| 摘要 |
PURPOSE:To make an efficient use of the output horsepower of a prime mover, by increasing the input horsepower of one variable displacement pump by controlling it only by the discharge pressure of this pump when the input horsepower of the other variable displacement pump is decreased in a control apparatus having two variable displacement pumps driven by a single prime mover. CONSTITUTION:In case that the discharge pressure Pb is equal to or higher than a reference pressure PR, a pressure control valve 17b is opened and pressure on the upstream side of a restriction 19b is increased gradually. Resultantly, a pilot piston 4b is at first moved to the left and a control valve 7b is shifted to a position A, so that the discharge pressure Pb is intercepted and a cylinder chamber 12b is communicated with a tank. Accordingly, a piston of a servo piston 5b is moved to the right-side end and the discharge quantity Q of a pump 1b is reduced to a minimum value QR. Subsequently, a changeover valve 14a is shifted to a position B and a mating pressure receiving section 6a is communicated with the tank, so that only the discharge pressure Pa is acted to a pilot piston 4a. Therefore, the discharge quantity Q of a pump 1a is controlled only by the discharge pressure Pa and the input horsepower of the pump 1a is made substantially equal to the output horsepower of a prime mover. |
