Rotor of a rotary electric machine
The rotor design with stabilizing retaining screws addresses the issue of screw movement under centrifugal forces by using a dual-diameter shank configuration, improving stability and reducing deformation in high-power electrical machines.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- VALEO ELECTRIFICATION SAS
- Filing Date
- 2025-12-19
- Publication Date
- 2026-06-25
AI Technical Summary
Rotating electrical machines experience issues with retaining screws moving within their insertion holes due to centrifugal forces, leading to lamination deformation and imbalance, particularly in high-power motors, which compromises the machine's robustness and equilibrium.
The rotor design incorporates retaining screws with a shank comprising a first stabilizing portion of a larger diameter and an extension portion of a smaller diameter, clamped between two retaining plates, to minimize radial displacement and weight, while maintaining mechanical strength.
This design effectively limits screw movement under centrifugal forces, optimizing weight and mechanical strength, thereby enhancing the rotor's stability and reducing deformation and imbalance.
Smart Images
Figure EP2025088332_25062026_PF_FP_ABST
Abstract
Description
Description Title of the invention: Rotor of a rotating electrical machine
[0001] The present invention relates to a rotor of a rotating electrical machine and a rotating electrical machine comprising such a rotor. The invention also relates to a retaining screw for such a rotor.
[0002] Rotating electrical machines are widely used in industry, particularly in the automotive sector, whether for the propulsion of electric vehicles or for various vehicle equipment.
[0003] Such electrical machines comprise a housing, a stator, and a rotor, the stator being mounted around the rotor. The rotor is rotationally mounted on a rotating shaft and consists of a lamination held between a first retaining plate and a second retaining plate by means of a plurality of retaining screws. Each retaining screw in the plurality of retaining screws is inserted through an insertion hole passing through the first retaining plate, the lamination, and the second retaining plate such that the first and second retaining plates axially clamp the lamination.
[0004] Beyond a certain rotor speed, it is possible for at least one of the retaining screws to move within its corresponding insertion hole. This can occur particularly with 25 kW electric motors. This movement can cause deformation of the lamination stack and / or deformation of at least one of the retaining screws. It can also lead to imbalances and loss of equilibrium.
[0005] It is therefore necessary to find a solution that allows for a more robust electrical machine, less sensitive to centrifugal forces.
[0006] To this end, the present invention relates to a rotor of an electrical machine mounted fixed for rotation on a rotating shaft and which comprises - a bundle of sheet metal, - a first retaining plate and a second retaining plate, - a plurality of retaining screws, each retaining screw of the plurality of retaining screws being inserted into an insertion hole formed through the first retaining plate, the sheet metal bundle, and the second retaining plate, - each of the retaining screws of the plurality of retaining screws comprising a screw head, a shank and a threaded portion, the sheet metal bundle being clamped between the first retaining plate and the second retaining plate by bearing the screw head of each of the retaining screws against the first retaining plate at one end of the sheet metal bundle and by bearing a bolt tightened around the threaded portion of each of the retaining screws against the second retaining plate at an opposite end of the sheet metal bundle, in which the shank comprises a first stabilizing portion of first diameter and an extension portion of second diameter, the first diameter being greater than the second diameter.
[0007] The invention thus makes it possible to limit the radial displacements of the retaining screw in the insertion hole, occurring in particular under the effect of centrifugal force.
[0008] The invention advantageously makes it possible to obtain a compromise between the weight of each of the retaining screws, which must be as low as possible, and the mechanical strength of such retaining screws, in particular with the resistance to the effects of centrifugation.
[0009] Indeed, by locally reducing the space between the retaining screw and a periphery of the insertion hole, not only is the amplitude of movement of the retaining screw inside the insertion hole limited, but also the weight of the retaining screw is optimized so that it is as low as possible.
[0010] In one embodiment of the invention, the diameter of the retaining screw is configured so as to be complementary to a diameter of the insertion orifice, that is to say that the diameter of the retaining screw must allow its insertion inside the insertion orifice while being capable of being inserted by interference with an inner periphery of the insertion orifice.
[0011] In one embodiment of the invention, the first stabilization portion is located only opposite the sheet metal bundle.
[0012] In one embodiment of the invention, the first stabilizing portion is located close to the screw head and away from the threaded part.
[0013] In one embodiment of the invention, the first stabilizing portion extends axially along a first length from the screw head towards the threaded portion such that, inside the insertion hole, the first stabilizing portion is positioned opposite the first retaining plate and opposite a portion of the sheet metal bundle. In this case, the retaining plate is fixed radially by the stabilizing portion and axially by tightening the screw.
[0014] In one embodiment of the invention, the first stabilizing portion forms a cylindrical section with a circular or serrated periphery. A serrated configuration of this first stabilizing portion advantageously allows for a further reduction in the weight of the retaining screw.
[0015] In one embodiment of the invention, each retaining screw includes a second stabilizing portion of a third diameter positioned close to the threaded portion and away from the screw head. This second stabilizing portion, in addition to the first stabilizing portion, limits the bending effect that can occur on the retaining screw under the effect of centrifugal force.
[0016] In one embodiment of the invention, the second stabilization portion is located in the extension portion.
[0017] In one embodiment of the invention, the third diameter is greater than the second diameter.
[0018] In one embodiment of the invention, the third diameter is equal to the first diameter.
[0019] In one embodiment of the invention, the second stabilizing portion extends axially over a second length from the screw head towards the threaded part such that, inside the insertion hole, the second stabilizing portion is positioned opposite another part of the sheet metal package.
[0020] In one embodiment of the invention, the second stabilization portion is arranged at a distance, in an axial direction, from the retaining plates.
[0021] In one embodiment of the invention, the second stabilization portion is arranged at a distance from the first stabilization portion.
[0022] In one embodiment of the invention, the second stabilizing portion forms a cylindrical section with a cross-section whose periphery is circular or crenellated.
[0023] In one embodiment of the invention, the sheet metal bundle is traversed by a plurality of pairs of permanent magnets, each of the permanent magnets of the plurality of pairs of permanent magnets being positioned radially below each of the retaining screws.
[0024] In one embodiment of the invention, the weight of the screw head is reduced by 10% compared to the weight of the state-of-the-art retaining screw head, i.e. with a rod of constant diameter.
[0025] In one embodiment of the invention, at least one of the retaining plates has a notch in which the retaining screw and / or bolt, respectively, are at least partially housed. This reduces the axial footprint of the rotor. For example, the first retaining plate has a notch in which the retaining screw is at least partially housed, and the second retaining plate has a notch in which the bolt is at least partially housed.
[0026] The invention also relates to a rotating electrical machine of a vehicle comprising a rotor as previously described.
[0027] The invention finally relates to a retaining screw suitable for use in a rotor as previously described, the retaining screw comprising a screw head, a shank and a threaded part, in which the shank comprises a first stabilizing portion of first diameter and an extension portion of second diameter, the first diameter being greater than the second diameter.
[0028] In one embodiment, the rod includes a second stabilizing portion spaced apart from the first stabilizing portion.
[0029] In one embodiment, the first stabilization portion and / or the second stabilization portion comprises a cylindrical portion with a cross-section whose perimeter is circular or crenellated.
[0030] Other features and advantages of the invention will become clearer upon reading the following description, given by way of illustrative and non-limiting example, and the accompanying drawings, among which:
[0031] [Figure 1] shows a diagram of a rotor of an electric machine, according to one embodiment of the invention, and
[0032] [Figure 2] represents a diagram of a method for making a retaining screw, according to an embodiment of the invention.
[0033] In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," will be used to designate, according to the definitions given in the description, elements of the rotor, stator, and / or electric machine. By convention, the "radial" orientation is directed orthogonally to the axial orientation. The axial orientation refers, depending on the context, to the axis of rotation of the rotor. The "circumferential" orientation is directed orthogonally to the axial direction and orthogonally to the radial direction. The terms "external" and "internal" are used to define the relative position of one element with respect to another, with respect to the reference axis; an element close to the axis is thus described as internal, as opposed to an external element located radially at the periphery.We will also use the terms "front" and "rear" to define the relative position of one element with respect to another, according to the direction with respect to an axial orientation determined by the main X axis of the electrical machine, "front" designating the part located on the left of Figure 1 and "rear" designating the part located on the right of Figure 1.
[0034] Figure 1 illustrates an electrical machine 1 comprising a rotor 2 and a stator (not shown) mounted around the rotor 2. The rotor 2 is intended to be rotationally connected to a rotating shaft 3 extending along a rotating axis X. The rotor 2 comprises a lamination stack 4, a first retaining plate 5, and a second retaining plate 6. The lamination stack 4 is axially clamped between the first retaining plate 5 and the second retaining plate 6 by means of a plurality of retaining screws 7 arranged circumferentially. Each of the retaining screws 7 extends axially through the rotor 2.
[0035] To this end, the rotor 2 is drilled with a plurality of insertion holes such as 8 extending circumferentially all around the rotor 2. Each of the insertion holes 8 extends axially through the rotor 2. Each of the retaining screws 7 of the plurality of retaining screws is intended to be inserted into a corresponding insertion hole 8. In the example according to the embodiment of the invention, ten insertion holes such as 8 extend through the rotor 2 and are each intended to receive a retaining screw such as 7. In particular, the insertion hole 8 is formed through the first plate The retaining screw 7 is inserted into a corresponding insertion hole 8. For the sake of simplicity, only one retaining screw 7 will be described below.
[0036] The retaining screw 7 extends along an elongation axis X' parallel to the rotation axis X. The retaining screw 7 comprises a screw head 9, a central portion 10, and a threaded portion 11. The retaining screw 7 is held to the sheet metal stack 4 by the screw head 9 bearing against the first retaining plate 5 and by a bolt 12 tightened around the threaded portion 11 bearing against the second retaining plate 6. Thus, the sheet metal stack 4 is axially clamped between the first retaining plate 5 and the second retaining plate 6.
[0037] The central portion 10 comprises a first stabilizing portion 13 of first diameter D1 and an extension portion 14 of second diameter D2, the first diameter D1 being larger than the second diameter D2. The first stabilizing portion 13 is located close to the screw head 9 and away from the threaded part 11. In one example, the diameter D1 is equal to 6.2 mm and the diameter D2 is equal to 6.0 mm.
[0038] The first stabilization portion 13 extends axially over a first length L1 from the screw head 9 to a point on the retaining screw 7 intended to be in view of the first retaining plate 5 and extends to another point on the retaining screw 7 intended to be in view of the sheet metal bundle 4.
[0039] In other words, the retaining screw 7 is inserted through the rotor 2 so that the first stabilizing portion 13 is positioned opposite the first retaining plate 5 and opposite part of the sheet metal bundle 4.
[0040] In another example illustrated in dotted lines on Figure 1, another first stabilization portion, similar to the first stabilization portion 13, could be positioned only at the level of the sheet bundle 4. In this example, the other first stabilization portion is made so as to be centered with respect to the sheet bundle 4.
[0041] The insertion hole 8 has a fourth diameter D4. The retaining screw 7 is thus dimensioned inside the insertion hole 8 such that a first distance d1, measured radially between an external surface 22 of the rod 10 located at the first stabilizing portion 13 and a periphery 17 of the insertion hole 8, is less than a second distance d2, measured between the external surface of the rod 10 located at the extension portion 14 and the perimeter 17 of the insertion orifice 8.
[0042] The first stabilizing portion 13 forms a cylindrical section with a circular periphery in this embodiment. In another embodiment not shown, the first stabilizing portion 13 forms a cylindrical section with a serrated periphery. The same may be true for the other first stabilizing portion. Such a shape allows for a further reduction in the weight of the retaining screw.
[0043] The rod 10 has a second stabilizing portion 15 with a third diameter D3. The third diameter D3 is larger than the second diameter D2 and less than or equal to the first diameter D1. The second stabilizing portion 15 is located close to the threaded part 11 and away from the screw head 9. In one example, the diameters D1 and D3 could each be equal to 6.20 mm.
[0044] Thus, the first diameter D1 is made in such a way that the space between the retaining screw 7 and the rotor 2 is as small as possible.
[0045] The second stabilizing portion 15 extends axially over a second length L2 from the screw head 9 towards the threaded part 11 so that, inside the insertion hole 8, the second stabilizing portion 15 is positioned opposite another part of the sheet metal package 4.
[0046] In this example, the second stabilization portion 15 is located in the extension portion 14.
[0047] As with the first stabilizing portion 13, the second stabilizing portion 15 forms a cylindrical section with a circular periphery in this embodiment. In another embodiment not shown, the second stabilizing portion 15 can form a cylindrical section with a serrated periphery. Such a shape allows for an even further reduction in the weight of the retaining screw.
[0048] The rotor 2 also includes a plurality of permanent magnets 16 arranged radially below the plurality of retaining screws 7. Each of the permanent magnets 16 is arranged through the stack of laminations 4. In the embodiment, the permanent magnets 16 are arranged one after the other.
[0049] Figure 2 illustrates, in diagram form, a method for manufacturing the retaining screw 7 according to an embodiment of the invention. The components of the retaining screw known to those skilled in the art will not be described here, but rather those components of the invention.
[0050] In particular, the first stabilization portion 13 is carried out as follows. In a first step 1), a first point 19 of a steel wire 18 is pinched using a first tool (represented schematically by means of the two opposing arrows in the diagram). In one example, the steel wire has a diameter of 6 mm. Then in a second step 2), an end 20 of the steel wire 18 is struck axially using a second tool (represented schematically by means of an arrow positioned opposite the end 20 of the steel wire 18) so as to cause a local increase in the diameter of the first point 19 of the steel wire 18 in the form of a bulge 21. Then in a third step 3), a rolling operation is carried out on the bead 21 using a rolling tool so as to flatten the surface of the steel wire 18 at the location of the bead 21.In one example, the surface of the bead 21 can be flattened in such a way as to obtain a diameter of 6.20 mm over a given length.
[0051] The same procedure will be used to obtain the second stabilization portion 15 at a second location 19' of the steel wire 18. The second stabilization portion 15 can be carried out either simultaneously or successively in the four stages described above for the first stabilization portion 13.
[0052] Of course, the preceding description has been given as an example only and does not limit the scope of the invention, which would not be exceeded by replacing the various elements with any other equivalents.
Claims
DEMANDS 1. Rotor (2) of an electrical machine (1) mounted fixed for rotation on a rotating shaft (3) and comprising - a bundle of sheet metal (4), - a first retaining plate (5) and a second retaining plate (6), - a plurality of retaining screws (7), each of the retaining screws of the plurality of retaining screws being inserted into an insertion hole (8) formed through the first retaining plate, the sheet metal bundle and the second retaining plate, - each of the retaining screws of the plurality of retaining screws comprising a screw head (9), a shank (10) and a threaded portion (11), the bundle of sheets being clamped between the first retaining plate and the second retaining plate by the screw head of each of the retaining screws bearing against the first retaining plate at one end of the bundle of sheets and by a bolt (12) tightened around the threaded portion of each of the retaining screws bearing against the second retaining plate at an opposite end of the bundle of sheets, in which the shank has a first stabilizing portion (13) of first diameter (D1) and an extension portion (14) of second diameter (D2), the first diameter being greater than the second diameter.
2. Rotor according to claim 1, wherein the first stabilizing portion (13) is located close to the screw head and away from the threaded part or the first stabilizing portion is located only opposite the sheet metal bundle.
3. Rotor according to any one of the preceding claims, wherein the first stabilizing portion (13) extends axially over a first length L1 from the screw head towards the threaded part such that, inside the insertion hole, the first stabilizing portion is positioned opposite the first retaining plate and opposite a part of the sheet metal bundle.
4. Rotor according to any one of claims 1 to 3, wherein the first stabilizing portion forms a cylindrical section with a cross-section whose periphery is circular or crenellated.
5. Rotor according to any one of claims 1 to 4, wherein each of the retaining screws comprises a second stabilizing portion (15) of third diameter (D3) which is positioned close to the threaded part and away from the screw head.
6. Rotor according to the preceding claim, wherein the second stabilizing portion is located in the extension portion.
7. Rotor according to claim 5 or 6, wherein the third diameter is greater than the second diameter and / or the third diameter is equal to the first diameter.
8. Rotor according to any one of claims 5 to 7, wherein the second stabilizing portion extends axially over a second length L2 from the screw head towards the threaded part such that, inside the insertion hole, the second stabilizing portion is positioned opposite another part of the sheet metal package.
9. Rotor according to any one of claims 5 to 8, wherein the second stabilizing portion forms a cylindrical section with a cross-section whose periphery is circular or crenellated.
10. Rotor according to any one of the preceding claims, wherein the lamination pack (4) is traversed by a plurality of pairs of permanent magnets, each of the permanent magnets of the plurality of pairs of permanent magnets being positioned radially below each of the retaining screws.
11. Rotating electric machine of a vehicle comprising a rotor according to one of the preceding claims.
12. Retaining screw for a rotor according to any one of claims 1 to 10, the retaining screw comprising a screw head (9), a shank (10) and a threaded portion (11), in which the shank comprises a first stabilizing portion (13) of first diameter (D1) and an extension portion (14) of second diameter (D2), the first diameter being greater than the second diameter.
13. Retaining screw according to claim 12, wherein the first stabilizing portion comprises a cylindrical portion with a cross-section whose perimeter is circular or crenellated.
14. Retaining screw according to claim 12 or 13, wherein the rod comprises a second stabilizing portion (15) spaced from the first stabilizing portion.
15. Retaining screw according to claim 14, wherein the second stabilizing portion comprises a cylindrical portion with a section whose perimeter is circular or crenellated.