Measuring and testing – Test stand – For engine
Patent
1996-10-15
1998-01-13
Dombroske, George M.
Measuring and testing
Test stand
For engine
731173, 123419, 123436, 36443107, G01M 1500
Patent
active
057082006
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for detecting faulty combustion in an internal combustion engine, and more particularly to a process of this type which involves the measurement of time intervals between predetermined angular positions of a target linked in rotation to the engine, and which is not dependent on the geometric tolerances of this target.
A process for detecting faulty combustion in an engine is known from the prior art, and more particularly from French patent No. 2,689,934 filed by the Applicant, which is an integral part of the present description, according to which, for each cylinder, a critical parameter representing the instantaneous angular speed variation is calculated. This parameter is obtained through a linear combination of time intervals between predetermined angular positions of a target linked in rotation to the engine, in a sampling window centered on a predetermined instant in the combustion phase of the cylinder in question. This critical parameter is then compared to a fault threshold obtained experimentally in a reference engine and stored in a mapping table so that information representing a combustion error can be deduced from it. However, this process has the drawback of being dependent on the precision of the target according to which the time intervals are measured. In effect, the critical parameter is calculated on the basis of measurements performed on the target of the engine in question, and the result of this calculation is compared with a fault threshold obtained in a reference engine. Because of this, the differences in the geometry of the targets, linked for example to the tolerances of mass production or to the tolerances for mounting these targets on the engines (offset, distortion, etc.) can introduce variations which can lead to false detections of faults or to the absence of a detection of a real fault.
The problem therefore resides in rendering such a process the least sensitive possible to the variations which can exist between the targets of the various engines in the series and the reference engine in which the fault thresholds were determined.
Also known from patent application WO 93/07497 is a process for electronically correcting the tolerances of a target. In this process, a range in which the engine is driven by the vehicle is considered to be the most capable of offering maximum operational regularity. Under these conditions, the duration of each tooth of the target is measured, this duration is corrected as a function of the angular acceleration, and its ratio to the duration of the first tooth taken as a reference is determined. From this, a correction coefficient for the duration of each tooth is deduced, after filtering, as a function of the first. This coefficient is then used to correct the duration measurements performed later, for example during the calculation of the rotation speed or of the operational regularity of the engine. This process has the drawback of proposing a correction which is intrinsic to the system in question, and has no connection to a reference engine which has been used to establish the fault thresholds. Moreover, the correction coefficients obtained depend on the precision with which the first tooth is produced and can only be used in a relative way. It also appears that such a process, when applied to the correction of a target which can include several tens of teeth, very quickly becomes extremely cumbersome, resource-intensive and difficult to implement in an engine control computer. Furthermore, it can prove unsuitable for engines which have an odd number of cylinders.
The object of the present invention, therefore, is to propose a process for detecting faulty combustion which is simple to implement, suitable for any number of cylinders in the engine in question and not overly sensitive to the differences and tolerances which can exist between the targets of the reference engine and those of the various engines in the series.
These objects of the invention, as well as others which will become apparent
REFERENCES:
patent: 5044195 (1991-09-01), James et al.
patent: 5307670 (1994-05-01), Imai et al.
patent: 5377535 (1995-01-01), Angermaier et al.
patent: 5377536 (1995-01-01), Angermaier et al.
patent: 5505079 (1996-04-01), Rossignol
patent: 5559705 (1996-09-01), McClish et al.
Dombroske George M.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Automotive S.A.
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