Recently, NIO revealed the secrets behind the quietness of NIO ES7, according to NIO Weibo.
What details create the quiet and comfortable cabin experience of the ES7?
Double-layer mute glass and mute tires, rigorous wind tunnel testing and styling optimization, electric drive gear shaft system optimization, harmonic injection of “black technology”… make the ES7 always quiet.
In daily driving, the body shape will become the main source of noise in high-speed driving due to the increase of vehicle speed and the generation of a large amount of airflow separation and friction. At the same time, the gaps in the body parts and the sealing system will also become a transmission path, making the wind noise more prominent.
ES7 adopts an avant-garde and dynamic design style, especially for rear-view mirrors, roof lidar and cameras, A-pillar surfaces, etc. After several rounds of rigorous wind tunnel, wind resistance testing and shape optimization, it not only reduces airflow separation and body turbulence, but also effectively reduces the energy of sound sources, and finally achieves an ultra-low drag coefficient of 0.263.
In order to improve the sealing performance of the ES7 cabin, edge sealing strips are used on the A and B-pillars of the body, and double tubular sealing strips are also used in the doors to minimize the generation of leakage noise.
In addition, ES7 adopts double-layer laminated mute glass on the front windshield and four-door side windows. Its Acoustic PVB film has excellent sound insulation effect, and the STL sound transmission loss rate is excellent, about 50%, creating a cabin atmosphere comparable to Library Quiet.
Because the mechanical structure is completely different, compared with the traditional gasoline vehicle equipped with an internal combustion engine, the motor of the electric vehicle has a significant improvement in NVH performance.
In order to further improve driving quietness, ES7 is still aimed at the electric drive assembly, controlling noise and vibration from both the source and the transmission path. According to the user’s daily working conditions, engineers have begun to optimize the motor’s internal gear design and tooth surface machining accuracy.
In addition, ES7 also uses “black technology” – harmonic injection to optimize the electromagnetic noise of the electric drive assembly, and comprehensively improve the pinion system to reduce high-frequency gear noise. Especially when the harmonics are injected, the 24th order frequency noise is significantly eliminated.
In addition to controlling noise and vibration at the “source”, ES7 also has a multi-pronged approach in the propagation path, as well as optimizing the torque control logic.
For example, optimizing high-frequency dynamic stiffness, improving high-frequency NVH performance, to further eliminate noise and vibration under comprehensive working conditions, and bring better dynamic perception quality to the cockpit.
The tire is the only contact part between the vehicle and the road, and it is also the main source of vibration and noise in the vehicle when driving at medium and low speeds. Therefore, ES7 chooses Pirelli P ZERO high-performance silent tires in a more targeted manner.
The tire technology is derived from Pirelli’s long-term motorsports experience. The optimized tread pattern and structure can effectively filter frequencies that are recognizable by the human ear, and suppress road noise during driving to enhance comfort.
At the same time, the tire also adopts the PNCS noise elimination system, that is, the inner liner of the tire is designed with porous and loose sound-absorbing cotton, which can reduce the vibration of the cavity gas in the tire during driving. It can also effectively suppress the noise generation inside.
In addition, the material of ES7 wheel cover and carpet area has also been developed with acoustic package. Under the premise of not increasing the weight, PU foam material with better sound insulation performance is used to absorb and isolate road noise more effectively.