| 摘要 |
<P>PROBLEM TO BE SOLVED: To add regeneration switching means c to a two-speed switching control valve 4 for controlling a boom cylinder BC to integrate them, thereby achieving downsizing and space-saving. <P>SOLUTION: In a first circuit system connected to a first main pump MP1, regeneration switching means c is added to a two-speed switching control valve 4 of a boom cylinder BC which is a switching control valve with less number of switching positions than other switching control valves, to integrate the two-speed switching control valve 4 and the regeneration switching means c. And, during no operation of the boom cylinder BC, the regeneration switching means c is also maintained in an open state. <P>COPYRIGHT: (C)2012,JPO&INPIT |
