HYDRAULIC DRIVE AND STEERING SYSTEMS FOR A VEHICLE

摘要

Front and rear wheeled units (13, 14) of vehicle are connected together for articulated steering. Wheels on at least one unit are mounted for swivelling relative to the respective unit to provide kingpin steering in combination with articulation steering. A first embodiment has front and rear kingpin steering and articulation steering performed manually and independently of each other. In a second embodiment, a steering integrator cooperates with actuators (162, 163, 212, 213, 236, 237) which control at least the articulation steering and kingpin steering of the front wheels (22, 23) to automatically integrate two types of steering so that a controlled relationship exists between an articulation angle of the front unit (13) with respect to the rear unit (14), and swivel angles of the front wheels (22, 23) with respect to the front unit (13). A manual steering control, e.g. a steering wheel (186), controls actuation of the steering integrator. Each wheel is powered by a hydraulic motor (32, 33, 44, 45) receiving pressurized fluid from a drive apparatus comprising a flow combiner and two flow restrictors connected in parallel with each other and communicating with outlets from the wheel motors. Bypass valves (114, 115) can be used to bypass the flow combiner and flow restrictors as needed in certain applications not requiring the flow combiner, to reduce generation of heat in the hydraulic fluid.