The general data on injection system Common Rail

Arrangement of elements of system of injection Common Rail on the diesel 4-cylinder engine

Basic element of system of injection of fuel is the fuel pump which is established on all diesel engines. Pressure of injection to 1350 bar is necessary for increase in capacity to 160 kw on the cylinder.

Many systems of injection of diesel fuel, in particular, direct injection (Dl) are during the last years developed. The problem not only increases in capacity of the engine, but also reduction of the expense of fuel and noise and decrease in toxicity of the fulfilled gases was thus pursued. In comparison with earlier used systems system of injection of fuel Bosch Common Rail (the storage fuel system) for direct injection of fuel (Dl) provides higher flexibility at adaptation to the power supply system of the diesel engine, for example:

– An extensive scope (for automobile and commercial cars with target capacities of 30 kw on the cylinder, together with for lorries of the big load-carrying capacity, locomotives and courts with target capacities of 200 kw on the cylinder;
– High pressures of injection of fuel to 1400 bar;
– Injection changes at engine start;
– Possibility of control, main and late injection;
– Provides conformity of pressure of injection to engine operating conditions.

Functioning of system of injection

The distinctive characteristic of system with the general pipeline Common Rail (storage fuel system) consists in division of the knot creating pressure, and knot of injection of fuel.

The system basis is made by the tank (accumulator). Pressure of injection does not depend on quantity of injected fuel and frequency of rotation of a cranked shaft of the engine. The fuel stock under pressure is in the high pressure accumulator Common Rail and is ready to injection. The quantity of injected fuel is defined on request of the driver, and pressure of injection pays off the management block (ECU) on the basis of the information from various gauges. ECU during precisely established moment transmits an excitation signal to the atomizer solenoid, meaning the beginning of giving of fuel. The quantity of injected fuel is defined by the period of opening of a spray and pressure in system. ECU and gauges of system of injection of fuel include:

– ECU;
– The gauge of frequency of rotation of a cranked shaft;
– The gauge of position of a camshaft;
– The gauge of position of a pedal of an accelerator;
– The pressure gauge in system with the general pipeline;
– The gauge of temperature of a cooling liquid;
– A measuring instrument of the expense of air.

On the basis of the information from the gauges set forth above and the requirement of the driver (position of a pedal of an accelerator) ECU defines the instant operational characteristic of the engine and the car as a whole. The block processes the signals developed by gauges and transferred on communication lines, and on the basis of this information operates injection system in a mode of the open or closed contour. Frequency of rotation of a cranked shaft of the engine is measured by the gauge of frequency of rotation of a cranked shaft, and the gauge of position of a camshaft defines sequence of injection of fuel (length of a phase). The electric signal from a potentiometer of position of a pedal of an accelerator transfers ECU a signal about degree of pressing by the driver to an accelerator pedal.

The measuring instrument of the expense of air tells ECU a signal with the data concerning an instant stream of air that allows to calculate process of full combustion of fuel with the minimum maintenance of harmful substances in the fulfilled gases. As the engine is equipped турбокомпрессором and adjustment of increase in pressure of pressurisation, the additional gauge also measures this pressure. At low external temperature and cold engine ECU defines the moment of injection and other parametres corresponding to a special operational mode. Depending on the car and increase of requirements to safety and comfort for information transfer ECU additional gauges can be used. In drawing the example of the diesel 4-cylinder engine with system of injection of fuel Common Rail is shown.

The basic functions

The basic functions of system consist in maintenance of injection of demanded quantity of fuel during strictly certain moment and under necessary pressure. It provides not only smooth work of the diesel engine, but also economic consumption of fuel.

Additional functions

Additional functions in the closed contour and function of management without a feedback serve in an operating mode for reduction of toxicity of the fulfilled gases and the expense of fuel and are used for improvement of safety, comfort and convenience.

For example: рециркуляция the fulfilled gases (EGR), adjustment of pressure of pressurisation of air, a gear change, an electronic immobilizer etc. System CAN provides data exchange with other systems of the car. At diagnostic check of the car it is possible to take the data which is in a reserve of the data of system.