Internal-combustion engines – High tension ignition system – Having dwell control
Patent
1997-12-15
1999-04-27
Solis, Erick R.
Internal-combustion engines
High tension ignition system
Having dwell control
123626, 123630, F02P 900
Patent
active
058968482
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a reciprocating internal combustion engine, and also concerns combined heat and power (CHP) apparatus provided with such an engine.
In such CHP apparatus the engine drives an electrical generator and also produces utilizable heat.
An economic case for using CHP apparatus is considerably dependent on the costs of routine maintenance of the apparatus, such as the cost of servicing the engine. Extending the service intervals of the engine can have a significant effect on the economic case for using CHP.
The spark plugs used in a CHP internal combustion engine need to be checked regularly to ensure that the gap between the plug electrodes does not increase to a size where misfire occurs.
An object of the invention is to provide a reciprocating internal combustion engine so adapted as to alter automatically the electrical ignition energy applied to the electrodes of a spark plug in a cylinder of the engine to substantially a minimum level required to ensure correct combustion of the fuel in the cylinder.
According to the invention a reciprocating internal combustion engine, which operates at a substantially constant speed and at a substantially constant air to fuel ratio, comprises at least one cylinder provided with a spark plug having at least two electrodes with a gap therebetween, and ignition spark duration control means whereby the duration of an ignition spark between said electrodes is automatically variable to bring said spark duration closer to a predetermined minimum duration over which predetermined minimum duration there would be supplied to the electrodes a minimum level of electrical ignition energy to substantially avoid misfire in the cylinder, and said minimum level being variable according to the size of said gap.
Thus there is avoided the need to apply excessive electrical ignition energy to the spark plug electrodes all the time in order to ensure there is enough energy to cause an adequate spark when either or both electrodes is/are worn and the spark gap has increased over the many hours of engine operation after the spark plug was fitted or its electrode gap set. Accordingly the avoidance of the need to continually use excessive electrical ignition energy slows the rate of spark plug electrode wear and slows the rate of increase of electrode gap size, for a given spark plug.
Engine test work has shown that for a given engine operating under constant conditions of speed, fuel to air ratio, (and also load) there is a minimum, fixed spark duration necessary to ensure correct combustion. For a given spark plug electrode gap, the fixed minimum spark duration requires a certain minimum electrical ignition energy to be supplied. An increase in the supplied electrical energy beyond this minimum level will not show any benefits, whereas a reduction will cause misfire. As the spark plug gap increases, then the said minimum energy level required, increases.
The invention will now be further described, by way of example with reference to the accompanying drawings in which:
FIG. 1 is a diagrammatic representation of a combined heat and power (CHP) apparatus comprising a reciprocating, internal combustion engine formed according to the invention;
FIG. 2 diagrammatically shows ignition spark duration control means in combination with an ignition system and spark plugs of the engine in FIG. 1;
FIG. 3 is a diagrammatic representation of an ignition spark duration monitor used in the apparatus in FIG. 2;
FIG. 4 is a set of graphs in which there is a common abscissa axis for time t, a plurality of ordinate axes for the voltages v of a plurality of different voltage signal outputs from respective component parts of the ignition spark duration control means in FIG. 2;
FIG. 5 is a diagrammatic representation of the arrangement in FIG. 2, as an aid to understanding FIGS. 5 and 6;
FIG. 6 is a diagrammatic representation of a fragment of a second embodiment of an internal combustion engine formed according to the invention, having an ignition system of the wasted spark type, and
FIG. 7 is
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BG plc
Solis Erick R.
LandOfFree
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