Rotor assembly for an electric machine and method for producing a rotor assembly

1. A rotor assembly for an electric machine, the rotor assembly comprising:

a rotor having a rotational axis extending in an axial direction of the rotor,

a first array of first cutouts extending parallel to the rotational axis and arranged radially spaced apart from the rotational axis by a first radial distance,

a second array of second cutouts extending parallel to the rotational axis and arranged radially spaced apart from the rotational axis by a second radial distance,

wherein the first cutouts have a first cross-section with a first geometric center located at the first radial distance,

the second cutouts have a second cross-section and a second geometric center located at the second radial distance,

the first cross-section and the second cross-section are not the same shape when viewed from a perspective of the rotational axis, and

a first balancing element that compensates for an unbalance of the rotor during rotation about the rotational axis,

wherein the first balancing element is attachable in one of the first cutouts by a press fitting connection between the one of the first cutouts and the first balancing element,

and a second balancing element attachable in one of the second cutouts by a press fitting connection between the one of the second cutouts and the second balancing element.

2. The rotor assembly of claim 1 , wherein the first cutouts and the second cutouts are arranged with a radial angle offset in relation to one another in the rotational direction with respect to the rotational axis.

3. The rotor assembly of claim 1 , wherein the first cross-section or the second cross-section have a surface with a geometry having at least two internal corners, each with an internal angle, wherein angle lines of symmetry of all the internal angles intersect at a point.

4. The rotor assembly of claim 3 , wherein the surface has a geometry defining a polygon with at least three sides and at least three internal corners, each with an internal angle.

5. The rotor assembly of claim 4 , wherein the surface has a geometry defining a polygon with equally long sides and equally large internal angles.

6. The rotor assembly of claim 3 , wherein the surface has a geometry defining at least two arcuate curves which connect the internal corners to one another.

7. The rotor assembly of claim 3 , wherein the surface has on at least one of the internal corners a corner rounded portion for reducing the notch stress at the at least one first cutout and/or the at least one second cutout.

8. The rotor assembly of claim 1 , further comprising a rotor laminated stack comprising a plurality of punched rotor sheet-metal disks, wherein at least one rotor sheet-metal disk includes punched holes the first array of first cutouts.

9. A method for producing a rotor assembly, the method comprising:

providing a plurality of similar sheet-metal disks, each having a center of gravity;

in at least one of the sheet-metal disks, cutting out a set of first holes spaced radially apart from the center of gravity of the respective sheet-metal disk at a first radial distance;

cutting out a set of second holes spaced radially apart from the center of gravity of the respective sheet-metal disk at a second radial distance; and

assembling the plurality of sheet-metal disks to form a rotor such that the set of first holes and the set of second holes define a first array and a second array, respectively, of cutouts configured for (a) receiving a balancing element that compensates for an unbalance of the rotor and (b) attaching the balancing element by a press fitting connection between at least one of the cutouts and the first balancing element;

wherein the first holes and the second holes have respective cross-sections of different shapes when viewed from a perspective of the center of gravity.

10. The method of claim 9 , further comprising pressing at least one balancing element into at least one cutout to compensate for the unbalance of the rotor such that a press fitting connection is created between the at least one cutout and the at least one balancing element.

11. An electric machine, comprising:

a rotor assembly comprising:

a rotor having a rotational axis extending in an axial direction of the rotor,

a first array of first cutouts extending parallel to the rotational axis and arranged radially spaced apart from the rotational axis by a first radial distance,

a second array of second cutouts extending parallel to the rotational axis and arranged radially spaced apart from the rotational axis by a second radial distance,

wherein the first cutouts have a first cross-section with a first geometric center located at the first radial distance,

the second cutouts have a second cross-section and a second geometric center located at the second radial distance,

the first cross-section and the second cross-section are not the same shape when viewed from the rotational axis, and

a first balancing element that compensates for an unbalance of the rotor during rotation about the rotational axis,

wherein the first balancing element is attachable in one of the first cutouts by a press fitting connection between the one of the first cutouts and the first balancing element,

and a second balancing element attachable in one of the second cutouts by a press fitting connection between the one of the second cutouts and the second balancing element.

12. The electric machine of claim 11 , wherein the first cutouts and the second cutouts are arranged with a radial angle offset in relation to one another in the rotational direction with respect to the rotational axis.

13. The electric machine of claim 11 , wherein the first cutouts or the second cutouts have a surface that comprises a geometry having at least two internal corners, each with an internal angle, wherein angle lines of symmetry of all the internal angles intersect at a point.

14. The electric machine of claim 13 , wherein the surface has a geometry defining a polygon with at least three sides and at least three internal corners, each with an internal angle.

15. The electric machine of claim 14 , wherein the surface has a geometry defining a polygon with equally long sides and equally large internal angles.

16. The electric machine of claim 13 , wherein the surface has a geometry defining at least two arcuate curves which connect the internal corners to one another.

17. The electric machine of claim 13 , wherein the surface has on at least one of the internal corners a corner rounded portion for reducing the notch stress at the at least one first cutout and/or the at least one second cutout.