Hyundai Excavator R450LC-7. Service and repair manual - page 7

2-37

RELIEF VALVE

Main relief valve
The oil discharged from P1 port via the poppet(LP) and the oil discharged from P2 port via the
poppet(RP) flow into the main relief valve through the passage(3).
When the main relief valve is operating, the maximum pressure of pump P1, P2 is controlled.

Overload relief valve
Overload relief valves are provided each cylinder ports of boom1, arm1 and bucket.  These
prevents the abnormal high pressure of actuators by external force.
Also, when the pressure of cylinder ports create back pressure, this valve opens allowing oil from
tank to cylinder port; and then prevents cavitation.

9)

(1)

(2)

45071MC13

2-40

SWING COMBINED OPERATION
When swing and boom up functions are operated, the poppet(S2-1) is seated by pressure of port
pc6 and the poppet(S2-3) only opened and the supply pressure of the parallel passage(L3) is rises
by orifice(S2-4).
As a result, boom and swing simultaneous operation is ensured even if lower load of swing section.

2)

45071MC15

2-42

6. RELIEF VALVE OPERATION

MAIN RELIEF VALVE

This relief valve is built-in between the neutral passage(HP) and low pressure passage(LP), and
the pressure oil fills up chamber(D) inside via orifice of main poppet(C).
Thus the sleeve(E) and  the main poppet(C) are securely seated by difference area of A an B.

1)

(1)

45071MC17

When the pressure in neutral passage(HP) reaches the setting force of spring, pilot poppet(F) is opened.
The oil flows around poppet and into the low pressure passage(LP)  via hole(G).

45071MC17-1

(2)

When above flow is formed, the pilot poppet is opened; the pressure of chamber(D) drops, the
main poppet(C) is opened and then the oil directly flows into the low pressure passage(LP).

45071MC17-2

(3)

High pressure setting pilot signal(Pi) : ON
The piston(H) moves to left by pilot pressure(Pi); set pressure of spring rises, making high
pressure setting.

45071MC17-3

(4)

2-43

OVERLOAD RELIEF VALVE

This relief valve is built-in the cylinder port(HP) and the low pressure(LP), and the pressure oil fills
up camber(G) inside via hole of piston(C).
Thus the sleeve(K) and the main poppet(D) are securely seated by difference area of A and B.

2)

(1)

45071MC18

When the pressure in cylinder port(HP) reaches the setting force of spring, the pilot poppet(E) is
opened.
The oil flows around poppet and into the low pressure passage(LP) via hole(H).

45071MC18-1

(2)

When above flow is formed, the pilot poppet(E) is opened.
The pressure drops before and behind orifice(I); piston(C) moves to right and the piston(C) is
seated at the tip of poppet(E).

45071MC18-2

(3)

2-44

The oil flow from the high pressure passage(HP) to the poppet(D) behind is only around poppet
and orifice(F); then the high pressure passage(HP) is higher than the poppet(D)behind pressure.
Thus the poppet(D) is pushed open and the oil directly flows into low pressure passage(LP).

45071MC18-3

(4)

Make up operation
This relief valve is built-in the cylinder port(HP) and the low pressure passage(LP), and the
pressure oil fills up camber(G) inside via hole of piston(C).
Thus the sleeve(K) and the main poppet(D) are securely seated by difference area of A and B.

45071MC18-4

(5)

2-45

LOW PRESSURE RELIEF VALVE

When pump does not operational

3)

(1)

45071MC19

When spool neutral
The neutral passage(HP) oil flows into the low pressure passage(LP) via signal orifice(S).
The signal port 4Ps(5Ps) pressure is raise by negative control orifice(A).

45071MC19-1

(2)

Operation of low pressure relief
When the oil pressure neutral passage(HP) reaches the setting force of spring, the poppet is
pushes open; the oil directly flows through passage(HP) to passage(LP) in order to prevent
abnormal pressure.

45071MC19-2

(3)

2-47

SWING MOTOR

1

Inner ring

2

Oil seal

3

Taper roller bearing

4

Level gauge assy

5

Backing spring

6

Cam plate

7

Return plate

8

Piston assy

9

Lining plate

10

Plate

11

O-ring

12

Piston

13

O-ring

14

Spring

15

Parallel pin

16

Piston

17

O-ring

18

Cap

19

Scrowave

20

Teflon ring

21

Bushing

22

Balance plate

23

Needle bearing

24

Snap ring

25

Cylinder assy

26

Housing

27

Collar

28

Plug

29

Snap ring

30

Bypass valve assy

31

Back up ring

32

O-ring

33

O-ring

34

Cover

35

Time delay valve

36

Hexagon socket bolt

37

O-ring

38

O-ring

39

Relief valve

40

O-ring

41

Hexagon socket bolt

42

Check

43

Spring

44

Cap

45

Back up ring

1)

45070SM06

2-48

REDUCTION GEAR

1

Pinion shaft

2

Collar

3

Plate

4

Snap ring

5

Roller bearing

6

Gear casing

7

Collar

8

Snap ring

9

Oil seal

10

Roller bearing

11

Parallel pin

12

Ring gear

13

Spur gear4

14

Thrust plate

15

Sun gear

16

Holder assy 1

17

Bolt

18

Lock washer

19

Holder assy 2

20

Shaft 2

21

Spur gear 5

22

Thrust plate 2

23

Spring pin

24

Holder 2

25

Plug

26

Plug

2)

45070SR01

2-49

4                   3       2             5       1

F1

F

θ

PCD

a

a

High
pressure oil

High
pressure oil

Low
pressure oil

S

F

2

2. FUNCTION

ROTARY PART
When high pressurized oil enters a cylinder through port(a), which is the inlet of balance plate(1),
hydraulic pressure acting on the piston causes axial force F.  The pressure force F works via the
piston(2) upon the return plate(3) which acts upon the swash plate(4) via an hydrostatic bearing.
Force F1 perpendicular to swash plate(4) and force F2 perpendicular to cylinder center.
Being transferred to the cylinder block(5) through piston, force F2 causes rotational moment at
surroundings of cylinder.
Since cylinder block has 9 equidistantly arrayed pistons, rotational torque is transmitted to cylinder
shaft in order by several pistons connected to the inlet port of high pressurized oil.  When the
direction of oil flow is reversed, rotational direction of cylinder is also reversed.  Output torque is
given by the equation.

p

×

q

F

T =            , q=Z

·

A

·

PCD

·

tan

θ

,  F1 =               , F

2

=F tan

θ

, S=PCD

×

tan

θ

2

Л

COS

θ

Where  p : Effective difference of pressure(kgf/cm

2

)

q : Displacement(cc/rev)
T : Output torque(kgf

·

cm)

Z : Piston number(9EA)
A : Piston area(cm

2

)

θ

: Tilting angle of swash plate(degree)

S : Piston stroke(cm)

1

1

)

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