According to one embodiment, the developing device includes a developing case containing toner, a mixer configured to diffuse the toner in the developing case, and a developing roller configured to develop a latent image formed on an image carrier. The developing case includes a circulation path through which air containing the toner flows. The developing roller is partially exposed from the developing case. The developing roller includes a sleeve rotating along with the movement of the image carrier and a plurality of magnetic pole portions disposed inside the sleeve. The developing roller holds the toner on the sleeve and supplies the toner to the image carrier to develop the latent image. The developing device further includes a magnet disposed apart from the developing roller. The magnet faces one of the magnetic pole portions across the sleeve.

An electrostatic charge image developer contains toner particles, layered-compound particles that are particles of a nitrogen-containing layered compound, and a resin-coated carrier that has magnetic particles and a resin layer covering the magnetic particles. The maximum height Ry of the roughness profile as defined in JIS B0601: 1994 of the surface of the resin-coated carrier is 0.01 μm or more and 0.20 μm or less.

An electrostatic charge image developer contains toner particles, layered-compound particles that are particles of a nitrogen-containing layered compound, and a resin-coated carrier that has magnetic particles and a resin layer covering the magnetic particles. The maximum height Ry of the roughness profile as defined in JIS B0601: 1994 of the surface of the resin-coated carrier is 0.01 μm or more and 0.20 μm or less.

A developing device includes a developer container, a developing roller, and a doctor member. The developer container contains a developer including a toner and a developer. The developing roller includes a developing sleeve bearing the developer, a magnet roller in the developing sleeve. The doctor member includes a regulating portion regulating an amount of the developer home on the developing sleeve to be a predetermined amount. The regulating portion is disposed with a first distance from the developing sleeve. The developing sleeve is disposed with a second distance from an image hearer, and when the developing sleeve bearing the predetermined amount of developer passes a vicinity of the image bearer, a value obtained by dividing the predetermined amount by the second distance is less than a threshold of occurrence of adherence of the developer to the developing sleeve.

A developing device includes a developer container, a developing roller, and a doctor member. The developer container contains a developer including a toner and a developer. The developing roller includes a developing sleeve bearing the developer, a magnet roller in the developing sleeve. The doctor member includes a regulating portion regulating an amount of the developer home on the developing sleeve to be a predetermined amount. The regulating portion is disposed with a first distance from the developing sleeve. The developing sleeve is disposed with a second distance from an image hearer, and when the developing sleeve bearing the predetermined amount of developer passes a vicinity of the image bearer, a value obtained by dividing the predetermined amount by the second distance is less than a threshold of occurrence of adherence of the developer to the developing sleeve.

A developing device includes a developing roller to rotate in a predetermined direction of rotation and opposed to or in contact with an image bearer to form a development range, a cover to cover the developing roller downstream from the development range in the predetermined direction of rotation, a sheet member cantilevered by the cover to contact the developing roller with a flat face of the sheet member while trailing along the predetermined direction of rotation at a position downstream from the development range. The cover includes a large gap portion to form a first gap in a first predetermined range in the predetermined direction of rotation and a small gap portion disposed adjacent to and downstream from the large gap portion in the predetermined direction of rotation to form a second gap smaller than the first gap in a second predetermined range in the predetermined direction of rotation.

A developing device, includes: a developing sleeve supported rotatably, the developing sleeve having a hollow, substantially cylindrical shape; a magnet part having a substantially columnar shape, the magnet part having magnetic poles disposed side by side around an axis, the magnet part being disposed substantially coaxially with the developing sleeve inside the developing sleeve; a rod fastened to the magnet part, the rod extending from one end in an extending direction of the axis of the magnet part, the rod being pulled out from one axial end of the developing sleeve; and a holder attached to a portion of the rod pulled out from the developing sleeve, the holder being fastened to a fastening target, the holder maintaining the rod, the holder regulating rotation of the magnet part, wherein adjustment of the holder in fastening position enables disposition and holding of the rod at an optional position.

A developing device includes a rotatable developing sleeve for carrying a developer including toner and a magnetic carrier and for developing an electrostatic latent image, formed on an image bearing member, in a developing region where the developer contacts the image bearing member; and a magnetic field generating portion provided inside the developing sleeve and having a developing pole provided at a position opposing the image bearing member in order to form the developing region, wherein a ratio of an 80%-value-width of magnetic flux density of the developing pole with respect to a normal direction of the developing sleeve to a half peak width of the magnetic flux density of the developing magnetic pole with respect to the normal direction is 0.65 or more, and with respect to a rotational direction of the developing sleeve, a magnetic force of the developing pole in the normal direction of the developing sleeve in each of neighborhoods of both end portions of the developing region is larger than a magnetic force of the developing pole at a central portion of the developing region.

A developing device includes a developing roller to rotate in a predetermined direction of rotation and opposed to or in contact with an image bearer to form a development range, a cover to cover the developing roller downstream from the development range in the predetermined direction of rotation, a sheet member cantilevered by the cover to contact the developing roller with a flat face of the sheet member while trailing along the predetermined direction of rotation at a position downstream from the development range. The cover includes a large gap portion to form a first gap in a first predetermined range in the predetermined direction of rotation and a small gap portion disposed adjacent to and downstream from the large gap portion in the predetermined direction of rotation to form a second gap smaller than the first gap in a second predetermined range in the predetermined direction of rotation.

A developing device includes a rotatable developing sleeve to carry and feed a developer including toner and a carrier toward a developing region, and a magnetic field generating portion provided inside the developing sleeve and having a developing magnetic pole for forming the developing region. The developing magnetic pole is disposed opposite to a closest position of the image bearing member to the developing sleeve. A ratio of an 80%-value-width of magnetic flux density of the developing magnetic pole with respect to a normal direction of the developing sleeve to a half peak width of the magnetic flux density of the developing magnetic pole with respect to the normal direction is 0.65 or more.