Common fault causes of the hottest full hydraulic

Common failure causes of full hydraulic steering system

full hydraulic steering system has the advantages of flexible and light steering, stable performance, low failure rate, convenient layout and so on. It is widely used in the steering system of loaders, rollers, excavators and other wheeled construction machinery. Based on many years of maintenance experience, the author analyzes the common fault causes of the full hydraulic steering system in detail, and puts forward the corresponding troubleshooting measures, hoping to provide some references for readers

1 cause analysis and troubleshooting of heavy steering of full hydraulic steering system

1.1 insufficient oil suction

1.1.1 the oil tank is short of oil or the oil in the oil tank is insufficient

resulting in the failure of the oil pump to suck oil. Check the liquid level of the oil tank and add enough hydraulic oil

1.1.2 the oil viscosity is too high

the selection of hydraulic oil brand is inappropriate or the ambient temperature is too low, resulting in difficulty in oil absorption of the oil pump. Replace proper oil; Take measures to increase the temperature of hydraulic oil

1.1.3 filter blockage

causes the oil pump to suck oil or the oil circulation is not smooth. Clean or replace the filter element

1.1.4 the inner holes of the oil inlet and outlet pipes are blocked

which makes it difficult for the oil pump to absorb oil or cannot absorb oil. Clean the oil inlet and outlet pipelines

1.1.5 there is air in the circuit

causing the oil pump to empty. Remove air from the circuit

1.1.6 oil pipe joint leakage

tighten the oil pipe joint to ensure good sealing

1.2 oil pump failure

1.2.1 the oil pump is excessively worn and the internal leakage is serious. Check the working condition of the oil pump, repair or replace the oil pump

1.2.2 oil pump drive part failure. The drive belt slips or the drive gear (key) is worn. Check the oil pump, adjust the belt tension, repair or replace the drive gear (key)

1.2.3 oil pump connection failure. The connecting bolts of the oil pump are loose or missing. Check the connecting parts of the oil pump to ensure that the oil pump is firmly and reliably connected

1.3 manual steering check valve failure

manual steering check valve is not installed; The steel ball of the check valve is not tightly sealed with the valve seat; The steel ball of the check valve falls between the valve sleeve and the ring groove of the valve body; The check valve spring is damaged

all the above reasons can lead to the loose closing of the check valve during power steering, and the oil inlet and outlet are connected. Check and ensure that the check valve is installed correctly; Check whether the oil is clean. Clean the steering gear; Check the sealing between the steel ball and the valve seat of the check valve. If the sealing is not tight, it can be repaired by grinding, and then install a new steel ball

1.4 steering gear safety valve failure

the setting pressure of steering gear safety valve is too low; The steering gear safety valve spring is damaged; The steering gear safety valve seat is not tightly sealed, which has excellent chemical corrosion resistance; The steering gear relief valve body is damaged

the above reasons can cause the steering gear safety valve to fail and open in advance. Check the set pressure of the safety valve, the sealing condition of the valve seat, and whether the spring is deformed or invalid. If the spring force is insufficient, add shims between the spring and the spring seat

1.5 the valve core and valve sleeve are deformed, causing them to be stuck

install the machine and go to the oil inlet to fill a small amount of hydraulic oil. The rotating valve core should be flexible. If it is stuck, grind it. Sometimes, when tightening the bolts at the bottom of the steering gear, the force is uneven, and the valve core will also be stuck. The correct method is to tighten the bolts evenly at intervals

1.6 steering mechanism failure

insufficient tire pressure; The steering knuckle and kingpin are too tight or lack of oil; The steering knuckle thrust bearing is lack of oil or damaged; The deformation of the front beam and frame causes the misalignment of the front wheel alignment; The connection and adjustment of longitudinal and transverse tie rod ball joints are too tight or lack of oil; Too much kingpin tilt back, too much kingpin tilt in or negative front wheel tilt out: these can cause the driver to feel heavy and laborious when turning the steering wheel left or right, without a sense of righting; When the vehicle turns or turns around at low speed, it is very difficult to turn the steering wheel, or even unable to move. Troubleshooting: ensure normal tire pressure; The fit of steering knuckle and kingpin is appropriate and well lubricated; The thrust bearing of the steering knuckle is intact without lack of oil; No deformation of front beam and frame; The front wheels are well aligned

2 cause analysis and troubleshooting of steering wheel deviation

2.1 the positioning spring between the valve core and the valve sleeve in the steering gear is damaged or too soft, so that the valve sleeve cannot automatically return to the neutral position. At this time, the positioning spring must be replaced

2.2 the movement of the valve sleeve is blocked due to dirty oil. Clean the valve sleeve to make it move flexibly

2.3 the valve sleeve is not in the middle position because the position of the valve sleeve and the step of the valve core is offset. Disassemble and repair the valve sleeve and valve element, and replace them if necessary

2.4 the flow control valve is stuck, resulting in excessive oil pressure of the oil pump and excessive pressure difference between the left and right cavities of the steering cylinder. Disassemble and repair the flow control valve

2.5 one side steering cylinder seal is damaged. Disassemble and repair the steering cylinder seals

2.6 the two front tires have different pressures or diameters. Check and adjust the tire pressure

2.7 the deflection of the left and right front leaf springs is not equal. Check and adjust the deflection of the leaf spring, and replace the steel plate if necessary

2.8 the front and rear axles or frames are bent in the horizontal plane. Check and correct the deformation

2.9 both sides of the frame are responsible for the amplifier range transformation, data collection, data transmission, experimental mode selection and LCD wheelbase of the whole machine. Adjust and ensure that the wheelbase is equal

2.10 the tightness of the two front wheel hub bearings or hub oil seals is different. Check the bearing or oil seal

2.11 the wheels at both ends of the front and rear axles have unilateral braking or unilateral dragging. Check and adjust the braking condition of the wheels

2.12 the camber angle, caster angle or caster angle of the two front wheels are different

2.13 toe in is too large or negative. Check and adjust the toe in

2.14 the road camber is large or there is a lateral wind

3 cause analysis and troubleshooting of different weight of left and right steering

3.1 the valve core of the steering gear deviates from the middle position, or although it is in the middle position, it is inconsistent with the gap size of the valve sleeve shoulder. Check and ensure that the shoulder is well sealed and the valve element is in the middle position

3.2 there is dirt blockage between the valve core and the valve sleeve, which makes the resistance different when moving left and right. Disassemble and clean the steering gear to ensure that the hydraulic oil is clean

3.3 the adjusting nut is improperly adjusted. Check and readjust the nut

high end furniture utilization of water-based paint; In terms of innovation of new materials and technologies, incubation and cooperation, 3.4 the causes of steering wheel deviation can also lead to different degrees of left and right steering during vehicle driving

4 cause analysis and troubleshooting of heavy steering wheel during fast rotation

4.1 oil pump drive sometimes fails. The drive belt slips or the drive gear (key) is worn. Check the oil pump, adjust the belt tension, repair or replace the drive gear (key)

4.2 oil pump connection failure. The connecting bolts of the oil pump are loose or missing. Check the connecting parts of the oil pump to ensure that the oil pump is firmly and reliably connected

4.3 flow control valve failure. The flow control valve spring is too soft or leaks seriously, resulting in insufficient oil supply during sharp steering. Check the flow control valve and replace it if necessary

4.4 the safety valve fails or leaks seriously. Check the safety valve and replace it if necessary

4.5 the oil pump is excessively worn and has serious internal leakage. Check the working condition of the oil pump, repair or replace the oil pump

4.6 the wrong type of oil pump makes the oil supply insufficient. Replace the proper oil pump

5 cause analysis and troubleshooting of noise during steering

5.1 the oil tank is short of oil or oil in the oil tank is insufficient, and the oil pump is easy to absorb air during operation. Troubleshooting: check the liquid level of the oil tank and add enough hydraulic oil

5.2 the oil seal of the oil pump shaft head is damaged, and the oil pump is easy to absorb air during operation. Replace the shaft head oil seal

5.3 the oil pump drive sometimes fails. The drive belt slips or the drive gear (key) is worn. Check the oil pump, adjust the belt tension, repair or replace the drive gear (key)

5.4 if the low-pressure pipeline is damaged or the pipe joint is loose, air will enter the system when the oil pump is working. Check the low-pressure pipelines to ensure that the low-pressure pipelines and pipe joints are free of air leakage

5.5 the filter is blocked. Elimination measures; Check, clean or replace the filter element

5.6 the inner holes of oil inlet and outlet pipes are blocked. The oil pump has difficulty in absorbing oil or cannot absorb oil. Clean the oil inlet and outlet pipelines

5.7 the oil pump is excessively worn and has serious internal leakage. Check the working condition of the oil pump, repair or replace the oil pump

6 cause analysis and troubleshooting of serious shaking of steering wheel

6.1 the wear between the connecting pin and the connecting pin seat increases the gap. Check the gap and replace the connecting pin and the connecting pin seat if necessary

6.2 the steering wheel bearing is damaged. Replace the bearing

6.3 there is air in the steering cylinder. Loosen the oil port connector on one side of the oil cylinder, turn the steering wheel, and make the steering gear fill oil into the cavity of the steering cylinder that has not loosened the connector, until the loosened connector does not emit bubbles and only flows oil, then tighten the connector

7 cause analysis and elimination measures of front wheel swing

7.1 the rotating quality of front wheel (including tire, rim, brake drum or disc, wheel hub, etc.) is unbalanced. Troubleshooting: check and ensure that the dynamic balance of the rotating parts of the front wheel is good. Replace the corresponding accessories if necessary

7.2 the radial circle or end face circle runout of the front wheel is too large. Troubleshooting: correct or replace the corresponding accessories

7.3 retreaded tires are used for front wheels, or the tire patterns are inconsistent or the tire wear degree is different. Elimination measures; When assembling tyres, the tyres assembled on the same vehicle shall be of the same brand, structure and performance. If this cannot be achieved, tyres of the same brand, specification, pattern and type should be assembled on the same axle; Tyres with the same rim diameter and different widths cannot be mixed; Radial tire and diagonal tire cannot be mixed; Tyres with different section widths shall not be mixed; When replacing a new tire, the whole vehicle or coaxial tire should be replaced at the same time; Tyres with directional patterns shall be installed in the specified rolling direction

7.4 the camber angle of the front wheel is too small; The kingpin has a negative caster or the kingpin caster is too large; Or toe in is too large. Elimination measures; Check and adjust to make "three inclinations and one bundle" within a reasonable range

7.5 the caster angle or caster angle of the two front wheels are inconsistent

7.6 the ball joints of longitudinal and transverse tie rods are loose. Troubleshooting: repair or replace the pull rod ball joint

7.7 the front wheel hub bearing is loose. Elimination measures; Adjust or replace the bearing

7.8 the front suspension shock absorber fails or the efficiency difference between the left and right shock absorbers is too large. Troubleshooting: adjust or replace the front suspension shock absorber

7.9 the height or rigidity of the front suspension of the left and right frames (the leaf spring is shown in the thickness, length, number of pieces, arc height or the degree of newness and old) are too different. Troubleshooting: adjust or replace the leaf spring

7.10 the U-bolt of the front leaf spring is loose or the fit between the leaf pin and the bushing is loose. Elimination measures; Firm the bolt or replace the bushing

7.11 the movement of steering system and front suspension interfere with each other. Troubleshooting: check and adjust so that the steering system and the front suspension do not interfere with each other

7.12 bending and torsional deformation of front beam or frame. Elimination measures; Correct the front beam or frame

7.13 when the road roughness is too large, and the impact frequency of the road on the wheel is consistent with the natural frequency of the front beam angular vibration, the front wheel will swing under the influence of the gyroscope effect

8 the steering wheel rotates and cannot return to the neutral position cause analysis and troubleshooting

this fault occurs when the steering gear is repaired or disassembled for maintenance and reassembly, the relative position of the valve core and the valve sleeve is installed incorrectly, resulting in the disorder of the oil distribution relationship of the steering gear. Reassemble the linkage so that the mark on the linkage spline is aligned with the mark on the rotor spline