DEVELOPING DEVICE

摘要

A magnet roller employs a magnetic pole pattern in which a first magnetic pole arranged substantially opposing a regulating blade in an upstream side of a rotation direction of a developing sleeve and a second magnetic pole next to the first magnetic pole in the upstream side have the same polarity, an opposing member having surface roughness higher than at least a particle diameter of carrier is arranged opposing the magnet roller at a position where magnetic force between the first magnetic pole and the second magnetic pole next to the first magnetic pole in the upstream side is almost zero, and an apex of a partition wall provided between a developer bearing member and a developer conveying member provided in a first chamber is positioned below a region where magnetic force formed by the magnet roller is almost zero.

主权项

1. A developing device, comprising:
a developer bearing member configured to bear developer including nonmagnetic toner and magnetic carrier and develops a latent image; a developer container configured to support the developer bearing member rotatably and contain therein the developer to be supplied to the developer bearing member, the developer container having a first chamber containing the developer therein, a second chamber being arranged below the first chamber and forming a circulation path, in which the developer is circulated, with the first chamber, and a partition wall partitioning the first chamber and the second chamber; a first conveying member, arranged in the first chamber, configured to convey the developer; a second conveying member, arranged in the second chamber, configured to convey the developer; a multipolar magnet which is arranged inside the developer bearing member; and a regulating member configured to regulate an amount of the developer borne on the developer bearing member; the multipolar magnet having a first magnetic pole which is arranged at a position opposing the regulating member or in an upstream side of a conveyance direction of the developer bearing member with respect to the position, and a second magnetic pole which is adjacent to the first magnetic pole in an upstream side of the first magnetic pole in the conveyance direction, and has the same polarity as that of the first magnetic pole,wherein
a peak position of magnetic force of the first magnetic pole is arranged above a center of the developer bearing member and a peak position of magnetic force of the second magnetic pole is arranged below the center of the developer bearing member,wherein
the partition wall has an opposed part opposing the developer bearing member along a circumferential surface of the developer bearing member, the opposed part having an apex positioned below an uppermost end of a low magnetic force region,wherein
the low magnetic force region, in which magnetic force is equal to or less than 50 gauss, is provided on a surface of the first developer bearing member which is on an upstream side of the first magnetic pole and on a downstream side of the second magnetic pole with respect to a rotation direction of the developer bearing member, andwherein
the opposed part has surface roughness higher than an average particle diameter of the carrier.