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

Structure and Function

SY215C

4-60

XBk

ZX225-1102019

[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

Structure and Function

SY215C

4-61

XAs

XBs

(254-101)

Swing motor

ZX225-1102020

4.5.3.6 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

Structure and Function

SY215C

4-62

Psp

ZX225-1102021

[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

Structure and Function

SY215C

4-63

XAo

XBo

ZX225-1102022

4.5.3.7 Option

Option spool is used to control optional equipment.

[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) Option operation

Structure and Function

SY215C

4-64

PTa

ZX225-1102023

4.5.3.8 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.

Structure and Function

SY215C

4-65

252-541

252-511

252-321

ZX225-1102024

(a)

(b)

513

4.5.3.9 Lock valve function

●

The lock valve option set (252) is installed
between the arm cylinder rod end (R) and
arm 2 spool (302) and arm 2 spool (306).
It is used to reduce the internal leakage of
the spool due to cylinder pressure.

●

Likewise, lockout option set (252) is also
installed between boom cylinder head end
(H) and boom 2 spool (303) to reduce the
internal leakage of he spool due to cylinder
pressure.

(1) Spool in neutral position

●

The following shows when boom 1 spool
(303) is in neutral position. (The same is
with arm 2 spool (306))

●

When boom 1 spool (303) is in neutral po-
sition, spool (252-511) in the lock valve op-
tion set is pressed against the valve seat
of the valve sleeve (252-541) inside the
lock valve option set, as shown in the illus-
tration, via the spring force of spring (252-
321).

●

At this position, working oil at the boom
cylinder head end (H)

ows in via hole (a)

and flows out from hole (b) through the
periphery of the lock valve option set spool
(252-511), pressing the cone valve (513)
against the valve seat of the valve block
via hole (b). By this means, oil leakage is
reduced.

Structure and Function

SY215C

4-66

252-511

(b)

(a)

PbL

XBb

(RH)

513

ZX225-1102025

●

When boom DOWN is operated, pilot pres-
sure oil is supplied to port PbL and port
XBb1. Spool (252-511) inside the lock
valve option set moves to the top by via pi-
lot pressure oil. Through the movement of
spool (252-511) inside the lock valve option
set, hole (a) is cutoff and working oil from
boom cylinder head end (H) does not

into spring chamber (RH). In addition, oil
in the spring chamber (RH)

ows into drain

circuit via hole (b). In this way, the cone
valve (513) is pushed up by the pressure
at boom cylinder head end (H) and the
function of the lock valve option set (252)
is released.

●

When boom DOWN is operated, pilot pres-
sure oil is supplied to port XAb1. The cone
valve (513) is pushed ope by the oil from

boom 1 spool (303) and working oil flows
into port Ab.

(2) Boom UP operation

(2) Boom DOWN operation

Structure and Function

SY215C

4-67

541

621

611

512

(a)

103

614

ZX225-1102026

4.5.3.10 Main relief valve function

The main relief valve is installed on the valve
block A (101). Its function is described below:

●

Working oil flows into chamber (a) from
passage (P) via the hole of valve seat (541)
and hole on valve rod (512). Valve rod (512)
is pressed against valve seat (541), form-
ing a tight seal.

●

When pressure in passage (P) exceeds
the elastic force of spring (621), cone valve
(611) is pushed open. Therefore, working
oil

ows through the hole on valve sleeve

(103) via the periphery of cone valve (611)

and enters low-pressure path (R).

●

Opening of cone valve (611) causes pres-
sure in chamber (a) to drop and valve rod
(512) is open. In this way, working oil in
passage (P) flows into low-pressure path
(R) directly.

●

When pressure oil high than 3MPa is sup-
plied to port Pz, this pressure oil pushes
plunger (614) to the left. The set load of
spring (621) is changed and pressure of
the main relief valve rises.

Structure and Function

SY215C

4-68

ZX225-1102027

301

511

541

ZX225-1102028

301

511

541

4.5.3.11 Port relief valve function

The port relief valve is installed between the
tank port and low-pressure path. In addition
to the function as relief valve, it has also the
function of anti-cavitation oil complement
check valve. Its function is described below:

(1) Relief valve function

●

Working oil

ows into chamber (B) via the

hole (A) on plunger (301). Valve rod (511)
is pressed against valve seat (541), and
valve seat (541) is pressed onto the valve
seat of the valve block, forming a tight seal.

Structure and Function

SY215C

4-69

ZX225-1102029

611

621

ZX225-1102030

611

621

●

When pressure in passage (P) exceeds
the elastic force of spring (621), cone valve
(611) is pushed open. Therefore, working
oil

ows through hole (C) via the periphery

of cone valve (611) and enters low-pres-
sure path (R).

Structure and Function

SY215C

4-70

ZX225-1102031

511

611

ZX225-1102032

511

611

●

Opening of cone valve (611) causes pres-
sure in chamber (B) to drop and valve rod
(511) is open. In this way, working oil in
passage (P) flows into low-pressure path
(R) directly.

Structure and Function

SY215C

4-71

541

ZX225-1102033

541

ZX225-1102034

(2) Anti-cavitation oil complement check
valve

●

When negative pressure is formed in path
(P), working oil is supplied from path (R).
When pressure in path (R) gets higher
than pressure in path (P), valve seat (541)
moves to the right direction. Therefore,
working oil is supplied from path (R) to
path (P) via the periphery of valve seat
(541) in order to prevent cavitation.

Structure and Function

SY215C

4-72

273×12

273×10

153

561

252

Dr7

252

PnA2

(Po)

XAtl

XBbl

XAk

XBo

XBa1

XBa2

AkR

AbR

AaR

(XBp1)

PCV1

AoR

XAb2

XBs

XAtr

978×2

977

Dr8 PnS

273×10

273×12

XBk

PCk

XAa2

XBp2

210

Dr6

Pns

274×4

CCo

CCk

(P5)

PnA2

XBa2

(XBp1)

Dr3

TRAVEL R

TRAVEL
STRAIGHT

TRAVEL L

BOOM1

BUCKET

ARM2

SWING

BOOM2

OPTION

ARM1

(BYPASS CUT1)

BYPASS CUT2

ZX225-1102035

Dr7

602

AaR

View O-O

153

561

(P5)

Viw P-P

4.5.4 Section view

Structure and Function

SY215C

4-73

101 159 541 542

543

166

550

(PTa)

XBtL

XAbL

PCk

XBk

ZX225-1102036

XAa2

551

514 521 561 551

561 521

514

CCk

CCo

View A-A

XBa2

XBb1

XAtL

XAk

151 168 151 168 151 168

156

2-156

View N-N

Section A-A, N-N

Structure and Function

SY215C

4-74

561

153

975

102

975

XAtr

XBs

XAb2

(XBo)

975

XBa1

(XBp1)

ZX225-1102037

975

165

975

(P3)

Psp

XAs

XBtr

XBp2

XAb1

(XAo)

Section B-B

Structure and Function

SY215C

4-75

201

336
332
335
321

320

332

261

163

314

165

163

511

521

551

561

165
163

163

XAtr

Atr

CP1

Btr

264

204

XBtr

(PTa)

154

ZX225-1102038

164

204

264

159

512

522

553

CMR2

CMR1

562

553

522

512

601

308

261

332

335

323

332

336

201

164

154

TRAVEL
RIGHT

TRAVEL
STRAIGHT

Viw C-C

Section C-C (Travel right, travel straight)

SANY Crawler Hydraulic Excavator SY215CLC (CUMMINS QSB6.7 engine). Shop Manual - page 10