Brushless motor and manufacturing method thereof

A brushless motor comprising:

• a motor shaft that is stationary held and extends between a first axial side and a second axial side;
• a rotor that is rotatable about the motor shaft and includes a generally cylindrical bearing holder, which is placed on a radially outer side of the motor shaft and extends in an axial direction of the motor shaft;
• a centerpiece that is placed on the second axial side of the rotor and includes:
• a motor shaft holder that is coaxial with the bearing holder and securely holds the motor shaft;
• an axial wall that is placed radially outward of the motor shaft holder and of the bearing holder and is radially spaced from the bearing holder by a gap, wherein the axial wall extends in the axial direction of the motor shaft, and an axial extent of the axial wall at least partially overlaps with an axial extent of the bearing holder in the axial direction of the motor shaft;
• and
• a connecting wall that connects between the motor shaft holder and the axial wall on the second axial side of the bearing holder, wherein a plurality of cooling air inlet openings axially penetrates through the connecting wall in the axial direction of the motor shaft;
• a first ball bearing that is received in an interior of the bearing holder and has an inner race, which receives the motor shaft, and an outer race, which is held by an inner peripheral portion of the interior of the bearing holder;
• a second ball bearing that is received in the interior of the bearing holder and is axially spaced from the first ball bearing on the second axial side thereof, wherein the second ball bearing has an inner race, which receives the motor shaft, and an outer race, which is held by the inner peripheral portion of the interior of the bearing holder;
• and
• a stator that is securely held by the axial wall of the centerpiece and generates a rotational magnetic field to rotate the rotor upon energization of the stator.