| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a structure of generating a foretoken sound without increasing the cost. SOLUTION: This hydraulic circuit is so constructed that oil pressure from a first pump P2 is supplied to first directional selector valves 2, 3, oil pressure from a second pump P2 is supplied to second directional selector valves 4, 5, 6, the first directional selector valves and second directional selector valves are respectively connected to each corresponding actuator, provided is a confluent valve 12 capable of supplying pressure oil from the second pump to the first directional selector valves, and during non-operation of the actuator, connection from the confluent valve to a downstream tank is made. In the hydraulic circuit, when a designated actuator starts to operate, the oil pressure on the upstream side of the confluent valve is increased, or the throttle opening of the confluent valve is decreased to increase the flow velocity of pressure oil passing through the confluent valve, thereby generating passing sound to be used as a foretoken sound for informing an operator of the operation start of the actuator. The confluent valve is controlled by the supply pressure of the second pump, the load pressure of the second actuator and a spring.</p> |
