Relief Valve - Kubota B1220 Workshop Manual

B1220, B1620, B1820, WSM

[5] RELIEF VALVE

The three point hydraulic system circuit has a relief
valve to restrict the maximum pressure in the circuit. The
relief valve is located in control valve body.
Among direct acting relief valves, this type is suited
to higher pressure and has large capacity. Furthermore,
this type is free from unstable operation, such as
chattering, which occurs often in direct acting relief
valves.
When the oil pressure in the circuit is lower than the
setting pressure of the relief valve, the relief valve is not
operated and the oil fed to the relief valve from the
hydraulic pump flows into the position control valve.
When the pressure rises above the relief valve
setting pressure, the oil reaches the room A through the
clearance "a" of the valve seat (4), then the poppet (3)
is pushed against the spring (2) force. This mechanism
relieves the shock of this hydraulic system. Finally, oil
flows out to the transmission case through T2 ports,
preventing any further rise in pressure. The poppet
closes again when enough oil is released to drop
pressure below the valve setting.
(Reference)
[B1220]
• Relief valve setting pressure
9.40 to 10.2 MPa
95.9 to 104 kgf/cm
1370 to 1470 psi
• Engine speed
Approx. 3100 min
• Oil temperature
45 to 55 °C (113 to 131 °F)
[B1620 and B1820]
• Relief valve setting pressure
11.5 to 12.3 MPa
118 to 125 kgf/cm
1670 to 1780 psi
• Engine speed
Approx. 2800 min
• Oil temperature
45 to 55 °C (113 to 131 °F)
NOTE
• Right side of valve seat (4) is connected with left
side of valve seat (4).
(1) Adjusting Plug
(2) Spring
(3) Poppet
(4) Valve Seat
(5) Control Valve Body
8-M9
HYDRAULIC SYSTEM
2
-1
(rpm)
2
-1
(rpm)
P : Pump Port
A : Room
T2 : Tank Port
a : Clearance (Oil Path)
9Y1210272HYM0013US0
KiSC issued 07, 2011 A
(EU)