Toyota RAV4>> Ignition system>> General information



The system of ignition is intended for ignition of a toplivovozdushny mix in each cylinder at a given time. In petrol engines it is reached at the expense of the electric spark (electric discharge) created between electrodes of a spark plug.
Reliable work of ignition in all range of operation of the engine is an essential factor for effective work of catalytic converter.
Ignition by a spark of a small cloud of a melkodispersny toplivovozdushny mix is enough to start burning process.
The spark plug defines length of a spark which also depends on type and a design of system of ignition, and also from conditions at which there is an ignition.
For spark emergence tension between electrodes of a candle should increase sharply from zero to the tension necessary for formation of an arch. After emergence of the spark category tension falls to level necessary for spark distribution, thus there is an ignition of a toplivovozdushny mix.
For obtaining energy of an iskroobrazovaniye the coil of ignition working by a principle of the autotransformer and accumulating energy of ignition is used. When giving current on primary winding of the coil of ignition energy of a current passes to energy of a magnetic field till current interruption of supply. The magnetic field thus sharply decreases, directing in a secondary winding of the coil of ignition a high-tension current arriving on high-voltage wires on one spark plug.
Between the initial moment of ignition of a working mix and its complete combustion passes about 2 ms. Therefore formation of a spark should occur earlier, than the piston will reach VMT that provides optimum combustion in all range of frequency of rotation of the engine. The moment of ignition is defined depending on frequency of rotation of a cranked shaft, loading, design features of the engine, quality of fuel and working conditions at the moment (start, idling, size of opening of a butterfly valve, etc.).
The spark plug serves for transfer of the high-tension current developed in the coil of ignition, to electrodes in the combustion chamber where this current makes the spark category for ignition of a working mix.