Planetary gear transmission systems or components – Variable speed or direction transmission combined with... – Transmission output shaft parallel to differential output...
Reexamination Certificate
2000-03-21
2001-05-29
Marmor, Charles A. (Department: 3681)
Planetary gear transmission systems or components
Variable speed or direction transmission combined with...
Transmission output shaft parallel to differential output...
C475S221000, C180S249000
Reexamination Certificate
active
06238317
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to transmissions for use in four-wheel drive vehicles. More particularly, the present invention is directed to a transmission having a multi-speed geartrain and a power transfer mechanism contained in a single unit.
As is known, the majority of four-wheel drive vehicles are equipped with a transfer case mounted to a multi-speed transmission for directing power from the engine to all four wheels. To accommodate different road surfaces and conditions, many transfer cases are equipped with a mode shift mechanism which permits the vehicle operator to selectively uncouple one set of wheels for establishing a two-wheel drive mode in addition to the four-wheel drive mode. In addition, some transfer cases are also equipped with a gear reduction unit for providing high-range and low-range four-wheel drive modes. Finally, some transfer cases are equipped with an interaxle differential for permitting torque proportioning and speed differentiation between the front and rear drivelines of the four-wheel drive vehicle.
In an effort to minimize the overall size of the drivetrain used in four-wheel drive vehicles, it has been proposed to utilize a transmission of a transaxle-type normally used to drive the front wheels of a front wheel drive vehicle as a four-wheel drive geartrain. In particular, British Patent No. 2,035,930 to Jones et al. teaches of rotating the front wheel drivetrain (i.e., engine and transaxle) 90° such that the transaxle outputs can be interconnected to the front and rear drivelines of the motor vehicle. While such an arrangement may provide an economical drivetrain layout for a full-time four-wheel drive vehicle, the practical applications for such an arrangement are severely limited. In particular, such an arrangement does not permit the vehicle operator to selectively shift “on-the-fly” between high and low four-wheel drive modes, nor can one of the outputs be selectively disconnected from its driveline for establishing a two-wheel drive mode.
Accordingly, the need exists for a transmission which can be used in most conventional four-wheel drive applications and which permits the vehicle operator to selectively shift between the available drive modes and speed ranges.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a transmission for use with four-wheel drive vehicles having a multi-speed geartrain and a power transfer mechanism integrated into a single unit.
According to yet another object, the transmission has a power transfer mechanism equipped with a transfer clutch for automatically controlling torque distribution and speed differentiation across an interaxle differential in response to slip between the front and rear output shafts.
The transmission of the present invention includes a multi-speed geartrain including a input shaft, a mainshaft, and a plurality of constant-mesh gearsets which can be selectively engaged to couple the mainshaft to the input shaft for driven rotation at various speed ratios. The mainshaft can be selectively coupled to a power transfer mechanism for establishing two alternative power transmission routes. In particular, the power transfer mechanism includes a synchronized range shift mechanism which is operable for establishing a high-range transmission route and a low-range transmission route from the mainshaft to the input of an interaxle differential. The torque delivered to the interaxle differential is split between the front and rear drivelines to establish a full-time four-wheel drive mode. Optionally, the power transfer mechanism further includes a transfer clutch which can be passively or automatically actuated to limit slip and bias the torque distribution between the front and rear drivelines.
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Brown David
Zajac Alan P.
Harness & Dickey & Pierce P.L.C.
Marmor Charles A.
New Venture Gear Inc.
Parekh Ankur
LandOfFree
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