Maeda MK0003, Service Manual, Page: 102 / 348

2-74
8.4 ACTIONS OF EACH SECTION
[1] Composition and actions of supply section
The supply section consists of a supply port (P) for supplying hydraulic oil from pump, oil channel to bring it to
operation section (switching section), and the discharge port (T) to discharge the return oil from actuator to tank; and
in addition, a back pressure valve (sequence valve), reducing valve, and relief valve.
The sequence valve is provided to secure the minimum operating pressure of pilot when magnetical switching under
no load and the reducing valve serves to maintain the pilot pressure at a specified value.
Since the sequence valve, reducing valve and relief valve are not working while no oil is allowed to flow, the paths of
pump to tank and pump to central bypass are closed, although the path from pump to the primary side of reducing
valve is allowed to flow.
When supplied from pump, the oil pushes the sequence valve to open and flows in the central bypass path. When the
switching valve in the downstream is not operated, the pump pressure at supply port (P) serves as the pressure of the
sequence valve.
(Cracking pressure: 1.34 to 1.49 MPa)
Concurrently, the reducing valve starts to maintain the pilot pressure at the set pressure of the reducing valve.
(Reducing valve set pressure: 1.42 to 1.47 MPa)
When the downstream switching valve is being operated, the pump pressure works as its load pressure, and as soon
as the negative pressure reaches the relief valve set pressure, the relief valve operates to maintain the circuit
pressure at the relief valve set pressure.
Also, when the emergency solenoid (SOL.9) is not excited, the circuit pressure can be set to the level of unloaded
state.
･ Limit the set pressure of relief valve within the range not exceeding the rated pressure of the valve.
Using it at a pressure exceeding the rated pressure may invite a performance drop, failure or breakage.
各ﾊﾟｲﾛｯﾄ
制御ﾗｲﾝへ
T
T
P
T
一次側（
P)
非常停止
(SOL 9
）
二次側
減圧弁
(
背圧弁
)
ﾘﾘｰﾌ弁
ｾﾝﾀｰﾊﾞｲﾊﾟｽ通路
Reducing valve
Primary side (P)
Relief valve
Set value: 20.6 MPa (210 k)
Filter receptacle
Each pilot on the secondary side
To the control line
Filter (10 μ m)
O-ring 1BP7
（
2 spots)
Filter plug
Spring guide
Sequence valve spring
Sequence valve
(Back pressure
valve)
Emergency stop
Unloading section - Assembly
Pilot spool (normally open)
Supplying section -
Assembly
Central bypass path