Rotor with magnet retention band for use with electric machines
A rotor assembly for an electric machine includes a rotor segment configured to rotate about an axis and having a rotor body, a side wall and an outer band that cooperate to form a cavity, a plurality of magnets located in the cavity, and an end plate configured to block the plurality of magnets within the cavity.
1 . A rotor assembly for an electric machine, the rotor assembly comprising
a rotor segment configured to rotate about an axis, the rotor segment having a rotor body arranged circumferentially about the axis, a side wall that extends radially away from the rotor body, and an outer band that extends axially away from the side wall to form a cavity radially between the rotor body and the outer band, wherein the side wall is integrally formed with the rotor body, and the outer band has a first end integrally formed with the side wall and a terminal second end axially opposite the first end,
a plurality of magnets located in the cavity and configured to apply a radially outward force to the outer band during rotation of the rotor assembly, and
an end plate configured to block the plurality of magnets within the cavity, the end plate having a shaft body arranged circumferentially around the axis and a cover plate that extends radially outward from the shaft body, a radial outer end of the cover plate being coupled with the terminal second end of the outer band to radially retain the second end, and wherein the end plate is coupled with the rotor segment to cause the cover plate of the end plate and the side wall of the rotor segment to cooperate and apply an axial compressive force to the plurality of magnets to transfer at least a portion of the torque axially from the rotor segment to the plurality of magnets.
2 . The rotor assembly of claim 1 , wherein the rotor body, side wall, and outer band are made of a non-magnetic material.
3 . The rotor assembly of claim 2 , wherein the non-magnetic material is a non-conductive material.
4 . The rotor assembly of claim 1 , wherein the rotor segment further includes an inner band arranged radially inward of the outer band relative to the axis to cooperate with the outer band to form the cavity.
5 . The rotor assembly of claim 4 , wherein the inner band comprises ferrous material.
6 . The rotor assembly of claim 1 , wherein the rotor segment further includes fasteners that extend axially through the end plate and into the outer band.
7 . The rotor assembly of claim 1 , wherein the cover plate is formed to define an axially and circumferentially extending channel and the second end of the outer band is received within the channel.
8 . The rotor assembly of claim 1 , wherein the cover plate includes a plate body and an engagement ring that extends axially away from the plate body, the engagement ring having a predetermined axial width sized with the side wall to apply a desired axial force load on the plurality of magnets.
9 . The rotor assembly of claim 1 , wherein the rotor segment further comprises one or more projections coupled to and extending radially away from the outer band, the one or more projections being configured to move air axially along the axis during rotation of the rotor assembly.
10 . The rotor assembly of claim 9 , wherein the one or more projections form a helix.
11 . An electric machine adapted for use in an aircraft propulsion system, the electric machine comprising,
a stator including a plurality of windings extending along an axis and configured to rotate about the axis,
a rotor segment axially aligned with the stator and configured to rotate adjacent to the stator, the rotor segment including a rotor body arranged circumferentially about the axis, a side wall that extends radially away from the rotor body, and an outer band that extends axially away from the side wall to form a cavity radially between the rotor body and the outer band, the cavity being adapted to receive a plurality of magnets therein, wherein the outer band has a first end integrally formed with the side wall and a terminal second end axially opposite the first end, and
an end plate configured to seal the cavity and having a shaft body arranged circumferentially around the axis and coupled to a shaft of the electric machine, and a cover plate that extends radially outward from the shaft body and coupled to the outer band to cause the cover plate and the outer band to cooperate and block radial deflection of the terminal second end of the outer band to contain the plurality of magnets within the cavity during rotation of the shaft, the rotor segment, and the end plate.
12 . The electric machine of claim 11 , wherein the rotor body comprises a shaft band coupled to and arranged circumferentially about the shaft, a support band spaced radially outward of the shaft band and coupled to the side wall, and an intermediate band interconnecting the shaft band and the support band.
13 . The electric machine of claim 12 , wherein the inner band is positioned radially between the outer band and the support band.
14 . The electric machine of claim 12 , wherein the intermediate band extends axially away from the shaft band towards the end plate.
15 . The electric machine of claim 12 , wherein the shaft band, the intermediate band and the support band cooperate to define a U-shaped passageway positioned radially between the shaft band and the support band, wherein the U-shaped passageway includes an opening that is axially aligned with the side wall.
16 . The electric machine of claim 11 , wherein the rotor segment further includes an inner band arranged radially inward of the outer band relative to the axis to cooperate with the outer band to form the cavity.
17 . The electric machine of claim 16 , wherein the inner band comprises ferrous material.
18 . A method comprising
providing a rotor assembly having a rotor segment and an end plate, the rotor segment including a rotor body arranged circumferentially about an axis, a sidewall that extends radially away from the rotor body, and an outer band that extends axially away from the sidewall towards the end plate,
rotating the rotor assembly about the axis such that the end plate and the side wall cooperate and apply an axial compressive force to a plurality of magnets located inside a cavity formed radially between the outer band and the rotor body to transfer at least a portion of the torque axially from the rotor segment to the plurality of magnets.
19 . The method of claim 18 , wherein the rotor body, side wall, and outer band are made of a non-magnetic material.
20 . The method of claim 19 , wherein the non-magnetic material is a non-conductive material.