Method for detecting oil deposits in an internal combustion engine

Abstract

Procedure with: - first step 100: initialization. During a phase with the foot off the accelerator, the gear engagement times for each tooth are learned over four engine revolutions. The time required for the first two engine rotations and the time for the following two rotations is measured, and during these two rotations, all tooth engagement times are measured; - second step 200: determination of a rate of change in rotational speed; - third step 300: use of the rate of change in speed to correct each of the measured tooth engagement times; - fourth step 400 (optional): calculation of an average of the corrected tooth engagement times; - fifth step 500: analysis of the measurements taken and processing of the calculated corrected values; - final step 600: evaluation of the calculations performed to deduce an estimate of the presence of oil deposits. Figure 3

Description

Title of the invention: Method for detecting oil deposits in an internal combustion engine

[0001] This disclosure relates to a method for detecting oil deposits in an internal combustion engine. technical field

[0002] This disclosure falls within the field of the automotive industry and relates more specifically to internal combustion engines. Previous technique

[0003] Conventionally, in an internal combustion engine, pistons slide within cylinders and, via a connecting rod and crankshaft system, drive a flywheel in rotation. This rotation is then transmitted to the vehicle's wheels to propel it. Combustion takes place in combustion chambers. Each piston forms a partition between its corresponding combustion chamber and a crankcase in which the connecting rod and crankshaft system moves. Oil is present in the crankcase to lubricate the moving parts.

[0004] To determine the position of the pistons in the engine, it is common practice to use, on the one hand, a sensor associated with a target linked to the crankshaft, which is 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 intake and exhaust of gases in the combustion chambers. In a so-called four-stroke engine, a combustion cycle takes place over two crankshaft revolutions (720°), and a camshaft rotates at a speed corresponding to half the crankshaft's rotational speed. 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 if the combustion cycle is at the beginning 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 the engine position to be determined modulo 360°CRK and the camshaft sensor allows the engine position to be determined modulo 720°CRK.

[0005] The engine's rotational speed corresponds to the crankshaft's rotational speed. The target associated with this crankshaft is generally a toothed circular target, with similar teeth evenly spaced around its periphery. Often, a tooth is provided every 6° around the periphery of the target (theoretically 60 teeth), with two teeth missing to create a singularity at the periphery of the target and thus mark each crankshaft revolution. All of this is known to a person skilled in the art, who knows that a This target is associated with a sensor (most often inductive) that detects each time a tooth passes in front of it and then provides a signal allowing, on the one hand, the instantaneous position of the motor and, on the other hand, its rotational speed. The sensor also allows the measurement of the time (duration) that elapses between the passage of one tooth and the next.

[0006] The (toothed) target is in contact with the oil in the crankcase, and oil sometimes deposits on the teeth of the target. Several factors can cause such a deposit. When the engine is frequently idled, and the vehicle is often driven on short trips, the oil may not circulate properly and can deposit. The oil may also be contaminated with impurities, metallic or otherwise, and / or with moisture (or condensation). Various factors can degrade the quality of the oil, leading to a change in its viscosity and causing it to deposit, for example, on the crankshaft target.

[0007] For optimal engine health, it is essential to use good quality oil in good condition. On the one hand, good oil is necessary to ensure proper lubrication, and on the other hand, it has been observed that in some cases, even if lubrication is sufficient, oil analysis can reveal an engine malfunction.

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

[0009] This disclosure provides a method for detecting oil deposits on the crankshaft toothed target. This information alerts the vehicle driver that the engine oil needs to be changed. The method is automated and requires no intervention from the driver.

[0010] A method for detecting an oil deposit in an internal combustion engine is proposed, said engine comprising a crankshaft equipped with a toothed target, characterized in that it comprises the following steps: - a - initialization step comprising the following sub-steps: - al - detection of an operating phase during which no combustion takes place in the engine, - a2 - determination of an initial rate of change of engine rotational speed and measurement of an initial passage time for each tooth of the toothed target over 360°CRK (angle corresponding to one crankshaft rotation), preferably 720°CRK, - a3 - determination of a corrected initial passage time for each tooth of the toothed target taking into account the rate of change of engine rotational speed, and - a4 - storage in a non-volatile memory of the initial corrected tooth passage times, - b - measurement step comprising the following sub-steps: - bl - detection of an operating phase during which no combustion takes place in the engine, - b2 - determination of a current rate of change of motor rotation speed and measurement of a current passage time for each tooth of the toothed target over the same interval (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 change of rotational speed of the motor, - b4 - memorization of corrected current tooth passage times, - c - analysis step comprising the following sub-steps: - c1 - comparison of the corrected current transit time for each tooth with an average transit time and calculation of a relative rate of change between these two times, - c2 - calculation of a factor representing the relative rates of change of the step - c1 - for all teeth, - c3 - calculation of the factor of step - 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.

[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 oil deposit in the engine.

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

[0013] - at step - a2 - and at step - b2 -, a first time T_1 necessary for is measured The motor is used to perform a first rotation of 720°CRK, and then during a second rotation of 720°CRK immediately following the first rotation of 720°CRK, we measure, on the one hand, a second time T_2 required for the motor to perform the second rotation of 720°CRK and, on the other hand, the passage times for each tooth, and in this the rate of change of speed DECEL is calculated according to the formula: DECEL=(T_2-T_1) / T_1 ; In addition, we can predict here that the CDF correction rate for calculating the corrected transit time at steps - a3 - and - b3 - is: CDF=DECEL*n / N for teeth located in the interval [(nl)*720°CRK ; n*720°CRK[, with N an integer and n<=N;

[0014] - at step - cl -, the relative rate of change TVR of the corrected current passage time T_mes_corr and the average transit 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 factor of the step - c2 - is constituted by a sum of positive numbers, by 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 includes an alert step when an oil deposit is detected at step - c4

[0017] According to another aspect, a computer program is proposed that includes instructions for implementing all or part of a process as defined herein when this program is executed by a processor. According to another aspect, a non-transient, computer-readable recording medium is proposed on which such a program is recorded.

[0018] According to another aspect, an electronic computer is proposed for the management of an internal combustion engine, characterized in that it includes means for the implementation of each of the steps of a process as defined herein.

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

[0020] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying 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 [Fig.1] with an oil deposit. Fig. 3

[0023] [Fig.3] shows a flowchart corresponding to a process according to this disclosure. Fig. 4

[0024] [Fig.4] schematically shows a vehicle for the implementation of this disclosure. Description of the implementation methods

[0025] The following description refers to a thermal combustion engine M ([Fig. 4]) comprising N cylinders, in each of which a piston slides. Each piston is connected by a connecting rod to a crankshaft driven in rotation by the sliding motion of the pistons in their cylinders. The rotational motion is transmitted via a transmission to the wheels of a vehicle V ([Fig. 4]). To determine the position of the pistons in the cylinders and also the engine's rotational speed, it is known to attach a target to the crankshaft. Typically, for a motor vehicle engine, the target has teeth on its periphery, with one tooth every 6°, for a total of 60 teeth. To create a singularity and recognize the beginning of a new crankshaft revolution, it is customary to remove two teeth and leave a corresponding gap.A sensor, usually inductive, is mounted fixedly facing the target and detects the passage of each of the target's teeth. It provides a signal that allows the precise determination of the time interval between the passage of two teeth. As those skilled in the art know, such a sensor preferentially 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 coated with oil. Oil often contains metallic particles, which can be detected by the inductive sensor associated with the toothed target, potentially leading to erroneous measurements. The idea behind this disclosure is to observe whether the tooth fronts detected by the sensor are always distributed in the same way around the periphery of the target, or whether the position of the detected fronts varies over time. It is therefore proposed to observe the position of the fronts when the engine is new, to store these positions for the engine's lifetime, and, through regular measurements, to compare the position of the fronts with their original position. A corresponding method is described below.

[0027] As is apparent from the presentation of the method proposed here, it is necessary, as soon as possible when 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 perform a tracking operation on the entire periphery of the target under predetermined, minimally disturbed conditions, that is, when there is no combustion in the engine. This occurs, in particular, when the driver removes their foot from the accelerator and the torque demand from the engine is zero. Such a phase of engine operation is called "pedal up off" or is also known by the equivalent English name "pedal up off" or PUC. The measurements which The following procedures will be followed and carried out under these conditions. The first step is therefore the detection of a phase where the driver lifts their foot off the accelerator.

[0029] During a phase of driving with the foot off the accelerator and a gear engaged, the vehicle's speed generally decreases unless it is on a (steep) downhill slope. Its speed varies, and with it, the engine speed. To determine the distribution of the tooth fronts at the periphery of the target, this deceleration must then be taken into account.

[0030] For improved repeatability, each measurement should ideally begin on the same cutting edge according to a preferred (but optional) operating procedure. Subsequent measurements are all preferably taken from the same piston position within the engine. This corresponds to a specific angular position of the engine on 720°CRK, i.e., a predetermined position for each complete combustion cycle of the engine. Preferably, this position corresponds to the passage of a tooth cutting edge in front of the sensor. Even more preferably, this tooth cutting edge is not a singular edge, such as the last cutting edge before the tooth gap or the first cutting edge after this gap.

[0031] For the same reasons of precision and repeatability, it is also proposed to take each measurement over two crankshaft revolutions (720°CRK), i.e., over a complete combustion cycle. This way, the measurement takes into account all the specific phenomena that may occur. A measurement taken over 360°CRK can, however, be considered and also provides results. If the engine is not a four-cylinder engine, the same starting point should always be chosen for the 360°CRK measurements. A measurement over 720°CRK is recommended (even with a four-cylinder engine), and in the remainder of this description, only this alternative will be discussed (even though it is possible to take measurements only over 360°CRK).

[0032] Having specified this, an initialization step can be described. First, a lift-off phase is detected. The passage of a reference edge is then awaited at the "correct" crankshaft rotation (as mentioned in the preamble and well known to those skilled in the art, the position of a camshaft allows the engine position to be determined modulo 720°CRK). A time measurement begins. The aim here is to determine how long it takes the engine to complete two revolutions (or 720°CRK): let T_720_l be this reference time.

[0033] The measurement continues, but during the third and fourth rounds, not only is the overall time to complete these two rounds measured, i.e., T_720_2, but the passage times for each tooth, called T_6_i for the i-th tooth, are also recorded, i varying here from 1 to 120. For the part of the target without a tooth, the measured passage time is divided by three (for two missing teeth) and one Time is memorized as if the missing teeth were present.

[0034] Since the average motor speed varies (most often) during this input, in order to compare the transition times, the speed variation must be taken into account. It is proposed to calculate a first rate of speed variation: DECEL=(T_720_2-T_720_l) / T_720_l

[0035] This yields a rate of change in velocity that can be considered to be substantially constant and varying relatively little. At the beginning of the time measurement T_6_i, for small i, no correction is necessary (or very small), but for large i, in the example close to 120, a correction rate corresponding substantially to DECEL must be applied.

[0036] A correction rate can be adapted for each time T_6_i. For example, DECEL*(i / 120) would be used as the rate for T_6_i.

[0037] Another proposal is made here. Since the engine's rotational speed variations are linked to the compression / expansion phases in the cylinders, a correction factor is applied for each cylinder. As indicated above, N is the number of cylinders in the engine under consideration. A CDFn factor per cylinder is determined for n ranging from 1 to N. We will have: CDFn = DECEL *n / N

[0038] From this correction rate, a corrected time will be calculated for each measurement T_6_i using the formula: T_6_cor_i = T_6_i * CDFn for i varying from [(nl)*120 / N+l] to 120*n / N.

[0039] All these values ​​are then stored in non-volatile memory. This serves as the reference that can be used subsequently to compare transit times and analyze whether there are any significant changes, and if so, alert the vehicle driver. These stored transit times are initial transit times.

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

[0041] It may be planned to perform the measurement several times when the engine is new. It may be possible to verify that the measurements are consistent and, for example, record / store the average values ​​of several measurements taken on the engine considered to be still new.

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

[0043] The measurement is carried out in the same manner as described above. First, a foot-off phase is detected and a rate of change in speed is calculated by taking 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 transit 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] Measurements can be taken here over 720°CRK. If the engine is still in the off-peak phase, one (or more) new measurements can be taken and an average of the corrected running times is calculated.

[0047] If oil deposits form on the teeth of the target, they are not uniform when the oil quality has deteriorated. When the oil is new, a uniform oil film may be present. Therefore, it is proposed to compare the current passage time of a tooth with the current passage time of the preceding tooth. It is thus proposed to calculate the difference in the current passage time of a tooth relative to an average current passage time: Delta_i = T_6_mes_cor_i - (T_720_2 / 120) with T_720_2 corresponds to the time that was required to complete the 720°CRK during which the T_6_mes_i measurements were taken and 120 corresponds to the number of teeth taken into account during the measurement, including missing teeth (i.e., 2*60 teeth)

[0048] Delta_i still has one 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.: Fac_i = Delta_i / T_moy or even Fac_i = (T_6_mes_cor_i / T_moy) - 1

[0049] Since this factor can be negative or positive, it is important here to know its absolute value or to take its square. We then propose to calculate an overall deposition factor FDG_mes using the formula: FDG_mes = SUM [( Fac_i )EXP2] for i varying from 1 to 120 or written differently: FDG = V"Fac i2

[0050] The overall deposition factor is calculated in the same way using the T_6_i values ​​of the initial transit times which have been stored in non-volatile memory, i.e. FDG_ini, which should normally be close to 0.

[0051] If the value of FDG_mes deviates too much from FDG_ini, then it is assumed that the oil should be changed. A threshold Th_Vid can be defined here such that if: I FDG_mes - FDG_ini I > Th_Vid then an alert is sent to the driver.

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

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

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

[0055] A first step 100 corresponds to the initialization step. During a phase of motor operation with the foot off the accelerator, as early as possible, the initial tooth engagement times are learned. This learning takes place over at least four motor revolutions in a preferred embodiment. The time required to complete the first two motor rotations and the time for the following two rotations is measured, and during these last two rotations, all the initial tooth engagement times are measured.

[0056] A second step 200 corresponds to the determination of a rate of change of rotational speed of the motor, corresponding to the change in speed of the next two rotations relative to the first two rotations.

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

[0058] An optional fourth step 400 involves calculating an average of the corrected tooth passage times. If the foot lift phase is sufficiently long, several successive measurements can be taken and the average of the corrected values ​​calculated. found for each tooth. This applies to both the initialization step and the measurement steps.

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

[0060] A fifth step 500 involves analyzing the measurements taken and processing the calculated corrected values. Here, it is appropriate to illustrate, preferably with a dimensionless factor, the variations in transit times relative to an average transit time. This involves calculating the overall deposition factor proposed above, but another number, preferably dimensionless, may be used.

[0061] Finally, a last step 600 corresponds to the evaluation of the calculations performed in order to deduce an estimate of the presence of oil deposits in the engine and / or the condition of the oil in the engine. This step preferably also includes sending an alert message, for example, illuminating a warning light or displaying a message, in the vehicle's cockpit. It may also include determining the rate of oil deposition in the engine. Industrial application

[0062] The present disclosure makes it possible to monitor the quality of the oil of 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 degradation in the quality of the engine oil used for engine lubrication.

[0064] There are no means / methods in the prior art for detecting poor oil quality apart from an analysis (for example visual and / or tactile) of the oil by accessing it, for example by checking the oil level using an oil dipstick or at the oil filter.

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

[0066] The initialization step can also be used, firstly, to verify the proper functioning of the engine angular position determination system and, secondly, to check the condition / machining of the crankshaft target. Indeed, the factor calculated to estimate the extent of oil deposits should always be essentially the same for a new engine. In the example above, this factor should be essentially zero. A value that is too different from the theoretical value, corresponding, for example, to the detection of significant oil deposits, even for a new engine, constitutes a warning sign that can be used as a means of engine self-monitoring.

[0067] This disclosure is not limited to the form of embodiment, options and variants described above are only examples, but it encompasses all the variants that a person skilled in the art could consider within the framework of the protection sought.

Claims

Claims

1. Method 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 rotational speed of the engine and measurement of an initial passage time for each tooth of the toothed target over 360°CRK, preferably 720°CRK, - a3 - determination of a corrected initial passage time for each tooth of the toothed target taking into account the rate of variation of rotational speed of the engine, and - a4 - storage in a non-volatile memory of the corrected initial tooth passage times,- b - measurement step comprising the following sub-steps: - bl - detection of an operating phase during which no combustion is carried out in the engine, - b2 - determination of a current rate of variation of rotational speed of the engine and measurement of a current passage time for each tooth of the toothed target over the same interval (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 rotational speed of the engine, - b4 - storage of the corrected current tooth passage times, - c - analysis step comprising the following sub-steps: - cl - comparison of the corrected current passage time for each tooth with an average passage time and calculation of a relative rate of variation between these two times, - c2 - calculation of a factor representative of the relative rates of variation of the step - cl - for all the teeth,- c3 - calculation of the factor of step - 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 is measured and, on the other hand, the passage times for each tooth, 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 the teeth located in the interval [(nl)*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 - cl -, 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: T VR= 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 computer to implement all the steps of a method according to one of claims 1

9. d / . Electronic calculator intended for the management of a combustion engine internal, 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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