Internal-combustion engines – High tension ignition system – Additional spark energy supply
Patent
1992-01-28
1993-02-23
Wolfe, Willis R.
Internal-combustion engines
High tension ignition system
Additional spark energy supply
123602, 123643, F02P 308
Patent
active
051880881
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to electronic ignition systems for internal combustion engines.
Published European Application No. 0 071 910 A2 discloses an electronic ignition system having individual spark plug ignition devices as well as an additional ignition device common to all spark plugs. In that system, transistor ignition devices with current regulation are used as the individual spark plug ignition devices and the common ignition device contains a regulated direct-current converter connected, by way of diodes, to the secondary windings of the ignition coils of those ignition devices. Both types of ignition devices may be controlled or regulated as a function of parameters of the internal combustion engine, such as rpm, load and knocking.
A disadvantage of this prior art ignition system is that essentially only a single ignition pulse is supplied by the direct-current converter for each ignition process. As a result, difficulties may occur in ignition with a lean mixture, especially in operating modes of the internal combustion engine which are of interest in view of modern reduced emission objectives.
In this respect, more favorable behavior is provided by a programmable transistor ignition system, hereinafter called a "PTI", such as is disclosed in German Offenlegungsschrift No. 23 40 865. That PTI contains an electronic switch connecting a direct-current voltage source into an output transformer and having a switching frequency which is a multiple of the firing frequency of each spark plug. Like the conventional ignition device, the PTI is controllable according to operating and environmental parameters. A disadvantage of this known PTI is the requirement for a mechanical distributor, which is known to be relatively susceptible to trouble. In addition, the PTI does not supply very precisely timed ignition sparks.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fully electronic ignition system for an internal combustion engine which overcomes the above-mentioned disadvantages of the prior art.
Another object of the invention is to provide a fully electronic ignition system which ensures satisfactory precisely timed ignition, even when the internal combustion engine is operated with a lean fuel-air mixture, and which does not require a mechanical distributor.
These and other objects of the invention are attained by providing an ignition system in which each spark plug is supplied from a separate high-voltage condenser ignition device, hereinafter called an "HVCI", having an output transformer and a plurality of spark plugs are controlled by a common PTI having an electronic switch operating at a frequency which is a multiple of the firing frequency of each spark plug and which controls the operation of the HVCI for each of the spark plugs as a function of operating and environmental parameters.
The use of a PTI as an ignition control device which supplies a series of spark impulses for each ignition process produces a relatively strong ionization of the combustion chamber gases in the vicinity of the spark plug, which results in greater assurance of complete ignition than does the use of a single direct-current converter. Because each spark plug is connected to a separate HVCI and an electronic distributor is used as in the transistorized coil ignition devices disclosed in the above-mentioned EP No. 0 071 910 A2, a mechanical distributor is not required.
Although the ignition energy supplied by each HVCI is limited, the HVCIs have a high timing accuracy. Consequently, in the ignition system according to the invention, the actual ignition energy is provided to the HVCIs by the PTI with relatively limited timing accuracy, while the HVCIs provide precisely timed high voltages to the individual ignition coils.
An additional advantage of the invention results from the fact that the HVCIs can be standard components since all of the features of the ignition system required by a particular engine are determined by the PTI.
Another advant
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Graf Vom Hagen Siegbert
Stamm Klaus
Volkswagen AG
Wolfe Willis R.
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