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EP-4742504-A1 - ELECTRIC MACHINE ROTOR, IN PARTICULAR FOR A SYNCHRONOUS MOTOR FOR TRACTION OF MOTOR VEHICLES

EP4742504A1EP 4742504 A1EP4742504 A1EP 4742504A1EP-4742504-A1

Abstract

An electric machine rotor (1), in particular for an electric motor for traction of motor vehicles, has two shaft portions (4,5) opposite one another and supported by respective bearings; one of said shaft portions (4) defines an inlet (7) and an outlet (8) for a heat exchange liquid, for cooling an annular wall (10) supporting a plurality of permanent magnets (13), and radially delimits an inner cavity (23) engaged by a core (24); the latter has an axial hole (45) communicating with the inlet (7) to supply a plurality of heat exchange channels (28) through delivery junction channels (44), which are separate from one another and are configured so as to divert the liquid into a radial direction; the liquid is then diverted into an axial direction towards the outlet (8) by return junction channels (38), which are also separate from one another; the delivery junction channels (44) and/or the return junction channels (38) are defined by two surfaces (43,42; 35,36), which axially face one another and define part of the core (24) and of a body distinct from the core (24), respectively.

Inventors

  • DE BENEDITTIS, Giacomo
  • CATALDI, MATTEO
  • DELLA FORNACE, Enrico
  • PELLONI, Simone

Assignees

  • FERRARI S.p.A.

Dates

Publication Date
20260513
Application Date
20251111

Claims (15)

  1. Electric machine rotor (1), in particular for an electric motor for traction of motor vehicles, the electric machine rotor (1) extending along a longitudinal axis (3) and comprising: - a first and a second shaft portion (4,5), which are axially opposite to each other and are suitable to be supported, in use, by respective bearings to rotate about said longitudinal axis (3); - an inlet (7) and an outlet (8) for a heat transfer liquid, at said first shaft portion (4); - an annular wall (10) which is coaxial to said shaft portions (4,5) and supports a plurality of permanent magnets (13); - an inner cavity (23) radially bounded by said annular wall (10); - a core (24) housed in said inner cavity (23) and having: a) at least one supply hole (45) extending along said longitudinal axis (3) and communicating with said inlet (7); b) a plurality of heat exchange channels (28) for cooling said annular wall (10) and/or said permanent magnets (13); - delivery junction channels (44), which are separate from each other, provide communication between said supply hole (45) and said heat exchange channels (28), and are configured to divert the heat transfer liquid into a radial direction; - return junction channels (38) which are separate from each other, provide communication between said heat exchange channels (28) and said outlet (8), and are configured to divert the heat exchange liquid into an axial direction; wherein - said delivery junction channels (44) are defined by a first and a second surface (43,42) axially facing each other and defining respectively part of said core (24) and of a first body distinct from said core (24), and/or - said return junction channels (38) are defined by a third and a fourth surface (35,36) axially facing each other and defining respectively part of said core (24) and of a second body (20) distinct from said core (24).
  2. The electric machine rotor according to claim 1, wherein - the second surface (42) of said first body is smooth, and the first surface (43) of said core (24) is provided with ribs (46), which separate said delivery junction channels (44) from each other in a circumferential direction; and/or - the fourth surface (36) of said second body (20) is smooth, and the second surface (35) of said core (24) is provided with ribs (46), which separate said return junction channels (38) from each other in a circumferential direction.
  3. The electric machine rotor according to any one of the preceding claims, wherein said delivery junction channels (44) and/or said return junction channels (38) radiate out from said longitudinal axis (3).
  4. The electric machine rotor according to any one of the preceding claims, wherein - the second surface (42) of said first body and the first surface (43) of said core (24) have curved profiles matching to each other; and/or - the fourth surface (36) of said second body and the second surface (35) of said core (24) have curved profiles matching to each other.
  5. The electric machine rotor according to any one of the preceding claims, wherein said first body is defined by an insert (41), which is at least partially housed in said second shaft portion (5) coaxially with said core (24).
  6. The electric machine rotor according to claim 5, wherein said core (24) and/or said insert (41) comprise a plastic material.
  7. The electric machine rotor according to claim 5 or 6, wherein said core (24) and/or said insert (41) are configured in such a way that they can be manufactured by a moulding technique.
  8. The electric machine rotor according to any one of the preceding claims, wherein said inner cavity (23) is axially bounded by a first flange (14), and wherein said fourth surface (36) joins an inner face (16) of said first flange (14) to an inner cylindrical surface of said first shaft portion (4).
  9. The electric machine rotor according to claim 8, wherein said second body (20) is a metal body comprising said first flange (14) and said first shaft portion (4).
  10. The electric machine rotor according to any one of the preceding claims, wherein said inner cavity (23) is axially bounded by a second flange (15), and wherein said second flange (15), said annular wall (10) and said second shaft portion (5) define parts of a further metal body (22).
  11. The electric machine rotor according to any one of the preceding claims, wherein said supply hole (45) is made centrally along said longitudinal axis (3) and, in correspondence with said delivery junction channels (44), is engaged by fins (55) so as to be split into a plurality of axial channels (56) parallel to each other.
  12. The electric machine rotor according to claim 11, wherein said fins (55) define part of said core (24).
  13. The electric machine rotor according to any one of the preceding claims, wherein said core (24) defines part of a further insert (32), axially ending with a shank (33) housed in said first shaft portion (4); and wherein said return junction channels (38) communicate with said outlet (8) through a gap (39) radially defined by an inner cylindrical surface of said first shaft portion (4).
  14. The electric machine rotor according to claim 13, wherein said gap (39) is split, in a circumferential direction, into a plurality of return channels (40) parallel to each other.
  15. The electric machine rotor according to claim 13 or 14, wherein said first shaft portion (4) is engaged by an interface element, which is coaxial to said shank (33) and has an axial hole defining said inlet (7); said outlet (8) being defined between said interface element and the inner cylindrical surface of said first shaft portion (4).

Description

Cross-reference to related applications This patent application claims priority from Italian patent application no. 102024000025269 filed on November 11, 2024, the entire disclosure of which is incorporated herein by reference. Technical field The invention relates to an electric machine rotor. In particular, the disclosure refers to electric machines defined by motors for traction of motor vehicles, without for this reason lacking generality. Background For traction of motor vehicles, synchronous electric motors are generally used, namely electric motors with permanent magnets. In particular, brushless motors can be used, wherein the permanent magnets are fixed on a support wall, which is part of the rotor, while the stator includes the windings that are electrically powered to generate the rotating magnetic field, which, in turn, will cause the rotation of the magnets and, therefore, of the entire rotor. Some electric motors are cooled by means of liquid heat exchange systems, for example with channels made in the stator. Applications regarding the traction of motor vehicles are relatively severe from the point of view of heating, both in terms of the heat generated by the electric current in the windings of the stator and in terms of the heat generated by eddy currents in the rotor, in the area of the permanent magnets and the of surface that supports them. Therefore, in order to prevent the heating from reaching levels that can compromise the efficiency of the motor, or even the operation thereof, the rotor - and not only the stator - needs to be cooled. To this aim, the rotor has a shaft, which extends along the rotation axis and must be provided with inner axial channels, communicating with an inlet and with an outlet for introducing and extracting the heat exchange liquid while the rotor rotates. In addition, in order to cool the radially outermost areas of the rotor, namely the permanent magnets and the wall that supports them, the heat exchange liquid must be diverted radially outwards, with respect to such axial channels. To this regard, it is appropriate to divide the overall radial flow into several channels or sectors, which are separate from one another and each have a relatively limited width in the circumferential direction, in order to avoid, or at least limit, fluid dynamic losses due to turbulence that may form because of Coriolis accelerations. At the same time, localized fluid dynamic losses should be limited when the liquid flow is diverted into the radial channels, starting from the rotor shaft, so as to consequently reduce the consumption and the size of the pump that supplies the heat exchange liquid. A possible cause generating localized losses is represented by the fact that the liquid in the radial channels also has a rotation component (due to the rotation of the rotor about its axis during operation), while in the rotor shaft the liquid flow is essentially axial, assuming that it is channelled into one single central supply channel, namely along the rotation axis. In these conditions, the flow is subjected to a sudden change in the motion conditions, when it enters the radial channels, with consequent fluid dynamic losses. In order to overcome this drawback, it is appropriate to divide the liquid flow in the rotor shaft into several axial channels, which are separate from one another, so that it already has a component of rotary motion inside the rotor shaft. Patent application US 2015/288255 A1 corresponds to the preamble of claim 1 and discloses solutions of this type, with a plurality of axial supply channels and with a plurality of return channels inside the rotor shaft. A further cause generating localized losses is defined by the sudden change in direction, when the liquid is diverted from the rotor shaft into the radial channels. To this regard, in document US 2015/288255 A1, the axial channels end in the area of respective holes, which are made in the rotor shaft by machining by machine tools, in substantially radial directions. Therefore, the liquid flows in the rotor shaft are subjected to an abrupt change in direction, at a right angle, when they enter such holes. The same configuration also occurs when the liquid flows radially flow back into the rotor shaft. As mentioned above, these sudden changes in direction cause localized fluid dynamic losses, which should be avoided. In other words, compared to US 2015/288255 A1, there is a need to join the axial channels to the radial channels by means of relatively wide bending radii, so that the change in direction is less abrupt. In addition to reducing fluid dynamic losses, other objects need to be achieved, compared to known solutions, for example: producing and/or assembling the rotor through operations that are relatively simple and economic and in a relatively short time; making the design of the rotor components more versatile; improving the characteristics that allow the channels to be separated from one another in