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.
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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.
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.
0. 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.
0. 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.
0. 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.
0. 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.
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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
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
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.
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This invention relates generally to tandem drive axle sets and, more particularly, to an inter-axle differential assembly for a tandem drive axle set.
A tandem drive axle set is used to distribute rotational power from a driveline input to a set of forward and rear wheels through a forward drive assembly and a rear drive assembly, respectively. Traditionally, the tandem drive axle set is designed such that the forward drive assembly has a ring gear and a pinion gear set that is a mirror image of the rear drive assembly ring gear and pinion gear set. Usually, the forward drive assembly has a right-hand pinion gear while the rear drive assembly has a left-hand pinion gear. It is necessary that the forward and rear drive assemblies be minor images of each other because, traditionally, the forward drive assembly has included a set of helical gears that are used to transfer half of the rotational power from an inter-axle differential to the forward drive assembly pinion and ring gear set. That is, the forward and rear drives require distinct parts, which requires increased inventory.
The inter-axle differential receives rotational input from the driveline of the vehicle. In such a design, the pinion gear of the forward drive assembly rotates in the opposite direction to that of the inter-axle differential. The inter-axle differential transmits the other half of its input to a through shaft which sends the input back to the rear drive assembly. In the rear drive assembly the pinion gear rotates in the same direction as the inter-axle differential. Because the helical gears are necessary in the forward drive assembly, the axis of the input to the forward drive assembly is offset from the pinion gear axis in the forward drive assembly by the centerline-to-centerline distance of the helical gears. Therefore, the output of the forward axle is on the same axis as the input while the input of the rear drive assembly is on the same axis as the forward axle drive pinion gear.
This difference in axis height between the forward axle output to the rear axle input requires different axle pinion angles to be utilized in order to set the driveline angles in the u-joints used in the driveline. Setting and maintaining the driveline angles is difficult. When the driveline angles at the u-joints are not the same it creates adverse torsional loading and vibrations in the drivetrain assembly. Such torsional loading and vibrations can lead to premature failure of the drivetrain assembly. Even when the driveline angles are properly set at the factory, the air ride suspensions commonly found in heavy duty trucks can alter the driveline working angles in an adverse manner.
Therefore, it is desirable to provide a tandem axle drive set wherein the input power to the forward drive assembly is set on the same axis as the input power to the rear drive assembly. This eliminates the need to set driveline angles and to provide distinct drive components.
In general terms, this invention provides a tandem axle drive set wherein the input power axis to the forward drive assembly of the tandem axle drive set is on the same axis as the input power axis to the rear drive assembly. In addition, the present design eliminates the traditional need for a set of helical gears in the forward drive assembly and permits commonality of design for many components in both the forward and rear drive assemblies of the tandem drive axle set.
Preferably, the tandem axle drive set comprises a forward drive assembly including an inter-axle differential having a pair of outer side gears, a main differential, and a hollow pinion gear. A through shaft has a first end secured to one of the outer side gears and extends through the hollow pinion gear toward a rear drive assembly. The rear drive assembly includes a rear pinion gear and a rear differential. The through shaft drives the rear pinion gear. Rotation of the inter-axle differential rotates the through shaft, the hollow pinion gear, and the rear pinion gear. The hollow pinion gear drives the main differential and the tear pinion gear drives the rear differential.
Thus, a tandem drive axle set is provided wherein the input to the forward drive assembly is on the same axis as the input to the tear drive assembly. This design eliminates the need for setting driveline angles between the forward and rear drive assemblies.
These and other features and advantages of this invention will become more apparent to those skilled in the art from the following detailed description of the presently preferred embodiment. The drawings that accompany the detailed description can be described as follows.
A tandem drive axle set is generally indicated at 20 in FIG. 1. Tandem drive axle set 20 includes a forward drive assembly 22 and a rear drive assembly 24. An driveline connection 26 provides rotational power input to forward drive assembly 22 through a yoke 28. An inter-axle differential assembly 50 receives power from yoke 28 and transfers it to forward drive assembly 22. A through shaft 30 transfers power from forward drive assembly 22 to rear drive assembly 24. A yoke 32 connects through shaft 30 to a driveline connection 34 that is then connected to rear drive assembly 24 through a yoke 36. An input 38 provides power to rear drive assembly 24 from driveline connection 34. Notably, inter-axle differential assembly 50 and shafts 30, 34 and 38 are coaxial. This design is contrary to the prior art wherein then was not a single axis for the drive. The use of this single axis eliminates many concerns forced by the prior art. Further, the single axis allows the use of common front and rear drive assembly components. As known by one of ordinary skill in the art, the inter-axle differential assembly shown at 50 combines the prior art use of a separate input shaft and inter-axle differential assembly.
In
Through shaft 30 includes a first end 63 that is secured to the inter-axle differential outer side gear 62. Through shaft 30 extends from inter-axle differential outer side gear 62 through a hollow pinion gear 64. Hollow pinion gear 64 includes a pinion gear head 68 and is rotated by the other outer side gear 66. Shaft 30 is not fixed to rotate with outer side gear 66 and gear 64. Outer side gear 66 and gear 64 are fixed to rotate together. Shaft 30, gear 64 and gear 66 do tend to all rotate at the same speed. A plurality of roller bearings 70 support hollow pinion gear 64 within a main differential cover 76. Preferably, roller bearings 70 are tapered roller bearings as shown. A pinion cage 72 is used to position a portion of the tapered roller bearings 70. Hollow pinion gear 64 drives a main differential assembly 74. The main differential assembly 74 is well known in the art and does not form a novel portion of the present invention.
A forward axle 78 is driven by main differential assembly 74. Through shaft 30 extends beyond forward axle 78 and passes closely adjacent either above or below forward axle 78. A seal 80 is utilized to seal one end of inter-axle differential cover 54 to yoke 28. As would be understood by one of ordinary skill in the art, forward axle 78 may be located either below or above through shaft 30.
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The present invention has been described in accordance with the relevant legal standards, thus the foregoing description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of this invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.
| Patent | Priority | Assignee | Title |
| 10208846, | Mar 10 2017 | ArvinMeritor Technology, LLC | Axle assembly having a drive pinion support bearing and a method of assembly |
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