Inter-axle differential assembly for a tandem drive axle set

Abstract

An inter-axle differential assembly for a tandem drive axle set is disclosed that permits a rear drive assembly and a forward drive assembly to have the same input axis. The forward drive assembly includes a hollow pinion gear. An inter-axle differential assembly receives input from a driveline connection and transfers this input to the hollow pinion gear and to a through shaft that extends through the hollow pinion gear. The hollow pinion gear drives a main differential assembly that in turn drives a forward axle. The through shaft extends toward a tear drive assembly and provides input to the rear drive assembly. The rear drive assembly utilizes a rear pinion gear to drive a rear differential. The rear differential in turn drives a rear axle. Thus, the present design permits a common axis to be shared by the input to the forward drive assembly and the input to the rear drive assembly. In addition, the present design eliminates the traditionally required helical gears from the forward drive assembly.

1. A tandem axle drive set comprising:
 a forward drive assembly including an inter-axle differential having a pair of outer side gears, a main differential, and a hollow pinion gear, said inter- axle differential being rotatably supported by at least a pair of roller bearings;    
 a through shaft having a first end secured to one of said outer side gears and extending through said hollow pinion gear, said through shaft not rotating with said hollow pinion gear;  
 a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear; and  
 rotation of said inter-axle differential rotating on said roller bearings resulting in rotation of said through shaft, said hollow pinion gear, and said rear pinion gear, with said hollow pinion gear driving said main differential and said rear pinion gear driving said rear differential.  
 
     
     
       2. A tandem axle drive set as recited in  claim 1 , wherein said hollow pinion gear is supported by at least one pair of roller bearings. 
     
     
       3. A tandem axle drive set as recited in  claim 2  wherein said roller bearings comprise tapered roller bearings. 
     
     
       4. A tandem axle drive set as recited in  claim 1  wherein said hollow pinion gear, said through shaft and said rear pinion gear all rotate about the same axis. 
     
     
       5. A tandem axle drive set as recited in  claim 1  wherein said rear drive assembly and said forward drive assembly each include at least one annular seal. 
     
     
       6. A tandem axle drive set as recited in  claim 1 , A tandem axle drive set comprising:
   a forward drive assembly including an inter - axle differential having a pair of outer side gears, a main differential, and a hollow pinion gear, said inter - axle differential being rotatably supported by at least a pair of bearings;    
   a through shaft having a first end secured to one of said outer side gears and extending through said hollow pinion gear, said through shaft not rotating with said hollow pinion gear;    
   a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear  wherein said rear pinion gear is supported by at least one pair of roller bearings; and  
   rotation of said inter - axle differential on said bearings resulting in rotation of said through shaft, said hollow pinion gear, and said rear pinion gear, with said hollow pinion gear driving said main differential and said rear pinion gear driving said rear differential.   
 
     
     
       7. A tandem axle drive set as recited in  claim 6  wherein said roller bearings comprise tapered roller bearings. 
     
     
       8. A tandem axle drive set as recited in claim l wherein said hollow pinion gear, said through shaft, and said rear pinion gear rotate in a first direction, said first direction based on the rotation direction of said inter-axle differential. 
     
     
       9. A tandem axle drive set as recited in  claim 1  A tandem axle drive set comprising:
   a forward drive assembly including inter - axle differential having a pair of outer side gears, a main differential, and a hollow pinion gear, said inter - axle differential being rotatably supported by at least a pair of bearings;    
   a through shaft having a first end secured to one of said outer side gears and extending through said hollow pinion gear, said through shaft not rotating with said hollow pinion gear;    
   a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;    
   rotation of said inter - axle differential on said bearings resulting in rotation of said through shaft, said hollow pinion gear, and said rear pinion gear, with said hollow pinion gear driving said main differential and said rear pinion gear driving said rear differential; and    
 wherein said forward drive assembly further includes a forward axle driven by said main differential, said through shaft passing adjacent said forward axle and extending beyond said forward axle toward said rear drive assembly.  
 
     
     
       10. A tandem axle drive set comprising:
 a forward drive assembly including an inter-axle differential having a pair of outer side gears, and a main differential having a forward pinion gear for supplying an input drive from said inter-axle differential to a pair of side gears;  
 a through shaft having a first end secured to one of said outer side gears and extending past said forward drive assembly, said through shaft rotating with said at least one outer side gear;  
 a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;  
 at least one tapered roller bearing rotatably supporting said inter- axle differential with  rotation of said inter-axle differential rotating said through shaft, said main differential, said rear pinion gear, and said rear differential; and  
 said inter-axle differential, said through shaft, said forward pinion gear, and said rear pinion gear being coaxial.  
 
     
     
       11. A tandem axle drive set as recited in  claim 1  wherein said at least a pair of roller bearings comprises a first bearing set and wherein said hollow pinion gear is supported by a second bearing set separate from said first bearing set. 
     
     
       12. A tandem axle drive set composing:
   a forward drive assembly including an inter - axle differential having a pair of outer side gears, a main differential, and a hollow pinion gear, said inter - axle differential being rotatably supported by at least a pair of bearings wherein said at least a pair of bearings comprises a first bearing set and wherein said hollow pinion gear is supported by a second bearing set separate from said first bearing set;        a through shaft having a first end secured to one of said outer side gears and extending through said hollow pinion gear, said through shaft not rotating with said hollow pinion gear;        a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;        rotation of said inter - axle differential on said bearings resulting in rotation of said through shaft, said hollow pinion gear, and said rear pinion gear, with said hollow pinion gear driving said main differential and said rear pinion gear driving said rear differential; and        a pinion cage having a first portion for sporting at least one bearing from said first bearing set and a second portion for supporting at least one bearing from said second bearing set.     
     
     
       13. A tandem axle drive set as recited in  claim 11  wherein said first bearing set comprises a first pair of tapered roller bearings and said second bearing set comprises a second pair of tapered roller bearings. 
     
     
       14. A tandem axle drive set as recited in  claim 13  including a main differential carrier for substantially enclosing said main differential, an inter- axle differential cover for substantially enclosing said inter - axle differential, and a pinion cage wherein said first pair of tapered roller bearings includes a first tapered roller bearing supported between said inter - axle differential and said inter - axle differential cover and a second tapered roller bearing supported between said inter - axle differential and said pinion cage and wherein said second pair of tapered roller bearings includes a third tapered roller bearing supported between said hollow pinion gear and said pinion cage and a fourth tapered roller bearing supported between said hollow pinion gear and said main differential carrier.   
     
     
       15. A tandem axle drive set as recited in  claim 14  wherein said first tapered roller bearing is positioned on an opposite end of said inter- axle differential from said second tapered roller bearing and wherein said third tapered roller bearing is positioned on an opposite side of a pinion gear head from said fourth tapered roller bearing.   
     
     
       16. A tandem axle drive set as recited in  claim 15  wherein said pinion cage is mounted between said main differential carrier and said inter- axle differential cover.   
     
     
       17. A tandem axle drive set as recited in  claim 11  wherein said first bearing set is solely comprised of a first pair of tapered roller bearings and said second bearing set is solely comprised of a second pair of tapered roller bearings. 
     
     
       18. A tandem axle drive set comprising:
   a forward drive assembly including a main differential having a forward pinion gear receiving input from an inter - axle differential, said inter - axle differential being rotatably supported by a first roller bearing set and having a first outer side gear and a second outer side gear;        a through shaft having a first end secured to said first outer side gear and a second end extending past said forward drive assembly, said through shaft rotating with said first outer side gear;        a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;        said second outer side gear in driving engagement with said forward pinion gear with rotation of said inter - axle differential rotating said through shaft, said main differential via said forward pinion gear, said rear pinion gear, and said rear differential; and        said inter - axle differential, said through shaft, said forward pinion gear, and said rear pinion gear being coaxial.     
     
     
       19. A tandem axle drive set as recited in  claim 18  wherein said forward pinion gear comprises a hollow pinion shaft with a pinion gear head, said through, shaft extending through said hollow pinion shaft. 
     
     
       20. A tandem axle drive set as recited in  claim 19  wherein said pinion shaft is rotatably supported by a second bearing set. 
     
     
       21. A tandem axle drive set as recited in  claim 20  wherein said first roller bearing set solely comprises a first pair of tapered roller bearings. 
     
     
       22. A tandem axle drive set comprising:
   a forward drive assembly including a main differential having a forward pinion gear receiving input from an inter - axle differential, said inter - axle differential being rotatably supported by a first bearing set and having a first outer side gear and a second outer side gear and wherein said forward pinion gear comprises a hollow pinion shaft with a pinion gear head, said through shaft extending through said hollow pinion shaft with said hollow pinion shaft being rotatably supported by a second bearing set solely comprising a pair of tapered roller bearings;        a through shaft having a first end secured to said first outer side gear and a second end extending past said forward drive assembly, said through shaft rotating with said first outer side gear;        a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;        said second outer side gear in driving engagement with said forward pinion gear with rotation of said inter - axle differential rotating said through shaft, said main differential via said forward pinion gear, said rear pinion gear, and said rear differential; and        said inter - axle differential, said through shaft, said forward pinion gear, and said rear pinion gear being coaxial.     
     
     
       23. A tandem axle drive set comprising:
   a forward drive assembly including a main differential having a forward pinion gear receiving input from an inter - axle differential, said inter - axle differential being rotatably supported by a first bearing set and having a first outer side gear and a second outer side gear;        said forward pinion gear comprising a hollow pinion shaft with a pinion gear head with said through shaft extending through said hollow pinion shaft, said hollow pinion shaft being rotatably supported by a second bearing set wherein first bearing set includes a first tapered roller bearing and a second tapered roller bearing and said second bearing set includes a third tapered roller bearing and a fourth tapered roller bearings;        a through shaft having a first end secured to said first outer side gear and a second end extending past said forward drive assembly, said through shaft rotating with said first outer side gear;        a rear drive assembly including a rear pinion gear and a rear differential, said through shaft driving said rear pinion gear;        said second outer side gear in driving engagement with said forward pinion gear with rotation of said inter - axle differential rotating said through shaft, said main differential via said forward pinion gear, said rear pinion gear, and said rear differential; and        said inter - axle differential, said through shaft, said forward pinion gear, and said rear pinion gear being coaxial.     
     
     
       24. A tandem axle drive set as recited in  claim 23  wherein said first tapered roller bearing is positioned at an opposite end of said inter- axle differential from said second tapered roller bearing and wherein said third tapered roller bearing is positioned on one side of said pinion gear head adjacent to said second tapered roller bearing and said fourth tapered roller bearing is positioned on an opposite side of said pinion gear head from said third tapered roller bearing.   
     
     
       25. A tandem axle drive set as recited in  claim 24  including a single piece pinion cage having a first cage portion for supporting said second tapered roller bearing and a second cage portion for supporting said third tapered roller bearing. 
     
     
       26. A tandem axle drive set as recited in  claim 25  including a main differential carrier and an inter- axle differential cover wherein said first tapered roller bearing engages said inter - axle differential cover and said inter - axle differential and said fourth tapered roller bearing engages said main differential carrier and said hollow pinion shaft.   
     
     
       27. A tandem axle drive set as recited in  claim 26  wherein said pinion cage is longitudinally positioned between said inter- axle differential and main differential carrier.