ROTOR FOR A ROTARY ELECTRIC MACHINE

Abstract

A rotor for a rotary electric machine, the rotor having an axis of rotation and including a rotor shaft extending parallel to the axis of rotation, a rotor body mounted on the rotor shaft and having a plurality of teeth protruding radially, and at least one field coil wound around the plurality of teeth, the field coil forming coil ends at axial ends of the teeth. At least one cover mounted on the rotor shaft and configured to cover the coil ends. The cover includes a plurality of holes configured to each receive a solid balancing element which provides an additional mass to the rotor in order to balance said rotor.

Claims

1. A rotor for a rotary electric machine, the rotor having an axis of rotation and comprising: a rotor shaft extending parallel to the axis of rotation; a rotor body mounted on the rotor shaft and having a plurality of teeth protruding radially; at least one field coil wound around the plurality of teeth, said field coil forming coil ends at axial ends of the teeth; at least one cover mounted on the rotor shaft and configured to cover the coil ends; characterized in that said cover comprises a plurality of holes configured to each receive a solid balancing element which provides an additional mass to the rotor in order to balance said rotor.

2. The rotor as claimed in claim 1, wherein the holes are blind holes.

3. The rotor as claimed in claim 1, wherein the holes are located on a geometrical line which is a circle centered on the axis of rotation.

4. The rotor as claimed in claim 3, wherein the holes are located on two concentric circles centered on the axis of rotation and having different diameters.

5. The rotor as claimed in claim 1, wherein the cover has a planar wall transverse, in particular perpendicular, to the axis of rotation, and an external circumferential skirt connected to the planar wall at a peripheral region of the planar wall, and at least some of the holes, in particular arranged on a circle, are formed through the planar wall in the peripheral region so that the holes extend from the planar wall towards the external skirt.

6. The rotor as claimed in claim 1, wherein the cover has a hub to be mounted on the rotor shaft and at least some of the holes, in particular arranged on a circle, are formed on a transverse wall of the hub, said transverse wall being transverse, in particular perpendicular, to the axis of rotation.

7. The rotor according to claim 5, wherein the cover comprises: a first portion said holes formed on said transverse wall of the hub; a second portion peripheral to said first portion, said second portion including at least a part of said planar wall; a third portion peripheral to said second portion including said holes extending from the planar wall towards the external skirt; the thickness of said cover in the first and third portions being higher than the thickness of the cover in the second portion.

8. The rotor as claimed in claim 1, wherein the holes belong to at least a first group of holes and a second group of holes, the holes of each group having the same diameters and the hole diameter of the first group being different from the hole diameter of the second group of holes.

9. The rotor as claimed in claim 8, wherein the holes of the first group and the second group are located on the same circle, in particular holes of respective first and second group being arranged in an alternated manner.

10. The rotor as claimed in claim 1, wherein the total number of holes on the cover for receiving solid balancing elements is higher than 10, or higher than 20.

11. The rotor as claimed in claim 1, wherein the holes are formed on the cover during the manufacturing of the cover, for instance during a die cast process to manufacture the cover.

12. The rotor as claimed in claim 1, wherein the solid balancing element comprises one of the following elements: a cylindrical pin to be pressed in the hole, a dowel pin to be pressed in the hole, a grub screw to be screwed in the threaded hole, a self-cutting grub screw to be inserted in the hole.

13. A method for balancing a rotor for a rotary electric machine, the rotor having an axis of rotation and comprising: a rotor shaft extending parallel to the axis of rotation; a rotor body mounted on the rotor shaft and having a plurality of teeth protruding radially; at least one field coil wound around the plurality of teeth, said field coil forming coil ends at axial ends of the teeth; at least one cover mounted on the rotor shaft and configured to cover the coil ends, said cover comprising a plurality of holes configured to each receive a solid balancing element which provides an additional mass to the rotor in order to balance said rotor; the method comprising the following step: balancing the rotor by inserting one or a plurality of solid balancing elements in the holes of the cover.

14. The rotor as claimed in claim 2, wherein the holes are located on a geometrical line which is a circle centered on the axis of rotation.

15. The rotor as claimed in claim 2, wherein the cover has a planar wall transverse, in particular perpendicular, to the axis of rotation, and an external circumferential skirt connected to the planar wall at a peripheral region of the planar wall, and at least some of the holes, in particular arranged on a circle, are formed through the planar wall in the peripheral region so that the holes extend from the planar wall towards the external skirt.

16. The rotor as claimed in claim 2, wherein the cover has a hub to be mounted on the rotor shaft and at least some of the holes, in particular arranged on a circle, are formed on a transverse wall of the hub, said transverse wall being transverse, in particular perpendicular, to the axis of rotation.

17. The rotor according to claim 5, wherein the cover comprises: a first portion said holes formed on said transverse wall of the hub; a second portion peripheral to said first portion, said second portion including at least a part of said planar wall; a third portion peripheral to said second portion including said holes extending from the planar wall towards the external skirt; the thickness of said cover in the first and third portions being higher than the thickness of the cover in the second portion.

18. The rotor as claimed in claim 1, wherein the holes belong to at least a first group of holes and a second group of holes, the holes of each group having the same diameters and the hole diameter of the first group being different from the hole diameter of the second group of holes.

19. The rotor as claimed in claim 2, wherein the total number of holes on the cover for receiving solid balancing elements is higher than 10, or higher than 20.

20. The rotor as claimed in claim 2, wherein the holes are formed on the cover during the manufacturing of the cover, for instance during a die cast process to manufacture the cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The invention will be better understood on reading the description that follows, and by referring to the appended drawings given as non-limiting examples, in which identical references are given to similar objects and in which:

[0065] FIG. 1 is a schematic diagram of an automotive electric or hybrid vehicle comprising a rotary electric machine according to an embodiment of the invention;

[0066] FIG. 2 is a schematic diagram of a rotor and a stator of the rotary electric machine of FIG. 1;

[0067] FIG. 3 is a schematic diagram in perspective of the rotor of FIG. 2;

[0068] FIG. 4 is a schematic diagram of a partial cut view of the rotor of FIG. 3.

DETAILED DESCRIPTION

[0069] FIG. 1 represents schematically an electric vehicle or a hybrid electric automotive vehicle EV comprising wheels and an electric drive system 100 configured to drive at least indirectly at least one of the wheels of the vehicle. The vehicle may comprise a high-voltage power supply battery B, preferably a rechargeable battery, for providing electric power to the electric drive.

[0070] The electric drive system 100 comprises a rotary electric machine 1 and an inverter I configured to convert a direct current (DC) voltage coming from the high-voltage power supply battery B into an alternating current (AC) voltage in order to drive the rotary electric machine 1. The rotary electric machine 1 may in particular be a three-phase rotary electric machine supplied with a three-phase AC voltage. A DC/DC converter 101 is provided between the battery B and the inverter I. An AC/DC converter 102 is provided between a network power supply and the inverter I in a known manner.

[0071] As illustrated in FIG. 2, the rotary electric machine 1 comprises a stator 2, referring to the fixed part of the rotary electric machine, and a rotor 3, referring to the rotating part of the rotary electric machine. The stator 2 presents an annular shape and surrounds coaxially the rotor 3. The rotary electric machine 1 comprises a casing 4 covering the stator 2 and the rotor 3. In a known manner, the stator 2 comprises a stator body formed of a stack of laminations having a plurality of stator teeth projecting radially, and stator windings wound around the stator teeth.

[0072] The rotor 3 is a separately excited rotor, also commonly referred as a wound rotor or a slip ring rotor. In this type of rotor, the rotor comprises field coils 10 connected to an external power supply through slip rings 6. The slip rings 6 correspond to electro-mechanical devices configured to allow the exchange of electric power between the field coils and the external power supply.

[0073] As illustrated in FIG. 3, the rotor 1 comprises the rotor shaft 5 configured to rotate around the axis X of rotation, and a rotor body 7 being configured to be mounted on the rotor shaft 5. The shaft 5 is made of steel.

[0074] The rotor body 7 has a plurality of teeth 11 protruding radially.

[0075] As visible on FIG. 4, field coils 10 are wound around the plurality of teeth 11, said field coils 10 forming coil ends 12 at axial ends of the teeth 11.

[0076] Longitudinal inserts 38 are mounted between consecutive teeth 11.

[0077] Two covers 15 are mounted on the rotor shaft 5 and configured to cover the coil ends 12 on both axial ends of the rotor body 7. Only one cover 15 is visible on FIG. 4. The other cover 15 is similar to the one shown on FIG. 4.

[0078] Each cover 15 has a mounting opening 16 receiving a portion 17 of the rotor shaft 5 so that the cover 15 and the portion 17 of the rotor shaft exert reciprocal radial force on each other to ensure the fixation. The covers 15 are made of aluminum.

[0079] The cover 15 has a planar wall 18 perpendicular to the axis of rotation X, and an external circumferential skirt 19 connected to the planar wall 18 at a peripheral region 20 of the planar wall 18.

[0080] Each cover 15 comprises a plurality of blind holes configured to each receive a solid balancing element 21 which provides an additional mass to the rotor 3 in order to balance said rotor 3.

[0081] Some holes 22 are arranged on an outer circle 23 in the peripheral region 20 so that the holes 22 extend through the planar wall 18 towards the external skirt 19.

[0082] The cover 15 has a hub 25 to be mounted on the rotor shaft 5.

[0083] Some holes 26 and 27 are arranged on an inner circle 28 on a transverse wall 29 of the hub 25, said transverse wall 29 being perpendicular to the axis of rotation X.

[0084] The concentric circles 23 and 28 are centered on the axis of rotation X and have different diameters.

[0085] The holes 22, 26 and 27 are located on the respective circle 23 and 28 with a constant pitch between the holes.

[0086] The holes 22, 26 and 27 are formed on regions of the cover 15 with sufficient depth so that the presence of the holes does not cause mechanical weaknesses on the cover.

[0087] The cover 15 comprises: [0088] a first portion 40 including the holes 26, 27 formed on the transverse wall 29 of the hub 25; [0089] a second portion 41 peripheral to said first portion, said second portion including at least a part of said planar wall 18; [0090] a third portion 42 peripheral to said second portion including the holes 22 extending from the planar wall 18 towards the external circumferential skirt 19.

[0091] As shown in FIG. 4, the thickness T1 of said cover 15 in the first portion 40 and the thickness T4 of the third portion 42 are higher than the thickness T3, T4 of the cover 15 in the second portion 41. Specifically, the second portion 41 is free from any holes configured to receive a solid balancing element. The second portion 41 has therefore a reduced thickness in order to reduce the dimension of the cover, and thereby the dimension of the rotor. Still, some thickness is left in the cover at the appropriate locations, specifically in the first 40 and third 42 portions for the holes 22, 26, 27. For example, this second portion 41 has a decreasing thickness from the first portion 40 to the third portion 42. The maximum thickness of the second portion 41 is T2 and its minimum thickness is T3.

[0092] In the present embodiment of the invention, T1 is in the range 15 mm to 25 mm, being in particular equal to 18 mm.

[0093] T2 is in the range 6 mm to 10 mm, being in particular equal to 8 mm.

[0094] T3 is in the range 6 mm to 10 mm, being in particular equal to 5 mm.

[0095] T4 is in the range 30 mm to 40 mm, being in particular equal to 32 mm.

[0096] The holes 26 and 27 belong to a first group of holes 26 and a second group of holes 27, the holes of each group having the same diameters and the hole diameter of the first group 26 being greater from the hole diameter of the second group of holes 27.

[0097] The holes 26 and 27 of respective first group and second group are arranged in an alternated manner.

[0098] The holes 22, 26 and 27 have three different diameters. The outer circle 23 on the peripheral region of the cover 15 has identical holes and the inner circle 28 on the transverse wall of the hub has holes 26 and 27 of two different diameters.

[0099] The holes 22, 26 and 27 have an axis parallel to the axis of rotation X.

[0100] The total number of holes 22, 26 and 27 on the cover for receiving solid balancing elements is higher than 10, or higher than 20.

[0101] The number of holes 26 and 27 on the inner circle 28 is higher than the number of holes 22 in the outer circle 23.

[0102] For instance, the outer circle 23 has 24 holes. The inner circle 28 has 22 small holes 27 and 22 big holes 26.

[0103] For instance, the hole diameter on the outer circle is 5 mm.

[0104] For instance, the hole diameter of the small holes 27 on the inner circle is 2 mm.

[0105] For instance, the hole diameter of the big holes 26 on the inner circle is 5 mm.

[0106] In case different solid balancing elements are present on the cover, biggest balancing elements 21 are able to add a higher mass due to the diameter during the balancing process. Smaller balancing elements are able to generate the fine balancing.

[0107] The holes 22, 26 and 27 can be threaded or not threaded.

[0108] The holes 22, 26 and 27 are formed on the cover 15 in aluminum, during the manufacturing of the cover, for instance during a die cast process to manufacture the cover.

[0109] The rotor 3 is balanced by the presence of at least one solid balancing element 21 inserted in one of the holes 22, 26 and 27.

[0110] In the embodiment of FIG. 3, three solid balancing elements 21 are inserted in three holes 22, 26 and 27.

[0111] In some are cases, the rotor 3 may not need any solid balancing element to balance the rotor.

[0112] Each solid balancing element 21 comprises one of the following elements: a cylindrical pin to be pressed in the hole, a dowel pin to be pressed in the hole, a grub screw to be screwed in the threaded hole, a self-cutting grub screw to be inserted in the hole.

[0113] Each solid balancing element 21 is made of steel.

[0114] The solid balancing elements 21 may have different lengths and thus masses.

[0115] The balancing of the rotor 3 is made by inserting one or a plurality of solid balancing elements 21 in the holes 22, 26 and 27 of the cover.