Method for detecting an oil deposit in an internal combustion engine

Abstract

The invention relates to a method which comprises: - a first initialization step 100, which involves, during a pedal up cut off phase, learning the passage times of each tooth over four engine revolutions. The time it takes for the first two rotations of the motor and the time for the two subsequent rotations are measured, and during the latter, all the tooth-passage times are measured; - a second step 200 of determining a rate of change of the rotational speed; - a third step 300 of using the rate of change of the speed in order to correct each of the measured tooth-passage times; - a fourth optional step 400 of calculating an average of the corrected tooth-passage times; - a fifth step 500 of analysing the measurements carried out and processing the calculated corrected values; and - a last step 600 of evaluating the calculations performed in order to deduce therefrom an estimation of the presence of oil deposits.

Description

Method for detecting oil deposits in an internal combustion engine Description

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

[0002] This disclosure relates to the automotive industry and relates more specifically to internal combustion engines. Prior art

[0003] Typically, in an internal combustion engine, pistons slide in cylinders and rotate a flywheel through 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 crankcase in which the connecting rod-crankshaft system moves. Oil is present in the crankcase to lubricate the moving parts.

[0004] To know the position of the pistons in the engine, it is usual to use, on the one hand, a sensor associated with a target linked to the crankshaft driven in rotation by the pistons via connecting rods, and, on the other hand, a sensor associated with a target linked to a camshaft, the latter controlling the inlets and outlets of gases in the combustion chambers. In a so-called four-stroke engine, a combustion cycle takes place over two revolutions (720°) of the crankshaft and a camshaft rotates at a rotation speed corresponding to half the rotation speed of the crankshaft. The target linked to the crankshaft allows, with the corresponding sensor, to know precisely the position of the crankshaft over one revolution (or 360° also called 360°CRK) while the target linked to a camshaft allows, with the corresponding sensor, to determine whether the combustion cycle is at the start of the cycle (between 0 and 360°CRK) or at the end of the cycle (between 360 and 720°CRK).In summary, the crankshaft sensor allows you to know the position of the engine modulo 360°CRK and the camshaft sensor allows you to know the position of the engine modulo 720°CRK.

[0005] The engine rotation speed corresponds to the crankshaft rotation speed. The target linked to this crankshaft is generally a circular toothed target, with similar teeth equally distributed around the periphery of the target. Often, one tooth is provided every 6° around the periphery of the target (i.e. theoretically 60 teeth) with however two missing teeth to create a singularity around the periphery of the target and thus identify each crankshaft revolution. All this is known to the person skilled in the art who knows that such a target is associated with a sensor (most often inductive) which detects each passage of a tooth in front of it and which then provides a signal making it possible, on the one hand, to know the instantaneous position of the engine and, on the other hand, its rotation speed. The sensor also allows you to know the time (duration) that elapses between the passage of one tooth and the next tooth.

[0006] The (toothed) target is in contact with the oil in the crankcase and it can deposit on (the teeth of) the target. Several causes can cause such a deposit. When the engine is often idling, and the vehicle often makes short journeys, then the oil risks circulating poorly and depositing. The oil can also be contaminated with impurities, metallic or not, and / or with humidity (or condensation water). Various causes can degrade the quality of the oil, causing a variation in its viscosity and causing it to deposit, for example on the crankshaft target.

[0007] For good engine health, it is important to have good quality oil in good condition. On the one hand, it is necessary to have good oil to ensure good lubrication, and on the other hand, it has been found that in some cases, even if the lubrication is sufficient, an oil analysis can reveal an engine operating problem.

[0008] Currently, to determine the quality of the oil, it is necessary to analyze it and therefore to access it. Access is generally via an opening provided for an oil dipstick or via a drain plug. Summary

[0009] The present disclosure provides a method for detecting an oil deposit on the toothed target of the crankshaft. This information makes it possible to inform the driver of the vehicle that the engine oil needs to be changed. The method is an automated process that does not require any intervention from the driver.

[0010] A method is proposed for detecting an oil deposit in an internal combustion engine, said engine comprising a crankshaft provided with a toothed target, characterized in that it comprises the following steps: - a - initialization step comprising the following sub-steps: - a1 - detection of an operating phase during which no combustion is carried out in the engine, - a2 - determination of an initial rate of variation of rotation speed of the engine and measurement of an initial time of passage for each tooth of the toothed target over 360°CRK (angle corresponding to the rotation of one crankshaft revolution), or 720°CRK, - a3 - determination of an initial corrected passage time for each tooth of the toothed target taking into account the rate of variation of the rotation speed of the motor, and - a4 - storage in a non-volatile memory of the initial corrected tooth passage times, - b - measurement step comprising the following sub-steps: - b1 - detection of an operating phase during which no combustion is carried out in the engine, - b2 - determination of a current rate of variation of rotation speed of the motor and measurement of a current passage time for each tooth of the toothed target over the same interval (360°CRK or 720°CRK) (in other words an interval of the same width as the 360°CRK or 720°CRK interval of step -a2-) - b3 - determination of a corrected current passage time for each tooth of the toothed target taking into account the current rate of variation of rotation speed of the motor, - b4 - memorization of current corrected tooth passage times, - c - analysis step comprising the following sub-steps: - c1 - for each tooth, comparison of the corrected current passage time with an average passage time, and calculation of a relative variation rate between these two times, - c2 - calculation of a factor representative of the relative variation rates of step - c1 - for all the teeth (in other words a factor representative of the relative variation rates of step - c1 -, associated with each of the teeth of the toothed target), - c3 - calculation of the factor of step - c2 - with the corrected initial passage times stored in step - a4 - (in other words a factor corresponding to the factor of step -c2-, by replacing each current corrected passage time with the corresponding corrected initial passage time and as stored in step -a4-), and - c4 - detection of an oil deposit if the factor calculated in step - c3 - differs from the factor calculated in step - c2 - beyond a predetermined value.

[0011] This process thus makes it possible, using only means present in almost all combustion engines of motor vehicles, to control the quality of the engine oil and / or to detect an abnormal deposit of oil in the engine.

[0012] The features set out in the following paragraphs may, optionally, be implemented, independently of each other or in combination with each other:

[0013] - in step - a2 - and in step - b2 -, a first time T_1 necessary for the motor to perform a first rotation of 720°CRK is measured, then during a second rotation of 720°CRK immediately following the first rotation of 720°CRK, a second time T_2 necessary for the motor to perform the second rotation of 720°CRK and, on the other hand, the passage times for each tooth are measured, and in that the rate of variation of speed DECEL is calculated according to the formula: DECEL=(T_2-T_1) / T_1; in addition, it can be provided here that the correction rate CDF for calculating the corrected passage time in steps - a3 - and - b3 - is: CDF=DECEL*n / N for the teeth located in the interval [(n-1)*720°CRK; n*720°CRK[, with N integer and n<=N ;

[0014] - at step - c1 -, the relative rate of variation TVR of the corrected current passage time T_mes_corr and of the average passage time T_moy is given by the formula: TVR= 1 -(T_mes_corr / T_moy), with T_moy corresponding to the sum of the current passage times (step - b2 -) divided by the number of current times measured over the measurement interval;

[0015] - the step factor - c2 - consists of a sum of positive numbers, for example a sum of absolute values ​​of relative rates of change or a sum of squares of relative rates of change;

[0016] - the method further comprises an alert step when an oil deposit is detected in step - c4

[0017] According to another aspect, there is provided a computer program comprising instructions for implementing all or part of a method as defined herein when such program is executed by a processor. According to another aspect, there is provided a non-transitory, computer-readable recording medium on which such a program is recorded.

[0018] According to another aspect, an electronic calculator is proposed for the management of an internal combustion engine, characterized in that it comprises means for implementing each of the steps of a method as defined herein.

[0019] According to another aspect, there is provided a motor vehicle comprising an internal combustion engine with a crankshaft and a toothed target secured to said crankshaft, characterized in that it comprises an electronic computer as defined above. Brief description of the drawings

[0020] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: Fig. 1

[0021] [Fig. 1] schematically shows two teeth of a crankshaft target in a new engine. Fig. 2

[0022] [Fig. 2] schematically shows the two teeth of Figure 1 with an oil deposit. Fig. 3

[0023] [Fig. 3] shows a flowchart corresponding to a method according to the present disclosure. Fig. 4

[0024] [Fig. 4] schematically shows a vehicle for implementing the present disclosure. Description of the embodiments

[0025] The following description is given with reference to a thermal combustion engine M (figure 4) comprising N cylinders in each of which slides a piston. Each piston is connected by a connecting rod to a crankshaft driven in rotation by the sliding movement of the pistons. in their cylinders. The rotational movement is transmitted via a transmission to the wheels of a vehicle V (figure 4). To determine the position of the pistons in the cylinders and also the engine rotation speed, it is known to make a target integral with the crankshaft. Conventionally for a motor vehicle engine, the target has teeth on its periphery, providing one tooth every 6°, for a total of 60 teeth. To create a singularity and recognize the start of a new crankshaft revolution, it is usual to remove two teeth and leave a corresponding free space. A sensor, generally inductive, is mounted fixedly opposite the target and detects the passage of each of the target's teeth. It provides a signal that makes it possible to precisely determine the time interval between the passage of two teeth.As is known to those skilled in the art, such a sensor preferably detects either the rising edges of a tooth or the falling edges.

[0026] Figure 1 schematically represents two teeth D of a target in a new engine while Figure 2 represents the same teeth D after use and covered with oil. The oil often contains metal particles and these can be detected by the inductive sensor associated with the toothed target and there is then a risk of making an erroneous measurement. The idea behind the present disclosure is to observe whether the tooth fronts detected by the sensor are always distributed in the same way at the periphery of the target or whether over time the position of the detected fronts varies. It is then proposed to look at the position of the fronts when the engine is new, to memorize these positions for the lifetime of the engine and, by regular measurements, to compare the position of the fronts with their original position. A corresponding method is described below.

[0027] As is clear from the presentation of the method proposed here, it is advisable as soon as possible after starting the engine to look at and memorize the position of the tooth fronts detected by the sensor associated with the crankshaft target.

[0028] It is proposed to carry out a survey over the entire periphery of the target under predetermined conditions, with the least disturbance possible, that is to say when there is no combustion in the engine. This happens in particular when the driver takes his foot off the accelerator and the torque demand to be provided by the engine is zero. Such an engine operating phase is called "foot up" or is also known by the equivalent English name "pedal up cut off" or PUC. The measurements that will be made in the following method will be made under these conditions. A first step is therefore first of all the detection of a foot-up phase in the driving of the vehicle.

[0029] During a phase of driving with the foot off the pedal, in gear, the vehicle generally sees its speed decrease unless it is on a (steep) downward slope. Its speed varies and with it the engine speed. To know the distribution of the tooth fronts at the periphery of the target, it will then be necessary to take this deceleration into account.

[0030] For better repeatability, it is also advisable to start each measurement on the same front according to a preferred (but optional) operating mode. Subsequent measurements are preferably all taken from the same piston position in the engine. This corresponds to a given angular position of the engine over 720°CRK, i.e. a predetermined position for each complete combustion cycle of the engine. Preferably, this position corresponds to a passage of a tooth front in front of the sensor. More preferably, this tooth front is not a singular front such as for example the last front before the tooth free space or the first front after this space.

[0031] For the same sake of precision and repeatability, it is also proposed to make each measurement over two crankshaft revolutions (720°CRK), i.e. over a complete combustion cycle. Thus, the measurement takes into account all the particular phenomena likely to occur. A measurement carried out over 360°CRK can however be considered and also gives results. If the engine is not a four-cylinder engine, it is advisable to always choose the same starting point for making the measurements over 360°CRK. A measurement over 720°CRK is recommended (even with a four-cylinder engine) and in the rest of the description, only this alternative will be mentioned (even if it is possible to make measurements only over 360°CRK).

[0032] This being specified, an initialization step can be described. First, a foot-lift phase is detected. We then wait for the passage of a reference front in the "right" rotation of the crankshaft (as mentioned in the preamble and perfectly known to those skilled in the art, the position of a camshaft makes it possible to know the position of the engine modulo 720°CRK). A time measurement begins. The aim here is to determine how long it takes the engine to make two revolutions (or 720°CRK): let T_720_1 be this reference time.

[0033] The measurement continues but during the third and fourth turns, we not only measure the overall time to complete these two turns, for example T_720_2, but we also record the passage times for each tooth called T_6_i for the i èmetooth, i varying here from 1 to 120. For the part of the target not presenting a tooth, the measured passage time is divided by three (for two absent teeth) and a time is stored as if the absent teeth were present.

[0034] As the average rotation speed of the engine varies (most often) during this capture, in order to be able to compare the passage times with each other, the speed variation must be taken into account. It is proposed to calculate a first speed variation rate: DECEL=(T_720_2-T_720_1) / T_720_1

[0035] We thus obtain a rate of variation of speed which can be considered as being substantially constant and varying relatively little. At the start of the measurement of times T_6_i, for small i, there is no correction to be made (or very small) but for large i, in the example close to 120, a correction rate corresponding substantially to DECEL will have to be applied.

[0036] We can plan to adapt a correction rate for each time T_6_i. For example, we would take DECEL*(i / 120) as the rate for T_6_i.

[0037] Another proposal is made here. Since the engine speed variations are related to the compression / expansion phases in the cylinders, a correction ratio is applied for each cylinder. As indicated above, N is the number of cylinders in the engine considered. A CDFn rate per cylinder is determined for n varying from 1 to N. We will have: CDFn = DECEL *n / N

[0038] From this correction rate, we will calculate a corrected time for each measurement T_6_i with the formula: T_6_cor_i = T_6_i * CDFn for i varying from [(n-1)*120 / N+1] to 120*n / N.

[0039] All these values ​​are then stored in a non-volatile memory. This is the reference that can be used later to compare the passage times and analyze whether there are any significant changes and, if necessary, alert the vehicle driver. These stored passage times are initial passage times (or initial times).

[0040] This first measurement is taken as soon as possible after starting the engine in the vehicle. It is preferably carried out within the first few kilometers of driving, or the first few dozen kilometers of driving.

[0041] It may be planned to carry out the measurement several times when the engine is new. It is possible to check that the measurements are consistent and to record / memorize, for example, the average values ​​of several measurements carried out on the engine considered to be still new.

[0042] Subsequently, once the initial value(s) have been memorized, new measurements are taken in the same way. These measurements can be taken at each off-peak phase, gear engaged, every 100 km when a off-peak phase occurs, etc.

[0043] The measurement is done in the same way as described above. First, a foot-lift phase is detected and a speed variation rate is calculated by making a first measurement T_720_1 over two revolutions, then a second measurement T_720_2 over the following two revolutions to finally calculate the DECEL rate.

[0044] During the second measurement, the current passage times T_6_mes_i corresponding to each tooth of the target are determined. Each time is corrected in the same way as the correction was made for the initial reference times. The corrected current times are thus determined: T_6_mes_cor_i = T_6_mes_i * CDFn

[0045] The corrected current times thus determined (T_6_mes_cor_i) are also stored for analysis.

[0046] Here, measurements can be taken at 720°CRK. If the engine is still in the off-load phase, one (or more) new measurements can be taken and an average of the corrected current times is taken.

[0047] If an oil deposit occurs on the target teeth, it is not regular when the oil quality has deteriorated. When the oil is new, a regular oil film may be present. Thus, it is proposed to compare the current passage time of a tooth with the current passage time of the previous tooth. It is therefore proposed to calculate a time difference of current passage of a tooth compared to an average current passage time: DeltaJ = T_6_mes_cor_i - (T_720_2 / 120) with T_720_2 corresponding to the time that was necessary to make the 720°CRK during which the measurements T_6_mes_i were made and 120 corresponds to the number of teeth taken into account during the measurement, including missing teeth (i.e. 2*60 teeth)

[0048] DeltaJ still has a dimension (it is a time). To obtain a representative, dimensionless and therefore comparable factor, it is proposed to divide it by the average current passage time of a tooth (T_moy = T_720_2 / 120), i.e.: FacJ = DeltaJ / T_moy or FacJ = (T_6_mes_corJ / T_moy) - 1

[0049] Since this factor can be negative or positive, it is important to know its absolute value or to take its square. We then propose to calculate a global deposition factor FDG_mes with the formula: FDG_mes = SUM [(FacJ)EXP2] for i varying from 1 to 120 or written differently:

[0050] The overall deposition factor is calculated in the same way using the T_6J values ​​of the initial passage times which have been stored in the non-volatile memory, i.e. FDGJni, which should normally be close to 0.

[0051] If the value of FDG_mes diverges too much from FDGJni, then it is estimated that the oil must be drained. Here we can define a threshold Th_Vid such that if: | FDG_mes - FDGJni | > Th_Vid then an alert is sent to the driver.

[0052] Of course, this alert can only be sent if the measurement of the overall deposition factor is above the threshold during two (or more) measurements carried out to avoid false alerts.

[0053] In the method according to the present disclosure, the values ​​of the overall deposition factor can be memorized and the evolution of this factor recorded. Thus, the FDG_mes factors can also be recorded in a non-volatile memory. Normally, this factor should increase when the condition of the engine oil decreases. The evolution of this factor can provide an index called "oil deposition rate". This rate can be an index. Indeed, if this rate is high, it can be assumed that the deterioration in the quality of the oil is abnormal and an action other than a simple oil change is a priori to be carried out.

[0054] Figure 3 is a flowchart summarizing the process described above. An electronic unit (CPU in Figure 4) is programmed to implement this flowchart.

[0055] A first step 100 corresponds to the initialization step. During a phase of off-load operation of the motor, as early as possible, learning of the initial passage times for each tooth is carried out. This learning is done over at least four engine revolutions in a preferred embodiment. The time required to make the first two rotations of the motor and that for the two following rotations are measured and during these last two, all the initial tooth passage times are measured.

[0056] A second step 200 corresponds to the determination of a rate of variation of rotation speed of the motor, corresponding to the variation of speed of the two following rotations relative to the first two rotations.

[0057] A step 300 then corresponds to the use of the speed variation rate to correct each of the measured tooth passage times.

[0058] A fourth optional step 400 corresponds to the calculation of an average of the corrected tooth passage times. If the foot lifting phase is long enough, several successive measurements can then be carried out and an average of the corrected values ​​found for each tooth can be calculated. This applies to both the initialization step and the measurement steps.

[0059] An arrow points from step 400 to step 200 to indicate that measurements can be continued as long as the foot-lift operation phase continues.

[0060] A fifth step 500 corresponds to the analysis of the measurements carried out and the processing of the calculated corrected values. Here it is appropriate to illustrate, preferably by a dimensionless factor, the variations in the passage times compared to an average passage time. This is the calculation of the overall deposition factor proposed above but another number, preferably dimensionless, can be used here.

[0061] Finally, a final step 600 corresponds to the evaluation of the calculations carried out to deduce an estimate of the presence of oil deposits in the engine and / or the state of the oil in the engine. This step preferably also includes the sending of an alert message, for example the lighting of a warning light or the printing of a message, in the cockpit of the vehicle. It may also include a determination of an oil deposit rate in the engine. Industrial application

[0062] The present disclosure makes it possible to monitor the quality of the oil in an internal combustion engine in an original and completely new way.

[0063] Many situations can cause oil deposits in the engine and these deposits often reflect a deterioration in the quality of the engine oil used for engine lubrication.

[0064] There are no means / methods in the state of the art for detecting poor oil quality other than an analysis (e.g. visual and / or tactile) of the oil by accessing this, for example by checking the oil level using an oil dipstick or at the oil filter level.

[0065] The method proposed here allows for automatic analysis and provides an alert to the driver when the oil needs to be changed. Abnormal detection of the presence of metal shavings can also be performed.

[0066] The initialization step can also allow, on the one hand, to check the correct operation of the system for determining the angular position of the engine and, on the other hand, to check the condition / machining of the crankshaft target. Indeed, the factor calculated to estimate the importance of the oil deposit should always be substantially the same for a new engine. In the example above, this factor should be substantially zero. A value too different from the theoretical value, corresponding for example to a detection of significant oil deposit, already for the new engine constitutes a warning sign which can be used as a means of control (self-control) of the engine.

[0067] This disclosure is not limited to the embodiment, options and variations described above, only as examples, but it encompasses all variations that may be envisaged by those skilled in the art within the framework of the protection sought.

Claims

Claims

1. Method for detecting an oil deposit on a toothed target of a crankshaft in an internal combustion engine, said engine comprising said crankshaft provided with said toothed target, characterized in that it comprises the following steps: - a - initialization step comprising the following sub-steps: - a1 - detection of an operating phase during which no combustion is carried out in the engine, - a2 - determination of an initial rate of variation of rotation speed of the motor and measurement of an initial passage time for each tooth of the toothed target over 360°CRK or 720°CRK, - a3 - determination of an initial corrected passage time for each tooth of the toothed target taking into account the rate of variation of the rotation speed of the motor, and - a4 - storage in a non-volatile memory of the initial corrected tooth passage times, - b - measurement step comprising the following sub-steps: - b1 - detection of an operating phase during which no combustion is carried out in the engine, - b2 - determination of a current rate of variation of rotation speed of the motor and measurement of a current time of passage for each tooth of the toothed target over the same interval of 360°CRK or 720°CRK, - b3 - determination of a corrected current passage time for each tooth of the toothed target taking into account the current rate of variation of rotation speed of the motor, - b4 - memorization of current corrected tooth passage times, - c - analysis step comprising the following sub-steps: - c1 - comparison of the current corrected passage time for each tooth with an average passage time and calculation of a relative variation rate between these two times, - c2 - calculation of a factor representing the relative variation rates of the step - c1 - for all teeth, - c3 - calculation of the step factor - c2 - with the corrected initial passage times stored in step - a4 -, and - c4 - detection of an oil deposit if the factor calculated in step - c3 - differs from the factor calculated in step - c2 - beyond a predetermined value.

2. Method according to claim 1, characterized in that in step - a2 - and in step - b2 -, a first time T_1 necessary for the motor to perform a first rotation of 720°CRK is measured, then during a second rotation of 720°CRK immediately following the first rotation of 720°CRK, a second time T_2 necessary for the motor to perform the second rotation of 720°CRK and, on the other hand, the passage times for each tooth are measured, and in that the rate of variation of speed DECEL is calculated according to the formula: DECEL=(T_2-T_1) / T_1.

3. Method according to claim 2, characterized in that the correction rate CDF for calculating the corrected passage time in steps - a3 - and - b3 - is: CDF=DECEL*n / N for teeth located in the interval [(n-1)*720°CRK; n*720°CRK[, with N integer and n<=N.

4. Method according to one of claims 1 to 3, characterized in that in step - c1 -, the relative rate of variation TVR of the corrected current passage time T_mes_corr and of the average passage time T_moy is given by the formula: TVR= 1 -(T_mes_corr / T_moy), with T_moy corresponding to the sum of the current passage times (step - b2 -) divided by the number of current times measured over the measurement interval.

5. Method according to one of claims 1 to 4, characterized in that the factor of step - c2 - consists of a sum of positive numbers, for example a sum of absolute values ​​of relative rates of variation or a sum of squares of relative rates of variation.

6. Method according to one of claims 1 to 5, characterized in that it further comprises an alert step when an oil deposit is detected in step - c4 -.

7. Method according to one of claims 1 to 6, characterized in that each measurement begins upon passage of a reference tooth front corresponding to a predetermined position modulo 720° of the motor.

8. A computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement all the steps of a method according to one of claims 1 to 7.

9. Electronic computer intended for the 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 7.

10. Motor vehicle comprising an internal combustion engine with a crankshaft and a toothed target secured to said crankshaft, characterized in that it comprises an electronic computer according to claim 9.

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