Method for limiting oil intake in an internal combustion engine

Abstract

Method for limiting oil intake with the following steps: - Confirmation step (100) in the absence of fuel combustion: - a) monitoring by measuring time interval durations (T_Seg_Mes_n) between two successive passes through top dead centers at the end of compression, - b) application of a deceleration correction factor (Rn), - c) comparison of the measured and corrected interval durations (T_Corr_Seg_Mes_n), and - d) detection of a measured and corrected interval duration shorter than the others and storage, - Determination step (200) of the quantity of oil burned in the engine with: - e) determination of a gradient (GR) representative of a variation in engine rotational speed, and - f) estimation of the quantity of oil burned (Q) from a predetermined map, - Adaptation step (300) of the air pressure admitted into the cylinders. Figure of the abbreviation: Figure 2.

Description

Title of the invention: Method for limiting oil suction in an internal combustion engine

[0001] The present disclosure relates to a method of limiting oil suction in an internal combustion engine. Technical field

[0002] The technical field of the present invention is thus the field of engine control for an internal combustion engine. It relates to an engine comprising several cylinders. The present disclosure is intended in particular for a motor vehicle or similar (motorcycle, truck, etc.) but can also be used for another type of vehicle (boat or other). Prior art

[0003] In an internal combustion engine, pistons slide in cylinders and rotate a flywheel via a connecting rod-crankshaft system, and this movement is transmitted to the vehicle's wheels to move it. Combustion takes place in combustion chambers. Each piston forms a partition between the corresponding combustion chamber and a casing in which the connecting rod-crankshaft system moves. This partition must be sealed first of all so that the pressure generated by the combustion can be fully transmitted to the piston and also to prevent oil used to lubricate the engine, in particular the connecting rod-crankshaft system, from entering the corresponding combustion chamber.

[0004] To achieve engine sealing at the level of a piston, that is to say between the piston and the cylinder in which it slides (or the liner), it is known to use annular "seals" called segments. It is usual to use three segments: a sealing segment in the center protected on the combustion chamber side by a segment called a fire segment which in particular makes it possible to limit the thermal stresses applied to the sealing segment and on the crankcase side by a scraper segment or segmentation ring, well known to those skilled in the art, which limits the quantity of oil which can come into contact with the sealing segment.

[0005] In a new engine, the segments most often function perfectly but it happens that as they age, particularly given the significant constraints to which the segments are subjected, sealing problems appear and oil then penetrates into a combustion chamber. Indeed, during an intake phase in a cylinder of a four-stroke engine, a vacuum is created in said cylinder in order to suck in outside air. If one or more segmentation ring(s) is(are) worn or broken or damaged, the vacuum prevailing in the corresponding cylinder(s) will generate a suction of the oil present in the crankcase. This phenomenon is referred to later in this disclosure as "oil suction". When burning, this oil can cause uncontrolled emissions. In addition, this combustion also generates an unexpected increase in power because the combustion of the oil generates unexpected torque. In some cases, oil consumption can cause damage to the engine. It is therefore important at the very least to detect abnormal consumption and it is preferable to limit and / or eliminate it.

[0006] It is possible to detect oil consumption, for example by monitoring the oil level in the engine. However, this monitoring does not allow the piston (or cylinder) in question to be identified and is only preventive and not curative.

[0007] The present disclosure improves the situation. Its purpose is to provide means for, on the one hand, detecting abnormal oil consumption due to combustion in a cylinder and, on the other hand, limiting this consumption to, if possible, avoid any risk of deterioration of the engine. Summary

[0008] A method is proposed for limiting, in an internal combustion engine comprising a plurality of cylinders in each of which a piston slides, an oil suction following a finding of the presence of said oil suction.

[0009] According to the present disclosure, this method comprises the following steps: - step of confirming the presence of suction, carried out in the absence of fuel combustion with the following sub-steps: - - a) monitoring by measuring time interval durations between two successive passages through top dead centers at the end of compression of the pistons in the cylinders, - - b) application of a corrective deceleration factor to be made to the measured interval duration, for each time interval, in order to take into account an average deceleration of the engine speed, - - c) comparison of measured and corrected interval durations, and - - d) possible detection of one (or more) measured and corrected interval duration(s) less than the other measured and corrected interval durations and storage of the detection result, - step of determining a quantity of oil burned in the engine if in the previous confirmation step at least one measured and corrected interval duration shorter than the others was detected with the following sub-steps: - - e) determination of a gradient representative of a variation in the rotation speed of the engine, and - - f) from said gradient, estimation of the quantity of oil burned from a predetermined and memorized mapping, - step of possible adaptation of the air pressure admitted into the cylinders, during which a variation of said pressure is controlled according to the quantity of oil burned previously determined.

[0010] In an original manner, a method is proposed which not only makes it possible to detect oil consumption, to possibly determine in which cylinder(s) oil is burned but also to have a restorative action by limiting the combustion of oil.

[0011] In the method proposed above, the corrective deceleration factor to be applied to sub-step b) can be determined, for example, as a function of the variation in the duration of a time interval from one cycle to another for a cylinder and the number of cylinders in the engine.

[0012] In a method above, the gradient representative of a variation in rotational speed of the engine in sub-step e) may be a gradient of variation of the duration of the measured and corrected time interval of shorter duration compared to the other durations of measured and corrected time intervals.

[0013] In a method above, the mapping of sub-step f) can be carried out beforehand on an engine of the same type not experiencing oil suction in which, in the deceleration phase for which no combustion is planned, an injection and a combustion of known quantities of fuel per engine cycle are carried out at various engine speeds and the influence of this injection and this combustion on the gradient used in step e) is measured.

[0014] In a method proposed above, it can be provided for example that during the adaptation step, the variation of the air pressure admitted into the cylinders is controlled by acting on at least one of the following elements of the engine: - air intake butterfly and / or - turbocharger, and / or - exhaust gas recirculation valve.

[0015] It may be provided to integrate into a method for limiting, in an internal combustion engine, an oil suction described above also as a preliminary step of detecting oil combustion and a step of determining a cylinder in which said combustion takes place. In such a method, it may be provided that the following steps are implemented to determine the presence of oil suction: - detection step carried out with the following sub-steps: - - i) first step of monitoring the engine operating stability at a first operating point at low load, - - ii) first step of determining a respective corrective factor to be applied, for each cylinder, in order to correct a quantity of fuel injected into said cylinder, with a view to regulating the engine speed on said first operating point, - - iii) first step of memorizing the respective corrective factors for each cylinder, corresponding to the first operating point, - - iv) second stage of monitoring the engine operating stability at a second high load operating point, - - v) second step of determining a respective corrective factor to be applied, for each cylinder, in order to correct a quantity of fuel injected into said cylinder, with a view to regulating the engine speed on said second operating point, - - vi) second step of storing the respective corrective factors for each cylinder, corresponding to the second operating point, - step of determining an oil combustion in a given cylinder if, for said cylinder, the ratio between a first predetermined corrective factor and the corrective factor corresponding to the first operating point during the detection step is less than a predetermined threshold, while for the same cylinder the ratio between a second predetermined corrective factor and the corrective factor corresponding to the second operating point during the detection step is within a predetermined interval around 1.

[0016] Advantageously, a method above further comprises an alert step when an oil suction is detected, the cylinder(s) concerned then being advantageously identified.

[0017] According to another aspect, a computer program is provided comprising instructions for implementing a method presented above when this program is executed by a processor, in particular an electronic control unit of an internal combustion engine.

[0018] According to another aspect, there is provided a non-transitory, computer-readable recording medium on which such a program is recorded.

[0019] According to another aspect, a computer is provided configured for managing an internal combustion engine comprising means for implementing each of the steps of a method described above.

[0020] According to another aspect, there is provided a motor vehicle comprising an internal combustion engine, characterized in that it comprises a computer according to the preceding paragraph. Brief description of the drawing

[0021] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawing, in which: Fig.l

[0022] [Fig.l] is an illustrative diagram of a deceleration of an engine without oil combustion illustrating, on the one hand, a rotation speed of the engine and, on the other hand, durations of time intervals, measured then corrected, each corresponding to the time elapsing between two successive passages of a piston at a top dead center at the end of compression. Fig. 2

[0023] [Fig.2] is a diagram corresponding to that of [Fig.l] for a deceleration of an engine with combustion of oil in a cylinder. Fig. 3

[0024] [Fig.3] is a curve that can be used to determine a quantity of oil burned in the engine considered. Fig. 4

[0025] [Fig.4] is a flowchart for implementing a limitation of an amount of oil burned in an engine according to the present disclosure. Fig. 5

[0026] [Fig.5] is a flowchart for implementing a method for detecting and limiting burnt oil in an engine according to the present disclosure. Fig. 6

[0027] [Fig.6] is an illustrative diagram of a closed loop used for the detection of oil combustion in an engine as a preliminary step to implementing a method for detecting and limiting burned oil in an engine according to the present disclosure. Fig. 7

[0028] [Fig.7] is a diagram comparing a detection step in a cylinder without oil combustion versus a cylinder with oil combustion for detection prior to implementing a method for detecting and limiting burnt oil in an engine according to the present disclosure. Fig. 8

[0029] [Fig.8] is a schematic view of a vehicle in which a method for detecting and limiting burnt oil in an engine according to the present disclosure can be implemented. Description of the embodiments

[0030] The present description is made in relation to an internal combustion engine, of the four-stroke type. As known to those skilled in the art, an internal combustion engine comprises one or more cylinders, inside each of which there is a combustion chamber. Each combustion chamber is associated with a piston which slides in a back and forth movement, passing successively through a point top dead center then a bottom dead center and so on. Seals, called segments, allow the seal between a piston and the corresponding cylinder and prevent, on the one hand, air or gas from escaping from the combustion chamber through the periphery of the piston and, on the other hand, engine lubricating oil from entering the corresponding combustion chamber. Valves called intake and exhaust, allow the flow to and from each combustion chamber respectively to be managed and an injector allows fuel to be injected into each combustion chamber.

[0031] The following description is given for a four-stroke engine with several cylinders and in the example chosen it is a four-cylinder engine. In a four-stroke engine, a complete working cycle is carried out over two engine revolutions, i.e. a passage through two top dead centers and two bottom dead centers. A complete working cycle therefore has four operating phases. These phases being known to those skilled in the art, they are briefly mentioned here. A first phase concerns the intake of air. The piston has a downward movement in the cylinder (increase in the volume of the chamber in the cylinder). The intake valve is open while the exhaust valve is closed. In the second phase, or compression phase, the piston has an upward movement and compresses the air (or the air / fuel mixture) admitted in the first phase.To allow an increase in pressure in the cylinder (combustion chamber) the two valves (intake and exhaust) are closed. In the third phase, the fuel is injected and burns and pushes the piston in a downward movement. The two valves remain closed. Finally, the fourth phase allows the evacuation of burnt gases. The piston rises in the cylinder and expels the burnt gases through the exhaust valve which is open, the other valve -intake- being closed. During an engine cycle, each piston of the engine passes through a top dead center at the end of the compression cycle.

[0032] When the engine is new, the injectors have similar characteristics so as to inject similar quantities of fuel for the same injection setpoint. Furthermore, it is assumed that the piston rings are perfectly sealed and that no oil enters a combustion chamber.

[0033] On the other hand, when the engine ages, oil can enter one (or more) combustion chambers by suction. This can cause uncontrolled emission of gases and the combustion of oil produces engine torque not taken into account by the engine management system.

[0034] Such oil suction must therefore be diagnosed and it is advisable, if possible, to limit the combustion of oil in the engine as much as possible (and possibly also to determine which cylinder is the cause in order to be able to repair the defective segment(s)).

[0035] Following detection, or suspicion, of an oil leak in the engine, it is proposed here to confirm that oil combustion is taking place in the engine. Indeed, there could be an oil leak without the leaking oil being burned. Then, we can quantify the amount of oil that is burned in the engine and act according to the extent of oil suction towards one or more combustion chambers.

[0036] There are several methods for detecting an oil leak. Such a leak can be determined, for example, simply by monitoring the oil level in an oil pan of said engine. Generally, if the oil level drops, the missing oil is burned in the engine, but it is also possible that the missing oil seeps through a seal between the engine block and the exterior.

[0037] To confirm that oil is being burned in the engine, the idea is to monitor the engine's behavior when the engine's fuel supply is cut off. This is particularly the case when a vehicle driver removes his foot from an accelerator pedal of the vehicle. The latter then decelerates. However, if there is a suction of oil towards a combustion chamber, this oil will be burned, will produce a torque at the engine output and will therefore influence the engine's behavior, in particular its deceleration.

[0038] Figures 1 and 2 illustrate a step of confirming oil combustion in an engine, here a four-cylinder engine. [Fig.l] serves as a reference and shows the behavior of an engine without oil suction and [Fig.2] is similar to [Fig.l] for an engine in which there is oil suction towards a combustion chamber.

[0039] In [Fig.l], a curve of variation of rotation speed of the motor is illustrated. This rotation speed oscillates around a line whose slope corresponds to the average deceleration of the rotation speed of the motor.

[0040] Below the speed curve, bars have been illustrated whose height is proportional to the duration (in seconds -s- or milliseconds -ms-) of the time interval separating the passage of a piston of the engine through a predetermined point of an engine cycle. On the curve illustrating the variation in rotational speed of the engine, a double arrow has been used to mark an interval corresponding to two successive passages through a relative maximum speed, which corresponds to the passage through a bottom dead center after combustion. Other passage points can be chosen, such as, for example, a top dead center at the end of an air compression phase in the corresponding cylinder (then corresponding to the rotational speed minima).

[0041] The height of the sticks corresponds to the length of the double arrows. As the engine is decelerating, the size of the sticks increases.

[0042] To more easily compare the size of the sticks, it is advantageous to correct their size in order to take into account the average deceleration of the engine (vehicle). In [Fig.l], while it is a four-cylinder engine, five sticks are illustrated. The first and the last correspond to the same cylinder. The measurements made for the same cylinder can be compared because they are made under similar conditions (similar relative position of a sensor and a target used to know the angular position of the engine and its speed). So if for example the height of the first stick is X and that of the fifth stick (which corresponds to the same cylinder is X+4, and if the deceleration is constant, we should have for the second stick a height of X+1, for the third a height of X+2 and the fourth a height of X+3. By then subtracting respectively 1, 2, 3 and 4 from the height of the 2nd, 3rd, 4th and 5th sticks, we obtain a constant height of the sticks (X) as illustrated at the bottom of [Fig. 1].

[0043] If then, as illustrated in [Fig.2], the size of the sticks after correction is not the same, apart from measurement uncertainties, and a stick, for example, is distinguished by a reduced height, then we deduce that oil is burned in the corresponding cylinder since this means that the time elapsing between two successive top dead centers corresponding to a cylinder is reduced: we can assume that acceleration due to uncontrolled combustion is the cause of this difference in height.

[0044] Equivalently, instead of subtracting a value from the duration of a time interval, a corrective factor can be applied to each measurement of the time elapsing between two passages through successive top dead centers.

[0045] Let N be the number of cylinders.

[0046] Let n be the number of a time interval between two successive passages through top dead centers at the end of compression, n being 1, 2, ..., N.

[0047] Let T_Seg_Mes_n be the duration of the time interval n.

[0048] Let Rn be the factor to be applied to an interval duration to obtain a corrected interval duration T_Corr_Seg_Mes_n=Rn*T_Seg_Mes_n.

[0049] In an equivalent (and generalized) manner to what was presented above, we will have:

[0050] Rn=([( T_Seg_Mes_n - T_Seg_Mes_l) / T_Seg_Mes_l] - Dec_Corr

[0051] with Dec_Corr = [n / N] * [(T_Seg_Mes_(lN) - T_Seg_Mes_l) / T_Seg_Mes_l]

[0052] Here we consider that the measurement T_Seg_Mes_(lN) corresponds to the measurement made in the previous cycle for interval 1.

[0053] The number 1 can be arbitrarily assigned to an interval. It is noted that each interval can be associated with a cylinder. Indeed, if an oil combustion takes place in a cylinder, it will essentially influence the duration of the time interval starting when the piston of said cylinder is at top dead center at the end of compression.

[0054] To determine whether a corrected value (T_Corr_Seg_Mes_n) is lower than the other corrected values, we can, for example, compare this corrected value T_Corr_Seg_Mes_n to the average of all the corrected values ​​for n varying from 1 to N. If, for example, an interval duration T_Corr_Seg_Mes_n is less than 97%, or 95% or even 90%, of the average duration of the intervals measured on the corresponding cycle, then we will consider that the interval n is of reduced duration and corresponds to an oil combustion.

[0055] Instead of taking the average of N interval durations, we can compare T_Corr_Seg_Mes_n to the average of the (Nl) largest corrected values. If then T_Corr_Seg_Mes_n is less than, for example, 95% or even 90% of this other average value, we can consider that there has been oil combustion in the corresponding cylinder.

[0056] The results of this confirmation step are stored because they can be used to determine the amount of oil that has been burned.

[0057] [Fig.3] illustrates a step for determining the quantity of oil burned, or at least for qualifying it. The curve illustrated in [Fig.3] is stored in an electronic unit of the engine. For the engine in question, during its development, tests are carried out to observe the influence of injecting a known quantity of fuel into a cylinder. With a new engine, deceleration conditions are reproduced and a known quantity of fuel, for example Img, then 2mg, etc. is injected and burned in a cylinder. The behavior of the engine is then observed as explained above: the times spent at top dead centers at the end of compression are observed, the durations of time elapsed between two passages through top dead centers at the end of compression are corrected and the behavior in the cylinder concerned is observed. A GR gradient of the corrected duration is then observed, as illustrated in [Fig.2].From the tests carried out on a new engine, a curve like that of [Fig.3] is established and memorized. In this [Fig.3], the abscissa axis indicates a time gradient (as illustrated in [Fig.2]) while the ordinate axis gives a quantity of fuel. An equivalence between a quantity of fuel and a quantity of oil can be established. We can also quantify the oil burned in a cylinder not in grams of oil but in "grams equivalent fuel". There can be several curves such as that of [Fig.3] for example for different engine speeds.

[0058] From the measurements made to confirm that oil combustion has taken place, the corrected duration gradient GR observed is therefore determined as illustrated in [Fig.2]. This gradient GR value is then entered into the graph in [Fig.3] and gives a quantity of oil burned Q (or fuel equivalent). This quantity can be, for example, a quantity of oil per engine cycle.

[0059] Originally, the method according to the present disclosure comprises a step for eliminating, or at least limiting, the oil suction which has been quantified.

[0060] In [Fig.4], the step 100 of confirming an oil combustion in the engine has been illustrated as well as the following step described above and which is a step of determining 200 the quantity of oil consumed. To prevent oil from being burned in the combustion chamber, it is necessary to prevent oil from entering said combustion chamber. This happens when the pressure in the combustion chamber is lower than that in the crankcase containing the engine's lubricating oil. Thus, to limit the quantity of oil entering the combustion chambers, it is advisable to increase the pressure in said chambers when possible. It is noted that during deceleration, the arrival of air in the cylinders is limited. As a result, the air pressure is limited. Measurements made in the cylinders show that the pressure in a combustion chamber can drop to values ​​of the order of 800mbar (or 80kPa). It is then possible to act to increase this pressure. Several means exist here.The existing method on (almost) all engines is to open a butterfly valve which regulates the flow of air entering the engine. During deceleration, this butterfly valve is generally closed and the pressure in the cylinders is then minimal. By opening this valve, the air pressure in the cylinders during deceleration therefore increases.

[0061] There are also other ways to act on the pressure inside the combustion chambers (in the absence of combustion). In some engines, equipped with a turbocharger (or other compressor), the air introduced into the engine can be compressed before entering the combustion chambers. By acting on the turbocharger, the pressure in the combustion chambers can be increased. Another way is to act on an exhaust gas recycling valve (EGR valve). By then reinjecting air leaving the engine into its intake, it is possible to increase the air intake pressure and therefore the air pressure in the combustion chambers.

[0062] In [Fig.4], a control step 300 is thus provided to increase the air pressure in the combustion chambers. This control step 300 is thus, for example, a step for controlling the opening of the engine's butterfly valve. This control step 300 then induces an increase in the pressure in the cylinders. The consequence is then a variation 400 in the quantity of oil entering the cylinder with a sealing problem.

[0063] A loop regulation is proposed to verify that the measures taken (variation of the opening of the butterfly valve or other) are effective and a new confirmation step 100 of the quantity of oil consumed is carried out.

[0064] [Fig. 5] illustrates a flowchart summarizing one embodiment of a method according to the present disclosure. This method relates to the management of an internal combustion engine in particular when oil burns (involuntarily and in controlled) in one or more combustion chamber(s). When the internal combustion engine is new, fuel injectors are mounted in the engine and they all have substantially the same characteristics so that for the same injection setpoint, they all inject the same quantity of fuel. As the engine ages, (lubricating) oil may enter one (or more) combustion chamber(s) and be burned. This oil, when burned, will generate unexpected additional torque. The process in [Fig.5] aims to reduce the quantity of (sucked) oil entering a combustion chamber and any risk of engine damage when the phenomenon of oil suction (or uncontrolled oil combustion) is detected.

[0065] The method is thus implemented when an oil leak (or consumption) detection is detected during a detection step 500 integrated here in [Fig.5]. This detection can be done in various ways.

[0066] It is proposed further on (with reference to figures 6 and 7) to look at how the engine behaves from a stability point of view when it is new and then to periodically look at the behavior of the engine to compare it with an initial behavior, that is to say the behavior of the new engine.

[0067] Once oil consumption has been observed, it is proposed to check (or confirm) that the consumed oil is (totally or partially) burned in a combustion chamber of the engine. This confirmation step 100 is carried out when the engine is operating in a phase during which no fuel combustion is commanded. The calculations carried out during this step are based on the analysis of the time elapsing between two successive passages of the engine pistons through top dead centers at the end of compression (i.e. before potential combustion). These time measurements are carried out using a crankshaft sensor which cooperates in a manner known to those skilled in the art with a toothed target secured to the crankshaft, this system making it possible in particular to know the angular position of the engine and its rotational speed.During this stage, no fuel is injected into the cylinders and the only combustions are possibly the uncontrolled ones of oil. This measurement phase using the crankshaft sensor is for example carried out during a deceleration phase, when the driver of the vehicle removes his foot from the accelerator pedal. As explained above, the measured times are corrected by a correction factor (additive and / or multiplicative) to take into account the deceleration of the engine (vehicle). If there is no combustion, the corrected measured times are approximately equal. Otherwise, it is deduced from the measurements that there has been at least one uncontrolled combustion. A corrected measured time is then shorter than the others.

[0068] A quantification of the burnt oil is carried out during the determination step 200. As indicated, one corrected measured duration is shorter than the others. Depending on the difference (gradient) between the other corrected measurements and the shorter measurement, it is possible to estimate the quantity of oil burned from a map previously carried out on a new engine of the same type.

[0069] A control step 300 is sent to an engine component to increase the pressure of the air entering the cylinders. This command is intended for an air flow butterfly valve and / or a turbocharger valve and / or an exhaust gas recirculation valve.

[0070] A return to the confirmation step is then provided to check that the command for limiting the suction of oil into a combustion chamber has been effective.

[0071] An example of detection (step 500) is proposed here as announced above with reference to figures 6 and 7. It is a question of determining the behavior of the engine in terms of stability, or regularity, by observing whether over a complete cycle (two revolutions of the crankshaft), the passages to the top dead centers corresponding to a combustion (i.e. at the end of compression) occur at the expected instant or in advance or late. Thus, for example, for a four-cylinder in-line engine, the times between two successive passages of top dead centers are ideally constant.

[0072] The stability of the engine is then observed when the engine load is low and when it is high. This observation is made a first time when the engine is new and then serves as a basis for comparison. Then, periodically, an observation is made and if the behavior of the engine varies, an analysis is made to determine whether this variation comes from an aspiration of oil towards a combustion chamber.

[0073] [Fig.6] illustrates an observation of the operating stability of the engine and its analysis with a view to carrying out a diagnosis.

[0074] The operating stability of the engine is achieved at a determined operating point. In some observations, the operating point corresponds to a low load, for example when the requested torque is less than 20% of the maximum available torque, or less than 15% of this maximum torque or even less than 10% of this maximum torque. The low load operating point may, for example, also correspond to idling operation of the engine. In other observations, the operating point corresponds to a high load, for example when the requested torque is greater than 50% of the maximum available torque, or greater than 60% of this maximum torque or even greater than 70% of this maximum torque.

[0075] In the case considered here, corresponding to a four-cylinder in-line engine, a reference rotation time is measured, necessary for the crankshaft to perform a rotation of 180°CRK. In a manner known to those skilled in the art, this 180° rotation time, or reference time, can be measured by means of a toothed wheel, called also target, fixed to the crankshaft and having at least one angular reference mark. A position sensor associated with the toothed wheel (target) detects the passage of the angular reference mark(s) and of each tooth. At each passage, the position sensor emits an electrical signal and the reference time is determined using these electrical signals.

[0076] For a “stable” engine, the reference times in steady state remain constant over an engine cycle.

[0077] The diagram at the top left of [Fig. 1] corresponds to a torque setpoint TI over an operating range for two cycles (i.e. 1440°CRK = 2 * 720°CRK) and the torque requests are numbered from 0 to 3 and are substantially constant.

[0078] Fuel is injected into each cylinder according to the torque request TI. Since this request is constant, it is planned to inject the same quantity of fuel into each cylinder. Whether the engine is new or not, manufacturing tolerances (injectors or engine machining) or on the homogeneity of the fuel mean that the torque produced (Torque) is different from the set torque TI. The diagram at the top right of [Fig.l] illustrates the actual torque provided by each of the combustions in the engine. Note that in this example, this torque is not constant. The combustions numbered 1 to 3 provide a substantially similar torque but the torque provided by the combustion numbered 0 is lower than that corresponding to combustions 1 to 3.

[0079] The reference time is representative of the torque provided by the combustion which occurs over the corresponding angular range of rotation of the engine. Thus, if the torque provided during a combustion is higher then the corresponding reference time will be lower and vice versa. Thus, in the previous example corresponding to [Fig.l], the reference time corresponding to the combustion numbered 0 will be lower than the reference time for the other combustions 1 to 3. The diagram at the bottom right of [Fig.l] illustrates the reference times in relation to an average reference time corresponding to the rotation speed of the engine. If RPM is the rotation speed of the engine in revolutions per minute, the average reference time is then, in seconds, 30 / RPM, or 30ms for a rotation speed of 1000rpm.Thus, the reference time for combustion 0 is less than the average reference time corresponding to the engine rotation speed while the reference times for combustions 1 to 3 are greater than the average reference time.

[0080] As shown in the diagram at the bottom right of [Fig.l], there is variability between the measured reference times. In order to obtain a reference time corresponding to a rotation of 180°CRK that is substantially equal for each combustion / cylinder, a fuel injection reference corrective factor FC is determined for each cylinder so as to obtain a sum of the corrective factors equal to N, N being the number of cylinders in the engine considered. A regulation on the reference times allows the different correction factors to be determined iteratively. The diagram at the bottom left of [Fig.l] shows the correction factors for the cylinders (the x-axis corresponds to the value 1). For example, FCO for cylinder 0 corresponding to combustion 0 is 1.10; FC1 and FC3 for cylinders 1 and 3 corresponding to combustions 1 and 3 are 0.96, while FC2 for cylinder 2 corresponding to combustion 2 is 0.98. In this example, the reference correction factor brings all the reference times, in the case of equivalent combustion, to the same value for a 180° rotation of the crankshaft. The engine management system then regulates the quantity of fuel introduced into each cylinder so as to obtain equal reference times, to the nearest reference correction factor.The quantity of fuel introduced into each cylinder thus differs by a reference corrective factor FCn compared to the quantity of fuel which should have been introduced if the regulation had not been applied.

[0081] The detection here comprises a first step which is a learning step. The engine is new, or almost new, and the purpose of this step is to take stock to know the characteristics of the engine before any wear. Monitoring of the stability of the engine is carried out at least once when the engine is at low load and at least once when the engine is at high load. The engine load ChM is for example determined by comparing the torque required by the engine management system and the maximum torque that the engine can deliver. For example, the engine load is considered to be low if the required torque is less than 20% of the maximum available torque, or 15% of the maximum available torque or 10% of the maximum available torque. Preferably, the engine stability monitoring will be carried out when the engine is hot and the oil used for lubricating the engine is under nominal pressure.The ChM motor load will be considered high for example if the required torque is greater than 50% of the maximum available torque, or 60% of the maximum available torque or 75% of the maximum available torque.

[0082] The stability monitoring step consists, as explained above, in measuring the reference times when the conditions corresponding to a predetermined operating point (low load or high load) are reached and stabilized. From these reference time measurements for all the cylinders (combustions) over one or more cycles, a determination of corrective factors (one factor for each cylinder) is carried out as explained above with reference to [Fig. 6]. These corrective factors are then stored, for example in a memory of the engine management system.

[0083] This stability monitoring step can be for example “doubled” or “tripled” to confirm the results found. Filtering of the results can be carried out.

[0084] At the end of this learning step, a corrective factor has been stored for each cylinder for low load operation and a corrective factor for each cylinder for high load operation (i.e. 2N values ​​in memory).

[0085] A waiting step is then proposed. It is in fact planned to periodically monitor the stability of the operation of the engine. This period may correspond to a time (for example in days or months) or to a mileage. During the waiting step, as long as the value of the variable (time or mileage) is less than a predetermined value Thn, the system remains in waiting. When the value of the variable is reached, a second stability monitoring step (or nth step) is again conducted: reference times are measured, at low load and at high load, corrective factors are determined and stored. At the end of this second step (or nth step) new values ​​of corrective factors are stored.Of course, as for the learning step, these stored values ​​are preferably confirmed by at least one new monitoring of the stability of the engine for the same (or close) operating point.

[0086] Once a new set of corrective factor values ​​(with 2N values) is memorized, a determination step is initiated. This involves comparing the new corrective factors with the corrective factors obtained during the first learning step. It appears clear that if the corrective factors have not changed (or have changed only slightly), then everything is fine and no aspiration is detected.

[0087] A suction is detected here if a corrective factor corresponding to the monitoring of the stability at low load has decreased while the corrective factor corresponding to the same cylinder at high load has not (or only slightly) changed, then a suction is detected on the cylinder corresponding to the corrective factor which has varied. A threshold is predetermined here, for example 0.9 or 90%, concerning the corrective factor measured at low load. At high load, an interval is also predefined. For example, the corrective factor is considered to vary little if it only varies by less than 5%. We then have an interval ranging from 95% to 105%.Thus in this previous example, if for a cylinder the corrective factor obtained becomes less than 90% of the corrective factor stored at the end of the learning at low load for the same cylinder and at high load, for this cylinder, the new corrective factor is between 95% and 105% of the value of the corrective factor at high load stored at the end of the first learning step, then the management system considers that there is a suction in the corresponding cylinder. The method therefore makes it possible not only to detect an oil suction but also to obtain information concerning the cylinder in question (or the piston of which at least one of the segments is defective). It is also possible that the above method highlights that several cylinders are involved.

[0088] According to a detection variant, it is possible, for example, also to look at the variation at high load. It is assumed that for a given cylinder the corrective factor at high load goes from 1.00 to 0.98, i.e. a ratio between the corrective factor of the detection step and the corrective factor of the learning step of 0.98. It will then be estimated that there is oil suction in the cylinder considered if the ratio between the corrective factor of the detection step and the corrective factor of the learning step at low load is less than (0.98-y) with y, for example, predetermined depending in particular on the characteristics of the engine. As a non-limiting illustrative example, y is for example included in the interval [0.1; 0.2].

[0089] An alert step 600 ([Fig.5]) can then be triggered. A message is then, for example, displayed on a dashboard of the corresponding vehicle or a warning light comes on. The above method also makes it possible to indicate which cylinder (piston) is at fault. This information is not necessarily accessible at the vehicle dashboard but will be accessible to the car repairer responsible for repairing the engine and eliminating the leak. However, statistically, there is little chance that two segments of two separate pistons will wear in parallel and the oil leaks will occur (and be detected) one after the other.

[0090] If no aspiration is detected, then a new limit Thn+1 substituting the old limit THn is implemented and a return to the waiting step is made.

[0091] [Fig.7] summarizes the detection method described above in a diagram.

[0092] In [Fig.7], an abscissa axis corresponds to the engine load and an ordinate axis corresponds to a proportion between a corrective factor obtained at the learning stage and a corrective factor obtained subsequently.

[0093] A first window (TEST_1) illustrates the operating points for performing low-load stability monitoring while a second window (TEST_2) illustrates the operating points for performing high-load stability monitoring. Low-load monitoring is thus, for example, performed when the engine load is between 10 and 25% of the maximum engine load while high-load monitoring is, for example, performed when the engine load is between 50 and 80% of the maximum engine load.

[0094] If the ratio between the correction factor carried out subsequently and the corresponding correction factor carried out during the learning step, at low load and at high load, is made, and these ratios are contained between the two dotted lines, then no suction is detected. Everything is in order (OK). If these ratios are between the two dashed lines, then oil suction is detected (NO): a problem must be reported.

[0095] This method is implemented by an electronic unit on board a vehicle, for example a motor vehicle. This electronic unit can be called management unit or calculator and is also known by the English acronym CPU. As illustrated schematically in [Fig.8], we have a vehicle V powered by an engine M, said engine being electronically managed by at least one electronic unit CPU. Industrial application

[0096] The present technical solution can be applied in particular in engine control to limit uncontrolled engine emissions, due here to the combustion of lubricating oil.

[0097] The proposed method, and the corresponding means for implementing this method, also optionally make it possible to indicate at which cylinder(s) of the engine an oil suction has been detected. It is therefore possible to intervene in a targeted manner on the cause of the oil suction in order to put an end to it.

[0098] The present disclosure is not limited to the proposed embodiment examples and the variants mentioned described above, only as examples, but it encompasses all the variants that a person skilled in the art may envisage within the framework of the protection sought.

Claims

Claims

1. Method for limiting, in an internal combustion engine comprising a plurality of cylinders in each of which a piston slides, an oil suction following a finding of the presence of said oil suction, characterized in that it comprises the following steps: - step of confirming (100) the presence of a suction, carried out in the absence of fuel combustion with the following sub-steps: - - a) monitoring by measuring time interval durations (T_Seg_Mes_n) between two successive passages through top dead centers at the end of compression of the pistons in the cylinders, - - b) application of a corrective factor (Rn) of deceleration to be made to the measured interval duration, for each time interval, in order to take into account an average deceleration of the engine speed, - - c) comparison of the measured and corrected interval durations (T_Corr_Seg_Mes_n),and - - d) possible detection of one (or more) measured and corrected interval duration(s) less than the other measured and corrected interval durations and storage of the result of the detection, - step of determining (200) a quantity of oil burned in the engine if in the previous confirmation step (100) at least one measured and corrected interval duration (T_Corr_Seg_Mes_n) less than the others was detected with the following sub-steps: - - e) determination of a gradient (GR) representative of a variation in rotational speed of the engine, and - - f) from said gradient, estimation of the quantity of oil burned (Q) from a predetermined and stored map, - possible adaptation step (300) of the air pressure admitted into the cylinders, during which a variation of said pressure is controlled as a function of the determined quantity of oil burned previously.,

2. Method according to claim 1, characterized in that the corrective deceleration factor (Rn) to be applied to sub-step b) is determined as a function of the variation in the duration of a time interval from one cycle to another for a cylinder and the number of cylinders in the engine.

3. Method according to claim 1 or 2, characterized in that the gradient (GR) representative of a variation in rotation speed of the engine at the sub-step e) is a gradient of variation of the duration of the measured and corrected time interval of shorter duration compared to the other durations of measured and corrected time intervals.

4. Method according to one of claims 1 to 3, characterized in that the mapping of sub-step f) is carried out beforehand on an engine of the same type not experiencing oil suction in which, in the deceleration phase for which no combustion is planned, an injection and a combustion of known quantities of fuel per engine cycle are carried out at various engine speeds and the influence of this injection and this combustion on the gradient used in step e) is measured.

5. Method according to claim 1 to 4, characterized in that during the adaptation step (300), the variation of the air pressure admitted into the cylinders is controlled by acting on at least one of the following elements of the engine: - air intake butterfly and / or - turbocharger, and / or - exhaust gas recirculation valve.

6. Method according to one of claims 1 to 5, characterized in that it also comprises a prior step of detecting (500) oil combustion and a step of determining a cylinder in which said oil combustion takes place.

7. Method according to claim 6, characterized in that it comprises the following steps for detecting the presence of oil suction: - detection step carried out with the following sub-steps: - - i) first step of monitoring the operating stability of the engine on a first operating point at low load, - - ii) first step of determining a respective corrective factor to be applied, for each cylinder, in order to correct a quantity of fuel injected into said cylinder, with a view to regulating the engine speed on said first operating point, - - iii) first step of storing the respective corrective factors for each cylinder, corresponding to the first operating point, - - iv) second step of monitoring the operating stability of the engine on a second operating point at high load, - - v) second step of determining a respective corrective factor to be applied,for each cylinder, in order to correct a quantity of, fuel injected into said cylinder, with a view to regulating the engine speed on said second operating point, - - vi) second step of memorizing the respective corrective factors for each cylinder, corresponding to the second operating point, - step of determining an oil combustion in a given cylinder if, for said cylinder, the ratio between a first predetermined corrective factor and the corrective factor corresponding to the first operating point during the detection step is less than a predetermined threshold, while for the same cylinder the ratio between a second predetermined corrective factor and the corrective factor corresponding to the second operating point during the detection step is within a predetermined interval around 1.

8. Method according to one of claims 1 to 7, characterized in that it further comprises an alert step (600) when an oil suction is detected.

9. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement all the steps of a method according to one of claims 1 to 4.

10. a o. Computer configured for management of an internal combustion engine, characterized in that it comprises means for implementing each of the steps of a method according to one of claims 1 to 8.

11. Motor vehicle comprising an internal combustion engine, characterized in that it comprises a computer according to claim 10.

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