METHOD FOR BALANCED FUEL MASS IN A LUBRICANT OF AN INTERNAL ENGINE, INTERNAL ENGINE AND MOTOR VEHICLE

Description

[0001] The following invention relates to a method for balancing the fuel mass in a lubricant of an internal combustion engine during operation of the internal combustion engine. The invention further relates to a control unit designed and configured to carry out such a method, as well as an internal combustion engine and a vehicle in which the method according to the invention is carried out using a suitable control unit.

[0002] To ensure the service life of modern engines for a minimum period, a reliable supply of lubricant to the components requiring lubrication is crucial. This is achieved using lubricating oils whose properties are optimized with additives, for example, regarding oxidation stability, corrosion protection, scuffing resistance, or viscosity-temperature behavior. Particular attention should be paid to system properties such as friction and wear.

[0003] However, during the operation of an internal combustion engine, the lubricating properties of the engine oil can change due to fuel dilution. In the worst-case scenario, the properties of the engine oil or lubricant can change so drastically that proper lubrication is no longer possible, leading to irreversible damage to the internal combustion engine and thus premature failure of engine components.

[0004] Fuel dilution of engine oil reduces its viscosity. This reduces the thickness of the lubricating film in the bearings and increases bearing wear due to mixed friction. Even a fuel content of just 4% reduces the viscosity of the engine oil by one SAE grade. This SAE (Society of Automotive Engineers) classification is used to indicate the viscosity of engine oils. It specifies the temperature ranges in which the oils are used. Lower numbers indicate thinner oils (lower viscosity), while higher numbers indicate thicker oils (higher viscosity). This fuel dilution can be reversed by the evaporation of the fuel when the lubricant is at operating temperature. This restores the original viscosity.

[0005] However, fuel vaporizing from the engine oil, which is drawn into the intake manifold (fresh air supply) of the combustion engine via the crankcase ventilation system, can potentially lead to an undesirable enrichment of the air-fuel mixture. The risk of this enrichment increases with the slope of the fuel's boiling point. Blended fuels such as E25 can evaporate almost instantaneously within a narrow oil temperature range, thus causing a significant enrichment of the air-fuel mixture.

[0006] Fuel enriched in the lubricant or engine oil increases the amount of fluid in the lubrication circuit, in addition to reducing its viscosity. This can lead to inaccurate readings in wet sump lubrication systems, potentially triggering the engine oil supply system's overfill warning. The increased fluid volume (mass) also results in additional churning losses, which increase the combustion engine's power loss if the engine oil level exceeds a critical threshold.

[0007] FR 2 866 957 A1 discloses a method for determining the lubricating oil dilution rate of a motor vehicle's heat engine. The lubricating oil dilution rate is determined using a dilution module and an evaporation module. The dilution module is used to determine the degree of oil dilution by the fuel based on an oil dilution map. The oil dilution map depends on the engine speed, fuel flow rate, and engine operating mode. The evaporation module is used to determine the evaporation of the lubricating oil based on an oil evaporation map. The oil evaporation map depends on the engine speed, fuel flow rate, engine operating mode, and oil temperature.

[0008] There are approaches that use a model to take into account fuel input and output from the lubricant, i.e., the engine oil. While determining a dilution value, as known, for example, from DE 10 2014 013 709 A1, allows for an assessment of the lubricant's condition, i.e., its quality, it fails to consider changes in the lubricant mass caused by engine oil input and output.

[0009] The task, therefore, is to provide an improved method suitable for calculating the mass of fuel in a lubricant.

[0010] This problem is solved by the inventive method according to claim 1, a control unit according to claim 9 and an internal combustion engine according to claim 10.

[0011] Further advantageous embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments of the present invention.

[0012] The inventive method for balancing a fuel mass in a lubricant of an internal combustion engine during operation of the internal combustion engine is characterized by the following steps: Starting an operating cycle of the internal combustion engine, detecting an operating mode, determining an engine oil mass, continuously determining a fuel differential mass in the engine oil mass, continuously determining a fuel sum from a starting value of the fuel sum and from the fuel differential mass, determining a normalized fuel equivalent from the fuel differential mass.

[0013] The process runs during the operation of the combustion engine and is initiated by starting an operating cycle. In the "Detect Operating Mode" step, a specific operating mode of the combustion engine is recorded and can be evaluated and classified according to certain criteria. This allows for the definition of a manageable number of operating modes, in which, for example, different fuel input and output patterns occur. Operating modes can be defined, for instance, in which the change in the fuel mass in a lubricant can be determined using appropriately adapted models. Different operating modes could include, for example, cold starts, particulate filter regeneration, and various combinations of engine load, speed, and / or temperature conditions in conjunction with different ambient or environmental conditions.The classification of typical operating modes makes it possible to map the entire operating range of an internal combustion engine to a limited number of typical and relevant operating modes, for which a so-called fuel differential mass can then be determined during operation (see below).

[0014] Determining the initial engine oil mass is the starting point of the procedure. This mass can be determined using, for example, an oil level signal or, if applicable, a recorded amount of oil added. A status signal indicating the oil level can also be considered. This status signal reflects the accuracy of the oil level measurement. For instance, if an average oil level reading is calculated during driving, the measurement accuracy improves once the minimum distance required for averaging has been covered.

[0015] Starting with this engine oil mass, a fuel differential mass within the engine oil mass is continuously determined. Depending on the relevant operating mode, which can change even within an operating cycle during the process, fuel input into or output from the engine oil is taken into account. This corresponds to a positive or negative fuel differential mass, respectively.

[0016] Starting with an initial fuel mass value (in the lubricant), the total fuel mass is continuously determined during the operating cycle, taking into account a cumulative fuel mass difference. From this total fuel mass, a normalized fuel equivalent is then calculated, which can be part of an algorithm used to determine an oil change interval or oil change time.

[0017] The method according to the invention thus makes it possible to determine the fuel differential mass in the engine oil mass on the basis of comparatively simple models and to provide a quantity in the form of a standardized fuel equivalent, which significantly improves the determination of an oil change time or the calculation of an oil change interval.

[0018] In a further development of the method, fuel input or fuel output is determined alternately depending on the operating mode. The operating modes are divided into two groups for this purpose. One group includes operating modes in which fuel input occurs in the various operating modes, and the other group includes operating modes in which fuel output is determined. This allows for a reduction in the operating parameters and thus simplifies the models without any expected degradation in the method's quality.

[0019] In a further development of the procedure, when recording one of these operating modes, a fundamental distinction is made between operating modes with fuel input and those operating modes with fuel discharge, thus defining the operating parameters (groups) to be taken into account.

[0020] In a further development of the procedure, in an operating mode with fuel injection, the fuel injection is determined on the basis of one of the following operating parameters: torque requirement, engine temperature and engine speed.

[0021] Another operating parameter can be, for example, the regeneration status of a particulate filter, during which additional fuel is injected and can enter the lubricant via the cylinder walls. The operating parameters torque demand, engine temperature, and engine speed are easily determinable quantities to which applied fuel injection quantities (in weight percent) can be assigned depending on an operating mode and which are then normalized to the engine oil mass.

[0022] Optionally, an interlock function can ensure that no fuel input is determined if errors occur in the determination of these operating parameters. Such an error can be detected, for example, if nonsensical combinations of operating parameters occur due to sensor malfunctions.

[0023] In a further development of the method, the following operating parameters are taken into account in operating modes involving fuel discharge: engine oil temperature and internal torque. These operating parameters also allow for simple models to determine fuel discharge during operation. For example, a higher proportion of fuel evaporates from the lubricant at elevated engine oil or lubricant temperatures.

[0024] When the piston cooling jets are activated, lubricant is sprayed against the pistons in the crankcase. This reduces the engine oil temperature in the cooling channel and thus also the lubricant loss through evaporation. It can therefore serve as a simple correction factor.

[0025] An important indicator of fuel loss can also be derived from the internal moment, which takes into account the main influencing factors of mixture formation and ignition, namely the fresh gas charge, the ignition angle, and the lambda value. These parameters are also easily determined and suitable for creating a simple, reliable model.

[0026] In a further development of the method, the fuel input and / or fuel output is determined using a map that takes into account at least one of the operating parameters mentioned above. The corresponding maps for determining the fuel input and / or fuel output are determined in test bench simulations and / or model calculations.

[0027] As an alternative to characteristic maps, calculation algorithms can also be used in which the fuel input or fuel output is determined on the basis of the operating parameters mentioned above.

[0028] In a further development of the method, the standardized fuel equivalent is periodically provided for a function to calculate an oil change interval. This improves the determination of the oil change interval.

[0029] The period of between 2 and 3 seconds is consistent with the timing of standard control units and is preferably 2.4 seconds.

[0030] In a further development of the method, the initial value of the fuel total can be selected depending on an operating criterion, in particular an ignition cycle and / or an oil change. For example, after an oil change, the fuel total can be reset to zero, since no fuel is then enriched in the oil.

[0031] When the ignition is switched on, the last saved value is used.

[0032] The invention further relates to a control unit designed and configured to perform the above-described method for balancing a fuel mass in a lubricant. With the aid of such a control unit, both the fuel quality and the oil change interval can be determined more reliably.

[0033] The same applies to an internal combustion engine with a lubricant supply arrangement and a control unit which is designed and configured to carry out the inventive method for balancing a fuel mass in a lubricant, and a motor vehicle with such an internal combustion engine.

[0034] Exemplary embodiments of the invention are now described by way of example and with reference to the accompanying drawing, which shows: Fig. 1 a schematic representation of an oil circulation system, Fig. 2 a block diagram as part of an engine control unit by carrying out the method according to the invention, and Fig. 3 a simplified flow diagram which illustrates an embodiment of the method according to the invention.

[0035] Fig. 1Figure 1 shows an internal combustion engine 1 comprising a lubrication supply arrangement 2. The internal combustion engine 1 and the lubrication supply arrangement 2 are shown as components of a motor vehicle 100.

[0036] The lubricant supply arrangement 2 includes an oil reservoir 3 in which the lubricant, here engine oil, is collected. The oil reservoir can, for example, be located in an oil pan.

[0037] For lubrication, the engine oil is pumped through a heat exchanger 5, which serves as an oil cooler, and an oil filter 6 into the internal combustion engine 1, and is then distributed to the individual lubrication and bearing points of the engine via distribution lines.

[0038] An engine control unit 7 is connected to the internal combustion engine 1 and components of the lubrication supply system 2 via several signal and data inputs 8 and signal and data outputs 9. The engine control unit 7 can also be connected to display devices or a screen inside the vehicle via signal and data inputs or outputs 8, 9 to indicate certain operating and maintenance conditions.

[0039] In the engine control unit 7, hardware and / or software process blocks are implemented that interact in such a way as to determine a standardized fuel equivalent Ä n, which is suitable to support the determination of an oil change time or the length of an oil change interval.

[0040] The method is characterized by the determination of fuel dilution into the engine oil for specific operating modes. This is achieved using applied characteristic maps. The necessary data for these maps can be determined through tests on the engine test bench and / or simulation methods, and are then compared with the actual fuel dilution into the engine oil in weight percent per hour and output as dilution factors.

[0041] In other operating modes BM, fuel discharge is determined. Here, corresponding discharge factors are applied in other characteristic curves or maps, depending on suitable engine parameters.

[0042] The difference between fuel input and fuel output is continuously summed over a defined time interval. This interval is typically 1 to 3 seconds (specifically 2.4 seconds). This sum is normalized to a real mass of engine oil (m) in the oil pan and provided as a normalized fuel equivalent (Än), essentially a wear equivalent, for calculating oil change intervals. This calculation takes into account that a continuously measured fuel input shortens the required oil change interval and indicates an earlier oil change time.

[0043] The determination of the standardized fuel equivalent Ä n is now carried out using the block diagram in Fig. 2 explained.

[0044] In the operating mode recognition block B1, the current operating mode BM is read and an operating status B s is output, to which a number NB corresponding to the operating mode is then assigned in an operating mode selection block B2, which indicates whether an operating state BM with fuel input or with fuel output exists.

[0045] Based on this number, either a fuel input block B3 or a fuel output block B4 is activated. Depending on the number NB of the operating mode, the corresponding block B3 or B4 is then activated.

[0046] In block B3, the parameters torque requirement MA, engine temperature TM, and engine speed n M are taken into account, and using one or more characteristic maps or curves, the corresponding applied weight percentages for fuel injection into the engine oil are read and normalized to the respective engine oil mass. This normalized value for the fuel mass injection EM is then processed further.

[0047] In block B5, an oil mass m oil is determined, which results from the oil volume V oil, an oil refill quantity V oil-n and a status of the oil fill level Z oil-st.

[0048] If the number NB indicates an operating condition with fuel loss, a fuel loss AM is determined in block B4 depending on other engine operating criteria. These criteria include, for example, internal torque M i, engine oil temperature T oil, or the status of the piston cooling nozzles Z KD, to which operating points are assigned in characteristic curves or maps. From this, applied weight percentages of fuel loss AM are then read and normalized to the engine oil mass m oil.

[0049] Both the fuel input block (B3) and the fuel output block (B4) have a locking function that is activated by a status signal S V_e for fuel input and a status signal S V_a for fuel output. The locking signals take into account when errors occur in determining the corresponding operating criteria / parameters. In such cases, the determination process is blocked.

[0050] The results from B3 and B4 are further processed in block B6, the fuel total. In block B6, the difference between fuel input (EM) and fuel output (AM) is summed, and the maximum value of this sum is continuously stored. After an ignition cycle, the sum determined in the previous cycle is read back in as the starting value in block B4, specifically in the fuel output block.

[0051] During an oil change between ignition cycles, the total value is reset via a reset signal for this oil change (Z Oil-w). This total value is only used in block B4 for fuel runoff. The amount of fuel runoff is determined by the mass in the oil pan (engine oil + fuel dilution). The higher the fuel dilution, the higher the fuel runoff at the same operating point.

[0052] In the illustrated embodiment, the values ​​for fuel input EM and fuel output AM are determined in a 100 ms grid. Every 2.4 seconds, an average value WM (in block B6) is determined: W m = 1 24 ∑ k = 1 24 E M − A M

[0053] This averaging is triggered by the status wear equivalent Z Vä.

[0054] The standardized fuel equivalent Ä n is then calculated taking into account a permissible fuel input in [%] E Mzul from the formula: Ä n = 1 24 ∑ k = 1 24 E M − A M m Ö l ⋅ E Mzul ∗ 100

[0055] During a period in which the stored cumulative difference does not increase because there is no fuel input (EM) or fuel output (AM), the difference EM - AM is set to zero. This ensures that only the inherently harmful fuel input is considered when calculating the standardized fuel equivalent Ä n. In other words, if there is no input or the output is greater than the input, zero is summed. Only when the input again exceeds the output, i.e., when new fuel is added to the oil, is the difference EM - AM added again.

[0056] The standardized fuel equivalent Ä n is then passed to a calculation routine, which is carried out in control unit 7 to determine an oil change time. The accounting described above thus makes it easier to determine the period or point in time for the oil change.

[0057] Fig. 3shows a schematic overview of the procedure, which includes the following steps: S1: Starting an operating cycle of the internal combustion engine 1 S2: Capturing an operating mode BM S3: Determining the mass of an engine oil M O S4: Continuous determination of a fuel differential mass in the engine oil mass as a function of the detected operating mode BM S5: Continuous determination of a fuel sum from a starting value of the fuel quantity and from the summed fuel difference mass S6: Determination of a fuel equivalent Ä n from the total fuel consumption.

[0058] In step S4, it is optional to switch between steps S4.1 and S4.2, where a fuel input EM or a fuel output AM can be taken into account.

[0059] Further variants and embodiments of the invention are apparent to the person skilled in the art within the scope of the claims. Reference symbol list

[0060] 100 Motor vehicle 1 Internal combustion engine 2 Lubricant supply arrangement 3 Oil reservoir, oil pan 4 Pump 5 Heat exchanger 6 Oil filter 7 Engine control unit 8 Signal / data inputs 9 Signal / data outputs 10 Display, indicator B1 Operating mode detection B2 Operating data selection B3 Fuel input B4 Fuel discharge B5 Oil mass B6 Fuel total B7 Equivalent BM Current operating mode A Standardized fuel equivalent SB Operating mode status NB Operating mode number MA Torque request TM Engine temperature n M Engine speed S V_e Fuel input lock EM Fuel input m Oil Oil mass V Oil Oil mass Z Oil_St Oil level status V Oil_N Oil refill quantity AM Fuel discharge T Oil Oil temperature Z KD Piston cooling nozzle status M i Internal torque S V_a Fuel discharge lock Z Oil-w Oil change status, oil change signal Z Vä Wear equivalent calculation status

Claims

1. Method for balancing a fuel mass in a lubricant of an internal combustion engine (1) during operation of the internal combustion engine (1), comprising: - starting an operating cycle of the internal combustion engine (1) - detecting an operating mode (BM, SB; NB) - determining an engine oil mass (mÖl) - continuously determining a fuel differential mass (EM - AM) from a fuel input (EM) and a fuel output (AM) in the engine oil mass (mÖl) on the basis of the detected operating mode (BM, SB; NB) - continuously determining a fuel sum from a starting value of the fuel sum and from the summed fuel differential mass (Σ (EM - AM)) - determining a normalized fuel equivalent (Än) from the fuel sum, wherein the normalized fuel equivalent (Än) is determined by the determination equation Ä n = 1 24 ∑ k = 1 24 E M − A M m Öl ⋅ E Mzul ∗ 100 with the engine oil mass (mÖl)and a permissible fuel input (EMzul), wherein the summand where index k = 1 is the starting value.

2. Method according to claim 1, wherein, when the fuel differential mass is determined, either a fuel input (EM) or a fuel output (AM) is determined on the basis of the operating mode (BM).

3. Method according to claim 1 or 2, wherein detecting an operating mode comprises: - differentiating and selecting between an operating mode (BM, SB; NB) with fuel input (EM) and an operating mode with fuel output (AM).

4. Method according to claim 3, wherein, in the operating mode (BM, SB; NB) with fuel input (EM), the fuel input is determined on the basis of one of the following operating parameters: torque requirement (MA), engine temperature (TM), engine speed (nM).

5. Method according to claim 3, wherein, in the operating mode (BM, SB; NB) with fuel output (AM), the fuel output is determined on the basis of one of the following operating parameters: lubricant temperature (TÖl), inner torque (Mi).

6. Method according to claim 5, wherein, in the operating mode (BM, SB; NB) with fuel output (AM), the fuel output is determined on the basis of a piston cooling nozzle status (ZKD).

7. Method according to claim 4, 5 or 6, wherein the fuel input (EM) and / or the fuel output (AM) is determined using a map which takes into consideration at least one operating parameter (MA; TM; nM; TÖl; Mi; ZKD).

8. Method according to claim 4, 5 or 6, wherein the fuel input (EM) and / or the fuel output (AM) is determined using an algorithm which takes into consideration at least one operating parameter (MA; TM; nM; TÖl; Mi; ZKD).

9. Method according to any of the preceding claims, wherein the normalized fuel equivalent (Än) is periodically provided for a function to calculate an oil change time.

10. Method according to claim 9, wherein the period is between 2 and 3 seconds and preferably 2.4 seconds.

11. Method according to any of the preceding claims, wherein the starting value of the fuel sum can be selected on the basis of an operating criterion, namely an ignition change.

12. Method according to any of claims 1 to 10, wherein the starting value of the fuel sum can be selected on the basis of an operating criterion, namely an oil change.

13. Control unit (7) which is designed and configured to perform a method for balancing a fuel mass in a lubricant according to any of claims 1 to 12.

14. Internal combustion engine (1) comprising a lubricant supply arrangement (2) and a control unit (7) according to claim 13.

15. Motor vehicle (100) comprising an internal combustion engine (1) according to claim 14.