Commutator having conductive rings

1. A commutator comprising:

a substantially tubular insulating core;

a first conductive ring fixed to the core;

a plurality of first bars electrically connected to the first conductive ring;

a second conductive ring fixed to the core; and

a plurality of second bars electrically connected to the second conductive ring;

wherein the first bars and the second bars are fixed to the outer surface of the core and are alternately arranged at equally spaced intervals in the circumferential direction of the core, the first conductive ring and the second conductive ring are arranged on the same side of the all first bars and the all second bars; the first and second conductive rings respectively comprise a top-planar contact surface that is substantially perpendicular to an axis of the commutator and the top-planar contact surface is configured for contacting brushes;

wherein the top-planar contact surfaces of the first and second conductive rings are substantially perpendicular to cylindrical contact surfaces of the plurality of first and second bars.

2. The commutator of claim 1 , wherein the first bars are integrally formed with the first conductive ring as a single piece stamping, and the second bars are integrally formed with the second conductive ring as a single piece stamping.

3. The commutator of claim 1 , wherein the first conductive ring is spaced from the second conductive ring in the axial direction of the commutator.

4. The commutator of claim 3 , wherein the core comprises a and a tubular body substantially perpendicular to the plate relative to a longitudinal axis, the plate is sandwiched between the first and second conductive rings, and the first and second bars are fixed to the outer surface of the tubular body.

5. The commutator of claim 4 , wherein the first conductive ring is disposed on a side of the plate that faces away from the tubular body, the second conductive ring is disposed on a side of the plate that faces towards the tubular body, and the first bars pass through the plate to electrically connect to the first conductive ring.

6. The commutator of claim 5 , wherein the outer diameter of the second conductive ring is greater than that of a circle formed by the first and second bars, the outer diameter of the first conductive ring is greater than that of the second conductive ring.

7. The commutator of claim 1 , wherein the second conductive ring is surrounded by the first conductive ring.

8. The commutator of claim 7 , wherein the outer diameter of the first conductive ring is substantially equal to that of a circle formed by the first bars and the second bars.

9. The commutator of claim 7 , wherein the first conductive ring comprises a ring-shaped extension axially extending from an edge thereof, the first bars comprise a protrusion axially protruding from an axial end thereof, the protrusions are surrounded by and electrically connected to the extension.

10. The commutator of claim 1 , wherein outer surfaces of the first and the second bars form the cylindrical contact surface for contacting brushes.

11. The commutator of claim 1 , wherein the top-planar contact surfaces of the first and second conductive rings are not coplanar with the cylindrical contact surfaces of the plurality of first and second bars.

12. The commutator of claim 1 , wherein the plurality of first bars are positioned above the first conductive ring, and the plurality of second bars are positioned above the second conductive ring along an axial direction of the commutator.

13. The commutator of claim 1 , wherein the top-planar contact surface of the second conductive ring covers a portion of the top-planar contact surface of the first conductive ring.

14. The commutator of claim 1 , wherein top surfaces of the plurality of first and second bars are coplanar along an axial direction of the commutator.