| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of hunting and cavitation and to prevent an oil-hydraulic motor from running by itself by a method wherein switching positions and control positions are provided at a main valve installed between an oil-hydraulic motor and a pump. SOLUTION: A pilot operated main valve 5 operated by pilot oil pressure of a remote control valve 13 is installed between an oilhydraulic motor 3 and a pump 6 for driving a travel equipment of a construction machine. Switching positions 5c, 5c' for making the oil-hydraulic motor 3 communicate with a tank 7 and the pump 6 are provided at the main valve 5. Furthermore, control positions 5b, 5b' wherein the opening from the oil-hydraulic motor 3 to the pump 6 is made smaller than the opening from the pump 6 to the oil-hydraulic motor 3 are provided. Then, the speed of the oil-hydraulic motor 3 is controlled with the main valve 5 swithced from the switching positions 5c, 5c' to the control positions 5b, 5b' when the machine is in descending travel on a slope. Thereby, cavitation can be prevented from occurring to the oil-hydraulic motor 3 and the construction machine can be prevented from running wild. |
