SANY Crawler Hydraulic Excavator SY195C9, SY205C9, SY215C9, SY225C9. Service Manual - page 8

4-31

Structure and Function

Structure

●

Cylinder block (7) is supported to shaft (1)
by spline (17).

●

Shaft (1) is supported by front and rear
bearings (18).

●

Tip of plunger (6) is shaped as a concave
ball and slipper (5) is caulked to it to form
one unit.

●

Plunger (6) and slipper (5) constitute the
spherical bearing.

●

Swash plate (4) has flat surface (A), and
slipper (5) is always pressed against this
surface while sliding in a circular move-
ment.

●

Swash plate (4) conducts high pressure oil
to cylinder surface (B), and forms a static
pressure bearing when it slides.

●

Plunger (6) carries out relative movement
in the axial direction inside each cylinder
chamber of cylinder block (7).

●

Cylinder block (7) seals the pressurized oil
to thrust plate (8) and carries out relative
rotation.

●

This surface is designed so that the oil
pressure balance is maintained at a suit-
able level.

●

The oil inside the respective cylinder cham-
bers of cylinder block (7) is sucked in and
discharged through thrust plate (8).

4-32

Structure and Function

Operation of pump

●

Cylinder block (7) rotates together with
shaft (1), and slipper (5) slides on 

fl

 at sur-

face (A).

●

When this happens, swash plate (4) moves
along cylindrical surface (B), so angle (a)
between central line (X) of swash plate (4)
and the axial direction of cylinder block (7)
changes.

●

(a) is named the swash plate angle.

●

With central line (X) of swash plate (4) at
a swash plate angle (a) in relation to the
axial direction of cylinder block (7), 

fl

 at sur-

face (A) acts as a cam in relation to slipper
(5).

●

In this way, plunger (6) slides on the in-
side of cylinder block (7), so a difference
between volumes (E) and (F) is created
inside cylinder block (7).

●

A single plunger sucks and discharges the
oil by the amount (F) – (E).

●

As cylinder block (7) rotates and the vol-
ume of chamber (E) becomes smaller, the
pressurized oil is discharged.

●

On the other hand, the volume of chamber
(F) grows larger and, in this process, the
oil is sucked.

●

As central line (X) of swash plate (4) over-
laps the axial direction of cylinder block (7)
(swash plate angle (a) = 0), the difference
between volumes (E) and (F) inside cylin-
der block (7)becomes 0.

●

Suction and discharging of pressurized
oil is not carried out in this state. Namely
pumping action is not performed. (In real-
ity, however, the swash plate angle is not
set to 0)

ZX215-1002021

1

4

5

7

B

X

a

A

ZX215-1002022

4

5

6

7

E

X

a

F

A

ZX215-1002023

7

4

E

F

4-33

Structure and Function

Control of delivery

●

If swash plate angle (a) becomes larger,
the difference between volumes (E) and
(F) becomes larger and pump delivery (Q)
increases.

●

Piston (13) is used for changing swash
plate angle (a).

●

Piston (13) carries out linear alternating
motion under the control of the  adjustor.

●

This linear motion is transmitted to swash
plate (4) via drive pin (16). The sliding of
the swash plate changes the swash plate
angle and changes the discharge amount
of the main pump.

ZX215-1002024

13

4

a

16

F

E

4-34

Structure and Function

4.4.4  

Pilot pump

ZX215-1002025

710

435

433

700

434

355

354

310

351

732

311

312

309

307

308

434

850

466

725

435

361

353

307: Valve stem
308: Valve base
309: Retainer
310: Spring
311: Adjusting screw
312: Nut
351: Body
353: Gear shaft
354: Gear shaft
355: Filter element

361: Body
433: Screw
434: Screw
435: screw
466: Plug
700: Washer
710: O-ring
725: O-ring
732: O-ring
850: Washer

Function

●

The engine actuates the main pump and
the drive shaft of the pilot pump through
the transmission case, and drives the pilot
pump through gear engagement.

NOTE: For the location of the pilot pump on the machine, see “Hydraulic equipment layout” on 
page 4-24.

4-35

Structure and Function

(KR3G-0E11-AV)

4.4.5  

Regulator 

NOTE: Both the front pump and the rear pump are equipped with a regulator. For the location of 
the hydraulic pump, see “Hydraulic equipment layout” on page 4-24.

G-OE11-V

(KDRDE5K)

P

SV

P

SV

a

a

KDRDE5C-1

079

325

496

408

755

466

407

643

651 652 733

631

731

624

627

B

A

A-A

A

646

897

924

801

402

656

614

755

708

611

733

724

887

SKY5P
- 17 - S

ZX225-1102002

418

415

496

601

543

756

545

541

N

‡

m

402, 407

408
415
418
466
496
614
801

M6

M8
M5

G1/4

G1/4
M10

NPTF1/16

12

29
6.9
16

8.8

36

29

Type

s/n

Name plate and s/n

Tightening tor

T

ue

Hydraulic schematic diagram

Direction B

Part No.

Thread size

Tightening tor

T

ue

4-36

Structure and Function

Category

Part No.

Part name

Q’ty

Remark

C

924

Hexagon socket head locating screw

1

/

897

Pin

1

/

887

Pin

1

D

801

Hexagon nut

1

JIS  B  1181  N-M10

D

756

O-ring

2

D

755

O-ring

2

D

733

O-ring

2

D

731

O-ring

1

D

724

O-ring

5

D

708

O-ring

1

/

656

Cover plate

1

/

652

Spool valve

1

/

651

Sleeve

1

/

646

Guide spring

1

/

643

Pilot plunger

1

/

631

Pf pilot sleeve

1

/

627

Adjusting roller

1

/

624

Spring seat

1

/

614

Plug

1

/

611

Feedback lever

1

/

601

Casing

1

/

545

Ball

2

/

543

Stopper

2

/

541

Valve seat

2

C

496

Embedded plug

9

C

466

VIP plug

1

D

418

Hex socket head bolt

2

JIS  B  1176  M5-12

D

415

Hex socket head bolt

6

JIS  B  1176  M8-50

D

408

Hex socket head bolt

1

JIS  B  1176  M6-40

D

407

Hex socket head bolt

4

JIS  B  1176  M6-30

D

402

Hex socket head bolt

4

JIS  B  1176  M6-16

/

325

Valve body

1

B

079

Sol proportional reducing valve

1

B

—

Regulator assembly

1

B: 

Assembly obtainable at the dealers (individual parts not purchasable)

/: 

Individual components included in assemblies of category B

C: 

Parts obtainable at the dealers

D: 

Parts obtainable on the market

4-37

Structure and Function

●

The regulator controls the pump discharge
amount according to the command signal
pressure, keeping the driving power of the
pump lower than the engine output.

●

Pumps 1 and 2 are both equipped with a
regulator. Key components of the regulator
include a solenoid proportional pressure
reducing valve (1), a positive 

fl

 ow regulator

(2), a servo reversing valve (3) and a servo
piston (4). The regulator opens and shuts
the oil circuit of the servo piston (3) and
changes the tilting angle of the hydraulic
tank according to various command signal
pressure so as to control the pump dis-
charge amount.

4.4.5.1  Control mechanism makeup

Current control

●

The inclination (output delivery amount)
of the pump can be controlled freely by
changing of the command current I flow-
ing into the solenoid proportional pressure
reducing valve. This regulator applies posi-
tive 

fl

 ow control (positive control), through

which output delivery amount Q changes
according to the increase of command cur-
rent. Necessary current for corresponding
operation can be input through this control
mechanism. The pump only delivers nec-
essary oil amount and wastes no useless
power.

P

SV

a

1

2

3

4

ZX225-1102003

Function

4-38

Structure and Function

4.4.5.2  Adjustment of the regulator

●

It is possible to adjust the maximum and
minimum 

fl

 ow by the adjusting screws (953,

954) in the pump block side. Flow control
features can be adjusted with the hexagon
socket head locating screw (924) on the
regulator.

ZX215-1002028

953

806

532

548 531

808

954

P

SV

KDRDE5C-1

924

SKY5P
- 17 - S

ZX225-1102004

531: Inclination pin

532: Servo piston

548: Feedback pin

806: Retaining nut

808: Retaining nut

953: Adjusting screw

954: Adjusting screw

4-39

Structure and Function

Maximum flow adjustment (pump block 
side)

●

Loosen the hexagon nut (808), and tighten
(or loosen) hexagon socket head locating
screw (954). No control features except the
maximum 

fl

 ow changes.

Minimum flow adjustment (pump block 
side)

●

Loosen the hexagon nut (806), and tighten
(or loosen) the hexagon socket head locat-
ing screw (953). Though this action is the
same as the adjustment of maximum 

fl

 ow

and all the other control features do not
change, power required under maximum
output pressure (overflow) is likely to in-
crease if over-tightened. Be careful in this
case.

ZX215-1002033

Output flow Q

Command current I

ZX215-1002034

Output flow Q

Command current I

4-40

Structure and Function

Flow control feature adjustment

●

After hexagon nut (810) is loosened, tight-
en (or loosen) the hexagon socket head lo-
cating screw (924) to carry out adjustment.
When the hexagon socket head locating
screw (924) is being tightened, the control
diagram (as shown) will move to the right.

ZX215-1002037

Output flow Q

Command current I

ZX215-1002030

Output flow Q

Command current I

4.4.5.3 Operation

Flow control

●

The output flow of the pump can be con-
trolled by the command current I, as
shown.

4-41

Structure and Function

Action of increasing fl ow rate

●

When command current I increases, the
solenoid proportional pressure reducing
valve secondary pressure P2 will increase,
and the spool valve (652) will move the
right with the help of the guide piston (643).
When a relative balance between the right-
ward hydraulic force and the spring force
of guide spring (646) is achieved, spool
valve (652) stops moving.

●

As spool valve (652) moves to the right,
because port cl and tank port are intercon-
nected, pressure of the large diameter
portion of the servo piston is released and
servo piston (532) moves to the left via the
output pressure P1 in the shall diameter
portion. The inclination becomes larger.

●

Since feedback lever (611) is integrated
with the servo piston and valve sleeve
(651), if servo piston (632) moves to the
left, feedback lever swings with point A as
the pivot. In this way, valve sleeve moves
to the right.

●

Through this movement, the opening por-
tion between the spool and the valve block
is closed slowly. The servo piston stops
moving when the opening portion is com-
pletely closed.

P1

P1

A

808
954

643

079

652

651

627 646

801

924
611

532

806
953

ZX225-1102005

Tilt angle large

P

SV

a

ZX225-1102006

4-42

Structure and Function

Action of reducing fl ow rate

●

When command current I decreases, the
solenoid proportional pressure reducing
valve secondary pressure P2 will decrease,
and guide piston (643) will move to the left.
However, as spool valve (652) moves, out-
put pressure P1 is introduced into the large
diameter chamber of the servo piston via
the port cl. On the other hand, output pres-
sure P1 is introduced into the small diam-
eter chamber of the servo piston and servo
piston moves to the right via are difference.
The inclination becomes smaller.

●

As servo piston (532) moves to the right,
the feedback lever swings with point A as
the pivot and the valve sleeve moves to the
left. Through this movement, the opening
portion between the spool and the valve
block is slowly closed. The servo piston
stops moving when the opening portion is
completely closed.

P1

P1

A

808
954

643

079

652

651

627 646

801
924
611

532

806
953

ZX225-1102007

Tilt angle small

P

SV

a

ZX225-1102008

Type of regulator

KR3G-0E11-AV

Rotating speed (min

-1

)

2050

Adjustment of max. 

fl

 ow

Adjusting screw (954) screw-in (rotation)

+1/4

Flow rate change (L/min)

-5.9

Adjustment of min. 

fl

 ow

Adjusting screw (953) screw-in (rotation)

+1/4

Flow rate change (L/min)

+4.7

Adjustment value of the regulator

4-43

Structure and Function

ZX225-1102009

Dr6

Pns

PnA2

Dr7

Dr3

XBp2

XAa1

(XAo)

BaR

BoR

Dr2

XAs

Psp

XBtr

XBtr

(PTa)

XBtL

BbR

BkR

XAb1

XAa2

P2

R1

R1

P1

SWING PRIORITY

Ba(Head)

(Bo)

Bs

Btr

Atr

Dr1

As

(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

Pz

AtL

PbL

Bk(Rod)

R2

Bb(Rod)

PCk

XBk

Ab(Head)

Ak(Head)

Aa(Rod)

PaL

BtL

Py

MR

DR3

AoR

AkR

AbR

AaR

PG

PX

4.5  

Hydraulic System, Part 2

4.5.1  

Control valve

NOTE: For the location of the control valve on the machine, see “Hydraulic equipment layout” on 
page 4-24.

4-44

Structure and Function

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
XBa:  Arm 1 (IN) pilot port
Dr1:   Drain port
Px:    Work equipment signal port
Py:    Travel signal port
Pz:    Main relief valve boosting pressure
PG:   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

fl

 uence (UP) pilot pressure

Psp:   Swing priority pilot port
R1:   Return port
R2:    Oil feed port
Atr:    R. travel motor port (reverse)
Btr:    R. travel motor port (forward)
(Ao): Option
(Bo): Option
Ak:    Bucket cylinder head end port (DIG)
Bk:    Bucket cylinder rod end port (DUMP)
Ab:    Boom cylinder head end port (UP)
Bb:    Boom cylinder rod end port (DOWN)
AtL:   L. travel motor port (reverse)
BtL:   L. travel motor port (forward)
As:    Swing motor port (left swing)
Bs:    Swing motor port (right swing)
Aa:    Arm cylinder rod end port (OUT)
Ba:    Arm cylinder head end port (IN)
P1:    Pump port (P1 side)
P2:    Pump port (P2 side)
MR:   Main relief valve
AR:    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

NOTE: For more technical information about the control valve, see “Control valve” on page 3-6.

4-45

Structure and Function

 Hydraulic circuit diagram (with bucket confl uence function)

XBtr

XAtr

Atr
Btr

Dr2
Dr6

XBs

XAs

As

Bs

Pns

Psp

XAb2

(XBo)

(XAo)

(Ao)
(Bo)

Dr3

AR

XAa1

XBa1

(HEAD)

Ba

BaR

(XBp1)

XBp2

P2

R1

(P3)

(P0)

CP1

LCs

4-

ĭ

2.1

2-

ĭ

1.0

2-

ĭ

2.0

CCb

LCo

AoR

BoR

LCa

CCk

CCo

(P5)

HVa

AaR

LCAP2

LCAT2

AkR

BkR

LCk

HVb

AbR

BbR

LCb

C2

CPG

(PTa)

P1

PG

MR

CMR2

CMR1

d1

ĭ

0.7

d2

ĭ

0.7

d3

ĭ

0.7

Pz

Px

Py

XBtl

XAtl

Btl

Atl

Dr1

XBb1

XAb1

Bb
(ROD)

Ab
(HEAD)

PbL

PCk

XBk

XAk

(ROD)

Bk

Ak
(HEAD)

PnA2

Dr7

XBa2

XAa2

Aa
(ROD)

PaL

R2

ZX225-1102010

TRAVEL R

SWING

SWING
PRIORITY

BOOM2

ARM1

BYPASS
CUT

OPTION

ARM2

BUCKET

BOOM1

TRAVEL L

TRAVEL
STRAIGHT

4-46

Structure and Function

4.5.2 Operating principle

[Main circuit]

4.5.2.1  When spool is in neutral position

●

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 pas-
sage (1). It passes 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 

fl

 ows back into the working oil

tank via return port (R1).

●

Working oil supplied from the hydraulic
pump (Rear) 

fl

 ows in through pump port P2

and is introduced into the main passage
(3). It passes the neutral bypass (2) (neutral
M-shaped spool mechanism) of the spools
of  R travel (301), swing (305), boom con-

fl

 uence (boom 2: 307), option (309), arm 1

(302), and flows back into the working oil
tank via return port (R1).