Electric machine comprising a knurled rotor shaft and method of manufacturing such a machine
The present invention relates to an electrical machine comprising a rotor ( 10 ) and a stator, rotor ( 10 ) being formed by assembling a rotor body ( 4 ) and a rotor shaft ( 1 ). According to the invention, rotor shaft ( 1 ) is knurled and the outside diameter of rotor shaft ( 1 ) is greater than the inside diameter of rotor body ( 4 ), by a value ranging between 0.05 mm and 0.3 mm. The present invention further relates to a method of manufacturing such an electrical machine.
1. An electrical machine comprising:
a rotor and a stator, the rotor including a body formed with a stack of laminations and which is fixed on a knurled shaft, the shaft being knurled over at least a length cooperating with the body and including an outside diameter of the shaft interfering with an inside diameter of a rotor bore in the body; and wherein
the body includes a series of axial recesses which house magnetic flux generators with the recesses disposed closest to the shaft each housing a magnetic flux generator; and
a material bridge extending between each recess disposed closest to the shaft housing a magnetic flux generator and an outside surface of the knurled shaft; and wherein
the outside diameter of the knurled shaft is greater than an inside diameter of the body by a dimension ranging from 0.015 mm and 0.3 mm and the knurling has flat ground ridges in lines on the outside diameter of the shaft and the inside diameter of the body is smooth, and engages the flat round ridges which deform the inside diameter of the rotor bore to form lines which are parallel to the flat ground ridges.
2. A machine as claimed in claim 1 , wherein the rotor shaft comprises straight knurling.
3. A machine as claimed in claim 1 , wherein the laminations are circular and comprise the axial recess which include magnets.
4. A machine as claimed in claim 1 , wherein the laminations are stacked and fixed together to form the rotor body.
5. A machine as claimed in claim 1 , wherein the electrical machine is a variable reluctance synchronous machine.
6. A method of manufacturing an electrical machine comprising a rotor and a stator, comprising:
a) stacking laminations to form a rotor body including axial recesses which house magnetic flux generators, the axial recesses which are disposed closest to an inside diameter of the rotor house magnetic flux generators spaced from an inside diameter of the rotor body by a material bridge;
b) knurling a rotor shaft over at least a length which cooperates with the rotor body with an outside diameter of the rotor shaft being greater than a smooth inside body of the rotor body by a dimension ranging between 0.05 mm and 0.3 mm;
c) fitting the rotor shaft into the smooth inside body to form an interference fit;
d) grinding an exterior knurled surface of the rotor shaft to have flat tops which are the outside diameter of the rotor shaft;
e) positioning the ground exterior surface of the rotor shaft with flat tops within the inside diameter of the rotor body so that the flat tops of the rotor shaft engage the smooth surface by the interference fit with the rotor shaft to deform an inside diameter of a rotor bore to forming lines parallel to the flat tops of the knurling; and
f) positioning the rotor in the stator.
7. A method as claimed in claim 6 , comprising forming the rotor shaft with the exterior surface comprising straight knurling.
8. A method as claimed in claim 6 , comprising press fitting the rotor shaft into the interference fit with the rotor body.
9. A method as claimed in claim 7 , comprising press fitting the rotor shaft into the interference fit with the rotor body.
10. A method as claimed in claim 6 , comprising at least one magnet is placed into at least one of the recesses.
11. A method as claimed in claim 7 , comprising placing at least one magnet into at least one of the recesses.
12. A method as claimed in claim 8 , comprising placing at least one magnet into at least one of the recesses.