Content .. 7 8 9 10 ..

SANY Crawler Hydraulic Excavator SY195C9, SY205C9, SY215C9, SY225C9. Service Manual - page 9

Structure and Function

(PTa)

XBtL

XAbL

PCk

X8k

XAa2

CCk

CCo

XBa2

XBb1

XAtL

(1)

(2)

(3)

XAk

XAtr

XBs

XAb2

(XBo)

XBa1

(XBp1)

ZX225-1102011

(P3)

Psp

XAs

XBtr

XBp2

XAa1

(XAo)

4-48

Structure and Function

4.5.2.2 Travel

[Pilot circuit]

●

When the left or right travel spool is
switched, the side bypass circuit is closed
and pressure at port Py (travel signal port)
rises.

[Main circuit]

●

When pressure at pilot port XBtL for left
travel spool (301) rises, neutral bypass (2)
at boom 1 side is closed, and working oil
supplied from the hydraulic pump (front) is
introduced into the left travel motor via port
Btl.

●

Likewise, when pressure at port XBtr for
the right travel spool (301) rises, neutral
bypass (2) at arm 1 side is closed, and
working oil supplied from the hydraulic
pump (rear) is introduced into the right
travel motor via port Btr.

●

On the other hand, return oil from the left
and right travel motor passes the left (right)
travel spool via port Atl (Atr), and returns to
working oil tank via return port (R1).

●

The principle is the same when travel on
the opposite side is operated (when pres-
sure at pilot port XAtr and XAtl rises).

XAtr

Atr

Btr

XBtr

ZX225-1102012

Travel motor

4-49

Structure and Function

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

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

ows into the tank circuit of

arm 1 and arm 2, and returns to working oil
tank via tank port (R1).

(1) Arm OUT

4-50

Structure and Function

ZX225-1102013

511

XAa2

XAa1

256-101

4-51

Structure and Function

[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

own into the parallel passage

pushes open the cone valve (511) of the
check valve and

ows into the arm 1 spool

(302) via the U passage. Then, it

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

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)

ows into the spool via the hole (a) on

the periphery of arm 1 spool (302). Then,
it

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

4-52

Structure and Function

●

Light load

XBa1

XBa2

(a)

(b)

ZX225-1102014

(302-317)

Arm weight

4-53

Structure and Function

●

When pressure at arm cylinder head end (H) rises

XBa1

XBa2

(c)

(257-211)

(a)

ZX225-1102015

(302-317)

4-54

Structure and Function

4.5.2.4 Boom

[Pilot circuit]

●

When the boom 1 spool (303) is switched,
the side path is closed and pressure at port
Px (work equipment signal port) rises.

[Main circuit]

●

When boom UP is operated, pilot pressure
oil is supplied into port XAb1 and boom 1
spool (303) moves to the left. Working oil
from port P1 is introduced into neutral by-
pass (2) via main passage (1). Neutral by-
pass is cut off by switching boom 1 spool
(303). Therefore, working oil in the parallel
passage pushes open the cone valve (511)
of the check valve, and

ows into the boom

1 spool (303) via the U passage. Then, it
flows into the periphery of boom 1 spool
(303) and is supplied into the boom cylin-
der head end (H) via port Ab.

●

At the same time, pilot pressure oil is also
supplied to port XAb2 and boom 2 spool
(307) moves to the right. Working oil from
port P2 is introduced into neutral bypass.
Neutral bypass is cut off by switching the
boom 2 spool (307). Therefore, working
oil in the parallel passage

ows into boom

2 spool (307) via the U passage. Then, it
pushes open the cone valve (511) of the
check valve and merges with port Ab and
is supplied into the boom cylinder head
end (H). This is called the boom conflu-
ence function.

●

On the other hand, return oil from the
boom cylinder rod end (H) via port Bb

ows

into the periphery of boom 1 spool (303)
and returns to the working oil tank via tank
port (R1).

(1) Boom UP

4-55

Structure and Function

511

XAb1

ZX225-1102016

XAb2

511

4-56

Structure and Function

[Pilot circuit]

●

When the boom 1 spool (303) 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 PbL and the release signal of lock
valve option set (252) is sent out.

[Main circuit]

●

When boom DOWN is operated, pilot pres-
sure oil is supplied to port XBb1. Boom 1
spool (303) moves to the right. As a result,
working oil from P1 is introduced into the
neutral bypass (2) via main passage (1).
Neutral bypass is cut off by switching boom
1 spool (303). Therefore, working oil

own

into the parallel passage pushes open the
cone valve (511) of the check valve and

ows into the boom 1 spool (303) via the U

passage. Then, it flows into the periphery
of boom 1 spool (303) and is supplied into
the boom cylinder rod end (R) via port Bb.

●

On the other hand, return oil from the
boom cylinder head end (H) passes the
hole (a) and the periphery of boom 1 spool
(303).

●

Return oil pressure rises due to the self
weight of the boom. Cone valve (303-317)
in the spool is pushed to the right. Return
oil

ows to the outside of spool. The pres-

sure oil is supplied into the boom cylinder
rod end (R) as the working oil for boom
DOWN operation. This is called the boom
regeneration function. Part of the oil that

ows into the inside passage of the spool

via hole (a) returns to the working oil tank
via hole (b).

(2) Boom DOWN

511

XBb1

(a)

(b)

(303-317)

ZX225-1102017

4-57

Structure and Function

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

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)

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

Pck

XAk

ZX225-1102018

4-58

Structure and Function

[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 DUMP is operated, pilot
pressure oil is supplied into port XBk and
bucket spool (304) moves to the left. Work-
ing oil from port P1 is introduced into neu-
tral bypass (2) via main passage (1). Neu-

tral bypass is cut off by switching bucket
spool (304). Therefore, working oil in the
parallel passage pushes open the cone
valve (511) of the check valve, and flows
into the bucket spool (304) via the U pas-
sage. Then, it flows into the periphery of
bucket spool (304) and is supplied into the
bucket cylinder rod end (R) via port Bk.

●

On the other hand, return oil from the buck-
et cylinder head end (H) flows in via port
Ak. Then, it flows to oil tank port (R1) via
the spool periphery and returns to working
oil tank.

●

When bucket DIG is operated, pilot pres-
sure oil is supplied into port XBp2 and the
neutral bypass cutoff valve spool (310) is
switched. Working oil from port P2 is in-
troduced into neutral bypass (2) via main
passage (3). Neutral bypass is cut off by

switching neutral bypass valve spool (310).
Therefore, working oil pushes open the
check valve, and interconnects with the U
passage via the inside path, and converg-
es with bucket spool (304).

(2) Bucket DUMP

(3) Bucket confl uence

XBk

ZX225-1102019

4-59

Structure and Function

4.5.2.6 Swing

[Pilot circuit]

●

When the swing spool (305) is switched,
the side path is closed and pressure at port
Px (work equipment signal port) rises.

[Main circuit]

●

When swing is operated, pilot pressure
oil is supplied into port XAs (or XBs) and
swing spool (305) is switched. Working
oil from port P2 is introduced into neutral
bypass (2) via main passage (3). Neutral
bypass is cut off by switching swing spool

(305). Therefore, working oil in the parallel
passage pushes open the logic cone valve
(2540-101) of the swing logic valve GP,
and

ows into the swing spool (305) via the

U passage. Then, it

ows into the periph-

ery of swing spool (305) and is supplied
into the swing motor via port As (or Bs).

●

On the other hand, return oil from the
swing motor flows in via port Bs (or port
As). Then, it flows into tank port (R1) via
the spool periphery and returns to the
working oil tank.

(1) Swing operation

XAs

XBs

(254-101)

ZX225-1102020

Swing motor

Structure and Function

[Pilot circuit]

●

Pilot pressure oil is supplied to port Psp
and swing priority spool (311) is switch.

[Main circuit]

●

Switch swing priority spool (311). The
opening area of the swing priority reduces.
As a result, working oil from arm 1 spool
(302) flows into swing spool (305) and
swing operation takes precedence.

(2) Swing priority function

Psp

ZX225-1102021

Structure and Function

4.5.2.7 Option

Option spool is used to control optional work equipment attachment.

[Pilot circuit]

●

When the option spool (309) is switched,
the side path is closed and pressure at port
Px (work equipment signal port) rises.

[Main circuit]

●

When option is operated, pilot pressure
oil is supplied into port XAo (or XBo) and
option spool (309) is switched. Working
oil from port P2 is introduced into neutral
bypass (2) via main passage (3). Neutral
bypass is cut off by switching option spool

(309). Therefore, working oil in the parallel
passage pushes open the cone valve (511)
of the check valve, and

ows into the op-

tion spool (309) via the U passage. Then,
it flows into the periphery of option spool
(309) and is supplied into the optional
equipment via port Ao (or Bo).

●

On the other hand, return oil from the op-
tional equipment flows in via port Bo (or
port Ao). Then, it

ows into tank port (R1)

via the spool periphery and returns to the
working oil tank.

(2) Option confl uence

●

To achieve option confluence, pilot pres-
sure oil is supplied into port XBp1 and the
bypass cutoff valve spool (310) is switched.
Working oil from port P1 is introduced into
neutral bypass (2) via main passage (1).

Neutral bypass is cut off by switching by-
pass valve spool (310). Therefore, work-
ing oil pushes open the cone valve (514)
of check valve, and converges with option
spool (309) via the inside path and the U
passage.

(1) Operation

XAo

XBo

ZX225-1102022

4-62

Structure and Function

4.5.2.8 Travel straight

When travel spool (301) and other spool are
operated simultaneously.

The following case shows when travel spool
(301) and swing spool (305) are operated si-
multaneously. (When pilot pressure oil is sup-
plied to port XAtL, port XAtr and port Xas)

[Pilot circuit]

●

The side path of right/left travel spool (301)
and the side path of the swing spool (305)
at the down

ow side are closed.

●

Pilot oil from port PG is supplied to port
PTa and straight travel spool (308) is
switched.

[Main circuit]

●

When straight travel spool (308) is
switched, the right/left travel spool (301)
are interconnected with port P2. The paral-
lel passage of swing/boom 2/option/arm
1 circuit and boom 1/bucket/arm 2 circuit
are interconnected with port P1. Therefore,
working oil supplied from port P2

ows into

port Atl and port Atr, and is supplied to the
two travel motors equally.

●

On the other hand, working oil from port P1
is supplied to the swing motor via port As.

●

When oil pressure at port P2 is lower than
that at port P1, part of the working oil form
port P1 is supplied to port P2. In this way,
sharp decrease of travel speed is averted.

PTa

ZX225-1102023

Content .. 7 8 9 10 ..