The present invention refers to a rotor for an electrical machine, and to an electrical machine comprising said rotor.

In particular, the invention refers to a rotor for a synchronous reluctance electrical machine, of the type with permanent magnets .

An electrical machine typically comprises a fixed part, the stator, and a moving part, the rotor, coaxially arranged one inside the other. Typically, the rotor is placed inside the stator, which comprises electric coils adapted to generate a magnetic field which allows rotating the rotor. The rotor typically comprises a body composed of a pack of sheets and placed on a rotation shaft. In the electrical motor with permanent magnets, the sheets comprise seats for the permanent magnets .

In the electrical machines, and in particular in high performance electrical motors with permanent magnets, an important parameter is given by the air gap between the rotor and the stator: the smaller the air gap, the better the performances of the electrical machine, but this implies costly high-precision workings. A problem of synchronous reluctance electrical machines, of the type with permanent magnets, is given by the vibrations generated by the torque ripples and the counter-electromotive force harmonics, which can generate rotor vibrations and high losses.

An object of the present invention is obtaining a rotor of an electrical machine and an electrical machine which guarantee a better efficiency, allowing to obtain better performances with a big air gap, which implies higher working tolerances of the rotor and lower costs .

Another object of the present invention is reducing the torque ripple and the counterelectromotive force harmonics.

The above and other objects and advantages of the invention, as will result from the following description, are obtained with a rotor for an electrical machine and an electrical machine as claimed in the independent claims.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appear from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a front view of a rotor for electrical machine according to the invention; Figure 2 shows a partial view of two poles and an enlarged detail of a rotor for electrical machine according to the invention; and

Figure 3 shows a partial view of two poles of a rotor for electrical machine according to the invention.

With reference to the Figures, the rotor 1 for an electrical machine of the invention comprises: a rotation shaft; a lamellar pack fastened onto the rotation shaft and comprising a plurality of identical sheets 3, comprising a central hole 2 crossed by the rotation shaft and a plurality of axial recesses 6, 7, 8, which cross the sheets 3 from part to part. In particular, each sheet 3 comprises: a plurality of first 6 and second 7 axial recesses, preferably of a trapezoidal, rectangular, parallelogram or squared shape, arranged radially one below the other and mutually spaced, the second axial recesses 7 being inclined from the radial direction; each sheet 3 further comprises magnetic flow generators inserted in the first 6 and second 7 axial recesses, preferably permanent magnets shaped as bars, and a plurality of third axial recesses 8 inclined from the radial direction, which start from the first 6 and second 7 axial recesses to arrive next to the edge of the sheet 3.

Preferably, each sheet 3 comprises a plurality of pairs of second axial recesses 7 having an inclined radial direction, each pair of second axial recesses 7 being inclined and symmetrically arranged with respect to a radius Rl, R2 of the sheet 3 passing by the rotation center C of the rotor 1, each of the second axial recesses 7 starting from another second axial recess 7 to arrive to the third axial recess 8 inclined from the radial direction.

Said third axial recesses 8, having an inclined radial direction, have a surface 12 substantially parallel to the edge of the sheet 3, joined with a first side surface 22 and a second side surface 23 through two connection radiuses R, as shown in the enlarged detail of Figure 2.

In a preferred way, the rotor 1 comprises six magnetic poles 13, 14, each comprising three flow barriers 9, 10, 11: an external flow barrier 9, an intermediate flow barrier 10 and an internal flow barrier 11.

In particular, each flow barrier 9, 10, 11 comprises: a first axial recess 6 adapted to house a flow generator, preferably a permanent magnet; a pair of third axial recesses 8 inclined and symmetrically arranged with respect to said first axial recess 6. In this way, each flow barrier 9, 10, 11 forms a design similar to a "V", whose base is flattened and formed by the first axial recess 6 and whose inclined arms are formed of the pair of second axial recesses 8.

Preferably, the external flow barrier 9 comprises: a first axial recess 6 adapted to house a flow generator, preferably a permanent magnet; a pair cf third axial recesses 8 inclined and symmetrically arranged with respect to said first axial recess 6, and forms a design similar to a "V", whose base is flattened and formed by the first axial recess 6 and whose inclined arms are formed of the pair of second axial recesses 8.

Preferably, the intermediate flow barrier 10 and the internal flow barrier 11 comprise: a first axial recess 6 adapted to house a flow generator, preferably a permanent magnet; a pair of second axial recesses 7 having an inclined radial direction and adapted to house a flow generator, preferably a permanent magnet; said pair of second axial recesses 7 being inclined and symmetrically arranged with respect to a radius Rl, R2 of the sheet 3 passing by the rotation center C of the rotor 1; a pair of third axial recesses 8 inclined and symmetrically arranged with respect to said first axial recess 6. In this way, each flow barrier 10, 11 forms a design similar to a "V", whose inclined arms are formed of the pair of second axial recesses 7 and third axial recesses 8.

Each flow barrier 9, 10, 11 corresponds to an opening angle Q13, Q14, Q15 which defines the width of the "V" shape.

Said opening angles Q13, Q14, Q15 are located by two straight lines passing each for an internal surface of the first 6 and second 7 inclined axial recesses of each flow barrier 9, 10, 11.

In a preferred way, the rotor 1 comprises three primary magnetic poles 13 and three secondary magnetic poles 14, each comprising three flow barriers 9, 10, 11. In particular, each of the three : primary magnetic poles 13 preferably comprises the internal flow barrier 11 whose opening angle Q13 is substantially equal to 180°±10°, the intermediate flow barrier 10 whose opening angle Q14 is substantially equal to 130°±10°, the external flow barrier 9 whose opening angle Q15 is substantially equal to 130°±10°; each of the four secondary magnetic poles 14 preferably comprises an internal flow barrier 11 whose opening angle Q13 is substantially equal to 180°±10°, an intermediate flow barrier 10 whose opening angle Q14 is substantially equal to 130°±10°, an external flow barrier 9 whose opening angle Q15 is substantially equal to 130°±10°.

The width of the three flow barriers 9, 10, 11 of each primary and secondary magnetic pole 13, 14 is defined by locating the opening angles Q1, Q2,

..., Q12, included between two straight lines projected by the theoretical rotation center C of the rotor 1 and each passing by a joining point R of the surface 12, substantially parallel to the edge of the sheet 3 of each third inclined axial recess 8, with the first or with the second side surface 22, 23 of each third axial recess 8 inclined .

In particular, for each flow barrier 9, 10, 11 internal opening angles Q1, Q3, Q5, Q7, Q9, Q11 and external opening angles Q2, Q4, Q6, Q8, Q10, Q12 are located, included between two straight lines projected by the rotation center C of the rotor 1 and passing by the joining point R, or tangent to the joining point R, of the surface 12 substantially parallel to the edge of the sheet 3 of each third inclined axial recess 8 with the first 22 or second 23 side surface of each third inclined axial recess 8.

The following Table 1 lists the values of the opening angles Q1, Q2, ..., Q12 for three pairs of primary magnetic poles 13 and secondary magnetic poles 14 of the rotor 1.

Table 1

For example, for the previously described rotor 1, having six poles (three pairs of poles), the angle Q1 is equal to 15° 55' ± 2°.

In particular, each of the primary magnetic poles 13 comprises: an internal flow barrier 11 whose external opening angle Q8 is included between 27° 55' and 31° 55', in a preferred way substantially equal to 29° 55'; an intermediate flow barrier 10 whose external opening angle Q10 is included between 42° 25' and 46° 25', in a preferred way substantially equal to 44° 25'; an external flow barrier 9 whose external opening angle Q12 is included between 57° 05' and 61° 05', in a preferred way substantially equal to 59° 05'; each of the secondary magnetic poles 14 comprises: an internal flow barrier 11 whose external opening angle Q2 is included between 20° 25' and 24° 25', in a preferred way substantially equal to 22° 25'; an intermediate flow barrier 10 whose external opening angle Q4 is included between 33° 45' and 37° 45', in a preferred way substantially equal to 35° 45' ; an external flow barrier 9 whose external opening angle Q6 is included between 49° 35' and 53° 35', in a preferred way substantially equal to 51° 35' .

Moreover, each of the primary magnetic poles 13 comprises: an internal flow barrier 11 whose internal opening angle Q7 is included between 21° 25' and 25° 25', in a preferred way substantially equal to 23° 25'; an intermediate flow barrier 10 whose internal opening angle Q9 is included between 36° 25' and 40° 25', in a preferred way substantially equal to 38° 25'; an external flow barrier 9 whose internal opening angle Q11 is included between 50° 35' and 54° 35', in a preferred way substantially equal to 52° 35'; each of the secondary magnetic poles 14 comprises: an internal flow barrier 11 whose internal opening angle 91 is included between 13° 55' and 17° 55', in a preferred way substantially equal to 15° 55'; an intermediate flow barrier 10 whose internal opening angle Q3 is included between 28° 55' and 32° 55', in a preferred way substantially equal to 30° 55'; an external flow barrier 9 whose internal opening angle Q5 is included between 43° 55' and 47° 55', in a preferred way substantially equal to 45° 55' .

Preferably, the connection radiuses R between the surface 12 substantially parallel to the edge of the sheet 3 and the first or the second side surface 22, 23 of each axial inclined recess 8 are included within the range 0.2 - 1 mm. Preferably, the rotor 1 comprises alternate primary magnetic poles 13 and secondary magnetic poles 14. In this way, the flow barriers 9, 10, 11 of two consecutive magnetic poles 13, 14 are mutually asymmetrical and this limits, with respect to known electrical machines, the torque ripple and the counter electromotive force harmonics.

It is anyway possible to have all distance spectra which satisfy the above specified angle values .

In a known way, an electrical machine comprises a fixed part, the stator, and a moving part, the rotor, arranged coaxially one inside the other. Typically, the rotor is placed inside the stator, which comprises electric coils adapted to generate a magnetic field which allows rotating the rotor .

The electrical machine according to the invention further comprises the previously described rotor 1, and between the rotor 1 and the stator, an air gap whose thickness is included between 0.5 mm and 1.5 mm.