2.2.4　Complex Hybrid

Text（课文）

There exist other configurations of HEVs which cannot be classified into the above three types.An example is shown in Figure 2.10 which has dual-axle four-wheel drive capability with multiple electric machines and an ICE.It is very much similar to the series-parallel hybrid system.However，the main difference is that the electric motor connected to the power split/combine device in the complex hybrid allows for bidirectional power flow，while the generator in the series-parallel hybrid only permits unidirectional power flow.This bidirectional power flow results in the three propulsion power（due to the ICE and two electric motors）operating modes that are impossible in the series-parallel hybrid.Another difference is that usually the series-parallel hybrid is propelled through front wheels by an engine and/or an electric motor.However，in the complex hybrid，the front-wheel axle and rear-wheel axle are separately driven by a hybrid power-train and an electric motor，respectively.In normal operation mode，the power from ICE is split to propel the front axle and to drive the electric motor（as a generator）to charge the battery.When the load request is low，the battery supplies power to the front electric motor to drive the front axle and it is unnecessary to use both the ICE and rear electric motor.If the vehicle is running at heavy load（e.g.acceleration），both the engine and front electric motor provide power to drive the front axle and meanwhile the rear electric motor propels the rear wheels.Both the front and rear electric motors become generators to charge the battery in the regenerative mode（braking or deceleration）.Another dual-axle complex hybrid system differs from the previous one in terms of function exchange between front and rear wheels，i.e.，icons of front and rear wheels exchange their positions.Other variations also exist，e.g.the Toyota Highlander，which employs three electric motors and an ICE to maximize the fuel economy of the vehicle，as well as to improve the vehicle driveability.Unfortunately，the complex hybrid suffers from the high complexity and cost，which is similar to the series-parallel hybrid.

Figure 2.10　Configuration of a complex HEV

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.However，the main difference is that the electric motor connected to the power split/combine device in the complex hybrid allows for bidirectional power flow，while the generator in the series-parallel hybrid only permits unidirectional power flow.然而主要的区别在于，复联式混合动力汽车中连接到功率分流或汇合装置的电动机允许双向功率流，而混联式混合动力的发电机只允许单向功率流。

★2.However，in the complex hybrid，the front-wheel axle and rear-wheel axle are separately driven by a hybrid power-train and an electric motor，respectively.然而在复联式混合动力电动汽车中，前轮和后轮分别由混合动力总成系统和一个电动机来驱动。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）Both the front and rear electric motors become generators to charge the battery in the regenerative mode（braking or deceleration）.

（2）When the load request is low，the battery supplies power to the front electric motor to drive the front axle.

（3）complex hybrid

◆2.Translate the following passages（expressions）into English（汉译英）

（1）再生模式

（2）一般运行模式

（3）双轴复联式混合动力电动汽车

◆3.Directions:Answer the following questions briefly according to the text Please draw the configuration of the complex hybrid HEV.

Reading material（阅读材料）

Toyota produced the world's first mass-marketed modern HEV in 1997，the Prius.The worldwide sales of the Prius exceeded 1 million units in 2009.It uses a planetary gear set to realize continuous variable transmission（CVT）.Therefore，conventional transmission is not needed in this system.The engine is connected to the carrier of the planetary gear while the generator is connected to the sun gear.The ring gear is coupled to the final drive，as is the electric motor.The planetary gear set also acts as a power/torque split device.During normal operations，the ring gear speed is determined by the vehicle speed，while the generator speed can be controlled such that the engine speed is in its optimum efficiency range.The 6.5（A·h），21 kW nickel metal hydride battery pack is charged by the generator during coasting and by the propulsion motor（in generation mode）during regenerative braking.The engine is shut off during low-speed driving.

The same technology has been used in the Camry hybrid，the Highlander hybrid，and the Lexus brand hybrids.However，the Highlander and the Lexus brand hybrids add a third motor at the rear wheel.The drive performance，such as for acceleration and braking，can thus be further improved.