Device comprising a plain bearing
A motor, suitable for driving a fan, features a plain bearing ( 36 ) that contains ferromagnetic material and serves for radial support of a rotor shaft ( 34 ) made of ferromagnetic material. The shaft ( 34 ) is arranged rotatably and axially displaceably in that plain bearing ( 36 ), and has a free end ( 35 ). Provided at the free end is a thrust bearing which has a dome-shaped end ( 66 ) provided at that free end ( 35 ), and a contact member ( 68, 69 ), coacting with the latter dome, the contact member being made at least partially of ferromagnetic material. Also provided is at least one permanent magnet ( 72 ) in order to form a magnetic circuit ( 82 ) from a first magnet pole ( 74 ) via the plain bearing ( 36 ), the free shaft end ( 35 ) and its dome-shaped end ( 66 ), and the contact member ( 68 ) to the other magnet pole ( 76 ), and thereby to bring about a defined magnetic attractive force between the dome-shaped end ( 66 ) and the contact member ( 68 ). The magnetic force minimizes rattling of the shaft ( 34 ), even in vibration-prone environments.
1. An arrangement comprising
a plain bearing ( 36 ) that contains sintered ferromagnetic material, and that serves for radial journaling of
a shaft ( 34 ) made of ferromagnetic material, which shaft ( 34 ) is arranged rotatably and axially displaceably in that plain bearing ( 36 ) and has a free end ( 35 );
an axial bearing, provided at that free end ( 35 ), which comprises a dome-shaped ending ( 66 ) of that free end and
a contact member ( 68 , 69 ), coacting with the dome-shaped ending, said contact member being made at least partially of ferromagnetic material; and
at least one permanent magnet ( 72 ) that is arranged in a region around the free shaft end ( 35 ) between the axial end of the plain bearing ( 36 ) there and the contact member ( 68 ), in order to bring about a magnetic circuit ( 82 ) from one pole ( 74 ) of the at least one permanent magnet ( 72 ) via the plain bearing ( 36 ), the free shaft end ( 35 ) and the dome-shaped ending ( 66 ), and the contact member ( 68 ) to the other pole ( 76 ) of the at least one permanent magnet ( 72 ),
to thereby to bring about a defined magnetic attractive force between the dome-shaped ending ( 66 ) and the contact member ( 68 ).
2. The arrangement according to claim 1 , which is implemented as part of an
external-rotor motor ( 20 ), the plain bearing ( 36 ) being arranged in a bearing support tube ( 38 ) to which an internal stator ( 44 ) of that motor ( 20 ) is joined.
3. The arrangement according to claim 2 ,
wherein the shaft ( 34 ) is mounted, with its end region ( 32 ) facing away from the free end ( 35 ), at the base of a cup-like external rotor part ( 24 ) of said motor ( 20 ).
4. The arrangement according to claim 3 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
5. The arrangement according to claim 2 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
6. The arrangement according to claim 1 ,
wherein said permanent magnet ( 72 ) is magnetized substantially axially and is implemented as a ring magnet ( 72 ) that is magnetized approximately in a direction parallel to its longitudinal axis.
7. The arrangement according to claim 6 ,
wherein the ring magnet ( 72 ) is guided with its outer periphery abutting the bearing support tube ( 38 ).
8. The arrangement according to claim 7 ,
wherein the ring magnet is implemented as a preferred-orientation ceramic ring magnet ( 72 ).
9. The arrangement according to claim 8 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
10. The arrangement according to claim 7 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
11. The arrangement according to claim 6 ,
wherein the ring magnet is implemented as a preferred-orientation ceramic ring magnet ( 72 ).
12. The arrangement according to claim 11 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
13. The arrangement according to claim 6 , wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
14. The arrangement according to claim 1 ,
wherein the permanent magnet ( 72 ), provided in order to generate a magnetic attractive force, is magnetized substantially parallel to the axial direction of the shaft ( 34 ).
15. The arrangement according to claim 1 ,
wherein a contact surface ( 69 ) made of plastic is provided, in the region where the dome-shaped ending ( 66 ) rests against the contact member ( 68 ), on the latter.
16. The arrangement according to claim 15 ,
wherein the contact surface ( 69 ) comprises a low-friction plastic.
17. The arrangement according to claim 16 , wherein said low-friction plastic comprises polytetrafluoroethylene (PTFE).
18. The arrangement according to claim 16 ,
wherein the contact surface ( 69 ) is dimensioned sufficiently thinly to avoid creating a magnetically effective air gap in a transition region from the contact member ( 68 ) to the permanent magnet ( 72 ).
19. The arrangement according to claim 15 ,
wherein the contact surface ( 69 ) is dimensioned sufficiently thinly to avoid creating a magnetically effective air gap in a transition region from the contact member ( 68 ) to the permanent magnet ( 72 ).