Until the 1960s, most automobile fuel delivery systems still used carburetors with simple structures.
With the rapid development of the automobile industry, the number of cars in the world increased dramatically in the 1960s. Due to the inaccurate adjustment of the traditional carburetor mixture, the exhaust gas content of automobile exhaust emissions was too high (CO, HC, NO compounds, etc.), the pollution to the atmosphere and environment is becoming increasingly serious, and it is an important factor causing global warming and the greenhouse effect. To this end, the United States proposed the Muskie Act in the 1960s, and Japan also proposed regulations to limit vehicle exhaust emissions in 1968, 1973, and 1976.
At the same time, with the continuous advancement of electronic electronics technology, especially the rapid development of transistors (diodes, transistors, etc.) and integrated electronic technology (IC technology), the full application of automotive electronic fuel injection technology in automobiles has Application lays the foundation.
As the fuel delivery system of gasoline engines, the gasoline injection system has a history of development for many years. From the perspective of injection control development, it has experienced two stages of development: the transformation from mechanical fuel injection to electronic fuel injection. The mechanical type has shortcomings such as complex structure, high price, high failure rate and maintenance cost, high fuel consumption, and low accuracy of mixture control. Automotive engineers developed a new electronically controlled gasoline injection system in the 1980s.
Automobile gasoline injection system
Traditional carburetors are prone to air lock, icing, and insensitive throttle response, and cannot supply fuel in multi-cylinder engines. Uniformity will cause unstable operation and is not conducive to high-power design. In order to make up for these shortcomings, as early as the 1930s, the gasoline injection system had been used as a research object in the research and development of aeroengines. After more than 10 years of in-depth research and development, in 1945, in the late stages of the end of World War II, the injection system began to be applied. on military fighter jets. It fully eliminates the shortcomings of the float-type carburetor that cannot be fully adapted to military fighter combat conditions, such as easy freezing point, air resistance, fuel spillage during combat rotation and tumbling due to physical effects such as inertia and gravity, and fuel and measuring holes. Due to separation and other shortcomings, gasoline injection technology came into being.
Although gasoline injection technology has many advantages, because its production was restricted by the social productivity, production process, and technology at that time, its manufacturing cost was very high. Therefore, automobile gasoline injection devices could only be used in a small number of vehicles at first. On a small number of racing cars, it can meet the large engine output and sensitive throttle response performance required by racing cars. By the late 1950s, most racing cars had adopted gasoline injection as their fuel delivery system.
Gasoline injection was applied to civilian mass-produced passenger car engines from 1950 to 1953 when Goliath and Gutorod first applied it to 2-cylinder, 2-stroke engines. A gasoline injection (in-cylinder injection) device was installed. In 1957, Mercedes-Benz adopted it in 4-stroke engines.
The gasoline injection used in cars in the 1950s was mechanical gasoline injection developed and evolved based on the principles and foundations of diesel engine fuel injection pumps. It was developed, produced and put into the market by Bosch, a world-famous automobile supporting manufacturer. It can be said that due to Bosch's active research and development, Bosch plays the role of leader and flagship in the field of automotive gasoline mechanical injection.
In 1958, Mercedes-Benz installed a fuel injector on the intake manifold for the first time on the 200SE, and the fuel was injected in groups. In this injection, an adjustable start valve and an automatic control switch are installed to control the car warm-up time. During starting and car warm-up conditions, the fuel injection amount can be appropriately increased, the air-fuel ratio can be increased, and at the same time, the intake air temperature, Changes in the atmospheric pressure of the driving environment can be controlled more accurately according to the changes in the air-fuel ratio compensation control. It is this kind of gasoline injection method that involves the induction of some electronic components and has preliminary simple electronic control, which laid the functional foundation for the current EFI electronic fuel control.
The birth of electronically controlled gasoline injection
With the rapid development of the automobile industry, air pollution caused by automobile exhaust emissions has become increasingly serious. Western countries have formulated strict automobile emission regulations. bill. At the same time, the impact of the energy crisis and the rapid development of electronic technology and computers have promoted the birth of electronically controlled gasoline injection engines. In 1953, Bendix of the United States first developed the electronic injector (Electrojector), which was officially launched in 1957, pioneering electronically controlled gasoline injection.
In this era, since various engine manufacturers emphasize the improvement of engine output power, in order to ensure the high torque output characteristics at full load, the air-fuel ratio control must be small to increase the fuel injection amount. Therefore, for The air-fuel ratio control accuracy is also relatively low. However, with the development and application of electronic control technology, various advantages of electronic fuel control have gradually emerged, including various fine compensation functions and good air-fuel ratio controllability, sensitive throttle response, and high-power output.
In addition, in terms of electronic technology, the transistor has been invented long ago, but due to its high cost and unstable performance, it cannot be well applied to automobiles. Therefore, Bendix used vacuum tubes to develop electronic computers during the development stage. When it was published in 1957, it was the era when transistors began to become practical. Therefore, the electronically controlled gasoline injection device she developed was only installed on Chrysler cars, one of the three major American automobile companies.
The development of electronically controlled gasoline injection
After 10 years after the release of the injector by Bendyx in the United States, in 1967, the German Robert Bosch Company purchased the Bendyx injector in the United States. Based on the patent of Max, the speed-density D-Jetronic electronically controlled gasoline injection device was launched, which was used by major automobile companies. Electronically controlled gasoline injection has achieved great development. D-Jetronic gasoline injection device already has all the elements of modern electronic gasoline injection and is the pioneer of modern electronic gasoline injection.
In 1973, 6 years after the release of D-Jetronic, Bosch developed mass flow L-Jetronic electronically controlled discontinuous injection and K-jetronic mechanical continuous injection. The former uses intake manifold pressure as a parameter to control the fuel injection amount, but the control effect is not good when the vehicle's operating conditions change drastically. The latter uses an air flow meter to measure the intake air flow and converts it into an electrical signal for transmission to the engine computer. To achieve precise control of fuel injection volume and reduce emission pollution.
In 1981, Bosch released the LH-Jetronic electronically controlled fuel injection system, which added more precise details to the control capabilities and further improved all aspects of engine performance. The biggest feature of the LH system is the use of a hot-wire air flow meter, where "H" is the first letter of "HOT" in English. The hot-wire air flow meter directly measures the intake air quality. It is small in size and has low intake resistance. Therefore, the air-fuel ratio can be controlled more accurately, the engine's power and economy can be improved, and engine emissions can be improved.
Based on the addition of electronic control circuits, K-Jetronic gasoline mechanical injection using flow mode was developed into KE-Jetronic electromechanical combined mechanical fuel injection in 1982. The E in KE-Jetronic stands for electronic control. Until now, the Mercedes-Benz 129, 126 series and Audi 100 models still use KE injection on the street. However, due to its shortcomings such as high fuel consumption, high failure rate, and high maintenance costs, it will also be ruthlessly eliminated.
What we discussed above is the intake pipe multi-point injection system. Its control accuracy is high, but the cost is also high. In order to reduce costs and enable electronically controlled gasoline injection systems to be further applied to ordinary vehicles, General Motors (GM) launched the TBI single-point throttle body injection system in 1979, and Bosch launched the MONO-Jetronic low-pressure central injection system in 1983.
The single-point fuel injection system is structurally similar to a carburetor. It is simple in structure, easy to maintain and adjust, and is superior to carburetors in terms of emission control. Therefore, it was also used in low-displacement cars in the 1980s and 1990s. been widely used. However, due to emission control and other reasons, this injection method has been eliminated and is no longer used in recent years.
While Bosch is working hard to develop fuel injection, other automobile manufacturers in the world are also conducting arduous research in this field:
In 1971, Toyota developed its EFI (Electronic Fuel Injection) Electronically controlled gasoline injection system. EFI control computers are divided into two types: one is an analog type that controls the injection timing based on the time required to charge and discharge the capacitor; the other is a microcomputer control type that uses data in the memory to determine the injection timing. It began to be equipped on cars in 1981.
In order to implement increasingly stringent emission regulations, in addition to researching and introducing exhaust gas reprocessing technologies such as secondary air injection combustion, catalysts, and mixed gas combustion, we have also further developed air-fuel ratio control With the new technology of precision, Os sensor and three-way catalyst appeared again. Three-way catalysis uses rare metals such as platinum as catalysts to reduce harmful gases such as CO, Nox, and CH in the exhaust gas into harmless gases such as CO2, N2, and H2O. However, the three-way catalyst can only exert its greatest effect in a very narrow range close to the theoretical air-fuel ratio. Therefore, Os needs to be used to detect the oxygen concentration in the exhaust gas, and the engine computer can accurately adjust the air-fuel ratio and control the fuel injection amount. The oxygenator feedback system used by Nissan and Toyota Motor Corporation in air flow gasoline injection devices in 1977 is still used in many vehicles today.
With the development of integrated circuits in electronic technology, microcomputer technology is developing rapidly. Similarly, automobile electronic control computers have also entered the digital era from the analog era. The first use of digital technology to control engines was the ignition timing control (MASIR) developed by General Motors in 1976. It can better control the ignition governor advance angle and negative pressure advance angle accurately according to the engine operating conditions.
In 1984, Toyota launched the speed-density T-LCS (Toyota Lean Combustion System) Toyota lean combustion system gasoline injection device, which can effectively control the injection time and ignition time under various operating conditions. , excellent control.
Due to the use of microcomputers and the development of microcomputer computing, storage, analysis, learning and other functions, complex logic and intelligent control calculations can be performed to control changes in engine operating speed, intake air flow and other working conditions. Being able to respond quickly, microcomputer-controlled gasoline injection has gradually become the main injection method. At the same time, it has also been fully developed in diesel injection methods. Looking at the current gasoline-injection cars, they have integrated high technology and high precision. The exhaust emissions they control, such as CO and HC, have reached a level of 0.00 orders of magnitude when measured with an exhaust gas meter, which is almost "zero" emissions.
At the same time, the central control computer not only participates in the control of the engine, but also uses the multiplex transmission system, various BUS lines and other electronic control systems of the body, such as ECT, ABS, TRC... to share information operations, One machine has multiple functions, which qualitatively improves the driving performance of the entire vehicle.