Motor vehicle starter with improved starter drive assembly

IS 2 268 114 T3

DESCRIPTION

Motor vehicle starts using improved starter heads.

Scope of the invention

The present invention relates to motor vehicle starters, and more specifically to starter heads comprising such starters.

State of the art

As shown in FIG. 1, a motor vehicle starter classically comprises a contactor 12, as well as an adapted electric motor M that must be directly or indirectly coupled, here by means of a reducer, to an output shaft 100, which carries a drive head. starter provided with a pinion 1. The pinion 1 is intended to cooperate with the gear of the start ring C of the internal combustion engine of the motor vehicle. It is movable on the output shaft between a resting position where it is withdrawn with respect to said starter crown and an advanced position where it engages with it in support on a work stop 6.

The contactor 12 extends parallel to the electric motor M thereon and comprises a winding 12a and a piston core 12b.

The supply of power to the electric motor M is guaranteed by the displacement of a mobile contact 13 between an open position and a closed position, since said contact 13 is pushed by said piston core 12b axially mobile with respect to the electric motor M when winding 12a is activated.

The contactor 12 also controls the displacement of the pinion 1. Its piston cores 12b are connected to the pinion 1 by mechanical means, indicated as a whole by the reference numeral 14.

These mechanical means comprise a band-shaped control lever provided at its upper end with the piston core 12b and at its lower end with an actuating element that also belongs to the starter head. The drive element is provided with a drive cover comprising a strip receiving groove. The band accompanies the starter head towards the advanced working position of the pinion.

The starter head also comprises a free wheel axially sandwiched between the drive cover and the pinion 1. The drive cover is internally provided with complementary helical grooves with external helical teeth driven locally by the output shaft carried by the electric motor M when it is electrically powered.

The band is pivotally mounted between its two ends on a casing that internally contains the mechanical means 14 and that carries the motor M and the contactor 12. The starter head with its pinion 1 moves with a helical movement when it is displaced by the band to come into contact with the starter ring gear.

This is done by feeding the winding 12a as a result of an impulse of the ignition key, which makes it possible to set in motion the piston core 12b, then attracted in the direction of a fixed core ascended to the end of a support of the winding 12a. This support has a U-shaped section to position the winding 12a and thus comprises a bottom that constitutes a bearing 12C. The core 12b is intended to move between a resting position and a contact position, in which it rests on the fixed core; this closing position of the magnetic circuit takes place after the closing of the movable contact 13 and, consequently, of the electric circuit.

The mechanical means also comprise a memory spring mounted around the core 12b to reposition it in the rest position, a cutting spring associated with the movable contact 13 to reposition it in the open position, and a spring 15, said teeth-to-teeth spring, placed in inside the core 12b and in contact with a first stem connected by an axis to the upper end of the band for its fixing to the core 12b. This spring 15 has a stronger resistance than the memory spring.

The band is thus sandwiched at its upper end between the core 12b and the shaft. The first stem is mounted within a knockout hole in the core 12b. The core 12b is intended, after a certain course, to be in contact with a second rod integral with the movable contact 13 and movably mounted inside the fixed core. In the closed position, the contact 13 cooperates with a fixed contact, in the form of pins connected respectively to the positive terminal of the battery and to the electric motor M, thus allowing the electric motor to be powered.

The bolts are integral with the closing cap of the contactor made of insulating material.

All of these elements are represented in Figure 1 and all were not referenced for simplicity.

The pinion 1 can thus come into contact with the crown C, that is to say, in the position of engagement with the crown C, before the moving contact is not closed.

Most often the pinion 1 comes into contact axially with the toothed abutment of the ring gear C before penetrating the latter.

Thus, the mechanical means 14 comprise, in particular, the spring 15, which is mechanically interposed between the piston core 12b and the pinion 1, and which allows the piston core 12b to continue its course to ensure, before its contact with the core fixed, the moving contact closing position, although pinion 1 is blocked butting against the teeth of the heat engine crown in a position where it does not mesh with this crown.

In this way, the free wheel, interposed between the pinion 1 and the cover of the starter head, has the main function of preventing that, when the internal combustion engine of the vehicle starts, the pinion 1 drives the electric motor at too high a speed , liable to deteriorate the latter.

The rollers that drive the freewheel are each subjected to the action of a circumferential spring action, so that this makes it possible to dampen the sudden vibrations of the torque that is transmitted between the drive cover and the pinion 1.

In order to reduce the volume, weight and cost of the free wheel with respect to its use proposed in document FR-A-2,772,433, according to the preamble of claim 1, a clutch fixing device is intervened of the conical type between the pinion and the drive element to take advantage of the starter head pinion.

In practice, the pinion and the drive element2

ES 2 268 114 T3 each have, integrally, respectively, a first frusto-conical friction surface and a second frusto-conical friction surface. These coaxial friction surfaces have a complementary shape, one of the frusto-conical friction surfaces meshing on the inside of the other frusto-conical friction surface emerging on the outer surface. These surfaces are pressed into contact with each other, with a force of a predetermined value, by the intermediation of elastic means of axial action that rest in a first embodiment on a first stop integral with the free end of a skirt belonging to a part , called for convenience part of fixation, of annular shape for its action on a second stop integral with the actuating element, so that the drive member can slide in rotation relative to the starter head pinion when the speed of rotation of the pinion is higher than that of the drive member. In an alternative, in a second embodiment, the elastic means rest on a first stop integral with the fixing part set on a ring belonging to the actuating element for its action on a second stop integral with the pinion.

The mean diameter of the friction surfaces is substantially equal to the diameter of the pitch circle of the teeth of the starter head pinion. In practice, the fixing part consists of a starter head bushing which has on its outer periphery an annular skirt directed axially towards the actuating element, which is cylindrical in shape and axially oriented. This bushing has a bottom, which in the first embodiment is axially supported on an excessive thickness of an axial extension of the pinion. In the second embodiment, the elastic axial action means are interposed between the bottom of the fixing part and the axial extension of the pinion.

The elastic means consist, in one embodiment, of a coil spring, and in another embodiment, of a corrugated disk. In an alternative, as described in document DEC-242194 the elastic means comprise tabs directed axially in the opposite direction.

These arrangements are satisfactory, but it may nevertheless be desirable, in a simple and inexpensive manner, to further increase the efficiency and reliability of operation of the cone clutch clamping device.

The object of the present invention is to respond to this desire.

Object of the invention

According to the invention, this problem is solved according to the characterizing part of claim 1.

Thanks to the invention, the force exerted by the elastic means is better controlled, so that the efficiency and reliability of the fixing device is increased since the elastic tabs generate a more constant force depending on the course of wear than those generated by an elastic disk of the wavy type.

Indeed, with a corrugated disc the axial force varies rapidly as a function of the course of wear, so that the force generated by this type of disc is important at the beginning of the life span of the starter head, then decreases accordingly. More specifically, the elastic means are mounted under pretension, so that at the level of the frusto-conical friction surfaces of the conical clutch, a friction torque greater than the screw torque of the actuator must be created on the grooves of the starter output shaft, Thus, it will be sought to have a minimum force at the end of the starter wear that guarantees this condition. With a wavy disc, the force must therefore be important at the beginning of the life of the starter head to fulfill this condition at the end of wear. This significant force is not enviable when the motor of the motor vehicle starts and comprises the electric starter motor, since a significant residual torque is transmitted from the pinion to this electric motor. A high value of this residual torque presents a risk of deterioration of the electric motor of the starter due to excessive speed.

With this type of wavy disc, a risk is taken from the point of view of the reliability of the starter, as well as from the point of view of the noise generated by the excessive speed of the electric starter motor.

Thanks to the tongues according to the invention, these drawbacks are not encountered since the variations in the forces exerted by these tongues on the conical clutch at the beginning and at the end of the life of the starter are less important.

The solution according to the invention makes it possible to increase the lifespan and the reliability of the starter, while at the same time making it less noisy at excessive speed.

With a helical spring, less significant force variations can be obtained provided the axial length thereof is increased, which leads to an increase in the axial length of the starter head.

Thanks to the invention, an axially compact solution is obtained.

The spring tabs are of a reduced axial dimension and bow axially in one embodiment, so that after mounting the bending forces bring the friction surfaces into contact with each other.

By playing on the circumferential length and thickness of the tabs, the load exerted by them is controlled. The tabs belong to an elastic zone of the elastic means in axial action.

This elastic zone is connected to a stop zone in translation of the starter head or pinion, used in the skirt of the fixing part. This stop zone is in contact with the first stop and moves axially with respect to the free end of the tabs.

In one embodiment, it is in the form of an annular bushing fixed, for example, by crimping or clamping on the skirt, which has a protrusion or a groove for this purpose. In an alternative, the stop zone is reduced to a single disk.

This disc, in one embodiment, is open, for example radially, so that it comprises like retaining washers that are mounted in a groove of the skirt.

The side of the throat that is furthest from the second stop constitutes the first stop.

This solution is simple and economical since, on the one hand, the throat is easy to make, for example by rolling and, on the other hand, the number of parts that must be assembled at the end is minimal; the elastic means finally close the pinion assembly with

ES 2 268 114 T3 the actuator, each constituting a subset.

In an alternative, the first stop belongs radially to a part projecting inwards and joined for example by welding, gluing or crimping on the free end of the skirt.

In an alternative, the disc is closed and a bayonet-type mount is produced for mounting on the skirt.

For example, the disc has radial protruding legs on its outer periphery that engage in leading passages, a part at the free end of the skirt, and another part at the groove.

The legs are engaged in the passage, and the legs are then rotated in the groove.

In an alternative, when the first stop extends radially inwards, it splits into annular sectors to make passages, the disc then presenting notches on its outer periphery for the passage of the annular sectors and allowing a rotation of the disc to bringing the outer periphery of this in the form of legs in contact with the first stop; the sectors advantageously comprise recesses to receive the legs and to block the disk in rotation.

Well understood, in an alternative, the elastic means are placed in position and then brought back to the first stop.

In one embodiment, the tabs are circumferentially cut from the disk.

In an alternative, the elastic zone is surrounded by the disk and is connected to the inner periphery of the disk by root zones.

The tabs are then made in the manner of an arm in the shape of an annular sector, which makes it possible to obtain a very large circumferential length, having an advantageous elastic characteristic.

More specifically, depending on the circumferential length of the arm and its section, the desired force is obtained as a function of the axial deflection of the arm.

In one embodiment, the circumferentially oriented arms extend circumferentially in projection on either side of a root zone.

The inner periphery of the disc that belongs to the stop zone is of a larger diameter than the diameter of the outer periphery of the arms.

The elastic zone is thus established below the inner periphery of the stop zone.

The elastic means according to the invention can be, for example, integrated in the bushing of figure 5 of the document FR-A 2,772,433 mentioned above. However, it may be desirable to make the starter head more robust and simplify it further, while increasing the reliability and performance of the starter head.

Thus, preferably the elastic means are carried by the skirt of the fixing part, which internally carries one of the frusto-conical friction surfaces. This skirt is, through the bottom of the fixing part, integral with the pinion-actuator element that is associated with the friction surface carried internally by the skirt, so that the average contact diameter of the first frusto-conical friction surface with the second frustoconical friction surface is greater than the diameter of the pitch circle of the pinion teeth.

Advantageously, said mean diameter is greater than the diameter of the head circle of the pinion teeth.

This mean diameter is, in case of excessive speed of the pinion with respect to the actuator, a mean friction diameter. The conical clutch according to the invention is reliably locked when the electric starter motor drives the internal combustion engine of the vehicle via the starter ring gear and is adapted to be released when the internal combustion engine drives the pinion at a higher rotational speed (excessive speed) to that of the actuator.

Thanks to these arrangements, the efficiency and reliability of the starter head are increased, since the average diameter of the first or second frusto-conical friction surface is greater due to the fact that this surface belongs to the skirt of the established fixing part. over a diameter greater than the diameter of the pinion head circle. The mean diameter of the first frusto-conical friction surface is thus increased with respect to the diameter of the grooves of the output shaft of the starter leading to the actuator. Well understood, the mean diameter of the second frusto-conical friction surface is also increased by the fact that the two frusto-conical friction surfaces are coaxial and complementary, the second surface penetrating into the interior of the first surface. These two frustoconical surfaces have the same taper angle.

Thus, thanks to the invention, for a given diametrical dimension of the starter head, the first friction surface and the second frusto-conical friction surface will therefore each have the largest possible mean friction diameter.

It will also be appreciated that the rings of Figures 3 and 5 of FR-A 2,772,433 are omitted, so that the starter head is simplified and more robust. The pinion is also simplified.

In a general way, the integration of the fixing part to the pinion or to the actuator makes it possible to reduce the number of parts that must be assembled at the end, the elastic means closing all of this. Advantageously, one of the frusto-conical friction surfaces is axially longer than the other frusto-conical friction surface and surrounds it completely, which makes it possible to further reduce the axial dimension of the starter head.

In all cases, the fixing part protects, through the intermediation of its skirt and also its integral bottom in one embodiment, in a pinion-tight manner, the frusto-conical friction surfaces and prevents them from staining, for example by oil and water.

The operation of the starter head is therefore reliable and long lasting.

The fact that the fixing part is, for example, integral with the pinion, makes it possible to reduce the axial dimension of the starter head from the fact, in particular, that the bottom of the fixing part does not extend with excessive thickness, and simplifies also the starter head assembly.

The starter head and the fixing part or the pinion and the fixing part constitute a manipulable, transportable and captive subassembly. This subassembly is easy to assemble with the second subassembly.

Furthermore, it is possible to make each of these subassemblies in a monobloc or in several parts, preferably in a different material adapted to the function to be performed.

It will also be appreciated that the weight and cost of the starter head are low.

According to one characteristic, the second surface of

ES 2 268 114 T3 stop is integral with a transverse rim that axially delimits the second or the first frusto-conical friction surface.

This arrangement makes it possible to further simplify the actuator or the pinion and to increase their mechanical behavior.

This also makes it possible to make the actuator by molding based on plastic material, thus allowing it to be reduced.

Furthermore, the elastic axial action means exert an action respectively on the actuator and the pinion according to an average diameter close to the average diameter of the second or the first frusto-conical friction surface, depending on the case. In one embodiment, the mean action diameter of the axial action spring means is globally equal to the smallest diameter of the second frusto-conical friction surface.

The action of the elastic means for axial action on the actuator or the pinion thus takes place in a thick area of ​​the latter, which is favorable, in particular, for their implantation.

Advantageously, the skirt is frusto-conical in shape to further reduce the dimension and weight of the starter head.

In one embodiment, the first stop is carried by a tubular-shaped extension of the skirt that constitutes the free end of the fixing part.

The tubular extension has an axial length that depends, in particular, on the applications and the axial thickness of the elastic means of axial action and makes it possible not to increase the radial dimension of the starter head, while facilitating the mounting of the starter head.

More specifically, this tubular extension serves in a simple way to fix a system for maintaining and closing the entire starter head, said system comprising the first stop and the elastic means for axial action.

In one embodiment, the mean diameter of friction and / or contact between the frustoconical friction surfaces is equal to or greater than 75% of the diameter of the tubular extension of the skirt.

Other characteristics, objectives and advantages of the invention will appear from reading the detailed description below, made with reference to the attached figures, in which:

Summary description of the drawings

Figure 1 represents a motor vehicle starter according to the state of the art;

Figure 2 schematically represents the forces acting within a starter head according to the invention when the starter drives the internal combustion engine of the motor vehicle;

- Figure 3 is an axial sectional view of the starter head for a first embodiment according to the invention;

- Figure 4 is a front view of the elastic disk of Figure 3;

- Figure 5 is a view similar to Figure 3 for a second embodiment according to the invention;

Figures 6 and 7 are views similar to Figures 3 and 4 for a third embodiment according to the invention;

- Figure 8 is a view with part removed similar to Figures 3 and 5 for a fourth embodiment according to the invention;

Figures 9 and 10 are respectively front and side views of an alternative embodiment of Figure 7.

Description of preferred embodiments of the invention

In Figures 2 to 8, in order to reduce, in particular, the number of parts of the starter head to be finally assembled and further increase the efficiency and reliability of operation of the starter head, according to a characteristic of the invention, The starter head of figure 1 was replaced by a starter head provided with a pinion 1 carrying a first frusto-conical friction surface 8 that cooperates in a complementary and coaxial manner with a second frusto-conical friction surface 8 'carried by the actuator 2 for the formation of a conical clutch (indicated by the numerical reference in figure 2), the mean diameter of contact of the first frusto-conical friction surface 8 with the second frusto-conical friction surface 8 'is greater than the diameter of the pitch circle of the pinion teeth. Here, said average contact diameter is greater than the diameter of the head circle of the pinion teeth and is, in case of excessive speed of the pinion relative to the actuator, a friction average diameter. The conical clutch and a clamping skirt 1b, of annular shape, belong in the aforementioned manner to a clamping device produced between the actuator 2 and the pinion 1 to couple the pinion to the actuator. The fixing skirt 1b is integral with the pinion (Figures 2, 3, 8) or with the actuator (Figures 5, 6), which makes it possible to reduce the number of parts that must be assembled at the end and to simplify them. Surfaces 8, 8 'have the same taper angle. According to an important characteristic, the skirt internally carries one of the frusto-conical friction surfaces 8, 8 '. According to another important characteristic, the skirt comprises at its free end elastic means of axial action, and in axial projection with respect to the other surface 8, 8 'not carried by the skirt. More specifically, the first frusto-conical friction surface in Figures 2, 3 and 8 is carried by the internal periphery of a skirt 1b of a hollow, annular-shaped fixing part, of which the annular bottom 1a is integral with the pinion 1 of the starter head, possibly in several parts, advantageously made of different materials adapted to their own function. This bottom is centrally perforated for the passage of the output shaft 100 as can be seen in Figure 2. The fixing part is produced, for example, economically by stamping a sheet. In an alternative, the fixing part is more solid. The skirt 1b is directed from the fixing part axially towards the actuator 2.

The actuator 2 has on its internal periphery, as in FIG. 1, helical grooves connected with helical grooves carried by the outer periphery of the shaft 100. The helical grooves thus intervene in a complementary manner between the shaft 100 and the actuator 2.

The skirt is connected to one of its axial ends, said first axial end, on the outer periphery of the bottom, generally oriented transversely to the fixing part. In figure 3 the bottom 1a is frusto-conical in shape, while in figure 8 it is transverse.

In a first embodiment, the skirt is

ES 2 268 114 T3 solid, as in FIG. 5, being annular in axial orientation at its outer periphery. Externally the skirt is thus cylindrical, and internally it is frustoconical in shape to carry the first frustoconical friction surface.

In another embodiment, as represented in these figures, to further reduce the mass of the starter head, the skirt is frusto-conical in shape, preferably of constant thickness, so that the fixing part is generally bell-shaped. . This part is, for example, in stamped sheet metal.

According to one characteristic, the skirt extends axially beyond the axial end with the largest diameter, said external diameter of the first frusto-conical friction surface 8 'by an annular end zone of axial orientation (1c in figure 3). The annular zone 1c thus forms a tubular extension of the first surface 8 of the skirt internally in a widened way in the direction of the actuator and extends axially with respect to the second surface 8 '.

This cylindrical zone 1c delimits the second axial end of the skirt, that is, its free end, and carries a first stop that extends radially inward, that is, transversely with respect to the axial symmetry axis XX of the starter head. . The first transverse stop, in order to reduce the number of parts that must be assembled at the end, is here formed in favor of a groove made in the internal periphery of this zone 1c which constitutes the free end of the skirt and the fixing part. That is, the transverse side of this groove the most distant from the actuator 2, which constitutes the first stop.

Some elastic axial action means 10, advantageously made of elastic steel, are carried by the skirt 1C, and rest on the first stop for their action on a second radial stop 4 ', that is to say, transverse, integral with the actuator 2 and holding the the second frustoconical friction surface 8 'integral with the actuator in complementary and coaxial contact with the first frustoconical friction surface integral with the skirt, and consequently the starter head pinion. The second frusto-conical surface 8 'is convex in shape, while the first frusto-conical surface 8 is concave in shape. Differently, said actuator 2 carries a penetrating male cone at least in part in a female cone carried by the pinion. As shown in figure 3, the first surface 8, which constitutes the radially external friction surface carried by the skirt 1b, completely surrounds the second radially internal friction surface 8 'carried by the actuator 2. Figure 5 illustrates a second embodiment in which the actuator 2 carries the skirt 2b, this skirt 2b then carrying the radially external friction surface 8 '. Thus, according to an advantageous mode of the invention, the elastic means 10 are carried by the free end of the skirt carrying the radially external friction surface 8, 8 '. This embodiment has the advantage of considerably simplifying the conception of the conical starter head described in document FR 2,772,443, in which the skirt carrying the elastic means carries the radially internal friction surface, which requires the making a ring.

These surfaces 8, 8 'have a mean diameter greater than the diameter of the head circle of pinion 6

1, 10, so that the average diameter of friction or contact of the two surfaces 8, 8 'is greater than the diameter of the head circle of the pinion teeth. The efficiency and reliability of operation of the starter head are thus increased. The axial dimension is also small. In addition, the wear of the surfaces is recovered; the first surface 8, which is according to a characteristic longer axially than the second surface 8 ', allows the actuator to be brought even closer to the pinion and the axial dimension of the starter head to be even more reduced. The mean diameter of contact and friction between the two friction surfaces 8, 8 'is therefore equal to the mean diameter of the second surface 8' which has a greater diameter at its axial end adjacent to the elastic means 10 than its other end. smaller diameter axial. The mean diameter is thus located in the middle of the axial length of the second surface 8 '; the first surface 8 extending axially on both sides of the second surface 8 '.

The elastic means 10 also belong to the fixing device and, more specifically, constitute with the first stop a system for maintaining or retaining and closing the complete starter head.

Thus, a first subassembly comprising the pinion and the fixing part provided with the first surface 8 and a second subassembly constituted by the actuator provided on its outer periphery with the second surface 8 'is manufactured, then it approaches the actuator with respect to the first sub-assembly by mounting the second surface on the first surface, and finally the elastic means 10 are established to close all of it.

These elastic means 10 are established in axial compression, it must be said under prestress, between the first stop and the second stop 4 'carried here, even to reduce the axial dimension of the starter head, by a transverse rim of the actuator that delimits, according to one characteristic, axially the second surface 8 'at the level of its largest diameter. The rim is formed by an annular withdrawal of material on the outer periphery of the actuator body, thus allowing the elastic means 10 to be positioned at least in part. This withdrawal of material is delimited by the transverse projection 4 'and by a globally axially oriented annular radius 4 "connecting to the inner periphery of flange 4 '. The elastic means 10 are placed here entirely in the removal of material and are supported directly on the flange 4 'or indirectly on it by means of a covering. In all cases, the stop 4 'is carried by the flange.

Well understood, alternatively when there are no radial dimension problems, the first stop is carried by an area that extends the first surface 8, which forces the radial size of the first stop to increase.

As can be seen in figure 4, the elastic means 10 comprise a disc 10a not closed, and consequently open at 10g. The opening 10g, here radial, confers a radial elasticity to the disc 10a, which can then be used as a retaining washer that is inserted into the aforementioned groove of the extension 1c, closing the slot 10g again. This disc 10 is advantageously made of spring steel. In an alternative, the opening 10g is sloped.

In an alternative, disk 10a is closed, such as 11

ES 2 268 114 T3 mo can be seen in Figures 7 to 9, and has on its outer periphery two radial legs, preferably diametrically opposed, each one adapted to cross an axial passage leading into the aforementioned groove, which comprises the first stop for bayonet-type mounting.

In an alternative, the first abutment extends radially inward relative to the inner periphery of the extension over a low height and is engaged, preferably by advancing, welding, crimping or riveting onto the extension 1c. The welding can be of the laser type. The crimping can be carried out in a similar way to that of figure 6, when the skirt is solid. In an alternative, the first stop is a disk that has radial legs protruding at its outer periphery. These legs are each coupled in a complementary manner in a hole made in the free end of the skirt. The side edges of the recesses are then flattened to make a crimp; the skirt is advantageously made of deep drawn sheet metal. In an alternative, the legs can be welded over the side edges of the recesses.

In an alternative, the first stop is made by a descent of material radially towards the interior of the free end of the extension 1c. The mounting of the disk 10a is also done by reclosing the slot 10g.

All combinations are possible, the starter head comprising two subassemblies and here additional elastic means 10. These elastic means 10 are a closing element of the starter head, since they close the two subsets 1, 2 of this starter head.

More specifically, the elastic means 10 are mounted under prestressing between the aforementioned stops and allow the second frusto-conical surface 8 'of the actuator to be held under pressure against the first frusto-conical surface 8 integral with the pinion 1, 10. It will be taken into account that the mean diameter of the first stop, that is to say of the groove, is greater than the average diameter of the second stop 4 '.

The elastic means 10 exert a predetermined force that is substantially constant over time and of relatively little value that depends on the applications.

More precisely, this initial pressure produces a friction torque between the actuator and the pinion that is still, by construction, higher than the torque necessary for screwing and for the development of the starter head on the shaft 100.

This condition allows the self-priming of the movement of the starter head between its rest position and its advanced position against the work stop, indicated by the numerical reference 6 in figure 2, at the beginning of the drive phase of the vehicle engine by means of the starter ring gear. When the pinion reaches the stop 6 there is compression of the surfaces 8, 8 'against each other with a lock.

This blocking of the movement between the pinion and the actuator depends, in particular, on the angles and diameters of the frusto-conical friction surfaces.

As can be seen in figure 2, during the drive of the internal combustion engine of the motor vehicle by the electric starter motor, the torque Cd - generated by the starter at the level of the output shaft 100 carried by the actuator 2 and transformed by the helical groove device 9 that occurs between the actuator 2 and the shaft 100 - creates an axial force Fa.

This force Fa is divided at the level of the frustoconical friction surfaces to create a normal contact force Fc, which generates a tangential force Ft to the frustoconical surfaces 8, 8 'as a function of the friction coefficient between these surfaces. The value of this force Ft multiplied by the average contact radius of the frusto-conical friction surfaces determines the torque Ce transmitted by the conical clutch 7.

In order for the pinion to engage normally without slipping, the Ce> Cd ratio must remain true.

All this depends on the applications, since the coefficient of proportionality between Cd and Fa depends on the angle of inclination of the grooves 9, the average radius of these grooves and the coefficient of slip between the output shaft 100 and the actuator.

The coefficient of proportionality between Fa and Fc depends on the taper angle between the two frusto-conical friction surfaces.

The value of Ft is linked to Fc and the coefficient of friction Fc between the two materials of the frustoconical friction surfaces of the clutch 7. To avoid any jamming, ensure the tangent relationship (a)> Fc, in which that is the value of half the angle at the top of the cone of contact between the frustoconical friction surfaces and Fc the coefficient of adhesion.

All these values ​​are calculated based on formulas of mechanics known per se and depend on the applications.

These formulas involve the coefficient of friction between the grooves of the shaft and the actuator, the mean radius of the grooves, the angle of taper of the surfaces 8, 8 'and the coefficient of friction of these. All of this influences the choice of materials for the actuator, skirt and pinion.

When the engine of the vehicle that is to start the pinion 1 rotates faster than the output shaft 100, it is allowed to unscrew the starter head on the shaft 100. The previously transmitted axial force disappears and no longer remains more than the low residual torque of the elastic means 10 that is transmitted to the electric starter motor. During this short phase of excessive speed the clutch behaves like a free wheel device, with a relative movement between the surfaces 8, 8 '. The average contact diameter between the two surfaces 8, 8 'is thus also a friction diameter in case of excessive speed.

The aim of the invention is to minimize this residual torque, while respecting the Ce> Cd ratio. Throughout the life span of the starter head.

Thus, according to the invention a boot of the aforementioned type is characterized in that the elastic means 10 comprise axially elastically deformable tabs 10b and in which the tabs extend circumferentially.

According to a characteristic of the invention, the tabs 10b extend axially in the same direction, abutting against the second stop.

By playing on the circumferential length and thickness of the tabs, the axial force developed by them is well controlled.

In Figure 4 the tabs 10b are shaped like

Arms 10b, which extend into the open disc 10a. The arms 10b are in the shape of an annular sector extending circumferentially leading on each side of a root zone 10d to the disk 10a. One of the zones 10d is affected symmetrically by the radial groove 10g. The two zones 10d are diametrically opposed so that the arms 10b extend inverted and axially in the same direction.

The internal periphery of the two arms 10b associated with the same area 10d are in the form of an arc of circumference that extends over more than 90 °. Well understood, the number of zones 10d and arm 10c can be increased.

The arm-shaped tabs 10c belong to the elastic zone of axial action of the elastic means 10, also including the zones 10d.

This elastic zone 10b extends radially under the disk 10a, which thus has an internal diameter greater than that of the external periphery of the arms 10b. The elastic means 10 comprise two zones 10a, 10b, namely an internal elastic zone split into tabs 10b, here in the form of an arm, of circumferential orientation and an external zone 10a for the stop in translation of the pinion 1 in the form of a disk 10a, here open and diametrically elastic.

The free ends of the tabs 10b are axially displaced with respect to the stop zone depending on the applications.

The zones 10d are zones of connection to the disk 10a.

According to another characteristic, these tabs have an inflection zone between their end of attachment to the zone 10d and their free end to better control the force they exert on the second stop 4 '. In general, the tabs are axially arcuate in the direction of the actuator 2 to keep the surfaces 8, 8 'in contact. In an alternative, the tabs are axially inclined, starting from their end in the clamping zone 10d, in the direction of the second stop 4 '. In an alternative, a sloped area connects the free end of a tab to its gripping end in area 10d. Thanks to the inclined area that creates a fold, the elasticity of the tongue is well controlled and the free end of a tongue can extend parallel to the second stop.

The free end of the tab may be convex for specific contact with the second stop.

The tongues 10b are generally displaced axially with respect to the disk 10a and this in the direction of the second stop 4 '.

This axial offset determines the preload of the tongues and therefore depends on the applications.

It will be appreciated that the arms 10b having a large circumferential length is favorable for controlling the axial force developed by these arms.

In an alternative, the tabs are circumferentially cut into the wider disc 10a.

The fixing part thus allows the actuator to be connected to the pinion by means of the frusto-conical friction surfaces and replaces the bushing in figure 1. The fixing part is integral with the pinion, being in one piece with the pinion in figures 2 and 3, or alternatively (figure 8) fixed on it. The walls of the fixing part (its bottom and its skirt) are continuous, so that the fixing part is tight, there being no opening between the bottom of the fixing part and the pinion. This is favorable for the reliability of the operation of the starter head since the surfaces 8, 8 'are not stained by leaks of oil, water, etc.

The starter head is also simplified, since it is devoid of an outer ring, contrary to the embodiment of Figures 3 and 5 of document FR-A-2 772 433.

For the sake of simplicity, in the figures the pinion assembly - will be called the bell pinion fixing part.

Thus, in Figures 2 and 6 the bell pinion is in one piece, being made of a single material or of two materials, while in an alternative (Figure 8) the bell pinion is formed in two parts, namely, the pinion and the bell; thus each part is chosen optimally according to the function to be performed.

In the figures, the bell pinion comprises, on the one hand, a toothed part that constitutes the pinion 1 and on the other hand, a frusto-conical part, indicated by the numerical reference 1b in figure 3, which belongs to the fixing part.

The toothed part is tubular in shape and has teeth in section on the generally trapezoidal-shaped sides necessary for meshing with the starter ring of the internal combustion engine of the motor vehicle. The pinion thus has teeth defined in a known manner by a head circle, a pitch circle and a foot circle.

It is the internal periphery of the frustoconical part that directly or indirectly constitutes the first frustoconical friction surface. Indeed, the internal periphery of the frusto-conical part 1b can be in contact directly against the second frusto-conical friction surface belonging to the actuator, or indirectly against the second frusto-conical friction surface, at least one of the two frusto-conical friction surfaces having a coating, such as a friction lining fixed for example by gluing. This makes it possible to control, in particular, the force Ft mentioned above.

As friction lining, a lining of the type described in EP A 0 816 707, comprising a bundle of fibers impregnated with a thermosetting resin, can be used. These fibers are carded to form a card sail and advantageously have a length of at least 40 mm. For example, glass is incorporated into the bundle. For more details they will be indicated in this document. With this type of lining, a remarkable stability of the friction coefficient of the material is obtained, as well as low wear.

The first frusto-conical friction surface thus belongs to the inner periphery of the skirt of the fixing part or engages on said inner periphery.

The second frusto-conical friction surface is the same, which is formed directly on the outer periphery of a frusto-conical radius belonging to the actuator 2 or is coupled on said radius of the external periphery.

In all cases at least one of the two frustoconical surfaces 8, 8 'comprises grooves that extend from one axial end to the other axial end of the frustoconical surface in question, and this in a rectilinear or curved manner. In an alternative, the grooves extend circumferentially. A network of circumferential and rectilinear and / or curved cross grooves can be made. This network can comprise

ES 2 268 114 T3 circumferential grooves connected to the axial ends of the frusto-conical surface affected by distinct grooves extending in a rectilinear or curved manner. All combinations are possible. For example, the grooves are provided on the outer periphery of the second surface, in an alternative to the inner periphery of the first surface.

Thanks to the grooves, dust is evacuated and the two surfaces detach from each other, particularly in the event of excessive speed.

As with conventional starter head pinions, the teeth of the toothed parts 1 are preferably provided at their free end, opposite the actuator 2, with a chamfer to facilitate penetration of the pinion into the visible starter ring at C in figure 1.

In these figures 2 and 3 the frustoconical bottom 1a is globally of transverse orientation, since it extends in an inclined manner with respect to the axis of axial symmetry XX of the starter head visible in figures 3, 5 and 8. This axis is, at the same time, the axis of symmetry of the shaft 100. In the alternative of Figure 8 the bottom extends perpendicular to the XX axis. In effect, the actuator can be standardized, and depending on the radial and axial size of the pinion, the more or less the bottom 1a can be tilted or the latter turned transverse. All of that depends on the applications.

Thus, in Figure 3 the pinion 1 has at its end facing the actuator 2 an inclined extension 1a which constitutes the bottom of the bell-shaped fixing part and which allows the parts 1, 1b to be connected to each other.

The bell pinion, for example, is obtained by molding. Advantageously, the bell pinion is obtained by sintering, being made of one material, or preferably two materials.

The sintering of two materials is very advantageous, since it is possible to choose for the toothed part a shade of material more specifically adapted to the needs of the gear with the starter ring (mechanical resistance, wear resistance, low noise emission, etc. ), while the frusto-conical part is specially adapted to the needs of the clutch 7 (wear resistance, value of the friction coefficient, etc.).

The toothed part 1 is obtained, for example, by extrusion, sintering, bar cutting or stamping. This toothed part 1 is in a different alternative to the bell, which has a centrally perforated arm for the passage of the shaft 100 and which constitutes the bottom of the bell. This arm 1a is extended on its outer periphery by the frustoconical skirt lb, itself extended by the tubular extension lc. The first frustoconical surface is constituted by the inner periphery of the skirt 1b.

In an alternative, as can be seen in figure 8, the arm 1a is coupled to its internal periphery by welding on the pinion, which provides for this to make on its internal periphery a tubular extension 1d that extends in axial projection towards the actuator and which allows the arm 1a to be centered on its internal periphery. This arm is fixed axially in one direction by the adjacent axial end of the pinion teeth and in the other direction by the welding made at the free end of the extension. The welding is carried out, in one embodiment, continuously, alternatively discontinuously. The welding is of the laser type, friction welding type or arc welding type.

Alternatively, the fixation is carried out by crimping, since the free end of the aforementioned tubular extension was lowered into contact with the arm 1a, resting on the teeth of the pinion 1. In this case, complementary connections can be used, for example the polygonal type, to lock the arm in rotation. The rotational locking of the bell on the pinion is carried out in a general way by cooperation of forms. Part of the pinion teeth can be removed to perform this setting. For example, the arm 1a is locally pressed to form at least one projection that penetrates in a complementary manner between two consecutive teeth of the pinion. Alternatively, the arm is pressed in the opposite direction to form at least one depression, into which the end of a pinion tooth penetrates at least in a complementary manner, this tooth, which is housed, must cooperate with the lateral edges of the depression. The number of projections and depressions depends on the applications.

In an alternative, immobilization connections can be made.

In all cases, an axial and rotational immobilization of the bell with respect to the pinion is obtained, that is to say, a fixation.

Alternatively, the pinion 1 is made of sintered material and the bell is made of solid metal, by means of its arm, with a slight grip on the protruding tubular extension 1d of the pinion 1, to remain correctly positioned on the pinion after manipulations of the assembly thus formed before the passage of this assembly to the furnace for sintering the pinion. During this passage to the furnace the metal of the pinion swells and thus guarantees, in addition to the metallurgical connections of the sintering, a definitive immobilization of these two parts. The aforementioned connections by cooperation in such ways, such as a polygonal fit, can be produced to contribute to the rotating connection between these two parts.

Alternatively, the bell is also made of a different sintered material, preferably the pinion material to obtain good friction characteristics. The two parts are then preassembled before passing into the sintering furnace. The coefficient of expansion of the pinion is as large as possible, like that of the bell, so that a tight contact between these two parts must be preserved and favor the creation of strong metallurgical connections. After sintering, a monobloc assembly is obtained with different mechanical characteristics depending on the areas in question.

In one embodiment, the toothed part is obtained by sintering two materials to obtain, on the one hand, good longitudinal sliding properties of the shaft 100 and, on the other hand, good properties for meshing with the starter ring.

It is conceivable that this toothed part is itself in two parts, namely, an internal sleeve of a material that allows a good longitudinal sliding of the shaft 100 and a pinion mounted on the external periphery of the sleeve and that presents a material that presents good properties for engagement with the starter ring gear. The tubular extension 1d then constitutes one of the axial ends of the sleeve.

IS 2 268 114 T3

This can be done in the same way as for mounting the hood with the pinion. For example, the toothed part is mounted in clamping on the extension 1d of the sleeve before a sintering operation of at least one of these parts. When the two parts are sintered, the coefficient of expansion of the sleeve is at least equal to that of the toothed part. Alternatively, a connection is made by locking.

In an alternative, the sleeve is integral with the bell, being in one piece with it or is fixed to it. The solution with attached sleeve is advantageous, since for a given shaft size 100, the sleeve can be standardized, if necessary with the bell, and the pinion mounted on the outer periphery of the sleeve can be adapted to each application, in particular, therefore which refers to its length. The toothed part can also be positioned axially as desired relative to the sleeve of greater axial length than the toothed part.

The bell pinion is thus made up of one, two or three parts. It will be taken into account that the bottom of the hood is connected to its skirt by means of a rounded area, or by means of a frustoconical area.

The same reasoning can be done for the actuator 2, which is therefore made up of one or more parts, each one in different material to optimally perform its own function. For example, as described in document FR-A 2,772,433, the actuator may have a metallic part, such as a ring provided with at least one collar, mounted on the body of the starter head to cooperate with the band of the actuators. mechanical means 14 of figure 1. The aforementioned ring comprises, in one embodiment, two collars so that it has a U-shaped section for receiving the band.

As can be seen in the figures, the actuator comprises three portions, namely, a first portion that has the second frusto-conical surface on its outer periphery. This first portion extends in axial and radial projection with respect to a second portion, which constitutes the cover of the actuator and which internally presents the adapted helical grooves that must cooperate in a complementary manner with the helical grooves of the shaft 100. An annular groove for receiving the band of the mechanical means 14 of figure 1 is provided on the outer periphery of the second portion. This groove, delimited by two adapted transverse sides that must cooperate with the band of means 14, belongs to the third portion of the actuator 2 and is axially displaced with respect to the first portion. This groove extends radially above the grooves of the second portion, which is axially shorter. The second frusto-conical surface, advantageously provided with grooves in the aforementioned manner, extends in radial projection with respect to the groove and is connected to the groove by means of the removal of material 4 ', 4 "made in the first portion for the accommodation of the elastic media 10. A frusto-conical face connects the end attached to the second portion to the smaller diameter end of the second frusto-conical surface to decrease the amount of actuator material, here advantageously fiber-reinforced moldable plastic material. Alternatively, anti-wear coatings are made on the two sides that delimit the throat, in particular, when the band of the mechanical means 14 is metallic. These coverings consist, for example, of metal discs fixed by molding on the sides of the groove, alternatively half discs or U-shaped part ratcheted on the sides of the groove. Alternatively, the side of the groove that is furthest from the pinion is formed in favor of a coupled disc, all combinations being possible. The second friction surface can also be formed in favor of a coating, such as the friction lining mentioned above, so that the body of the actuator, and consequently the second portion thereof, is advantageously made of a material having the qualities required for cooperate with the grooves of the shaft 100. Alternatively, the actuator 2 is obtained by sintering in a single material, or alternatively, in several materials such as the pinion. It will be appreciated that when the bell and / or actuator are made of sintered material, the desired loads can be incorporated therein to obtain the desired coefficient of friction for the surfaces 8, 8 '. For example, these surfaces can contain copper dust, carbon for example in the form of graphite, silica and molybdenum.

The band of means 14 is advantageously made of plastic material to limit fouling phenomena in the actuator and reduce noise. In an alternative, the groove, and consequently the second portion of the actuator, may extend radially over the second surface 8 'and the skirt of the clamping portion.

Well understood, the structure of the ring-shaped and hollow fixing part that then belongs to the actuator 2 can be reversed.

The free end of the skirt 2b of the fixing part extends in axial projection with respect to the first surface 8 and carries the elastic means 10.

Thus, in Figure 5 the skirt 2b and the arm 2a of the bell-shaped fixing part belong to the actuator 2, which carries a female cone on its outer periphery, into which a male cone carried by the pinion penetrates. The second frusto-conical friction surface 8 'surrounds the first frusto-conical friction surface, being axially longer than the latter. That is, the actuator 2 carrying the bell provided with an annular skirt 2b directed axially towards the teeth of the pinion. This skirt is of a non-constant thickness on its outer periphery, delimited by an annular wall of axial orientation, that is to say, cylindrical, and on its inner periphery by the second surface 8 'of concave shape, the first surface 8 being complementary in shape. convex. The skirt is connected thanks to the transverse arm 2a to the aforementioned second portion of the actuator 2. The bell belongs to the first portion of the actuator 2. The mounting groove of the disk of Figures 3 and 4 belongs to the free end of the skirt, while the withdrawal of housing material from the elastic means 10 is formed in a supplementary portion of the pinion 1 equivalent to the first portion of the actuator of the mode embodiment of Figures 3 and 4. The same disk can therefore be used for Figures 3 and 5.

It will be taken into account that the supplementary portion of the pinion constitutes an extension that extends radially and axially with respect to the teeth of the pinion 1. It is the outer periphery of this extension that carries the first surface 8, the mean diameter of which constitutes the mean diameter. contact of the surfaces 8, 8 '. This mean diameter is greater than

ES 2 268 114 T3 diameter of the head circle of the toothed part of the pinion 1.

In Figures 3 and 5, the smallest diameter of the first surface 8 is greater than the diameter of the head circle of the toothed part of the pinion 1. The extension is molded with the pinion 1.

The skirt 2b is solid, since the groove is made at the free end of the skirt 2b at the projecting part of the second surface 8 'with respect to the first surface 8'. The arm 2a, here transverse in a frusto-conical alternative, and the skirt 2b are monoblocks with the actuator 2. In an alternative, the bell is coupled on the actuator, for example in the same way as the assembly of figure 8. In this case, the second portion of the actuator has internally a protruding and supported tubular extension for its mounting and its axial penetration in a direction of the arm 2a. All the aforementioned forms of assembly are transportable in this configuration mode and vice versa.

It will be taken into account that the arm 2a forms one of the sides of the receiving throat of the band of the media 14.

Alternately well understood (Figures 6 and 7), the disk 10a is continuous and is extended at its outer periphery by a tubular part 10f provided at its free end with legs 10c mounted in contact with an inclined face 2d belonging to a protrusion 2e annular having the skirt 2a in radial projection on its outer periphery. This protrusion connects to the transverse face of the free end of the skirt and has a cylindrical centering radius 2f for the tubular part 10f.

The elastic means therefore comprise a zone of stoppage in translation of the pinion in the form of an annular bushing carried by the skirt.

The transverse face of the free end of the skirt constitutes the first stop.

The inclined face 2d may be provided with depressions for locking the bushing in rotation by cooperation of the legs 10c with the lateral edges of the depressions. The bushing is axially immobilized thanks to the face 2d and the face of the free end of the skirt.

In the previous figures the axial immobilization is carried out with a slight play by mounting the disc 10a in the groove.

Alternatively, a groove is made at the radius 2f and the tubular part is locally pressed 10f into the groove. The crimping legs 10c are then omitted.

Alternatively, the tubular part 10f is pressed locally in advance in advance and the mounting of the tubular part 10f on the spoke 2f is performed by ratcheting the pressed areas of the part 10f in the groove of the part 10f.

Alternatively, the disk 10a has axial legs on its outer periphery each provided at their free end with a hole for ratcheting mounting on a complementary pawl resulting from the outer periphery of the skirt. To do this, each hole belongs to an elastic zone formed, for example, by accordion folding.

Alternatively, the axial legs are provided at their free end with elastically deformable inclined projections for the formation of claws intended to be ratcheted with the claws.

Alternatively, the claws are formed thanks to the root zones 10d, as can be seen in Figures 9 and 10. These claws 10e are then elastically coupled with the internal periphery of the extension 1c or 2c of the skirt that constitutes its free end. In FIG. 10 a part of the extension 1c is shown in dotted line. In this case, the disk 10a is then continuous and has four arms 10b and two root zones 10d as in figure 7. The zones 10d are circumferentially delimited on their outer periphery by two blind grooves 110 which are each connected to a claw 10 extending radially with respect to the outer periphery of the disc 10a. The height of these claws is low here. These claws 10e are connected to one another by a flat section 111 that delimits the outer periphery of a root zone 10d.

The claws are each delimited by the edge of a slot 110, a rectilinear section constituting the outer periphery of the claw 10e and an inclined section connecting to the flat section 111.

Each root zone 10d thus has on its outer periphery a tongue 112 less wide circumferentially than said zone 10d.

Each tab 112 has, at each of its ends, a claw 10e. The tabs 112 can be bent axially.

The external diameter of the jaws 10e is slightly larger than the internal diameter of the extension 1c, so that when the elastic means are fixed axially in the extension 1c the tabs are bent axially, so that the jaws remain engaged under pressure with the bore. internal extension of the internal extension 1c, as can be seen in figure 10 when the elastic means 10 are the object of a force that acts in the opposite direction to that of the press fit, the elastic means are locked by braking. The tabs 112 are generally in the shape of a cat's head with two ears formed by claws 10e.

The groove of Figures 3 and 5 can be omitted. Alternatively, the groove is retained so as to improve the axial locking of the elastic means.

10.

Alternatively, the throat is replaced by jaw receiving depressions 10e.

Advantageously, the claws 10e are mounted under pressure in the groove or the recesses to prevent any movement due to vibrations.

Thus it is evident from the description and the drawings that the torque transmission capacity of the starter head is increased by a significant friction mean diameter for a given diametral dimension. The number of parts is also reduced, as well as the axial and diametrical dimension of the starter head. A good seal is obtained as regards the projections of oil or water directed towards the pinion thanks to the bell. You have the possibility of choosing different materials, one well adapted to the mechanical characteristics required by the pinion, since the other adapts to the friction and wear resistance needs of the conical clutch.

Alternatively, the bush of figures 6 and 7 can replace the bush of figure 5 of document FR-A-2 772 433, which allows a reduction in the number of parts.

Advantageously, an electronic command device is used to power the

ES 2 268 114 T3 winding 12a and of the electric starter motor to reduce the duration of the phase of operation "in free wheel" of the conical clutch and to free the reaction time of the driver. For example, the electronic device is of the type described in document FR A 2,795,884, which feeds the winding 12a by means of a transistor according to a voltage in the sector of the "Pulse Width Modulation" (PWM) type in French. More specifically, it makes the effective current in the winding 12a vary during the displacement of the core 12b towards its contact position, to close the movable contact 13 and power the electric motor M. It is adopted during this displacement:

- a first phase of driving with an effective current sufficiently high to set the core 12b in motion, then,

- a second phase of impulsion of lower effective current,

- a continuous increase of the effective intensity is applied during the second phase, after a predetermined or determined time. For more details, refer to this document.

Thanks to the electronic device, a less noble friction material can be chosen for the friction surfaces 8, 8 ', since the phase of excessive speed and consequently of sliding between the two surfaces is better controlled. This allows to reduce costs. Advantageously, to provide the starter head with conical clutch, a circumferentially acting elastic means damper and / or a torque limiter are alternatively associated with the starter head.

Thus, in a first embodiment, the torsion damper and the torque limiter are associated with the epicyclic gear reducer of Figure 1 interposed between the electric motor and the output shaft 100 on which the actuator 2 is mounted.

For this, the solution described in document FR 9916726, deposited on 12/30/1999, can be adopted, for example. The torque limiter is then interposed axially between the gearbox crown and an arm of a box into which the crown gear is rotatably raised.

The elastic means then consist of at least the elastically deformable damper block, being for example made of elastomer, mortar in rotation in the case of a disk belonging to the torque limiter. Alternatively, the starter ring belongs to the secondary mass of a damping flywheel linked to the gearbox of the motor vehicle. This secondary mass is connected by a torsional damper and a torque limiter to a primary flywheel linked to the vehicle's crankshaft, as described in document FR A 2,598 475.

Alternatively, only one of the two torsional damping torque limiting devices is present.

Alternatively, the two aforementioned devices can be provided.

The presence of a band is not mandatory. The starter can thus have the constitution of that described in document EP-A-0 867 613, which describes a solution with a reducer, the output shaft of which acts on the starter head.