SANY LATIN AMERICA
4-116
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
3. Fine control (When control lever is
returned)
●
When lever (5) starts to return, plunger
(1) is pushed up by the force of centering
spring (3) and pressure at port (P1).
●
Because of this, ori
fi
ce (f) is connected to
drain chamber (D), and the pressurized oil
at port (P1) is released.
●
If the pressure of port (P1) is lowered ex-
cessively, plunger (1) is pushed down by
metering spring (2).
●
Ori
fi
ce (f) is shut off from drain chamber (D),
and it is almost simultaneously intercon-
nected to pump pressure chamber (PP).
●
Pump pressure is supplied until the pres-
sure at port (P1) recovers to the level
equivalent to the lever position.
●
When the spool of the control valve re-
turns, the oil in drain chamber (D)
fl
ows in
from ori
fi
ce (f) in the valve on the side that
is not working. The oil passes through port
(P2) and enters chamber (B) to replenish
the chamber with pressurized oil.
4. At full stroke
●
Lever (5) pushes down piston (4), and re-
tainer (9) pushes down plunger (1).
●
Ori
fi
ce (f) is shut off from drain chamber (D),
and is interconnected to pump pressure
chamber (PP).
●
Therefore, the pilot pressure oil from
the self pressure reducing valve passes
through orifice (f) and flows to chamber
(A) from port (P1) to push the control valve
spool.
●
The oil returning from chamber (B) passes
from port (P2) through ori
fi
ce (f) and
fl
ows
to drain chamber (D).
ZX215-1002123
f’
P1
P2
B
A
1
P
f
D
T
PP
5
3
2
Pilot pump
Control valve
ZX215-1002124
f’
P1
P2
B
A
1
P
f
D
T
PP
5
4
9
Pilot pump
Control valve
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