Drive Concepts using Super Reduction Hypoids Combined with Cylindrical Gear Reductions

摘要

Why Transmissions in Electric Vehicles? Compact electric vehicles require a costeffective and compact solution for the location of the electric motor and the transmission. Yes, even today electric vehicles require a transmission, if the maximal possible motor efficiency has to be available in the majority of drive conditions. Transmissions also allow higher motor rpm, resulting in smaller size electric motors with improved dynamic properties. The torque and efficiency optimal rpm of an 80kw electric motor for a compact vehicle is between 6,000 and 10,000 rpm. For example if the nominal driving speed is 80km/h and the optimal motor speed is 10,000 rpm, the optimal ratio between motor and wheels (using a wheel diameter of 410 mm) is 9.66: i = (n_(Motor)·D·n)/v. Whereas: i Transmission ratio. n_(Motor) Optimal motor rpm [1/min]. D Outer tire diameter [m]. v Average vehicle speed [m/min]. A variety of eDrive concepts have been developed during the past years. One example which has already been introduced in Chapter 1 is the design shown in Figure 1 (Ref. 1). It is very compact, but like most concepts, it does not solve the three major obstacles of the "inline design," which are: Large width between the front wheels used for drive unit. Asymmetric weight distribution. Higher heat radiation to the wheel and tire on the side of the electric motor. The large width between the wheels requires short drive shafts. Each of the drive shafts has two CV-joints which wear fast in the case of short drive shafts due to the steering inclination and control arm swings. This will also result in a reduced efficiency and front axle noise.