Absorber is used to suppress the vibration and impact from the road surface during the rebound of a spring after absorption. Widely used in automobiles to accelerate the attenuation of frame and body vibrations and improve the smoothness of vehicle travel. When passing through uneven road surfaces, although the shock absorber spring can filter the vibration of the road surface, the spring itself will also have reciprocating motion, and the shock absorber is used to suppress this spring jumping.
working principle
In the suspension system, vibration is generated due to the impact of elastic elements. To improve the smoothness of vehicle driving, shock absorbers are installed in parallel with elastic elements in the suspension. To attenuate vibration, hydraulic shock absorbers are often used in the suspension system of automobiles. Their working principle is that when there is relative motion between the frame (or body) and the axle due to vibration, the piston inside the shock absorber moves up and down, and the oil in the shock absorber chamber repeatedly flows from one chamber to another through different pores. At this time, the friction between the hole wall and the oil, as well as the internal friction between the oil molecules, form damping forces on the vibration, converting the vibration energy of the car into oil thermal energy, which is then absorbed and emitted into the atmosphere by the shock absorber. When the cross-section and other factors of the oil channel remain unchanged, the damping force increases or decreases with the relative motion speed between the frame and the axle (or wheel), and is related to the viscosity of the oil.
Shock absorbers and elastic components bear the task of buffering and damping. Excessive damping force can deteriorate the elasticity of the suspension and even damage the shock absorber connectors. Therefore, it is necessary to adjust the contradiction between the elastic element and the shock absorber.
(1) During the compression stroke (when the axle and frame are close to each other), the damping force of the shock absorber is relatively small, in order to fully utilize the elastic effect of the elastic element and alleviate the impact. At this point, the elastic element plays a major role.
(2) During the suspension extension stroke (with the axle and frame moving away from each other), the damping force of the shock absorber should be high, quickly reducing the impact.
(3) When the relative speed between the axle (or wheels) is too high, it is required that the shock absorber can automatically increase the fluid flow rate to maintain the damping force within a certain limit, in order to avoid bearing excessive impact loads.
Tube type shock absorbers are widely used in automotive suspension systems, which can provide shock absorption during both compression and extension strokes, known as bi-directional shock absorbers. There are also new types of shock absorbers, including inflatable shock absorbers and resistance adjustable shock absorbers.
Explanation of the working principle of the two-way action cylinder shock absorber: During the compression stroke, when the car wheels move closer to the body, the shock absorber is compressed, and the piston inside the shock absorber moves downward. The volume of the lower chamber of the piston decreases, the oil pressure increases, and the oil flows through the flow valve to the chamber above the piston (upper chamber). Part of the space in the upper chamber is occupied by the piston rod, so the increased volume in the upper chamber is smaller than the decreased volume in the lower chamber. As a result, some of the oil pushes open the compression valve and flows back to the oil storage cylinder. These valves contribute to the damping force of compression motion in the suspension by conserving oil. When the shock absorber is extended, the wheels move away from the body and the shock absorber is stretched. At this point, the piston of the shock absorber moves upwards. The oil pressure in the upper chamber of the piston increases, the flow valve closes, and the oil in the upper chamber pushes open the expansion valve and flows into the lower chamber. Due to the presence of the piston rod, the oil flowing from the upper chamber is not sufficient to fill the increased volume of the lower chamber, which mainly creates a vacuum degree in the lower chamber. At this time, the oil in the oil storage cylinder pushes open the compensating valve 7 and flows into the lower chamber for replenishment. Due to the throttling effect of these valves, they provide damping for the suspension during stretching motion.
Due to the design of the stiffness and preload force of the tension valve spring being greater than that of the compression valve, under the same pressure, the total channel load area of the tension valve and its corresponding normally open gap is smaller than the total cross-sectional area of the compression valve and its corresponding normally open gap channel. This makes the damping force generated by the extension stroke of the shock absorber greater than the damping force generated by the compression stroke, achieving the requirement of rapid shock absorption.
Product Usage
To accelerate the attenuation of frame and body vibrations and improve the ride comfort of cars, shock absorbers are installed inside most car suspension systems.
The shock absorption system of a car is composed of springs and shock absorbers. Shock absorbers are not used to support the weight of the vehicle, but to suppress the vibration caused by spring rebound and absorb the energy of road impact. Springs play a role in mitigating impacts, transforming "high-energy single impact" into "low-energy multiple impacts", while shock absorbers gradually reduce "low-energy multiple impacts". If you have driven a car with a broken shock absorber, you can experience the bouncing of the car after passing through every pothole and undulation, and the shock absorber is used to suppress this bouncing. Without a shock absorber, it is impossible to control the rebound of the spring. When the car encounters rough roads, it will produce severe bouncing, and when cornering, the up and down vibration of the spring will also cause the loss of tire grip and tracking.
Matching skills
1, Check if the product provides a 2-3 inch height requirement. Some products only provide a 2-inch height requirement, and it is easy to pull to the limit and cause damage in off-road situations when used reluctantly until a 3-inch height is reached.
2, Whether the diameter of the center telescopic rod of the shock absorber can reach 16 millimeters or more is a basic indicator of strength.
3, Whether the upper and lower connecting sleeves of the shock absorber are high-strength polyurethane sleeves is also an important basis for ensuring long-term high-strength use, as ordinary rubber is difficult to use for a long time under high strength.
Shock absorbers are mainly used to suppress the vibration and impact from the road surface during the rebound of springs after absorption. When passing through uneven road surfaces, although the shock absorber spring can filter the vibration of the road surface, the spring itself will also have reciprocating motion, and the shock absorber is used to suppress this spring jumping. If the shock absorber is too soft, the body will jump up and down, and if the shock absorber is too hard, it will bring too much resistance, hindering the normal operation of the spring. Shi Xiaohui stated that in the process of modifying the suspension system, hard shock absorbers should be paired with hard springs, and the hardness of the springs is closely related to the weight of the vehicle. Therefore, heavier cars generally use harder shock absorbers. Continuous experimentation is required during modification to design the optimal combination of shock absorbers and springs. Professional modification shops can generally find the best combination for car owners.
Oil leakage fault
If a car shock absorber leaks oil, it is undoubtedly a very dangerous thing for the shock absorber. So, once an oil leak is discovered, timely remedial measures should be taken. The key inspection items are the oil seal gasket, seal gasket rupture and damage, oil storage cylinder cover, and checking whether these components have loose nuts.
If oil leakage is found, first tighten the oil cylinder head nut. If the shock absorber still leaks oil, it may be due to damage and failure of the oil seal and sealing gasket, and a new seal should be replaced. If the oil leakage still cannot be eliminated, the shock absorber rod should be pulled out. If there is any jamming or uneven weight, further check whether the gap between the piston and the cylinder is too large, whether the shock absorber piston connecting rod is bent, and whether there are scratches or pull marks on the surface of the piston connecting rod and the cylinder.
If there is no oil leakage in the shock absorber, the connecting pins, connecting rods, connecting holes, rubber bushings, etc. of the shock absorber should be checked for damage, detachment, cracking, or detachment. If the above inspection is normal, the shock absorber should be further disassembled to check whether the clearance between the piston and the cylinder is too large, whether the cylinder is pulled, whether the valve seal is good, whether the valve disc and valve seat are tightly fitted, and whether the tension spring of the shock absorber is too soft or broken. Depending on the situation, repair should be carried out by grinding or replacing parts.
In addition, shock absorbers may produce noise during actual use, mainly due to collisions with steel plate springs, frames or shafts, damage or detachment of rubber pads, deformation of shock absorber dust cylinders, insufficient oil, and other reasons. The cause should be identified and repaired.
After inspection and repair, the shock absorber should undergo performance testing on a specialized test bench. When the resistance frequency is 100 ± 1mm, the resistance during the extension and compression strokes should comply with the regulations. The maximum resistance of Cheng is 392~588 N; The maximum resistance during the extension stroke of Dongfeng vehicles is 2450-3038N, and the maximum resistance during the compression stroke is 490-686N. If there are no experimental conditions, we can also adopt an empirical approach, which is to insert an iron rod into the lower end suspension ring of the shock absorber, step on both ends with both feet, hold the upper suspension ring with both hands and pull it back and forth 2-4 times. When pulling upwards, there is a lot of resistance, and when pressing downwards, there is no effort. Moreover, the resistance to stretching has recovered compared to before repair, and there is no sense of empty stroke, indicating that the shock absorber is basically normal.
