Axial flux electric machine stator by radial tooth insertion

Abstract

The invention relates to a stator and an axial flux electric machine. The stator comprises a yoke and teeth (4) around which coils (5) are wound. The yoke comprises an internal annular portion (2) about a longitudinal axis and radial elements (3) extending outward from said internal annular portion (2). Each tooth (4) is positioned between two of said radial elements (3), and the teeth (4) are substantially evenly distributed around the circumference of the yoke. Furthermore, each tooth (4) comprises a groove (6) on each lateral surface opposite the radial elements (3) for inserting the tooth (4) into the opposite radial element (3), each groove (6) extending along the entire length of the tooth (4) in question. The invention also relates to methods of manufacturing the stator and the electric machine. Figure 1 to be published

Description

Title of the invention: Stator for an axial flux electric machine by radial tooth insertion technical field

[0001] The invention relates to the field of axial flux electrical machines and more particularly to a stator for this type of electrical machine.

[0002] This type of axial flux electric machine can find applications in electric or hybrid vehicles, such as cars, buses, trucks, and construction equipment. This type of machine can also be used for stationary applications, such as industrial charging machines or electric generators. Previous technique

[0003] In recent decades, the development of electrical machines has focused primarily on radial flux electrical machines.

[0004] Radial flux electric machines generally comprise a coaxial rotor and stator, one surrounding the other. Thus, the magnetic flux can pass radially from the rotor to the stator and vice versa, via a radial air gap which is defined as the radial clearance between the rotor and the stator.

[0005] On the contrary, axial flux machines are characterized by at least one rotor and at least one stator arranged successively one behind the other in the axial direction (of the rotor's axis of rotation), such that the path of the magnetic flux between the rotor and the stator is axial. In other words, the rotor and the stator face each other and are separated by an air gap of axial thickness (or axial clearance between the rotor and the stator).

[0006] The rotor of axial flux permanent magnet electric machines generally comprises permanent magnets glued to the rotor yoke or inserted into a rotor body and, in this case, the permanent magnets are separated by radial arms from the rotor body.

[0007] The stator generally comprises a ferromagnetic stator body, which may or may not have teeth. The electrical winding in the stator slots may be distributed or concentric, i.e., each winding then surrounds a tooth.

[0008] In the context of the development of high power and torque density machines for electric or hybrid traction, particularly for electric or hybrid vehicle applications, axial flux machine topology is among those with the highest potential, notably due to the high constraint axial footprint. Axial flux electrical machines are also of interest for stationary applications as well as for wind power applications.

[0009] In general, axial flux electrical machines allow higher power and torque densities than radial flux electrical machines due to their geometry.

[0010] This gain is generally achievable by increasing the number of pole pairs in the rotor, which implies an increase in the electrical frequency of the electrical and magnetic quantities, with in particular a negative impact on rotor losses (mainly losses in the magnets) due to space harmonics and electromagnetic effects.

[0011] The manufacturing of the stators for these machines is a crucial challenge for the development of axial flux electric machines. Stators, obtained by winding coils around teeth, are subject to constraints in the manufacturing of the yoke and teeth, as well as constraints in the winding process on the teeth and the closing of slots to hold the coils in position. For these reasons, segmented stators (particularly those with teeth attached to the stator yoke) represent a relevant approach for simplifying stator manufacturing. This solution avoids winding directly onto the teeth and facilitates the closing of slots. However, this architecture requires that the teeth be held in position on the yoke with sufficient precision to ensure the magnetic flux loop.

[0012] Patent applications EP 2 224 577 A1 and US 2005 / 0 073 213 A1 relate to segmented rotors where the teeth are attached to the yoke, which is a substantially annular part. However, these solutions require a fairly large axial space for inserting the tooth onto the yoke. Furthermore, these solutions do not allow for good direct cooling of the tooth because the yoke limits the cooling of the teeth. In addition, the solution described in patent application EP 2 224 577 A1 presents a complex yoke design for radial insertion: in fact, machining the yoke from rolled sheet metal complicates this design. Moreover, the rigidity required to maintain the teeth / yoke assembly appears difficult to guarantee. This solution may also degrade the passage of magnetic flux.US patent application 2005 / 0 073 213 A1 also relates to the stator of an axial flux electric machine in which the teeth are inserted axially onto the cylinder head, which is therefore more complex to implement. Furthermore, the ability to retain the stator-housing assembly is reduced.

[0013] Thus, the invention seeks to enable a simple manufacturing of an axial flux electric machine stator, while improving heat transfers, and minimizing magnetic field leakage. Summary of the invention

[0014] The invention relates to an axial flux electric machine stator comprising a yoke and teeth around which coils are wound, the yoke comprising an internal annular part around a longitudinal axis and radial elements extending from said internal annular part and directed outwards, the radial elements being separated from each other by openings so that the yoke is open radially between said radial elements, over the entire thickness of the yoke, each tooth being positioned between two of said radial elements, the teeth being substantially regularly distributed over the circumference of the yoke, each tooth comprising a groove on each lateral surface opposite the radial elements for the insertion of each opposite radial element into the groove concerned, each groove extending over the entire length of the tooth concerned.Furthermore, the width of each groove is approximately equal to the thickness of the cylinder head to allow the insertion of each radial element into the groove.

[0015] Preferably, said cylinder head is axially rolled and / or said teeth are rolled.

[0016] Advantageously, the section of said teeth, between the radial elements, in a plane orthogonal to the longitudinal axis is substantially trapezoidal or rectangular.

[0017] Preferably, the stator includes at least one locking means for locking the position of at least one tooth in the cylinder head.

[0018] According to a variant of the invention, said radial elements comprise an excess length relative to the teeth, this excess length being preferably suitable for allowing the radial position of the tooth to be locked in the radial elements by deformation or crimping.

[0019] Preferably, at least one locking means comprises an external locking device positioned between two radial elements for external locking of the tooth positioned between said two radial elements, said external locking device preferably being a key.

[0020] According to another variant of the invention, the teeth are longer than the radial elements and at least one locking means includes an external ring positioned around the teeth for locking the teeth in the cylinder head.

[0021] The invention also relates to an axial flux electric machine comprising at least one rotor, at least one stator according to one of the variants or combinations of variants described above, and an outer casing, the at least one rotor and at least one stator being placed in said outer casing, the electric machine comprising an assembly system for fixing the stator to the outer casing.

[0022] Preferably, the assembly system includes screws for fixing the outer casing to the stator, preferably some of said screws being positioned in said radial elements of the cylinder head.

[0023] Advantageously, at least some of the screws are positioned on at least an external portion of the radial elements of the cylinder head and preferably on at least an internal portion of the radial elements or on the internal annular part of the cylinder head.

[0024] According to one configuration of the invention, at least some of said screws are positioned on a central part of the radial elements.

[0025] Preferably, the assembly system includes at least one screw in each radial element.

[0026] According to one embodiment of the invention, the cylinder head includes through bores for the passage of the screws and the outer casing includes threads for screwing the screws or the cylinder head includes threads, preferably tapped and shouldered inserts, for screwing the screws and the outer casing includes openings for the passage of the screws.

[0027] Advantageously, some of said screws are positioned in threaded holes located in teeth or in threaded inserts located in teeth.

[0028] The invention relates to a method of manufacturing the stator according to one of the variants or combinations of variants described above, in which the teeth are positioned so that the grooves in the lateral surfaces allow the insertion of the teeth into the radial elements around each tooth, and then each tooth is slid along the grooves in the direction of the longitudinal axis for the insertion of the teeth radially into the cylinder head.

[0029] Preferably, the position of each tooth is locked in the cylinder head.

[0030] Advantageously, the teeth are positioned so that the grooves of the Lateral surfaces allow the insertion of the teeth into the radial elements around each tooth, then each tooth is slid along the grooves towards the longitudinal axis for the insertion of the teeth radially into the cylinder head, then preferably the position of each tooth is locked in the cylinder head, and the stator is fixed to the outer casing. List of figures

[0031] Other features and advantages of the stator, the electric machine and the methods of manufacturing the stator and the electric machine according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below. [Fig 1]

[0032] Fig. 1 represents a perspective view of an embodiment of an axial flux electric machine stator according to the invention. [Fig 2]

[0033] Fig. 2 represents a view of a portion of an axial flux electric machine stator according to the invention with a means for locking the teeth on the cylinder head according to a first variant. [Fig 3]

[0034] Fig. 3 represents a perspective view of an axial flux electric machine stator according to the invention with a locking means according to a second variant. [Fig 4]

[0035] Fig. 4 represents a view of an axial flux electric machine stator according to the invention, with an assembly system according to a first configuration. [Fig 5]

[0036] Fig. 5 represents a view of an axial flux electric machine according to the invention with an assembly system according to a second configuration. [Fig 6]

[0037] Fig. 6 represents a view of an axial flux electric machine according to the invention, with an assembly system according to the configuration of Fig. 5. [Fig 7]

[0038] Fig. 7 represents a view of an axial flux electric machine according to the invention, with an assembly system according to another configuration. [Fig 8]

[0039] Figure 8 illustrates a three-dimensional view of a tooth of an axial flux electric machine stator according to the invention. [Fig 9]

[0040] Figure 9 illustrates a view of an axial flux electric machine according to the invention, with an assembly system. [Fig 10]

[0041] Fig. 10 illustrates a view of an axial flux electric machine according to the invention, with an assembly system according to another configuration. Description of the implementation methods

[0042] The "longitudinal" direction is the direction of the longitudinal axis of the stator and the electric machine.

[0043] The terms "front" and "rear" are understood in relation to the longitudinal axis, the term "front" being understood for the stator on the side of the coils, therefore on the side of the rotor, and the term "rear" being on the side opposite the coils (opposite the rotor, which may correspond to the side of the casing).

[0044] Thickness is understood to mean a length in the longitudinal direction.

[0045] The terms "internal" and "external" are understood relative to each other, the internal term being relatively closer to the axis of rotation than the external term.

[0046] The invention relates to an axial flux electric machine stator comprising a yoke and teeth around which coils are wound. The yoke comprises an internal annular portion about a longitudinal axis and radial elements extending outward from said internal annular portion. The radial elements are separated from each other by openings along the entire axial thickness (length of the yoke in the axial direction) of the stator, such that the yoke is radially open between these radial elements. Preferably, the width (length in a direction orthogonal to the longitudinal and radial directions) of the radial elements can be constant along the radial axis. Thus, the yoke has the shape of a sun with an internal ring and rays extending outward from the internal ring. The space between the radial elements allows for the placement of teeth between these radial elements.Therefore, the teeth axially traverse the entire thickness (length in the axial direction) of the cylinder head. This configuration allows, on the one hand, for easier assembly of the teeth onto the cylinder head and significantly reduces the additional axial bulk of the stator, and on the other hand, facilitates direct cooling of the teeth because, on the rear face of the teeth (the face orthogonal to the longitudinal axis which is opposite the coils), the heat flux has a direct passage to the cooling source without having to pass through the cylinder head and any additional interfaces or air gaps.

[0047] The thickness (in the axial direction) of the internal annular portion is equal (or substantially equal) to the thickness (in the axial direction) of the radial elements and also corresponds to the total thickness (in the axial direction) of the cylinder head. In other words, the front and rear faces of the internal annular portion are coplanar with the front and rear faces of the radial elements, respectively. Preferably, no grooves or shoulders are formed in the radial elements or in the internal annular portion. Consequently, manufacturing the cylinder head is simple, particularly when the cylinder head is rolled.

[0048] The rear face of the teeth can be coated with a thermal conduction paste or thermal resin to improve heat transfer by conduction, to improve the cooling of the stator, by allowing direct cooling of the teeth, without passing through the cylinder head which generates additional thermal resistance.

[0049] The teeth are substantially regularly distributed around the circumference of the cylinder head, between the radial elements, and each tooth includes a groove on each lateral surface opposite the radial elements. The lateral surfaces are understood of surfaces substantially orthogonal to the circumferential direction: they therefore extend globally in the radial direction and in the axial direction.

[0050] By substantially regularly distributed teeth, we mean a regular distribution within the limits of manufacturing precision. The grooves on these lateral surfaces of the teeth serve to insert each radial element, along its axial thickness, opposite it in the relevant groove, on each side of the tooth. Thus, the axial thickness of the tooth is greater than the axial thickness of the cylinder head (particularly of the radial elements) and the width (in the axial direction) of the groove corresponds substantially (within the clearance required for assembly) to the thickness of the radial elements of the cylinder head (and therefore to the thickness of the cylinder head) opposite it to allow this insertion.This means that the groove can be very slightly larger than the thickness of the radial elements of the cylinder head to allow the radial elements to be mounted in the groove: the width of the groove is therefore equal to the thickness of the elements, minus the functional clearance required for assembly (hence the use of the term "approximately"). In other words, the tooth protrudes axially on both sides of the cylinder head, on one side for mounting the coils around the tooth (on the rotor side) and on the other side for the tooth's protrusion, allowing the tooth's groove to surround the radial element of the cylinder head for insertion. This configuration is particularly advantageous because it does not require machining such as a shoulder or groove in the cylinder head (especially when it is rolled), which simplifies its manufacture. It also facilitates cooling of the tooth and therefore of the coils.Furthermore, each groove extends along the entire length (in the radial direction) of the tooth in question so that the tooth can slide between the radial elements from the outside in.

[0051] In addition, the depth of the groove can be constant over the entire radial length of the tooth so as to simplify manufacturing and assembly.

[0052] The cylinder head connects all the teeth and ensures the stator is mounted. The resulting assembly thus corresponds to a segmented stator.

[0053] Thus, the invention has the advantage of having a simple implementation and a limited axial footprint, while minimizing magnetic field leakage in the teeth and in the cylinder head caused by the play between these parts.

[0054] Furthermore, the invention provides a substantial tooth surface area at the rear, which maximizes heat transfer due to the absence of cylinder head contact on the rear portion of the teeth. Heat transfer in the rear face of the teeth can be further improved by the addition of a thermal conductivity paste or a thermal resin.

[0055] Preferably, the tooth cross-section on the rear face (opposite side to that of the coils) is substantially identical to the tooth cross-section at the level of the coil passage (in a plane parallel to the rear face) and the tooth cross-section located between the The radial elements (in a plane parallel to the rear face) have a slightly restricted cross-section compared to the tooth cross-section on the rear face (and the tooth cross-section at the coil passage) due to the grooves on each of the lateral faces. This configuration is particularly advantageous for heat transfer.

[0056] Preferably, the cylinder head can be axially rolled and / or said teeth can be rolled. The cylinder head can, for example, be formed from stacked sheets, and the stacked sheets of the cylinder head can advantageously be stacked in the longitudinal direction.

[0057] The teeth can, for example, each be formed by a stack of sheets. The stacking of the sheets of the teeth can advantageously be substantially in the radial direction, therefore orthogonal to the direction of the stacking of the sheets of the cylinder head.

[0058] The rolling of the stacked plates of the cylinder head and teeth allows the electromagnetic flux to be directed to maximize performance. The orthogonal direction of the stacking of the cylinder head plates and that of the teeth plates allows for simplified assembly, thus offering a good compromise between electromagnetic performance and assembly time (and cost).

[0059] According to one embodiment of the invention, the cross-section of said teeth, between the radial elements of the cylinder head, in a plane orthogonal to the longitudinal axis, can be substantially trapezoidal or rectangular. In other words, the portion of the teeth located over at least the thickness of the groove has a trapezoidal or rectangular cross-section. The trapezoidal cross-section is particularly advantageous because the shape is especially well-suited for distributing the teeth around the circumference of the cylinder head. Furthermore, the trapezoidal cross-section allows the tooth to be clamped in the cylinder head under the effect of a radial force on the tooth, thus providing better positioning. This also reduces the clearance between the tooth and the cylinder head along the entire length of the grooves, thereby limiting the degradation of electromagnetic performance. This solution also maximizes the heat flow between the teeth and the cylinder head.

[0060] Advantageously, only the internal surface of the tooth (in the region close to the longitudinal axis of the stator) is not in contact with the cylinder head.

[0061] Advantageously, each tooth can have a cross-section that can be trapezoidal (or rectangular) in all planes orthogonal to the longitudinal direction, along the longitudinal axis. All the cross-sections of the tooth are therefore preferably either trapezoidal or rectangular.

[0062] When they are rectangular, the lengths (in the radial direction) of the different rectangles of the different sections can be identical and the widths can depend on the position of the section: the width (in the orthogonal direction to the radial direction) of the section of the tooth extensions (the tooth having extensions on the front face to ensure the coils are held in position) may be greater than the section width of the portion around which the teeth are wound; the section width of the portion around which the teeth are wound may be the same or substantially the same as the section width of the back face; the section width of the part between the radial elements may be less (by the sum of the depths of the grooves on each side of the tooth) than the section width of the portion around which the teeth are wound (and by the section width of the back face).

[0063] When they are trapezoidal, the heights (in the radial direction) of the different trapezoids of the different sections can be identical and the lengths of the small and large bases of the trapezoids can depend on the position of the section: the length of the small and large bases (in the direction orthogonal to the radial direction) of the section of the extensions can be greater than the length of the small and large bases of the section of the portion around which the teeth are wound; the length of the small and large bases of the section of the portion around which the teeth are wound can be identical or substantially identical to the length of the small and large bases of the section of the rear face;The length of the small and large bases of the section of the part located between the radial elements can be (from the sum of the depths of the grooves on each side of the tooth) to the length of the small and large bases of the section of the portion around which the teeth are wrapped (and the length of the small and large bases of the section of the back face).

[0064] By "substantially" trapezoidal or rectangular, it is understood that the sections may have rounded rather than sharp angles at the intersections of the edges.

[0065] Advantageously, the stator may include at least one locking means for locking the position of at least one tooth in the cylinder head. This improves position retention, thereby preventing performance losses and machine degradation.

[0066] According to one embodiment of the invention, said radial elements may include an excess length relative to the teeth. In other words, the radial elements are longer, in the radial direction, than the teeth. This excess length extends in the radial direction and may preferably be adapted to allow the radial position of the tooth to be locked in the radial elements by deformation or crimping. Indeed, portions of this excess length can, for example, be folded over, notably by crimping around the tooth, to lock the tooth in each radial element. The excess length can be positioned radially on the outside to facilitate the deformation operation and to lock the outside of the tooth.

[0067] For the purposes of the present invention, "excess length" means a length that exceeds or a longer part: for example, if the radial element has an excess length in relation to the teeth, this means that the length of the radial element is greater than the length of the tooth and therefore that it has a part that exceeds in relation to the tooth.

[0068] According to one aspect of the invention, at least one locking means may comprise an external locking device positioned between two radial elements for externally locking the tooth positioned between said two radial elements, said locking device preferably being a key (preferably made of a non-magnetic material). This solution allows for assembly and disassembly of the unit, ensuring secure locking of the tooth in the cylinder head. This key may, for example, include an elastic zone to guarantee constant contact regardless of the machine's operating conditions.

[0069] According to another embodiment, the teeth may be radially longer than the radial elements of the breechblock. In other words, the teeth have an axial overhang that extends axially beyond the peripheral portion of the radial elements. For this embodiment, the locking means may include an external ring positioned around the teeth to lock all the teeth in the breechblock. This external ring may be a ring tightly mounted on the teeth. Alternatively, this external ring may include a strap or a band, which may be a metal band. This configuration allows for effective positioning and simple assembly to hold the teeth in position with a single piece.

[0070] The invention also relates to an axial flux electric machine comprising at least one rotor, at least one stator according to one of the variants or combinations of variants described above, and an external casing (also called a "housing"). The at least one rotor and the at least one stator are housed within said external casing. The rotor is free to rotate about an axis of rotation which corresponds to the longitudinal axis of the stator and therefore to that of the electric machine.

[0071] According to the invention, the electrical machine includes an assembly system for fixing the stator to the outer casing.

[0072] Advantageously, the assembly system may include screws for fixing the stator to the outer casing.

[0073] Preferably, some (a first quantity) of said screws can be positioned in said radial elements of the cylinder head so as to ensure good fixing and to limit the risks of vibrations.

[0074] Advantageously, at least some (a portion of the first quantity or the first quantity) of the screws can be positioned on at least one external portion of the radial elements of the cylinder head and preferably on at least one internal portion radial elements or the internal annular portion of the cylinder head. By fixing the screws to the external portion, better positioning and retention are ensured. By fixing them to both the external and internal portions of the cylinder head (radial elements or the internal annular portion), positioning and retention are further improved. Furthermore, the external or internal positioning of the screws helps limit magnetic field leakage because the magnetic flux is low in these areas.

[0075] Alternatively or additionally, at least some (a second quantity) of said screws may be positioned on a central portion of the radial elements. This solution offers a compromise between the quantity of screws required and the retention in position.

[0076] According to one configuration of the invention, the assembly system may include at least one screw in each radial element to ensure proper fixing of the entire stator.

[0077] According to one embodiment, the cylinder head may include through bores for the passage of screws, and the outer casing may include threaded holes for screwing the screws. Therefore, the screws can be tightened by passing them through the through bores of the cylinder head from inside the machine and screwing them into the threaded holes of the outer casing.

[0078] Alternatively, the cylinder head may include threaded holes, preferably shouldered and threaded inserts (preferably made of non-magnetic material), for screwing in the bolts, and the outer casing may include openings for the passage of the bolts. Therefore, the bolts can be screwed in by passing them through the openings in the outer casing from outside the machine and screwing them into the threaded holes in the cylinder head. When the cylinder head includes threaded inserts, manufacturing is simpler, particularly when the cylinder head is made of rolled sheet metal. The shoulder of the threaded inserts facilitates tightening the bolts. During tightening, the bolt pulls on the cylinder head, which then presses against the tooth, and the tooth then presses against the outer casing.

[0079] According to one configuration of the invention, some (a third quantity) of said screws can be positioned in threaded holes located in teeth or in threaded inserts located in teeth. When the teeth include threaded inserts, manufacturing is simpler, particularly when the teeth are made of rolled sheet metal. The shoulder of the threaded inserts facilitates tightening the screws. In this configuration, the screws are advantageously inserted from the outside through the outer casing (the outer casing includes openings for the passage of the screws) and the screws are positioned in the threaded holes of the teeth or in the threaded inserts of the teeth, so as to allow tightening and thus fastening. During tightening, the screw pulls on the tooth, which then presses against the cylinder head, the cylinder head then presses itself into the outer casing.

[0080] Alternatively, the thread or insert of the tooth can be replaced by a countersunk hole. In this case, the screw is then introduced from inside the electric machine, passes through the countersunk hole (the countersunk hole allows the screw to be countersunk into the tooth, i.e. not to protrude from the tooth) of the tooth to screw into a thread in the outer casing.

[0081] The invention also relates to a method of manufacturing the stator according to one of the variants or combinations of variants described above, in which the teeth are positioned so that the grooves in the lateral surfaces allow the teeth to be inserted into the radial elements around each tooth, and then each tooth is slid along the grooves in the direction of the longitudinal axis (i.e., by sliding the tooth from the outside in) for radial insertion of the teeth into the cylinder head. Thus, mounting the teeth in the cylinder head is simple and the axial space required is reduced.

[0082] Advantageously, the position of each tooth in the cylinder head can be locked by a locking means, such as an external ring or a key in particular, to ensure good retention in position.

[0083] The invention also relates to a method of manufacturing the electric machine according to one of the variants or combinations of variants described above, in which the teeth are positioned so that the grooves in the lateral surfaces allow the teeth to be inserted into the radial elements around each tooth, then each tooth is slid along the grooves in the direction of the longitudinal axis (i.e., by sliding the tooth from the outside in) for radial insertion of the teeth into the yoke, then preferably the position of each tooth in the yoke is locked, and the stator is fixed to the outer casing, for example by an assembly system comprising screws. As a result, the assembly of the entire electric machine is simple.

[0084] Fig. 1 illustrates, schematically and not in a limiting manner, a first embodiment of the invention of an axial flux electric machine stator according to the invention.

[0085] The stator comprises a radially open breechblock, including an internal annular portion 2 and radial elements 3 extending outwards from the internal annular portion 2. As a result, the breechblock has a "sun" shape with rays directed outwards. The breechblock therefore has openings between the radial elements, these openings extending over the entire thickness of the breechblock.

[0086] Between the radial elements 3, teeth 4 are positioned. As a result, the stator constitutes a segmented stator.

[0087] The teeth 4 have grooves 6 on their lateral surfaces, the lateral surfaces being opposite the radial elements. The radial elements 3 are positioned in the grooves 6 and serve as guides when the teeth are inserted into the stator. In other words, the width of the grooves 6 corresponds approximately to the thickness of the radial elements 3 at the yoke 1. Consequently, the teeth protrude axially on either side of the yoke. As shown, the cross-section of the teeth 4, between the radial elements 3, is substantially trapezoidal but could have another shape and could, in particular, be rectangular.Furthermore, the tooth section on the rear face (opposite side to the spools) is substantially identical to the tooth section at the spool passage (in a plane parallel to the rear face), and the tooth section between the radial elements (in a plane parallel to the rear face) is slightly restricted compared to the tooth section on the rear face (and the tooth section at the spool passage) due to the grooves on each of the lateral faces.

[0088] Around each tooth, coils 5 are placed on the part of the teeth which protrudes from the cylinder head.

[0089] In addition, holes 7 and 8 are positioned respectively on the external part of the radial elements 3 and on the internal part of the radial elements 3. These holes 7 and 8 allow the passage of screws to fix the stator to an external casing of the electrical machine (not shown). These holes 7 and 8 can be bores or threaded inserts.

[0090] Fig. 2 illustrates, schematically and not in a limiting manner, an example of an axial flux electric machine stator according to the invention with a locking means for locking the position of at least one tooth 4 in the cylinder head 1.

[0091] The tooth 4 is positioned between two radial elements 3. Furthermore, a locking means is positioned on the outside of the tooth to secure it in the cylinder head. The locking means is a key 10 positioned between the two radial elements 3 located on either side of the tooth 4. The teeth 4 have a radial length shorter than the radial length of the radial elements 3. Consequently, the radial elements 3 have a radial excess length (compared to the teeth), which allows the insertion of the key 10.

[0092] Fig. 3 illustrates, schematically and not in a limiting manner, an example of an axial flux electric machine stator according to the invention with another locking means for locking the position of at least one tooth 4 in the yoke 1 which includes an internal annular part 2 and radial elements 3.

[0093] The tooth 4 is positioned between two radial elements 3. In addition, a locking means is positioned outside the teeth to ensure that all the teeth are locked in the breech. The locking means here is an external ring 11 (a ring or a ribbon for example) which surrounds the teeth 4. The teeth 4 here have a radial length greater than the radial length of the radial elements 3.

[0094] Fig. 4 illustrates, schematically and not in a limiting manner, a view of an axial flux electric machine stator according to the invention, with an assembly system according to a first configuration.

[0095] The stator comprises a radially open breechblock, including an internal annular portion 2 and radial elements 3 extending outwards from the internal annular portion 2. As a result, the breechblock has a "sun" shape with rays directed outwards. The breechblock therefore has openings between the radial elements, these openings extending over the entire thickness of the breechblock.

[0096] Between the radial elements 3, teeth 4 are positioned. As a result, the stator constitutes a segmented stator.

[0097] The teeth 4 have grooves on their lateral surfaces, the lateral surfaces being opposite the radial elements. The radial elements 3 are positioned in the grooves and serve as guides when the teeth are inserted into the stator. In other words, the width of the grooves corresponds substantially to the thickness of the radial elements 3 at the yoke. As shown, the cross-section of the teeth 4, between the radial elements 3, is substantially trapezoidal but could have another shape and could, in particular, be rectangular.Furthermore, the tooth section on the rear face (opposite side to the spools) is substantially identical to the tooth section at the spool passage (in a plane parallel to the rear face), and the tooth section between the radial elements (in a plane parallel to the rear face) is slightly restricted compared to the tooth section on the rear face (and the tooth section at the spool passage) due to the grooves on each of the lateral faces.

[0098] Around the teeth, coils 5 are placed on the part of the teeth which protrudes from the cylinder head.

[0099] In addition, holes 7 and 8 are positioned respectively on the external part of the radial elements 3 and on the internal part of the radial elements 3. These holes 7 and 8 allow the passage of screws to fix the stator to an external casing of the electrical machine (not shown). These holes 7 and 8 can be bores or threaded inserts.

[0100] Fig. 5 illustrates, schematically and not in a limiting manner, a view of an axial flux electric machine according to the invention with an assembly system according to a second configuration.

[0101] In this figure, the assembly system comprises screws 17 which are inserted from outside the electrical machine, which pass through the outer casing 13 via an opening in the outer casing (here a countersunk hole), and which are screwed into a tapped and shouldered insert 12 positioned in the cylinder head 1, more precisely, in a radial element of the cylinder head.

[0102] Teeth 4 are positioned between the radial elements of the cylinder head. A portion of the teeth protrudes from the cylinder head for the placement of the coils 5 around this portion of the teeth 4 and protrudes on the other side of the cylinder head, on the outer casing side 13.

[0103] [Fig.6] illustrates, schematically and not in a limiting manner, a view of an axial flux electric machine according to the invention, with a locking system according to the configuration of [Fig.5].

[0104] The stator comprises a radially open breechblock, including an inner annular portion and radial elements 3 extending outwards from the inner annular portion. As a result, the breechblock has a "sun" shape with rays directed outwards. The breechblock therefore has openings between the radial elements, these openings extending across the entire thickness of the breechblock.

[0105] Between the radial elements 3, teeth 4 are positioned. As a result, the stator constitutes a segmented stator.

[0106] The teeth 4 have grooves on their lateral surfaces, the lateral surfaces being opposite the radial elements. The radial elements 3 are positioned in the grooves and serve as guides when the teeth are inserted into the stator. In other words, the width of the grooves corresponds substantially to the thickness of the radial elements 3 at the yoke. As shown, the cross-section of the teeth 4, between the radial elements 3, is substantially trapezoidal but could have another shape and could, in particular, be rectangular.Furthermore, the tooth section on the rear face (opposite side to the spools) is substantially identical to the tooth section at the spool passage (in a plane parallel to the rear face), and the tooth section between the radial elements (in a plane parallel to the rear face) is slightly restricted compared to the tooth section on the rear face (and the tooth section at the spool passage) due to the grooves on each of the lateral faces.

[0107] Around the teeth, coils 5 are placed on the part of the teeth which protrudes from the cylinder head.

[0108] In addition, holes 7 positioned on a central portion of the radial elements 3 serve as screw passages for fixing the stator to an external casing of the electrical machine (not shown). Given the presence of the coils 5 on the front face of the stator, the screws are inserted from the outside, pass through an opening in the external casing 13, and are screwed into threaded holes or threaded inserts in the central portion of the radial elements 3.

[0109] Fig. 7 illustrates, schematically and not in a limiting manner, a view of an axial flux electric machine according to the invention, with a locking system according to a fourth configuration.

[0110] Screws 17 are positioned from the outside, pass through the outer casing 13, and are then screwed into a threaded hole (or a threaded and preferably shouldered insert) in the tooth 4. Tightening the screw 17 in the tooth 4 allows the tooth 4 to be pressed into the cylinder head 1, and the cylinder head 1 to be pressed against the outer casing 13 of the electric machine.

[0111] Fig. 8 illustrates, schematically and not in a limiting manner, an example of a tooth of an electrical machine stator according to the invention.

[0112] The tooth 4 includes grooves 6 on each lateral surface 20a and 20b of the tooth. These grooves 6 allow the insertion of the radial elements of the cylinder head, their thickness being substantially equal to the width L of the groove, in the axial direction.

[0113] The tooth 4 includes a portion 15 around which the coils (not shown) are wound. On the front face 22, opposite the rotor of the electric machine, the tooth includes a portion with extensions 16 which ensure that the coils are held in position around the portion 15.

[0114] The section of portion 15 around which the coils are wound is substantially trapezoidal (and could alternatively be rectangular), just as the section of the rear face 21 and the section of portion 15 around which the coils are wound is substantially identical to the section of the rear face 21.

[0115] The cross-section of part 14 of the tooth, without a plane orthogonal to the longitudinal direction of the tooth, between the two grooves, i.e., between the radial elements on either side of the tooth 4, is substantially trapezoidal (and could alternatively be rectangular). This cross-section of part 14 is slightly smaller than the cross-section of the tooth on the back face 21 and that of portion 15, taking into account the depth p of the grooves 6 on each lateral side of the tooth 4.

[0116] According to the figure, the tooth has a trapezoidal cross-section (but which could alternatively be rectangular) in all planes orthogonal to the longitudinal direction, along the longitudinal axis. All the cross-sections of the tooth are therefore trapezoidal (they could alternatively all be rectangular).

[0117] For these trapezoidal sections, the heights (in the radial direction) of the different trapezoids of the different sections are identical and the lengths of the small and large bases of the trapezoids depend on the position of the section: the length of the small and large bases (in the direction orthogonal to the radial direction) of the section of the extensions 22 is greater than the length of the small and large bases of the section of the portion 15 around which the teeth are wound; the length of the small and large bases of the section of the portion 15 around which the teeth are wound is identical or substantially identical to the length of the small and large bases of the section of the rear face 21; the length of the small and large bases of the section of the part 14 located between the radial elements is less (by the sum of the depths p of the grooves on each side of the tooth) than the length of the small and large bases of the section of the portion 15 around which the teeth are wrapped (and by the length of the small and large bases of the section of the rear face).

[0118] If they were rectangular, the lengths (in the radial direction) of the different rectangles of the different sections could be identical and the widths could depend on the position of the section: the width (in the direction orthogonal to the radial direction) of the section of the extensions 22 could be greater than the section width of the portion 15 around which the teeth are wound; the section width of the portion 15 around which the teeth are wound could be identical or substantially identical to the section width of the back face 21; the section width of the part 14 located between the radial elements could be less (by the sum of the depths of the grooves on each side of the tooth) than the section width of the portion 15 around which the teeth are wound (and by the section width of the back face).

[0119] Fig. 9 illustrates, schematically and not in a limiting manner, an example of an axial flux electric machine according to the invention, with an assembly system.

[0120] This view is in a plane including the longitudinal axis.

[0121] In this figure, a screw 17 is inserted from the inside, it passes through the cylinder head by a bore through the entire thickness of the cylinder head 1 and it is tightened in a threaded bore in the outer casing 13.

[0122] The teeth 4 protrude from each axial side of the cylinder head 1. Coils 5 surround a portion of the teeth 4.

[0123] In the present figure, the screw is positioned in a central part of the radial element of the cylinder head 1.

[0124] Fig. 10 illustrates, schematically and not in a limiting manner, an example of an axial flux electric machine according to the invention, with another assembly system.

[0125] This view is in a plane including the longitudinal axis.

[0126] In this figure, screws 17 are inserted from the inside, they pass through the cylinder head 1 through bores through the entire thickness of the cylinder head 1 and they are tightened in threaded bores in the outer casing 13.

[0127] The teeth 4 protrude from each axial side of the cylinder head 1. Coils 5 surround a portion of the teeth 4.

[0128] In the present figure, the screws 17 are positioned in an internal portion and in an external portion of the radial element of the cylinder head 1.

[0129] Of course, the invention is not limited to the embodiments presented but includes all variants and combinations of variants of these embodiments, as long as they remain technically compatible with each other.

Claims

Demands

1. An axial flux electric machine stator comprising a yoke (1) and teeth (4) around which coils (5) are wound, the yoke (1) comprising an internal annular portion (2) about a longitudinal axis and radial elements (3) extending outward from said internal annular portion (2), the radial elements (3) being separated from each other by openings such that the yoke is radially open between said radial elements (3) over the entire thickness of the yoke (1), each tooth (4) being positioned between two of said radial elements (2), the teeth (4) being substantially regularly distributed around the circumference of the yoke (1), each tooth (4) comprising a groove (6) on each lateral surface opposite the radial elements (3) for the insertion of each opposing radial element (3) into the relevant groove, each groove (6) extending over the entire length of the tooth (4) concerned,characterized in that the width of each groove is substantially equal to the thickness of the cylinder head to allow the insertion of each radial element into the groove.

2. Stator according to claim 1, wherein said cylinder head (1) is axially rolled and / or said teeth (4) are rolled.

3. Stator according to any one of the preceding claims, wherein the section of said teeth (4), between the radial elements (3), in a plane orthogonal to the longitudinal axis is substantially trapezoidal or rectangular.

4. Stator according to any one of the preceding claims, wherein the stator comprises at least one locking means for locking the position of at least one tooth (4) in the cylinder head (1).

5. Stator according to any one of the preceding claims, wherein said radial elements (3) comprise an excess length relative to the teeth (4), this excess length preferably being suitable for enabling the radial position of the tooth (4) to be locked in the radial elements (3) by deformation or crimping.

6. Stator according to claim 5, wherein at least one locking means comprises an external locking device positioned between two radial elements (3) for externally locking the tooth (4) positioned between said two radial elements (3), said external locking device preferably being a key (10).

7. Stator according to claim 4, wherein the teeth (4) are longer than the radial elements (3) and at least one locking means comprises an outer ring (11) positioned around the teeth (4) for locking the teeth (4) in the cylinder head (1).

8. An axial flux electric machine comprising at least one rotor, at least one stator according to any one of claims 1 to 7, and an outer casing (13), the at least one rotor and at least one stator being placed in said outer casing (13), the electric machine comprising an assembly system for fixing the stator to the outer casing (13).

9. Electric machine according to claim 8, wherein the assembly system includes screws (17) for fixing the outer casing (13) to the stator, preferably some of said screws being positioned in said radial elements (3) of the cylinder head.

10. Electric machine according to claim 9, in which at least some of the screws (17) are positioned on at least an external portion of the radial elements (3) of the cylinder head and preferably on at least an internal portion of the radial elements (3) or on the internal annular part (2) of the cylinder head.

11. Electric machine according to any one of claims 9 or 10, wherein at least some of said screws (17) are positioned on a central part of the radial elements (3).

12. Electric machine according to any one of claims 9 to 11, wherein the assembly system comprises at least one screw in each radial element (3).

13. An electric machine according to any one of claims 9 to 12, wherein the cylinder head (1) includes through bores for the passage of screws and the outer casing (13) includes threads for screwing screws or the cylinder head (1) includes threads, preferably tapped and shouldered inserts, for screwing screws and the outer casing (13) includes openings for the passage of screws.

14. Electric machine according to any one of claims 9 to 13, wherein some of said screws are positioned in threads located in teeth (4) or in threaded inserts located in teeth (4).

15. A method of manufacturing the stator according to any one of claims 1 to 7, wherein the teeth (4) are positioned such that the grooves (6) of the lateral surfaces allow the insertion of the teeth (4) into the radial elements (3) around each tooth (4), then each tooth (4) is slid along the grooves (6) in the direction of the longitudinal axis for the insertion of the teeth (4) radially into the cylinder head (1).

16. Manufacturing method according to the preceding claim, wherein the position of each tooth (4) is locked in the cylinder head (1).

17. Method of manufacturing the electric machine according to any one of claims 8 to 14, wherein the teeth (4) are positioned so that the grooves (6) of the lateral surfaces allow the insertion of the teeth (4) into the radial elements (3) around each tooth (4), then each tooth (4) is slid along the grooves (6) in the direction of the longitudinal axis for the insertion of the teeth (4) radially into the yoke (1), then preferably the position of each tooth (4) is locked in the yoke (1), and the stator is fixed to the outer casing (13).

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