Variable suspension

Variable suspension means that the height or hardness of suspension can be changed manually or automatically to meet the driving needs of different roads.

The problem of suspension is a factor that consumers are concerned about, because it directly affects the comfort and handling of vehicles. However, at today's technical level, it is difficult for ordinary spring dampers to achieve the best of both worlds. In the process of people's constant pursuit of perfection in the automotive field, the variable suspension system was born. The function of variable suspension is to change the height/hardness of suspension manually or automatically to meet the driving needs of different roads.

Air suspension

Technical features: the chassis can be lifted and lowered, and it is widely used.

Insufficient technology: the reliability is not as good as that of spiral spring.

Applicable models: Mercedes S350, Audi A8L, Porsche Cayenne, etc.

In fact, when it comes to active suspension system, air suspension is naturally our first thought, and it is also widely used. In terms of system composition, it mainly consists of control computer, air pump, pressure storage tank, pneumatic front and rear shock absorbers and air distributor. The main purpose is to control the horizontal movement of the car body, adjust the horizontal height of the car body and adjust the hardness of the shock absorber.

Generally speaking, vehicles equipped with air-type adjustable suspension have ground distance sensors near the front and rear wheels. The driving computer will judge the height change of the car body according to the output signal of the ground distance sensor, and then control the air compressor and exhaust valve to make the spring automatically compress or stretch, thus reducing or increasing the ground clearance of the chassis, and increasing the stability of the high-speed car body or the passability of complex road conditions.

In daily adjustment, the air suspension will have several states. 1, keep the state. When the vehicle is lifted off the ground by the elevator, the air suspension system will close the relevant solenoid valves, and the computer will remember the height of the vehicle body to keep the original height after landing: 2. Normal state, that is, engine running state. During driving, if the body height changes beyond a certain range, the air suspension system will adjust the body height every once in a while: 3. Awakening state. When the air suspension system is awakened by the remote key, door switch or rear compartment lid switch, the system will check the height of the vehicle body through the vehicle body level sensor. If the height of the car body is lower than the normal height to a certain extent, the air storage tank will provide pressure to raise the car body to the normal height. At the same time, the air suspension can adjust the stiffness of the shock absorber, including soft state, normal state and hard state (also marked as comfort mode, normal state and motion mode, etc.). ), the driver can control it through the control buttons in the car.

Of course, compared with the traditional suspension, because the structure of the air-type adjustable suspension is more complicated, its failure probability and frequency will be higher than that of the spiral spring suspension system. Using air as power source to adjust the height of chassis, the tightness of related components is also a problem. In addition, if the chassis height is adjusted frequently, it may cause local overheating of the air pump system and greatly shorten the service life of the air pump. Of course, with the continuous improvement of technical level, many problems have been well solved, and the application of vehicles has become more and more extensive.

Electromagnetic adjustable suspension

Technical features: advanced technology and rapid system response.

Insufficient technology: high cost, mostly used in luxury models, and its stability needs to be tested.

Application models: Audi TT, Cadillac SLS and Cadillac CTS.

The so-called electromagnetic adjustable suspension is a suspension mode which uses electromagnetic response to realize the height change of automobile chassis, and it can respond in a very short time. So as to suppress vibration and keep the vehicle body stable. Especially in some relatively extreme environments, such as sudden bumps at high speed, the advantages of electromagnetic suspension will be very obvious, and its response speed can be five times faster than that of traditional suspension.

In terms of system composition, the electromagnetic levitation system consists of driving computer, wheel displacement sensor, electromagnetic hydraulic rod and linear shock absorber. There is a wheel displacement sensor at the joint of each wheel and the car body, which is connected with the traveling computer, and the traveling computer is connected with the electromagnetic hydraulic rod and the linear shock absorber. The mystery of electromagnetic shock absorber lies in electromagnetic oil as damping medium, which is composed of synthetic hydrocarbons and fine iron particles. Under normal circumstances, these metal particles will be randomly distributed in the liquid, but with the generation of electromagnetic field and the change of magnetic flux, they will be arranged according to a certain structure, and the viscosity coefficient will also change, thus changing the damping. The intensity of the electromagnetic field can only be controlled by changing the current. In other words, the control of this system can achieve the purpose of controlling the damping coefficient only by changing the current.

In fact, this damping process is mainly that when the vehicle runs on the bumpy road and causes the wheels to jump, the sensor will quickly transmit the signal to the control system, and the control system will send corresponding instructions and send electrical signals to the electronic coils of each shock absorber, so that the movement of current will generate a magnetic field, and under the action of the magnetic field, the viscosity of electromagnetic fluid will be changed, so as to achieve the purpose of controlling the vehicle body and damping. And such a complicated process is actually completed in a flash. For example, when you read the above lines, this process may have been completed 3000 times. (Up to 1000 times per second)

Hydraulic adjustable suspension

Technical features: the chassis can be lifted and lowered, and hydraulic oil is used for better durability.

Insufficient technology: the technical level is relatively old and the response speed is slow.

Applicable models: Citroen C5 (overseas) Citroen C6

Hydraulic adjustable suspension. As the name implies, it is to use the change of hydraulic pressure to adjust the suspension system of the car body. Its core component is the built-in electro-hydraulic integrated module, which can adjust the expansion frequency and degree of the shock absorber according to the vehicle speed. In addition, due to the different distribution of the center of gravity of different vehicles, it is usually necessary to install a longitudinal and lateral acceleration yaw gyro sensor near the center of gravity of the vehicle to collect signals such as car body vibration, wheel jump and tilt state. These signals are calculated by the driving computer, and the corresponding execution signals are transmitted to the four execution cylinders, and the ground clearance is changed by increasing or decreasing the hydraulic oil.

Similar to the air adjustable suspension system, the hydraulic adjustable suspension can also raise the chassis or adjust automatically. For example, let's take the hydraulic adjustable suspension on the old Citroen C5 model as an example. When it stops, its body height is automatically reduced to the lowest, and the body height is restored after the car starts. When the vehicle is running, the standard height shall be adopted when the vehicle speed is lower than 1 10 km/h on urban roads; When the vehicle speed exceeds 1 10 km/h, the electro-hydraulic integrated block controls the head of the vehicle to descend 15 mm and the tail to descend11mm. Lowering the center of gravity can improve the driving stability of the vehicle, reduce the maximum cross section of the windward side, reduce the sensitivity to crosswind and reduce the fuel consumption. When the vehicle speed is lower than 90km/h, the vehicle body returns to the standard height; When the road conditions are bad, the electro-hydraulic integrated block controls the car body to rise, ensuring the length and comfort of shock absorption stroke to the maximum extent.

Electrohydraulic adjustable suspension

Technical features: accurate control and quick response.

Insufficient technology: the stability needs to be tested.

Applicable models: Buick New LaCrosse and Opel Astra (overseas)

Electro-hydraulic adjustable suspension, also known as continuous damping control system (CDC), is also a kind of active suspension. The system can independently control the suspension damping of each wheel. Its electronic sensor can adjust the shock absorber in time according to the read road information, so that it can switch between soft and hard frequently. So as to control the roll, pitch and yaw of the vehicle body more quickly and accurately. Improve the stability of high-speed driving and cornering of vehicles.

Different from the traditional hydraulic adjustable suspension, electro-hydraulic suspension relies more on electronic equipment. The core components are composed of central control unit, CDC shock absorber, body acceleration sensor, wheel acceleration sensor and CDC control valve. The shock absorber is based on the traditional hydraulic shock absorber structure. The shock absorber is filled with oil and has two chambers, and the oil can flow through a small hole connecting the two chambers. When the wheel bumps, the piston in the shock absorber will move up and down in the sleeve, and the oil in the cavity will flow back and forth between the two cavities under the reciprocating motion of the piston. The mutual friction between oil molecules and the friction between oil and the hole wall form resistance to the movement of the piston, which converts the kinetic energy of vibration into heat and radiates it into the air through the shell of the shock absorber, thus realizing the shock absorption process of the shock absorber.

Then again, CDC is not a very advanced suspension technology, and it can only be said that it is rarely used in medium-sized vehicles of joint venture brands. In fact, in 2004, this system was already equipped on the Opel Astra model. In other words, CDC was applied to production models at least five years ago. By 2008, Opel's Insignia (the prototype of the new Regal) was born on a brand-new medium-sized car platform-epsilon II, and its FlexRide adaptive chassis system was based on CDC system.

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