Internal-combustion engines – High tension ignition system – Responsive to engine or environmental condition
Patent
1999-01-15
2000-12-05
Yuen, Henry C.
Internal-combustion engines
High tension ignition system
Responsive to engine or environmental condition
12340624, 12340637, 731173, 73 3508, F02P 1712, G01L 2322
Patent
active
061552410
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for determining knocking combustion in an internal combustion engine, as disclosed in the reference DE 44 09 749 A1.
Knocking combustion develops as a result of excessively high maximum pressures in the combustion chambers of the internal combustion engine, which cause an increase in the temperature of the unburnt fuel-air-mixture and lead toself-ignition of the fuel-air-mixture. These excessively high maximum pressures in the combustion chambers occur most often when the internal combustion engine is operating at full load.
In order to determine knocking combustion, the pressure development inside the combustion chamber is detected for all combustion chambers of the internal combustion engine by means of an ion current measurement. An ion current measurement technique is known, for example, from the reference DE 33 27 766 A1. According to this technique, knocking combustion can be determined through the occurrence of pressure peaks and fluctuations in the combustion chamber pressure development. For this, an alternating current is supplied immediately after the ignition of the fuel-air-mixture via the ignition coil to the spark plug which simultaneously functions as ion current probe. During the combustion of the fuel-air-mixture, this alternating current is modulated by ions in dependence on the pressure inside the combustion chamber. The modulated alternating current is then supplied to an evaluation circuit.
An ion current measurement is not possible during the ignition of the fuel-air-mixture by the spark plug. It is therefore necessary to reduce the spark burning time of the spark plug to a minimum in order to detect the combustion chamber pressure development immediately afterwards and to determine a possible knocking combustion.
The requirement for a short spark burning time at the spark plug is aided by the easy flammability of the fuel-air-mixture when the internal combustion engine is operating at full load. In addition, the rate of residual gas remaining in the combustion chambers from the preceding operating cycle is low during the full-load operation of the internal combustion engine, which could counter an easy flammability of the fuel-air-mixture.
In the partial load range, the power output of an internal combustion engine is controlled with a throttle valve. If the throttle valve closes, the combustion chamber receives less fuel-air-mixture, which in turn reduces the power output of the internal combustion engine. Owing to the lower amount of fuel, the combustion chamber pressure development during the operating cycle clearly shows lower maximum pressures. In addition, the rate of residual gas remaining in the cylinder from the preceding operating cycle increases. If an exhaust gas mixture from the combustion is additionally fed via an external combustion gas return-flow line to the fuel-air-mixture for a throttle release of the internal combustion engine, then the fuel-air-mixture in the combustion chamber requires a high ignition energy and a long spark burning time for a safe ignition.
The requirement for a long spark burning time for the partial load operation is met in that the maximum pressures in the combustion chamber pressure development are clearly lower than for the full-load operation of the internal combustion engine. That is the reason why an ion current measurement to detect knocking combustion can be omitted for the partial-load operation in the lower range. The spark burning time of the spark plug, if necessary, can extend over the complete operating cycle.
The feature according to which the required spark burning time of the spark plugs during the partial load operation and the necessity of conducting an ion measurement during the full-load operation complement each other positively during the operating cycle, as concerns the distribution of the available time, has already been described in the above-mentioned generic reference DE 44 09 7 49 A1. It was suggested in this reference that the ion-current detecting device be combined with a hi
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Hohner Peter
Schirmer Jens
Daimler-Benz Aktiengesellschaft
Kunitz Norman N.
Spencer George H.
Vo Hieu T.
Yuen Henry C.
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