A transfer unit includes first and second rollers, first and second bearing members, a roller holder, first and second urging members, a switching cam, and a driving mechanism. The switching cam includes first and second guide holes with which first and second engaging portions formed on the first and second bearing members engage. The first and second guide holes are formed, each in an approximately arcuate shape, at positions at different distances from the rotation center of the switching cam. By rotating the roller holder, one of the first and second rollers is arranged opposite an image carrying member and, by rotating the switching cam, the first or second roller arranged opposite the image carrying member is arranged selectively either at a reference position where the first or second roller is in pressed contact with the image carrying member or at a released position.

An image forming apparatus includes a developing case housing a developer. A doctor blade is separated from an outer surface of a developing sleeve, the both ends of the doctor blade in a longitudinal direction are fixed to a developing case, and the doctor blade includes a through hole in the central portion in the longitudinal direction. An adjusting portion adjusts the distance between the doctor blade and the outer surface of the developing sleeve. A rotating portion is provided on one surface of the base portion, inserts the through hole, and rotates with respect to the doctor blade and the developing case.

A transfer unit includes first and second rollers, first and second bearing members, a roller holder, first and second urging members, a switching cam, and a driving mechanism. The switching cam includes first and second guide holes with which first and second engaging portions formed on the first and second bearing members engage. The first and second guide holes are formed, each in an approximately arcuate shape, at positions at different distances from the rotation center of the switching cam. By rotating the roller holder, one of the first and second rollers is arranged opposite an image carrying member and, by rotating the switching cam, the first or second roller arranged opposite the image carrying member is arranged selectively either at a reference position where the first or second roller is in pressed contact with the image carrying member or at a released position.

A developing device includes a developing container, a first stirring conveyance member, a second stirring conveyance member, a developer carrying member including a developing sleeve and a magnet, and a regulation member. The regulation pole in the magnet has a region extending over 10° or more in which a maximum value of a vertical magnetic force is not more than 65 [mT] and a vertical magnetic force gradient is not more than 0.3 [mT/°]. A peak position of the vertical magnetic force gradient of the regulation pole is arranged at a position opposed to the second stirring conveyance member, and when a value of the vertical magnetic force gradient and a value of the vertical magnetic force at the peak position of the vertical magnetic force gradient are indicated as A [mT/°] and K [mT], respectively, A≥2.8 and A×K≥62.5 are satisfied.

An electrostatic charge image developing carrier includes: magnetic particles; and a resin layer coating the magnetic particles and containing inorganic particles, in which an exposed area ratio of the magnetic particles is 0.1% or more and 4.0% or less, an average particle diameter of the inorganic particles is 5 nm or more and 90 nm or less, and a ratio B/A of a surface area B of the electrostatic charge image developing carrier to a plan view area A of the electrostatic charge image developing carrier is 1.020 or more and 1.100 or less when a surface of the electrostatic charge image developing carrier is three-dimensionally analyzed.

A developing device includes a developer container configured to contain a developer, a developing carrying member configured to carry and feed the developer to a developing position, and a regulating member configured to regulate an amount of the developer carried by the developer carrying member, wherein the developer carrying member includes a magnet provided non-rotatably and stationarily inside the developer carrying member, and wherein the developer carrying member is provided with information regarding magnetic flux density of the magnet.

An imaging system includes a developing chamber, a first conveyance path, a second conveyance path, a first air passage and a second air passage. A developing roller located in the developing chamber carries a developer to a developing region where the developing roller is closest to an image carrier. A first stirring-conveying portion is located in the first conveyance path adjacent the developing roller to supply the developer to the developing roller. A second stirring-conveying portion is located in the second conveyance path adjacent the first conveyance path to circulate the developer between the second conveyance path and the first conveyance path. The first air passage has an inlet coupled to the developing chamber and an outlet coupled to the second conveyance path, and the second air passage has an inlet coupled to the second conveyance path and an outlet coupled to the developing chamber.

A developing unit includes a conveying member which rotates to convey the developer to the developer bearing member. The conveying member includes a sheet portion with one end fixed to a rotation shaft and a free end which enters the developing chamber through an opening when the conveying member rotates around a rotation center, wherein relations C>A and B>A are satisfied, where A is a distance from the rotation center to an upstream end of the opening in a rotational direction, B is a distance from the rotation center to a downstream end of the opening in the rotational direction, and C is a length from the rotation center to the free end of the sheet portion in an unbent state. The upstream end of the opening is lower in a direction of gravitational force than the downstream end at an orientation in use.

A developing unit includes a conveying member which rotates to convey the developer to the developer bearing member. The conveying member includes a sheet portion with one end fixed to a rotation shaft and a free end which enters the developing chamber through an opening when the conveying member rotates around a rotation center, wherein relations C>A and B>A are satisfied, where A is a distance from the rotation center to an upstream end of the opening in a rotational direction, B is a distance from the rotation center to a downstream end of the opening in the rotational direction, and C is a length from the rotation center to the free end of the sheet portion in an unbent state. The upstream end of the opening is lower in a direction of gravitational force than the downstream end at an orientation in use.

An absolute value of a first maximum value is smaller than an absolute value of the second maximum value. With respect to a rotational direction of a rotatable developing member, an angle from a second maximum position to a position where a magnetic flux density of a regulating pole in a normal relative to an outer peripheral surface of the rotatable developing member is a half value of the second maximum value on a side downstream of the second maximum position is smaller than an angle from a position where the magnetic flux density of the regulating pole in the normal direction relative to the outer peripheral surface of the rotatable developing member is a half value of the first maximum value on a side upstream of the first maximum position to the first maximum value.