EP1559895A1 - Method for diagnosing the operational condition of a vehicle diesel engine - Google Patents

Abstract

The invention relates to a method for diagnosing the operating state of a diesel engine (10) for a motor vehicle, said engine (10) comprising a chain (18a, 18b, 18c, 18d) for pressure acquisition associated with each cylinder (12a, 12b, 12c, 12d) of the engine to acquire the pressure in each cylinder, a chain (30) for acquiring the angle of the motor shaft adapted to deliver the crankshaft angle of each cylinder and on-board correction means (34) adapted to correct a predetermined set of malfunctions and drifts of the cylinders and acquisition chains, characterized in that it comprises at least the steps of: analyzing (102) the operation of each cylinder and pressure acquisition chains in the cylinder and the angle of the drive shaft, comprising identifying an operating state of the set consisting thereof among a nominal operating state, and a set of malfunctions and drifts predetermined according to predetermined characteristics of the signal delivered by the pressure acquisition chain in the cylinder; and correction (106) of correcting identified malfunctions and drifts belonging to the predetermined set of malfunctions and drifts corrigeable by the onboard correction means. <IMAGE>

Description

The present invention relates to a method for diagnosing the state of operation of a diesel engine for a motor vehicle.

It is known in the state of the art of diagnostic systems the operating status of a diesel engine for a motor vehicle that use information provided by signal acquisition channels associated with the engine, generally pressure acquisition lines in the cylinders and a chain of acquisition of the angle of the motor shaft typically associated with the diesel engine, in particular to establish a diagnosis of leaks in the cylinders.

In addition, there are known strategies for controlling the functioning of the engine using a cylinder pressure signal for other functions of the engine control. The type of systems using such strategies assumes that the acquisition channels are working properly and are perfectly calibrated. Therefore, if at least one acquisition chain fails, a leak diagnosis can be established even if the cylinder or cylinders set cause function satisfactorily, or motor control can cause malfunctions and an increase in emissions pollutants in case of failure to take into account this failure or drift.

Moreover in case of a predetermined failure or drift of the motor or acquisition systems, these systems of the state of the art issue only a diagnosis to the attention of the user of the vehicle for a human repair intervention while, in general, the motor is associated with on-board correction means adapted to correct these failures and / or drifts.

Moreover, in a conventional manner, such systems implement implement algorithms based on parametric models of the engine or the evolution of the pressure in the cylinders. These algorithms require generally a large number of operations, so that the implementation corresponding data processing by an on-board computer in the vehicle, generally a micro-controller with reduced computing capacity, is difficult to envisage.

The present invention aims to solve the aforementioned problems by providing a method of diagnosing the state of operation of a diesel engine for a motor vehicle consisting in testing the good operation of the pressure acquisition chains in the cylinders and of the chain of acquisition of the angle of the motor shaft and to identify malfunction and drift of engine operation according to the evolution of the pressure in the cylinders of it.

Another object of the invention is to propose a diagnostic method initiating an automatic correction thereof by means on-board correction in the motor vehicle.

• d'analyse du fonctionnement de chaque cylindre et des chaínes d'acquisition de pression dans le cylindre et de l'angle de l'arbre moteur, consistant à identifier un état de fonctionnement de l'ensemble composé de ceux-ci parmi un état nominal de fonctionnement, et un ensemble de dysfonctionnements et de dérives prédéterminés en fonction de caractéristiques prédéterminées du signal délivré par la chaíne d'acquisition de pression dans le cylindre ; et
• de correction consistant à corriger des dysfonctionnements et des dérives identifiées appartenant à l'ensemble prédéterminé de dysfonctionnements et de dérives corrigeables par les moyens de correction embarqués.

For this purpose, the subject of the invention is a method for diagnosing the operating state of a diesel engine for a motor vehicle, this engine comprising a pressure acquisition chain associated with each cylinder of the engine to acquire the pressure in each cylinder, a chain for acquiring the angle of the motor shaft adapted to deliver the crankshaft angle of each cylinder and on-board correction means for correcting a predetermined set of malfunctions and drifts of the cylinders and chains of acquisition, characterized in that it comprises at least the steps:

• for analyzing the operation of each cylinder and the cylinder pressure acquisition lines and the motor shaft angle, comprising identifying an operating state of the set composed of these from a nominal state operating mode, and a set of malfunctions and drifts predetermined according to predetermined characteristics of the signal delivered by the pressure acquisition chain in the cylinder; and
• correction device for correcting identified malfunctions and drifts belonging to the predetermined set of malfunctions and drifts correctable by the on-board correction means.

According to another characteristic, the method is characterized in that further comprises a step of determining (114) the state of operation of each cylinder with respect to a predetermined state of nominal cylinder operation of identifying a state of operation of the cylinder among the predetermined operating state nominal value of the cylinder and a predetermined drift state according to the evolution of the pressure in the cylinders, and what is suitable for triggering the stage (102) when the determining step (114) determines at least one drift state of a cylinder.

• de détermination d'un écart de variation entre la variation du signal délivré par la chaíne d'acquisition de pression pour une première plage prédéterminée d'angles vilebrequin du cylindre et un modèle prédéterminé de variation de pression dans le cylindre ;
• de détermination d'un écart d'angle entre l'angle de pression maximale de la phase de compression du cycle du cylindre et un modèle prédéterminé d'angle de pression maximale de la phase de compression du cylindre ; et
• d'identification de l'état de fonctionnement du cylindre et des chaínes d'acquisition de pression dans le cylindre et de l'angle de l'arbre moteur en fonction des écarts de variation et d'angle déterminés et de plages prédéterminées d'écarts de variation et d'écart d'angle de pression maximale de la phase de compression.

According to another characteristic, the method is characterized in that the step of analyzing the operation of each cylinder and the pressure acquisition chains in the cylinder and the angle of the motor shaft comprises the steps of:

• determining a difference in variation between the variation of the signal delivered by the pressure acquisition chain for a first predetermined range of crank angle of the cylinder and a predetermined model of pressure variation in the cylinder;
• determining an angle difference between the maximum pressure angle of the cylinder cycle compression phase and a predetermined maximum pressure angle model of the cylinder compression phase; and
• for identifying the operating state of the cylinder and the pressure acquisition chains in the cylinder and the angle of the driving shaft according to the determined variations of variation and angle and predetermined ranges of deviations variation and maximum pressure angle deviation of the compression phase.

According to another characteristic, the method is characterized in that that the step of determining the variation of variation consists in acquiring a population of a predetermined number of values of the variation of the signal delivered by the pressure acquisition chain into the cylinder for the first time predetermined range of crank angle and to determine the deviation as the difference between the average of this population and a value predetermined reference of pressure variation in the cylinder for the predetermined range of crankshaft angles.

According to another characteristic, the method is characterized in that the step of determining the angle difference is to acquire a population of a predetermined number of values of maximum pressure angle of the compression phase of the cylinder cycle and to determine the angle difference as the difference between the average of this population and a value predetermined reference angle of maximum pressure angle of the phase of compression of the cylinder.

According to another characteristic, the method is characterized in that the stage of identification of the state of operation consists in identifying the state nominal operating cylinder and pressure acquisition lines in the cylinder and the angle of the motor shaft if the variation deviation determined is included in a first predetermined range of variations of variation and if the determined angle deviation is within a first predetermined range differences in angle.

According to another characteristic, the method is characterized in that the stage of identification of the state of operation consists in identifying the state nominal operating cylinder and pressure acquisition lines in the cylinder and the angle of the motor shaft if the variation deviation determined is included in a first predetermined range of variations of variation and if the angle deviation determined is within a first predetermined range differences in angle and if the variance of the population of variation values is below a predetermined threshold of variance of variation and if the variance of the population of angle values is less than a predetermined threshold of angle variance.

According to another characteristic, the method is characterized in that the stage of identification of the operating state of the cylinder and chains of pressure acquisition in the cylinder and the angle of the motor shaft further consists in identifying a malfunction or drift in the cylinder and / or the pressure acquisition chain in the cylinder and / or the chain for acquiring the motor angle when the nominal operating state is not identified, and to determine if the malfunction or drift identified belongs to the predetermined set of malfunctions and drifts corrigeable by the correction means on board the vehicle automobile.

According to another characteristic, the method is characterized in that consists of issuing a necessary intervention signal if at least one malfunction is identified as uncorrectable by the means of on-board correction, and in that the correction step is triggered if at least a malfunction is identified as correctable by the means of embedded correction.

According to another characteristic, the method is characterized in that the step of analyzing the operation of each cylinder, and chains of pressure acquisition in the cylinder and the angle of the motor shaft is triggered following the first start of the engine or the start of the latter following predetermined interventions, the engine being idle.

• de détermination d'un écart de ratio entre le ratio d'une variation de pression dans le cylindre sur la somme de variations de la pression dans les autres cylindres et un modèle prédéterminé de ratio, chacune des variations de la pression dans un cylindre correspondant à la variation de pression pour une seconde plage prédéterminée d'angles vilebrequin ; et
• d'identification d'un état de dérive du fonctionnement du cylindre parmi l'état nominal et l'état de dérive de fonctionnement du cylindre en fonction d'une plage prédéterminée d'écarts de ratio.

According to another characteristic, the method is characterized in that the step of determining the operating state of each cylinder with respect to the predetermined nominal operating state comprises the steps:

• determining a ratio difference between the ratio of a pressure variation in the cylinder to the sum of variations of the pressure in the other cylinders and a predetermined ratio model, each of the variations of the pressure in a cylinder corresponding to the variation of pressure for a second predetermined range of crank angle; and
• of identifying a state of drift of the cylinder operation among the nominal state and the operating drift state of the cylinder according to a predetermined range of ratio deviations.

• une étape d'acquisition d'une population d'un nombre prédéterminé de n-uplets des valeurs de variation de pression pour la seconde plage d'angles vilebrequin dans chaque cylindre du moteur, où n est le nombre de cylindres du moteur ;
• une étape de génération pour chaque n-uplet du ratio de la valeur de la variation de pression dans le cylindre sur la somme des valeurs de la variation de pression dans les autres cylindres afin d'obtenir une population de ratios pour le cylindre ; et
• une étape de détermination de l'écart de ratio comme la différence entre la moyenne de la population de ratios pour le cylindre et une valeur de référence prédéterminée de ratio pour le cylindre.

According to another characteristic, the method is characterized in that the step of determining a ratio deviation comprises:

• a step of acquiring a population of a predetermined number of n-tuples of the pressure variation values for the second crank angle range in each engine cylinder, where n is the number of engine cylinders;
• a generation step for each n-tuple of the ratio of the value of the pressure variation in the cylinder to the sum of the values of the pressure variation in the other cylinders in order to obtain a population of ratios for the cylinder; and
• a step of determining the ratio deviation as the difference between the average of the ratio population for the cylinder and a predetermined ratio reference value for the cylinder.

According to another characteristic, the method is characterized in that the step of identifying the drift state of the cylinder operation consists of to determine the nominal operating state of the cylinder if the ratio deviation is included in the first predetermined range of ratios.

According to another characteristic, the method is characterized in that the pressure ratio reference value in the cylinder and the first range of ratio deviations are respectively the mean and a confidence interval predetermined risk of a Gaussian distribution of the mean of the ratio of pressure in the cylinder, determined after the first start of the engine.

According to another characteristic, the method is characterized in that the step of determining the drifts of the operation of each cylinder is triggered if the nominal operating state has been identified for each cylinder and the chains of acquisition of the pressure in the cylinder and the angle of the motor shaft.

According to another characteristic, the method is characterized in that the step of determining the operating state of each cylinder is triggered regularly.

According to another characteristic, the method is characterized in that includes a step of evaluating the results of the correction implemented by the onboard correction means, and in that it consists in transmitting a intervention signal required if the evaluation of the correction results determines a failure of the correction.

The present invention also relates to a system of diagnosis of the operating state of a Diesel engine of the type mentioned above implementing the method according to the invention.

• la figure 1 est une vue schématique d'un moteur Diesel à rampe commune d'alimentation équipé de chaínes d'acquisition de pression dans les cylindres et d'une chaíne d'acquisition de l'angle de l'arbre moteur, et d'une unité de contrôle du fonctionnement du moteur;
• la figure 2 est un organigramme des principales étapes du procédé selon l'invention ;
• la figure 3 est un plan de diagnostic de l'état de fonctionnement des cylindres et des chaínes d'acquisition de la pression dans les cylindres et de l'angle de l'arbre moteur ;
• la figure 4 est un organigramme de l'étape d'analyse, pour chaque cylindre du moteur, du fonctionnement de ce cylindre et des chaínes d'acquisition de pression dans ce cylindre et de l'angle de l'arbre moteur du procédé selon l'invention;
• la figure 5 est un organigramme de l'étape de détermination des dérives du fonctionnement de chaque cylindre par rapport à l'état nominal de fonctionnement prédéterminé du cylindre du procédé selon l'invention ; et
• la figure 6 est une vue schématique d'un mode de réalisation préféré de l'unité de diagnostic de l'état de fonctionnement entrant dans la constitution du système de la figure 1.

The present invention will be better understood on reading the description which follows, given solely by way of example, and taken in conjunction with the appended drawings, in which identical references refer to identical or similar elements, and in which:

• FIG. 1 is a schematic view of a diesel engine with a common feed ramp equipped with pressure acquisition chains in the cylinders and a chain for acquiring the angle of the driving shaft, and a unit controlling the operation of the engine;
• Figure 2 is a flow diagram of the main steps of the method according to the invention;
• Figure 3 is a diagnostic plan of the operating state of the cylinders and chains of acquisition of the pressure in the cylinders and the angle of the motor shaft;
• FIG. 4 is a flowchart of the analysis step, for each cylinder of the engine, of the operation of this cylinder and of the pressure acquisition lines in this cylinder and of the angle of the driving shaft of the process according to FIG. 'invention;
• FIG. 5 is a flow chart of the step of determining the drifts of the operation of each cylinder with respect to the predetermined nominal operating state of the cylinder of the method according to the invention; and
• FIG. 6 is a schematic view of a preferred embodiment of the operating state diagnostic unit forming part of the system of FIG. 1.

In FIG. 1, is illustrated under the general reference 10 an engine Diesel for a motor vehicle equipped for example with four cylinders 12a, 12b, 12c, 12d. Each cylinder of the engine comprises an injector 14a, 14b, 14c, 14d, a yoke 18a, 18b, 18c, 18d, a piston 20a, 20b, 20c, 20d and a combustion chamber 22a, 22b, 22c, 22d delimited by the piston and the cylinder head of the cylinder. The cylinder injector, included in the cylinder head, is connected to a common supply rail 24 of the engine and is suitable for supplying the combustion chamber 22a, 22b, 22c, 22d of the cylinder fuel according to at least one pilot injection and one main injection of fuel, as is known in the state of the art.

Each cylinder is also associated with a chain 24a, 24b, 24c, 24d of pressure acquisition in the cylinder, comprising for example a 26a, 26b, 26c, 26d deformation sensor with inserted piezoelectric element in the cylinder head or integrated with the glow plug, and fit for measure deformations of the latter under the effect of pressure variations in the combustion chamber of the cylinder. Pistons 20a, 20b, 20c, 20d are connected to a motor shaft 28 of the motor 10. The motor shaft 28 is associated with a chain 30 for acquiring the motor shaft angle, comprising for example a Hall effect sensor associated with a gear wheel fixed to the motor shaft. This chain is furthermore suitable for delivering the crankshaft angle of each cylinder in a manner known per se.

The chains 24a, 24b, 24c, 24d of pressure acquisition in the cylinders and the chain 30 of acquisition of the angle of the motor shaft are connected to a unit 32 for controlling the operation of the engine adapted to control the operation of the motor according to the measurements of pressure in the cylinders and angle of the motor shaft. The control unit 32 of operation is connected to the engine cylinder injectors and to the common feed ramp 24 and is suitable for controlling different engine operating parameters like for example the characteristics of the injections, etc., according to pressure measurements and angle of the motor shaft delivered by the different chains of acquisition.

The control unit 32 comprises means 34 for correcting the embedded malfunctions / drifts adapted to correct a set predetermined malfunctions and drifts of the engine and chains pressure acquisition in the cylinder and the angle of the motor shaft as for example a bad calibration of a sensor, a bad calibration angular, an inversion of some branches etc ...

Finally, the control unit 32 includes a diagnosis unit 36 of the operating state of the engine implementing the method that is the object of the invention.

Fig. 2 is a flowchart of the state diagnostic method operation of a diesel engine according to the invention implemented by the unit 36 of the engine operation control unit and applied to the diagnosis of the operating state of the motor of FIG.

At a first step 100, following an engine start 10, the method consists in testing whether the start is the first start of the motor or is consequential to an intervention included in a set predetermined number of interventions. If the result of this test is positive, a step 102 analysis, for each cylinder of the engine, the operation of the cylinder and chains of pressure acquisition in the cylinder and the angle of the shaft engine, is triggered.

The analysis step 102, implemented when the engine is at the idle, consists in determining for each set composed of a cylinder, the chain of acquisition of pressure in this cylinder and the chain of acquisition the angle of the motor shaft, if this assembly operates in a nominal condition predetermined operating condition or is subject to malfunction or a predetermined drift, and to identify the malfunction or drift if this together does not work in a nominal way, as will be explained in more detail later.

When the engine starts for the first time or following a human intervention of the predetermined set of interventions, some malfunctions are likely to occur, such as a bad connection of electrical connections, a pressure sensor defective, incorrect angular setting of the sprocket of the chain acquisition of the angle of the motor shaft, a leak in a cylinder, a misalignment of a pressure chain in a cylinder, etc.

If one or more malfunctions or drifts have been identified in step 102, the method tests in a step 104 whether each malfunction and drift identified (e) belongs to the predetermined set of dysfunctions and drifts that can be corrected by means 34 of correction of embedded malfunctions / drifts. If each malfunction and each drift identified is indeed correctable by the correction means 34, the method according to the invention then consists of in a non-nominal state correction step 106, to be corrected by the means 34 on-board correction identified malfunctions.

Once the correction is made for each malfunction corrigibly, the method then consists, in a step 108, of evaluating the results of the correction. If the assessment is negative, ie if the correction failed, the method is clean, in a step 110, to issue a signal to the vehicle user to indicate that a intervention is necessary. The process then switches, in a step 112, following step 110 of transmitting the intervention signal, the engine in a degraded mode of predetermined operation.

If the result of the test implemented during step 104 is negative, that is, if an identified malfunction or drift does not belong to the predetermined set of corrective malfunctions and drifts by the on-board correction means 34, the signal transmission step 110 necessary intervention is then triggered.

If the analysis process 102 determines the nominal operation for each cylinder and the chains for acquiring the pressure in it and the angle of the motor shaft, and thus the absence of malfunction, the The method then consists, in a step 113, of determining and memorizing values used in a step 114 of determining the state of operation of each cylinder, as will also be explained more in detail thereafter.

The process 114 determines in particular if each cylinder operates in its nominal state and determines a drift state of operation of it if this is not the case.

The drift state of a cylinder is thus determined once diagnosed that pressure acquisition chains and the angle of the tree engine operate satisfactorily, so that this determination is not distorted by an element of defective acquisition lines or operating unsatisfactorily.

Once the determination step 114 has been carried out, if at least one derives from the operation of a cylinder has been diagnosed, the process loops on step 102 for analyzing the operation of the cylinder and chains of pressure acquisition in the cylinder and the angle of the shaft engine to identify this at least one drift.

When the test result of step 100 of the process to find out if starting is the first start of the engine or is consecutive to a intervention of the predetermined set of interventions is negative, the process consists, in a step 118, of testing a triggering condition of step 114 of determining the drift state of each cylinder. By example the process 118 tests whether the number of kilometers traveled by the vehicle since the last determination of the drifts is greater than or equal to a predetermined value of kilometers. The process 118 also tests whether the engine operation control unit 32 has committed a fault included in a predetermined list of faults. This predetermined list includes for example faults of the control unit 32 which have for consequence of non-consistent values of motor control regulation in function of the cylinder pressure signals delivered by the acquisition lines pressure in the cylinders.

If the result of this test is negative, the occurrence of the satisfaction of the trigger condition continues to be scanned. If the result of this test is positive, the determination step 114 is then triggered.

Finally if the result of the evaluation of the results of the state correction nominal value implemented in step 108 of the process is positive, step 118 of test the trigger condition of step 114 of determining the drifts is then triggered.

It will now be described, in connection with FIG. 3 and FIG. step 102 of analysis, for each cylinder of the engine, the operation of this cylinder and pressure acquisition chains in this cylinder and the angle of the motor shaft.

The analysis step 102 is implemented cylinder by cylinder of sequentially, with the engine idling, removing the pilot injection on the cylinder being diagnosed as well as by underlining the injection main so that the combustion starts more than 5 ° crankshaft after the top dead center, and / or by eliminating exhaust gas recirculation, hereinafter "EGR", if the precision of the determination and the identification of malfunctions and drifts is improved on the type of vehicle to which the process according to the invention is applied as has been determined in a preliminary statistical study.

Step 102 consists, for a cylinder, first of all to analyze simultaneously the amplitude of the signal delivered by the chain of acquisition of pressure in the cylinder and the maximum pressure angle of the curve of compression of the cylinder cycle, hereinafter "APMC". More particularly, process consists in acquiring during the compression phase of the cycle of cylinder, the value of the signal delivered by the pressure acquisition chain in the cylinder and the value of the angle of the motor shaft delivered by the chain acquisition of the angle of the motor shaft to obtain the evolution of the signal delivered by the acquisition chain according to the crankshaft angle of the cylinder.

Direct search of the maximum value of the signal delivered by the chain of acquisition of pressure in the cylinder does not present a generally a good precision because a small variation in pressure in the immediate vicinity of the top dead center of the cylinder cycle can be drowned in the measurement noise.

The process 102 first samples the signal delivered by the acquisition chain in a predetermined window of ± 5 ° crankshaft around an estimate of the dead point and thus obtains a sampled curve.

Then, the process 102 determines the center of symmetry of this curve, that is to say the APMC, by adjusting for example by the least squares a polynomial of the second degree to the sampled data of the curve then determines the position of the maximum of this polynomial and therefore the APMC.

l'APMC est déterminé par le processus 102 selon la relation :

Advantageously, the least squares APMC determination requires very few calculations. Indeed, this position value of the maximum is expressible in polynomial form. Noting xi the angle values at the sampling points, and yi the pressure values at these points, and if the samples are taken symmetrically around zero in order to have

the APMC is determined by the process 102 according to the relation:

The amplitude analysis consists in comparing the variation ΔS = S (α ₂ ) -S (α ₁ ) of the value S of the signal delivered by the pressure acquisition chain in the cylinder, between two predetermined crank angle α ₁ and α ₂ of the compression phase of the cylinder cycle, to a predetermined value corresponding to a pressure variation representative of a set of engines of the diesel engine family to which the method according to the invention applies.

Similarly, the analysis of the maximum pressure angle of the compression curve is to compare the observed APMC from the cylinder to a predetermined value corresponding to a maximum pressure angle of the compression phase representative of the set of engines of the family of the diesel engine, to which the method according to the invention applies.

In a previous study, populations of pressure variations between the crankshaft angles α ₁ and α ₂ APMC were observed for the cylinders of the engine set in different wear conditions and different operating conditions, but with nominal operating state of the cylinders and acquisition lines. For the sake of brevity, a cylinder of a motor associated with pressure acquisition chains therein and acquisition of the angle of the motor shaft which operate in a nominal manner will be described later. "Nominal cylinder assembly". This statistical study also determines whether the cutting of the aforementioned EGR advantageously improves the diagnostic accuracy for the type of diesel engine that is the subject of the diagnosis implemented by the method according to the invention.

A statistical study of the population of pressure variations thus acquired establishes that the pressure increase, for a nominal cylinder assembly between the predetermined crank angles α ₁ and α ₂ of the compression phase, is a Gaussian random variable of average m _ΔP and of variance σ ² _ΔP . In a similar way, a statistical study of the APMC population thus acquired establishes that the APMC for a nominal cylinder assembly is a Gaussian random variable of average m _APMC and variance σ ² _APMC .

Figure 3 is a partition of a diagnostic plan also obtained in the previous study. This plane makes it possible to characterize the operation of the cylinder and the pressure acquisition chains therein and the angle of the motor shaft as a function of the operating deviations of this assembly with respect to the pair of values (m _ΔP , m _APMC ) representative of the nominal operating state.

This diagnostic plan is provided with an orthogonal reference frame of origin (m _ΔP , m _APMC ) whose abscissa locates the average of an observed population of N variations ΔS ^obs of the value of the signal delivered by the acquisition chain of pressure in the cylinder between the crank angle α ₁ and α ₂ to which is subtracted the value m _ΔP , and whose ordinate locates the average of an observed population of M maximum pressure angles of the compression curve APMC ^obs cylinder subtracted from the value m _APMC , where M and N are predetermined numbers.

où, LIC_ΔP,1 et LSC_ΔP,1 sont les bornes inférieure et supérieure respectivement d'un premier intervalle de confiance prédéterminé, de risque r_ΔP,1, et LIC_ΔP,2 et LSC_ΔP,2 sont les bornes inférieure et supérieure respectivement d'un second intervalle de confiance prédéterminé, de risque r_ΔP,2, d'une variable aléatoire selon la relation :

   où x and_i, i=1,..., N, est une variable aléatoire gaussienne de moyenne m_ΔP et de variance σ² _ΔP.The x-axis is divided into five segments, namely

where, LIC _{ΔP, 1} and LSC _{ΔP, 1} are the lower and upper bounds respectively of a first predetermined confidence interval, of risk r _{ΔP, 1} , and LIC _{ΔP, 2} and LSC _{ΔP, 2} are the lower and upper bounds respectively a second predetermined confidence interval, of risk r _{ΔP, 2} , of a random variable according to the relation:

where x and _i , i = 1, ..., N, is a Gaussian random variable of mean m _ΔP and variance σ ² _ΔP .

et

où LIC_APMC,1 et LSC_APMC,1 sont les bornes inférieure et supérieure respectivement d'un premier intervalle de confiance prédéterminé, de risque r_APMC,1, et LIC_APMC,2 et LSC_APMC,2 sont les bornes inférieure et supérieure respectivement d'un second intervalle prédéterminé de confiance, de risque r_APMC,2 de la variable aléatoire selon la relation :

   où y and_i, i=1,..., M, est une variable aléatoire de moyenne m_APMC et de variance σ² _APMC.The y-axis is also divided into five segments, namely

and

where LIC _{APMC, 1} and LSC _{APMC, 1} are the lower and upper bounds respectively of a first predetermined confidence interval, of risk r _{APMC, 1} , and LIC _{APMC, 2} and LSC _{APMC, 2} are the lower and upper bounds respectively a second predetermined interval of confidence, of risk r _{APMC, 2} of the random variable according to the relation:

where y and _i , i = 1, ..., M, is a random variable of mean m _APMC and variance σ ² _APMC .

où w and_i, i=1,..., N, est une variable aléatoire gaussienne de moyenne m_w et de variance σ² _w , est l'intervalle

où t_α est un nombre tel que la probabilité P(G < t_α) qu'une réalisation G de la variable aléatoire G and gaussienne centrale réduite soit égale à 1 - α / 2. It can be recalled that a confidence interval [LIC; LSC] of α risk associated with a Gaussian random variable

where w and _i , i = 1, ..., N, is a Gaussian random variable of mean m _w and of variance σ ² _w , is the interval

where t _α is a number such that the probability P (G <t _α ) that a realization G of the reduced central G and Gaussian random variable is equal to 1 - α / 2 .

Each of the predetermined ranges S _{ΔP, i} × S _{APMC, j} , i = 1,2, ..., 5; j = 1,2, ..., 5 is representative of a predetermined operating state of the cylinder and of the chains for acquiring the pressure therein and the angle of the driving shaft, that is, ie the nominal state, a predetermined malfunction or a predetermined drift.

The central range S _{ΔP, 3} × S _{APMC, 3} is representative of the nominal operating state. If the operation of the cylinder and associated acquisition chains is such that the torque (X, Y), constituted by an embodiment of the variable X and and an embodiment of the variable Y and respectively, deviates from the torque (m _{ΔP ,} m _APMC ) of an amount such that it is in the range SΔP, ₃ × S _{APMC, 3} , then it is diagnosed that the cylinder and the associated acquisition chains operate in the nominal operating state and do not therefore, there is no malfunction or drift.

• les plages S_ΔP,2 × S_APMC,3 et S_ΔP,4 × S_APMC,3 sont représentatives d'une dérive de la chaíne d'acquisition de pression dans le cylindre. Celle-ci n'est plus calibrée de manière satisfaisante et renvoie une mesure de la pression non représentative de la valeur réelle de la pression dans le cylindre ;
• la plage S_ΔP,2 × S_APMC,2 est représentative d'une fuite sur le cylindre ;
• les plages S_ΔP,1 × S_APMC,i i = 1,..., 5, sont représentatives d'une absence du signal délivré par la chaíne d'acquisition de pression ;
• les plages S_ΔP,5 × S_APMC,i, i = 1,..., 5, sont représentatives d'une saturation de la chaíne d'acquisition de pression ; et
• les autres plages sont représentatives d'un problème de calage angulaire de la chaíne d'acquisition de l'angle de l'arbre moteur.

The other ranges correspond to a non-nominal state of operation. Each of these is representative of a malfunction or drift among a predetermined set of malfunctions and drifts. More particularly:

• the ranges S _{ΔP, 2} × S _{APMC, 3} and S _{ΔP, 4} × S _{APMC, 3} are representative of a drift of the chain of acquisition of pressure in the cylinder. This is no longer calibrated satisfactorily and returns a measurement of the pressure that is not representative of the actual value of the pressure in the cylinder;
• the range S _{ΔP, 2} × S _{APMC, 2} is representative of a leak on the cylinder;
• the ranges S _{ΔP, 1} × S _{APMC, i} i = 1, ..., 5, are representative of an absence of the signal delivered by the pressure acquisition chain;
• the ranges S _{ΔP, 5} × S _{APMC, i} , i = 1, ..., 5, are representative of a saturation of the pressure acquisition chain; and
• the other ranges are representative of a problem of angular wedging of the chain of acquisition of the angle of the motor shaft.

Advantageously, the risks r _{ΔP, 1} and r _{APMC, 1} are equal to 1%. Thus, if the average of a population of observed variations of the signal delivered by the pressure acquisition chain in the cylinder is not included in S _{ΔP, 3} , then the probability that the cylinder and the associated acquisition chains do not function as a nominal cylinder assembly characterized by a gaussian pressure variation, of mean m _ΔP and of variance σ ² _ΔP , is less than 1%. Similarly, if the average of an APMC population observed is not within the range S _APMC, then the probability that the cylinder and the associated acquisition chains do not function as a nominal cylinder assembly characterized by a Gaussian APMC, of mean m _APMC and variance σ ² _APMC , is less than 1%.

Figure 4 is a flowchart of the analysis step 102, for each cylinder of the engine, the operation of this cylinder and chains pressure acquisition in this cylinder and the angle of the motor shaft.

Successively in step 100 of the method according to the invention described in connection with FIG. 1, with the engine idling, an initialization step 200 is triggered and consists in particular of initializing at zero a counter k of cylinders and a list L _dys dysfunction / drift. In a next step 202, the cylinder counter k is incremented by an increment step of one, and a test is then performed in a step 204 to know if the value of this counter k is greater than the total number n of cylinders of the motor.

de N variations du signal délivré par la chaíne d'acquisition de pression dans le k^ième cylindre du moteur entre les angles vilebrequin α₁ et α₂ de la phase de compression du cycle du cylindre.If the result of this test is negative, the method according to the invention consists, in a step 206, in eliminating the pilot injection on the cylinder being diagnosed and in sub-stalling if necessary the main injection for that the fuel combustion of the main injection starts more than 5 ° crankshaft after top dead center, and possibly to remove the EGR if it improves the diagnostic accuracy as previously described. Step 206 then acquires a population

N variations of the signal issued by the channel pressure acquisition in the k ^th engine cylinder between the crankshaft angles α ₁ and α ₂ of the compression phase of the cylinder cycle.

de cette population est alors ensuite générée dans une étape 208 du procédé, ainsi qu'une valeur X selon la relation X = ΔS ^obs- m_ΔP.The average

of this population is then generated in a step 208 of the method, as well as a value X according to the relationship X = .DELTA.S ^obs - m _ΔP .

de M APMC pour le k^ième cylindre du moteur. La moyenne

est alors ensuite générée dans une étape 212 successive ainsi qu'une valeur Y selon la relation : Y =APMC obs-mAPMC. When the result of the test on the value of the cylinder counter k is negative, the method also consists, in a step 210, in acquiring a population

of M APMC for the k ^th cylinder of the engine. The average

is then generated in a successive step 212 and a value Y according to the relation: Y = APMC obs -m APMC .

The method then consists, in a step 214, triggered when the steps 208 and 212 of the method are completed, to generate the value pair (X, Y) for the k ^th cylinder, then to test in a step 216 if this pair belongs at the predetermined range S _{ΔP, 3} × S _{APMC, 3} representative of the nominal operating state of the assembly formed by the k ^th cylinder and the pressure acquisition lines therein and the angle of the engine shaft.

If the result of this test on the torque value (X, Y) is positive, the process then loops on step 202 to test the next cylinder. If the result of this test is negative, that is to say if a malfunction or drift is determined (e) for the assembly consisting of the k ^th cylinder and pressure acquisition chains in this k ^th cylinder and of the angle of the motor shaft, the method identifies, in a step 218, a malfunction or drift according to the predetermined range at which the pair of values (X, Y) belongs and then updates the list L _dys malfunctions / deviation by adding the malfunction or drift identified (e). The process then loops on step 202.

If the result of the test on the value of the cylinder counter k is positive, that is to say that all the sets consisting of a cylinder and pressure acquisition chains in this cylinder and the angle of the cylinder motor shaft have been tested, the process tests in step 220 the state of the list L _dys malfunctions / drifts. If the list L _dys is empty, that is to say if no malfunction or drift has been identified, the nominal operating condition of the cylinders and acquisition chains is then diagnosed. Otherwise a non-nominal state is diagnosed and the list L _dys dysfunctions / drifts is used in a step 222 for the identification of malfunctions and drifts corrigeable by the onboard correction means. For this purpose, the method determines whether each dysfunction and each drift listed in the list L _dys belongs to all the malfunctions and drifts corrigeable by the onboard correction means.

et si la variance σ² _{APMC_obs} de la population

du k^ième cylindre sont inférieures à des valeurs prédéterminées de variance LSC_{var_ΔP} et LSC_{var_ APMC} respectivement. Si à la fois le couple (X, Y) appartient à S_AP,3 × S_APMC,3 et la variance σ² _{Δs_obs} est inférieure à LCS_{var_ΔP} et la variance σ² _{APMC_obs} est inférieure à LSC_{var_APMC} alors l'état nominal de fonctionnement du k^ième cylindre et des chaínes d'acquisition de pression dans ce k^ième cylindre et de l'angle de l'arbre moteur est diagnostiqué. Tester simultanément la moyenne et la variance des populations

accroít ainsi la capacité du procédé à diagnostiquer l'état nominal de fonctionnement.Another embodiment of the method according to the invention consists in the test step 216 to know if the pair of values (X, Y) belongs to the predetermined range S _{ΔP, 3} × S _{APMC, 3} to be tested also if the variance σ ² _{ΔS_obs} of the population

and if the variance σ ² _{APMC_obs} of the population

of the k ^th cylinder are less than predetermined values of variance LSC _{var_ΔP} and LSC _{var_ APMC} respectively. If both the pair (X, Y) belongs to S _{AP, 3} × S _{APMC, 3} and the variance σ ² _{Δs_obs} is lower than LCS _{var_ΔP} and the variance σ ² _{APMC_obs} is lower than LSC _{var_APMC} then the nominal state of The operation of the k ^th cylinder and the pressure acquisition lines in this k ^th cylinder and the angle of the driving shaft is diagnosed. Simultaneously test population mean and variance

thus increasing the ability of the method to diagnose the nominal operating state.

   où χ² _M-1 est la fonction inverse de la fonction de distribution cumulée de la loi du chi-deux à M - 1 degré de liberté.The APMC of a nominal cylinder assembly being a Gaussian random variable of average m _APMC and variance σ ² _APMC , it is known that the random variable according to the relation (M -1) σ 2 APMC_obs_nom σ 2 APMC follows a chi- _square law at M-1 degree of freedom, where σ ² _{APMC_obs_nom} is the estimated variance of a population of M APMC of a nominal cylinder assembly. It is therefore possible to determine a threshold value LSC _{var_APMC} of predetermined risk confidence r _{var_APMC} , for example 1%, based on the law of chi-two according to the relation:

where χ ² _M-1 is the inverse function of the cumulative distribution function of the chi-square law at M - 1 degree of freedom.

In a similar way, a predetermined risk threshold value LSC _{var_ΔP} of risk, for example 1%, is determined for the variance of the population

It will now be described, in connection with FIG. 5, the step of determination of the operating state of each cylinder with respect to the state nominal operating temperature of the process cylinder according to the invention.

In a step 300, the method initializes a counter v to zero, then then increments in step 302 the counter value v by one step increment of one.

est acquise, où ΔS^obs _j,i , j=1,...,N, i=1,...,Q est une i^ème variation observée de la valeur du signal délivré par la chaíne d'acquisition de pression dans le j^ème cylindre entre deux angles vilebrequin prédéterminés α₃ et α₄ de la phase de compression du cycle du cylindre. Chaque n-uplet est par exemple acquis au cours d'un cycle de l'arbre moteur.At step 304, a population of a predetermined Q number of n-tuples

is acquired, where ΔS ^obs _{j, i} , j = 1, ..., N, i = 1, ..., Q is an i ^th observed variation of the value of the signal delivered by the pressure acquisition chain in the j ^th cylinder between two predetermined crank angles α ₃ and α ₄ of the compression phase of the cylinder cycle. Each tuple is for example acquired during a cycle of the motor shaft.

The method then generates in a step 306, for each n-tuple of the population and for each cylinder, a ratio according to the relation:

It is thus obtained a population of Q n-tuples of ratios

   où

j=1,...,n, est la moyenne des ratios relatifs au j^ième cylindre.The next step 308 is to form the ratio mean tuple

or

j = 1, ..., n, is the average of the ratios relative to the ^ith cylinder.

The method then generates in a step 310 the tuple Z = (Z ₁ , Z ₂ , ..., Z _n ), where Z _j = R _j ^obs -m _j, j = 1, ..., n, and m _j is a predetermined reference value representative of the ratio of the nominal operating ^jth cylinder.

   où

j=1,...,n, est une plage prédéterminée représentative du fonctionnement nominal du j^ième cylindre, et LIC_R,j et LSC_R,j sont la borne inférieure et supérieure respectivement d'un intervalle prédéterminé de confiance de risque prédéterminé r_j associé à une variable aléatoire gaussienne représentative de l'état nominal de fonctionnement du j^ième cylindre, comme cela sera expliqué plus en détail par la suite. Un cylindre j est alors diagnostiqué comme ne fonctionnant pas de manière nominale si la j^ième composante du n-uplet Z n'est pas comprise dans la plage

The next following step 312 of the method according to the invention consists in testing whether the tuple Z belongs to a first predetermined range P ₁ representative of the nominal operating state of all the cylinders of the engine. The range P ₁ is centered on the tuple (m ₁ , m ₂ , ..., m _n ), and is equal to:

or

j = 1, ..., n, is a representative predetermined range of the nominal operation of the ^j-th cylinder, and LIC _{R, j} and LSC _{R, j} are the lower and upper bound, respectively of a predetermined interval of predetermined risk trust r _j associated with a Gaussian random variable representing the nominal operating condition of the j ^th cylinder, as will be explained in more detail later. A cylinder j is then diagnosed as not working nominally if the j ^th component of the tuple Z is not within the range

If the nominal operating state of all the cylinders is not diagnosed in step 312, that is, if the tuple (Z ₁ , Z ₂ , ..., Z _n ) n is not in the range P ₁ , a test is carried out in a step 314 to find out if the value of the counter v is greater than or equal to a predetermined value v _max . If the result of this test is negative, the method according to the invention then loop on step 302.

If the result of this test is positive, that is to say if v _max successive diagnoses have determined that at least one cylinder does not operate in a nominal manner, a drift state of this at least one cylinder, and finally engine, is diagnosed. The method then loops on the step 102 previously described for drift identification as previously described.

As can be seen, step 114 of determination includes less calculation and acquisition operations than step 102 of analysis. So, he is particularly advantageous to implement such a step for diagnose drifts rather than implement systematic step 102 of analysis.

The determination of the reference values of ratio m _j and the associated confidence intervals is carried out during step 113 of the method of FIG.

Following the first start of the engine or human intervention of the predetermined set of interventions, when the step 102 of the method determines that the cylinders and chains of pressure acquisition in the cylinders and the angle of the motor shaft operate in the nominal operating state, that is to say without exhibiting a malfunction or drift, the method consists in the step 113 of acquiring a population of T n-tuple ratios {( R ^obs _{1, i} , R ^obs _{2, i} , ..., R ^obs _{n , i} ); i = 1, ..., T } for the angles α ₃ and α ₄ of the compression phase of the cylinder cycle in a manner similar to steps 304 and 306 described above in relation to FIG. 5, where T is a predetermined number.

de cette population d'une manière analogue à l'étape 308 décrite ci-dessus et enregistre ce n-uplet en tant que le n-uplet (m₁,m₂,...,m_n) de valeurs de référence de ratio.The process 113 then determines the ratio average tuple

of this population in a similar manner to step 308 described above and records this tuple as the tuple (m ₁ , m ₂ , ..., m _n ) of ratio reference values. .

de cette population, où σ ² _Rj est la variance des ratios relatifs au j^ième cylindre et détermine ensuite l'ensemble des intervalles de confiance

en fonction de ces variances, selon la relation

où t _j est un nombre tel que la probabilité P(G < t_j ) qu'une réalisation G de la variable aléatoire G and gaussienne centrale réduite soit égale à 1- r _j / 2.The process 113 also determines the tuple of ratio variances

this population, where σ ² is the variance of _Rj related to ratios j ^th cylinder and then determines the set of confidence intervals

according to these variances, depending on the relationship

where t _j is a number such that the probability P ( G < t _j ) that a realization G of the reduced central G and Gaussian random variable is equal to 1- r _j / 2.

Advantageously, the crankshaft angles α ₃ and α ₄ are equal to the crankshaft angles α ₁ and α ₂ respectively, so that it is possible to use the populations of variations of the signals delivered by the pressure acquisition chains in the rolls, acquired in step 206 of the process 102 described in connection with FIG. 4, for calculating the ratio reference values and the confidence intervals as previously described. The process does not then include a population acquisition step of variations, which accelerates the process according to the invention.

The statistical test on the .DELTA.S variation of the signal delivered by an acquisition chain of the pressure in a cylinder, for example the ^jth cylinder implemented in steps 206, 208 and 214 described in connection with Figure 1, may be replaced by the ratio test R _I ^obs , the principle of the process remaining the same.

It will now be described with reference to FIG. preferred arrangement of the diagnostic unit 36 of the operating state of the unit 32 for controlling the operation of the engine forming part of the constitution of the system of FIG. 1, and implementing the method which is the subject of the invention as previously described in connection with FIGS. 2 to 5.

Means 500 for acquiring means and variances of populations of signal variations delivered by a pressure acquisition system and APMC are inputted by the signals delivered by the pressure acquisition chains in the cylinders and the signal delivered by the chain of acquisition of the angle of the motor shaft. The means 500 for acquiring means and variances are suitable for determining for each cylinder of the engine, the average .DELTA.S ^obs and the variance σ ² _{ΔS_obs} of a population of N observed variations of the value of the signal delivered by the pressure acquisition chain in the cylinder by implementing the steps of the method 206 and 208 as described in connection with the figure 4, and the average APMC ^obs and the variance σ ² _{APMC_obs} of a population of M APMC observed by implementing the steps 210 and 212 of the method as described in relation with FIG. 4.

The value of the averages is then supplied to means 502 for generating torque which are further connected to a list 504 of the reference means m _ΔP and m _APMC of a non-volatile memory 506. The means 502 are suitable for generating a torque values (X, Y) as a function of the values of the averages received as inputs and of the reference means values by implementing step 214 of the method described above in relation to FIG. 4.

The pair (X, Y) is then supplied to first comparison means 508 which receive as a second input all the ranges S _{ΔP, i} and S _{APMC, j} of a list 510 of the ranges S _{ΔP, i} and S _{APMC , j} of the non-volatile memory 506. Moreover, the variances σ ² and σ ² _{ΔS_obs APMC_obs} are provided with second means 512 for comparison which also receive the values LCS _{var_ΔP} and LSC _{var_APMC} a list 514 of variance threshold values nonvolatile memory 506.

The first comparison means 508 determines which range the pair (x, Y) belongs to, and the second comparison means 512 determines whether each of the variances is less than its associated variance threshold value. The first and second comparison means determine in particular whether the entire cylinder and associated acquisition chains operate in the nominal operating state characterized by the range S _{ΔP, 3} × S _{APMC, 3} and the variances less than their value. respective threshold by implementing the step 216 previously described in connection with FIG.

The results of these comparisons are then provided to means 516 for identifying malfunctions and drifts which comprise storage means (not shown) of the L _dys list of the malfunctions / drifts and are able to update it by according to the comparison results by implementing step 218 of the method described with reference to FIG. 4.

en mettant en oeuvre les étapes 304, 306 et 308 du procédé selon l'invention comme décrit précédemment en relation avec la figure 5.In addition, the system according to the invention comprises means 518 for acquiring ratio averages having, as inputs, the signals delivered by the pressure acquisition lines in the cylinders and the signal delivered by the angle acquisition chain. of the motor shaft. The acquisition means 518 are adapted to acquire a tuple of ratio means

implementing steps 304, 306 and 308 of the method according to the invention as described previously with reference to FIG.

Means 518 provide the ratio average tuple to tuple generation means 520. The means 520 for generating n-tuple furthermore receive as second input the reference values of ratio m ₁ , m ₂ ,..., M _n of a list 522 of ratio reference values of the non-volatile memory 506. The generation means 520 then generate in response the tuple Z = (Z _1, Z ₂ , ..., Z _n ) by implementing step 310 of the method that is the subject of the invention as a function of the inputs that 'they receive.

The tuple (Z ₁ , Z ₂ ,..., Z _n ) thus generated is supplied to third comparison means 524 which determine whether this tuple belongs to the range P1 received as the second entry of a list 526. intervals of confidences of the non-volatile memory 506.

Means 516 for identifying malfunctions and drifts and the third comparison means 524 are connected to means 530 Central Management. These central management means 530 are furthermore connected to means 532 boot type identification. The means 532 boot type identification are suitable for determining, by implementing step 100 of the method, if a starting of the engine is the first start or if the start is successive to an intervention belonging to a predetermined list 534 of interventions stored in the non-volatile memory 506, and return the result of their determination to the means 530 central management.

The central management means 530 furthermore receive as input the number of KM kilometers traveled by the motor vehicle. They are also connected to the non-volatile memory 506 to receive a list 536 malfunctions and drifts corrigeable by the means of correction embedded in the motor vehicle.

The central management means 530 also receive as input the result of tests implemented by test means 531 adapted for determine whether the engine operation control unit 32 has committed a fault of the predetermined set of faults.

The means 530 of central management are also connected to means 538 for transmitting the necessary intervention signal, to the means 34 on-board correction, and means 540 of correction analysis by elsewhere connected to the on-board correction means 34.

The central management means 530 are adapted to trigger the different steps of the method according to the invention by controlling the means 500, 502, 516, 518, and 520 by generating a control signal E according to the entries they receive.

If a start determined by the starting means 532 is the first start of the vehicle, or a successive start to an intervention of a predetermined type, the central management means 530 generates an activation signal of the means 500, 502 and 516 which then determine together whether the cylinders and the acquisition chains are operating in the nominal operating state or not. The means 530 receive in return the list L _dys malfunctions / drifts.

If the list L _dys malfunctions / deviation is not empty, the means 530 determine whether central management malfunctions and drifts in the list are correctable by on-board means 34 and correction by implementing step 222 of the method of 'invention..

If the malfunctions are correctable, the central management means 530 deactivate the means 500, 502 and 516 and activate the on-board correction means 34 and the correction analysis means 540. The correction means 34 then receive the list L _dys of the corrections to be made and provide the correction analysis means 540 with the results of the correction. The correction analysis means 540 then evaluate the correction and in return provide their evaluation to the central management means 530.

If the correction has failed, the central management means 530 then activate the means 538 for transmitting the necessary intervention signal.

If the correction is successful, the central management means 530 deactivate the correction and correction analysis means and then activate the means 518, and 520.

If the list L _dys is empty, the central management means 530 determine and memorize the ratio reference values and the associated confidence intervals by implementing the step 113 of the method described in relation with FIG. 2 and activate the means 518 and 520 for carrying out step 114 of the method.

If the first start is neither a first start nor a successive start to an intervention of the predetermined set intervention, the central management means 530 deactivate the means 500, 502 and 516 and subsequently implement the trigger test step 118 of the method according to the invention as a function of the number of kilometers traveled KM by the vehicle and test results delivered by the means 531.

The means 530 then activate the means 518 and 520 which determine the drift state of the engine cylinders if the result of this test is positive.

The means 518, and 520 together then determine the state of drift cylinders and the central management means 530 then activate according to of the results delivered by the means 524 for comparing the means 500, 502 and 516 if a drift state is diagnosed.

Many variations can be envisaged not the man of the job. For example, rather than triggering a correction if each malfunction or drift is identified as correctable, it is possible to trigger the correction by the on-board correction means of a malfunction or drift identified as corrigeable, even if other malfunctions or drifts are also identified as not correctable.

Claims (19)

A method for diagnosing the operating state of a motor vehicle engine (10), said engine (10) comprising a pressure acquisition chain (18a, 18b, 18c, 18d) associated with each cylinder (12a, 12b, 12c, 12d) of the engine to acquire the pressure in each cylinder, a chain (30) for acquiring the angle of the motor shaft adapted to deliver the crankshaft angle of each cylinder and means (34) of on-board correction adapted to correct a predetermined set of malfunctions and drifts of the cylinders and acquisition chains, characterized in that it comprises at least the steps: analyzing (102) the operation of each cylinder and the cylinder pressure acquisition lines and the motor shaft angle, identifying a state of operation of the set consisting of them a nominal operating state, and a set of malfunctions and drifts predetermined according to predetermined characteristics of the signal delivered by the pressure acquisition chain in the cylinder; and correction device (106) consisting in correcting identified malfunctions and drifts belonging to the predetermined set of malfunctions and drifts that can be corrected by the on-board correction means. A method according to claim 1, characterized in that it further comprises a step (114) of determining the operating state of each cylinder with respect to a predetermined nominal cylinder operating state of identifying an operating state of the cylinder. one of the predetermined nominal cylinder operating state and a predetermined drift state as a function of the pressure change in the cylinders, and in that it is adapted to initiate the analysis step (102) when the determining step (114) determines at least one drift state of a cylinder. Process according to claim 1 or 2, characterized in that the step of analyzing (102) the operation of each cylinder and the pressure acquisition lines in the cylinder and the angle of the motor shaft comprises the steps : determining (206, 208) a difference in variation between the variation of the signal delivered by the pressure acquisition chain for a first predetermined range of crank angle of the cylinder and a predetermined model of pressure variation in the cylinder; determining (210, 212) an angle difference between the maximum pressure angle of the cylinder cycle compression phase and a predetermined maximum pressure angle model of the cylinder compression phase; and identification (216, 218) of the operating state of the cylinder and the pressure acquisition chains in the cylinder and the angle of the motor shaft according to the variations of variation and angle determined and predetermined ranges of variations of variation and of maximum pressure angle deviation of the compression phase. Method according to claim 3, characterized in that the step (206, 208) of determining the difference of variation consists in acquiring a population of a predetermined number of values of the variation of the signal delivered by the acquisition chain. of pressure in the cylinder for the first predetermined range of crank angle and determining the difference in variation as the difference between the average of that population and a predetermined reference value of pressure variation in the cylinder for the predetermined range of crankshaft angles. A method according to claim 3 or 4, characterized in that the angle difference determining step (210, 212) comprises acquiring a population of a predetermined number of maximum pressure angle values of the phase compressing the cylinder cycle and determining the angle difference as the difference between the average of that population and a predetermined reference value of the maximum pressure angle of the cylinder compression phase. A method according to claim 3, 4 or 5, characterized in that the operating state identification step (216, 218) is to identify the nominal operating state of the cylinder and the pressure acquisition lines. in the cylinder and the angle of the motor shaft if the determined variation deviation is within a first predetermined range of variation and if the determined angle deviation is within a first predetermined range of angle deviations. A method according to claim 3, 4 or 5, characterized in that the operating state identification step (216, 218, 222) is to identify the nominal operating state of the cylinder and acquisition lines. of pressure in the cylinder and the angle of the motor shaft if the determined deviation difference is within a first predetermined range of variation and the angle deviation determined is within a first predetermined range of angle deviations and if the variance of the population of variation values is less than a predetermined variance of variation threshold and the variance of the population of angle values is less than a predetermined threshold of angle variance . Method according to any one of the preceding claims, characterized in that the step of identifying (216, 218, 222) the operating state of the cylinder and the cylinder pressure acquisition and angle chains. of the motor shaft further comprises identifying a malfunction or drift in the cylinder and / or the pressure acquisition chain in the cylinder and / or the motor angle acquisition chain when the nominal state of operation is not identified, and to determine if the malfunction or the drift identified belongs to the predetermined set of malfunctions and drifts corrigeables by the onboard correction means in the motor vehicle. Method according to any one of the preceding claims, characterized in that it consists in transmitting a necessary intervention signal if at least one malfunction is identified as non-correctable by the on-board correction means, and in that the step of correction is triggered if at least one malfunction is identified as correctable by the onboard correction means. Method according to any one of the preceding claims, characterized in that the step (102) for analyzing the operation of each cylinder, and the pressure acquisition chains in the cylinder and the angle of the driving shaft is triggered following the first start of the engine or starting it after predetermined interventions, the engine being idle. A method according to claim 2 and any one of claims 3 to 10, characterized in that the step (114) of determining the operating state of each cylinder with respect to the predetermined nominal operating state comprises the steps : determining (304, 306, 308, 310) a ratio difference between the ratio of a pressure variation in the cylinder to the sum of variations of the pressure in the other cylinders and a predetermined ratio model, each of changes in the pressure in a cylinder corresponding to the variation of pressure for a second predetermined range of crank angles; and identifying (312, 314) a state of drift of the cylinder operation among the nominal state and the operating drift state of the cylinder as a function of a predetermined range of ratio deviations. A method according to claim 11, characterized in that the step (304, 306, 308, 310) of determining a ratio deviation comprises: a step (304) of acquiring a population of a predetermined number of n-tuples of the pressure variation values for the second crank angle range in each cylinder of the engine, where n is the number of engine cylinders ; a generation step (306) for each tuple of the ratio of the value of the pressure variation in the cylinder to the sum of the values of the pressure variation in the other cylinders in order to obtain a ratio population for the cylinder ; and a ratio deviation step (308, 310) such as the difference between the average of the ratio population for the cylinder and a predetermined ratio reference value for the cylinder. Method according to Claim 11 or 12, characterized in that the step (312, 314) for identifying the drift state of the cylinder operation consists in determining the nominal operating state of the cylinder if the ratio deviation is included in the first predetermined range of ratios. Method according to one of Claims 11 to 13, characterized in that the reference value of the pressure ratio in the cylinder and the first range of ratio deviations are respectively the mean and a predetermined risk confidence interval of a Gaussian distribution of the average of the pressure ratio in the cylinder, determined after the first start of the engine. Method according to Claim 2 and any one of Claims 3 to 14, characterized in that the step of determining the drifts of the operation of each cylinder is triggered if the nominal operating state has been identified for each cylinder and the chains of acquisition of the pressure in the cylinder and the angle of the motor shaft. Method according to Claim 2 and any one of Claims 3 to 15, characterized in that the step (114) for determining the operating state of each cylinder is triggered regularly. Method according to any one of the preceding claims, characterized in that it comprises a step (108) for evaluating the results of the correction implemented by the on-board correction means, and in that it consists in transmitting a intervention signal required if the evaluation of the results of the correction determines a failure of the correction. Diagnostic system (32) for the operating state of an engine (10) Diesel for a motor vehicle, this engine (10) comprising a chain (18a, 18b, 18c, 18d) for acquiring pressure associated with each cylinder (12a, 12b, 12c, 12d) of the engine to acquire the pressure in each cylinder and a chain (30) for acquiring the angle of the motor shaft adapted to deliver the crankshaft angle of each cylinder, and means On-board correction devices (34) adapted to correct a predetermined set of malfunctioning cylinders and acquisition chains and cylinder operating drifts, characterized in that it comprises at least: means (500, 502, 516) for analyzing the operation of each cylinder and the pressure acquisition lines in the cylinder and the angle of the driving shaft, adapted to identify a state of operation of the set composed of these among a nominal operating state and a set of malfunctions and drifts predetermined according to predetermined characteristics of the signal delivered by the pressure acquisition chain in the cylinder; and correction means (34, 530) adapted to correct malfunctions and identified drifts belonging to the predetermined set of malfunctions and drifts corrigeable by the onboard correction means (34). System according to Claim 18, characterized in that it is suitable for carrying out the process according to any one of Claims 2 to 17.

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