Patent ID: 7309301

Claim:
A powertrain for transmitting power to the drive wheels of a vehicle, comprising: a transaxle case; a transaxle drive mechanism located in the transaxle case including an input and an output, for producing variable ratios of a speed of the output and a speed of the input; a differential mechanism secured to the output and located in the transaxle case, for transmitting power between the output and a first set of drive wheels; and a transfer clutch located in the transaxle case, secured to the output, for transmitting power between the output and the wheels of a second set of drive wheels; and a control system located in the transaxle case for hydraulically actuating the transfer clutch and including a source of hydraulic feed pressure; pressure regulator valve for producing a source of regulated hydraulic pressure in response to the hydraulic feed pressure; a first solenoid-operated valve communicating with the source of regulated hydraulic pressure, for alternately opening and closing communication between a high-low pressure output and the source of rcgulated hydraulic pressure; a second solenoid-operated valve communicating with the source of regulated hydraulic pressure, for producing a variable pressure output; a transfer gain control valve communicating with the high-low pressure output and variable pressure output, for outputting a relatively low pressure when the first solenoid-operated valve is closed and a variable pressure when the first solenoid-operated valve is open; and a clutch pressure regulator valve communicating with the output of the transfer gain control valve, the variable pressure output produced by the second solenoid-operated valve, and the source of hydraulic feed pressure for regulating clutch pressure.