Wire guide for the rotor of a wound-rotor synchronous motor

Abstract

The invention relates to a guide device for winding an electric conductor around a plurality of poles (30) of a rotor (1) of an electric machine, the plurality of poles being distributed around a shaft (2) extending axially in the rotor, the device comprising a guide head (4) capable of being mounted on the shaft (2), characterised in that the guide head (4) comprises a metal base structure (5) provided with a plurality of arms (51) extending radially from an inner portion (52) of the metal base structure provided with a central opening (53), and a plastic structure (6) overmoulded onto the metal base structure (5) in a manner rearwardly disposed relative to a cylindrical inner surface (53a) of the central opening (53), so that the cylindrical inner surface (53a) of the central opening (53) of the metal base structure (5) is designed to be in direct contact with the shaft of the rotor so as to be mounted on the shaft of the rotor by interference fit.

Description

Technical Field

[0001] The present invention relates to the field of wound rotor synchronous machines and more particularly to a guide device for winding an electrically conductive wire around a plurality of poles of a rotor of an electric machine, the plurality of poles of the rotor of the electric machine being distributed around a shaft extending axially through the rotor, the device comprising a guide head which can be mounted on the shaft. Background Art

[0002] The rotor of a wound rotor synchronous machine has a rotor shaft intended to be mounted to rotate about its axis, a set of laminations coaxially mounted on the rotor shaft, the set of laminations having a plurality of radially projecting poles around each pole of which a winding of an electric conductor is intended to be wound. Heads for guiding the electric conductor around each pole of the rotor are axially arranged on both sides of the set of laminations, each guide head being provided with a central orifice through which a shaft passes.

[0003] The invention has as its field of application electric machines for electric or hybrid motor vehicles.

[0004] Patent document FR 2 984 034 describes a wound rotor, used in particular in electric machines for electric traction motor vehicles, incorporating guide means for fixing the wires of the winding around the poles made from a lamination stack.

[0005] High-speed rotors are subject to difficult operating conditions and, in particular, to high stress loads in the radial direction. In particular, the windings of the rotor are subject to high centrifugal forces during the operation of the rotor and must be properly retained. The two guides (also referred to as "coil head guides") for the winding wires are also subject to high stresses of the centrifugal forces during the rotation of the rotor and must therefore be adapted to function under such conditions. In addition, conventionally, each guide is fixed to a crown, which is an independent part of the body of the rotor and is arranged at the periphery of the guide, so as to form a device for radially retaining the guide. More specifically, the crown has an annular configuration around the periphery of the guide, and its profile has an L-shaped shape with wings oriented axially and resting on the periphery of the guide, and wings oriented radially towards the axis and resting on the radial end faces of each pole of the guide. In order to allow the crown to be fixed to the guide, the crown has an orifice in its radial wing, which is intended to allow the through bolt to pass. The radial end faces of the poles of the seeker and the set of laminations have corresponding holes so that through bolts can be axially passed through the crown, the seeker and the set of laminations to the opposite side of the rotor, wherein a locking nut is screwed on the free end of each through bolt coming out of the opposite crown. When the nuts are tightened with sufficient torque (typically to the plastic limit of the through bolts), the assembly is firmly held so as to remain assembled when the rotor is subjected to high centrifugal forces.

[0006] However, this arrangement for radially retaining the crown of the seeker requires a large number of parts, namely the crowns themselves, through bolts and nuts, which ultimately leads to increased weight. In addition, this arrangement requires a large number of assembly operations (through bolts, tightening nuts), and it is desirable to try to reduce these assembly operations.

[0007] Alternatively, to balance the rotor, a balancing ring can be fixed to the outside of the radial wings of the crown, the ring being provided with cavities distributed around its circumference. The operation of balancing the rotor consists in inserting weights in some of the cavities distributed along the circumference, or removing material from the ring by drilling it. However, the disadvantage of this balancing device is that the weights are mounted on the balancing ring. This therefore requires the presence of a ring, which is disadvantageous for weight, and the operation of fixing this balancing ring to the crown.

[0008] It is also known to lock the lamination stack of the rotor by means of metal retaining rings which are conventionally arranged around the shaft on both sides of the lamination stack. This arrangement makes it possible to protect the rotor from shocks, especially in the event of an accident, ensuring that the lamination stack remains in its initial position, but conflicts with the need to lighten the rotor, reduce its axial dimensions and reduce the number of rotor assembly operations. Summary of the invention

[0009] In this context, the present invention aims to remedy these drawbacks by proposing a guide device which otherwise corresponds to the generic definition given in the above preamble, the essential characteristics of which are that the guide head comprises a metal basic structure and a plastic structure, the metal basic structure being provided with a plurality of legs extending radially from an inner part of the metal basic structure provided with a central opening, the plastic structure being overmolded onto the metal basic structure in a manner set back from a cylindrical inner surface of the central opening, the cylindrical inner surface not being overmolded with the plastic structure, so that the cylindrical inner surface of the central opening of the metal basic structure is designed to be in direct contact with the shaft of the rotor so as to be mounted on the shaft of the rotor by means of an interference fit.

[0010] By means of this arrangement, a seeker is provided which consists of a single, in particular rigid part, the metal part of which is mounted on the shaft of the rotor by means of an interference fit, ensuring that the seeker is firmly held relative to the shaft, thereby eliminating the crown and the associated through-bolts which have hitherto been used to ensure this function. As a result, the rotor assembly operations are thus simplified.

[0011] Furthermore, when the guide head according to the invention is mounted on the shaft of the rotor on each side of the lamination stack, the guide head also makes it possible to effectively absorb the axial loads to which the rotor is subjected, in particular in the event of a crash. The guide head according to the invention thus also performs a part of the function currently performed by the retaining ring, i.e., holding the lamination stack in position on the shaft, so that the retaining ring can also be omitted.

[0012] Advantageously, the metal basic structure has at least one solid balancing portion protruding axially from the outside of the inner portion, at least one surface of the at least one solid balancing portion extending in a radial plane being free of the overmolded plastic structure so as to be accessible. In particular, if a rotor balancing operation proves necessary, this radial surface can provide access to a rotor balancing tool which removes material from the solid balancing portion(s) protruding from the outside of the inner portion of the metal basic structure, typically by drilling.

[0013] Preferably, a plurality of solid balancing portions are provided, which are located adjacent the outer edge of the inner portion and each solid balancing portion extends between two respective legs of the metal base structure.

[0014] Advantageously, the radial surface is free of the overmoulded plastic structure by means of a plurality of open cavities distributed circumferentially on the overmoulded plastic structure.

[0015] Advantageously, the metallic base structure is produced in one piece from an aluminum alloy or a steel alloy by stamping or casting.

[0016] The invention also relates to a rotor of a wound rotor synchronous machine having a rotor shaft intended to be mounted to rotate about its axis, a set of laminations coaxially mounted on the rotor shaft, the set of laminations having a plurality of radially projecting poles and at least one axial opening, a winding of an electrically conductive wire intended to be wound around each pole, characterised in that the rotor comprises a guide device as described above, which is mounted on the shaft on both sides of the set of laminations.

[0017] According to one embodiment, a balancing plate can be inserted between the set of laminations and each seeker so that the cylindrical outer surface of the balancing plate is accessible. In particular, if a rotor balancing operation proves necessary, the cylindrical outer surface can provide access to a rotor balancing tool that typically removes material from the balancing plate by drilling.

[0018] The invention also relates to a method for assembling a rotor as described above, the method comprising:

[0019] The steps of assembling each of the guide heads on both sides of the group of laminations on the rotor shaft by interference fit, and assembling the group of laminations on the rotor shaft by interference fit,

[0020] as well as

[0021] The step of winding a conductive wire around each pole by means of said seeker.

[0022] Advantageously, when the metallic basic structure of the seeker is provided with at least one solid balancing portion as described above, the method may comprise the step of removing material from said at least one solid balancing portion of said metallic basic structure to balance the rotor.

[0023] Advantageously, according to an embodiment of a rotor having a balancing plate as described above, the method may comprise the step of balancing the rotor by removing material from said balancing plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further particular characteristics and advantages of the invention will become apparent on reading the following description of a particular embodiment of the invention given by way of non-limiting indication with reference to the accompanying drawings, in which:

[0025] - Figure 1 A perspective view schematically shows a metal basic structure of a seeker according to an embodiment of the present invention;

[0026] - Figure 2 Schematically shows the Figure 1 A perspective view of a partial cross-section of an overmolded seeker of an embodiment of FIG.

[0027] - Figure 3 Schematically shows Figure 2 A cross-sectional view of the overmolded seeker head is shown;

[0028] - Figure 4 schematically illustrates a perspective view of an overmolded seeker mounted on the shaft of a rotor according to a specific embodiment of the invention;

[0029] - Figure 5 schematically illustrates a perspective view of a partial cross section of an overmolded seeker according to another specific embodiment of the present invention;

[0030] - Figure 6 Schematically shows an exploded view of a rotor according to the invention, the rotor having Figure 5 A seeker mounted on a rotor and a balancing plate according to a specific embodiment. DETAILED DESCRIPTION

[0031] Figure 6A rotor 1 of an electric machine is schematically illustrated. The rotor 1 comprises a shaft 2 which extends axially through the rotor 1 .

[0032] A set of laminations 3 is coaxially mounted on the rotor shaft. The set of laminations 3 is formed by axial stacking of laminations extending in a radial plane perpendicular to the axis of the rotor shaft. In the radial plane, the laminations in the set of laminations all have the same shape. The set of laminations has salient poles 30 that are regularly distributed in the circumferential direction and protrude from the shaft toward the periphery of the rotor. In the exemplary embodiment described with reference to the accompanying drawings, the set of laminations has eight salient poles 30. However, the present invention is not limited to this type of configuration, but is applied to a set of laminations having multiple salient poles (and preferably at least three poles).

[0033] This set of laminations 3 is mounted by interference fit on the cylindrical outer surface of the rotor shaft 2. Therefore, this set of laminations 3 is assembled to the cylindrical outer surface of the rotor shaft in a hot state.

[0034] Each pole 30 is constituted by an arm 31 extending radially towards the periphery of the rotor. The free end 32 of the pole 20 ends with a circumferentially protruding turn on both sides of the arm 31. The function of the protruding turn 32 of each pole 30 is to retain the conductive field winding wound around the radial arm 31 of each pole 30 in the radial direction to resist the centrifugal forces to which the field winding is subjected during the rotation of the rotor.

[0035] Each pole 30 thus has a field winding. Figure 6 The guide heads 4 (only one guide head is shown) are mounted coaxially with the shaft 2 of the rotor on both sides of the stack of laminations 3 in order to guide the wires constituting the field winding around each pole 30. Each guide head 4 placed on both sides of the stack of laminations 3 has the shape of a general disk extending in a radial plane perpendicular to the axis of the shaft of the rotor.

[0036] Figures 1 to 3 The structure of the seeker is shown in more detail. According to the present invention, the seeker has a structure consisting of Figure 1 The particular feature of the illustrated metal basic structure 5 is constituted by a plastic structure 6 overmolded thereon, such as Figure 2 and Figure 3 What is shown.

[0037] In other words, according to the invention, the metal basic structure 5 constitutes a metal insert of the seeker 4, preferably made of an aluminum alloy or a steel alloy, and the seeker 4 is obtained by at least partially coating the metal insert 5 by means of overmolding with a high mechanical strength plastic material (such as a thermosetting plastic material), thereby forming a plastic structure 6 of the seeker 4.

[0038] like Figure 1As shown, the metal insert 5 is provided with a plurality of legs 51 , for example eight, extending radially from an internal portion 52 of the insert provided with a central orifice 53 for coaxial mounting on the shaft of the rotor on which the seeker is intended to be mounted.

[0039] Each leg 51 of the metal insert 5 has a main portion 51 a extending radially from the outer edge 52 a of the inner portion 52 and delimited at its end opposite to the outer edge 52 a by two shoulders 51 b , 51 c .

[0040] like Figures 1 to 3 The illustrated metal insert 5 is preferably obtained by stamping a metal sheet.

[0041] Thus, each radial leg 51 of the metal insert 5, once overmolded with the plastic structure 6, forms a radial leg of the seeker 4, which is intended to be positioned next to the corresponding pole 30 of the rotor 1, so as to allow winding. More specifically, the main portion 51a, once coated with the overmolded plastic structure 6, is intended to receive a set of wires, said plastic overmolded main portion 51a being arranged next to the radial arm 31 of each pole 30 of the set of laminations 2 of the rotor 1, while the two shoulders 51b, 51c, similarly coated with the overmolded plastic structure 6, are intended to be arranged next to the circumferentially projecting folds 32 on either side of the arm 31 of each pole 30. Thus, the wires of the field winding of each pole are coiled around the main portion of the corresponding leg of the seeker between the two shoulders, in a direction parallel to the shoulders.

[0042] According to the invention, it is provided that the plastic structure 6 overmolded on the metal insert 5 is set back relative to the cylindrical inner surface 53a of the central orifice 53 of the metal insert 5. In other words, the metal cylindrical inner surface 53a is not overmolded with a plastic layer 6, so that it can be in direct contact with the cylindrical outer surface 21 of the shaft of the rotor in order to mount the seeker on the shaft of the rotor by means of an interference fit. In other words, two concentric surfaces, namely the cylindrical outer surface 21 of the shaft of the rotor and the cylindrical inner surface 53a of the seeker 4, are connected by means of an interference fit.

[0043] Advantageously, the seeker 4 is fixed to the rotor shaft by means of an interference fit, while the set of laminations 3 is assembled on the rotor shaft by means of an interference fit.The operation of winding the wire around the poles of the rotor can then proceed.

[0044] Therefore, the seeker 4 also acts as a retaining ring on both sides of the lamination stack, simply because it is mounted on the shaft by means of an interference fit. In particular, the amount of winding on the seeker is negligible compared to the amount of winding on the poles of the rotor. The risk of separation of the lamination stack by the inertia of the winding mass is greater than for the seeker, and therefore, mounting the seeker on the shaft by means of an interference fit will be sufficient to lock the lamination stack relative to the inertial rotation.

[0045] The design of the guide head according to the invention as described above makes it possible to ensure that the guide head is more reinforced and thus provides greater resistance to the risks of fractures and cracks, especially with respect to the high centrifugal forces that may be applied during the operation of the rotor. The guide head consists of a metal basic structure or a metal insert that is overmolded with a plastic structure.

[0046] This design also makes it possible to dispense with parts such as the crown and the associated through-bolts and retaining rings, thereby lightening the rotor and reducing the number of rotor assembly operations.

[0047] Reference Figure 2 and Figure 3 , a plastic structure 6 overmolded thereon may be provided on the outside of the metal insert 5 (i.e. on the opposite side of the lamination stack of the rotor with respect to the seeker when the seeker is mounted on the rotor), the plastic structure having circumferentially distributed cavities 60, which are open axially towards the outside of the seeker via openings 60a extending in radial planes. Preferably, each cavity 60 extends circumferentially between two radial legs of the seeker 4. These cavities 60 in the overmolded plastic structure 6 of the seeker 4 are more particularly suitable for receiving counterweights in order to remedy possible rotor balancing defects.

[0048] Figure 4 and Figure 5 Concerning a particular embodiment of the seeker head according to the invention, the seeker head is designed such that, if it proves necessary to balance the rotor, the distribution of mass on the rotor can be optionally varied without having to add additional counterweights thereto.

[0049] For this purpose, refer to Figure 4, a metal insert of the seeker head is adapted, wherein the metal insert has a solid balancing portion 54 protruding axially from the outside of the inner portion of the metal insert and having a surface 54a extending in a radial plane, which surface is free of the overmolded plastic structure 6, so that this radial surface 54a of the solid balancing portion 54 may be accessible. This radial surface 54a thus makes it possible to provide access in the axial direction to a rotor balancing tool, which removes material from this solid balancing portion 54 protruding from the outside of the metal insert of the seeker head, for example by drilling, thereby making it possible to change the distribution of mass on the rotor.

[0050] It should be noted that the outer face of the metal insert is understood to be the face oriented axially towards the outside of the rotor, ie the face facing away from the lamination stack relative to the seeker head when the seeker head is mounted on the rotor.

[0051] according to Figure 4 In a specific embodiment, the solid balancing portion 54 of the metal insert forms a continuous crown protruding from the outside, and the cylindrical inner surface 54b and the cylindrical outer surface 54c of the solid balancing portion extend near the central orifice of the metal insert and near the outer edge of the inner portion of the metal insert, respectively.

[0052] The radial surface 54a of the solid balancing portion 54 is also provided with radial grooves 54d extending between the cylindrical inner surface 54b and the cylindrical outer surface 54c of the solid balancing portion 54, which grooves are intended to provide passage for and protect the winding wires during balancing operation.

[0053] Figure 5 An embodiment variant of the balancing means provided on the metal insert 5 of the seeker 4 is shown. According to this embodiment variant, the balancing means of the metal insert 5 consists of a plurality of solid balancing portions 54' which protrude axially from the outside, near the outer edge 52a of the inner portion 52 of the metal insert 5 and each extend between two respective legs 51 of the metal insert 5. A cavity 60 in the plastic structure 6 is then overmolded around the plurality of protruding solid balancing portions 54' so that a respective radial surface 54'a of each of these solid balancing portions 54' passes through an opening 60a towards the outside of these cavities 60 without the overmolded plastic structure 6. The radial surface 54'a is arranged in a flush manner in the plane of the opening 60a of the cavity 60.

[0054] Figure 4 and Figure 5The embodiments of the seeker head presented in , which describe rotor balancing means integrated in a metal insert of the seeker head, make it necessary to adapt the method of manufacturing the metal insert 5 , which in this context is preferably obtained by casting moulding.

[0055] Figure 6 Yet another embodiment for realizing a possible rotor balancing operation is described. According to this embodiment, a metal balancing plate 7 produced by casting, the shape of which closely matches the profile of the poles of the rotor, is mounted on the shaft between the set of laminations 3 and each guide 4 axially arranged on both sides of the set of laminations 3. The balancing plate 7 has an outer peripheral cylindrical surface 71 capable of providing access in the radial direction to a rotor balancing tool, which removes material from this balancing plate, for example by drilling, if it proves necessary to change the distribution of mass on the rotor.

Claims

1. A guide device for winding an electrically conductive wire around a plurality of poles (30) of an electric machine rotor (1), the plurality of poles of the electric machine rotor being distributed around a shaft (2) extending axially through the rotor, the device comprising a guide head (4) which can be mounted on the shaft (2), characterized in that The seeker (4) comprises a metal base structure (5) provided with a plurality of legs (51) extending radially from an inner portion (52) of the metal base structure provided with a central opening (53), and a plastic structure (6) overmolded on the metal base structure (5) in a manner disposed behind a cylindrical inner surface (53a) of the central opening (53), the cylindrical inner surface not overmolded with the plastic structure, so that the cylindrical inner surface (53a) of the central opening (53) of the metal base structure (5) is designed to be in direct contact with the shaft of the rotor so as to be mounted on the shaft of the rotor by means of an interference fit.

2. The guiding device according to claim 1, characterized in that The metal base structure (5) has at least one solid balancing portion (54, 54') protruding axially from the outside of the inner portion (52), at least one radial surface of the at least one solid balancing portion extending in a radial plane being free of the overmolded plastic structure (6) so as to be accessible.

3. The guiding device according to claim 2, characterized in that The metal base structure (5) comprises a plurality of solid balancing portions (54') which are located near the outer edge (52a) of the inner portion (52) and each solid balancing portion extends between two corresponding legs (51) of the metal base structure (5).

4. The guiding device according to claim 3, characterized in that The radial surface is free of the overmolded plastic structure (6) by means of a plurality of open cavities (60) which are circumferentially distributed on the overmolded plastic structure (6).

5. A guiding device according to any one of the preceding claims, characterized in that The metal base structure (5) is produced in one piece from an aluminum alloy or a steel alloy by stamping or casting.

6. A rotor (1) of a wound rotor synchronous machine having a rotor shaft (2) intended to be mounted for rotation about its axis, a set of laminations (3) coaxially mounted on the rotor shaft (2), the set of laminations (3) having a plurality of radially projecting poles (30) and at least one axial opening, a winding of an electric conductor intended to be wound around each pole, characterised in that The rotor comprises two guide devices as claimed in any one of the preceding claims, which are mounted on the shaft (2) on both sides of the set of laminations (3).

7. The rotor according to claim 6, characterized in that The rotor comprises a balancing plate (7) which is inserted between the set of laminations (3) and each seeker (4) such that the outer peripheral cylindrical surface (71) of the balancing plate (7) is accessible.

8. A method for assembling a rotor as claimed in any one of claims 6 and 7, the method comprising: The steps of assembling each of the guide heads (4) on both sides of the group of laminations on the rotor shaft (2) by means of interference fit, and at the same time assembling the group of laminations (3) on the rotor shaft (2) by means of interference fit, as well as The step of winding a conductive wire around each pole (30) by means of the guide head (4).

9. The method according to claim 8, characterized in that The rotor comprises two guide devices according to any one of claims 2 to 4, the method comprising the step of balancing the rotor by removing material from the at least one solid balancing portion (54, 54') of the metal basic structure (5).

10. The method according to claim 8, characterized in that The rotor is a rotor according to claim 7 and the method comprises the step of balancing the rotor by removing material from the balancing plate (7).

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