Driving coupler having locking structure and power transmission structure

An image forming apparatus, comprising:

• a main body by which a driving shaft is supported;
• and
• a driving coupler having,
• a cylindrical body coupled to one end of the driving shaft, and
• an axial protrusion protruding from the cylindrical body in an axial direction of the driving shaft, the axial protrusion having a driving force transmission surface and a locking protrusion protruding from the driving force transmission surface,
• wherein the locking protrusion is to lock with a locking groove of a passive coupler of a toner cartridge to mount the toner cartridge on the main body,
• wherein, based on the driving shaft providing a rotational force to the driving coupler in a first rotational direction, the locking protrusion of the driving coupler rotating in the first rotational direction is insertable into the locking groove of the passive coupler to lock with the passive coupler, and
• wherein the driving force transmission surface of the axial protrusion of the driving coupler and a driving force receiving surface of the passive coupler are in contact with each other to transmit the rotational force to the passive coupler in the first rotational direction.