A developer cartridge may include: a first gear having a small-diameter gear portion and a large-diameter gear portion; and a second gear including: a first columnar portion centered on a second axis; a second columnar portion having a smaller diameter than the first columnar portion; a first engagement portion extending along a portion of a peripheral surface of the first columnar portion and engageable with the small-diameter gear portion; a second engagement portion extending along a portion of a peripheral surface of the second columnar portion and positioned closer to a housing than the first engagement portion in an axial direction and engageable with the large-diameter gear portion; and a protruding portion protruding in the axial direction and rotatable together with the first engagement portion and the second engagement portion. The second engagement portion may engage the large-diameter gear portion after the first engagement portion engages the small-diameter gear portion.

A development device includes a development container and a second agitation member. The development container includes a second transport chamber and a developer discharge port which is provided at the end portion of the second transport chamber on a downstream side. The second agitation member includes a second transport blade, a damming member which dams a developer, a regulation portion which transports the developer in a direction opposite to the second transport blade and a discharge blade which discharges the developer from the developer discharge portion. A second rotation shaft includes a large shaft diameter portion on which the second transport blade is provided, a small shaft diameter portion on which the regulation portion and the discharge blade are provided and a shaft diameter change portion. The damming member is arranged between the shaft diameter change portion and the end portion of the second transport blade on the downstream side.

An image forming apparatus includes a main casing, a developing roller, a connecting tube, and a toner container. The main casing includes a sheet supply tray. The developing roller is provided in the main casing. The connecting tube has one end portion and another end portion inside the main casing. The toner container is for accommodating toner. The one end portion of the connecting tube is connected to the toner container. The toner container has an inlet opening for replenishing toner. The toner container is pivotally movable between a first position and a second position about the connecting tube. A position of the inlet opening at the second position is higher than a position of the inlet opening at the first 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.

A development device includes a development container, a first conveying member, a second conveying member, a toner concentration sensor, and a developer carrier. The first and second conveying members are equal to each other in outer diameter and shaft diameter, the outer diameter being 1.3 times the shaft diameter or more but 1.6 times the shaft diameter or less. Where L represents an axial length of the first conveying member, K represents a distance of a center position of the sensing surface of the toner concentration sensor from a downstream end of a first conveying chamber of the development container in the first direction, P represents a pitch of the conveying blade of the first conveying member, and R represents a rotational speed of the first conveying member, formula (1) is satisfied: 30000<(P×R×L)/K<45000 (1).

A development device includes a development container, a first conveying member, a second conveying member, a toner concentration sensor, and a developer carrier. The toner concentration sensor is arranged at a wall portion of the first conveying chamber in which the first conveying member is arranged. The first and second conveying members are equal to each other in outer diameter and shaft diameter, the outer diameter being 2.3 times the shaft diameter or more but 3.0 times the shaft diameter or less. Where D represents the shaft diameter of the first conveying member, L represents an axial length of the first conveying member, and K represents a distance of a center position of a sensing surface of the toner concentration sensor from a downstream end of the first conveying chamber in the first direction, formula (1) is satisfied: 500<(L.sup.2×K)/D.sup.4<2500 (1).

An image forming apparatus includes a motor, a container detection sensor, and a controller. When a toner container is attached, the motor generates a driving force for rotating a toner conveying member in the toner container. The container detection sensor is arranged at a position where the container detection sensor comes into contact with an outer periphery of a cam connected to the toner conveying member when the toner container is attached. The controller distinguishes between at least three attachment states of the toner container based on a sensor signal of the container detection sensor.

A toner conveying device includes a case storing toner; a conveyance member rotatably supported at both ends by the case, including a spiral blade extending along a rotational axis, and configured to rotate to convey the toner inside the case in a predetermined conveying direction; and a pushing member pushed against an outer peripheral portion of the conveyance member in a first direction intersecting with the rotational axis and configured to slide on the outer peripheral portion as the conveyance member rotates. The pushing member is composed of a flexible sheet member and includes a base portion secured at a securing position inside the case and protruding pieces aligned along the rotational axis and protruding from the base portion toward the conveyance member to abut on the outer peripheral portion. An alignment interval between the protruding pieces is different from a pitch of the spiral blade along the rotational axis.

A toner conveying device for conveying toner, comprising: a first conveying portion; and a second conveying portion conveying the toner conveyed from the first conveying portion. The first conveying portion further includes: a first screw which includes a first rotation shaft and a first blade portion, the first screw including an engaging portion and a first protruded portion on a first end portion; and a first conveying passage forming member having a first inner wall face which forms a first conveying passage. The second conveying portion includes: a second screw which includes a second rotation shaft and a second blade portion, the second screw including an engaged portion and a second protruded portion on a second end portion; and a second conveying passage forming member having a second inner wall face which forms a second conveying passage, and which is connected with the first conveying passage forming member.

A cleaning device includes a housing, a cleaning blade, a toner conveyance path, a conveyance screw, and a first flicker. The conveyance screw includes a rotary shaft and a helical vane. The first flicker includes a first base portion and first contact pieces and uses the first contact pieces to press the conveyance screw in a first direction away from a bottom part of the toner conveyance path. The first base portion includes a secured portion and a blade opposed portion. A reinforcement member is stacked on the blade opposed portion.