M and I spark! Highlights of BMW i4 technology revealed
[Aika Auto New Energy Original]
It has long been an open secret that BMW has a soft spot for internal combustion engines. In the face of the sweeping EV wave, people in the four-cylinder building in Munich are still obsessed with engine development, suggesting a little disdain for electrification. As early as 2013, BMW introduced i3 and i8, which were at least one position ahead of competing products in time rhythm. However, it was not until i8 stopped production that BMW failed to produce a new generation of BMW i products, which not only lagged behind two old rivals, but also missed the opportunity to compete with Tesla for the market. Fortunately, BMW is not short of technical reserves. This time, they brought a brand-new pure electric medium-sized car with enthusiasm — — Bmw i4.
In March, 2020, the BMW Concept i4 concept car was officially released, which triggered a hot discussion in the car circle, and the brand-new grille design became the focus of debate. After a year, BMW i4 finally went into mass production. In view of the consistent "efficiency" of the Germans, such progress is not easy in the context of the COVID-19 epidemic. Nowadays, people seem to be used to the visual impact brought by "big nostrils", and the law of true fragrance is staged again.
Talking about BMW is inseparable from the word "sports", and the M family is synonymous with pure driving pleasure. On the other hand, I brand symbolizes electrification and intelligence, and it is an important springboard for BMW to move into the future. Once upon a time, I and M had no intersection, but the appearance of BMW i4 broke the shackles. At the initial stage of listing, i4 will provide two versions of eDrive40 and M50, which marks the first integration of I and M.. Of course, the conservatism of the Germans has not changed, and BMW has played M chess carefully. The "m" of i4 M50 is M Performance, not M Power.
I don’t know when it started, but people kept their mouths shut and all of them were pure electric platforms, but they ignored the essence of products. Yes, i4 can’t get away from the close relationship with Series 4, both of which are products of BMW CLAR platform. Last year, BMW successively released a brand-new 4-Series Coupe (coupe coupe) with code G22 and a brand-new 4-Series Convertible (convertible coupe) with code G23. However, the 4 Series Gran Coupe (four-door coupe) has not been replaced. Interestingly, BMW i4 came out before the new generation 4 Series Gran Coupe, and they shared the chassis number — — G26。
The full English name of CLAR is Cluster Architecture, which means Cluster Architecture. CLAR covers almost all BMW models above Series 3. If you understand it broadly, you can say that Series 3 and X7 are products of the same platform. As everyone knows, the CLAR platform can be further subdivided to form four micro-cluster architectures. According to the different structure of the front, CLAR can be divided into small-size clusters and large-size clusters. According to the different chassis heights, the clusters of two sizes can be further subdivided into low chassis groups and high chassis groups.
Although BMW has no exclusive platform for pure electricity, it has made great achievements in the field of batteries. The battery pack has a compact structure, especially the vertical dimension is very restrained, which is an important advantage for the coupe style i4. As a pure electric vehicle, i4 has a lower center of gravity and stronger body stiffness, but it also has to face the weight disadvantage. In the face of inertia, how will BMW stick to its original heart?
The BMW 3 Series and its derivative models are very fond of the front axle with double ball joints and vibration reduction struts, and the i4, which is also part of the CLAR small-size cluster, is no exception. The front axle with two-ball joint damping struts sounds fantastic, but it is actually a modified McPherson suspension. Different from the traditional McPherson, the two-ball McPherson divides the lower control arm into two parts, which are connected to the steering knuckle respectively. The extension lines of the two control arms form a virtual intersection outside the steering knuckle, and the parameters of the kingpin can be dynamically changed during steering, which helps the wheels to fit the ground better and optimizes steering feedback. At the same time, the front suspension control arm is made of aluminum alloy, which effectively reduces the unsprung weight.
The five-bar structure is used in the rear axle without accident, and the longitudinal rigidity and lateral rigidity are fully guaranteed, leaving enough room for setting characteristics. Due to the addition of power battery, the kerb quality of i4 is obviously higher than that of other vehicles in the same cluster, especially the rear axle load is obviously improved. If the spring stiffness and damper damping are simply improved, the handling stability may be guaranteed, but it is extremely unfavorable to comfort. However, the traditional value of BMW cannot be lost, and engineers have devoted a lot of effort to it.
As a member of G2x family, i4 is equipped with a series of chassis technologies from Series 3 and Series 4, and its damping characteristics tend to be diversified, trying to cover more application scenarios. The spring adopts two-stage design, and the stiffness of the main spring is different from that of the auxiliary spring, so as to give consideration to comfort and sports as much as possible. When encountering large-amplitude road excitation, the suspension compression damping is softer, which reduces the jacking feeling; In the middle and small trips, the suspension can provide sufficient support and contribute to the body control.
As for the shock absorber, i4 applied the HRS hydraulic recovery stop technology, and the supplier was Jingxi Heavy Industry (BWI). Based on HRS, the damping of shock absorber can be changed according to the recovery (stretching) stroke, instead of only being linked to the moving speed like the traditional hydraulic shock absorber. At the end of the recovery stroke, the HRS stopper provides a strong damping force, thus quickly attenuating the impact energy and avoiding the blunt limit impact. In this way, i4 not only has a steady and ground-touching driving texture, but also can keep calm in the face of bad roads, which is probably the best interpretation of the concept of coupe.
In order to cope with the sharp increase of the rear axle load, BMW i4 comes standard with rear axle air suspension. Thanks to the existence of air spring, the rear suspension can automatically increase its support under heavy load and adjust the car body to a horizontal height. M50 comes standard with M adaptive shock absorber, whose damping characteristics can be adjusted according to driving conditions or driving modes, making the chassis more versatile. EDrive40 comes standard with ordinary hydraulic shock absorber (with HRS) and optional M adaptive shock absorber.