Cooling arrangement for an electric machine, and electric machine

1. A cooling arrangement for a heat-generating, rotating component of an electric machine ( 1 , 1 a , 1 b ), comprising:

a rotor shaft ( 2 ) extending in an axial direction (A) along an axis of rotation (D), a rotor shaft outer side ( 5 ) of the rotor shaft ( 2 ) extending in the axial direction (A), each of a first front-end ( 31 ) of the rotor shaft ( 2 ) and a second front-end ( 26 ) of the rotor shaft ( 2 ) positioned at a respective end of the rotor shaft ( 2 ) in the axial direction (A);

a rotatably mounted hollow shaft ( 11 ) mounted coaxially to the rotor shaft ( 2 ) and rotationally fixed to the rotor shaft ( 2 ), a hollow shaft inner side ( 12 ) of the hollow shaft ( 11 ) facing the rotor shaft outer side ( 5 ), a hollow shaft outer side ( 13 ) of the hollow shaft ( 11 ) positioned opposite the hollow shaft inner side ( 12 ), the hollow shaft inner side ( 12 ) spaced apart from the rotor shaft outer side ( 5 ) in a radial direction (R) in order to form an annular gap ( 14 );

at least one cooling duct for a cooling lubricant, the at least one cooling duct comprising a hollow shaft duct ( 18 ), a feed duct ( 20 ), and an outlet duct ( 25 ),

wherein the hollow shaft duct ( 18 ) is positioned between the hollow shaft inner side ( 12 ) and the hollow shaft outer side ( 13 ) and extends in the axial direction (A),

wherein the feed duct ( 20 ) opens into the hollow shaft duct ( 18 ) in order to feed the cooling lubricant to the hollow shaft duct ( 18 ), and

wherein the outlet duct ( 25 ) extends from the hollow shaft duct ( 18 ) to the annular gap ( 14 ) in order to release the cooling lubricant flowing through the hollow shaft duct ( 18 ) into the annular gap ( 14 ).

2. The cooling arrangement of claim 1 , wherein the hollow shaft duct ( 18 ) extends in the axial direction (A) parallel to the hollow shaft outer side ( 13 ).

3. The cooling arrangement of claim 1 , wherein the feed duct ( 20 ) is arranged facing the first front-end ( 31 ) and the outlet duct ( 25 ) is arranged facing the second front-end ( 26 ).

4. The cooling arrangement of claim 1 , further comprising a transmitter wheel ( 3 ) with a distribution duct ( 37 ) for the cooling lubricant, a first rotor shaft-facing side of the transmitter wheel ( 3 ) arranged at the first front-end ( 20 ) of the rotor shaft ( 2 ) and rotationally fixed to the first front-end ( 20 ) of the rotor shaft ( 2 ), a second side of the transmitter wheel ( 3 ) facing away from the rotor shaft ( 2 ) and positioned opposite the first rotor shaft-facing side of the transmitter wheel ( 3 ), the distribution duct ( 37 ) arranged in the transmitter wheel ( 3 ), the distribution duct ( 37 ) open toward the second side of the transmitter wheel ( 3 ).

5. The cooling arrangement of claim 4 , further comprising:

a rotationally fixed bearing cover ( 4 ) for mounting the transmitter wheel ( 3 ), the bearing cover ( 4 ) arranged on the second side of the transmitter wheel ( 3 ), the bearing cover ( 4 ) comprising a passage that extends in the axial direction (A) and is adjacent the distribution duct ( 37 ); and

a hydraulic connecting bush ( 40 ) and a hydraulic screw connection ( 41 ), the hydraulic connecting bush ( 40 ) arranged in the passage, the hydraulic screw connection ( 41 ) clamped to the hydraulic connecting bush ( 40 ) such that the hydraulic screw connection ( 41 ) forms a fluid connection with the distribution duct ( 37 ) via the hydraulic connecting bush ( 40 ).

6. The cooling arrangement of claim 5 , wherein the hydraulic screw connection ( 41 ) is L-shaped.

7. The cooling arrangement of claim 4 , further comprising a rotationally fixed bearing cover ( 4 ) for mounting the transmitter wheel ( 3 ), the bearing cover ( 4 ) arranged on the second side of the transmitter wheel ( 3 ), the bearing cover ( 4 ) comprising a continuous, L-shaped bearing cover bore ( 23 ) fluidically connected to the distribution duct ( 37 ) such that the cooling lubricant is flowable into the distribution duct ( 37 ) via the bearing cover bore ( 23 ).

8. The cooling arrangement of claim 1 , wherein the feed duct ( 20 ) is a continuous bore through the transmitter wheel ( 3 ) and the hollow shaft ( 11 ), the bore intersecting the hollow shaft duct ( 18 ) at a first point of intersection (S 1 ) such that the cooling lubricant is flowable from the feed duct ( 20 ) into the hollow shaft duct ( 18 ), the continuous bore comprising a seal to block leakage of the cooling lubricant at the hollow shaft outer side ( 13 ).

9. The cooling arrangement of claim 1 , wherein the outlet duct ( 25 ) is a continuous bore through the hollow shaft ( 11 ), the continuous bore intersecting the hollow shaft duct ( 18 ) at a second point of intersection (S 2 ) such that the cooling lubricant is flowable from the hollow shaft duct ( 18 ) into the annular gap ( 14 ) via the outlet duct ( 25 ), the continuous bore comprising a seal to block leakage of the cooling lubricant at the hollow shaft outer side ( 13 ).

10. The cooling arrangement of claim 1 , further comprising multiple cooling ducts distributed over a circumference of the hollow shaft ( 11 ), the multiple cooling ducts spaced equidistantly from one another.

11. The cooling arrangement of claim 1 , wherein the hollow shaft outer side ( 13 ) comprises a cylindrical lateral surface.

12. The cooling arrangement of claim 11 , wherein the cylindrical lateral surface comprises multiple longitudinal grooves ( 32 ) arranged in parallel to one another and extending along the axial direction (A).

13. The cooling arrangement of claim 12 , wherein the multiple parallel longitudinal grooves ( 32 ) are uniformly distributed over a circumference of the hollow shaft outer side ( 13 ).

14. An electric machine ( 1 , 1 a , 1 b ), comprising the cooling arrangement of claim 1 and a rotor ( 27 ) mounted coaxially to the hollow shaft ( 11 ), the rotor ( 27 ) rotationally fixed to the hollow shaft ( 11 ).

15. A method for cooling the rotor in the electric machine ( 1 , 1 a , 1 b ) of claim 14 , the method comprising:

guiding cooling lubricant out of a cooling lubricant sump with a cooling lubricant line to a bearing cover ( 4 );

flowing the cooling lubricant into the distribution duct ( 37 ) via the bearing cover ( 4 ), and flowing the cooling lubricant through the distribution duct ( 37 ) to at least one cooling duct;

flowing the cooling lubricant into the at least one cooling duct, which is fluidically connected to the distribution duct ( 37 ), and flowing the cooling lubricant through the at least one cooling duct to the annular gap ( 14 );

flowing the cooling lubricant into the annular gap ( 14 ), which is fluidically connected to the at least one cooling duct, and flowing the cooling lubricant through the annular gap ( 14 ) to a return duct ( 30 ); and

flowing the cooling lubricant into the return duct ( 30 ) and guiding the cooling lubricant to the cooling lubricant sump fluidically connected to the return duct ( 30 ).