Structure Design for Power-Split Hybrid Transmission

Abstract—The HEV plays the key role in the energy saving and carbon emission reduction. Typically an HEV combines two power components, an internal combustion engine and an electrical motor. And the large capacity lithium or the Ni-MH battery is also needed. The power-split power train configuration of an HEV has the individual advantages of the series and parallel types of HEV power train configurations. And the planetary gear set (PGS) plays the key role in it. This paper presents a particular power-split power train configuration. The state of the device can switch in the six modes, according to the driving requirement. This improves the over-all efficiency of the power train. As the mode switching strategy has great effect on the vehicle dynamic performance, the interrelationship between SOC and velocity on the mode switching strategy is researched.
According to the mechanical design, there are three categories of HEVs: Series hybrids, parallel hybrids and power-split hybrids. The serial configuration is shown in Fig.1. A motor is applied to drive the wheels. And the electrical power is supplied by either a battery, or a generator transforming the engine power into electric power, or both. The advantage of this configuration is that the engine could work under its optimal condition most time, as the engine operation is independent from the vehicle speed and road load. But the overall power-train efficiency will be reduced because of the motor drive, since the engine power must be converted to the electrical energy first.

Figure 1 The series hybrid configuration
Manuscript received March 20, 2010
Aimin Du is with School of Automotive Studies, Tongji University. China. (e-mail:
Xudong Yu is with School of Automotive Studies, Tongji University. China. (e-mail:
Junjie Song is with School of Automotive Studies, Tongji University. China. (e-mail:
The parallel...