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In order to quickly attenuate the vibration of the frame and the body and improve the smoothness and comfort of the car, shock absorbers are generally installed on the vehicle suspension system. Currently widely used in cars is a two-way drum shock absorber. The shock absorber is a wearing part during the use of the automobile, and the work of the shock absorber is good or bad, which will directly affect the smooth running of the automobile and the life of other parts.
First, the shock absorber works
Hydrodynamic two-way cylinder shock absorbers are generally mounted on the outside of the front suspension of the vehicle and are connected to the frame and the bracket on the axle via rubber bushes and connecting pins, respectively. The shock absorber has three concentric steel cylinders, the outer cylinder is a dust cover, the middle is a storage cylinder, and the inside is a working cylinder; the upper end of the piston rod is integrated with a dust cover and a lifting ring, and the piston is fixed at the lower end. The expansion valve and the circulation valve are installed; the compression valve and the compensation valve are installed on the lower bearing of the cylinder. When the shock absorber is working, the storage cylinder and the work cylinder are moved together with the axle, and the dust cover, the piston rod and the piston move together with the frame. The working cylinder is filled with oil and the cylinder contains a certain amount of oil. The upper part of the cylinder is equipped with a guide seal. The flow-through valve and the compensation valve are one-way valves. The spring is soft and can be opened or closed by a small hydraulic pressure. The extension valve and the compression valve are unloading valves, and the oil pressure of opening and closing is high. The work process of the shock absorber is divided into two strokes: compression and extension.
As the axle moves closer to the frame, the shock absorber is compressed. During the compression stroke, the piston moves down, so that the volume of the lower chamber is reduced and the oil pressure is increased; the volume of the upper chamber is increased and the oil pressure is reduced; the flow valve of the lower chamber is opened and the flow-through valve enters the upper chamber of the piston. Because the piston rod occupies part of the upper chamber volume, the increased volume of the upper chamber is less than the reduced volume of the lower chamber, excess fluid can only open the compression valve into the reservoir cylinder. The throttling resistance generated when the oil flows through the above-mentioned valve hole dampens the vibration of the frame and attenuates the vibration. At this time, the special structure of the circulation valve and the compression valve make the hydraulic pressure and the damping force not too large, and the leaf spring can fully exert the buffering and damping effect.
Second, shock absorber disassembly
When the shock absorber is disassembled, dust on the outer surface of the shock absorber housing is first cleaned, and the lower connection ring of the shock absorber is clamped on the vise. Pull on the rings, pull the shock absorber as far as possible, clamp the oil reservoir assembly vertically on the vise, and use a special wrench to unscrew the top cover. Pull up the dust cover upwards, and the connecting rod assembly, connecting rod, guide seat and piston assembly can be completely removed from the cylinder barrel.
The damper assembly sequence is as follows: Turn the dust cover with connecting rod upside down and clamp the upper ring with a vise. Install the oil reservoir nut, connecting rod oil seal cap, seal ring, connecting rod oil seal, oil seal washer, oil seal spring and guide seat. The limit seat is reversed on the step at the front end of the connecting rod, and then the flow-through valve spring piece, the flow valve piece, the piston, the return valve piece, the bearing seat, the return valve spring, and the compression nut are sequentially loaded. With the hand pressure, the compression valve assembly is pressed into the working cylinder to bring it into close contact. Hold the lower ring of the oil tank above the vise and install the cylinder assembly into the oil tank so that the end of the compression valve is downward. According to the relevant requirements, inject proper amount of oil. Put the connecting rod of the piston into the working cylinder so that the end of the guide seat fits into the working cylinder. Position the rubber seal ring on the guide seat and use a special spanner to tighten the oil reservoir nut.
Third, the shock absorber parts repair requirements
1. Rings. When the desoldering rings need to be welded, they must be grooved and the rings should be in the center of the cylinder without skewing. Otherwise, after the installation, there will be “destroyed†and cause excessive wear or damage.
2. The storage tank is the main component of the shock absorber, and the inspection must be carried out in the following aspects: The screw part must not be disorderly buckled or slipped. Otherwise, the storage tank nut could not be tightened, causing the work cylinder to bob up and down, not only generating noise. It will also cause deformation, directly affecting the vehicle's adhesion performance and driving safety.
3. The shock absorber leaks at the connecting rod, mostly due to the damage of the oil seal, and the excessively worn oil seal and the aged oil seal should be replaced.
4. The outer diameter of the piston has a very important influence on the stability of the damper resistance. The valve line that acts as a seal on the outer surface of the piston, once broken by the valve plate, directly affects the vibration-damping performance of the shock absorber and can be restored after repair. The method of repair is to use auxiliary tools to grind manually or with higher precision, so that the throttle orifice can reach the corresponding accuracy, and ensure that the valve wire plane is 0.03-0.05 mm higher than the bearing surface, which can obviously increase the resistance of the shock absorber. If the valve line is damaged in many places, the piston cannot be repaired and new parts should be replaced.
5. The four claws of the compression valve leaf spring are deformed or broken, so that the damping resistance of the shock absorber is reduced or lost. Since the compression valve assembly is riveted and riveted into a non-detachable unit, the assembly can only be replaced if necessary.
6. After long-term use, the damper fluid will become black and thicken. If the piston is a cast iron or powder metallurgy piston, the oil will contain powdered iron scraps that can be milled by hand. When the damper oil turns black, the oil must be replaced.
7. When welding the cylinder barrel base and the oil storage cylinder, the oxide scale and welding slag produced by high-temperature seam welding are likely to remain in the bottom of the cylinder and will fall off under the scour of high temperature and high pressure liquid flow, blocking the orifice or being sandwiched between the cylinder and the piston. Pull the cylinder and piston. Therefore, it is best to use high-pressure or ultrasonic cleaning of the fuel tank, cleaned and blown with compressed air.
8. Three embossing points are usually punched on the base of the cylinder to position the compression valve seat on which the cylinder is to be placed. Because the stamping deformation is large, cracks are easily generated at the root of the protrusion and oil leakage occurs. Therefore, the pressure of the oil storage tank must be checked.
9. The three embossing points of the storage cylinder should be located in the same conical surface and should be centered after the cylinder is placed on. If the three rods do not reciprocate when the connecting rod is not in the same conical surface, the working cylinder will sway with it, which will not only generate noise, but also cause the connecting rod and cylinder to issue cards, which will cause early wear and tear. In order to identify the above faults, the position of the embossment can be observed by comparing the light after the shock absorber is disassembled and cleaned. If there is a significant bright point, it means that the convex point and the other two convex points are not on the same conical surface. The cylinder can also be placed in the reservoir to see if it is centered. If no skew occurs, it means that the three convex points are not on the same cone surface.