6Steering System ENGLISH-G9180

CONTENTS

6

Steering System ... 6-1

61

General ... 6-1

611

Location of Steering System Components ... 6-2

612

Steering System Principle Description ... 6-3

62

Description, Disassembly and Assembly of Main Components ... 6-6

621

Steering Pump ... 6-6

622

Priority Valve ... 6-11

623

Steering Gear ... 6-12

624

Steering Control Mechanism Assembly ... 6-18

625

Front Axle ... 6-19

626

Steering Cylinder ... 6-38

63

Pressure Measurement of Steering Hydraulic System ... 6-39

64

Deflation of Steering Hydraulic System ... 6-40

6 Steering System

61 General

G9180 grader is equipped with full hydraulic steering system. The system has the advantages of compact structure, high sensitivity, good stability, flexible and easy operation, shock absorption and free of extra lubricating device. Besides, manual steering is available when steering power source (pressure oil) is cut off.

Fig. 6-1 Principle diagram of steering system

1 Steering cylinder 2 Steering gear 3 Priority valve 4 Steering pump ① Working hydraulic system ② Brake hydraulic system

611 Location of Steering System Components

612 Steering System Principle Description

The principle of hydraulic steering system is illustrated in Fig. 6-1. Steering system and the left multitandem valve share the same high-pressure gear pump, the pump absorbs oil from hydraulic tank, pressure oil enters the priority valve through port P, then the oil flows into steering gear from port CF of priority valve. When turning the steering wheel, steering gear will send pressure oil into steering cylinder to carry out front-wheel steering.

When the steering gear is in neutral position

Steering gear Priority valve Oil tank Steering pump Filter

Fig. 6-3 Oil line when steering gear is in neutral position

As shown in Fig. 6-3, if the engine flames out, the pump will stop supplying; the control spring of priority valve will force the spool to move right to connect port CF. After the engine is started, hydraulic oil in the tank flows into priority valve through steering pump, the priority valve will allocate oil to steering gear through port CF. The pressure oil in CF port will also act on both ends of the priority valve, and the oil in the left end will flow back to the radiator through the orifice in steering gear and port LS, pressure loss will be formed in this case. Resultant force of the spring and pressure oil in the left end is smaller than the force produced by the pressure oil in the right end, the spool will move to left, opening degree of port EF will increase, while that of port CF will decrease, at this point, oil flow in CF oil line is very small and most oil will be sent to working hydraulic

system. When working system is not working, the pressure oil will return to hydraulic oil tank through neutral position of multitandem valve.

When steering

When relative angular displacement is produced between the valve spool and valve bush of steering gear, the variable orifice in steering gear will communicate with metering motor, and the passage to the radiator will closed in the meantime. This change will result in pressure rise of oil in left end of priority valve, and force the spool to find a new equilibrium position. If increase the rotating speed of steering wheel, in the moment of change, the value of flow in the steering gear is less than the product of steering wheel rotating speed and steering gear displacement, and rotating speed of valve bush driven by metering mechanism is lower than rotating speed of spool driven by steering wheel, so angular displacement of spool to valve bush increases and opening degree of variable orifice increases. At this point, larger flow is needed to produce the same differential pressure as the one before the change between two ends of the variable orifice to force the priority valve spool to move right. So CF port opening degree of priority valve increases with the increase the increase of steering wheel rotating speed. Finally, the flow valve in the steering gear will equal to the product of steering wheel rotating speed and steering gear displacement.

Steering gear

Priority valve

Filter

Oil tank Steering pump

When steering load exceeds the rated value or the steering cylinder reaches its stroke end When steering load exceeds the rated value or steering cylinder reaches its stroke end and if you keep turning the steering wheel, the oil cannot flow in to the cylinder. At this point, loading pressure skyrockets, while differential pressure between two ends of variable orifice reduces sharply. When steering oil line pressure exceeds the setting valve of steering safety valve, this valve will open to work. Pressure loss produced when pressure oil flows through variable orifice, and this differential pressure pass to two ends of priority valve spool to force the spool to move left, which result in decrease of CF port opening degree, and decrease of EF port opening degree, in this way, the pressure of oil in steering line will reduce.

Steering when engine flames out

When engine is not working, the metering mechanism can work as an oil pump, it can supply pressure oil to the steering cylinders. Under this circumstance, the oil in oil return chamber of steering cylinder will return to upstream of the variable orifice through the check valve inside the steering gear.

The grader adopts dynamic signal load sensing non-reactive steering gear. Features of the steering system are:

1. Good compensation for steering load change.

2. The steering hydraulic system and working hydraulic system are designed without interference to each other.

3. The main circuit always takes supplying pressure oil to steering system as first priority.

4. Only small flow goes through steering gear when steering wheel is in neutral position, which is energy-saving. The main circuit always takes supplying pressure oil to steering system as first priority, the steering operation is reliable.

5. Neutral position pressure characteristic is not subject to displacement, flow amplifying function is available.

6. Compared static signal steering gear, starting performance in cold climates is improved, as well as reliability and stability of the system.

62 Description, Disassembly and Assembly of Main Components

621 Steering Pump

The steering pump is double pump. The pump is connected with transmission box output port, and it transmits input mechanical energy from transmission box into oil pressure energy, and outputs pressure oil flow into the system. It’s the power source of steering system.

Technical parameters

Fig. 6-5 Steering pump

1 Oil outlet of brake pump 2 Oil outlet of steering pump 3 Oil absorption port

4 Brake pump 5 Steering pump

Fault diagnosis of steering pump (working pump) Table 6-1

S/N Fault phenomenon Causes Elimination method

1

Oil in hydraulic tank reduces, while oil in transmission box increases.

Damaged oil seal.

Measure the pressure and replace oil seal ring or the pump.

2

Oil in hydraulic tank increases, while oil in transmission box reduces.

Damaged oil seal.

Measure the pressure and replace oil seal ring or the pump.

3 Oil leaking from pump body junction surface.

Damaged O-ring or loose bolt.

Replace the O-ring or fasten the bolt.

4 Oil leakage of pump body Pump body crack. Check and replace the pump.

5 Abnormal sound produced by steering pump.

Excessive wear of spline shaft.

Replace the spline shaft or the pump.

Excessive wear of side plate.

Replace the side plate or the pump.

Out of tolerance of spine shaft.

Replace the spline shaft or the pump.

Bearing failure. Replace the bearing or the pump.

6 Insufficient output flow result in slow motion.

Excessive wear of side plate or gear.

Replace the relevant parts or the pump.

Nominal

displacement 32/16ml/r

Nominal pressure Steering pump: 25MPa Brake pump: 20MPa Max. pressure Steering pump: 31.5MPa

Disassembly of working pump

ATTENTION

1. Before disassembling the steering pump, please park the machine in maintenance position properly. Refer to Page 10 in Safety & Environment.

2. When dismantling the hydraulic pipeline, do not screw off the nut connecting to the oil port rashly. Loosen the nut gradually until the oil spills out so as to prevent the oil splash due to incomplete pressure relief.

3. During dismantling the steering system, necessary protective measures should be taken for each pipeline and oil port to prevent debris like dust from entering the steering system.

4. During dismantling the steering system, please collect the remnant hydraulic oil with appropriate vessel when disconnecting a pipe, and pour the collected oil into a dedicated hydraulic oil recycling bin after the maintenance work.

5. When assembling, be sure to replace the seal with a new one, related standards of tightening torque in this manual must be strictly followed.

1. Connect a hose to the oil drain valve on the bottom of hydraulic tank, and put a clean vessel under the other end of the hose. Open the drain valve of the tank to drain the hydraulic oil out. (Open the filling cap of the tank to accelerate the draining speed)

ATTENTION

Cover up the discharged oil to avoid contamination.

1 2 Fig. 6-6

1 Oil drain valve 2 Hose

2. Remove the fixing bolts of the cover plate, take down the bolts and cover plate.

Cover plate

3. Remove the fixing bolts of steering pump oil absorption steel pipe, take down the bolts and fission flange, and then remove the steel pipe and O-shape ring.

4. Disconnect the oil outlet rubber hose of steering pump, and the oil outlet rubber hose of brake pump.

1 2 Fig. 6-7

1 Cover plate 2 Cover plate

1 Fig. 6-8

1 Oil absorption steel pipe

1 2 Fig. 6-9

1 Oil outlet of steering pump 2 Oil outlet of brake pump

5. Remove the connecting bolts of steering pump and transmission box, take down the bolts and gaskets.

6. Hang the pump with lifting rope, and then use a copper bar to knock it gently, take down the pump and the sealing gasket.

Steering pump

7. Remove the fixing screws of the two straight joints (on the two oil outlet ports), and then take down the fission flanges and straight joints.

Assembly of steering pump

1. Install the two straight joints to the two oil outlet ports of the double pump with screws and fission flange respectively.

2. Install the double pump to the transmission box with M12×35 nuts, gaskets and sealing gasket.

Steering pump

ATTENTION

Be sure to tighten the studs first.

3. Put an O-ring in the O-ring groove of each straight joint. Connect the oil outlet rubber hose of steering pump, and the oil outlet rubber hose of brake pump to the corresponding straight joint with four M10×30 and a fission flange respectively.

1 Fig. 6-10 1 Bolt 1 Fig. 6-11 1 Bolt 1 2 Fig. 6-12

1 Oil outlet of steering pump 2 Oil outlet of brake pump

4. Put O-ring in the O-ring groove of the pump oil absorption steel pipe joint. Fix the pipe on the oil absorption port with four M10×35 and a fission flange.

5. Install the cover plate. Cover plate

6. Fill hydraulic oil to specified level. 1 2

Fig. 6-14

1 Cover plate 2 Cover plate 1

Fig. 6-13

1 Oil absorption steel pipe

1 Fig. 6-15

622 Priority Valve

The priority valve is a constant differential reducing component. Regardless of the changes of loading pressure and oil supply, the priority valve can maintain almost the same pressure differential between two ends of variable orifice, which can ensure the flow valve in the steering gear always equal to the product of steering wheel rotating speed and steering gear displacement. Port P of priority valve is connected with steering pump oil outlet hose, port CF is connected with port P of steering gear, port EF is connected with port P of the left multitandem valve, and port LS is connected with port LS of steering gear.

Technical parameters

Fig. 6-16 Priority valve oil ports

Fig. 6-17 Priority valve

Nominal flow rate 150L/min Opening pressure of safety

valve 140Bar

Dynamic signal introcontrol,

623 Steering Gear

The grader adopts dynamic signal load sensing non-reactive steering gear.

Port P of steering gear is connected with port CF of priority valve, port L and port R is connected with steering cylinder respectively, and oil in port T flows into oil tank through radiator. Port LS of steering gear is connected with port LS of priority valve.

Technical parameters

Fig. 6-18 Steering gear

The steering gear and steering cylinder constitute a position control system. The displacement of the steering cylinder piston rod is proportional to the angular displacement of the steering gear valve element. The cycloid motor inside the steering gear is a metering mechanism (it can work as an oil pump when engine is not working), and it converts the volume of oil distributed to the steering cylinder into the angular displacement of the steering gear valve bush. The relative angular displacement of valve sleeve to the valve element determines the opening area of the oil-distributing window. The higher the steering wheel speed, the bigger the relative angular displacement, and so is the opening area of the oil-distributing window. When the steering wheel stops rotating, the relative angular displacement is

zero and the oil-distributing window shuts itself down to achieve feedback control. The return spring makes the valve sleeve go over the dead zone and align with the valve element.

Function of combination valve inside the steering gear

Inlet check valve: The check valve will be open when oil flows into steering gear. It is used to

Connection type SAE involute

spline

Displacement 320ml/r

Max. inlet pressure 17.2MPa Max. continuous backpressure 2.1MPa Max. system temperature 93oC

Steering torque 2.8~4.0Nm

Fig. 6-19 Internal oil line of steering gear

1 Bi-directional overload valve 2 Bi-directional oil refill valve 3 Inlet check valve

prevent external impact at low steering speed; it can also prevent high pressure oil from flowing back, which will lead to shake of steering wheel. If the oil flows inversely, the valve closes.

Bi-directional overload valve: When the steering cylinder is influenced by external shock, pressure of oil in the cylinder will rise and if it gets to setting value of overload valve (20MPa), the valve will open to load off to protect the cylinder.

Bi-directional oil refill valve: When overload valve is open and in order to avoid cavitation phenomenon, the oil refill valve will open and absorb oil from returning port of combination valve, to supplement pressure oil to cylinder left chamber or right chamber timely.

Precautions when maintaining steering gear

1. Make sure all parts and components are clean to prevent dirt from entering steering gear or hydraulic system.

2. Keep the oil ports and pipe joints clean, and never use thread seal tape to replace seal rings for sealing.

3. Make sure the oil ports of steering gear combination valve and oil ports of steering gear are correct connection relationship.

4. Avoid exerting axial force on the steering gear input end when assembling. 5. Deflate the steering gear after assembling.

6. Never dismantle the steering gear arbitrary, unless you are sure that the steering gear is faulty. 7. Never dismantle the combination valve arbitrary, pressure adjustment of the combination valve

must be verified by tests.

8. Make sure all parts and components are clean when disassembling and assembling steering gear, and beware of collisions.

9. When disassembling and assembling, the valve element and valve bush assembly should be removed or installed vertically, to avoid falling out of pin(s) inside.

10. Align the mark points when assembling the universal driving shaft and rotor. 11. Do not forget to install the steel ball of check valve and pin(s).

Disassembly of steering gear

ATTENTION

1. Before disassembling the steering gear, please park the machine in maintenance position properly. Refer to Page 10 in Safety & Environment.

2. When dismantling the hydraulic pipeline, do not screw off the nut connecting to the oil port rashly. Loosen the nut gradually until the oil spills out so as to prevent the oil splash due to incomplete pressure relief.

3. During dismantling the steering system, necessary protective measures should be taken for each pipeline and oil port to prevent debris like dust from entering the steering system.

4. During dismantling the steering system, please collect the remnant hydraulic oil with appropriate vessel when disconnecting a pipe, and pour the collected oil into a dedicated hydraulic oil recycling bin after the maintenance work.

5. When assembling, be sure to replace the seal with a new one, related standards of tightening torque in this manual must be strictly followed.

1. Remove the fixing bolts of the left and right guard plates, take down the guard plates.

2. Remove the fixing bolts of the top guard plate, take down the guard plate.

1 Fig. 6-20

1 Left guard plate

1 Fig. 6-21

3. Remove the beam.

4. Disconnect the oil pipes from steering gear.

ATTENTION

Mark the oil pipes properly to prevent confusion.

5. Remove the connecting bolts of steering column holder and cab.

6. Remove the connecting bolts of steering column holder and steering gear support. 1

Fig. 6-22 1 Beam

1 2 3 4 Fig. 6-24

1 Bolt 2 Steering column holder 3 Pin 4 Steering gear support

1 Fig. 6-23 1 Pipe

7. Remove the connecting bolts of steering column and steering gear. Take down the steering gear.

8. Remove the straight joints.

Assembly of steering gear

1. Install the straight joints to the corresponding oil ports.

2. Connect steering column and steering gear with four M10×25 bolts and gaskets.

3. Install the pin to connect the steering column holder and steering gear support.

4. Install the steering column holder to cab with four M10×25 bolts and gaskets.

1 2 Fig. 6-25

1 Bolt 2 Straight joint

1 2 3 Fig. 6-27

1 Bolt 2 Steering column holder 3 Pin

1 2 3 4 Fig. 6-26

1 Steering column 2 Bolt 3 Gasket 3 Steering gear support

5. Connect the oil pipes to the corresponding oil ports of steering gear.

6. Install the beam fixing bolts.

7. Install the top guard plate. 1 Fig. 6-29 1 Beam Fig. 6-28 1 2 Fig. 6-30

8. Install the left and right guard plates.

624 Steering Control Mechanism Assembly

Fig. 6-32

1 Steering wheel 2 Steering column 3 Nut 4 Gasket

5 Pressing plate 6 Protective cover 7 Steering column holder 8 Cotter pin

9 Gasket 10 Bolt 11 Steering gear support 12 Pin

1 Fig. 6-31

625 Front Axle

Fig. 6-33 Front axle assembly

1 Front axle 2 Gasket 3 Bolt 5 Rim 6 Oil cup 7 Lock washer 8 V-shape seal ring 9 Swing shaft 10 Bolt 11 Gasket 12 Support

Fig. 6-34 Front axle

1 Left steering frame 2 Left steering knuckle 3 Retainer ring 4 Shaft 5 Retainer ring 6 Front wheel tilt cylinder 7 Oil cup 8 Connecting rod 9 Retainer ring 10 Knuckle bearing 11 Bolt 12 Gasket 13 Support 14 Articulated shaft 15 Composite bearing 16 Cotter 17 Front axle frame 18 Lock washer 19 Composite bearing 20 Articulated shaft 21 Support 22 Gasket 23 Bolt 24 Screw 25 Gasket 26 Screw 27 Cover plate 28 Screw 29 Gasket 30 Pin 31 Right steering knuckle 32 Gasket 33 Gasket 34 Gasket 35 Right steering frame

36 Wheel axle 37 V-shape seal ring 38 Seal ring 39 Screw 40 Hub cover 41 O-ring 42 Nut 43 Lock washer 44 Gasket 45 Tapered roller bearing 46 Screw 47 Screw 48 Hub 49 Gasket 50 Lining 51 Nut 52 Right swivel head 53 Lock nut 54 Cotter 55 Left swivel head 56 Clamp 57 Nut

58 Bolt 59 Pull rod 60 Shaft 61 Pin 62 Plain radial bearing 63 Retainer ring 64 Plate 65 Right steering cylinder 66 Bolt 67 Articulated shaft

68 Support 69 Left steering cylinder

The front axle assembly of grader is different from common axle. Apart from having steering function, it also has front-wheel wide-angle tilting function and horizontal swing function. Because of the design, the grader can balance itself during working, and the working accuracy is improved. Under special working condition, it can increase adhesive force of the front wheels, which is beneficial for the grader to satisfy all kinds of working conditions.

Maintenance of front wheel bearing must be conducted by specialized person in accordance with specific procedures. Non-specialized person is not allowed to disassemble the front axle.

Disassembly of front axle assembly

1. Put the machine in maintenance position. 2. Start the engine, and operate the control handle

of the shovel blade rotary cylinder until the blades are perpendicular to the front frame. And then operate the control handle of the shovel blade lifting cylinder to lower the blades to the prepared wood support. Shut down the engine.

ATTENTION

Before performing the following maintenance work, you must prop up the shovel blades. Otherwise the grader may tip over and cause personnel injury.

1 Fig. 6-35

Removal of front wheel

1. Loosen the fixing bolts of front wheels. Start the engine and operate the control handle of the shovel blade lifting cylinder to lower the blades, in this case, the front end of grader is elevated. Put reliable support under the front end of the grader and operate the control handle of the shovel blade lifting cylinder to lift the blades, to let the front end of the grader fall on the support slowly. Shut down the engine.

2. Remove the fixing bolts of front wheels, take down the bolts and gaskets. Remove the wheels.

Removal of front wheel hub

1. Hang the hub with lifting appliance, remove the fixing bolts of the hub cover, take down the bolts and hub cover.

Hub

2. Remove the O-ring from the hub cover. 1 2

Fig. 6-37

1 Hub cover 2 Inside hexagon bolt

1 2 Fig. 6-38

1 Hub cover 2 O-ring 1 Fig. 6-36

3. Remove the outside lock nut, and then take down the lock nut, lock washer, and the lock nut and gasket under the washer.

4. Use special tool to remove the hub.

ATTENTION

In the process of removing the hub, the tapered roller bearing may fall off at any moment.

Structurally, middle part of the wheel axle is lower, so do not knock to remove the hub, to avoid damaging the tapered roller bearing.

Fig. 6-41

1 2 3 4 5 Fig. 6-39

1 Hub 2 Gasket 3 Lock nut 4 Lock washer 5 Lock nut

1 Fig. 6-40

5. Use special tool to remove the tapered roller bearing. Take down the V-shape seal ring and O-ring.

Removal of drag link

1. Hang the drag link with lifting appliance, and then remove the cotter pin.

2. Screw off the slotted nut, and take down the nut and gasket.

1 2 3 Fig. 6-42

1 Tapered roller bearing

2 V-shape seal ring 3 O-ring

1 2 3 4 Fig. 6-43

1 Cotter pin 2 Slotted nut 3 Gasket 4 Drag link

3. Use copper bar to knock the swivel head off (knock from bottom).

4. Do the same to the swivel head on the other end, and then lift down the drag link.

5. Remove the fixing bolt of the clamp, take down the clamp and separate the swivel head and drag link.

Removal of steering cylinder

1. Disconnect the oil pipes from the steering cylinder. 1 Fig. 6-44 1 Swivel head 1 Fig. 6-45 1 Clamp 1 Fig. 6-46 1 Oil pipe

2. Remove the fixing bolt of the steering cylinder piston-side connecting pin, take down the bolt, gasket and the bottom support. Then use a copper bar to remove the pin.

3. Remove the cotter pin from the slotted nut, and then screw off the slotted nut. Take down the nut and gasket.

4. Use a copper bar to knock the swivel head off the steering frame.

5. Lift down the steering cylinder. Remove the connecting bolt of the swivel head and steering cylinder piston rod, and take down the swivel head. 1 Fig. 6-47 1 Bolt 1 Fig. 6-48 1 Slotted nut 1 Fig. 6-49 1 Bolt

Removal of wheel axle

1. Remove the connecting bolts of the wheel axle and steering frame, and then take down the wheel axle.

Wheel axle

Removal of steering frame

1. Remove the fixing bolts of the cover plate, take down the bolts and cover plate.

2. Remove the inside hexagon bolt, take down the bolt and gasket.

1 2 Fig. 6-51

1 Cover plate 2 Bolt 1 Fig. 6-50

1 Bolt

1 Fig. 6-52

3. Remove the pin.

4. Use the same method to disconnect the other end connection, lift the steering frame away. Steering frame

Removal of front wheel tilt cylinder

1. Hang the tilt cylinder with lifting appliance. 2. Disconnect the oil pipes from the tilt cylinder.

3. Remove the fixing bolt of the tilt cylinder piston-side connecting pin, take down the bolt and gasket. Then use special tool to remove the pin.

1 2 3 Fig. 6-54

1 Tilt cylinder rod-side connecting hose 2 Tilt cylinder piston-side rubber hose

1 Fig. 6-53 1 Pin 1 Fig. 6-55 1 Bolt

4. Use snap ring plier to remove the snap ring of tilt cylinder rod-side connecting pin. Then use a copper bar to remove the pin. Lift the tilt cylinder away.

Front wheel tilt cylinder

Removal of connecting rod

1. Use snap ring plier to remove the snap ring on both ends of the pin.

2. Use the same method to remove the snap rings on the other end of the connecting rod. Hang the connecting rod away with lifting appliance. Connecting rod

3. Use snap ring plier to remove the snap ring. Then remove the connecting pin(s).

1 Fig. 6-57 1 Snap ring 1 Fig. 6-56 1 Snap ring 1 Fig. 6-58 1 Snap ring

Removal of steering knuckle

1. Remove the fixing bolt of steering knuckle and front axle bracket connecting pin, take down the bolt and gasket. Use special tool to remove the connecting pin, and lift the steering knuckle away.

Steering knuckle

Removal of front axle bracket

1. Remove the fixing bolt of front axle bracket and frame connecting pin, take down the bolt and gasket.

2. Use special tool to remove the connecting pin, and lift the front axle bracket away.

Front axle bracket

1 Fig. 6-60 1 Bolt 1 Fig. 6-59 1 Bolt

Assembly of front axle assembly

Assembly of front axle bracket

1. Hang the front axle bracket with lifting appliance, align it to the frame for assembling, and then install the pin to connect them.

Front axle bracket

2. Install the pin fixing bolt and gasket.

Assembly of steering knuckle

1. Hang the steering knuckle with lifting appliance, align it to the front axle bracket for assembling, and then install the pin to connect them.

Steering knuckle

2. Install the pin fixing bolt and gasket. 1 Fig. 6-61 1 Bolt 1 Fig. 6-62 1 Bolt

Assembly of connecting rod

1. Preassemble the two connecting pins to the steering knuckle first, and install the snap rings.

2. Install the knuckle bearing to the pin, and fix it with snap ring.

3. Hang the connecting rod with lifting appliance, align it to the steering knuckle for assembling, connect them with the two preassembled pins, and install the snap rings.

Connecting rod

Assembly of front wheel tilt cylinder

1. Lift the tilt cylinder to suitable position for assembling.

Front wheel tilt cylinder

2. Install the cylinder piston-side connecting pin, and fix the pin with bolt and gasket.

3. Install the cylinder rod-side connecting pin and fix the pin with snap ring.

1 2 Fig. 6-63

1 Pin 2 Snap ring

1 Fig. 6-64 1 Bolt 1 Fig. 6-65 1 Snap ring

4. Connect the piston-side and rod-side rubber hoses.

Assembly of steering frame

1. Hang the steering frame with lifting appliance, align it to the steering knuckle for assembling, and then install the pin to connect them.

Steering frame

2. Install the inside hexagon bolt. 1 2 3

Fig. 6-66

1 Tilt cylinder rod-side connecting hose 2 Tilt cylinder piston-side rubber hose

1 Fig. 6-67

1 Pin

1 2 Fig. 6-68

3. Install the fixing bolts of the cover plate.

Assembly of wheel axle

1. Use lifting appliance to lift the wheel axle to suitable position for assembling. Then install the connecting bolts of the wheel axle and steering frame.

Wheel axle

Assembly of steering cylinder

1. Connect the steering cylinder to the swivel head with bolt.

2. Use lifting appliance to lift the steering cylinder assembly to suitable position for assembling. Then connect the swivel head to the steering frame.

1 Fig. 6-70

1 Bolt

1 2 Fig. 6-69

1 Cover plate 2 Bolt

1 Fig. 6-71

3. Tighten the slotted nut to fix the swivel head. Then install the cotter to fix the nut.

4. Install the fixing bolt of the steering cylinder piston-side connecting pin.

5. Connect the oil pipes to the steering cylinder. 1 Fig. 6-72 1 Slotted nut 1 Fig. 6-73 1 Bolt 1 Fig. 6-74 1 Oil pipe

Assembly of drag link

1. Install the clamp to connect the swivel head and drag link.

2. Use lifting appliance to lift the drag link to suitable position for assembling. Then connect the swivel head to the steering frame.

3. Tighten the slotted nut to fix the swivel head. Then install the cotter to fix the nut.

1 Fig. 6-75

1 Clamp

1 2 3 Fig. 6-77

1 Cotter pin 2 Slotted nut 3 Gasket

1 Fig. 6-76

Assembly of front wheel hub

1. Install the tapered roller bearing and seals to the hub.

ATTENTION

A refrigerated bearing is easier to be assembled.

2. Use lifting appliance to lift the hub to suitable position for assembling. Then install the hub to wheel axle.

Hub

3. Install the outside tapered roller bearing.

1 Fig. 6-79

1 Tapered roller bearing 1 2 3 Fig. 6-78

1 Tapered roller bearing

4. Install the gasket, lock nut, lock washer and the outside lock nut orderly.

5. Install the O-ring from the hub cover. Then install the hub cover to wheel hub.

6. Install and tighten the fixing bolts of the hub cover.

1 2 Fig. 6-82

1 Hub cover 2 Inside hexagon bolt 1 2 3 4 5

Fig. 6-80

1 Hub 2 Gasket 3 Lock nut 4 Lock washer 5 Lock nut

1 2 Fig. 6-81

Assembly of front wheel

1. Use bolts and nuts to fix the wheel on hub. Wheel

626 Steering Cylinder

Single-rod double-acting hydraulic cylinder

Technical parameters

Cylinder diameter 63mm Piston rod diameter 45mm

Piston stroke 340mm

Fig. 6-84 Steering cylinder 1 Fig. 6-83

63 Pressure Measurement of Steering Hydraulic System

Pressure gauge with measuring range of 0~25MPa Pressure measuring points

Quick pressure measuring joints on steering cylinder (Specification of thread on the port M16×2)

Fig. 6-85 Steering system pressure measuring point Pressure measuring method

1. Connect the pressure gauge to the pressure measuring joint.

2. Start the engine and turn the steering wheel to the extreme position to build pressure. 3. Read and record the reading on pressure gauge.

Standard working hydraulic system pressure Set pressure of steering system: 140±3.5Bar.

64 Deflation of Steering Hydraulic System

After replacing steering pump, steering gear, priority valve, steering cylinder and the hydraulic pipes in steering circuit, air bleeding must be done by performing the following steps:

1. Park the loader in maintenance position properly, lower the front bulldozing plate to the ground and jack up the front wheel (off ground), and then open the filling cap of hydraulic oil tank. 2. Start and run the engine idly, turn the steering wheel gently to let steering cylinders stretch out

and draw back (about 50~60mm, from the bottom of the stroke) for 2~3 times.

3. After the hydraulic oil is fully circulated, turn the steering wheel left and right within a narrow range for several times. Be sure not to let the steering cylinder gets to its stroke end.

4. Keep the engine run at high speed, turn the steering wheel gently to let steering cylinders stretch out and draw back in full stroke for 3~5 times to drain the air in the circuit out.

5. After air bleeding, set the machine and working device in standard position (the steering wheel should be in neutral position; front frame and rear frame should be in the same line; the front bulldozing plate should be lower to ground and be 90o to the frame; the scarifier should be lowered close to the ground). Then check the oil level and tighten the filling cap.

65 Diagnosis and Solutions for Common Faults of Steering System

1. Steering hard

1. The built-in check valve of steering gear is damaged and the inlet is blocked.

2. Steering gear failure, the check valve steel ball is jammed and couldn’t reset.

3. Priority valve LS pipe is twisted together or too long, the damping hole is blocked or oil leakage.

4. The steering column is damaged and requires larger driving torque.

5. Interference between steering column and steering gear connecting part, extra axial or radial force is formed and acts on steering gear valve element after assembling.

6. Low set pressure of priority valve relief valve, or the main valve element is stuck, or the damping hole is blocked.

7. Low set pressure of safety valve of steering gear combination valves.

8. Oil return filter is blocked.

9. The pump is severely worn, whose volume efficiency, output pressure and flow rate can no longer meet system requirement. 10. Somewhere in the steering circuit is blocked that results in

severe throttle.

11. Main valve element of priority valve is jammed or the main spring rigidity is reduced.

12. Interference in front axle steering mechanism.

2. Vehicle snaking

1. Check for cavitation phenomenon.

2. The pump oil absorption steel pipe or pipe joint has air leakage problem.

3. Low oil level in hydraulic oil tank.

4. Steering cylinder connecting pin is loose or the piston rod is distorted.

5. Steering cylinder has severe internal leakage problem.

6. The bi-directional overload valve or bi-directional refill valve has oil leakage problem

3. Vehicle off tracking

1. Check whether the connecting rod of steering cylinder is loose. 2. Internal leakage of steering cylinder.

3. There is large pressure differential between the two tires. 4. Leakage in one side of bi-directional oil compensation valve or

bi-directional overload valve. 5. Oil contains too much air.

4. Self-steering when steering wheel is in neutral.

1. Check the connecting rod of steering cylinder is loose. 2. Internal leakage of steering cylinder.

3. Leakage in one side of bi-directional oil compensation valve or bi-directional overload valve.

4. Oil contains too much air. 5. Transient steering is not

flexible after the machine is just started.

1. The machine is off work for too long, large temperature differential between steering gear components and hydraulic oil.

6. Steering is inaccurate.

1. Too much air in the steering system. 2. Steering cylinder pin is loose. 3. Heat shock.

4. Main valve element of priority valve is jammed. 5. Oil leakage in steering cylinder.

6. Low efficiency of steering pump results in unstable pressure. 7. Steering cylinder

creeping 1. Too much air in the steering system.

8. Steering wheel can be turned freely, but there is no force feeling or the machine fails to steer.

1. Nuts of steering wheel and steering column fall off.

2. The connection between steering column central spindle and steering gear valve element is failed.

3. Low hydraulic oil level. 9. Steering wheel can be

turned easily, but the machine doesn’t steer or steers slowly.

1. Severe leakage in bi-directional oil compensation valve or bi-directional overload valve.

10. Idle motion of steering wheel.

1. Nut of steering wheel is loose.

2. The connection between steering column and steering gear is severely worn or damaged.

3. Oil contains too much air.

4. Leakage in bi-directional oil compensation valve or bi-directional overload valve.

5. The steering cylinder linkage is damaged or worn (big gap). 6. Leakage of steering cylinder.

11. Bad return or dragging turning of steering wheel

1. The connection between steering column and steering gear is too tight or interference exists.

2. Too large return backpressure results in bad return.

3. Big contamination particle enters into the gap between valve bush and valve element that results in unable to return.

4. Steering gear spring sheet is damaged or with small rigidity.

12. Components of steering gear is damaged

1. Big and hard contamination particle enters into the gap between stator and rotor.

2. Severe grind damage. 3. Pull pin cracked

4. Heat shock. (50oC differential)

13. Steering wheel trembles or self-rotation

1 Wrong assembly relationship. For reassembly, corresponding spline tooth in universal driving shaft pull pin groove should be aligned to rotor internal spline tooth concave.

2 Connect the oil inlet pipe to port R or port L, and the steering gear will self-rotate as the motor.

14. Steering wheel and the machine turning in opposite direction

1. Pipe of port L and port R are inversely connected.