Stator for rotating electric machine and manufacturing method thereof

Abstract

The invention relates to a stator for an electric machine, comprising a stator yoke (14) having a circular surface (16) and a plurality of stator teeth standing on the circular surface (16), each of the stator teeth (18) comprising: on one hand, a stack (20) of plates (32) made of grain oriented steel having a first end (22) connected to the yoke (14) and an opposite second free end (24); and, on the other hand, each of the wire windings (25), the plates (32) extend in a direction perpendicular to the rounded surface (16), while the grains are oriented parallel to the vertical direction. Each of the plates (32) is cut into a T shape forming two outlets (38, 40) such that the second free end (24) has two opposing free wings (42, 44); and each of the plates (32) is treated to deorient the grains at their two outlets (38, 40).

Description

[0001] The invention relates to a stator for a rotating electrical machine for an electric or hybrid vehicle and to a method for producing such a stator.

[0002] Known rotating electrical machines (so-called "axial flux" machines) comprise a rotor mounted coaxially between two stators.

[0003] The rotor comprises a disk divided into identical angular sectors and having in each of the angular sectors one or more compartments to accommodate one or more permanent magnets.

[0004] As for the two stators between which the disk rotates, each of them comprises a stator yoke having a circular housing surface extending according to a plane and a plurality of stator teeth standing uniformly on the circular housing surface at equal distances from each other so as to be able to conform to the angular sectors of the rotor.

[0005] Each of the stator teeth comprises a stack of grain-oriented steel sheets having a first end connected to the yoke and an opposite second free end capable of facing the disk of the rotor.

[0006] Each of the stator teeth comprises a winding of wire around the stack so that a magnetic field can be induced through the stack.

[0007] Furthermore, each of the plates extends according to a direction perpendicular to the circular receiving surface, while the grains are oriented substantially parallel to the perpendicular direction.

[0008] Reference may be made to document WO 2020 / 078667, which describes the implementation of such a material in a rotating electrical machine.

[0009] Grain oriented steels are advantageously implemented in applications related to rotating machines because they provide better magnetic permeability, particularly in the direction of the orientation of the grains.

[0010] On the other hand, in contrast, these materials have a strong magnetoresistance or reluctance when the magnetic field extends in a direction transverse to the orientation of the grains.

[0011] Furthermore, the free ends of the stack of stator teeth are separated from the permanent magnets of the rotor by a functional air gap, since the rotor is driven in a rotary motion relative to the stator. And the performance of the rotating electrical machine is adjusted, in particular with a reduction of this air gap.

[0012] Furthermore, the problem that arises and that the present invention aims to solve is that of providing a stator capable of reducing this air gap without interfering with other elements that already allow the performance of the machine to be improved.

[0013] In order to solve this problem and in accordance with the first object, there is provided a stator for a rotating electric machine for a motor vehicle, the stator comprising a stator yoke having a circular receiving surface and a plurality of stator teeth standing uniformly on the circular surface at a distance from each other, each of the stator teeth comprising: on the one hand, a stack of plates made of grain-oriented steel having a first end connected to the yoke and an opposite second free end; and on the other hand, a wire winding around the stack, each of the plates extending in a direction perpendicular to the circular receiving surface, with the grains being oriented substantially parallel to the perpendicular direction. Each of the plates is cut into a T-shape forming two opposite lips, so that the second free end of the stack of plates has two opposite free flanges formed by the lips of the stack of plates; and each of the plates is treated to misorient the grains at their two opposite lips.

[0014] One characteristic of the invention therefore consists in the realization of plates each cut in T-shape to form a stack and, furthermore, in locally treating each of these plates at the level of each of two opposite lips so as to locally misorient the grains of the steel at the level of these lips.

[0015] In fact, the lips of the plates allow, when they are stacked, to form two opposite free flanges of a stack, these free flanges allowing the wire windings to be retained.

[0016] Nevertheless, the magnetic field lines extending substantially parallel to said direction perpendicular to the core of the stack diverge at the level of the free ends of the stack and tend to pass through the free flange according to an inclined direction with respect to the vertical.

[0017] However, the grains are oriented according to a direction substantially parallel to the vertical direction, including in the plate at the level of the free flanges in the absence of treatment, and like steel, which has poor magnetic permeability when the magnetic field lines intersect the direction of the grains, the stacked free flanges provide high reluctance and high iron losses if the orientation of the grains is not modified at this level.

[0018] And in particular, according to the invention, the grains are misoriented at the level of the lip of the plate in order to reduce this magnetic resistance.

[0019] Preferably, the grains are misoriented independently of each other in random directions. In this way, the steel is locally returned to "non-oriented grains" so that the magnetic resistance is reduced compared to the case where the grains are oriented substantially parallel to the perpendicular direction.

[0020] According to a non-limiting variant, the two opposite lips of each of the plates are heat treated to deorient the grains.By supplying thermal energy to the plates at the level of the lips, a metallurgical modification is induced which randomly redistributes the orientation of the grains.

[0021] Furthermore, this local energy supply is easily possible after the board has been cut.

[0022] According to another variant of the invention, the two opposite lips of each of the plates are folded, or folded and unfolded according to lines transverse to the lips, spaced from each other, to misorient the grains. This mechanical operation of bending and straightening the plate at the level of the lips according to transverse lines also allows to redistribute the orientation of the grains. This bending may consist in folding the portions of the lips to each other, for example less than 90°, and then unfolding them in an opposite way. Finally, the lips extend freely in a given plane of the steel plate.

[0023] Advantageously, the transverse bending lines of the lips are substantially parallel to each other.

[0024] According to a hybrid variant of the invention, both thermal and mechanical treatments are continued.

[0025] According to yet another variant, two opposite lips of each of the plates are etched by a laser beam according to longitudinal lines oriented towards the top end of the lips and spaced apart from each other, so as to misorient the grains. Such a technique allows to modify the metallurgical structure of the steel easily without contact. Moreover, it is easily integrated into common production systems for manufacturing plates and stacks.

[0026] It also allows to obtain a more random redistribution of the orientation of the grains in the material.

[0027] Furthermore, the longitudinal lines are preferably substantially parallel to each other. In this way, a locally random redistribution can be obtained.

[0028] According to a particularly advantageous but non-limiting mode of implementation of the invention, the stator yoke is made of grain-oriented steel, and the first end of the stack and the yoke portion located in the vicinity of the first end are treated to deorient the grains. The stator yoke can also be made of a superposition of grain-oriented steel plates. And, at the level of the junction between the stack and the superposition of the plates, the grains of the superimposed steel extend substantially perpendicularly to the grains of the steel of the stacked plates. Therefore, the magnetic field lines extending parallel to the vertical direction generated by the wire windings around the stack then extend perpendicularly to the oriented grains of the superimposed plates forming the yoke. Therefore, the yoke locally provides a considerable magnetic resistance at the level of the junction.

[0029] Furthermore, to overcome this, the first end of the stack and the yoke portion connected thereto are processed, for example by means of a laser beam, as will be explained in more detail below, in order to randomly redistribute the orientation of the grains at the level of the joining point.

[0030] In this way, the magnetic resistance at the level of the junction is reduced in the same way.

[0031] According to a particularly advantageous but non-limiting embodiment of the invention, the stator yoke has a containing circular surface of cylindrical general shape. In other words, the resulting rotating electrical machine is a so-called "radial flux" machine. More specifically, the rotor rotates inside the stator and the magnetic field induced by the stack of plates extends according to a radial direction.

[0032] According to another embodiment of the invention, the stator yoke has a circular receiving surface extending according to a plane. In other words, the resulting rotating electrical machine is a so-called "axial flux" machine.

[0033] According to another object, a method for producing a stator of a rotating electrical machine for a motor vehicle as described above is provided, according to which a stator yoke is provided having a circular receiving surface and a plurality of stator teeth standing uniformly on the circular surface at a certain distance from each other, each of the stator teeth comprising: on the one hand, a stack of plates made of grain-oriented steel, which have a first end connected to the yoke and an opposite second free end; and on the other hand, a wire winding around the stack, each of the plates extending in a direction perpendicular to the circular receiving surface, while the grains are oriented substantially parallel to the perpendicular direction; and, each of the plates is cut into a T-shape forming two opposite lips, each of the plates being treated so as to misorient the grains at the level of their two opposite lips, so that the second free end of the stack of plates has two opposite free flanges formed by the lips of the stack of plates.

[0034] Preferably, the grains are misoriented independently of each other in random directions.

[0035] Other characteristics and advantages of the invention will become apparent on reading the following description of particular embodiments of the invention given for the purpose of indication and not limitation with reference to the accompanying drawings, in which:

[0036] [ Figure 1 ] is a partial schematic diagram of a radial cross section of a stator according to the present invention according to an implementation mode;

[0037] [ Figure 2A ]yes[ Figure 1 ] a schematic perspective detailed view of;

[0038] [ Figure 2B ]yes[ Figure 2A ] a schematic front view of an element of an object;

[0039] [ Figure 3 ] is based on a variant of [ Figure 1 ] is a schematic axial cross-sectional view of the elements shown in FIG.

[0040] [ Figure 4 ] is based on another variant of [ Figure 1 ] is a schematic axial cross-sectional view of the elements shown in FIG.

[0041] [ Figure 5 ] is a schematic side view of a stator according to the present invention according to another implementation mode;

[0042] [ Figure 6 ]yes[ Figure 5 ] a schematic front detailed view according to arrow F of the stator shown in ]; and,

[0043] [ Figure 7 ] is according to arrow Z [ Figure 6 ] is a schematic perspective bottom view of the elements shown in ].

[0044] [ Figure 1 ] Partially shows a stator 10 inside which a rotor 12 is mounted so as to be able to form a rotating electrical machine. The latter is a so-called "radial flux" machine.

[0045] Thus, the stator 10 comprises a stator yoke 14 having a cylindrical inner surface with a circular base 16 and a plurality of stator teeth 18 standing uniformly on the cylindrical surface 16 at a distance from one another.

[0046] Thus, each of the stator teeth 18 comprises a stack 20 of plates made of grain-oriented steel, which will be described below, extending radially between a first anchoring end 22 anchored in the stator yoke 14 and an opposite second free end 24 extending opposite the rotor 12. In other words, each of the plates extends according to a direction perpendicular to the circular housing surface.

[0047] Furthermore, each of the stator teeth 18 comprises a wire winding 25 in order to be able to induce a magnetic field through the stack 20 and the magnetic field extends according to a radial direction R.

[0048] The rotor 12 has a cylindrical outer surface with a circular base 26 provided with a plurality of permanent magnets 28 mounted at a distance from each other and evenly spaced.

[0049] And the space extending between the permanent magnet 28 and the second free end 24 of the stack 20 of teeth 18 forms an air gap 30 .

[0050] Now refer to [ Figure 2A ]、[ Figure 2B ]、[ Figure 3 ]and[ Figure 4 ] to describe in detail the stack 20 of grain-oriented steel sheets.

[0051] The stack 20 is therefore made of steel sheets 32 cut into T-shapes in a steel strip, usually less than 2 mm thick (so-called "electrical steel"). These steel sheets 32 are cut, for example, by punching or stamping, in order to obtain them at favourable costs.

[0052] Flat metallurgical products of this type are specially designed to obtain specific magnetic properties and in particular high magnetic permeability.

[0053] To this end, it is known to ensure that the grains of the steel are oriented in the same direction, due to metallurgical transformations, specifically to obtain these specific properties.

[0054] Therefore, it is cut into [ Figure 2B The T-shaped steel plate 32 shown in FIG. 1 has a stem 35, and a root 34 and a head 36 opposite to each other. And it is cut so that the crystal structure or grains are aligned parallel to each other from the root 34 to the head 36 according to a given direction D.

[0055] Furthermore, by its T-shaped structure, the steel plate 32 has two opposite lips 38, 40 extending transversely and terminating in two apexes 39, 41 respectively. The grains are thus oriented according to a direction D, including the level of the lips 38, 40, and they therefore extend in a transverse direction relative to the lips 38, 40.

[0056] It is an object of the present invention to misorient the crystal structure of the lips 38, 40 (as will be explained below).

[0057] therefore,[ Figure 2B ] are stacked and fastened to each other to form the steel plates 32 of the type shown in [ Figure 2A ] is partially shown in cross-section in the stack 20. The steel plates 32 are coated with varnish to electrically insulate them from each other. This known lamination technology allows the eddy currents through the stack 20 to be reduced.

[0058] Thus, the lips 38 , 40 of the stacked steel sheets 32 form two opposing free flanges 42 , 44 .

[0059] [ Figure 3 ] shows the stack 20 anchored in the yoke 14. Furthermore, a wire winding 25 around the stack 20 between the yoke 14 and two opposing free flanges 42, 44 is shown.

[0060] Furthermore, it can be observed that the yoke 14 is also made of stacked grain-oriented laminations, and the grains are oriented according to a direction L perpendicular to the direction D according to which the grains of the steel sheets themselves are oriented.

[0061] Furthermore, when the wire of the winding 25 is energized, it then induces a magnetic field at the core of the winding 20 oriented according to the direction D of the oriented grains.

[0062] On the other hand, outside the winding 25, at the level of both the first anchoring end 22 and the opposite second free end 24, the magnetic field tends to diverge and the field lines, two of which 46, 48 have been partially shown for illustration, bend outwards and away from each other. In other words, the magnetic field, in particular in the two opposite free flanges 42, 44, is inclined with respect to the orientation of the grains. The magnetic permeability is therefore reduced and the object of the present invention is to overcome this.

[0063] For this reason, and according to [ Figure 3 ], two opposite lips 38, 40 of each of the plates 32 are etched by means of a laser beam according to first longitudinal etching lines 50, 52 oriented towards the top ends 39, 41 of the lips 38, 40. The first etching lines 50, 52 are spaced apart from each other and are preferably parallel to each other so as to be able to uniformly misorient the grains in the lips 38, 40.

[0064] For example, the first etch lines 50 , 52 are each inclined with respect to the original direction D of the crystal structure by an angle comprised between 60° and 80°.

[0065] This local treatment at the level of the lips 38 , 40 of the plate 32 does not allow reorienting the grains according to another identical direction, but ensures that their orientation is randomly distributed. Therefore, fewer grains or crystal structures are statistically oriented in an oblique manner relative to the magnetic field lines 46 , 48 .

[0066] Therefore, the magnetic permeability decreases less than in the case where the grains remain oriented according to the same original direction D. Therefore, the performance of the rotating electrical machine is improved.

[0067] Such a treatment operation can be performed on each of the steel sheets 32 and each of their lips 38 , 40 , before stacking thereof, by means of a laser.

[0068] Furthermore, after assembly of the steel sheets 32 and thus of the stack 20 formed on the yoke 14 , the first end 22 of the stack 20 and the portion of the yoke in which the first end 22 is anchored are also treated to misorient the grains.

[0069] To this end, second etching lines 54, 56 are formed by means of a laser beam across the stack 20 and the first end 22 of the yoke 14. These second etching lines 54, 56 are inclined substantially 45° relative to the direction D of the orientation of the grains of the plate 32 and the direction L of the grains of the stacked laminations of the yoke, respectively.

[0070] In this way, when the magnetic field is tilted relative to the orientation of the grains of the yoke 14 at the first end 22 of the stack 20 , the grains are randomly and locally misoriented at the level of the junction between the stack 20 and the yoke 14 so as to avoid reducing the magnetic permeability.

[0071] The laser beam implementation is advantageous because it enables remote localized processing without contact with the material. In addition, it can be easily industrialized on existing production lines.

[0072] According to another variant, thermal energy is supplied by any means to the lips 38 , 40 of the steel plate 32 in order to be able to deorient the crystal structure and thus increase the magnetic permeability.

[0073] according to[ Figure 4 ], a further variation is shown in which a mechanical action is applied to the lips 38', 40' of the steel plate 32'. Figure 4 ] and the reference numerals in the annotations are the same as those in [ Figure 3 ] are the same as the reference numerals annotated in the , and they are assigned an apostrophe symbol: «'", allowing this variant to be distinguished from the previous ones.

[0074] therefore,[ Figure 4 ] The stack 20' is partially shown with its two opposing free flanges 42', 44' formed by the lips 38', 40' of the steel plate 32'.

[0075] According to this third variant, the two opposite lips 38 ′, 40 ′ of each of the sheets 32 ′ of the stack 20 ′ are folded and unfolded according to transverse folding lines 58 , 60 respectively spaced apart from each other about the lips 38 ′, 40 ′ also to misorient the grains.

[0076] For each lip 38', 40', the transverse fold lines 58, 60 are parallel to each other, respectively. Furthermore, the lip 38', 40' of each of the steel sheets is folded uniformly from the base to the top end 39', 41'.

[0077] Advantageously, the transverse folding lines 58, 60 extend in a direction inclined at an angle comprised between 20° and 45° relative to the orientation direction D' of the crystal structure of the steel sheet. In this way, a random redistribution of the orientation of the crystal structure in the lips 38', 40' is obtained.

[0078] Furthermore, according to a variant, both a heat treatment of the lip and a bending of the lip are performed in order to obtain a better random distribution of the orientation of the grains.

[0079] According to [ Figure 5], a stator 10" comprises a stator yoke 14" having a first circular surface 16" extending according to a plane P and a plurality of stator teeth 18" standing uniformly on the circular surface 16" at a certain distance from each other.

[0080] In addition, each of the stator teeth 18" includes a substantially trapezoidal stack 20" of grain-oriented steel sheets (which will be described in more detail below) that extends radially between a first anchor end 22" anchored in the stator yoke 14" and an opposing second free end 24" that extends opposite the rotor 12".

[0081] Each of the stator teeth 18 ″ comprises a wire winding (not shown for reasons of clarity of the drawing) in order to be able to induce a magnetic field through the stack 20 ″ and the magnetic field extends according to the axial direction A.

[0082] The rotor 12" has a second circular surface 26, which is provided with a plurality of permanent magnets 28", which are adjusted to be spaced a certain distance from each other and evenly spaced.

[0083] And the space extending between the permanent magnet 28" and the second free end 24" of the stack 20" of teeth 18" forms an air gap 30".

[0084] [ Figure 6 ] shows a stator 10" and its stator yoke 14", on which four trapezoidal stator teeth 18" are mounted, which is for illustration purposes only.

[0085] These trapezoidal stator teeth 18 ″ are observed from their second free end 24 ″ and their two opposite free flanges 42 ″, 44 ″ can be distinguished, including the lips 38 ″, 40 ″ of the steel plate 32 ″ forming them, treated so as to misorient their crystal structure.

[0086] Furthermore, it can be observed that the two opposing free flanges 42 ″, 44 ″ diverge from each other outwardly from the center identified by the axial direction A. In other words, the width of the steel plates 32 ″ forming the stack 20 ″ decreases progressively from the center outwardly, although the plates 32 ″ have the same general shape.

[0087] therefore,[ Figure 7 ] shows a single stack 20" with a trapezoidal cross-section. It is made of a series of grain-oriented steel plates 32" between a narrow first 62 and a wide last 64. On the other hand, the opposite lips 38", 40" of the intermediate plates between the first 62 and the last 64 extend laterally with the same amplitude and have the same shape so as to form two divergent opposite free flanges 42", 44".

[0088] Furthermore, the opposing lips 38", 40" of all the plates have been subjected to a heat treatment in order to deorient the crystal structure or grains; the crystal structure of the remainder of the plate remains aligned from the first anchoring end 22" to the second free end 24".

[0089] Thus, like in the first mode of realisation, the magnetic permeability of the two divergent opposite free flanges 42 ″, 44 ″ is increased due to the random reorientation of the crystal structure or grains.

[0090] In this way, the performance of the rotating electrical machine is thereby improved.

[0091] The invention also relates to a method for producing a stator 10 for a rotating electrical machine for a motor vehicle.

[0092] According to the method, a stator yoke 14 is provided, which has a circular receiving surface 16 and a plurality of stator teeth 18 standing uniformly on the circular surface 16 at a distance from each other.

[0093] To manufacture these stator teeth 18, plates 32 made of grain-oriented steel are provided and each of the plates 32 is cut into a T-shape forming two opposite lips 38, 40. Each of the plates 32 is then treated to misorient the grain at the level of their two opposite lips 38, 40.

[0094] The treatment can be performed according to the aforementioned treatment mode. Advantageously, the grains are misoriented independently of each other in random directions. In other words, the grains are no longer oriented according to a preferred direction and their orientation is randomly distributed in the lips 38, 40.

[0095] Thus, a stack of steel plates is formed having a first end 22 opposite a second free end 24, thereby forming two opposite flanges 42, 44 formed by the lips of the stacked plates.

[0096] Furthermore, for each of the teeth, the wire 25 is wound around the stack and each of the plates 32 then extends according to a direction perpendicular to the circular housing surface 16 , while the grains of the plates are oriented substantially parallel to said perpendicular direction, except at the level of their two opposite lips 38 , 40 .

Claims

1. A stator (10) for a rotating electric machine of a motor vehicle, the stator (10) comprising a stator yoke (14), the stator yoke (14) having a circular receiving surface (16) and a plurality of stator teeth (18) standing uniformly on the circular surface (16) at a certain distance from each other, each of the stator teeth (18) comprising: In one aspect, a stack (20) of plates (32) made of grain-oriented steel, the stack (20) having a first end (22) connected to the yoke (14) and an opposing second free end (24); and on the other hand, around said stacked wire windings (25), each of said plates (32) extends in a direction perpendicular to said circular receiving surface (16), and said grains are oriented substantially parallel to said perpendicular direction; characterised in that each of said plates (32) is cut into a T-shape forming two opposite lips (38, 40), so that said second free end (24) of said stack (20) of plates has two opposite free flanges (42, 44) formed by said lips of said plates of said stack; as well as Each of the plates (32) is treated so as to misorient the grains at the level of two opposing lips (38, 40) of the plate (32).

2. The stator according to claim 1, characterized in that: The grains are misoriented independently of each other in random directions.

3. The stator according to claim 1 or 2, characterized in that: The two opposing lips (38, 40) of each of the plates (32) are heat treated to deorient the grains.

4. The stator according to any one of claims 1 to 3, characterized in that: The two opposing lips (38', 40') of each of the plates are folded, or folded and unfolded according to lines (58, 60) spaced apart from each other and transverse to the lips, to misorient the grains.

5. The stator according to claim 4, characterized in that: The transverse lines (58, 60) are substantially parallel to each other.

6. The stator according to any one of claims 1 to 5, characterized in that: The two opposing lips (38, 40) of each of the plates (32) are etched by a laser beam according to longitudinal lines (50, 52) oriented towards the top ends (39, 41) of the lips and spaced apart from each other, to misorient the grains.

7. The stator according to claim 6, characterized in that The longitudinal lines (50, 52) are substantially parallel to each other.

8. The stator according to any one of claims 1 to 7, characterized in that: The stator yoke (14) is made of grain-oriented steel, and the first end (22) of the stack and a portion of the yoke located near the first end are processed to misorient the grains.

9. The stator according to any one of claims 1 to 8, characterized in that: The stator yoke (14) has a receiving circular surface (16) of cylindrical overall shape.

10. The stator according to any one of claims 1 to 8, characterized in that: The stator yoke (14") has a circular receiving surface (16) extending in a plane.

11. A method for producing a stator (10) for a rotating electrical machine for a motor vehicle according to any one of claims 1 to 10, characterized in that A stator yoke (14) is provided, the stator yoke (14) having a circular receiving surface (16) and a plurality of stator teeth (18) standing uniformly on the circular surface (16) at a distance from each other, each of the stator teeth (18) comprising: on the one hand, a stack (20) of plates (32) made of grain-oriented steel, the stack (20) having a first end (22) connected to the yoke (14) and an opposite second free end (24); and on the other hand, a wire winding (25) surrounding the stack, each of the plates (32) extending according to a direction perpendicular to the circular receiving surface (16), the grains being oriented substantially parallel to the perpendicular direction; and Each of the plates (32) is cut into a T-shape forming two opposing lips (38, 40), and each of the plates (32) is treated to misorient the grains at the level of the two opposing lips (38, 40) of the plates (32), so that the second free end (24) of the stack (20) of plates has two opposing free flanges (42, 44) formed by the lips of the plates of the stack.

12. The production method according to claim 11, characterized in that: The grains are misoriented independently of each other in random directions.

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