EP0924425B1 - Starter for automotive vehicle comprising an improved pinion - Google Patents

Description

The present invention relates to a starter for a motor with motor vehicle combustion.

The invention relates more particularly to a starter of the type comprising an electric motor, the motor shaft of which is provided with helical grooves for the rotational drive of a coach, in the form of a drive sleeve, belonging to a launcher which can slide axially on the motor shaft, between a rear position of rest and a position before engagement of a starter pinion with a crown gear of the flywheel of the combustion engine, and of the type in which the starter pinion is axially coupled to the socket drive to which it is linked in rotation by a device allowing rotation of the drive sleeve relative to the starter pinion when the starter rotation speed is greater than that of the drive sleeve.

In conventional starters, it is a freewheel which is interposed between the starter pinion and the bushing drive. The main function of this freewheel is to prevent, when the engine starts, the pinion of the coach drives the electric starter motor at too high a speed likely to damage the latter.

The roller freewheel device also dampens the sudden vibrations of the torque which is transmitted between the socket and the pinion of the starter.

This type of freewheel with rollers is very efficient, in particular when the excessive speed of the pinion in relation to the bush training lasts for a long time, which happens especially when the driver does not cut the power to the starter immediately after starting the engine.

The latter phenomenon is all the more frequent as passenger compartments of modern vehicles are increasingly isolated from the point from an acoustic point of view, this soundproofing harming the perception by the conductor of the engine starting which is generally done by auditory detection of variations in engine noise.

New electronically controlled starters include means for detecting the starting of the heat engine and starter switch command to cause the return of the launcher to its rest position by means of the control on which the contactor acts.

These starters thus use electronic modules of control of their electric motor which allow to cut automatically supply the electric motor to the starter and simultaneously return the coach to its rear position of rest in which the starter pinion is no longer meshed with the flywheel of inertia of the heat engine.

The "freewheeling" operating phase is thus extremely short duration and it is independent of the time of vehicle driver reaction.

A freewheel of known design, in particular of the type with pebbles, is then oversized compared to its use, that is to say especially in relation to the short duration of his intervention.

Such a freewheel is therefore too bulky, too heavy and of a cost too high compared to its use.

It has already been proposed to completely remove the presence of a freewheel device, but by removing this freewheel, we also eliminates the shock absorption function, to the detriment the mechanical strength of the starter and its operating noise which results in particular from the fact that the resistive torque imposed by the engine varies significantly over a revolution of the crankshaft due to the cyclic compression efforts of the gases present in the engine cylinders.

The document FR 2066173 also proposes a design inertia launcher in which the coupling ring has a conical rim whose section decreases towards the coach, circumference on which commits, during the start-up process, the enlarged cone-shaped coach attacking the ring elastic coupling. In this device, a compression spring leans against the pinion and against the stop ring fixed on the shaft armature.

However, it can be seen in this conception that the spring of compression plays a double role: to prestress the two cones and ensuring the return to rest of the launcher and its maintenance at rest. From this in the working position, the spring develops a maximum force which increases the residual torque during freewheeling while it would need a weak force not to transmit an overspeed excessive at armature.

The object of the invention is to remedy the drawbacks which have just been mentioned by proposing a starter for a motor with motor vehicle combustion of the type in which the pinion launcher is linked in rotation to the drive sleeve by a device allowing rotation of the drive sleeve relative to the starter pinion when the starter rotation speed is higher than that of the drive sleeve, characterized in that the device interposed between the drive sleeve and the pinion launcher has two front and rear friction surfaces complementary, carried respectively by the starter pinion and the drive sleeve, in that the starter pinion is mounted movable axially with respect to the drive bushing to which it is coupled, and in that the two friction surfaces are stressed elastically in contact with each other by a valuable effort predetermined, so that the drive sleeve can slide in rotation relative to the starter pinion when the speed of rotation of the latter is greater than that of the socket drive.

• les surfaces de frottement sont deux surfaces tronconiques complémentaires ;
• la surface tronconique arrière de frottement est convexe et s'étend axialement vers l'arrière depuis l'extrémité avant de la douille d'entraínement, et la surface avant de frottement est concave complémentaire et s'étend axialement vers l'avant depuis l'extrémité arrière du pignon de lanceur ;
• le diamètre moyen des surfaces de frottement est sensiblement égal au diamètre du cylindre primitif du pignon de lanceur ;
• l'une au moins des deux surfaces de frottement est revêtue d'une garniture de friction ;
• les moyens d'attelage entre le pignon de lanceur et la douille d'entraínement comportent deux surfaces de butée avant et arrière, d'orientation radiale, qui sont portées respectivement par la douille d'entraínement et le pignon de lanceur et entre lesquelles des moyens élastiques sont montés comprimés axialement pour solliciter les deux surfaces de frottement au contact l'une de l'autre ;
• la surface de butée avant, ou arrière, est une collerette radiale interne appartenant à un capot d'attelage dont une autre collerette radiale interne s'étend en regard d'un épaulement radial externe de la douille d'entraínement, ou du pignon de lanceur ;
• la douille d'entraínement est déplacée axialement d'arrière en avant par une extrémité d'un levier de commande reçue axialement dans une gorge radiale de la douille d'entraínement.

According to other characteristics of the invention:

• the friction surfaces are two complementary frustoconical surfaces;
• the frustoconical rear friction surface is convex and extends axially towards the rear from the front end of the drive sleeve, and the front friction surface is concave complementary and extends axially towards the front from the rear end of the starter pinion;
• the mean diameter of the friction surfaces is substantially equal to the diameter of the pitch cylinder of the starter pinion;
• at least one of the two friction surfaces is coated with a friction lining;
• the coupling means between the starter pinion and the drive sleeve comprise two front and rear abutment surfaces, of radial orientation, which are carried respectively by the drive sleeve and the starter pinion and between which means elastics are mounted axially compressed to urge the two friction surfaces in contact with each other;
• the front stop surface, or rear, is an internal radial flange belonging to a coupling cover of which another internal radial flange extends opposite an external radial shoulder of the drive sleeve, or of the starter pinion ;
• the drive sleeve is moved axially from back to front by one end of a control lever received axially in a radial groove of the drive sleeve.

• la figure 1 est une vue schématique partielle en coupe longitudinale d'un démarreur de véhicule automobile selon l'état de la technique dans lequel le lanceur comporte un dispositif de roue libre à galets ;
• la figure 2 est une vue en section axiale d'un premier mode de réalisation d'un lanceur conforme aux enseignements de l'invention ; et
• les figures 3 à 5 sont des vues similaires à celle de la figure 2 qui illustrent trois variantes de réalisation du lanceur 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 schematic view in longitudinal section of a motor vehicle starter according to the prior art in which the launcher comprises a freewheel device with rollers;
• Figure 2 is an axial sectional view of a first embodiment of a launcher according to the teachings of the invention; and
• FIGS. 3 to 5 are views similar to that of FIG. 2 which illustrate three alternative embodiments of the launcher of FIG. 2.

In the following description, identical components, similar or analogous are designated by the same numbers of reference in the various figures.

FIG. 1 shows part 10 of a drive shaft a starter 12 for an internal combustion engine of a vehicle automobile, driven by an electric motor 11.

The motor shaft 10 is mounted rotating in a casing 14 by through a needle bearing 16.

A launcher 19 is slidably mounted axially on the end front of tree 10.

According to a known design, the launcher comprises a socket 18 located axially rearward, that is to say towards the right considering figure 1, and a starter pinion 20.

The starter pinion 20 is guided in sliding on a smooth cylindrical section 22 of the front end of the motor shaft 10 by through a pad 24.

The drive bush 18 is axially coupled to the pinion launcher 20 by a roller freewheel device 26 which allows the drive bush 18 to drive the starter gear 20 in a direction of rotation, said motor direction of shaft 10, while in the other sense, the freewheel device 26 disengages the rotational drive of the pinion 20 relative to the motor shaft 10.

The drive sleeve 18 is itself driven in rotation by the drive shaft 10 via two series of helical splines 28, 29 formed respectively on the shaft motor 10 and in an internal cylindrical portion of the sleeve training 18.

The sliding movements of the socket 18 and the starter pinion 20 in the motor shaft 10 are controlled, according to a known design, by a fork pivoting 30 of starter 12 which is itself controlled by a contactor 32 of known conventional design.

The launcher 19 constituted by the coupling of the launcher pinion 20 and the drive sleeve 18 can therefore slide axially between its rear rest position illustrated in FIG. 1, and an active position before meshing of the starter pinion teeth 20 with a wheel gear (not shown) of the flywheel of the internal combustion engine, this position corresponding to an axial offset of the launcher 19, towards the left considering figure 1, until the transverse face front 34 of the pinion 20 comes into axial abutment against a washer of stop 36 carried by the shaft 10.

In accordance with the teachings of the invention, it is proposed to remove the roller freewheel 26 and replace it with a other device, a first example of which is illustrated in figure 2.

In accordance with the teachings of the invention, the socket 18 and the starter pinion 20 are linked in rotation by a device 38 similar to a friction clutch 38 which has two surfaces, front 40 and rear 42, complementary friction.

The surface 40 is a concave frustoconical surface coaxial with the axis of the launcher 19 and therefore to the axis of the launcher pinion 20 which carries this friction surface 40.

Indeed, as can be seen in Figure 2, the toothed part of the starter pinion 20 extends axially towards the rear in direction of the drive sleeve 18 by a tubular section 44, made integrally with the body of the starter pinion 20, inside which the friction surface 40 is produced.

The starter pinion 20 is thus delimited axially towards the rear by an annular transverse edge at the rear end 46.

The rear tubular section 44 is delimited radially towards the exterior by a cylindrical surface 48 and forwards by a front radial shoulder 50.

The drive sleeve 18 comprises, according to a design known, a tubular body 52, inside which are formed the helical grooves 29, which is delimited by a transverse face rear annular 54 and by a front annular transverse face 56.

The front part, to the left when considering figure 2, of the tubular body 52 of the drive sleeve 18 is of a thickness more important than the rear part so that it is delimited radially outward through the frustoconical friction surface convex 42 which extends axially rearward from the end transverse before 56 and this over about half of the axial length total of the drive sleeve 18.

The two frustoconical friction surfaces 40 and 42 are coaxial and complementary, that is to say they are of the same angle.

The axial length of the two friction surfaces, corresponding to the distance between the rear ends 46 of the pinion launcher 20 and before 56 of the drive sleeve, and the angle of frustoconical surfaces are such that the mean diameter D of the surfaces frustoconical 40 and 42 is substantially equal to the diameter of the cylinder primitive CP of the starter pinion 20.

The starter pinion 20 is axially coupled to the sleeve drive 18 by a coupling cover 58 which is for example a sheet metal part cut and folded.

The cover 58 has an annular cylindrical outer skirt 60, a front flange 62 of internal radial orientation which extends radially in the direction of the body of the starter pinion 20 and the internal peripheral part extends in particular axially opposite the front shoulder 50 which delimits the rear section 44 of the pinion of launcher 20.

The cover 58 also includes a rear flange 64 which is crimped, when assembling the launcher, radially inwards in look of a rear shoulder 66, of frustoconical profile, formed in a ferrule 68 of the drive sleeve 18.

Ferrule 68, which gives a bell shape to the front part of the drive sleeve 18, extends axially forward and it is connected to the front section of the body 52 of the drive sleeve 18 by a rear radial wall 70, while its transverse edge front free end ring 72 constitutes a support for the portion of the internal face opposite the radial flange 62 of the crimped cover 58 which determines the axial position of the latter relative to the socket 18 after crimping.

In accordance with the teachings of the invention, a washer elastic with axial action 74 is mounted compressed axially between the front radial shoulder 50 of the starter pinion 20 and the internal face vis-à-vis the internal radial flange 62 of the crimped cover 58 of so as to elastically stress the frustoconical surfaces of friction 40 and 42 in mutual contact with a predetermined axial force F which applies these two friction surfaces against each other.

The rear axial part 52 of the drive sleeve 18 is externally shaped as a very wide radial groove 76 axial which receives the free ends of the fork 30.

The groove 76 is delimited axially forwards by the face transverse rear radial orientation 78 of the wall 50 and towards the rear by an external radial flange 80 belonging to a ring 82 which is attached to the tubular rear part of small thickness of the body 52 of the drive sleeve 18.

For this purpose, the ring 82 includes a front tubular shell 84 which is threaded axially on the rear cylindrical section 86 of the rear part of the tubular body 52, the ring 82 being retained axially on the drive bush 18 by an elastic ring 88 received in a groove complementary to the surface 86.

The ring 82 is preferably force-fitted by its ferrule 84 on the rear part of the tubular body 52 of the sleeve training 18.

In the case where the drive sleeve 18 is made in plastic material, the presence of the ferrule 84 makes it possible to obtain an effect hooping of the rear part of the tubular body 52 of the sleeve drive 18 so as to oppose bursting efforts, radially outward, resulting from the reaction forces between the helical teeth 28 of the shaft 10 and 29 of the drive sleeve 18.

The elastic means, here constituted by the elastic washer compressed 74, transmit an initial torque C of the drive sleeve 18 to the starter pinion 20 by through the conical friction clutch 40, 42, the value of torque C being equal to the product of the force F by a coefficient K which is a construction factor which depends in particular on the average diameter D, the coefficient of friction between the two surfaces 40 and 42 and the angle of the cone of these surfaces.

When starting, when the electric motor of the starter starts to rotate and the starter pinion 20, driven axially forward through the drive bush 18, begins to penetrate axially into the starter ring of the flywheel of the motor, the initial torque C, which is much lower than the torque required to cause the drive of the starter ring by the starter, is sufficient to allow the launcher to be screwed onto the helical splines 28 of the shaft 10 and to bring the pinion of launcher 20 in abutment against the abutment ring 36.

The launcher 19 can no longer advance axially towards the left considering the figures, and the axial pressure force of the clutch 38, that is to say the axial force which applies the surfaces frustoconical frictions 40 and 42 against each other, increases with the resistant torque that the starter ring opposes to the engine thanks to the effect of the "screw-nut" system produced by the cooperation of helical splines 28 and 29 which transform the torque into an effort axial.

The choice of different geometric parameters and realization, that is to say in particular the angle of the cone, the coefficient of friction of the surfaces 40 and 42 and the helix angle of the splines 28 and 29, ensures a torque transmissible by the device clutch 38 which is greater than the torque to be transmitted.

Under these conditions, the torque of the electric motor 11 of the starter is fully transmitted to the starter pinion 20 so as to allow the engine to start.

After the engine has started, the launcher 19 being always maintained axially with the pinion 20 which cooperates with the starter ring via contactor 32 as long as this the latter is powered, the starter pinion 20 rotates faster than the shaft output 10, 22 of the electric motor 11 of the starter, which allows the unscrewing the launcher 19 on the shaft 10.

The axial force, which was previously produced by the couple transmitted, disappears and only the initial residual torque C remains (due to the action of elastic means 74) which is transmitted to the engine electric starter. This initial residual torque C is of value reduced and it is notably insufficient to communicate to the tree 10 an overspeed for the rotating parts of the electric motor.

This short phase of overspeed operation, during which the friction clutch 38 behaves almost like a freewheeling device, of course only possible if the angle of the cone, taking into account the coefficient of friction on surfaces 40 and 42, is important enough to avoid any jamming phenomenon axial by cone effect between surfaces 40 and 42, i.e. if there is always a possibility of a slight reduced relative axial displacement between the starter pinion 20 and the drive sleeve 18, that is to say between the friction surfaces 40 and 42.

We will now describe the variant embodiment illustrated in Figure 3. In this figure, the elastic means are constituted by a compression helical spring 74 which is axially interposed between a rear abutment surface which is here constituted by the flange internal rear radial 64 of cover 58 and a front abutment surface which here is constituted by a face opposite an external radial edge 90 of the tubular part 68 of the body 52 of the drive sleeve 18.

In the embodiment illustrated in FIG. 4, the means elastic again consist of an elastic washer 74 which is axially interposed between a rear stop surface formed by the internal rear radial flange 64 of the cover 58 and a surface of front stop constituted by the annular face opposite a radial edge external 90 of the front part of the body 52 of the drive sleeve 18.

The front face 78 of the groove 76 is constituted by a washer 78 which is held axially in abutment forward by the ferrule 84 of the ring 82.

Finally, the variant illustrated in FIG. 5 differs from the mode of embodiment of Figure 2 by the constitution of the groove 76 whose faces front 78 and rear 80 consist of two orientation flanges radial produced integrally with the body 52 of the sleeve training 18.

According to other variants not shown in the figures, the coupling cover 58 can be fixed on the drive sleeve by any medium, for example by elastic interlocking, by welding, by collage, etc.

The elastic washer 74 or the coil spring of Figure 3 compression can be replaced by any other equivalent elastic element such as a rod, a block of material elastomer, etc.

The frustoconical friction surfaces 40 and 42 can be inverted, i.e. the convex frusto-conical surface can be associated with the starter pinion while the tapered surface concave is formed in the drive sleeve 18.

Finally, in order to obtain the desired coefficient of friction between the friction surfaces 40 and 42 and / or improve the resistance to wear of the friction clutch 38, it is of course possible to coating one and / or the other of the two surfaces 40 and 42 with a gasket friction material.

Claims (6)

1. Starter for a motor vehicle internal combustion engine of the type comprising an electric motor (11) whose drive shaft (10, 22) is provided with helical flutes (28) for rotationally driving a driver, in the form of a drive sleeve (18), belonging to a starter head (19) which is able to slide axially on the drive shaft (22) between a rear idle position and a front position of meshing of a driver-head pinion (20) with a toothed wheel on the internal combustion engine flywheel, and of the type in which the starter-head pinion (20) is axially coupled to the drive sleeve (18), to which it is rotationally connected by a device (38) allowing rotation of the drive sleeve (18) with respect to the starter-head pinion (20) when the speed of rotation of the latter is greater than that of the drive sleeve (18), in which the device (38) comprises two complementary friction surfaces, front (40) and rear (42), the said friction surfaces (40, 42) being two complementary frustoconical surfaces carried respectively by the starter-head pinion (20) and the drive sleeve (18), and in which the starter-head pinion (20) is mounted so as to be able to move axially with respect to the drive sleeve (18) to which it is coupled and in which the two friction surfaces (40, 42) are elastically forced in contact with each other, characterised in that means of coupling (58) between the starter-head pinion (20) and the drive sleeve (18) comprise two radially oriented stop surfaces, front (62) and rear (50), which are carried respectively by the drive sleeve (18, 58) and the starter-head pinion (20) and between which elastic means (74) are mounted so as to be compressed axially in order to force the two friction surfaces (40, 42) in contact with each other by a force with a predetermined value (F), so that the drive sleeve (18) can slide in rotation with respect to the starter-head pinion (20) when the speed of rotation of the latter is greater than that of the drive sleeve (18).
2. Starter according to Claim 1, characterised in that the rear frustoconical friction surface (42) is convex and extends axially towards the rear from the front end (56) of the drive sleeve (18, 52), and in that the front friction surface (40) is concave and complementary and extends axially towards the front from the rear end (46) of the starter-head pinion (20).
3. Starter according to either one of Claims 1 or 2, characterised in that the mean diameter of the friction surfaces (40, 42) is substantially equal to the diameter of the pitch cylinder (CP) of the starter-head pinion (20).
4. Starter according to any one of the preceding claims, characterised in that at least one of the two friction surfaces (40, 42) is covered with a friction lining.
5. Starter according to Claim 1, characterised in that the front (62) or rear stop surface is an internal radial collar belonging to a coupling cap (58), another internal radial collar (64) of which extends opposite an internal radial shoulder (66) of the drive sleeve (18, 68), or of the starter-head pinion (20).
6. Starter according to any one of the preceding claims, characterised in that the drive sleeve (18) is moved axially from rear to front by one end of a control lever received axially in a radial groove (76) in the drive sleeve (18, 82).

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