Rotor assembly for brushless motor for a power tool

Patent metadata

Field	Value
Publication number	US-9450472-B2
Application number	US-201113712320-A
Country	US
Kind code	B2
Filing date	Jun 14, 2011
Priority date	Jun 14, 2010
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A power tool includes a brushless DC motor having a stator assembly and a rotor assembly at least a portion of which is arranged pivotably inside the stator assembly. The rotor assembly includes a rotor lamination stack housing a permanent magnets and a rotor fixedly housed inside a center portion of the lamination stack to pivot therewith. A fan may be fixedly attached to the rotor and arranged adjacent the stator assembly. The fan includes a back plate and blades longitudinally projecting from a periphery of the back plate towards the stator assembly, where a middle portion of the back plate is contoured away from an end cap of the motor to accommodate a projecting portion of the end cap. The permanent magnets may extend beyond the longitudinal length of the rotor lamination stack towards a magnet sensor to facilitate sensing of the permanent magnet via the magnet sensor.

First claim

The invention claimed is:

1. A power tool comprising:
a housing;
a transmission assembly;
a brushless DC motor housed inside the housing, the motor comprising a stator assembly, and a rotor assembly at least a portion of which is arranged pivotably inside the stator assembly, the rotor assembly including a rotor lamination stack housing a plurality of permanent magnets, a rotor shaft fixedly housed inside a center portion of the lamination stack to pivot therewith, and a fan fixedly attached to the rotor shaft, the fan having a back plate and a plurality of blades longitudinally projecting from a periphery of the back plate towards the stator assembly; and
a ring gear mount affixed to an end of the stator assembly between the motor and the transmission assembly, the ring gear mount integrally forming a motor end cap facing the motor such that the fan is arranged between the stator assembly and the motor end cap and an outer portion of the fan plate that supports the fan blades nests inside the ring gear mount between the stator assembly and the end cap, the ring gear mount further supporting at least one component of the transmission assembly on a side thereof opposite the motor end cap.

2. The power tool of claim 1 , wherein the rotor assembly further includes a rotor bearing affixed to the rotor shaft, and the rotor end cap includes a bearing support portion arranged to receive the rotor bearing therein, wherein a projecting portion of the motor end cap is located around the bearing support portion to support the rotor bearing inside the bearing support portion.

3. The power tool of claim 1 , wherein the projecting portion partially protrudes inside the middle portion of the back plate.

4. The power tool of claim 1 , wherein the fan plate is securely fastened to the rotor shaft via a rotor encapsulation portion.

5. The power tool of claim 1 , wherein the ring gear mount integrally includes a support portion to receive a ring gear of the transmission assembly.

6. The power tool of claim 5 , wherein the ring gear mount includes a second support portion to receive at least one planetary gear of the transmission assembly.

7. A power tool of claim 1 , wherein a middle portion of the back plate is contoured away from the motor end cap to accommodate a projecting portion of the motor end cap therein.

8. The power tool of claim 7 , wherein the back plate is contoured away from the end cap by 1 mm to 5 mm.

9. A power tool comprising:
a housing;
a brushless DC motor housed inside the housing, the motor comprising a stator assembly and a rotor assembly at least a portion of which is arranged pivotably inside the stator assembly, the rotor assembly including a rotor lamination stack and a rotor shaft fixedly housed inside a center portion of the rotor lamination stack to pivot therewith, the rotor lamination stack housing a plurality of permanent magnets longitudinally arranged inside the lamination stack and extending beyond the longitudinal length of the rotor lamination stack in at least one direction towards at least one magnet sensor to facilitate sensing of the permanent magnets via the at least one magnet sensor
the rotor assembly further comprising a magnet retaining cap arranged adjacent to an end of the rotor lamination stack where the plurality of permanent magnets longitudinally extend, the magnet retaining cap including a plurality of slots to receive and firmly hold portions of the plurality of permanent magnets extending beyond the longitudinal length of the rotor lamination stack to prevent axial movement of the plurality of magnets.

10. The power tool of claim 9 , the rotor assembly further comprising an end cap arranged on a second end of rotor lamination stack and configured to prevent the plurality of permanent magnets from extending beyond the second end of the rotor lamination stack.

11. The power tool of claim 9 , wherein the magnet retaining cap comprises non-conductive material.

12. The power tool of claim 9 , wherein the plurality of magnets comprises four flat magnets arranged in an N-S-N-S configuration.

13. The power tool of claim 9 , wherein the at least one magnet sensor comprises a Hall Effect sensor.

14. The power tool of claim 9 , wherein the at least one magnet sensor is coupled to a control unit and is configured to sense a magnetic flux of the plurality of permanent magnets and provide the control unit with sense signals identifying at least a polarity of the magnet being sensed.

15. The power tool of claim 9 , wherein the at least one magnet sensor is arranged on a sensor board mount adjacent the stator assembly.

16. The power tool of claim 9 , wherein the at least one magnet sensor is arranged optimally with respect to the plurality of permanent magnets to sense only one pole of each magnet at any given time.

Assignees

• Hatfield Eric E
• Stauffer Joseph G
• Ortt Earl M
• Black & Decker Inc

Inventors

• Hatfield Eric E
• Stauffer Joseph G
• Ortt Earl M

Classifications

• H02K7/116

  with gears · CPC title

• H02K11/21

  Devices for sensing speed or position, or actuated thereby (specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14) · CPC title

• H02K9/06 Primary

  with fans or impellers driven by the machine shaft · CPC title

• H02K21/16

  having annular armature cores with salient poles (with homopolar co-operation H02K21/20) · CPC title

• H02K3/28

  Layout of windings or of connections between windings (windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32) · CPC title