Steering System

DL Wheel Loader

Feb, 2009
Overseas Product Support Team
Text No. HYD0043
Steering system

¾ Simple system logic (DL200)

Steering unit Cushion valve

Steering cylinder

pump Priority valve

Main control valve

No steering, Load & steering pump oil goes to main control valve
Pump → priority valve → steering unit → cylinder

1
Steering system

¾ Simple system logic (DL250, DL300)

Steering unit Cushion valve

Steering cylinder

pump EHPS Valve

Main control valve

No steering, Load & steering pump oil goes to main control valve
Pump → EHPS valve & steering unit → cylinder

2
Steering system

¾ Simple system logic (DL400, DL500)

Steering unit Jerk softner Cushion valve

Steering cylinder
Pump
Main control valve
Flow amplifier valve

No steering, Load & steering pump oil goes to main control valve.
Pump → Flow amplifier valve & steering unit → cylinder

3
Steering system

¾ Steering system (DL400, DL500)

1. Supply line to main control valve

2. Steer pump
3. Flow amplifier
4. Steering unit
5. Steering cylinder
6. Cushion valve
7. Jerk softener
8. Main LS block
9. Transmission

4
Steering system

¾ Steering pump.

DL200 Fixed gear pump DL250,DL300 Fixed vane pump DL400, DL500 Variable piston pump

5
Steering system

¾ Steering pump (DL400, DL500 Variable piston pump)

Not use

LS Port
Suction port

Out let port

Not use

Pressure control adjust screw

Drain port Flow control adjust screw

6
Steering system

¾ Steering pump (DL400, DL500 Variable piston pump)

LS Signal

Control valve Flow control spool

(Setting Pressure ΔP : 20 bar)

Pressure control spool

(Setting Pressure : 250 bar)

S1 L1 L

7
Steering system

¾ Steering unit.

DL200 ( LS line) DL250, DL300 DL400,DL500 (LS line)

8
Steering system

¾ Schematic of steering unit.

DL200 DL250, DL300 DL400, DL500

9
Steering system

¾ Steering unit of DL200.

LS relief valve

LS relief valve

10
Steering system

¾ Steering unit of DL250 / DL300.

11
Steering system

¾ Steering unit of DL400 / DL500.

12
Steering system

¾ Operation of steering unit (DL300)

Neutral position Steering position

13
Steering system

¾ Operation of steering unit (LS type - DL200/DL250/DL400/DL500)

Neutral position (LS line is opened) Steering position (LS line is closed)

14
Steering system

¾ Priority valve for DL200.

15
Steering system

¾ Operation of priority valve for DL200.

- Neutral condition.

No steering, most steering pump oil

goes to main control valve.

Priority valve is not switched.

– LS line is opened to tank.

16
Steering system

¾ Operation of priority valve for DL200.

- Steering condition.

All steering pump oil goes to

steering system.

Priority valve is switched by LS

pressure.
– LS line is connected with steering
system line on steering unit.

17
Steering system

¾ Exterior of EHPS (Electro hydraulic power steering) valve. ( for DL250, DL300)

6
1
Pilot relief valve (12 Bar)

Priority valve

2 3 4 5
1. To Tank 2. LS Pressure check point
8 11
7 9 10 12 3. To main control valve
4. From main pump 5. To steering unit P- port
6. From steering unit T-port
7. From steering unit L-port
8. Shock & suction valve (Left side - 270 Bar)
9. To steering cylinder (Left side)
10. To steering cylinder (Right side)
11. Shock & suction valve (Right side - 270 Bar)
13 14 12. From steering unit R-port
13. LS Relief valve (190 Bar)
14. KV2 Check valve 18
Steering system

¾ Internal section of EHPS valve ( I ).

15. Main steering spool

16. Pressure reducing valve
17. Metering spool
18. Priority spool

19
Steering system

¾ Internal section of EHPS valve ( II )

20
Steering system

¾ Internal parts of EHPS valve.

LS relief valve (190bar) Shock & Suction valve (230 bar)

Metering spool (12 bar) KV2 Check valve

Main steering spool

Pilot reducing valve (30bar)

S3 Check Valve Priority spool
21
Steering system

¾ Schematic. Shock & Suction valve (230 bar)

Main steering spool

S3 Check Valve

KV2 Check valve

KV1 Check Valve
(In Main steering spool) Metering spool (12 bar)

Pilot reducing valve (30bar)

Priority valve

LS relief valve (190 bar)

22
Steering system

¾ Major valves of EHPS.

LS relief valve (190bar) Pilot reducing valve (30bar)

23
Steering system

¾ EHPS (Steering neutral)

No steering, most steering

pump oil goes to main control
valve through priority valve.

LS pilot line is opened to tank

through main spool.

190 bar

24
Steering system

¾ EHPS Steering neutral (Stop engine)

- DL250, DL300 System.

Priority valve is switched to right

side by spring force in valve.

25
Steering system

¾ EHPS Steering neutral (Running engine)

- DL250, DL300 System.

Most steering oil goes to

main control valve.

Priority valve is switched to left

side by steering pressure.

( Left side spool chamber on

priority valve is opened to
tank through metering spool)

26
Steering system

¾ Steering neutral
(Running engine)
- DL250, DL300 System.

Most steering oil goes to

main control valve.

Priority valve is switched to left

side by steering pressure.

( Left side spool chamber on

priority valve is opened to
tank through metering spool)

27
Steering system

¾ Steering.
- DL250, DL300 System.

All steering oil goes to

steering system.

Priority valve is switched to right

side by steering pressure
& spring force.

28
Steering system

¾ Steering.
- DL250, DL300 System

All steering oil goes to

steering system.

Priority valve is switched to right

side by steering pressure
& spring force.

29
Steering system

¾ Flow amplifier valve exterior ( For DL400 / Dl500)

LS Pressure relief valve

30
Steering system

¾ Flow amplifier valve internal section.

1. Housing
2. Shock & Suction valve
3. Back pressure valve
4. Directional spool
5. LS pressure relief valve (180 bar)
6. Priority valve
7. Amplification valve

31
Steering system

¾ Flow amplifier valve internal section & schematic.

Shock & Suction valve

Directional spool

LS pressure
relief valve

Priority valve

Amplification valve

32
Steering system

¾ Flow amplifier valve internal section & schematic. To Steering cylinder

From steering
From steering
unit ” L”
unit ” R”

To Steering unit

To Control
valve

From steering To Tank

From pump unit & steering
pump 33
Steering system

¾ Flow amplifier valve ( No steering). – DL400, DL500 System.

C/V
LS line is open to tank. So most of steering
oil goes to main control valve

34
Steering system

¾ Flow amplifier valve (Steering neutral).

- DL400, DL500 System.

Most steering oil goes to main control valve.

35
Steering system

¾ Flow amplifier valve (Steering) - DL400, DL500 System.

36
Steering system

¾ Flow amplifier valve (Steering).

- DL400, DL500 System.

All steering oil goes to steering system.

37
Steering system

¾ Cushion valve.

Absorb beginning & end of steering shock.

15 bar 15 bar

Schematic

Section drawing
38
Steering system

¾ Cushion valve (Absorb beginning steering pick pressure)

Neutral Fast flow oil goes to Steering

other cylinder chamber
(Absorbing pick pressure) 39
Steering system

¾ Cushion valve (Absorb end steering pick pressure)

X X

Steering Stop steering

Neutral
Cylinder is still moving by inertia power
40
Steering system

¾ Jerk softener.

From steering unit “L”

(To Amplifier valve “L”)

To Amplifier From
valve “R” Steering unit “R”

From Amplifier To steering cylinder

valve “CR”
From Amplifier valve “CL”
To steering cylinder 1. Relief valve
2. Body

41
Steering system

¾ Jerk softener.

Steering Steering
Unit Unit

Neutral Absorb beginning of steering shock by slow moving

direction spool. pick pressure oil from steering unit
goes to opposite chamber of steering cylinder.
42
Steering system

¾ Emergency steering system.

If steering system occurs any problem, emergency

steering system will be working with electric steering motor.
And supply high pressure oil to steering system

1. Pump & DC Motor

2. Steering pump
3. Flow amplifier valve
4. Check valve
5. Check valve

43
Steering system

¾ Operation of emergency steering

Travel speed exceeds 5 km/h

& the pressure at the check
valve is under 3.0 Bar,
emergency steering system
will be working for 60 seconds
by the timer.

44
Steering system

¾ Checking for emergency steering system.

1. The ignition switch must be in position “I” (ON).

2. Test switch is pressed during test, turn steering wheel for testing, at that time indicator light should turn
“ON”

45
Steering system

¾ DL400 / DL500 Steering system.

1. Supply line to main control valve.

2. Steer pump (Variable flow pump)
3. Flow amplifier.
4. Steering unit.
5. Steering cylinder.
6. Cushion valve.
7. Jerk softener.
8. Main LS block.
9. Transmission.

46