Fig. 1 Differences between e-POWER and conventional HEV 1. Introduction2. Challenge to higher quietnesssystems3. Reducing the frequency of engine operation*Customer Performance & Vehicle Test Department **Chassis Engineering Department ***Body Engineering DepartmentIn Nissan's electrification strategy, the e-POWER system works as a sustainable technology that satisfies both environmental and driving requirements and is an important solution in addition to battery electric vehicles (BEV). Although this system has an internal combustion engine (ICE), it uses 100% electric power to drive a vehicle (Fig. 1) and can maintain the acceleration performance and quietness, which are the advantages of BEVs, while offering the convenience of not requiring charging; therefore, it is widely used.Unlike conventional ICE-equipped vehicles, the e-POWER system switches the engine on and off without synchronizing with the driving operation of the driver; therefore, it is important to reduce the difference in noise level when the engine is switched on and off.This section describes the evolution of quietness realization technology that enables the e-POWER system, which has been developed for compact cars, to be applied to C-segment SUVs.The concepts of the new X-TRAIL include “Tough Gear” and “High Quality.” To realize quietness, which is an important factor of “high quality,” performance development is conducted to achieve the following three points:(1) Reduce the frequency of engine operations (Section 3).(2) Quiet the engine noise (Section 4) (3) Match the engine sound to the driver's intention to accelerate (Section 5).The engine used for power generation is changed to a high-output 3-cylinder downsized turbo engine to match the vehicle class of the C-segment SUV. Further, the entire vehicle, including the engine mounts, exhaust systems, active noise control, and vehicle bodies, is optimized to overcome NV-related issues such as low-frequency booming noise and vehicle body vibration.Furthermore, the overall vehicle balance and noise insulation performance are significantly improved to ensure that customers can feel the overwhelming quietness the moment they enter or start the car. The quietness technology of the vehicles is described in Section 6.Engine noise tends to stand out when background noise is low, such as when driving at low speeds. Thus, under such conditions, it is important to not operate the engine as far as possible. To this end, energy management control is implemented for actively generating power and storing it in driving scenes with high background noise. When driving at high speeds, the level of wind noise is high, which masks the engine noise and makes it less noticeable; therefore, power is actively generated. Conversely, when the vehicle speed is low (the background noise is also low), the engine is controlled so that it operates as little as possible based on the state of charge (SOC).A road surface detection control system is adopted to control the engine start based on the road noise level to make the engine noise as inconspicuous as possible even under continuous low-speed driving conditions and to mask the engine noise with road noise.Previous e-POWER-equipped vehicles needed to satisfy certain conditions to start the engine regardless of 25Mengze Li* Shinichi Suganuma* Toshihisa Kuwata* Nobunari Funatsu**Hiroaki Fukuoka** Takefumi Mitani** Kazushige Maeda**Yasutsune Terashima*** Yuichi Igarashi*** Kazuhisa Okada*5. NV Technology to Achieve EV-Level Quietness
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