Electric motor

1. An electric motor having an internal stator ( 21 ) and an external rotor ( 2 ), said external rotor ( 2 ) including a rotor housing ( 3 ) and a plurality of magnets ( 9 ) and being adapted to rotate, in operation, about a rotation axis ( 10 ) of said rotor, wherein

said magnets ( 9 ) are formed as bar magnets,

said rotor housing ( 3 ) has an inner surface ( 7 ), a first axial end ( 5 ), and a second axial end ( 6 ) located opposite the first end ( 5 ), said inner surface ( 7 ) being formed with respective receiving surfaces ( 11 ) adapted to receive said bar magnets ( 9 );

said receiving surfaces ( 11 ) each define, with respect to a remainder of said inner surface ( 7 ), a channel depression ( 13 ),

said receiving surfaces ( 11 ) have formed at least predominantly planar both in a direction parallel to the rotation axis ( 10 ) of the rotor housing ( 3 ) and in a circumferential direction along the inner surface ( 7 ),

wherein said bar magnets ( 9 ) are respectively fastened onto one of the respective receiving surfaces ( 11 ) using an adhesive mounting agent ( 36 ),

wherein a dimension (E 1 P), of the respective receiving surfaces ( 11 ) in a first direction (DIRP) that is parallel to the rotation axis ( 10 ), is larger than a dimension (E 2 P) of the associated magnets ( 9 ) in the first direction (DIRP), and

in which a dimension (E 1 T), of the respective receiving surfaces ( 11 ) in a second direction (DIRT) that is perpendicular to the first direction (DIRP), is larger than a dimension (E 2 T) of the associated magnet ( 9 ) in the second direction (DIRT),

and further comprising, at said second end ( 6 ) of the rotor housing ( 3 ), a first bearing seat ( 14 ) formed in said rotor housing and a first bearing cage ( 15 ) mounted in said first bearing seat ( 14 ).

2. The electric motor according to claim 1 , wherein

the respective receiving surfaces ( 11 ) and the associated magnets ( 9 ), at interfaces therebetween, define a series of respective connecting regions ( 38 ) in which said magnets ( 9 ) are arranged adjacently to one another, the receiving surfaces ( 11 ) each extending laterally beyond the respective connecting region ( 38 ) on all sides, thereby avoiding any need to provide a magnet abutment shoulder on the inner surface ( 7 ) of the rotor housing ( 3 ).

3. The electric motor according to claim 1 , wherein a cross-sectional contour of a transition portion ( 35 ) of the inner surface ( 7 ), between two adjacent receiving surfaces ( 11 ), has a generally concave shape.

4. The electric motor according to claim 1 , wherein the transition portion of the inner surface ( 7 ) has a polygonally shaped cross-sectional contour.

5. The electric motor according to claim 4 , wherein the inner surface ( 7 ) has a 14-sided polygonal cross-sectional contour.

6. The electric motor according to claim 1 , wherein the channel depressions ( 13 ) extend in a direction parallel to the rotation axis ( 10 ) of the rotor.

7. The electric motor according to claim 1 , wherein the channel depressions ( 13 ) have, in a direction parallel to the rotation axis ( 10 ), a first length (L 1 ) that is greater than a second length (L 2 ) of the magnets ( 9 ), which second length (L 2 ) extends in a direction parallel to the rotation axis ( 10 ).

8. The electric motor according to claim 1 , wherein

the rotor housing ( 3 ) has an inside diameter (D) that is constant or decreasing, proceeding from the first end ( 5 ) of the rotor housing ( 3 ) to the second end ( 6 ) of the rotor housing ( 3 ).

9. The electric motor according to claim 1 , wherein the rotor housing ( 3 ) has, at the second end ( 6 ), a first rotor housing portion ( 301 ) having an inside diameter, which inside diameter is smaller than an inside diameter (D) of the rotor housing ( 3 ) in a second rotor housing portion ( 302 ) in which the magnets ( 9 ) are mounted, thereby defining, at said second end ( 6 ), a bearing seat ( 14 ).

10. The electric motor according to claim 9 , wherein the rotor housing ( 3 ) tapers in a third rotor housing portion ( 303 ), arranged between the first rotor housing portion ( 301 ) and the second rotor housing portion ( 302 ), said taper forming a shoulder ( 305 ).

11. The electric motor according to claim 9 , wherein the bearing seat ( 14 ) and the rotor housing ( 3 ) are implemented as a single integral element.

12. The electric motor according to claim 1 , wherein the magnets ( 9 ) are implemented as cuboidal bar magnets.

13. The electric motor according to claim 1 , wherein a lateral distance between two adjacent magnets ( 9 ), within a predefined radial inner-surface distance range (ID) from the respectively associated inner surface ( 7 ) of the rotor housing ( 3 ), decreases, at least locally, as the inner-surface distance increases.

14. The electric motor according to claim 1 , wherein a predefined minimum lateral distance (D 3 ) is always provided between each two adjacent magnets ( 9 ).

15. The electric motor according to claim 1 , wherein the plurality of magnets ( 9 ) are each formed predominantly of a magnetically anisotropic material.

16. The electric motor according to claim 1 , wherein the plurality of magnets ( 9 ) are each formed of a permanently magnetic material.

17. The electric motor according to claim 1 , wherein the magnets ( 9 ) each comprise sintered material.

18. The electric motor according to claim 1 , wherein the rotor housing ( 3 ) is implemented as a deep drawn part by means of a deep-drawing process.