Appeal 2006-1399
Application 10/666,712
components. Further, poorly timed engagement of the front axle can
damage the transfer case and axle components resulting in vehicle downtime
and increased costs for replacement of components (Specification 1).
Therefore, the Appellants’ invention takes into consideration both the
relative rotational speeds of the front and rear axle output shafts and the
ground conditions (Specification 1). In this regard, the Appellants’ system
includes a controller that first determines whether there is wheel slippage
and then determines whether the rotational speeds of the front axle output
shaft 54 and rear axle output shaft 52 are within a predetermined speed range
and only then engages the front wheel axle shaft 54. If the rotational speeds
of the front axle output shaft 54 and rear axle shaft 52 are not within the
predetermined speed range, the controller controls the engine output torque
or the wheel brake torque to bring the front axle output shaft 54 and the rear
axle output shaft 52 within the predetermined speed range. Once the front
axle output shaft 54 and the rear axle output shaft 52 are within the
predetermined speed range, the controller engages the front axle output shaft
54 (Specification 7).
When there is no longer wheel slippage, the transfer case declutch
mechanism disengages the front axle shaft (Specification 6). Appellants
recognize that it may be difficult to determine when ground conditions have
improved sufficiently but suggest various measures to solve this potential
problem i.e., the transfer case could include a spring disengagement
mechanism or a time delay device (Specification 6-7). In any case, once it is
determined that there is no wheel slippage, by whatever method, the front
axle shaft is disengaged.
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Last modified: September 9, 2013