STEERING SYSTEM - STRUCTURE AND OPERATING PRINCIPLE

NEUTRAL MANUAL STEERING (RIGHT TURN)

When turning the steering wheel and holding it in that position, the sleeve, which is fixed to the steering wheel, stops simultaneously with the steering wheel, but the spool, which was turning 10 to 15° behind the sleeve, turns 10 to 15° further and then stops. This is due to the force of the leaf spring installed to the sleeve and spool. In this state, the oil passage to the steering cylinder through the Gerotor between the spool and sleeve is blocked, but the oil passage to return the oil from the steering unit is opened. Therefore, the hydraulic oil supplied through the port (P) is returned through the port (T) and the cylinder stops its operation.

The steering wheel should be forced to be turned in some occasions, for example, when the engine does not start or the hydraulic pump is damaged. When turning the steering wheel to the right, not only the sleeve and spool rotate, but also the Gerotor pump rotates. In this state, the oil passage is formed by the sleeve and spool as the power steering operation. As the Gerotor pump is rotated by force from an operator, the oil flows as shown in the circuit diagram. At this time, there is no oil supplied to the port (P). Therefore, the oil drained from the steering cylinder is not led to the port (T), but is recirculated by the check valve, forming one closed circuit for manual steering.

STEERING SYSTEM - STRUCTURE AND OPERATING PRINCIPLE

RIGHT TURN OPERATION OF RELIEF VALVE (FOR RIGHT TURN)

When turning the steering wheel clockwise, the oil passage for the right turn is formed by the cylindrical sleeve and cylindrical spool in the steering unit as long as holding the steering wheel turned. The spool is fixed to the steering wheel so it is turned simultaneously with the steering wheel. However, the sleeve is designed to turn approx. 10° to 15° behind the spool. Therefore, while the steering wheel is turned, the oil passage for turning, different from the neutral oil passage, is formed. At that time, the hydraulic oil from the port (P) passes the Gerotor pump through the sleeve and spool, and then it is supplied to the steering cylinder through the port (L) after passing through the sleeve and spool again. As the oil is supplied to one side of the steering cylinder, the cylinder piston is moved for steering operation and the right cylinder is compressed. Therefore, the oil returned to the right cylinder escapes and returns to the port (T) through the return passage formed by the sleeve and spool in the steering unit. As the oil supplied to the steering cylinder flows to the Gerotor pump after passing the steering unit, the steering power for the front wheels is enhanced and the steering wheel can be turned with less force by power steering operation.

If the steering cylinder rod is completely drawn out and does not move, the rod does not move due to the stopper even when its stroke is not complete or the wheels do not move due to the excessive load on the steering, the relief valve (110+50 kgf/cm2) is open to drain the oil from the port (P) through the relief valve to the port (T) immediately.

STEERING SYSTEM - STRUCTURE AND OPERATING PRINCIPLE

The operation for the left turn is the same as the one for the right turn except for the oil direction.

STEERING SYSTEM - STRUCTURE AND OPERATING PRINCIPLE

2.4 STRUCTURE AND OPERATING PRINCIPLE

This steering cylinder is both ends-rod double acting type cylinder which has a piston in the center of its rod and two hydraulic chambers on sides of the piston. These hydraulic chambers expand and contract to move the rod to the left/ right for vehicle steering. As the cylinder rod functions as a tie rod, no tie rod is needed for this cylinder.

STEERING SYSTEM - TROUBLESHOOTING

3. TROUBLESHOOTING

SYMPTOM CAUSE SOLUTION

• Improper front tire size, inflation pressure or shape

• Worn or damaged ball joint end inflation pressure or replace tires

Tractor pulls to right or left

• Improper toe-in, damaged steering cylinder rod and rod hinge pin

• Damaged inner area of front axle

• Worn or damaged ball joint end

• Improper toe-in

Excessive steering wheel reaction

• Damaged front axle

• Low relief pressure of steering unit

• Leakage in steering unit

• Damaged steering unit

Locked steering wheel

• Damaged steering wheel or deflected rod

• Damaged front axle pivot or thrust bearing

• Leakage in steering hose

• Leakage in steering unit hose

Leakage

• Leakage in hose connection

• Damaged steering cylinder oil seal and replace O-ring steering cylinder

Steering wheel vibrates

• Abnormally worn tire rug, abnormal size or deflection, insufficient inflation pressure

• Damaged axle bearing and gear

• Loose steering wheel mounting nut

• Leakage in steering unit or damaged steering unit

• Leakage in steering cylinder

Steering wheel idles

• Air entered steering system or no hydraulic fluid

• Air entered hydraulic system or no hydraulic fluid

• Leakage in steering unit

Abnormal steering noise

• Prematurely open steering relief valve