I'm a freshman now, and I'm studying mixed direction. I hope I can learn it well. But now a lot of knowledge is scarce!

At the initial stage of vehicle driving, the battery is fully charged, and its energy output can meet the requirements of the vehicle, and the auxiliary power system does not need to work; When the battery charge is lower than 60%, the auxiliary power system is started: when the energy demand of the vehicle is large, the auxiliary power system and the battery pack simultaneously provide energy for the drive system; When the energy demand of the vehicle is small, the auxiliary power system provides energy for the drive system and also charges the battery pack. Because of the existence of the battery pack, the engine works in a relatively stable working condition and the emission is improved. Not all hybrid cars rely on electric engines, batteries and wires. Some vehicles are driven by hydraulic engine, bell line and battery. Recently, the price of gasoline has reached a record high, which makes consumers standing in front of the gas pump tremble with fear. However, compared with the operators of heavy truck transport fleets, the pain of these consumers can only be regarded as minor pain. From the point of view of fuel economy, trucks carrying parcels and garbage for us need to bear several adverse effects. Weight is one of the main factors. A fully loaded heavy transport vehicle generally weighs between 14000 and 33000 pounds. In addition to the weight factor, many of these vehicles also have the duty cycle of fuel combustion, and they need to start and stop constantly. In the past year, UPS has been testing and running a six-class delivery truck using a hydraulic hybrid system in Michigan. The company has also put into use 50 electric hybrid trucks. Therefore, it will not be surprising to anyone that several largest truck fleet operators have started to chase the trend of hybrid vehicles. Lynn Brown, a spokesperson for WasteManagement, the largest garbage transportation company in the United States, said that FedEx and UPS have added dozens of hybrid trucks to their transportation fleets in the past two years. Both companies use hybrid trains provided by Eaton, and the company is still evaluating a series of hybrid solutions for muck transportation vehicles. However, it may be surprising that FedEx, UPS and waste management companies are considering the types of hybrid systems used in some of the heaviest vehicles. Unlike Toyota Prius, these hybrid systems use electric engines, batteries and wires, but use the combined action of hydraulic pump engines, high-voltage clock lines and batteries to drive vehicles. This most radical model of hydraulic hybrid power completely gets rid of the traditional mechanical power transmission system. On these vehicles, the diesel engine drives the hydraulic pump engine, which in turn stores energy for the high-pressure accumulator. The accumulator drives the oblique shaft hydraulic motor on the rear wheel to drive the vehicle. A low-pressure accumulator is used to collect liquid, and then it is sent back to the first hydraulic pump engine, thus forming a complete hydraulic circulation system. Like the electric hybrid engine, the hydraulic hybrid engine has the ability to provide regenerative braking. Cargo transport vehicles and muck transport vehicles often have to brake. When the vehicle brakes, the hydraulic pump engine will store energy for the high-pressure accumulator. When the truck moves forward again, the energy stored in the accumulator can be used to reduce the load of the diesel engine. When the engine is turned off, such as when the vehicle is running indoors, these energies will also limit the generation of propulsion. For ordinary consumers or some engineers, in such an increasingly electrified world, hydraulic engine technology seems to be somewhat outdated. The hydraulic pump engine and accumulator can provide a reliable and low-cost way to apply torque and store energy, which is exactly what hybrid vehicles need. Moreover, hydraulic engines have obvious power density advantages over electric systems, at least for now. "Hydraulic engines seem to be very effective, at least for most heavy-duty truck series," commented Dr. John Desico, a mechanical engineer and a member of the Advanced Automobile Strategy Society of the Environmental Protection Foundation.

Hydraulic drive mode

Nowadays, there are three main ways of hydraulic hybrid power system, and they are all developing. Researchers from the Office of Transportation and Air Quality (OTAQ) of the US Environmental Protection Agency (EPA) have jointly developed a hybrid power system with Eaton, Southwest Research Institute (SwRI) and other partners. Since June, 2006, the system has been tested and operated on UPS delivery trucks in Detroit. The United States Environmental Protection Agency also signed a separate cooperative research and development agreement with Parker Hannifin, and began to design hydraulic hybrid power. In some respects, the hydraulic hybrid power system is similar to its matching electric hybrid power system. The hydraulic system uses hydraulic pump engine, bell wire and accumulator to generate torque and store energy, instead of motor, wire and battery. Eaton Company and Parker Hannifin Company have also developed hydraulic hybrid power systems with independent intellectual property rights. Eaton has developed a parallel system assisted by hydraulic starting, but its main propulsion still comes from mechanical power train. Parker Hannifin has developed a new hydraulic hybrid design in the past year and a half, and some load cycle data come from waste management companies. Dr. Joe Kovach, vice president of Parker Hannifin Company and mechanical engineer in charge of innovative design of hydraulic power department, reported that his company will build a muck transport vehicle with the new hydraulic hybrid system later this year. When it comes to the development of energy saving, environmental protection and new energy sources for automobiles, in China, it often stays in the exploration of electric vehicles. Indeed, the global automobile industry did not work hard on electric vehicles, but in the end they all came to a dead end. In the new century, the technical route of automobile development tends to be reasonable and unified: in the near future, hybrid electric vehicles will greatly reduce fuel consumption and emissions; In the long run, cars will be redefined by hydrogen fuel cells which are extremely rich in resources and completely pollution-free. Under the general trend of global automobile industry downturn, Toyota can be called "outstanding". In 2003, Toyota's net profit was US$ 65,438+US$ 0,065,438 +0 billion, far higher than the combined profits of the three major American automobile companies. There are many factors for Toyota's success, one of which is the development and application of new technologies. Toyota's first commercial hybrid vehicle, Pioneer, sold 265,438+0.783 vehicles in the United States in the first half of this year, up 65,438+0.20% year-on-year. Customers have to wait six months or even raise the price to get the car. "Pioneer" is therefore called Toyota's "money-making machine" in the American market, which makes the peers salivate. Worldwide, Pioneer has sold 220,000 cars. Five years ago, when I interviewed the Detroit Auto Show, I asked Akio Fujio, president of Toyota Motor Corporation of Japan: What will be the decisive factor for the global auto industry competition in the next decade? President Zhang's answer is clear: it is environmental protection technology. In the future, any company with advanced energy and environmental protection technology will be invincible. 200 1, go to Toyota in Japan to test drive the hybrid car "Pioneer". At the same time, it is equipped with two systems: gasoline engine and electric motor. When starting, accelerating and going uphill, the two systems output at the same time; When braking, the energy is reversely stored in the storage battery; When driving smoothly, the battery-driven motor outputs independently, and no oil is burned. Counting the general ledger, hybrid vehicles can save half of gasoline, and exhaust pollution will naturally be reduced by half. At that time, the market price of the hybrid car was 2,654,380,000 yen (RMB 6,543,380,000 yuan), which was 400,000 yen more expensive than the car of the same class. However, the government subsidizes private car purchases by 250,000 yen, and the extra money spent by car owners can be earned back from the gasoline expenses saved for more than a year. In particular, it is convenient for consumers, and hybrid vehicles only need to refuel at ordinary gas stations without changing their usage habits; Governments and enterprises do not need to invest in new charging equipment or gas stations to promote this product. In recent years, Toyota in Japan, GM in the United States, Mercedes-Benz in Germany and other automobile companies with strong technological advantages have reached the same goal in dealing with the biggest issue of the global automobile industry: to strive to improve hybrid vehicles in the near future; In the long run, hydrogen-powered fuel cell vehicles will move from concept cars to commercialization. The development and production of electric vehicles were abandoned because of the high cost and the fast knot of short driving distance after charging. It is reported that American and Japanese automobile companies have started to compete in the hybrid vehicle market, and it is estimated that the whole market will reach 654.38+0 million vehicles within three to five years. China's automobile industry and scientific and technological circles once had a special liking for the development of electric vehicles, mainly for the following reasons: China, a traditional automobile country, was several decades behind developed countries; There is no big breakthrough in electric vehicles all over the world. We are now beginning to study them. Standing on the same starting line with developed countries, it is entirely possible for latecomers to catch up. However, this foolishness of "cutting corners" eventually came to a dead end with the announcement that the American and Japanese automobile industries gave up the research and development of electric vehicles. It should be said that the development thinking of China automobile industry should be shifted to a pragmatic and capable direction. Hydrogen-powered fuel cell vehicle is a cutting-edge technology that must be paid attention to, but it can only be paid attention to. The research and development of hybrid vehicles should be the top priority. First, the hybrid car is not a distant high-tech, and there are mature commercial models to learn from. Second, hybrid electric vehicles are especially suitable for the national conditions of traffic congestion and frequent braking in big cities in China, and can give full play to the effects of energy saving and pollution control. In fact, if the oil price in China continues to rise or the fuel tax is implemented, it will be difficult to fundamentally improve the road congestion, and the market demand for hybrid vehicles will be very urgent. It is estimated that joint venture production or import of hybrid vehicles will soon be put on the agenda by savvy manufacturers or dealers. Hybrid electric vehicle will become a new business opportunity in China automobile market.