Reconstruction of Beijing Aisen Shock Absorbing System
Classification of shock absorbers
Structurally, there are
Single tube-shock absorbers that emphasize movement are mostly single tube, because the piston area is large, the damping oil directly contacts the outer tube, and the heat dissipation is fast, and there is only one piston. Twin tube)-Most original shock absorbers are double-tube type. The piston contacts the inner barrel through the piston and the bottom valve, and damping oil flows between the inner barrel and the outer barrel.
Classification of Beijing Eisen Shock Absorbing System
According to the position of damping piston rod and piston
Upright? -The piston rod of the shock absorber is located above the piston, and most shock absorbers are upright. Inverted? —— The damping piston rod is located below the piston. The biggest advantage is that under the premise of ensuring the strength of the shock absorber, there is no need to use too thick shock absorber core (because the outer wall of the working cylinder also plays a guiding role), and the unsprung weight is reduced. When riders modify shock absorbers, there are generally two options.
Fixed damping shock absorber
Billstam B8 series is common in Europe, and KYB yellow barrel series is common in Japan. The damping of this kind of shock absorber is fixed by the factory engineer through continuous optimization (that is, my current work), which is dedicated to special vehicles and the barrel can't be opened.
The damping of the shock absorber achieves the balance between sportiness and comfort, which is suitable for those car owners who just want to make their cars more sporty and don't want to be bothered by the adjustment of the twisted-tooth shock absorber.
This kind of shock absorption is generally matched with the original spring or supporting short spring, which is less difficult to install but has obvious effect and is a worry-free choice.
Damping adjustable shock absorber
Presumably, this type of shock absorber is the one that most cool car friends are interested in.
Because the damping can be adjusted, a set of shock absorbers can be matched with different springs to bring different driving feelings. Very suitable for riders who like to toss, study and get off the track.
At the same time, it can be divided into two types: full-length fixed type and full-length adjustable type, which are related to the pre-tightening force of the spring. Among the common adjustable damping tooth dampers in the market, KWV1–V3, Bilstein B 14/B 16 and Steinsaz are all fixed in full length. Changing the vehicle height will affect the working range of the spring.
According to the number of adjustable channels, it is divided into the following categories, and we will explain it to you by borrowing the BC brand model.
1 direction adjustment
Only one knob can change the compression and rebound damping at the same time: V 1, BR, DR and RM of BC product line are all shock absorbers with 1 mode adjustment (where RM is an inverted shock absorber).
Bidirectional regulation
Two knobs, one for compression and one for rebound: er with external nitrogen cylinder and HM with inverted shock absorber.
Three-way regulation
Three knobs, one for low-speed compression, one for high-speed compression and one for rebound.
Four-way regulation
Four knobs, high and low speed compression and high and low speed rebound: BC products have no 4-way adjustment for the time being, which represents the TTX series models in olins.
Shock absorber with external nitrogen tank
ER and ZR, which can adjust the nitrogen pressure BC, are the models of take-away nitrogen bottles.
As for the adjustment of damping, it will be mentioned in later chapters.
Internal structure and damping curve of shock absorber
First of all, we should understand what damping is, what damping the shock absorber has, what feelings different damping gives people, and what factors will affect these feelings.
What is damping?
Damping can be described in the simplest way, that is, when the piston moves up and down in damping oil, the oil passes through the hole on the piston and pushes the valve plate away. Resistance is usually proportional to the speed at which the piston moves.
Oil passes through the holes of the piston or bottom valve, and damping force is generated by pushing open the valve plate group covering these holes.
As for the direction of the hole on the piston, the height of the step, the shape and thickness of the valve plate, the collocation of the whole valve plate group is very complicated knowledge, which is mastered by every manufacturer.
The real development of shock absorber is more about the choice of piston and the matching of valve plate. Without professional knowledge system and skills, ordinary riders can't do it, so these contents are not discussed in this paper.
We are more concerned about how to change the damping curve of the shock absorber through the external knob.
When the volume of the piston rod immersed in the shock absorber decreases, the resistance is the rebound damping force, and when the volume increases, the resistance is the compression damping force. When the reaction force is on the wheel, the upward movement of the wheel is compression damping and the downward movement of the wheel is rebound damping.
Because the spring provides great force when the wheel goes up, the compression damping is much smaller than the rebound damping.
The abscissa is the piston movement speed, and the ordinate is the damping force. The upper part is rebound damping and the lower part is compression damping.
Here comes the point!
The low-speed damping and high-speed damping of the shock absorber do not refer to the vehicle speed, but to the speed of piston movement.
Generally speaking, the low speed is below 0. 1m/s, the medium speed is between 0. 1m/s and 1m/s, and the high speed is above 1m/s. The corresponding situations are the body movement during cornering and cornering, daily ups and downs and the piston when passing through the speed bump.
Composite cylinder shock absorber
The inner cylinder of the multi-cylinder shock absorber is the working chamber, and there is a bottom valve between the inner and outer cylinders, which mainly controls the compression damping (the valve group on the compression side is thick), and the piston mainly controls the rebound damping (the valve group on the rebound side is thick). The compound barrel has large oil loading capacity, long working stroke and good comfort. At present, there are the following models of multi-barrel torsional shock absorbers on the market:
Stan-Salz, Salz, FZ, SF series Cusco Street series KW V series.
As mentioned just now, the compression damping of the composite cylindrical shock absorber is mainly provided by the bottom valve, and the 1 road composite cylindrical shock absorber whose damping is adjusted by the central knob of the shock absorber core in the market can basically only adjust the rebound damping.
In order to prevent the oil pair from reversely flowing through the needle valve during the compression stroke, there is a 1 check valve at the top of the piston, which is a single valve.
Adjustment of Beijing Eisen Damping System
Then add some high-order shock absorbers with compression adjustment, taking KW V3 as an example.
The knob above the shock absorber core controls the rebound stroke bypass flow, while the bottom valve knob controls the compression stroke bypass flow.
3/4 direction adjustment
Usually 3-way adjustment will divide the compression damping into low speed and high speed (remember the speed of the piston), and the high-speed compression damping usually corresponds to the situation of pressing on the shoulder. More advanced is 4way adjustment, and the compression rebound can be adjusted at high and low speeds respectively.
Usually, adjusting the damping at low speed will improve the damping at full speed, but the force value at the valve opening point (inflection point on the curve) remains unchanged.
Adjusting the high-speed damping only affects the valve opening point, but has little effect on the low-speed damping and the slope of the whole curve. If you want to change the adjustment range of damping, you need to change the hardware configuration of the valve plate group (valve plate, spring).
The advantages of this kind of shock absorber are: low manufacturing cost, which is beneficial to mass production; The existence of the outer cylinder can make the damping oil of the inner cylinder flow out, and the oil chamber and the air chamber are not in a straight line, which has a longer actuating stroke; Adopt low-pressure nitrogen seal, which is more comfortable than single cylinder and reduces piston resistance; The double-cylinder design improves the influence of the deformation of the outer cylinder on the movement of the inner piston.
Disadvantages: less damping oil storage and poor heat dissipation; The diameter of piston is smaller than that of single cylinder; When the shock absorber is in the extension stroke, the shock absorber oil with atmospheric pressure absorbed from the oil chamber of the piston lower cavity is easy to generate eddy vacuum, and bubbles are generated when it is dissolved in the oil; Damping oil and air are not completely separated, and oil-gas mixing may occur. Double tube design is heavier than single tube shock absorber.
Single tube shock absorber
Function of Beijing Eisen Shock Absorbing System
The single-tube shock absorber has only one working chamber, and the piston is in direct contact with the inner wall of the working chamber.
The piston is immersed in damping oil, and the lower part of the damping cylinder is high-pressure gas encapsulated by floating piston, in which the air pressure can reach 20bar. Without an external nitrogen bottle, the piston directly controls the rebound and compression damping.
Characteristics of Beijing Eisen Shock Absorbing System
This is the most common twisted-tooth shock absorber structure on the market. Single cylinder, upright, 1 directional adjustment.
As you can clearly see, the knob we usually turn is the green arrow in the figure, which changes the amount of oil that does not pass through the piston and valve group.
Therefore, when the knob is completely closed clockwise (i.e. the hardest), the damping is determined by the piston valve plate. When the knob rotates counterclockwise gradually, the amount of oil flowing through the piston valve plate group increases gradually, and the damping becomes smaller and smaller.
Because oil can flow from two directions, the knob adjusted by 1-way affects both compression and rebound damping.
When ordinary riders use this kind of shock absorber, they may have good support and poor comfort, or good support and poor comfort. There is always something you are not satisfied with.
When you want good support, you need to increase the damping, but at the same time, if the rebound damping is too large, the body will bump. The opposite is true.
In order to solve the problem that a knob affects compression and rebound at the same time, there are more advanced 2-way adjustable shock absorbers.
If you want to use the shock absorber core to only control compression or rebound, it is very simple. You only need to add a one-way valve at the top of the piston on the basis of 1 pass, so that the needle valve of the shock absorber core can only control one-side damping (oil cannot pass through the shock absorber core from the compression side).
However, the single-tube shock absorber only has a piston valve without a bottom valve, so the usual practice is to add a nitrogen tank and a one-way regulating valve for compression stroke on the channel between the working cylinder and the nitrogen tank to realize two-way adjustment.
In general, the shock absorber with 3-way adjustment will be equipped with an additional nitrogen cylinder, which is separated from the oil and gas through IFP- internal floating piston.
Rebound damping is still on the shock absorber core, and high and low speed compression damping are all on the nitrogen cylinder to control the damping of damping oil flowing into the nitrogen cylinder. Among them, low-speed damping is the flow controlled by needle valve; High-speed damping is to adjust high-speed damping by changing the pre-tightening force of the spring on the valve group.
At the same time, at the bottom of the external nitrogen tank, there is also a gas nozzle filled with nitrogen to control the nitrogen pressure of the whole system. However, the nitrogen pressure is too high, the initial pressure of the system is too high, and the resistance of the floating piston in the nitrogen tank is too large, so the system is easy to overheat due to friction.
The resulting improvement method is to replace the floating piston (IFP) with an airbag, which has the advantages of no friction and no heat generation. The initial stage of compression is sensitive.
Advantages of this kind of shock absorber: simple structure; The piston area is large, the damping oil flow per unit time is large, the large instantaneous pressure can be eliminated, and the reaction is fast; Single cylinder design, large oil storage, good heat dissipation effect, effectively reducing the negative impact of damping oil foaming and damping thermal attenuation.
Disadvantages: the oil chamber and air chamber are in-line configuration, and the stroke is limited; The oil seal needs a high degree of pressure resistance, because it directly bears the pressure in the upper cavity of the piston when it is actuated, and it needs special attention, because its processing needs high precision and fineness; Because the piston is in direct contact with the shock absorber cylinder, the shock absorber is easy to be scrapped because the cylinder is slightly damaged by foreign objects, and the diameter of the piston rod is small, so the suspension structure with excessive lateral force is not adopted. The inverted single-tube shock absorber can reduce the influence of lateral force to a certain extent by shifting the center of gravity of the cylinder on the suspension, but due to the design of the structure itself, it still cannot completely improve the consequences of scrapping the shock absorber due to cylinder injury. )
Generally speaking, single-cylinder and multi-cylinder shock absorbers have their own advantages and disadvantages: the oil chamber and gas chamber of multi-cylinder are not vertically distributed, and the working stroke of piston is longer than that of single-cylinder shock absorber; Double cylinder is filled with low pressure nitrogen, which is better than single cylinder in comfort; The design of the compound cylinder greatly improves the consequences of directly scrapping the shock absorber because the cylinder is impacted and deformed by external force; Single-tube shock absorber can contain more damping oil in the same volume, improve heat dissipation efficiency and improve damping attenuation; The piston area of single-cylinder shock absorber is larger than that of double-cylinder shock absorber, and the compression area increases accordingly, which can stably produce slight damping, and the damping oil and gas are completely separated, and there will be no mixed discharge of oil and gas; The unique single-cylinder inverted design greatly improves the lateral stress problem, reduces the unsprung weight, and greatly improves the response sensitivity of the shock absorber and the handling of the car; The double-barrel design of composite barrel directly leads to heavier weight than single barrel.
The manufacturing cost, comfort and durability of compound cylinder are better than that of single cylinder. Most original cars or street upgrade kits prefer the composite cylinder design, but the response sensitivity, fatigue resistance and heat dissipation of single-cylinder shock absorber are higher than those of composite cylinder, so the single cylinder is more competitive in design positioning. There is no good or bad shock absorber, only the one that suits you is the best!
Problems needing attention in refitting Beijing Eisen damping system
I hope everyone will pay more attention to the following in the future modification process:
★ Shock absorber is a component directly related to driving safety. When choosing a shock absorber, you must choose a big factory product with excellent quality. Never choose inferior products for cheap. You'd rather not change them to ensure safety.
★ When replacing the shock absorber, be sure to know your own needs. Changing the sports shock absorber will bring about problems such as decreased comfort and reduced passability. At the same time, it is best to do it in one step to avoid greater losses caused by unsatisfactory replacement in the future;
★ You must go to an experienced refit shop to replace the shock absorber, and you need a certain technical foundation to adjust the shock absorber. You must not blindly adjust yourself;
★ Shock absorption is not as low/as hard as possible, and the balance of the whole vehicle must be taken into account.