Motor

A motor comprising:

• an upper housing;
• a lower housing coupled to the upper housing to provide an internal space;
• a shaft disposed within the internal space and coupled to a hydrodynamic bearing assembly;
• a rotor core coupled to the shaft and rotated together with the shaft;
• and
• a balancing unit coupled to the shaft to correct a rotational imbalance at the time of rotation of the shaft and the rotor core,
• wherein the hydrodynamic bearing assembly includes:
• a fixed part having a central hole into which the shaft is inserted and rotatably supporting the shaft;
• an upper sealing part coupled to an upper portion of the shaft and disposed to form a micro clearance with regard to an upper portion of the fixed part;
• and
• a lower sealing part coupled to a lower portion of the shaft and disposed to form a micro clearance with regard to a lower portion of the fixed part,
• the fixed part being provided with a separation groove depressed from an inner peripheral surface of the fixed part to separate a lubricating fluid provided in a clearance between the shaft and the fixed part into upper and lower portions in an axial direction and being provided with a communications part allowing the separation groove to be in communication with the outside.