| 摘要 |
<p>During manual operation, pilot pressure discharged from a pilot pump (41) is fed from a manual operation valve (44a) or (44b) through an electromagnetic change valve (49a) or (49b) to a main control valve (33). During automatic operation, pilot pressure which is output from an automatic-mode selecting valve (46) is fed through an electromagnetic proportional control valve (48a) or (48b) as well as an electromagnetic change valve (49a) or (49b), all of which are controlled by a controller (21), to main control valve (33). When limiting the operation range of the attachment during manual operation, pilot pressure output from manual operation valve (44a) or (44b) is fed through electromagnetic proportional control valve (48a) or (48b) as well as electromagnetic change valve (49a) or (49b) to main control valve (33). At that time, main control valve (33) is returned to the neutral position by causing electromagnetic proportional control valve (48a) or (48b), which are both controlled by control signals from controller (21), to block the pilot pressure.</p> |
