SANY LATIN AMERICA
4-51
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
[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.
At the same time, pressure oil is supplied
to port PaL and the release signal of lock
valve option set (252) is sent out.
[Main circuit]
●
When arm In is operated, pilot pressure oil
is supplied to port XBa1 and port XBa2.
When pilot pressure oil is applied at the
two sides of port XBa1 and port XBa2,
arm 1 spool and arm 2 spool is switched to
the left. As a result, working oil from P2 is
introduced into the neutral bypass (2) via
main passage (3). Neutral bypass is cut off
by switching arm 1 spool (302). Therefore,
working oil
fl
own into 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
fl
ows into
the periphery of arm 1 spool (302) and is
supplied into the arm cylinder head end (H)
via port Ba.
●
On the one 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 Ba via the
inner passage of arm 2 spool (306) and is
supplied into the arm cylinder head end (H).
●
On the other hand, pressure of the return
oil from the arm cylinder rod end (R) rises
under the weight the arm, and the return
oil returns to port Aa. Working oil that re-
turns to port Aa
fl
ows into the inside of the
valve spool via the holes on the periph-
ery of the arm 1 spool (302), and pushes
open the cone valve (302-317) in the spool
only under light load. It merges with port
Ba through the holes on the spool. This is
called the regeneration function of the arm.
●
If the pressure at the arm cylinder head
end and in the U passage rises, arm re-
generation check valve spool (257-211)
switches to the left. And, at the same time,
the back pressure of the cone valve (302-
317) in the spool is closed. Therefore,
arm regeneration function is released and
return oil from the arm cylinder rod end
(R)
fl
ows into the spool via the hole (a) on
the periphery of arm 1 spool (302). Then,
it
fl
ows into arm regeneration check valve
set (257) via hole (c) on the periphery of
arm 1 spool (302), and returns to the work-
ing oil tank via tank port R1.
(2) Arm IN
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