Power tool

1. A power tool comprising a housing and a brushless motor, the brushless motor including a stator and a rotor disposed inside the housing, the rotor including a rotor core having a plurality of axially extending through holes and a permanent magnet disposed in each of the plurality of through holes,

wherein:

the rotor includes a plurality of axially extending concavities in an outer surface of the rotor by which the rotor core is holdable in a desired circumferential orientation while the permanent magnets are inserted into the through holes and at least one convexity located between an adjacent pair of the concavities,

the rotor core viewed in cross section perpendicular to the axis of rotation comprises first and second pairs of opposed arc sections, each of the arc sections having a longest chord,

the adjacent pair of concavities is located on the outer surface of the rotor between circumferentially adjacent arc sections of the first and second pairs of arc sections, and

each of the permanent magnets has a width greater than a length of the longest chord.

2. The power tool according to claim 1 , wherein each of the concavities has first and second mutually perpendicular, axially extending walls.

3. The power tool according to claim 1 , wherein portions of the permanent magnets extend into the convexities.

4. The power tool according to claim 1 , wherein the rotor core is formed from a plurality of laminations and wherein the permanent magnets are retained in the through holes by an injection molded resin body.

5. The power tool according to claim 1 , wherein the rotor core is formed from a plurality of laminations and wherein the permanent magnets are retained in the through holes by a body of injection molded magnet material.

6. The power tool according to claim 1 , wherein each of the plurality of magnets is located adjacent one of the longest chords and is located radially inward of the respective adjacent longest chord.

7. The power tool according to claim 1 , wherein:

each of the plurality of magnets includes a radially outer wall,

the radially outer walls of the plurality of magnets lie on a side of a regular convex polygon and

each of the sides of the regular convex polygon extends along the outer wall of one of the plurality of magnets.

8. The power tool according to claim 7 wherein the regular convex polygon is a square.

9. The power tool according to claim 7 , wherein the regular convex polygon extends beyond the outer surface of the rotor.

10. The power tool according to claim 9 , wherein the regular convex polygon is a square.

11. A power tool comprising:

a housing; and

a brushless motor in the housing, the brushless motor including a stator, a rotor having a longitudinal axis of rotation and a rotor core having a plurality of axially extending through holes, and a permanent magnet in each of the plurality of through holes,

the rotor core having a radially outer surface, the radially outer surface being non-circular when viewed in cross section perpendicular to the axis of rotation,

wherein the outer surface includes at least two axially extending concavities by which the rotor core can be held in a desired circumferential orientation while the permanent magnets are inserted into the through holes,

wherein the rotor core viewed in cross section perpendicular to the axis of rotation comprises first and second pairs of opposed arc sections, circumferentially adjacent arc sections of the first and second pairs of arc sections being separated by one of the at least two axially extending concavities,

and further including at least one convexity between the concavities and between the circumferentially adjacent arc sections of the first and second pairs of arc sections,

wherein portions of the permanent magnets extend into the convexities.

12. The power tool according to claim 11 , wherein each of the concavities has first and second mutually perpendicular, axially extending walls.

13. The power tool according to claim 11 , wherein the core is formed from a plurality of laminations and wherein the permanent magnets are retained in the through holes by an injection molded resin body.

14. The power tool according to claim 11 , wherein the core is formed from a plurality of laminations and wherein the permanent magnets are retained in the through holes by a body of injection molded magnet material.

15. A power tool comprising:

a housing and

a brushless motor, the brushless motor including a stator and a rotor disposed inside the housing, the rotor including a rotor core having a plurality of axially extending through holes and a permanent magnet disposed in each of the plurality of through holes,

wherein:

the rotor includes a plurality of axially extending concavities in an outer surface of the rotor by which the rotor core is holdable in a desired circumferential orientation while the permanent magnets are inserted into the through holes,

the rotor further includes at least one convexity located between an adjacent pair of the concavities,

the rotor core viewed in cross section perpendicular to the axis of rotation comprises first and second pairs of opposed arc sections, each of the arc sections having a longest chord,

the adjacent pair of concavities are located on the outer surface of the rotor between circumferentially adjacent arc sections of the first and second pairs of arc sections,

each of the plurality of magnets is located adjacent one of the longest chords and is located radially inward of the respective adjacent longest chord,

each of the plurality of magnets includes a radially outer wall, the radially outer walls of the plurality of magnets lying on a side of a regular convex polygon,

each of the sides of the regular polygon extends along the outer wall of one of the plurality of magnets, and

the regular convex polygon extends beyond the outer surface of the rotor.

16. The power tool according to claim 15 , wherein the regular convex polygon is a square.

17. The power tool according to claim 16 , wherein each of the permanent magnets has a width greater than a length of the longest chord.

18. The power tool according to claim 15 , wherein each of the concavities has first and second mutually perpendicular, axially extending walls.

19. The power tool according to claim 15 , wherein the rotor core is formed from a plurality of laminations and the permanent magnets are retained in the through holes by an injection molded resin body.

20. The power tool according to claim 15 , wherein the rotor core is formed from a plurality of laminations and the permanent magnets are retained in the through holes by a body of injection molded magnetic material.