# US 2021/0242735 A1 · Rotary electric machine with lightened rotor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0242735 A1 - Document ID: US20210242735A1 - Status: Published application - Kind: A1 - Application number: 17/167,781 - Filed: 2021-02-04 - Published: 2021-08-05 - Earliest claimed: 2020-02-05 - Assignees: Ferrari S.P.A. - Applicants: FERRARI S.p.A. - Inventors: Davide FERRARA; Luca POGGIO; Paolo FAVERZANI - Web page: https://patentgrep.com/patent/US20210242735A1 ## CPC - H02K 1/2783: with magnets arranged in Halbach arrays - H02K 1/2753: the rotor consisting of magnets or groups of magnets arranged with alternating polarity - H02K 1/28: Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures - H02K 1/30: using intermediate parts, e.g. spiders - H02K 1/32: with channels or ducts for flow of cooling medium - H02K 3/12: arranged in slots - H02K 5/207: {with openings in the casing specially adapted for ambient air} - H02K 5/04: Casings or enclosures characterised by the shape, form or construction thereof - H02K 5/18: with ribs or fins for improving heat transfer - H02K 5/24: specially adapted for suppression or reduction of noise or vibrations - H02K 9/06: with fans or impellers driven by the machine shaft - H02K 21/14: with magnets rotating within the armatures - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract Electric machine having: a shaft; a rotor with permanent magnets that is fitted to the shaft; a stator having a magnetic core which consists of a series of laminations made of ferromagnetic material and longitudinally crossed by a plurality of stator slots; and a stator winding having a plurality of rigid bars that are inserted in corresponding stator slots and that are covered, on the outside, with an insulating coating. The rotor has a plurality of magnetic elements, which are arranged beside one another around the rotation axis so as to form a closed ring. Each magnetic element is formed by a plurality of permanent magnets which are axially arranged one after the other according to a Halbach array. ## Claims ### Claim 1 1) An electric machine (1) comprising: a shaft (2), which is mounted so as to rotate around a central rotation axis (3); a rotor (4) with permanent magnets which is fitted to the shaft (2) so as to rotate together with the shaft (2); a stator (5) with a tubular, cylindrical shape, which is arranged around the rotor (4) so as to enclose, on the inside, the rotor (4) and has a magnetic core (6), which consists of a series of laminations made of a ferromagnetic material and is longitudinally crossed by a plurality of stator slots (7); and a stator winding (8) comprising a plurality of copper rigid bars (9), which are inserted in corresponding stator slots (7) and are covered, on the outside, with an insulating coating (14); wherein the rotor (4) comprises a plurality of magnetic elements (22), which are axially oriented, arranged beside one another around the rotation axis (3) so as to form a closed ring, and all have a similar magnetic configuration; and wherein each magnetic element (22) is formed by a plurality of permanent magnets (23) which all have a same shape, axially arranged one after the other and have polarities oriented in a different way according to a Halbach array. ### Claim 2 (depends on 1) 2) The electric machine (1) according to claim 1, wherein: in each magnetic element (22) groups of four permanent magnets (23) are repeated cyclically; and in each group of four permanent magnets (23), the four permanent magnets (23) respectively have: a polarity axially arranged in a first direction, a polarity circumferentially arranged in a second direction that is perpendicular to the first direction, a polarity axially arranged in a third direction opposite to the first direction, and a polarity arranged circumferentially in a fourth direction opposite to the second direction. ### Claim 3 (depends on 2) 3) The electric machine (1) according to claim 2, wherein each magnetic element (22) consists of an integer of groups of four permanent magnets (23) and thus comprises a number of permanent magnets (23) which is a integer multiple of four. ### Claim 4 (depends on 1) 4) The electric machine (1) according to claim 1, wherein the permanent magnets (23) in each magnetic element (22) are arranged so as to nullify the magnetic field radially on the inside of the permanent magnets (23) and to maximize the magnetic field radially on the outside of the permanent magnets (23). ### Claim 5 (depends on 1) 5) The electric machine (1) according to claim 1, wherein the rotor (4) is free from a ferromagnetic material arranged radially on the outside of the permanent magnets (23) and is free from a ferromagnetic material arranged radially on the inside of the permanent magnets (23). ### Claim 6 (depends on 1) 6) The electric machine (1) according to claim 1, wherein the rotor (4) comprises a containment element (24), which is arranged around the magnetic elements (22). ### Claim 7 (depends on 1) 7) The electric machine (1) according to claim 1, wherein, in each magnetic element (22) the single permanent magnets (23) are glued to one another through the interposition of a first glue (25), which preferably is an electric insulation. ### Claim 8 (depends on 1) 8) The electric machine (1) according to claim 1, wherein the magnetic elements (22) are directly mounted on an outer wall of the shaft (2). ### Claim 9 (depends on 8) 9) The electric machine (1) according to claim 8, wherein each magnetic element (22) is glued to the outer wall of the shaft (2) by means of a second glue (26), which preferably is an electric insulator. ### Claim 10 (depends on 8) 10) The electric machine (1) according to claim 8, wherein the outer wall of the shaft (2) has a plurality of seats (27), each of which is adapted to accommodate a corresponding magnetic element (22). ### Claim 11 (depends on 1) 11) The electric machine (1) according to claim 1, wherein the shaft (2) has a hub (28) supported by bearings, a rim (29), which is arranged around the hub (28) at a given distance from the hub (28) and supports the magnetic elements (22), and a plurality of spokes (30), which develop radially and connect the hub (28) to the rim (29) so that between the hub (28) and the rim (29) there is some empty space. ### Claim 12 (depends on 11) 12) The electric machine (1) according to claim 11, wherein between the rim (29) and the magnetic elements (22) an electrically insulating layer is interposed. ### Claim 13 (depends on 11) 13) The electric machine (1) according to claim 11, wherein the spokes (30) are shaped so as to cause the air present inside the shaft (2) to have an axially oriented component of motion. ### Claim 14 (depends on 13) 14) The electric machine (1) according to claim 13, wherein: a casing (31) is provided, which houses, on the inside, the stator (5) and has a cylindrical central body (32), which is arranged around the magnetic core (6) of the stator (5), and two caps (33), which close the central body (32) on the opposite sides thereof; and between an outer surface (18) of the magnetic core (6) of the stator (5) and an inner surface (19) of the central body (32) of the casing (31) an annular hollow space (34) is obtained, which is designed to allow an air flow to circulate. ### Claim 15 (depends on 13) 15) The electric machine (1) according to claim 13, wherein an air flow generated by the rotation of the spokes (30) closes by exclusively flowing through an air gap existing between the rotor (4) and the stator (5) in an opposite direction. ### Claim 16 (depends on 13) 16) The electric machine (1) according to claim 13, wherein: a casing (31) is provided, which houses, on the inside, the stator (5) and has a cylindrical central body (32), which is arranged around the magnetic core (6) of the stator (5) and two caps (33) which close the central body (32) on the opposite sides thereof; and inside the two caps (33) a plurality of fins are arranged that are shaped so as to guide an air flow from the centre to the periphery and vice versa. ### Claim 17 (depends on 11) 17) The electric machine (1) according to claim 11, wherein the spokes (30) are shaped so as to generate, during the rotation of the shaft (2), a predetermined sound. ### Claim 18 (depends on 1) 18) The electric machine (1) according to claim 1; wherein: a casing (31) is provided, which houses, on the inside, the stator (5) and has a cylindrical central body (32), which is arranged around the magnetic core (6) of the stator (5) and two caps (33) which close the central body (32) on the opposite sides thereof; and a heat exchanger (35) is coupled to at least one cap (33). ### Claim 19 19) An electric machine (1) comprising: a shaft (2), which is mounted so as to rotate around a central rotation axis (3); a rotor (4) with permanent magnets which is fitted to the shaft (2) so as to rotate together with the shaft (2); a stator (5) with a tubular, cylindrical shape, which is arranged around the rotor (4) so as to enclose, on the inside, the rotor (4) and has a magnetic core (6), which consists of a series of laminations made of a ferromagnetic material and is longitudinally crossed by a plurality of stator slots (7); and a stator winding (8) comprising a plurality of copper rigid bars (9), which are inserted in corresponding stator slots (7) and are covered, on the outside, with an insulating coating (14); wherein the shaft (2) has a hub (28) supported by bearings, a rim (29), which is arranged around the hub (28) at a given distance from the hub (28) and supports the permanent magnets (23), and a plurality of spokes (30), which develop radially and connect the hub (28) to the rim (29) so that between the hub (28) and the rim (29) there is an empty space; and wherein the spokes (30) are shaped so as to generate, during the rotation of the shaft (2), a predetermined sound.