An electrophotographic image forming apparatus may include an imaging cartridge and a toner cartridge that are detachably attached to a main body, a first optical sensor that is mounted in the imaging cartridge and detects a toner level in a development chamber, and a second optical sensor that is mounted in the toner cartridge and detects a toner level in the development chamber.

A developer detector includes a sensor housing portion, an optical sensor, and a cleaning portion. The sensor housing portion can be installed on a wall surface of a hopper storing a developer. The sensor housing portion includes a detection surface, and a step surface protruding a smaller amount from the wall surface than the detection surface to form a step height from the detection surface. The optical sensor is housed in the sensor housing portion and detects the developer through the detection surface. The cleaning portion moves in a moving region including a first region facing the detection surface and a second region facing the step surface and cleans the detection surface on the way of moving. The cleaning portion includes a flexible member and makes the flexible member slide on the detection surface while making the flexible member contact the detection surface under pressure in the first region.

An image forming apparatus includes an image bearing member, a charging member, a development member, a developer accommodating portion, a first acquiring portion which acquires developer amount information related to an amount of the developer accommodated in the developer accommodating portion, a second acquiring portion which acquires development drive information related to a movement distance of a surface of the development member, and a control portion which is capable of executing a first mode and a second mode, whose frequency of driving the development member lower than that of the first mode, as an image forming mode. The control portion proposes or determines a change from the first mode to the second mode of the image forming mode on the basis of the developer amount information and the development drive information.

A developing device includes a development unit, a developer amount detector, an accuracy requirement determiner, and a detection count setting unit. The development unit includes a developer container configured to store a developer. The development unit is configured to supply the developer from the developer container to a latent image bearer, on which an electrostatic latent image is to be formed according to image data, to form a developer image. The developer amount detector is configured to detect a developer amount in the toner container of the development unit in every detection period. The accuracy requirement determiner is configured to a determine accuracy requirement required as a detection accuracy of the developer amount by the developer amount detector. The detection count setting unit is configured to set a number of times of detection of the developer amount by the developer amount detector based on the accuracy requirement.

An electrophotographic image forming apparatus includes for example a toner supply unit including a toner containing unit and a toner discharging unit having a toner outlet; a photoreceptor unit including a photoreceptor; a development unit including a development roller that supplies toner to develop the electrostatic latent image on the photoreceptor and a supply roller that supplies toner to the development roller; a first toner supply member that supplies toner of the toner containing unit to the toner discharging unit; and a second toner supply member that transports toner of the toner discharging unit to the toner outlet. The first toner supply member is located in a second quadrant from among first through fourth quadrants based on a vertical line and a horizontal line which intersect at the second toner supply member, and the photoreceptor, the supply roller, and the development roller are located in the fourth quadrant.

An electrophotographic imaging system according to one example embodiment includes a toner cartridge including a housing having a reservoir for storing toner. A shaft is rotatably positioned within the reservoir and includes a threaded portion. A partition mounted on the threaded portion of the shaft moves axially along the threaded portion when the shaft rotates. The partition divides the reservoir into a first toner compartment and a second toner compartment. A sensing arrangement monitors an axial position of the partition along the shaft. The sensing arrangement includes a plurality of sensors arranged at predetermined axial locations relative to the shaft and a sensed member connected to the partition. The plurality of sensors are positioned to detect an axial position of the sensed member relative to the shaft for determining the axial position of the partition along the shaft.

An electrophotographic image forming apparatus may include an imaging cartridge and a toner cartridge that are detachably attached to a main body, a first optical sensor that is mounted in the imaging cartridge and detects a toner level in a development chamber, and a second optical sensor that is mounted in the toner cartridge and detects a toner level in the development chamber.

A developing device includes a housing to accommodate toner, a rotation member installed in the housing, a lens including an optical surface oriented in an axial direction of the rotation member, and a wiper installed in the rotation member and configured to repeatedly wipe the optical surface while the rotation member rotates and supported by the rotation member so as to be movable in the axial direction.

A developer detector includes a sensor housing portion, an Optical sensor, and a cleaning portion. The sensor housing portion can be installed on a wall surface of a hopper storing a developer. The sensor housing portion includes a detection surface, and a step surface protruding a smaller amount from the wall surface than the detection surface to form a step height from the detection surface. The optical sensor is housed in the sensor housing portion and detects the developer through the detection surface. The cleaning portion moves in a moving region including a first region facing the detection surface and a second region facing the step surface and cleans the detection surface on the way of moving. The cleaning portion includes a flexible member and makes the flexible member slide on the detection surface while making the flexible member contact the detection surface under pressure in the first region.

An electrophotographic image forming apparatus may include an imaging cartridge and a toner cartridge that are detachably attached to a main body, a first optical sensor that is mounted in the imaging cartridge and detects a toner level in a development chamber, and a second optical sensor that is mounted in the toner cartridge and detects a toner level in the development chamber.