ROTOR ASSEMBLY FOR BRUSHLESS MOTOR FOR A POWER TOOL

• US 20130270932A1
• Filed: 06/14/2011
• Published: 10/17/2013
• Est. Priority Date: 06/14/2010
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Stauffer, Joseph G., Ortt, Earl M., Hatfield, Eric E.
• Granted Patent: US 9,450,472 B2
• Time in Patent Office: Days
• US Class Current: 310/50
• CPC Class Codes: H02K 1/276 Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
• CPC Class Codes: H02K 11/20 for measuring, monitoring, testing, protecting or switching rectifiers H02K11/04; power electronics H02K11/33
• CPC Class Codes: H02K 11/21 Devices for sensing speed or position, or actuated thereby specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14
• CPC Class Codes: H02K 11/215 Magnetic effect devices, e.g. Hall-effect or magneto-resistive elements
• CPC Class Codes: H02K 11/30 Structural association with control circuits or drive circuits
• CPC Class Codes: H02K 11/33 Drive circuits, e.g. power electronics H02K11/38 takes precedence
• CPC Class Codes: H02K 21/12 with stationary armatures and rotating magnets
• CPC Class Codes: H02K 21/16 having annular armature cores with salient poles with homopolar co-operation H02K21/20
• CPC Class Codes: H02K 2203/03 Machines characterised by the wiring boards, i.e. printed circuit boards or similar structures for connecting the winding terminations
• CPC Class Codes: H02K 2203/09 Machines characterised by wiring elements other than wires, e.g. bus rings, for connecting the winding terminations
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02K 3/522 for generally annular cores with salient poles
• CPC Class Codes: H02K 5/225 Terminal boxes or connection arrangements specially adapted for submersible motors H02K5/132
• CPC Class Codes: H02K 7/116 with gears
• CPC Class Codes: H02K 7/145 Hand-held machine tool
• CPC Class Codes: H02K 9/06 with fans or impellers driven by the machine shaft
• CPC Class Codes: H02K 9/22 by solid heat conducting material embedded in, or arranged in contact with, the stator or rotor, e.g. heat bridges
• CPC Class Codes: H02K 9/227 Heat sinks

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.

Claims

1. 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 housing a plurality of permanent magnets, a rotor fixedly housed inside a center portion of the lamination stack to pivot therewith, and a fan fixedly attached to the rotor and arranged adjacent the stator assembly, the fan having a back plate and a plurality of blades longitudinally projecting from a periphery of the back plate towards the stator assembly, wherein 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.

2. The power tool of claim 1, wherein the projecting portion of the end cap encapsulates an end bearing of the rotor.

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 via a rotor encapsulation portion.

5. The power tool of claim 1, further comprising a transmission assembly, wherein the motor further comprises an integrated ring gear mount integrally including the end cap of the motor on a first side and supporting at least one component of the transmission assembly on a second side.

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

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

8. A power tool of claim 5, wherein an outer portion of the fan plate that supports the fan blades nests inside the ring gear mount.

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

10. A power tool of claim 1, further comprising a transmission housing, wherein an outer portion of the fan plate that supports the fan blades nests inside the transmission assembly along an axis of an end bearing of the rotor.

11. 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 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 magnet via the at least one magnet sensor.

12. The power tool of claim 11, the rotor assembly further comprising a magnet retaining cap arranged adjacent to a first end of the rotor lamination stack, the magnet retaining cap including a plurality of slots to receive portions of the plurality of permanent magnets extending beyond the longitudinal length of the rotor lamination stack.

13. The power tool of claim 12, wherein the magnet retaining cap is configured to firmly hold the portions of the plurality of permanent magnets extending beyond the longitudinal length of the rotor lamination stack within the plurality of slots to prevent axial movement of the plurality of magnets.

14. The power tool of claim 12, 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.

15. The power tool of claim 12, wherein the magnet retaining cap comprises non-conductive material.

16. The power tool of claim 11, wherein the plurality of magnets comprises four flat magnets arranged in an N-S-N-S configuration.

17. The power tool of claim 11, wherein the at least one magnet sensor comprises a Hall Effect sensor.

18. The power tool of claim 11, 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.

19. The power tool of claim 11, wherein the at least one magnet sensor is arranged on a sensor board mount adjacent the stator assembly.

20. The power tool of claim 11, 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.