A developing apparatus includes a mode in which a control of differentiating a relationship between a rotational speed (Vsc) of a conveying portion (31 and 32) and a rotational speed (Vsl) of a developer carrier (6) in forming no image from that in forming an image is executed. In the mode, the developing apparatus executes at least one of controls of restraining a trouble otherwise caused by the control of differentiating the relationship such as a control of decreasing a ratio of rotational speeds (Vsc/Vsl) as compared to the ratio of rotational speeds in forming the image, a control of circulating the developer between first and second chambers by driving the conveying portion (31 and 32) and the developer carrier (6) at rotational speeds lower than those in forming the image.

A developing device includes a developer holder that holds a developer containing toner and carrier and being supplied to an image holder forming an electrostatic latent image; and a conveyance section that agitates and conveys the developer flowing in from an inlet using a rotation member to cause the developer to flow out toward the developer holder at an outlet, that includes, as a part constituting a portion of the rotation member, a first blade part for conveyance to the outlet and a second blade part for conveyance in a direction opposite to the outlet, and in which a greater amount of the developer flows in from the inlet than the developer flows out from the outlet.

A developing apparatus that develops an electrostatic latent image on an image supporting body using developer including toner and carrier includes a circulation path where the developer circulates, a discharge path connected to the circulation path through which some of the developer passes, and a first recycle path connected to the discharge path and allowing some of the developer flowing into the discharge path to return to the circulation path. The discharge path includes a discharge opening for discharging the developer flowing into the discharge path, and a first return opening for connecting to the first recycle path. The first return opening is located on an upper side in a vertical direction with respect to the discharge opening and located on an upstream side in a pass-through direction of the developer flowing into the discharge path.

A development device includes a development container having a first conveyance chamber and a second conveyance chamber above it, first and second stirring conveyance members that stir developer in the first and second conveyance chambers and convey it in the opposite directions, a developer carrying member that carries on its surface the developer in the second conveyance chamber, and a regulation blade. Feeding of the developer to the developer carrying member and collection of the developer from the developer carrying member are performed in the second conveyance chamber. A horizontal straight line L1 through the center of the rotation shaft of the second stirring conveyance member is above a horizontal straight line L2 through the center of the rotation shaft of the developer carrying member and the straight line L2 is above a horizontal straight line L3 through the center of the rotation shaft of the first stirring conveyance member.

A development device includes a developer container having a first conveyance chamber and a second conveyance chamber above it, a first stirring-conveyance member, a second stirring-conveyance member, a developer carrying member, and a regulation blade. The developer carrying member includes a magnetic member having a regulation pole, a main pole, a release pole, and an attracting pole. A release start position at which the magnetic force of the release pole becomes 5 [mT] or less is below a straight line L1 horizontally passing through the center of a rotation shaft of the second stirring-conveyance member and when the central angle of a developer releasing region where the magnetic force between the release pole and the attracting pole is 5 [mT] or less is represented by X [] and the peak magnetic force of the attracting pole is represented by Y [mT], Y2.1X32.7 is satisfied.

A toner cartridge includes a housing configured to contain toner. The housing includes a main body, a first side plate, and a second side plate. The main body has a tubular shape extending in a first direction. The main body is made of paper. The first side plate is located at one end of the main body in the first direction. The first side plate is made of resin. The second side plate located at an other end of the main body in the first direction. The second side plate is made of resin. The main body includes a peripheral surface having a discharge opening. The discharge opening is configured to discharge toner in the housing.

According to an image forming device of the present disclosure, a required replenishment amount is calculated based on a printing rate derived from image data, and toner is replenished to a development device by a toner replenishment device for a required replenishment time in accordance with the required replenishment amount. Then, a time difference obtained by subtracting a printing time per sheet from the required replenishment time is accumulated, and a determination regarding forcible replenishment of the toner is made based on a comparison between an accumulated required replenishment time and an accumulated required replenishment time threshold value.

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.