Internal-combustion engines – Combustion chamber having multiple spark gaps
Patent
1998-02-19
1999-09-21
Kwon, John
Internal-combustion engines
Combustion chamber having multiple spark gaps
12340626, F02P 1502
Patent
active
059540249
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for controlling ignition and ionisation current measurements in a combustion engine.
BACKGROUND OF THE INVENTION
It is known to use ionic current sensors in order to monitor the combustion process in combustion engines. This type of sensing technique has been implemented in Otto-engines, using the existing spark plug as sensor. As disclosed in U.S. Pat. No. 4,648,367, a ion current sensing circuit is arranged in the ground connection of the primary winding of the ignition coil, using the spark plug gap as the sensor element.
In the ion-sensing system mentioned above, the spark plug is used as an actuator as well as a sensor. The actuator function is initiated at generation of the spark, and the sensor function is initiated shortly thereafter. These two functions can not be initiated simultaneously, because the spark discharge interferes with ionization current measurements within the combustion chamber.
It is known to use additional measuring gaps integrated in the spark plug. As disclosed in U.S. Pat. No. 5,180,983 and JP,A,57202078, besides the conventional spark gap the spark plug is equipped with an additional measuring gap. This type of spark plug is capable of detecting the ionization current without adverse effects of noise generated at the ignition. However, this type of spark plug is rather expensive. The spark plug is a disposable article of consumption, which brings operation costs up.
Another concept is known having additional measuring gaps located at a distance from the spark plug. As disclosed in U.S. Pat. No. 5,036,669; U.S. Pat. No. 4,665,737; U.S. Pat. No. 4,377,140; U.S. Pat. No. 4,304,203; U.S. Pat. No. 4,308,519 and DE,A,3833465 an additional measuring gap or a number of measuring gaps can be arranged at a distance from the spark plug. These types of systems require at least one extra sensor element, either an additional spark plug which is only used as sensor or additional measuring gaps integrated in the cylinder head gaskets or other engine parts.
A conflict arises when using the spark plug gap of a conventional spark plug as a common actuator and sensor at highly diluted air-fuel mixtures, for example during high EGR-ratios and/or lean burn control at lambda values in the range .lambda.=1.2-1.4, or above. In order to maintain a stable combustion at high dilution ratios, more ignition energy is needed. A concept used is the so called configurable spark, having a configurable spark duration. A spark duration up to 3 ms is beneficial for a stable combustion during high diluted air-fuel ratios. However, due to the sequential nature of function between the actuator phase and the sensing phase, the spark duration should be restricted to not more than 0.5 ms at high engine speed. The spark phase must have attenuated properly before any ion current measurements can be made. An ignition coil having low impedance is preferable, where the coil ringing is of short duration not interfering with the ion current measurements.
The spark duration limits for an engine where a knocking condition is detected through ion current measurements at the spark plug gap could be as follows. If the engine is operating at 6000 rpm, having an ignition timing at 20 Crankshaft Degrees (=CD) before Top Dead Centre (=TDC) and where a knocking combustion typically starts 17-20 CD after TDC, then the spark phase should have a duration shorter than 1.12 ms. At lower engine speeds successively longer spark duration are allowable. At 3000 rpm a spark duration up to 2.24 ms is allowable, assuming the same conditions as of ignition timing and occurrence of a knocking combustion.
During some operating conditions the knocking condition can occur during a long period or a large crank angle from 17 CD up to 50 CD. In those cases the arc duration can be extended further. Operating the engine at high diluted air-fuel ratios is necessary in order to meet future requirements of low emission levels and fuel consumption.
SUMMARY
An object of the invention for combustion engines having
REFERENCES:
patent: 4377140 (1983-03-01), Latsch
patent: 4648367 (1987-03-01), Gillbrand et al.
patent: 5003945 (1991-04-01), Hoeptner
patent: 5087882 (1992-02-01), Iwata
patent: 5327864 (1994-07-01), Regueiro
Patent Abstracts of Japan, vol. 7, No. 44, M-195 abstract of JP,A,57-193777 (Nissan Jidosha K.K.), Nov. 29, 1982.
Duhr Joel
Goras Anders J
Henkel Corporation
Jaeschke Wayne C.
Kwon John
Szoke Ernest G.
Wisdom Norvell E.
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