Transmission mechanism for vehicles having HST and pressure oil supply system therefor

A pressure oil supply system for a vehicle comprising a hydraulic device,

• the vehicle being so adapted that power from a drive source installed in a body of the vehicle is transmitted to a drive axle via an hydrostatic transmission (HST) disposed adjacently to the drive source along the longitudinal direction of the vehicle and via a differential gear device coupled to the HST along said longitudinal direction,
• the HST comprising an HST pump having a pump shaft extending longitudinally of the vehicle and connected to the drive source by a shaft, an HST motor cooperative with the HST pump and having a motor shaft, and a housing accommodating the HST pump and the HST motor therein,
• the differential gear device having a casing supporting the drive axles, and a differential gear unit housed in the casing and operatively connected to the motor shaft,
• the pressure oil supply system comprising:
• a hydraulic pump having a drive shaft supported by the housing so as to cause one end thereof to project outward from the housing, and a pump case formed continuously with the housing so as to liquid-tightly surround the projecting end of the drive shaft, the hydraulic pump being adapted to perform a pumping action by the rotation of the drive shaft;
• a hydraulic output cooperative mechanism configured for coupling the pump shaft of the HST pump to the drive shaft;
• an intake line having one end connected to the casing of the differential gear device and the other end connected to the pump case;
• and
• a discharge line having one end connected to the pump case and the other end connected to the hydraulic device.