Abstract:
A vehicle alternator comprising a case, a stator winding, and an electrically-insulating element interposed between the case and the winding, the insulating element being a solid body mounted on one of the case and the winding. The insulating element has at least one duct extending through an orifice in the case.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to alternators or to alternator-starters. 
     A vehicle alternator is known that comprises a case, a stator winding, and a solidified electrically-insulating varnish impregnating the end turns and the twisted leads of the winding so as to insulate them electrically from the adjacent case and so as to reinforce their mechanical strength. The neutral points of the winding are insulated in the same manner. Nevertheless, when subjected to the vibration due to operation, there is a major risk of the varnish being abraded and thus of the electrical insulation of the end turns, the twisted leads, and the neutral points disappearing. 
     U.S. Pat. No. 4,658,165 discloses a vehicle alternator in which an electrically-insulating screen is provided in the form of a separate piece extending between the stator winding and the case. That avoids the risk of abrasion. However, that patent provides for the twisted leads to be returned along the screen and complicates connection thereof. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the invention is to ensure that the insulating protection is long-lasting without complicating the connection of the twisted leads. 
     To achieve this object, the invention provides a vehicle alternator comprising a case, a stator winding, and an electrically-insulating element interposed between the case and the winding, the insulating element being a solid body mounted on one of the case and the winding, wherein the insulating element has at least one duct extending through an orifice in the case. 
     There is thus no risk of abrasion of the insulating element and as a result the protection is long-lasting. 
     In addition, the duct can receive a twisted lead of live outlet wires from the winding, which twisted lead is thus electrically insulated from the case where it passes through the case, e.g. at the back plate of the case. In addition, the duct can receive the twisted lead before being installed in the case, thus making it possible to guarantee the position of the twisted lead relative to the winding, e.g. a rectilinear position, prior to being received in the case. 
     Advantageously, the duct extends from a front face of the insulating element. 
     Advantageously, the duct extends so as to project from an inner side face of the insulating element towards an axis of the stator. 
     Thus, the duct is suitable for an arched twisted lead, i.e. one which does not leave the stator in register with a slot in the stack of laminations but is offset so as to be better placed, given the design of the electronic portion of the alternator, e.g. situated at the rear of the case. 
     Advantageously, the or each duct receives a live wire twisted lead of the winding. 
     Advantageously, the insulating element is interposed between the case and the winding radially relative to an axis of the stator. 
     Advantageously, the insulating element is interposed between the case and the winding axially relative to an axis of the stator. 
     Advantageously, the insulating element extends in register with an inner side face of the winding. 
     Advantageously, the insulating element has an indexing portion, in particular a stud, enabling the angular position of the stator around an axis of the stator to be identified. 
     Thus, the angular position of the stator about its axis is identified, making it easier to install, and guaranteeing that the twisted leads of live wires are properly positioned relative to the case, and in particular relative to the orifices therein. 
     Advantageously, the case has a second indexing portion, in particular a groove, suitable for cooperating with the indexing portion of the insulating element. 
     The invention also provides a method of manufacturing a vehicle alternator comprising a case, a stator winding, and an electrically-insulating element interposed between the case and the winding, wherein: the insulating element is supplied in the form of a solid body having at least one duct; the insulating element is mounted on one of the case and the winding; and the duct is inserted through an orifice in the case. 
     Advantageously, the insulating element is mounted on the winding. 
     Advantageously, the insulating element is mounted on the case. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment and of a variant given as non-limiting examples. In the accompanying drawings: 
     FIG. 1 is a fragmentary axial section view of an alternator of the invention showing the stator and the case; 
     FIGS. 2 and 3 are two perspective views from above and from below of the insulating element of FIG. 1; 
     FIGS. 4 and 5 are two views analogous to FIG. 1 showing a variant embodiment, respectively level with one of the twisted leads of live wires and level with the neutral point; and 
     FIGS. 6 and 7 are two views analogous to FIGS. 2 and 3, showing the insulating element of FIGS.  4  and  5   
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1 to  3 , the alternator  2  comprises in conventional manner a shaft of axis  5  and a case of which only a shell  4  is shown herein. The shell has a plane rear wall  6  perpendicular to the axis  5  forming a rear plate with a bearing for the shaft, and a cylindrical side wall  8  about the axis  5 . The shell is closed by a cover that forms a front bearing and that is not shown. The alternator has a stator  10  comprising a stack of laminations  12  on which a winding  14  is wound. The wires of the winding are received in slots (not shown) in the stack of laminations  12  extending parallel to the axis. The winding  14  has end turns that emerge through the rear axial end of the stack of laminations  12 . This winding has twisted leads  16  of live wires, in this case three such leads since the winding is a so-called “single” winding. The twisted leads  16  emerge from a rear axial end face of the winding  14 . 
     In accordance with the invention, the alternator has an electrically-insulating element  18  which is constituted in this case by a single piece of plastics material. This element  18  is generally annular in shape about the axis  5 . Its section in a plane radial to the axis  5  is in the form of a channel section defining a plane web or rear axial end wall  20  and two flanges or cylindrical side walls about the axis  5 , comprising an outer flange  22  and an inner flange  24  that face each other. The insulating element  18  has three cylindrical ducts  26  extending with axes parallel to the axis  5  so as to project from the web  20  away from the flanges  22  and  24 . The three ducts  26  are close to one another around the axis  5 . 
     The outer flange  22  carries a stud  28  extending radially outwards. The side wall  8  of the shell has an inside groove  30  extending parallel to the axis  5  and suitable for receiving the stud  28  when the stator is mounted in the case. In FIG. 1, the stud  28  and the groove  30  are shown as lying in the section plane of the figure for greater clarity, however the preferred position for the stud  28  (and thus for the groove  30 ) is as shown in FIG.  3 . 
     During assembly of the alternator, the stator is built and the insulating element  18  that has previously been made by molding is mounted coaxially on the winding  14 , being placed over its end turns and with its three twisted leads  16  being inserted into the three ducts  26  respectively. As a result, the insulating element  18  covers the inner and outer faces and the axial end face of the end turns. The edges of the insulating element  18  come into axial abutment against the stack of laminations  12 . Thereafter, the stator  10  is mounted inside the shell  4 . Having the stud  28  received in the groove  30  then makes it possible to ensure that the stator  10  is properly positioned relative to the shell  4  and angularly about the axis  5  so that the twisted leads  16  and the ducts  26  are in register with orifices  32  formed through the rear wall  6  of the shell, and then penetrate through said orifices  32 . Once assembly has been completed, the insulating element  18  is interposed axially between the end wall  6  and the winding  14 , and radially between the side wall  8  and the winding  14 . In addition, it extends in register with an inside side face of the winding. This ensures that the end turns and the twisted leads are electrically insulated from the case  4 , including where they pass through the orifices  32 . 
     In the variant of FIGS. 4 to  7 , the winding  14  is identical to that of FIG. 1, except that the twisted leads  16  have been offset so as to project from the winding in a radial direction towards the axis  5 . Consequently, the ducts  26  are likewise formed to project from the inner flange  24  of the insulating element  18  so as to receive the twisted leads  16  in this configuration. In addition, the live wire twisted leads  16  are six in number in this embodiment since the winding is said to be “double”. There are thus also six ducts  26 . The neutral points  34  of the winding  14  is shown in FIG.  5 . 
     It is possible to mount the insulating element  18  in the shell  4  prior to fitting the stator  10  thereon. 
     The insulating element  18  can be built up from a plurality of parts fixed to one another prior to being fitted to the alternator.