6.2. System of injection of fuel of the diesel engine - the general information
General information
Are a part of fuel system: established in a back part of the car (under a pillow of a back seat) the fuel tank, the fuel filter, nozzles, fuel tubes and hoses, the fuel reserve sensor located in a tank and the block of electronic control the engine.
Fuel moves the special pump via the filter. In the filter the dirt and water which is contained in fuel accumulates.
During the operation of the diesel engine in its cylinders clean air which contracts to high pressure is soaked up.
At the same time air temperature rises to 700 - 900 °C, the exceeding temperature of ignition of diesel fuel. Fuel is injected into the cylinder with some advancing and ignites. Thus, spark plugs for ignition of fuel are not used.
For reduction of a share of harmful substances in the fulfilled gases diesel engines have the diesel oxidizing catalytic converter. At the same time the system of recirculation provides essential decrease in the fulfilled gases the content of oxides of nitrogen. It is reached thanks to supply of the fulfilled gases to the air which is soaked up by the engine that provides decrease in concentration of oxygen in the air coming to engine cylinders. It leads to decrease in a delay of ignition and to lower temperature of combustion that as a result reduces formation of NOx. Process of recirculation of the fulfilled gases has to be dosed however precisely, otherwise the maintenance of a soot increases in the fulfilled gases. For this purpose the amount of the sucked-in air is defined by the measuring instrument that allows the electronic device to operate recirculation process.
The injection of fuel is made directly in the combustion chamber.
Function chart of system of injection of the diesel engine
Pneumoconnections on sensors
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VAC
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Depression from the vacuum pump |
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ATM
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The ventilating channel conducting to salon |
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OUT
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From the Y31/1 sensor to the switching valve of system of recirculation Y27 |
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OUT
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From the Y31/4 sensor to the vacuum drive of the valve of the distributor operating air pressure |
The engine is operated the electronic system similar to a control system of petrol engines. The system operates operation of the engine, analyzing information arriving from a large number of sensors.
Scheme of laying of vacuum connections
Scheme of laying of vacuum lines (turbodiesel engine of 3.0 l)
On diesel models there is no accelerator cable. Instead of it on a pedal the sensor of its situation is installed.
The fuel cut-off valve at switching off of ignition is absent. To kill the engine at switching off of ignition, the control unit of the engine sends a signal which, in turn, stops supply of fuel to nozzles to the TNVD control unit.
The fuel system is designed so that not to allow air "suction" in the absence of fuel in a tank. The control unit constantly checks fuel level in a tank, processing information arriving from the sensor of a reserve of the fuel located in a tank. When falling a reserve of fuel to a certain level the control unit lights the warning lamp on the control panel then forcibly causes admissions of supply of fuel, limiting to that the maximum speed. It proceeds until fuel level in a tank does not exceed an admissible mark.
Information on position of the crankshaft and speed of rotation of the engine comes to the control unit from the sensor of position of the crankshaft (CKP). The inductive head of the sensor is located opposite to a flywheel and constantly scans special tags (36 pieces) applied on its surface. When passing a tag by a sensor head it sends an impulse to the control unit. Tags are evenly applied on a flywheel surface, but one tag is passed. It has to settle down in 90 ° to VMT of the first cylinder. At the time of passing by a flywheel of this point the sensor does not send an impulse to the control unit. Blok distinguishes this pause and precisely defines VMT moment. Duration of this pause is used for determination of speed of rotation of the engine.
Information on quantity and temperature of the air coming to the engine arrives from the sensor of absolute pressure the inlet pipeline (MAP) and air temperature sensors. The sensor of absolute pressure is connected to the pipeline a vacuum hose and measures pressure in it. Two sensors of air temperature are installed. One is established before a turbocompressor, and another - after the intercooler. Temperature and pressure of air are used for calculation of exact amount of fuel which it is necessary to fall to nozzles.
The traditional sensor of temperature of cooling liquid is replaced with the block head temperature sensor. It takes temperature of a head and sends the obtained information to the control unit. Analyzing this information, the control unit corrects structure and the moment of injection of fuel mix, and also operates system of warming up of the cold engine.
The switch of stoplights and the sensor of a pedal of a brake informs the control unit on the current provision of a pedal of a brake. When receiving signals from these sensors the control system instantly transfers the engine to idling until receives a signal from the sensor of provision of a pedal of an accelerator.
The cable of an accelerator is absent. Instead of it on the sensor of provision of a pedal of an accelerator is installed. The sensor constantly informs the control unit on the provision of a pedal which, in turn, precisely counts injection parameters. Single turns are also regulated by the control unit and cannot be adjusted manually. Analyzing information arriving from various sensors, the control unit counts the size of turns of idling, correcting them depending on load of the engine and its temperatures.
The system of injection of fuel is system of direct injection. In the bottoms of pistons there are vortex cameras providing a turbulence of the fuel coming to combustion chambers. For optimization of combustion of fuel of a nozzle open in two stages (for this purpose in each nozzle there are two springs). When opening a nozzle a small part of fuel gets on internal components of a nozzle, greasing them, and comes back to the fuel tank.
Control of warming up of the cold engine is exercised of the control unit of the engine. At the cold engine the moment of injection is displaced by the control unit. The control unit of the engine, in turn, operates work of candles of an incandescence. Glow plugs are installed in each cylinder and join before start of the engine, I work during an engine provorachivaniye with a starter and some time after start of the engine. Candles considerably facilitate start of the cold engine. After inclusion of ignition on the control panel the corresponding control lamp (address to the car Equipment, an arrangement of devices and governing bodies of the Head the Operation manual), signaling about inclusion of candles of an incandescence lights up. As soon as the lamp goes out, you can start the engine. If air temperature very low, candles continue to work still some time after start of the engine. It reaches stable operation of the engine and decrease in harmful impurity in the fulfilled gases.
Owing to high starting qualities of the engine with direct injection in a cold state preliminary heat is required only at a temperature below -10 °C.
Fuel passes through the fuel filter. In the filter fuel separates from water and pollution. Therefore it is important to delete water from fuel and to make timely replacement of the filtering element.
The fuel system of diesel engines is very reliable. When using pure fuel and performing regular service it has to function regularly before the termination of service life of the car. After very big run internal components of nozzles can wear out, and they will need to be repaired. As the pump - nozzles have a difficult design, repair is recommended to be carried out in a specialized workshop.