An image forming apparatus includes a developing device that forms a toner image on a sheet; a supply device provided with a cartridge for accommodating toner and supplying the toner in the cartridge to the developing device; a sensor that acquires a physical quantity relating to an amount of toner in the developing device; a timer that counts time; and a controller that drives the supply device until a condition that the acquired physical quantity indicates that the amount of toner is equal to or greater than a predetermined value is satisfied when a condition that the physical quantity indicates that the amount of toner becomes small is satisfied, counts time during which the supply device is being driven with the timer, and determines that the amount of toner in the cartridge becomes smaller than a predetermined amount if the counted time is longer than a predetermined threshold value.

According to one embodiment, an image forming apparatus includes a printer and a controller. The printer performs image formation on a sheet at a first speed relating to a speed of image formation or at a second speed slower than the first speed. The controller acquires information on deterioration of developer contained in an own apparatus, and controls the printer to perform image formation at the first speed when the information does not satisfy a predetermined condition indicating that the developer is deteriorated and to perform image formation at the second speed when the information satisfies the predetermined condition.

According to one embodiment, an image forming apparatus includes a printer and a controller. The printer performs image formation on a sheet at a first speed relating to a speed of image formation or at a second speed slower than the first speed. The controller acquires information on deterioration of developer contained in an own apparatus, and controls the printer to perform image formation at the first speed when the information does not satisfy a predetermined condition indicating that the developer is deteriorated and to perform image formation at the second speed when the information satisfies the predetermined condition.

An image forming apparatus includes an image forming portion, a high-voltage generation circuit, a current detection portion and a control portion. The image forming portion includes an image carrying member, a charging device, an exposure device and a developing device which includes a developer carrying member for carrying a developer including a carrier and a toner. The control portion can perform a development ghost prediction mode that includes a step of measuring the amount of charge of the toner within the developing device at the time of non-image formation, a step of measuring, as a carrier current, the direct-current component of a development current when the amount of development of the toner is 0 [mg/cm.sup.2] and a step of estimating the level of occurrence of development ghost and the cause of occurrence based on the amount of charge of the toner and the carrier current which are measured.

In an image forming apparatus, a controller controls a toner container so that toner in a toner container is supplied to a developing section according to replenishment amount information stored in storage. The developing section includes a developer container that contains toner supplied from the toner container, and a sensor that detects a concentration of the toner in the developer container. The controller changes a replenishment amount indicated in the replenishment amount information based on a predicted toner concentration value in the developer container after the toner is supplied to the developer container under control of the toner container, and a detected toner concentration value detected by the toner sensor.

An image forming apparatus includes a developing section, storage, a first calculation section, a comparing section, and an executing section. The developing section develops an electrostatic latent image with toner. The storage stores coverage rates. The first calculation section calculates a first coverage rate and a second coverage rate. The comparing section compares the first coverage rate with the second coverage rate. The first coverage rate includes one or more coverage rates stored earlier in the storage than the second coverage rate. The second coverage rate includes coverage rates of a specified number of latest images individually formed on a specified number of sheets. A running-in operation is driving the developing section. The executing section executes the running-in operation.

According to one embodiment, there is provided a toner cartridge used in an image forming apparatus including a processor which forms a toner pattern image on a photoconductive member, transfers the toner pattern image on a medium, and changes an image forming condition based on a detection result obtained by optically detecting the toner pattern image transferred onto the medium, the toner cartridge including: a toner accommodating container accommodating a toner, and a memory. The memory stores reference data which is determined according to toner characteristics in the toner accommodating container, and is used for applying a reference value for an optical detection result of a toner pattern formed by the toner on the medium.

An image forming apparatus includes a latent-image forming unit that forms an electrostatic latent image onto an image carrier, a developing member that develops the electrostatic latent image held on the image carrier with a developer, a container that contains the developer supplied to the developing member, a stirring member that stirs the developer by rotating in the container, a density detecting unit that is disposed in the container and that detects a density of the developer, and a switching unit that switches an image formation condition by using a period of a signal output by the density detecting unit.

A developer supply device includes a developer container, an adjustment mechanism, and a controller. The developer container is configured to supply developer by rotating. The adjustment mechanism is configured to adjust a rotation angle of the developer container. The controller is configured to control the rotation angle of the developer container by the adjustment mechanism according to a developer remaining amount in the developer container.

A screw is rotated to replenish toner from a hopper to a developing device. Rotation of the screw, toner stored in the hopper, and a toner density in the developing device are detected. Whether or not to replenish toner from the hopper to the developing device is controlled based on a detection result of rotation of the screw. The number of rotations of the screw during a predetermined time period is acquired. The predetermined time period corresponds to a time period during which the replenishment processing is being executed and over which a state in which toner in the hopper is detected is changed to a state in which toner in the hopper is not detected. An abnormality of the hopper is detected if the number of rotations in the predetermined time period is larger than a predetermined number.