Electric motor rotor with circulated air cooling
A rotor for an electric machine includes an air circulation cooling system. The rotor includes a rotor core having cavities internal to the rotor core. The rotor core extends longitudinally between two ends. The cavities are defined by the rotor core. The cavities extend through the rotor core and open through at least one of the ends. The rotor core operates to circulate air through the cavities by rotation of the rotor core.
1 . A rotor system with an air circulation cooling system for an electric machine, the rotor system comprising:
a shaft configured to rotate about an axis;
a rotor core having a first axial end, a second axial end, a radially outer surface, and at least one cavity internal to the rotor core and passages in an outer perimeter of the rotor core at the radially outer surface, the rotor core disposed on the shaft and extending along the axis from the first axial end to the second axial end, with a first void defined as a first space axially adjacent to the first axial end and outside the rotor core and a second void defined as a second space axially adjacent to the second axial end and outside the rotor core, and
a first end ring and a second end ring, wherein:
the rotor core includes laminations stacked together in a stack,
the first end ring is disposed against a first end of the stack and the second end ring is disposed at a second end of the stack,
the at least one cavity comprises a first cavity and a second cavity that extend axially through the laminations of the rotor core,
the cavities are configured as flux barriers,
the first cavity has a first radial end and a second radial end, wherein the first radial end is disposed radially inward from the second radial end,
the second cavity has a third radial end and a fourth radial end, wherein the third radial end is disposed radially inward from the fourth radial end, and
the first end ring includes an entry opening that registers with the first cavity at the first radial end and with the second cavity at the third radial end,
the passages extend through an entirety of the rotor core in an axial direction from the first axial end to the second axial end,
the at least one cavity extends through the rotor core and opens through at least one of the first axial end into the first void and the second axial end into the second void and the rotor core is configured to circulate an air flow through the at least one cavity by rotation of the rotor core, and
an air circuit is defined through the at least one cavity of the rotor core, through the first void, through the passages, through the second void, and back into the at least one cavity, the air circuit defining a path through which the air flow circulates during rotation of the rotor core.
2 . The rotor system of claim 1 , wherein the passages comprise grooves that extend through the laminations and openings that are scallop shaped in both the first end ring and the second end ring, wherein the openings register with the grooves.
3 . The rotor system of claim 1 , wherein at least one of the first end ring and the second end ring includes a ramp registering with the entry opening, the ramp configured to induce the air flow into the at least one cavity.
4 . The rotor system of claim 1 , wherein:
the at least one cavity extends completely through the laminations, and
the second end ring includes an exit opening that registers with the at least one cavity.
5 . The rotor system of claim 4 , comprising a stator disposed around the rotor core with an air gap defined between the rotor core and the stator, wherein a radial passage opens the cavities into the air gap.
6 . The rotor system of claim 1 , comprising a stator disposed around the rotor core with a gap defined between the stator and the rotor core, wherein the laminations of the rotor core comprise a lamination stack and comprising:
a blocking plate disposed in the lamination stack of the rotor core, the blocking plate extending from the shaft radially outward and continuously to the outer perimeter disposed in the gap between the rotor core and the stator; and
wherein a first air circuit is defined on a first side of the blocking plate and a second air circuit is defined on a second side of the blocking plate, with the air flow split at the blocking plate and directed axially outward in the gap into two split flows in opposite directions from the blocking plate.
7 . The rotor system of claim 6 , wherein two complete air circuits are defined through the rotor core, wherein the two complete air circuits are directed through the gap axially in their entirety.
8 . The rotor system of claim 1 , comprising a first opening defined through the first end ring and a second opening defined through the second end ring, wherein:
the second opening defines an exit from the at least one cavity;
a first ramp is defined in the first end ring adjacent to and leading into the entry opening, and the first ramp slopes inward from an exterior surface of the first end ring;
a second ramp is defined in the second end ring adjacent to and leading out of the exit;
the entry opening has a first radial dimension and the first ramp has a second radial dimension, wherein the first radial dimension is approximately the same as the second radial dimension;
the exit has a third radial dimension and the second ramp has a fourth radial dimension, wherein the third radial dimension is approximately the same as the fourth radial dimension; and
the first end ring is identical to the second end ring and the first opening is configured to induce the air flow into the rotor core and the second opening is configured to educe the air flow out of the rotor core.
9 . The rotor system of claim 1 , wherein the shaft includes a liquid opening and a bore that opens the liquid opening to at least one of the first void and the second void.
10 . The rotor system of claim 1 , comprising an oil circuit configured to provide cooling of the electric machine by a liquid and comprising a stator, with an air gap defined between the stator and the rotor core, wherein the rotor core includes grooves configured to recirculate the air flow in the air circuit around the rotor core, wherein the air flow is induced solely by rotation of the rotor core without an air pump, the air circuit configured to inhibit the liquid from entering the air gap.
11 . A rotor system with an air circulation cooling system for an electric machine, the rotor system comprising:
a shaft configured to rotate about an axis;
a rotor core having a first axial end, a second axial end, a radially outer surface and a plurality of cavities internal to the rotor core and passages in an outer perimeter of the rotor core at the radially outer surface, the rotor core disposed on the shaft and extending along the axis from the first axial end to the second axial end with a first void defined as a first space axially adjacent to the first axial end and outside the rotor core and a second void defined as a second space axially adjacent to the second axial end and outside the rotor core, and
a lamination stack in the rotor core with a first end ring on one end of the lamination stack and a second end ring on another end of the lamination stack, with a first opening defined through the first end ring and a second opening defined through the second end ring, wherein:
the first opening defines an entry into at least one cavity of the plurality of cavities;
the second opening defines an exit from the at least one cavity;
a first ramp is defined in the first end ring adjacent to and leading into the entry, and the first ramp slopes inward from an exterior surface of the first end ring;
a second ramp is defined in the second end ring adjacent to and leading out of the exit;
the entry has a first radial dimension and the first ramp has a second radial dimension, wherein the second radial dimension is narrower than the first radial dimension to tune an air flow into the entry;
the exit has a third radial dimension and the second ramp has a fourth radial dimension, wherein the fourth radial dimension is narrower than the third radial dimension to tune the air flow out of the exit; and
the first end ring is identical to the second end ring and the first opening is configured to induce the air flow into the rotor core and the second opening is configured to educe the air flow out of the rotor core,
the passages extend through an entirety of the rotor core in an axial direction from the first axial end to the second axial end,
the plurality of cavities extend through the rotor core and open through at least one of the first axial end into the first void and the second axial end into the second void,
the rotor core is configured to circulate the air flow through the plurality of cavities by rotation of the rotor core, and
an air circuit is defined through the at least one cavity of the rotor core, through the first void, through the passages, through the second void, and back into the at least one cavity, the air circuit defining a path through which the air flow circulates during rotation of the rotor core.
12 . The rotor system of claim 11 , wherein each of the first end ring and the second end ring includes openings that register with the plurality of cavities, wherein the passages comprise grooves that extend through the lamination stack and openings that are scallop shaped in both the first end ring and the second end ring, wherein the openings register with the grooves.
13 . The rotor system of claim 11 , wherein the first end ring and the second end ring each include the entry as openings that register with the plurality of cavities, wherein at least one of the first end ring and the second end ring includes ramps registering with the openings, the ramps configured to induce the air flow into the plurality of cavities.
14 . The rotor system of claim 11 , wherein:
the plurality of cavities extend completely through the lamination stack,
the first end ring includes the entry as openings that register with the plurality of cavities, and
the second end ring includes exit openings that register with the plurality of cavities.
15 . The rotor system of claim 14 , comprising a stator disposed around the rotor core with an air gap defined between the rotor core and the stator, wherein a radial passage opens the cavities into the air gap.
16 . The rotor system of claim 11 , comprising a stator disposed around the rotor core with a gap defined between the stator and the rotor core, and comprising:
a blocking plate disposed in the lamination stack of the rotor core, the blocking plate extending from the shaft radially outward and continuously to the outer perimeter disposed in the gap between the rotor core and a stator;
the entry includes first entry openings defined through the first end ring and second entry openings defined through the second end ring,
wherein a first air circuit is defined on a first side of the blocking plate and a second air circuit is defined on a second side of the blocking plate, with the air flow split at the blocking plate and directed axially outward in the gap into two split flows in opposite directions from the blocking plate.
17 . The rotor system of claim 16 , wherein two complete air circuits are defined through the rotor core, wherein the two complete air circuits are directed through the gap axially in their entirety.
18 . The rotor system of claim 11 , wherein the shaft includes a liquid opening and a bore that opens the liquid opening to at least one of the first void and the second void.
19 . The rotor system of claim 11 , wherein:
the first end ring is disposed against a first end of the stack and the second end ring is disposed at a second end of the stack,
wherein the at least one cavity comprises a first cavity and a second cavity that extend axially through the lamination stack of the rotor core,
the cavities are configured as flux barriers,
the first cavity has a first radial end and a second radial end, wherein the first radial end is disposed radially inward from the second radial end,
the second cavity has a third radial end and a fourth radial end, wherein the third radial end is disposed radially inward from the fourth radial end, and
the first end ring includes the entry that registers with the first cavity at the first radial end and with the second cavity at the third radial end.
20 . A rotor system with an air circulation cooling system for an electric machine of a vehicle, the rotor system comprising:
a shaft configured to rotate about an axis;
a rotor core having a first axial end, a second axial end, a radially outer surface and a plurality of cavities internal to the rotor core and passages in an outer perimeter of the rotor core at the radially outer surface, the rotor core disposed on the shaft and extending along the axis from the first axial end to the second axial end with a first void defined as a first space axially adjacent to the first axial end and outside the rotor core and a second void defined as a second space axially adjacent to the second axial end and outside the rotor core, wherein the passages extend through an entirety of the rotor core in an axial direction from the first axial end to the second axial end;
a stator disposed around the rotor core with an air gap defined between the stator and the rotor core, wherein the rotor core comprises a lamination stack;
a blocking plate disposed in the lamination stack of the rotor core, the blocking plate extending from the shaft radially outward and continuously to the outer perimeter disposed in the gap between the rotor core and the stator;
a first end ring on one end of the lamination stack; and
a second end ring on another end of the lamination stack, with a first entry opening defined through the first end ring and a second entry opening defined through the second end ring,
wherein a first air circuit is defined on a first side of the blocking plate and a second air circuit is defined on a second side of the blocking plate, with an air flow that is split at the blocking plate and directed axially outward in the air gap into two split flows in opposite directions from the blocking plate,
wherein the plurality of cavities extend through the rotor core and open through at least one of the first axial end into the first void and the second axial end into the second void,
wherein the rotor core is configured to circulate the air flow through the plurality of cavities and through the air gap by rotation of the rotor core,
wherein at least one of the first air circuit and the second air circuit is defined through the at least one of the cavities of the rotor core, through the first void, through the passages, through the second void, and back into the at least one cavity, at least one of the first air circuit and the second air circuit defining a path through which the air flow circulates during rotation of the rotor core.