A bearing assembly for use in an electric motor minimizes the generation
of a negative pressure. In the bearing assembly, gaps are formed between
a shaft provided with a flange portion, a ring member mounted on the
shaft, and a sleeve member with a through hole formed therein are
continuously filled with lubrication oil. When a rotor rotates, the rotor
is supported by a fluid dynamic pressure. In the bearing assembly,
herringbone grooves are formed in an upper surface of the flange portion
of the shaft fixed to a base plate. When the sleeve member rotates with
respect to the shaft, ends of all of the herringbone grooves and the
through hole are superposed on each other sequentially. Thus, the
lubrication oil can be efficiently supplied to an outer peripheral region
in the thrust dynamic pressure bearing mechanism in which the negative
pressure is most prone to be generated, and generation of the negative
pressure can be efficiently minimized.