Transfer case engagement and disengagement system

A control circuit for use in automotive vehicle that comprises an engine for powering the vehicle, a drivetrain, including a transmission, through which the engine can deliver torque to road-engaging driven wheels for propelling the vehicle, a transfer case associated with the transmission for operating auxiliary equipment, and a system for engaging and disengaging the wheels from the transmission and for engaging and disengaging the auxiliary equipment from the transmission through the transfer case, a first electric-operated device that is selectively operable to a first state that causes the driven wheels to be engaged with the transmission and to a second state that causes the driven wheels to be disengaged from the transmission, and a second electric-operated device that is selectively operable to a first state that causes the auxiliary equipment to be disengaged from the transmission and to a second state that causes the auxiliary equipment to be engaged with the transmission, the control circuit comprising:

• a first input for requesting concurrent operation of the first and second electric-operated devices to their respective second states;
• a second input for signaling transmission output shaft speed;
• a third input for signaling full engagement of the auxiliary equipment with the transmission through the transfer case;
• and
• the control circuit being effective, once the third input has signaled full engagement of the auxiliary equipment with the transmission through the transfer case, to prevent both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission until the second input signals a speed predetermined to be a speed suitable for allowing both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission.

A circuit for use in an automotive vehicle that comprises an engine for powering the vehicle, a drivetrain, including a transmission, through which the engine can deliver torque to road-engaging driven wheels for propelling the vehicle, a transfer case associated with the transmission for operating auxiliary equipment, and a system for engaging and disengaging the wheels from the transmission and for engaging and disengaging the auxiliary equipment from the transmission through the transfer case, a first electric-operated device that is selectively operable to a first state that causes the driven wheels to be engaged with the transmission and to a second state that causes the driven wheels to be disengaged from the transmission, and a second electric-operated device that is selectively operable to a first state that causes the auxiliary equipment to be disengaged from the transmission and to a second state that causes the auxiliary equipment to be engaged with the transmission, the circuit comprising:

• a first input for receiving a request for concurrent operation of the first and second electric operated devices to their respective second states;
• a second input for receiving a speed signal indicating transmission output shaft speed;
• a third input for receiving a signal indicating full engagement of the auxiliary equipment with the transmission through the transfer case;
• and
• the circuit being effective, once a signal indicating full engagement of the auxiliary equipment with the transmission through the transfer case has been received, to issue a signal preventing both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission until a speed signal representing a speed suitable for allowing both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission has been received.