US-12620850-B2 - Rotor, manufacturing method, synchronous electric machine, and vehicle

US12620850B2US 12620850 B2US12620850 B2US 12620850B2US-12620850-B2

Abstract

A rotor ( 1 ) with N poles, wherein N is an even integer, wherein said rotor ( 1 ) is devoid of permanent magnets comprising rare earth elements and comprises a cylindrical body ( 2 ) and a filling material ( 16 ). The cylindrical body ( 2 ) extends along a body axis (X) and—in a plane perpendicular to the body axis (X)—delimits N adjacent angular sectors ( 4, 6 ). Each angular sector ( 4, 6 ) delimits cylindrical cavities ( 8, 12, 14, 8′, 12′, 14 ′) which have curvilinear cross-sections, where concave surfaces ( 18, 20, 22, 18′, 20′, 22 ′) of said cylindrical cavities ( 8, 12, 14, 8′, 12′, 14 ′) are directed in the opposite direction to the body axis (X). The filling material ( 16 ) fills at least partly the cylindrical cavities ( 8, 12, 14, 8′, 12′, 14 ′) and comprises or consists of a polymer matrix. At least one angular sector ( 6 ) delimits cylindrical cavities ( 8′, 12′, 14 ′) with a first geometry (type A) and at least one second angular sector ( 4 ) delimits cylindrical cavities ( 8, 12, 14 ) with a second geometry (type B) different from said first geometry. The first angular sector ( 6 ) is arranged angularly alternating with the second angular sector ( 4 ).

Inventors

Alessandro TASSI

Assignees

SPIN APPLICAZIONI MAGNETICHE S.R.L.

Dates

Publication Date: 20260505
Application Date: 20220621
Priority Date: 20210624

Claims (8)

1 . A rotor with N poles, wherein N is an even integer, wherein said rotor is devoid of permanent magnets comprising rare earth elements and comprises: a cylindrical body which extends along a body axis and which—in a plane perpendicular to the body axis—delimits N adjacent angular sectors; wherein each angular sector delimits cylindrical cavities which have curvilinear cross-sections, wherein concave surfaces of said cylindrical cavities are directed in the opposite direction to the body axis; wherein each of the N poles extends axially along the body axis from a first cylinder base to a second cylinder base, opposite to the first cylinder base, of the cylindrical body; a filling material which fills at least partly the cylindrical cavities and comprising or consisting of a polymer matrix; wherein at least one first angular sector delimits cylindrical cavities with a first geometry or type A geometry and wherein at least one second angular sector delimits cylindrical cavities with a second geometry or type B geometry, different from said first geometry, said first angular sector being arranged angularly alternating with said second angular sector, wherein the cylindrical cavities with the first geometry or type A geometry have internal volumes, forms and/or lengths of the outer perimeters and/or specific radial arrangements different from the cylindrical cavities with the second geometry or type B geometry, in particular the cylindrical cavities with the first geometry or type A geometry have a different width than the width of the corresponding cylindrical cavities with the second geometry or type B geometry, and the shape of the extremities of the cylindrical cavities with the first geometry or type A geometry is different from the shape of the extremities of the cylindrical cavities with the second geometry or type B geometry, wherein at least one of the cylindrical cavities is crossed by a radial mid-plane, wherein the cylindrical body is circumscribed by an outer cylindrical surface and wherein said cylindrical cavities are separated from the outer cylindrical surface by means of a dividing wall which has a variable thickness in a circumferential direction of the cylindrical body and a minimum thickness point, and wherein a radial plane includes the body axis and the minimum thickness point of a dividing wall, wherein said radial plane circumscribes an angle with said mid-plane, and wherein at least one of the cylindrical cavities delimited by the first angular sector is characterized by a first angle, wherein at least one corresponding cylindrical cavity delimited by the second angular sector is characterized by a second angle different from said first angle, and wherein the difference between said angles determines the first geometry or the second geometry of the cylindrical cavities.
2 . The rotor according to claim 1 , wherein the cylindrical body is formed by a plurality of cylinder plates, which are superimposed in the axial direction and joined together so that the polarities of each of the N poles of a cylinder plate correspond axially to the polarities of the N poles of an adjacent cylinder plate.
3 . The rotor according to claim 1 , wherein each cylindrical cavity circumscribes an internal volume, is delimited by an outer perimeter, and has a specific angular arrangement in the angular sector and wherein the cylindrical cavities delimited by the first angular sector have internal volumes, forms and/or lengths of the outer perimeters and specific radial arrangements different from those of the cylindrical cavities delimited by the second angular sector.
4 . The rotor according to claim 1 , wherein the cavities comprise a proximal cylindrical cavity, at least one intermediate cylindrical cavity and a distal cylindrical cavity spaced in a radial direction from the body axis, wherein the proximal cylindrical cavity and the at least one intermediate cylindrical cavity have a mirror-image symmetry with respect to radial bridges which centrally divide said proximal cylindrical cavities and said at least one intermediate cylindrical cavity; and wherein the cylindrical cavities delimited by the first angular sector have different: i—radial distances of the proximal cylindrical cavities and of the at least one intermediate cylindrical cavity from the body axis; ii—radial distances of convex surfaces of said cylindrical cavities with respect to an outer cylindrical surface or circumference of said rotor; iii—lengths and/or widths of the radial bridges; and iv—radii of curvature of one or more concave surfaces or of a part of said concave surfaces; v—radii of curvature of one or more convex surfaces or of a part of said convex surfaces; vi—optionally length, alternating arrangement and/or incidence of any straight sections located along one or more concave surfaces; compared to the cylindrical cavities delimited by the second angular sector.
5 . The rotor according to claim 1 , wherein said filling material has: a residual flow density or remanence—determined in accordance with DIN EN 60404-5—comprised from 150 mT to 450 mT; a coercive field intensity or coercivity—determined in accordance with DIN EN 60404-5—comprised from 130 kA/m to 350 kA/m; and a maximum energy product—determined in accordance with DIN EN 60404-5—comprised from 10 kJ/m3 to 20 kJ/m3.
6 . The rotor according to claim 1 , wherein: said polymer matrix is a thermoplastic matrix or a thermosetting matrix; and the filling material comprises one or more magnetizable or magnetized fillers embedded in said polymer matrix, wherein said magnetizable filler is selected from magnetite, ferrite, and mixtures thereof.
7 . The rotor according to claim 1 , wherein the polymer matrix is PA6 or PPS and said magnetizable filler is ferrite comprising exclusively strontium as metallic element.
8 . The rotor according to claim 1 , wherein the number N of poles is equal to four or equal to six.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national phase of PCT/IB2022/055756, filed Jun. 21, 2022, and claims priority to Italian Patent Application No. 102021000016667, filed Jun. 24, 2021, the entire contents of both of which are hereby incorporated by reference. FIELD OF THE INVENTION The present invention relates to a rotor comprising a cylindrical body and a filling material. The present invention also relates to a method for manufacturing a rotor or a rotor module. The present invention also relates to a synchronous electric machine comprising said rotor, or a rotor obtained using said manufacturing method. The present invention also relates to an electric or hybrid vehicle comprising said synchronous electric machine. PRIOR ART Reluctance motors are motors which technologically date back to almost a century ago. In particular, “Kostko” polyphase synchronous reaction motors date back to 1923. Reluctance motors are characterized by a rotor structure which does not have windings and is magnetically anisotropic. Reluctance motors are machines with technological limitations which, hitherto, have not favoured their large-scale use. One technological limitation consists in a relatively low power factor due to a phase-displacement angle between voltage and current: an “active” current amount may produce a useful mechanical force, while another current amount—which is phase-displaced by 90° with respect to the voltage—is “reactive” so that, although managing to excite the rotor, it does not produce any useful effect. Another technological limitation consists in the torque ripple (vibration) which is generated by the air chambers of the rotor and which results in noisiness and resonance. The documents US 2015/0372546 A1, US 2019/207490 A1 and WO 2017/021078 A1 illustrate rotors for reluctance motors according to the prior art. SUMMARY OF THE INVENTION The Applicant, after long and intense research and development activity and in the firm conviction that reluctance motors will be of increasingly greater interest in the coming years (for example, but not exclusively, in the electric mobility sector), has developed a rotor, a manufacturing method, a synchronous electric machine and a vehicle which are able to provide a suitable response to the limitations, drawbacks and existing problems. In fact, the Applicant has surprisingly found that—by introducing asymmetries into the cavities of the rotor—it is possible to reduce the torque ripple (and therefore the noisiness and resonance) of the rotor and increase the mean value of the torque of the machine which comprises said rotor. Therefore, the present invention relates to a rotor comprising a cylindrical body and a filling material, having the features as defined in the attached claims. The present invention also relates to a method for manufacturing a rotor or a rotor module, having the features as defined in the attached claims. The present invention also relates to a synchronous electric machine comprising said rotor, or a rotor obtained using said manufacturing method, having the features as defined in the attached claims. The present invention also relates to an electric or hybrid vehicle comprising said synchronous electric machine, having the features as defined in the attached claims. DESCRIPTION OF THE FIGURES The preferred embodiments of the present invention will be described hereinbelow by way of a non-limiting example with reference to the drawings wherein: FIGS. 1 and 2 shows plan views of a rotor and a cylindrical body, respectively, according to possible embodiments of the present invention; FIGS. 3 and 4 show a detail, on larger scale, of a first angular sector and a second angular sector, respectively, in accordance with possible embodiments; FIGS. 5 and 6 show a detail, on a larger scale, of the zones V and VI highlighted in FIG. 2, in accordance with further possible embodiments; FIGS. 7A and 7B show perspective views, respectively, of a cylindrical body and a modular element, in accordance with possible embodiments; FIG. 8 shows a torque/position diagram of the rotor comparing the torque ripple and the mean torque of an asymmetrical rotor according to the present invention and rotors with symmetrical axial cavities according to the prior art; FIGS. 9, 10 and 11 show a perspective view, longitudinally sectioned view and cross-sectioned view, respectively, of a synchronous electric machine according to the present invention; FIGS. 12 and 13 show a detail, on a larger scale, of the zones V and VI highlighted in FIG. 2, in accordance with further possible embodiments of a first angular sector and a second angular sector; FIG. 14 shows a plan view of a cylindrical body according to another possible embodiment of the present invention; FIGS. 15 and 16 show a detail, on larger scale, of a first angular sector and a second angular sector, respectively, in accordance with the embodiment of FIG. 14. DETAILED DESCRIPTION With referenc