EP3216111A2

EP3216111A2 - Stator for an alternator or an electric machine

Info

Publication number: EP3216111A2
Application number: EP15787231.8A
Authority: EP
Inventors: Eric Simon; Matthieu BONNICI; Olivier SAVINOIS; Bruno DANDRE; Vincent Ramet; Stéphane DE CLERCQ; Xavier Dunesme; Jean-François GAUTRU; Pierre Faverolle
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2014-11-03
Filing date: 2015-10-30
Publication date: 2017-09-13
Also published as: CN107148722B; WO2016071225A2; FR3028110A1; JP2017537591A; US20180083498A1; FR3028110B1; CN107148722A; WO2016071225A3

Abstract

The invention relates to a stator (13) for an alternator or an electric machine, which comprises: a cylindrical hub (14) in which a plurality of slots (201) that extend in the axial direction are formed, and a coil (12) mounted in said slots; in which said stator core (14) comprises: a cylindrical base portion (203) forming a cylinder head (203), a plurality of teeth (202) arranged such as to extend from the base portion towards an axial centre (X-X), said plurality of slots (201) being defined by said base portion and by an adjacent pair of said teeth (202). For each notch (201) the width at the opening of the notch (l_eo) is smaller than the width (l_ec) at the cylinder head (203).

Description

STATOR FOR AN ALTERNATOR OR ELECTRIC MACHINE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a stator for an alternator or for an electric machine, it also relates to an alternator or an electric machine comprising such a stator.

The invention finds a particularly advantageous application in the field of alternators and alternator-starters of a motor vehicle.

BACKGROUND TECHNOLOGY

As is known, a rotary electric machine of the single phase or polyphase type comprises at least two coaxially arranged parts, namely an armature and an inductor. A first of the parts surrounds the second of the parts, which is conventionally secured to a rotary shaft.

The first of the parts constitutes a stator, while the second part constitutes the rotor of the machine. When the armature is formed by the rotor, this machine constitutes an electric motor and transforms electrical energy into mechanical energy. This machine transforms mechanical energy into electrical energy when the armature is formed by the stator to operate as an electric generator and constitute for example an alternator. Of course, the electric machine can be reversible and also convert electrical energy into mechanical energy to form, for example, a motor vehicle starter-alternator, in particular enabling the motor vehicle internal combustion engine to be started while having an alternator function. . FIG. 1, which is a half-sectional view, shows a polyphase rotating electric machine in the form of an alternator of the three-phase type with internal ventilation for a motor vehicle with an internal combustion engine of the type described in EP-A. A-0 515 259 to which reference will be made. The alternator comprises, going from left to right of FIG. 1, that is to say from front to back, a driving pulley 1 1 secured to the front end of a shaft 2, the rear end carries slip rings 10a, 10b belonging to a manifold 1. The axis XX of the shaft 2 constitutes the axis of rotation of the machine and the collector.

Locally the shaft 2 carries the rotor 4 with an excitation winding 5, the ends of which are connected by wire links to the collector 1, as can also be seen in FIG. 11 of the documents FR 2 710 197, FR 2. 710 199 and FR 2 710 200. The rotor 4 is here a claw rotor and therefore comprises two pole wheels 6,7 each respectively carrying a front fan 8 and rear 9 each having blades as in EP-A-0 515 259.

Each wheel has axial teeth directed towards the other wheel with intermeshing of the teeth from one wheel to the other for forming magnetic poles when the winding 5 is activated thanks to the collector rings of the collector 1 each in contact with a brush (no referenced) carried by a brush holder 100 integral in this embodiment of a non-visible voltage regulator. The brushes are radially oriented relative to the X-X axis, while the rings 10a, 10b are axially oriented with respect to the X-X axis.

The regulator is connected to a direct current rectifying device DC 1 10, such as a diode bridge (of which two are visible in Figure 1) or alternatively transistors of the MOSFET type, especially when the alternator is reversible type and consists of an alternator-starter as described for example in WO 01/69762. This device 1 10 is itself electrically connected, on the one hand, to the outputs of the phases belonging to the windings 12, which comprises the stator 13 of the alternator, and on the other hand, to the onboard network and the battery of the motor vehicle. This stator 13, forming an armature in the case of an alternator, surrounds the rotor 4 and comprises a body 14 provided internally with axial notches (not visible) and with coils 12. The axial notches are provided with the wires or pins of the coils 12. These windings 12 have buns (no referenced) extending, on the one hand, in axial projection on either side of the body14; and, on the other hand, radially above the fans 8, 9.

As a reminder, the function of the voltage regulator is to control the current flowing in the excitation winding 5 in order to regulate the voltage delivered to the vehicle's on-board network and battery via the current rectifying device 1 10.

The fans 8, 9 extend in the vicinity respectively of a front flange, called front bearing 150, and a rear flange, called rear bearing 160 belonging to the fixed housing of the electrical machine connected to ground. The bearings 150, 160 are perforated for internal ventilation of the alternator via the fans 8, 9 when the fan assembly 8, 9 - rotor 4 - shaft 2 is rotated by the pulley 1 1 connected to the engine of the motor vehicle by a transmission device comprising at least one belt engaged with the pulley 1. This ventilation makes it possible to cool the windings 12, 5 as well as the brush holder 100 with its regulator and the straightening device 1 10. The arrows in FIG. 1 show the path followed by the cooling fluid, here in FIG. air, through the different openings of the bearings 150, 1 60 and inside the machine.

This device 1 10, the brush holder 100, and a perforated protective cover (not referenced) are carried here by the rear bearing 1 60 so that the rear fan 9 is more powerful than the front fan 8. So known, the bearings 150, 160 are interconnected, here with screws or tie rods not visible, to form a housing to be mounted on a fixed part of the vehicle. The bearings 150, 1 60 each centrally carry a ball bearing 17, 18 for rotatably supporting the front and rear ends of the shaft 2 passing through the bearings 150, 1 60 to carry the pulley January 1 and the rings 10a, 10b of collector 1.

These bearings have a hollow shape and here each have a portion of perforated transverse orientation carrying the bearing 17, 18 and a portion of axial orientation perforated and internally staggered in diameter to axially centering and retaining the stator 13 when the two bearings are connected together to form the housing.

The blades of the fans 8, 9 extend radially above the housings that have the bearings 150, 160 for mounting the bearings 17 and 18; which are thus broken down.

Figure 2 shows the cylindrical core or body 14 of the stator 13 in a plane perpendicular to the axis X-X. The cylindrical core of the stator comprises in a circumferential direction an alternation of notches and teeth, each notch being delimited by two teeth. Moreover, each tooth is provided with two tooth roots extending circumferentially on either side of said tooth. According to this stator known to those skilled in the art, the stator slots have parallel flanks. That is to say that for each notch, the shape of the pair of two teeth delimiting said notch is such that the notch has two parallel flanks. The design of a rotating electrical machine comprises in particular a step of determining the number of slots of the stator, a step of determining the number of phases of the winding, a step of determining the outer diameter of the stator yoke, and a sizing step. notches and teeth of the stator. The sizing of the slots and stator teeth must satisfy several constraints, including three. First, the width of the teeth must be large enough to allow sufficient mechanical strength, secondly, the width of the teeth must be sufficient to allow a good recovery of the magnetic flux from the end of the teeth to the breech and thirdly the notch surface must be large enough to allow the introduction of a large amount of copper wire which avoids a winding resistance too important.

It appears that the optimum of each of these three constraints is not attainable separately. Indeed, for example by wanting to increase the mechanical strength and the magnetic flux raised from the end of the teeth to the cylinder head, we obtain large tooth widths which for an outside diameter of the cylinder head and a given number of notches leads to notches whose surface is too small, which induces a resistance of significant winding and significant losses by Joule effects. And vice versa, when it is desired to increase the notch surface, the width of the teeth for an outside diameter of the cylinder head and a given number of notches is reduced, which greatly limits the magnetic flux raised from the end of the teeth. towards the breech.

A satisfactory dimensioning of the notches and teeth of the stator therefore consists in obtaining a good compromise with respect to these three constraints. For example, the stator has a dimensioning of the notches and teeth of the stator illustrated in Figure 2 which is perfectible since it mainly allows an increase of the notch surface that is to say an improvement in the coefficient filling but do not address the other two criteria. The invention proposes to overcome the drawbacks of known stators by providing a stator having a better dimensioning of the notches and teeth of the stator which satisfies the three constraints stated above.

OBJECT OF THE INVENTION

The invention thus relates to a stator for an alternator or an electric machine, comprising:

a cylindrical core in which a plurality of axially extending slots are formed;

a winding mounted in said slots;

wherein said stator core comprises:

a cylindrical base portion forming a cylinder head;

a plurality of teeth arranged to extend from said base portion to an axial center and said plurality of slots being defined by said base portion and an adjacent pair of said teeth.

According to a general characteristic of the invention, each notch the width at the opening of the notch is less than the width at the yoke. A good compromise is obtained which makes it possible on the one hand to avoid the saturation of the teeth at the level of the tips of the teeth so as to bring back a large flow, and secondly to have a large surface notch allowing a larger section of copper, which allows to limit the phase resistance.

According to one embodiment, for each tooth the width at the end is greater than the width at the yoke. Because of this shape, the flow back through the teeth is optimized. Indeed, the further away from the end, the less the magnetic flux is slowed by the saturation due to the limited tooth surface. Indeed, as one moves away from the tooth end the radius increases which has the effect of limiting the saturation for a given tooth width. Thus, for a tooth, the most critical place for the upward flow of magnetic flux from the end of the tooth to the breech is the end whereas, on the contrary, the place where the constraints are the least important of this. point of view is the breech. Thus, by maximizing the tooth width at its end and minimizing it at the yoke, a maximum upward flow is obtained while having a large notch surface due to recesses made in the tooth. These recesses being due to the reduction of the width of the teeth at the breech.

According to one characteristic of this embodiment, for each tooth the ratio between the width at the end and the width at the yoke is between 1.8 and 2.2.

These ratios allow a good compromise between upstream maximized flow, good notch surface and sufficient mechanical strength.

According to another embodiment, for each tooth the width at the end is less than the width at the yoke. For a given minimum tooth width, such a configuration allows a saturation zone on a smaller tooth height than with a tooth shape with parallel flanks.

According to another embodiment, for each tooth the width at the end is greater than the width of the tooth obtained at a position radially spaced from the yoke by a value between 0.3 and 0.7 times the height of the tooth. This recess obtained by reducing the tooth width to an intermediate position between the end and the yoke relative to the tooth width at the end allows an increase in the notch surface. However, such a reduction in width does not increase the saturation if it is practiced at a sufficient distance from the end of the tooth since as one moves away from the tooth end the radius increases which has the effect of limiting the magnetic saturation for a given tooth width.

According to another characteristic of this other embodiment, the minimum width of the tooth is obtained at a position radially spaced from the yoke by a value between 0.4 and 0.6 times the height of the tooth.

The positioning at the height of the tooth of the minimum width thus allows a minimization of the increase of the magnetic saturation.

According to another characteristic of this embodiment, the ratio between the minimum width of the tooth and the tooth width at the end is between 0.2 and 0.7.

The relationship between the width at the end of the tooth and the minimum width allows a good compromise between the increase of the notch surface and the increase of the magnetic saturation. According to another embodiment, each tooth comprises on each of these sides a flank having a straight shape of constant direction and without point of inflection.

This provides an ease of industrialization and realization.

According to a characteristic of this other embodiment, for each notch the ratio between the width at the yoke and the width at the opening of the notch is between 1 .1 and 2, preferably between 1. 3 and 1 .5.

The ratio thus proposed allows an optimum compromise between electrotechnical improvement and mechanical resistance. According to another embodiment, the teeth have at their end feet of teeth.

The widths of the tooth or notch at the aperture defined beforehand on the side of said axial center are understood to be measured just below said tooth feet, not including the feet of the tooth. Tooth feet allow an improvement of the electrotechnical properties of the stator and a maintenance of the son in the notches.

According to a characteristic of this other embodiment, for each tooth, the circumferential width of the tooth root to the left of the tooth is different from the circumferential width of the tooth root to the right of the tooth.

The method of manufacturing the stator comprises a step of installing the winding in the notches. The differences in different circumferential widths make it easier to facilitate this installation step when the winding comprises conductors formed by wires. For example, in the case of a winding installation in the anticlockwise direction, a smaller tooth root on the right makes it easier to introduce wires forming the conductors.

According to another characteristic of this other embodiment, the ratio between the circumferential width of the tooth root to the left of the tooth and the circumferential width of the tooth root to the right of the tooth is between 1, 2 and 1.5.

Such a ratio according to the tooth pitch is less important on the right allows introduction of the wires forming the conductors more simple and also from a value of the tooth feet to the right and left which are not too different one of the other a good compromise even a conservation of the electromagnetic characteristics and maintenance compared to symmetrical tooth feet.

According to one embodiment, the flanks of the teeth are aligned with the spokes of the stator. This arrangement is particularly advantageous in the case of a hexaphase winding. The invention also relates to an electric machine for example an alternator comprising a rotor, said electric machine comprises a stator as defined above which surrounds the rotor.

According to one embodiment, said coil mounted in said slots of the cylindrical core of the stator comprises 6 phases.

According to another embodiment, the coil mounted in said slots of the cylindrical core of the stator comprises conductors having in the notches a rectangular section.

According to yet another embodiment, the coil mounted in said slots of the cylindrical core of the stator comprises 4 or 6 conductors per notch.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention. Figure 1, already described, is a schematic cross-sectional view of an electric machine rotor according to the state of the art; Figure 2, already described, is a representation of the cylindrical core of a stator in a plane perpendicular to the axis X-X; Figures 3 and 4 are representations of the cylindrical core of a stator according to the invention in a plane perpendicular to the axis X-X; Figures 5 and 6 are representations of a tooth of the cylindrical core of a stator according to the invention in a plane perpendicular to the axis X-X; and Figures 7 and 8 are representations of a notch provided with a winding according to the invention in a plane perpendicular to the axis X-X.

Identical, similar or similar elements retain the same reference from one figure to another. DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

Figure 3 is a representation of the cylindrical core 14 of a stator 13 in a plane perpendicular to the X-X axis.

The stator core 13 comprises: a cylindrical base portion 203 forming a yoke, said yoke having a radial thickness hc;

a plurality of teeth 202 arranged to extend from said base portion to an axial center X-X and said plurality of slots 201 being defined by said base portion 203 and an adjacent pair of said teeth 202;

As can be seen, firstly for each notch 201, the width at the opening of the notch l_eo is less than the width l_ec at the yoke 203 and secondly for each tooth 202 the width at the end l_do is greater than the width l_dc at the breech. For example, for each tooth 202 the ratio between the width at the end l_do and the width l_dc at the yoke 203 is between 1, 8 and 2.2.

Figure 4 is a representation of the cylindrical core 14 of a stator 13 in a plane perpendicular to the X-X axis.

The stator core 13 comprises: a cylindrical base portion forming a yoke 203;

a plurality of teeth 202 arranged to extend from said base portion 203 toward an axial center XX and said plurality of slots 201 being defined by said base portion 203 and an adjacent pair of said teeth 202; As can be seen, firstly for each slot forming a notch 201, the width at the opening of the notch l_eo is less than the width l_ec at the yoke 203 and secondly for each tooth 202 the width at the end l_do is less than the width l_dc at the yoke 203.

In addition, each tooth 202 comprises on each of these sides a flank having a straight shape of constant direction and no point of inflection. FIG. 5 is a representation of a tooth 202 of the cylindrical core illustrated in FIG. 4. As can be seen, for each tooth 202, the width at the end l_do is less than the width l_dc at the level of the yoke 204.

For example, the ratio between the width l_ec at the level of the yoke 204 and the width at the opening of the notch l_eo is between 1 .1 and 2, preferably between 1 .3 and 1 .5.

Figure 6 is a representation of a tooth 202 of the cylindrical core 14 of a stator 13 in a plane perpendicular to the X-X axis. As can be seen, for each tooth the width at the end l_do is less than the width l_dc at the yoke.

According to Figure 6, the width at the end l_do is greater than the width of the tooth 202 obtained at a radially spaced position of the yoke with a value between 0.3 and 0.7 times the height of the tooth h_d.

According to a preferred embodiment, the minimum width l_min of the tooth 202 is obtained at a position radially spaced from the yoke by a value between 0.4 and 0.6 times the height of the tooth h_d.

For example, the ratio between the minimum width l_min of the tooth 202 and the tooth width at the end l_do is between 0.2 and 0.7.

Figure 7 is a representation of a notch 201 provided with a coil in a plane perpendicular to the axis XX. The notch 201 illustrated in Figure 7 is delimited by two teeth. The two teeth 202 each comprise at their end and on both circumferential sides of these ends a foot of teeth d_r and d_g respectively. In FIG. 7, only one flank f of each tooth 202 is illustrated, so that for each only one tooth root that of the illustrated sidewall is shown in FIG. Advantageously, for each tooth 202, the circumferential width of the left tooth root d_g of the tooth 202 is different from the circumferential width of the tooth root to the right d_r of the tooth. For example, the ratio between the circumferential width of the tooth root to the left of the tooth is and the circumferential width of the tooth root to the right of the tooth is between 1, 2 and 1.5.

The notch of the stator 13 illustrated in FIG. 7 is integrated in an electric machine, for example an alternator, as illustrated in FIG. 1, which comprises a rotor, said stator surrounding said rotor 4. The electric machine comprises a mounted winding 12 in said slots 201 of the cylindrical core 14 of the stator which comprises 6 phases. For example, the coil 12 mounted in said slots 201 of the cylindrical core of the stator 14 comprises conductors 204 having in the notches a rectangular section. Advantageously, the coil 12 mounted in said slots 201 of the cylindrical core of the stator comprises 4 conductors per notch. In the case where the winding 12 comprises four conductors 204 aligned radially in the notch 201 along two columns of two conductors 204, such a winding of quad is qualified.

Figure 8 is a representation of a notch 201 provided with a coil in a plane perpendicular to the X-X axis. The notch 201 provided with a winding of FIG. 8 differs from that illustrated in FIG. 7 by the number of conductors 204 per slot 201 which is 6 for FIG. 8 whereas it is 4 for FIG. 7. These conductors 204 are advantageously aligned radially in the notch 201 along two columns of three conductors 204.

Claims

1. Stator (13) for an alternator or an electric machine, comprising:

a cylindrical core (14) in which a plurality of axially extending notches (201) are formed;

a winding (12) mounted in said slots;

wherein said stator core (14) comprises:

a cylindrical base portion (203) forming a yoke (203);

a plurality of teeth (202) arranged to extend from said base portion to an axial center (X-X) and said plurality of slots

(201) being defined by said base portion and an adjacent pair of said teeth (202);

characterized in that for each notch (201) the width at the opening of the notch (l_eo) is less than the width (l_ec) at the yoke (203).

2. Stator according to claim 1, characterized in that for each tooth (202) the width at the end (l_do) is greater than the width (l_dc) at the yoke (203).

3. Stator according to claim 1 or 2, characterized in that for each tooth (202) the ratio between the width at the end (l_do) and the width (l_dc) at the yoke (203) is between 1 , 8 and 2.2.

4. Stator according to claim 1, characterized in that for each tooth (202) the width at the end (l_do) is less than the width (l_dc) at the yoke (203).

5. Stator according to claim 4, characterized in that for each tooth (202) the width at the end (l_do) is greater than the width of the tooth

(202) obtained at a position radially spaced from the yoke (203) by a value between 0.3 and 0.7 times the height of the tooth (h_d).

6. Stator according to claim 4 or 5, characterized in that the minimum width (l_min) of the tooth (202) is obtained at a position radially spaced from the yoke (203) by a value between 0.4 and 0.6 times the height of the tooth (h_d).

7. Stator according to claim 6, characterized in that the ratio between the minimum width of the tooth (l_min) and the tooth width at the end (l_de) is between 0.2 and 0.7.

8. Stator according to claim 4, characterized in that each tooth comprises on each of these sides a flank (f) having a straight shape of constant direction and no point of inflection.

9. Stator according to any one of claims 4 to 8, characterized in that for each notch (201) the ratio between the width (l_ec) at the yoke (203) and the width at the opening of the notch (l_eo) is between 1 .1 and 2, preferably between 1 .3 and 1 .5.

10. Stator according to one of the preceding claims, characterized in that the teeth (202) have at their end of the teeth (d_r, d_g).

1 1. Stator according to the preceding claim, characterized in that for each tooth (202), the circumferential width of the tooth root on the left (d_g) of the tooth is different from the circumferential width of the tooth root on the right (d_r) of the tooth .

12. Stator according to the preceding claim, characterized in that the ratio between the circumferential width of the tooth root on the left (d_g) of the tooth and the circumferential width of the tooth root on the right (d_r) of the tooth is between 1 , 2 and 1, 5.

13. Electric machine for example an alternator, comprising a rotor (4) characterized in that it comprises a stator (13) according to one of the preceding claims, said stator surrounding said rotor (4).

14. Electrical machine according to claim 13, characterized in that said coil (12) mounted in said slots (201) of the cylindrical core (14) of the stator comprises six phases.

15. Electrical machine according to claim 14, characterized in that said coil (12) mounted in said slots (201) of the cylindrical core (14) of the stator comprises conductors (204) having in the notches a rectangular section.

An electric machine according to claim 14 or 15, said winding

(12) mounted in said slots (201) of the cylindrical core of the stator (14) comprises 4 or 6 conductors (204) per notch.