| 摘要 |
PURPOSE:To improve the inching performance of slewing by a method in which other control valves are connected in parallel through a set pressure-variable sequence valve in relation to a control valve for slewing, and the sequence valve is made variable only when the return oil for slewing is less than a set pressure. CONSTITUTION:A control valve 29 for arm and a control valve 34 for boom are connected in parallel to an oil-pressure pump 1 through a control valve 4 for slewing and a set pressure variable sequence valve 19. Pilot pressure for slewing is directed through the valve 38 to the set pressure control port of the sequence valve 19, and the valve 38 is opened only when the pressure of the return pipe 8 of the slewing circuit during the composite operation is less than a set pressure. The slewing pressures are finely adjusted by fine operation of the lever to raise the inching performance of slewing. |
