Stator of an axial flux machine and method for assembling such a stator

Abstract

The present invention relates to a stator (1) of an axial flux machine, the stator comprising teeth (14) projecting from a yoke (10), a winding support (16) fitted onto at least one of the teeth, and at least one winding arranged around the winding support (16), the stator (1) being characterised in that it comprises holding means (24, 168) for holding the winding support (16) fitted onto the tooth (14), the holding means being arranged in a circulation space (11) for a cooling fluid between the tooth (14) and the winding support (16).

Description

Description Title of the invention: Stator for an axial flux machine and method for assembling such a stator

[0001] The present invention relates to the fields of electrical engineering and mechanics and more specifically concerns an axial flux electric machine stator and its assembly.

[0002] Axial flux electric machines have a higher power density than radial flux electric machines, and are therefore an attractive option in the equipment of electric or hybrid vehicles, due to the need to reduce the size of the components present in the engine compartment of such a vehicle, these components increasing with the number of features implemented by the vehicle.

[0003] A stator of an axial flux electric machine typically consists of an annular yoke on which magnetic cores, also called stator teeth, are arranged angularly and regularly. A winding is arranged around each magnetic core, the windings constituting the phases of the electric machine's stator.

[0004] When the stator is in operation, the windings heat up and require cooling. The most critical temperature is found inside the windings, in a portion of the windings located axially closer to the electric machine's rotor than to the stator yoke. Winding cooling typically uses a heat transfer fluid that either immerses the windings or circulates through channels that may be arranged in the stator teeth or in the stator winding supports.

[0005] The use of winding supports simplifies the assembly of the stator phases. This is achieved by winding the phases onto the winding supports and then threading the winding supports onto the stator teeth, rather than winding the stator phases directly onto the teeth themselves, which have limited space between them for this purpose. In particular, the teeth are inseparable from the yoke when they are manufactured as a single unit with the stator yoke, rather than being assembled onto the yoke.

[0006] However, it is essential to securely attach the winding supports to the stator, especially when coolant flows through it, particularly near the winding sections closest to the rotor. Coolant circulation in this area can indeed cause the winding support to shift or become misaligned with the tooth.

[0007] To overcome this problem, angular extensions can be mounted on the free ends of the stator teeth, but this adds a cost to the manufacturing of the stator.

[0008] There is therefore a need to create circulation channels as close as possible to the windings of an axial flux machine stator, when these windings are housed in winding supports, without harming the retention and centering of the winding supports around the teeth, and without significantly increasing the manufacturing cost of the stator.

[0009] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an axial flux electric machine stator, and a method for assembling an electric machine comprising this stator, which make it possible to simply maintain in position winding supports threaded onto the teeth of the stator, without adding angular extensions to these teeth, and while allowing a channeling of a heat transfer fluid in the vicinity of the windings.

[0010] To this end, the invention proposes an axial flux machine stator, comprising teeth protruding from a yoke, a winding support fitted onto at least one of the teeth, and at least one winding arranged around the winding support, the stator being characterized in that it comprises means for retaining the winding support fitted onto the tooth, the retaining means being arranged in a space for the circulation of a cooling fluid between the tooth and the winding support.

[0011] Thanks to the invention, the cooling fluid can circulate between the tooth and the winding support, which makes it possible to efficiently cool the hottest areas of the winding when the stator is in operation, and this without requiring the winding support to be pressed against the cylinder head by adding angular extensions to the tooth surrounded by this winding support.

[0012] The cooling fluid can be, for example, oil, glycol water, and / or a gas. The cooling fluid can also be air, with or without oil or glycol water spray. When the cooling fluid is in a liquid state, it is circulated by an external pump to the axial flow machine. When the coolant is in a gaseous state, it is circulated by the rotation of the rotor, via a propeller in particular.

[0013] The stator according to the invention preferably comprises a winding support fitted around each tooth of the stator, each winding support housing a winding, and being held around the tooth by holding means arranged between the tooth and the winding support.

[0014] In the invention, the retaining means delimit, for example, the circulation space of the cooling fluid on at least one of the faces of the tooth. The circulation space extends, for example, all around the tooth, being closed at the axial ends of the stator, except at a coolant inlet and outlet, preferably located between the radial ends of the tooth and the winding support, on the cylinder head side. It is understood that the retaining means are arranged to allow the coolant to circulate all around the tooth. The retaining means therefore do not impede this circulation.

[0015] It should be noted that in this request, an axial direction is parallel to an axis of rotation of a rotor of the electric machine, i.e. parallel to a central axis of symmetry of the stator, a radial direction is orthogonal to the axial direction while passing through the axis of rotation, and an ortho-radial or angular direction is orthogonal to the axial direction and to a radial direction.

[0016] Furthermore, the stator teeth and yoke according to the invention are, for example, formed in a single piece by winding a magnetic sheet metal strip, in order to reduce the production cost of the stator and the electrical losses due to eddy currents when the stator is in operation. The magnetic sheet metal is, for example, made of grain-oriented or grain-non-grain-oriented electrical steel. Alternatively, the stator teeth and yoke are formed by SMC or by a stack of electrical steel.

[0017] This winding can form teeth having angular extensions at their free ends. These angular extensions extend radially from one radial end of the tooth to the other, axially closing the flow space between the winding support and the tooth along radial faces of the tooth. To also axially close the flow space between the winding support and the tooth along angular faces of the tooth, the winding support can include axially closing elements at the free ends of the teeth. These axial closing elements extend angularly from one radial wall of the winding support to another. Alternatively, the stator can include means attached to the teeth for closing this flow space at the free ends of the teeth, such as a sealing membrane described later.

[0018] As an alternative embodiment, the stator body can be segmented, i.e. the teeth can be attached to the yoke, and formed for example of sintered soft magnetic composite.

[0019] Furthermore, slot closure shims made of soft magnetic material can be integrated into the winding support to improve the stator's magnetic performance during operation. More precisely, these slot closure shims are integrated into or onto winding retaining fins, which are part of the winding support. These fins extend radially and are located on either side of the tooth at an axial end of the winding support that is intended to face a rotor of the electric machine.

[0020] In one embodiment of the invention, the winding support comprising two radial walls and two angular walls, arranged opposite two radial faces and two angular faces of the tooth respectively, the retaining means comprise on at least one radial wall, an outgrowth projecting inside the circulation space.

[0021] The protrusion is, for example, a radial rib on the radial wall, or is formed by tabs arranged on the radial wall. The radial wall of the winding support is, for example, made of synthetic polymer (plastic) or composite material. The protrusion is then, for example, formed from the material along with the radial wall.

[0022] More specifically, the winding support comprises, for example, a molded body made of plastic, such as polyphthalamide (PPA) or polyphenylene sulfide (PPS), possibly filled with a non-conductive material such as glass fiber or mineral fiber. When the winding support incorporates slot closure wedges in winding retaining fins, these wedges are, for example, formed of soft magnetic composite (SMC) bars inserted into slots provided for this purpose in the winding retaining fins. Alternatively, instead of these slot closure wedges, these winding retaining fins are made of plastic filled with a magnetically conductive material such as magnetic steel powder.

[0023] In this embodiment of the invention, the retaining means comprise, for example, at least one elastic element projecting from the radial face opposite the radial wall, the protrusion being axially blocked by the elastic element. It is understood that the elasticity of the elastic element allows, when the winding support is fitted around the tooth, the protrusion to be forcibly inserted under the elastic element, which then retains the protrusion in the opposite direction to the direction in which the winding support is fitted onto the tooth.

[0024] The protrusion and the cooperating elastic element are arranged so that when the winding support is fully fitted onto the tooth, the protrusion is in contact with the elastic element. When the protrusion is a radial rib, its cross-section is sized to be retained by the elastic element. This cross-section can be, for example, round or triangular in shape. The radial rib preferably extends along the entire length of the elastic element, for example, along the whole radial wall or along only a portion of it. Of course, it can also be in several parts extending along the elastic element. It is positioned axially so as to be in contact with the elastic element, for example, at the midpoint of a tooth height measured from the yoke to the free end of the tooth, or closer to the yoke than to the free end of the tooth.

[0025] The tooth, for example, has a radial branch on its radial face, with the elastic element positioned in the radial groove. In this embodiment of the invention, the elastic element is positioned in the radial groove before the winding support is fitted onto the tooth.

[0026] In an alternative embodiment, the elastic element is fixed to the radial wall of the winding support and is inserted into a recess on the radial face of the tooth. In other words, in this embodiment, the elastic element is inserted into the recess when the winding support is fitted onto the tooth.

[0027] In one embodiment of the invention, the elastic element comprises a spring. The spring may be a wave spring, a helical spring, or an inclined helical spring. It may have a round or rectangular cross-section. The advantage of this type of spring is that it absorbs play between two surfaces that are not perfectly parallel, without losing elasticity or strength.

[0028] Alternatively, the spring can be composed of several springs arranged in series, or forming, for example, a curtain of winding metal wires. The spring is preferably metallic, for example made of steel, and preferably non-magnetic. As an alternative, the spring is not made of metal, but of a non-magnetic material such as ceramic.

[0029] In one embodiment of the invention, the spring forms at least part of one arm of a U-shaped profile, each arm of the U being positioned between one of the two radial walls and one of the two radial faces containing a spring, and the ends of the U forming two hooks that engage on either side of one of the angular faces of the tooth. The U-shaped profile is therefore a wire element forming two elastic components on either side of the tooth, on each radial face of the tooth, and each locking a protrusion arranged on a radial wall separate from the winding support. The hooks allow these elastic components to be easily held against the radial faces of the tooth.

[0030] In another embodiment of the invention, the spring forms at least part of one side of a trapezoidal profile fitted around the tooth. Each side of the trapezoidal profile is positioned between one of the two radial walls and one of the two radial faces containing a spring. One of the bases of the trapezoidal profile has a spring capable of defining the clearance between an angular wall of the winding support and an angular face of the tooth. It is understood that the trapezoidal profile is a wire element whose elasticity allows it to be fitted and held around the tooth.

[0031] In one embodiment of the invention, the tooth being formed of radially stacked magnetic sheets, the elastic element comprises at least one tongue formed by an angular extension of at least one sheet.

[0032] The angular extension is formed from the sheet metal. In this embodiment of the invention, the elastic element axially blocking the protrusion is, for example, formed of several tabs. For example, certain sheet metal parts of the tooth are cut so as to form, on each radial face of the tooth, tabs forming an elastic element that axially blocks a protrusion arranged on a radial wall of the winding support, opposite the radial face.

[0033] For example, in the stack of laminations forming the tooth, one lamination in at least two stacked laminations has these angular extensions. For example, one lamination in four stacked laminations has these angular extensions. The angular extensions are formed, for example, in a mid-portion of the tooth, relative to its axial dimension. They are preferably of the same size. Furthermore, they can be bent so as to angle towards an outer periphery of the stator.

[0034] Furthermore, in one embodiment of the invention, the winding support is configured to maintain its radial position relative to the tooth by friction with the elastic element. For example, the radial wall has an additional thickness against which the elastic element grips once the winding support is fitted onto the tooth. More generally, the radial wall is configured, for example, to deform upon contact with the elastic element, this deformation being capable of radially fixing the winding support relative to the elastic element, which is itself fixed to the tooth.

[0035] The stator according to the invention optionally includes means for radially positioning the winding support relative to the tooth. The angular faces of the tooth comprise an external angular face located on the outer radial periphery of the stator, and an internal angular face located on the inner radial periphery of the stator. The angular walls of the winding support comprise an external angular wall opposite the external angular face and an internal angular wall opposite the internal angular face. The radial positioning means may, for example, include an axial rib on the internal angular wall. Alternatively, the radial positioning means may include, for example, a tab projecting radially from the internal angular face of the tooth. This tab may be cut from a sheet metal forming this external angular face.These radial positioning means are complementary to radial support means for the winding support, such as the overthicknesses on the radial walls of the winding support to which the elastic elements attach.

[0036] In one embodiment of the invention, the stator according to the invention comprises at least one radial retaining spring interposed between the outer angular wall and the outer angular face. This radial retaining spring is part of the means for radially retaining the winding support and can be used instead of, or in addition to, the aforementioned reinforcements. This radial retaining spring is, for example, an inclined helical spring or a simple helical spring, or a leaf spring. It is arranged, for example, along its length axially between the outer angular wall and the outer angular face, or angularly between the outer angular wall and the outer angular face. It can have a round or rectangular cross-section. It can be made of several springs arranged in series, or forming, for example, a curtain of windings of metal wire. The spring is preferably metallic, for example, steel, and preferably non-magnetic.Alternatively, the spring is not made of metal, but of a non-magnetic material such as ceramic.

[0037] It should be noted that, alternatively, the radial positioning means are arranged between the external angular wall of the winding support and the external angular face of the tooth, while the radial holding means are arranged between the internal angular wall of the winding support and the internal angular face of the tooth.

[0038] The invention also relates to a method for assembling an electrical machine comprising a stator according to the invention, at least one stator tooth being surrounded by a winding support receiving a winding, the winding support being held around the tooth by retaining means arranged in a space for the circulation of a cooling fluid between the tooth and the winding support, the assembly method comprising the steps of: - wind the winding support to form a winding, - fit the winding support onto the tooth until the winding support is axially locked by the retaining means.

[0039] Optionally, when the electric machine has a closing cover in which the cylinder head is fixed, the fitting step is for example followed by a step of gluing a sealing membrane on a free face of the tooth and on a perimeter of the closing cover, forming a sealed chamber intended to receive a coolant.

[0040] When the means for retaining the stator include on at least one radial wall of the winding support, a protrusion projecting inside the circulation space, and a spring positioned in a radial groove of a radial face of the tooth, opposite the radial wall, the spring axially blocking the protrusion, the step of fitting the winding support onto the tooth is preceded by a step of positioning the spring in the radial groove of the tooth.

[0041] When the stator includes at least one radial retaining spring interposed between an outer angular wall of the winding support and an outer angular face of the tooth, the step of fitting the winding support onto the tooth is preceded or followed by a step of positioning the radial retaining spring against the outer angular wall. The radial retaining spring may be attached to the winding support before it is fitted onto the tooth, or it may be inserted after this fitting, between the winding support and the tooth.

[0042] 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 attached schematic drawings on the other hand, in which:

[0043] [Fig.1] is a perspective view of a portion of an axial flux machine stator according to the invention, in a first embodiment of the invention, a portion on which a single winding support, housing a winding, is shown fitted onto a tooth of the stator,

[0044] [Fig.2] represents different views of a stator tooth in a first variant of the first embodiment of the invention, and of means for retaining a winding support shown fitted onto the tooth in the three right-hand views of this [Fig.2],

[0045] [Fig.3] represents steps of an assembly process according to the invention, of a stator according to the invention, in the first variant of the first embodiment of the invention,

[0046] [Fig.4] represents different views of a stator tooth in a second variant of the first embodiment of the invention, and of means for retaining a winding support shown fitted onto the tooth,

[0047] [Fig.5] is a side view of the tooth, the retaining means and the winding support of [Fig.4], in a section plane extending axially and radially, and located between the retaining means and a radial wall of the winding support,

[0048] [Fig.6] represents different views of a stator tooth in a third variant of the first embodiment of the invention, and of means for retaining a winding support shown fitted onto the tooth,

[0049] [Fig.7] is a side view of the tooth, the retaining means and the winding support of [Fig.6], in a section plane extending axially and radially, and located between the retaining means and a radial wall of the winding support,

[0050] [Fig.8] represents steps of an assembly process according to the invention, of a stator according to the invention, in the second and third variants of the first embodiment of the invention,

[0051] [Fig.9] represents assembly steps of a stator according to the invention, and in particular the mounting of a winding support on a tooth of a stator according to the invention, in a fourth variant of the first embodiment of the invention,

[0052] [Fig. 10] represents assembly steps of a stator according to the invention, and in particular the mounting of a winding support on a tooth of a stator according to the invention, in a second embodiment of the invention, and

[0053] [Fig.11] represents examples of the realization of means for positioning and radially holding the winding support of the first and second embodiments of the invention.

[0054] According to a first embodiment of the invention represented in [Fig.1], a stator 1 according to the invention, of an axial flux electric machine, comprises an annular yoke 10 from which protrude teeth 14, which are magnetic cores of windings 18 surrounding the teeth 14.

[0055] Each winding 18 is first made around a winding support 16, which is then fitted onto one of the teeth 14. In [Fig.1], only one winding 18 is shown, but of course each tooth 14 receives a winding support 16 housing a winding 18.

[0056] In this first embodiment of the invention, the cylinder head 10 and the teeth 14 are formed as a single unit by winding a magnetic sheet metal strip, for example made of grain-oriented steel. The layers of the strip are stacked radially.

[0057] Each tooth 14 has a free axial end face and four lateral faces 141, 143, 145, 147, referenced [Fig. 2]. The lateral faces extending angularly and axially are angular faces 141, 143, the angular face located at the inner periphery of the stator being the inner angular face 141, and the angular face located at the outer periphery of the stator being the outer angular face 143. The lateral faces extending radially and axially are radial faces 145, 147.

[0058] The internal and external angular faces 141, 143 are flat while the radial faces 145, 147 each have a radial groove 140 extending over the entire radial dimension of the tooth 14. They also each have a radial rib 144 extending over the entire radial dimension of the tooth 14 and axially extending the head 10, as well as a radial rib 142 extending over the entire radial dimension of the tooth 14 and angularly extending the free axial end face of the tooth 14.

[0059] When the winding support 16 is fitted onto the tooth 14, the radial ribs 142, 144 contribute to creating a circulation space 11 for a heat transfer fluid between the winding support 16 and the tooth 14, while partially axially closing this circulation space 11 at the free axial end face of the tooth 14, and at the yoke 10. In order for the heat transfer fluid to also circulate at the angular faces of the tooth 14, the winding support 16 leaves a space between each angular face 141, 143 and the tooth 14. The heat transfer fluid is, for example, a dielectric fluid such as oil, intended to cool the windings 18.

[0060] In a first variant of the first embodiment of the invention, represented [Fig.2], the winding support 16 is held around the tooth 14 by holding means, which here comprise a wire piece 24 with a trapezoidal profile, which surrounds the tooth 14.

[0061] This wire part 24 is formed, for example, from a steel wire, closed on itself. The small base of the trapezoidal profile is a straight segment of the steel wire, pressed against the inner angular face 141. Two sides of the trapezoidal profile, adjacent to this small base, are inclined helical springs formed by the steel wire, and are each inserted into a radial groove 140 of the tooth 14. The large base of the trapezoidal profile is a series of two inclined helical springs, formed by the steel wire, and arranged so as to be symmetrical to each other, with respect to an axial plane of symmetry of the tooth 14.

[0062] The wire part 24 has, due to the presence of the springs, an elasticity allowing it to be threaded around the tooth 14.

[0063] The winding support 16 has four walls laterally surrounding the tooth, namely an internal angular wall 161 opposite the internal angular face 141 of the tooth 14, an external angular wall 163 opposite the external angular face 143 of the tooth 14, and two radial walls 165, 167 opposite the respective radial faces 145, 147 of the tooth 14. The four walls of the winding support 16 extend at their ends parallel to the yoke 10 of the stator 1, outwards from the tooth 14, in order to axially confine the winding 18, particularly during the winding of the winding supports 16. These extensions form upper fins 162 surrounding the free axial end face of the tooth 14, and lower fins 164 surrounding one foot of tooth 14.

[0064] The two radial walls 165, 167 each have a protrusion projecting into the circulation space 11, this protrusion being a radial rib 168 formed from the material with the winding support 16. This radial rib 168 is located opposite one of the axial ends of the radial groove 140 of the tooth 14, this end being proximal to the yoke 10 relative to the other of the axial ends of the radial groove 140 of the tooth 14. This radial rib 168 cooperates with springs of the wire part 24, which constitute elastic means arranged in protrusion from each radial face 145, 147, to axially lock the winding support 16 on the tooth 14, as detailed later.

[0065] The internal angular wall 161 also forms an axial rib 166 for radial positioning of the winding support 16 around the tooth 14. This axial rib 166 for radial positioning extends axially over one half of the internal angular wall 161, distal to the yoke 10.

[0066] Figure 3 shows steps of an assembly process according to the invention, of the stator 1.

[0067] The winding supports 16 are first wound 102. Then the wire piece 24 is threaded around each tooth 14, the springs of the wire piece 24, forming the non-parallel sides of the trapezoidal profile, being inserted 104 into the radial grooves 140 of the tooth 14.

[0068] The winding supports 16 are then each fitted 106 around a tooth 14, the axial rib 166 of the internal angular wall 161 being pressed against the internal angular face 141 of the tooth 14, until lower fins 164 touch the yoke 10, which locks the winding support 16 around the tooth 14. Indeed, in this position, the radial ribs 168 of the radial walls 165, 167 of the winding support 16 are blocked in the axial direction in the direction of the yoke 10 towards the free axial ends of the teeth 14, by the springs which are themselves blocked in the radial groove 140 of the tooth 14.

[0069] After the fitting 106 of the winding supports 16, a sealing membrane 40 (represented [Fig.6] in connection with another variant of the invention) is glued 108 on the free axial end faces of the teeth 14, on which glue 30 is disposed.

[0070] Indeed, in this first embodiment of the invention, the electric machine includes a closing cover not shown, in which the cylinder head 10 of the stator 1 is fixed, the closing cover having an external cylindrical wall and an internal cylindrical wall radially confining the stator 1, and whose free ends arrive axially at the level of the free axial ends of the teeth 14.

[0071] The sealing membrane 40, bonded to the teeth 14, is also bonded to the internal and external cylindrical walls of the closing cover. The sealing membrane 40 and closing cover together form a sealed chamber for receiving a coolant. The flat wall of the closing cover has, for example, holes, possibly fitted with tubes or inserts, to supply the coolant to the circulation spaces 11 of each tooth 14.

[0072] Of course, the assembly steps 100 are preferably performed simultaneously for each tooth 14 of the stator according to the invention. Furthermore, the order of the steps is modifiable; in particular, the positioning of the springs in the radial grooves 140 can take place before, during, or after the winding of the winding supports 16.

[0073] The circulation space 11 of the coolant around a tooth 14 is delimited in part by the retaining means comprising the springs inserted in the radial grooves 140, and the radial ribs 168, since they maintain a distance between the radial walls 165, 167 and the respective radial faces 145, 147. The circulation space 11 goes around the tooth 14, considering: - the space between the radial walls 165, 167 and the respective radial faces 145, 147, the angular dimension of which is determined by the compression of the springs present in the radial grooves 140; - the space between the internal angular wall 161 and the internal angular face 141, which is completely clear over the height of the tooth 14 between the yoke 10 and the axial radial positioning rib 166, the height here referring to the axial dimension of the tooth 14; and - the space between the external angular wall 163 and the external angular face 143, determined by the springs forming the large base of the wire part 24, which are compressed between the external angular wall 163 and the external angular face 143 of the tooth 14. This compression makes it possible to keep the axial radial positioning rib 166 against the internal angular face 141 and thus to guarantee a good radial positioning of the winding support 16 relative to the tooth 14.

[0074] The circulation of the coolant in the circulation space 11 is represented on the right of [Fig.2], by dashed arrows. It can be seen that the coolant runs, in the axial direction, along the internal radial periphery of the cylinder head 10, then the internal angular face 141 of the tooth 14, entering between the internal angular wall 161 and the internal angular face 141, then deviates its trajectory, to circulate between the radial walls 165, 167 and the radial faces 145, 147, then arrives on either side of the external angular face 143 to exit between this and the external angular wall 163, towards the cylinder head 10.

[0075] It is understood that the sealing membrane 40 makes it possible to completely close the spaces present between the winding support 16 and the free axial end face of the tooth 14. However, this closure can be achieved by other means, for example by a particular shape of the winding support 16.

[0076] We now describe, in relation to figures 4 and 5, a second variant of the first embodiment of the invention.

[0077] In this second embodiment, the teeth 14 and the yoke 10 of the stator according to the invention are identical to those of the stator 1 according to the invention. Only the winding supports 16b threaded around the teeth 14, and the means for retaining these winding supports 16b, differ from the first embodiment.

[0078] Indeed, as can be seen [Fig.4], the means of retention here include for each tooth 14, a wire piece 24b having a U-shaped profile, rather than a wire piece with a trapezoidal profile.

[0079] This wire part 24b is formed, for example, from a steel wire. The base of the U-profile is a straight segment of the steel wire, pressed against the inner angular face 141 of the tooth 14. The arms of the U-profile, connected to its base, each have an inclined helical spring, inserted into a radial groove 140 of one of the radial faces 145, 147 of the tooth 14. The ends of the U-profile form two hooks engaged on either side of the outer angular face 143 of the tooth 14.

[0080] The wire part 24b has, due to the presence of the springs, an elasticity which allows it to be fixed around the tooth 14.

[0081] Furthermore, in this second embodiment of the invention, the winding support 16b is identical to the winding support 16 except for its external angular wall 163b which has an axially extending groove 169 receiving a radial retaining spring 34. The axially extending groove 169 is arranged in the middle of the external angular wall 163b.

[0082] The radial retaining spring 34 is here an inclined helical spring, arranged axially in its length, and having at its ends hooks which are each fixed at a distinct axial end of the external angular wall 163b. For example, it includes holes to accommodate these hooks.

[0083] The winding support 16b always includes the radial ribs 168 cooperating with the springs of the U-profile, to maintain the winding support 16b around the tooth 14. The springs of the U-profile constitute elastic means of the means of maintaining the winding support 16 on the tooth 14. In this second embodiment of the invention, a stator assembly method 200, shown [Fig.8], includes an additional step compared to the assembly method 100 of the first embodiment of the invention.

[0084] Indeed, after winding 202 of the winding support 16b, the U profile springs are inserted 204 into the radial grooves 140. Then the radial retaining spring 34 is fixed 206 in the groove 169 of the external angular wall 163b. Only then is the winding support 16b fitted 208 around the tooth, the axial rib 166 of the internal angular wall 161 being pressed against the internal angular face 141 of the tooth 14, until the winding support 16b is locked around the tooth 14, that is to say until the radial ribs 168 are positioned axially beyond the springs which are fixed in the radial grooves 140, that is to say between these springs and the yoke 10. Finally the sealing diaphragm 40 is glued 210 onto the free axial end of the tooth 14.

[0085] Of course, these steps are preferably performed simultaneously for each tooth 14 of the stator according to the invention. The order of the steps is also modifiable; in particular, the positioning of the springs in the radial grooves 140 can take place before, during, or after the winding or the attachment of the radial retaining spring 34 to the winding support 16b.

[0086] It should also be noted that, alternatively, the radial positioning spring 34 is fixed to the external angular face 143 of the tooth rather than to the external angular wall 163b of the winding support.

[0087] It is understood that the radial positioning spring 34 has the same function as the springs of the trapezoidal profile wire part, which are located between the external angular wall 163 and the external radial face 143, namely to maintain a good radial positioning of the winding support 16b around the tooth 14 while allowing the heat transfer fluid to circulate between the external angular wall 163b and the external angular face 143.

[0088] A third embodiment of the first version of the invention is now described in relation to Figures 6 and 7. This third embodiment differs from the second embodiment of the first version only in that: - that the radial grooves 140c on the radial faces 145, 147 of each tooth 14 of the stator according to the invention are located axially just above the lower fins 164, that is to say that these radial grooves 140c are located at an axial end of the heat transfer fluid circulation space, which is closest to the yoke 10; - that the winding support 16c fitted onto each tooth 14 has radial grooves 168c on the radial walls 165c, 167c of the winding support 16c, these radial grooves 168c being positioned axially very close to the lower fins 164 of these radial walls 165c, 167c, just above the radial ribs 144 of the foot of the tooth 14; - that the external angular wall 163c of the winding support 16c has two axially extending axial grooves 169c, each receiving a radial retaining spring 34. The axially extending grooves 169c are arranged in a median portion of the external angular wall 163c; and - that the stator has two radial retaining springs 34 per tooth 14 instead of one; the radial retaining springs 34 have hooks at their ends and the external angular wall 163c has four holes receiving these hooks.

[0089] The stator assembly in this third embodiment is similar to the stator assembly in the second embodiment.

[0090] Figure 9 illustrates a fourth embodiment of the invention, in which the stator teeth 14 are identical to those of the second embodiment of the invention, although the stack of laminations constituting them is shown in this figure. The winding support 16d surrounding each tooth 14, in this fourth embodiment, is identical to that of the second embodiment except for two modifications explained below, concerning the upper fins 162d of the winding support 16d and the number of radial ribs 168d of the winding support 16d.

[0091] In this fourth embodiment of the invention, the winding support 16d surrounding each tooth 14 has upper fins 162d provided with a magnetic material. More specifically, the upper fins 162d located at the axial ends of the radial walls of the winding support 16d each have a bar 17 of soft magnetic material molded into this upper fin 162d. These bars 17 improve the magnetic properties of the stator.

[0092] Furthermore, in this fourth embodiment, a U-shaped wire piece identical to that of the second embodiment is arranged around each tooth 14, the springs of the U-shaped wire piece being inserted into the radial grooves of the tooth 14. Each radial wall of the winding support 16d has two radial grooves 168d enclosing each spring of the U-shaped wire piece. The purpose of these two radial grooves 168d per radial wall 165, 167 is explained later in relation to [Fig. 10].

[0093] A radial retaining spring 34 is inserted between the outer angular wall 163 of the winding support 16d and the outer angular face 143 of the tooth 14. The stator assembly method, in this fourth embodiment of the invention, is therefore identical to that of the second embodiment of the invention.

[0094] Figure 10 illustrates a second embodiment of the invention, in which a stator according to the invention, of an axial flux electric machine, comprises an annular yoke from which protrude teeth 14b, receiving winding supports 16e in which windings 18 are housed.

[0095] As in the first embodiment of the invention, the yoke and the stator teeth 14b are formed as a single unit by winding a magnetic sheet metal strip, for example made of grain-oriented steel. The winding layers of the strip are stacked radially.

[0096] Each tooth 14b has a free axial end face and four lateral faces 141b, 143b, 145b, 147b. The lateral faces extending angularly and axially are angular faces 141b, 143b, the angular face located at the inner periphery of the stator being the inner angular face 141b, and the angular face located at the outer periphery of the stator being the outer angular face 143b. The lateral faces extending radially and axially are radial faces 145b, 147b.

[0097] The radial faces 145b, 147b each have a radial rib 144 extending over the entire radial dimension of the tooth 14b and axially extending the cylinder head, as well as a radial rib 142 extending over the entire radial dimension of the tooth 14b and angularly extending the free axial end face of the tooth 14b, these radial ribs being identical to those of the first embodiment of the invention.

[0098] Unlike the first embodiment of the invention, in this second embodiment, a portion of the stacked laminations forming the tooth 14b have a tab 146 projecting from each radial face 145b, 147b of the tooth 14b, and axially centered on the radial face. It should be noted that although the stator is formed from a winding of the same sheet metal strip, the different layers of winding of this strip forming the tooth 14b are, for the sake of simplicity, referred to as stacked laminations.

[0099] In the embodiment illustrated in [Fig. 10], a sheet stacked three high has these slightly rounded tabs 146, thus forming a series of radially aligned median lugs on either side of the tooth 14b. Alternatively, a sheet stacked three high or five high, for example, has two of these tabs 146.

[0100] The tabs 146 form an elastic element capable of axially blocking the winding support 16e once it has been fitted onto the tooth 14b.

[0101] The winding support 16e is identical to the winding support 16d of the fourth variant of the first embodiment, except that it does not contain magnetic material and its angular and radial walls are configured to axially close the space for the circulation of the heat transfer fluid, at the level of the free axial end of the tooth 14b. The angular walls of the winding support 16e are further configured to allow the heat transfer fluid arriving from the stator closing cover to pass between the angular walls and the angular faces 141b, 143b of the tooth 14b, as shown by the dashed arrows of the circulation of the heat transfer fluid, in [Fig. 10].

[0102] The winding support 16e has two radial ribs 168e on each of its radial walls, capable of gripping the tabs 146 once the winding support 16e is fitted onto the tooth 14b, which axially locks the winding support 16e around the tooth.

[0103] More specifically, when the winding support 16e is fitted onto the tooth, the lower fins 164e of the winding support 16e touch the stator yoke, as shown in the middle of [Fig. 10], one of the two radial ribs 168e of each radial wall of the winding support 16e being located between the yoke and the tabs 146, while a second of the two radial ribs 168e presses on the tabs 146, which by elasticity push back this second radial rib 168e and positions the winding support 16e in its final position shown to the right of [Fig. 10]. In other words, the tabs form elastic means for axially locking the winding support 16e on the tooth 14b and also form means for axially positioning the winding support 16e on the tooth 14b.

[0104] The radial positioning of the winding support 16e around the tooth uses, for example, the axial rib 166 on the internal angular wall 161 of the winding support 16e, and a radial positioning spring 34, as in the second variant of the first embodiment of the invention.

[0105] Fig. 11 illustrates different means of radially positioning a winding support around one of the teeth 14 or 14b.

[0106] The left part of [Fig.11] shows the means for radial positioning of the winding support 16b, using a radial retaining spring 34. We have seen in the first and third variant of the first embodiment that this radial retaining spring 34 can be replaced by one of the springs of the wire part 24 having a trapezoidal profile, or by two radial retaining springs 34.

[0107] The central part of [Fig.1 1] shows a winding support 16f, identical to the winding support 16 except that the radial walls 165f, 167f of the winding support 16f each have an overthickness 15. The overthicknesses 15 are configured so that the springs of the wire part 24b having a U-shaped profile, catch on these overthicknesses 15 and radially lock the winding support 16f, once the latter is fitted onto the tooth 14 and positioned radially by means of the axial rib 166 of the winding support 16f. Similarly, these overthicknesses 15 are configured so that the tabs 146 of the tooth 14b catch on these overthicknesses 15 and radially lock the winding support 16f, once it has been fitted onto the tooth 14b and positioned radially thanks to the axial rib 166 of the winding support 16f.

[0108] The overthicknesses 15 therefore form a means of radially maintaining the winding support 16f relative to the tooth 14 or 14b.

[0109] The right-hand side of [Fig. 11] shows a winding support 16g, identical to winding support 16 except that its outer angular wall 163g has a recess 169g, which partially receives a radial retaining spring 34g. This radial retaining spring 34g is a rectangular leaf spring. It is compressed between the outer angular wall 163g and the outer angular face 143b of the tooth 14b around which the winding support 16g is fitted. It therefore plays the same role as the radial retaining spring 34 of the second embodiment of the first embodiment of the invention. Of course, in this right-hand side of [Fig. 11], the tooth 14b can be replaced by the tooth 14 of the first embodiment of the invention.

[0110] In the various embodiments and modes presented above, the yoke and stator teeth are simply made by winding a sheet metal strip, and the winding supports are, for example, made by molding. Therefore, known and inexpensive tools for manufacturing the stator according to the invention are reused.

[0111] Furthermore, no adhesive is used to fix the winding supports to the teeth, thus eliminating drying time compared to an embodiment using adhesive. Moreover, the described axial and radial support means prevent axial, angular, or rotational movement of the winding supports, and therefore vibrations, even though they allow for considerable clearances during the assembly and manufacturing of the teeth and winding supports. Indeed, the teeth may unexpectedly have non-straight surfaces, but the elastic means absorb these variations and satisfactorily center the winding supports around the teeth. Their structure does not impede the circulation of the heat transfer fluid and generates very few eddy currents.

[0112] The invention is not limited to the examples just described, and numerous modifications can be made to these examples without departing from the scope of the invention. In particular, the features of the various embodiments and variants mentioned in this application can be combined to carry out the invention, provided that these embodiments and variants are not incompatible with each other.

Claims

Demands

1. Stator (1) of an axial flux machine, comprising teeth (14, 14b) projecting from a yoke (10), a winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) fitted onto at least one of the teeth, and at least one winding (18) arranged around the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g), the stator (1) being characterized in that it comprises means for retaining (24, 24b, 146, 168, 168c, 168d, 168e) the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) fitted onto the tooth (14, 14b), the retaining means being arranged in a space (11) for the circulation of a cooling fluid between the tooth (14, 14b) and the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g).

2. Stator (1) of an axial flux machine according to claim 1, wherein the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) comprises two radial walls (165, 165c, 165f, 167, 167c, 167f) and two angular walls (161, 163, 163b, 163c, 163g), arranged opposite two radial faces (145, 145b, 147, 147b) and two angular faces (141, 141b, 143, 143b) of the tooth (14, 14b), the retaining means (24, 24b, 146, 168, 168c, 168d, 168e) comprising on at least one radial wall (165, 165c, 165f, 167, 167c, 167f), an outgrowth (168, 168c, 168d, 168e) protruding into the circulation space (11).

3. Stator (1) of axial flux machine according to claim 2, wherein the retaining means comprise at least one elastic element (24, 24b, 146) arranged projecting from the radial face (145, 145b, 147, 147b) disposed opposite the radial wall (165, 165c, 165f, 167, 167c, 167f), the protrusion (168, 168c, 168d, 168e) being axially blocked by the elastic element (24, 24b, 146).

4. Stator (1) of axial flux machine according to claim 3, wherein the tooth (14) has a radial groove (140, 140c) on the radial face (145, 147), the elastic element (24, 24b) being disposed in the radial groove (140, 140c).

5. Stator (1) of axial flux machine according to claim 3 or 4, wherein the elastic element (24, 24b) comprises a spring.

6. Stator (1) of axial flux machine according to claim 5, wherein the spring forms at least in part one arm of a U profile, each arm of the U disposed between one of the two radial walls (165, 165c, 165f, 167, 167c, 167f) and one of the two radial faces (145, 147) comprising a spring, and the ends of the U forming two hooks engaged on either side of one of the angular faces (143) of the tooth (14).

7. Axial flux machine stator according to claim 3, wherein the tooth (14b) is formed of radially stacked magnetic sheets, the elastic element (146) comprises at least one tongue formed by an angular extension of at least one sheet.

8. Stator (1) of axial flux machine according to any one of claims 3 to 7, wherein the winding support (16f) is configured to maintain its radial position relative to the tooth (14, 14b), by friction with the elastic element (24b, 146).

9. Stator (1) of axial flux machine according to any one of claims 2 to 8, comprising means for radially positioning the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) relative to the tooth (14, 14b).

10. Stator (1) of an axial flux machine according to claim 9, wherein the angular faces (141, 141b, 143, 143b) comprise an external angular face (143, 143b) disposed on the external radial periphery of the stator (1), and an internal angular face (141, 141b) disposed on the internal radial periphery of the stator, and the angular walls (161, 163, 163b, 163c, 163g) comprise an external angular wall (163, 163b, 163c, 163g) opposite the external angular face (143, 143b) and an internal angular wall (161) opposite the internal angular face (141, 141b), and wherein the radial positioning means comprise an axial rib (166) on the wall internal angular (161).

11. Stator (1) of an axial flux machine according to claim 10, comprising at least one radial retaining spring (34, 34g), interposed between the external angular wall (163b, 163c, 163g) and the external angular face (143, 143b).

12. A method (100, 200) for assembling an electrical machine comprising a stator (1) according to any one of claims 1 to 11, at least one tooth (14, 14b) of the stator being surrounded by a winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) receiving a winding (18), the winding support being held around the tooth by retaining means (24, 24b, 146, 168, 168c, 168d, 168e) arranged in a space (11) for the circulation of a cooling fluid between the tooth and the winding support, the assembly method comprising the steps of: - wind (102, 202) the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) so as to form a winding (18), - fit (106, 208) the winding support onto the tooth (14, 14b) until the axial locking of the winding support (16, 16b, 16c, 16d, 16e, 16f, 16g) by the retaining means (24, 24b, 146).

13. Method (100, 200) of assembly according to claim 12, wherein the electric machine comprises a closing cover in which the cylinder head (10) is fixed, and wherein the fitting step (106, 208) is followed by a step of gluing (108, 210) a sealing membrane (40) onto a free face of the tooth (14, 14b) and onto a periphery of the closing cover, forming a sealed chamber intended to receive a coolant.

14. Method (100, 200) of assembling according to claim 12 or 13, of an electrical machine comprising a stator according to claims 4 and 5, wherein the step of fitting the winding support (16, 16b, 16c, 16d, 16f, 16g) onto the tooth (14) is preceded by a step of positioning (104, 204) the spring in the radial groove (140, 140c) of the tooth (14).

15. Method (200) of assembling according to any one of claims 12 to 14, an electrical machine comprising a stator (1) according to claim 11, wherein the step of fitting (208) the winding support (16b, 16c, 16g) onto the tooth (14, 14b) is preceded or followed by a step of positioning (206) the radial retaining spring (34, 34g) against the external angular wall (163b, 163c, 163g).

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