In various examples, colorant sensors can include a printing device comprising a hopper to receive a colorant, a supply to receive the colorant from the hopper, an aperture disposed between the hopper and the supply, a light emitter to emit light that passes through the aperture, and a light sensor located on the opposite side of the aperture relative the light emitter to sense a portion of the emitted light that passes through the aperture to permit determination of whether colorant present in the aperture based on the portion of the emitted light sensed by the light sensor.

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.

An image forming apparatus according to one embodiment includes an image carrier that moves in a first direction, a developing device, a detector, and a determination unit. The developing device uses a developer on the surface of the image carrier to forma strip-shaped image inclined with respect to the width direction perpendicular to the moving direction of the image carrier. The detector detects the density difference occurring in the strip-shaped image formed on the surface of the image carrier while moving in the width direction. The determination unit determines based on a detection result by the detector whether or not there is an abnormality.

An image forming apparatus includes an image carrier, a developing device, a voltage applier, a current detector, a weight detector, and a control device. The control device acts as a first measurer, a second measurer, and an estimator. The first measurer acquires a toner use amount indicating weight per unit area, of the toner that has migrated from the developing agent carrier to the image carrier, according to a detection result provided by the weight detector. The second measurer acquires the developing current from the current detector. The estimator calculates a value of decision coefficient, obtained by dividing variance of an estimated value in a regression model between the toner use amount and the developing current, by variance of a sample value, and estimates deterioration status of the toner, according to the value of the decision coefficient.

An image forming apparatus includes an image bearing member, a rotatable developer carrying member, a rotatable toner supplying member, and a toner accommodating unit. A developing unit including the developer carrying member and the toner accommodating unit are capable of being independently exchanged. The image forming apparatus further includes a current detector and a controller configured to execute a process for notifying information on a lifetime of the developing unit, on the basis of a detection result of the current detector at predetermined timing after use of a fresh toner accommodating unit is started.

A toner container according to one example embodiment includes a housing having a reservoir for holding toner and a rotatable auger in the reservoir. A screw flight of the auger is configured to move toner away from a first end of the auger and toward a second end of the auger when the auger rotates in an operative rotational direction. A segment of the screw flight at a first end of the screw flight has an outer diameter that is reduced in comparison with an outer diameter of the screw flight outside the segment of the screw flight to reduce an efficiency of the auger at the first end of the screw flight for reducing toner packing against an interior wall of the housing when the auger rotates in a direction counter to the operative rotational direction.

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.

According to one embodiment, an image forming apparatus includes an image carrier, an exposing apparatus, a developing device, a transfer device, a fixing device, a history acquisition unit, an estimation unit, and an output unit. The exposing device exposes the image carrier to form an electrostatic latent image on the image carrier. The developing device includes a layer forming member to form a toner layer on a developing roller and forms a toner image by developing the electrostatic latent image. The transfer device transfers the toner image to a sheet. The fixing device fixes the toner image to the sheet. The history acquisition unit acquires a history regarding a temperature around the developing device. The estimation unit estimates a possibility that an image defect caused by the layer formation may occur on the basis of the history. The output unit outputs estimation results of the estimation.

An image forming apparatus includes an image forming part, a toner storage part, a toner conveyance part, a drive motor and a control part. The image forming part forms an image on a sheet using a toner. The toner storage part stores the toner replenished to the image forming part. The toner conveyance part conveys the toner. The drive motor generates a drive force by which the toner conveyance part conveys the toner. The control part generates a control signal for controlling the drive motor, based on information showing a rotational speed of the drive motor. The control part executes a determination processing for determining whether a driving of the drive motor is stopped, based on the control signal.

A powder transport device includes a transport unit, a spiral first transport member, and a first driving unit. The transport unit has a transport path. The first transport member is rotatably disposed in the transport path and rotates forward to transport powder. The first driving unit drives the first transport member to rotate. The first driving unit rotates the first transport member in reverse when both (i) a non-operation time during which the first transport member is not rotated and (ii) detection information on a temperature satisfy a condition.