What are the similarities and differences between solving the NVH of traditional cars and solving the NVH of new energy vehicles?

Compared with traditional cars, new energy vehicles have added many new components in structure, and their power system, braking system, climate control system and other structures are very different from traditional cars. At the same time, the problems such as road noise, wind noise and abnormal sound highlighted by the change of background noise are also different from those of traditional cars: changing the system power system, transmission system, electrical system, braking system, body system, suspension system, active air intake and exhaust system, changing the contents of interior and exterior decoration system, canceling the engine, replacing the motor and its controller, canceling the transmission, replacing the single-stage reducer, increasing the electric heating and cooling water pump, Replace the electric compressor, electric window, wiper, blower and instrument, basically borrow and replace the electric vacuum pump or increase the car body lifting under the brake recovery of the front engine room, increase the beam bracket, install the controller and other components, and re-match the suspension system. The general trend is to increase the stiffness of suspension, increase the active sound system, cancel the intake and exhaust system, and maintain the prototype as a whole. Based on the man-machine aspect, the carpet thickness may be reduced, and with the change of structural system, the problems that new energy vehicles focus on and solve in the process of NVH performance development are far from those of traditional vehicles. NVH refers to noise, vibration and unevenness; Because the above three factors appear at the same time and are inseparable in mechanical vibration such as automobiles, they are often studied together. Acoustic vibration roughness refers to the quality of noise and vibration, which describes the subjective feeling of human body to vibration and noise, and cannot be directly measured by objective measurement methods. Because acoustic vibration roughness describes the uncomfortable feeling caused by vibration and noise, some people call it roughness. Because acoustic vibration acoustic vibration roughness is often used to describe the extremely uncomfortable transient response caused by impact excitation, some people call it impact characteristics. When the car passes through the joint or convex hull, it will produce transient vibration, including impact and buffering. The greater the stiffness of the system, the greater the amplitude of transient vibration of the car body and the more serious the impact. At the same time, the increase of natural frequency makes the vibration attenuation faster and the buffering effect better. At the same time, the empirical formulas of shock and cushioning feeling grades obtained by multiple regression model are given. Generally speaking, the description of acoustic vibration roughness is the feeling of extreme fatigue caused by vibration and noise. Simply put, all the tactile and auditory feelings of the occupants in the car belong to the study of NVH characteristics of the car, in addition, it also includes the strength and life of the car parts caused by vibration. From the perspective of NVH, the automobile is a system composed of excitation sources (engine, transmission, etc.). ), vibration transmitter (composed of suspension system and side fittings) and noise transmitter (body). The research on NVH characteristics of automobile transmission system takes automobile transmission system as the research object and belongs to the subsystem of automobile NVH characteristics research. At present, the research on NVH characteristics of automobile transmission system is mainly to study the NVH characteristics of transmission system which is generated by engine as excitation source or the automobile is under certain working conditions. The research on the vibration characteristics of powertrain abroad started earlier, and advanced foreign automobile manufacturers have included the dynamic characteristics of automobile structure into the routine content of product development since the 1980 s. Especially since 1990s, engineering research centers of Toyota, GM, Ford, Chrysler and other automobile companies have set up NVH branches to study the noise, vibration and noise-induced acoustic roughness of automobiles. Compared with traditional cars, new energy vehicles have added many new components in structure, and their power system, braking system, climate control system and other structures are very different from traditional cars. At the same time, the problems such as road noise, wind noise and abnormal noise highlighted by the change of background noise are also different from those of traditional vehicles. With the change of structural system, the problems that new energy vehicles focus on and solve in the development of NVH performance are also far from those of traditional vehicles:-1 NVH power system performance: the total sound pressure level of the motor and related accessories is significantly reduced, and the vibration level of the power system is about 1/65438+ of the engine. NVH performance of transmission system: the single-stage reducer is less complicated than the traditional gearbox; NVH performance of electrical system: it is difficult to control the NVH performance of new electrical components, while the NVH performance of the original electrical components is very demanding; 4 channel noise: channel noise is the most important noise source; Due to the reduction of the noise level of the whole vehicle, the abnormal noise of the prototype vehicle is prominent, such as the abnormal noise of the seat, instrument, dome light, seat belt and other parts, while the abnormal noise of the new parts of the electric vehicle is mainly concentrated in the chassis and power board; The adjustment of acoustic packaging scheme is generally small, and the sound insulation and sound absorption performance are basically unchanged. Based on the characteristics of electric vehicles, it is suggested to increase the high-frequency sound absorption performance of engine room and firewall to improve the low-frequency barrier performance of car body; Wind noise: the appearance, exterior decoration and dynamic seal of the whole vehicle are basically unchanged, and the wind noise is basically unchanged. Wind noise can be improved by acoustic packaging. @20 19