Method and apparatus for detecting misfires in a controlled ignition internal combustion engine
First Claim
1. Method of detecting misfires in a controlled ignition internal combustion engine, comprising the steps of:
- a) deriving, for each combustion-expansion phase in each cylinder of the engine, a signal representative of a measure of a gas torque produced in each corresponding cylinder during the corresponding combustion expansion phase,b) measuring a rotational speed of the engine and deriving (4) a signal representative of this rotational speed during at least an intake phase preceding the combustion-expansion phase of each corresponding cylinder,c) measuring a pressure at an air inlet manifold for each corresponding cylinder, and deriving a signal representative of this pressure during at least the intake phase preceding the combustion-expansion phase of the corresponding cylinder,d) entering speed and inlet manifold pressure signals as addresses in a map of reference theoretical gas torque, and deducing therefrom a signal representative of a reference torque,e) assigning the reference torque a multiplier weighting coefficient associated with each corresponding cylinder and/or a steady-state or transient operating mode of the engine, and deducing therefrom a signal representative of an expected theoretical torque, andf) comparing the signals of the measured gas torque and of the expected theoretical torque and concluding that there is a misfire when a ratio of the gas torque to the expected theoretical torque becomes less than a defined ratio threshold.
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Accused Products
Abstract
Method for producing of catalytic converter diagnostic signals and/or signals indicating that the harmful component emission threshold in exhaust gases has been exceeded. To produce the signal, the gas torque (Cg) for each combustion stroke in each cylinder is determined; the engine speed (N) and air inlet manifold pressure (Pca) during the corresponding previous inlet stroke is measured; the reference torque (C ref), which is a function of N and Pca, is calculated by interpolation from a map; C ref is weighted, for example, by multiplication with a coefficient (K) associated with the corresponding cylinder and/or with the steady or transient engine running mode in order to deduce the expected theoretical torque (Cpr) which is compared with the gas torque (Cg) to ascertain a combustion misfire if Cg/Cpr is less than S2 and if Cpr-Cg exceeds the S3 or S4 threshold, depending on whether the engine is in transient or steady mode.
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Citations
20 Claims
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1. Method of detecting misfires in a controlled ignition internal combustion engine, comprising the steps of:
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a) deriving, for each combustion-expansion phase in each cylinder of the engine, a signal representative of a measure of a gas torque produced in each corresponding cylinder during the corresponding combustion expansion phase, b) measuring a rotational speed of the engine and deriving (4) a signal representative of this rotational speed during at least an intake phase preceding the combustion-expansion phase of each corresponding cylinder, c) measuring a pressure at an air inlet manifold for each corresponding cylinder, and deriving a signal representative of this pressure during at least the intake phase preceding the combustion-expansion phase of the corresponding cylinder, d) entering speed and inlet manifold pressure signals as addresses in a map of reference theoretical gas torque, and deducing therefrom a signal representative of a reference torque, e) assigning the reference torque a multiplier weighting coefficient associated with each corresponding cylinder and/or a steady-state or transient operating mode of the engine, and deducing therefrom a signal representative of an expected theoretical torque, and f) comparing the signals of the measured gas torque and of the expected theoretical torque and concluding that there is a misfire when a ratio of the gas torque to the expected theoretical torque becomes less than a defined ratio threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. Apparatus for detecting misfires of a controlled ignition internal combustion engine, comprising:
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at least one engine rotational speed sensor delivering an engine speed signal, at least one air inlet manifold pressure sensor, delivering a corresponding signal for each cylinder of the engine, at least one engine phase sensor for identifying each cylinder of the engine, means for calculating a gas torque from the engine speed signal, and memory means for storing maps and thresholds, a calculating means and storing values of a reference torque of an expected torque of a weighting coefficient, of a gas torque to expected torque ratio, of a difference of expected torque and gas torque and a comparing means for comparing the values with the thresholds in order to determine a presence of misfires.
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Specification