When a cartridge is in a posture in which it is installed in an image forming apparatus and used for image formation, a developing chamber is positioned below a storage chamber. At least a portion of an opening is located above a supply roller. A stirring shaft is located above the opening. A second stirring sheet member is provided on the side opposite to a first stirring sheet member with respect to an imaginary line passing through the center of rotation of the stirring shaft. The first stirring sheet member and the second stirring sheet member each have a length that allows the other ends thereof to reach the opening when the stirring shaft rotates.

An image forming apparatus includes a photoconductor; a charging device to charge a first surface of the photoconductor; and a developing device including a developing roller to: rotate in one direction while contacting the first surface of the photoconductor; and develop a latent image of toner on the first surface of the photoconductor; and collect the toner adhered to the first surface of the photoconductor; and a supply roller to: rotate in the one direction while contacting a second surface of the developing roller; supply the toner in the developing device to the second surface of the developing roller; and collect foreign matter adhered to the second surface of the developing roller, the foreign matter moved from the first surface of the photoconductor to the second surface of the developing roller.

A developing device includes a developer container, a developer carrier, and a stirring/conveying member. The developer container includes: a lower housing having a first accommodating portion and a first edge portion formed in a top end portion of it; and an upper housing having a second accommodating portion and a second edge portion formed in a bottom end portion of it. The first edge portion has a depression extending along the first edge portion, a first contact face formed inward of the depression, and a first opposite face formed outward of the depression. The second edge portion has an elevation inserted in the depression, a second contact face making contact with the first contact face, and a second opposite face facing the first opposite face. When the first and second contact faces are in contact, the first and second opposite faces face each other across a predetermined interval.

A developing device includes a developer bearer, a first conveying screw conveying developer from one end to another end of a first conveyance path in a first direction, a second conveying screw conveying the developer in a direction opposite to the first direction in a second conveyance path, and a partition having a first communication port communicating the one end of the first conveyance path and the second conveyance path. A shaft diameter of the first conveying screw from one end to a position away from the first communication port by a first predetermined distance is smaller than a shaft diameter of another portion of the first conveying screw. A shaft diameter of the second conveying screw from one end to a position away from the first communication port by a second predetermined distance is larger than a shaft diameter of another portion of the second conveying screw.

A drum cartridge includes: a drum frame to which a developing cartridge including a storage medium having an electrical contact surface is detachably attachable; a photosensitive drum; a transfer roller; and a conveying roller. The drum is rotatable about a first axis extending in a first direction and positioned at one end portion of the frame in a second direction. The transfer roller is rotatable about a second axis extending in the first direction and in contact with the drum. The conveying roller is rotatable about a third axis extending in the first direction and separated from the transfer roller in the second direction. A first opening of the frame is positioned between the transfer roller and the conveying roller in the second direction. The electrical contact surface is exposed to an outside through the first opening in a case where the developing cartridge is attached to the frame.

A drum cartridge includes: a drum frame to which a developing cartridge including a storage medium having an electrical contact surface is detachably attachable; a photosensitive drum; a transfer roller; and a conveying roller. The drum is rotatable about a first axis extending in a first direction and positioned at one end portion of the frame in a second direction. The transfer roller is rotatable about a second axis extending in the first direction and in contact with the drum. The conveying roller is rotatable about a third axis extending in the first direction and separated from the transfer roller in the second direction. A first opening of the frame is positioned between the transfer roller and the conveying roller in the second direction. The electrical contact surface is exposed to an outside through the first opening in a case where the developing cartridge is attached to the frame.

A magnet member is non-rotatably secured inside a developing sleeve, and includes a plurality of magnetic poles arranged along a rotation direction of the developing sleeve. The magnetic poles include a main pole facing the image carrying member, and a peeling pole that is disposed downstream of and adjacent to the main pole in the rotation direction of the developing sleeve and that peels off the developer carried on the developer carrying member. A magnetic-flux-density peak-position of the main pole is located below a horizontal line passing through a rotation center of the developing sleeve, and as viewed from an axial direction, an angle that a line extending from the magnetic-flux-density peak-position of the main pole to the rotation center of the developing sleeve forms with respect to the horizontal line passing through the rotation center of the developing sleeve is 40 or larger but 80 or smaller.

A developing apparatus includes a developing container, a first rotatable developing member, a first magnet provided non-rotatably and stationarily inside the first rotatable developing member, a second rotatable developing member, a second magnet provided non-rotatably and stationarily inside the second rotatable developing member, and a duct including a suction port that is an inlet through which the developer scattered in the developing container is sucked. The position on the outer peripheral surface of the second rotatable developing member where the absolute value of the normal component of the magnetic flux density of a sixth magnetic pole of the second magnet becomes maximum is positioned downstream of an edge of a first duct wall of the duct on the suction port side with respect to the rotational direction of the second rotatable developing member.

Toner cartridge includes a housing, an agitator, an auger, a first protrusion, and a second protrusion. The housing includes a first toner accommodating portion having and a second toner accommodating portion. The auger is rotatable about a second axis extending in a first direction and is configured to convey toner from a first toner accommodating portion to the second toner accommodating portion. The first protrusion is positioned at a first side of the second toner accommodating portion. The first protrusion extends in the first direction. The second protrusion is positioned at a second side of the second toner accommodating portion and extends in the first direction.

A drum cartridge includes: a drum frame to which a developing cartridge including a storage medium having an electrical contact surface is detachably attachable; a photosensitive drum; a transfer roller; and a conveying roller. The drum is rotatable about a first axis extending in a first direction and positioned at one end portion of the frame in a second direction. The transfer roller is rotatable about a second axis extending in the first direction and in contact with the drum. The conveying roller is rotatable about a third axis extending in the first direction and separated from the transfer roller in the second direction. A first opening of the frame is positioned between the transfer roller and the conveying roller in the second direction. The electrical contact surface is exposed to an outside through the first opening in a case where the developing cartridge is attached to the frame.