Internal-combustion engines – Combustion chamber means combined with air-fuel mixture...
Patent
1997-05-23
1998-09-15
Wolfe, Willis R.
Internal-combustion engines
Combustion chamber means combined with air-fuel mixture...
F02P 5152
Patent
active
058064893
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for returning to nominal advance if no pinging is detected.
The phenomenon known as "pinging" is well known. This is the self-ignition of the air/fuel mixture in the cylinder of an internal combustion engine before the ignition spark is produced. This abnormal combustion of the mixture gives rise to strong pressure waves and an acoustic noise called "pinging". When pinging is intense, it may lead to substantial damage to the engine, such as: example.
To eliminate this phenomenon of pinging, known practice is to act especially on the ignition advance. By retarding the ignition advance the sparking plugs ignite earlier. This means that the combustion of the air/fuel mixture takes place a little earlier in the combustion cycle. If this combustion takes place early enough, then pinging can no longer occur.
Patent FR 2 689 183 (Siemens Automotive S.A.) relates to a method for retarding the ignition advance. In this patent, the law governing the retarding of the ignition advance takes into account not only the intensity of the pinging measured but also the history of this pinging for a given cylinder. Furthermore, the method according to this patent uses fuzzy logic to calculate the retard to be applied. Such a method makes it possible not to apply a fixed retard (which is penalizing to engine torque) but a retard which is proportional to the intensity of the pinging detected.
Of course, when retarding the ignition advance has made it possible to eliminate the pinging, the ignition needs to be set back to the nominal advance.
Strategies for returning to nominal advance, as shown, for example, in the document EP 0 087 162, recommend that return should be uniform and slow irrespective of the strength of pinging corrected. Now, for as long as an engine is not running at nominal advance, it is not producing its optimum torque. Furthermore, substantial corrections in advance are detrimental to engine stability.
The object of the present invention is therefore to look for a method for returning to nominal advance which allows the engine as quickly as possible to work in its optimum conditions, without, however, giving rise to further pinging.
For this purpose, the present invention relates to a method for returning to nominal advance, it being intended for said method to be put into practice in the context of a strategy of electronic control of an internal combustion engine when a phenomenon of pinging has been detected and a method of retarding the ignition advance has led to the disappearance of the pinging, said method according to the invention being one which consists in: given number of combustion cycles, eliminating the false detections of pinging which are due to variations in speed and/or in air-inlet pressure, of the pinging and calculating the mean energy level corresponding to the counted number of detections, predetermined thresholds in order thereby to formulate a law governing optimum return to nominal advance.
Thus the method according to the invention makes it possible to keep track of the intensity of the pinging previously corrected but also stores in memory the history of this pinging in order therefrom to deduce the optimum law governing return to nominal advance.
Advantageously, the number of detections of pinging is recorded by a simple counter and the return law to be followed is determined simply by comparing a weighted number of detections with a set of empirically predetermined thresholds.
According to a preferred embodiment of the invention, only detections of pinging carried out over the last four combustion cycles are taken into account.
Advantageously, only the "good detections" of pinging are taken into account. Effectively any "false pinging" due especially to a variation in engine speed or to a variation in air-inlet pressure is eliminated.
Further objectives, features and advantages will be better understood from reading the description which follows, by way of non-limiting example, and with reference to the attached drawings in which:
FIG. 1
REFERENCES:
patent: 4300503 (1981-11-01), Deleris et al.
patent: 4347820 (1982-09-01), Deleris
patent: 4527524 (1985-07-01), Guipaud
patent: 4631680 (1986-12-01), Korb et al.
patent: 4658789 (1987-04-01), Morita
Japanse Patent Abstract No. 56-75965 (Sugiura), dated Jun. 23, 1981.
Japanese Patent Abstract No. 59-41666 (Suematsu et al.), dated Sep. 1, 1982 .
Greenberg Laurence A.
Lerner Herbert L.
Siemens Automotive S.A.
Vo Hieu T.
Wolfe Willis R.
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