SANY LATIN AMERICA
4-57
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
4.5.2.5 Bucket
[Pilot circuit]
●
When the bucket spool (304) 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 at
port XBp2.
[Main circuit]
●
When bucket DIG is operated, pilot pres-
sure oil is supplied into port XAk and buck-
et spool (304) moves to the right. Working
oil from port P1 is introduced into neutral
bypass (2) via main passage (1). Neutral
bypass is cut off by switching bucket spool
(304). Therefore, working oil in the paral-
lel passage pushes open the cone valve
(511) of the check valve, and flows into
the bucket spool (304) via the U passage.
Then, it
fl
ows into the periphery of bucket
spool (304) and is supplied into the bucket
cylinder head end (H) via port Ak.
●
On the other hand, return oil from the buck-
et cylinder rod end (R)
fl
ows in via port Bk.
Then, it flows to oil tank port (R1) via the
spool periphery and returns to working oil
tank.
●
When boom UP and bucket DIG are oper-
ated simultaneously, pilot pressure oil is
supplied to port Pck. Therefore, the stroke
of bucket spool is not limited at stroke end,
but on any position halfway. As a result,
bucket cylinder passage is throttled and
working oil flows into boom 1 spool (303)
via bucket spool (304). In this way, boom
UP operation takes precedence.
(1) Bucket DIG
Ak
Bk
Pck
XAk
ZX225-1102018
H
H
R
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