Process and device for detecting combustion irregularities in an engine particularly at medium and high speed

Claim 1

A process for detecting combustion irregularities of an internal combustion engine, serving to make a combustion diagnosis, particularly at medium and high speed, wherein time intervals are measured between predetermined angular positions of a rotating part integral with a craftshaft, a parameter representative of a variation in speed is calculated from these differences,and this parameter is compared with a fault threshold, said process comprising the steps of: (a) for each phase of combustion of the engine, defining a sampling window, centered on an angular reference position, corresponding to a predetermined moment of a reference combustion phase, said sampling window having a width less than twice the angular distance between two combustions, (b) in each sampling window, taking a series of measurements of time intervals angularly distributed on both sides of the reference position, in order to obtain a set of samples ΔT 1 , . . . ΔT n on said window, the width of each sampling window having a substantially maximum number of samples in the set of samples for one of said two combustions without any substantial influence on said set of samples by the other of said two combustions, (c) for each set of samples, forming a linear combination of the values measured ΔT 1 , . . . ΔT n in order to obtain a critical parameter, which is representative of a variation in instantaneous speed at the moment of combustion, (d) comparing the critical parameter resulting from the linear combination with the fault threshold, and providing information representative of a fault if said threshold is exceeded.

Claim 12

A device for detecting combustion irregularities in an internal combustion engine, comprising: an angular position sensor with a toothed wheel carried by a rotating part integral with a crankshaft of the engine, said sensor generating angular position information for each engine cycle, as well as absolute position information, a counter adapted to transmit time difference values from the information generated by the sensor, means for storing the time difference values, means for storing fault thresholds, means for determining engine speed and load of the engine, and computation means for processing the time distance values and their comparison with the fault thresholds, the angular position sensor and the counter being adapted to provide a time resolution less than 1 μs, the computation means being programmed: to group the time difference values in sets of samples, each set being centered on a reference angular position calculated from the absolute position information, and being contained in a predetermined window framing this reference position, said predetermined window having a substantially maximum number of samples in the set of samples associated with a first combustion without any substantial influence or said maximum number of samples by a successive second combustion, to carry out a linear combination on each set of samples in order to obtain a critical parameter at each cycle, to read, in the means for storing fault thresholds, a respective threshold corresponding to a respective speed and load provided by the means for determining, to compare the critical parameter with this respective fault threshold, and to generate information representative of a fault in the case where said respective fault threshold is exceeded.

Claim 13

A device for detecting combustion irregularities in an internal combustion engine, comprising: an angular position sensor with a toothed wheel carried by a rotating part integral with a crankshaft of the engine, said sensor generating angular position information for each engine cycle, as well as absolute position information, a counter adapted to transmit time difference values from the information generated by the sensor, means for storing the time difference values, means for storing fault thresholds, means for determining engine speed and load of the engine, and computation means for processing the time distance values and their comparison with the fault thresholds, the angular position sensor and the counter being adapted to provide a time resolution less than 1 μs, the computation means being programmed: to group the time difference values in sets of samples, each set being centered on a reference angular position calculated from the absolute position information, and being contained in a predetermined window framing this reference position, said predetermined window having a substantially maximum number of samples in the set of samples associated with a first combustion without any substantial influence or said maximum number of samples by a successive second combustion, to carry out a linear combination on each set of samples in order to obtain a critical parameter at each cycle, to read, in the means for storing fault thresholds, a respective threshold corresponding to a respective speed and load provided by the means for determining, to compare the critical parameter with this respective fault threshold, and to generate information representative of a fault in the case where said respective fault threshold is exceeded.