What Is Vibration Damping?

Shock absorber, English] Shock absorber is a device to accelerate the attenuation of the frame and body vibration to improve the ride comfort (comfort) of the car. The shock absorber is installed inside the suspension system of most cars.

Shock absorber, English] Shock absorber is a device to accelerate the attenuation of the frame and body vibration to improve the ride comfort (comfort) of the car. The shock absorber is installed inside the suspension system of most cars.

Chinese name

Shock absorber

Foreign name

Shock absorber

Function

Absorb vibration energy, accelerate vibration attenuation, etc.

Location

Car suspension system

Classification

Double acting cylinder type, inflatable type, etc.

Technical characteristics of shock absorber

When the frame and the axle are reciprocating relative to each other, and the piston in the shock absorber also reciprocates in the cylinder, the oil in the shock absorber shell repeatedly passes through a small cavity through an inner cavity. Into another lumen. At this time, the friction between the hole wall and the oil and the internal friction of the liquid molecules form a damping force on the vibration, so that the vibration energy of the vehicle body and the frame is converted into thermal energy, which is absorbed by the oil and the shock absorber shell, and Into the atmosphere. The magnitude of the damping force of the shock absorber increases and decreases with the increase and decrease of the relative speed of the frame and the axle (or wheel), and is related to the viscosity of the oil. It is required that the viscosity of the oil used in the shock absorber is as small as possible affected by temperature changes; and it has the properties of anti-vaporization, anti-oxidation, and non-corrosive effect on various metal and non-metal parts. As shown in Figure 1. ^[1]

Figure 1 Schematic diagram of shock absorber installation

Shock absorber classification

There are three types of shock absorbers used in automobiles: two-way barrel shock absorbers, inflatable shock absorbers, and adjustable damping shock absorbers.

The double-acting barrel damper is generally composed of 4 valves, 3 cylinders, two lifting ears, and a piston and piston rod, as shown in Figure 2.

Figure 2 Schematic diagram of a double-acting cylinder damper

The cylinder tube 10 is a dust cover. The cylinder 5 is an oil storage cylinder, which contains a part of the oil, and the lower end of the cylinder 5 is connected to the axle through lifting eyes welded to the base. The cylinder tube 2 is a working cylinder, which is filled with oil and sealed at the upper end. The upper end of the piston rod 1 is welded integrally with the dust cover 10 and the lifting lug to the frame, and the lower end is provided with a piston 3. The piston divides the working cylinder into upper and lower chambers. There are extension valve 4 and flow valve 8 on the piston. A compression valve 6 and a compensation valve 7 are arranged on a support at the lower part of the working cylinder. The springs of the flow valve and the compensating valve are relatively soft and can be closed or opened by lower oil pressure. The springs of the compression valve and the extension valve are relatively hard, and require a large oil pressure to open, and the oil pressure is lowered and closed immediately.

The working principle is that when the frame and the axle make relative reciprocating movements, and the piston reciprocates in the cylinder, the oil in the shock absorber reciprocates between two isolated internal chambers through the narrow pores on the valve. Due to the friction between the hole wall and the oil and the internal friction of the liquid molecules, a damping force is formed, so that the mechanical energy of the body vibration is converted into thermal energy, which is absorbed by the oil and the shell, and then dispersed into the atmosphere. The damping force is related to the cross-sectional area through the oil passage, the valve spring stiffness, and the viscosity of the oil.

When the wheel jumps up, the shock absorber is compressed, and the piston moves downwards relative to the cylinder, so the volume of the lower chamber of the working cylinder decreases, the oil pressure rises, and the oil flows into the upper chamber of the working cylinder through the flow valve. Because the upper cavity takes up a part of the space by the piston rod, the increased volume of the upper cavity is smaller than the reduced volume of the lower cavity, so a part of the oil pushes open the compression valve and flows back to the oil storage cylinder 5. These valves restrict the oil flow. Damping force for compression motion of suspension. When the wheel falls, the shock absorber is stretched, and the piston moves up the cylinder, so the oil pressure in the upper chamber of the working cylinder rises, the flow valve closes, and the oil pushes the extension valve into the lower chamber. Similarly, due to the existence of the piston rod, the oil flowing from the upper cavity into the lower cavity is not sufficient to fill the increased volume of the lower cavity, and a certain degree of vacuum is generated in the lower cavity. At this time, the oil in the oil storage cylinder opens the compensation valve and flows into the lower cavity. supplement. In this process, the throttle effect of the valve forms a damping force on the extension movement of the suspension.

The inflatable shock absorber consists of a cylinder, two pistons, a seal ring and two valves. As shown in Figure 3.

Figure 3 Inflatable shock absorber

The working cylinder is equipped with a working piston and a floating piston. The working piston is on the upper side and the floating piston is on the lower side. The working cylinder is divided into three parts. The closed air chamber formed between the lower part of the floating piston and the cylinder is filled with high-pressure nitrogen, and the large-section O-ring seal at the edge of the floating piston separates the oil above the floating piston from the nitrogen below. The working piston is provided with a compression valve and a stretch valve that can change the passage area of the channel as the piston's movement speed changes. Both valves are composed of a set of spring steel sheets of the same thickness and different diameters, arranged from large to small.

When the wheels move relative to the frame, the working piston reciprocates in the oil, causing a pressure difference between the upper and lower chambers of the working piston, and then the pressure oil pushes the compression valve or extension valve to flow back and forth. Because the valve produces a large damping force on the pressure oil, the vibration is attenuated. The cylinder volume change caused by the existence of the piston rod is compensated by the up and down movement of the floating piston.

A piston with adjustable resistance damper is installed in the cylinder, and a hollow connecting rod is installed in the middle hole of the piston. The upper end of the hollow connecting rod is fixed on the lower casing of the air chamber. A plunger rod and a plunger are also installed in the hollow connecting rod. The upper end of the plunger rod abuts on the spring seat and the diaphragm. A spring is installed between the spring seat and the plunger rod. The lower end of the hollow connecting rod is provided with a throttle hole near the upper surface of the piston. As shown in Figure 4.

Figure 4 Schematic diagram of adjustable resistance shock absorber

Drag-adjustable shock absorbers are used on suspensions with air springs. When working, as the load of the car increases, the air pressure in the air spring increases, and the air pressure in the air chamber communicating with it increases, and presses the diaphragm downward until it is in equilibrium with the pressure generated by the spring. When the diaphragm is moved down, the plunger rod and the plunger at its lower end are also pressed to move down. When the position of the plunger relative to the orifice on the hollow connecting rod starts to be blocked, the cross-sectional area of the orifice begins to decrease, so the amount of liquid passing through the orifice decreases, that is, the resistance to oil flow is increased. When the load of the car is reduced, the plunger moves up, and the flow passage area of the orifice increases, which reduces the flow resistance of the oil.

Shock Absorber Replacement Cycles and Options

The shock absorber is usually checked every 100,000 kilometers, and the maintenance intervals between different models may be slightly different.

1. Before purchasing goods, please be sure to check the car model, displacement and other information to ensure that you buy the correct model accessories. You can find your car maintenance manual.

2. There are four shock absorbers on each car, which are front left, front right, rear left, and rear right. If the shock absorbers need to be replaced, it is best to replace them two at a time. There is one front or rear shock absorber. When the problem occurs, it is necessary to replace the front shock absorber or the rear shock absorber with FAW to avoid uneven load on the car's balance, which causes the shock absorber to have different forces, and a shock absorber problem occurs.

3. Choose quality products. Although counterfeit shock absorbers are inexpensive, their life span is less than half of the original shock absorbers. During the stretching process, oil leakage will occur due to poor sealing, and oil leakage will not play a damping role, and a severe bumpy feeling will be generated when driving. What's more, it will suddenly fail during high-speed driving, causing the body to tilt, and the safety of people and vehicles will be seriously threatened.