Car carburetor[汽车修理知识]

To makecarTo be able to work continuously (driving), it is necessary to continuously supply oil and air to the engine, not only to supply, but also to mix them properly, and the exhaust gas must be smoothly discharged after the combustion is completed.For this, the fuel needs to be stored in atankInside, to send the fuel in the fuel tank to the engine, there must be a fuel pump and pipeline.In order to prevent the fuel from being contaminated, it is necessaryFilterFilter it.The outside air contains sand and dust, and the air sent to the engine needsair filterTo be filtered.How to mix clean air and fuel as needed requires a non-default part, that isCarburetor(figure 2). The car carburetor must do two things: one is to vaporize the fuel; the other is to mix the vaporized fuel with a certain proportion of air to form a mixture. The air from the outside enters the car carburetor after being filtered, and the amount of air intake is controlled by the change of the choke position. The air rushes through the throat pipe in the carburetor to generate suction to suck the fuel from the float chamber through the nozzle and atomize it.After the atomized fuel and air are mixed, there is noIntake manifoldInhaled by the cylinder. The intake of the mixture is controlled by an accelerator pedal, which is located in the accelerator (Throttle) Controlled by. The amount of oil pumped into the float chamber by the gasoline pump is controlled by the float in the float chamber. The float rises and lowers with the amount of oil in the float chamber. When the float chamber is full of gasoline, the float floats up and uses its needle valve to block the oil inlet.The driver changes the engine's engine speed by controlling the throttle opening.Rotating speed, This is the working principle of a simple carburetor (Figure 3). The concentration of the mixture gradually becomes thicker as the throttle is opened. The working conditions of the car engine must often change in a wide range. For example, before the car starts and waits for the green light to be released at the intersection, the engine runs at idling speed. At this time, the load is zero, the throttle opening is the smallest, and the speed is the lowest; the car is fully loaded and climbs. When driving on a flat road, the throttle does not have to be fully opened, the engine emits a medium load, and the speed and speed are medium; when driving on a highway, the engine may be at full load and the speed reaches the maximum. Under so many complicated working conditions, the requirements for mixed gas cannot be the same. For example, at idling speed and light load, the former requires the mixture to be very dense, while the latter requires the concentration to gradually become thinner; under medium load, in order to save fuel, the carburetor is required to supply the mixture with the least fuel consumption; Under load, in order to allow the engine to emit maximum power, the carburetor is required to provide a rich mixture. In addition, for example, when a car is cold starting, a thicker mixture is required; when accelerating, the carburetor is required to supply additional fuel when the throttle is suddenly opened. To sum up, under normal working conditions of gasoline engines, the carburetor is required to supply a mixture that changes from richer to leaner as the load increases, and at full load, the carburetor is required to change from lean to richer. According to the above requirements, the simple carburetor introduced above cannot be satisfied. In order to meet these requirements, a series of mixed gas concentration compensation devices are equipped on the modern oiler. Such as the main fuel supply pump, idle speed system, economizer, acceleration system and starting system, etc., to ensure that the carburetor can supply the appropriate concentration of mixed gas under different working conditions of the gasoline engine. Regardless of the small size of the carburetor, but with so many systems integrated inside, the structure becomes complicated. The seed guarantees that the carburetor can always work normally, so its regular maintenance is very important. The main disadvantage of using a carburetor is that the distribution of charge to the cylinder and the mixture is not ideal, which affects the improvement of the engine's power and economy, and is very unfavorable for meeting the emission requirements. In recent years, in order to meet environmental protection requirements, various countries have adopted direct fuel injection to replace carburetor. The advantages of direct injection are high charging efficiency, large output power, uniform distribution of mixed gas, supply of mixed gas of the best composition according to changes in working conditions, and low fuel consumption. The disadvantage is that it is difficult to arrange on the cylinder head and the manufacturing cost is high. According to the injection position, it can be divided into two types: in-cylinder injection and intake pipe injection. According to the control system, there are two types: mechanical and electronic injection (electronic injection). Since the 1960s, electronically controlled gasoline injection systems have been gradually adopted in car engines produced in Europe, the United States and other countries.In the EFI system, there is a regulating device that can precisely control the composition of the mixed gas, and theThree-way catalytic converter, So that the harmful components in the exhaust gas are greatly reduced. The basic principle of the EFI system is through thesensor, The collected information is fed back into a microcomputer for processing, and it sends instructions to control the ratio of air to fuel in the mixture, so that the supplied mixture can adapt to the needs of the engine in various operating conditions.For example, the computer based on the air flowsensorAnd engine speed, even knotsValveThe information collected by the sensors such as the position of the cooling water, the temperature of the cooling water and the air temperature are judged and the basis of the fuel injection is calculated, the opening time of each fuel injector is determined, and a command is issued to the fuel injector to inject fuel. Each sensor receives different information in different parts: such asDistributorIgnition coilsReceive information on engine revolutions; air flow sensor receives information on intake air flow; startswitchReceive start information; throttle switch throttle opening position information; cooling water temperature sensor receives water temperature information, and air temperature sensor receives air temperature information. This information is fed back to the computer through the circuit. In addition to the computer, the most important component in the EFI system is the fuel injector. A general engine has only one injector for each cylinder, which is located above the intake valve. The fuel is atomized by the fuel injector and mixed with the air entering the cylinder from the intake pipe. In order to meet the requirements of exhaust emission regulations, some cars are equipped with a mixture control system in the electronic injection system.It mainly uses one of the tracheaOxygen Sensor, It can feed back information that the mixture is thin or thick to the computer. The computer re-instructs the injector according to the information to get the correct amount of fuel injection. The gasoline injection system has been harmonized in the new generation of enginesIgnition systemThe combination is one, which embodies the optimal control of the mixture composition and ignition time, and greatly improves the performance of the engine. The above description is multi-point injection. Since the injection is done separately, the four injectors of the 4-cylinder engine will be injected separately.CrankshaftEach cylinder sprays once per revolution. In addition, there is currently a single point injection system, also known as a throttle body injection system. There is only one fuel injector on a multi-cylinder engine, which is installed above the throttle body and injects fuel into the intake pipe, which is mixed with air and then distributed to various cylinders through the intake pipe. The single point injection is also controlled by a computer. Although the performance is slightly worse (low fuel injection pressure), it has the advantages of simple structure, low cost, reliable work, and convenient maintenance due to the small number of fuel injectors used. The other parts are basically the same as multi-point injection. Automobile related knowledge ·Basic knowledge of circuit[汽车维修常识]
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