Motor

1. A brushless DC motor configured to convert an alternating current to a direct current and to generate a torque with resulting direct current, the motor comprising:

a stationary portion fixed to a frame of an apparatus to be driven by the motor through a support member; and

a rotating portion configured to rotate about a central axis extending in a vertical direction relative to the stationary portion; wherein

the rotating portion includes:

a shaft extending along the central axis;

a rotor holder including a top plate portion extending around the shaft, and a cylindrical wall portion extending axially downward from an outer end portion of the top plate portion; and

a magnet fixed to an inner circumferential surface of the wall portion directly or through a yoke;

the stationary portion includes:

a bearing portion configured to rotatably support the shaft;

a housing including a cylindrical bearing holding portion configured to hold the bearing portion;

a plurality of coils arranged in a circumferential direction radially outside the housing and radially inside the magnet;

an attachment portion fixed to each of the housing and the support member either directly or indirectly through another member; and

a circuit portion electrically connected to the coils;

the circuit portion includes:

a plate-shaped first circuit board located axially below the coils and axially above the attachment portion, and to which end portions of conducting wires defining the coils are connected;

a plate-shaped second circuit board located axially below the attachment portion, and arranged to have an AC to DC conversion portion mounted thereon; and

an electrical connection portion configured to electrically connect the first and second circuit boards to each other;

the first circuit board includes a through hole or a cut-out defined therein;

the housing extends in the vertical direction through the through hole or the cut-out;

the second circuit board includes:

a first region axially aligned with the first circuit board;

a second region axially aligned with the through hole or the cut-out; and

a third region which does not axially overlap with any of the first circuit board, the through hole, or the cut-out; and

the support member is fixed to the third region;

the attachment portion includes:

a central portion fixed to the housing; and

a plurality of arm portions, each of which is arranged to extend radially outward from the central portion; and

each arm portion is fixed to the support member.

2. The motor according to claim 1 , further comprising a sensor configured to detect a rotational position of the rotating portion, and mounted on an upper surface of the first circuit board.

3. The motor according to claim 2 , wherein the AC to DC conversion portion is mounted on a lower surface of the second circuit board.

4. The motor according to claim 3 , wherein the AC to DC conversion portion includes an electrolytic capacitor.

5. The motor according to claim 4 , further comprising a transistor array mounted on a lower surface of the second circuit board.

6. The motor according to claim 5 , further comprising a control IC mounted on the lower surface of the second circuit board.

7. The motor according to claim 1 , wherein

the first circuit board includes a body portion that is circular or substantially circular in a plan view;

the second circuit board is circular or substantially circular in a plan view; and

the body portion has an outside diameter smaller than an outside diameter of the second circuit board.

8. The motor according to claim 7 , wherein the support member is fixed to the second circuit board at a position radially outward of the body portion.

9. The motor according to claim 8 , wherein the electrical connection portion includes at least one of a connector or a lead wire.

10. The motor according to claim 9 , wherein the attachment portion is a plate-shaped member extending perpendicularly or substantially perpendicularly to the central axis.

11. The motor according to claim 1 , wherein the second circuit board is fixed to the support member at a circumferential position different from a circumferential position of each arm portion.

12. The motor according to claim 11 , wherein each arm portion is fixed to the support member at a position axially overlapping with the third region of the second circuit board.

13. The motor according to claim 12 , wherein

each arm portion includes a board contact surface arranged at an axial level higher than that of an upper surface of the central portion; and

a lower surface of the first circuit board is arranged to be in contact with the board contact surface.

14. The motor according to claim 13 , wherein

each arm portion includes a board fixing portion including at least a portion of the board contact surface; and

the first circuit board is fixed to the board fixing portion.

15. The motor according to claim 14 , wherein the attachment portion is directly fixed to the support member.

16. The motor according to claim 1 , wherein

a lower end portion of the housing is arranged axially above an upper surface of the second circuit board; and

neither the first region nor the second region of the second circuit board includes a through hole or a cut-out used to arrange any other member therein.

17. The motor according to claim 16 , wherein

the stationary portion further includes:

a stator core arranged radially outside the housing and radially inside the magnet; and

an insulator made of resin and attached to the stator core;

the insulator includes:

an insulating portion located to intervene between the stator core and the coils;

a leg portion arranged to extend axially downward from the insulating portion, with a lower end portion of the leg portion being located axially below the coils; and

a claw portion arranged to project radially outward from the lower end portion of the leg portion; and

a lower surface of the first circuit board is arranged to be in contact with an upper surface of the claw portion.

18. The motor according to claim 17 , wherein an upper end portion of the shaft is arranged axially above an upper surface of the top plate portion.