Brushless motor system for power tools

Patent metadata

Field	Value
Publication number	US-10786894-B2
Application number	US-201615292673-A
Country	US
Kind code	B2
Filing date	Oct 13, 2016
Priority date	Oct 14, 2015
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A power tool is provided including a tool housing and a brushless DC (BLDC) motor disposed within the tool housing. The motor includes a stator assembly and a rotor assembly having a rotor lamination stack mounted on a rotor shaft to rotate therewith. The power tool also includes a power module for driving the motor, which includes: a printed circuit board, power switches operatively connected to the motor disposed on a first surface of the printed circuit board, positional sensors disposed on a second surface of the printed circuit board around a periphery of a center portion of the printed circuit board, and a heat sink having a substantially planar surface facing the second surface of the printed circuit board and disposed between the motor and the printed circuit board. The heat sink includes a through-hole therein sized to axially expose the positional sensors in the direction of the motor.

First claim

The invention claimed is:

1. A power tool comprising:
a tool housing;
a brushless DC (BLDC) motor disposed within the tool housing, the motor including a stator assembly, and a rotor assembly rotatably disposed within the stator assembly, the rotor assembly comprising a rotor core mounted on a rotor shaft to rotate therewith, and a fan in rotational connection with the rotor shaft, the stator assembly comprising a stator core having a core and a plurality of teeth projecting radially-inwardly from the core, and a plurality of stator windings wound around respective ones of the plurality of stator teeth; and
a power module for driving the motor, comprising: a printed circuit board, a plurality of power switches operatively connected to the motor disposed on a first surface of the printed circuit board, a plurality of positional sensors disposed on a second surface of the printed circuit board around a periphery of a center portion of the printed circuit board, and a heat sink disposed between the printed circuit board and an end of the motor closer to the printed circuit board, the heat sink comprising:
a first surface that is substantially planar facing the second surface of the printed circuit board with no airgap therebetween in an axial direction of the motor,
a second surface facing the end of the motor so as to not radially overlap any portion of the stator windings, and
a through-hole formed in the heat sink to axially expose the positional sensors in the direction of the motor, the through-hole being sized such that an extension axis intersecting at least one of the plurality of stator windings also intersects a portion of the heat sink.

2. The power tool of claim 1 , wherein the power module further comprises a thermal interface secured between the heat sink and the printed circuit board.

3. The power tool of claim 1 , wherein the power module further comprises a clamp ring arranged on the first surface of the power board opposite the heat sink to cover an outer surface of the power switches.

4. The power tool of claim 1 , wherein the printed circuit board includes a through-hole at the center portion thereof to receive the motor shaft, the through-hole of the heat sink having a radius approximately 1.5 to 3 times a radius of the through-hole of the printed circuit board.

5. The power tool of claim 1 , wherein the heat sink is substantially disk shaped having substantially the same radius as the printed circuit board.

6. The power tool of claim 1 , wherein the printed circuit board and the heat sink each include a plurality of fastening through-holes aligned to receive fasteners therein to secure the printed circuit board and the heat sink to corresponding fastening receptacles of the motor.

7. The power tool of claim 1 , wherein the heat sink has a larger surface area that the printed circuit board, and the printed circuit board is attached to the heat sink via a first plurality of fasteners, and the heat sink is attached to corresponding fastening receptacles of the motor via a second plurality of fasteners near the outside periphery of the heat sink.

8. The power tool of claim 1 , wherein the motor further comprises a plurality of power input terminals arranged at approximately a periphery of the stator assembly and extending axially from the stator assembly for coupling to the power module.

9. The power tool of claim 8 , wherein the printed circuit board includes a plurality of peripheral slots to sized to fittingly receive and make contact with distal ends of the power input terminals therein, and the heat sink includes a plurality of peripheral slots recessed radially through the outer circumference of the heat sink and sized to allow passage of the power input terminals without contact.

10. The power tool of claim 9 , wherein the motor further comprises a motor housing disposed within the tool housing, motor housing having a substantially cylindrical main body with a rear end and an open end opposite the rear end to receive the motor therein, the power module being located adjacent the rear end of the motor, wherein the rear end of the motor housing includes a plurality of openings through which the power input terminals project outside the rear end of the motor housing to be received by the peripheral slots of the printed circuit board.

11. The power tool of claim 10 , further comprising a plurality of insulating pads disposed around the plurality of power input terminals between the rear end of the motor housing and the power module.

12. The power tool of claim 1 , wherein the motor further comprises a motor housing disposed within the tool housing, motor housing having a substantially cylindrical main body with a rear end including a radial wall and an open end opposite the rear end to receive the motor therein, the power module being located adjacent the rear end of the motor housing with the heat sink being substantially parallel to the radial wall of the motor housing and the radial wall of the motor housing being located between the heat sink and the stator.

13. The power tool of claim 12 , further comprising a rotor bearing mounted on the rotor shaft, wherein the motor housing includes a bearing pocket disposed at its rear end to receive the rotor bearing therein.

14. The power tool of claim 13 , further comprising a sense magnet affixed to the rotor shaft, the rotor bearing being located between the rotor core and the sense magnet, and the through-hole of the heat sink being located radially-outward of the sense magnet.

15. The power tool of claim 14 , wherein the motor housing includes a through-hole formed within the radial wall of the rear end positioned to receive the sense magnet therein, the sense magnet being disposed in close proximity to the positional sensors of the power module though the through-hole at the rear end of the motor housing.

16. The power tool of claim 15 , wherein the sense magnet is at least partially received through the through-hole of the heat sink.

17. The power tool of claim 15 , further comprising a ring-shaped labyrinth disposed around the through-hole on the rear end of the motor housing facing the power module to substantially block entry of debris and contamination into the rotor assembly through the through-hole on the rear end of the motor housing.

18. A power tool comprising:
a tool housing;
a brushless DC (BLDC) motor disposed within the tool housing, the motor including a stator assembly and a rotor assembly rotatably disposed within the stator assembly, the stator assembly comprising a stator core, a plurality of teeth projecting radially from the core, and a plurality of stator windings wound around respective ones of the plurality of teeth, the rotor assembly comprising a rotor core mounted on a rotor shaft to rotate therewith; and
a power module for driving the motor, comprising:
a printed circuit board,
a plurality of power switches operatively connected to the motor disposed on a first surface of the printed circuit board,
a heat sink disposed between the printed circuit board and an end of the motor closer to the printed circuit board, the heat sink having a first surface that is substantially planar facing the second surface of the printed circuit board with no airgap therebetween in an axial direction of the motor and a second surface facing the end of the motor and intersecting an extension axis of at least one of the plurality of stator windings so as to not radially overlap any portion of the stator windings,
a thermal interface secured between the heat sink and the printed circuit b

Assignees

• Black & Decker Inc

Inventors

• Coates Marcell E
• Purohit Madhur M
• Seeley Timothy J
• Lewis Joshua M
• Smith David J
• Wells Bryce A

Classifications

• H02K9/227

  Heat sinks · CPC title

• H02K5/207

  with openings in the casing specially adapted for ambient air · CPC title

• H02K2203/12

  Machines characterised by the bobbins for supporting the windings · CPC title

• H02K7/145

  Hand-held machine tool · CPC title

• H02K11/33

  Drive circuits, e.g. power electronics (H02K11/38 takes precedence) · CPC title