| 摘要 |
PROBLEM TO BE SOLVED: To provide an economical, hydraulic four-wheel drive vehicle capable of ensuring its stable tractive force and running speed and prolonging the life of its hydraulic equipment. SOLUTION: A hydraulic four-wheel drive vehicle, having for its four-wheel drive a variable displacement hydraulic pump 1 and front-wheel side hydraulic motors 2F and a rear-wheel side hydraulic motor 2R which receive pressure oil from the variable displacement hydraulic pump 1 to rotate, is provided with a front-wheel side closed-center directional control valve 3F for the front- wheel, side hydraulic motors 2F, a rear-wheel side closed-center directional control valve 3R for the rear-wheel side hydraulic motor 2R, a pump-flow control means for controlling the oil-discharge quantity Q of the pump to hold the differential pressure ΔP between the front-wheel side and the rear-wheel side directional control valves 3F and 3R constant, and an interconnection valve 5 disposed between a front-wheel side oil passage laid from the front-wheel side directional control valve 3F to the front-wheel side hydraulic motors 2F and a rear-wheel side oil passage laid from the rear-wheel side directional control valve 3R to the rear-wheel side hydraulic motor 2R for interconnecting or interrupting these passages.
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