| 摘要 |
PURPOSE:To prevent the occurrence of the so-called 4 a catching phenomenon due to the supply flow shortage for sudden operation even if a steering device is suddenly operated. CONSTITUTION:An auxiliary orifice 41 which is closed when the pressure on the surplus flow port 4 side becomes above the preset pressure is formed on a main spool 6, and the auxiliary orifice is joined to the downstream sides of control orifices 26, 27 through a pressure chamber 19 formed on the main spool. In this arrangement, when the pressure on the surplus flow port side is below the preset pressure, a supply flow which flows in from the auxiliary orifice is forced to join a supply flow which goes through the control orifices. |
