Relief Valve - Kubota B2410 Workshop Manual

B7800HSD (SUPPLEMENT), WSM

2. RELIEF VALVE

The implement control system circuit has a relief
valve to restrict the maximum pressure in the circuit. The
relief valve is located in the control valve body.
The relief valve is of the guide piston type with
damping effect.
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.
As shown in the figure, the guide is attached to the
poppet (5) and a valve chamber D.C. (called the damping
chamber) is formed at the right of the guide piston. The
inlet of the valve leads to the chamber via a clearance
between the sliding portion of the guide and the seat (6),
minimizing valve vibration with the damping effect of the
chamber.
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 implement control valve.
As the oil pressure in the circuit increases, so does
the pressure in the damping chamber D.C. When the
pressure rises above the valve setting and overcomes
the spring force, the valve opens. Oil then flows out to
the transmission case through T port, preventing any
further rise in pressure. The valve closes again when
enough oil is released to drop pressure below the valve
setting.
(Reference)
• Relief valve setting pressure: 13.2 to 14.2 MPa
• Engine speed: Maximum
• Oil temperature: 40 to 50 °C
104 to 122 °F
(1) Plug
(2) Washer
(3) Shim
(4) Hydraulic Cylinder Body
(5) Poppet
(6) Seat
1-M3
HYDRAULIC SYSTEM
2
135 to 145 kgf/cm
1920 to 2064 psi
D.C.: Damping Chamber
P: Pump Port
C: Cylinder Port
T: Tank Port
W1013000
KiSC issued 09, 2007 A