An electric motor includes a rotor and a stator. The stator is fixed with respect to the drive-unit housing and includes windings, and the rotor is configured to rotate inside the stator about an axis. An air gap is defined between the rotor and the stator. The electric motor also includes an end-ring fixed to the rotor for rotation therewith. The electric motor is cooled by gravity feed via a fluid flowing onto and past the stator windings, from the windings to the rotor, and from the rotor back to the stator. The end-ring includes an annular channel configured to catch the fluid flowing from the windings to the rotor and divert the fluid away from the air gap as the fluid flows from the rotor back to the stator, thereby limiting spin losses in the electric motor. An electro-mechanical drive-unit employing the above-described electric motor is also disclosed.
1. An electro-mechanical drive-unit connectable with at least one power source for launching and propelling a vehicle, comprising:
an input member and an output member;
a drive-unit housing;
a gearing arrangement operatively connected to each of the output and input members;
a pump configured to circulate fluid inside the drive-unit housing; and
an electric motor including:
a stator fixed with respect to the drive-unit housing and having windings;
a rotor operatively connected to the gearing arrangement and configured to rotate within the stator about an axis, wherein an air gap is defined between the rotor and the stator; and
an end-ring fixed to the rotor for rotation therewith;
wherein:
the electric motor is cooled by gravity feed via the fluid flowing onto and past the windings of the stator, from the windings to the rotor and an interior portion of the rotor, and draining from the rotor back to the stator;
the end-ring includes an annular channel configured to catch the fluid flowing from the windings to the rotor and divert the fluid away from the air gap as the fluid flows from the rotor back to the stator, thereby limiting spin losses in the electric motor;
in a cross-sectional view the end-ring includes a stepped portion and the channel is arranged at least partially in the stepped portion; and
the stepped portion is configured to guide away from the air gap the fluid that drains from the interior portion of the rotor.
2. The electro-mechanical drive-unit according to claim 1 , wherein the end-ring includes an outer circumference, and wherein the channel extends continuously around the outer circumference.
3. The electro-mechanical drive-unit according to claim 2 , wherein the outer circumference includes a sharp edge positioned in a plane that is perpendicular to the axis, and wherein the sharp edge is configured to generate detachment of the fluid from the end-ring.
4. The electro-mechanical drive-unit according to claim 1 , wherein in the cross-sectional view the channel includes a slanted profile configured to direct the fluid away from the air gap.
5. The electro-mechanical drive-unit according to claim 1 , wherein the stepped portion includes a section having increased amount of material relative to remainder of the stepped portion, and wherein the section is configured for balancing of the rotor by removal of at least some of the increased amount of material from the section.
6. The electro-mechanical drive-unit according to claim 1 , wherein the end-ring is constructed from a non-magnetic material.
7. The electro-mechanical drive-unit according to claim 1 , wherein the end-ring is attached to the rotor via at least one of a press-fit, staking, and welding.
8. An electric motor comprising:
a stator having windings;
a rotor configured to rotate within the stator about an axis, wherein an air gap is defined between the rotor and the stator; and
an end-ring fixed to the rotor for rotation therewith;
wherein:
the electric motor is cooled by gravity feed via a fluid flowing onto and past the windings of the stator, from the windings to the rotor and an interior portion of the rotor, and draining from the rotor back to the stator; and
the end-ring includes an annular channel configured to catch the fluid flowing from the windings to the rotor and divert the fluid away from the air gap as the fluid flows from the rotor back to the stator, thereby limiting spin losses in the electric motor;
in a cross-sectional view the end-ring includes a stepped portion and the channel is arranged at least partially in the stepped portion; and
the stepped portion is configured to guide away from the air gap the fluid that drains from the interior portion of the rotor.
9. The electric motor according to claim 8 , wherein the end-ring includes an outer circumference, and wherein the channel extends continuously around the outer circumference.
10. The electric motor according to claim 9 , wherein the outer circumference includes a sharp edge positioned in a plane that is perpendicular to the axis, and wherein the sharp edge is configured to generate detachment of the fluid from the end-ring.
11. The electric motor according to claim 8 , wherein in the cross-sectional view the channel includes a slanted profile configured to direct the fluid away from the air gap.
12. The electric motor according to claim 8 , wherein the stepped portion includes a section having increased amount of material relative to remainder of the stepped portion, and wherein the section is configured for balancing of the rotor by removal of at least some of the increased amount of material from the section.
13. The electric motor according to claim 8 , wherein the end-ring is constructed from a non-magnetic material.
14. The electric motor according to claim 13 , wherein the end-ring is attached to the rotor via at least one of a press-fit, staking, and welding.
15. An electric motor comprising:
a stator having windings;
a rotor configured to rotate within the stator about an axis, wherein an air gap is defined between the rotor and the stator; and
an end-ring fixed to the rotor for rotation therewith;
wherein:
the electric motor is cooled by gravity feed via a fluid flowing onto and past the windings of the stator, from the windings to the rotor and an interior portion of the rotor, and draining from the rotor back to the stator;
the end-ring includes an annular channel configured to catch the fluid flowing from the windings to the rotor and divert the fluid away from the air gap as the fluid flows from the rotor back to the stator, thereby limiting spin losses in the electric motor;
the end-ring includes an outer circumference, and wherein the channel extends continuously around the outer circumference;
in a cross-sectional view the end-ring includes a stepped portion and the channel is arranged at least partially in the stepped portion; and
the stepped portion is configured to guide away from the air gap the fluid that drains from the interior portion of the rotor and includes a section having increased amount of material relative to remainder of the stepped portion, such that the section is configured for balancing of the rotor by removal of at least some of the increased amount of material from the section.
16. The electric motor according to claim 15 , wherein in the cross-sectional view the channel includes a slanted profile configured to direct the fluid away from the air gap.
17. The electric motor according to claim 15 , wherein the outer circumference includes a sharp edge positioned in a plane that is perpendicular to the axis, and wherein the sharp edge is configured to generate detachment of the fluid from the end-ring.