CN108292869B

CN108292869B - Claw-pole rotor of a rotating electrical machine provided with at least one chamfer formed on the trailing edge of the claw

Info

Publication number: CN108292869B
Application number: CN201680068174.9A
Authority: CN
Inventors: M.拉科托沃; A.坦-金; V.兰弗朗基
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2015-12-01
Filing date: 2016-11-23
Publication date: 2020-03-03
Anticipated expiration: 2036-11-23
Also published as: FR3044482A1; CN108292869A; DE112016005485T5; FR3044482B1; WO2017093635A1

Abstract

The invention relates in particular to a rotor of a rotating electrical machine of a motor vehicle, comprising: at least one pole wheel comprising a plurality of claws (29); each jaw (29) comprises a leading edge (51) and a trailing edge (52) extending between the base (53) and the free end (54) of the respective jaw (29); the rotor (12) is characterized in that at least one claw (29) comprises a chamfer (57) formed in at least one trailing edge (52), and in that the ratio of the maximum width (chb _ max) of the chamfer (57) to the pole pitch is in the range of 0.16 to 0.37 over a range of operating speeds.

Description

Claw-pole rotor of a rotating electrical machine provided with at least one chamfer formed on the trailing edge of the claw

Technical Field

The present invention relates to a rotor of a rotating electric machine, which is provided with at least one chamfer formed on a trailing edge of a claw. The invention has particularly advantageous, but not exclusive, application in the field of alternators and reversible electric machines for motor vehicles. The alternator converts mechanical energy into electrical energy. The reversible machine can also convert electrical energy into mechanical energy, in particular for starting the thermal engine of the vehicle.

Background

In a known manner, the alternator described in document EP0762617 comprises a casing, inside which a claw rotor rotating integrally, directly or indirectly, with a shaft, and a stator surrounding the rotor with an air gap. The pulley is fixed at the front end of the shaft.

The stator comprises a body in the form of a set of plates provided with recesses equipped with recess insulators for fitting the windings of the stator. The winding includes a plurality of phase windings passing through notches in the body and, along with all of the phase windings, forms a front bun and a back bun on both sides of the stator body. The windings are obtained, for example, from continuous wires covered with enamel or from conductive elements in the form of strips (for example pins in the form of "U"), the ends of which are connected to one another, for example by welding.

These phase windings are for example three-phase windings connected in star or delta form, the output of which is connected to at least one electronic rectifier module comprising rectifier elements, such as diodes or transistors.

In addition, the rotor comprises two magnetic wheels. Each magnet wheel has a flange with a transverse orientation, which flange is provided on its outer circumference with claws, for example having a trapezoidal shape and an axial orientation. The claws of one wheel are axially directed towards the flange of the other wheel. Each claw of the magnetic wheel penetrates into a space existing between two adjacent claws of the other magnetic wheel so that the claws of the magnetic wheels are superposed with respect to each other. A cylindrical core is axially inserted between the flanges of the wheel. The core supports on its outer periphery an excitation winding wound in an insulator interposed radially between the core and the winding.

This type of motor is known to emit noise caused by vibrations created by the presence of magnetic forces. This noise is particularly harmful in the low rotational speed range, in particular in the range of 1800 to 4000 rpm. In fact, in addition to this, the aerodynamic noise of the fan is overlaid with the magnetic noise, so that the latter no longer needs to be reduced.

Disclosure of Invention

The object of the present invention is to effectively minimize magnetic noise by proposing a rotor of a rotating electrical machine of a motor vehicle, said rotor comprising:

-at least one magnetic wheel comprising a plurality of claws;

-each jaw comprises a leading edge and a trailing edge extending between the base and the free end of the respective jaw;

-the rotor is characterized in that at least one claw comprises a chamfer formed on the trailing edge, and the ratio of the maximum width of the chamfer to the pole pitch is in the range of 0.16 to 0.37 over the operating speed range.

Thus, by forming this type of chamfer configuration on the trailing edge, the size of the air gap is locally increased, thereby significantly reducing the magnetic force and the resulting noise. A reduction in noise is obtained without reducing the magnetic properties of the motor.

According to one embodiment, the chamfer is formed only on the trailing edge of the claw.

According to one embodiment, the rotor comprises a first magnetic wheel and a second magnetic wheel, and the claws of the first magnetic wheel each comprise a first chamfer associated with a first ratio for a low speed of the operating speed range, and the claws of the second magnetic wheel each comprise a second chamfer associated with a second ratio for a high speed of the operating speed range. The optimum chamfer depends on the rotational speed of the rotor, a configuration of this type making it possible to minimize the magnetic noise in an optimum manner over the entire working range of the rotor.

According to one embodiment, said chamfer is associated with an optimal ratio of the average between a first ratio equal to the low speed of the operating speed range and a second ratio for the high speed of the operating speed range. This therefore defines an alternative claw configuration which can minimise magnetic noise in an optimum manner over the entire operating range of the rotor.

According to one embodiment, the operating speed range is in the range of 1800 to 4000 rpm.

According to one embodiment, the surface area of the chamfer decreases towards the free end of the respective claw.

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

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

According to one embodiment, the chamfer extends axially between the base and the free end of the respective jaw.

According to one embodiment, the radial cross section of the chamfer extends along a straight line.

According to one embodiment, the radial cross-section of the chamfer extends along a circular arc.

According to one embodiment, the claws of the magnetic wheel are symmetrical.

According to one embodiment, the claws of the magnetic wheel are asymmetrical.

According to one embodiment, the rotor comprises inter-pole magnets each positioned within a space separating two consecutive jaws.

The invention also relates to a rotary or reversible electric machine of the alternator type, characterized in that it comprises a rotor as defined previously.

Drawings

The invention will be better understood upon reading the following description and examining the accompanying drawings. These figures are provided purely by way of illustration and in no way limit the invention.

FIG. 1 is a schematic longitudinal cross-sectional view of an alternator according to the present invention;

figures 2a and 2b are schematic side and top views respectively of a claw provided with a chamfered magnetic wheel according to the invention;

FIG. 3 is a graph showing two curves representing the noise level of a three-phase alternator according to the ratio between the maximum chamfer width and the pole pitch, where each curve corresponds to a particular rotational speed of the alternator;

FIG. 4 is a partial schematic view in cross section of a pawl of a magnetic wheel according to the present invention;

figure 5 shows a schematic variant embodiment of the rotor according to the invention, in which the chamfers of the claws have two different configurations from one magnet wheel to the other;

fig. 6 shows a schematic variant embodiment of a rotor with asymmetrical jaws according to the invention.

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

Detailed Description

Fig. 1 shows a compact multiphase alternator 10, particularly for a motor vehicle. The alternator 10 converts mechanical energy into electrical energy and may be reversible. This type of reversible alternator 10, called alternator starter, can convert electrical energy into mechanical energy, in particular for starting the thermal engine of the vehicle.

The alternator 10 includes a housing 11, and inside the housing 11, a claw rotor 12 fitted on a shaft 13, and a stator 16, the stator 16 surrounding the rotor 12 with an air gap 17. The pulley 14 is fixed to the shaft. This pulley belongs to the means for transmitting the motion through the belt between the alternator 10 and the thermal 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 set of plates provided with recesses, for example of the semi-closed type, equipped with recess insulators for the phases of the stator 16. Each phase includes at least one winding that passes through a notch in the body 19 of the stator 16 and, along with all phases, forms a front bun 20 and a back bun 21 on both sides of the stator body 19.

The windings are obtained, for example, from continuous wires covered with enamel or from conductive elements, for example in the form of bars of pins, connected to one another, for example by welding. These windings are, for example, three-phase windings connected in star or delta form, the output of which is connected to at least one rectifier bridge comprising rectifier elements such as diodes or MOSFET type transistors, in particular when referring to an alternator starter as described, for example, in document FR 2745445.

The rotor 12 comprises two

magnet wheels

24, 25, each having a flange 28 with a transverse orientation, which flange 28 is provided on its outer circumference with claws 29, the claws 29 having, for example, a trapezoidal form and an axial orientation. The claws 29 of one

wheel

24, 25 are axially directed towards the flange 28 of the other wheel. Each jaw 29 of a

magnetic wheel

24, 25 penetrates into the space existing between two adjacent jaws 29 of the other magnetic wheel, so that the jaws 29 of the

magnetic wheels

24, 25 are superposed with respect to each other.

The outer circumference of the claws 29 together with the inner circumference of the main body 19 of the stator 16 define the air gap 17 between the stator 16 and the rotor 12. The inner circumference of the claw 29 is inclined so that the claw 29 is thinner at its free end 54 side, as shown in fig. 2 a.

A cylindrical core 30 is axially inserted 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. The core 30 supports, on its outer periphery, an excitation coil 31 wound in an insulator interposed radially between the core 30 and the coil 31.

In addition, the housing 11 includes a front bearing 35 and a rear bearing 36 assembled together. The

bearings

35, 36 have a hollow form and each centrally supports a

ball bearing

37, 38 for rotational engagement with the shaft 13 of the rotor. The rear bearing 36 supports a brush holder 40 provided with brushes 41 designed as rings 44 of triboelectric collectors 45, which are connected to the field winding 31 by a wired connection. The brushes 41 are electrically connected to a voltage regulator fitted on the outside of the motor.

The front and

rear bearings

35, 36 comprise substantially lateral front and

rear openings

60, 61 for cooling the alternator 10 by the circulation of air formed by the rotation of one 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. Front side opening 60 and rear side opening 61 are opposite front bun 20 and rear bun 21, respectively.

As can be seen in fig. 2b, each jaw 29, which has a trapezoidal form, comprises a leading edge 51, which leading edge 51 is first in contact with the air according to the direction of rotation of the rotor 12 indicated by the arrow SR, and a trailing edge 52 located on the opposite side with respect to the leading edge 51. These rims 51, 52 extend between a base 53 of the claw 29 (which partially coincides with the periphery of the respective flange 28) and a free end 54 of the claw 29.

In this case, a chamfer 57 is formed on the rear edge 52 of each claw 29 of the

magnet wheels

24, 25. As a variant, chamfers 57 are formed only on some of the claws 29 of the

magnetic wheels

24, 25. In each case, a chamfer 57 is formed on the outer radial surface 56 of the respective jaw 29. Chamfer 57 preferably extends axially between base 53 and free end 54 of respective jaw 29, i.e. along the entire axial length of jaw 29.

The chamfer 57 is in particular defined by two lateral sides 58, 59, the two lateral sides 58, 59 being connected at the free end 54 of the pawl 29. Thus, the surface area of the chamfer 57 having an overall triangular shape decreases towards the free end 54 of the pawl. The surface area of chamfer 57 at free end 54 of pawl 29 is substantially zero.

The ratio R between the maximum width Chb _ max of the chamfer 57 and the pole pitch Tp is defined, i.e. R Chb _ max/Tp. The pole pitch Tp is equal to the ratio of the stator inner circumference to the machine pole count, i.e. Tp ═ pi D/2p, where D is the stator inner diameter and p is the machine pole count in pairs.

The maximum width Chb _ max is measured in the circumferential direction, i.e. in a direction parallel to the direction in which the flange 28 of the

respective magnet wheel

24, 25 extends. Each chamfer 57 may have a flat form, i.e. the radial cross section of the chamfer 57 extends along a straight line.

Alternatively, chamfer 57 has a radial cross-section extending along a circular arc, i.e. chamfer 57 has corners rounded according to 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 jaws 29 and tangent to the rounded portion and the intersection between the flat portion 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 pawl 29 is for example in the range 60 ° to 78 °.

As shown by the curve in fig. 3, for a range P of operating speeds between 1800 and 4000rpm, the optimum ratio R is in the range 0.16 to 0.37 in terms of noise reduction. It should be noted that the aforementioned operating ranges do not correspond to the minimum and maximum operating speeds of the alternator, but to speed ranges having a significant level and in which the magnetic noise, not covered by the aerodynamic noise of the fan, must be attenuated.

Preferably, chamfer 57 is formed only on trailing edge 52 of pawl 29. In fact, it has been shown that forming chamfers 57 on the leading and trailing edges 51, 52 of each jaw 29 has the effect of reducing the magnetic performance of the motor.

Since the optimum chamfer 57 depends on the rotational speed of the rotor 12, the claws 29 of one of the magnet wheels 24 may each have a first chamfer 57, the first chamfer 57 having a maximum width chb _ max1 associated with a first ratio R1 which is optimum for low speeds of the operating speed range in terms of noise reduction. The ratio R1 is for example 0.17 for 1800 rpm. The claws 29 of the other magnet wheel 25 may each have a second chamfer 57' with a width chb _ max2 associated with a second ratio R2 which is optimal for high speeds of the operating speed range in terms of noise reduction. For 4000rpm, the ratio R2 is, for example, 0.36. In fig. 5, the respective rotor 12 is shown with chamfers 57, 57' that differ from one magnet wheel 24 to the other magnet wheel 25.

As shown in the table below, this type of configuration makes it possible to minimize the magnetic noise in an optimal manner over the entire operating range P of the rotor 12. In fact, it appears that an average acoustic power reduction of about 1.5dB is obtained compared to the optimal chamfer configuration for low speeds of the operating speed range P, and an average acoustic power reduction of about 2.6dB is obtained compared to the optimal chamfer configuration for high speeds of the operating speed range P.

Alternatively, the chamfer 57 formed on each claw 29 is associated with a ratio Rmoy equal to the average between a first ratio R1 for low speeds of the operating speed range P and a second ratio R2 for high speeds of the operating speed range P. Thus, in the previous example, Rmoy ═ (0.15+0.27)/2 ═ 0.26.

In an example of embodiment, the claws 29 of the

magnet wheels

24, 25 are symmetrical, i.e. the centre line M passes through the centre of the base 53 and also through the free end 54 of the claw 29 (see fig. 2 b).

As a variant, as shown in fig. 6, the jaws 29 of the

magnetic wheels

24, 25 are asymmetrical, i.e. the median line M passing through the centre of the base 53 of the jaw 29 is offset with respect to a parallel straight line passing through the free end 54 of the respective jaw 29. The asymmetrical claw 29 may be inclined in the rotational direction SR (see arrow F1) or in the opposite direction to the rotational direction SR (see arrow F2). As shown in fig. 6, the claws 29 of the two

magnet wheels

24, 25 may be inclined in the same direction or in opposite directions.

If appropriate, the rotor 12 may include inter-pole magnets 46 as shown in fig. 5 and 6, each located in a space 66 separating two successive claws 29. The magnets 46 may be located within all of the inter-pole spaces 66, or only some of them, and are regularly distributed around the circumference of the rotor 12. The magnet 46 may be made of the rare earth NeFeB (neodymium iron boron) or SmCo (samarium cobalt). The choice of material and the number of inter-pole magnets 46 is such that the magnetic properties of the rotor 12 can be readily adapted to the desired power of the alternator.

It is understood that the foregoing description is provided purely by way of illustration and does not limit the field of the invention, which does not constitute a departure from the field of the invention by replacing various elements with any other equivalent.

Claims

1. A rotor (12) of a rotating electrical machine of a motor vehicle, comprising:

-at least one magnetic wheel (24, 25) comprising a plurality of claws (29);

-each jaw (29) comprises a leading edge (51) and a trailing edge (52) extending between the base (53) and the free end (54) of the respective jaw (29);

-the rotor (12) being characterized in that at least one claw (29) comprises a chamfer (57) formed on the trailing edge (52), and in that in the operating speed range (P) in the range 1800 to 4000rpm, the ratio of the maximum width of the chamfer (57) to the pole pitch (Tp) is in the range 0.16 to 0.37.

2. The rotor as recited in claim 1, characterized in that chamfers (57) are formed only on the trailing edges (52) of the claws (29).

3. Rotor according to claim 1 or 2, characterized in that it comprises a first magnetic wheel (24) and a second magnetic wheel (25), and in that the pawls (29) of the first magnetic wheel (24) each comprise a first chamfer (57) associated with a first ratio (R1) for low speeds of the operating speed range (P), and in that the pawls (29) of the second magnetic wheel (25) each comprise a second chamfer (57') associated with a second ratio (R2) for high speeds of the operating speed range (P).

4. The rotor according to claim 1 or 2, characterized in that the chamfer (57) is associated with an optimal ratio equal to the average between a first ratio (R1) for a low speed of 1800rpm for the operating speed range and a second ratio (R2) for a high speed of 4000rpm for the operating speed range.

5. The rotor as recited in claim 1, characterized in that the surface area of the chamfer (57) decreases towards the free end (54) of the respective claw (29).

6. A rotor according to claim 5, characterized in that the surface area of the chamfer (57) is substantially zero at the free end (54) of the claw (29).

7. The rotor according to claim 1, characterized in that the jaws (29) have an outer radial surface (56) and the chamfer (57) is formed on the outer radial surface (56).

8. The rotor according to claim 1, characterized in that the chamfer (57) extends axially between the base (53) and the free end (54) of the respective claw (29).

9. The rotor as recited in claim 1, characterized in that the radial cross section of the chamfer (57) extends along a straight line.

10. The rotor as recited in claim 1, characterized in that the radial cross section of the chamfer (57) extends along a circular arc.

11. The rotor according to claim 1, characterized in that the claws (29) of the magnet wheels (24, 25) are symmetrical.

12. The rotor according to claim 1, characterized in that the claws (29) of the magnet wheels (24, 25) are asymmetrical.

13. The rotor according to claim 1, characterized in that it comprises interpolar magnets (46) each located in a space separating two consecutive jaws (29).

14. A rotating electric machine of the alternator or inverter type, characterized in that it comprises a rotor (12) as defined in any one of the preceding claims.