Engine control device
By acquiring the amount of diluted fuel in the engine oil and determining whether to reset the air-fuel ratio learning value based on a threshold, the problem of deteriorating exhaust emissions after changing the engine oil is solved, and the air-fuel ratio learning value is quickly converged, thus improving the efficiency of engine control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2025-11-26
- Publication Date
- 2026-06-09
Smart Images
Figure CN122169940A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an engine control device. Background Technology
[0002] As engine oil is used continuously, the amount of fuel diluted with the engine oil, i.e., the amount of diluted fuel, gradually increases. Fuel vaporized from the engine oil is burned as blow-by gas in the engine's combustion chamber. Therefore, the amount of fuel dilution is reflected in the air-fuel ratio learning value learned in the air-fuel ratio feedback control. Thus, when the engine oil is changed, since the amount of fuel dilution is zero, the air-fuel ratio learning value is reset to its initial value (e.g., see Patent Document 1).
[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-137083 Summary of the Invention
[0004] If the air-fuel ratio learning value is reset to the initial value, the air-fuel ratio learning process will begin again from the initial value. For example, if the above reset is performed even when the amount of diluted fuel before changing the engine oil is very small, it will take time for the air-fuel ratio learning value to converge during the subsequent learning process, during which exhaust emissions may deteriorate.
[0005] Therefore, the object of the present invention is to provide an engine control device that suppresses the deterioration of exhaust emissions.
[0006] The above objective can be achieved by the following engine control device: comprising: a learning unit that learns the steady-state error of the air-fuel ratio deviation in air-fuel ratio feedback control based on the air-fuel ratio deviation of the engine relative to the target air-fuel ratio as an air-fuel ratio learning value; an acquisition unit that acquires the amount of fuel diluted in the engine oil, i.e., the amount of diluted fuel; and a determination unit that, when the engine oil has been changed, determines whether the amount of diluted fuel before the engine oil change is below a threshold value. If the determination unit makes an affirmative determination, the learning unit resets the air-fuel ratio learning value to an initial value; if the determination unit makes a negative determination, the learning unit maintains the air-fuel ratio learning value. The threshold value is set to an upper limit of the amount of diluted fuel that, compared to resetting the air-fuel ratio learning value to the initial value, reduces the time required until the air-fuel ratio learning value converges after the engine oil change.
[0007] The air-fuel ratio learning value includes a first learning value learned in the first load region of the engine and a second learning value learned in the second load region of the engine where the load is different from the first load region. The first learning value is more affected by the amount of diluted fuel than the second learning value. The learning unit can reset the first learning value to its initial value and maintain the second learning value if the determination unit makes a positive determination, and maintain both the first and second learning values if the determination unit makes a negative determination.
[0008] Invention Effects
[0009] According to the present invention, an engine control device can be provided that suppresses the deterioration of exhaust emissions. Attached Figure Description
[0010] Figure 1 It is a schematic structural diagram of a vehicle equipped with an engine.
[0011] Figure 2 This is a flowchart illustrating the learning control performed by the ECU. Detailed Implementation
[0012] [General Vehicle Structure]
[0013] Figure 1 This is a schematic structural diagram of a vehicle 1 equipped with an engine 10. Vehicle 1 includes an engine 10, an Electronic Control Unit (ECU) 30, and drive wheels 40. The engine 10 is the power source for the vehicle 1; it is a gasoline engine, but it can also be a diesel engine. Furthermore, vehicle 1 can be a hybrid vehicle that, in addition to the engine 10, also has an electric motor as a power source. The engine 10 is, for example, a four-cylinder inline engine, but is not limited to this.
[0014] Engine 10 has a cylinder head 10a, a cylinder block 10b, and a crankcase 10c. Air is drawn into a combustion chamber 11 formed within the cylinder head 10a through an intake passage 12, and fuel is supplied via an injection valve 13. The injection valve 13, located in the cylinder head 10a, is a fuel injection valve that directly injects fuel into the combustion chamber 11. Alternatively, an intake port injection valve that injects fuel into the intake port may be provided instead of the injection valve 13, or in addition to the injection valve 13. When the mixture of intake air and injected fuel is ignited by a spark plug 14, the mixture burns, and the piston 15 reciprocates within the cylinder block 10b, thereby rotating the crankshaft 16 of engine 10. The rotational power of the crankshaft 16 is transmitted to the drive wheel 40 via a transmission (not shown). The burned mixture is discharged as exhaust from the combustion chamber 11 of engine 10 to an exhaust passage 17. A catalyst 17a for purifying the exhaust is provided in the exhaust passage 17.
[0015] Engine oil is stored in the crankcase 10c and supplied to various lubrication points via an oil pump (not shown). The engine oil used for lubrication is then recycled back into the crankcase 10c. One end of the blow-by passage 10d is connected to the crankcase 10c, and the other end is connected to the intake passage 12, which is located downstream of the throttle valve 19 located in the intake passage 12. A positive crankcase ventilation (PCV) valve 18 is installed in the blow-by passage 10d. The PCV valve 18 opens when the intake negative pressure downstream of the throttle valve 19 in the intake passage 12 becomes greater than a predetermined value. Thus, the blow-by gas generated in the crankcase 10c is released into the combustion chamber 11 via the blow-by passage 10d and the intake passage 12 for combustion.
[0016] ECU 50 performs various controls for driving the vehicle 1. ECU 50 includes a central processing unit that performs various calculations related to these controls, a non-volatile memory that stores the programs or data required for the calculations, a volatile memory that temporarily stores the calculation results of the central processing unit, and input and output ports for inputting and outputting signals to and from external sources.
[0017] Various sensors are connected to the ECU 50. These sensors include a throttle opening sensor 32, an air flow meter 34, a crankshaft angle sensor 35, and an air-fuel ratio sensor 36. The throttle opening sensor 32 detects the opening of the throttle valve 19. The air flow meter 34 detects the amount of air drawn in through the intake passage 12. The crankshaft angle sensor 35 detects the rotational speed of the crankshaft 16, i.e., the engine speed of the engine 10. The air-fuel ratio sensor 36 detects the air-fuel ratio of the exhaust gas flowing into the catalyst 17a.
[0018] The ECU 50 uses output signals from various sensors to monitor the engine 10's speed, load, and other driving conditions. Based on this monitoring, the ECU 50 controls the opening of the throttle valve 19, the amount of fuel injected from the in-cylinder injection valve 13, and the ignition timing of the air-fuel mixture via the spark plug 14. While details about the ECU 50 will be described later, it functionally implements a learning unit, an acquisition unit, and a decision unit. The ECU 50 is an example of an engine control unit.
[0019] A portion of the fuel injected from the in-cylinder injection valve 13 adheres to the cylinder wall of the cylinder block 10b and drips into the crankcase 10c, mixing with the engine oil. Thus, the engine oil is diluted by the fuel. The amount of fuel that dilutes the engine oil is called the dilution fuel amount. Therefore, this fuel is also contained in the blow-by gas released into the combustion chamber 11 via the blow-by passage 10d and the intake passage 12. The more dilution fuel, the more fuel is contained in the blow-by gas. Because blow-by gas is released into the combustion chamber 11, if the dilution fuel amount is high, the air-fuel ratio of the engine 10 tends to be biased towards the fuel-rich side relative to the target value.
[0020] ECU 50 performs learning control, which learns the steady-state error of the air-fuel ratio deviation in the air-fuel ratio feedback control based on the deviation of the actual air-fuel ratio from the target air-fuel ratio of engine 10 as the air-fuel ratio learning value. The target air-fuel ratio is determined according to the driving state of engine 10. The actual air-fuel ratio is detected by air-fuel ratio sensor 36. In the feedback control, the fuel injection quantity of engine 10 is controlled based on the air-fuel ratio deviation of the actual air-fuel ratio from the target air-fuel ratio to eliminate the air-fuel ratio deviation. Furthermore, the steady-state error generated by the stable deviation is calculated based on the shift of the air-fuel ratio deviation, and the steady-state error is learned as the air-fuel ratio learning value. The above-described learning control is an example of control performed by the learning unit. As described above, the amount of diluted fuel is reflected in the air-fuel ratio of engine 10 and also in the air-fuel ratio learning value. The learning control will be described in detail below.
[0021] [Learning Control]
[0022] Figure 2 This is a flowchart illustrating the learning control performed by ECU 50. This control is repeatedly executed during ignition. ECU 50 acquires the amount of dilution fuel (step S1). The amount of dilution fuel is calculated, for example, based on the cumulative amount of intake air up to the coolant temperature at engine 10 startup or until the coolant temperature reaches 40°C after startup. For example, if engine 10 is frequently stopped before warm-up is complete, the amount of dilution fuel increases. Furthermore, the amount of dilution fuel can be any of an estimated value, a calculated value, or a detected value. These calculation, estimation, and detection methods can be arbitrary or known methods. Step S1 is an example of the processing performed by the acquisition unit.
[0023] Next, the ECU 50 determines whether the engine oil has been changed (step S2). For example, if a switch operation for an oil change performed by a dealer has been performed, the determination in step S2 is "yes". Also, if the user has input the oil mileage, the determination in step S2 is "yes". The oil mileage is a system that reminds the user to change the oil when the specified distance has been reached after an oil change, and the user inputs the notification to change the oil. Furthermore, the determination of whether the engine oil has been changed can also be achieved using other known methods. For example, if the engine oil drain plug is detected to be open or the engine oil level has increased, it can be determined that the engine oil has been changed. If the result in step S2 is "no", this control ends. Step S2 is an example of the processing performed by the determination unit.
[0024] If "Yes" is true in step S2, it is determined whether the amount of diluted fuel before changing the engine oil is below a threshold (step S3). If "No" is true in step S3, the ECU 50 resets the air-fuel ratio learning value to the initial value (step S4). Therefore, after resetting the air-fuel ratio learning value, air-fuel ratio learning is performed again from the initial value. If "Yes" is true in step S3, the ECU 50 maintains the air-fuel ratio learning value (step S5). In this case, the air-fuel ratio learning value before changing the engine oil is maintained and air-fuel ratio learning continues, and the above-mentioned feedback control is performed based on the air-fuel ratio learning value. In addition, if "Yes" is true in step S2, the amount of diluted fuel is reset to zero. Step S3 is an example of the process performed by the determination unit. Steps S4 and S5 are examples of the processes performed by the learning unit.
[0025] The condition "Yes" in step S3 indicates that the difference in diluted fuel quantity before and after changing the engine oil is small. Furthermore, since the replaced engine oil is new, the diluted fuel quantity after the replacement is zero. That is, a condition "Yes" in step S3 is considered to indicate that the difference in diluted fuel quantity before and after changing the engine oil is small, and the difference in the convergence value of the air-fuel ratio learning value before and after the replacement is also small. Therefore, when the difference in the convergence value of the air-fuel ratio learning value before and after the replacement is small, it is considered that maintaining the air-fuel ratio learning value and continuing to learn the air-fuel ratio is more effective in shortening the time required for the air-fuel ratio learning value to converge after the replacement compared to resetting the air-fuel ratio learning value to its initial value.
[0026] In step S3, a "No" result indicates a large difference in the amount of diluted fuel before and after an engine oil change, and consequently, a large difference in the convergence value of the air-fuel ratio learning value before and after the change. Therefore, when the difference in the convergence value of the air-fuel ratio learning value before and after the change is large, it is considered that resetting the air-fuel ratio learning value to its initial value and continuing air-fuel ratio learning is more effective in shortening the time required for the air-fuel ratio learning value to converge after the oil change compared to maintaining the initial value. As described above, the threshold in step S3 is set as the upper limit of the amount of diluted fuel required to shorten the time required for the air-fuel ratio learning value to converge after an engine oil change, compared to resetting it to its initial value. The threshold is determined in advance through experiments or analysis.
[0027] As described above, if step S3 is "No", the air-fuel ratio learning value is reset to its initial value; if step S3 is "Yes", the air-fuel ratio learning value is maintained. This shortens the time from engine oil change until the air-fuel ratio learning value converges, suppressing exhaust emission deterioration. Furthermore, one condition for purging evaporated fuel adsorbed in the activated carbon canister (not shown) into the intake passage 12 is that the air-fuel ratio learning value has converged. Since the time from engine oil change until the air-fuel ratio learning value converges is shortened, the purging of evaporated fuel can also be performed earlier.
[0028] Here, the air-fuel ratio is learned according to the load region of each engine 10. That is, the air-fuel ratio learning value is calculated according to the load region of each engine 10. For example, the air-fuel ratio learning value in the low load region is different from the air-fuel ratio learning value in the high load region. The air-fuel ratio learning value reset to the initial value in step S4 is the air-fuel ratio learning value in the load region where the dilution fuel quantity has a large impact on the air-fuel ratio learning value. The load region where the dilution fuel quantity has a large impact on the air-fuel ratio learning value is the load region where the air-fuel ratio learning value also increases significantly with the increase or decrease of the dilution fuel quantity. Generally, the impact of the dilution fuel quantity on the air-fuel ratio learning value is greater in the low load region than in the high load region. This is because, in the low load region, the intake air quantity and fuel injection quantity are relatively small, and the dilution fuel quantity has a large impact on the air-fuel ratio.
[0029] Therefore, in step S4, for example, the air-fuel ratio learning value in the low-load region is reset to its initial value, while the air-fuel ratio learning value in the high-load region is maintained. This maintains the air-fuel ratio learning value in the load region where the effect of the diluted fuel amount on the air-fuel ratio learning value is small. This suppresses exhaust emission deterioration during the period until the air-fuel ratio learning value is reset and converges again. In step S5, any air-fuel ratio learning value in the low-load and high-load regions is maintained. The low-load and high-load regions are examples of the first and second load regions, respectively. The air-fuel ratio learning value in the low-load region is an example of the first learning value. The air-fuel ratio learning value in the high-load region is an example of the second learning value.
[0030] Furthermore, the load region where the amount of diluted fuel has a significant impact on the air-fuel ratio learning value varies for each engine. Therefore, this load region is not limited to the low-load region. Moreover, air-fuel ratio learning can be performed for more than three load regions. In this case, for example, the air-fuel ratio learning value in the load region where the amount of diluted fuel has the greatest impact on the air-fuel ratio learning value can be reset to its initial value. Furthermore, the air-fuel ratio learning values in the load regions where the amount of diluted fuel has the greatest impact on the air-fuel ratio learning value, and the air-fuel ratio learning values in the second most influential load regions, can also be reset to their initial values.
[0031] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments described above. Various modifications and alterations can be made within the scope of the spirit of the present invention as set forth in the claims.
[0032] Symbol Explanation
[0033] 1-Vehicle, 10-Engine, 50-ECU (Engine Control Unit, Learning Unit, Acquisition Unit, Judgment Unit).
Claims
1. An engine control device, characterized in that, have: The learning unit learns the steady-state error of the air-fuel ratio deviation in the air-fuel ratio feedback control, which is based on the deviation of the engine's air-fuel ratio from the target air-fuel ratio, as the air-fuel ratio learning value. The acquisition unit acquires the amount of fuel used to dilute the engine oil, i.e., the amount of diluted fuel; and The determination unit, in the case of an engine oil change, determines whether the amount of diluted fuel before the engine oil change was below a threshold. If the determination unit makes an affirmative determination, the learning unit resets the air-fuel ratio learning value to its initial value; if the determination unit makes a negative determination, it maintains the air-fuel ratio learning value. The threshold is set as an upper limit of the amount of diluted fuel that, compared to resetting the air-fuel ratio learning value to the initial value, reduces the time required for the air-fuel ratio learning value to converge after the engine oil is changed.
2. The engine control device according to claim 1, characterized in that, The air-fuel ratio learning value includes a first learning value learned in the first load region of the engine, and a second learning value learned in a second load region of the engine where the load is different from the first load region. The first learning value is more affected by the amount of diluted fuel than the second learning value. If the determination unit makes an affirmative determination, the learning unit resets the first learning value to the initial value and maintains the second learning value; if the determination unit makes a negative determination, it maintains both the first and second learning values.