Measuring and testing – Vehicle chassis – Steering
Patent
1995-07-05
1997-02-25
Chilcot, Richard
Measuring and testing
Vehicle chassis
Steering
G01M 1500
Patent
active
056061196
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
U.S. Pat. No. 5,044,194 describes a method of detecting misfires, consisting, for each combustion-expansion phase (power stroke) of an engine, in calculating the rotational acceleration and speed of the engine, then, over a series of such phases, the mean acceleration which is compared with the measured acceleration in order to deduce an acceleration discrepancy therefrom. In parallel, a reference torque value is obtained by map-based interpolation from operating parameters of the engine, such as speed and intake air flow rate. Then a power loss coefficient is calculated, equal to the ratio of the acceleration discrepancy to the reference torque. Then the reference torque is compared with a torque threshold, and if it is higher than the latter, a second comparison is carried out. The latter consists in comparing the power loss coefficient with a power loss threshold, and if this coefficient is higher than the corresponding threshold, it is concluded that there is a misfire. The essential criterion determining the presence of a misfire resides in the power loss coefficient, equal to the ratio of an acceleration discrepancy over a reference torque, and in its comparison with a power loss coefficient threshold.
JP-A-62-54138 also describes a method of detecting misfires consisting in calculating a discrepancy between a pressure measured at the inlet air manifold and a reference pressure obtained by map-based interpolation from detected values of the load on the engine, then in comparing the discrepancy between the measured pressure and the reference pressure with a threshold, in order to deduce therefrom the presence of a misfire. In this method, the essential criterion for determining the presence of a misfire resides in the pressure discrepancy and its comparison with a pressure threshold.
SUMMARY OF THE INVENTION
To this end, the invention proposes a method of detecting misfires in a controlled ignition internal combustion engine, which is characterized in that it comprises the stages consisting in: cylinder of the engine, a signal representative of the value of the gas torque Cg produced in the corresponding cylinder by the corresponding combustion, representative of this speed during at least the intake phase preceding the combustion-expansion phase of the corresponding cylinder, corresponding cylinder, and deriving a signal representative of this pressure during at least the intake phase preceding the combustion-expansion phase in the course of the same engine cycle of the corresponding cylinder, addresses in a map of reference theoretical gas torque, and deducing therefrom a signal representative of a reference torque C ref, associated with the corresponding cylinder and the steady-state or transient operating mode of the engine, and deducing therefrom a signal representative of an expected theoretical torque Cpr, and theoretical torque Cpr and concluding that there is a misfire when the ratio of the gas torque Cg to the expected theoretical torque Cpr becomes less than a defined ratio threshold.
This ratio threshold may be constant, for example equal to 0.5; however, advantageously, it is drawn from a map established as a function of the rotational speed N of the engine and of the pressure Pca at the air inlet manifold.
It will be understood that the idea at the base of the invention consists, for each combustion-expansion phase, in predicting or estimating an expected theoretical gas torque, as a function of the rotational speed of the engine or engine RPM, of the pressure at the inlet manifold, and of a weighting coefficient, taking into account the state of each of the cylinders of the engine for the corresponding combustion-expansion phases, as well as the modes of transient or steady-state operation of the engine, and that this expected torque is next compared with the gas torque measured for the combustion-expansion phase in question, in order to deduce therefrom whether there is or is not a misfire during this phase, depending on the result of this comparison, which a
REFERENCES:
patent: 4691288 (1987-09-01), Kay et al.
patent: 4843870 (1989-07-01), Citron et al.
patent: 5044194 (1991-09-01), James et al.
patent: 5200899 (1993-04-01), Ribbens et al.
patent: 5501109 (1996-03-01), Naito et al.
Genin Christophe
Wallerand Philippe
Chilcot Richard
Magneti Marelli France
McCall Eric S.
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