Brushless DC motor

A brushless DC motor comprising:

• (a) a housing including:
• a cup-shaped upper housing comprising a disk-like main plate, an annular wall, and a front bearing disposed at a center thereof;
• and
• a cup-shaped lower housing including a disk-like main plate provided with openings, an annular wall, and a rear bearing disposed at a center thereof;
• (b) a stator assembly disposed in the housing, comprising:
• a stator core having a plurality of pole tooth portions;
• a circular portion;
• and
• coils wound around each of the pole tooth portions,
• wherein the pole tooth portions radially extend from the circular portion;
• (c) a rotor assembly rotatably disposed in the stator assembly, comprising:
• a shaft;
• a sleeve attached around the shaft;
• and
• a magnet disposed on an outer periphery of the sleeve;
• (d) a spacer ring disposed in the lower housing of the housing,
• wherein the spacer ring is engaged with the stator core and disposed between the stator core and the main plate of the lower housing in an axially direction;
• and
• (e) a circuit board mounted with an IC component to control a driving current,
• wherein the circuit board is secured to an outer face of the main plate of the lower housing, and the IC component mounted on the circuit board protrudes into the lower housing through one of the openings formed at the main plate of the lower housing,
• wherein the sleeve has an annular recess portion in its surface facing the IC component, and a part of the IC component is housed with the annular recess portion, and
• wherein the stator core has a plurality of axially-extending recesses provided at an outer circumference thereof, and wherein the spacer ring is provided with a plurality of axial-extending protrusions at an upper side and a lower side thereof, the plurality of protrusions provided on the upper side of the spacer ring are engaged with the plurality of recesses of the stator core, and the plurality of protrusions provided on the lower side of the spacer ring are engaged with the circuit board through the other opening formed at the main plate of the lower housing.