Interior rotor for a rotary electrical machine and method of assembling it

1. A buried-magnet internal rotor for an electric rotating machine, the rotor comprising:

a shaft,

a plurality of polar parts made of a magnetic material surrounding the shaft, the polar parts delimiting housings between them;

a first lateral shroud and a second lateral shroud positioned axially on each side of the polar parts and mounted on the shaft, the shaft passing through each lateral shroud through a central opening in each lateral shroud;

an external ring;

at least one tie-rod per polar part, the tie-rod clamping each polar part between the lateral shrouds; and

a plurality of permanent magnets placed in the said housings so that one permanent magnet is positioned between adjacent polar parts;

wherein the shaft is shaped so as to form an internal shoulder forming an axial abutment against which the first lateral shroud is held axially by the external ring radially secured to the shaft; and

wherein the second lateral shroud is mounted on the shaft so as to be capable of sliding along the shaft.

2. The rotor according to claim 1 , wherein the external ring is shrink-fitted onto the shaft.

3. The rotor according to claim 1 , wherein the central opening of the second lateral shroud is such that it can pass over the internal shoulder of the shaft.

4. The rotor according to claim 1 , wherein the shoulder of the shaft interacts with a facing made in the thickness of the first lateral shroud.

5. The rotor according to claim 1 , wherein the polar parts consist of a stack of magnetic metal sheets.

6. The rotor according to claim 1 , wherein the shaft comprises a splined central portion, the internal shoulder being defined by one of the ends of the splined central portion.

7. An electric rotating machine comprising a rotor according to claim 1 .

8. A method for manufacturing a rotor according to claim 1 , wherein a subassembly comprising at least the polar parts is initially assembled, the lateral shrouds and the tie-rods independently of the shaft before, secondly, the subassembly is placed on the shaft.

9. The method according to claim 8 , further comprising a step of axially attaching the said subassembly to the shaft by immobilizing the first lateral shroud between the internal shoulder of the shaft and the external ring secured to the shaft.

10. The method according to claim 9 , wherein the external ring is secured to the shaft by radial shrink-fitting.

11. The rotor according to claim 1 , wherein longitudinal faces of each of the polar parts have a spline formed therein, and further comprising a plurality of wedges having two flanges, each wedge being positioned between adjacent polar parts so that each flange of each wedge rests on one spline of one polar part and so that each wedge mechanically secures one of the permanent magnets radially relative to the shaft, wherein an outer surface of each wedge is flush with an external surface of the adjacent polar parts.

12. The rotor according to claim 1 , wherein longitudinal faces of each of the polar parts have a spline formed therein, and further comprising a plurality of wedges having two flanges, each wedge being positioned between adjacent polar parts so that each flange of each wedge rests on one spline of one polar part and so that each wedge mechanically secures one of the permanent magnets radially relative to the shaft, wherein an outer surface of each wedge is domed so as to follow a curvature of an external surface of the adjacent polar parts.