(19)
(11) EP 0 311 020 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
28.11.1990 Bulletin 1990/48

(43) Date of publication A2:
12.04.1989 Bulletin 1989/15

(21) Application number: 88116411.5

(22) Date of filing: 04.10.1988
(51) International Patent Classification (IPC)4: G03G 15/09
(84) Designated Contracting States:
DE ES FR GB IT

(30) Priority: 05.10.1987 JP 249759/87

(71) Applicant: FUJITSU LIMITED
Kawasaki-shi, Kanagawa 211 (JP)

(72) Inventor:
  • Nishio, Yukio c/o FUJITSU LIMITED
    Nakahara-ku Kawasaki-shi Kanagawa 211 (JP)

(74) Representative: Sunderland, James Harry et al
HASELTINE LAKE & CO Hazlitt House 28 Southampton Buildings Chancery Lane
London WC2A 1AT
London WC2A 1AT (GB)


(56) References cited: : 
   
       


    (54) Angular positioning of magnets in a developer roller used in electrophotographic apparatus or the like


    (57) An extended portion of an axle (9) supporting magnets (10a) in a developer roller (4) is provided with a gear (27) and a lever plate (28). A magnetic sensor (91), such as a Hall element, is arranged in place of a photosensitive drum (1) where there is the narrowest gap between the developer roller (4) and the photosensitive drum (1). The sensor (91) detects the magnetic field of the magnets (10a) while the magnets are rotated by an external drive (93, 94) via the gear (27). At an angular position of the magnets (10a) where a peak of magnetic field of a particular magnet pole (N₁) facing the drum (1) is detected, the lever plate (28) is fixed to a frame (25), which rotatably supports the axle (9), of a developer unit including the developer roller (4) by, for example, fastening a screw (30) on the frame. Accordingly, the angular position of the magnets (10a) can be adjusted easily and accurately enough to achieve quality printing.







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