Motor and electric power steering device

1. A motor comprising:

a rotor including a shaft extending in an axial direction;

a stator surrounding a radially outer side of the rotor;

a heat sink axially above the stator; and

a board that is axially above the heat sink and on which an electronic component is mounted; wherein

the stator includes a coil around which a coil wire is wound and a busbar to which the coil wire is connected;

the heat sink includes a first portion and a second portion that is located on a circumference identical to the first portion and that extends along a circumferential direction;

an axial thickness of the first portion is larger than an axial thickness of the second portion;

a lower surface of the second portion is located axially above a lower surface of the first portion; and

the busbar is located axially below the second portion.

2. The motor according to claim 1 , wherein

the second portion includes a recess recessed axially upward; and

a connection portion between the busbar and the coil wire is located axially below the recess.

3. The motor according to claim 1 , wherein the heat sink further includes a fixing portion provided radially outside of the first portion.

4. The motor according to claim 1 , wherein the stator includes:

a stator core including an annular core back; and

a plurality of teeth that extend from the core back in a radial direction and that are provided in the circumferential direction;

the coil wire includes an output wire end connected to the board and a ground wire end connected to the busbar;

a slot is provided between the teeth adjacent in the circumferential direction; and

at least one of a plurality of the output wire ends is drawn out from the slot identical to another ground wire end.

5. The motor according to claim 1 , wherein the stator includes:

a stator core including an annular core back; and

a plurality of teeth that extend from the core back in a radial direction and that are provided in the circumferential direction;

the coil wire includes a output wire end connected to the board and a ground wire end connected to the busbar;

a slot is provided between the teeth adjacent in the circumferential direction;

the coil wire includes a crossover portion connecting the coil and the output wire end or the ground wire end, the crossover portion extending in the circumferential direction;

the crossover portion is located axially below the heat sink; and

at least one of a plurality of the crossover portions connects the coil located at a position overlapping the first portion when viewed in the axial direction and the output wire end or the ground wire end located at a position overlapping the second portion when viewed in the axial direction.

6. The motor according to claim 1 , wherein

the stator further includes a busbar holder that holds the busbar;

the heat sink includes:

an inner region; and

an outer region located radially outside of the inner region;

an axial thickness of the inner region is larger than an axial thickness of the outer region;

a lower surface of the outer region is located axially above a lower surface of the inner region;

the inner region at least partially overlaps the electronic component in the axial direction;

the busbar holder is located axially below the outer region, and overlaps the inner region in the radial direction; and

the outer region includes the first portion and the second portion.

7. The motor according to claim 6 , further comprising:

a bearing that rotatably supports the shaft; wherein

the heat sink holds the bearing; and

the bearing and the busbar holder overlap each other in the radial direction.

8. The motor according to claim 6 , wherein

the heat sink further includes an outer wall portion on a radially outer side of the outer region; and

the outer wall portion surrounds a radially outer side of the busbar holder.

9. The motor according to claim 8 , wherein an axial thickness of the outer wall portion is larger than an axial thickness of the inner region.

10. The motor according to claim 8 , wherein at least a portion of the outer wall portion is exposed to an outside.

11. The motor according to claim 6 , wherein the inner region includes:

an inner wall portion extending axially downward at a radially inner end; and

a rib on a lower surface and extending radially outward from the inner wall portion.

12. The motor according to claim 6 , wherein the stator includes:

a stator core including a plurality of core backs disposed in the circumferential direction; and

an insulator covering at least a portion of the stator core; and

the busbar holder is fixed to a radially outer side of the insulator or an axial upper side of the core back.

13. The motor according to claim 1 , wherein the second portion includes a through hole through which the coil wire is inserted.

14. An electric power steering device comprising the motor according to claim 1 .