According to an embodiment, an image forming apparatus includes an image bearing body, a developing unit, a supplying unit, a detecting unit, and a control unit. The supplying unit supplies a recording agent from a recording agent cartridge to the developing unit. The detecting unit detects a residual amount of the recording agent. The control unit controls, if the recording agent cartridge is not replaced, the supplying unit to supply the recording agent to the developing unit if the detected residual amount decreases to a first residual amount or less and controls, if the recording agent cartridge is replaced, the supplying unit to supply the recording agent in the recording agent cartridge after the replacement to the developing unit if the detected residual amount of the recording agent in the recording agent cartridge before the replacement decreases to a second residual amount or less.

An image forming apparatus includes a developing device to contain a developer, the developer including a toner; a developer cartridge to supply the developer to the developing device; a toner concentration sensor to sense a toner concentration of the toner included in the developer contained in the developing device; and a controller. The controller controls, during a non-printing operation a sensor control voltage to adjust an output level of the toner concentration sensor, to control an output of the toner concentration sensor to satisfy a controlling condition, and detects an shape of the output of the toner concentration sensor after the controller controls the sensor control voltage to adjust the output level. The controller adjusts, during a printing operation, the output of the toner concentration sensor, based on the detected shape of the output of the toner concentration sensor, and adjusts supplying the developer from the developer cartridge to the developing device, according to the adjusted output of the toner concentration sensor, to control the toner concentration.

Methods of determining a level of a print substance in a print substance reservoir are disclosed. A reference capacitance of a reference sensor is measured. The reference capacitance is representative of one of a full print substance reservoir and an empty print substance reservoir. A level capacitance of a level sensor is measured. A correlation between the reference sensor and the level sensor is applied to the measured reference capacitance to determine an adjusted reference capacitance. A fill level ratio is determined based on the measured level capacitance and the adjusted reference capacitance.

A printer including a body, a developer cartridge, and a developer level sensor. The body includes a printing unit to print an image on a print medium based on electrophotography. The developer cartridge is attachable to the body and includes a developer container including a developer, and a developer outlet provided at a length-direction side of the developer container to supply the developer from the developer container to the printing unit. The developer level sensor is installed on the body near the developer outlet to generate an electrical detection signal based on a developer level in the developer container.

A replaceable unit for an electrophotographic image forming device includes a housing having a reservoir for holding toner. An electrical connector is positioned on a first side of the housing. The electrical connector includes an electrical contact for contacting a corresponding electrical contact in the image forming device and a magnetic sensor electrically connected to the electrical contact. The electrical connector is movable between a first position and a second position. When the electrical connector moves from the first position to the second position, the electrical contact of the replaceable unit moves from a retracted position to an operative position. When the electrical connector moves from the first position to the second position, the magnetic sensor moves from a misaligned position to an aligned position with a point in a path of movement of a magnet for sensing a magnetic field of the magnet.

A toner amount detector detects an amount of toner in a toner bottle. The toner amount detector includes at least one pair of electrodes disposed opposite each other via the toner bottle, grounding members disposed outboard of the at least one pair of electrodes and electrically grounded, circuitry to switch a first detection processing and a second detection processing, and an indicator to indicate that a positional deviation of the at least one pair of electrodes has occurred. The grounding members face the at least one pair of electrodes. The first detection processing detects the amount of toner based on a first capacitance between the at least one pair of electrodes, and the second detection processing detects a positional deviation based on a second capacitance between each of the grounding members and a corresponding one of the at least one pair of electrodes.

An example toner refill cartridge includes a body to accommodate toner, a plunger inserted into the body and movably coupled to the body in a longitudinal direction of the body, and capable of pushing the toner out of the body, a toner injection amount detector to detect each of a plurality of movement positions of the plunger in accordance with the movement of the plunger, and a connection interface to connect to an image forming apparatus to transmit a signal corresponding to each of the detected movement position to the image forming apparatus.

An image forming apparatus including: a printing unit; a bottle which is rotationally driven in a predetermined rotation direction, whereby the waste developer conveyed from the printing unit to the opening is accommodated inside and the waste developer inside is conveyed to a second end side in the longitudinal direction; and a capacitive sensor having a first detection electrode and a first ground electrode arranged in parallel, where a first detection surface of an electrostatic capacitance formed by the first detection electrode and the first ground electrode is arranged to directly face a portion of an outer peripheral surface of the bottle which is positioned obliquely upward with respect to a center line of rotation of the bottle in a region which moves from a bottom to a top when the bottle rotates in the predetermined rotation direction.

A powder amount detector detects an amount of powder in a powder container of a cylindrical shape arranged horizontally. The powder amount detector includes a pair of measuring electrodes configured to detect capacitance between the pair of measuring electrodes to detect the amount of powder. The pair of measuring electrodes is disposed around the powder container. One of the pair of measuring electrodes has a flat shape, and the other of the pair of measuring electrodes has an arc shape following a shape of the powder container.

A print agent vessel is disclosed that comprises a circuit, the circuit comprising a first electrically conductive portion to couple to a first terminal of a printing device, a second electrically conductive portion to couple to a second terminal of the printing device, and an electrically conductive component capacitively coupled to the first electrically conductive portion. The circuit has a variable capacitance that is indicative of a parameter of the component.