| 摘要 |
PURPOSE:To recover the potential energy of boom by using a system in which when oil pressure on the bottom side of a boom cylinder is higher than that on rod side, an oil chamber on the bottom side is shortcircuited with an oil chamber on the rod side in terms of oil pressure. CONSTITUTION:In case a holding pressure is present in the bottom side oil chamber of a boom cylinder 7, a valve 22 connects the circuit of pilot pressure signal P2 to a valve 21 by a pressure difference between the bottom side oil chamber and the rod side oil chamber, whereby permitting the pilot pressure signal P2 to be put in the valve 21. Under the condition, when the pilot pressure signal P2 is sent out by an operating lever 19, the signal P2 acts on the valve 21 through the valve 22 to open it, and the bottom side oil chamber of the boom cylinder 7 is shortcircuited with the rod side oil chamber in terms of oil pressure. At the same time, a direction switch valve 14 is switched to the left side by the signal P2. By this, part of oil is flowed into the rod side oil chamber by the holding pressure of the bottom side oil chamber, the rest of oil is released to a tank 17 through the valve 14, the rod of the boom cylinder 7 is shrunk, and the boom is lowered and potential energy is recovered. |
