EP2917558B1 - Heat engine starter provided with a device for shock absorption by shearing - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a motor starter with a shear absorption device.

The invention finds a particularly advantageous application, but not exclusive, with vehicles equipped with the function of stopping and restarting the engine (function called "stop and start" in English) depending on traffic conditions.

STATE OF THE ART

In order to start a combustion engine, also called an internal combustion engine, in particular a motor vehicle, it is known to use a rotating electrical machine in the form of a starter provided with a launcher capable of transmitting rotational energy. from the starter to a crankshaft of the engine through a drive gear.

This launcher is mounted on an output shaft of the electric machine. In one embodiment, a speed reducer is interposed between this output shaft, constituting the launcher shaft, and the shaft of the electric motor that comprises the rotating electrical machine. The interposition of the reducer has the advantage of using a faster electric machine and thus obtain a higher starting torque while reducing the size and weight of the machine for a given power. As described in the document FR2632094 , this speed reducer can be formed by a toothed wheel in the form of a pinion fixed at one end of the shaft of the electric motor of the electric machine and a ring gear rotationally fixed by friction means of the thrower shaft; this ring having inner teeth meshing with the pinion. In this case, the electric motor shaft and the launcher shaft are offset relative to each other.

Alternatively, as described in the document WO2005 / 054664 , the speed reducer is formed by an epicyclic gear comprising planet wheels mounted rotatably about axes carried by a planet carrier comprising a transverse plate secured to the rear end of the starter shaft. These planet gears mesh with the pinion integral with the shaft of the electric motor and with the inner teeth of the ring gear stationary in rotation relative to the housing that comprises the starter. In this case, the electric motor shaft and the launcher shaft are coaxial.

Furthermore, the launcher comprises a pinion provided with teeth configured to mesh with teeth of the drive ring, also called start ring, rigidly or resiliently fixed to the crankshaft of the engine to start. This launcher can undergo significant mechanical shocks during operation of the starter, especially during the launch of the engine. For example, at the start of start, when the rotation of the starter begins, the teeth of the pinion can slide against the teeth of the drive ring before engaging between them. The axial overlap of the respective teeth of the pinion and the drive ring can then be very low and the kinetic energy of rotation of the starter is abruptly transmitted to the ring gear. At this time, the contact stresses are very high, which can, with wear, cause the destruction of teeth of the crown. This phenomenon is known as milling.

In addition, during the start of the engine, if the injection system of the vehicle has random malfunctions, it can occur premature explosions in the combustion cycle, usually called back fire, which are likely to generate significant shocks when meshing the pinion with the driving ring. Shocks can also occur when stopping the engine. These shocks present the risk of causing the breakage of teeth of the pinion or the driving ring, resulting in a major incident.

In order not to damage the starter during these starts, it is known to equip the gearbox of damping sprockets. A conventional assembly consists of a ring of plastic material on which are molded dampers elastomeric thermoplastic material capable of being compressed during the application of an over-torque. See for example EP 1 450 038 A1 . The compression is effected by a relative angular displacement of the dampers integral in rotation with the ring gear with respect to compressor elements integral in rotation with the starter housing intended to bear against the dampers to compress them.

However, it is found that absorption of shocks by compression implies a fairly sudden absorption of shocks to the extent that the torque absorbed as a function of the displacement angle of the ring changes exponentially, as shown in FIG. figure 1 . Such a change in the absorbed torque results in rapid wear of the dampers during successive uses of the starter and a transmission of significant forces to the starter traction chain, which reduces its life.

OBJECT OF THE INVENTION

The invention aims to effectively remedy these disadvantages.

• un moteur électrique comportant un arbre,
• un arbre de sortie sur lequel est monté un pignon d'entraînement destiné à engrener avec une couronne de démarrage du moteur thermique,
• un ensemble réducteur ayant une couronne dentée, l'ensemble réducteur étant installé entre l'arbre du moteur électrique et l'arbre de sortie et reliant en rotation l'arbre du moteur électrique à l'arbre de sortie,
• un carter,
• au moins un dispositif d'absorption des chocs installé entre la couronne dentée et le carter liant en rotation la couronne au carter, caractérisé en ce que le dispositif d'absorption de choc est monté pour absorber par cisaillement des chocs subis par la couronne lors d'un démarrage du moteur thermique engendrant un déplacement angulaire relatif de la couronne par rapport au carter du démarreur.

For this purpose, the subject of the invention is a starter for a motor vehicle engine, comprising:

• an electric motor having a shaft,
• an output shaft on which is mounted a drive pinion for meshing with a starting ring of the heat engine,
• a gear unit having a ring gear, the gear unit being installed between the shaft of the electric motor and the output shaft and rotatingly connecting the shaft of the electric motor to the output shaft,
• a housing,
• at least one shock absorbing device installed between the ring gear and the casing which rotates the ring gear to the casing, characterized in that the shock absorbing device is mounted to shear absorb shocks to the ring gear during 'an engine start thermal generating relative angular displacement of the ring relative to the starter housing.

The invention thus makes it possible to damp the shocks in a more progressive manner than a damper working in compression, insofar as the absorbed torque evolves in a linear manner as a function of the rotation angle of the ring during the shearing of an element. elastic. The invention therefore makes it possible to increase the life of the traction chain.

Shear absorbing device means an absorption device which is mounted to deform predominantly by shear to dampen the impact.

• une plaque de support solidaire en rotation avec le carter, et
• au moins un élément élastique ayant une première face solidaire en rotation de la plaque de support et une deuxième face opposée à la première face solidaire en rotation avec la couronne apte à tourner par rapport au carter en cas de chocs subis par la couronne.

According to one embodiment, the shear absorption device comprises:

• a support plate secured to rotate with the housing, and
• at least one elastic element having a first face rotationally fixed to the support plate and a second face opposite to the first face integral in rotation with the crown rotatable relative to the housing in case of shocks to the crown.

The fact of using a support plate makes it easier to mount the absorption device in the casing of a starter. Indeed without this plate, one of the mounting methods would be the bonding of a surface of the elastic element to the housing.

In addition, the fact that the elastic element has two of these faces integral in rotation with the crown on the one hand and the housing on the other hand allows the elastic element to work significantly in shear.

According to a first embodiment, the first face of the elastic element comprises a radial surface integral in rotation with the support plate and in that the second face comprises a radial surface integral in rotation with the ring. Radial surface means a surface whose projection is perpendicular to the axis of the ring.

According to a second embodiment, the first face of the elastic element comprises an axial surface integral in rotation with the support plate and in that the second face comprises an axial surface integral in rotation with the ring. Axial surface means a surface whose projection is parallel to the axis of the crown.

According to another embodiment, at least one of the first or second faces of the elastic element is of conical shape.

According to one embodiment, the second face of the absorption device and mounted against a transverse wall of the ring.

This embodiment makes it possible to arrange the damping device axially to reduce the radial space requirement.

According to another embodiment, the shock absorbing device is mounted radially between the crown and the housing.

This embodiment reduces the axial size of the starter.

According to one embodiment, the shear absorbing device further comprises an insert plate secured to the second face of the elastic element, this plate being mounted integral in rotation with the transverse wall of the ring.

In one embodiment, the insert plate is attached to the second face of the elastic member.

In one embodiment, the wafer is attached to the elastic element by overmolding or gluing.

In one embodiment, the support plate is attached to the first face of the elastic member.

According to one embodiment, the support plate is fixed to the elastic element by overmolding or gluing.

According to one embodiment, the insert plate substantially covers the entire surface of the second face of the elastic element.

According to one embodiment, the transverse wall of the crown is fixed by gluing to the second face of the elastic element.

This reduces clutter.

According to one embodiment, the transverse wall of the ring has openings for receiving pads from the insert plate. This allows for a means of fixing in easy rotation. According to one embodiment, to homogenize the stresses experienced by the material during shearing, the first and second faces of the elastic element are inclined with respect to each other.

According to one embodiment, the starter further comprises a compression shock absorption device adapted to be biased when the ring exceeds an angular displacement threshold so as to limit the stress experienced by the shear absorption device.

The shear absorbing device and the compression shock absorber are mounted in the starter so that, during an impact, the shearing device initially deforms to the angular displacement threshold and then the two shock absorbers deform to absorb the shock.

According to another embodiment, the shear absorbing device and the compressive shock absorption device are mounted in the starter so that, during an impact, the device for absorbing shear impact is deformed in a first step up to the angular displacement threshold and then only the compression shock absorber deforms to absorb the shock.

In these two embodiments, in the first stage (up to the tripping threshold), only the shear absorbing device deforms.

In one embodiment, the angular displacement threshold is between 15 and 25 degrees. This allows the shear absorption device to absorb non-abruptly part of the shock.

According to one embodiment, the device for absorbing shocks by compression comprises at least one damper integral in rotation with one of the transverse wall of the crown and the support plate and at least one corresponding compressor element integral in rotation with the other element intended to bear against the damper during the angular displacement of the ring beyond the angular displacement threshold.

According to one embodiment, the compression damper is integral in rotation with the support plate while the compressor element belongs to the transverse wall of the ring.

According to one embodiment, a portion of the damper is inserted into a rigid receiving cage located on the opposite side with respect to the compressor element forming a stop.

In one embodiment, the damper has beveled corners on the side of the compressor element.

In one embodiment, the shear absorbing device comprises two diametrically opposed elastic elements having a ring portion shape.

According to one embodiment, the compression shock absorption device comprises two dampers each located between two ends of the elastic elements facing one another and two compressor elements each located between an elastic member and a damper.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1, déjà décrite, montre une représentation graphique de l'évolution du couple absorbé en fonction d'un angle de rotation de la couronne d'un ensemble réducteur lors d'un choc subi par le démarreur selon l'état de la technique;
• La figure 2 montre une vue en coupe longitudinale d'un démarreur selon l'invention ;
• Les figures 3a et 3b représentent des vues en perspective sous deux angles différents d'une couronne d'un ensemble réducteur et des dispositifs d'absorption des chocs selon l'invention qui lui sont associés ;
• Les figures 4a et 4b montrent des vues éclatées de l'avant et de l'arrière de la couronne et des dispositifs d'absorption des chocs selon l'invention qui lui sont associés;
• La figure 5 est une vue de dessus de la couronne et des dispositifs d'absorption des chocs selon l'invention;
• La figure 6 montre une vue en coupe transversale suivant l'axe A-A de l'ensemble de la figure 5;
• Les figures 7a-7c représentent les différents états des dispositifs d'absorption des chocs selon l'invention lors de l'absorption d'un choc subi par le démarreur selon l'invention;
• La figure 8 montre une représentation graphique de l'évolution du couple absorbé en fonction d'un angle de rotation de la couronne d'un ensemble réducteur lors d'un choc subi par le démarreur selon l'invention.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention.

• The figure 1 , already described, shows a graphical representation of the evolution of the absorbed torque as a function of an angle of rotation of the crown of a reduction unit during a shock to the starter according to the state of the art;
• The figure 2 shows a longitudinal sectional view of a starter according to the invention;
• The Figures 3a and 3b represent perspective views from two different angles of a ring gear of a gear unit and shock absorption devices according to the invention associated with it;
• The Figures 4a and 4b show exploded views of the front and rear of the crown and the shock absorbing devices according to the invention associated with it;
• The figure 5 is a top view of the crown and shock absorbing devices according to the invention;
• The figure 6 shows a cross-sectional view along the axis AA of the whole of the figure 5 ;
• The Figures 7a-7c represent the different states of the shock absorption devices according to the invention during the absorption of an impact suffered by the starter according to the invention;
• The figure 8 shows a graphical representation of the evolution of the absorbed torque as a function of an angle of rotation of the crown of a reduction unit during an impact on the starter according to the invention.

Identical, similar or similar elements retain the same reference from one figure to another.

DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

In the following description, use will be made of an axial orientation from back to front corresponding to the right-to-left orientation in accordance with the figure 2 .

With reference to the figure 2 , the rotating electrical machine is a starter motor 10 similar to the starter described in the document WO2005 / 054664 , so that the elements identical or similar to those of the figure 1 of this document WO2005 / 054664 , to which reference will be made for more details, will be assigned the same reference signs. The starter comprises in this embodiment an output shaft 43, a launcher 30 mounted on the shaft 43 and an electric motor 11 composed of an inductor stator 12 and a rotor 13 induced coaxially mounted, the stator 12 surrounding the rotor 13, which is rotatably mounted about an axis 14 inside a cylinder head 15. The latter is secured to a metal support of the starter for attachment to a fixed part of the motor vehicle. The support 16 is here moldable material, for example based on aluminum and belongs to the housing of the machine.

In known manner, the stator 12 comprises in one embodiment a plurality of permanent inductor magnets carried by the inner periphery of the cylinder head 15. Alternatively, as shown in the embodiment of FIG. figure 2 , the stator 12 comprises an inductor winding 17 comprising two pairs of windings 18, which are each wound around a polar mass 19 integral with the cylinder head 15. The polar masses 19 are fixed with screws 20 to the cylinder head 15, here metallic, as described in the document FR2611096 . Each winding 18 is composed of a continuous conductor wound around the polar mass 19 in the direction of its thickness so as to form concentric contiguous turns of increasing diameter as better visible in the Figures 2 to 5 of the document EP749194 . The axis of each winding 18 is radial relative to the axis 14 of the rotor 13, which constitutes the axis of rotation of the electric motor 11.

The rotor 13 comprises a bundle of plates provided with grooves for mounting electrical conductors 21 in the form of pins. These conductors 21 are interconnected to form a rotor winding in connection with the conductive blades 22 belonging to a collector 23 with an electrically insulating body integral with the shaft 24 of the electric motor 11. In a variant, the winding is in continuous wire.

Brushes 25 rub on the collector slats 22 of the manifold 23 to supply the rotor winding. Brushes 25 belong to a brush holder 26 equipped with guiding cages and receiving brushes, which are biased towards the slats 22 by means of springs 27. The brush holder 26 is integral with a metal rear bearing 29 having in the central part a housing for mounting a needle bearing 28. The bearing 29 serves for rotatably mounting the rear end of the shaft 24 of the electric motor 11. The axis of this shaft 24 coincides with the axis 14 of the rotor 13, and with the axis of the output shaft 43 of the starter constituting the starter shaft 30. The rear bearing 29 serves as a centering device at the rear end of the yoke 15, and is connected by tie rods 31 to the support 16 of the starter 10. Two threaded holes (not referenced) are formed in the support 16 for screwing the tie rods. The tie rods 31 are located outside the cylinder head 15. Here a small clearance exists between the tie rods and the outer periphery of the cylinder-shaped cylinder head 15. The metal cylinder head is interposed between the metal support 16 and the metal rear bearing 28. The starter housing thus comprises the bearing 28, the cylinder head 15 and the support 16. This casing is intended to be connected to the mass of the vehicle. automobile via its support 16.

The starter 10 also comprises an electromagnetic contactor 32 extending parallel to the electric motor 11 by being radially implanted above it. The contactor 32 has a metal tank 33 carried by the support 16, and equipped with an excitation coil B provided with at least one winding. The tank 33 is closed at the rear by a cover 34 made of electrically insulating material. The fixing of the cover 34 is made by folding the material of the free end of the tank 33. A shoulder of the tank 33 ensures the axial setting of a fixed core 35, which is wedged axially in the other direction by the cover 34 carrying terminals 36, 37 of power supply.

The terminals 36, 37 are shaped to each form a fixed contact 38 inside the cover 34. One of the terminals 36 is intended to be connected to the positive terminal of the battery, the other 37 is connected by the intermediate of a cable 39 at the input of the inductor winding 17 of the stator and brushes 25 of positive polarity. In known manner during the excitation of the coil B, a mobile core 40 is attracted by magnetic attraction towards the fixed core 35 to, firstly, act after catching a game on a rod (not referenced) carrying a movable contact (not referenced) to cause the closure of the contacts of the contactor 32 and supply the electric motor of the starter, and, on the other hand, operate a lever 41 for controlling the launcher.

The output shaft 43 is rotatably mounted in a bearing 42 before the support 16. This bearing 42 is constituted by way of example by a needle bearing alternatively by a plain bearing. This shaft 43 carries at the front a stop 53 adjacent to the bearing 42 to limit the movement of the launcher 30. The rear end of the shaft 43 is configured to be secured to a plate of a planet carrier 47, for example by crimping, this planet carrier 47 belonging to an epicyclic gear train constituting the speed reducer 45 gear. This planet carrier 47 carries satellites 47.1 meshing on the one hand with a ring 46 (described in more detail below) and with a sun gear 51 integral with the front end of the shaft 24 of the electric motor. The gearbox 45 is of the type described in the document FR2787833 which will be referred to, the latter showing the mounting of the front end of the shaft 24 of the electric motor 11 in the rear end of the shaft 43 having a blind hole in which is housed the front end of the shaft 24 with the interposition of a plain bearing and a ball. The satellites 47.1 are therefore rotatably mounted each about an axis. These axes extend between two plates of transverse orientation relative to the axis of the shaft 43 being carried by these plates, one of which is thicker than the other and is here fixed by crimping to the rear end of the shaft 43. In a variant, the planet carrier 47 comprises a single plate fixed to the rear end of the shaft 43 and carrying the axes.

The launcher 30 is slidably mounted on the output shaft 43, and comprises a drive gear 50, a driver 51 configured to be actuated by the control lever 41 pivoting, and a free wheel 52 with rollers interposed axially between the 51 and the pinion 50. In known manner the teeth of the pinion 50 belong to a sleeve extended at the rear to form the cylindrical inner track of the free wheel 52 roller. The driver 51 is axially extended at the front by a bushing configured internally to form the profiled external track of the freewheel 52 with wheels and to house the springs acting in known manner on the rollers. More specifically, the driver 51 comprises a sleeve integral with the front of a flange of transverse orientation relative to the axis of the shaft 43. This flange is integral at its outer periphery with the sleeve of axial orientation by relative to the axis of the shaft 43 for forming a roller receiving cage closed at the front by washers. The driver 51 carries a washer (not referenced) defining with the flange of the driver 51 a groove for receiving the fingers of the lower end of the lever 41 fork-shaped. The upper end of the lever 41 is mounted in known manner to articulation on a rod (not referenced to the figure 2 ) elastically connected to the movable core 40 via a spring housed in the movable core 40. Of course alternatively, the lever 41 is hingedly mounted on the movable core 40 and the spring surrounds the sleeve of the driver by bearing on the flange of the coach as described for example in the document DE2822165 .

In known manner, the sleeve of the driver 51 is internally provided with helical splines (not referenced) in complementary engagement with external helical teeth carried by the output shaft 43 in the vicinity of its rear end here cylindrical and moreover large diameter. The launcher 30 is thus animated by a helical movement when it is moved by the lever 41 in the direction of the stop 53 to come, via its pinion 50, in engagement with the drive ring, called the crown of starting (not shown), a heat engine also called internal combustion engine.

It is clear that the freewheel device 52 can be replaced by a conical clutch coupling device, of the type described in the document FR2772433 or a clutch with multiple disks. Similarly, it is clear that the launcher 30 variant is implanted in part outside the support 16 at the front thereof. More precisely, the pinion 50 of the launcher 30, instead of being implanted in the support (cf. figure 2 ), can be implanted outside the support as visible for example in the document FR2745855 which will be referred to for more details.

The control lever 41 is coupled, here elastically in a variant rigidly in the aforementioned manner, by its upper end to the movable core 40 of the contactor 32, and comprises in its middle part a pivot axis 54, which according to a characteristic is distinct, the toothed gear gear reducer gear ring 46 due to the structure of the assembly described below. The lever 41 is in a molded part, preferably made of rigid thermoplastic material to reduce noise, preferably reinforced by fibers. The mounting of the pivot axis 54 is for example made using a support piece as in the documents DE2822165 and FR2787833 or in the support 16 provided with projections for this purpose, the axis 54 being separate or integrated in the lever 41. In the embodiment of the figure 2 as in the document DE2822165 , there is provided a sealing pad 158 of elastomer to absorb dimensional variations. This stud 158 is in contact with the contact surface of the contactor and is integral with a plastic part 155 configured to replace the tongue or tabs 55 of the figure 1 of the document WO2005 / 054664 ; the housing of the support 16 being retained. Alternatively, the pad 158 is removed and it is the plastic part 155 which is then in contact with the contact surface of the contactor. The solution described in the document can also be used WO01 / 31195 . It all depends on the applications.

The ring 46 of the X-axis speed reducer 45 coincides with the axis 14 is of hollow form and has a wall 58 transverse to the outer periphery of which extends an annular skirt 46.1 of axial orientation provided with inner teeth meshing with satellites 47.1. This transverse wall 58 is pierced centrally and mounted on a hub 68 reported to ensure its centering. The hub 68 has at its center a through opening allowing the passage of the shaft 43. As visible on the figure 3a , the skirt 46.1 is axially oriented relative to the axis X and therefore has a cylindrical shape. The teeth 46.4 of the skirt 46.1 have an axial orientation. The ring 46 is closed at the rear by a cover 200 (cf. figure 2 ). The inside of the ring 46 can thus be filled with lubricating grease of the satellites 47.1 and the sun gear 49.

In order to absorb the shock experienced by the ring 46 during successive uses of the starter 10, the starter 10 comprises a shock absorbing device 61 installed between the ring gear 46 and the starter housing, in this case the carrier 16, adapted to absorb shear shocks suffered by the ring 46 during overtemperature generated by the start of the engine.

More precisely, as is clearly visible on the Figures 3a and 3b , the device 61 comprises a support plate 62 of annular shape also of X axis having on one of its faces of radial orientation of the pins 64 intended to be inserted inside unrepresented openings made in the support 16 The support plate 62 is thus integral in rotation with the support 16 and thus with the starter housing. The pins 64 are angularly distributed regularly at the outer periphery of the support plate 62. In this case, these six pins 64 have a parallelepiped shape. A central opening 67 of the support plate 62 allows the passage of the shaft 43. The support plate 62 is for example made of metal and the pins 64 are made of material with the support plate 62.

The support plate 62 further comprises an indexing means 65 formed by a recess shown in FIG. figure 3a made at its outer periphery intended to cooperate with a projection of the support 16. This facilitates the angular positioning of the plate 62 relative to the support 16.

Alternatively, as shown on the Figures 4a and 4b , the support plate 62 is devoid of pins 64 and has an annular shoulder 66 at its outer periphery of axial orientation and a lug 78 of generally rectangular shape for its indexing and its connection in rotation with the support 16. At this Indeed, the lug 78 is intended to cooperate with a housing, not shown, of complementary shape formed in the support 16. The support plate 62 also comprises an annular sleeve 79 of X axis delimiting the opening 67 on which is positioned the crown 46.

As clearly visible on the figure 4a the shock absorbing device 61 also comprises two elastic elements 69 fixed on a radial face of the support plate 62 opposite the face comprising the pins 64 or the shoulder 66. The fixing of the elastic elements 69 on the support plate 62 is effected for example by bonding a face 70 of the elastic elements 69 to the support plate 62. Each elastic element 69 has, for example, a portion shape. annular extending for example on an angle A of the order of 112 degrees. Each elastic element 69 has an inner radius R1 greater than an outer radius R2 of the sleeve 79 and an outer radius R3 slightly smaller than an outer radius R4 delimiting the plate 62. The elastic elements 69 are for example made of rubber. The elastic elements 69 have for example a Shore hardness of between 72 and 73 ShA at 80 degrees Celsius.

In addition, as shown on the figure 6 , an insert plate 71 is integral with a face 72 of each elastic element 69 opposite the face 70 fixed to the support plate 62. This plate 71 follows an outer contour of the face 72 (cf. figure 4a or 7a ) so that the wafer 71 has substantially the same surface as the face 72. In other words, the wafer 71 covers substantially the entire surface of the face 72. The face 72 of the elastic element 69 carrying the wafer 71 is inclined relative to the face 70 fixed to the support plate 62. The stresses experienced by the material during shearing of the elastic elements 69 are thus homogenized. More specifically, the face 70 extends in a radial plane with respect to the axis. X. The face 72 is inclined with respect to the face 70 towards the inside of the plate 62 so that the cross-section of each element 69 tends to decrease when moving from the outside to the inside of the plate. plate 62. The angle of inclination B 'of the two faces relative to each other is for example of the order of 5 degrees. The face of the wafer 71 attached to the element 69 has a corresponding inclination. The plates 71 take for example each in the form of a thin plate made of metal.

The transverse wall 58 of the ring 46 is made integral in rotation with the wafer 71. For this purpose, as shown in FIGS. Figures 4a , 6 , 7a-7c the wall 58 has openings 74 intended to receive studs 75 coming from the plates 71. In this case, each plate 71 comprises three studs 75 positioned on the same circumference between the inner periphery and the outer periphery of the elastic element. These studs 75 are intended to cooperate with two sets of three diametrically opposed openings 75 formed in the transverse wall 58 of the ring 46 (cf. figure 5 ). In addition to or in substitution for this connection system, the transverse wall 58 is fixed by gluing to the wafer 71.

The starter 10 further comprises a compression damping device 80 biased when the ring 46 exceeds a threshold K1 angular displacement. The threshold K1 of angular displacement is between 15 and 25 degrees and is preferably of the order of 23 degrees.

For this purpose, the device 80 comprises two dampers 81 integral in rotation with the support plate 62 used in combination with two compressor elements 82 integral in rotation with the ring 46. In the idle state, each compressor element 82 is spaced angularly by relative to the damper 81 of an angle C equal to the threshold K1 of angular displacement (cf. figure 7a ). Each compressor element 82 is thus intended to bear against the damper 82 when the angular displacement of the ring 46 exceeds the threshold K1. Preferably, a portion of each damper 82 is inserted inside a rigid receiving cage 84 located on the opposite side to the compressor element 82 associated therewith. The cage 84 thus forms a stop, so that when a compressor element 82 acts on a damper 81, the latter is compressed between the cage 84 and the compressor element 82.

In this case, the dampers 81 are diametrically opposite one another and have a ring portion shape. As shown on the figure 4a , the ring portions extend over an angle D at least two times smaller than the angle A on which the elastic elements 69 extend. The inner and outer radii delimiting respectively the inner and outer periphery of the dampers 81 are substantially identical to those R1, R3 of the elastic elements 69. Each damper 81 has bevelled angles on the side of the compressor element 82. The bevel is made on an angle E shown on the figure 7a worth, for example, 10 degrees. Each damper 81 is positioned between two ends of the elastic elements 69 facing one another. The dampers 81 are fixed to the support plate 62 by means of tabs shown from the support plate 62 penetrating the dampers 81. The dampers 81 are for example made of elastomeric thermoplastic material.

The compressor elements 82 take for example the form of ribs coming from material with the support plate 62. These ribs of substantially parallelepiped shape have a trapezoidal section.

The elastic elements 69, the dampers 81 and the compressor elements 82 have a substantially identical height L, as clearly Figures 3a, 3b , and 4a .

Hereinafter described with reference to the Figures 7a to 7c , the operation of the shock absorption system according to the invention. These figures show the states of only one of the elastic elements 69 and only one of the dampers 81 but it is clear that the other elastic element 69 and the other damping 81 not shown have corresponding states. It should also be noted that in these figures the compressor element 82 is connected in rotation with the transverse wall 58 of the ring 46 which has not been shown for the sake of clarity. The representation of the support plate 62 is also simplified.

As shown on the figure 7a when the ring 46 does not undergo a shock when starting the engine and therefore remains stationary, which corresponds to a state of rest, the elastic elements 69 are not sheared by a displacement of the ring 46 while the damper 81 is not constrained by the compressor element 82.

As shown on the figure 7b , in the event of shocks to the ring 46, the latter rotates along the arrow F about the X axis relative to the starter housing, which has the effect of moving in a tangential direction Dt the wafer 71, and therefore the face 72 of the elastic member 69, while the face 70 of the elastic member 69 connected to the support plate 62 remains stationary. Note that the tangential direction Dt of displacement of each point of the wafer 71 (and of the face 72) corresponds to a direction perpendicular to a radius R1 passing through the axis X of the plate 62 and each point of the wafer 71, this direction Dt itself located in a plane parallel to the face 70 fixed to the support plate 62. Such a displacement of the two faces 70, 72 of the elastic element 69 relative to each other creates a shearing effect to absorb shocks in a linear fashion as shown on the figure 8 by the part of the curve referenced P1. As long as the angular displacement of the ring 46 remains below the angular displacement threshold K1, the device 80 is not stressed and therefore does not participate in the absorption of the shocks to the extent that the compressor element 82 does not enter. in support against the shock absorber 81.

As shown on the Figure 7c when the angular displacement of the ring 46 exceeds the threshold K1, the compressor element 82 which has moved freely to the damper 81 begins to compress the damper 81 which is sandwiched, that is to say stuck between the receiving cage 84 forming a stop and the compressor element 82. During this time, the elastic element 69 continues to deform by shearing. The absorbed torque then evolves exponentially as shown on the figure 8 by the part of the curve referenced P2. The device 80 for compressive shock absorption thus makes it possible to limit the stress imposed on the elastic elements 69 during their shearing.

Of course, those skilled in the art can modify the structure of the shock absorbing devices 61 and 80 previously described without departing from the scope of the invention. Thus, in an equivalent manner, the dampers 81 may be made integral in rotation with the transverse wall 58 of the ring 46, while the compressor elements 82 are made integral in rotation with the support plate 62. Of course, the number of elastic elements 69 may be greater than or less than two and in all cases at least one. It depends on the application. It is the same for the number of dampers 81 of the device 80 which may vary depending on the application. Alternatively, the starter could also comprise only a shear absorbing device 80 and be devoid of device 61 for compressive shock absorption.

Claims (15)

1. A starter (10) for a combustion engine of an automotive vehicle comprising:

   - an electric motor (11) comprising a shaft (24),

   - an output shaft (43), on which a drive pinion (50) is mounted which is intended to engage with a starting ring gear of the combustion engine,

   - a reduction gear unit (45) having a ring gear (46), the reduction gear unit being installed between the shaft (24) of the electric motor and the output shaft (43) in order to connect the shaft of the electric motor to the output shaft in a rotational manner,

   - a casing (16),

   - at least one shock absorber (61) installed between the ring gear (46) and the casing (16) connecting the ring gear to the casing in a rotational manner, characterised in that the shock absorber is capable of absorbing by shear shocks experienced by the ring gear (46) during a start-up of the combustion engine giving rise to a relative angular displacement of the ring gear (46) with respect to the casing (16) of the starter.
2. The starter according to claim 1, characterised in that the shear shock absorber (61) comprises:

   - a support plate (62) connected in a rotationally fixed manner to the casing, and

   - at least one elastic element (69) having a first face (70) connected in a rotationally fixed manner to the support plate (62) and a second face (72) opposite the first face (70) connected in a rotationally fixed manner to the ring gear (46) capable of rotating with respect to the casing in the event of shocks experienced by the ring gear (46).
3. The starter according to claim 2, characterised in that the shear shock absorber (61) further comprises an attached plate (71) connected fixedly to the second face (72) of the elastic element (69), this plate being mounted in a rotationally fixed manner with the side wall (58) of the ring gear.
4. The starter according to claim 3, characterised in that the attached plate (71) essentially covers the whole of the surface of the second face (72) of the elastic element (69).
5. The starter according to claim 3 or 4, characterised in that the side wall (58) of the ring gear (46) is fixed by gluing to the attached plate (71).
6. The starter according to any one of claims 3 to 5, characterised in that the side wall (58) of the ring gear (46) comprises openings intended to receive studs (75) emerging from the attached plate (71).
7. The starter according to any one of claims 2 to 6, characterised in that the first (70) and the second face (72) of the elastic element (69) are inclined with respect to one another.
8. The starter according to any one of claims 1 to 7, characterised in that it also comprises a compression shock absorber (80) mounted between the ring gear and the support plate in a manner such as to be stressed only when the ring gear (46) exceeds an angular displacement threshold (K1) in such a way as to limit the stress experienced by the shear shock absorber (61).
9. The starter according to claim 8, characterised in that the angular displacement threshold (K1) is between 15 and 25 degrees.
10. The starter according to claims 2 and 8 or 9, characterised in that the compression shock absorber (80) comprises at least one damper (81) connected in a rotationally fixed manner to one of the elements among the side wall (58) of the ring gear (46) and the support plate (62) as well as at least one corresponding compressor element (82) connected in a rotationally fixed manner to the other element intended to come to rest against the damper (81) during the angular displacement of the ring gear (46) beyond the angular displacement threshold (K1).
11. The starter according to claim 10, characterised in that the damper (81) is connected in a rotationally fixed manner to the support plate (62) whilst the compressor element (82) belongs to the side wall (58) of the ring gear (46).
12. The starter according to claim 10 or 11, characterised in that a part of the damper (81) is inserted into a rigid receiving cage (84) located at the opposite side with respect to the compressor element (82) forming a stop.
13. The starter according to any one of claims 10 to 12, characterised in that the damper (81) has bevelled angles on the side facing the compressor element (82).
14. The starter according to any one of claims 1 to 13, characterised in that the shear shock absorber (61) comprises two diametrically opposed elastic elements (69) having a shape of a ring portion.
15. The starter according to claims 10 and 14, characterised in that the compression shock absorber (80) comprises two dampers (81) each located between two ends of the elastic elements (69) opposite one another and two compressor elements (82) each located between an elastic element (69) and a damper (81).

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