Internal-combustion engines – High tension ignition system – High frequency ignition system
Patent
1992-02-24
1993-01-19
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
High frequency ignition system
123598, 123620, F02P 306
Patent
active
051799286
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an ignition device for an internal combustion engine intended, more particularly but not exclusively, for the propulsion of a motor vehicle.
Conventionally such a device comprises a high voltage generator and several spark plugs each placed in one of the cylinders of the engine.
A distributor cyclically ensures the connection of each plug with the generator at predetermined instants of the cycle of the engine, reference relative to the top dead centre of each piston in the associated cylinder, so that the high voltage transmitted to the plug by electrical cables causes the formation of a spark between the electrodes of the plug, which spark causes the ignition of the air-fuel mixture compressed by the piston in the cylinder.
This device, used universally, has however shown some weaknesses. The first has to do with the mechanical nature of the distributor. Firstly, it is subjected to wear from a center rubbing electrical contact. There is also the risk of electrical arc breakdown in the distributor region rather than that of the plug. There is furthermore degradation of the electrical contacts due to the spark between a rotor arm and the contacts. Moreover, with such a mechanical distributor the range of possible variations of the ignition advance is limited. Finally, the distributor being mounted on a rotating shaft driven by the motor, this arrangement involves an add-on cost due to these additional parts.
A second weakness has to do with the presence and the length of the cables which transmit the high voltage between the distributor and each plug. The passage of this high voltage in these cables can, through leakages, be dangerous for a person inspecting the motor and who happens to touch a defective cable. This high voltage can also create electromagnetic interference, particularly damaging in modern vehicles which include more and more sensors, electronic boxes, actuators, interconnected through electrical wires, whose operation can be disturbed by this interference.
In order to escape from these disadvantages, it has been conceived to eliminate the distributor, a solution which implies that, for each plug, there is an associated high voltage generator which is individual to it. The generator is then mounted directly on the plug, which clearly eliminates the high-voltage cables and the electrical and electromagnetic problems which are associated with them.
The problem then comes down to designing a high voltage generator sufficiently compact to be able to be mounted directly on a plug.
If an ignition of the inductive type is chosen, the energy necessary for the ignition is stored in the magnetic circuit of a transformer which constitutes, at the moment of the discharge of this energy, the high voltage generator. The volume of this magnetic circuit is substantially proportional to the energy which must be stored. Taking into account the large quantity of energy to be supplied to the plug in order to obtain the ignition of the air-fuel mixture, it has been found that it was not possible to reduce the dimensions of the transformer sufficiently to enable it to be comfortably installed on the plug.
If an ignition of the capacitive type is chosen in which the ignition energy is stored in a capacitor then discharged on the plug with the help of a transformer, it is possible to greatly reduce the dimensions of this transformer since the latter no longer has to store the ignition energy. However, it is known that ignitions of the capacitive type give short duration sparks which have the disadvantage of providing an unstable ignition of the air-fuel mixture, above all at low speed. From FR-A-2, 090, 101 is known an internal combustion engine ignition device which creates ignition sparks by amplification at resonance of an oscillator signal generated by a fixed Jensen oscillator whereby the current is reduced by a shift in frequency caused by a gap in transformer magnetic core once a spark has been created.
The object of the present invention is to construct an ignition device de
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Cour Marie M. H.
Vernieres Raymond F. J.
Greenberg Laurence A.
Lerner Herbert L.
Nelli Raymond A.
Siemens Aktiengesellschaft
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