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 developer storage chamber configured to store developer to be supplied to the development chamber, a partition configured to separate a development chamber and the developer storage chamber and having an opening allowing communication between the developer storage chamber and the development chamber, and a protruding portion configured to protrude toward the inside of the developer storage chamber from the partition on a downstream side of the opening in the rotation direction of a rotating shaft, and within one turn of rotation of the rotating shaft, a receiving member moves while contacting the protruding portion according to the rotation of the rotating 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.

An optical sensor has a light emission section and a light reception section so arranged as to sandwich an opening part of a toner container from both sides when the toner container is attached, and a shutter slides in conjunction with the attachment and detachment of the toner container and has a top surface member opening and closing a toner exhaust port of a cleaning device and a side surface member transmitting and blocking light of the optical sensor. A slit orthogonal to a sliding direction of the shutter is formed at the side surface member of the shutter, and the control section performs detection of attachment and detachment of the toner container based on a waveform pattern of light transmitted through the slits which pattern appears in a signal of the optical sensor.

A developing device includes a developer storage chamber configured to store developer to be supplied to the development chamber, a partition configured to separate a development chamber and the developer storage chamber and having an opening allowing communication between the developer storage chamber and the development chamber, and a protruding portion configured to protrude toward the inside of the developer storage chamber from the partition on a downstream side of the opening in the rotation direction of a rotating shaft, and within one turn of rotation of the rotating shaft, a receiving member moves while contacting the protruding portion according to the rotation of the rotating shaft.

An image forming apparatus includes an apparatus body, an image bearing member, and a process unit attached to the apparatus body. The process unit includes a frame including a storage portion configured to store developer, a developer bearing member configured to supply developer to the image bearing member to develop an electrostatic latent image, and a circuit board attached to the frame. The circuit board includes a light emitting portion configured to emit light, and a light receiving portion configured to receive the light emitted from the light emitting portion and having passed through an interior of the storage portion.