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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Electronics in the car. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices Today you will not surprise anyone with the abundance of electronics in a car, especially high-class ones - in the Lincoln of the Mark VIII model there are only more microprocessors than on any other modern fighter. The automotive electronics market is one of the four fastest growing sectors of the electronics industry (after telecommunications, computer and industrial equipment), which, in turn, is the fastest growing - an average of 8...10% per year - the largest industry in the world. Moreover, the main share of the cost of electronic devices abroad falls not on service devices (radio recorders, burglar alarms, etc.), but on the means of controlling the car’s own systems and ensuring security. Their share in the cost of a modern car is also increasing, reaching now an average of 10...15%, although analysts predict its stabilization in the near future at about 20...25%. Given, however, the continuous decline in the unit cost of electronic devices (in terms of one function), there is no doubt that the number of functions performed by electronic devices in the car, and their variety will steadily expand further, at least until as long as the consumer is able to use them. Thanks to the gradual restoration of ties between the Russian and world economies, the imbalance in prices between electronics and other engineering products that existed in Soviet times is becoming a thing of the past. Along with this, the need to simultaneously increase the efficiency, environmental friendliness and improve the driving performance of cars is becoming relevant for domestic car factories. Firstly, this is due to the fact that the export of obsolete products to developed countries becomes almost impossible, even at low prices, and enterprises need hard currency to pay for imported components. Secondly, recently in our country, more stringent standards for permissible levels of air pollution and car safety have been adopted and should soon be put into effect, which will bring us closer to the conditions prevailing in the global automotive market. In this regard, turning to the experience of the global automotive industry looks completely natural and justified. In our country, VAZ now equips more than 40% of manufactured cars with electronic control systems for injection and ignition. At present, the most important and economically justified is the widespread introduction of electronic systems that improve performance and reduce the cost of operating the engine and transmission, as well as systems to improve safety - both active (ABS - anti-blocking system (AntiBlocking System), APS - traction control) and passive (airbags). In addition, other electronic systems have been developed and are already being used - suspension controls, navigation, parking, etc., but they are still more of a luxury than a necessity. For a long time, the only electronic component in a car, apart from the radio, was the ignition system. The classical spark ignition system was first proposed by Philippe Lebon in 1801, and it found its first industrial application on the Lenoir gas engine in 1860-1864. However, due to the low level of electrical engineering of the time, spark ignition did not work reliably. Therefore, until the 90s of the last century, most internal combustion engines were built using glow ignition (a highly heated body in the combustion chamber). The situation changed with the creation by Robert Bosch of a completely reliable and compact magneto. Further, in the 10s of our century, thanks to the improvement of the design of the spark plug, the ignition coil and the selection of contact materials, it was possible to achieve satisfactory operation from the battery ignition system. Nevertheless, she, especially contacts, still remained one of the most unreliable and maintenance-requiring parts of the car. Fundamentally different solutions were needed. The first electronic ignition systems were created in the 1940s on the basis of gas-filled thyratrons, but they were not widely used due to the bulkiness and fragility of the design. Mass application of transistorized ignition systems - first contact, then non-contact - was found in the early 1960s, when General Motors Corp. (GMC) began to equip their production cars with them. The further spread of electronic ignition systems is well known. Of particular interest is the Direct Ignition (SAAB) high-frequency discharge system, borrowed from jet engines. When it was created, the circumstances were used that the breakdown voltage for a high-frequency (80 ... 200 kHz) voltage turns out to be two to three times less than for a low-frequency one, and instead of a thin filamentous spark, a spherical discharge with a significantly larger surface is obtained. Reducing the voltage makes the system less sensitive to oiling and soot on candles, and the spherical shape of the spark discharge accelerates ignition and increases the reliability of igniting lean mixtures. However, the design complexity and higher cost of this system, as well as the fact that it generates abundant radio interference, led to its removal from production after the introduction of electronically controlled distributed injection systems (The operating conditions of candles and the ignition system as a whole on such engines are much easier than on carburetors). Contrary to popular belief, fuel injection is also not a new invention. Moreover, it was the injection system that was originally used in almost all internal combustion engines that ran on liquid fuel. However, it soon became clear that it required a rather complex mechanism for regulating the amount of injected fuel and fuel metering pumps made with high precision. At the beginning of the century, this was very expensive, but at a reasonable price, it did not provide the necessary reliability and stability of characteristics. Therefore, after the invention of a simple and cheap spray carburetor by Donat Banki, injection systems in the automotive industry were almost forgotten. They remained only in diesel engines, the increased cost of which, by the way, is largely due to the high cost of high-pressure direct injection equipment. Due to their high price, mechanical injection control devices were almost never used on mass-produced cars. The first electrically controlled systems were created as early as 1939 (Moto Guzzi, Italy), but they remained technically exotic. In 1957, Chrysler introduced an automotive electronic fuel injection system based on vacuum tubes, which also did not find wide application due to its high cost. Transistor systems became more widespread in the early 1970s and were used in German (Volkswagen, 1967) and Japanese (Nissan, 1971) cars exported to the United States. At the turn of the 70s and 80s in Japan, the USA and somewhat later in Germany, they began to introduce integrated microprocessor control systems as an engine. The carburetor has many disadvantages: instability of adjustments, especially when changing temperature and fuel type; uneven distribution of fuel over the cylinders; low accuracy at low loads, forcing the carburetors to be adjusted in such a way that at idle and low load the combustible mixture is too rich. In addition, the carburetor increases air intake resistance. Due to the presence of a float chamber, the performance of the carburetor deteriorates in conditions of strong shaking, acceleration in corners and when the car tilts. For the time being, these shortcomings in relation to mass-produced cars were fully compensated by the simplicity and cheapness of carburetors. Nevertheless, in expensive cars, as well as in piston aviation, since the end of the 30s, there has been a return to the use of mechanically controlled fuel injection systems. They were very complex and expensive, but they made it possible to increase the efficiency and stability of the engines. However, as the requirements for environmental cleanliness of exhaust became more stringent and the maintenance of a mass-produced car was simplified, it turned out to be almost impossible to ensure their implementation by improving carburetors (A typical requirement in the US market is the need for the first maintenance of the engine and transmission no earlier than after 80 ... 100 thousand km). miles). The essence of the problem is that, if the combustible mixture is poor, it ignites poorly, burns unsteadily, is prone to detonation, and produces a lot of nitrogen oxides NOx during combustion. Once in the atmosphere and combined with water, these oxides form nitric and nitrous acids. If there is more fuel in the mixture than can be burned in the available amount of oxygen, then incomplete combustion of the fuel leads to emissions of hydrocarbons CmHn, carbon monoxide CO, benzopyrenes, aldehydes, and with an even greater excess of fuel - very carcinogenic soot (smoke). With a strong violation of the ratio between the amounts of air and fuel, the air-fuel mixture generally ceases to ignite, which, no doubt, is familiar to many motorists. It is possible to sharply - more than ten times - reduce the amount of harmful emissions using a catalytic converter (afterburner) of exhaust gases, however, its operation requires a very specific composition of exhaust gases. In particular, the converter does not tolerate operation on leaded gasoline. Violation of these conditions leads to irreversible failure of the converter. Nevertheless, the emergence and rapid reduction in the cost of microprocessor technology made it possible to create fuel injection systems for gasoline engines, firstly, that do not require expensive precision mechanical devices, and, secondly, that have significantly greater capabilities than mechanical ones. As a result, the use of electronic fuel injection and ignition control systems since the late 1980s in developed countries has become economically justified on cars of almost all classes. The electronically controlled injection system (EFI - Electronic Fuel Injection) when using an oxygen content sensor in the exhaust gases (l-probe) allows for a very stable (+ 0,5%) observance of the optimal ratio by weight of the supplied fuel and the intake air for each cylinder ( 1:14,65 for gasoline). This is necessary both to ensure the performance of the catalytic converter, and to achieve the best compromise between engine power and economy. That is why in practice it is possible to ensure a long service life and performance of catalytic converters only when using Fuel injection systems are conditionally divided into three groups - with central injection, when there is one spray nozzle for the entire intake manifold (Sometimes it has to be supplemented with a second one - a starting nozzle that works with a cold engine and turns off as it warms up), with distributed (multi-point) injection, if injectors are installed in the intake pipes of each cylinder near the intake valves, and with direct (direct) injection, when the nozzle is mounted directly in the cylinder wall or head and delivers fuel directly to the cylinder on the compression stroke when the valves are already closed. In the first two cases, the fuel pressure during its supply does not exceed 4 ... 10 kg / cm2, while with direct injection in a diesel engine it can reach 600, and in a gasoline engine - 50 kg / cm2. The cheapest system - with central injection - actually gives only two significant advantages - vibration resistance and the absence of the need for frequent adjustments. The best price/quality ratio is currently provided by multipoint injection systems into the inlet pipes (Fig. 1). Direct injection systems in gasoline engines are justified so far only in supercharged engines, since they make it possible to exclude the carry-over of the air-fuel mixture into the exhaust manifold with wide valve timing and an absolute boost pressure of more than 1,5 kg / cm2.
There are also systems of continuous and pulsed (intermittent) injection. In continuous injection systems, the nozzle works constantly, only its performance changes, in pulse systems, fuel is injected in portions at certain moments. Continuous injection has many disadvantages and is now considered obsolete in automotive engines. The use of multiport injection provides other advantages over the use of carburetors. Firstly, this is the possibility of ensuring high stability of the composition of the combustible mixture over a wide range of temperatures and engine loads, and practically regardless of the viscosity of the fuel (the throughput of the carburetor jets strongly depends on the viscosity of the fuel). Secondly, the use of multi-point injection (especially direct) allows not only to ensure uniform distribution of fuel over the cylinders, but also to eliminate the need to heat the intake air and intake manifold. Moreover, the evaporating fuel, on the contrary, cools the intake air and engine cylinders. As a result, the density of the intake air turns out to be 7 ... 10% higher (For the same purpose - to reduce the air temperature - even on cheap cars with injection, they try to suck in air not from the engine compartment, where it is hot, but directly "from the street", providing for this, if necessary, additional air intakes (Opel "Cadett") . Increasing the density of the air, and therefore the amount of oxygen entering the cylinders, allows you to burn more fuel and get more power. Lowering the intake air temperature allows the compression ratio to be increased, which improves engine efficiency. Eliminating the carburetor reduces air intake resistance, allowing the use of a resonant intake, which also improves power. The approach of the injector to the cylinder in multiport injection systems prevents fuel condensate from falling out. This makes it easier to start the engine, reduces the formation of carbon deposits on the spark plugs and flushing of oil from the cylinder walls. The absence of fuel condensation increases stability and engine torque, especially at low and medium speeds, where it is most needed. If the increase in maximum power when switching the engine to fuel injection is usually about 10%, then the increase in torque at low and medium speeds can reach 15 ... 20%. Of course, such an increase in driving performance of the car can be achieved "on the forehead", by increasing the working volume of the engine by about 20 ... expenses. The use of distributed injection systems provides another opportunity to reduce fuel consumption - turning off the fuel supply to some of the cylinders in order to load the rest to a greater extent. The expediency of such a solution is due to the fact that at a low load, the efficiency of an internal combustion engine is sharply reduced not only due to mechanical losses, but also due to a non-optimal operating cycle. The increase in the efficiency of loaded cylinders more than compensates for mechanical losses in the off cylinders, so the economy at low loads can be increased by 25 ... 30%, especially on multi-cylinder engines. A similar technique - alternately skipping injection cycles - is also widely used on multi-cylinder Japanese and American cars. There is another application of the cycle skipping method - cooling the "disconnected" cylinders with intake air, which allows you to maintain engine performance and reach your destination even after a complete loss of coolant (GMC North Star engine, etc.). The use of electronics ensures optimal control not only of the engine, but also of the chassis of the vehicle. Firstly, these are well-known anti-lock braking systems, which in most cases allow you to maintain controllability of the car during emergency braking, while simultaneously providing the shortest possible braking distance. Secondly, a function close to them is performed by anti-slip systems, which have become very relevant in connection with the spread of front-wheel drive vehicles, in which controllability is lost when the drive wheels slip or lock. Since the front wheels are unloaded during acceleration of the car (which is why all racing and prestigious cars that must have good acceleration dynamics are still designed with a drive either to the rear ("Daimler-Benz", "BMW"), or to all wheels ( "Audi A8"), in order to avoid loss of control and prevent excessive tire wear, it is highly desirable to have a front-wheel drive car along with anti-lock and traction control. With the help of electronic devices, the antagonism between gearboxes with automatic and manual shifting is also smoothed out. Recall that the classic automatic transmission to ensure smooth switching requires the use of an expensive and bulky torque converter, which also has large mechanical losses (low efficiency). The gearbox with manual shifting is structurally much simpler, more compact, cheaper and more reliable. True, it is less convenient to use. The integrated engine and transmission control system automates the process of gear shifting without the use of torque converters and additional clutches - by automatically controlling the clutch and engine speed, while maintaining all the operational advantages of both automatic (convenience) and manual gearboxes (reliability, low cost, low losses energy). In addition, electronic control virtually eliminates the risk of damage due to incorrect handling. Such a transmission does not differ in manufacturing cost from a manual transmission, and its control functions are usually integrated into an integrated engine and transmission control system. Gearshift algorithms have recently been built to adapt to the driving style of a particular owner, not to mention the fact that there are always several standard modes to choose from (high-speed, urban, economical, etc.). An equally important role in a modern car is played by electronic security systems. It is customary to subdivide it into active (prevention of accidents) and passive (reducing the severity of their consequences). As for active safety, it is provided by improving the accelerating and braking dynamics of the car, as well as increasing cornering stability by maximizing the track width and lowering the center of gravity (this is clearly visible if we compare the silhouette of domestic and foreign cars of a similar class, such as VAZ- 2108 and Volkswagen "Golf III" or "Golf IV") in combination with an electronic suspension control system. On expensive cars, a radar system is sometimes used to prevent head-on collisions and collisions (maintaining a distance), but it does not save from a log or a hole in the asphalt. To reduce the likelihood of collisions, upper (salon) brake lights are used, visible at a great distance. This was not enough, and then a system was developed with a transceiver radio channel that automatically turns on the indicator in case of emergency braking or an accident in front of the car. At present, this system, which received the gold medal of the exhibition of inventions in Brussels, is being finalized with subsequent standardization in most developed countries. Accelerating dynamics are improved, first of all, by the introduction of electronic fuel injection and transmission control systems (a microprocessor can shift gears much faster and more accurately than a person; as a result, the car accelerates), and on front-wheel drive vehicles, also by improving the rubber composition and tread pattern wheels, brake - the use of anti-lock braking systems that prevent excessive slippage of the wheels relative to the road, which allows you to get the maximum possible braking force and, in most cases, maintain vehicle controllability even during emergency braking. A certain contribution to the increase in active safety is made by the steering servo control with variable gear ratio and steering response - to ensure an equal turn of the wheels at high speed, a larger steering angle is required than at low speed. Sometimes an additional device is introduced to prevent the wheels from being torn off by lateral force. This virtually eliminates the risk of skidding during sharp turns at high speeds. All these advantages, however, remain only as long as the servo system is working properly .... Passive safety is increased both by constructive measures (increasing the course of deformation of crushed parts of the body while strengthening the interior, replacing a conventional steering wheel with a safety one), and by introducing electronic devices that actuate airbags and a belt tensioning mechanism. By the way, the widespread introduction of electronics in cars in the United States began precisely after, at the turn of the 60s and 70s, Congress passed a law on the mandatory installation of systems that block the engine start until the seat belts on the two front seats are fixed. . Nowadays, as a rule, an integrated control system for belts and airbags is used. The sensor in it is a uniaxial (or biaxial when using side airbags) accelerometer, most often a semiconductor one (Fig. 2), a control unit with threshold devices and a set of squibs, some of which, when triggered, act on the impellers tightening the belts (Fig. 3) , and part - fills the airbags. The activation of the squibs of the belt tightening mechanism is usually set somewhat earlier than the moment of deployment of the airbags.
The operation of this system allows you to get off with fright, scratches or bruises in a head-on collision with a fixed obstacle at a speed of 50 km / h (EC standard), and sometimes more - up to 80 km / h. At speeds above 80 km / h, the acceleration experienced by a person at the moment of extinguishing the energy of movement on the way, about 0,7 ... weight even in the absence of external damage. Speaking of electronic security systems, it is also worth mentioning a simple but very useful device for monitoring the health of signal lamps and wiring. The principle of its operation is that a small current is passed through the lamps and wiring with the ignition on, which does not cause the lamps to glow, but allows diagnosing a short circuit, an open circuit and the condition of the lamp - at the end of the service life, the resistance of the filament increases slightly, which serves as a warning to the driver in advance . Recently, a certain popularity, at least on cars of a class above the average, has begun to acquire the use of electronic control of suspension parameters - the stiffness and damping coefficient of shock absorbers, and changes in ride height. Such a suspension is often called active, although in fact we are only talking about a relatively slow adaptation of the suspension parameters to road conditions, that is, it is more accurate to consider it adaptive or semi-active. A truly active suspension system, strictly speaking, should, with the help of a powerful servo system, track each bump and dampen shocks even at the moment of their occurrence, as happens on comfortable ships and many warships (“rolling stabilizers”). In Europe and even, perhaps, in the world, the leader in "suspension building" is Citroen, which has long and successfully used the most advanced - hydropneumatic - suspensions in combination with electronic control of their parameters. Mitsubishi seems to be the leader among Japanese firms. Americans, with excellent roads and a 55-mile speed limit in most states, prefer more traditional solutions - increased dimensions and, therefore, the moment of inertia of the car body, combined with large diameter wheels and soft suspensions, in which electronic systems usually control only the damping factor. The use of electronic devices also made it possible to improve a number of traditional devices, first of all, electric drives (windshield wipers, power windows, seat adjustment, etc.), lighting and signaling devices. Traditionally, in automotive technology, collector electric motors are used, which have three main disadvantages - limited service life, insufficient reliability (tendency to get stuck) and radio interference. These shortcomings are due to the use of rubbing contacts in the collector. The development of electronics has led to the fact that contactless (brushless, brushless) motors have become price-competitive with traditional ones, surpassing them in reliability, manufacturability and adjustment capabilities. Wide range of control options make it possible to simplify the kinematics of a number of devices, such as a windshield wiper, where electrical reversing can be used instead of mechanical reversing. Therefore, at present, almost all leading automobile manufacturers are gradually replacing collector motors in their cars with non-contact ones, which also have the advantage that their control units can have an interface for direct control from a microprocessor. As for lighting devices, the introduction of metal halide discharge lamps, which are gaining popularity, would simply be impossible without the use of electronic control units for them. The main advantages of metal halide lamps compared to incandescent lamps are the significantly smaller size of the luminous area, which makes it possible to reduce the size of headlight reflectors while maintaining the quality of beam focusing, to achieve better efficiency (higher light output with equal power consumption), stable spectral and brightness characteristics, regardless of the degree of rarefaction battery, and durability. Another electronic system that improves driving safety is the headlight position corrector, which provides constant illumination of the road when driving on uneven or winding roads, regardless of the load and the position of the body, in the latter case it monitors the steering wheel. In addition, the corrector reduces the blinding effect of headlights on drivers of oncoming vehicles. Signal lights on many American cars have recently been made on the basis of ultra-bright LED blocks. They are more economical, smaller and more reliable than traditional incandescent lamps, especially in flashing mode, they provide greater brightness and purer colors (better visible during the day). The brightness of the LEDs is easier to change depending on the ambient light. Sound signals also do not go unnoticed - the traditional contact electromagnetic horns are being replaced by non-contact electrodynamic and piezoelectric horns with appropriate electronic amplifiers and control units. The advent of digital signal processors and the gradual reduction in prices for these devices led to the creation of active low-frequency noise suppression systems in the car interior. The essence of the idea is to feed into the cabin through the speakers of the built-in audio system signals that are antiphase noise. In this case, the noise signals are mutually compensated. In practice, due to the wave properties of sound, the desired effect can only be obtained at a frequency below 200 ... 300 Hz, and the noise reduction does not exceed 8 ... 15 dB. It would seem a little, but, given that the fight against low-frequency noise in other ways is ineffective, such an electronic system saves 10 ... 25 kg of Dynamat sound absorber or other material that is by no means cheap. The widespread introduction of electronic control with the traditional approach leads to a sharp complication of electrical wiring, and consequently, an increase in the complexity of its laying and the likelihood of errors during maintenance during operation. The abundance of wires threatened to turn the car into an "electric cabinet" on wheels. In search of a solution to this problem, automakers turned to the experience of aviation: at one time, the mass of electrical cables there reached 30% of the weight of aircraft electrical equipment and tended to increase further. The problem was solved by introducing systems of the "common line with serial transmission" type, when most electronic devices are connected to each other in parallel using a common three-wire interface, and information is exchanged between them over the same wires, but separated in time, in the same way as it does in Ethernet computer networks. Similar solutions called multiplex wiring began to be used in the automotive industry in the early 90s. Initially, as usual, there was a "war of standards", which included J1850 (SAE), CAN (Controller Area Network), CarLink, VAN, A-bus, etc. To date, the CAN standard, jointly developed by Bosch, has received the most recognition. and Motorola. It provides a transfer rate of up to 1 Mbps and allows you to use both copper wires and fiber optics for information transmission. Author: S. Ageev, Moscow
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