Patent Publication Number: US-2009227382-A1

Title: Pinion shaft formed with an integral inner race of a constant velocity joint

Description:
BACKGROUND OF THE INVENTION 
     a) Field of the Invention 
     This invention relates generally to a vehicle drivelines utilizing constant velocity joints. 
     b) Description of Related Art 
     Conventional vehicle differential gear assemblies transfer rotational torque from a rotary driver member such as the output shaft of a change gear transmission to a pair of rotary driven members such as a pair of substantially axially aligned spaced-apart axle shafts mounted for rotation and having wheels mounted on their respective outboard ends. The differential gear assembly is driven by a pinion gear which in turn is coupled to a driveline component (propeller shaft) of a vehicle. 
     In many convention configurations of a vehicle&#39;s driveline, a universal joint is connected to the input shaft of the drive pinion gear by way of a yoke welded to each end of the propeller shaft. This arrangement of power transfer components ideally serves to compensate for any changes in the driveline. However, with such an arrangement, the power transfer may not be as efficient as possible between the propeller shaft and the differential. In one prior art arrangement, U.S. Pat. No. 5,916,055, the drive bevel pinion also acts as the outer race of a constant velocity joint. However, this arrangement requires drastic modification to the differential housing, bearings, seals and other component which increases the size and weight of the entire differential axle assembly and otherwise prohibits retrofit, or incorporation into standard axle assemblies and their associated housings. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a vehicle driveline assembly including: a drive shaft; a pinion shaft and a constant velocity joint coupling the drive shaft to the pinion shaft. The constant velocity joint has an inner race integrally formed on an end of the pinion shaft. The pinion shaft and associated pinion gear drive an axle assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic layout of a vehicle drive system incorporating the pinion shaft and constant velocity joint. 
         FIG. 2  is a cross-sectional view of the constant velocity joint with integrated inner race and pinion shaft of an axle assembly. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       FIG. 1  depicts a drive train of an all-wheel drive (AWD) or four-wheel drive (4WD) motor vehicle in accordance with an embodiment of the present invention. The AWD drive train comprises an internal combustion engine  20  mounted to a front end of the motor vehicle and coupled to a transmission unit  22 . A transfer case  24  is secured to the rear of the transmission unit  22 . The transmission unit  22  is connected to an input shaft (not shown) of the transfer case  24 . The transfer case  24  includes a rear output shaft or yoke  26  connected to a forward end of a rear drive shaft  15  by a constant velocity joint coupling  11 . The rearward end of the rear drive shaft  15  is coupled to an pinion shaft  3  of a rear differential assembly  2  by means another constant velocity joint as shown in  FIG. 1 . As previously discussed, the rear differential  1  is adapted to provide torque from the rear drive shaft  14  to output shafts which in turn rotate the rear wheels. 
     The transfer case  24  includes a front output shaft or yoke  36  connected to a forward end of a front drive shaft  35  by a constant velocity joint coupling  11 . The front drive shaft  35  has a forward end connected to an input shaft or yoke of a front differential unit  31  of a front (secondary) on-demand axle assembly by means of another constant velocity joint coupling  27  and is adapted to divide torque received from the drive shaft  35  between the vehicle front wheels. 
       FIG. 2  is depicts an axle assembly  1  having an active differential assembly  2 . A pinion shaft  3  is connected to a pinion gear  4  which engagable drives a ring gear  5  in a conventional manner. The ring gear  5  is connected to a differential case  6  rotatably mounted within the housing  7  via bearings  8   a ,  8   b . The differential case  6  contains a gear set (side gears  9  and spider gears  10 , etc.) to allow differential rotational speed between a pair of opposing output shafts  12   a ,  12   b . The details of the operation of conventional differential assemblies will not be further elaborated as such is well within the knowledge of one of ordinary skill in the art. 
     The pinion shaft  3  is rotatably mounted and extends through the housing  7  via bearings  13   a ,  13   b  and is sealed in a conventional manner. The pinion gear  4  may be unitarily formed with the pinion shaft  3 . As previously discussed, the pinion shaft  3  is connected to the drive shaft  15  via constant velocity joint  1 . The end of the pinion shaft  3 , opposite the pinion gear  4 , is splined  14  to receive a complimentarily splined inner race  16 . A clip  14   a  may be employed to secure the longitudinal position of the inner race  16  with respect to the pinion shaft  3 . The inner race may also be formed integrally with the pinion shaft  3  by other techniques such as unitarily forming the inner race with the pinion shaft  3 . 
     As shown in  FIG. 2 , the constant velocity joint is a fixed center ball and cage type constant velocity universal joint. The ball and cage assembly includes cage  17  having a plurality of balls  18  rotatably seated therein. The cage and ball assembly is disposed between the inner race  16  of the pinion shaft  3  and the outer race  19  of the constant velocity joint. The assembly provides improved articulation between the pinion shaft  3  and drive shaft  15  during rotation. Integrally forming the inner race  16  to the pinion shaft  16  provides for improved assembly techniques, more compact arrangement and efficient torque transfer between the drive shaft  15  and pinion shaft  3 . As can also be seen a boot assembly is secured to the outer race and pinion shaft  3  to prohibit entrance of foreign matter such as dust, dirt and the like. 
     The foregoing invention has been shown and described with reference to a preferred embodiment. However, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.