Hybrid electric vehicles are expected to become the leading product in the automotive industry

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Hybrid electric vehicles are expected to become the leading product in the automotive industry [Copy link]

Early development of hybrid electric vehicles
Hybrid electric vehicles (HEV) are new models that have been developed before the ideal high-quality specific energy and mass-to-power vehicle power supply can be found. The development of electric vehicles is temporarily hindered. HEV is both a transitional model and an independent model. In the 21st century, HEV will develop rapidly. In
1991, Volkswagen launched the Zico hybrid electric microcar, which is 3150mm long, 1600mm wide, and 1480mm high. It can accommodate 4 people and has a curb weight of 78kg. It uses a 0.636L, 9.3:1 compression ratio, 25kW/(6000r·min) three-cylinder gasoline engine and a 6kW/(1280r·min) electric motor to form a hybrid drive system. The gasoline engine and the electric motor drive the vehicle through two automatic clutches and a five-speed transmission, and the drive axle drives the vehicle. When the speed is lower than 60km/h, the power battery pack provides power, and the vehicle is driven by an electric motor. When the speed is 60km/h, the gasoline engine drive axle is started to drive the vehicle. When the vehicle accelerates or climbs a slope, the engine and the electric motor form a hybrid drive mode to drive the vehicle.
Hybrid electric vehicles HEV first appeared in Europe, attracting the attention of major American automobile companies. In order to reduce dependence on oil imports, improve air pollution, and meet California's emission standards. In order to have stronger competitiveness and a larger market in the automotive industry, it is necessary to seize the leading position in HEV complete vehicles and key technologies. In September 1993, the US government agencies and the American Automobile Research Association and some related units jointly established the "New Generation Vehicle Coordination Council" PNGV. Through PNGV, the US government has reached a variety of cooperative research and development agreements with the automotive industry, and coordinated the human and material resources of relevant government departments, national laboratories and the three major automobile companies. Its research direction represents the interests of the three major automobile companies and their users.
PNGV proposed that the standards to be achieved by the newly developed concept car prototype are: to be able to accommodate 5-6 people, have a vehicle mass of 898kg, consume 3L of fuel, accelerate from 0 to 96.56km/h in 12s, and have a driving range of 612km within 10 years. After years of research, development, and testing, the three major American automobile companies have launched hybrid electric vehicle HEV concept cars or prototypes. General Motors' concept car is the precept concept car, Ford's concept car is the prodigy concept car, and Chrysler's concept car is the Dodge ESX3. Basically, they all use an engine-based configuration with an electric motor as the auxiliary configuration to meet the above standards.
Classification and characteristics of hybrid electric vehicles

The fuel engine cars currently in common use have various drawbacks. Statistics show that under more than 80% of road conditions, an ordinary car only uses 40% of its power potential, and it will drop to 25% in urban areas. What is more serious is that exhaust gas pollutes the environment. Since the 1990s, the voices of countries around the world for improving environmental protection have been growing, and various electric vehicles have emerged. Although it is generally believed that the future belongs to electric vehicles, the current battery technology problems hinder the application of electric vehicles. Since the energy density of batteries is hundreds of times lower than that of gasoline, it is far from the value required by people. Experts estimate that electric vehicles will not be able to replace fuel engine cars within 10 years (unless there is a major breakthrough in fuel cell technology).
Reality forced engineers to come up with a best of both worlds and developed a hybrid electric vehicle (HEV). The so-called hybrid electric vehicle is to combine an electric motor and an auxiliary power unit in a car as a driving force. The auxiliary power unit is actually a small fuel engine or power generator set. To put it in a more figurative way, it is to make the traditional engine as small as possible and let part of the power be borne by the battery-motor system. This hybrid device not only takes advantage of the engine's long continuous working time and good power, but also takes advantage of the motor's pollution-free and low noise. The two "fight side by side" and complement each other. The thermal efficiency of the car can be increased by more than 10%, and the exhaust emissions can be improved by more than 30%.
Hybrid electric vehicles are mainly divided into two types according to the form of energy synthesis: series (SHEV) and parallel (PHEV).
The series power consists of three power assemblies: engine, generator and motor, which are connected in series to form the power unit system of SHEV. When the load is small, the battery drives the motor to drive the wheels to rotate, and when the load is large, the engine drives the generator to generate electricity to drive the motor. When the electric vehicle is in the working conditions of starting, accelerating, and climbing, the engine-motor group and the battery group jointly provide electrical energy to the motor; when the electric vehicle is in the working conditions of low speed, sliding, and idling, the battery group drives the motor, and the engine-generator group charges the battery group. No matter what the working conditions of this series electric vehicle are, the motor will eventually drive the wheels. For example, Ford's "New Energy Level-2010" SHEV uses fuel cells as its battery. When driving in urban areas, the fuel cells drive the motors, which drive the wheels through the reducer (transmission) and the drive axle, meeting the "zero emission" requirement. When driving at high speeds and climbing slopes, the engine-motor group and the fuel cell group jointly supply power to the motors to drive the wheels.
The engine and motor of the parallel device drive the car in a mechanical energy superposition manner. The engine and motor belong to two systems and can independently provide torque to the vehicle's drive system. They can be driven together or separately on different roads. The motor can be used as both a motor and a generator, and is also called an electric-generator group. Since there is no separate generator, the engine can directly drive the wheels through the transmission mechanism, so the device is closer to the traditional car drive system and is widely used. For example, Volkswagen's Golf PHEV, the engine drives the electric-generator through the clutch on one side, and the output torque drives the vehicle through the clutch on the other side. When starting from a standstill, the battery supplies power to the electric-generator, and the electric-generator is the starter of the engine. After the engine is started, it drives the wheels as the vehicle's sole power source, and drives the electric-generator to generate electricity to charge the battery, just like a traditional car. When driving in the city, the engine is turned off, one clutch is disengaged and the other clutch is engaged, and the battery is used as the only energy source to power the electric motor, which replaces the engine to drive the wheels. When the electric vehicle requires high speed or high load, the engine is started and the clutch is closed, and the engine and electric-generator system form a compound drive to drive the vehicle with maximum power.
Working principle of hybrid vehicles

Hybrid vehicles have become increasingly mature in developed countries, and some have entered the practical stage. Due to their complex structure and high cost, hybrid vehicles are only a transitional product before the arrival of the electric vehicle era.
HEVs must use engines as power, and also impose various restrictions on the energy saving and environmental protection of the engine, so that the fuel consumption of the engine is reduced to the minimum, and the emission of harmful gases from the engine meets the requirements of the "ultra-low pollution" standard. The power of the engine must be used to ensure the basic power required for normal driving of HEVs. By controlling the engine speed range, reducing the maximum engine speed, keeping the engine running stably and evenly, and adopting an "on-off" control method, the engine can avoid the fuel economy reduction and increase in harmful exhaust gas emissions caused by incomplete fuel combustion when starting, idling and sudden changes in speed, thereby controlling the engine to always operate in the best state. In addition, HEVs can also widely use rotary engines, gas turbines and Stirling engines as HEV engines.
HEVs use electric motor drive as an auxiliary power for engine drive, but the mass of the battery pack and the curb weight of the vehicle must be restricted to reduce the total mass of the HEV. Therefore, the general electric/generator only works when the HEV engine is started, the vehicle starts, accelerates or climbs. The electric/generator is also the flywheel of the engine, which plays a role in regulating the engine output power. The electric/generator also acts as a generator, converting the engine's kinetic energy into electrical energy and storing it in the battery pack. When the HEV goes downhill or brakes, the vehicle's inertial kinetic energy is converted into electrical energy and stored in the battery pack. Therefore, with the auxiliary role of the electric motor, the HEV can achieve energy saving and "ultra-low pollution" requirements. Since the 1990s, the world has set off a wave of competition in the research, development and manufacturing of HEVs. In the 21st century, HEVs may become the leading products of the automotive industry.
When starting, driving, accelerating and stopping, the control system of the HEV automatically determines and controls what kind of power to use, so that the energy consumption and emission indicators of the vehicle are controlled within the optimal range. When the vehicle starts, the engine is inefficient and the power is provided by the electric motor. When waiting for the signal, the engine will automatically stop running, avoiding the fuel consumption of idling. During normal driving, the car controls the engine to run in the optimal area, part of the power is used to overcome road resistance, and the other part of the power is used to charge the battery.
When the vehicle starts to accelerate or climbs a slope, in addition to the electric energy generated by the unit, it is transmitted to the motor driving the wheels through the control device. In addition, the battery pack also supplies power to the motor driving the wheels to ensure that the vehicle has sufficient traction. When the vehicle is running at a constant speed on a flat road, only the generator set (or battery pack) needs to provide electric energy to drive the vehicle. When the vehicle decelerates, the electric energy generated by the generator set is charged to the battery pack through the control device; during the vehicle braking process, the motor driving the wheels will be converted into a generator and charged to the battery through the control device. This braking method that can convert the vehicle's kinetic energy into electrical energy and recover it is called "regenerative braking".
Hybrid vehicles can improve engine efficiency and save energy by combining the best combination of engine, rechargeable battery and electric motor, and can also clean emissions and reduce environmental pollution. In addition to the engine charging the battery, this type of vehicle can recover power during deceleration, and the brake can convert mechanical energy into electrical energy, avoiding energy waste. The fuel economy of vehicles equipped with hybrid power systems can be doubled compared to ordinary vehicles, while reducing the CO2 emissions that cause global warming by half.
Hybrid-powered vehicles can replenish electric energy to the battery pack during operation, so there is no need to stop in the garage (or charging station) for a long time to charge, as electric vehicles (battery vehicles) do. Hybrid-powered vehicles have the advantages of energy saving, low emissions, and low noise, and maintain the inherent characteristics of traditional internal combustion engine-driven vehicles with long driving range. Hybrid-powered vehicles will have huge development potential and promising market prospects in the fields of small cars and large vehicles (such as buses). Hybrid electric vehicles
(HEVs) are not heavy, and their power system includes internal combustion engines and battery packs, combining the advantages of internal combustion engine vehicles and electric vehicles. They combine internal combustion engines, electric motors, and energy storage devices of a certain capacity through a control system. The electric motor can supplement the torque required for vehicle starting and acceleration, and can also store and absorb the surplus power of the internal combustion engine and the braking energy of the vehicle, thereby significantly reducing fuel consumption and pollutant emissions. Although hybrid electric vehicles have not achieved zero emissions, their comprehensive indicators such as power, economy and emissions can meet the current stringent requirements and alleviate the contradiction between automobile demand and environmental pollution and oil shortage. Compared with traditional internal combustion engine vehicles, their main advantage is that they use high-power energy storage devices (flywheels, supercapacitors or batteries) to provide instantaneous energy to the vehicle, which can improve efficiency, save energy and reduce emissions. Therefore, the economy and emissions are significantly improved, and the technical and economic feasibility is strong. Compared with pure electric vehicles, their main advantages are: the driving range and power can reach the level of internal combustion engine vehicles; air conditioning, vacuum assistance, steering assistance and other auxiliary electrical appliances, with the help of the prime mover power, do not need to consume the limited power of the battery pack, thereby ensuring the comfort of riding; and the technical difficulty of hybrid electric vehicles is relatively small and the cost is relatively low. Hybrid electric vehicles are between traditional vehicles and pure electric vehicles and fuel cell vehicles. They are a kind of electric vehicle product that inherits the past and opens up the future and tends to be mature in both economy and technology.
Market application of hybrid electric vehicles
Since 1995, major automobile manufacturers in the world have shifted their research focus to the research and development of hybrid electric vehicles. Toyota Motor Corporation of Japan has developed a hybrid car. The three major automobile companies in the United States have all developed hybrid vehicles including sedans, vans and trucks. At present, hybrid vehicle technology and the market are optimistic. There are more than 70,000 hybrid electric vehicles in Japan, and it is expected to reach 2.1 million in 2010. General Motors will sell 1 million hybrid vehicles in 5 years. At present, Toyota Motor Corporation is an automobile company at the forefront of hybrid vehicle research and development, and the hybrid vehicles it has developed have reached the level of practical application. In 1997, Toyota launched the world's first mass-produced hybrid vehicle, and then launched hybrid vans and Crown sedans in 2001. By the end of 2002, the cumulative sales of hybrid vehicles produced by Toyota Motor Corporation in Japan and overseas exceeded 100,000, and now they are on the market in more than 20 countries around the world. The characteristics of Toyota Hybrid System (THS) electronic control device are: it can work simultaneously using electricity, gasoline or a combination of the two. According to the vehicle speed and load conditions, THS can control the power ratio provided by each energy source to ensure that the vehicle runs in the most efficient mode. During the driving process of the vehicle, passengers cannot feel the conversion of THS. The key part of the THS system is the power split device. This device uses a set of planetary gears to directly transmit the engine power to the front wheels and generator of the car. The electronically controlled transmission mixes the power output of the gasoline engine, generator and electric motor to meet the needs of accelerating and decelerating the car. In 2002, Toyota's hybrid van was put into production. Its hybrid system adopted the world's first mass-produced electric 4-wheel drive and 4-wheel drive force/brake force integrated control system, which brought revolutionary improvements to the driving performance of hybrid vehicles. All of this shows that Toyota has taken the lead in the world's industry in popularizing the low fuel consumption, low emissions and improved driving performance of hybrid systems. Toyota Motor Corporation plans to use gasoline-electric hybrid engines in all its automobile products in 2012 to improve fuel economy and reduce emission pollution.
According to statistics, nearly 70,000 hybrid vehicles have been sold in the US market, and the scale of the US hybrid vehicle market reached 35,000 in 2002. Nearly 20 cities in the United States are trialing hybrid buses. Major European automobile manufacturers have also launched hybrid vehicles. The French BE Group has successively launched the Behringer and Sara hybrid vehicles. The emission is 35% lower than that of similar ordinary cars, and the driving range can be up to 1000km.
In the late 1990s, China began to research and develop hybrid vehicles. In 1999, Tsinghua University and Xiamen Jinlong United Automotive Industry Co., Ltd. successfully developed the first hybrid light passenger car in China. At the end of 2001, the National 863 Electric Vehicle Science and Technology Research Project was officially launched. The first batch of projects mainly focused on hybrid vehicles and are currently underway. FAW and Dongfeng Motor Group, together with local universities and research institutes, have developed hybrid-drive buses and large buses on their respective bus chassis. In addition, Dongfeng Electric Vehicle Company has also undertaken the research and development of hybrid cars. The goal of the 15th Five-Year Plan is to overcome key technologies and launch new products. The main research contents include: various unit technologies such as engines, motors, and batteries; electronic control technologies of various systems and optimization and control technologies of the power system of the whole vehicle, which should save 50% of fuel and reduce emissions by 80%; brake energy recovery technology, which should be able to recover 30% of braking energy.
At present, Dongfeng Electric Vehicle Co., Ltd. has developed a hybrid vehicle. Among them, the EQ720OHEV hybrid car is developed based on the Fengshen Bluebird car platform to meet the future needs of urban business and taxi vehicles. It makes maximum use of Dongfeng's existing product platform and social resources to achieve product serialization, universalization and standardized design. Main technical parameters: maximum speed 160km/h, lithium-ion battery. The EQ6110V hybrid city bus adopts a hybrid solution and is specially developed for the 2008 Beijing Olympic Games bus. Main performance parameters: Dongfeng Cummins 6BTA diesel engine (maximum torque 488N·m, rated speed 2200r/min; AC motor developed by the Institute of Electrical Engineering of the Chinese Academy of Sciences, pure battery electric operation maximum speed 31km/h; maximum power 27kW, maximum current 119A; The engine and motor are driven together with a maximum speed of 72km/h.
Tianjin Qingyuan Electric Vehicle Co., Ltd. has developed a hybrid medium-sized bus. Its main technical features: it uses dual energy sources, fuel and electricity, while taking into account the convenience of traditional cars and the environmental performance of electric cars; emissions meet Euro III standards, and fuel economy is improved by more than 15%, which is suitable for public transportation between cities and inter-city areas.
Shenzhen Minghua Environmental Protection Automobile Co., Ltd. has developed a hybrid electric light bus. Its technical features: it adopts a parallel hybrid system, the internal combustion engine uses a diesel engine that meets Euro II emission standards, and the electric motor uses an internationally advanced asynchronous AC motor with a vector control system with variable frequency speed regulation; self-reverse charging function: the internal combustion engine is used as a power source to drive the vehicle while it is driving, and the electric motor can be used simultaneously. The engine/generator function is interchangeable, and the engine is used as a generator to charge the on-board battery pack to replenish energy and increase the electric driving range.
FAW Group Corporation, American Electric Vehicles (Asia) Company, and Shantou National Electric Vehicle Experimental Demonstration Zone have jointly launched a hybrid car - CA718OAE. This series hybrid car is a mid-to-high-end model, with a 13kW gasoline engine, a 15kW DC motor, a 144V (105Ah) lead-acid battery, a 4×2 front drive form, and a maximum speed of 135km/h.
Problems faced by hybrid vehicles
For hybrid vehicles to become practical, they need energy storage devices with high specific energy and high specific power, low-cost, high-efficiency power electronic equipment, and high fuel economy. Low-emission engine. The key technologies faced and the problems that need to be solved include the following aspects. First, the control and implementation of the optimal coupling power distribution ratio between the internal combustion engine and the electric motor, and the design of the power distribution device and its integration with the transmission. The frequent starting and shutting down of the hybrid vehicle engine makes the power management of the drive system and accessories complicated, so advanced detection and control systems are needed; the existing hybrid power units based on thermal engines need to improve the conversion efficiency while converting fuel into useful work, while also meeting strict emission standards. The second is to improve battery performance. Energy storage device---must have a higher specific power to meet the needs of high power when the car accelerates and climbs; at the same time, it must have a higher specific energy and a longer The third is to reduce the size of power electronic devices, reduce the weight and reduce the manufacturing cost. The industrial development of hybrid vehicles depends on the progress or breakthrough of the primary or secondary power battery technology of the above-mentioned electric vehicles, and also depends on the improvement of traditional internal combustion engine technology. More importantly, it is to improve the system integration of the drive system and control system.
The prospects and prospects of hybrid vehicles
As we all know, China's oil accounts for only 2% of the world's oil resources, while China's population accounts for 22% of the world's total. Then China's per capita oil resources account for only 1/10 of the world. Under such circumstances, we must find ways to save energy and reduce the resources consumed by a large number of cars in China. Hybrid vehicles are a product of the times. This is one of them. Second, the development of the automobile industry has brought great pressure to environmental protection. Automobiles not only emit exhaust gas, but also noise will affect the environment of our city. The development of hybrid vehicles can reduce environmental pollution and make further contributions to providing us with a better living environment. Third, the automobile industry is an important pillar of our country's economic development. According to general saying, a hundred yuan investment in real estate can drive 180 to 220 yuan, and a hundred yuan investment in the automobile industry can drive 150 to 170 yuan. Of course, from the analysis of the input-output table, the transportation industry ranks third in the influence coefficient, so it is very important for our country's economic development.
In short, hybrid vehicles have become an unstoppable force, changing the structure and composition of automobile products, and moving towards practical application in large quantities. According to the "Auto Mfg & Production" journal, it is expected that in 2005, hybrid vehicles will reach 750,000 in the world automobile market, 1 million in 2010, 15% in 2015, and 25% in 2020. This is a considerable proportion of the number of hybrid vehicles. We roughly estimate that if the global automobile production in 2020 is 100 million, then hybrid vehicles will be 25 million. In short, hybrid vehicles have broad prospects for quite a long time, and are popular in the market, and gradually become the leading products in the automobile industry.