of Classification Search 399/267,
399/269, 275, 276, 282, 229, 119, 120 See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
4,637,973 A * 1/1987 Shigetaetal 430/122.2
A developing apparatus in which a first magnet of a first developing sleeve includes a first magnetic pole near a potion opposing to an image bearing member, and a second magnetic pole being downstream of the first magnetic pole; and a second magnet of a second developing sleeve includes a third magnetic pole near a portion opposing to the first sleeve. Assuming that a magnetic force obtained by combining normal direction forces Frl and Fr2 of magnetic forces generated by the first and second magnets, respectively, near the first sleeve is Fr, a center direction component of the first sleeve of the force Fr becomes positive between the first magnetic pole and a peak value position of the second magnetic pole, and a center direction component of the force Fr becomes negative between the peak value position and the closest position between both sleeves.
4 Claims, 8 Drawing Sheets