: Section 2.2 The IC engine/electric hybrid vehicle A hybrid vehicle has two or more power sources, and there are a large number of possible variations. The most common types of hybrid vehicle combine an internal combustion engine with a battery and an electric motor and generator ( 发电机 ). There are two basic arrangements( 布置形式 )for hybrid vehicles, the series hybrid an the parallel hybrid. In the series hybrid the vehicle is driven by one or more electric motor supplied either from the battery, or from the IC engine driven generator unit, or from both. However, in either case the driving force comes entirely from the electric motor or motors. In the parallel hybrid the vehicle can either be driven by the IC engine working directly through a transmission system to the wheels, or by one or more electric motors, or by both the electric motor and the IC engine at once. In both series and parallel hybrids the battery can be recharged by the engine and generator while moving, and so the battery does not need to be anything like as large as in a pure battery vehicle. Also, both types allow for regenerative braking, for the drive motor work as a generator and simultaneously slow down the vehicle and charge the battery. The series hybrid tends to be used only in specialist applications. For example, the diesel powered railway engine is nearly always a series hybrid, as are some ships. Some special all- terrain vehicles are series hybrid, with a separately controlled electric motor in each wheel. The main disadvantage of the series hybrid is that all the electrical energy must pass through both the generator and the motors. The adds considerably to the cost of such systems ( 系统成本大大增加) There are several hybrid vehicles currently on the market, and this is a sector that is set to grow rapidly in the years ahead. The Toyota Prius, shown in Figure 2.4, is the vehicle which really brought hybrid vehicles to public attention. Within two years of its launch in 1998 it more than doubled the number of electric vehicles on the roads of Japan. The Prius uses a 1. 5petrol engine and a 33kw electric motor either in combination or separately to produce the most fuel –efficient performance. A nickel metal hydride battery is used. At start up or at low speeds the Prius is powered solely by the electric motor, avoiding the use of the internal combustion engine when it is at its most polluting and least efficient. This car uses regenerative braking and has a high overall fuel economy of about 56. 5 miles per US gallon(68 miles per UK gallon ) The Prius has a top speed of 160 kmh ( 100 mph ) and accelerates to 100 kmh (62mph) in 13. 4 seconds. The Prius battery is only charged from the engine and does not use an external socket. It is therefore refueled with petrol only, in the conventional way. In addition, it seats four people in comfort, and the luggage space is almost unaffected by the somewhat larger than normal battery. The fully automatic transmission system is a further attraction of this car that has put electric cars well into the realm( 领域 ) of the possible for ordinary people making the variety of journeys they expect their cars to cope with. The Toyota Prius mainly has the characteristics of a parallel hybrid, as in Figure 2. 3, in that the IC engine can directly power the vehicle. However, it does have a separate motor and generator, can operate in series mode, and is not a pure parallel hybrid. It has a fairly complex power splitter gearbox, based onepicyclic gears( 行星齿轮 ), that allows power from both the electric motor or the IC engine, in almost any proportion to be sent to the wheels or gearbox. Power can also be sent from the wheels to the generator for regenerative braking. Most of the major companies are now bringing out vehicles that are true parallel hybrids. The Honda Insight, shown in Figure 2.5,and whose powertrain parameters are given in Table 2.1, is a good example. There is also now a parallel hybrid electric version of the popular Honda Civic available.