EP0921307B1 - Starter for automotive vehicle with gear reductor comprising an impact limiting device - Google Patents

Description

The present invention relates to a starter for motor vehicle.

The invention relates more particularly to a starter of the type comprising an electric motor of which the output shaft rotates a coaxial launcher with interposition of a gear reducer, in particular of the type with planetary gear.

In order to limit the value of the maximum torque transmissible between the output shaft of the electric motor and the launcher shaft, it is known to provide a device for torque limitation.

To this end, it has already been proposed, for example in the document JP-A-06.078.495, a starter whose train epicyclic has a cylindrical housing inside which the crown, toothed internally, is rotatably mounted and of the type in which the crown is linked in rotation to the case by means of a friction torque limiting device axially interposed between the crown and a lateral flange of the housing.

In this document, the friction device includes a annular friction disc which is rotatably linked to the crown and which is in axial abutment against the internal face of one of the flanges of the case against which the friction disc is stressed axially by a frustoconical elastic washer.

This design therefore calls for at least two additional components, compared to a train epicyclic without torque limiting device, i.e. the friction washer and elastic frustoconical washer.

In addition to this large number of components, the design proposed in this document complicates the planetary gear crown design, increases the axial size of the planetary gear and makes particularly complex the assembly operations of different components.

According to another conception, and always in order to reduce the strong mechanical overloads transmitted to starter rotating parts, which result from sudden variations in speed (s) occurring during the starting due to sudden engine slowdowns which may occur following the first explosions too far ahead of shifting to top dead center pistons, it has also been proposed to associate with a gear reducer epicyclic one or more shock absorbers made up of blocks of rubber which stop in rotation the external crown gear train. This solution is however bulky, requires additional components and causes a significant additional cost while complicating the assembly operations of the components of the reducer and / or starter.

The object of the invention is to propose a new design of a starter of the type mentioned previously which remedies the disadvantages which have just been mentioned.

To this end, the invention provides a starter for motor vehicle of the type comprising a housing in which is arranged an electric motor whose output shaft drives in rotation a coaxial launcher with the interposition of a reducer having an internally toothed crown which is mounted in a housing cavity in which it is immobilized in rotation and which comprises an annular skirt cylindrical toothed internally closed at one of its axial ends by a radial wall pierced at its center for the passage of a gearbox output shaft, the crown toothed comprising an elastically deformable zone in twist which is arranged at one of the axial ends of the internally toothed skirt to intervene between the latter and an adjacent part of the crown comprising means for immobilizing the crown in rotation in its cavity, characterized in that the deformable zone elastically consists of a series of link arms elastically deformable, of substantially axial orientation, which connect the axial end of the toothed skirt to the part adjacent to the ring gear comprising the means immobilization in rotation.

• les bras de liaison sont répartis angulairement de manière régulière autour de l'axe de la couronne ;
• deux bras de liaison adjacents sont séparés par un évidement formé au moins en partie dans l'épaisseur radiale d'une portion d'extrémité axiale de la jupe dentée intérieurement ;
• l'évidement traverse radialement la portion d'extrémité axiale de la jupe dentée intérieurement :
• la zone déformable élastiquement est agencée à l'extrémité axiale de la jupe dentée intérieurement qui est fermée par la paroi radiale ;
• l'évidement s'étend axialement dans la paroi radiale ;
• les moyens d'immobilisation en rotation de la couronne dentée dans sa cavité comporte au moins un ergot porté par la couronne qui est reçu dans un logement complémentaire du boítier ;
• l'ergot s'étend axialement à partir de la face externe de la cloison radiale de la couronne ;
• le réducteur est du type à train épicycloïdal.

According to other characteristics of the invention:

• the link arms are distributed angularly in a regular manner around the axis of the crown;
• two adjacent link arms are separated by a recess formed at least in part in the radial thickness of an axial end portion of the internally toothed skirt;
• the recess crosses radially the axial end portion of the toothed skirt internally:
• the elastically deformable zone is arranged at the axial end of the internally toothed skirt which is closed by the radial wall;
• the recess extends axially in the radial wall;
• the means for immobilizing the toothed crown in rotation in its cavity comprises at least one lug carried by the crown which is received in a complementary housing of the housing;
• the lug extends axially from the external face of the radial partition of the crown;
• the reduction gear is of the planetary gear type.

• La figure 1 est une vue en section axiale partielle du moteur électrique d'un démarreur associé à son train épicycloïdal comportant un dispositif limiteur de couple réalisé conformément aux enseignements de l'invention ;
• la figure 2 est une vue en section axiale et à plus grande échelle de la couronne dentée du réducteur à engrenages du démarreur de la figure 1 ; et
• la figure 3 est une vue en perspective de la couronne dentée de la figure 2.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

• Figure 1 is a partial axial sectional view of the electric motor of a starter associated with its planetary gear comprising a torque limiting device produced in accordance with the teachings of the invention;
• Figure 2 is an axial section on a larger scale of the ring gear of the gear reducer of the starter of Figure 1; and
• FIG. 3 is a perspective view of the toothed ring of FIG. 2.

Part 1 of a motor vehicle starter 10 of the type comprising a electric motor 12 whose rotor 14 is mounted rotating, around an axis X-X inside a rear part 16 of the starter housing which is completed by a front part 18 hood-shaped.

The upper part (not shown in detail) of the starter 10 includes an electromagnetic contactor which, by means of a fork 20 in the form of a fork, acts known manner on a launcher 22 which is slidably mounted on a starter shaft 24 coaxial with the output shaft 26 of the engine electric 12.

The output shaft 26 of the electric motor 12, linked at rotation to rotor 14, projects axially forwards beyond of the front face 28 of the stator 30 and it rotates a pinion 32 which is the sun pinion of a planetary gear train 34 which constitutes a gear reducer interposed between the shaft 26 and the starter shaft 24.

The sun gear 32 cooperates with the pinions planetary gears 34 satellites 34 which are rotatably mounted around axes 38 which are carried by a radial plate 40 planet carrier which is linked in rotation to the output shaft 42 of the reducer 34 which is a hollow shaft inside which is received the rear splined end (not shown) of the shaft launcher 24 for the rotational drive of the latter by the output shaft 42.

The planetary gear 34 also includes a crown 44 internally toothed inside which mesh the satellites 36 and which is immobilized in rotation relative to the starter housing 10.

The toothed crown 44, produced in accordance with lessons of the invention, consists essentially of by a cylindrical annular skirt 46 which is open axially at its rear end 48 and whose front end is closed by a radial wall 50 which is pierced in its center of a hole 52 in which, the rotation shaft is mounted exit 42.

The peripheral surface 56 of the skirt 46 is a cylindrical surface and the ring gear 44 is received in a complementary hollow cylindrical cavity 58 formed in the cover 18 of the starter housing 10 and which is open axially backwards to allow axial insertion, from right to left considering figure 1, from ring gear 44 in the cavity 58, the latter being axially delimited by a radial shoulder 60.

The internal cylindrical surface of the skirt 46 is toothed and it has for this purpose a series of teeth 62 which extend over the entire axial length of the internal surface toothed 61, that is to say notably substantially to the bottom of the ring gear 44 formed by the internal radial face 64 of the wall 50.

In accordance with the teachings of the invention, and in order to constitute an elastically deformable zone 66 in torsion, the front axial end portion of the skirt 46 comprises a series of recesses 70 distributed angularly from evenly around the X-X axis of the ring gear 44.

The recesses 70, which pass radially through in part the thickness of the material constituting the skirt 46, define between them as many link arms 72 each of which extends axially to connect the skirt 46 to the radial wall of background 50.

The set of arms 72 constitutes the zone 66 elastically deformable in torsion, i.e. their elastic deformation allows, by transverse bending arms 72, to generally rotate the skirt 46 by relative to the wall 50.

The ring gear 44 is linked in rotation to the housing 10 by a series of lugs 74, here three in number, of which each extends axially forward from the face external radial 76 of the wall 50.

The cylindrical upper face 78 of each lug 74 is in the extension of the external cylindrical face 56 of the skirt 46 and each lug 74 is received in a housing complementary formed in the bottom shoulder 60 of the cavity 58.

As we can see in particular in Figure 2, each recess 70 extends axially towards the rear in the bottom wall 50 to open into the front radial face 76 of the latter, the recess being delimited radially towards the interior by an interior edge 75.

When the ring gear 44 is in position in the cover 18 of the starter housing as illustrated in Figure 1, it is generally immobilized in rotation by the lugs 74.

However, due to the presence of the area deformable 66, the toothed skirt 46 can rotate relative to the wall 50 and therefore relative to the housing.

According to the invention, the starter 10 thus comprises elastic damping means in twist arranged at the gear reducer 34 which do not use any additional components compared to a starter fitted with a conventional planetary gear, only the gear design being changed in accordance with the teachings of the invention.

The invention is not limited to the case of a reduction gear with planetary gear but also found to apply in other case, for example when the reduction gear 34 is a gear offset gears with a ring gear internally.

Claims (9)

1. Motor vehicle starter (10) of the type comprising a casing (18) in which there is arranged an electric motor (12) whose output shaft (26) drives a coaxial starter head (22) with the interposing of a reduction gear (34) comprising an internally toothed ring (44), which is mounted in a cavity (58) in the casing in which it is immobilised in rotation and which comprises a cylindrical annular skirt (46) toothed internally and closed at one of its axial ends by a radial wall (50) pierced at its centre for the passage of an output shaft (42) of the reducing gear, the toothed ring (44) comprising a zone (66) which is elastically deformable under torsion and which is arranged at one of the axial ends of the internally toothed skirt (46) in order to act between the latter and an adjacent part of the ring comprising means (74) for the rotational immobilisation of the ring (44) in its cavity (58), characterised in that the elastically deformable zone consists of a series of elastically deformable connecting arms (72), substantially axial in orientation, which connect the axial end of the toothed skirt (46) to the adjacent part (50) of the toothed ring (44) comprising the means (74) of immobilising in rotation.
2. Starter according to Claim 1, characterised in that the connecting arms (72) are angularly distributed in a regular manner around the axis (X-X) of the ring.
3. Starter according to Claim 2, characterised in that two adjacent connecting arms (72) are separated by a recess (70) formed at least partly in the radial thickness of an axial end portion of the internally toothed skirt (46).
4. Starter according to Claim 3, characterised in that the said recess passes radially through the axial end portion of the internally toothed skirt.
5. Starter according to any one of the preceding claims, characterised in that the elastically deformable zone (66, 70, 72) is arranged at the axial end of the internally toothed skirt which is closed by the radial wall (50).
6. Starter according to Claim 5 taken in combination with one of Claims 3 or 4, characterised in that the said recess (70) extends axially in the radial wall (50).
7. Starter according to any one of the preceding claims, characterised in that the means for rotational immobilisation of the toothed ring in its cavity comprise at least one toe (74) carried by the ring (44) which is received in a complementary housing (60) in the casing.
8. Starter according to Claim 7, characterised in that the toe (74) extends axially from the external face (76) of the radial partition (50) of the ring (44).
9. Starter according to any one of the preceding claims, characterised in that the reducing gear (34) is of the epicyclic train type.

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