An example method of operating an image forming apparatus includes measuring a toner concentration supplied to a developing apparatus through a toner concentration sensor provided in the developing apparatus as a supply mode for supplying toner to the developing apparatus in the image forming apparatus is executed, increasing a driving speed of the developing apparatus when it is determined that the toner concentration has not reached a target toner concentration, measuring the toner concentration in the developing apparatus through the toner concentration sensor as the supply mode is executed in a state where the driving speed of the developing apparatus is increased, and determining an operating state of the image forming apparatus based on a remaining amount of toner when it is determined that the toner concentration has not reached the target toner concentration in the state where the driving speed of the developing apparatus is increased.

An image forming apparatus including a developing unit with a developing container configured to contain a developer including a toner and a carrier, and configured to develop the electrostatic latent image by using the developer in the developing container. A sensor, which is provided on an outer wall of the developing container, is configured to output a pulse signal that changes in frequency depending on a toner concentration of the developer in the developing container. A controller is provided to control supply of the toner to the developing unit by detecting the toner concentration based on the time required for the pulse number to reach a predetermined count number.

An image forming apparatus measures, using a toner concentration sensor installed in a developing apparatus of the image forming apparatus, a toner concentration of a developer stored in the developing apparatus to obtain an output waveform. The image forming apparatus calculates, based on the output waveform, a first characteristic value corresponding to a volume of the developer. Based on a result of comparing the first characteristic value with a reference value calculated from a reference output waveform obtained in an initial state of the developing apparatus, the image forming apparatus determines whether to execute a discharge mode for discharging the developer from the developing apparatus and to control an amount of the developer. The image forming apparatus discharges, according to a result of the determining, a portion of the developer from the developing apparatus by controlling a driving speed of the developing apparatus when the discharge mode is executed.

An image forming apparatus includes an acquisition unit and a determination unit. The acquisition unit acquires a print setting about at least one of items including a size of a recording medium used for printing, a type of the recording medium, and a conveyance speed of the recording medium. The determination unit determines a printing method to be executed among a plurality of printing methods including a first printing method for drawing an image having a density and a second printing method for drawing an image having a density that is higher than the density of an image printed by the first printing method. Where the print setting is acquired by the acquisition unit, the determination unit determines whether to permit execution of printing by the second printing method based on the print setting acquired by the acquisition unit.

An image forming apparatus includes: an image carrier configured to carry an image; a developing unit configured to develop the image carried by the image carrier with a developer; and a developer replenishing unit configured to supply the developer to the developing unit, the developer replenishing unit being configured to predict, in advance, an amount of developer consumed by the image carrier at a start or an end of image formation apart from developer consumed in the image formation, to replenish the predicted amount of the developer.

An image forming apparatus includes an image carrier; an exposure device which draws an electrostatic latent image on the image carrier; a developer which uses a developing roller facing the image carrier to supply a developing agent to the electrostatic latent image formed on the image carrier and to develop a toner image; a developing current detector which detects a developing current flowing between the image carrier and the developing roller during developing by the developer; and a controller which controls the above. The controller performs forced toner discharge control in which a predetermined toner image is developed on the image carrier by the developer and the toner is forcibly discharged from the developer. The controller controls a toner discharge amount in the forced toner discharge control based on a current value detected by the developing current detector.

An image forming apparatus includes an image forming unit configured to form an image using developer, a mount section on which a container containing the developer is mounted, a drive mechanism that includes a motor that rotates to supply the developer to the image forming unit from the container mounted on the mount section, and a controller configured to obtain an output value related to a load of the motor while rotating the motor without mounting the container on the mount section after the container is detached from the mount section, and detect a failure of the container detached from the mount section based on the output value.

According to one embodiment, a developing device forms a toner image on a photoconductive image carrier with toner supplied from a toner cartridge. A toner supply motor supplies the toner from the toner cartridge to the developing device based on the toner concentration. A processor detects an empty toner based on a toner supply rate, a print rate of the image data, and toner characteristics that are characteristics of the toner supplied from the toner cartridge to the developing device, the toner supply rate being calculated based on a pixel count value that is an integrated value of pixel values of the image data and a toner supply motor count value that is an integrated value of drive times of the toner supply motor.

An image forming apparatus includes: an image carrier that carries an image; a developing device that develops a latent image formed on the image carrier into a visible image formed of powder; an intermediate transfer body to which the visible image is transferred from the image carrier and that temporarily transports the visible image; a transfer device that transfers the visible image on the image carrier to the intermediate transfer body; a first cleaning device that cleans the image carrier by collecting powder that remains on the image carrier; a first collection container that receives the powder collected by the first cleaning device; a second cleaning device that cleans the intermediate transfer body by collecting powder that remains on the intermediate transfer body; a second collection container that receives the powder collected by the second cleaning device; a feeding device that supplies a transfer-process bias to the transfer device; and a changing unit that changes the transfer-process bias supplied by the feeding device when a waste powder image is formed on the image carrier, the transfer-process bias being changed so as to adjust amounts of powder in the waste powder image received by the first collection container and the second collection container.

According to one embodiment, an apparatus includes a photoconductor, an exposure device, a developing device, a toner concentration sensor, a supply motor, and a processor. The exposure device exposes the photoconductor based on image data. The developing device forms a toner image on the photoconductor with toner supplied from a toner cartridge. The toner concentration sensor detects a toner concentration in the developing device. The supply motor supplies the toner from the toner cartridge to the developing device based on the toner concentration. The processor detects a toner container supply abnormality based on a toner supply rate and a print rate of the image data, the toner supply rate being calculated based on a pixel count value that is an integrated value of pixel values of the image data and a supply motor count value that is an integrated value of drive times of the supply motor.