Rotor of a rotating electrical machine
The rotor design with stabilizing retaining screws addresses screw movement issues by minimizing radial displacement and weight, improving the machine's robustness against centrifugal forces.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- VALEO EAUTOMOTIVE GERMANY GMBH
- Filing Date
- 2024-12-20
- Publication Date
- 2026-06-26
AI Technical Summary
Rotating electrical machines experience retaining screw movement within insertion holes at high rotor speeds, leading to lamination deformation and imbalance due to centrifugal forces, particularly in 25 kW electric motors.
The rotor design incorporates retaining screws with a first stabilizing portion of a larger diameter than the screw head, positioned near the head and a second stabilizing portion near the threaded part, to minimize radial displacement and weight, while maintaining mechanical strength.
This design limits retaining screw displacement and weight, enhancing the robustness of the electrical machine against centrifugal forces, reducing deformation and imbalance.
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Abstract
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 and especially in the automotive field, whether for the propulsion of electric vehicles or for the various equipment of the vehicle.
[0003] Such electrical machines comprise a housing, a stator, and a rotor, the stator being mounted around the rotor. The rotor is rotatably mounted on a rotating shaft and is formed of a lamination held between a first retaining plate and a second retaining plate by means of a plurality of retaining screws. Each of the retaining screws 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 that at least one of the retaining screws may 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 a 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
[0007] - a bundle of sheet metal,
[0008] - a first retaining plate and a second retaining plate,
[0009] - a plurality of retaining screws, each of the retaining screws of the plurality of screws the retaining plate being inserted into an insertion hole formed through the first retaining plate, the sheet metal bundle, and the second retaining plate,
[0010] - each of the retaining screws of the plurality of retaining screws comprising a head of screws, a shank and a threaded portion, the sheet metal bundle being clamped between the first retaining plate and the second retaining plate by the screw head of each retaining screw bearing against the first retaining plate at one end of the sheet metal bundle and by a bolt tightened around the threaded portion of each retaining screws against the second retaining plate at an opposite end of the sheet metal bundle, in which
[0011] the rod comprises a first stabilizing portion of first diameter and an extension portion of second diameter, the first diameter being greater than the second diameter.
[0012] The invention thus makes it possible to limit the radial displacements of the retaining screw in the insertion orifice, occurring in particular under the effect of centrifugal force.
[0013] 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.
[0014] Indeed, by locally reducing the space between the retaining screw and a periphery of the insertion orifice, not only is the amplitude of displacement of the retaining screw inside the insertion orifice limited, but also the weight of the retaining screw is optimized so that it is reduced as much as possible.
[0015] 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.
[0016] In one embodiment of the invention, the first stabilization portion is located only opposite the sheet metal bundle.
[0017] In one embodiment of the invention, the first stabilization portion is located close to the screw head and away from the threaded part.
[0018] In one embodiment of the invention, the first stabilizing portion extends axially over 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.
[0019] 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.
[0020] In one embodiment of the invention, each of the retaining screws includes a second stabilizing portion of a third diameter which is 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.
[0021] In one embodiment of the invention, the second stabilization portion is located in the extension portion.
[0022] In one embodiment of the invention, the third diameter is greater than the second diameter.
[0023] In one embodiment of the invention, the third diameter is equal to the first diameter.
[0024] In one embodiment of the invention, the second stabilizing portion extends axially over a second length from the screw head towards the threaded part so that, inside the insertion hole, the second stabilizing portion is positioned opposite another part of the sheet metal package.
[0025] In one embodiment of the invention, the second stabilizing portion forms a cylindrical section with a cross-section whose periphery is circular or crenellated.
[0026] 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.
[0027] 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.
[0028] The invention also relates to a rotating electrical machine of a vehicle comprising a rotor as previously described.
[0029] 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.
[0030] In one embodiment, the rod includes a second stabilizing portion spaced from the first stabilizing portion.
[0031] In one embodiment, the first stabilization portion and / or the second stabilization portion comprises a cylindrical portion with a section whose perimeter is circular or crenellated.
[0032] Other features and advantages of the invention will become more apparent upon reading the following description, given by way of illustrative and non-limiting example, and the accompanying drawings, among which:
[0033] [Fig-1] represents a diagram of a rotor of an electric machine, according to a mode of realization of the invention, and
[0034] [Fig.2] represents a diagram of a method for making a retaining screw, according to an embodiment of the invention.
[0035] In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," shall 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.The terms "front" and "rear" will also be used 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 to the left of [Fig.1] and "rear" designating the part located to the right of [Fig.1].
[0036] 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.
[0037] 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 retaining plate 5, the stack of laminations 4, and the second retaining plate 6. 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.
[0038] 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 part 11. The retaining screw 7 is held to the sheet metal bundle 4 by the screw head 9 bearing against the first retaining plate 5 and by a bolt 12 tightened around the threaded part 11 bearing against the second retaining plate 6. Thus, the sheet metal bundle 4 is axially clamped between the first retaining plate 5 and the second retaining plate 6.
[0039] The central portion 10 comprises a first stabilizing portion 13 of first diameter DI and an extension portion 14 of second diameter D2, the first diameter DI 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 portion IL. In one example, the diameter DI is equal to 6.2 mm and the diameter D2 is equal to 6.0 mm.
[0040] 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.
[0041] 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 a part of the sheet metal bundle 4.
[0042] In another example illustrated in dotted lines on [Fig.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.
[0043] 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 dl measured radially between an external surface 22 of the rod 10 located at the level of 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 level of the extension portion 14 and the periphery 17 of the insertion hole 8.
[0044] In this embodiment, the first stabilizing portion 13 forms a cylindrical section with a circular periphery. 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.
[0045] The rod 10 has a second stabilizing portion 15 of third diameter D3. The third diameter D3 is greater than the second diameter D2 and less than or equal to the first diameter Dl. 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 Dl and D3 can each be equal to 6.20 mm.
[0046] Thus, the first diameter Dl is made in such a way that the space between the retaining screw 7 and the rotor 2 is as small as possible.
[0047] The second stabilizing portion 15 extends axially over a second length L2 from the screw head 9 towards the threaded part 11 such that, inside the insertion hole 8, the second stabilizing portion 15 is positioned opposite another part of the sheet metal package 4.
[0048] In this example, the second stabilization portion 15 is located in the extension portion 14.
[0049] 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 may form a cylindrical section with a serrated periphery. Such a shape allows for a further reduction in the weight of the retaining screw.
[0050] 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.
[0051] Figure 2 illustrates, in diagram form, a method for manufacturing the retaining screw 7 according to an embodiment of the invention. The elements of the retaining screw known to those skilled in the art will not be described here, but rather those elements forming part of the invention.
[0052] 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), one end 20 of the steel wire 18 is struck axially with a second tool (represented schematically by means of an arrow positioned with respect to the end 20 of the steel wire 18) so as to cause a local increase in the diameter of the first place 19 of the steel wire 18 in the form of a bead 21. Then in a third step 3), a rolling is carried out on the bead 21 with a rolling tool so as to flatten the surface of the steel wire 18 at the place of the bead 21.In one example, the surface of the bead 21 can be flattened to obtain a diameter of 6.20 mm over a given length.
[0053] 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 produced either simultaneously or successively in the four stages described above for producing the first stabilization portion 13.
[0054] Of course, the preceding description has been given by way of 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 lamination pack (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 lamination pack 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 sheet metal bundle 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 sheet metal bundle and by a bolt (12) tightened around the threaded part of each of the retaining screws bearing against the second retaining plate at an opposite end of the sheet metal bundle, in which the rod comprises a first stabilizing portion (13) of first diameter (D1) and an extension portion (14) of second diameter (D2), the first diameter being larger 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 has a second stabilizing portion (15) of third diameter (D3) which is positioned close to the threaded portion 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 sheet metal bundle (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 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.