The wheel excavator with full hydraulic deflection front wheel steering system often has the fault of front wheel steering sluggish when it is in a sharp turn. Most of the faults are caused by the low volumetric efficiency and system pressure of the hydraulic steering system, resulting in poor oil circuit. The following is an introduction to the judgment and troubleshooting of this fault.
When the front wheel steering is slow when the excavator is making a sharp turn, the method of shifting to a low gear and increasing the throttle can be used to see whether the machine can turn. If it can turn, it means that the hydraulic steering system is not short of oil, otherwise it will not be able to turn at all. According to the working principle of the hydraulic steering system of the excavator, it can be concluded that the fault is caused by the low volume efficiency and system pressure of the hydraulic steering system, resulting in the poor oil circuit. The main reason for the low volumetric efficiency of hydraulic steering system is the serious internal leakage, which can be checked and eliminated by the following methods.
1. When the clearance between the piston ring and the inner wall of the cylinder is too large or the piston ring and gasket are damaged, part of the high-pressure oil in the high-pressure chamber will flow into the low-pressure chamber, reducing the amount of high-pressure oil actually entering the high-pressure chamber to do work, resulting in the slow action of the steering cylinder and the untimely mechanical steering.
Inspection method: remove the steering cylinder and replace it on another excavator with no steering fault for test inspection. If there is also slow steering, it is proved that the fault lies in the sealing performance of the steering cylinder. At this time, the seal or assembly can be replaced according to the situation.
2. When the inner cylindrical surface and sealing ring of the excavator central rotary joint shell are seriously worn, the whole oil and gas system passing through the rotary joint will collude with each other at the sealing failure, resulting in the insensitivity of each system. When steering, its high-pressure oil leaks into the air path or other hydraulic pipelines, reducing the amount of hydraulic oil supplied to the steering cylinder.
Inspection method: pull up the air switch operated by the wheel brake hand. If the gas ejected from it contains oil mist, it means that the central rotary joint is seriously worn and the oil has leaked into the air circuit. At this time, it is necessary to replace the central rotary joint and its sealing ring.
3. When the low pressure pipe head is not tightened or the oil pipe is broken, air will enter the hydraulic steering system, which will also cause slow steering.
Inspection method: start the engine and observe the oil tank while turning the steering wheel. If there are bubbles in the oil tank, it means that the low-pressure oil pipe leaks. The pipe joint should be tightened or the damaged low-pressure oil pipe should be replaced in time.
4. When the working face of stator and rotor of cycloid gear motor of steering gear and the working face of steering valve are seriously worn, the actual high pressure oil passing through the steering cylinder will also be reduced.
Inspection method: if the performance of the steering cylinder and the central rotary joint is in good condition, the steering wheel can be killed after the engine is turned off. If the front wheel of the machine can deflect immediately and the handle is not heavy, it means that there is something wrong with the steering gear and it should be repaired or replaced immediately.
5. If there is serious leakage in the steering pump, the machine will turn slowly. Another important reason for the serious internal leakage of the steering pump is that the clearance between the side face of the rotor and blade of the steering pump and the end face of the side plate is too large.
Inspection method: when the performance of the steering cylinder, intermediate swivel and steering gear is in good condition, a new steering pump shall be installed for comparative test. If the steering performance recovers well after changing the pump, it is proved that the fault lies in the steering pump, and it shall be replaced in time.
6. When the spring force of the overflow valve of the hydraulic steering system is weakened, the steering cylinder can also work weakly, which makes the machine steering slowly.
Inspection method: remove the nylon plug from the base of the relief valve, install the oil pressure gauge, start the engine, turn the steering wheel to the left or right, and set obstacles on the side of the front wheel. If the pressure value is less than 7MPa, screw the adjusting screw of the relief valve in properly.
7. If the hydraulic oil is not clean or there are foreign matters in the oil tank, it will also cause the hydraulic steering system oil circuit is not smooth or the steering pump is stuck, which will also cause the machine to turn slowly. If it is not clean after inspection, replace the hydraulic oil and clean the hydraulic steering system in time.