8. Ignition system
Base design completely electronic system of ignition
Former systems of ignition with energy accumulation – ignitions consisting of the coil, the distributor of ignition, the condenser, a rotor of the distributor of ignition, contacts of the breaker and a cable of ignition of a high voltage – helped with inductance, at the concerning the limited flexibility, to carburettor engines of old designs sometimes to hold «on a lead»: the ignition coil "made" capable pressure to breakdown and the mechanical distributor gave once to spark plugs a lot of "fire". In the top range of frequencies of rotation it occurred to modest early ignition, at once before the top dead point of the piston which was directly in a compression step. Speaking in other words: the engine periphery, all components for preparation of a gas mixture and drives of valves to a greater or lesser extent depended on static productivity of system of ignition. Systems of ignition with energy accumulation in inductance "distributed" the sparks with flexibility match a box.
Not so affairs during an epoch of electronic control by the engine are: behind side scenes and it is absolutely imperceptible for not skilled eyes use electronic components "igniting" and flexible connections (look the head Engines).
Without the special equipment there are not enough chances – for the fan in modern system of ignition
For the fan and ambitious «винтоверта» it can have consequences: strongly integrated into a control system of the engine of system of ignition without the special equipment hardly probable will offer basic points for appropriate homework. Also under cowl Mondeo do not jump over a spark without "orders" of a control mean transmission (РСМ) and different black boxes.
The internal life of these electronic components can be learnt, certainly, in the presence of necessary special knowledge and high-sensitivity devices. However it will not give you possibility to take care about them and can even disappoint: completely electronic systems of ignition (VZ), have for a long time the children's illnesses and meanwhile long support a car life in full "juice". However here nevertheless it will be useful to give the small review of type «in the world of the igniting sparks operated electronics».
Touch management: Igniting sparks in Mondeo. In engines DuraTec-HE the management block (it is specified by an arrow) directly on a head of the block of cylinders directly near to the quarter cylinder is established. This module translates onboard pressure of 12 Volt in pressure of ignition of 30 000 Volt.
Constantly in «double packing» – igniting sparks in Mondeo
It is structurally caused that two-spark coils of ignition in Mondeo give out the high voltage on spark plugs in «double packing»: the first spark ignites the fresh fuel mix which is in the cylinder, on a compression step while another "is thrown" on a pushing out step in "the opposite" cylinder. It is accurately visible on engine Duratec-HE example: cylinders 1 and 4, and also cylinders 3 and 2 always receive «the sparks» simultaneously.
РСМ supplies with the base data – the SKR-GAUGE
As a basis for calculation of each separate igniting spark the signal of the item gauge of a cranked shaft (СКР), first of all, serves. Its signal operates, after it has been transformed in РСМ to the digital form, a primary winding by the ignition coil. For this purpose РСМ quickly interrupts РСМ there current giving. Thereof there is a high voltage (pressure of ignition) which moves on a high voltage cable on spark plugs and there is discharged.
That sparks appeared in due time – the engine management block (РСМ) with various spatial parametrical characteristics
For "appropriate" coordination of igniting sparks in Mondeo bears responsibility РСМ. The theoretical base data is stored In its memory among the other under the diversified spatial characteristics of a corner of an advancing of ignition. Closely to connect the foggy theory with practice, the onboard computer processes with a step in some milliseconds corresponding signals of gauges from engine periphery. For example, it supplements the «the information on a hard disk» with the current data from the item gauge of a cranked shaft and the gauge of detonation combustion. Besides before each gas exchange РСМ contacts an accelerator pedal, the oxygen gauge, the gauge of frequency of rotation both various temperature gauges and air flowmeter, being under an engine cowl.
Depending on a loading condition (idling, the partial loading, full loading) and qualities of fresh air the fuel mix burns down in chambers of combustion with various speed. That as it is possible to use is better fuel energy, the black box changes the parametrical characteristic of a corner of an advancing of ignition according to a condition of loading for each separate cylinder. The best instant accordingly appears when the fresh fuel mix ignites at the moment of the maximum compression. In four-clock engines it is the moment when the piston from movement upwards on a compression course passes to movement downwards on a working step.
In due time to carry out – ignition and combustion
The three-dimensional characteristic: the spatial parametrical characteristic of a corner of an advancing of ignition. Each separate igniting spark on the threshold of is prepared from the point of view of the expense of fuel, a twisting moment, the fulfilled gas, distance from border of a detonation of the engine, temperature of the engine, movement and so forth. Depending on philosophy моторопроизводителя this or that "point of view" receives a various priority. This procedure occurs on the spatial parametrical characteristic of a corner of an advancing of ignition, three-dimensional «surfaces from mountains and valleys» to almost 4000 separately caused corners of an advancing of ignition. Supervision over it «a landscape from craters» carries out the engine management block (РСМ).
Naturally, the ignition moment not precisely occurs in the top dead point (ВМТ). As before mix ignition it is necessary approximately a three-thousandth fraction of a second. Therefore igniting sparks even during piston movement upwards receive «green light».
The maximum pressure of combustion, on the contrary, is established when the piston passes at once ВМТ. As топливовоздушной for ignition identical time always is necessary for a mix, the moment of ignition with growth of frequency of rotation of the engine moves further from ВМТ.
Invisible assistants (the general data)
Pressure regulator: by means of a hose incorporates to an inlet collector, it hands over to a control mean the information on the lowered pressure in the soaking up pipeline. The gauge is the crystal chip sensitive to pressure, it changes the electric resistance depending on the corresponding lowered pressure. On the basis of the received difference, and also the information on frequency of rotation the management block "learns" about a current working condition.
The gauge of a detonation of combustion: works on a basis пьезокерамики, that is a material which in gas heating systems already replaces for a long time кремень. Пьезокерамика will transform mechanical energy, for example, effort of draught or pressure to electric pressure., For example, arising at «explosive combustion» uncontrollable vibrations of the block of cylinders of the engine it is, quite enough, minimum disharmonies that the gauge became more active. It traces vibrations and informs on them on the onboard COMPUTER. On its basis the moment of ignition of the corresponding cylinder is corrected at once (nearby–5 °). Other cylinders work in the mode until the gauge will not reveal at them corresponding to non-uniformity and will inform on them. The ignition moment moves, proceeding from the set moment of ignition and on each working step, until then in a direction of late ignition while combustion process again will not settle into shape. The maximum range of regulation makes–15 °.
At appropriate combustion after a while the ignition moment in the cylinder consistently again is established in a direction "early".
The gauge of frequency of rotation: the inductive gauge which by means of the management block includes or disconnects current giving to both coils of ignition. The electromagnet and the coil are built in the gauge. Management is carried out by special pulse crosspieces on an engine flywheel. Always, when the crosspiece passes the gauge, the electromagnetic field in constant magnets changes – then in the coil pressure is generated. Now to register position of a cranked shaft as a convincing VMT-SIGNAL, on a flywheel for the first and last cylinders – before their corresponding ВМТ – as initial labels pulse crosspieces are placed. The management block processes these signals of pressure as a source of the information on frequency of rotation of the engine.
Precisely works in angular units: the item gauge of a cranked shaft.