Control strategy for operating a locking differential

Abstract

A drive train having a locking differential and a control unit for controlling operation of the locking differential. The control unit is responsive to selected vehicle characteristics to sua sponte activate or inactivate a locking mechanism of the locking differential to cause the locking differential to operate in a locked manner or an unlocked manner, respectively. A method for operating a locking differential is also provided. The method includes: utilizing only preselected vehicle criteria indicative of the operational state of the vehicle to identify a situation in which a locking mechanism associated with the locking differential is to be energized; and responsively energizing the locking mechanism.

1 . A drive train for a vehicle, the drive train comprising:
 a first locking differential having a first locking mechanism; and   a control unit for controlling operation of the first locking differential, the control unit being responsive to selected vehicle characteristics to sua sponte activate or inactivate the first locking mechanism of the first locking differential to cause the first locking differential to operate in a locked manner or an unlocked manner, respectively.   
     
     
         2 . The drive train of  claim 1 , further comprising a first axle assembly including an axle housing and a first pair of axle shafts, wherein the axle housing houses the first locking differential. 
     
     
         3 . The drive train of  claim 2  wherein the first pair of axle shafts are coupled to opposite sides of the first locking differential. 
     
     
         4 . The drive train of  claim 3  wherein the first locking differential is configured to receive a first rotary input from a first propeller shaft and selectively transmit the first rotary input to the first pair of axle shafts in one of the locked or unlocked manner. 
     
     
         5 . The drive train of  claim 4 , further comprising a second axle assembly having a second differential having a second locking mechanism, the second axle assembly having a second pair of axle shafts, wherein the control unit is responsive to the vehicle characteristics to sua sponte activate or inactivate the second locking mechanism of the second locking differential to cause the second locking differential to operate in a locked manner or an unlocked manner, respectively. 
     
     
         6 . The drive train of  claim 1  wherein the control unit communicates with a differential sensor that is configured to sense a parameter indicative of the operational state of the locking differential. 
     
     
         7 . The drive train of  claim 6  wherein the control unit is configured to activate the locking mechanism in response to a control signal generated by operation of one of a manually actuated switch or a shift into a four-wheel drive mode. 
     
     
         8 . The drive train of  claim 6  wherein the selected vehicle characteristics comprise a throttle position, a steering wheel angle, a wheel slip, a vehicle acceleration, a vehicle speed and a vehicle yaw rate and wherein the control unit is configured to activate the locking mechanism automatically based on all of the vehicle characteristics satisfying a predetermined threshold. 
     
     
         9 . The drive train of  claim 7  wherein the control unit is configured to inactivate the locking mechanism in response to a control signal generated by operation of one of a manually actuated switch or a shift into a four-wheel drive mode. 
     
     
         10 . The drive train of  claim 8  wherein the control unit is configured to unlock the locking mechanism automatically based on one of the vehicle characteristics satisfying a predetermined threshold. 
     
     
         11 . The drive train of  claim 1  wherein the selected vehicle characteristics include an identification that the vehicle is ascending a hill. 
     
     
         12 . A method for operating a locking differential in a vehicle, the method comprising:
 utilizing only preselected vehicle criteria indicative of an operational state of the vehicle to identify a situation in which a locking mechanism associated with the locking differential is to be energized; and   responsively energizing the locking mechanism.   
     
     
         13 . The method of  claim 12  wherein utilizing only the preselected vehicle criteria comprises determining a status of a manually actuated switch. 
     
     
         14 . The method of  claim 12  wherein utilizing only the preselected vehicle criteria comprises determining a status of a four-wheel drive mode. 
     
     
         15 . The method of  claim 12  wherein utilizing only the preselected vehicle criteria comprises determining a throttle position, a steering wheel angle, a wheel slip, a vehicle acceleration, a vehicle speed and a vehicle yaw rate. 
     
     
         16 . The method of  claim 15  wherein responsively energizing the locking mechanism comprises activating the locking mechanism automatically based on all of the vehicle criteria satisfying a predetermined threshold. 
     
     
         17 . The method of  claim 12  wherein utilizing only the preselected vehicle criteria comprises determining if the vehicle is ascending a hill and responsively energizing the locking mechanism based on the determination. 
     
     
         18 . The method of  claim 16 , further comprising:
 utilizing the preselected vehicle criteria to identify a situation in which the locking mechanism is to be disabled; and   responsively disabling the locking mechanism.   
     
     
         19 . The method of  claim 18  wherein responsively disabling the locking mechanism comprises disabling the locking mechanism automatically based on one of the vehicle criteria satisfying a predetermined threshold.