Outer-rotor brushless motor for a power tool

Patent metadata

Field	Value
Publication number	US-12176794-B2
Application number	US-202117455688-A
Country	US
Kind code	B2
Filing date	Nov 19, 2021
Priority date	Nov 19, 2021
Publication date	Dec 24, 2024
Grant date	Dec 24, 2024

Abstract

An outer-rotor brushless direct-current motor is provided. The motor includes a motor can that supports the motor components and a fan mounted on a rotor shaft inside the motor can to generate an airflow through the motor can. The motor can includes exhaust openings formed around the fan to allow the airflow to be expelled radially away from the fan, and intake openings formed at a distance from the exhaust openings to allow an airstream to be received radially into the motor can.

First claim

The invention claimed is:

1. A power tool comprising a housing, a brushless direct-current (BLDC) motor disposed within the housing, and a battery receptacle configured to receive a removable battery pack, the BLDC motor comprising:
a rotor shaft on which a rear motor bearing and a front motor bearing are mounted;
a motor can through which the rotor shaft extends and including a substantially cylindrical body having an open end and a radial wall distanced from the open end, the radial wall forming a first bearing pocket arranged to receive the front motor bearing therein;
a stator assembly including a stator core having an aperture extending therethrough, a plurality of stator teeth radially extending outwardly from the stator core and defining a plurality of slots therebetween, and a plurality of stator windings wound around the plurality of stator teeth;
a stator mount including an axial member on which the stator assembly is mounted, and a radial member coupled to the open end of the motor can, the radial member forming a second bearing pocket arranged to support the rear motor bearing;
an outer rotor comprising a cylindrical rotor core supporting at least one permanent magnet around an outer surface of the stator core; and
a fan mounted on the rotor shaft inside the motor can to generate an airflow through the motor can;
wherein the motor can includes a plurality of exhaust openings formed around the fan to allow the airflow to be expelled radially away from the fan, and a plurality of intake openings formed at a distance from the plurality of exhaust openings along a radial plane between a rear end of the stator assembly and the stator mount to allow an airstream to be received radially into the motor can for generating the airflow through the motor can.

2. The power tool of claim 1 , wherein the motor further comprises a rotor mount configured to secure the outer rotor to the rotor shaft, the rotor mount including an outer rim arranged to couple to the outer rotor, at least one radial element extending inwardly from the outer rim, and an inner body mounted on the rotor shaft.

3. The power tool of claim 2 , wherein the at least one radial element of the rotor mount comprises a series of spaced apart radial elements forming the fan.

4. The power tool of claim 1 , wherein the radial member of the stator mount includes a plurality of openings that allow a secondary airstream to be received axially into the motor can, the airstream and the secondary airstream cooperatively generating the airflow through the motor can.

5. The power tool of claim 1 , wherein the housing comprises a plurality of exhaust openings aligned with the plurality of exhaust openings of the motor can to allow the airflow to be expelled radially away from the housing.

6. The power tool of claim 5 , wherein the housing further comprises a plurality of intake openings aligned with the plurality of intake openings of the motor can to receive the airstream to be received radially into the housing.

7. The power tool of claim 1 , wherein the power tool does not include any additional fans for cooling the motor.

8. The power tool of claim 1 , wherein the fan includes a maximum diameter that is smaller than or equal to an outer diameter of the outer rotor.

9. The power tool of claim 8 , wherein the outer diameter of the outer rotor is smaller than approximately 35 mm.

10. The power tool of claim 8 , wherein the outer diameter of the outer rotor is smaller than approximately 32 mm.

11. A brushless direct-current motor comprising:
a rotor shaft on which a rear motor bearing and a front motor bearing are mounted;
a motor housing;
a stator assembly including a stator core having an aperture extending therethrough, a plurality of stator teeth radially extending outwardly from the stator core and defining a plurality of slots therebetween, and a plurality of stator windings wound around the plurality of stator teeth;
a stator mount including an axial member on which the stator assembly is mounted, and a radial member coupled to the motor housing, the radial member forming a bearing pocket arranged to support the rear motor bearing;
an outer rotor comprising a cylindrical rotor core supporting at least one permanent magnet around an outer surface of the stator core; and
alignment features comprising a tongue and groove arrangement extending axially along an inner surface of the stator core and an outer circumferential surface of the axial member of the stator mount to radially affix the stator core on the axial member.

12. The motor of claim 11 , wherein the stator core comprises a stack of steel laminations, and the alignment feature of the stator core is formed integrally in the stack of steel laminations.

13. The motor of claim 11 , wherein the alignment feature of the stator core extends through at least half an axial length of the stator core.

14. The motor of claim 11 , wherein the alignment feature of the axial member of the stator mount is a groove formed through the outer circumferential surface of the axial member.

15. The motor of claim 14 , wherein the axial member of the stator mount includes an elongated cylindrical member projecting axially from the radial member into the aperture of the stator core.

16. The motor of claim 11 , wherein the motor housing includes a substantially cylindrical body having an open end and a radial wall distanced from the open end, the radial wall forming a second bearing pocket arranged to receive the front motor bearing therein.

17. A power tool comprising a housing, the brushless direct-current (BLDC) motor of claim 11 disposed within the housing, and a battery receptacle configured to receive a removable battery pack.

Assignees

• Black & Decker Inc

Inventors

• Zhou Yuming
• Xie Fuchun
• Zheng Tong
• Jin Ming
• Jin Fujun
• Qian Weifeng

Classifications

• H02K1/2786

  Outer rotors · CPC title

• B25F5/008

  Cooling means · CPC title

• B25F3/00

  Associations of tools for different working operations with one portable power-drive means; Adapters therefor · CPC title

• H02K1/187

  to inner stators · CPC title

• H02K7/086

  radially supporting the rotor around a fixed spindle; radially supporting the rotor directly (H02K7/09 takes precedence) · CPC title