SANY LATIN AMERICA
4-49
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
4.5.2.3 Arm
[Pilot circuit]
●
When the arm 2 spool (306) is switched,
the side path is closed and pressure at port
Px (work equipment signal port) rises.
[Main circuit]
●
When arm OUT is operated, pilot pres-
sure oil is supplied into port XAa1 and port
XAa2. When pilot pressure oil is applied at
the two sides of port XAa1 and port XAa2,
arm 1 spool and arm 2 spool are switched
to the left as shown in the illustration. As
a result, working oil from P2 is introduced
into neutral bypass (2) via main passage
(3). Neutral bypass is cut off by switching
arm 1 spool (302). Therefore, working oil
in the parallel passage pushes open the
cone valve (511) of the check valve, and
fl
ows into the arm 1 spool (302) via the U
passage. Then, it flows into the periphery
of arm 1 spool (302) and arm 2 spool (306)
and is supplied into the arm cylinder rod
end (R) via port As.
●
On the other hand, working oil from port
P1 is introduced into neutral bypass (2) via
main passage (1). Neutral bypass is cut off
by switching the arm 2 spool (306). There-
fore, working oil in the parallel passage
pushes open the logic cone valve (256-101)
of the arm 2 logic valve GP, and working oil
from neutral bypass pushes open the cone
valve (511) of the check valve and flows
into the arm 2 spool (306) via the U pas-
sage. Then, it merges with port As via the
inner passage of arm 2 spool (306) and is
supplied into the arm cylinder rod end (R).
●
Return oil from the arm cylinder head end
(H) via port Ba
fl
ows into the tank circuit of
arm 1 and arm 2, and returns to working oil
tank via tank port (R1).
(1) Arm OUT
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