SANY Crawler Hydraulic Excavator SY215CLC (CUMMINS QSB6.7 engine). Shop Manual

Structure and Function

SY215C

4-44

4.5

Hydraulic System, Part 2

4.5.1

Control valve

ZX225-1102009

Dr6

Pns

PnA2

Dr7

Dr3

XBp2

XAa1

(XAo)

BaR

BoR

Dr2

XAs

Psp

XBtr

(PTa)

XBtL

BbR

BkR

XAb1

XAa2

SWING PRIORITY

Ba(Head)

(Bo)

Btr

Atr

Dr1

(Ao)

PCV1

Dr3

ARM1

OPTION

XAb2

XBs

SWING

XAtr

BOOM2

(XBp1)

(BYPASS CUT 1)

XBa1

(XBo)

TRAVEL RIGHT

TRAVEL STRAIGHT

TRAVEL LEFT

BOOM1

BUCKET

ARM2

XBa2

XAk

XBb1

XAtL

AtL

PbL

Bk(Rod)

Bb(Rod)

PCk

XBk

Ab(Head)

Ak(Head)

Aa(Rod)

PaL

BtL

DR3

AoR

AkR

AbR

AaR

Structure and Function

SY215C

4-45

XAtr  : R. travel (reverse) pilot port
XBtr  : R. travel (forward) pilot port
(XAo)  : (Option pilot port)
(XBo)  : (Option pilot port)
XAk

: Bucket (DIG) pilot port

XBk

: Bucket (DUMP) pilot port

XAb1  : Boom 1 (UP) pilot port
XBb1  : Boom 2 (DOWN) pilot port
XAa2  : Arm 2 (OUT) pilot port
XBa2  : Arm 2 (IN) pilot port
XAtL  : L. travel (reverse) pilot port
XBtL  : L. travel (forward) pilot port
XAs

: Swing (left) pilot port

XBs

: Swing (right) pilot port

XAa1 : Arm 1 (OUT) pilot port
XBa1 : Arm 1 (IN) pilot port
Dr1

: Drain port

: Work equipment signal port

: Travel signal port

: Main relief valve boosting pressure

: Pilot pressure resource port

Pns

: Swing logic control valve pilot port

PCK : Bucket (DIG) stroke limit pilot port
PnA2 : Arm 2 logic control valve pilot port
Dr2

: Drain port

Dr3

: Drain port

Dr6

: Drain port

Dr7

: Drain port

Pal

: Lock valve pilot port (arm rod end)

PbL

: Lock valve pilot port (boom head end)

(XBp1) : Bypass cut spool pilot port (P1 side)
XBp2 : Bypass cut spool pilot port (P2 side)

XAb2 : Boom con

uence (UP) pilot port pres-

sure
Psp

: Swing priority pilot port

: Return port

: Oil feed port

Atr

: R. travel motor port (reverse)

Btr

: R. travel motor port (forward)

(Ao) :

Option

(Bo) :

Option

: Bucket cylinder head end port (DIG)

: Bucket cylinder rod end port (DUMP)

: Boom cylinder head end port (UP)

: Boom cylinder rod end port (DOWN)

AtL

: L. travel motor port (reverse)

BtL

: L. travel motor port (forward)

: Swing motor port (left swing)

: Swing motor port (right swing)

: Arm cylinder rod end port (OUT)

: Arm cylinder head end port (IN)

: Pump port (P1 side)

: Pump port (P2 side)

: Main relief valve

: Arm regeneration check valve

AbR  : Port relief valve
BbR  : Port relief valve
AkR  : Port relief valve
BkR  : Port relief valve
AoR  : Port relief valve
BoR  : Port relief valve
AaR  : Port relief valve
BaR  : Port relief valve

Structure and Function

SY215C

4-46

Item

Specifi cation

Model

KMX15RB

Standard

ow rate (equivalent to one pump)

220L/min

Maximum pressure

When main relief valve is normal

34.3MPa

When main relief valve is boosting

37.3MPa

Maximum pressure

When port relief valve is normal

39.2MPa

Working oil temperature

-20~90°C

Drained oil maximum pressure

0.3MPa

Specifi cations

Structure and Function

SY215C

4-47

4.5.2

Hydraulic circuit diagram (with bucket confl uence function)

XBtr

XAtr

Atr
Btr

Dr2
Dr6

XBs

XAs

Pns

Psp

XAb2

(XBo)

(XAo)

(Ao)
(Bo)

Dr3

XAa1

XBa1

(HEAD)

BaR

(XBp1)

XBp2

(P3)

(P0)

CP1

LCs

2.1

1.0

2.0

CCb

LCo

AoR

BoR

LCa

CCk

CCo

(P5)

HVa

AaR

LCAP2

LCAT2

AkR

BkR

LCk

HVb

AbR

BbR

LCb

CPG

(PTa)

CMR2

CMR1

0.7

XBtl

XAtl

Btl

Atl

Dr1

XBb1

XAb1

Bb
(ROD)

Ab
(HEAD)

PbL

PCk

XBk

XAk

(ROD)

Ak
(HEAD)

PnA2

Dr7

XBa2

XAa2

Aa
(ROD)

PaL

ZX225-1102010

TRAVEL R

SWING

SWING
PRIORITY

BOOM2

ARM1

BYPASS
CUT

OPTION

ARM2

BUCKET

BOOM1

TRAVEL L

TRAVEL
STRAIGHT

Structure and Function

SY215C

4-48

4.5.3 Operating principle

[Main circuit]

When all the spools are in neutral position,
working oil supplied from the hydraulic pump
(Front) flows in through pump port P1 and is
introduced into the main passage (1). It pass-
es the neutral bypass (2) (neutral M-shaped
spool mechanism) of the spools of straight
travel (308), L. travel (301), boom 1 (303),
bucket (304) and arm 2 (306), and

ows back

into the working oil tank via return port (R1).

Working oil supplied from the hydraulic pump
(Rear) flows in through pump port P2 and is
introduced into the main passage (3). It pass-
es the neutral bypass (2) (neutral M-shaped
spool mechanism) of the spools of R travel
(301), swing (305), boom confluence (boom
2: 307), option (309), arm 1 (302), and flows
back into the working oil tank via return port
(R1).

4.5.3.1 When spool is in neutral position

Structure and Function

SY215C

4-49

(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)

Structure and Function

SY215C

4-50

XAtr

Atr

Btr

XBtr

ZX225-1102012

Travel motor

4.5.3.2 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).

Structure and Function

SY215C

4-51

4.5.3.3 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

Structure and Function

SY215C

4-53

[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

Structure and Function

SY215C

4-56

4.5.3.4 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

Structure and Function

SY215C

4-58

511

XBb1

(a)

(b)

(303-317)

ZX225-1102017

[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

Structure and Function

SY215C

4-59

Pck

XAk

ZX225-1102018

4.5.3.5 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

SANY Crawler Hydraulic Excavator SY215CLC (CUMMINS QSB6.7 engine). Shop Manual - page 9