Patent ID: 7857079

Claim:
A four-wheel vehicle comprising: a prime mover; a pair of left and right steerable wheels; a pair of left and right non-steerable driving wheels; a transmission system for transmitting power of the prime mover to the pair of left and right non-steerable driving wheels and for independently controlling rotational speeds of the left and right non-steerable driving wheels, wherein the transmission system includes an operative part for controlling the rotational speeds of the left and right non-steerable driving wheels; a steering operation device for steering the pair of left and right steerable wheels; a fluid supply device whose fluid supply is controlled by operating the steering operation device; a hydraulic power steering actuator fluidly connected to the fluid supply device and operatively connected to the steering operation device; and a pair of left and right gear assemblies interposed between the actuator and the respective left and right steerable wheels, wherein, in each of the gear assemblies, a first non-circular gear operatively connected to the steering operation device meshes with a second non-circular gear operatively connected to each of the left and right steerable wheels, and wherein the actuator is also operatively connected to the operative part of the transmission system so as to control a differential rotation of the left and right non-steerable driving wheels according to operation of the steering operation device.