Developer cartridge, developing unit and image forming apparatus having the same

A developing unit, comprising:

• a developing cartridge;
• and
• a developer cartridge removably received in the developing cartridge, the developer cartridge comprising,
• a developer discharge port, and
• a remaining developer detecting unit arranged in proximity of the developer discharge port, and an agitating unit rotatably arranged inside the developer cartridge to convey developer accommodated in the developer cartridge toward the developer discharge port,
• wherein the developing cartridge comprises a sensor hole formed to face the remaining developer detecting unit so that the remaining developer detecting unit is exposed through the sensor hole.

An image forming apparatus, comprising:

• a main body comprising an optical sensor comprising a light emitting unit and a light receiving unit to detect an amount of remaining developer;
• a developing cartridge removably received in the main body, the developing cartridge comprising a sensor hole formed to face the optical sensor;
• and
• a developer cartridge removably received in the developing cartridge, the developer cartridge comprising,
• a developer discharge port,
• a remaining developer detecting unit arranged, in a position proximate to the developer discharge port, and to face the optical sensor through the sensor hole when the developer cartridge is received in the developing cartridge, and
• an agitating unit rotatably arranged inside the developer cartridge to convey the developer accommodated in the cartridge body toward the developer discharge port.

A developer cartridge, comprising:

• a cartridge body defining an inner volume for storing therein a quantity of developer, the cartridge body including a developer discharge port, through which the developer is discharged from the inner volume;
• a developer detecting unit disposed in the inner volume at a location proximate to the developer discharge port, the developer detecting unit being configured to detect the presence of developer in the vicinity of the developer discharge port;
• and
• an agitating unit rotatably arranged inside the cartridge body to move the developer accommodated in the inner volume toward the developer discharge port.

A developing unit, comprising:

• a developing cartridge body;
• a developer feeding unit disposed in the developing cartridge body, the developer feeding unit being configured to feed developer to a photosensitive medium for developing a latent image formed on the photosensitive medium;
• a developer storage chamber for storing therein a quantity of the developer, the developer storage chamber including a developer discharge port, through which the developer is discharged from the developer storage chamber to the developer feeding unit;
• a developer detecting unit disposed in the developer storage chamber at a location proximate to the developer discharge port, the developer detecting unit being configured to detect the presence of the developer in the vicinity of the developer discharge port;
• and
• an agitating unit rotatably arranged inside the developer storage chamber to move the developer accommodated in the developer storage chamber toward the developer discharge port.