FR3044482A1 - ELECTRIC ROTOR ROTOR WITH ROTATING ELECTRIC MACHINE PROVIDED WITH AT LEAST ONE CHAMFER REALIZED IN A LEAVE EDGE OF A CLAW - Google Patents

Abstract

The invention relates mainly to a motor vehicle rotating electrical machine rotor comprising: - at least one pole wheel comprising a plurality of claws (29), - each claw (29) having a leading edge (51) and an edge leakage device (52) extending between a base (53) and a free end (54) of the corresponding claw (29), - said rotor (12) being characterized in that at least one claw (29) has a chamfer (57) made in at least one trailing edge (52), and in that a ratio of a maximum width (chb_max) of said chamfer (57) on a polar pitch is between 0.16 and 0.37 in a range of operating speeds.

Description

ELECTRIC ROTOR ROTOR WITH ROTATING ELECTRIC MACHINE PROVIDED WITH AT LEAST ONE CHAMFER REALIZED IN A LEAVE EDGE OF A CLAW

The present invention relates to a rotary electric machine rotor provided with at least one chamfer made in a trailing edge of a claw. The invention finds a particularly advantageous, but not exclusive, application in the field of alternators and reversible electric machines for a motor vehicle. An alternator transforms mechanical energy into electrical energy. A reversible machine also makes it possible to convert electrical energy into mechanical energy, in particular to start the engine of the vehicle.

In a manner known per se, an alternator as described in document EP0762617 comprises a housing and, inside thereof, a claw rotor, fixed in rotation directly or indirectly to a shaft, and a stator which surrounds the rotor with the presence of a gap. A pulley is attached to the front end of the shaft.

The stator comprises a body in the form of a pack of sheets with notches equipped with notch insulators for mounting the stator winding. The coil comprises a plurality of phase windings passing through the notches of the body and forming, with all the phase windings, a front bun and a rear bun on either side of the stator body. The windings are obtained for example from a continuous wire covered with enamel or from bar-like conductor elements, such as U-shaped pins whose ends are interconnected for example by welding.

These phase windings are, for example, three-phase windings connected in a star or in a triangle, the outputs of which are connected to at least one electronic rectification module comprising rectifying elements, such as diodes or transistors.

In addition, the rotor has two pole wheels. Each pole wheel has a flange of transverse orientation provided at its outer periphery claws for example of trapezoidal shape and axial orientation. The claws of one wheel are directed axially towards the flange of the other wheel. Each claw of a pole wheel enters the space between two claws adjacent to the other pole wheel, so that the claws of the pole wheels are nested relative to each other. A cylindrical core is interposed axially between the flanges of the wheels. This core carries at its outer periphery an excitation coil wound in an insulator radially interposed between the core and this coil.

It is known that this type of electrical machines emits an acoustic noise due to the vibrations generated by the magnetic forces present. This noise is particularly harmful in a low rotation speed range, especially between 1800 and 4000 revolutions / min. In fact, beyond the aeraulic noise of the fan covers the magnetic noise so that it is no longer necessary to reduce the latter. The aim of the invention is to effectively minimize magnetic noise by proposing a motor vehicle rotating electrical machine rotor comprising: at least one pole wheel comprising a plurality of claws, each claw comprising a leading edge and a trailing edge; extending between a base and a free end of the corresponding claw, - said rotor being characterized in that at least one claw comprises a chamfer made in a trailing edge, and in that a ratio of a maximum width of said claw chamfer on a polar pitch is between 0.16 and 0.37 in a range of operating speeds.

Thus, by making such a chamfer configuration on the trailing edge, the size of the air gap is locally increased so as to reduce the magnetic forces and therefore the noise generated significantly. This noise reduction is obtained without reducing the magnetic performance of the electric machine.

In one embodiment, chamfers are made only in the edges of leaks claws.

According to one embodiment, said rotor comprises a first pole wheel and a second pole wheel, and in that claws of said first pole wheel each comprise a first chamfer associated with a first ratio for a low speed of said range of speeds. operation, and claws of said second pole wheel each comprise a second chamfer associated with a second ratio for a high speed of said range of operating speeds. Since the optimum chamfer depends on the speed of rotation of the rotor, such a configuration makes it possible to minimize the magnetic noise optimally over the entire operating range of the rotor.

In one embodiment, said chamfer is associated with an optimal ratio equal to an average between a first ratio for a low speed of the operating speed range and a second ratio for a high speed of the operating speed range. An alternative claw configuration is thus defined which makes it possible to minimize the magnetic noise optimally over the entire operating range of the rotor.

According to one embodiment, the range of operating speeds is between 1800 and 4000 revolutions / minute.

According to one embodiment, a chamfer surface decreases when moving towards the free end of the corresponding claw.

According to one embodiment, the surface of said chamfer is substantially zero at the free end of the claw.

According to one embodiment, the claw has an outer radial surface, and in that the chamfer is formed on said outer radial surface.

In one embodiment, the chamfer extends axially between the base and the free end of the corresponding claw.

In one embodiment, a radial section of the chamfer extends along a straight line.

In one embodiment, a radial section of the chamfer extends along an arc.

In one embodiment, said claws of said pole wheel are symmetrical.

According to one embodiment, said claws of said pole wheel are asymmetrical.

According to one embodiment, said rotor comprises interpolar magnets each positioned inside a space separating two successive claws. The subject of the invention is also a rotating electrical machine of the alternator type or a reversible machine characterized in that it comprises a rotor as defined above. The invention will be better understood on reading the description which follows and the examination of the figures which accompany it. These figures are given for illustrative but not limiting of the invention.

Figure 1 is a schematic longitudinal sectional view of an alternator according to the present invention;

Figures 2a and 2b are respectively schematic side and top views of a polar wheel claw according to the present invention provided with a bevel;

FIG. 3 is a graph showing two curves representing the noise level of a three-phase alternator as a function of a ratio between a maximum chamfer width and a polar pitch, each curve corresponding to a specific rotation speed of the alternator;

Figure 4 is a schematic partial cross-sectional view of a polar wheel claw according to the present invention;

FIG. 5 shows a schematic variant embodiment of the rotor according to the present invention in which the chamfers of the claws have two different configurations from one pole wheel to the other;

FIG. 6 illustrates a schematic variant embodiment of a rotor according to the present invention with asymmetrical claws.

Identical, similar or similar elements retain the same reference from one figure to another. In the following description, it is considered that a "front" element is located on the side of the pulley of the machine and a "rear" element is located on the opposite side.

FIG. 1 shows a compact and polyphase alternator 10, in particular for a motor vehicle. This alternator 10 transforms mechanical energy into electrical energy and can be reversible. Such a reversible alternator 10, called an alternator / starter, makes it possible to convert electrical energy into mechanical energy, in particular to start the engine of the vehicle.

This alternator 10 comprises a housing 11 and, inside thereof, a claw rotor 12 mounted on a shaft 13, and a stator 16, which surrounds the rotor 12 with the presence of an air gap 17. A pulley 14 is fixed on the shaft 13. This pulley belongs to a belt motion transmission device between the alternator 10 and the engine of the motor vehicle. The axis X of the shaft 13 forms the axis of rotation of the rotor 12.

The stator 16 comprises a body 19 in the form of a pack of sheets provided with notches, for example of the semi-closed type, equipped with slot insulator for mounting the phases of the stator 16. Each phase comprises at least one winding through the notches of the body 19 of the stator 16 and forms, with all phases, a front bun 20 and a rear bun 21 on either side of the stator body 19.

The windings are obtained for example from a continuous wire covered with enamel or from bar-like conductor elements, such as pins connected together for example by welding. These windings are, for example, three-phase windings connected in a star or in a triangle, the outputs of which are connected to at least one rectifier bridge comprising rectifying elements such as diodes or transistors of the MOSFET type, in particular when it is a question of an alternator-starter as described for example in the document FR2745445.

The rotor 12 comprises two pole wheels 24, 25 each having a flange 28 of transverse orientation provided at its outer periphery with claws 29 for example of trapezoidal shape and axial orientation. The claws 29 of a wheel 24, 25 are directed axially towards the flange 28 of the other wheel. Each claw 29 of a pole wheel 24, 25 enters the space between two claws 29 adjacent to the other pole wheel, so that the claws 29 of the pole wheels 24, 25 are interleaved with each other.

The outer periphery of the claws 29 defines with the inner periphery of the body 19 of the stator 16 the gap 17 between the stator 16 and the rotor 12. The inner periphery of the claws 29 is inclined, so that the claws 29 are thinner on the side their free end 54, as can be seen in Figure 2a.

A cylindrical core 30 is interposed axially between the flanges 28 of the wheels 24, 25. In this case, the core 30 consists of two half-cores each belonging to one of the flanges 28. This core 30 carries at its outer periphery a excitation coil 31 wound in an insulator radially interposed between the core 30 and the coil 31.

In addition, the casing 11 has front 35 and rear 36 bearings assembled together. The bearings 35, 36 are of hollow form and each bear a central bearing 37, 38 ball for the rotational mounting of the shaft 13 of the rotor. The rear bearing 36 carries a brush holder 40 provided with brushes 41 intended to rub against rings 44 of a manifold 45 connected by wire links to the excitation winding 31. The brushes 41 are electrically connected to a voltage regulator mounted on the outside of the machine.

The front 35 and rear 36 bearings comprise substantially lateral front 60 and rear 61 openings in order to allow the cooling of the alternator 10 by air circulation generated by the rotation of a fan 62 positioned on the front face of the rotor and another fan 63 positioned on the rear face of the rotor. Each fan 62, 63 is provided with a plurality of blades 64. The front lateral openings 60 and rear 61 are opposite the bunches respectively before 20 and rear 21.

As can be seen in FIG. 2b, each claw 29 of trapezoidal shape comprises a leading edge 51 entering firstly into contact with the air in the direction of rotation of the rotor 12 indicated by the arrow SR and a trailing edge 52 located on the opposite side from the leading edge 51. These edges 51, 52 extend between the base 53 of the claw 29, which coincides locally with the outer periphery of the flange 28 corresponding, and the free end 54 of the claw 29.

In this case, a chamfer 57 is made in the trailing edge 52 of each claw 29 of the pole wheels 24, 25. As a variant, a chamfer 57 is made only in certain claws 29 of the pole wheels 24, 25. case, the chamfer 57 is formed on an outer radial surface 56 of a corresponding claw 29. The chamfer 57 preferably extends axially between the base 53 and the free end 54 of the corresponding claw 29, that is to say over the entire axial length of the claw 29.

This chamfer 57 is defined in particular by two lateral sides 58, 59 joining at the free end 54 of the claw 29. Thus, the surface of the chamfer 57 of generally triangular shape decreases when moving towards a free end 54 of the claw 29. The surface of the chamfer 57 is substantially zero at the free end 54 of the claw 29.

A ratio R is defined between a maximum width Chb_max of chamfer 57 and a polar pitch Tp, ie R = Chb_max / Tp. The polar pitch Tp is equal to the ratio between the internal circumference of the stator and the number of poles of the machine, ie Tp = πϋ / 2ρ with D being the internal diameter of the stator and p being the number of pairs of poles of the machine.

The maximum width Chb_max is measured in a circumferential direction, that is to say in a direction parallel to the direction in which the flange 28 of the corresponding pole wheel 24, 25 extends. Each chamfer 57 may have a flat shape, that is to say that a radial section of the chamfer 57 extends along a straight line.

Alternatively, the chamfer 57 has a radial section extending along an arc of a circle, that is to say that the chamfer 57 has a rounded corner along a radius of curvature L1, as can be seen in FIG. 4. In this case, the maximum width Chb_max is measured between a straight line D1 parallel to the median plane PM of the claw 29 and tangent to the rounded corner and the intersection between the flat part of the chamfer 57 and the machining radius L2 of the rotor 12. The angle K between the flat portion of the chamfer 57 and the median plane PM of the claw 29 is for example between 60 and 78 degrees.

As illustrated by the curves of FIG. 3, for a range P of operating speeds of between 1800 and 4000 revolutions / minute, the optimal ratio R in terms of noise reduction is between 0.16 and 0.37. It should be noted that the aforementioned operating range does not correspond to the minimum and maximum operating speeds of the alternator but to the range of speeds for which the magnetic noise, which has a significant level and which is not covered by the fan noise, should be attenuated.

Preferably, the chamfers 57 are made only in the trailing edges 52 of the claws 29. In fact, it has been demonstrated that the realization of chamfers 57 in the leading edge 51 and the trailing edge 52 of each claw 29 has the effect of reducing the magnetic performance of the electric machine.

Since the optimal chamfer 57 depends on the speed of rotation of the rotor 12, the claws 29 of one of the pole wheels 24 may each have a first chamfer 57 of maximum width chb_max1 associated with a first ratio R1 which is optimal in terms of reduction. of noise for the low speed of the operating speed range. The ratio R1 is, for example, 0.17 for 1800 revolutions / min. The claws 29 of the other pole wheel 25 may each have a second chamfer 57 'of width chb_max2 associated with a second ratio R2 which is optimal in terms of noise reduction for the high speed of the operating speed range. The ratio R2 is, for example, 0.36 for 4000 revolutions / min. The corresponding rotor 12 having chamfers 57, 57 'different from a pole wheel 24 to the other 25 is illustrated in FIG.

As can be seen from the table below, such a configuration makes it possible to minimize the magnetic noise optimally over the entire operating range P of the rotor 12. Indeed, it appears that an average power reduction is obtained. 1.5dB acoustics compared to the optimum chamfer configuration corresponding to the low speed of the operating speed range P, and an average reduction of sound power of the order of 2.6dB compared to the optimal configuration chamfer corresponding to the high speed of the operating speed range P.

Alternatively, the chamfer 57 made on each of the claws 29 is associated with a ratio Rmoy equal to an average between the first ratio R1 for the low speed of the operating speed range P and the second ratio R2 for the high speed of the range. Thus, in the preceding example, Rmoy = (0.15 + 0.27) /2=0.26 is obtained.

In the exemplary embodiment, the claws 29 of the pole wheels 24, 25 are symmetrical, that is to say that the median M passing through the center of the base 53 also passes through the free end 54 of the claw 29. (see Figure 2b).

Alternatively, as shown in Figure 6, the claws 29 of the pole wheels 24, 25 are asymmetrical, that is to say that the median M through the center of the base 53 of a claw 29 is shifted relative to a parallel straight line passing through the free end 54 of the corresponding claw 29. An asymmetric claw 29 can be inclined in the direction of rotation SR (see arrow F1) or in the direction opposite to the direction of rotation SR (see arrow F2). The claws 29 of the two pole wheels 24, 25 can be bent in the same direction or in opposite directions, as is

shown in Figure 6.

The rotor 12 may optionally include interpolar magnets 46 visible in Figures 5 and 6 each positioned within a space 66 between two claws 29 successive. The magnets 46 may be positioned inside all the interpolar spaces 66 or only inside some of them and evenly distributed along the circumference of the rotor 12. The magnets 46 may be made of rare earth NeFeB (Neodyme-Iron-Boron) or SmCo (Samarium-Cobalt). The choices of the material and the number of interpolar magnets 46 make it possible to easily adjust the magnetic properties of the rotor 12 to the desired power of the alternator.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention which would not be overcome by replacing the different elements by any other equivalent.

Claims (15)

Motor vehicle rotating electrical machine rotor (12) comprising: - at least one pole wheel (24, 25) comprising a plurality of claws (29), - each claw (29) having a leading edge (51). and a trailing edge (52) extending between a base (53) and a free end (54) of the corresponding claw (29), - said rotor (12) being characterized in that at least one claw (29) ) comprises a chamfer (57) made in a trailing edge (52), and in that a ratio of a maximum width of said chamfer (57) on a polar pitch (Tp) is between 0.16 and 0, 37 in a range of operating speeds (P) · 2. Rotor according to claim 1, characterized in that chamfers (57) are made only in the edges of leaks (52) of the claws (29). 3. Rotor according to claim 1 or 2, characterized in that it comprises a first pole wheel (24) and a second pole wheel (25), and in that claws (29) of said first pole wheel (24) each comprise a first chamfer (57) associated with a first ratio (R1) for a low speed of the operating speed range (P), and claws (29) of said second pole wheel (25) comprise, each a second chamfer (57 ') associated with a second ratio (R2) for a high speed of the operating speed range (P). 4. Rotor according to claim 1 or 2, characterized in that said chamfer (57) is associated with an optimum ratio equal to an average between a first ratio (R1) for a low speed of the operating speed range and a second ratio (R2) for a high speed of the operating speed range. 5. Rotor according to any one of claims 1 to 4, characterized in that the operating speed range is between 1800 and 4000 revolutions / minute. 6. Rotor according to any one of claims 1 to 5, characterized in that a chamfer surface (57) decreases when moving towards the free end (54) of the corresponding claw (29). 7. Rotor according to claim 6, characterized in that the surface of said chamfer (57) is substantially zero at the free end (54) of the claw (29). 8. Rotor according to any one of claims 1 to 7, characterized in that the claw (29) has an outer radial surface (56), and in that the chamfer (57) is formed on said outer radial surface (56). ). 9. Rotor according to any one of claims 1 to 8, characterized in that the chamfer (57) extends axially between the base (53) and the free end (54) of the corresponding claw (29). 10. Rotor according to any one of claims 1 to 9, characterized in that a radial section of the chamfer (57) extends along a straight line. 11. Rotor according to any one of claims 1 to 9, characterized in that a radial section of the chamfer (57) extends along a circular arc. 12. Rotor according to any one of claims 1 to 11, characterized in that said claws (29) of said pole wheel (24, 25) are symmetrical. 13. Rotor according to any one of claims 1 to 11, characterized in that said claws (29) of said pole wheel (24, 25) are asymmetrical. 14. Rotor according to any one of claims 1 to 13, characterized in that it comprises interpolar magnets (46) each positioned inside a space separating two claws (29) successive. 15. Alternating type electrical rotating machine or reversible machine characterized in that it comprises a rotor (12) as defined in any one of the preceding claims.