Abstract:
To brake a drive output shafts ( 5 ) of an electrically powered driving axle, the differential comprises a brake ( 6 ) which, when actuated, connects a differential cage ( 2 ) and the drive output shaft ( 5 ) with a flange ( 23 ).

Description:
This application claims priority from German Application Serial No. 10 2005 018 907.5 filed Apr. 22, 2005. 
   FIELD OF THE INVENTION 
   The present invention concerns a differential for an electrically powered driving axle. 
   BACKGROUND OF THE INVENTION 
   DE 200 10 563 U1 discloses an electrically powered, driving axle with a differential in which the electric drive motor drives the differential cage via a planetary gearset and the drive output shafts drive the driving wheels each via a planetary gearset. In the area of these planetary gearsets, a brake is arranged in each case and these brake the drive output shaft close to the wheels. 
   The purpose of the present invention is to provide a differential, in particular for an electrically powered, driving axle, which is made so that it can be braked and whose structure is simple. 
   SUMMARY OF THE INVENTION 
   According to the invention, the differential cage of the differential is driven, whereby the axle shaft gear wheels of the differential are driven by the differential gear wheels. The differential comprises a brake with rotating and static disks, at least one rotating disk being connected to the differential cage and at least one other rotating disk to the axle shaft, gear wheel. The static disk is connected to the housing of the differential. If the brake is actuated now in the closing direction, the differential cage and the axle shaft, gear wheel are braked relative to the differential housing. It is, therefore, possible to brake the vehicle completely with only one brake and also keep it braked on ground surfaces with various frictions, which is not normally possible with only one braked vehicle wheel and a differential, because the second vehicle wheel has not been braked by the differential. 
   In another embodiment, the brake comprises an actuator for an operating brake and an actuator for a parking brake. The actuator for the operating brake can be made as a positively acting, hydraulically actuated, working brake, such that it is moved in the closing direction when pressurized, while the parking brake is made as a mechanically applied brake actuated, for example by a cable and a manual brake lever. It is also possible to make the operating brake and/or the parking brake as a negative brake such that, for example, a spring engages the brake when it is not pressurized, while pressurizing the brake moves it in the release direction. 
   In a further embodiment, the brake can be actuated, via a ball ramp. The ball ramp consists of at least one fixed and one rotating component, such that when the latter is rotated by the ball ramp this actuator is enlarged in the axial direction, whereby the brake is moved in the closing direction. The rotating component can be turned, for example, by a hydraulic cylinder for the operating brake and by a twist-stud for the parking brake. 
   In another embodiment, the differential can be made with differential gears formed as bevel gears and axle shaft gears also formed as bevel gears, but the differential can also be made as a planetary differential. 
   In a further embodiment, the differential cage is in active connection with a ring gear. The ring gear is driven by a drive pinion that is in direct active connection with the electric motor. This enables the electric motor to be flanged on the differential housing so that the electric motor is at right-angles to the drive output shafts. That makes it possible to provide the differential housing with a large opening through which the complete, pre-assembled, structural unit “differential with brake” can be inserted into the differential housing. Then only the drive output shafts, which can be made for example as plug-in shafts, are inserted. This simplifies assembly considerably. 
   In another embodiment, the parking brake has a forked brake lever such that the ends of the fork press against a pressure plate of the brake in order to actuate the brake in its closing direction. The forks are arranged on a rotating stud which can be turned with the aid of a lever and the brake cable. 
   In a further embodiment of the invention, several hydraulic pistons are arranged between the ring gear and the disks. These hydraulic pistons are distributed uniformly around the periphery of the disks and, when pressurized, actuating the brake in the closing direction as an operating brake. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
       FIG. 1  is a section through the differential; 
       FIG. 2  is a perspective view of the assembled differential with cutaway differential housing and actuation of the operating brake by way of pistons that can be hydraulically pressurized, and 
       FIG. 3  is a perspective view of the pre-assembled differential with actuation of the brake by a ball ramp 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 : 
   A driven ring gear  1  is in rotationally fixed connection with a differential cage  2 , which drives drive output bevel gears  4 , via differential bevel gears  3 . The drive output bevel gears  4  are in rotationally fixed connection with drive output shafts  5 . The drive output shafts  5  can drive vehicle wheels  31 , for example via a planet gear  29 . In the area a brake  6 , the drive output shaft  5  comprises an inner disk carrier  7 , which is in rotationally fixed connection with inner disks  8 . The differential cage  2  has a neck  9  which, in the area of the brake  6 , is formed as an inner disk carrier  10  and is in rotationally fixed connection with inner disks  11 . The neck  9  can be connected to the differential cage as one piece or in more than one piece. In the area of the brake  6 , a differential housing  12  is formed as an outer disk carrier  13  and is in rotationally fixed connection with outer disks  14 . Between the inner disks  8  and the inner disks  11  is arranged a plate  15 . Uniformly around the periphery of the inner disks  11  are arranged pistons  16  which, when pressurized, press against a pressure plate  17  and fully actuate the brake  6  in the closing direction since a pressure plate  18  rests via a locking ring  19  against the brake  6 . Thus, by pressurizing the pistons  16 , the operating brake is realized, whereby the brake  6  connects both the differential cage  2  and the drive output shaft  5  with a flange  23  so that both drive output shafts  5  are braked. When the parking brake  27  is actuated, a shaft  20  is rotated mechanically, for example by actuating a manual brake lever and the cable connected thereto, whereby forks  21  press against the pressure plate  18  and the brake  6  is moved in the closing direction. 
     FIG. 2 : 
   The drive pinion  22  drives the ring gear  1 . The drive pinion  22  is mounted in a flange  23  that can be connected directly to the electric motor. The electric motor is, therefore, at right-angles to the drive output shafts  5 . In the area of the flange  23 , the differential housing  12  has an opening large enough for the complete pre-assembled differential with the brake to be attached to the flange  23  and introduced through the opening in the differential housing  12  into the housing. The rotary shaft  20  of the parking brake  27  and the forks  21  can already be fitted in the differential housing  12  already before joining together. When the operating brake is actuated, the pistons  16  press against the pressure plate  17 . 
     FIG. 3 : 
   The pre-assembled structural unit of the differential on the flange  23 , which is connected to an electric motor  24 , can be inserted into the differential housing  12  and bolted in place. The brake in  FIG. 3  differs from the brakes in  FIGS. 1 and 2 , in that the brake in  FIG. 3  is actuated by a ball ramp  33 . The ball ramp  33  has a movable and a rotationally static plate such that the plate that can rotate is actuated by pressurizing a piston  25  with the effect of an operating brake. 
   REFERENCE NUMERALS 
   
       
         1  ring gear 
         2  differential cage 
         3  differential bevel gears 
         4  drive output bevel gears 
         5  drive output shafts 
         6  brake 
         7  inner disk carrier 
         8  inner disks 
         9  neck 
         10  inner disk carrier 
         11  inner disks 
         12  differential housing 
         13  outer disk carrier 
         14  outer disks 
         15  plate 
         16  piston 
         17  pressure plate 
         18  pressure plate 
         19  locking ring 
         20  shaft 
         21  fork 
         22  drive pinion 
         23  flange 
         24  electric motor 
         25  piston 
         27  parking brake 
         29  planet gear 
         31  wheel 
         33  ball ramp