Fiat Kobelco EX355 Tier2, Technical Manual

Page: 117 / 968

EX355 T3-3-23
CONTROL VALVE
ARM ANTI-DRIFT VALVE (On Rod Side) /
BOOM ANTI-DRIFT VALVE
The anti-drift valves (on the arm cylinder rod side and
boom cylinder bottom side) are provided to reduce
cylinder drift.
NOTE: The construction of the arm anti-drift valve is
identical to the boom anti-drift valve.
When the control valve is in neutral: Holding Op-
eration
The oil pressure in the arm cylinder rod side (the boom
cylinder bottom side) is routed to port B6 (B3). Then,
the pressure in port B6 (B3) is routed to oil chamber
(a) through the spool. Thereby, the check valve is
pushed to block the oil flow from the cylinder to the
spool so that the cylinder drift is reduced.
When the control valve is operated: Deactivation
When the arm is rolled in (the boom is lowered), the
pressure oil from the arm (boom) spool opens the
check valve so that the pressure oil flows to the cyl-
inder via port B6 (B3).
When the arm is rolled out (the boom is raised), the
pilot oil pressure moves the spool so that the oil in oil
chamber (a) flows back to the hydraulic oil tank,
reducing pressure in oil chamber (a). Then, the re-
turn oil from the arm cylinder rod side (the boom
cylinder bottom side) passes port B6 (B3), opens the
check valve, and flows to the arm spool (the boom
spool).
To the Arm Cylinder.
To the Boom Cylinder.
Spool
Check Valve To the Arm Spool.
To the Boom Spool.
Arm Roll-Out Pilot Pressure
Boom Raise Pilot Pressure
To the Hydraulic Oil
Tank.
SM6079
SM6082
Spool
Pilot Pressure
Arm Spool
Boom Spool
Oil Chamber
(a)
Check Valve Port B6 (B3)
Deactivation (Arm Roll-Out, Boom Raise)
SM6081
Spool
Arm Spool
Boom Spool
Oil Chamber
(a)
Check Valve Port B6 (B3)
Deactivation (Arm Roll-In, Boom Lower)
Pilot Pressure
Spool
Arm Spool
Boom Spool
Oil Chamber
(a)
Check Valve Port B6 (B3)
Holding Operation
SM6080