In a spindle motor utilizing dynamic-pressure bearings having a full-fill structure,
a bearing configuration that balances and sustains at or above atmospheric pressure
the internal pressure of the bearing oil. Thrust and radial bearing sections are
configured within oil-filled bearing clearances in between the rotor, the shaft,
and a shaft-encompassing hollow bearing member. A communicating passage one end
of which opens on, radially inwardly along, the thrust bearing section is formed
in the bearing member. Either axial ends of the bearing clearance in between the
bearing member and shaft communicate through the passage. The communicating passage
enables the oil to redistribute itself within the bearing clearances. Pressure
difference between the axial upper and lower ends of the oil retained in between
the bearing member and the shaft is compensated through the communicating passage,
preventing incidents of negative pressure within the oil and of over-lift on the rotor.
