Patent ID: 7044259

Claim:
A hydraulic transmission for driving and steering wheels of a vehicle, said vehicle having at least a first pair of laterally disposed wheels comprising: a first pair of hydraulic motors having output shafts respectively and drivingly connected to said first pair of laterally disposed wheels, and having inlet/outlet ports fluidly connected to each other with parallel fluid passages; a second pair of hydraulic motors having output shafts each operatively connected to a corresponding one of said output shafts of said first pair of hydraulic motors, and having inlet/outlet ports fluidly connected to each other with fluid passages; a first hydraulic pump operatively connected to a driving source and having inlet/outlet ports respectively and fluidly connected to a high pressure side and a low pressure side of the parallel fluid passages; a second hydraulic pump operatively connected to said driving source and having inlet/outlet ports respectively and fluidly connected to a high pressure side and a low pressure side of said fluid passages between said second pair of hydraulic motors; wherein said first hydraulic pump is of a variable displacement type that varies the amount of hydraulic fluid to be discharged and supplied, based upon the displacement amount of a first output adjustment member, said displacement amount being varied by operating said first output adjustment member via a driving-speed operation member; said second hydraulic pump is of a variable displacement type that varies the amount of hydraulic fluid to be discharged and sucked, based upon the displacement amount of a second output adjustment member, said displacement amount being varied by operating said second output adjustment member via a steering operation member; and rotational power is input from each of said second pair of hydraulic motors to a corresponding one of the output shafts of the first pair of hydraulic motors by a magnitude corresponding to the operational amount of the steering operation member in a different rotational direction from each other.