Abstract:
A differential drive with a rotatably arranged differential carrier ( 11 ) in which a multi-plate coupling ( 23 ) is arranged so as to be effective between the differential carrier ( 11 ) and a sideshaft gear ( 29 ), wherein the differential carrier ( 11 ) includes a dish-shaped carrier part ( 12 ) in which there are received sideshaft gears ( 28, 29 ) and differential gears ( 26, 27 ). The differential carrier includes a dish-shaped cover ( 14 ) which receives the plates of the multi-plate coupling ( 23 ).

Description:
TECHNICAL FIELD 
     The invention relates to a differential drive with a rotatably arranged differential carrier in which a multi-plate coupling is inserted so as to be effective between the differential carrier and a sideshaft gear. 
     BACKGROUND 
     Such multi-plate couplings are used in lockable differential drives wherein, by actuating the multi-plate coupling, there is built up a locking moment between the differential carrier and one of the sideshaft gears and thus, also indirectly, between the sideshaft gears, so that a torque introduced into the differential carrier is effectively built up at both sideshafts gears even in those cases where there is no counter moment at one of the sideshaft gears. Differential drives of said type are used in motor vehicles in the form of axle differentials between the driving wheels of a driving axle or as central differentials between two driving axles. In the case of prior art differential carriers, the space needed for the multi-plate coupling requires a very deep carrier part which is difficult to machine. 
     SUMMARY OF THE INVENTION 
     The object of the present invention provides an improved differential drive whose differential carrier does not feature the existing disadvantages and which has advantageous effects. 
     In particular, the differential carrier comprises a dish-shaped carrier part in which there are received sideshaft gears and differential gears, and the differential carrier comprises a dish-shaped cover attached thereto which receives the plates of the multi-plate coupling. This solution achieves the required axial depth in the cover of the differential carrier, which depth is needed for the plate package of the multi-plate coupling, so that the carrier part is axially shorter and thus stiffer, while, at the same time, the cover, due to its dish shape, can take over additional functions. The dish shape of the carrier part and cover means that each is provided with a base and a casing and, for inter-connection purposes, flange portions can be provided at the aperture end. The flange portions at the two carrier parts required for fixing a driving ring gear are now positioned more centrally with reference to the longitudinal extension of the parts, so that, with reference to the bearings of the differential carrier, the introduction of power is more advantageous. 
     According to one embodiment of the invention, in the sense of rotation, the outer plates of the multi-plate coupling are form-fittingly held in the cover and, in the sense of rotation, the inner plates of the multi-plate coupling are form-fittingly held on a hub connected to a sideshaft gear. This means that there is no need for any intermediate carriers or the like for the multi-plate coupling and that it is possible to pre-assemble the multi-plate coupling in the cover with the inserted coupling hub and side gear, and, finally, the carrier part can be placed on to said pre-assembled unit in which the other sideshaft gear and the differential gears can be securely held by the bearing journal for the differential gears. The assembly procedure for the entire differential carrier is thus substantially simplified. 
     Furthermore, according to another embodiment, on the outside of the cover, there is arranged a sleeve which axially supports an actuator for the locking coupling; the actuator can also be radially supported on the sleeve, provided it is not supported in a contact-free way relative to the sleeve in the differential housing. 
     For improving the cooling of the multi-plate coupling, it is possible to provide the cover with apertures through which any oil contained in the differential housing can constantly flow towards the coupling plates. Furthermore, the apertures can be associated with blades with a centripetal effect on the oil in the differential housing, which blades, when the differential carrier rotates, scoop up oil from the outside on to the multi-plate coupling. The blades are adapted to the preferred direction of rotation of the differential carrier, which direction corresponds to the forward driving direction of the motor vehicle comprising the differential drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention is illustrated in the drawings and will be described below. 
         FIG. 1  shows an inventive differential carrier in a perspective view. 
         FIG. 2  shows a differential carrier according to  FIG. 1  in a longitudinal section. 
         FIG. 3  shows a cover of the differential carrier according to an embodiment of the invention in a longitudinal section. 
         FIG. 4  shows the cover in a cross-section according to the sectional line  4 - 4  in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a differential carrier  11  which, substantially, consists of a carrier part  12  with a formed-on flange  13  and of a cover part  14  with a formed-on flange  15 . A first bearing sleeve  16  on to which it is possible to slip a rolling contact bearing is formed on to the carrier part  12 . A second bearing sleeve  17  on to which it is possible to slip a second rolling contact bearing is formed on to the cover  14 . The rolling contact bearings are used to rotatably support the differential carrier in a drive housing (not illustrated). The flanges  13 ,  15  are shown to comprise through-bores  18  by means of which the parts  12 ,  14  of the differential carrier can be bolted together, and a ring gear (not shown) for rotatingly driving the differential carrier can be bolted to the flanges. The carrier part is shown to comprise first bores  19  into which there are inserted journals  25  for differential gears, which journals  25  are secured by securing rings  20 . Furthermore, there are shown second apertures  21  which allow the supply of oil to the interior of the differential carrier. 
     The cover part  14  is provided with apertures  22  through which it can be seen that a plate package  23  is arranged inside the cover  14 . Scooping wings or blades  24  are associated with the apertures; when the differential carrier rotates, said blades  24  are used to supply oil on to the outside of the plate package  23 . An actuator  31  is arranged coaxially relative to the cover  14  and, substantially, comprises a rotatingly drivable setting disc  32  with a tooth segment  33  and an axially displaceable pressure disc  34  which, by a claw  35 , is held in a rotationally fast way relative to a journal  36  fixed in the housing. The setting disc  32  is axially supported against a supporting disc  37  which, by means of a securing ring  38 , is fixed to a largely covered sleeve inside the actuator. The actuator  31  is arranged so as to be in a stationary condition relative to the housing (not illustrated), whereas the differential carrier  11  is normally permanently driven so as to rotate. 
     In  FIG. 2 , any details identical to those shown in  FIG. 1  have been given the same reference numbers. To that extent, reference is made to the description of same. As far as details are concerned, it can be seen that into the carrier part  12  there have been inserted journals  25  which intersect one another and on which there are supported differential gears  26 ,  27 . The differential gears  26 ,  27  engage sideshaft gears  28 ,  29 . A first sideshaft gear  28  is slidingly supported in the carrier part  12 , whereas a second sideshaft gear  29  is guided substantially self-centeringly between the differential gears  26 ,  27 . The latter sideshaft gear  29  is produced so as to be integral with a coupling hub  30  and carries the inner plates of the plate package  23 . The outer plates of the plate package  23  are form-fittingly held in the cover  14  which is shown in section in the region of the blades  24  and the apertures  23 . Between the cover  14  and the hub  30  a supporting disc  39  can be identified. The actuator  31  is shown to comprise further details in addition to the rotatingly drivable setting disc  32 , the pressure disc  34  being held so as to be rotationally fast and the supporting disc  37  being axially secured by the securing ring  38 ; said further details being an axial bearing  41  between the setting disc  32  and the supporting disc  37 , a radial bearing  42  via which the setting disc  32  is supported on a sleeve  51  and balls  43  running in pairs of ball grooves in the discs  32 ,  34 . A plurality of balls  43  is circumferentially distributed in a cage  44  and held at identical distances. As is known the depth of the ball grooves (not individually identified) in the opposing surfaces of the discs varies around the circumference, so that, when the setting disc  32  is rotated relative to the pressure disc  34 , the balls run from the deeper groove regions into she shallower groove regions. Thereby, the pressure disc  34  held so as to be non-rotatable, pushes itself axially away from the setting disc  32 . Via a further axial needle bearing  45  and a first pressure plate  46 , the inner pressure disc  48  is pressure-loaded and axially displaced by journals  47  which axially pass through the cover  14 . Said inner pressure disc  48  pushes together the plate package  23  which is supported on an annular face  49  of the carrier part  12 . When the setting disc  32  is returned, the pressure plate  46  is pushed pack via a plate spring  50 , so that the load is removed from the plate package  23 . By closing the plate package, there is built up a locking moment between the sideshaft gears  28 ,  29 . 
       FIG. 3  shows the cover according to  FIG. 2  in a slightly modified form as a detail. Any details identical those shown in  FIG. 2  have been given the same reference numbers. Inside the cover  14 , there are circumferentially distributed longitudinal grooves  52  which can be engaged in a form-fitting way by projections provided at the outer plates of the plate package  23 . Inside the sleeve  17  it is possible to identify a lubricating groove  53 . It can be seen more easily that the blades  24  are associated with the apertures  22 . 
     In  FIG. 4 , any details identical to those shown in  FIGS. 2 and 3  have been given the same reference numbers. The cover  14  is provided with longitudinal grooves  52  to allow a form-fitting and positive engagement of the outer plates of the plate package  23 , and with axial through-holes  54  into which the above-mentioned journals  47  are inserted. It is also possible to see in detail the shape and functioning of the blades  24  in cooperation with the apertures  22  which assumes a clockwise movement of the cover  14 . In addition to the blades, it is possible to see cooling ribs  40  which at the same time reinforce the cover  14 . 
     The cover  14  shown in  FIGS. 3 and 4 , together with the plate package shown in  FIG. 2  and the sideshaft gear  29 , can be removed and replaced by a second sideshaft gear symmetrical to the sideshaft gear  28  and by a substantially flat cover in order to obtain—starting from the same dish part  12 —an open differential which is not separate. 
     Differential Carrier with an Inner Plate Package 
     List of Reference Numbers 
       11  multi-plate coupling 
       12  dish part 
       13  flange 
       14  cover part 
       15  flange 
       16  bearing sleeve 
       17  bearing sleeve 
       18  bolt hole 
       19  through-hole 
       20  securing ring 
       21  aperture 
       22  aperture 
       23  plate package 
       24  blade 
       25  journal 
       26  differential gear 
       27  differential gear 
       28  sideshaft gear 
       29  sideshaft gear 
       30  coupling hub 
       31  actuator 
       32  setting disc 
       33  tooth segment 
       34  pressure disc 
       35  claw 
       36  journal 
       37  supporting disc 
       38  securing ring 
       39  disc 
       40  cooling rib 
       41  axial bearing 
       42  axial bearing 
       43  ball 
       44  ball cage 
       45  axial bearing 
       46  pressure disc 
       47  journal 
       48  pressure disc 
       49  supporting face 
       50  plate spring 
       51  sleeve