Electric motor
An electric motor includes a stator having multiple magnetic poles and a rotor rotatably mounted to the stator. The rotor includes a shaft, a commutator and a rotor core fixed to the shaft; and windings wound on the rotor core and electrically connected to the commutator. The rotor core is formed by stacking a plurality of laminations. Each lamination includes an inner ring having a hole for fixing the shaft; an outer ring radially spaced from the inner ring; multiple teeth extending outwardly from the outer ring, and multiple ribs connecting the inner ring to the outer ring. Each rib has a width w measured in a circumferential direction of the lamination. The number of ribs is n. The width w and the number n satisfy the formula: 0.75≤n×w 2 ≤64, where the width w is measured in millimeters.
1. An electric motor comprising:
a stator having a plurality of magnetic poles; and
a rotor rotatably mounted to the stator, the rotor comprising:
a shaft;
a commutator fixed to the shaft;
a rotor core comprising a stack of laminations fixed to the shaft and located adjacent to the commutator; and
rotor windings wound on the rotor core and electrically connected to the commutator,
wherein each lamination comprises:
an inner ring having a hole for fixing the shaft;
an outer ring radially spaced from the inner ring;
a plurality of teeth extending outwardly from the outer ring; and
a number of ribs connecting the inner ring to the outer ring, each rib having a width w measured in a circumferential direction of the lamination;
wherein the number of ribs is n, the width w and the number n satisfy the formula: 0.75≤n×w 2 ≤64, where the width w of each rib is measured in millimeters, reducing the harshness of the electric motor.
2. The motor of claim 1 , wherein the number n and the width w satisfy the formula: 6.75≤n×w 2 ≤18.
3. The motor of claim 1 , wherein n is three and w is 2.0 mm.
4. The motor of claim 1 , wherein n is three or four and w is 1.5 mm.
5. The motor of claim 1 , wherein n is three and w is 0.65 mm.
6. The motor of claim 1 , wherein n is four, and w is 4 mm.
7. The motor of claim 1 , wherein w is in the range of 0.60 mm-4 mm.
8. The motor of claim 1 , wherein each rib extends radially from the inner ring to the outer ring.
9. The motor of claim 1 , wherein each rib extends in a non-radial direction.
10. The motor of claim 9 , wherein each rib is inclined with respect to a radial direction crossing a radially inner end of the rib.
11. The motor of claim 9 , wherein each rib extends along a curved path from the inner ring to the outer ring.
12. The motor of claim 11 , wherein each rib is substantially S shaped.
13. The motor of claim 9 , wherein the ribs are arranged asymmetrically with respect to the rotational center of the lamination.
14. The motor of claim 13 , wherein each rib has a radially outer end, the radially outer ends of two adjacent ribs are angularly spaced from each other by a central angle, and the central angles between radially outer ends of different adjacent ribs are different.
15. The motor of claim 14 , wherein the central angle between radially outer ends of two adjacent ribs is between 66° to 78°.
16. The motor of claim 14 , wherein an average central angle is defined as 360°/n; and
a difference value between the average central angle and the central angle between radially outer ends of each two adjacent ribs is in the range of 0° to 6°.
17. The motor of claim 9 , wherein the width w is in the range of 1.0 mm to 3.0 mm.
18. A lamination for an electric motor, comprising:
an inner ring having a hole for fixing a shaft;
an outer ring radially spaced from the inner ring;
a plurality of teeth extending outwardly from the outer ring; and
a plurality of ribs connecting the inner ring to the outer ring, each rib having a width w measured in a circumferential direction of the lamination;
wherein the number of ribs is n, the width w and the number n satisfy the formula: 0.75≤n×w 2 ≤64, wherein the width w is measured in millimeters, reducing the harshness of the electric motor.
19. The lamination of claim 18 , wherein the number n and the width w satisfy the formula: 6.75≤n×w 2 ≤18.
20. The lamination of claim 18 , wherein the number of ribs is three and the width of each rib is 2.0 mm.
21. The lamination of claim 18 , wherein each rib extends in a non-radial direction.
22. The lamination of claim 18 , wherein each rib extends along a curved path from the inner ring to the outer ring.
23. The lamination of claim 18 , wherein the ribs are arranged asymmetrically with respect to the rotational center of the lamination.
24. The lamination of claim 23 , wherein each rib has a radially outer end, the radially outer ends of two adjacent ribs are angularly spaced from each other by a central angle, and the central angles between radially outer ends of different adjacent ribs are different.
25. The lamination of claim 24 , wherein an average central angle is defined as 360° divided by n, wherein n is the number of ribs; and
a difference value between the average central angle and the central angle between radially outer ends of each two adjacent ribs is in the range of 0° to 6°.