Stator for rotating electrical machine

Abstract

Stator for a Rotating Electric Machine. The present invention relates to a stator (1) for a rotating electric machine with radial flux, comprising an annular wall (2) centered about an axis of revolution (3), the annular wall (2) comprising an inner face (5) oriented towards the axis of revolution (3), the inner face (5) defining an internal diameter of the stator (1) and being provided with a plurality of slots (6) regularly distributed along the inner face (5) and configured to receive a stator winding (1), characterized in that the inner face (5) comprises at least two grooves (9) distinct from the slots (6), each of the grooves (9) being configured to receive a rib of a stator support tool (1). The invention also covers a varnishing system comprising such a stator (1) and a method for varnishing such a stator (1). (Figure 1)

Description

Title of the invention: Stator for rotating electrical machine

[0001] The present invention relates to the field of radial flux rotating electrical machines for electric or hybrid vehicles and more particularly concerns a stator for such rotating electrical machines.

[0002] Electric or hybrid motor vehicles use rotating electrical machines, in particular electric motors with at least one stator and one rotor, which are often radial flux machines. In such machines, the rotor and stator are coaxial and arranged around each other, such that windings on the stator, when energized by an electric current, generate a magnetic flux in a radial direction with respect to an axis of rotation of the rotating electrical machine. This magnetic flux is made to rotate around the axis of rotation by appropriate control of the electric current. The rotor, equipped with magnetic elements, is thus driven in rotation by the rotating magnetic flux and ensures the transmission of mechanical energy to the vehicle via a drive shaft forming an axial extension of the rotor.In an alternator-type operating mode, the rotating electrical machine can be used to generate and store electrical energy following a mechanical movement of the rotor.

[0003] During the assembly process of the rotating electrical machine, one of the steps consists of assembling the stator, and in particular, fitting the previously assembled stator body with the winding. Slots arranged axially along an internal annular wall of the stator body allow the insertion of conductive segments of the winding within the stator body. These conductive segments are connected to each other, from one conductive segment in one slot to another, via curved axial end portions, in order to create electrical continuity and extend the winding over the entire annular wall. It is known, in particular, to have wire-type windings, with a continuous electrical wire wound from slot to slot, successively forming a conductive segment within a slot and a curved axial end portion until the winding is complete.It is now common to have pin-wound windings, with U-shaped pins having two arms forming straight conductive segments and linked by a curved axial end portion, each pin being inserted into the stator body with one arm in one of the stator slots, the winding being completed by soldering two-to-two the free ends of one arm of one pin with one arm of another pin.

[0004] It is known to line the slot with insulating paper to prevent contact between a conductive segment and the stator body. Furthermore, to ensure this insulation, once the winding is complete, the stator, and more specifically the slots in the stator body, is impregnated with varnish that provides insulation for the winding.

[0005] To this end, during stator assembly, the stator is mechanically held by a support tool comprising arms bearing radially against an inner face of the annular wall. Each arm has a plate bearing against the annular wall to allow the stator to be rotated by rotating the support tool while varnish is applied, particularly to the portion of the winding extending axially from the stator body. The varnish spreads by capillary action along the conductive segments within the slots, and the stator rotation, as well as the varnish flow rate and duration, are controlled to ensure that the stator is properly coated with varnish.

[0006] The support of each arm forms a contact surface between the plate of an arm and the inner face of the annular wall so that during the varnishing operation, the propagation of the varnish by capillary action at the level of this contact surface is blocked by the presence of the arm and an excess thickness of varnish is formed around each of the plates of the tool.

[0007] This presence of varnish on the inner face around the plates forms a local overthickness and modifies an internal diameter of the stator body, which can greatly impair the proper functioning of the rotating electrical machine by hindering the mounting of the rotor within the stator, a tolerance of the internal diameter of the stator being on the order of a tenth of a millimeter.

[0008] The present invention falls within this context and proposes a stator for a rotating electric machine with radial flux, comprising an annular wall centered around an axis of revolution, the annular wall comprising an inner face oriented towards the axis of revolution, the inner face delimiting an internal diameter of the stator and being provided with a plurality of notches distributed regularly along the inner face and configured to receive a stator winding, characterized in that the inner face comprises at least two grooves distinct from the notches, each of the grooves being configured to receive a rib of a stator support tool.

[0009] The grooves allow the contact surface between the support tool and the stator to be located in a recessed area within the stator material. Therefore, any excess varnish deposited while the support tool is resting on the inner face of the stator's annular wall generates a localized thickness in the corresponding groove, which does not protrude inward from the stator and does not alter the stator's internal diameter. Furthermore, the grooves contribute to creating a receiving area for the support tool, with the edges of each groove acting as anti-escape means of the support tool when it is positioned in the corresponding groove, which can limit the size of the support tool and thus limit the points of contact between the inner face of the stator and the support tool and the obstruction to the propagation of the varnish which can generate local areas of thick varnish which do not conform to the tolerance of the internal diameter of the stator.

[0010] The stator is radial flux and therefore at least partially delimits a volume intended to contain the rotor, which can be driven into rotation by the rotating magnetic flux generated by the stator when the latter is electrically powered. The internal volume is delimited by the annular wall extending around the axis of revolution of the stator, which can be considered as an axis of rotation of the rotor.

[0011] The inner face of the annular wall is oriented towards the rotor once the rotating electrical machine is fully assembled. Slots are formed in this annular wall and open onto its inner face to receive the winding extending along the stator. The slots allow, for example, a pin-wound stator winding. The slots are formed from one axial end to the other of the stator body.

[0012] The grooves are specifically formed in the annular wall of the stator, distinct from the notches, to cooperate with a support tool during stator assembly and varnishing. These grooves extend along the inner face of the stator and are sized to receive at least one rib of the support tool. The contact between the ribs of the support tool and the grooves of the stator constitutes the only contact between the stator and the support tool, thus limiting the risk of unwanted varnish runoff due to contact of the support tool against the inner face of the stator.

[0013] It should be noted that when the rotating electrical machine is assembled, with the rotor arranged within the stator, the grooves are at least partially filled with varnish and are no longer functional insofar as they do not cooperate with other elements of the electrical machine.

[0014] According to one feature of the invention, each groove comprises a bottom wall and side walls connecting the bottom wall to the inner face of the stator, said groove being dimensioned so that the bottom wall forms a stop face for the rib and so that at least one lateral clearance zone is formed between a side wall and the rib. In other words, the groove is dimensioned such that, on the one hand, its depth, or radial dimension, allows the point of contact between the support tool and the stator to be radially offset so that this point of contact, here formed by the bottom wall of the groove, is sufficiently inside the stator, that is to say, within the annular envelope defining the body of the stator. And this dimensioning is such that, on the other hand, the width of the groove, or orthoradial dimension, is greater The rib is sized to the corresponding dimension so that it contacts the bottom wall of the groove without touching the two side walls. The stability of the contact between the rib and the groove is ensured by the pressure exerted by the rib on the bottom wall of the groove, which is sufficient to maintain the mechanical connection between the stator and the support tool when the assembly needs to be rotated to allow the varnish to spread. Having one or two lateral clearance zones creates varnish collection areas in the immediate vicinity of the contact point between the rib and the stator. Thus, the varnish that spreads along the inner face of the stator and is blocked by the rib can accumulate in these clearance zones, within the annular envelope defining the stator body, and therefore without forming bulges that could alter the internal diameter of the stator.

[0015] According to one feature of the invention, the grooves are straight and parallel to a principal dimension of the notches, parallel to the axis of revolution. The grooves are advantageously parallel to an axial dimension of the stator and the notches in order to improve the stability of the support tool and to prevent the latter from extending through a notch via one of its ribs.

[0016] According to one feature of the invention, at least one groove has a bottom wall in the shape of an arc of a circle along a cutting plane perpendicular to the axis of revolution.

[0017] According to another feature of the invention, at least one groove is polygonal in shape along a cutting plane perpendicular to the axis of revolution.

[0018] It can be seen from reading these characteristics that the shapes of the grooves can be diverse, the essential thing being to ensure a complementarity of shapes between the portions intended to be in contact when the support tool cooperates with the stator, that is to say the bottom wall of the groove and the free end of the rib of the support tool.

[0019] According to one feature of the invention, the grooves are each arranged between two adjacent notches. Each groove is framed on both sides by a notch. Preferably, depending on their number and the configuration of the support tool, the grooves are evenly distributed over the diameter delimited by the inner face of the stator.

[0020] According to a feature of the invention, at least one of the grooves is arranged at an equal distance from the two adjacent notches.

[0021] According to another feature of the invention, two adjacent notches are separated within the stator by a tooth whose free end, turned towards the inside of the stator, forms a tooth root, at least one of the grooves extending along an orthoradial dimension over a width at least equal to 25% of the orthoradial extent of the corresponding tooth pedicle. More specifically, such a groove can extend over an orthoradial distance of approximately 30% to 35% of the orthoradial dimension of the corresponding tooth pedicle.

[0022] The teeth are formed by the stator material interposed between two adjacent notches. The tooth roots constitute an internal radial end of the teeth and contribute to forming the inner face of the stator's annular wall. Having a groove width less than a given threshold value prevents weakening of the tooth roots.

[0023] The tooth roots may, in particular, comprise, orthoradially, a central portion and lateral extensions, or branches, which limit the opening size of the slots and prevent the winding pins from escaping their slots once positioned. The grooves, providing sufficiently rigid mechanical support, are arranged in the central portion of the tooth roots, in the axial extension of the tooth, to form the grooves in the stack of laminations forming the stator. It is understood that the groove cannot be formed in the branches of the tooth root due to their small radial dimension, so the groove is advantageously formed in the central portion of the tooth root.

[0024] According to another feature of the invention, the groove is arranged at an equal distance from the notches framing it on both sides.

[0025] According to another feature of the invention, two adjacent notches are separated within the stator by a tooth whose free end, facing inward toward the stator, forms a tooth root that helps to partially close each of the two adjacent notches, at least one of the grooves extending radially to a depth at least equal to 3% of the radial extent of the corresponding tooth. More particularly, such a groove may have a radial dimension of approximately 3.5% to 6% of the radial extent of the corresponding tooth.

[0026] According to one feature of the invention, at least one groove extends over at least 30% of the axial dimension of the annular wall. More particularly, such a groove can extend over a distance of between 30% and 100% of the axial dimension of the annular wall. More particularly, such a groove can extend over a distance of approximately 35% to 55% of the axial dimension of the annular wall. More particularly, such a groove can extend over 100% of the axial dimension of the annular wall, that is to say, all the laminations of the sheet metal bundle are provided with a portion of the groove. Such an axial dimension is dependent on the axial dimension of the rib of the support tool. A high axial dimension increases the number of contact points between the support tool and the stator and thus improves stability. The dimension of such a groove thus allows for the accommodation of a rib of the support tool long enough to ensure the stability of the assembly when the support tool is pressed against the body of the stator, or to accommodate a plurality of aligned ribs of the support tool, again to ensure the stability of the assembly.

[0027] According to one feature of the invention, the stator comprises at least two grooves aligned between two identical notches. In this alternative, it is understood that the at least two grooves arranged between two identical notches extend mainly along an axis parallel to the axis of rotation and the axis of elongation of the notches, and are aligned along this axial direction to form the equivalent of an interrupted groove, each groove being intended to cooperate with a rib of a pair of aligned ribs of a support tool.

[0028] According to one feature of the invention, the stator comprises a winding, the winding comprising conductive segments housed in slots, the slots and the inner face of the stator being coated with insulating varnish, each of the grooves being at least partially filled with insulating varnish. The insulating varnish protects the winding once it is installed within the stator. The varnish is also spread evenly on the inner face of the stator, thanks to the stator according to the invention, which prevents the support tool from generating a localized accumulation of varnish on the inner face of the stator outside the grooves formed for this purpose. The formation of varnish ridges in the areas of the stator in contact with the support tool during the varnishing operation is thus concentrated in the grooves, and these ridges do not result in a non-compliant internal diameter of the stator.

[0029] The invention also covers a varnishing system for a rotating electrical machine, comprising at least one stator as described above and at least one stator support tool, the support tool comprising a main body centered on the axis of revolution of the stator and at least two arms projecting from the main body and extending radially to the inner face of the stator, each arm comprising at least one rib disposed at a peripheral end of the arm, each rib being inserted within one of the grooves of the stator.

[0030] The varnishing system further includes varnishing means, configured to deposit varnish in appropriate areas of the stator so that the varnish can spread at least within the notches of the stator body.

[0031] The stator support tool is initially responsible for the technical problem solved by the present invention due to the contact surface of the arms against the inner face of the stator, which risks forming unwanted varnish accumulations. This risk is avoided here because, with the varnishing system according to the invention, the only contacts between the support tool and the stator are made within the groove, with at least one possible clearance zone provided between the rib housed within of the groove and the side walls delimiting this groove so that any possible bead of insulating varnish due to the support of the rib against the groove and the blocking of the propagation of this varnish is located within the groove and does not generate a modification of the internal diameter of the stator.

[0032] The support tool is positioned at least partially within the internal volume defined by the stator, with the arms extending radially until they are in contact with the inner face of the stator's annular wall. The support tool thus comprises at least two arms, each having at least one rib at its peripheral end. Advantageously, there are as many ribs as there are grooves in the stator. The arms provide mechanical support to the stator, allowing the winding and stator assembly to rotate during the varnishing operation.

[0033] The invention also covers a method for varnishing a stator as described above, comprising: - a step of positioning a support tool inside the stator, said support tool having at least two ribs, each rib of the support tool being housed in one of the grooves of the stator, - a stator varnishing step during which varnish is applied in the stator notches.

[0034] The support tool, as mentioned above, is positioned so that the rib of each arm is inserted into a groove in the stator. The support tool may therefore include a mechanism for extending or retracting the arms to accommodate different stator diameters.

[0035] Prior to these stages of the varnishing process according to the invention, a winding operation is carried out so that the winding is put in place, in a braided or pin-like manner, the winding being mainly arranged in the notches of the stator.

[0036] Once the stator and winding assembly is complete, the varnishing process, including the varnishing operation, can be implemented. This varnish is used to hold the winding in the stator slots and act as an insulator. For this purpose, the stator and winding assembly is connected to a support tool, which rotates the assembly during varnish application. Once the varnish has been applied and spread throughout the stator, the support tool can be removed.

[0037] According to one feature of the process, the varnishing step is carried out by pouring varnish onto the rotating stator. The varnish is deposited onto winding elements that protrude from the conductive segments housed in the slots, and the varnish flows along the conductive segments to fill said slots. The stator can be Driven in rotation by the support tool, more precisely by the main body of the support tool, which can be centered around a shaft and thus rotated, the arms of the support tool, and therefore by extension the stator, are also rotated. Before rotation and varnish application, the stator is pivoted so that its axis of revolution takes on an orientation different from the vertical. For example, the axis of revolution can be positioned horizontally or inclined relative to the horizontal by an angle of approximately 10° to 50°. The varnish is applied above the stator and against the stator at the winding's winding end, that is, at the part of the winding that extends beyond the stator body, so that the varnish can then flow by capillary action into the slots filled by the conductive segments of this winding.More specifically, the varnish is poured at the level of the notch opening area from which the winding protrudes, and an inclination of the axis of revolution as just mentioned can facilitate the pouring of the varnish into this precise area.

[0038] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0039] [Fig.1] is a perspective representation of a stator body according to the invention,

[0040] [Fig.2] represents a variant of the stator illustrated in [Fig.1],

[0041] [Fig.3] is a top view representation of a varnishing system according to the invention, comprising the stator and a support tool,

[0042] [Fig.4] illustrates a first example of cooperation between a groove in the stator and a rib in the support tool,

[0043] [Fig.5] illustrates a second example of cooperation between the stator groove and the rib of the support tool,

[0044] [Fig.6] is a detailed view of the cooperation between the stator and the support tool to illustrate the propagation of the varnish during the varnishing process implementing the varnishing system according to the invention,

[0045] [Fig.7] is a flowchart illustrating the different stages of a varnishing process forming an aspect of the present invention,

[0046] [Fig.8] schematically illustrates the varnishing system of the invention during one of the steps of the varnishing process illustrated in [Fig.7],

[0047] [Fig.9] schematically illustrates a variant of the invention, implementing a support tool different from that illustrated in the other figures and involving a corresponding modification of the number of grooves in the stator.

[0048] Figure 1 illustrates the body of a stator 1 according to the invention. The stator 1 is intended to be integrated into a rotating electrical machine also comprising a rotor that can be driven in rotation by the stator 1 by means of a rotating radial magnetic field generated using a stator winding (not shown in Figure 1) and a suitable power supply to the winding. Such a rotating electrical machine thus ensures the transmission of electrical or mechanical energy, enabling the operation of an electric or hybrid motor vehicle.

[0049] The stator 1 is formed by a stack of thin sheets of magnetic steel independent of each other, also called laminations.

[0050] The stator 1 comprises an annular wall 2 centered around an axis of revolution 3. The annular wall 2 delimits a volume 4 that can partially house the rotor. The axis of revolution 3 is also an axis of rotation of the rotor when the rotating electrical machine is in operation.

[0051] The annular wall 2 comprises an inner face 5 which defines an inner diameter of the stator 1. The inner face 5 thus corresponds to the face of the stator 1 oriented towards the axis of revolution 3 and towards the rotor when the stator and rotor are mounted together. The annular wall 2 comprises a plurality of notches 6 formed in the material of the wall and opening respectively onto the inner face 5 of this annular wall 2, the notches 6 being dimensioned to receive the winding when the stator 1 is mounted. The notches 6 extend regularly around the axis of revolution 3 so that the winding can be evenly distributed along the entire length of the annular wall 2.

[0052] The adjacent notches 6 are separated from each other by teeth 7, and each tooth 7 includes a tooth foot 8 constituting an internal end of each tooth 7 and participating in delimiting the internal face 5 and closing the notches 6 separated by said tooth 7.

[0053] During the assembly of the stator 1, the winding is thus arranged, for example in a hairpin shape, within the notches 6, inside which a sheet of insulating paper is previously placed to contribute to the insulation of the winding, which is placed against the walls delimiting the notch.

[0054] Once the winding is installed, the slots 6 are coated with varnish, which serves to insulate and protect the winding. During this stator varnishing step, varnish is applied to the winding so that it can spread by capillary action inside the slots. As will be detailed below with reference to Figures 6 to 8, varnish can escape from the slot by spreading between overlapping layers of insulating paper and eventually reach the inner face 5 of the stator, either by exiting through the slot opening on this inner face or by spreading through the gaps in the laminations of the bundle of sheets forming the body of the stator, that is to say between two sheets superimposed one on the other along the direction of the axis of revolution of the stator.

[0055] The dimensions of the stator 1, particularly its internal diameter, must meet strict requirements to ensure the proper functioning of the rotating electrical machine, since the air gap, i.e., the radial distance between the rotor and the stator, affects the electromagnetic efficiency of the rotating electrical machine. The tolerance for the internal diameter is very small, for example, on the order of a millimeter. The varnish that spreads and reaches the inner face 5 of the stator's annular wall must therefore be of negligible thickness and not form any ridges on this inner face.

[0056] During the varnishing of the stator 1, it is mechanically held in place by means of a support tool described in detail below. The support tool then rests against a portion of the inner face 5 of the stator 1. The inventors have observed that the presence of this support tool against the inner face 5 is problematic with regard to the propagation of the varnish during the varnishing operation of the stator 1. The support tool can indeed disrupt the distribution of the varnish, which is caused to spread and propagate along the inner face 5, potentially forming localized and thick accumulations of varnish, generating a local modification of the internal diameter of the stator and thus impairing the proper functioning of the rotating electrical machine once fully assembled.

[0057] To overcome this, the stator 1 also includes at least two grooves 9 arranged on the inner face 5 of the annular wall of the stator 1. These grooves 9 are configured so as to be able to receive a rib of the previously mentioned support tool. Thus, the only points of contact between the support tool and the stator 1 are located between the ribs of the support tool and the grooves 9 of the stator 1.Such a configuration allows, on the one hand, a reduction in the contact area between a rib and the annular wall of the stator 1, since the groove forms a hollow which makes it easier to center and lock the rib of the support tool, and on the other hand, it allows the formation of a varnish buildup to be localized around the contact area between the support tool and the annular wall of the stator 1, by targeting the formation of this varnish buildup in a groove which thus does not form a protruding boss on the internal diameter of the annular wall of the stator.

[0058] The grooves 9 are distinct from the notches and are specifically designed to receive the ribs of the support tool and to be at least partially filled with varnish; they have no other functions once assembly is complete. These grooves 9 are straight and parallel to the axis of revolution of the stator, extending parallel to an axial orientation of the notches 6.

[0059] In [Fig. 1], there are two grooves 9, one opposite the other. This arrangement allows the support tool to be mounted in such a way as to balance the distribution of forces exerted by the support tool on the entire stator 1, and thus to improve the stability of the stator on the support tool. It is understood that the important thing is that these grooves are evenly distributed around the axis of revolution of the stator. Also according to [Fig. 1], the grooves 9 extend over the entire length of one axial dimension of the annular wall 2. Generally, at least one of the grooves 9 extends over at least 30% of the axial dimension of the annular wall 2. By way of example, the groove 9 can extend over a distance of approximately 35% to 55% of the axial dimension of the annular wall.

[0060] Each groove 9 is advantageously arranged between two adjacent notches 6, on the tooth foot arranged between these two notches, where appropriate in the center of the tooth 7.

[0061] Each groove 9 can be formed by a grooving operation once the stator has been formed, or by stacking preforms made from each of the sheets intended to be stacked to form a stator body. In the latter case, attention is paid to the orientation of the stacked sheets so that this stacking contributes to forming both the notches and the grooves.

[0062] Figure 2 is a variant of the representation in Figure 1 and also represents a stator 1 according to the invention. This variant differs from the stator illustrated in Figure 1 only in the structure of the grooves 9. In Figure 2, two grooves 9 are aligned with each other along an axial direction parallel to the axis of revolution of the stator, between two identical notches 6. Such a configuration allows interaction with a support tool comprising two distinct ribs aligned with each other.

[0063] The number of grooves 9 present at different teeth 7 can also vary. In [Fig. 2], three teeth 7 each include a pair of grooves 9, this being adapted for a support tool comprising three pairs of ribs to ensure optimal interaction with the stator 1 shown in [Fig. 2]. The grooved teeth 7 are regularly distributed around the periphery of the stator body, at 120° around the axis of revolution, only the grooves associated with one of the teeth being visible here.

[0064] Figure 3 is a partial, top-view representation of a varnishing system 10 according to the invention, comprising the stator 1 as described above, and the support tool 11 mentioned above. It should be noted that in this figure, the winding associated with the stator is not shown to simplify the reading of the figures, and similarly, a varnish application tool is not shown here.

[0065] The support tool 11 consists of a main body 12 preferably centered around the axis of revolution of the stator 1 and a plurality of arms 13 extending from the main body 12 to the inner face 5 of the stator 1. Each arm 13 includes a peripheral end 14 provided with the rib(s) mentioned previously and not visible here because they are engaged in the corresponding groove in the stator. The interaction between the grooves of the stator 1 and the ribs of the support tool 11 will be described in detail later.

[0066] The peripheral end of each arm may specifically include an anti-adhesive coating which prevents the accumulation of varnish on the contact points of the support tool with the stator.

[0067] In [Fig.3], the support tool 11 shown comprises three arms 13 extending radially from the main body 12 to the inner face 5 of the stator 1. The arms 13 are preferably spaced equally apart from each other in order to distribute the mechanical stresses evenly on the stator 1. Of course, the number of arms of the support tool corresponds to the number of teeth of the stator equipped with grooves as mentioned previously.

[0068] The support tool 11 is specifically installed during a stator 1 varnishing process, and more particularly during a positioning step of the support tool 11 in this varnishing process, so as to engage each rib of the support tool 11 in a corresponding groove of the stator 1, ensuring that the free end of the rib rests against a bottom wall of the groove. By "specific installation," it should be understood that this mounting tool is not in place during a preliminary stator assembly step, during which the stator is fitted with the winding, and that this support tool 11 is only installed once the winding is complete, just before the varnish is applied.

[0069] The support tool 11 may for example include a mechanism not shown allowing the arms 13 to be extended and retracted to adapt to different stator diameters.

[0070] The rib / groove connection as implemented during the varnishing process is more precisely illustrated in Figures 4 and 5. These two figures each illustrate an example of a rib / groove connection between the support tool 11 and the stator 1.

[0071] As illustrated, the arm 13 of the support tool 11 extends to the inner face 5 of the stator 1, and the rib 15 disposed at the peripheral end 14 of the arm 13 is inserted within the groove 9 of the stator 1. Such an interaction is repeated at each rib / groove connection of the varnishing system according to the invention.

[0072] As previously mentioned, the groove 9 is arranged on a tooth shank 8 between two adjacent notches 6. More specifically, and as this is Particularly visible in figures 4 and 5, it is advantageous for the groove 9 to be centered on the tooth 7 and on the corresponding pedicle 8, in order to prevent this groove from extending onto a branch forming a lateral projection of the pedicle 8. Thus, it is ensured that the groove 9 is formed on a central portion of the pedicle 8, which extends in the axial continuation of the tooth 7, rather than on a branch which has a smaller orthoradial dimension than that of the central portion of the pedicle.

[0073] Advantageously, the groove 9 extends along an orthoradial dimension over a width at least equal to 25% of the orthoradial extent of the corresponding tooth pedicle 8. By way of example, the groove 9 can extend over an orthoradial distance of approximately 30% to 35% of the orthoradial dimension of the corresponding tooth pedicle.

[0074] Furthermore, the groove 9 advantageously extends over a depth at least equal to 3% of the radial extent of the corresponding tooth 7. By way of example, the groove 9 may have a radial dimension of approximately 3.5% to 6% of the radial extent of the corresponding tooth.

[0075] This ensures that the rib of the support tool has sufficient grip in the groove, and the stator can thus be rotated without the risk of the rib of the support tool coming out of the groove.

[0076] Advantageously, the rib 15 and the groove 9 have complementary shapes at the contact face, substantially perpendicular to the radial direction along which the rib 15 extends mainly.

[0077] More particularly, and as referenced in [Fig.4], a groove 9 comprises a bottom wall 91 and side walls 92 connecting the bottom wall 91 to the inner face 5 of the stator.

[0078] The depth of the groove 9, equal to the radial distance between the bottom wall 91 and the inner face 5 of the stator defining the internal diameter of the stator, is such that the free end of the rib, opposite the arm 13, can come into contact with the bottom wall 91, without the arm coming into contact with the body of the stator. The bottom wall 91 is thus intended to be in contact with the rib 15, the latter pushing on the bottom wall 91 to ensure that the stator remains in position on the tool.

[0079] According to the example illustrated in [Fig. 4], the free end of the rib 15 and the bottom wall 91 of the groove 9 are shaped like an arc of a circle along a cutting plane perpendicular to the axis of revolution of the stator. The complementary shapes of these two surfaces intended to be in contact ensure a large contact area and optimize the transmission of forces from the tool to the stator to ensure that the latter is held in place when the tool is rotated. According to another example illustrated in [Fig. 5], the rib 15 and the groove 9 are polygonal in shape according to this same cutting plane. The shape of the branches 9 and the ribs 15 can be identical for each groove-rib connection or be different from one connection to another, for example for the purpose of preventing error of the support tool 11.

[0080] For each of the grooves 9, the width of the groove 9, i.e. its orthoradial dimension, is greater than the corresponding dimension of the rib such that at least one lateral clearance zone 90 is formed between a lateral wall 92 and the rib 15 when the latter is engaged in the groove 9.

[0081] The advantage of the groove according to the invention, which aims to relocate the contact area between the support tool and the inner face of the stator and to position it within the stator's material casing, is particularly visible in [Fig. 6], where an enlargement shows the two notches 6 arranged on either side of the tooth root 8 in which the groove 9 is formed. The diagram schematically illustrates the conductive segments of the winding 16 housed in these notches 6, the insulating paper sheet 17 provided in these notches 6 to contribute to the insulation between the winding and the stator, and the varnish 18, shown in dashed lines. This illustration notably highlights the possible propagation of the varnish 18 during the varnishing step, here along two propagation paths P1 and P2.

[0082] When the varnish 18 has spread inside the slots, along the conductive segments 16, it at least partially fills the volume defined inside the insulating paper sheet 17 covering the walls of the slot. The varnish application step, as illustrated below, is indeed parameterized so that sufficient varnish is deposited to fill this internal volume of the slot. The insulating paper sheet 17 is positioned against the walls delimiting the slot with an overlap area between the two end edges of the sheet to ensure that none of the conductive segments 16 are in contact with the stator body. However, these end edges of the insulating paper sheet 17 overlapping each other are not glued to each other and varnish is likely to spread by capillary action between the edges and thus reach the walls of the notch.

[0083] According to a first propagation path PI, the varnish is likely to propagate along the walls of the slot and pass through the slot opening, bypassing the tooth root 8, to propagate along the inner face 5 of the stator, defining the internal diameter of the stator. The portion of varnish continuing to move at a distance from the slot opening is brought into the groove 9 before encountering the rib, which forms a point blocking its propagation. The varnish can then accumulate in the lateral clearance zone 90 formed between the lateral wall 92 of the groove and the rib 15.

[0084] According to a second propagation path P2, the varnish is likely to spread within the stator body by capillary action between two stacked plates forming the stator body. Part of this varnish reaches the inner face 5 of the stator, defining the internal diameter of the stator in an area far from the groove, and then joins the first propagation path PI, possibly ending in the groove and the lateral clearance area 90. Another part of this varnish flows directly into the groove 9. If this part of the varnish is blocked in its propagation by the presence of the rib, it is directed towards the lateral clearance area 90 and can remain there, without risk of altering the internal diameter of the stator by creating a bulge.

[0085] The varnishing process 100 according to the invention will now be described with reference to [Fig.7], which consists of a flowchart illustrating the execution of at least the two main steps of the process, namely the positioning of the stator on the support tool on the one hand and the varnishing operation on the other.

[0086] Prior to the use of the support tool 11 and the implementation of the varnishing process according to the invention as such, a winding step S0 is implemented during which winding segments are arranged within the notches 6. Once the winding segments have been installed within the notches and then connected by at least one welding operation of the winding segments two by two, the varnishing process 100 can begin.

[0087] A first main step consists of a positioning step SI of the support tool 11 against the inner face 5 of the stator 1, by making the ribs 15 of the support tool 11 cooperate with the grooves 9 of the stator. The support arms at their ends of the ribs 15 are deployed to ensure that the ribs bear against the bottom wall of the grooves 9 and that the stator is immobilized under the effect of these compressive forces generated in opposite directions. In this position, as mentioned previously, clearance zones 90 are formed in each groove between the rib 15 housed in the groove and the walls delimiting the groove and connecting the bottom wall to the inner face 5 of the stator.

[0088] Once the stator is immobilized, the support tool can be tilted, in an adjustment substep SI 1 within this positioning step SI, so that the axis of revolution 3 of the stator is inclined at an angle α with respect to a horizontal plane PH, as shown in [Fig. 8]. In this inclined position, the support tool 11 can be moved under a varnishing station 20 which has at least one varnish supply nozzle 21. In the example shown in [Fig. 8], the varnishing station 20 has one nozzle 21. In an alternative not shown, the varnishing station has two nozzles 21 whose position and inclination allow for supply in varnish at two diametrically opposite points of the wound stator, without this being limiting of the invention.

[0089] A second main step S2 of the varnishing process 100 consists of depositing varnish on the winding, and in particular as illustrated in [Fig. 8] in an area where the conductive segments emerge from the insulating paper placed in the notch associated with these conductive segments. The support tool 11 is then driven to rotate around an axis coinciding with the axis of revolution of the stator, and each notch is thus brought into contact with one of the feed nozzles 21 of the varnishing station 20. This rotation is initiated by the support tool 11, and more particularly by the main body 12, which can be driven by a shaft and which can drive the stator 1 with it thanks to the cooperation of the ribs and grooves mentioned above.

[0090] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0091] By way of non-limiting example, [Fig. 9] illustrates a variant of the invention, in which the support tool comprises pairs of ribs 15, one of these pairs being illustrated in particular here. In other words, it differs from what has been previously described in that the stator is held in the support tool not by the cooperation in several zones of a groove made in the stator and a rib carried by an arm of the support tool, but here by the cooperation in several zones of two grooves 9 arranged in two successive tooth roots 8 formed on either side of a notch 6 with two ribs 15 carried by the same arm 13 of the support tool 11. This ensures greater local stability of the stator in the support tool and secures the position of the stator during rotation by the support tool.As before, each groove is sized to form at least one clearance area in which varnish is likely to accumulate without generating a bulge that impacts the internal diameter of the stator.

[0092] The invention, as described above, achieves its intended purpose and provides a stator that ensures safe assembly, and more specifically varnishing, without the risk of varnish buildup altering the stator's internal diameter and impairing the proper functioning of the rotating electrical machine. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they include a stator conforming to the invention.

Claims

Demands

1. Stator (1) for rotating electric machine with radial flux, comprising an annular wall (2) centered about an axis of revolution (3), the annular wall (2) comprising an inner face (5) oriented towards the axis of revolution (3), the inner face (5) delimiting an internal diameter of the stator (1) and being provided with a plurality of notches (6) distributed regularly along the inner face (5) and configured to receive a winding of the stator (1), characterized in that the inner face (5) comprises at least two grooves (9) distinct from the notches (6), each of the grooves (9) being configured to receive a rib (15) of a support tool (11) of the stator (1).

2. Stator (1) according to claim 1, wherein each groove (9) comprises a bottom wall (91) and side walls (92) connecting the bottom wall (91) to the inner face (5) of the stator, said groove (9) being dimensioned so that the bottom wall (91) forms a stop face for the rib (15) and so that at least one lateral clearance zone (90) is formed between a side wall (92) and the rib (15).

3. Stator (1) according to claim 1 or 2, wherein the grooves (9) are straight and parallel to a principal dimension of the notches (6), parallel to the axis of revolution (3).

4. Stator (1) according to any one of claims 11 3, wherein at least one groove (9) has a bottom wall (91) in the shape of an arc of a circle along a cutting plane perpendicular to the axis of revolution (3).

5. Stator (1) according to any one of claims 11 3, wherein at least one groove (9) is polygonal in shape along a cutting plane perpendicular to the axis of revolution (3).

6. Stator (1) according to any one of claims 1 to 5, wherein the grooves (9) are each arranged between two adjacent notches (6).

7. Stator (1) according to claim 6, wherein at least one of the grooves (9) is disposed at an equal distance from the two adjacent notches (6).

8. Stator (1) according to any one of claims 1 to 7, wherein two adjacent notches (6) are separated within the stator (1) by a tooth (7) whose free end turned towards the inside of the stator (1) forms a tooth foot (8) which helps to partially close each of the two adjacent notches (6), at least one of the grooves (9) extending along an orthoradial dimension over a width at least equal to 25% of the orthoradial extent of the corresponding tooth foot (8).

9. Stator (1) according to any one of claims 1 to 8, wherein two adjacent notches (6) are separated within the stator (1) by a tooth (7) whose free end facing inward of the stator (1) forms a tooth root (8) which helps to partially close each of the two adjacent notches (6), at least one of the grooves (9) extending along a radial dimension over a depth at least equal to 3% of the radial extent of the corresponding tooth (7).

10. Stator (1) according to any one of claims 1 to 9, wherein at least one groove (9) extends over at least 30% of the axial dimension of the annular wall (2).

11. Stator (1) according to any one of claims 1 to 10, comprising at least two grooves (9) aligned between two of the same notches (6).

12. Stator (1) according to any one of claims 1 to 11, comprising a winding, the winding comprising conductive segments housed in the slots (6), the slots (6) and the inner face (5) of the stator (1) being coated with insulating varnish, each of the grooves (9) being at least partially filled with insulating varnish.

13. A varnishing system (10) for a rotating electrical machine, comprising at least one stator (1) according to any one of claims 12 and at least one support tool (11) for the stator (1), the support tool (11) comprising a main body (12) centered on the axis of revolution (3) of the stator (1) and at least two arms (13) projecting from the main body and extending radially to the inner face (5) of the stator (1), each arm (13) comprising a rib (15) disposed at a peripheral end (14) of the arm (13), each rib (15) being inserted within one of the grooves (9) of the stator (1).

14. A method for varnishing a stator (1) according to any one of claims 1 to 12, comprising:

15. - a step of positioning a support tool (11) inside the stator (1), said support tool having at least two ribs (15), each rib (15) of the support tool (11) being housed in one of the grooves (9) of the stator (1), - a varnishing step of the stator (1) during which a varnish is applied in the notches (6) of the stator (1). Varnishing method according to claim 14, wherein the varnishing step is carried out by pouring varnish onto the rotating stator (1), the varnish being deposited on winding elements forming protrusion of conductive segments (16) housed in the slots (16), the varnish flowing along the conductive segments (16) to fill said slots (6).

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