A developing apparatus includes a developer carrier configured to carry developer, a developer container having a first chamber and a second chamber, a first conveying member provided in the first chamber, and including a first conveying unit and, on a downstream side in a first direction, a reverse conveying unit, a second conveying member, a discharge unit configured to discharge the developer, and a partition wall having a first communication port and a second communication port and configured to partition the first chamber and the second chamber. In addition, a plurality of protruding portions are provided so as to oppose the first conveying member at a position above a region between the first conveying unit and the reverse conveying unit in a vertical direction, each of the protruding portions extending along the first direction, wherein the plurality of protruding portions are arranged in a row in a direction orthogonal to the first direction.

The developing device includes a developer bearer, a conveyor, a casing including a ceiling, and a seal. The developer bearer is configured to bear a developer and develop a latent image. The conveyor is configured to convey and stir the developer. The casing is configured to contain the developer, the developer bearer, and the conveyor. The seal is configured to seal the inside of the casing to form a closed space that encloses the developer in the developing device. The conveyor is configured to be partially or entirely buried in the developer enclosed in the closed space in both of a normal posture and an upside-down posture of the developing device. A cross-sectional area of the closed space in a horizontal plane gradually increases from a top of the ceiling of the casing toward a bottom of the developing device in the normal posture of the developing device.

A feeding screw for feeding a developer includes a rotation shaft, and a helical blade provided on the rotation shaft and including a plurality of threads. The helical blade includes a first blade helically formed with a single thread on the rotation shaft, a second blade helically formed with a single thread on the rotation shaft, and a third blade helically formed with a single thread on the rotation shaft. With respect to a direction along the rotation shaft, a gap is provided between a downstream end portion of the second blade and an upstream end portion of the third blade. A volume of the second blade is not more than 75% of the first blade between an upstream end portion of the second blade and the upstream end portion of the third blade with respect to the direction.

A developing apparatus includes: a housing that accommodates developer and has a plurality of constituent parts; a vibrator that vibrates parts, which are two or more of the plurality of the constituent parts and to which scattered toner may adhere, as vibrated portions; an adjuster provided for at least one of the vibrated portions and the vibrator so as to adjust and match natural frequencies of the two or more of the vibrated portions; and a hardware processor that controls the vibrator.

A developing apparatus includes: a housing that accommodates developer and has a plurality of constituent parts; a vibrator that vibrates parts, which are two or more of the plurality of the constituent parts and to which scattered toner may adhere, as vibrated portions; an adjuster provided for at least one of the vibrated portions and the vibrator so as to adjust and match natural frequencies of the two or more of the vibrated portions; and a hardware processor that controls the vibrator.

A developing apparatus includes: a developer carrier configured to carry developer; a developer container having a first chamber and a second chamber; a first conveying member provided in the first chamber, and including a first conveying unit and, on a downstream side in a first direction, a reverse conveying unit; a second conveying member; a discharge unit configured to discharge the developer; a partition wall having a first communication port and a second communication port, and configured to partition the first chamber and the second chamber; and a plurality of protruding portions provided so as to oppose the first conveying member at a position above a region between the first conveying unit and the reverse conveying unit in a vertical direction, each of the protruding portions extending along the first direction, wherein the plurality of protruding portions are arranged in a row in a direction orthogonal to the first direction.

A toner container includes containing chambers, a shaft member, rotary members, and stirring members. The containing chambers are arrayed in a first direction and partitioned from each other. The containing chambers contain respective toners of different colors. The shaft member extends in the first direction, passes through the containing chambers, and is rotatable about a rotational axis extending in the first direction. The rotary members are disposed in the respective containing chambers and each have a through-hole extending in the first direction. The rotary members are rotatable in response to rotation of the shaft member in an inserted state of the shaft member in the through-holes. The stirring members are supported by the respective rotary members and each extend in a second direction intersecting the first direction. The stirring members are pivotable in response to rotation of the respective rotary members. The stirring members have different pivoting positions upon pivoting.

A development device includes a developer bearing, a regulation portion, and a magnetic field generation member that is provided inside of the developer bearing member. The magnetic field generation member includes a development pole a first magnetic pole, and a second magnetic pole. The magnetic field generation member has a region satisfying |(Br(a)Br(c))/10|<0.3, wherein Br(a) is a magnetic flux density in a normal direction relative to the surface of the developer bearing member on a position shifted by 5 from a point nearest to the regulation portion on the developer bearing member around a center of the developer bearing member, and Br(c) is the magnetic flux density around the developer bearing member on a position shifted by +5 from the point nearest to the regulation portion on the developer bearing member.

A toner container includes containing chambers, a shaft member, rotary members, and stirring members. The containing chambers are arrayed in a first direction and partitioned from each other. The containing chambers contain respective toners of different colors. The shaft member extends in the first direction, passes through the containing chambers, and is rotatable about a rotational axis extending in the first direction. The rotary members are disposed in the respective containing chambers and each have a through-hole extending in the first direction. The rotary members are rotatable in response to rotation of the shaft member in an inserted state of the shaft member in the through-holes. The stirring members are supported by the respective rotary members and each extend in a second direction intersecting the first direction. The stirring members are pivotable in response to rotation of the respective rotary members. The stirring members have different pivoting positions upon pivoting.

A developer cartridge includes a casing; and a sub-unit. The casing has a first opening and a developer chamber. The sub-unit is detachably attached to the developer chamber through the first opening. The sub-unit includes a cap; a developer container; and an agitation member. The cap seals the first opening. The developer container is disposed in the developer chamber and hermetically accommodating developer therein. The agitation member is disposed in the developer chamber. The agitation member has a first end portion and a second end portion. The agitation member is rotatable relative to the casing about an axis. The axis extends between the first end portion and the second end portion in an axial direction.