| 摘要 |
<p>PURPOSE:To effectively utilize the output of a prime mover by controlling the pressure-receiving area of two pilot pressure receiving members to make it a value proportional to the total discharge amount of the main pumps in the unload valve of an oil-pressure circuit with plural pumps. CONSTITUTION:In an oil-presssure circuit having the main pumps 2 and 3 and an accelerating pump 4 whose oil pressure is jointed with the oil pressure of the main pump 3, the discharge pressures of the main pumps 2 and 3 as pilot pressures are acted on an unload valve 6, and the accelerating pump 4 is unloaded in the position II. Then, in the unload valve 6, the values of the pressure-receiving areas A and B of the pilot pressure-receiving members 15 and 16 are controlled so as to proportionate to the total discharge amounts D1 and D1+D2 (where D1 is the discharge amounts of the main pumps 2 and 3 and D2 is the discharge amount of the accelerating pump 4. And, when the formula D1Sp1+(D1+D2)Sp1>=F where S is a constant, p1 is the discharge pressure of the main pump 2, and F is the pushing force of a spring 14, is met, the valve 6 is switched to the position II.</p> |
