CN108141085B

CN108141085B - Stator of rotating electric machine with improved magnetic properties

Info

Publication number: CN108141085B
Application number: CN201680052669.2A
Authority: CN
Inventors: B.瓦尔姆; M.拉库图沃
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2015-09-11
Filing date: 2016-09-07
Publication date: 2021-07-27
Anticipated expiration: 2036-09-07
Also published as: WO2017042489A1; EP3347974A1; CN108141085A; FR3041188A1

Abstract

The invention mainly relates to a stator (9) of a rotating electrical machine, in particular for an electric compressor of a motor vehicle, the stator (9) comprising: -a yoke (28); -a plurality of teeth (27) angularly distributed on the inner periphery of the yoke (28); a plurality of grooves (29), each groove being defined by two adjacent teeth (27); -a winding (17) comprising a plurality of coils (50), each coil (50) being formed by a wire (51) wound around a tooth, characterized in that the ratio between the diameter (expressed in millimeters) of the electrically conductive part of the non-enamelled wire (51) and the number of turns of each coil (50) is in the range of 5% to 25%, in particular in the range of 10% to 20%.

Description

Stator of rotating electric machine with improved magnetic properties

Technical Field

The present invention relates to a stator of a rotating electric machine having improved magnetic properties. The invention has particular, but not exclusive, application to electric compressors for motor vehicles.

Background

In a known manner, a rotary electric machine comprises a stator and a rotor integral with a shaft. The rotor may be integral with the drive shaft and/or the driven shaft and may be of a rotary electrical machine in the form of an alternator, an electric motor or an inverter which may operate in both modes.

The rotor comprises a body formed by a stack of metal sheets held in a pack by means of a suitable fixing system. The rotor comprises poles formed by permanent magnets housed in cavities provided in the rotor body.

Further, the stator is fitted in a housing configured to rotate the shaft, for example, by a bearing. The stator comprises a body consisting of a stack of thin metal plates forming a yoke in the form of a ring, the inner surface of which is provided with an inwardly open recess to receive a phase winding.

In a distributed-ripple type of winding, the winding is obtained, for example, by a continuous wire covered with an enamel coating or by conductive elements in the form of pins connected to one another by welding. Alternatively, in a "concentric" type winding, also called "concentrated" type, the phase winding is constituted by a coil which closes on itself, wound around the teeth of the stator. These windings are multi-phase windings connected in star or delta form, the outputs of which are connected to the control electronics.

Motors coupled to the shaft of an electric compressor are known. The electric compressor makes it possible to at least partially compensate for the power losses of heat engines with reduced cubic volume used on many motor vehicles, in order to reduce their consumption and the discharge of pollutant particles (so-called miniaturisation principle). For this purpose, the electric compressor comprises a turbine arranged on the intake duct upstream or downstream of the heat engine, so as to make it possible to compress the air in order to optimize the filling of the cylinders of the heat engine. The electric machine is started to drive the turbine in order to minimize the torque response time, in particular during transient phases of acceleration or in automatic restart phases of the heat engine after a standby mode (stop and start function).

However, it is difficult to provide the different elements, in particular the body of the stator and the corresponding winding wires, with optimal dimensions, given the small dimensions of the electrical machine and the required high performance level.

Disclosure of Invention

The object of the present invention is in particular to eliminate this difficulty by proposing a stator of a rotary electric machine, in particular an electric compressor designed for motor vehicles, comprising a main body having:

-a yoke;

-a plurality of teeth angularly distributed on the inner periphery of the yoke;

-a plurality of notches, each notch being defined by two adjacent teeth; and

a winding comprising a plurality of coils, each coil being formed by a wire wound on a tooth,

characterized in that the ratio between the diameter of the electrically conductive part of the non-enamelled wire (expressed in millimetres) and the number of turns of each coil is comprised in the range 5% to 25%, and in particular in the range 10% to 20%.

According to one embodiment, the teeth are integral with a yoke forming a continuous outer annular portion of the body and extending between the base of the recess and the outer periphery of the stator.

In other words, the yoke forms a ring having continuity of material around its circumference and formed radially over at least a portion of its thickness.

The invention thus makes it possible to optimize the magnetic properties of the electrical machine, while facilitating the insertion of the winding pins into the recesses for forming the coils around the teeth of the stator in the case of a concentric type of winding.

According to one embodiment, the wire comprises a conductive portion having a diameter in the range of 1 to 2 mm.

According to one embodiment, each coil is formed by a plurality of turns comprised in the range of 5 to 20.

According to one embodiment, each coil is formed of nine turns. For low voltages, the choice of the number of wires and the coil connections is very limited, since it is not possible to achieve the required performance level within the turns, in particular in terms of acceleration of the motor. In the present invention, the structure with 9 turns in the form of a triangle makes it possible to satisfy the technical requirements of the compressor, while the corresponding coupling in the form of a star will not work, since it is necessary to form a wire with a 9/square root (3) equal to 5.2 and a wire diameter equal to 1.5 square root (3)) equal to 1.97 mm, which corresponds to a wire that is difficult to wind, and cannot satisfy the filling level. In addition, if more turns are made, the fill level will increase, but the winding channels will be lost, making it no longer possible to use a non-segmented stator.

As a variant, each coil is formed by 18 turns and the diameter of the copper cross section of the wire is equal to 1.06 mm.

According to one embodiment, the stator comprises 6 coils.

According to one embodiment, said winding is of the three-phase type, each phase being formed in particular by two coils of opposite diameter.

According to one embodiment, the coils are electrically connected in pairs in parallel.

According to one embodiment, the coils are coupled in a triangular fashion. This type of coupling makes it possible to minimize the number of connections to be made.

According to one embodiment, the number of turns on the yoke side is greater than the number of turns on the axis side of the stator around each tooth.

According to one embodiment, in the recess, a part of the coil filling the recess is formed by three turns. As a variant, it is possible to form only two layers of turns.

According to one embodiment, each notch has an area extending along the entire length of the stator.

According to one embodiment, the ratio between the diameter of the conductive part of the wire and the inner diameter of the stator is comprised in the range of 3 to 10%, in particular in the range of 5 to 7%, for example in the range of 5.2 to 6.3%. This type of characteristic makes it possible to obtain the best compromise between the inertia of the machine and the filling level of the notches of the stator.

According to one embodiment, by defining a plurality of notches between two adjacent teeth, the ratio between the smaller notch opening measured between two adjacent roots and the outer diameter of the stator is comprised in the range of 5% to 25%, in particular in the range of 5% to 15%. This thus makes it possible to optimize the magnetic properties of the machine, while facilitating the insertion of the winding pins into the recesses in order to form the coils around the teeth of the stator.

According to one embodiment, the stator body is made up of a plurality of metal sheets axially superposed on one another.

According to one embodiment, at least one sheet comprises on its surface studs designed to mate with hollows in an adjacent sheet, and the ratio between the larger diameter of the studs and the outer diameter of the stator is comprised in the range 5% to 15%, in particular 2% to 10%. This type of ratio is such as not to interrupt the magnetic flux to the stator, while ensuring that the set of metal plates of this type of stator has a good mechanical resistance and is reduced in size.

According to one embodiment, the stator body comprises at least one through fixing hole opening on each axial end face side of the stator body, and the ratio between the distance between the axis of the stator and the axis of the fixing hole and half of the outer diameter of the stator is comprised in the range 80% to 97%, in particular in the range 85% to 95%. This thus makes it possible to obtain an optimal compromise between good mechanical resistance and the magnetic properties of the machine fitted with the stator.

The invention also relates to a stator of a rotary electric machine, particularly designed for an electric compressor of a motor vehicle, said stator comprising a body having:

-a yoke;

-a plurality of teeth angularly distributed on the inner periphery of the yoke;

-a plurality of notches, each notch being defined by two adjacent teeth; and

characterized in that it comprises six coils, each comprising a number of turns equal to 9 or 18, and in that said coils are coupled in the form of a triangle.

According to one embodiment, the electric machine comprises a rotor provided with embedded permanent magnets, for example four of which.

According to one embodiment, the rotor body has an outer periphery delimited by a cylindrical surface having an outer diameter comprised in the range 20mm to 50mm, in particular comprised in the range 24mm to 34mm, and preferably about 28 mm.

According to one embodiment, the motor has a response time comprised in the range 100ms to 600ms, in particular comprised in the range 200ms to 400ms, for example about 250ms, in order to be from 0 or 5,000 to 70,000 rpm.

According to one embodiment, a positioning element is interposed between the rotor body and each permanent magnet.

The foregoing features may be applied to the present invention alone or in combination.

Finally, the subject of the invention is a rotary electric machine comprising a stator as described previously and a rotor provided with embedded permanent magnets.

Drawings

The invention will be better understood upon reading the following description and examining the appended drawings. These figures are provided purely by way of illustration of the invention and do not in any way limit it.

Fig. 1 is a cross-sectional view of an electric compressor including a rotating electric machine according to the present invention;

fig. 2 shows a perspective view of a stator of a rotating electric machine according to the present invention;

fig. 3 is a top view of an individual stator of the rotating electric machine according to the present invention;

figure 4 is a top view of a stator according to the invention provided with turns for forming part of a coil occupying a half-notch;

figure 5 shows a partial cross-sectional view of the configuration of the teeth of a stator according to the invention;

fig. 6 is a cross-sectional view of a wire for forming a coil belonging to a stator winding according to the present invention;

fig. 7 shows the development of the percentage of the filling level (O1) and the inverse of the inertia (O2) of the motor according to the ratio between the diameter of the conductive portion of the winding wire and the inner diameter of the stator;

fig. 8 is a cross-sectional view showing nesting between metal sheets of a stator in the case of assembly by buttons;

fig. 9 shows a perspective view of a rotor of a rotating electric machine according to the present invention;

fig. 10 is a cross-sectional view of a rotor of a rotating electric machine according to the present invention;

fig. 11 shows the development of the percentage of the filling level (O7) and the power of the motor (O8) proportional to the reciprocal of the number of turns, according to the ratio between the diameter of the conductive part of the winding wire and the number of turns of each coil.

Identical, similar or analogous elements retain the same reference numerals from one figure to the next.

Detailed Description

Fig. 1 shows an electric compressor 1 comprising a turbine 2 provided with fins 3, which via an input 4 can take in non-compressed air obtained from an air source (not shown) and via an output 5 discharge compressed air after entering a volute referenced 6. The output 5 may be connected to an intake distributor (not shown) located upstream of the heat engine in order to optimize the filling of the cylinders of the heat engine. In this case, the intake of air takes place in the axial direction, i.e. along the axis X1 of the turbine 2, and the discharge takes place in a radial direction perpendicular to the axis X1 of the turbine 2. As a variant, the suction is radial, while the discharge is axial. Alternatively, the suction and discharge are performed in the same direction (axial or radial) with respect to the turbine axis.

For this purpose, the turbine 2 is driven by an electric motor 7 fitted inside a casing 8. The motor 7 comprises a stator 9, which stator 9 may be multi-phase, surrounding a rotor 10 in the presence of an air gap 11. The stator 9 is fitted in a housing 8, the housing 8 being configured to rotate a shaft 12 via a bearing 13. The shaft 12 is rotationally connected to the turbine 2 and the rotor 10. The stator 9 is preferably mounted in the housing 8 by straps.

In order to minimize the inertia of the turbine 2 during the acceleration requested by the driver, the electric machine 7 has a short response time comprised in the range 100ms to 600ms, in particular comprised in the range 200ms to 400ms, for example about 250ms, in order to go from 0 or 5,000 to 70,000 rpm. Preferably, the voltage used is 12V. Preferably, the motor 7 can provide current spikes, i.e. current spikes lasting less than 3 seconds, comprised in the range of 150A to 300A, in particular in the range of 180A to 250A.

As a variant, the electric machine 7 can operate in alternator mode, or it can be a reversible type of electric machine.

As shown in fig. 2, the stator 9 includes a main body 16 and windings 17. The stator body 16 has an annular cylindrical shape with an axis X and is composed of axially stacked flat metal plates. More specifically, the stator body 16 is radially delimited by an inner cylindrical surface 21 and an outer cylindrical surface 22. The body 16 is also axially bounded by end faces 23 and 24.

The body 16 comprises teeth 27 which are regularly angularly distributed around the inner circumference of the yoke 28. These teeth 27 define recesses 29 such that each recess 29 is defined by two successive teeth 27. The yoke 28 thus corresponds to a solid outer ring portion of the body 16 which extends between the base of the recess 29 and the outer periphery of the stator 9.

The recess 29 opens axially to the axial end faces 23, 24 of the body 16. The recess 29 also opens radially in the inner cylindrical surface of the body 16.

As is clearly visible in fig. 3 and 4, the teeth 27 of the stator 9 preferably have parallel edges, so that the mutually opposite inner surfaces of the recesses 29 are inclined with respect to one another. The notches 29 are regularly angularly distributed about the axis X.

Preferably, the stator 9 is provided with a tooth root 34 on the side of the free end of the teeth 27 (see fig. 5). Each root 34 extends circumferentially on either side of the corresponding tooth 27.

The stator 9 is a non-segmented component made of laminated metal sheets made of magnetic material. Further, the teeth 27 are integral with the yoke 28. As a variant, however, the stator 9 may be segmented, i.e. it is formed by a plurality of angular segments assembled to one another. In this case, the yoke 28 has a material continuity radially over its entire thickness according to its circumference. As a variant, the teeth 27 can be added with respect to the yoke 28 and fixed on the inner periphery of the yoke by a system of the mortise and tenon type.

Advantageously, the ratio between the radial thickness L1 of the air gap 11 and the outer diameter L2 of the stator 9 is comprised in the range 0.1% to 2%, in particular in the range 0.2% to 1%. This ratio makes it possible to maximize the torque produced by this type of machine with a small-sized stator 9. The air gap 11 is selected according to the thickness L13 of the permanent magnets 62 of the rotor 10 (see fig. 10). Therefore, the second ratio between the thickness of the air gap 11 and the thickness of the magnet L13 is contained in the range of 0.9 to 0.15.

Furthermore, in order to optimize the passage of the magnetic flux in the stator 9 while having an effective mechanical resistance, the ratio between the thickness L3 of the yoke 28 measured radially and the inner diameter L4 of the stator 9 measured between two diametrically opposite teeth 28 is in the range 9% to 20%, for example 10% to 20%, in particular 12% to 15%, and preferably about 9% or 13%.

In addition, the ratio of the inner diameter L4 to the outer diameter L2 of the stator 9 is in the range of 40% to 60%, preferably about 51.5%. This makes it possible to optimize the space of the recess 29 that can be wound and the inertia of the rotor 10.

As can be seen in fig. 2, the stator body 16 is preferably formed by an axial stack of metal sheets 37, each extending in a radial plane perpendicular to the axis X. The stator body 16 is made of a ferromagnetic material. The metal plate 37 is held by a fixing means 41 to form an assembly that can be handled and transported. For this purpose, a plurality of fixing holes 40 are provided in the stator body 16 so as to each allow the passage of a means 41 for fixing the metal plate of the stator body 16. In this case, the fixing holes 40 are preferably through holes, i.e. they open axially onto each

axial end

23, 24 of the stator body 16, so that it is possible to pass, inside each fixing hole 40, a stem 41, which stem 41 is provided or not with a head 42 at its end, and its other end or ends or will be deformed, for example by an upsetting process, to ensure the axial retention of the set of plates.

Advantageously, the ratio between the distance L5 between the axis X of the stator 9 and the axis Z of the fixing hole 40 (see fig. 3) and half the outer diameter L2 of the stator 9 is in the range 80% to 97%, in particular in the range 85% to 95%. This makes it possible to obtain an optimal compromise between good mechanical resistance and the magnetic properties of the electric machine 7 in which the stator 9 is fitted. The axis Z of each fixing hole 40 is contained on the symmetry plane P of the corresponding tooth 27. The axis Z of the fixing hole 40 also preferably lies on a single circle C (see fig. 3).

The stator 9 comprises a certain number of fixing holes 40, these fixing holes 40 being comprised between three and the number of teeth 27, in this case six. Furthermore, the fastening holes 40 pass through the yoke 28, in particular only through the yoke 28, i.e. do not penetrate into the respective tooth 27. The ratio between the maximum diameter L6 of each fixing hole 40 and the outer diameter L2 of the stator 9 is in the range of 2% to 10%.

As a variant, stem 41 has no head 42, then both ends are deformed by an upsetting process. As a variant, the fixing holes 40 may have a square, rectangular or any other form of cross section suitable for the passage of the fixing means 41.

Alternatively, the metal plates may be held together by snap-fitting, adhesive or laser welding.

In the embodiment of fig. 8, each sheet 37 comprises on its surface studs 45, the studs 45 being designed to cooperate with hollows 46 in the adjacent sheets. The last sheet was pierced. The ratio between the maximum diameter L7 of the stud 45 and the outer diameter L2 of the stator 9 is comprised in the range 5% to 15%, in particular 2% to 10%. This type of ratio allows a plate pack of this type of stator 9 to have good mechanical resistance and to have reduced dimensions, while limiting the magnetic interference associated with the presence of the studs 45. In addition, this type of ratio makes it possible to facilitate the production of the sheets 37, while ensuring the precise positioning of one sheet 37 with respect to the other.

Each sheet 37 of metal comprises a face which is in direct contact with a single face of the other sheet 37. Preferably, the maximum diameter of each stud 45 is comprised in the range 0.5mm to 5mm, and preferably 3 mm. The number of studs 45 per plate 37 is comprised between two and the number of teeth of the stator 9. On the metal sheet 37, the stud 45 is arranged on a first face, and the hollow 46 is arranged on a second face opposite to the first face. In addition, each hollow 46 is axially aligned with a respective stud 45, according to the axis marked a1 in fig. 8. According to one embodiment, a stud 45 on the sheet is located in the middle of each tooth 27 and on the same diameter, for example about 47 mm. As a variant, the yoke 28 is solid and has a continuity of material according to its circumference and radially over its entire thickness.

As can be seen in fig. 2 and 4, to form the windings 17 of the stator 9, a plurality of phase windings (six in this case) are formed by the coils 50 wound on the teeth 27 of the stator 9. Each coil 50 is formed from a wire 51. The wire 51 (shown in cross-section in fig. 6) is provided with a conductive portion 52, the conductive portion 52 being formed, for example, of copper or aluminum, covered with an insulating layer 53, for example, lacquered.

Fig. 7 shows the development of the filling level (curve C1) and the inverse of the inertia of the motor (curve C2) according to the ratio between the diameter L8 of the conductive part of the wire 51 and the inner diameter L4 of the stator 9. This ratio is comprised in the range of 5 to 10%, in particular in the range of 5 to 7%, for example in the range of 5.2 to 6.3%. Preferably, this ratio is substantially equal to 5.4%, which corresponds to the intersection between the two curves C1 and C2.

The diameter L8 of the conductive part of the wire 51 is about 1.5mm in the case when the stator comprises 9 turns. The diameter of the wire is 1.602 mm by the coating layer. As a variant, the diameter L8 of the conductive portion of the lead 51 is about 1.06mm in the case when the stator comprises 18 turns. The choice of the diameter of the wire 51 is an important choice for ensuring the feasibility of a concentric type of winding. Furthermore, the choice of the inner diameter L4 of the stator is guided by the minimization of inertia (or 1/inertia maximization which is optimal when the ratio is close to 1) and the feasibility of the windings. In fact, the greater the increase in the internal diameter of the stator 9, the greater the increase in the external diameter of the rotor, and the greater the increase in inertia.

According to the calculation method, the stator may thus have a notch filling level of about:

-50% when calculated according to a first calculation method, wherein the ratio between the cumulative total surface area of copper in said recess (cross section) and the total surface area of the recess (minus the space occupied by the insulation and starting from the principle that the section of the wire is square) when the enamelling is assimilated to copper is determined; or

73% when calculated according to a second calculation method corresponding to the first method, except for the surface from which the passing cross section of the winding needle is subtracted from the surface area of the notch cross section. The second method provides the result of a so-called "useful" fill level.

The following table shows the fill levels of the two methods described above:

-a first method:

-a second method:

in addition, preferably, the ratio between the smaller notch opening L9 measured between two adjacent tooth roots 34 (see fig. 4) and the outer diameter L2 of the stator 9 is comprised in the range of 5% to 25%, in particular in the range of 5% to 15%. This therefore facilitates the insertion of the winding pins into the recesses 29.

Around each tooth 27, the number of turns 54 on the yoke 28 side is greater than or equal to the number of turns 54 on the axis X side of the stator 9. It will be remembered here that the turns 54 correspond to a revolution to the wire around the teeth 27. In a given recess 29, the part of the coil 50 that fills the recess 29 is formed, for example, by three turns 54. In each layer, the turns 54 are positioned side-by-side. Each coil 50 is preferably formed of nine turns 54.

In this case, the winding 17 is of the three-phase type, each phase being formed in particular by two diametrically opposite coils 50. The diametrically opposed coils 50 are electrically connected in parallel in pairs. The phases each formed by two coils 50 connected in parallel are preferably connected in the form of a triangle. This type of winding makes it possible to minimize the number of connections to be made. Furthermore, it should be noted that for low voltages, the choice of the number of wires and the coupling of the coil 50 is very limited, in that within one turn 54 it may become impossible to achieve the required level of performance, in particular in terms of motor acceleration.

In the present invention, the configuration of nine turns 54 with triangular form makes it possible to achieve the technical requirements of the compressor, while the corresponding coupling in the form of a star will not work, since it is necessary to form 9/square root (3) ═ 5.2 turns 54, the wire diameter is equal to 1.5 × square root (3)) -1.97 mm, which corresponds to a wire that is difficult to wind, and the filling level cannot be met. In addition, if more turns 54 are formed, the fill level will increase, but the winding channels will be lost, making it no longer possible to use the non-segmented stator 9.

As a variant, the coupling can be made in the form of a triangle or in the form of a star of coils connected in series, the coils being connected in series or in parallel.

In order to optimize the magnetic properties of a winding 17 of this type formed in situ on the stator 9, the ratio between the diameter L8 (expressed in mm) of the conductive portion 52 of the wire 51 and the number of turns 54 of each coil 50 is chosen to be comprised in the range 5% to 25%, in particular 10% to 20%. Thus, for a diameter L8 of about 1.5mm and 9 turns per coil, the ratio is about 16.7%.

Fig. 11 shows a curve C8 representing the filling level as a percentage and a curve C7 representing the power of the motor proportional to the reciprocal of the number of turns, with optimum values for the above-mentioned ratio. It should be noted that other parameters of the stator and rotor set for obtaining said curves are included within the ranges provided in the embodiments indicated below.

In the particular embodiment of fig. 3, the protection between the set of plates 16 and the winding wires 51 is ensured by an insulator 57 overmoulded on the inner surface of the recess 29. To facilitate legibility of the figure, the overmolded insulator 57 is shown only on a portion of the stator body 13. The surface of the tooth root 34 facing the axis X of the stator 9, i.e. the surface of the tooth root 34 in contact with the air gap 11 extending according to a portion of a cylinder, is free of insulators 57. This thus prevents interruption of the passage of flux in the air gap 11.

Preferably, the overmolded insulator 57 covers the axial end faces of the teeth 27 and/or the axial end faces of the yoke 28. In other words, the overmolded insulator 57 may also cover the axial end faces 23, 24 of the stator body 16.

This type of construction makes it possible to facilitate the placement of the notched insulator in place, in particular for stators 9 having a small diameter, compared to the use of insulating paper, as is the case in fig. 2.

According to one embodiment, the air gap L1 is approximately 0.3 mm. The outer diameter L2 of the stator 9 is comprised in the range 40mm to 60mm, and preferably 52 mm. The inner diameter L4 of the stator 9 is comprised in the range of 15mm to 35mm, in particular in the range of 20mm to 30mm, for example about 26.8 mm. Advantageously, as previously mentioned, the wire 51 comprises a conductive portion 52, the diameter L8 of the conductive portion 52 being comprised in the range 1mm to 2mm, and preferably 1.5mm, while each coil 50 comprises a number of turns 54 comprised in the range 5 to 20, in particular equal to 9. The thickness L3 of the yoke 28 may advantageously be comprised in the range 2mm to 5mm, and preferably 3.5 mm. In addition, the radial length L10 of each tooth 27 (see fig. 5) is contained in the range of 5mm to 15 mm. The minimum notch opening L9 measured between two adjacent roots 34 is approximately 4 mm. The fixing hole 40 may have a diameter L6 comprised in the range 0.6mm to 3mm and may be, for example, 3mm, while the distance L5 between the axis X of the stator 9 and the centre of the fixing hole 40 is about 47 mm.

In addition, the rotor 10 with the rotation axis Y shown in detail in fig. 9 and 10 has permanent magnets. The rotor body 60 includes a set of metal plates made up of axially stacked metal plates. The rotor body 60 may be rotationally connected with the shaft 12 in different ways, for example by force fitting the ribbed shaft 12 in a central opening 65 in the rotor 10, or by means of a key arrangement.

Preferably, the ratio between the outer diameter L2 of the stator 9 and the axial length L11 of the rotor 10 is comprised in the range 3 to 4, and preferably 3.25. This ratio makes it possible to reduce the inertia of the rotor 10 and therefore the time required to reach high speed rotation, corresponding for example to the operating speed of the electric compressor. Advantageously, the ratio between the outer diameter L12 of the rotor 10 and the length L11 of the rotor 10 is comprised in the range 1.1 to 1.8 and is for example about 1.6.

According to one embodiment, the rotor 10 has an axial length L11, for example comprised in the range 10mm to 20mm, and preferably 16mm, an outer diameter L12 comprised in the range 20mm to 50mm, in particular comprised in the range 24mm to 34mm, and preferably about 26mm, and an inner diameter L13 of about 10 mm.

A rotor 10 of the type having embedded magnets 62 comprises a plurality of cavities 61, in each of which at least one permanent magnet 62 is housed. The magnet 62 has a radial magnetization, i.e. two

surfaces

63, 64 parallel to each other with a radial orthogonal orientation are magnetized, for example so as to be able to generate a magnetic flux according to an orientation radial with respect to the axis Y.

As is clearly visible in fig. 10, the magnets 62 located in two consecutive cavities 61 have alternating polarities, in the case where the letters N and S correspond to north and south poles, respectively.

In the present case, the permanent magnet 62 has a rectangular parallelepiped shape, the angle of which is slightly inclined. The inner surface 63 and the outer surface 64 of each magnet 62 are flat in this case. As a variant, the outer surface 64 of each magnet 62 is curved, while the inner surface 63 of the magnet 62 is flat, or vice versa. Alternatively, both faces 63, 64 are curved in the same direction, so that each magnet 62 has the form of a tile as a whole.

In addition, the magnets 62 do not completely fill the cavities 61, such that there are two empty spaces 67 along the radially orthogonal direction on both sides of a given magnet 62. The air volume delimited by all the spaces 67 of the rotor makes it possible to reduce the inertia of the rotor 10 and to optimize the magnetic flux.

In order to maximize the magnetic power of the motor 7, the magnet 62 is preferably made of rare earth. However, as a variant, they may be made of ferrite, depending on the application and the power required by the motor 7. Alternatively, the magnets 62 may be of different grades to reduce cost.

Furthermore, a positioning element 70 is interposed between the rotor body 60 and each magnet 62 to ensure that each permanent magnet 62 is retained within the respective cavity 61. The positioning member 70 is positioned on the axis Y side of the rotor 10. As a variant, the positioning element 70 may be positioned on the air gap 11 side of the electrical machine.

Each positioning element 70 is constituted by an elastically deformable bent spring strip. As a variant, the positioning element 70 consists of a pin, a helical spring or a spring which is compression fitted according to its height between the rotor body 60 and the permanent magnet 62 by compression. For further details regarding the construction of the rotor 10, reference may be made to french application number 1554136 filed by the applicant on 5, 7/2015 and which is incorporated by reference in the present application.

It should be understood that the foregoing description has been provided purely by way of example, and does not limit the field of the invention, the departure from which is not intended to be construed as being any replacement of various elements thereof by any other equivalent.

Claims

1. Stator of a rotating electrical machine designed for an electrical compressor (1) of a motor vehicle, the stator (9) comprising a main body (16) having:

a yoke (28);

a plurality of teeth (27) distributed angularly on the inner periphery of the yoke (28);

a plurality of notches (29), each notch being defined by two adjacent teeth (27); and

a winding (17) comprising a plurality of coils (50), each coil (50) being formed by a wire (51) wound on a tooth,

characterized in that the ratio between the diameter (L8) in millimetres of the conductive portion (52) of the wire (51) and the number of turns (54) of each coil (50) is comprised in the range 5% to 25%,

the teeth (27) being integral with the yoke (28), the yoke (28) forming a continuous outer annular portion of the body (16) and extending between the base of the recess (29) and the outer periphery of the stator (9),

the ratio between the smaller recess opening measured between two adjacent tooth roots (34) and the outer diameter (L2) of the stator (9) is comprised in the range of 5% to 25%.

2. A stator according to claim 1, characterized in that the ratio between the diameter (L8) in millimetres of the conductive portion (52) of the wire (51) and the number of turns (54) of each coil (50) is comprised in the range 10% to 20%.

3. A stator according to claim 1, characterized in that the wire (51) comprises a conductive portion (52) having a diameter in the range of 1 to 2 mm.

4. A stator according to claim 1 or 2, characterized in that each coil (50) is formed by a number of turns (54) comprised in the range 5 to 20.

5. A stator according to claim 4, characterized in that the number of turns is equal to 9 or 18.

6. Stator according to claim 1, characterized in that said winding (17) is of the three-phase type.

7. A stator according to claim 6, characterized in that each phase is formed by two diametrically opposed coils (50).

8. A stator according to claim 1, characterized in that the coils (50) are electrically connected in parallel in pairs.

9. Stator according to claim 1, characterized in that the coils (50) are coupled in the form of a triangle.

10. A stator according to claim 1, characterized in that around each tooth (27), the number of turns (54) on the yoke (28) side is greater than the number of turns (54) on the axis side of the stator (9).

11. A stator according to claim 1, characterized in that in a recess (29), a part of the coil (50) filling the recess (29) is formed by three turns.

12. A stator according to claim 1, characterized in that each notch (29) has an area extending along the entire length of the stator.

13. Stator according to claim 1, characterized in that the ratio between the diameter (L8) of the conductive portion (52) of the wire (51) and the inner diameter (L4) of the stator (9) is comprised in the range of 3% to 10%.

14. Stator according to claim 13, wherein the ratio between the diameter (L8) of the conductive portion (52) of the wire (51) and the inner diameter (L4) of the stator (9) is comprised in the range of 5% to 10%.

15. Stator according to claim 14, wherein the ratio between the diameter (L8) of the conductive portion (52) of the wire (51) and the inner diameter (L4) of the stator (9) is comprised in the range of 5% to 7%.

16. Stator according to claim 15, wherein the ratio between the diameter (L8) of the conductive portion (52) of the wire (51) and the inner diameter (L4) of the stator (9) is comprised in the range of 5.2% to 6.3%.

17. Stator according to claim 1, characterized in that the ratio between the smaller notch opening measured between two adjacent tooth roots (34) and the outer diameter (L2) of the stator (9) is comprised in the range of 5% to 15%.

18. Stator according to claim 1, characterized in that said main body (16) is constituted by a plurality of metal sheets (37) axially superimposed one on the other,

at least one of the plurality of metal sheets (37) comprises on its surface studs (45) designed to cooperate with hollows (46) in the adjacent sheet, and the ratio between the greater diameter of said studs and the outer diameter (L2) of the stator is comprised in the range 5% to 15%;

the body (16) comprises at least one through fixing hole opening on each axial end face side of the body, and the ratio between the distance between the axis of the stator and the axis of the hole and half of the outer diameter of the stator is comprised in the range 80% to 97%.

19. A rotating electrical machine (7) comprising a stator (9) according to any of the preceding claims 1-18 and a rotor (10) provided with embedded permanent magnets (62).