STARTER FOR INTERNAL COMBUSTION ENGINE

Description

[0001] The present invention relates to the technical field of internal combustion engine starters. In a preferred but not exclusive application, the invention relates to a motor vehicle internal combustion engine starter.

[0002] Such a starter generally comprises an electric motor associated with means for driving the internal combustion engine. The drive means are most often adapted to be coupled to the moving parts of the internal combustion engine during a starting phase of the latter and to be uncoupled from the internal combustion engine when the latter is operating. For this purpose, the starter comprises an electromagnetic switch adapted to, on the one hand, control the power supply to the electric motor and, on the other hand, control the coupling and uncoupling of the drive means from the internal combustion engine. The drive means comprise a launcher which is movable in rotation on itself and which is movable in axial translation between a rest position and a drive position of the internal combustion engine.The starter is then moved between its rest and drive positions by a lever operated by the electromagnetic switch. Since starting the internal combustion engine requires a relatively large drive torque, the drive means include a reduction gear which is interposed between the starter and a drive pinion of the electric motor.

[0003] In order to have a starter as compact as possible, it has been proposed to implement an epicyclic gear reducer as is, for example, described in applications FR 2 937 933 and WO 2005 / 0 54664. Other combustion engine starters with dampers are described in WO2008071896A2, DE4302854C1, EP1457670A2, EP1450038A1 and FR2591824A1. The starter then comprises a starter head comprising a casing which delimits a reduction chamber and which comprises means for fixing the electric motor. The starter head also comprises a speed reducer arranged in the reduction chamber and consisting of an epicyclic gear train comprising in particular satellite pinions, intended to be driven in rotation by the drive pinion of the electric motor, and an outer ring gear of axis Δ, linked to the casing by rotational connection means.

[0004] Such a starter head and the starter motor that incorporates it are fully satisfactory in terms of their starting function in the early stages of use. However, it has become apparent that after a certain period of use of this starter motor, the moving parts of the starter head are likely to deteriorate so that the starter motor is no longer able to perform its function and must be replaced. After study, it appears that one of the causes of these malfunctions could be the shocks suffered by the rotating parts of the launcher and the reduction gear during engine starting, particularly during the first explosions occurring in the cylinders before the starter motor is disconnected. These shocks are notably due to speed variations that induce an inertial torque.

[0005] The need therefore arose for a new starter head which was able to withstand these shocks without deteriorating so as to offer greater reliability and longevity of operation than starters according to the prior art.

[0006] In order to achieve this objective, the invention relates to an internal combustion engine starter head according to claim 1 attached hereto.

[0007] According to the invention, this starter head for an internal combustion engine starter is characterized in that: the reduction chamber comprises a bore, cylindrical of revolution with axis Δ, for receiving the outer crown which has an external cylindrical shape of revolution complementary to that of the receiving bore, the rotational connection means comprise at least one torsion damping buffer which is mounted between the crown and the casing to dampen a torque between the casing and the crown and which is engaged at least in part in a housing arranged in the casing, the housing comprising at least one axial stop adapted to prevent a translation of the damping buffer.The implementation of rotational connection means between the outer ring and the casing, which comprise at least one damping buffer, advantageously allows shocks due to sudden variations in speed and torque forming an inertial torque, induced by the internal combustion engine in its starting phase while it is still coupled to the starter. Thus, the energy induced by these variations in torque and rotational speed is dissipated by the damping buffers, thus avoiding breakage of the teeth of the starter, of the various toothed wheels constituting the reducer or of the drive pinion of the electric motor.It should be noted that, given the complementary shape of the outer crown and the receiving bore, the fact that the crown is rotatable relative to the casing means that in the absence of the rotational connection means the outer crown would be rotatable in the receiving housing so as to be able to rotate through 360°.

[0008] According to the invention, the torsion damping buffer is mounted in axial compression in the housing between the axial stop and the crown. This prevents the buffer(s) from moving unexpectedly and therefore prevents them from tearing.

[0009] According to the invention, the torque between the casing and the crown is damped by means of the damping buffers and in that the rotation is stopped by at least this damping buffer in compression. This makes it possible to prevent an excessively violent torque between the crown and the casing from causing an impact damaging all the starter equipment.

[0010] According to the invention, the starter head further comprises at least one axial bearing forming an axial stop adapted to prevent axial translation of the outer ring opposite the mounting face.

[0011] In addition, the presence of an axial stop preventing the translation of each damping pad parallel to the axis Δ of rotation of the reducer prevents untimely movements of the damping pad(s) under the effect of the forces they undergo due to sudden variations in rotation speed and torque. This perfect alignment of the damping pads contributes to the safety of the damping pads being held in place to prevent dissociation with the crown. This therefore improves the reliability of the starter head and the reducer according to the invention and therefore of the starter which incorporates it.

[0012] According to the invention, the damping pad may be made in any suitable manner. However, the damping pad is preferably made of an elastically deformable polymer material suitable for withstanding mechanical stresses as well as temperature and chemical attack conditions specific to the environment of an internal combustion engine.

[0013] According to a characteristic of the invention, aimed at guaranteeing the effectiveness of the damping of variations in rotational speed and torque, the rotational connection means comprise at least three damping pads, each engaged at least partly in a housing provided in the casing, each housing comprising at least one axial stop adapted to prevent translation of the corresponding damping pad from the reduction assembly towards one end of the casing surrounding the pinion.

[0014] According to another characteristic of the invention, each damping pad is immobilized in axial translation in both directions by, on the one hand, the axial stop of the casing and, on the other hand, the outer ring. This mounting method allows simple immobilization of each damping pad with a reduced number of parts so as to limit the manufacturing cost of the starter head according to the invention.

[0015] According to one embodiment of the invention, the casing comprises a launcher chamber which is located opposite the mounting face relative to the reduction chamber while the starter head comprises, in the launcher chamber, an output shaft, of axis Δ, which is driven in rotation by the reduction gear and which carries a launcher comprising a pinion intended to cooperate with a starting crown of a heat engine.

[0016] According to a variant of this embodiment, the outer ring comprises a flange which carries a guide bearing for the output shaft. The integration of the flange into the outer ring makes it possible to reduce the number of components of the starter head according to the invention.

[0017] According to a feature of this variant, the flange separates the reduction chamber from the launcher chamber. The separation thus achieved makes it possible to protect the epicyclic gear reduction assembly and possibly to confine lubricating greases in the reduction chamber.

[0018] According to another feature of this variant, the rotational connection means are arranged in the launcher chamber. This feature makes it possible in particular to reduce the volume of the reduction chamber by using part of the volume of the launcher chamber which is not useful for the movements of the launcher.

[0019] The invention also relates to a starter for a thermal engine comprising a starter head according to the invention and an electric motor which is fixed to the casing and whose drive pinion drives the speed reducer.

[0020] According to a characteristic of the invention, the starter comprises a reduction chamber closing plate interposed between the casing and the electric motor. This closing plate advantageously makes it easier to assemble the starter and ensures confinement of the epicyclic gear reducer.

[0021] According to a variant of this characteristic, the closing plate ensures a blocking of the axial translation of the outer crown.

[0022] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0023] Furthermore, various other characteristics of the invention emerge from the description given with reference to the appended drawings which illustrate a non-limiting embodiment of a starter head according to the invention and of a starter incorporating this speed reducer. There figure 1 is a schematic view of a starter for a thermal engine according to the invention. The figure 2 is a partial perspective in axial section of the starter head according to the invention, illustrated in figure 1 . There figure 3 is a section, according to plan III-III of the figure 1 , of the constitutive epicyclic gear reducer intended to equip the starter illustrated in the figure 1 . There figure 4 is a perspective showing on a larger scale a detail of the figure 3 .

[0024] As is evident from the figure 1 , a starter D, according to the invention, for a thermal engine comprises a starter head 1 on which is fixed an electric motor M controlled by an electromagnetic switch C which also controls a launcher L integrated into the damping system 1. The embodiment of such a starter and its constituent elements are well known to those skilled in the art so that only the characteristics necessary for understanding the invention will be described. For more information on the details of the production of a starter which would not be described subsequently, it is possible to refer to documents FR 2 934 933, FR 2 843 427 and WO 2005 / 054664.

[0025] The starter head 1, according to the invention, comprises a casing 2 on which the electric motor M is fixed. The casing 2 comprises fixing lugs 3 intended to allow fixing of the starter D on a thermal engine which it is intended to start. The casing 2 also comprises means 9 for fixing the electric motor M.

[0026] As shown in the figure 2 , the casing 2 is hollow and delimits a reduction chamber 4 adjacent to a face 5 for mounting the electric motor M on the casing 2. The reduction chamber 4 extends, opposite the face 5, by a launcher chamber 6 inside which the launcher L is located.

[0027] The starter head 1 also comprises a speed reducer 10 which is arranged in the reduction chamber 4. The reducer 10 comprises, as is apparent from the figure 3 , an outer ring 11 which has a general shape symmetrical in revolution with axis Δ. The peripheral outer surface 12 of the ring 11 is smooth and cylindrical in revolution with axis Δ while the peripheral inner face 13 of the outer ring 11 is toothed. The toothed inner face 13 of the outer ring 11 cooperates with three planetary pinions 14 which are rotatable along axes parallel to the axis Δ. The planetary pinions 14 mesh with a planetary pinion 15 coaxial with the outer ring 11. The planetary pinion 15 has a housing 16 for receiving the drive pinion 17 of the electric motor M. The housing 16 has a shape complementary to that of the pinion 17 so that when the pinion 17 is engaged in the housing 16, the planetary pinion 15 is secured to a drive shaft of the motor with axis Δ and not visible in the figures.

[0028] As is known to those skilled in the art, the planetary pinions 14 are integral with a plate 18 linked in rotation to an output shaft 19 coaxial with Δ'axis. The output shaft 19 extends into the launcher chamber 6 while being supported by rotation guide means 20 arranged in a wall of the casing 2 opposite the reducer 10. The output shaft 19 carries the launcher L which is linked in rotation to the output shaft 19 while being movable in translation on the latter between a rest position R, illustrated in solid lines at figure 1 , and an internal combustion engine drive position E shown in dot-and-dash lines at figure 1 . In this drive position E, the launcher L is intended to cooperate with a starting ring, not visible in the figures, which extends partly inside the launcher chamber through a window 21 of the casing 2. The launcher L is moved between its rest positions R and drive E by a lever 22 operated by the electromagnetic switch C.

[0029] In order to ensure the rotational guidance of the plate 18 and the output shaft 19, the outer ring 11 comprises, at its face oriented towards the launcher chamber 6, a flange 25 which carries a guide bearing 26 for the output shaft 19. The flange 25 also contributes to separating the reduction chamber 11 from the launcher chamber 6 so as to protect the reduction assembly 10.

[0030] The reduction chamber 4 comprises a cylindrical bore of revolution with axis Δ which has a shape complementary to that of the external surface 12 of the outer ring gear 11. The ring gear is rotatable relative to the casing 2. The outer ring gear 11 is mounted between, on the one hand, an axial bearing surface 27, forming a stop, arranged in the reduction chamber 4, at the boundary between the latter and the launcher chamber 6, and on the other hand a portion of the closing plate 28 interposed between the casing 2 and the motor M. The closing plate 28 and the axial bearing surface 27 make it possible to limit the axial translation of the outer ring gear 11 and thus limit the axial deformation of the damper buffers 36. The closing plate 28 contributes to confining the pinions 14 and 15 as well as the internal surface 13 of the ring gear 11 so as to protect the reducer 10.According to the example illustrated, the closing plate 28 comprises, at a central bore 29, means for guiding the rotation of the induced shaft of the electric motor.

[0031] In order to allow the transmission of the rotation of the drive pinion 17 to the planet gears 14 and therefore to the output shaft 19, the outer ring 11 must be connected in rotation to the casing 2. For this purpose, means 35 are used for connecting in rotation the outer ring 11 with the casing 2. The rotational connection means 35 comprise at least one and, according to the example illustrated, six damping buffers 36 of which only three are visible at the figure 2 .

[0032] Each damping buffer 36 is engaged in a housing 37, of the casing 2, arranged in the wall of the launcher chamber 6 at its end located towards the reduction chamber 4. Each housing 37 has a shape complementary to that of the corresponding damping buffer 36 and is open towards the interior of the launcher chamber 6. Each housing 37 is, in addition, open towards the reduction chamber 4 so as to allow engagement of the corresponding buffer 36 according to a translational movement parallel to the axis Δ. According to another example described, the bottom of the housing is inclined relative to the axis Δ, (by bottom of the housing is meant the face of the housing furthest from the axis Δ). Each housing 37 also comprises two side walls 38 each defined by an intermediate rib 39 which separates the housing 37 from an adjacent housing.Each housing extends, from the peripheral wall of the launcher chamber 6, in a substantially radial direction towards the interior of said launcher chamber 6.

[0033] The connecting means 35 also comprise a skirt 40 which extends from the flange 25 inside the launcher chamber 6. The skirt 40 forms with the flange 25 and the outer ring 11 a single-piece assembly. The skirt 40 comprises in relation to each buffer 36 at least one radial rib 41 which extends inside said buffer 36 so as to connect it to the skirt 40 and therefore to the outer ring 11.

[0034] In order to ensure blocking of the movements of the buffers in axial translation, that is to say parallel to the axis Δ, each housing 37, for receiving a damping buffer 36, comprises at least one axial stop 45 adapted to prevent a translation of the damping buffer 36 parallel to the axis Δ towards the inside of the launcher chamber 6, opposite the reduction chamber 4. According to the example illustrated, the axial stops 45 are arranged in the wall of the launcher chamber 6 while being separated from each other by notches 46 arranged in the wall of the launcher chamber 6. The notches 46 promote the circulation of a cooling air flow of the system 1. In addition, these notches 46 allow a saving of material and therefore of weight.

[0035] The damping buffers 36 are furthermore axially immobilized by the outer ring 11 located opposite the axial stops 45 relative to the damping buffers 36. Thus, each damping buffer 36 is perfectly immobilized in its housing 37 so that it does not risk moving under the effect of shocks induced by the variations in torque when starting the engine which the starter according to the invention starts.

[0036] According to the example illustrated, the outer crown 11 is made of plastic material and the buffers 36, made of viscoelastic material such as an elastomer, are overmolded onto the latter so as to facilitate the assembly of the starter head 1 and the starter D according to the invention.

[0037] Of course, such an embodiment is not strictly necessary for the invention and various modifications could be made to the embodiment of the invention described above, within the scope of the appended claims.

Claims

1. Internal combustion engine starter head, comprising: - a casing (2) which delimits a reduction chamber (4) and which comprises a mounting face (5) for mounting an electric motor M comprising a drive pinion (16), - a speed reducer (10) which is arranged in the reduction chamber (4) and which comprises an epicyclic geartrain comprising planet pinions (14), intended to be driven in rotation by the drive pinion (16) of the electric motor (M), and an external ring gear (11) of axis Δ, connected to the casing (2) by rotational-connection means (35), - the reduction chamber (4) comprises a bore, which is a cylinder of revolution of axis Δ, for receiving the external ring gear (11) which has an exterior shape that is a cylinder of revolution complementary to that of the receiving bore, in which the ring gear is movable in rotation with respect to the casing (2) - the rotational-connection means (35) comprise torsion damping blocks (36) which are mounted between the ring gear and the casing (2) and are in contact with the casing (2) and the ring gear (11) to damp a torque between the casing (2) and the external ring gear (11) and which is engaged at least in part in a housing (37) provided in the casing (2), the housing comprising at least one axial stop (45) adapted to impede axial translation of the damping blocks (36) away from the mounting face (5); the torsion damping blocks (36) are mounted in axial compression in the housing between the axial stop (45) and the ring gear (11); characterized in that the torque between the casing (2) and the ring gear (11) is damped by means of the damping blocks and in that the rotation is arrested by the damping blocks (36) in compression, and in that said head further comprises at least one axial bearing surface (27) forming an axial stop (27) adapted to impede axial translation of the external ring gear (11) away from the mounting face (5).

2. Starter head according to the preceding claim, characterized in that the rotational-connection means comprise at least three damping blocks (36) each engaged at least partially in a housing (37) provided in the casing (2), each housing (37) comprising at least one axial stop (45) adapted to impede a translation of the damping block (36) away from the mounting face (5).

3. Starter head according to either one of Claims 1 and 2, characterized in that each damping block (36) is immobilized in axial translation in both directions by, on the one hand, the axial stop (45) of the casing (2) and, on the other hand, the external ring gear (11).

4. Starter head according to one of Claims 1 to 3, characterized in that: - the casing (2) comprises a starter-drive chamber (6) which is located on the opposite side of the reduction chamber (4) from the mounting face (5), - it comprises, in the starter-drive chamber (6), an output shaft (19), of axis Δ, which is driven in rotation by the reduction gear (10) and which carries a starter drive assembly (L) comprising a pinion intended to cooperate with a starter ring gear of a combustion engine.

5. Starter head according to any one of the preceding claims, characterized in that the external ring gear (11) comprises a flange (25) which carries a guide bearing for an output shaft.

6. Starter head according to Claims 4 and 5 taken in combination, characterized in that the flange (25) separates the reduction chamber (4) from the starter-drive chamber (6).

7. Starter head according to either one of Claims 4 and 6, characterized in that the rotational-connection means (35) are disposed in the starter-drive chamber (6).

8. Starter for a combustion engine, comprising a starter head according to one of Claims 1 to 7 and an electric motor which is fixed to the casing (2) and the drive pinion (16) of which drives the speed reducer (10).

9. Starter according to Claim 8, characterized in that it comprises a closure plate closing off the reduction chamber (4) and interposed between the casing (2) and the electric motor.

10. Starter according to Claim 9, characterized in that the closure plate blocks the axial translation of the external ring gear (11).