Brushless motor and manufacturing method thereof

1. A manufacturing method of a brushless motor, comprising:

installing a second ball bearing from a first axial side toward a second axial side into an interior of a bearing holder of a rotor through an opening of the bearing holder, so that an outer race of the second ball bearing is press fitted to an inner peripheral portion of the interior of the bearing holder; and

installing a first ball bearing from the first axial side toward the second axial side into the interior of the bearing holder of the rotor through the opening of the bearing holder after the installing of the second ball bearing, so that an outer race of the first ball bearing is press fitted to the inner peripheral portion of the interior of the bearing holder and is axially spaced from the outer race of the second ball bearing.

2. The manufacturing method according to claim 1 , further comprising installing a stator, which generates a rotational magnetic field to rotate the rotor upon energization of the stator, from the first axial side toward the second axial side such that the stator is installed to and is securely held by an axial wall of a centerpiece.

3. The manufacturing method according to claim 2 , further comprising installing a motor shaft from the first axial side toward the second axial side such that the motor shaft is installed into and is securely held by a motor shaft holder of the centerpiece, which is placed radially inward of the axial wall and is connected to the axial wall by a connecting wall.

4. The manufacturing method according to claim 3 , further comprising installing the rotor from the first axial side toward the second axial side over the motor shaft.

5. The manufacturing method according to claim 4 , wherein the installing of the second ball baring into the interior of the bearing holder is executed before or after the installing of the rotor.

6. The manufacturing method according to claim 5 , wherein:

the installing of the second ball bearing into the interior of the bearing holder is executed before the installing of the rotor;

the installing of the rotor includes receiving the motor shaft through an inner race of the second ball bearing, which is held by the bearing holder of the rotor; and

the installing of the first ball bearing into the interior of the bearing hole is executed after the installing of the rotor.

7. The manufacturing method according to claim 3 , further comprising contacting a plurality of projections of a jig to a bottom portion of the bearing holder and axially supports the bottom portion of the bearing holder on the second axial side thereof prior to the installing of the first ball bearing.

8. The manufacturing method according to claim 7 , wherein the contacting of the plurality of projects of the jig to the bottom portion of the bearing holder includes inserting the plurality of projections of the jig through a plurality of cooling air inlet openings, respectively, which penetrate through the connecting wall in the axial direction of the motor shaft to place the plurality of projections of the jig in position before making the contacting of the plurality of projections to the bottom portion of the bearing holder.

9. The manufacturing method according to claim 1 , further comprising installing an urging means from the first axial side toward the second axial side into the interior of the bearing holder through the opening of the bearing holder after the installing of the second ball bearing and before the installing of the first ball bearing.

10. The manufacturing method according to claim 9 , wherein the installing of the urging means includes installing a spring as the urging means from the first axial side toward the second axial side around the motor shaft.