| 摘要 |
<p>A hydraulic circuit device for construction machines wherein a first pressure regulator (130) for controlling the downstream pressure of first variable throttles (107, 107a) to a value corresponding to a first signal pressure is disposed between the first variable throttles of a directional control valve (47) for leftward running and a first running motor (57), and wherein a second pressure regulator (133) for controlling the downstream pressure of second variable throttles (108, 108a) to a value corresponding to a second signal pressure is disposed between the second variable throttles of a directional control valve (49) for rightward running and a second running motor (57). A negative pressure of either the first or second running motor, whichever is higher, is detected by a shuttle valve (136) as a maximum negative pressure, and signal switching valves (131, 135, 170) are caused to operate during combination operation in which the first and second running motors and at least one of a plurality of work machine actuators (53 to 56) are simultaneously driven, whereby themaximum negative pressure is imparted to the first and second pressure regulators as first and second signal pressures. Even when this enables a communication circuit (110) to be put into operation as the work machine actuators are put into operation during combination operation in which running and the operation of the work machine are simultaneously effected to thereby allow a pressure oil supply circuit (104) of the second directional control valve for rightward running and a pressure oil supply circuit (103) of the first directional control valve for leftward running to communicate with each other, differences in pressure across the first and second throttles become substantially equal to each other, thereby making it possible to secure a straight running capability.</p> |
