Different models have different tendencies, sports, comfort, grocery shopping... But comfort and exercise are the two ends of the scale, strong exercise, comfort will decline, but some people say, are adults, can you want it? Thus, the variable suspension appeared.
For the suspension system, it is inseparable from two elements, the elastic element and the damping element, the former represents the spring and the latter represents the damper, and the variable suspension changes these two. The gas spring can change the elastic coefficient K, while the adjustable damping shock absorber can change the damping factor C.
In general, adjustable damping shock absorbers can be used alone, while air springs are used in conjunction with adjustable damping shock absorbers. There are exceptions, that is, Tesla's Model X, which has an air spring, but no damping adjustable, and its air spring mainly plays a role in adjusting the height of the body.
Compared with the two, the adjustable damping shock absorber has a relatively low cost, better reliability, and more applications in the model. This session will talk about adjustable damping shock absorbers.
How does the damping of the shock absorber affect the vehicle's mobility and comfort?
The process of the vehicle driving on the road, after simplification and simplification, can be regarded as a whole of suspension and wheels, which is a single degree of freedom with damping free vibration process. It can be described with a formula:
That is, the acceleration (vibration) of the body is inversely proportional to the mass of the vehicle, and is proportional to the unevenness of the road surface, damping, elastic coefficient, and speed, and the heavier the body, the smaller the vibration; the more uneven the road surface, the faster the speed, the harder the suspension, the greater the vibration.
Among these influencing factors, relative to the stroke of the vehicle suspension, the unevenness of the road surface is actually not very large, that is, the displacement is not large, you can see the map, and the better road surface will not exceed 5 cm. In this process, the elastic coefficient plays a small role, and the main role is the damping coefficient of the shock absorber. The damping is small, and when facing the bumps in the road, it can better dissolve and absorb.
However, the damping is too small, when the vehicle turns, the body attitude will be unstable, the roll of the vehicle will be too large, the roll is large, and the shift of the vehicle's center of gravity will be large. This is not good for manipulation.
Therefore, if the damping is not adjustable, the car can only have one characteristic, either to be comfortable and not to control, or to sacrifice comfort for the sake of control.
Damping is adjustable, how to adjust?
When I was a child, I played with syringe, and when pumping water with a syringe, the faster I pulled/pressed the ground, the greater the force required, and it had nothing to do with the location of the plunger, which is the characteristic of damping and speed. The thinner the opening of the syringe barrel, the more viscous the liquid drawn by the syringe barrel and the greater the resistance.
The shock absorber can be imagined as an enlarged syringe barrel, when the wheel moves up and down, the oil inside the shock absorber flows in and out through the valve train, creating a force that hinders the movement. Shock absorbers regulate damping on the same principle as syringes, changing the opening size of the valve system or changing the viscosity of the oil.
According to the damping adjustment method, it can be roughly divided into two categories: passive mechanical regulation and electronically controlled active regulation. The former uses the mechanical structure of the shock absorber itself to achieve a change in the damping force, which is passive, while the latter can use the electronic control system to actively control the damping force.
Mechanical adjustment can be divided into stroke adaptation self-adjustment and frequency adaptation self-regulation.
Stroke adaptive shock absorbers
Citroën PHC
On the basis of ordinary shock absorbers, PHC adds progressive stretch hydraulic shock absorbers and compression hydraulic shock absorbers at the upper and lower stop points of shock absorbers, respectively. It was as if a few more holes had been opened in the side wall of the syringe. When driving on normal roads, the up and down travel of the suspension is small, at this time all the holes in the syringe barrel allow the oil to flow, and the damping force of the shock absorber is smaller.
Image source: Sohu Auto
When cornering quickly, or encountering large bumps, the suspension compression/stretch amplitude is larger, a little more than the position of the hole on the side wall, and the hydraulic valve closes one by one. A progressively increasing damping is produced, inhibiting further movements of the suspension.
Frequency adaptive shock absorbers
The PHC grasps the difference between comfortable and sporty scenes: the range of travel of the suspension. Small suspension travel is utilized on ordinary pavements, where small damping can provide better comfort, while longer suspension travel during large bumps and high-speed corners require greater damping to provide better support.
The difference between comfortable and sporty application scenarios is not only this, the excitation of uneven road surface is generally high frequency (10Hz and above), and the faster the speed, the higher the frequency. The roll caused by the control-related cornering is low frequency (1Hz), the frequency adaptive shock absorber adds one or more oil circuits on the basis of the ordinary shock absorber, and through the special spring valve plate, the opening of the valve plate changes linearly with the oil pressure change, so as to control the damping with the frequency change. It achieves damping variation through a purely mechanical structure that does not require additional electronics.
The representative product of this type of shock absorber is KONI FSD, which is equipped with wuling star, Nissan Qashqai, BMW X3 (F25) and other models.
The adaptive shock absorber is up, and the electronically controlled adjustable shock absorber. The entry-level product of this shock absorber is electronically controlled dual-mode adjustable, which is ideal for ones, providing both sporty and comfortable damping.
As you can imagine, there are two oil paths inside the shock absorber, one thick and one narrow. Naturally, from the coarse path to go, the damping force is small, from the narrow road, the damping is large, through the electronic control valve, control the path of the internal oil of the shock absorber, to achieve two levels of damping adjustment.
The advantage of this shock absorber is that it can be manually distinguished from the current operating conditions, such as the comfort mode can be used when cruising in the city, and if you want better support, you can change the movement. But its disadvantage is also that it is manually switched, soft is soft, hard is hard, but it can not be automatically adjusted according to the actual road conditions like the mechanical adaptive suspension mentioned above. For example, the comfortable suspension may be less supportive in the face of sudden emergency changes. And there are only two damping adjustments that face a variety of road conditions, and not every time can achieve a good shock absorption effect.
The electronically controlled continuously adjustable damping damping shock absorber compensates for the shortcomings of the dual-mode damper, whose damping is continuously variable in the upper and lower limits and can be matched to the most suitable damping for a variety of different road surfaces.
There are two ways to achieve continuously adjustable damping shock absorbers, one is to adjust the damping by adjusting the opening of the solenoid valve and changing the diameter of the oil flow. Representative manufacturers of CDC technology for ZF-Sachs and Menroe CVSA technology for Tennak. Weilai ET7 is used in the former, and Extreme Kr 001 is a representative of the latter.
Taking the CVSAe technology equipped with the Kr 001 as an example, a tapered solenoid valve is placed on the basis of the ordinary shock absorber, which controls the degree of penetration of the cone valve into the oil circuit to control the damping.
The direction of this shock absorber is to increase the dimension of control, such as the advanced version of CVSAe CVSA2, which provides two external solenoid valves, which can independently control the damping of the suspension compression and tensile process, expanding the control range of damping, and obtaining better comfort and movement.
The other is the use of special oil, which can change its viscosity under the action of electric or magnetic fields, thereby changing the damping coefficient of the shock absorber, which is called magneto-rheological/electro-current liquid, respectively. CADILLAC's MRC electromagnetic suspension is a typical application for magneto-rheological shock absorbers.
The biggest advantage of the magnetororor compared to the CDC technology that uses the adjustment valve is that its speed of adjusting the damping is very fast, reaching 1000Hz, that is, it can be adjusted 1000 times per second. Due to the movement process of the mechanical structure, CDC technology can only reach a regulated frequency of about 200Hz at the earliest.
However, for this kind of electronically controlled shock absorber, the control technology has a greater difference in its use experience than the structural form. Unlike dual modes, the continuously adjustable electronically controlled shock absorber has an infinite number of options within the upper and lower limits of damping
The displacement, acceleration, angle sensor on the steering mechanism on the suspension, advanced body roll sensor, ESP data, throttle/brake pedal signal (for starting head,brake nod suppression, etc.) and other sensors to collect a variety of data, real-time calculation of the current road conditions, driving conditions should be used how much damping should be used to test the calibration technology of the car company.
The calibration technology of car companies cannot be reflected in the parameter table, and higher specification shock absorbers only provide a possibility, raising the upper limit, but not raising the lower limit. Therefore, for configurations such as variable suspension, it does not make sense to look at the parameters alone, or to actually test drive for experience.
Finally, to summarize several variable damping shock absorbers:
The stroke adaptive shock absorber can provide additional damping force at the upper and lower stop points of the suspension, improving the support force under the suspension limit, so that the initial section is soft and the rear section is tough.
Frequency adaptive shock absorbers can automatically match the appropriate damping value according to the current state of motion of the vehicle, so that it is comfortable enough when driving the suspension at high frequency, and better support when driving the suspension in low-frequency movement. But it varies one-to-one, with one frequency corresponding to a fixed damping value, and it is impossible to switch the tendency according to the user's needs.
The dual-mode electronically controlled adjustable shock absorber can switch the suspension soft and hard according to user needs, but cannot be adjusted in real time according to the condition of the road surface.
The continuously adjustable electronically controlled shock absorber has the greatest damping adjustment ability, which combines the advantages of frequency adaptive shock absorber and dual mode shock absorber, but it is extremely testing the calibration ability of car companies, and the actual experience effect varies from car to car.
Finally, a small question, since the extreme krypton 001 uses CVSAe from Tiannak, why is it still advertising the 1000Hz adjustment capability?
This article is written by The Kickbox Gang Route 64