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SANY Crawler Hydraulic Excavator (SY195C9, SY205C9, SY215C9, SY225C9). Shop Manual (2013) - page 8

Structure and Function

256-101

511

XAa2

XAa1

511

ZX225-1102013

4-50

Structure and Function

(2) Arm IN

[Pilot circuit]

from neutral bypass pushes open the cone

valve (511) of the check valve and flows

Ɣ When the arm 2 spool (306) is switched,

into the arm 2 spool (306) via the U pas-

the side path is closed and pressure at

sage. Then, it merges with port Ba via the

port Px (work equipment signal port) rises.

inner passage of arm 2 spool (306) and is

At the same time, pressure oil is supplied

supplied into the arm cylinder head end (H).

to port PaL and the release signal of lock

valve option set (252) is sent out.

On the other hand, pressure of the return

oil from the arm cylinder rod end (R) rises

[Main circuit]

under the weight the arm, and the return

oil returns to port Aa. Working oil that re-

When arm In is operated, pilot pressure oil

turns to port Aa flows into the inside of the

is supplied to port XBa1 and port XBa2.

valve spool via the holes on the periph-

When pilot pressure oil is applied at the

ery of the arm 1 spool (302), and pushes

two sides of port XBa1 and port XBa2,

open the cone valve (302-317) in the spool

arm 1 spool and arm 2 spool is switched to

only under light load. It merges with port

the left. As a result, working oil from P2 is

Ba through the holes on the spool. This is

introduced into the neutral bypass (2) via

called the regeneration function of the arm.

main passage (3). Neutral bypass is cut off

by switching arm 1 spool (302). Therefore,

If the pressure at the arm cylinder head

working oil flown into the parallel passage

end and in the U passage rises, arm re-

pushes open the cone valve (511) of the

generation check valve spool (257-211)

check valve and flows into the arm 1 spool

switches to the left. And, at the same time,

(302) via the U passage. Then, it flows into

the back pressure of the cone valve (302-

the periphery of arm 1 spool (302) and is

317) in the spool is closed. Therefore,

supplied into the arm cylinder head end (H)

arm regeneration function is released and

via port Ba.

return oil from the arm cylinder rod end

(R) flows into the spool via the hole (a) on

On the one hand, working oil from port P1

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

is introduced into neutral bypass (2) via

it flows into arm regeneration check valve

main passage (1). Neutral bypass is cut off

set (257) via hole (c) on the periphery of

by switching the arm 2 spool (306). There-

arm 1 spool (302), and returns to the work-

fore, working oil in the parallel passage

ing oil tank via tank port R1.

pushes open the logic cone valve (256-101)

of the arm 2 logic valve GP, and working oil

4-51

Structure and Function

Ɣ Light load

Arm weight

XBa2

(302-317)

XBa1

(b)

(a)

ZX225-1102014

4-52

Structure and Function

Ɣ When pressure at arm cylinder head end (H) rises

XBa2

(302-317)

XBa1

(c)

(257-211)

(a)

ZX225-1102015

4-53

Structure and Function

4.5.2.4 Boom

(1) Boom UP

[Pilot circuit]

At the same time, pilot pressure oil is also

supplied to port XAb2 and boom 2 spool

Ɣ When the boom 1 spool (303) is switched,

(307) moves to the right. Working oil from

the side path is closed and pressure at port

port P2 is introduced into neutral bypass.

Px (work equipment signal port) rises.

Neutral bypass is cut off by switching the

boom 2 spool (307). Therefore, working

[Main circuit]

oil in the parallel passage flows into boom

Ɣ When boom UP is operated, pilot pressure

2 spool (307) via the U passage. Then, it

oil is supplied into port XAb1 and boom 1

pushes open the cone valve (511) of the

spool (303) moves to the left. Working oil

check valve and merges with port Ab and

from port P1 is introduced into neutral by-

is supplied into the boom cylinder head

pass (2) via main passage (1). Neutral by-

end (H). This is called the boom conflu-

pass is cut off by switching boom 1 spool

ence function.

(303). Therefore, working oil in the parallel

On the other hand, return oil from the

passage pushes open the cone valve (511)

boom cylinder rod end (H) via port Bb flows

of the check valve, and flows into the boom

into the periphery of boom 1 spool (303)

1 spool (303) via the U passage. Then, it

and returns to the working oil tank via tank

flows into the periphery of boom 1 spool

port (R1).

(303) and is supplied into the boom cylin-

der head end (H) via port Ab.

4-54

Structure and Function

511

XAb1

XAb2

511

ZX225-1102016

4-55

Structure and Function

(2) Boom DOWN

[Pilot circuit]

passage. Then, it flows into the periphery

of boom 1 spool (303) and is supplied into

Ɣ When the boom 1 spool (303) is switched,

the boom cylinder rod end (R) via port Bb.

the side path is closed and pressure at

port Px (work equipment signal port) rises.

Ɣ On the other hand, return oil from the

At the same time, pressure oil is supplied

boom cylinder head end (H) passes the

to port PbL and the release signal of lock

hole (a) and the periphery of boom 1 spool

valve option set (252) is sent out.

(303).

[Main circuit]

Ɣ Return oil pressure rises due to the self

weight of the boom. Cone valve (303-317)

Ɣ When boom DOWN is operated, pilot pres-

in the spool is pushed to the right. Return

sure oil is supplied to port XBb1. Boom 1

oil flows to the outside of spool. The pres-

spool (303) moves to the right. As a result,

sure oil is supplied into the boom cylinder

working oil from P1 is introduced into the

rod end (R) as the working oil for boom

neutral bypass (2) via main passage (1).

DOWN operation. This is called the boom

Neutral bypass is cut off by switching boom

regeneration function. Part of the oil that

1 spool (303). Therefore, working oil flown

flows into the inside passage of the spool

into the parallel passage pushes open the

via hole (a) returns to the working oil tank

cone valve (511) of the check valve and

via hole (b).

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

511

XBb1

(b)

(a)

(303-317)

ZX225-1102017

4-56

Structure and Function

4.5.2.5 Bucket

(1) Bucket DIG

[Pilot circuit]

Then, it flows into the periphery of bucket

spool (304) and is supplied into the bucket

Ɣ When the bucket spool (304) is switched,

cylinder head end (H) via port Ak.

the side path is closed and pressure at port

Px (work equipment signal port) rises. At

Ɣ On the other hand, return oil from the buck-

the same time, pressure oil is supplied at

et cylinder rod end (R) flows in via port Bk.

port XBp2.

Then, it flows to oil tank port (R1) via the

spool periphery and returns to working oil

[Main circuit]

tank.

Ɣ When bucket DIG is operated, pilot pres-

Ɣ When boom UP and bucket DIG are oper-

sure oil is supplied into port XAk and buck-

ated simultaneously, pilot pressure oil is

et spool (304) moves to the right. Working

supplied to port Pck. Therefore, the stroke

oil from port P1 is introduced into neutral

of bucket spool is not limited at stroke end,

bypass (2) via main passage (1). Neutral

but on any position halfway. As a result,

bypass is cut off by switching bucket spool

bucket cylinder passage is throttled and

(304). Therefore, working oil in the paral-

working oil flows into boom 1 spool (303)

lel passage pushes open the cone valve

via bucket spool (304). In this way, boom

(511) of the check valve, and flows into

UP operation takes precedence.

the bucket spool (304) via the U passage.

XAk

Pck

ZX225-1102018

4-57

Structure and Function

(2) Bucket DUMP

[Pilot circuit]

tral bypass is cut off by switching bucket

spool (304). Therefore, working oil in the

Ɣ When the bucket spool (304) is switched,

parallel passage pushes open the cone

the side path is closed and pressure at port

valve (511) of the check valve, and flows

Px (work equipment signal port) rises. At

into the bucket spool (304) via the U pas-

the same time, pressure oil is supplied at

sage. Then, it flows into the periphery of

port XBp2.

bucket spool (304) and is supplied into the

bucket cylinder rod end (R) via port Bk.

[Main circuit]

Ɣ On the other hand, return oil from the buck-

Ɣ When bucket DUMP is operated, pilot

et cylinder head end (H) flows in via port

pressure oil is supplied into port XBk and

Ak. Then, it flows to oil tank port (R1) via

bucket spool (304) moves to the left. Work-

the spool periphery and returns to working

ing oil from port P1 is introduced into neu-

oil tank.

tral bypass (2) via main passage (1). Neu-

XBk

ZX225-1102019

(3) Bucket confluence

Ɣ When bucket DIG is operated, pilot pres-

switching neutral bypass valve spool (310).

sure oil is supplied into port XBp2 and the

Therefore, working oil pushes open the

neutral bypass cutoff valve spool (310) is

check valve, and interconnects with the U

switched. Working oil from port P2 is in-

passage via the inside path, and converg-

troduced into neutral bypass (2) via main

es with bucket spool (304).

passage (3). Neutral bypass is cut off by

4-58

Structure and Function

4.5.2.6 Swing

(1) Swing operation

[Pilot circuit]

(305). Therefore, working oil in the parallel

passage pushes open the logic cone valve

Ɣ When the swing spool (305) is switched,

(2540-101) of the swing logic valve GP,

the side path is closed and pressure at port

and flows into the swing spool (305) via the

Px (work equipment signal port) rises.

U passage. Then, it flows into the periph-

ery of swing spool (305) and is supplied

[Main circuit]

into the swing motor via port As (or Bs).

Ɣ When swing is operated, pilot pressure

Ɣ On the other hand, return oil from the

oil is supplied into port XAs (or XBs) and

swing motor flows in via port Bs (or port

swing spool (305) is switched. Working

As). Then, it flows into tank port (R1) via

oil from port P2 is introduced into neutral

the spool periphery and returns to the

bypass (2) via main passage (3). Neutral

working oil tank.

bypass is cut off by switching swing spool

XBs

XAs

(254-101)

Swing motor

ZX225-1102020

4-59

Structure and Function

(2) Swing priority function

[Pilot circuit]

Ɣ Switch swing priority spool (311). The

opening area of the swing priority reduces.

Ɣ Pilot pressure oil is supplied to port Psp

As a result, working oil from arm 1 spool

and swing priority spool (311) is switch.

(302) flows into swing spool (305) and

swing operation takes precedence.

[Main circuit]

Psp

ZX225-1102021

4-60

Structure and Function

4.5.2.7 Option

Option spool is used to control optional work equipment attachment.

(1) Operation

[Pilot circuit]

(309). Therefore, working oil in the parallel

passage pushes open the cone valve (511)

Ɣ When the option spool (309) is switched,

of the check valve, and flows into the op-

the side path is closed and pressure at port

tion spool (309) via the U passage. Then,

Px (work equipment signal port) rises.

it flows into the periphery of option spool

(309) and is supplied into the optional

[Main circuit]

equipment via port Ao (or Bo).

Ɣ When option is operated, pilot pressure

oil is supplied into port XAo (or XBo) and

Ɣ On the other hand, return oil from the op-

option spool (309) is switched. Working

tional equipment flows in via port Bo (or

oil from port P2 is introduced into neutral

port Ao). Then, it flows into tank port (R1)

bypass (2) via main passage (3). Neutral

via the spool periphery and returns to the

bypass is cut off by switching option spool

working oil tank.

XAo

XBo

ZX225-1102022

(2) Option confluence

Neutral bypass is cut off by switching by-

pass valve spool (310). Therefore, work-

Ɣ To achieve option confluence, pilot pres-

ing oil pushes open the cone valve (514)

sure oil is supplied into port XBp1 and the

of check valve, and converges with option

bypass cutoff valve spool (310) is switched.

spool (309) via the inside path and the U

Working oil from port P1 is introduced into

passage.

neutral bypass (2) via main passage (1).

4-61

Structure and Function

4.5.2.8 Travel straight

When travel spool (301) and other spool are

[Main circuit]

operated simultaneously.

Ɣ When straight travel spool (308) is

The following case shows when travel spool

switched, the right/left travel spool (301)

(301) and swing spool (305) are operated si-

are interconnected with port P2. The paral-

multaneously. (When pilot pressure oil is sup-

lel passage of swing/boom 2/option/arm

plied to port XAtL, port XAtr and port Xas)

1 circuit and boom 1/bucket/arm 2 circuit

are interconnected with port P1. Therefore,

[Pilot circuit]

working oil supplied from port P2 flows into

port Atl and port Atr, and is supplied to the

Ɣ The side path of right/left travel spool (301)

two travel motors equally.

and the side path of the swing spool (305)

at the downflow side are closed.

Ɣ On the other hand, working oil from port P1

is supplied to the swing motor via port As.

Ɣ Pilot oil from port PG is supplied to port

PTa and straight travel spool (308) is

Ɣ When oil pressure at port P2 is lower than

switched.

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

4-62

Structure and Function

4.5.2.9 Lock valve function

Ɣ The lock valve option set (252) is installed

Ɣ When boom 1 spool (303) is in neutral po-

between the arm cylinder rod end (R) and

sition, spool (252-511) in the lock valve op-

arm 2 spool (302) and arm 2 spool (306).

tion set is pressed against the valve seat

It is used to reduce the internal leakage of

of the valve sleeve (252-541) inside the

the spool due to cylinder pressure.

lock valve option set, as shown in the illus-

tration, via the spring force of spring (252-

Ɣ Likewise, lockout option set (252) is also

321).

installed between boom cylinder head end

(H) and boom 2 spool (303) to reduce the

Ɣ At this position, working oil at the boom

internal leakage of he spool due to cylinder

cylinder head end (H) flows in via hole (a)

pressure.

and flows out from hole (b) through the

periphery of the lock valve option set spool

(1) Spool in neutral position

(252-511), pressing the cone valve (513)

against the valve seat of the valve block

Ɣ The following shows when boom 1 spool

via hole (b). By this means, oil leakage is

(303) is in neutral position. (The same is

reduced.

with arm 2 spool (306))

252-321

252-511

252-541

(b)

513

(a)

ZX225-1102024

4-63

Structure and Function

(2) Boom DOWN operation

Ɣ When boom DOWN is operated, pilot pres-

into spring chamber (RH). In addition, oil

sure oil is supplied to port PbL and port

in the spring chamber (RH) flows into drain

XBb1. Spool (252-511) inside the lock

circuit via hole (b). In this way, the cone

valve option set moves to the top by via pi-

valve (513) is pushed up by the pressure

lot pressure oil. Through the movement of

at boom cylinder head end (H) and the

spool (252-511) inside the lock valve option

function of the lock valve option set (252)

set, hole (a) is cutoff and working oil from

is released.

boom cylinder head end (H) does not flow

252-511

(b)

(RH)

513

(a)

PbL

XBb

ZX225-1102025

(2) Boom UP operation

Ɣ When boom DOWN is operated, pilot pres-

boom 1 spool (303) and working oil flows

sure oil is supplied to port XAb1. The cone

into port Ab.

valve (513) is pushed ope by the oil from

4-64

Structure and Function

4.5.2.10 Main relief valve function

The main relief valve is installed on the valve

and enters low-pressure path (R).

block A (101). Its function is described below:

Ɣ Opening of cone valve (611) causes pres-

Ɣ Working oil flows into chamber (a) from

sure in chamber (a) to drop and valve rod

passage (P) via the hole of valve seat (541)

(512) is open. In this way, working oil in

and hole on valve rod (512). Valve rod (512)

passage (P) flows into low-pressure path

is pressed against valve seat (541), form-

(R) directly.

ing a tight seal.

Ɣ When pressure oil high than 3MPa is sup-

Ɣ When pressure in passage (P) exceeds

plied to port Pz, this pressure oil pushes

the elastic force of spring (621), cone valve

plunger (614) to the left. The set load of

(611) is pushed open. Therefore, working

spring (621) is changed and pressure of

oil flows through the hole on valve sleeve

the main relief valve rises.

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

541

611

621

512

(a)

103

614

ZX225-1102026

4-65

Structure and Function

4.5.2.11 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

Ɣ Working oil flows 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.

301

511

541

ZX225-1102027

301

511

541

ZX225-1102028

4-66

Structure and Function

Ɣ When pressure in passage (P) exceeds

the elastic force of spring (621), cone valve

(611) is pushed open. Therefore, working

oil flows through hole (C) via the periphery

of cone valve (611) and enters low-pres-

sure path (R).

611

621

ZX225-1102029

621

611

ZX225-1102030

4-67

Structure and Function

Ɣ 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.

511

611

ZX225-1102031

511

611

ZX225-1102032

4-68

Structure and Function

(2) Anti-cavitation oil complement check

valve

Ɣ 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.

541

ZX225-1102033

541

ZX225-1102034

4-69

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