Patent Publication Number: US-4649285-A

Title: Electric starter incorporating a base plate supporting the carcase of its electric motor and the yoke of its contactor

Description:
The present invention relates to electric starters for internal combustion engines comprising an actuator controlled by a lever which is pivoted by means of a solenoid contactor parallel to the electric motor of said starter whose housing is mounted on a base plate which also supports the yoke of the contactor. 
     French Patent No. 1 354 018, presently expired, discloses an electric starter for internal combustion engine wherein the housing of the electric motor is supported by a base plate on which the nose of the starter is mounted. 
     In Applicants&#39; French Patent No. 2,410,148, such a plate further supports the contactor adapted to control the pivoting of the actuating lever. In this Patent, the base plate constitutes a means for centering the shaft of the electric motor so that, at rest, the vibrations of the latter are very largely reduced. 
     According to the invention, the base plate supports a bearing in which rotates the satellite ring of an epicycloidal reduction gear of which the input shaft is that of the armature. The bearing in question is maintained in position by means of a disc made of plastics material moulded over the base plate. The disc in question is advantageously extended by a tubular fixed ring oriented in the direction of the armature of the electric motor. The fixed ring&#39;s inner face is provided with a toothing adapted to constitute the front ring of the epicycloidal reduction gear mentioned above. 
     Due to the relatively easy production of a mould for injection of plastics material, the bearing, which is made in the form of an annular bushing, may be placed so that its concentricity with the fixed ring gear is precise. Alternatively a housing for supporting a bushing perfectly concentric with the fixed ring gear may similarly be obtained. 
     Moreover, it is sure that the toothing of the latter is perfectly perpendicular to the base plate. 
     Whether the bushing is mounted with or without clearance in the base plate, the epicycloidal reduction gear as well as the general assembly of the starter are thus considerably simplified. 
     The presence of the plastic disc may allow the formation of a lateral tab constituting support for the pivot pin of the actuator lever. 
     Finally, part of the overmoulded disc may be used for forming a seal between the housing of the electric motor and the base plate. 
    
    
     The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which: 
     FIG. 1 is a partial longitudinal section of an electric starter incorporating the improvements according to the invention. 
     FIG. 2 is a partial view on a larger scale of a modified embodiment. 
    
    
     Referring now to the drawing, a base plate 1 made of sheet metal constitutes the support for the contactor 2 of the starter and for its electric motor 3 and more particularly for the housing 4 thereof. This base plate is assembled on the nose 5 of the starter by means of tie-rods 6. 
     Said starter is of the type having a reduction gear, i.e. the shaft of the armature 7 of the electric motor bears a central pinion 8 meshing with satellite gears 9 conventionally mounted on pins 10 fixed to a satellite-ring 11 which constitutes the output shaft of the reduction gear, so that it is fixed to a secondary shaft 12 adapted to drive the actuator of the starter, referenced 13, in rotation. Of course, the satellite gears roll with respect to an internally toothed fixed ring 14 as is well known in the art. 
     According to the invention, the satellite-ring 11 rotates with guidance by a bearing made in the form of a sintered bushing 15 supported by the base plate 1. This bushing may be forced-fitted in a central bore in the plate or may be maintained with respect to this bore by a plastic disc 16 moulded over the base plate and said bushing. In the event of the latter being force-fitted in the central bore of the base plate, the disc 16 comprises two annular cheeks 16c, 16d which maintain the two faces of the bushing 15 laterally so that it cannot move parallel to the axis of the electric motor. 
     In the other case, the bushing 15 is placed with clearance in the central bore of the base plate, so that the disc 16 then centers the bushing with respect to the plate, in addition to its role of lateral hold. 
     The bearing may also be fitted after overmoulding. In that case, a lateral hold such as 16c or 16d will be eliminated. This type of assembly is necessary if the bearing cannot support overmoulding: i.e. in the case of a bushing made of impregnated sintered material or in the case of a roller bearing. It is also possible to envisage an overmoulding at the centre of the disc 16 which would define a central housing in which the bushing 15 would be fitted. In that case, one of the cheeks 16c or 16d would obviously be eliminated and possibly replaced by any stop system 20, FIG. 2. This solution would be employed if the bushing 15 could not withstand the rise in temperature due to overmoulding, for example if this bush is made of impregnated sintered material or if the bush is replaced by a roller bearing. 
     It is advantageous to extend the disc 16 so that it also constitutes the internally-toothed ring 14 which, under these conditions, is automatically centred precisely with respect to the bore of the bush 15, so that, since the satellite ring is perfectly concentric to the toothing of the ring 14, the latter and the satellite gears are quite precisely in mesh. Moreover, as has been indicated above, the toothing of the ring 14 may be easily made so that it is oriented with precision perpendicularly to the base plate 1. 
     The presence of the disc 16 may be profitably employed to form on its periphery a lug 16a located on the face of the base plate 1 turned to extend towards the actuator 13, said lug constituting the base of a tab 17 perpendicular to the base plate and supporting the pin 18 of the lever 19 actuating the actuator 13. It will be observed that the lug 16a is anchored in the plate 1 by means of an extension 16b of the disc 16 penetrating in a widened perforation 1a in the base plate. Similarly, openings 1b are provided about the central bore of the base plate 1 so that the two cheeks 16c, 16d of the disc 16 disposed on either side of the bush 15 and consequently located on the two faces of the plate 1, are perfectly connected. 
     The cheek 16d of the disc 16 may be shaped so as to constitute a seal between the housing 4 of the electric motor 3 and the base plate. Reference 16e designates the flange surrounding the ring 14 to this end. 
     A structure has thus been produced which considerably simplifies the construction of the epicycloidal reduction gear whilst facilitating the general assembly of the starter. 
     It must, moreover, be understood that the foregoing description has been given only by way of example and that it in no way limits the domain of the invention which would not be exceeded by replacing the details of execution described by any other equivalents.