Patent ID: 7892142

Claim:
A servocontrolled hydraulically transmission ( 7 ) for a road vehicle ( 1 ) provided with an internal combustion engine ( 5 ); the servocontrolled transmission ( 7 ) comprises: a servocontrolled mechanical gearbox ( 12 ) operated by at least one first hydraulic actuator ( 16 , 17 ) and provided with a primary shaft ( 13 ) connectable to a drive shaft ( 6 ) and with a secondary shaft ( 14 ) connected to a transmission shaft ( 8 ) which transmits a motion to driving wheels ( 3 ); a servocontrolled clutch ( 15 ) operated by at least one second hydraulic actuator ( 18 ) and interposed between the drive shaft ( 6 ) and the primary shaft ( 13 ) of the gearbox ( 12 ) to connect and disconnect the drive shaft ( 6 ) to the primary shaft ( 13 ) of the gearbox ( 12 ); a hydraulic circuit ( 19 ) comprising a hydraulic accumulator ( 21 ), which contains pressurised control fluid which is used by the hydraulic actuators ( 16 , 17 , 18 ), and a pump ( 22 ), which is directly operated by the internal combustion engine ( 5 ) to supply the pressurised control fluid to the hydraulic accumulator ( 21 ); a park-lock device ( 24 ) operatable to block the rotation of the driving wheels ( 3 ); and a control unit ( 11 ), which, when the internal combustion engine ( 5 ) is turned off, uses a remaining pressure of the control fluid within the hydraulic accumulator ( 21 ) to automatically bring the servocontrolled mechanical gearbox ( 12 ) in a neutral position.