| 摘要 |
<p>A hydraulic circuit for turning, wherein a discharge path (20a) of a hydraulic pump (20) is connected to a variable relief valve (21) and to a direction switch valve (22), first and second actuator ports (25, 26) of the direction switch valve are connected to a hydraulic motor for turning (27), a pilot pressure of a pilot valve (33) is introduced into pressure chambers (31, 32) for controlling a spool of the direction switch valve and into a pressure chamber (40) for controlling a set pressure, of the variable relief valve, a portion (42) on a meter-in side, which causes a pressure oil to flow from the pump port of the spool to the first and second actuator ports, has such a shape as not to generate flow force, and a portion (45) on a meter-out side for causing the pressure oil to flow from the first and second actuator ports of the spool to the tank port has such a shape as to generate the flow force. According to this construction, flow rate control with pressure compensation can be made on the meter-out side, so that the start and stop of turning can be made at the same lever position, the flow rate characteristics with respect to the lever position remain unaltered at the time of acceleration and deceleration, and acceleration and deceleration can be carried out in the same pattern irrespective of the size of a suspended cargo and the size of a turning radius.</p> |
