WO2006111657A1

WO2006111657A1 - Alternator comprising an antifriction bearing having a fastening collar

Info

Publication number: WO2006111657A1
Application number: PCT/FR2006/000868
Authority: WO
Inventors: James Perillat; Bernard Chaudier; Christophe Nicot
Original assignee: S.N.R. Roulements
Priority date: 2005-04-22
Filing date: 2006-04-20
Publication date: 2006-10-26
Also published as: DE112006001010T5; FR2884979A1; FR2884979B1

Abstract

The invention relates to an electrical machine, particularly an alternator, comprising a casing (1) housing a stator (2) in which a rotor (3) is rotationally mounted by means of an antifriction bearing whose outer ring (6) is fixed to the casing (1), and the inner ring (7) is fixed to the rotor (3). Said machine comprises a means (5) for transmitting a mechanical torque that is fixed to the rotor (3) outside the casing (1), in which the outer ring (6) comprises a radial collar (9), said collar being provided with a means for fastening the ring to the casing (1).

Description

Alternator comprising a clamping flange bearing

The invention relates to an electric machine comprising a stator in which a rotor is mounted, said rotor being secured to a means for transmitting a mechanical torque.

Such an electric machine can function as a current generator by transforming mechanical energy into electrical energy. In particular, such a generator may be an alternator for example for a motor vehicle. The invention also applies to electric motor machines that convert electrical energy into mechanical energy, or to an electric machine that can function as a generator and as a motor.

In known manner, such an electric machine comprises a bearing provided near the transmission means so as to ensure the guiding of the rotation of the rotor. The outer race of the bearing is then secured to the housing housing the stator. To ensure this connection, it has been proposed to fit the outer ring in a housing of the housing and axially fix said bearing by screwing a stop member into the housing. In particular, this embodiment requires that the screwing is performed close to the outer ring so that the stop member bears on the bearing.

This achievement is not satisfactory because, under conditions of use such as those experienced by alternators of a motor vehicle (mechanical torque, temperature, vibration, ...), there is a life of the bearing which is insufficient. In particular, spalling of the outer ring of the bearing tends to appear prematurely, which is probably partly due to deformation of the outer ring during screwing.

In particular, the invention proposes an electric machine whose mounting of the bearing allows a service life of it which is improved. The invention also aims to propose an electric machine presenting alone or in combination of the following advantageous characteristics with respect to the prior art:

the cooling is ensured in an improved manner;

- disassembly of the rotor is simplified; axial size is reduced;

- The spill torque of the transmission means on the bearing is reduced;

- the number of pieces is reduced;

- The realization of the housing is simplified and requires less material.

For this purpose, the invention proposes an electric machine comprising a casing housing a stator in which a rotor is rotatably mounted by means of a bearing whose outer ring is integral with the casing and the inner ring is secured to the rotor, said machine comprising means for transmitting a mechanical torque which is secured to the rotor outside the housing, wherein the outer ring comprises a radial flange, said flange being provided with means for fixing the ring to the housing.

Other objects and advantages of the invention will become apparent from the following description, made with reference to the appended drawings, in which:

- Figure 1 is a partial longitudinal sectional view of an alternator showing the mounting of the rotor on the housing by means of a bearing according to a first embodiment; Figure 2 is a perspective view of the part of the alternator according to Figure 1;

- Figure 3 is a partial longitudinal sectional view of an alternator showing the mounting of the rotor on the housing by means of a bearing according to a second embodiment; Figure 4 is a perspective view of the part of the alternator according to Figure 3; - Figures 5 and 6 are similar figures respectively to Figures 3 and 4 for a variant of the second embodiment;

- Figure 7 is a partial longitudinal sectional view of an alternator showing the mounting of the rotor on the housing by means of a bearing according to a third embodiment; FIG. 8 is a perspective view of the portion of the alternator according to FIG. 7.

In connection with the figures, there is described an alternator for a motor vehicle without however that the invention is limited to this type of electric machine. Indeed, the invention finds application in all types of machines such as a current generator for converting mechanical energy into electrical energy and / or such as a motor transforming electrical energy into mechanical energy.

An alternator comprises, in a known manner, a casing 1 housing a stator 2 forming an armature in which a rotor 3 is rotatably mounted forming an inductor so that, by rotation of said rotor, an alternating electric current is produced. The casing 1 is conventionally made of aluminum and includes openings allowing air circulation for cooling. In addition, to improve the air cooling, a cooling fin 4 is secured to the rotor 3 inside the casing 1.

To drive the rotation of the rotor 3, a means for transmitting a mechanical torque is secured to the rotor 3 outside the casing 1. In the embodiments shown, the transmission means is formed of a pulley 5 which comprises a rim 5a arranged to carry a belt, said belt being rotated by the engine of the motor vehicle.

To guide the rotor 3 in rotation in the casing 1, a bearing is provided, said bearing comprising a fixed outer ring 6 which is integral with the casing 1 close to the pulley 5 and a rotating inner ring 7 fitted on the rotor 3. In known manner, a second bearing (not shown) is also provided for, at a distance from the pulley 5, guiding the rotation of the rotor 3 in the casing 1.

The two rings 6, 7 are each provided with a rolling track disposed opposite to form a raceway in which rolling bodies 8 are arranged to allow the relative rotation of said rings. Alternatively, one can provide other types of bearings, including several rows of rolling bodies and / or rolling bodies of different geometry.

When using the alternator, the bearing is subjected to mechanical stresses (torque transmitted, acyclism, vibrations, ...) and thermal (operating temperature up to 160 ^° C) which, in the assemblies of the prior art, lead to a significant limitation of the life of said bearing.

To solve this problem, the invention mainly proposes to postpone the attachment of the bearing on the casing 1 away from the raceway. Thus, a limitation of the mechanical fastening stresses is obtained at the level of the race where the mechanical rotational stresses apply mainly. To do this, the outer ring 6 comprises a radial flange 9 which is provided with means for fixing the ring 6 to the casing 1.

In the embodiments described, the fastening flange 9 comprises four radial tabs 10 equidistributed angularly fixing means. The end part of the lugs 10 is provided with an axial fixing orifice 11 in which a screw or a dowel is intended to be introduced. In addition, the housing 1 comprises an axial opening 12 in which the flange 9 is disposed. More particularly, the opening 12 comprises four internal projections 13 extending from the front face of the periphery of said opening. The projections 13 each comprise a front support zone 14 for the rear face of a lug 10, said projections comprising an axial orifice 15 arranged to receive the fixing screw or bolt. In a variant, provision may be made for the lugs 10 to be arranged so that their front face bears on a rear support zone of respectively a projection 13.

This embodiment makes it possible, in particular by providing that the cooling fin 4 is arranged opposite the opening 12, to improve cooling by circulation of air in the spaces of the opening 12 which are left free between the legs 10. In particular, this limits the dilatation differential between the casing 1 and the bearing, which also contributes to increasing the life of said bearing. According to one embodiment, it is possible to have a perforated protection member inside the opening 12 so as to prevent the accidental introduction of foreign bodies into the casing 1.

In addition, the casing 1 according to the invention is simpler to produce and requires less material, which is advantageous from a cost and weight point of view. In addition, the fixing of the bearing requires a reduced number of parts, which also simplifies the assembly and limits the weight of the alternator.

According to the invention, it is also possible to modulate the rigidity of the fastening of the bearing on the casing 1, in particular by providing stiffening ribs on the flange 9 and / or on the lugs 10, which contributes to the mechanical strength without complicating the embodiment of the casing 1. In addition, it solves the problem of the lack of rigidity of the casing 1 when it is made of weakly rigid material such as aluminum.

In the first two embodiments shown in Figures 1 to 6, the outer ring 6 is made of sheet metal in particular stamped and the inner ring 7 is a solid annular piece, for example obtained by forging and machining. A running track is formed on the outer surface of the inner ring 7. The outer ring 6 comprises a generally axial portion 6a comprising the raceway and an extension 6b extending generally radially from the axial portion 6a, said radial portion forming the fastening flange 9.

In the embodiments shown in relation to the first two modes, the fixing lug 10 comprises an axi-radial portion 10a extending from the flange 9 and a radial portion 10b comprising the fixing orifice 11, this geometry being obtainable from particularly advantageous manner because of the use of a ring 6 stamped sheet. This embodiment makes it possible, by axially shifting the fixing of the bearing relative to the raceway, to reduce the axial space requirement. In particular, the plane P1 containing the rear lateral face of the pulley 5 is shifted axially inwards by relative to the plane P2 containing the front lateral face of the casing 1, namely the plane P2 containing the front faces of the projections 13.

In addition, a reduction of the axial distance X2 is obtained between the median plane of the pulley 5 of that of the raceway, which limits the spill torque on the bearing, and therefore limits the mechanical stresses experienced by said bearing when the rotation of the rotor 3. Furthermore, the inner ring 7 is fitted on the rotor 3 by providing a rear spacer 16.

In the first embodiment (Figures 1 and 2), the pulley 5 is mounted on the rotor 3 by means of a flange 17 fitted on the rotor 3 against the front face of the inner ring 6, said flange being secured in the bore of the rim 5a. In an exemplary embodiment, the pulley 5 is overmolded on the flange 17, or clipped into a groove provided for this purpose on the bore.

In the second embodiment (FIGS. 3 to 6), the pulley 5 is made in one piece with the inner ring 7, which further limits the number of parts to be assembled. To do this, the inner ring 7 comprises an axial annular portion 7a comprising the raceway, and a radial extension 7b on which is formed the rim 5a.

Alternatively shown in Figures 5 and 6, the inner diameter Y1 of the housing opening at the projections 13 is set at a value greater than the outer diameter Y2 of the rotor 3 at the inductor. In this variant, the length of the lugs 10 is also increased, in particular at the radial portion 10b, so as to ensure attachment to the projections 13. Thus, it is possible to assemble / disassemble the assembly pulley - bearing - rotor by fixing / disconnecting the bearing and the casing 1, which simplifies the realization of the alternator and allows in particular a standard exchange of all only.

The third embodiment (FIGS. 7 and 8) provides for the outer ring 6 to comprise a solid annular piece on which the fastening flange 9, for example made of plastic material, is overmolded. The pulley 5 is fitted on the rotor 3 with its central portion 18 bearing on the front face of the inner ring 7. This embodiment provides the advantages mentioned above while maintaining a standard bearing comprising massive rings.

In the embodiments of FIGS. 1 and 7, the seal of the bearing is ensured on both sides of the running space by the arrangement of respectively a seal 19 between the rings 6, 7. These seals 19 are of conventional structure, that is to say comprising an armature of association with a ring and a sealing lip in rubbing contact on the other ring or on an armature associated with the other ring.

In the embodiments of FIGS. 3 and 5, the integration of the pulley 5 with the inner ring 7 makes it possible to provide a seal 20 which is associated with the outer ring 6 and whose sealing lip comes into contact. rubbing on the rear face of the radial extension 7b. On the other side of the running space a conventional seal 19 is provided between the rings 6, 7.

Claims

Electric machine comprising a housing (1) housing a stator (2) in which a rotor (3) is rotatably mounted by means of a bearing whose outer ring (6) is integral with the housing (1) and the ring interior (7) is integral with the rotor (3), said machine comprising means for transmitting a mechanical torque (5) which is secured to the rotor (3) outside the housing (1), said machine being characterized in the outer ring (6) comprises a radial flange (9), said flange being provided with means for fixing the ring to the casing (1).

2. Electrical machine according to claim 1, characterized in that the fastening means comprises at least one radial lug (10) whose end portion is provided with an axial fixing hole (11).

3. Electrical machine according to claim 1 or 2, characterized in that the housing (1) comprises an axial opening (12) in which the flange (9) is disposed.

4. Electrical machine according to claim 3, characterized in that the opening (12) comprises internal projections (13) on which the fixing is carried out.

5. Electrical machine according to claim 3 or 4, characterized in that the inner diameter (Y1) of the opening (12) is greater than the outer diameter (Y2) of the rotor (3).

6. Electrical machine according to any one of claims 3 to 5, characterized in that it further comprises a cooling fin (4) which is secured to the rotor (3) facing the opening (12).

7. Electrical machine according to any one of claims 1 to 6, characterized in that the outer ring (6) comprises an annular piece on which the fixing flange (9) is overmolded.

8. Electrical machine according to claim 1 to 6, characterized in that the outer ring (6) is made of sheet metal, said ring comprising a generally axial portion (6a) having a rolling track and an extension (6b) extending generally radially from the axial portion (6a), said radial portion forming the fastening flange (9).

9. Electrical machine according to claims 2 and 8, characterized in that a fixing lug (10) comprises an axi-radial portion (10a) and a radial portion (10b) comprising the fixing hole (11).

10. Electrical machine according to claim 9, characterized in that the plane (P1) containing the rear side face of the transmission means is axially offset inwardly relative to the plane (P2) containing the front side face of the housing (1). ).

11. Electrical machine according to any one of claims 1 to 10, characterized in that the transmission means comprises a pulley (5).

12. Electrical machine according to claim 11, characterized in that the pulley (5) is formed in one piece with the inner ring (7).

13. Electrical machine according to any one of claims 1 to 12, characterized in that it forms alternator, in particular for a motor vehicle.