| 摘要 |
<p>PURPOSE:To enable to perform composite control during straight running, by a method wherein, when switching valves, except a valve on the uppermost stream, of the one valve group are controlled, the pressure oil of a hydraulic pump for the other valve group is simultaneously fed to the running switching valves of the two valve groups and therefore, a switching valve is changed over. CONSTITUTION:Pressure oil of a first hydraulic pump P1 is fed to a running switching valve 11, a bucket switching valve 12, a boom switching valve 13, and an arm speed increasing valve 14, and is fed to the upper stream of a running switching valve 15 which receives pressure oil of a second hydraulic pump P2 from the upper stream of the running switching valve 11 through a switching valve 24 available during changeover. Meanwhile, pressure oil of the second hydraulic pump P2 is fed in parallel to the running switching valve 15, a slewing switching valve 16, a boom speed increasing valve 17, and an arm switching valve 18 through a second switching valve 29 in a normal position. The first and second switching valves 24 and 29 are controlled by pressure oil from the downstream of the center bypass of the running switching valve 15 of the valve group of the second hydraulic pump P2.</p> |
